UK opposition parties have agreed not to back Boris Johnson's demand for a general election before the EU summit in mid-October.
Labour, the Lib Dems, the SNP and Plaid Cymru say they will vote against the government or abstain in Monday's vote on whether to hold a snap poll.
But the PM said the parties were making an "extraordinary political mistake".
Meanwhile, a bill designed to prevent a no-deal Brexit has been approved by the House of Lords and will pass into law.
It will force the prime minister to ask the EU for the Brexit deadline to be extended beyond 31 October if no deal is agreed by the UK and Brussels by 19 October.
Mr Johnson wants an election to take place on 15 October, ahead of that date and the EU summit on 17 and 18 October.
He argues that a snap poll will allow the government to "get on" with delivering Brexit by the end of October.
But opposition MPs - who, along with Conservative rebels, have already defeated one attempt by the government to bring in an early election - say Mr Johnson is trying to push through a no-deal exit.
During the past week the prime minister has suffered several defeats over Brexit in Parliament, expelled 21 of his own MPs for rebelling and seen his younger brother, Jo Johnson, resign from government.
In other developments:
Following the meeting of opposition parties on Friday, a Labour Party spokesman said: "Jeremy Corbyn hosted a positive conference call with other opposition party leaders this morning.
"They discussed advancing efforts to prevent a damaging no-deal Brexit and hold a general election once that is secured."
By John Pienaar, BBC deputy political editor
As good weeks go, for Boris Johnson this wasn't one.
Defeated and defeated again in the Commons, choosing to sack more than 20 of his most respected though rebellious colleagues - provoking uproar from Tories who say that was brutally heavy-handed, and now trying to sound conciliatory.
The list of Tory MPs standing down at the next election has continued to grow, and they look like reinforcing Mr Johnson's critics.
And the House of Lords sent legislation to ban no-deal, and maybe force the PM to seek a Brexit extension, to become law.
He won't break his word. Civil servants are clear he can't break the law. Mr Johnson needs a way to force an election, or salvage his plan to deliver Brexit - maybe without getting an EU deal first. In Downing Street there's no sign they've found one.
The options on No 10's table - after another expected defeat on election timing next week - range from quitting office in hope of getting back in, to counting on the EU to deny the UK the Brexit extension the PM doesn't want.
If there's a cunning plan - and many people, in and out of government, don't believe there is - it seems to need more work. And soon.
SNP Westminster leader Ian Blackford said he was "desperate for an election", but it could not happen until an extension to Article 50 - the process by which the UK is leaving the EU - had been secured.
"It's not just about our own party interests; it's about our collective national interests," he said. "So we are prepared to work with others to make sure we get the timing right."
He said they wanted to make sure the UK did not "crash out" in a no-deal Brexit.
Liz Saville Roberts, Plaid Cymru's Westminster leader, said there was an "opportunity to bring down Boris" and "we should take that".
And a Lib Dem spokeswoman said the group was clear that "we are not going to let Boris Johnson cut and run".
"The Liberal Democrat position for a while now is that we won't vote for a general election until we have an extension agreed with the EU. I think the others are coming round to that," she said.
"As a group we will all vote against or abstain on Monday."
But Housing, Communities and Local Government Secretary Robert Jenrick said the public were "sick of watching politicians bicker" about Brexit and it was time for an election.
He said opposition parties should "stop being cowardly, put the matter to the public, and get resolution at last, so the country can move forward with confidence and optimism for the future".
Mr Johnson has promised the UK will leave the EU "do or die" on 31 October, with or without a deal.
But he said on Friday that he would go to Brussels on 17 October and reach a deal.
He added that resigning as prime minister if he did not get one by then was "not a hypothesis" he would be willing to contemplate.
He also said he was "perplexed" by the decision of opposition parties to "run away" from an election.
"All I see is Corbyn and the SNP clubbing together to try and lock us into the EU when it's time to get this thing done," he said.
"It's the most sensational paradox - never in history has the opposition party been given the chance for election and has turned it down."

An internal UK government memo on the consequences of Boris Johnson's Brexit deal renegotiation singles out the removal of the word "adequate" from the UK-EU Political Declaration to describe mechanisms for enforcing common social, environmental, and labour standards after Brexit.
The word "adequate" appears to have been replaced by the word "appropriate".
Extracts of a note written for the government's cross-Whitehall Economic Partnership Steering Group, and seen by the BBC, say the "parties will include "appropriate" (rather than "adequate") mechanisms for dispute settlement" of key "level playing field commitments" in a future trade deal with the European Union.
The consequence of that change, the note says, is that it means that it is now possible to argue it is "inappropriate for the future UK-EU relationship" that disputes about these commitments on employment, environment, tax, state aid and other standards should be subject to binding arbitration.
The memo, first leaked to the Financial Times and marked "Official Sensitive", contains a series of claimed negotiation wins from the Brexit deal renegotiation, weakening the scope and strength of Level Playing Field Commitments (LPF), a crucial element in a future UK-EU trade arrangement.
"The previous Protocol applied wide-ranging LPF measures on a UK-wide bases as a response to UK access to the EU market through the single customs territory.
"UK negotiators successfully resisted the inclusion of all UK-wide LPF rules" says the memo, with the last four words put in bold for emphasis.
"The only level playing field provisions in the revised Protocol are those necessary to support the operation of the Single Electricity Market and state aid measures that affect trade between NI and the EU," it says.
The title of the memo is "Update to EPSG (Economic Partnership Steering Group) on Level Playing Field Negotiations".
This is the first acknowledgement that changing the Level Playing Field commitments agreed by Theresa May was a specific aim of the PM's renegotiation.
In public, the PM focused on changing what he referred to as "the anti-democratic backstop", which had been rejected by the government's parliamentary allies, the Democratic Unionists.
In the end, the PM's new solution, creating a new trade and regulatory border in the Irish Sea, further alienated the DUP. Backbench eurosceptic Conservative MPs have, however, been won over to the deal.
Theresa May's original 2018 deal included a range of specific enforceable common standards for the UK and the EU within the legally binding Withdrawal Treaty.
Some of these standards were related to EU law, others referred to the OECD (Organisation for Economic Cooperation and Development), International Labour Organisation and the Council of Europe.
These were all removed, along with the backstop, and the only reference remaining in the overall deal was in the non-binding Political Declaration.
The memo shows that within Whitehall, weakening these provisions was a key part of the renegotiation.
Regarded as an internal success, their removal paves the way for a "much more open starting point for future relationship negotiations" that allow for "a range of landing zones" for a future deal.
"The Political Declaration text provides us with a framework for negotiating FTA-style commitments on Level Playing Field," the memo concludes under the headline "Next Steps".
That is a reference to the fact that, unlike the original Brexit deal agreed by Theresa May, dispute settlement mechanisms have not applied to existing standard EU Free Trade Agreements.
Sam Lowe, trade fellow at the Centre for European Reform, said: "The Level Playing Field commitments in the EU's Free Trade Agreements with Canada and Japan are unenforceable, because they are specifically excluded from the dispute settlement mechanisms. The government appears to be aiming for the same treatment."
Speaking on the BBC's Andrew Marr Show on Sunday, Conservative Party chairman James Cleverly rejected suggestions there are attempts to relax workplace rights or environmental protections.
"In many areas we have already gone further than the European Union," he said. "We are making hard improvements on worker rights through an increase in the National Living Wage."
The government was also strengthening rules on maritime protection and animal welfare, he added.
On Saturday, ministers said stories about the leaked memo were "not correct" and "way exaggerated".
The government also said: "The UK government has no intention of lowering the standards of workers' rights or environmental protection after we leave the EU.
"UK level playing field commitments will be negotiated in the context of the future UK-EU free trade agreement, where we will achieve a balance of rights and obligations which reflect the scope and depth of the future relationship."

Former Chancellor Philip Hammond has accused the PM of trying to wreck the chance of a new Brexit deal, by making demands the EU could never accept.
In a Times article, Mr Hammond said a no-deal Brexit would be "a betrayal" of the 2016 referendum result.
He told the BBC he was "confident" that Parliament "has the means" to express its opposition to a no-deal exit.
A No 10 source said the UK would leave on 31 October despite Mr Hammond's "best efforts to the contrary".
The source added that Mr Hammond, as chancellor, "did everything he could" to block preparations for leaving and had "undermined negotiations".
The former chancellor rejected this suggestion in a tweet, saying he wanted to deliver Brexit "and voted to do so three times".
Prime Minister Boris Johnson has said he wants to leave the EU with a deal, but the UK must leave "do or die" by the latest Brexit deadline of 31 October.
He wants the EU to ditch the Irish border backstop plan from the deal negotiated by former PM Theresa May, which was rejected three times by Parliament.
But the EU has continued to insist that deal, including the backstop arrangements, is the only agreement possible.
Many of those who voted against the deal had concerns over the backstop, which if implemented, would see Northern Ireland staying aligned to some rules of the EU single market.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
These arrangements would apply unless and until both the EU and UK agreed they were no longer necessary.
Speaking on BBC Radio 4's Today programme, Mr Hammond said a no-deal exit would be "just as much a betrayal of the referendum result as not leaving at all".
He said that Mr Johnson's demand for the backstop to be entirely removed from the deal meant a no-deal was inevitable on the current 31 October deadline.
He said that agreeing to changes now would "fragment" the EU, adding: "they are not going to take that risk".
"Pivoting to say the backstop has to go in its entirety - a huge chunk of the withdrawal agreement just scrapped - is effectively a wrecking tactic," he said.
He also told Today that he was "very confident" MPs would be able to pass legislation to express their opposition to a no-deal exit.
However he said he did not favour the tactic of replacing the PM with a national unity government designed to prevent no deal, saying: "I don't think that's the answer".
In his Times article, Mr Hammond said "the unelected people who pull the strings of this government know that this is a demand the EU cannot, and will not, accede to."
BBC political correspondent Tom Barton said that remark was an apparent aim at the prime minister's closest adviser, Dominic Cummings - the former Vote Leave campaign director.
It was a "travesty of the truth", Mr Hammond wrote, to pretend that Leave voters backed a no-deal Brexit in the 2016 referendum.
But Leave-supporting former Tory leader Iain Duncan Smith, also speaking on the Today programme, said he was "astounded" by Mr Hammond's remarks.
"Talk about hubris. This man did nothing to prepare us for leaving with no deal," he said.
"The fact we are now doing that means we have a much better chance to get some kind of agreement from them because they now know we're going to leave with no deal and he's undermining that."
Mr Hammond's comments come as Downing Street said it expected a group of MPs to try to block a no-deal Brexit by attempting to pass legislation when Parliament returns next month.
The Daily Telegraph reports that Commons Speaker John Bercow told an audience at the Edinburgh Fringe festival that he "strongly" believes the House of Commons "must have its way".
He said he would "fight with every breath in my body" any attempt by the prime minister to suspend Parliament to force through a no-deal against MPs' wishes.
On Tuesday, Work and Pensions Secretary Amber Rudd urged Mr Johnson not to force through a suspension.
She told the BBC: "I remain a great admirer of Parliament and of parliamentary sovereignty and I will continue to argue for the executive of the government that I'm part of to work with Parliament, not against them."
Meanwhile, 20 other senior Tory MPs have written to the prime minister to say his demand to scrap the Irish backstop "set the bar so high that there is no realistic probability of a deal being done".
The MPs said they were "alarmed by the 'Red Lines' you have drawn which, on the face of it appear to eliminate the chance of reaching agreement with the EU".
The group also demands that Mr Johnson declares he is firmly committed to leaving the EU with a deal and is ready to compromise to get one - pointing out those were assurances he gave during the leadership campaign "both publicly and privately".
Seven other former cabinet ministers have signed the letter, including David Lidington, David Gauke, Rory Stewart and Greg Clark, all of whom resigned before Mr Johnson took office.

A no-deal Brexit poses a risk to the public because the UK would lose access to EU-wide security powers and databases, police leaders have warned.
Police and crime commissioners say law enforcement agencies "face a significant loss of operational capacity" if the arrangements stop.
They have asked the home secretary to confirm his contingency plans.
The Home Office says it will continue to make the case for the retention of the capabilities.
In a letter to Home Secretary Sajid Javid, the Association of Police and Crime Commissioners' cross-party Brexit Working Group stresses the importance of continued co-operation with European policing and justice bodies after March 2019.
It says 32 measures are currently being used on a daily basis including the European Arrest Warrant;  the Schengen Information System -  a database of "real time" alerts about certain individuals - and the European Criminal Records Information System.
"The UK and EU share a common and ever evolving threat picture. We believe that a comprehensive partnership in all areas of policing and security co-operation is of mutual benefit to all," they add.
The commissioners say after discussions with National Crime Agency and the National Police Chiefs' Council, they understand "considerable additional resource would be required for policing to operate using non-EU tools and that such tools would be sub-optimal - potentially putting operational efficiency and public safety at risk".
They add: "We are therefore concerned that a 'no deal' scenario could cause delays and challenges for UK policing and justice agencies."
The EU's chief negotiator Michel Barnier has indicated the UK would not be able to remain part of the European Arrest Warrant after Brexit and said it would not have the same access to organisations such as police agency Europol.
But in June, the prime minister complained EU negotiators were blocking agreement on deals, risking the safety of EU and UK citizens.
A Home Office spokesman told the Guardian: "There is widespread recognition that the UK and EU can most effectively combat security threats when we work together.
"It is important we maintain operational capabilities after Brexit, and we will continue to make this case to the European Commission."
He said the government was confident co-operation would continue but it was also preparing for "every eventuality, including no deal".

The Scottish National Party is calling on Labour to work with other opposition parties to keep Britain in the single market and customs union after Brexit.
Its Commons leader Ian Blackford asked for help to stop the "catastrophic damage" of "extreme" Brexit.
"It is time for MPs of all parties to put politics aside," he said.
Labour says the UK should "stay aligned" to the EU after Brexit and could pay to access the single market like Norway.
Mr Blackford said he would invite other opposition leaders to a summit on 8 January when MPs return from the Christmas recess.
He said: "As we saw with the successful amendments to the EU Withdrawal Bill, when opposition parties work together effectively it is possible to secure a parliamentary majority and deliver change in the national interest."
The SNP, Liberal Democrats, Plaid Cymru and the Greens have all said they want the UK to stay in the single market and customs union after Brexit - something Prime Minister Theresa May has already ruled out.
Labour's leader, Jeremy Corbyn, has also faced criticism over his refusal to support a second referendum on the final terms of the UK's exit from the EU.
He told the i newspaper: "We have had a referendum which came to a decision. The negotiations are still ongoing, albeit well behind schedule, and we've set out the kind of relationship we want to have with Europe in the future."
Tom Brake, Brexit spokesman for the Liberal Democrats, said the Labour leadership had "shirked their responsibility" to provide effective opposition to the government.
"The Labour leadership has constantly played a game of smoke and mirrors over their Brexit position.
"But here they are nailing their colours to the mast in support of hard Brexit," he added.

Theresa May will update MPs on Tuesday about recent Brexit talks as she continues to seek support for her deal.
She visited Dublin and Brussels last week seeking EU agreement on changes to the backstop - the "insurance" policy to avoid the return of visible Northern Ireland border checks.
Last month MPs - who will debate Brexit on Thursday - voted for the PM to find alternatives to the current backstop.
But the EU has said it would not renegotiate the withdrawal agreement.
However, efforts to come up with a solution acceptable to both sides continue.
Brexit Secretary Steve Barclay met a group of Tory MPs working on possible alternatives to the backstop, before he travelled to Brussels and held talks with EU negotiator Michel Barnier.
Following the meeting, Mr Barnier said the talks had been "constructive", but added it was "clear from our side we're not going to reopen the withdrawal agreement, but we will continue our discussions in the coming days".
A statement from the Department for Exiting the European Union said Mr Barclay and Mr Barnier had agreed to further talks "in the coming days". Their teams would continue to work in the meantime "on finding a way forward", it added.
The statement to the House of Commons on Tuesday - a day earlier than had been expected - follows an exchange of letters between Mrs May and Jeremy Corbyn.
The Labour leader wrote to the PM on Wednesday with a list of five demands to secure his party's support for her deal, including a permanent customs union.
The prime minister struck a conciliatory tone in her response overnight and said she looked forward to the two parties meeting again "as soon as possible" to discuss ways forward on Brexit.
But No 10 said it rejected any proposals to remain in a customs union with the EU.
Some of her cabinet members also quashed the idea, with International Trade Secretary Liam Fox calling Mr Corbyn's proposal a "dangerous delusion".
Mrs May told the Labour leader: "It is good to see that we agree that the UK should leave the European Union with a deal and that the urgent task at hand is to find a deal that honours our commitments to the people of Northern Ireland, can command support in Parliament and can be negotiated with the EU - not to seek an election or second referendum."
This is despite Mr Corbyn repeatedly saying there should be a general election if Mrs May cannot get a deal through Parliament. He has also faced pressure from some of his MPs to push for another public vote on Brexit.
Shadow Brexit Secretary Keir Starmer said his "key question" about Mrs May's response was: "Is she prepared to move her red lines and find a consensus?"
"I don't see that in the letter," he said.
"The point of the exercise was to say, look, there is a majority for a close economic relationship, if you're prepared to try to find it, and I've said for some time we should test that by having a vote on a customs union."
Labour MP David Lammy - who supports the "People's Vote" campaign for a new referendum - said Mrs May's letter "makes it clear there is no hope of her agreeing" with Mr Corbyn's demands and said his party should campaign now for a fresh vote.
But fellow Labour MP Lisa Nandy told the BBC's Politics Live that there were between 40 and 60 of her colleagues "who are actively looking for ways to support" a revised Brexit deal.
She said the government needed to "get serious" about policy on a customs union and guarantee to "legislate for the protections around workers' rights".
The anti-Brexit Liberal Democrats said it was "astonishing" the two leaders were starting "serious discussions about delivering disastrous Brexit together" 900 days after the vote to leave the EU.
Brexit spokesman Tom Brake added: "It is time for Jeremy Corbyn to give up the letters and instead draw his attention to Labour Party policy and get behind the campaign for a People's Vote."
The GMB union criticised the government's "dangerous brinkmanship" after Mrs May rejected remaining in a customs union. It has urged the extension of Article 50 - the mechanism by which the UK is set to leave the EU on 29 March.
Meanwhile, speaking in Luxembourg, Mr Barnier said he would judge how interested the UK was in changes to the accompanying political declaration, which sketches out the shape of the future relationship.
He said the EU was waiting for a clear and stable majority to emerge in the House of Commons, not just for the passage of the withdrawal agreement, but for the subsequent legislation too.
Mr Corbyn's letter to the prime minister was "interesting in tone and substance", Mr Barnier said.
Elsewhere, members of the Alternative Arrangements Working Group - including Conservative MPs Steve Baker, Marcus Fysh, Owen Paterson, Damian Green and Nicky Morgan - met government officials in Westminster.
Mr Baker said the talks had been "constructive" and they were "looking forward to hearing how Stephen Barclay gets on with Michel Barnier".
The group has met several times to discuss alternative arrangements to the proposed Irish border "backstop".
By Norman Smith, BBC assistant political editor
It could have been a very different sort of letter.
Mrs May could have just underscored her red lines: No to extending Article 50. No to another referendum. No to a customs union.
Instead, it's a much more conciliatory and consensual letter.
There's praise for Mr Corbyn in accepting the priority now should be on reaching a Brexit deal, rather than pressing for a general election.
Praise too for his acknowledgement that the backstop has got to be changed.
And there's some movement on employment rights and the promise of more cash for hard pressed communities.
Even on the customs union - their key dividing area - Mrs May's language is more nuanced, even though privately her aides insist there can be no question of accepting a permanent customs union.
It's unlikely to be anywhere near enough to win over Mr Corbyn.
But it may be enough for those Labour MPs in leave supporting constituencies, who are looking for political cover to back or abstain on Mrs May's deal.
In his letter, Mr Corbyn asked for five changes to be made to the Brexit deal.
The Labour leader called for a "permanent and comprehensive UK-wide customs union" with the EU to be introduced to the deal, with the same external tariff.
He said it would give the UK a say on any future trade deals that the EU may strike.
In her reply, Mrs May said the political declaration - the second part of her deal which is a non-legally binding statement on the future relationship between the UK and EU - "explicitly provides for the benefits of a customs union", with no tariffs, fees, charges and restrictions.
But, she said, it also allows for the UK to strike up its own trade deals elsewhere.
She added her reassurance that securing frictionless trade with the EU was "one of our key negotiating objectives".
Speaking in Switzerland, where Mr Fox has just signed a deal to see the country trade with the UK on the same terms it does now, the minister said the idea was "not workable".
Mr Corbyn also wanted the deal to include a promise for the UK to be closely aligned with the Single Market after it leaves the EU, "underpinned by shared institutions and obligations".
Mrs May quoted the EU as saying the current deal provides for the closest relationship possible outside the Single Market.
She added: "I am not sure what exactly you mean when you say 'shared institutions and obligations', but our teams can explore that."
The PM also repeated the EU's warning that completely frictionless trade is only possible if the UK stays in the Single Market.
"This would mean accepting free movement, which Labour's 2017 General Election manifesto made clear you do not support," she added.
Labour has called for the UK to stay in step with the EU on rights and protections for workers, which was included in Mr Corbyn's letter.
On this point, Mrs May said the government had already made commitments on workers' rights, adding: "We are examining opportunities to provide further financial support to communities that feel left behind."
This could be referring to proposals that were said to have been discussed earlier this month from a group of Labour MPs in predominantly Leave-supporting constituencies, to allocate more funds to their communities for big infrastructure projects.
The PM also said that while she had "always been clear that Brexit should not be at the expense of workers' rights or environmental protections", she did not support automatically following EU rules in these areas.
The Labour leader called for a promise to participate in EU agencies and funding programmes on the environment, education and industry regulation after Brexit.
The prime minister said the government supports participation in EU programmes in a number of areas, as set out in the political declaration - which includes areas such as science and innovation, youth, culture and education, and overseas development.
Finally, Mr Corbyn demanded agreements with the EU on security, such as access to the European Arrest Warrant database.
Mrs May said the government "shares your ambition in relation to security arrangements".
She said the political declaration secured agreement on the exchange of Passenger Name Record, DNA, fingerprint and vehicle registration data and on arrangements "akin to the European Arrest Warrant to surrender suspected and convicted persons efficiently and expeditiously."
But, she added, there is a challenge that as a third country outside of the EU, there are restrictions on the UK's ability to participate in some EU tools and measures.
Labour is yet to respond to the letter.

The government has granted a two-week extension in the process to decide who will make UK passports after Brexit.
British company De La Rue - which had lost the £490m contract to French-Dutch Gemalto in March - had requested the longer "standstill period", which has now been agreed by the Home Office.
It means a final decision will now be made on Tuesday 17 April.
De La Rue is also taking initial steps "towards initiating appeal proceedings against the provisional decision".
However, it has refused to clarify what this means legally or how any appeal process might proceed.
The firm says the time extension will give it more time for close scrutiny of the criteria that the Home Office used in coming to its decision to award the contract to Gemalto.
It says it will assess that information and whether it might help it in its arguments.
De La Rue's bid was not the cheapest, but it said it was "the highest quality and technically most secure".
"We have a preferred bidder, which demonstrated it was best able to meet the needs of the passport service, delivering a high quality and secure product and providing best value for money for the taxpayer… that remains the government's position," said the prime minister's official spokesman.
But the extension "will give all bidders the chance to find out more detail and get more information from the Home Office… this is standard process."
The spokesman added: "This has been a rigorous, fair and open process."
The current EU-themed burgundy passport, in use since 1988, will revert to its original blue and gold colour from October 2019. However, people are expected to keep their current passports until they expire.
Before the bidding process extension, a spokesperson for De La Rue had said: "We can accept that we weren't the cheapest, even if our tender represented a significant discount on the current price.
"It has also been suggested that the winning bid was well below our cost price, which causes us to question how sustainable it is."
The decision to give a foreign company the contract had been criticised by pro-Brexit government figures.
Under EU procurement rules, the Home Office was required to open up the bidding process to European firms, although De La Rue has manufactured UK passports since 2009.
The Home Office had said the proposed Gemalto deal could save the taxpayer £100m-£120m and that 70 new jobs would be created in the UK, at sites in Fareham, in Hampshire, and Heywood in Lancashire.
It comes as a Daily Mail petition calling for the Home Office to give the contract to a British firm reached 273,000 signatures.
The Home Office issues more than six million passports annually and is the only provider of passports to British citizens.

The EU's negotiator says he is worried by the UK's post-Brexit proposals for the Northern Ireland border.
Michel Barnier said the UK was asking for EU laws, its customs union and single market to be suspended at a "new external border".
He said the UK wanted Northern Ireland to be a "test case" for future customs arrangements with the EU.
The UK said both sides were "closely aligned" in what they wanted to achieve.
Northern Ireland is the only part of the UK that will share a land border with an EU state after Brexit.
The impact of Brexit on Northern Ireland and the Republic of Ireland is one of the key issues being discussed in the early stages of UK-EU negotiations.
Fears have been raised that a return to border checks could undermine the Good Friday peace agreement and damage the economy.
The UK - which plans to leave the EU's customs union - has said it wants an "unprecedented solution", avoiding physical checks at the border.
Instead, the government is arguing for a wide-ranging exemption under which small and medium-sized businesses would not have to comply with any new customs tariffs.
Unveiling the EU's position, Mr Barnier said: "What I see in the UK's paper on Ireland and Northern Ireland worries me."
He added: "Creativity and flexibility can't be at the expense of the integrity of the single market and customs union.
"This would be not fair for Ireland and it would not be fair for the European Union."
Mr Barnier said the peace process should be preserved, the common travel area between Ireland and the UK protected and that there should be no return to a "hard border", all of which the UK has also said it is seeking.
"Irish citizens in Northern Ireland must continue to enjoy their rights as EU citizens," Mr Barnier continued, calling for the UK to come up with a "unique" solution.
As the UK had chosen to leave the EU, it was its responsibility to come up with solutions, he said.
The UK government, which released its own position paper on Northern Ireland last month, said there was now a "good basis on which to continue to make swift progress" on the subject.
It welcomed the EU's view there should be no "physical infrastructure" at the border, but added that "unilateral UK flexibility will not be sufficient to meet our shared objectives".
Brussels has refused to discuss the UK's future relationship with the EU - notably how they will trade with each other - until the initial discussion issues, including Northern Ireland, have been settled.
The EU's paper suggests specific provisions being written into the final departure deal to protect cross-border co-operation in areas like health, education, transport and fishing.
The Liberal Democrats said the EU's document "demolishes another of the Leave campaign's fantastical claims - that Brexit would have no impact on the Irish border".
MP Tom Brake said the only solution to the border question was for the UK to stay in the single market and customs union.
Unveiling the Northern Ireland plans at a press conference, Mr Barnier also attacked the UK over one of the sticking points in the Brexit negotiations - the size of any "divorce" bill required as it leaves the EU.
The UK has said it will honour its financial commitments but also that it has a "duty to our taxpayers" to "rigorously" examine the EU's demands.
Mr Barnier said Brussels expected Britain to deliver on commitments made in the multi-year EU budget signed up to by David Cameron and approved by the Westminster Parliament.
"I have been very disappointed by the UK position as expressed last week, because it seems to be backtracking on the original commitment of the UK to honour its international commitments, including the commitments post-Brexit," he said.
"Every euro spent has a specific legal base," he added.
"There is a moral dilemma here. You can't have 27 paying for what was decided by 28. What was decided by the 28 member states has to be borne out by 28 member states, right up to the end. It's as simple as that."
Mr Barnier was also asked about comments which have emerged by European Commission president Jean-Claude Juncker about Brexit Secretary David Davis.
In newly-published minutes of a 12 July meeting between Mr Juncker and Mr Barnier, Mr Juncker was recorded as questioning the "stability and accountability" of Mr Davis.
Mr Juncker also said Mr Davis's "apparent lack of involvement... risked jeopardising the success of the negotiations".
In the meeting, which came after the first round of negotiations, Mr Barnier was recorded as saying the UK negotiating strategy involved "using past debts as a means of buying future access to parts of the single market, something which the Union could not accept".
Mr Barnier brushed off the comments at a Brussels press conference, insisting he had "cordial" relations with the Brexit secretary and praising his "professionalism".
And the Department for Exiting the European Union responded: "These are clearly out-of-date comments and it is abundantly clear that the secretary of state has been fully engaged and involved throughout the discussions, in the same way as Mr Barnier."
In another position paper from the EU, it called for the UK to continue to honour the protected legal status given to delicacies like Parma ham or Champagne after Brexit.
The European Commission first acted in 1992 to establish a list of products which could only be described by their place of origin if they really were produced in that place.
It also includes UK products like Cornish clotted cream, Dorset Blue cheese, and Jersey Royal potatoes.
Under the EU's intellectual property proposals, the UK would implement the "necessary domestic legislation providing for their continued protection".
The impact of Brexit on food was also considered in the House of Commons, where Labour's Jenny Chapman warned against imposing tariffs on European food imports, and asked whether the government was planning a "return to consuming Spam and tinned peaches".
Brexit Minister Steve Baker assured her this was not the case and described her comments as a "fantastical proposal".

Facebook has suspended a Canadian data firm that played a key role in the campaign for the UK to leave the EU.
The social media giant said AggregateIQ (AIQ) may have improperly received users' data.
It cites reported links with the parent company of Cambridge Analytica (CA), the consultancy accused of improperly accessing the data of millions.
AIQ denies ever being part of CA, its parent company SCL or accessing improperly obtained Facebook data.
The Vote Leave campaign paid AIQ £2.7m ($3.8m) ahead of the 2016 EU referendum.
An ex-volunteer with the campaign has also claimed Vote Leave donated £625,000 to another group to get around campaign spending limits, with most of the money going to AIQ. Vote Leave has denied any wrongdoing.
AIQ's website once quoted Vote Leave chief Dominic Cummings saying: "Without a doubt, the Vote Leave campaign owes a great deal of its success to the work of AggregateIQ. We couldn't have done it without them." The quote has since been removed.
In total, AIQ was given £3.5m by groups campaigning for Brexit, including Vote Leave, the Democratic Unionist Party and Veterans for Britain. The UK's Electoral Commission reopened an investigation into Vote Leave's campaign spending in November.
"In light of recent reports that AggregateIQ may be affiliated with SCL and may, as a result, have improperly received FB user data, we have added them to the list of entities we have suspended from our platform while we investigate," a Facebook spokesperson said.
"Our internal review continues, and we will co-operate fully with any investigations by regulatory authorities."
In a message posted to its website, AIQ says it is "100% Canadian owned and operated" and "has never been and is not a part of Cambridge Analytica or SCL".
It adds: "Aggregate IQ has never managed, nor did we ever have access to, any Facebook data or database allegedly obtained improperly by Cambridge Analytica."
It also denied ever employing Chris Wylie, the Canadian whistleblower who alleged that the data of 50m people was improperly shared with Cambridge Analytica. Facebook has since said the number of people affected could be closer to 87m. CA says it obtained the data of no more than 30m people and has deleted all of it.
Analysis by technology correspondent Rory Cellan-Jones
It was three weeks ago that Facebook suspended Cambridge Analytica just hours before a whistleblower's revelations to the Observer newspaper triggered the current scandal over improper use of data.
Christopher Wylie insisted that Aggregate IQ was closely linked to Cambridge Analytica, and supplied documents to the Department for Digital, Culture, Media and Sport select committee which he said proved it.
Now Facebook's decision to suspend the Canadian firm from its platform appears to give further validation to Mr Wylie's claims. It also throws the spotlight back onto the potential use of Facebook data during the Brexit campaign.
Facebook says it is looking into whether the data that Cambridge Analytica acquired improperly from as many as 87 million people - 1 million of them in the UK - ended up with Aggregate IQ. The firm worked for both Vote Leave and BeLeave during the EU referendum campaign, but has always insisted it has never been a part of Cambridge Analytica, and has not had access to any of its Facebook data.
AIQ is a small company operating out of Victoria, British Columbia. It uses data to help micro-target voters and was founded by two Canadian political staffers.
Apart from its Brexit work the company has also been accused by Mr Wylie of distributing "incredibly anti-Islamic" content on social media ahead of the 2015 Nigerian presidential election to discredit Muslim opposition candidate Muhammadu Buhari, who went on to win the contest.
The BBC has approached AIQ for a response to the Nigeria allegations.
Mr Wylie has said that AIQ was referred to among Cambridge Analytica staff as "our Canadian office". He told the Guardian he helped to set up the firm as a "Canadian entity for people who wanted to work on SCL projects who didn't want to move to London" and that he had known the firm's co-founder, Jeff Silvester, since he was 16.
AIQ says it "has never entered into a contract with Cambridge Analytica" and that "Chris Wylie has never been employed by AggregateIQ".
Cambridge Analytica is at the centre of a row over whether it used the personal data of millions of Facebook users to sway the outcome of the US 2016 presidential election and the UK Brexit referendum.

The Irish government has said Brexit trade deal talks should not proceed until there is a firm commitment to preventing a "hard" Irish border.
Taoiseach (Irish Prime Minister) Leo Varadkar said the assurance must be written down before the talks move on.
"Before we move to phase two talks on trade, we want taken off the table any suggestion that there will be a physical border," Mr Varadkar said.
He was speaking at a European summit, attended by Prime Minister Theresa May.
Mrs May's spokesperson said both leaders had agreed to work together to find solutions ensuring there is "no return to the borders of the past".
But Sammy Wilson from the Democratic Unionist Party (DUP) accused the Irish government of trying to "keep the UK chained to the EU".
Earlier, Mr Varadkar's message was echoed by Irish Foreign Minister Simon Coveney, who held talks with his UK counterpart, Boris Johnson, in Dublin.
Mr Coveney said there was "a sense of jumping into the dark" for Ireland, as the future operation of its border with Northern Ireland had not been agreed.
"Yes, we all want to move onto phase two of the Brexit negotiations, but we are not in a place right now that allows us to do that," the foreign minister said.
The UK is due to leave the EU in March 2019, but Mr Coveney suggested the exit process could take up to five years.
In response, DUP MP Sammy Wilson claimed the Irish government was "fully signed up with the European establishment to thwart the referendum result in the UK to leave the EU."
In a statement, the MP accused Irish ministers of "trying to block the UK moving on to substantive negotiations about leaving the EU, and then suggesting that an interim or transitional period of five years is going to be needed before we can leave".
"The objective is quite clear; keep the UK chained to the EU until after the next election, when the Irish government hope that Corbyn's Brexit-breaking MPs might be in power," Mr Wilson added.
He said it seemed like the Irish government were content to involve themselves in the affairs of another state.
The MP for East Antrim said that the DUP will support the passing of legislation which would mean "deal or no deal, the UK will exit the EU in March 2019".
Despite cordial exchanges between the two foreign ministers, one thing was clear: Ireland and the UK are still at odds about whether enough progress has been made in the EU-UK divorce talks to allow the two sides to move onto discussions about future relationships.
Despite British assertions that there will be no hard border on the island of Ireland, Dublin doesn't see how that position can be married with the UK leaving the customs union and the single market.
Nor does Dublin think a two-year transitional deal for business to adjust to Brexit is long enough.
With Taoiseach Leo Varadkar delivering the same message to Theresa May in Sweden, there is a sense that "make-your-mind-up time" for all sides is fast approaching.
During his talks in Dublin, Mr Johnson said it was necessary to move on to the second stage of negotiations, where issues raised by Mr Coveney would be thrashed out.
"Now is the time to make haste on that front," the UK foreign secretary said.
Mr Coveney said he understood the British "aspiration" to avoid a hard border, but more clarity was needed about the future.
"We are in the heat of the negotiations right now and, of course, we want to move on to the negotiations on trade, but there are issues that need more clarity," he said.
"This is a very fundamental change in the relationship between Ireland and Britain and Britain and the EU and it will require significant adjustment.
"The appropriate timetable is closer to four or five years than it is to two."
Mr Coveney added: "We simply don't see how we can avoid border infrastructure.
"Once standards change it creates differences between the two jurisdictions and a different rule book.
"When you have a different rule book you are starting to go down the route of having to have checks."
Asked whether the government was constrained by its confidence and supply arrangement with the Democratic Unionist Party, Mr Johnson said that was "not at all an issue".
The DUP agreed to support Theresa May's minority government after June's election in return for £1bn of extra funding for Northern Ireland.
European leaders say talks can only progress if enough progress has been made on the Irish border, citizens' rights and Britain's EU budget contributions.
Meanwhile, Ken Clarke has said the UK remaining in the single market and customs union is vital for peace and stability in Northern Ireland.
It is the obvious solution as no-one wants physical border controls, the former chancellor and now Conservative "rebel" told BBC NI's The View.
"The border problem in Northern Ireland, the supreme importance of keeping the settlement in place, retaining peace in Northern Ireland is probably the single biggest, most important reason why it would be preferable for the United Kingdom as a whole to stay in the single market and the customs union," he said.
"If the Brexiteers, these right-wing nationalists, won't allow us to do that then the best solution after that, I agree with the taoiseach actually, is to have a border down the Irish Sea."

A former Conservative minister has compared Theresa May's Brexit plan to a "ghastly cockroach" and vowed to vote against it in Parliament.
Owen Paterson said the package agreed at Chequers in July would hamper the UK's ability to negotiate free trade deals with other countries.
Senior ministers have been defending the plan, which Eurosceptics say will keep the UK shackled to EU rules.
The chancellor said it "delivers on the decision of the British people".
Speaking at the Conservative Party conference in Birmingham, Philip Hammond dismissed EU warnings the model would not work, saying: "That's what people said about the light bulb in 1878."
But Mr Paterson, the former Northern Ireland secretary, dismissed it when he appeared alongside other Eurosceptic Tories at a conference fringe event.
The UK should be "actively negotiating" free trade deals with the likes of the United States, he said, but "while Chequers is floating around, like some ghastly cockroach, crawling forwards... they're not going to start talking to us.
"It's absolutely pointless."
He added: "My whip is here taking notes and so I'll say it to him directly - I'm voting down Chequers."
Also on day two of the Tories' conference, three serving EU ambassadors to London publicly criticised Foreign Secretary Jeremy Hunt for comparing the European Union to the Soviet Union.
Mr Hunt had accused Brussels of seeking to "punish" Britain for wanting to leave the EU and compared it to the USSR trying to stop its citizens leaving.
Ambassadors from Estonia, Latvia and Sweden all tweeted their disapproval, with the tweet from the Latvian ambassador being retweeted by the EU Commission's deputy chief negotiator, Sabine Weyand.
Earlier Brexit Secretary Dominic Raab told the EU to "get serious" if it wants a Brexit deal, warning the UK may have "no choice" but to leave without one.
And Mr Hammond hit back at former foreign secretary Boris Johnson, who has led criticism of the Chequers proposals, saying he was a "big picture man" whereas what was needed was "a very detailed and complex negotiation".

Brexit. It's all about Britain, right?
Well, not entirely.
There is the rest of the club to consider - what has become known, rather inelegantly, as the EU-of-27.
They are about to lose - depending on your point of view - a curmudgeonly whinger who was dragging the whole project down or one of their largest economies and the most powerful defence and security power in Europe.
So what to do?
There are those who think, genuinely, good riddance.
"General de Gaulle was right all along," they mutter. "We should never have let them join in the first place.
"Freed from the shackles of British ministers objecting to integration here and integration there, we can get on with it."
Closer co-operation on EU defence policy is high on their list; and it has been given an extra boost by the new president of the United States musing out loud about Nato and whether it is all worth it.
Others are dismayed by the British decision to leave, but after getting over the initial shock - and it really was a shock - they too are determined to make the best of it.
And when it comes to negotiating the UK divorce bill, make no mistake. For the people who matter, the unity of the remaining 27 is more important than trying not to upset the Brits as they wave goodbye.
The bill will be big - up to 60 billion euros - and European diplomats are bracing themselves for what one called "the very real possibility" that the UK will walk out in a huff.
But the likelihood is that after one too many late-night summits - and one too many outraged tabloid headlines - a deal of sorts will emerge from the rubble.
The consequences of Brexit will rumble on for years; there are trade deals that will have to be done. But the EU is in no position to wait for the dust to settle.
In many ways, it has already moved on. So long Britain, and thanks for the memories.
Later this month, leaders of the 27 (the 28th has already sent her apologies) will meet in Rome to celebrate the 60th anniversary of the EU's founding treaty.
I say celebrate, but there is no illusion about the challenges facing the union.
Could the forces that prompted Brexit spread to other countries? Will anti-EU populists continue to rise in France, the Netherlands and parts of Central Europe?
It is certainly not impossible, and EU leaders know it. The idea that the EU could fall apart - unthinkable a few years ago - is now the subject of serious discussion.
Which is why they need a new plan to reinvigorate the project on its 60th birthday, and make it fit for future purpose.
The European Commission has now produced a series of policy options for the best way forward, ranging from shrugging its shoulders to throwing up its hands in horror.
But the most likely solution is to make more use of what is known as multi-speed Europe.
That's the idea that "coalitions of the willing" can move forward on big projects even if others want to linger on the starting line.
It is already happening with the euro, and with the passport-free Schengen area - not all EU countries are members of everything. An inner core may want to push ahead, if (and it's a big if) it can take public opinion along for the ride.
The other Commission proposal that looks to have legs is the idea that Brussels would return some powers to member states, as long as the EU was given greater responsibilities in major policy areas such as trade, migration, security and defence.
Variations on this theme have been around for some time. The EU needs to be big on the big things, they said, and smaller on smaller things.
And the biggest of the big things - in a competitive field - is probably the need to fix the eurozone.
The single currency remains half-formed, and - as a result - not yet secure. There is talk of a eurozone finance minister and a single eurozone budget.
But if you centralise economic power, you have to make sure it is politically accountable.
In an era of populist, anti-establishment rage, that is a difficult balancing act. Much will depend on who wins national elections this year in Germany and, in particular, France.
Political leadership will be at a premium.
But as the UK prepares to leave and enter a whole new world, the status quo is no longer an option for the countries that remain.
The EU either needs to move forward towards closer integration, or transfer significant power back to nation states.
It continues to be a bold experiment in Europe. But the halfway house has been built on sand.

Michel Barnier has dismissed Boris Johnson’s Brexit proposals to replace the Irish border backstop as a “trap”.
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The EU negotiator warned a group of senior MEPs that the EU could be locked into a string of commitments if the measure vetoed by the Northern Ireland Assembly. According to a source in the meeting, he said: “The EU would then be trapped with no backstop to preserve the single market after Brexit.” European officials are concerned that the Prime Minister’s demand for a “firm commitment by both parties to never conduct checks at the border in future” would leave the EU powerless to protect its single market if the DUP rejects the backstop.
Guy Verhofstadt, the EU Parliament’s Brexit co-ordinator, said he was “absolutely not positive about Johnson’s proposals”.He added: “It doesn’t provide the necessary safeguards for Ireland.”Jean-Claude Juncker, the European Commission’s President, said the UK plan to offer the DUP a veto is “problematic” but promised to work through the issue.Senior EU diplomats have said giving such an influential role to Stormont is “unacceptable”.
Mr Barnier has pleaded for “more time” to look at the proposals before they are rejected out of hand by other EU figures.During private meetings, his Article 50 task force told diplomats that the backstop proposals don’t meet the three necessary criteria.Officials warned claimed proposals don’t protect the EU’s single market, the Good Friday Agreement and questioned whether Mr Johnson can secure a Common’s majority.MUST READ: Queen’s Speech date: When is Queen’s Speech to open Parliament?
EU negotiators also rejected the Government’s request to hold the next round of negotiations in a so-called “tunnel” - a period of secret and intense talks.Capitals have already expressed their frustrations at not being allowed access to the 44-page alternative to the backstop.David Frost, the Prime Minister’s top adviser, will resume talks on Friday in Brussels.DON'T MISSBoris Johnson’s most critical error could still cost Britain Brexit [EXCLUSIVE]Varadkar deals major blow to Boris's Brexit plan [INSIGHT]Five reasons Brexiteers can celebrate Boris's Brexit plan – REVEALED [ANALYSIS]
Domestically, Mr Johnson’s proposals have gone down far better.The DUP has signalled it could accept the new system - even though Northern Ireland would align to the EU’s single market rules for agri-food and industrial goods.Steve Baker, chair of the eurosceptic European Research Group, said he would support the new deal if the DUP followed suit.
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“On the union it's clear to me we don't have a right to trump the DUP,” he said.Meanwhile, Mr Johnson announced a short prorogation to hold a Queen’s speech.Parliament will be suspended from next Tuesday until October 14 to allow a new legislative programme to be set.
Brexit has "turned out less badly than we first thought", David Cameron has said.
The former prime minister was recorded at the World Economic Forum in Davos saying the Leave vote was "a mistake not a disaster".
Mr Cameron called the 2016 referendum on the UK's membership of the EU, campaigned to stay in and resigned after the Leave side won.
His apparently unguarded comments were highlighted by Channel 5 News.
"As I keep saying, it's a mistake not a disaster," he was heard saying in a conversation with steel tycoon Lakshmi Mittal.
"It's turned out less badly than we first thought. But it's still going to be difficult."
The Remain campaign during the referendum warned of an immediate economic impact on the UK of a vote to leave the European Union.
In a speech to Vauxhall car workers, in Ellesmere Port, four months before the referendum, he warned voters about the economic shock that he said would be caused by a vote for Brexit.
"Let's just remember what a shock really means. It means pressure on the pound sterling. It means jobs being lost. It means mortgage rates might rise. It means businesses closing. It means hardworking people losing their livelihoods."
He stepped up his warnings as the referendum date approached, warning on 6 June that Brexit would be like putting a "bomb" under the UK economy and telling MPs a week later that "nobody wants to have an emergency Budget, nobody wants to have cuts in public services, nobody wants to have tax increases", but the economic "crisis" that would follow a vote to leave could not be ignored.
"We can avoid all of this by voting Remain next week," he added.
He described a vote to leave the EU as a "self-destruct option" for the UK, after a Treasury analysis warned it would tip the UK into a year-long recession, with up to 820,000 jobs lost within two years.
At other times he sounded more optimistic about the prospect of leaving, saying, in May 2016, "Britain is an amazing country. We can find our way whatever the British people choose."
A leading Brexit supporter, former Conservative and UKIP MP Douglas Carswell, welcomed Mr Cameron's comments.
The BBC's chief political correspondent, Vicki Young, said Tory Brexit cheerleaders she had spoken to were "thrilled", telling her the former PM had come round to their "way of thinking".
But she said one leading Remain campaigner in the party said it was "far too early" to tell what the long-term consequences of leaving the EU would be.
Former Labour MP Gisela Stuart, who now heads pro-Brexit campaign group Change Britain, said the former PM's "scaremongering" about the economic damage of Brexit had proved to be "baseless".
"I hope that pro-EU MPs who continue to do Britain's economy down join Mr Cameron in admitting they're wrong, and focus their energies on getting the best Brexit deal for the UK," she said.
Although the pound fell sharply after the vote, the UK economy has continued to grow, and unemployment has fallen to a 42-year low. Mortgage rates have stayed at generally the same low levels they have been since the financial crisis in 2008.
The UK and the EU are currently negotiating the terms for the UK's exit and future relations, and the date for Brexit has been set for 29 March 2019.

The UK will continue to take part in the Erasmus student exchange programme until at least the end of 2020, the prime minister has said.
Theresa May praised Erasmus+ and confirmed the UK would still be involved after Brexit in March 2019.
Whether it is involved long term is among issues likely to be discussed during the next stage of negotiations.
Erasmus+ sees students study in another European country for between three and 12 months as part of their degree.
The prime minister is in Brussels where she will have dinner with EU leaders on Thursday.
On Friday, without Mrs May, they are expected to formally approve a recommendation that "sufficient progress" has been made in Brexit negotiations so far to move them onto the next stage.
Mrs May agreed a draft deal with European Commission President Jean-Claude Juncker last week which would mean the UK would continue its funding of EU projects, including Erasmus, until the end of this EU budget period in 2020.
If EU leaders approve the draft deal, Brexit negotiations can begin on the next phase, covering the future relationship between the UK and EU and a two-year transition or implementation deal from March 2019. It is not clear whether this would include Erasmus+.
Mrs May said that British students benefitted from studying in the EU while UK universities were a popular choice for European students.
Speaking during a discussion on education and culture at the summit in Brussels, she added: "I welcome the opportunity to provide clarity to young people and the education sector and reaffirm our commitment to the deep and special relationship we want to build with the EU."

The UK has "danced to the EU's tune" during the Brexit negotiations, former UKIP leader Nigel Farage has claimed.
In a debate in Strasbourg, he called the British Prime Minister, Theresa May, "Theresa the appeaser", saying she had "given in on virtually everything".
The European Parliament later voted to endorse an agreement struck by the UK and European Commission which is set to move the talks on to their next phase.
But MEPs also insisted the UK must honour the commitments it has made.
Amid concerns about whether Friday's agreement on citizens' rights, the Northern Ireland border and the so-called "divorce bill" is legally binding, Guy Verhofstadt, the European Parliament's Brexit spokesman, said he had been reassured the UK would not "back-track" on its commitments.
The agreement should be converted into a legal text in weeks, not months, he added.
In a symbolic but politically significant vote, the European Parliament backed the European Commission's view that sufficient progress had been made on so-called divorce issues to move to talks covering a transition phase and the EU's future relations with the UK.
The EU's negotiator  Michel Barnier said there was "no going back" on Friday's agreement - which is expected to be rubber-stamped by all other 27 EU members later this week.
"It has been noted and recorded and is going to have to be translated into a legally binding withdrawal agreement," he said.
During the debate, several MEPs criticised the UK's Brexit Secretary, David Davis, for suggesting in an interview on Sunday that the first-phase agreement was more of a "statement of intent" than a "legally enforceable thing" - comments he has since backed away from.
German Christian Democrat MEP Manfred Weber, who leads the centre-right EPP group, said the remarks were "not helpful" for building trust between the two sides.
Meanwhile, Mr Farage - who has campaigned for 20 years to take the UK out of the EU - also attacked the British government, saying Mr Barnier "didn't need" to make many concessions to Theresa May.
"I'm not surprised you're all very pleased with Theresa the appeaser - who has given in on virtually everything," he said.
"She has danced to your tune all the way through this. You must be very, very happy indeed."
Warning of a further betrayal of Brexit voters, he said the prospect of a two-year transition after the UK left in March 2019 would be the "biggest deception yet", meaning the UK would have left the EU "in name only".
"I think Brexit at some point in the future may need to be refought all over again," he added.
But defending the British prime minister, Conservative MEP Syed Kamall said both sides had needed to make compromises and concessions in order to "avoid a no-deal situation".
Important progress had been made, he added, when both sides "understood the need for flexibility and focused on building a better future rather than looking back at the past".

Theresa May has said the UK is "on course to deliver on Brexit" as she arrived in Brussels, the day after her first Commons defeat as prime minister.
She said she was "disappointed" at the vote on the EU Withdrawal Bill, but the legislation was making "good progress".
MPs backed an amendment giving them a legal guarantee of a vote on the final Brexit deal struck with Brussels.
EU leaders are expected to formally agree to start the next phase of negotiations on Friday.
The European Commission has said "sufficient progress" has been made on the first phase to move onto discussing the framework of a future relationship between the EU and UK - on issues such as security and trade.
Mrs May told fellow EU leaders at dinner on Thursday that she wanted to get agreement on the "implementation period" as a priority but wanted to talk about trade "as soon as possible".
She said was personally committed to delivering a "smooth Brexit" and she wanted to approach the next phase of talks "with ambition and creativity".
Speaking to reporters earlier, she said: "I'm disappointed with the amendment but actually the EU Withdrawal Bill is making good progress through the House of Commons and we are on course to deliver Brexit."
Asked whether she felt she would have to compromise more to win over rebels from her own party, she told BBC political editor Laura Kuenssberg: "We've actually had 36 votes on the EU Withdrawal Bill, and we've won 35 of those votes with an average majority of 22."
Mrs May lost by just four votes, as MPs backed an amendment to the EU Withdrawal Bill by 309 to 305.
Labour leader Jeremy Corbyn described it as a "humiliating loss of authority" for the PM and warned that his party would vote against another bit of the bill - the plan to put a fixed Brexit date into law.
He said setting an "arbitrary date" was not sensible and there "should be some flexibility".
It will not derail Brexit but MPs who voted against the government hope it will give them a bigger say in the final deal Theresa May strikes with Brussels.
BBC Brussels reporter Adam Fleming said that as other EU leaders also run minority or coalition governments they would see the vote defeat as a small-scale domestic political issue.
The government had promised a "meaningful vote" for MPs on the final Brexit deal, but this defeat means that promise now has legal force and must happen before any UK-EU deal is implemented in the UK.
Ministers had wanted to be able to start implementing any deal as soon as it was agreed - in case, for instance, it was only agreed at the last minute.
BBC political editor Laura Kuenssberg said it would embolden the opposition and showed there was a majority in Parliament against a "hard Brexit".
Cabinet Minister Jeremy Hunt told the BBC the vote was "not going to stop Brexit".
Labour joined forces with the SNP, the Liberal Democrats and the Green Party in a cross-party alliance.
If all Conservative and DUP MPs had voted against the amendment the government would have won. But 11 Conservatives resisted the arm-twisting by their party managers to vote with the opposition.
The Tory rebels were Dominic Grieve, Heidi Allen, Ken Clarke, Jonathan Djanogly, Stephen Hammond, Sir Oliver Heald, Nicky Morgan, Bob Neill, Antoinette Sandbach, Anna Soubry and Sarah Wollaston. Another Conservative MP, John Stevenson, officially abstained by voting for and against the amendment.
Two Eurosceptic Labour MPs - Frank Field and Kate Hoey - voted with the Conservatives and the DUP.
Emotions ran high before, during and after Wednesday's Commons debate, with Eurosceptic Conservatives accusing the rebels of trying to "frustrate" Brexit.
In dramatic scenes, the rebels shouted "too late" as Justice Minister Dominic Raab announced a concession shortly before voting began and Tory whips could be seen attempting to twist the arm of MPs thinking of voting against the government.
Leading rebel Anna Soubry said she had found a woman MP "upset and shaken" on Tuesday evening after a whip tried to persuade her not to revolt. She told MPs on Thursday morning, that none of the rebels took any pleasure in defeating the government, adding that "nobody drank champagne".
After the result was announced, one of the rebels, former cabinet minister Nicky Morgan, tweeted: "Tonight Parliament took control of the EU Withdrawal process."
This did not go down well with Tory MP Nadine Dorries, who called for the deselection of rebel Tories for "undermining the PM", and accused their leader, Dominic Grieve of "treachery".
Rebel Tory Sarah Wollaston hit back on Twitter, saying: "Get over yourself Nadine."
Dominic Grieve tried to calm the mood, insisting he was merely trying to ensure Brexit was carried out in an "orderly, sensible way".
BBC political editor Laura Kuenssberg
It's certainly true that the Tory party is so divided over how we leave the EU that the Parliamentary process was always going to be very, very choppy.
But another minister told me the defeat is "bad for Brexit" and was openly frustrated and worried about their colleagues' behaviour.
Read the rest of Laura's blog
Theresa May has travelled to Brussels to attend a dinner with the 27 other EU leaders, at which she will urge them to approve an agreement to move Brexit talks on to a second phase.
They are all but certain to agree.  Talks could then start next month on the two-year transition period the UK wants to ease it out of the EU after it formally leaves in March 2019.
But the EU wants more detail from the UK government before starting talks on a future relations - including trade - with the UK.
Brexit Secretary David Davis has said he wants to complete the "substantive portion" of trade negotiations by March 2019, leaving open the possibility that the detail will be hammered out during the two-year transition period.
The EU Withdrawal Bill is a key part of the government's exit strategy.
Its effects include ending the supremacy of EU law and copying existing EU law into UK law, so the same rules and regulations apply on Brexit day.
MPs have been making hundreds of attempts to change its wording - but Wednesday's vote was the first time one has succeeded.
Unless the government manages to overturn it further down the line, it means a new Act of Parliament will have to be passed before ministers can implement the withdrawal deal struck with Brussels.
Labour's Shadow Brexit Secretary Sir Keir Starmer urged David Davis not to undermine Wednesday night's vote when the EU Withdrawal Bill reaches the next stage of its passage into law.
Mr Davis said the vote would lead to a "very compressed timetable" for Brexit legislation and the government "will have to think about how we respond to it".
There is also a row brewing over a vote next week on putting the precise date and time of Britain's exit from the EU - 11pm on 29 March 2019 - into law.
Sir Keir described the vote as the next "accident waiting to happen", telling Mr Davis: "Rather than repeat last night's debacle, will the government now commit to dropping that ill-conceived gimmick?"
Mr Davis told Sir Keir: "Unlike him, I do not view votes of this House of Commons as accidents. They are decisions taken by the House, and that decision we respect, as we will the next one."
Lib Dem Brexit spokesman Tom Brake also warned the prime minister she was heading for defeat if she did not drop the "silly idea" of enshrining the Brexit date and time in law, adding: "Parliament has now shown it is not prepared to be bullied."


Labour today said it will seek to amend the upcoming vote on triggering Article 50 by demanding MPs be given votes throughout the EU talks. 
It not only threatens to delay Theresa May's timetable for starting Brexit talks but also risks frustrating the entire two-year negotiation with the EU.  
And Jeremy Corbyn also admitted today that Labour MPs will only be 'asked' to vote in favour of triggering Article 50, rather than imposing a three-line whip on his party.
But shadow home secretary Diane Abbott caused further confusion by saying 'we don't know what amendment we're going to move,' before adding: 'But we are clear that we will not vote to bloc it [Article 50].'  

Dozens of pro-Remain MPs pledged to go further than the Labour leadership and vote against starting Brexit talks altogether, despite last June's vote to leave the EU. 
Shadow Chancellor John McDonnell said Labour will demand the Government allow 'full parliamentary scrutiny throughout the process'. 
He wants 'regular statements' from ministers and frequent votes on the Government's progress. He said that would ensure Britain gets the 'compromise that will work' for both Britain and Europe. 
Mr Corbyn said Labour would use the parliamentary vote on authorising Article 50 to be triggered to 'make demands' on access to Europe's single market and protecting workers' rights.
He insisted Labour would not vote against Article 50, the formal mechanism for leaving the EU, but again refused to say if he will order a three-line whip on his MPs. 
Fresh questions were raised today over whether Jeremy Corbyn voted for Brexit. 
John Longworth - the former director of the British Chambers of Commerce who was forced to quit after saying Britain could have a 'brighter future' outside the EU - said the Labour leader was the 'first person' to congratulate him on his speech in March last year. 
Mr Corbyn was attacked for his lack of enthusiasm for the EU during the referendum despite being part of the Remain campaign. He insisted he voted Remain but even some of his own MPs doubt he did. 
Today Mr Longworth said Labour were 'all over the place' on Brexit. 
And he revealed: 'When I made my fateful speech to the British Chambers of Commerce – which led me to resign and fight the campaign to leave – the first person to come up to me in the green room after I'd made the speech and congratulate me, shake my hand and say what a fantastic speech, was Jeremy Corbyn.
'So that tells you exactly where Labour are on this on this issue.'  
Remarkably Ms Abbott said she was unable to say whether Labour would whip the Article 50 vote. 
She told the BBC: 'We are going to amend it. We can only tell you exactly how we’ll amend it when we understand what sort of legislation the government is bringing forward. 
'And in the course of moving those amendments we will ask the questions that the people of Britain, actually, whether they voted Leave or Remain, want answered.
Asked whether there would be a three-line whip on the vote, she answered: 'I can’t tell you what the whipping will be because we haven’t seen the government’s legislation.'
Tory MP Maria Caulfield said today's comments from the Labour leadership was further proof that the Opposition are 'hopelessly divided and confused over how to respond to the referendum result'.
She said: 'They can't agree over whether we should leave the single market, can't say whether they will have an agreed position in Parliament – and have said this morning they will also find new ways of frustrating the process of leaving.
'Labour are flailing about, irrelevant, incompetent and completely out of touch with ordinary working people.'
MPs will be given the final say on triggering Article 50 if the Government loses its appeal in the Supreme Court.
Judges will announce their decision on Tuesday and if the Government loses, as is expected, ministers will present legislation to the Commons to give the Prime Minister the authority to trigger the clause.
A cross-party group of MPs have told the Observer they will amend any Article 50 Bill to make what they call Mrs May's 'extreme Brexit' with no deal impossible.
Former deputy prime minister Nick Clegg told the newspaper he had been talking to MPs from other parties about how to gather support for amendments 'because the situation is so serious we are condemned to work together on amendments that we can all support.'
Prominent Labour parliamentarians such as Lord Hain and Mike Gapes are among those promising to vote against triggering Article 50 and there have been suggestions that dozens of MPs in pro-Remain seats could rebel against the leader over the matter. 
Anti-Brexit campaigner Gina Miller today attacked American tech firms for refusing to hand data to police that could help catch her abusers. 
She said she and her family had received a barrage of death threats since she won her High Court case that ruled the Government could not start Brexit talks without a vote in Parliament.
Ms Miller, the public face of the court case, appeared to single out Facebook for failing to do enough to help police catch internet trolls. 
One opponent posted 'all of my contact details on Facebook so they [the threats] were coming straight to me' she told the BBC today. 
Police have made arrests and have issued six cease and desist letters. 
But Ms Miller said: ‘The problem is that some of it the American technology communication organisations are not great at providing the data they need to track this, which is a big issue in itself so there are 12 or odd cases still being pursued.'
The Government appealed the High Court decision in November that the Prime Minister must win the approval of MPs before triggering Article 50 - the formal mechanism for leaving the EU. 
Supreme Court judges will deliver its verdict on Tuesday.
But the Government expects to lose and ministers have already drafted legislation to rush through Parliament so Theresa May can stick to her timetable of triggering Article 50 by the end of March. 




Meanwhile dozens of Labour MPs have written to the Prime Minister condemning her threat to leave the EU with no trade deal.
Mrs May insisted in her speech last week that she will walk away from negotiations with Brussels if she is only offered a bad deal, threatening to adopt a Singapore-style low-tax, low-regulation economic model to maintain competitiveness.
The group of Labour MPs have attacked Mrs May's idea, saying it would make Britain 'the sweatshop of Europe' with public services, workers' rights and environmental protections all at risk.
The letter was organised by senior Labour MP Chuka Umunna, who chairs Vote Leave Watch and said he would not rebel against Jeremy Corbyn over triggering Brexit. 
Mr Umunna said: 'Personally, as a democrat and having agreed to the rules under which the referendum was fought, I would find it hard to vote against triggering Article 50.
'But the content of the Brexit deal is a different matter - I am not prepared to give the Tories a blank cheque to make life harder for middle and lower income households in my constituency, a sentiment which is shared across the House of Commons.'
The signatories include former deputy Labour leader Harriet Harman, two members of the current Labour frontbench, 10 former members of the shadow cabinet, and 15 MPs whose constituencies voted to leave the EU. 
Meanwhile, shadow Brexit secretary Sir Keir Starmer said he would fight any attempts to water down human rights or environmental protections once the UK leaves the EU.
The so-called 'Great Repeal Bill', which transposes all EU law into UK law, giving Parliament the power to decide which bits to keep, could include a 'Henry VIII clause' allowing ministers to ditch or change sections through secondary legislation with minimal scrutiny by MPs.

That is because it the Bill is expected to pass before the Prime Minster concludes a final Brexit deal with the Government.
Sir Keir said Labour would fight against any attempts to push through changes without full parliamentary approval.
He told the Independent: 'It would be wrong for these rights to go into our law and then be capable of being amended or removed by statutory instrument.
'I think that's a really important principle that we must fire to the beginning of any discussion on the Great Repeal Bill.' 
 
As a proud member of Her Majesty’s Press, I am reluctant to admit this: but yesterday’s most significant story about the forthcoming Brexit negotiations came not in the British Sunday newspapers, but in Welt am Sonntag.
While our own newspapers made a lot of intimations that Theresa May’s much-anticipated speech on the matter tomorrow will make it clear she is prepared for the UK to leave both the European Single Market and the Brussels-negotiated Customs Union, that German paper had a remarkable on-the-record interview with the Chancellor Philip Hammond.
Hammond had been seen in Germany —and across the Continent — as their biggest ally in the Cabinet against what those bitterly opposed to the UK’s departure from the EU invariably call ‘Hard Brexit’.
Even after the referendum result, Mr Hammond continued to issue gloomy statements about what would ensue (he had been a Remainer) — so much so that one Cabinet minister snapped: ‘It’s as though George Osborne had never left.’
But in his interview for Welt am Sonntag, Mr Hammond dashed the hopes of those who saw the Treasury as a drag anchor against what might be called the Full Brexit. He insisted the leaders of the EU ‘need to respect the British people’s sense that our history and destiny is an engagement with the rest of the world . . . historically we have never been a nation that was focused on continental Europe’.
Threat
And he issued a direct threat of what Britain would do if the EU attempted to restrict in any way our ‘access to the European market’. He declared that rather than ‘lie down and say, too bad, we’ve been wounded — if we are forced to be something different, then we will have to become something different’.
He went on to warn that Germany will pay a high price if that happened: ‘I think Mercedes-Benz and BMW and Volkswagen would also like to sell their cars in the UK market without tariffs. Germany’s biggest bank has a large operation in London and I assume it would like to continue that operation.’
I’m told the Welt am Sonntag journalists were so surprised by the tone of these remarks that they called the Treasury afterwards to check that the Chancellor really wanted to say all this on the record. The response was: Yes, he does.
It has gone off like a bomb in Berlin. The head of the Bundestag’s foreign affairs committee, Norbert Roettgen, accused our Chancellor of ‘making threats damaging the UK itself’. But then he added: ‘We should focus on common interests and compromises.’ Which actually makes a pleasant change from what we have been hearing so far from such sources, consisting entirely of warnings that Britain can expect only pain.
The interesting question is, why has Mr Hammond suddenly changed his tone from warning the British, to warning the Germans? In part, I am sure, it is because the Treasury’s predictions of what would happen to the British economy — simply as a result of voting for Brexit — have been proved scaremongering nonsense.
But it is also, in part, a negotiating tactic. The main reason David Cameron got such a pathetic deal in his so-called ‘renegotiation of our EU membership’ was that he was never prepared to walk away from the table. And Brussels knew it.
It’s not enough for Theresa May to say that if she doesn’t get a bespoke UK/EU free trade deal outside the Single Market and the Customs Union, she will walk away and risk the imposition of tariffs on both sides. She has to mean it — and be believed.
Anathema
Such rough talk from her supposedly ultra-cautious Chancellor gives her much greater credibility in such a stand-off.
But Mr Hammond’s change of tone is not just a negotiating ploy. As he also pointed out to his German interviewers: ‘Since the referendum, we have seen, on the European side, movement away from the UK positions . . . to things that are anathema to the UK: more political integration.’
Some of that ‘movement’ would now be causing political mayhem in the UK, if we had not already voted to leave. Here are just four examples.
Last week, details leaked of an EU White Paper suggesting Brussels be allowed to impose taxes directly on member states, to include a levy on CO2 emissions, an electricity tax and an EU-wide corporate income tax.
Last month, the European Court of Justice ruled that British laws allowing the security services retention of bulk data on calls and emails would not be allowed to stand as they ‘exceeded what is strictly necessary’.
Also last month, Brussels ruled that all members of the Single Market had to impose a requirement that every off-road vehicle — every quadbike, every golf-cart — had to be covered by insurance for ‘third-party injury and damage’. Our own Department for Transport said that it ‘opposed measures which impose an unreasonable burden on the public’ but that it would have to abide by the new rule until Britain exits the EU.
And, only a few days ago, Brussels ruled that even motorists who break the law by driving without insurance should be protected if their car is damaged — so law-abiding drivers face an increase in insurance bills to cover that cost.
Hostility
It is only because we are leaving the EU that these four power-grabs — proposing new EU-wide taxes; adversely affecting MI5’s ability to protect the British people; creating a totally new overhead for farmers and families playing around with quadbikes; and driving up the costs of running a car — have not caused an even sharper spike in the British people’s hostility to our membership.
Yesterday, the former Deputy PM, Nick Clegg, pleaded that Mrs May should go for a ‘Norway model’ — that is, Britain outside the EU, but still members of its Single Market. This is the same Nick Clegg who, before the referendum vote, mocked this ‘solution’: ‘Norway have to pay into EU coffers, they have to obey all EU laws: it all gets decided by everyone else in Brussels and they have to translate it into law in Oslo. They have no power whatever, all the rules get made by foreigners: utter powerlessness.’
So the most eminent representative in Westminster of the die-hard Remainers thinks such ‘powerlessness’ is better than leaving the Single Market — and, as Mrs May put it in her Conservative Party conference speech, getting ‘an agreement between an independent, sovereign United Kingdom and the European Union’.
Sorry, Mr ex-Deputy Prime Minister: you’ve lost the argument, first with the British people and, now, with the Tories who were once on your side.
Living longer? No sweat!
For years, I have had a weekly telling-off from a fine woman called Wendy. Ferociously fit and steel-muscled, every Tuesday morning she stands over me barking commands like a regimental sergeant-major, while I do the exercises she prescribes.
Each week, she asks me what exercises I’ve done since last time, and each week I tell her: ‘None whatsoever.’ Wendy then rebukes me for not doing the right thing by my own health . . . and I have no answer (anyway, I’m panting too much to make sense).
But now I have a newspaper cutting to wave at her, while I gasp and groan. Last week, the Mail reported on a research study of 64,000 British adults over a decade, which showed that just a once-weekly exercise was much more effective than had been supposed as a means of sharply reducing the chance of a premature death from heart disease.
Better still, the researchers stated that this reduction in mortality risk was no less than that experienced by people who exercised every day: ‘Those who exercised once or twice a week but did not meet the recommended levels gained similar health benefits.’
What a relief to be vindicated in my laziness. I feel better already.
Quailing at the charge that it is perpetuating ‘blackface’ — when a white actor puts on make-up to play the part of a black man — Sky Arts has pulled from the schedules its satirical drama in which Joseph Fiennes played the part of Michael Jackson.
It was the late pop-star’s daughter, Paris, protesting that she was ‘incredibly offended’ by the portrayal, which seemed to settle the matter. But would Michael Jackson himself have been offended? He had spent part of his fortune on cosmetic procedures which lightened his skin to appear more, well, like a white man.
I suspect he would have been content to be played by Fiennes. But who knows? He was very strange.
The former Tory Party leader Michael Howard has been roundly criticised for suggesting that Theresa May should be prepared to go to war to protect Gibraltar, as Margaret Thatcher did to defend the Falkland Islands after they had been invaded by Argentina.
He has been lambasted by normally sensible people for supposedly being bellicose and insulting an ally. 
The Spanish Foreign Minister, Alfonso Dastis, sniffed loftily that Britain had ‘lost composure’.
Maybe Lord Howard could have chosen his words more carefully. He was interviewed at home, and was perhaps unguarded. 
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But he was absolutely right to stress how high the stakes have become since Spain insisted it should have a veto over any final post-Brexit deal applying to Gibraltar. 
There are two crucial facts which anyone discussing the future of the British territory should bear in mind. 
One is that the Spanish authorities are absolutely obsessed with it. Gibraltar may be a small place, but gaining control of it is high in their priorities.
The second inescapable truth is that the Foreign Office and many British politicians would be happy to hand Gibraltar over to the Spanish. 
Indeed, in 2002 the Blair government cooked up a plan for joint sovereignty that was only scuppered because it was rejected in a referendum by 99 per cent of Gibraltarians in an 88 per cent turnout.
Let me give some examples of Spain’s fixation with the Rock, which seems sometimes to border on psychosis. 
It was, of course, legally ceded by Spain to Britain in 1713, and became a vital military and naval base for the British Empire.
In 1954, the fascist dictator General Franco revived Spain’s long-dormant claim to the territory after the Queen visited her loyal subjects there. 
She has not visited Gibraltar since because successive British governments have not wished to upset the prickly Spanish.
More than 99 per cent of Gibraltarians voted in 1967 against Spanish sovereignty. 
Naturally, this did not please the undemocratic, nationalist Franco, and the land border with Spain was effectively closed from 1969 to 1982.
Even with Franco’s death and the dawn of a democratic era in Spain, politicians in Madrid did not stop coveting the Rock. 
Queues periodically built up on the border as Spanish customs officials made people’s lives a misery by obstructing them as they tried to pass in and out of the territory — most recently in 2013.
Whenever British warships dock in Gibraltar, Spanish ministers are liable to be thrown into a tizz. 
There was uproar when Charles and Diana boarded the Royal Yacht Britannia off the Rock on their honeymoon in 1981. 
When he heard of their plans in advance, King Juan Carlos I of Spain boycotted their wedding.
So when Alfonso Dastis accuses the British of having ‘lost composure’, I’m afraid I have to pinch myself in disbelief. 
For years the Spanish have been anything but composed. They have been peevish, petty and sometimes bullying.
Speaking personally, if there were a tiny Spanish enclave on the coast of Cornwall, where one could pop over for a tapas and a glass of rioja, I should be delighted. 
But the macho political class in Madrid regard the very existence of Gibraltar as an affront to their honour.
They are also guilty of gross hypocrisy since the same politicians who react hysterically to the British presence in Gibraltar passionately defend Spain’s possession of Ceuta and Melilla, two enclaves in Morocco, whose government believes should be Moroccan.
The latest manifestation of Spain’s inability to accept that 99 per cent of the population of Gibraltar regard themselves as British, not Spanish, is its demand to have a say in the territory’s post-Brexit future. 
This is shameless opportunism, and it is disgraceful that the EU should have allowed it.
It can’t be stated too loudly that all 30,000 Gibraltarians are legally British, and it is the responsibility of the British Government — not Madrid or Brussels — to safeguard their rights after we have left the European Union.
The final piece of evidence that illustrates just how unbalanced the Spanish government has become was illustrated this week by a photograph of a minuscule British patrol boat (all we dare keep in Gibraltar these days) escorting a large Spanish warship out of the enclave’s territorial waters.
Such illegal incursions are frequent. This one was deliberately provocative, timed to take place days after the announcement of Spain’s diplomatic coup in obtaining from Brussels a role in discussions about the territory’s future.
Isn’t it obvious that Madrid is deadly serious — as well as pretty loopy — on this matter? 
I don’t suggest it has any intention of invading Gibraltar. As a democratically elected government, which is moreover a fellow member of the Nato military alliance, it can presumably be expected not to overturn the rule of law. 
But short of armed force, the Spanish government will try almost anything to achieve its ends. 
The trouble is that its preoccupation with Gibraltar is neither reasonable nor measured. 
So it might do something drastic. The more weakness we show, the greater the danger.
Here, I fear, we are vulnerable. For the Spanish may have seen the extreme criticisms of Lord Howard’s intervention as evidence that the British are prepared to be flexible where the future of Gibraltar is concerned.
After all, we have been so in the past, bending over backwards in order not to offend Madrid. 
In 2002, the Labour government accepted the principle of joint sovereignty with the Spanish. 
In the mind of the Foreign Office, this was doubtless one step away from handing over the Rock entirely.
Although the then foreign secretary, Jack Straw, had intimated there would be a vote on the issue, the British government wanted to present the people with a fait accompli. 
The Gibraltar government wisely decided to go ahead with a referendum of its own. The result was overwhelming. 
I’m sure Theresa May and even Foreign Secretary Boris Johnson are being genuine when they say they will respect the right of the people of Gibraltar to remain British so long as they want to — which is self-evidently for as far as anyone can see.
But there are plenty of people in Whitehall and Labour, and even some Tories, who secretly believe the enclave is an embarrassing anachronism, and the sooner it is returned to Spain the better.
The pusillanimous Foreign Office had similar thoughts about the Falklands in 1981. 
The watering down of British citizenship rights for their inhabitants, as well as the withdrawal of a major supply vessel, persuaded the Argentines that we were no longer committed to defending the islands. 
However, treacherous mandarins had not counted on Margaret Thatcher’s conviction and courage.
We can easily imagine what such people will say when Spain threatens to unpick a Brexit deal unless it can obtain concessions over Gibraltar. 
They will bleat that 30,000 people can’t be allowed to stand in the way of an agreement.
So despite his somewhat clumsy language, I’m on Lord Howard’s side. He realises the enormity of the danger facing our fellow British citizens. 
Never forget: Spain craves Gibraltar, and will move heaven and earth to get it.
The issue could come to a head as soon as today with leading Brexiteers branding the Treasury 'Brexit saboteurs'
PHILIP Hammond is blocking calls to increase spending on No Deal planning at this month’s Budget - as hopes of a Brussels breakthrough grow.
The Chancellor has been urged by some in Government to set aside even more funds to prepare for a collapse in negotiations, beyond the £3 billion he earmarked in 2017.
But Treasury insiders say he is resisting any increase, even if it strengthened Theresa May’s negotiating hand and is likely the cash will never have to be spent.
The issue could come to a head as soon as today as the Cabinet discuss the Budget.
One Cabinet Minister told The Sun “it seems like a no-brainer” as Brexit talks go to the wire, as it would send the message to Brussels that Britain really is ready to walk away.
And a senior Government source added they “definitely need” more cash to prepare for the doomsday scenario of Britain exiting the EU without a trade deal in place next March.
But Treasury sources insisted there was already enough funding for emergency planning scenarios.
Last night leading Brexiteer Iain Duncan Smith publicly backed calls for more money, saying: “How can the PM say we are preparing to leave the EU without a deal when her Chancellor is refusing to pay for it?”
And in an extraordinary blast, the former Tory leader added: “If the money isn’t forthcoming the it means the Treasury is acting like government saboteurs - hell bent on wrecking Brexit.”
The spat comes as the business chiefs urged Mr Hammond to use his fiscal statement in two weeks time to radically prepare the country for exit with a £3 billion package.
The CBI’s plans include more than doubling the tax breaks export firms get to invest in their own factories to £500,000 and doubling apprenticeship investment to get Britain Brexit ready.
They also suggest a business rates holiday for any firm that conducts a major overhaul of their store, factory or office.
Boss Carolyn Fairburn said: “As the UK leaves the EU, there is no better moment than this Budget to show the Government is committed to real partnership with business.”
The issue could come to a head as soon as today with leading Brexiteers branding the Treasury 'Brexit saboteurs'
PHILIP Hammond is blocking calls to increase spending on No Deal planning at this month’s Budget - as hopes of a Brussels breakthrough grow.
The Chancellor has been urged by some in Government to set aside even more funds to prepare for a collapse in negotiations, beyond the £3 billion he earmarked in 2017.
But Treasury insiders say he is resisting any increase, even if it strengthened Theresa May’s negotiating hand and is likely the cash will never have to be spent.
The issue could come to a head as soon as today as the Cabinet discuss the Budget.
One Cabinet Minister told The Sun “it seems like a no-brainer” as Brexit talks go to the wire, as it would send the message to Brussels that Britain really is ready to walk away.
And a senior Government source added they “definitely need” more cash to prepare for the doomsday scenario of Britain exiting the EU without a trade deal in place next March.
But Treasury sources insisted there was already enough funding for emergency planning scenarios.
Last night leading Brexiteer Iain Duncan Smith publicly backed calls for more money, saying: “How can the PM say we are preparing to leave the EU without a deal when her Chancellor is refusing to pay for it?”
And in an extraordinary blast, the former Tory leader added: “If the money isn’t forthcoming the it means the Treasury is acting like government saboteurs - hell bent on wrecking Brexit.”
The spat comes as the business chiefs urged Mr Hammond to use his fiscal statement in two weeks time to radically prepare the country for exit with a £3 billion package.
The CBI’s plans include more than doubling the tax breaks export firms get to invest in their own factories to £500,000 and doubling apprenticeship investment to get Britain Brexit ready.
They also suggest a business rates holiday for any firm that conducts a major overhaul of their store, factory or office.
Boss Carolyn Fairburn said: “As the UK leaves the EU, there is no better moment than this Budget to show the Government is committed to real partnership with business.”
Lawyers urged the gypsy community to ensure they gather the right paperwork as soon as possible
GYPSIES and travellers have been warned they could be deported after Brexit if they don't have proof they can stay.
Lawyers have urged the community to get their paperwork in order as soon as possible - or risk being thrown out of the country.
The situation could end up seeing travellers forced to leave the UK because they don't have the right documents, in an echo of the Windrush generation scandal.
The Traveller Movement national annual conference heard that gypsies may have difficulty gathering official paperwork to prove they have the right to live here.
Poor literacy, the inability to use computers, the cost of applying and distrust of the state were all cited as barriers to claiming the "settled status" which non-citizens need to have in order to stay in Britain after Brexit.
Lawyer Christopher Desira said travellers should start gathering paperwork such as tax documents, education certificates, bank statements or employment contracts.
He warned that they could end up confined in a detention centre, particularly if they don't have a passport.
Charity worker Sarah Zawacki added: "Our work found that there was also a very low awareness of the need to apply to secure their position in the UK.
"Now they know there is this application, but it's £65 - many are on very low incomes and have very large families and it's just unfeasible.
"Then there is the language barrier - many speak some English but it's not the level needed to access this application."
Around 300,000 members of the Roma community are believed to live in the UK.
Some were born and brought up in the country, but others moved here from other parts of the EU.
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Lawyers urged the gypsy community to ensure they gather the right paperwork as soon as possible
GYPSIES and travellers have been warned they could be deported after Brexit if they don't have proof they can stay.
Lawyers have urged the community to get their paperwork in order as soon as possible - or risk being thrown out of the country.
The situation could end up seeing travellers forced to leave the UK because they don't have the right documents, in an echo of the Windrush generation scandal.
The Traveller Movement national annual conference heard that gypsies may have difficulty gathering official paperwork to prove they have the right to live here.
Poor literacy, the inability to use computers, the cost of applying and distrust of the state were all cited as barriers to claiming the "settled status" which non-citizens need to have in order to stay in Britain after Brexit.
Lawyer Christopher Desira said travellers should start gathering paperwork such as tax documents, education certificates, bank statements or employment contracts.
He warned that they could end up confined in a detention centre, particularly if they don't have a passport.
Charity worker Sarah Zawacki added: "Our work found that there was also a very low awareness of the need to apply to secure their position in the UK.
"Now they know there is this application, but it's £65 - many are on very low incomes and have very large families and it's just unfeasible.
"Then there is the language barrier - many speak some English but it's not the level needed to access this application."
Around 300,000 members of the Roma community are believed to live in the UK.
Some were born and brought up in the country, but others moved here from other parts of the EU.
We pay for your stories! Do you have a story for The Sun Online politics team? Email us at tips@the-sun.co.uk or call 0207 782 4368. We pay for videos too. Click here to upload yours
Brexiteers fear that soon they’ll either have to take the blame for a no-deal Brexit or be bounced into backing a flawed deal — and Theresa May’s 'astonishingly upbeat' mood is a signal
IT is quiet out there, too quiet in the views of many Brexiteers in government.
Their suspicions are raised by the fact that when things go silent in Brussels, that’s when the real negotiating is being done. They fear that right now a deal is being done that they’ll be bounced into supporting.
They worry that since last week’s Cabinet meeting, there hasn’t been any new Brexit offer put either to Cabinet or the inner cabinet, yet technical talks have resumed in Brussels.
They fear that a deal will be agreed. Then, they’ll be faced with a choice of rejecting it and having to take the blame for no deal and the chaos that would involve or accepting the agreement with all its flaws.
This fear of being bounced has been heightened by Theresa May’s mood. Those who have seen her this week describe her as “astonishingly upbeat” and convinced that a deal will soon be done.
I understand that she will update the Cabinet on the state of negotiations on Tuesday.
Dominic Raab, the Brexit Secretary, is more optimistic than most Leavers in Cabinet. He has been reassuring Cabinet colleagues that press reports about where the deal is going to end up aren’t right and that the final phase of the negotiations will be politically — not technically — led. In other words ministers, not civil servants, will be in charge.
But this has not been enough to assuage some of his colleagues’ concerns.
They point out that at crucial points in these negotiations, Downing Street has presented ministers with a done deal and challenged them to quit if they don’t like it. The Chequers plan, which David Davis and Boris Johnson resigned over, was just one example of this approach.
These ministers have concluded that the level of concern the Cabinet expressed about the negotiations means that Mrs May will not come to the Cabinet and ask ministers for permission to make further concessions. Rather, they’ll simply be presented with them.
At the top level of government, they are keen to get the EU to agree to a special Brexit meeting this month.
They believe that will give them more time to get the deal through parliament. An agreement in November would also allow them to avoid some of the most difficult no-deal planning choices. For instance, I understand that at Cabinet on November 13 they must decide whether to book space on ferries to bring in essential supplies in the event of no deal.
Number 10 is confident of getting a Brexit deal through the Commons. One of those who has discussed the matter with Mrs May tells me “you can see how opposition melts away” in the face of worries about both no deal and a Corbyn government.
At the same time, the May circle believe the carrot of a future trade deal with the EU and the Government having more money to spend if the withdrawal agreement is passed will ease its passage.
But Theresa May should beware buyer’s remorse. She may well be able to bounce her Cabinet and the bulk of her MPs into supporting a deal.
But if they end up regretting their vote or are left angry, they’ll know who to blame. Mrs May will find herself facing a confidence vote next spring.
“A MASTERCLASS in how to give people something and p**s them off at the same time” – that’s how one senior Tory describes Philip Hammond telling schools that they could have £400million to buy the “little extras they need”.
Schools funding is one of the issues that cost the Tories most at the last election. But the Budget did little to deal with this question: More than 80 per cent of the extra spending announced went to the NHS and there was more new money for potholes than schools.
Education is threatening to turn into a major political problem for the Tories.
A new TV series called School, starting on Tuesday on BBC2, looks at how schools are struggling to cope with budgetary constraints. At the same time, the Tories and their anonymous Education Secretary Damian Hinds are oddly quiet about their achievements.
The free schools set up under this Government are outperforming all other schools. But the Government barely whispers about this, when it should be shouting it from the rooftops.
Downing Street defends the emphasis on the NHS to Tory MPs by pointing out that their polling shows it is the overwhelming public-spending priority of their supporters. But as one influential Tory complains to me, this ignores the fact that people now only become more likely to vote Tory than Labour at age 47.
“If you want to have some supporters who are less elderly, you might want to push education up the agenda,” he fumes.
The Tories won’t win back their majority without more support from those in their thirties and early forties – and they won’t win over parents with school-age children unless they show them that education is as much of a priority for the Government as it is for them.

THE view in Westminster is that Monday was Philip Hammond’s last Budget. There are whispers in Whitehall that his travel schedule and raised international profile suggest he realises as much.
So, who will replace Hammond as Chancellor? Well, the rumour in government circles is that Amber Rudd, cleared now of blame for the Windrush scandal, might. She is a former banker who knows the Treasury well and would be the first female Chancellor.
Mrs Rudd would, from No10’s point of view, also be less of a threat than other contenders. Her small majority in Hastings and her position on Brexit make her less of a challenge to Mrs May’s position.

JEREMY Hunt is determined to banish the idea that Brits can only speak two languages: English and English slower and louder.
After giving a speech in Japanese in September, he is giving one entirely in French on Thursday.
Let’s hope that Mr Hunt fares better than Tory Blair. When he gave a speech in French to their parliament, there were complaints that his accent owed too much to his time as a barman in Paris.

AN incompetent minister in a competent department can be dealt with.
A hyper-competent minister can stop an incompetent department making too many mistakes.
But put together an incompetent department and an incompetent minister and you have a guaranteed disaster on your hands.
But that is what we have with immigration right now. Caroline Nokes, the Immigration Minister, is one of the weakest members of the Government, while the Home Office is still not fit for purpose ­– as the Windrush scandal showed.
What makes all this so dangerous is that Brexit will have huge consequences for immigration policy.
THIS week has shown why the Tories should be more afraid of John McDonnell than Jeremy Corbyn.
It was Mr McDonnell who realised that Labour would be walking into an elephant trap if they opposed plans to raise the higher rate tax threshold to £50,000.
Mr McDonnell knows that if Labour is to win next time, they’ve got to make people think that only “the rich” and big business will end up paying more tax.

Brexiteers fear that soon they’ll either have to take the blame for a no-deal Brexit or be bounced into backing a flawed deal — and Theresa May’s 'astonishingly upbeat' mood is a signal
IT is quiet out there, too quiet in the views of many Brexiteers in government.
Their suspicions are raised by the fact that when things go silent in Brussels, that’s when the real negotiating is being done. They fear that right now a deal is being done that they’ll be bounced into supporting.
They worry that since last week’s Cabinet meeting, there hasn’t been any new Brexit offer put either to Cabinet or the inner cabinet, yet technical talks have resumed in Brussels.
They fear that a deal will be agreed. Then, they’ll be faced with a choice of rejecting it and having to take the blame for no deal and the chaos that would involve or accepting the agreement with all its flaws.
This fear of being bounced has been heightened by Theresa May’s mood. Those who have seen her this week describe her as “astonishingly upbeat” and convinced that a deal will soon be done.
I understand that she will update the Cabinet on the state of negotiations on Tuesday.
Dominic Raab, the Brexit Secretary, is more optimistic than most Leavers in Cabinet. He has been reassuring Cabinet colleagues that press reports about where the deal is going to end up aren’t right and that the final phase of the negotiations will be politically — not technically — led. In other words ministers, not civil servants, will be in charge.
But this has not been enough to assuage some of his colleagues’ concerns.
They point out that at crucial points in these negotiations, Downing Street has presented ministers with a done deal and challenged them to quit if they don’t like it. The Chequers plan, which David Davis and Boris Johnson resigned over, was just one example of this approach.
These ministers have concluded that the level of concern the Cabinet expressed about the negotiations means that Mrs May will not come to the Cabinet and ask ministers for permission to make further concessions. Rather, they’ll simply be presented with them.
At the top level of government, they are keen to get the EU to agree to a special Brexit meeting this month.
They believe that will give them more time to get the deal through parliament. An agreement in November would also allow them to avoid some of the most difficult no-deal planning choices. For instance, I understand that at Cabinet on November 13 they must decide whether to book space on ferries to bring in essential supplies in the event of no deal.
Number 10 is confident of getting a Brexit deal through the Commons. One of those who has discussed the matter with Mrs May tells me “you can see how opposition melts away” in the face of worries about both no deal and a Corbyn government.
At the same time, the May circle believe the carrot of a future trade deal with the EU and the Government having more money to spend if the withdrawal agreement is passed will ease its passage.
But Theresa May should beware buyer’s remorse. She may well be able to bounce her Cabinet and the bulk of her MPs into supporting a deal.
But if they end up regretting their vote or are left angry, they’ll know who to blame. Mrs May will find herself facing a confidence vote next spring.
“A MASTERCLASS in how to give people something and p**s them off at the same time” – that’s how one senior Tory describes Philip Hammond telling schools that they could have £400million to buy the “little extras they need”.
Schools funding is one of the issues that cost the Tories most at the last election. But the Budget did little to deal with this question: More than 80 per cent of the extra spending announced went to the NHS and there was more new money for potholes than schools.
Education is threatening to turn into a major political problem for the Tories.
A new TV series called School, starting on Tuesday on BBC2, looks at how schools are struggling to cope with budgetary constraints. At the same time, the Tories and their anonymous Education Secretary Damian Hinds are oddly quiet about their achievements.
The free schools set up under this Government are outperforming all other schools. But the Government barely whispers about this, when it should be shouting it from the rooftops.
Downing Street defends the emphasis on the NHS to Tory MPs by pointing out that their polling shows it is the overwhelming public-spending priority of their supporters. But as one influential Tory complains to me, this ignores the fact that people now only become more likely to vote Tory than Labour at age 47.
“If you want to have some supporters who are less elderly, you might want to push education up the agenda,” he fumes.
The Tories won’t win back their majority without more support from those in their thirties and early forties – and they won’t win over parents with school-age children unless they show them that education is as much of a priority for the Government as it is for them.

THE view in Westminster is that Monday was Philip Hammond’s last Budget. There are whispers in Whitehall that his travel schedule and raised international profile suggest he realises as much.
So, who will replace Hammond as Chancellor? Well, the rumour in government circles is that Amber Rudd, cleared now of blame for the Windrush scandal, might. She is a former banker who knows the Treasury well and would be the first female Chancellor.
Mrs Rudd would, from No10’s point of view, also be less of a threat than other contenders. Her small majority in Hastings and her position on Brexit make her less of a challenge to Mrs May’s position.

JEREMY Hunt is determined to banish the idea that Brits can only speak two languages: English and English slower and louder.
After giving a speech in Japanese in September, he is giving one entirely in French on Thursday.
Let’s hope that Mr Hunt fares better than Tory Blair. When he gave a speech in French to their parliament, there were complaints that his accent owed too much to his time as a barman in Paris.

AN incompetent minister in a competent department can be dealt with.
A hyper-competent minister can stop an incompetent department making too many mistakes.
But put together an incompetent department and an incompetent minister and you have a guaranteed disaster on your hands.
But that is what we have with immigration right now. Caroline Nokes, the Immigration Minister, is one of the weakest members of the Government, while the Home Office is still not fit for purpose ­– as the Windrush scandal showed.
What makes all this so dangerous is that Brexit will have huge consequences for immigration policy.
THIS week has shown why the Tories should be more afraid of John McDonnell than Jeremy Corbyn.
It was Mr McDonnell who realised that Labour would be walking into an elephant trap if they opposed plans to raise the higher rate tax threshold to £50,000.
Mr McDonnell knows that if Labour is to win next time, they’ve got to make people think that only “the rich” and big business will end up paying more tax.

Last modified on Tue 8 Jan 2019 11.51 GMT
Moves to ask parents to submit the country of birth of their children this week as part of the school census have caused a significant backlash on social media, with parents being urged to boycott the survey via the #BoycottSchoolCensus hashtag campaign. Here are the answers to some of the key questions about the census and the campaign against it.
State schools in England supply details about their pupils to the Department for Education for what is known as the school census once every term. The census includes details such as age, address and academic attainments, and these are recorded in the national pupil database (NPD). National statistics from the survey are published every year. Here’s the 2016 edition.
Last year, long before the EU referendum, the DfE decided to add new components for the 2016-17 census, including pupils’ country of birth and nationality. It also started to ask schools to judge children’s proficiency in English if it is not their first language. The DfE has collected data on pupils’ ethnicity for many years.
No. There are reports that many schools have reacted to the new questions on birth and nationality by asking to do so, but the DfE says parents are not obliged to comply.
Schools and local authorities are allowed to ask for proof of date of birth during the admissions process, but the DfE’s code specifically states they must not ask for “long” birth certificates or “other documents which include information about the child’s parents”.
At a basic level the DfE uses the school census for funding and planning. Its intention in adding nationality and language ability was to help gauge the “targeting of support” for pupils and schools. Academics and journalists conducting research also make extensive use of the database. Figures showing that grammar schools have a tiny number of pupils on free school meals, for example, are likely to have come via the NPD.
Access to the NPD is restricted, and the restrictions increase with the level of detail. The highest level of access – known as tier one and which could identify individual pupils – is only open to a small number of approved applicants, and details identifying individual pupils cannot be divulged.
Condition of access includes compliance with the Data Protection Act 1998. This means providing proof of registration with the information commissioner’s office, having appropriate security arrangements in place to process the data, using the data only for the specific purpose requested, keeping it only for the specified length of time and not sharing it without prior written approval.
Update: the highest level of access to data is tier one, not tier four as previously stated.
Some people fear the Home Office could use the database to identify foreign-born families, or match the findings to its own immigration database. The timing of the census has heightened this worry.
The change was suggested a year ago, but the subsequent vote in favour of leaving the European Union has left the immigration status of EU nationals living in the UK much less clear than it was 12 months ago. With Liam Fox suggesting that they could be “one of our main cards in the negotiations” for Brexit, and the home secretary, Amber Rudd, suggesting companies could be forced to reveal how many foreign workers they have, the political atmosphere is highly charged.
Campaigners say the Home Office has a record of accessing other government departments’ data, but the DfE’s official line is that the information will not be shared: “These data items will not be passed to the Home Office. They are solely for internal DfE use for analysis, statistics and research,” it said.
It is worth noting that the Home Office could already do something similar through existing HMRC tax records.
Yes, to a point. The DfE’s guidance to schools allows parents and carers to refuse to supply the information on nationality and place of birth. It is the first time parents have been given that right in the school census. The school will still supply all the other data it already collects on pupils.
It’s very much a matter of personal conscience.
It is unlikely the Home Office is trawling the NPD looking for immigrants. It doesn’t currently have the capacity, though it could perhaps in the future. Many school leaders are in favour of the data collection, because it helps them argue for further funding for new places and additional support for those needing to learn English.
Boycotting the data collection would send a strong signal to the DfE that they are being too intrusive in their methodology, and that parents are concerned about the potential abuse of the data in the future. One thing is clear though: no schools should be badgering parents to see passports, and parents are entirely right to be refusing these requests.
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From The Socialist newspaper, 28 September 2016
TUSC parliamentary candidates in 2015, photo Senan   (Click to enlarge)
Jeremy Corbyn's re-election triumph is a significant defeat for the capitalist establishment - the corporate bosses, media tops, and their political representatives, both those outside and inside the Labour Party. Prior to Jeremy's election as leader last summer this elite had achieved unchallenged control of the Labour Party for over 20 years, effectively disenfranchising working class voters by removing any choice at the ballot box.
The capitalists benefitted enormously from the transformation of Labour into Tony Blair's New Labour and they will not lightly accept the new situation. Consolidating Jeremy's victory against their continued opposition - by really transforming Labour into an anti-austerity, socialist, working-class mass movement - is the critical task facing socialists in Britain today.
The first meeting of the Trade Unionist and Socialist Coalition (TUSC) national steering committee after Jeremy Corbyn's re-election takes place on 12 October. The Socialist Party will be presenting proposals on how TUSC can contribute to the central task at hand.
TUSC was established in early 2010 and initially involved the Socialist Party and a number of leading trade unionists participating in a personal capacity.
These included Bob Crow, the general secretary of the 80,000-strong RMT transport workers' union, which had been expelled from the Labour Party in 2004. The RMT's predecessor union was one of the founding organisations of the Labour Party.
In 2012 the RMT's annual delegate general meeting (AGM) agreed that the union would formally participate as a constituent organisation of TUSC, with representatives appointed to the coalition's steering committee. The RMT's continued involvement has been endorsed, not without debate, at every AGM since.
The Socialist Workers' Party was invited into TUSC in 2010 and independent socialists also participate. By providing a common electoral umbrella for trade unionists and working class community campaigners to challenge establishment politicians at the ballot box in defence of core socialist policies, TUSC's aim has been to push forward the process of re-establishing a vehicle for working class political representation.
The TUSC founding statement recognised that there were "different strategic views" about the way to advance this cause, "whether the Labour Party can be reclaimed by the labour movement, or whether a new workers' party needs to be established." But aside from recognising that there would be Labour candidates "who share our socialist aspirations" who would not be challenged by TUSC, to date TUSC has not taken a policy position on what would be required to transform the Labour Party. Jeremy Corbyn's re-election poses this question point blank.
The Socialist Party is proposing that TUSC makes a clear policy statement that a critical step would be to re-establish within the Labour Party a role for trade unions, the biggest voluntary organisations in Britain, commensurate with their importance as the collective voices of millions of workers.
Under Blair, Brown and Miliband the unions' power within the Labour Party was gutted. The real social weight of the RMT, for example, is shown when it is routinely denounced by the capitalist media as 'holding the country to ransom' every time it is forced to take strike action to defend its members and public safety on the railways.
But if the union was to affiliate to the Labour Party today it would have less say than the House of Lords Labour Group in the party's national policy-making forum! As the RMT's political strategy endorsed by this year's AGM says, Labour does not currently have "structural/constitutional arrangements that would make affiliation in the union's interests."
The Socialist Party is not proposing that TUSC draws up an alternative constitution for the Labour Party. TUSC is a coalition whose component parts have different views. But it could agree a broad policy to take into the labour movement: that the unions must have their collective representation and proportionate weight restored in the formation of Labour Party policy, the selection and re-selection of Labour Party candidates, and the administration of the party locally and nationally.
The RMT rulebook commits the union "to work for the supersession of the capitalist system by a socialistic order of society." There should be no problem for TUSC to also adopt policy that socialists excluded from the Labour Party should be allowed in.
The best way to achieve this - above board and undercutting media scares about 'infiltrators' - would be to allow for affiliation to the Labour Party for socialist parties and organisations. This right should also be extended to anti-austerity, anti-racist, socialist feminist, and Green campaigners and organisations, in a modern version of the early federal structure of the Labour Party which encompassed trade unions, the co-operative movement, women's suffrage campaigners, and a number of independent socialist parties.
But this call obviously raises the question of TUSC's electoral activity.
The Co-operative Party, an independent party separately registered with the Electoral Commission, has an affiliate status agreement with the Labour Party on the basis that it does not contest seats against Labour. The Socialist Party will be proposing at the October steering committee that TUSC should campaign for a similar arrangement for its constituent components.
Since Jeremy Corbyn's initial victory, TUSC has already re-calibrated its electoral activity.
In the May 2016 local elections, for example, no TUSC candidates were even considered to be run without local TUSC groups seeking a dialogue with the sitting Labour councillor or prospective candidate on the critical issue of their preparedness to resist cuts to local council jobs and services (see www.tusc.org.uk/txt/380.pdf for a full report of TUSC's participation in the 2016 elections).
The Socialist Party is proposing that TUSC continues its campaign for Labour councils to join the resistance to the Tories' austerity agenda. TUSC supporters have played an important role in winning backing for a fighting strategy to oppose cuts to local public services in the main local government unions, Unison, Unite, and the GMB, as well as this year's Wales TUC conference.
This campaign should be resumed in the autumn, as councils begin preparing their 2017-18 budgets, with the added urgency of the need to coordinate an organised defiance of the new Housing and Planning Act. Labour councillors should be pushed to fight the Tories or resign and make way for those who will.
However the responsibility for removing alleged 'Labour' representatives who implement Tory policies does not rest with TUSC alone. TUSC candidates have polled over 350,000 votes in various elections since its formation and the prospect of an electoral challenge from the left can add to the pressure on 'Labour' cutters.
But with Jeremy Corbyn's re-affirmed mandate it is not the only way to bring them into line. The councillors on the Labour-controlled Greater Manchester Fire and Rescue Service Authority, for example, who are planning to sack one in five firefighters and re-employ the rest on worse contracts, should be suspended from the Labour Party unless they back down.
Consequently, the Socialist Party is proposing that TUSC agrees to make no further preparations for contesting the May 2017 local elections in England and Wales pending discussions with Jeremy Corbyn and his supporters on the new possibilities opening up following his re-election victory.
Many other organisational and political steps would need to be taken for the Labour Party to be fully consolidated as a working class, socialist, anti-austerity mass movement. This would include measures to defeat the opposition that will continue to Jeremy Corbyn's leadership from Labour's right.
TUSC's constituent components will have different views on how best a movement can be built that is capable of defeating the pro-capitalist consensus upheld by the establishment politicians, their media, and other institutions.
But October's steering committee discussion, in welcoming Jeremy Corbyn's re-election triumph, provides an opportunity to signal that TUSC will fully participate in that struggle.
The coronavirus crisis has laid bare the class character of society in numerous ways. It is making clear to many that it is the working class that keeps society running, not the CEOs of major corporations.
The results of austerity have been graphically demonstrated as public services strain to cope with the crisis.

Amnesty to conduct research into racism in the UK
‘Some people now feel licensed to express racist views in a way we haven’t seen for decades’ – Kate Allen
Amnesty International today announced a new emergency campaign to combat racism and xenophobia in the UK, prompted by reports of a rise in racial abuse in the wake of the EU referendum.
The announcement comes amid news that reports to police of online hate crimes rose over the weekend since Thursday’s referendum. The UN has also raised concern over the reported rise.
Amnesty will conduct research into the rise in racism and xenophobia across the UK. The new research will examine reports of abuse and their causes, including the public and political discourse around both the EU referendum and the London mayoral election.
Amnesty has issued an urgent call on all local councils to condemn racism in all its forms, and to commit to ensuring that all local bodies and programmes have the support and resources needed to fight and prevent racism and xenophobia. Amnesty aims to get every local council to sign up to the commitment. (www.amnesty.org.uk/againsthate)
Meanwhile Amnesty is encouraging people to show their solidarity with people experiencing abuse, using the #AgainstHate hashtag.
Kate Allen, Amnesty’s UK Director, said:
“Some people now feel licensed to express racist views in a way we haven’t seen for decades.
“The referendum campaign was marked by divisive, xenophobic rhetoric as well as a failure from political leaders to condemn it. We are now reaping the referendum rhetoric whirlwind.
“Amnesty is deeply concerned at reports of verbal abuse, attacks on buildings, racist slogans on t-shirts, calls for people to leave the country and other acts of intimidation and hate.
“People across the UK have suddenly found themselves in a country where they’re unsure of their future, their family’s future and the security of their jobs and homes. They need to be urgently reassured that they can feel safe, protected and welcome here.
“We’re simply not prepared to stand by and let hate become the norm in Britain.”
A member of Amnesty’s Belfast group was verbally racially abused on Saturday night by a man who asked him if he was from the European Union before telling him to “get the fuck out of our country”.
Mohammed Samaana, a nurse in a Belfast hospital, was verbally attacked in a city-centre Belfast bar. He describes the incident:
“On Saturday night, a man I have never met before said to me: “You from the EU? Fuck off back to your country. Get the fuck out of our country.”
“At first I thought he was joking, but then he continued the abuse and started shaking his fists at me. At that point I decided it was better to leave rather than have the incident escalate.
“What makes me really sad is that the three men and three women who were with him didn’t say a word, condoning his racism by their silence. I think everyone now needs to speak out and challenge racism wherever and whenever we see it.”
Mr Samaana is a dual Palestinian-UK citizen who has lived in Northern Ireland for fifteen years and works as a nurse in a Belfast hospital.
Today the UN High Commissioner for Human Rights Zeid Ra’ad Al Hussein issued a statement on xenophobic attacks in the United Kingdom:
“I am deeply concerned at reports of attacks and abuses targeting minority communities and foreign citizens in the United Kingdom over the last few days. Racism and xenophobia are completely, totally and utterly unacceptable in any circumstances. I urge the U.K. authorities to act to stop these xenophobic attacks and to ensure that all those suspected of racist and anti-foreigner attacks and abuses are prosecuted.”

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Prime Minister Pedro Sánchez has said Spain will reject the draft Brexit withdrawal deal without a clarification of the text on future talks on the status of Gibraltar.
Spain maintains a claim to the peninsula, ceded to the British crown under the 1713 Treaty of Utrecht.
It wants to ensure that future EU talks with the UK do not cover Gibraltar.
"As things stand today if there are no changes regarding Gibraltar, Spain will vote no on Brexit," said Mr Sánchez.
Throughout the Brexit negotiations, Spain - along with Ireland and Cyprus - has conducted separate talks with the UK about specific border issues.
On Monday Spanish Foreign Minister Josep Borrell said that the draft Brexit deal had failed to make clear that talks on Gibraltar were "separate negotiations" and not part of future talks between the UK and EU.
Mr Sánchez added his weight to those remarks on Tuesday at a forum in Madrid, emphasising that any future negotiations on Gibraltar had to be bilateral.
"As a country we cannot assume that whatever happens in the future with Gibraltar would be negotiated by the UK and EU - it will have to be negotiated between Spain and the UK," he said.
Article 184 of the draft Brexit deal says the EU and the UK will seek to "negotiate rapidly the agreements governing their future relationship" between the official day of withdrawal on 29 March 2019 and the end of a transition period in December 2020.
But Spain believes the article in question is ambiguous and wants to ensure that this does not apply to the future of Gibraltar. It insists on its future right to discuss the status of the peninsula bilaterally with the UK, and is seeking clarity that this draft deal will allow it to do so.
Asked about the Spanish objection to Article 184, a European Commission spokesman said they were aware of Spain's concerns. He said the EU's position on Gibraltar had been made clear in April 2017 guidelines, that after Brexit no agreement between the EU and UK could apply to Gibraltar without the agreement of the UK and Spain.
Gibraltar's Chief Minister Fabian Picardo accused Spain of adopting a "well-known tactic" of raising issues at the last minute. He said Spain's position "does little to build mutual confidence and trust going forward".
A spokesperson for UK Prime Minister Theresa May said the draft deal covered Gibraltar as well as "the other overseas territories and the crown dependencies".
"We will get a deal that works for the whole UK family."
By Gavin Lee, Europe reporter
Spain and Britain have been running parallel negotiations over the future of Gibraltar, alongside the main EU-UK Brexit negotiations. Those talks have led to a "protocol" being agreed and three Spanish-British committees being set up to tackle tobacco smuggling, oversee cross-border workers rights, and co-operate on environmental protection and border control.
There seemed to be no drama on the horizon and the Spanish prime minister told me a few weeks ago he had "no significant concerns over Gibraltar", that the "behaviour of the British government was good" and an agreement could be reached.
So what has changed?
The Spanish government says that its "bone of contention" is with one specific article in the draft Withdrawal Agreement that was only added last week, just before it was signed off by the European Commission, and wasn't seen by Spanish negotiators.
A senior Spanish diplomat told me that Spain wanted the following words (or similar) added to Article 184: "This does not apply to Gibraltar, which will be subject to bilateral talks between the UK and Spain."
Underlying all of this is the fact that Spain still disputes that Gibraltar as a British overseas territory. Spanish officials refer to the rock as a "British colony" and, although the Spanish government isn't seeking to use the Brexit talks to push that claim, it is making it clear that any decision over the future of Gibraltar can only happen with the approval of Madrid.
Though Spain ceded the peninsula under the 1713 treaty, it has tried several times to regain control over it.
A referendum in the territory in 1967 saw 99.6% of residents vote to remain British. A proposal for joint sovereignty was also decisively rejected by Gibraltarians in a 2002 vote.
Spain closed its border with Gibraltar after the 1967 vote and did not fully reopen it until 1985, the year before Spain joined the European Economic Community - the forerunner of the EU.
Gibraltar profile

Brexit talks have made "little" progress since March, the EU's chief negotiator has said.
Michel Barnier said there was a "risk of failure" in two key areas - Northern Ireland, and how the agreement will be governed.
He said June's EU summit was a "key rendezvous" to reach a deal that can be ratified before the UK leaves.
And he defended the EU's stance over the UK's involvement in the new Galileo sat-nav system.
The UK has played a key role in the programme's development so far, but faces being shut out of key elements of the programme after Brexit.
UK ministers are now considering setting up a rival version.
Mr Barnier said there had been "misunderstandings" in the coverage of the story, adding: "We are not kicking the UK out of Galileo. The UK decided unilaterally and autonomously to withdraw from the EU. This implies leaving its programmes as well."
EU rules mean the UK and its companies cannot participate in the "development of security sensitive matters", he said, adding that this did not mean the UK could not use an encrypted signal from the system as a third country.
Earlier Science Minister Sam Gyimah said the EU's position was "extremely disappointing".
"The EU is playing hard ball with us," he told BBC Radio 4's Today programme.
"We have helped to develop the Galileo system. We want to be part of the secure elements of the system and we want UK industry to be able to bid for contracts on a fair basis.
"It is only on those terms that it makes sense for the UK to be involved in the project."
Mr Barnier was speaking after updating the remaining EU member states on the latest in the Brexit negotiations.
Asked about the progress that had been made since March, he said: "I would say little, not very little."
He said the transition period that is expected to follow Brexit day in March 2019 depended on "operational solutions" being found on the issue of Northern Ireland's border with the Republic.
"The clock is ticking" to reach an agreement before October or November which can be ratified by the UK and European Parliaments and the EU Council, he said.
"So, little progress but we are working on technical issues which is always useful.
"None of these issues are negligible. The two key points which remain, where there is risk of failure, are the governance of the agreement and the  Ireland-Northern Ireland issue."
The UK government has yet to settle on the model it wants to replace the customs union in order to avoid checks at Northern Ireland's border with the EU.
Prime Minister Theresa May met Conservative MPs at Downing Street to set out the government's two proposals.
Earlier Health Secretary Jeremy Hunt warned Foreign Secretary Boris Johnson - who has described one, a customs partnership, as "crazy" - to keep discussions private.
"On the EU side, if they see divisions in the open, they will exploit that," Mr Hunt said.
At a press conference with his French counterpart, Mr Johnson was asked why he had not resigned given his differences with the prime minister -  but he did not repeat his criticism of the partnership option and said he thought Mrs May's position was "completely right".
Mrs May's key Brexit committee of senior ministers - which is divided over the customs issue - meets again on Tuesday.

A legal challenge to try to prevent Boris Johnson shutting down parliament to force through a no-deal Brexit has begun in a Scottish court.
A group of MPs and peers wants the Court of Session in Edinburgh to rule that suspending parliament to make the UK leave the EU without a deal is "unlawful and unconstitutional".
The prime minister has repeatedly refused to rule out such a move.
Lord Doherty agreed to hear arguments from both sides in September.
However he refused to accelerate the case through the Scottish courts, with the petitioners voicing fears that they may run out of time before the UK is due to leave the EU on 31 October.
The start of the legal action came as it emerged the UK government expects a group of MPs to try to block a no-deal Brexit by attempting to pass legislation when Parliament returns next month.
A No 10 source said they expected the challenge to come in the second week of September, when MPs are due to debate a report on Northern Ireland.
The source assumes the EU will wait until after that date before engaging in further negotiations.
More than 70 politicians have put their names behind the move, including Lib Dem leader Jo Swinson and SNP MP Joanna Cherry.
A challenge brought by the same group of anti-Brexit politicians last year saw the European Court of Justice rule the UK can cancel Brexit without the permission of the other 27 EU members.
Jolyon Maugham QC, director of the Good Law Project which is supporting the latest challenge, said: "A man with no mandate seeks to cancel parliament for fear it will stop him inflicting on an unwilling public an outcome they did not vote for and do not want.
"That's certainly not democracy and I expect our courts to say it's not the law."
The UK is currently due to leave the EU on 31 October, with the prime minister pledging that Brexit will definitely happen on that day regardless of whether or not a deal has been agreed with the EU.
Most MPs at Westminster are opposed to a no-deal Brexit, and there has been speculation that Mr Johnson could try to get around this by closing parliament in the run-up to 31 October.
This is known as proroguing, and would require the permission of the Queen.
Mr Johnson argued during the Conservative leadership contest that he would not "take anything off the table", saying it would be "absolutely bizarre" for the UK to "weaken its own position" in negotiations with European leaders.
But the group of pro-Remain politicians involved in the legal action at Scotland's highest court argue that shutting down parliament in this manner would be unlawful.
The case is beginning in the Scottish courts because they sit through the summer, unlike their English counterparts.
During a procedural hearing in Edinburgh, lawyers argued that the case could ultimately be decided in the UK Supreme Court - but only after it has moved through the Scottish system.
Lord Doherty refused a motion from the petitioners to skip the first step of this, saying arguments must be heard in the outer house of the Court of Session before they proceed to the next stage, the inner house.
However he did agree to move swiftly, fixing a full hearing for 6 September.
The Commons Speaker John Bercow has said the idea of the parliamentary session ending in order to force through a no-deal Brexit is "simply not going to happen" and that that was "so blindingly obvious it almost doesn't need to be stated".
One of the petitioners, Edinburgh South Labour MP Ian Murray, said: "When Boris Johnson unveiled his vacuous slogan 'taking back control', voters weren't told that this could mean shutting down parliament.
"The prime minister's undemocratic proposal to hold Westminster in contempt simply can't go unchallenged."

"Waited 12 months for that", the prime minister's chief of staff, Gavin Barwell, has just tweeted.
That's both a compliment to his boss, and a revelation perhaps too.
With the complexities of Brexit, the divisions in her party, the calamity of last year's conference speech, the antics of the former foreign secretary, and of course, her own fragilities, Theresa May has struggled to find her voice - and that's got nothing to do with running out of Strepsils.
Well today she found it, and in the words of one of her cabinet colleagues, not a particularly close ally, "she found her mojo".
From the moment she danced on to the stage - who would have thought we'd ever see that - she looked comfortable in her own skin, actually happy to be there.
It sounds strange, but it is so rare to see her overtly enjoying her job.
On so many occasions the public has seen a politician who seems constricted, conflicted, and ill-at-ease. For voters, frankly, if she doesn't look like she is enjoying being prime minister, why should any of us be happy about the fact she's doing it.
Beyond the vital dynamics of the hall, there was a consistent message - this was May the moderate of summer 2016, not May the leader cleaving to one side of her party, the Eurosceptics who have the power to unseat her. A message to her party and the country that in a time of some anxiety, huge uncertainty, and toxic politics, she'll chart a middle course.
There was a big claim that austerity was over. Given that Chancellor Philip Hammond has not got extra cash to throw around and is already looking to raise tax for the NHS, that was a bold claim that may come to haunt the government.
And a direct appeal to Labour voters, and indeed Labour MPs, who may be uncomfortable with the direction of Jeremy Corbyn's travel. Overtly centre-ground stuff, a pitch for an era after Brexit when, perhaps, perhaps, the tensions and bitterness of the last couple of years could fade. That is a big if.
This was a total contrast to last year's disaster. A good outing on the platform doesn't make any of Mrs May's enormous dilemmas disappear. Nor will it magic away the concerns and criticisms of her handling of Brexit.
There are restive forces in her party. She has no majority in Parliament. The Conservatives have huge questions they can't answer about who they are and what they are for.
The fact remains, many of her colleagues simply can't see her taking them into the next election. But Theresa May looks today less like a leader at the total mercy of events, more like a prime minister who knows what she wants and might, just might, have an idea how to get there.

Multiple cabinet ministers expressed significant doubts about the prime minister's preferred Brexit plan from the start, the BBC has learned.
Parts of Theresa May's plan were described as "worrying", "disappointing" and "concerning" by members of her top team back in July.
Mrs May is struggling to broker an agreement on Brexit with ministers.
Two ministers have told the BBC they believe there is little chance the deal would get Parliament's backing.
One of them said it was "self-harming" for the PM to keep pursuing the same strategy.
Mrs May is trying to arrange an agreement in cabinet on the current negotiations in time for a hoped-for summit in Brussels later this month.
Her preferred plan for future relations with the EU after Brexit were agreed at Chequers - the prime minister's country retreat - in July, in a marathon cabinet meeting lasting nearly 12 hours.
Afterwards, Mrs May said the cabinet had reached a "collective" agreement, although former Brexit secretary David Davis and ex-foreign secretary Boris Johnson resigned from the Cabinet in protest at the plans 48 hours later.
And, according to the BBC's political editor Laura Kuenssberg, cabinet sources have now revealed there were widespread doubts about various aspects from many other ministers from the start, including from some former Remain supporters.
For many of those present, she said that the Chequers deal was an undesirable compromise, rather than a set of proposals to which they were signing up with enthusiasm.
One cabinet minister said the group endorsed the proposal "with a very heavy heart".
Trade Secretary Liam Fox expressed strong doubts about elements of the plan for trading arrangements as they could harm the ability of the UK to do trade deals after Brexit.
Home Secretary Sajid Javid, who backed Remain, is understood to have had some similar views, describing the proposal for a common rule book with the EU for parts of the economy as "very worrying" and suggesting that there should be a review of the arrangements after five years.
The leader of the House of Lords, Baroness Evans, is understood to have agreed, telling her colleagues that she found it difficult to accept some aspects of the proposals, and might struggle to explain them in Parliament.
Penny Mordaunt and Esther McVey - Brexiteers who have both been reluctant to give public support for the plan - are said to have expressed significant unhappiness and questioned whether Brexiteer MPs would be able to support such a deal in Parliament.
Meanwhile, Transport Secretary Chris Grayling is said to have warned his colleagues that as many as 40 Eurosceptic MPs might "go on strike".
Sources close to him would not confirm that, but said he had been "extremely cautious from the start" about the Chequers proposal.
And as has previously emerged, the leader of the Commons, Andrea Leadsom, said that she "hated" the proposals and called on the prime minister to treat those who had voted for Brexit with respect.
Chancellor Philip Hammond told his colleagues that the government was living on "borrowed time" because some businesses were hesitating over whether to invest in the UK.
He argued for the Chequers approach to bring clarity as soon as possible. But he is understood to have questioned whether such a deal could actually be achieved, warning that the UK would have to persuade EU member states to defy the European Commission which is running the negotiation.
And the Defence Secretary, Gavin Williamson - also a former Remainer - said there were many concerns with the paper and it must be made clear it was as far as the government would be willing to compromise.
Several ministers on both sides of the argument are understood to have called on the prime minister to be honest with the public about the shift in position towards a closer arrangement with the EU.
Mrs May is trying to arrange an agreement in cabinet on the current negotiations in time for a hoped-for summit in Brussels later this month.
A Number 10 spokesman said: "Everyone has to move a little to get a deal that works for everyone on both sides of the argument."
But Shadow Brexit Secretary Sir Keir Starmer said it appeared Mrs May had proceeded without the "solid backing" of her cabinet, having also declined to get Parliament's support for her negotiating objectives.
Sir Keir also said the option of a fresh referendum was still "on the table", despite Labour's leader Jeremy Corbyn saying at the weekend that Brexit could not be stopped.
In his column for the Daily Telegraph on Monday, Boris Johnson called the prime minister's deal "a recipe for continued strife, both in the Tory Party and the country".
And former cabinet minister John Whittingdale cast doubt on whether Mrs May could stay in office if Parliament rejected any deal she reached with the EU.
"I think if the PM's Brexit plan doesn't get through Parliament, I think it's quite difficult to see how the prime minister can continue because she has staked her credibility," he told BBC Radio 4's Westminster Hour.

Often the hype about a political event is in inverse proportion to the drama of what actually comes to pass. Maybe not this time.
Cabinet ministers will today meet at Chequers with the aim of approving the prime minister's blueprint for the UK's future relationship with the EU after Brexit.
But Brexiteer ministers have warned that the 120-page plan as written is flawed. They were discussing late on Thursday how to respond during the cabinet meeting.
And to say that they are a bit miffed with the plan, which they only received in its entirety on Thursday afternoon, is an understatement. There is plenty in there that they don't like, and it's easy to see why.
The BBC understands that the plan includes:
The paper also suggests that, while trade deals with other countries like the US would be possible, they might be harder to do because under rules agreed with the EU, it would be harder to meet other countries' "asks".
One cabinet minister also expressed unhappiness with the proposed customs model - the facilitated customs arrangement - saying that it was like "customs partnership minus" - simply a revision of the customs partnership model that was rejected by the inner Brexit cabinet committee weeks ago.
One senior Tory suggested that "the party wouldn't wear it". A senior Brexiteer minister said that a lot of the document was "problematic", and that there was a "lot of scope for argument".
Essentially, for those who want a dramatic break with the EU, it falls far short, even though Number 10 insists it is merely an evolution of what the prime minister has already promised.
Frankly, from what we have heard, language is doing a lot of the heavy lifting, with much of it "opaque".
It does sketch out a relationship with the EU that is much tighter than Brexiteers had argued for. Would it really be Brexit? Number 10 would say yes, Jacob Rees Mogg would say no.
For the rest of us? That depends what you think the country voted for.
Tension around the meeting is high, with ministers being instructed in an email that they will have to hand in their phones and Apple watches on arrival at Chequers.
Brexiteer ministers shared concerns at a meeting in the foreign secretary's office on Thursday night over the plan, with a source saying "it's not going to fly".
They said that they will "simply reject it if she tries formally to impose it". But another Brexiteer source said they would have to "talk it out" before coming to any conclusions about the plan.
But a cabinet minister who has been pushing for a tight relationship with the EU told the BBC that while the plan was "fiendishly complicated... no one had a better idea".
A former cabinet minister who advocates closer ties to the EU told the BBC that they had urged the prime minister to consider sacking Brexiteers who refuse to sign up.
They suggested that "blood on the carpet" might not be a bad thing. They said they believed the prime minister "has had enough steel put in her spine" to be able to command ministers to back her plan or carry out a reshuffle.
There is however concern in the City, too, over the suggestion of giving up the prospect of a close deal on services to guarantee an end to free movement. One insider suggested that Chancellor Philip Hammond may try to "wedge" services back into the draft agreement on Friday.
Sources on all sides of the argument suggest that it is too early to tell how the talks tomorrow will end. There are demands for "significant redrafting". The discussions start at around 10:00 BST and are expected to wrap up at about 22:00 BST.
Insiders also suggest that with the EU likely to reject much of the plan, the real debate will focus on what to do if and when Brussels says no, with Brexiteers pushing a "Canada plus" model.
Another cabinet minister told the BBC that even though the EU was unlikely to accept it straight off, the point of this week's talks was not to find a final agreement, but simply to "start a conversation" with Brussels so that vital talks on the future relationship can get going.
Until now, the negotiations have focused on the withdrawal agreement - the divorce deal - with no formal engagements over the long-term arrangements. An outline of the political agreement on that deal is supposed to be in place by October.
To have any hope of a genuine and substantial deal by the autumn, the prime minister needs Brussels to take her, and her approach, seriously. If she fails to get agreement, her ability to project the authority that's needed for that to happen will be seriously put into question.
But if she pushes ahead with the plan she will have to face down a powerful and vocal wing in her party.
Some of her colleagues might heave a huge sigh of relief, and think, "about time too". But her party, and the rest of us, have no way of knowing tonight if that decision - which would risk her leadership - is one she is really willing to take.

Theresa May has called for discussions about future NHS funding to remain private after Boris Johnson publicly called for more money after Brexit.
Before Tuesday's cabinet meeting, it was widely reported that the foreign secretary would pitch for a £100m a week "Brexit dividend" for the NHS.
The BBC understands he did not end up mentioning "specific figures".
No 10 said Mrs May chaired a discussion on post-Brexit funding options but made clear conversations should be private.
The BBC's political editor Laura Kuenssberg said the PM's remarks on the need for confidentiality were "pointed".
However, she said Mr Johnson was backed by some colleagues while the principle that the NHS would get some of the money which will become available after the UK leaves in March 2019 was agreed.
In the run-up to Tuesday's cabinet meeting - in which Health Secretary Jeremy Hunt gave an update on the "significant" winter pressures" facing the NHS - it was reported that Mr Johnson wanted to kick start a wider debate about NHS funding.
In a highly unusual move, sources told the BBC Mr Johnson would not only call for a £5bn annual injection of funding after Brexit but warn his party against "abandoning the territory" to Labour, which vowed at last year's election to spend £37bn more over the next five years.
If you can't see the NHS Tracker, click or tap here.
A source close to Mr Johnson said he was frustrated at what he perceived as Downing Street's lack of action on the issue given the levels of public anxiety about how the NHS is faring.
During the referendum campaign, Vote Leave - of which Mr Johnson was a leading supporter - claimed £350m went to the EU each week and money could instead go to the NHS, a claim he has repeatedly defended since.
However, when it came to it, the BBC's assistant political editor Norman Smith said neither Mr Johnson nor any other minister raised a specific figure during what No 10 said was a "wide ranging" hour-long discussion.
Firmly, in one sense.
A No 10 spokesman said the prime minister and "a large number of Cabinet ministers" had made clear that their discussions should take place in private.
On the broader political point, Downing Street said the PM reminded ministers that the government has repeatedly said contributions to the EU budget which end after Brexit would be able to be spent on domestic priorities including the NHS.
"There will also be other calls upon that money but we will discuss those priorities at that time," a spokesman said.
In a further rebuff to Mr Johnson, Chancellor Philip Hammond said he had given the NHS an extra £6bn in November's Budget, including £2.8bn to be spent over the next two years,
Mr Hammond, who was in Brussels for a meeting of EU finance ministers, told reporters Mr Johnson was "the foreign secretary" not health secretary and the right time to revisit the long-term issue of NHS spending was at the next departmental spending review expected early next year.
No, far from it. The BBC understands that Chris Grayling and Michael Gove were among other cabinet ministers to rally round Mr Johnson at Tuesday's meeting.
Growing numbers of Tory MPs are openly expressing their frustration with what they say is No 10's unwillingness to confront the long-term financial challenges facing the health service.
Conservative MP Mark Pritchard told the BBC News Channel the foreign secretary was right to speak out.
"I support Boris, he's right. But I think whether it's Boris or Theresa May or Jeremy Hunt, in the longer term there needs to be political leadership about how we fund the NHS going forward in the twenty-first century."
As for Jeremy Hunt, he said no health secretary would "not support potential extra resources" for the NHS.
Asked how he felt about Mr Johnson being the one to make the case, he said there was "a Brexit debate and an NHS debate and just occasionally these two debates come together".
Labour's shadow health secretary Jonathan Ashworth said he welcomed calls for more funding but accused Mr Johnson of seeking to "weaponise" the NHS for his own "tedious political games".
"If the government was really serious about putting money into the NHS, they would have done it in the Budget last autumn," he told the BBC's Victoria Derbyshire show. "We did not hear a peep from him then."
The Institute for Fiscal Studies - a think tank - has said the UK will almost certainly have to increase the share of income devoted to health funding to deal with demographic challenges.
Its director Paul Johnson said "that will mean higher taxes" and "governments will need to explain that honestly".
Lib Dem leader Vince Cable suggested Mr Johnson and his colleagues begin this process now.

The future relationship between the UK and the EU will not be negotiated within two years, says the former head of the Foreign Office.
Separation talks could be completed within the two year deadline set out in Article 50, but a future relationship would take longer to negotiate, Sir Simon Fraser told BBC Newsnight.
Sir Simon said "transitional arrangements" would be necessary.
Prime Minister Theresa May will invoke Article 50 on Wednesday.
"It's certain that we won't have resolved everything in the period before the expiry of the Article 50 process," Sir Simon Fraser told BBC Newsnight.
"The EU side want to start with negotiating the terms of the separation... And the British side, on top of that, wants to move rapidly to discuss the future relationship - both political and economic - between Britain and the EU. And that is a very complex second set of negotiations."
Because of the difficulty of defining the future relationship, Sir Simon, who held senior posts in Brussels and Whitehall before becoming the head of the diplomatic service, believes talks will soon shift to the nature of 'transitional arrangements'. This means vital questions about how the UK does business with the EU could be left unresolved far beyond 2019.
Many Brexit supporters had hoped informal negotiations with the EU could start before the Article 50 clock begins ticking this week. Negotiations are limited to two years.
But Sir Simon said the European Commission has thwarted such plans: "There has been a very disciplined position across the EU, and I don't think that there has been a lot of informal behind the scenes discussion of the agenda or of the key issues yet."
Sir Simon is also sceptical that the UK will be able to play off different countries among the EU's 27 countries.
"The UK has got to negotiate with the EU as a whole through the EU's appointed negotiator, which will be essentially led by the Commission."
He added: "I think it would be a mistake to try divide and rule because I don't think that that will work."
While Article 50 allows up to two years to reach an agreement, the EU's chief negotiator, Michel Barnier, has said he wants the outline of a deal to be ready by autumn 2018, in the hope that it can then go before the European Parliament for ratification and member states for agreement well before the deadline is up.
But many diplomats, Sir Simon Fraser among them, believe that there will be no serious political discussions before this autumn, following the German elections.
While Brexit dominates national debate in the UK, it is a secondary issue for many European governments.
This could lead to delays in negotiations with many governments not taking positions until they have to. Combined with the complexity of the Brexit discussions, many diplomats believe that the UK could find itself close to a "cliff edge" without final agreement.
Sir Simon said while it was in the interest of both sides to avoid such a scenario, there was a "risk of political ill will and turbulence - both political and economic" if a deal is not reached within the Article 50 timeframe.
It is for this reason that Mr Barnier may want to make transitional arrangements dependent on a resolution of one of the first items on the EU's divorce agenda: getting the UK to agree to paying a bill of tens of billions into the Commission's coffers.
Mark Urban is diplomatic and defence editor for BBC Newsnight

Home Secretary Amber Rudd has appeared to cast doubt on the government's policy of not being in a customs union with the EU after Brexit.
She told journalists she would not be "drawn" on the issue and said there were discussions to be had about it in cabinet to agree a "final position".
Later she tweeted that she "should have been clearer" but had not wanted to get into "ongoing cabinet discussions".
The PM Theresa May has ruled out being in an EU customs union after Brexit.
The comments came on the day Ms Rudd faced fresh calls to resign over her handling of the Windrush scandal, which has seen relatives of people from Caribbean countries who settled in the UK decades ago being declared illegal immigrants, if they could not prove they had lived continuously in the UK.
She was forced to admit in the House of Commons that immigration removal targets had existed, a day after telling a committee of MPs that there weren't any.
But the issue of whether or not the UK would be in a customs union after Brexit came up as she addressed a lunch for parliamentary journalists
She replied: "I'm not going to be drawn on that. We still have a few discussions to be had in a really positive, consensual and easy way among some of my cabinet colleagues in order to arrive at a final position."
Labour's Sir Keir Starmer said: "Amber Rudd appears to have let slip that discussions around the cabinet table about negotiating a customs union with the EU have not in fact concluded.
"If that is so, then the prime minister should rethink her approach and listen to the growing chorus of voices in Parliament and in the businesses community that believe she has got it wrong on a customs union."
And Tory backbencher Peter Bone tweeted:
Ms Rudd later tweeted a clarification:
The prime minister is under pressure from both sides of the EU debate on the issue of the customs union, which allows for goods to be transported tariff-free between EU member states.
The Financial Times reports that Mrs May is expected to try to secure agreement on an alternative to the customs union, in a Brexit cabinet committee meeting next week.
Ministers were defeated on the issue in the House of Lords last week and the government faces key votes in the Commons next month.
On Thursday, the prime minister's spokesman said: "The government is clear we are leaving the customs union and not joining a customs union."
Brexiteers have criticised a suggested "customs partnership" to replace the current arrangements, while pro-EU campaigners say a customs union is the only way to prevent a hard border in Northern Ireland.
MPs debated a non-binding motion on Thursday calling on the government to include in its negotiating objectives with the EU "the establishment of an effective customs union between the two territories".
With few pro-Brexit MPs attending the debate, the motion was approved without a vote, prompting Labour's Chris Leslie to suggest it "was now the default consensus view of this House" and said the government should respond.
Crunch votes are expected next month when Remain-supporting MPs will push for a change of course.
A customs union is when countries agree to apply the same taxes on imports to goods from outside the union.
This means when goods have cleared customs in one country, they can be shipped to others in the union without further tariffs being imposed.
If the UK remains part of the customs union, it would be unable to strike trade deals with countries around the world, but supporters say it would help keep an open border between Ireland and Northern Ireland.
During the debate, Labour's Yvette Cooper said the UK exported more than £230bn of goods and services to the EU every year and warned that to "rip up" existing trade arrangements would be "deeply damaging".
She argued that existing trade deals should be "cherished" as it was becoming harder to negotiate new ones "as communities across different individual countries become more worried about both the losers and the winners of big changes to trade arrangements".
Pro-European Conservative Ken Clarke told MPs: "You will damage the economy of this country... if you suddenly decide to erect new barriers at the border between the UK and our major trading partners."
And former Conservative cabinet minister Nicky Morgan warned: "If we undermine and ignore the evidence for peace in Northern Ireland, and we undermine the business and financial security of the people in this country, we will not be forgiven for a generation."
Labour MP Kate Hoey, one of the few Brexiteers at the debate, said she felt "alone" in the chamber: "There are a lot of people here today who are using the issue of the customs union to start the process again of wanting to stay in the European Union."
She argued that if the UK stayed in the customs union, it would be a "transition" to remaining, and would not allow Britain to "take back control" of its trade.
Labour leader Jeremy Corbyn has backed a customs union, but only if the UK had a say in future EU trade deals.
Mrs May has ruled out joining a customs union but has come up with two options to avoid a hard border in Ireland.
One of them is a "customs partnership" that would involve the UK collecting the EU's tariffs on goods coming from other countries on the EU's behalf.
If those goods didn't leave the UK and UK tariffs were lower, companies could then claim back the difference.
This option has been heavily criticised by some Brexiteers, with influential backbench Tory MP Jacob Rees-Mogg branding it "completely cretinous".
The other option being proposed by the government would be to minimise checks rather than getting rid of them altogether, by using new technologies and putting in place a trusted trader scheme.

Boris Johnson has warned EU leaders not to give the UK "punishment beatings" for Brexit "in the manner of some World War Two movie".
The foreign secretary said penalising "escape" was "not in the interests of our friends and our partners".
PM Theresa May set out her Brexit strategy, including leaving the EU single market, in a speech on Tuesday.
European Commission President Jean-Claude Juncker promised to work for "good results" from Brexit talks.
Meanwhile, the Supreme Court has announced it will give its verdict next Tuesday on the government's legal battle over whether MPs must be consulted before Brexit is triggered.
And HSBC announced it was preparing to move 1,000 staff from London to Paris when the UK leaves the EU.
At Prime Minister's Questions, Mrs May clashed with Labour leader Jeremy Corbyn, telling him she had a "plan" and he did not "have a clue".
Mr Corbyn accused her of "threatening to turn Britain into an offshore tax haven".
With just over two months to go before the UK government is due to get Brexit talks under way, Mr Johnson was asked on a trip to India about comments by an aide to French President Francois Hollande, who said the UK should not expect a better trading relationship with the EU after leaving it.
He replied: "If Monsieur Hollande wants to administer punishment beatings to anybody who chooses to escape, rather in the manner of some World War Two movie, then I don't think that is the way forward.
"I think, actually, it's not in the interests of our friends and our partners."
Downing Street later said Mr Johnson "was not in any way suggesting anyone was a Nazi".
The spokeswoman said the remarks were "all being hyped up" and that the foreign secretary had used a "theatrical comparison", adding: "There is not a government policy of not talking about the War."
But a Labour spokesman said: "The foreign secretary has a habit of making wild and inappropriate comments. Talking about World War Two in that context is another one of those and not something that's going to improve the climate for negotiations."
Former cabinet minister and Brexit campaigner Michael Gove hit back, tweeting that people offended by Mr Johnson's "witty metaphor" were "humourless, deliberately obtuse, snowflakes".
EU leaders have begun to deliver their verdicts on Mrs May's speech, in which she also warned against trying to "punish" the UK for Brexit and hinted she could walk away from talks if not happy, stating that "no deal for Britain is better than a bad deal for Britain".
German Chancellor Angela Merkel said: "The be-all and end-all is that Europe does not let itself be divided, and we will ensure that with very intensive contacts.'' EU governments would consult their business sectors, she added, and she was "not worried that we will not stick together".
Mr Juncker said he would work to ensure Brexit talks are carried out "according to the rules and they yield good results".
He added: "I welcome the clarifications given by Mrs May, but I said to her last night that a speech will not launch the negotiations."
Analysis - By James Landale, BBC diplomatic correspondent
Not surprisingly, uproar has ensued.
Former Labour leader Ed Miliband said Boris Johnson had shown once again that he could be "supremely clever and yet immensely stupid".
To some Britons, Mr Johnson's remarks will be seen as colourful but unexceptional language that echoes the popular World War Two film The Great Escape.
To many of Mr Johnson's generation, these films were part of their childhood and are subject to frequent cultural reference. Former Prime Minister David Cameron has seen The Guns of Navarone more than 17 times and once quoted a line from the film in a party conference speech.
Read James's blog in full
Guy Verhofstadt, the European Parliament's lead Brexit negotiator, said: "You can say, 'I want to leave the European Union, I want to leave the judicial courts, I want to leave the customs union.'
"But you cannot at the same time then say, 'Oh, and that little piece that interests me, and that is something that I like.' No way."
However, European Council President Donald Tusk was more conciliatory, tweeting: "We took note of Prime Minister May's warm, balanced words on European integration. Much closer to narrative of Churchill than President-elect Trump."
Downing Street said European leaders spoken to by Mrs May in a series of phone calls had welcomed the "clarity" of her plans.
In its headline, the Times sums up the prime minister's message to the EU as "Give us a fair deal or you'll be crushed".
Meanwhile, the Brexit-supporting Daily Mail draws parallels with Margaret Thatcher, saying Mrs May exhibited the "steel of the new Iron Lady".
The Guardian, which opposed Brexit in the referendum, found the speech a "doubly depressing event" - a reality check for those who want to keep the UK in the single market while being riddled with its own streak of "global fantasy".
The Financial Times praises the prime minister's "bold vision" but warns that the road ahead will be perilous.
The Sun's front page is mocked up as a Biblical tablet of stone bearing the single-word headline "Brexodus".
Read The Papers in full
In her speech, the prime minister suggested the UK could cut its corporate tax rates to compete with the EU if denied access to the single market.
And she promised that Parliament would get to vote on the final Brexit deal.
Asked what would happen if MPs and peers rejected it, Brexit Secretary David Davis told Today: "They won't vote it down. This negotiation will succeed. It will succeed."
The government says it will invoke Article 50 of the Lisbon Treaty, getting formal Brexit talks with the EU under way, by the end of March, with discussions set to last up to two years after that.
A "catalogue of demands with some threats thrown in" is German news magazine Der Spiegel's description of Theresa May's Brexit speech. It says that her desire to leave the single market while retaining access to trade with Europe shows that her government is "not just nasty but also blind to reality".
Germany's Die Welt also mocks her with the headline "Little Britain" and accuses her of leading the country into "isolation".
In Italy, La Repubblica's front page reads "Brexit: London raises its wall 'away from the EU and the single market'".
France's Liberation remarks that Mrs May's comment that no deal is better than a bad one suggests that she is threatening to turn Britain into a tax haven. "If this is not blackmail, it looks a lot like it," it says.
At Prime Minister's Questions, Mr Corbyn urged Mrs May to "stop her threat of a bargain basement Brexit, a low-paid tax haven on the shores of Europe".
He added: "It won't necessarily damage the EU but it would certainly damage this country."
Mrs May told MPs:  "What I set out yesterday was a plan for a global Britain, bringing prosperity to this country and jobs to people and spreading economic growth across this country."
UKIP leader Paul Nuttall said: "It's clear that Britain is going global, as a result of that momentous [EU referendum] vote on 23 June."

The EU Commission President, Jean-Claude Juncker, has urged Belgium to grant citizenship to British EU staff worried about their post-Brexit status.
About 1,100 UK citizens work for the EU in Brussels and Luxembourg.
Mr Juncker called Belgium a kind host and asked its prime minister, Charles Michel, to "show the same generosity when it comes to granting Belgian citizenship" to British EU staff.
When the UK leaves the EU next March Britons will lose their EU citizenship.
The UK and EU have already pledged to protect citizens' rights after Brexit, but that does not mean granting nationality.
Article 49 of the EU staff rules states that "an official may be required to resign" if he or she loses their EU citizenship and is no longer a national of an EU member state.
Many British EU staff are longstanding residents with families.
An internal EU Commission document quoted by Politico news last month said Article 49 would not mean British staff losing their EU jobs, apart from cases involving "conflicts of interest or international obligations".
Responding to Mr Juncker's plea during a European Parliament debate, Mr Michel said Belgium's citizenship law in the context of Brexit was "contradictory", but he did not specify the difficulties.
"The government is examining the judicial possibilities on this question, which affects a number of people who have been living in our country for a long time," he said.
European Commission spokesman Margaritis Schinas said later that Mr Juncker's remarks were meant as a reminder for the Belgian leader. "We live up to the promise that our colleagues of British nationality should be given maximum guarantees to stay, not only with their employment but also if they want to stay as Belgian citizens. But this is entirely in the hands of the Belgian government, not ours," he said.
EU citizenship is described in Article 20 of the Treaty on the Functioning of the European Union and includes the rights to:
Michael Ashbrook of Solidarity, Independence, Democracy (SID), a trade union representing EU staff, told the BBC that "all the British staff are trying for EU citizenship". "They are very worried", he said, referring to the impact of Brexit on their jobs.
"There has been talk of dismissing British 'contract agents' on Brexit day, rather than letting them complete their fixed-term contracts," he said.
Resolving the status of British staff, to keep them in their jobs, would take the Commission "just a few minutes", he said.
Brexit sets a legal precedent for the EU and raises a host of new legal challenges, because no state has left the 28-nation bloc before.
In the debate the Belgian leader clashed with UKIP's Nigel Farage, an anti-EU MEP.
"Belgium is not a nation; it's an artificial creation," Mr Farage said. The Dutch- and French-speaking parts of Belgium "dislike each other intensely", he alleged.
Mr Michel replied ironically: "I'm happy to hear this sound advice from Nigel Farage on the future of Belgium. He has been busy with the future of Britain, with Brexit - and we can see where Britain has got to with that."
To qualify for Belgian citizenship, an applicant must have lived in Belgium for at least five years legally and passed a language test.
Luxembourg requires at least five years' residence and competence in Luxembourgish, a language with only about 390,000 native speakers.

Businesses will not have to carry out new checks on EU staff in the event of a no-deal Brexit, the government says.
"Employers will not be expected to differentiate between resident EU citizens and those arriving after exit," the Home Office said.
On Tuesday, minister Caroline Nokes said employers would have to carry out "rigorous checks" on EU staff who arrived after March 2019.
Labour accused her of misleading Parliament.
Shadow immigration minister Afzal Khan suggested Ms Nokes lacked "even the most basic level of understanding and knowledge" of her own immigration policy and demanded she "come to Parliament to set the record straight".
The government insists EU free movement will end in March 2019, the scheduled date for the UK's departure from the EU.
But in practice, EU nationals will still be able to come and work in the UK, until the end of the planned 21-month "transition period". The only difference is that they will have to register with the authorities.
Ms Nokes was questioned at length on Tuesday about what would happen if there was no "transition period" - because the UK leaves the EU without having agreed a withdrawal deal - and whether employers would be expected to check if potential staff had the right to work in the UK.
Committee chair Yvette Cooper asked how an employer could be expected to differentiate between someone who had arrived in the UK after Brexit - and an EU citizen who had been a long term resident and had the right to work, but had not yet applied for "settled status".
Ms Nokes admitted it would be "almost impossible for an employer to differentiate between a new arrival and somebody who has been here for 10 years and has simply not yet been through the scheme".
But she said: "If somebody has been through the settled status scheme, they will be able to evidence that. If somebody has not been here prior to the end of March next year, then employers will have to make sure that they go through adequately rigorous checks to evidence somebody's right to work."
Her remarks were met with "deep concern" from the Federation of Small Businesses, whose chairman Mike Cherry said:  "The reality is that many of these businesses wouldn't have the first idea of where, or how, to check whether or not their EU staff have the right to work here."
The 3million, which campaigns for the rights of EU citizens in the UK, reported that the Home Office had emailed to confirm current checks "will not change next March in the event we leave the EU without a deal".
And that "EU citizens will continue to be able to evidence their right to work by showing a passport or national identity card." Employers would not be expected to differentiate between "resident EU citizens and those arriving after exit".
On Friday, the Home Office confirmed that statement and added: "We will protect EU citizens' rights when we leave the EU, in both a deal or no deal scenario.
"We are considering a number of options for the unlikely event that we reach March 2019 without a deal, and will set out more information shortly."
Under current rules, employers must carry out "right to work" checks on new staff.
For British citizens, this means providing a passport or birth certificate and a National Insurance number while EU citizens must provide their passport or ID card and people from outside the EU must provide their biometric residence permit.

We all know what it's like - having to play nice with the person you don't have very much in common with, because it's the right thing to do.
Knowing that lots of people you DO like would be upset if you don't put on a show.
Well, how about this: having to "play nice" publicly with a person you don't have very much in common with, when they have said that the way you are trying to do your job doesn't really work.
Add in the embarrassment if they happen to be the leader of the free world.
From the moment of his election, Donald Trump was an awkward friend for Theresa May.
He runs towards a fight. She does everything in public to avoid one.
Well, just before they were due to appear alongside each other on UK soil he publicly, and at length, gave a "both barrels" verdict on her most important policy.
Her approach to Brexit has been to slowly, gently, incrementally, carry the Ming vase across one side of the room to another on a slippery floor.
To talk about being pragmatic, to smooth over the contradictions, to do whatever it takes to get to the other side, without smashing that vase (her party and the country) to bits.
In walks President Trump, to call out one of the claims that No 10 has been making of late - in essence, smashing the vase to bits.
In an interview with The Sun, he shoots down the chances of a trade deal with the US if she sticks to her carefully crafted compromise Brexit plan.
That matters because the government has been clinging to the idea of trade deals with countries outside the EU as one of the benefits of Brexit, and claiming that the choice in the Chequers deal to stay close to the EU doesn't exclude those opportunities.
This isn't about what side anyone was on in the referendum. In fact, Remainers and Leavers unite in saying the Chequers deal can't live up to all it claims.
For former Remainers, it's nuts to think that trade deals with non-EU countries can ever make up for what might be lost.
For some Leavers, it's nuts to claim we can make the most of the world outside if we are still sticking to EU rules.
And President Trump drives a bulldozer through the government's central claims about its compromise - that the UK would be able to get decent trade deals with the wider world, while sticking to the EU rules.
A lot of this visit has been carefully choreographed, as the prime minister and the president dance around each other.
But if the president really wanted to help her build support for her controversial compromise, this isn't the way to do it.

The UK would be welcome to stay in the EU if it changed its mind about Brexit, Donald Tusk has suggested.
The European Council President told MEPs that the UK would leave the bloc unless it had a "change of heart".
"We haven't had a change of heart. Our hearts are still open for you."
The comments were welcomed by MPs who want a referendum on the final Brexit deal but Environment Secretary Michael Gove said the British public had voted in record numbers to leave the EU.
"We have a great future outside the European Union and we should be embracing that," he said.
The government has said there will be no second vote ahead of the UK's exit in March 2019.
Labour leader Jeremy Corbyn has also dismissed the idea while insisting that MPs have a "meaningful vote" in Parliament on the terms of the withdrawal agreement.
Former UKIP leader Nigel Farage has said the prospect of a second vote cannot be ruled out, although he was confident it would return a larger margin for Leave than in 2016 - when 17.4 million people voted for Brexit.
The EU, he told BBC World Service, was intent on "putting something on the table so unattractive to Britain that Parliament will vote for us to have a second referendum".
As it stands, the UK is due to leave the EU in March 2019.
The two sides reached a deal on so-called "divorce issues", including money and citizens' rights, in December and talks are now moving onto transitional arrangements and future co-operation.
Revised draft EU guidelines obtained by several UK newspapers suggest the EU is toughening its stance on what changes the UK can make on immigration, trade and fishing during a roughly two year transition period.
Speaking in the European Parliament in Strasbourg, Mr Tusk said he believed the other 27 EU members would maintain their unity when the talks resumed in March.
"The hardest work is still ahead of us, and time is limited," he said.
"If the UK government sticks to its decision to leave, Brexit will become a reality - with all its negative consequences - in March next year. Unless there is a change of heart among our British friends.
"Wasn't it David Davis himself who said 'if a democracy cannot change its mind, it ceases to be a democracy'.
"We, here on the continent, haven't had a change of heart. Our hearts are still open to you."
Former Lib Dem leader Nick Clegg, who has said Parliament should have the power to reject any deal reached and force ministers back to the negotiating table, welcomed Mr Tusk's remarks.
Labour MP Daniel Zeichner, a supporter of the Best for Britain group, which was launched last year by pro-EU campaigner Gina Miller, said the option to remain in the EU must be kept open.
"We are stronger together, and it becomes increasingly clear that the current path is extremely damaging," he said.
But Leave Means Leave, which grew out of the Vote Leave campaign during the 2016 referendum, said Brussels had a history of not listening to the views of voters.
"Donald Tusk and Jean-Claude Juncker need to accept that Britain is a democracy - something the EU knows very little about," said its co-chair Richard Tice.
"The British people voted to leave the EU and this decision will not be reversed, despite their best efforts."
Mr Tusk's sentiments were also dismissed by prominent Brexiteers in the European Parliament.

David Davis has hit out at the EU over its decision to exclude the UK from the Galileo satellite navigation system.
The Brexit secretary accused the European Commission of "shooting itself in the foot just to prove that the gun works".
He said throwing the UK out of Galileo would delay it by three years and cost the EU £1bn more.
The UK has played a major role in developing satellites for Galileo, an alternative to the US GPS system.
But Brussels has cited legal issues about sharing sensitive information with a non-member state for its decision to shut British firms out of the project. Brussels has also said it will restrict access to encrypted signals from Galileo.
The move has sparked a furious reaction from the UK government, which is demanding £1bn back from the EU and has threatened to build a rival satellite system, at an estimated cost of £5bn.
In a speech on post-Brexit security co-operation, Mr Davis said: "We should be able, as trusted allies and friends of Europe to get an agreement that allows sensitive information to be shared."
He said British companies were being discriminated against and blocked from contracts - despite the fact that excluding the UK would delay Galileo by three years or more.
"This is not an issue isolated to Galileo," he added.
"The same is at risk of happening with the new European Defence Fund."
The UK had originally opposed the creation of the European Defence Fund, which co-ordinates joint operations by member states.
The government wants to continue contributing troops, equipment and money to overseas EU military operations after Brexit.
But Mr Davis said the EU's attitude to "third countries" - which the UK will become after Brexit - was standing in the way of that ambition.
"All of these unhelpful precedents and assumptions on how third countries should operate with the EU is hindering projects that would help the entire continent," he said in his speech.
The UK had also opposed the creation of Galileo, when it was first proposed 18 years ago, but Britain's space industry had been a major player in the project, which is meant to be fully operational by 2026.
It comes as the European Commission announced plans to pump an extra €5bn (£4.4bn) into space projects, including Galileo and the Copernicus Earth Observation Programme, which will be delivered in partnership with the European Space Agency.
Britain will remain a member of the European Space Agency, which is not an EU body, after Brexit, and is willing to pay a fee of around £1bn to the European Commission to remain part of its space plans.
But the Commission's spending proposals on are based on the assumption that it will get no more cash from the UK after Brexit.

A Welsh Conservative MP has quit as a minister in anger at concessions being given to Brexiteers by Theresa May.
Guto Bebb resigned as minister for defence procurement in order to vote against the government on amendments it accepted to its Brexit Customs Bill.
MPs voted 305 to 302 on Monday to back a change Remainers said would undermine Mrs May's negotiating position.
Welsh Secretary Alun Cairns said he was "very sorry" the Aberconwy MP felt he had to resign over the issue.
Mr Bebb had staunchly defended the prime minister amid the turmoil which has followed the unveiling of her blueprint for post-Brexit relations with the EU.
He branded Boris Johnson's resignation as foreign secretary "a selfish act" and attacked former Brexit Minister David Jones for criticising Mrs May's plan.
Mr Cairns told BBC Radio Wales he was "going to miss" Mr Bebb, who had served under him as a junior Wales Office minister.
Speaking on Good Morning Wales, he said: "Guto was an excellent minister and a close colleague and a good friend.
"I'm very sorry that he felt in order to vote last night that he needed to leave the government."
Glyn Davies, Conservative MP for Montgomeryshire, said: "I am very upset that Guto has felt the need to resign from the government. He is a good friend and was an outstanding minister.
"Guto is a man of deep principle. He is such a talented politician that I cannot believe he will not find another important role in the future."
Leave campaigner and Monmouth Conservative MP David Davies said he was "sad to see him go", adding: "He's a friend and he was doing a really good job in the MoD [Ministry of Defence].
"Guto is strong-minded though and in some ways I'm not surprised."
Mr Bebb was appointed minister for defence procurement in January 2018 after serving as parliamentary under secretary of state at the Wales Office and a government whip from March 2016.
He was elected MP for Aberconwy in May 2010 and voted Remain in the 2016 EU referendum.
The Customs Bill amendment was tabled by Brexiteer Tories and the government's backing of it sparked a backlash from pro-EU Tory MPs, who said the PM had "capitulated".
But Downing Street, which agreed to accept the four amendments, said they were "consistent" with the White Paper where it sets out how it wants to trade with the EU in years to come.
MPs backed the amendment that prevents the UK from collecting taxes on behalf of the EU unless the rest of the EU does the same for the UK.
Applying EU tariffs to products destined for the EU is part of Mrs May's plan to avoid friction at UK borders after Brexit.
Another amendment, to ensure the UK is out of the EU's VAT regime, was backed by 303 to 300.
Clwyd West MP David Jones - a former Brexit minister and Welsh secretary who led the Vote Leave campaign in Wales - said the government was right to listen to its Brexiteer critics but believed "a lot more listening" needed to be done.
Guto Bebb voted Remain in the Brexit referendum and it was no secret he had become increasingly frustrated by the actions of some of the Brexiteers in his party.
He accused former Brexit Minister David Jones of sour grapes after he criticised the prime minister's plan for future trade with the EU.
He also attacked senior cabinet ministers for "inflammatory" and "unworthy" comments after then-Health Secretary Jeremy Hunt said threats from business over Brexit were "inappropriate".
But after a string of resignations by Brexiteers, Guto Bebb's decision to leave a job he obviously enjoyed has surprised many.
What may seem strange is that he resigned so he could vote for what was the prime minister's own position a few hours earlier.

The DUP did not like what was proposed on "regulatory alignment", but Brexit Secretary David Davis suggests that the concept will still be key to making progress.
"Regulatory alignment" effectively means continuing to follow at least some of the rules of the EU's single market.
The taoiseach (Irish prime minister) said that the EU and UK had agreed that, short of a comprehensive trade agreement, there would be ongoing alignment between the two parts of Ireland sufficient to avoid a hard border.
In his answer he explained what he understood by the term.
He referred Mrs Cooper to the prime minister's Florence speech, in which Theresa May spoke about how the EU and UK "share a commitment to high regulatory standards".
Mr Davis said the Prime Minister had made the case that the two sides would, in some areas, want to reach the same regulatory outcomes, but by different methods.
This is a concept which the the UK government had previously proposed.
In its paper on Northern Ireland, published earlier this year, it raised the idea of regulatory equivalence on agri-food measures.
It stated that the UK and the EU could agree to achieve "the same outcome and high standards, with scope for flexibility in relation to the method for achieving this".
Mr Davis went on to to say that this sort of alignment would apply to the whole of the United Kingdom, rather than just Northern Ireland.
The Scottish Conservatives leader, Ruth Davidson, expanded on this point in a statement.
"If regulatory alignment in a number of specific areas is the requirement for a frictionless border, then the prime minister should conclude this must be on a UK-wide basis," she said.
So perhaps the government thinks they can persuade the DUP that regulatory alignment will be something for the UK as a whole, not just Northern Ireland.
However, there could be a difficulty with this all-UK approach, as the Institute for Government pointed out in a recent report, subtitled "Can the UK have its Brexit cake and eat it?'"
It points out that while the UK is trying to reassure the EU that it intends to meet the same regulatory outcomes it is also talking about having "flexibility" on the legal rules and standards underpinning them.
The institute suggests that the EU may interpret flexibility as a risk to its environmental, social and health and safety standards.
For example, in August the EU's chief negotiator Michel Barnier said: "The UK wants to take back control, it wants to adopt its own standards and regulations.
"But it also wants to have these standards recognised automatically in the EU... This is simply impossible."
The EU has been consistent in its belief that Northern Ireland will need a special deal to cater to its unique circumstances.
But it has been equally clear that such a deal cannot apply across the UK as a whole.

Tory MP Jacob Rees-Mogg has called for a fundamental change in ministers' tone on Brexit, accusing UK negotiators of being "cowed by the EU".
The Eurosceptic backbencher said in a speech that "close alignment" with the EU after Brexit would be unacceptable.
Chancellor Philip Hammond, meanwhile, has said he hopes the UK and EU economies will only move "very modestly" apart after Brexit.
He said they were already "completely interconnected and aligned".
BBC political editor Laura Kuenssberg said the war of words went right to the heart of Mrs May's struggle to keep her party together over its biggest project - how the UK will leave the EU.
While the majority of ministers thought she was the only person able to do it, the mood in the party had turned sour in recent weeks with one senior Conservative MP saying they were "in the mood for regime change".
The UK is due to leave the European Union in March 2019, and negotiations are taking place between the two sides.
One of the key questions is how close their trading relationship will be once the UK has left.
Mr Rees-Mogg, one of the leading Eurosceptic voices on the Conservative benches, has recently become the chairman of the European Research Group of Tory MPs.
In his speech, he warned against Brexit being treated like a "damage limitation exercise".
People "did not vote for the management of decline", he said.
"They voted for hope and opportunity and politicians must now deliver it."
The North East Somerset MP said some of the "really obvious opportunities" to improve people's lives from Brexit were at risk, if a model similar to the EU's single market and customs union was adopted.
This would leave the UK "divested of even the limited influence we currently have".
Mr Rees-Mogg also said businesses will suffer unless the UK can set its own regulations, independent of the EU.
And he criticised the UK negotiators, who are led by Brexit Secretary David Davis.
"For too long our negotiators seemed to have been cowed by the EU," he argued.
"Their approach seems to be that we must accept what the EU will allow us to do and build from there. This is no way to negotiate and it is no way for this country to behave."
Mr Rees-Mogg told BBC Radio 5live's Brexitcast that his aim in criticising the government's approach to Brexit was to "support the prime minister against naysayers".
Speaking at the World Economic Forum in Davos, Mr Hammond said the UK was not seeking an "off-the-shelf" model to replace its membership of the EU single market and customs union.
The starting point is a position of "high levels of bilateral trade in goods and services," he said.
"So instead of doing what we're normally doing in the trade negotiations - taking two divergent economies with low levels of trade and trying to bring them closer together to enhance that trade - we are taking two completely interconnected and aligned economies with high levels of trade between them, and selectively, moving them, hopefully very modestly, apart.
"And so we should be confident of reaching something much more ambitious than any free trade agreement has ever achieved."
A Cabinet source told the BBC: "The UK is leaving the EU, the sooner Hammond realises that the better. Very modest changes are not what the 52% voted for."
Eurosceptic Tory backbencher Bernard Jenkin told the BBC: "Either the chancellor's been just a little careless in the ambiguity of his remarks or, rather as we suspect, the Treasury's got rather a different agenda. But I think it would be much easier for the prime minister to do her job if everyone just stuck to her script and I think that is what he should do."
He added that while he didn't want one "maybe [the prime minister] needs another reshuffle in order to give herself more ministers who support her policy" but denied he was suggesting Mr Hammond be sacked.
Mr Hammond tweeted:
Former Conservative MP and Scottish secretary Lord Forsyth told the BBC's Question Time that the prime minister "needs to get a grip on the cabinet and the cabinet needs to get behind her".
He added that Mr Hammond seems to be saying "something that's completely at odds with what the prime minister said in her Lancaster House speech."
Downing Street said Theresa May had used major speeches to talk about the "opportunities that Brexit will provide for the country", and that the government was confident of securing these opportunities in the next phase of negotiations.
Asked whether she agreed with Mr Hammond's comments, the spokesman said: "The cabinet has signed up to the vision the PM has set out in her speeches."

European Commission President Jean-Claude Juncker has warned the UK it faces a "very hefty" bill for Brexit.
He promised two years of "tough negotiation", when discussions on leaving terms get under way between the government and the European Union.
Exit will not come "at a discount or at zero cost", he said in a speech to the Belgian Federal Parliament.
Reports suggest the UK could have to pay the EU up to 60 billion euros (£51bn) after Brexit talks start.
Mr Juncker's comments came as the House of Lords held a second day of discussion of the government's European Union (Notification of Withdrawal) Bill, which, if passed into law, will allow Prime Minister Theresa May to trigger Article 50 of the Lisbon Treaty, allowing formal talks with the EU to start.
She is hoping to do this before the end of March, with EU negotiations expected to take up to two years.
Discussions are taking place in Brussels on the size of the bill to be presented to Mrs May when she launches the talks. The amount will cover the UK's share of the cost of projects and programmes it signed up to as a member, as well as pensions for EU officials.
In his speech, Mr Juncker, a former prime minister of Luxembourg, said: "It will be a tough negotiation which will take two years to agree on the exit terms. And to agree on the future architecture of relations between the United Kingdom and the European Union we will need years.
"The British people have to know, they know already, that it will not be at a discount or at zero cost. The British must respect commitments they were involved in making. So the bill will be, to put it a bit crudely, very hefty."
Unpicking 43 years of treaties and agreements covering thousands of different subjects was never going to be a straightforward task.
It is further complicated by the fact that it has never been done before and negotiators will, to some extent, be making it up as they go along.
The post-Brexit trade deal is likely to be the most complex part of the negotiation because it needs the unanimous approval of more than 30 national and regional parliaments across Europe, some of whom may want to hold referendums.
All you need to know about Brexit
He added:  "We need to settle our affairs not with our hearts full of a feeling of hostility, but with the knowledge that the continent owes a lot to the UK. Without Churchill, we would not be here - we mustn't forget that, but we mustn't be naive.
"Our British friends will need to understand that we want to continue to develop European integration."
But an ally of German Chancellor Angela Merkel said it was "not very smart" of the European Commission to ram home the cost of Brexit at this stage.
Stephan Mayer, a CDU member of the German Parliament, told the BBC that while Brexit would be "expensive for both the UK and the EU", much would depend on which EU programmes the UK continued to participate in.
"I am not so happy with this aggressive line," he told BBC Radio 4's Today.
"I am convinced that Germany has a special interest in stable and good relationships with the UK. I fear in a certain way that this harsh pressure, which is put by the European Commission on the UK, is not in Germany's interests."
Mrs May has already said the UK will leave the European single market, but has promised to push for the "freest possible trade" with European countries.
In a speech in January outlining her priorities for Brexit, she warned the EU that to "punish" the UK for leaving would be "an act of calamitous self-harm".
Earlier this month, the House of Commons overwhelmingly backed the EU Bill and the government has said the Lords must not "frustrate" its passage into law.

This is the resignation letter that Lord Adonis says he sent to Downing Street while quitting as the government's infrastructure adviser.
The Right Hon Lord Adonis
House of Lords, London SW1
The Right Hon Theresa May MP
10 Downing Street
London SW129 December 2017
Dear Prime Minister,
The hardest thing in politics is to bring about lasting change for the better, and I believe in co-operation across parties to achieve it.
In this spirit I was glad to accept reappointment last year as Chair of the independent National Infrastructure Commission, when you also reaffirmed your support for HS2, which will help overcome England's north-south divide when it opens in just eight years time. I would like to thank you for your courtesy in our personal dealings.
The Commission has done good work in the past 27 months, thanks to dedicated public servants and commissioners. Sir John Armitt, my deputy chair, and Phil Graham, chief executive, have been brilliant throughout. I am particularly proud of our plans for equipping the UK with world-class 4G and 5G mobile systems; for Crossrail 2 in London and HS3 to link the Northern cities; and for transformational housing growth in the Oxford-Milton Keynes-Cambridge corridor.
I hope these plans are implemented without delay. However, my work at the Commission has become increasingly clouded by disagreement with the Government, and after much consideration I am writing to resign because of fundamental differences which simply cannot be bridged.
The European Union Withdrawal Bill is the worst legislation of my lifetime. It arrives soon in the House of Lords and I feel duty bound to oppose it relentlessly from the Labour benches.
Brexit is a populist and nationalist spasm worthy of Donald Trump. After the narrow referendum vote, a form of associate membership of the EU might have been attempted without rupturing Britain's key trading and political alliances. Instead, by allying with UKIP and the Tory hard right to wrench Britain out of the key economic and political institutions of modern Europe, you are pursuing a course fraught with danger. Even within Ireland, there are set to be barriers between people and trade.
If Brexit happens, taking us back into Europe will become the mission of our children's generation, who will marvel at your acts of destruction.
A responsible government would be leading the British people to stay in Europe while also tackling, with massive vigour, the social and economic problems within Britain which contributed to the Brexit vote. Unfortunately, your policy is the reverse. The Government is hurtling towards the EU's emergency exit with no credible plan for the future of British trade and European co-operation, all the while ignoring - beyond sound bites and inadequate programmes - the crises of housing, education, the NHS, and social and regional inequality which are undermining the fabric of our nation and feeding a populist surge.
What Britain needs in 2018 is a radically reforming government in the tradition of Attlee, working tirelessly to eradicate social problems while strengthening Britain's international alliances. This is a cause I have long advocated, and acted upon in government, and I intend to pursue it with all the energy I can muster.
Britain must be deeply engaged, responsible and consistent as a European power. When in times past we have isolated ourselves from the Continent in the name of "empire" or "sovereignty", we were soon sucked back in. This will inevitably happen again, given our power, trade, democratic values and sheer geography. Putin and the rise of authoritarian nationalism in Poland and Hungry are flashing red lights. As Edmund Burke so wisely wrote, "people will not look forwards to posterity who do not look backwards to their ancestors."
However, I would have been obliged to resign from the Commission at this point anyway because of the Transport Secretary's indefensible decision to bail-out the Stagecoach/Virgin East Coast rail franchise. The bailout will cost taxpayers hundreds of millions of pounds, possibly billions if other loss-making rail companies demand equal treatment. It benefits only the billionaire owners of these companies and their shareholders, while pushing rail fares still higher and threatening national infrastructure investment. It is even more inexcusable given the Brexit squeeze on public spending.
The only rationale I can discern for the bailout is as a cynical political manoeuvre by Chris Grayling, a hard right Brexiteer, to avoid following my 2009 precedent when National Express defaulted on its obligations to the state for the same East Coast franchise because it too had overbid for the contract. I set up a successful public operator to take over East Coast services and banned National Express from bidding for new contracts. The same should have been done in this case. Yet, astonishingly, Stagecoach has not only been bailed out: it remains on the shortlist for the next three rail franchises.
The East Coast affair will inevitably come under close scrutiny by the National Audit Office and the Public Accounts Committee, and I need to be free to set out serious public interest concerns. I hope the PAC calls Sir Richard Branson and Sir Brian Souter to give evidence. I am ready to share troubling evidence with the PAC and other parliamentary committees investigating the bailout.
As you know, I raised these concerns with the Chancellor and the Transport Secretary as soon as the bailout became apparent from the small print of an odd policy statement on 29 November majoring on reversing Beeching rail closures of the 1960s. I received no response from either Minister beyond inappropriate requests to desist.
Brexit is causing a nervous breakdown across Whitehall and conduct unworthy of Her Majesty's Government. I am told, by those of longer experience, that it resembles Suez and the bitter industrial strife of the 1970s, both of which endangered not only national integrity but the authority of the state itself.
You occupy one of the most powerful offices in the history of the world, the heir of Churchill, Attlee and Gladstone. Whatever our differences, I wish you well in guiding our national destiny at this critical time.
Yours sincerely,
(Signed)
ANDREW ADONIS

The European Parliament has backed a motion setting out its position for the Brexit negotiations by 516 to 133.
Although MEPs will not participate directly in the exit talks they will have to vote in favour of the final deal for it to go ahead.
UKIP's Nigel Farage accused MEPs of trying to impose conditions that were "impossible for Britain to comply with" and likened them to the "mafia".
The motion for debate was supported by the two largest groups of MEPs.
It set out general principles at the start of the two year negotiations for the UK to leave the European Union under the Article 50 process.
At a press conference following the vote, Guy Verhofstadt, the European Parliament's Brexit negotiator, said the vote meant that "the UK on the one hand and the [European] Commission on the other hand now know the position of the Parliament, what the red lines are".
He said "the interests of our citizens is our first priority" and called for an early resolution of the status of EU citizens in the UK and UK citizens elsewhere in Europe.
The motion backs a number of positions taken by EU leaders, including the need for a "phased approach" to negotiations.
This would require progress on the terms of Britain's withdrawal, including settling financial commitments, before talks on a future trading relationship can start.
It also backs the call for transparency in the talks, and for the UK to be considered liable for financial commitments that apply after it leaves the EU.
It also says:
During the debate in Strasbourg Manfred Weber, chairman of the largest group of MEPs, the centre-right European People's Party, said: "Cherry-picking will not happen. A state outside the European Union will not have better conditions than a state inside the European Union."
Gianni Pitella, chairman of the European Socialists and Democrats also argued that the UK "can not benefit from the same conditions as members do" and added: "If you leave the house, you still have to pay the bills."
The motion is not binding on European Commission officials but President of the European Commission Jean-Claude Juncker told MEPs: "The role of this parliament is more important than ever. You must scrutinise and validate the final agreement."
He added: "We will of course negotiate in friendship and openness and not in a hostile mood, with a country that has brought so much to our union and will remain close to hearts long after they have left, but this is now the time for reason over emotion.
"What's at stake here are the lives of millions of people. Millions have family or professional links to the United Kingdom."
The EU's chief Brexit negotiator, Michel Barnier, warned that "a disunited union could actually lead to there being no deal".
He added: "The 'no deal' scenario is not the scenario we are looking for. We are looking for success, not against the United Kingdom but with the United Kingdom."
Helga Stevens from the Conservatives and Reformists group, which includes MEPs from the UK's ruling Conservative Party, said Brexit "should not be a nasty breakup" and cautioned MEPs against "making excessive demands in advance" of Brexit talks.
"If we do anything less, history will judge us harshly as being small and petty," she claimed.
But UKIP MEP Mr Farage argued: "Already you've made a series of demands which are not just unreasonable but in some cases clearly impossible for Britain to comply with."
He accused the EU of seeking to impose a bill of £52bn on the UK and likened this to "a form of ransom demand", adding: "What you could have mentioned is we're actually shareholders in this building and other assets and actually you should be making an offer to us that we can't refuse, to go."
When he accused MEPs of behaving like the mafia, the parliament's Italian president, Antonio Tajani, intervened to object. Mr Farage responded:  "I do understand national sensitivities. I'll change it to gangsters."
The former UKIP leader also insisted that Gibraltar should be a "deal breaker" in any negotiations.
Later, Spanish centre-right MEP Esteban Gonzalez Pons accused the UK government of "preventing Scotland staying part of Europe while at the same time they want... Gibraltar to continue to be a tax haven".
At the post-debate press conference, Mr Tajani emphasised the need to uphold the Good Friday Agreement in Northern Ireland and "working for peace".
He also highlighted security co-operation with the UK, saying: "Terrorists know no borders and they do not care about Brexit."

MPs will vote again on how much of a say Parliament should have on Brexit, after another House of Lords defeat for the government.
Peers decided MPs should have to approve whatever the government decided to do next if there was no final agreement with the EU.
Their amendment to the EU (Withdrawal) Bill was backed by 354 votes to 235.
It means the issue is sent back to the House of Commons for a debate on Wednesday.
Leading Tory Eurosceptic Jacob Rees-Mogg accused the Lords of being "cavalier" towards the UK's constitution.
The UK is due to leave the European Union in March 2019. And negotiations have been taking place over the terms of its departure.
But there is an ongoing row about what happens if Parliament votes to reject the final deal reached between the two sides - or if no deal is reached.
One side says Parliament should intervene to prevent the UK from "crashing out" of the EU without a deal - but critics say the prospect of this happening would undermine the UK's negotiating hand.
Last week, Theresa May avoided defeat on the issue - but rebels said they were not happy with the concessions they had been offered in return for not voting against the government.
Now, peers have backed an amendment from former Conservative cabinet minister Lord Hailsham, which goes further than the government's proposals on how much power MPs could get.
The 119 majority was 28 more than the last time peers voted on the so-called "meaningful vote" issue.
Lord Hailsham, who described Brexit as a "national calamity" in his speech, said his amendment represented what had been agreed "in good faith" by the would-be Tory rebels, led by former Attorney General Dominic Grieve, and Downing Street last week.
"It's a matter of honour," he said.
He also said his proposals were in the "national interest", adding: "In order to safeguard our nation's vital interests, in the event that there be no deal on the table, Parliament should have the authority to intervene."
Lord Hailsham described his amendment as "Grieve Two", meaning it was a new version of proposals tabled last week by former Attorney General Dominic Grieve, who wants Parliament to get more of a say over Brexit.
It would apply in three scenarios:
Under these circumstances, the government has said, a minister will make a statement in Parliament, setting out the government's next steps.
The government had offered MPs the chance to vote "on neutral terms" on this statement. But the amendment backed by the Lords on Monday goes further, saying the statement would have to be approved by MPs.
Lord Hailsham also criticised what he called "disgraceful" newspaper attacks on Mr Grieve and said it was "perfectly true" that he had held talks with other parties in drawing up his amendment.
"I make absolutely no apology for that," he said.
"This is the high court of Parliament, and we are not party hacks."
Lord Hailsham's fellow Tory peer Lord True said ministers had already "made a serious attempt to compromise" with the rebels' demands.
"People outside Parliament are getting a little bit tired of the parliamentary games," he said.
"They actually want to know when they're going to get Brexit, when it will be delivered and when it will be done."

Former Liberal Democrat leader Nick Clegg says people should consider joining Labour in an attempt to prevent Brexit from happening.
In his new book, Mr Clegg said it was "a time of national emergency" and he told people worried about Brexit to "make your voice heard".
He also said joining the Conservatives was "another route to make your views felt".
Mr Clegg, the former deputy PM, lost his seat in June's general election.
He has remained an outspoken critic of the UK's departure from the EU, and his new book is called "How to stop Brexit".
In it, he says it "may seem odd" for a former Lib Dem leader to be advocating joining Labour, adding that he himself would not be doing so.
"But if you are someone who has never joined a party, or perhaps has been inclined to join Labour but has never got round to it, or if you are simply someone who recognises that the importance of Brexit is far greater than individual," he writes.
"At a time of national emergency, and for as long as Parliament is dominated by Labour and Conservative MPs, it is undoubtedly true that what happens within the two larger establishment parties is of the greatest importance.
"So if you can't stomach joining the Labour Party, if you are ideologically inclined in a Conservative direction in any event and if you also believe that Brexit is the issue of our times, then joining the Conservatives is another route to make your views felt."

Nicola Sturgeon has warned Theresa May that she is not "bluffing" on the promise of a second independence referendum if Scotland is "driven off a hard Brexit cliff".
Scotland's first minister told the BBC's Andrew Marr she felt the prime minister had "no plan" in terms of her strategy for the UK leaving the EU.
She said she was prepared to compromise and wants Mrs May to do the same.
The UK government has said a special deal for Scotland is unrealistic.
The prime minister said on Sunday morning the government's thinking on Brexit "isn't muddled at all".
In an interview on Sky News, she said her priority was to get the "best possible deal in terms of our trading relationship with the European Union".
Brexit talks with the EU are expected to begin as early as April.
Scottish opposition parties have called for Ms Sturgeon to rule out a second independence referendum.
Voters in Scotland backed the UK staying in the EU by 62% to 38%.
Ms Sturgeon has said she wants the UK to retain membership of the European single market, the so-called soft Brexit option.
She has also indicated a soft Brexit would see the prospect of Scottish independence "put aside" in the short term.
However, in an interview for the Andrew Marr programme, she warned the UK government and Mrs May that "they will be making a big mistake if they think I am in any way bluffing" on the prospect of another Scottish independence referendum.
She said that if the UK opts for leaving the single market then she would "give Scotland the opportunity to decide whether it wants to be driven off a hard Brexit cliff by right-wing Tory Brexiteers or whether it wants to take control of its own future".
Asked if she was looking at a referendum "much quicker" than in five or 10 years' time following a hard Brexit she said: "I would think, yes. But let me not get away from this point, I'm putting to Theresa May a compromise solution."
Ms Sturgeon also told the BBC presenter that discussions with the UK government over the Brexit options had left her "frustrated".
She said: "I don't feel as if I know any more about her (Theresa May's) negotiating objectives than I did six months ago."
Asked if she seriously thinks "there is no plan", the first minister said: "Yes I do".
She added: "I say that with a lot of regret as that puts every part of the UK into a very perilous position."
Nicola Sturgeon has warned she isn't bluffing over a second independence referendum. But she's also been careful to emphasise she is offering a 'compromise' that would take one off the table. For now all options remain in play.
A key influencing decision will be whether Scotland stays in the EU single market, either as part of the UK or in a separate arrangement. Prime Minister Theresa May said today she does not intend to keep bits of membership - instead she wants an ambitious trade deal with Europe.  More details in the next couple of weeks.
But the first minister will also be reluctant to call one unless she's confident she'll win; at the moment polls suggest support for independence has not increased since 2014.
Ms Sturgeon has tried to put the ball in the prime minister's court; asking her will she listen to the views of the Scottish government? If not, Ms Sturgeon thinks Scotland will have to ask itself if it's happy with the decision. Watch this space.
Ms Sturgeon highlighted a meeting at Downing Street in October which also involved the first ministers of Wales and Northern Ireland.
She said: "I'm not exaggerating too much when I say the prime minister sat on the other side of the table at that meeting and said 'Brexit means Brexit' and not a lot more.
"I came out of that meeting more frustrated, after a meeting of that nature, than I have ever been before."
In the interview, the SNP leader also said she accepted "it looks at the moment as though the UK is going to leave the EU".
She called on Theresa May to work towards a "compromise" and "common ground that avoids the worst impacts".
The prime minister has pledged to trigger Article 50 of the Lisbon Treaty - getting leaving talks with the EU under way - by the end of March.
Talks can take up to two years, unless an agreement is reached to prolong the process.
Responding to Ms Sturgeon's comments, Scottish Conservative leader Ruth Davidson said: "This week we've seen Nicola Sturgeon say that she was going to take a referendum off the table, only for her and Alex Salmond to put it back on the table again today.
"The first minister needs to start acting in the interests of all Scots, not simply playing to her nationalist base."
Kezia Dugale, Scottish Labour leader, accused the SNP of sowing "division and uncertainty".
"With a growing crisis in our NHS and a shameful gap between the richest and the rest in our schools, the challenges facing Scotland are too great for the SNP government to be distracted by another referendum," she said.
Scottish Liberal Democrat leader Willie Rennie said Ms Sturgeon was causing "damaging uncertainty".
He added: "She rightly criticises the prime minister for a lack of clarity on Brexit but the first minister is making matters worse with a similar lack of clarity on independence."
The full interview with Nicola Sturgeon was broadcast on The Andrew Marr Show and will be available later on the BBC iPlayer.

The Polish Prime Minister has said Britain will have to continue making financial contributions to the European Union if it wants to enjoy privileged access to the single market.
Mateusz Morawiecki said the EU would take a tough stance on Britain's desire for a comprehensive free trade deal.
He said he wanted a positive relationship, but that costs would be attached.
But a UK minister told me Britain would not agree to that "at the outset".
When I spoke to Mr Morawiecki in Davos I asked him whether Britain would have to pay to get "a good deal".
"I hope so," he told me.
"There has to be some price for full access and to what extent this access is going to be available has to be made dependent on some other contributions, potentially including this financial contribution."
Such a move could be controversial among many Brexit supporters in Britain - a point Mr Morawiecki agreed with.
"Yes, but you cannot have your cake and eat the same cake," he said.
The Polish PM's comments come a few hours after David Davis, the Secretary of State for Exiting the EU, rejected any plans to continue making contributions.
Mr Davis said Britain was a "proud country" and would not pay "some sort of Danegeld".
A Danegeld was a tax levied on the English to pay off Viking raiders.
Mr Morawiecki, who was formerly an adviser to Donald Tusk, the president of the European Council, said he believed there was a small chance that Britain could remain in the EU.
"I still have a little bit of hope that there will be a way of keeping the UK as part of the EU," he said.
"I fully respect the decision from the referendum, but maybe there will be other ways for the UK [to remain] as part of the EU.
"Because I think it's in the interests of the trans-Atlantic community - the pax-Americana, pax-European peace type of model - and for the rest of the world.
"It is extremely important for security, and global trade, and positive trends in the world."
He said if there was no reversal of the referendum - which the UK government has categorically ruled out - then he hoped "the deal between the UK and EU will be as positive for both parties as possible, because I don't want to punish anybody".
I asked the Polish PM whether Britain could have its own bespoke deal, which Theresa May has signalled she wants.
"I would like to indicate two other nations and countries which are [in a different position] - one of them is part of the EEA [the European Economic Area] like Norway, and they do have some financial contribution for the whole of the EU.
"The other one is where we are today, Switzerland, which has a series of bilateral agreements.
"So I think there are examples of how the new agreement can be shaped so that there is a real convergence, a real integration between the UK and the EU, despite Brexit."
Britain is a net contributor to the EU budget and government sources have told me that it is likely the UK will have to pay for special access - possibly via contributions to specific bodies such as for medicines - despite the public position that no payments will be made.
The issue is very important for Poland as it is a net recipient of EU funds and there are concerns that funding could be cut when Britain leaves the EU.
Dr Liam Fox, the International Trade Secretary, said that during the Brexit negotiations both sides would set out - often opposing - positions, and that compromises would have to be reached.
"It sounds to me like the opening shots of a negotiation and there is a long way to go in that," he told me in response to Mr Morawiecki's comments.
"There is no way the UK would agree at the outset to do that.
"What we are looking at is a balance.
"The UK will want access [to the EU] in services, particularly financial services.
"The European Union will want access to Britain's goods market, given that they have got a £82bn surplus with the United Kingdom.
"These things will be netted out over trade agreements.
"In a trade agreement both sides have to give something otherwise you don't get an agreement.
"As we have seen with the TPP [the Trans-Pacific Partnership] agreement, it can sometimes take a few little bumps before people get to the final place.
"So I think we don't assume that any opening positions will be the final positions."

The European Parliament has overwhelmingly approved a non-binding resolution that lays out its views on the Brexit negotiations.
The parliament will have no formal role in shaping the Brexit talks. The negotiations will be led by the European Commission on behalf of the EU's remaining 27 member states. Their draft negotiating guidelines were issued last week.
But the parliament's views still matter because under the Article 50 rules it will get a vote on the final EU-UK "divorce" deal and if it does not like what has been agreed it could demand changes and delay the process.
BBC Reality Check correspondent Chris Morris teases out some of the key sentences from the resolution and explains their significance.
 - A revocation of notification needs to be subject to conditions set by all EU-27, so that it cannot be used as a procedural device or abused in an attempt to improve on the current terms of the United Kingdom's membership;
This is interesting. It implies that the European Parliament thinks the UK can change its mind about Article 50 (whereas the UK government has implied the opposite). The truth is that irrevocability is the subject of legal dispute and, as this is a matter of interpreting a European treaty, the ultimate arbiter would be the European Court of Justice. Either way, the parliament makes clear here that it would not allow the UK to plead for a better deal if it tried to return - even the package of measures offered to David Cameron in February 2016 (remember this?) is now null and void.
 - Reiterates the importance of the withdrawal agreement and any possible transitional arrangement(s) entering into force well before the elections to the European Parliament of May 2019;
In theory the two-year Article 50 negotiating period could be extended if all parties agreed, but no-one really wants that to happen. And this is one of the reasons why the timetable is so tight. If the UK was still part of the European Union in May 2019, it might have to hold elections to elect British MEPs, despite being on the verge of leaving. It would raise all sorts of complications that the European Parliament is determined to avoid.
 - Stresses that the United Kingdom must honour all its legal, financial and budgetary obligations, including commitments under the current multiannual financial framework, falling due up to and after the date of its withdrawal;
Another reminder of the looming fight about settling the accounts (also known as the divorce bill). Parliament insists that the UK must honour all its commitments under the current multiannual financial framework - a kind of long-term budget -  which runs until 2020. Because of the way the EU budget process works, that would mean the UK would have to help pay for things like infrastructure projects in poorer EU countries several years after it had left the Union.
 - States that, whatever the outcome of the negotiations on the future European Union-United Kingdom relationship, they cannot involve any trade-off between internal and external security including defence co-operation, on the one hand and the future economic relationship, on the other hand;
I think this is probably cleared up by now, but the implied link between security co-operation and trade in Theresa May's Article 50 letter raised a few eyebrows elsewhere in the EU. Cooler heads suggested it was there for domestic consumption and the UK government said it was all a misunderstanding. But the parliament is putting down an explicit marker that trade-offs between security and the future economic relationship won't be acceptable.
 - Stresses that any future agreement between the European Union and the United Kingdom is conditional on the UK's continued adherence to the standards provided by international obligations, including human rights and the Union's legislation and policies, in, among others, the field of the environment, climate change, the fight against tax evasion and avoidance, fair competition, trade and social rights, especially safeguards against social dumping;
The resolution suggests that the future relationship could be built upon an agreement under which the UK would have to accept EU standards over a wide range of policy areas from climate change to tax evasion. In some areas that might be exactly what the UK government wants to do anyway, given that the UK has played a leading role in forging those policy positions in the first place. But domestic politics in the UK means any wholesale acceptance of EU policies could be a tough sell.
 - Believes that transitional arrangements ensuring legal certainty and continuity can only be agreed between the European Union and the United Kingdom if they contain the right balance of rights and obligations for both parties and preserve the integrity of the European Union's legal order, with the Court of Justice of the European Union responsible for settling any legal challenges; believes, moreover, that any such arrangements must also be strictly limited both in time - not exceeding three years - and in scope, as they can never be a substitute for European Union membership;
Two important points here. Firstly, the parliament is determined that the jurisdiction of the European Court of Justice would continue to run during any transition period. The draft guidelines produced by the European Council last week made the same point but in less explicit language. If it wants a transition, the UK will have to accept a role for the ECJ. Secondly, the parliament says the transition should last no longer than three years, which is a shorter period than some might think necessary.

Brexit talks will be on a "humongous scale" involving "difficult trade-offs", the UK's ex-EU ambassador says.
Sir Ivan Rogers predicted much of the talks would be "conducted very publicly" with "name-calling" and an "extremely feisty atmosphere".
He added that EU Commission chiefs were saying the UK should pay 40-60bn euros to leave and thought a trade deal could take until the mid-2020s to agree.
Sir Ivan, who had been due to leave his post in October, resigned last month.
In December he attracted criticism from some MPs when his warning to ministers that the European consensus was that a deal might not be done until the early to mid-2020s was revealed by the BBC.
Giving evidence to the Commons European Scrutiny Committee, he said this had come from a briefing he had written for Prime Minister Theresa May in October, based on the views of key figures in the EU and the remaining member states.
He said he did not know how it became public.
The government says it can conclude all separation negotiations, including a new free trade deal, within two years, having given notice of the UK's departure from the EU by the end of March.
Asked about the anticipated timescale, Sir Ivan said a comprehensive free trade agreement such as the one Mrs May was seeking would be the most comprehensive ever negotiated by the EU, and previous agreements have taken "an awful lot of time".
He said he believed an agreement with the UK could be concluded more quickly, but said the Brexit negotiation would be "unprecedentedly large" covering "huge tracts of Whitehall".
"It's a negotiation on the scale that we haven't experienced ever, certainly not since the Second World War."
Sir Ivan said there was a "big financial debate coming up" about the amount to which the UK should be expected to pay as it leaves the EU.
EU commission chief negotiator Michel Barnier and other key figures were "openly" saying the UK's total financial liabilities would be in the order of 40 to 60bn euros, Sir Ivan said, describing this as a "predictably hard line".
From the EU's point of view, UK withdrawal will "explode a bomb" under its seven-year budget, he said.
Sir Ivan told MPs the 27 remaining EU states would spend "an awful lot of time debating with each other" before negotiating with the UK, agreeing a common position.
Asked how confidential the negotiations would be, he said: "I think an awful lot will leak, Brussels is very leaky...stuff will get out, and incessantly in my view."
He added: "Expect an awful lot of this negotiation to be conducted very publicly."
Sir Ivan said that after a "phoney war period" talks "usually end up in a fairly mercantilist fist-fight" before finally resolving themselves in a deal of some sort.
A determination on both sides to make progress would be crucial, he said.
"That involves generating a momentum and generating an atmosphere so that even when we get into name-calling and an extremely feisty atmosphere - and we undoubtedly will in both exit negotiations and future trade and economic negotiations - there is still an atmosphere to proceed and finalise agreement."
He said there was "no doubt" the UK would be able to negotiate free trade deals more quickly than the EU once it leaves, but said it may not have the same "negotiating heft".
Sir Ivan has been replaced by Sir Tim Barrow, a former UK ambassador to Russia.
Giving evidence to a separate Commons committee, International Trade Secretary Liam Fox said the suggestion the UK could face a bill upon leaving the EU was "absurd".
"I find it bizarre because the UK is using a legal power that we have under the Lisbon Treaty, a provision that was freely entered into by all our European partners," he said.
"Why should they then turn round to say that we should pay their costs for a process that everybody equally entered into at the time? So it seems to me an absurd argument."

The EU's chief Brexit negotiator has told the UK the time has come for it to "resolve the contradictions" in its Irish border policy.
Michel Barnier was writing in Ireland's Sunday Independent newspaper ahead of a visit to the country on Monday.
He said there will need to be "substantial progress" on the border issue by the next major meeting of EU leaders.
They are due to assess progress on the border issue at a summit in June.
Last week the Brexit Secretary David Davis suggested the EU was trying to create an "artificial deadline" in June as a negotiating tactic.
The Brexit secretary also rejected reports that the European Commission has completely rejected the UK's plans for avoiding customs checks at the Irish border when the UK leaves the customs union.
October is the presumed deadline for a withdrawal agreement which will give the UK a smooth exit path from the EU.
In March, EU leaders agreed to a 21-month Brexit transition period between March 2019 - when the UK officially leaves - and the end of 2020.

The EU summit on Thursday and Friday will discuss a number of pressing issues, including migration, economics, security and Brexit. But what do different countries want from the Brussels talks and where does Brexit stand in their priorities?
It's tempting to imagine what Angela Merkel and Theresa May might say to one another in a private moment on the margins of the summit.
Both leaders, after all, face dissent and open rebellion from within their own ranks. And both are in a bind over borders.
But that's exactly why it's unlikely that the German chancellor will pay much attention to Brexit this week. She's far too busy trying to realise her long-promised European migration strategy - and saving her own political skin.
Her fragile government hangs precariously in the balance.
And it could fall apart if she can't return home with a solution strong enough to see off the rebellion from her interior minister - and coalition partner - who's threatening to unilaterally impose greater migration controls at the German border.
In such serious times here, the problem of Brexit seems far a less significant issue to preoccupied lawmakers.
But it's not that Germany isn't interested. Industry - in particular the mighty car manufacturing lobby - is beside itself at the thought of a no-deal Brexit.
In recent days, Joachim Lang, the director general of the Federation of German Industries, warned that the UK is "hurtling towards a disorderly Brexit". He added that only by remaining in the customs union and single market can the Irish border question be answered.
Most here want more clarity from Britain about how it perceives its future relationship with the EU, but Mrs May will encounter strong resistance to any proposals that even hint at the reinstatement of a border.
Mrs Merkel, on the other hand, whose experience was shaped by her own early life behind the Iron Curtain in East Germany, now finds herself in an EU openly discussing how and where to strengthen - or even reimpose - Europe's boundaries.
France is going into this summit with two concerns uppermost in its mind.
The first is President Macron's beloved long-term project to tie the eurozone economies more closely together.
The German chancellor seems to have finally agreed in principle to a watered-down version of his plan, including a common budget for the eurozone and extra measures to help countries facing a recession, though the details are still vague. This summit will be a chance to put their ideas to the other EU countries.
The other issue dominating French minds is migration.
President Macron angered Italy earlier this month by saying it was "irresponsible" and "cynical" to refuse a rescue ship carrying illegal migrants. Italy accused France of hypocrisy, in return.
The issue of how to relieve pressure on the front-line states in Europe's migrant crisis is divisive.
In 2015, the former French government promised to take 30,000 refugees from Greece and Italy, but a year later little more than 1,000 had arrived.  And while the French government backs proposals for closed processing centres in front-line states, it does not want to see them on French territory.
With all this occupying French minds, there's little room to devote much attention to Brexit.
France has stuck pretty firmly to the EU line of "no cherry-picking", saying that freedom of goods, services and people cannot be separated.
But there are those in Paris who believe that appetite is growing to find wiggle room on frictionless goods trading, to protect French exporters to the UK. Though there's little indication that Paris will budge on the issue of a "passport" for the City of London and its financial services.
Spain's new prime minister, Pedro Sánchez, has made clear he intends to respect commitments his country has made to the EU and the European project in general.
But with a range of other issues occupying his agenda - particularly increasing numbers of migrants reaching Spanish shores and tensions in Catalonia - Brexit is not a main priority for the socialist premier.
However, he will not be able to ignore the impact the UK's exit could have on Gibraltar, whose British ownership Spain disputes.
At the summit, Mr Sánchez is expected to report on the status of recent negotiations between London and Madrid over Gibraltar's future status. Those talks, due to conclude by October, have focused on the possible shared use of the rock's airport and the exchange of tax information on citizens.
The EU has agreed that Spain can veto a Brexit accord if it is unhappy with the arrangements for Gibraltar.
The summit might offer clues as to whether or not Mr Sánchez intends to continue with the relatively tough line on Gibraltar pursued by the previous Spanish government. Either way, he will want to shore up support from his EU partners on the issue.
To Italy's new populist government, Brexit is a rather distracting sideshow.
It wants to do business with a post-EU UK and it wants to ensure that the rights of Italian citizens living in the UK are protected. But beyond that, Italy's main preoccupation is migration across the Mediterranean.
In this respect, the country has two main objectives: to get EU countries to share the burden of sheltering those who've already reached this continent, and to prevent any more migrants from making the sea journey to Europe.
In particular, Italy wants to get rid of the EU's Dublin Regulation, which calls for migrants to be screened in the first place in which they arrive. Italy believes that this places far too much pressure on front-line countries, including Spain and Greece.
But Italy may face resistance from fellow populist governments in central and eastern Europe, who do not want to take in any more migrants.
Italy's influential Interior Minister, Matteo Salvini, also wants the EU to accept an Italian-Libyan plan announced on 25 June to set up migrant holding centres on Libya's southern borders.
In theory, migrants from Africa would be directed to these centres, and prevented from making the journey across the Mediterranean.
Hungarian Prime Minister Viktor Orban goes into this European summit in confident, but cautious mood.
He feels he's winning the argument on migration, but he knows he hasn't won it yet. Brexit, for him, is already yesterday's story.
His arch-enemy, Angela Merkel, looks wounded. The new government in Rome shares his anti-immigrant rhetoric, as does the government in Vienna.
He can count on Sebastian Kurz, the Austrian Chancellor, to beat the anti-migrant drum for the next six months, as Austria holds the rotating EU presidency.
His allies in Bavaria, Horst Seehofer's CSU, are on the warpath. And the other Visegrad countries are right behind him.
But Mr Orban is playing for time - he sees his real chance after next year's European parliamentary elections, when he counts on a much bigger role for populist parties like his own, and populist leaders like himself, in the running of the European Union.
In the meantime, he still has to face annoying distractions, like criticism in the European Parliament for his crackdown on human rights groups.
He'll be hoping the summit is over as quickly as possible, so he can get back to watching the football. He hasn't missed a match yet, he told Hungarian radio.

"It's all kicking off," an MP texts tonight.
It's not surprising given what's at stake, and that we are seven days away from a critical EU summit. But it's not a drama that can easily be dismissed.
The government's backers the DUP are threatening to pull support if the PM doesn't bend to their position on Brexit. Don't be in any doubt, that could in theory mean the government collapsing because they can't get anything done.
Rather than pulling back from the threat, the DUP will in the next 24 hours be trying to turn the pressure up even further.
And to make the threats real the small Northern Irish party has already tonight decided not to back the government in a vote in the Commons - a reminder that the  government's vulnerability in the Commons is real, it's not some theoretical threat.
It's a warning - not an obscure abstention on a little-noticed piece of legislation. And remember, remember December. It was the DUP (and some very strong Brexiteer voices too) who sank the prime minister's original Brussels agreement, humiliating her before she snatched victory from the jaws of defeat a few days later.
As we enter the next phase of this drama, catch up on the last big denouement here.
In Brussels, contrary to some reports, there has not been some sudden breakthrough on the clashes across the negotiating table.
Well-placed sources on both sides tell me that while the "show is on the road", and officials have been "working well" in the last three days, neither Team Barnier nor Team Robbins are buckling and bending.
So, it follows, neither Team Barnier nor Team Robbins can claim victory, and more importantly, neither Team Barnier nor Team Robbins can say at this moment with complete confidence that the progress they hope for to allow Theresa May to move closer to a Brexit deal has been achieved.
That's not of course to say that it won't or can't still happen.
There is a significant chance that by Monday Dominic Raab and Michel Barnier will be side by side at the podium gleefully reporting the progress their worker bees have been able to make - a springboard for a successful summit a week tonight.  But they are not there yet.
In cabinet too there are plenty of reservations too about the prime minister's direction of travel as well as a loyal brigade.
The jokingly named "Chequers Defence Committee", a group of the most senior ministers and those whose departments are most affected by Brexit, are being called into Number 10 late tomorrow afternoon.
But sources suggest this is not to make any kind of decision about the Brexit deal. It's to keep them broadly on board, and to avoid accusations further down the line that Number 10 has bounced ministers into signing up.
One of the profound criticisms of the prime minister has often been that she and her officials are intensely secretive, and don't seek genuine buy-in from colleagues.
It's not mad to argue that with such divisions in her party that's been the way to survive.
But it has infuriated some of her colleagues. And it also means that objections and concerns have developed rather than been fully argued out and discussed.  It's also why the finger often gets pointed at the officials leading the talks.
Brexiteer knives have been out for Olly Robbins, the lead negotiator, for a long time now. It often seems the Brexit deal is being struck by him and Number 10 with the Brexit department looped in, rather than by the government as a whole.
But as one well-placed source acidly suggests: "Robbins does not get the SW1 politics of this - but it's ultimately her fault for letting a civil service man do a woman's political job."
There are of course plenty of loyalists - plenty of MPs and ministers who think the PM is faced with an absolute nightmare, in office but not in power with no majority, and simply trying to do a sensible best.
But there are concerned Brexiteer ministers, worried former Remainer ministers and as we've discussed many times here, widespread discontent on the Tory backbenches on all sides at the prime minister's hoped-for compromise.
Even some of Theresa May's most ardent backers worry that there's a disconnect that might go badly wrong.
While the government believes they probably do have the numbers when it gets to a final vote as I wrote here, I've heard from former Remainers as well as Brexiteers this week who say the same - "I just can't see how they get anything through."
It was of course always extremely likely that in the closing weeks of this negotiation the situation would be extremely febrile and it would all be "kicking off".
The second last episode in any box set is almost always when the heroes teeter on the edge of disaster before miraculously coming back from the brink.
In a couple of months this might seem like froth. But tonight the prime minister's vital backers are threatening to pull stumps; her cabinet is yet to be convinced; her backbenches certainly can't be relied on and the talks themselves are not sorted.
It certainly is all kicking off, and the government may well get hurt.

The woman who started the record-breaking anti-Brexit petition says she is "shaking like a leaf" after receiving three death threats by phone.
Margaret Georgiadou, 77, began the Revoke Article 50 petition, which had topped four million signatures by Saturday morning.
She said she was "totally amazed" it had become the most popular petition submitted to the Parliament website.
But Mrs Georgiadou said the "horrible" phone calls left her scared and angry.
The retired lecturer says she has also received abuse via her Facebook account.
She said: "I feel terrible, I feel angry with myself because I thought I was tougher than that. But I was scared."
"I haven't even told my husband because he is very old and he would become hysterical."
Mrs Georgiadou said she created the petition to stop people "moaning" about how awful they thought Brexit was going to be.
It has broken the record for the biggest petition on the Parliament's website, previously held by another Brexit-related petition from 2016.
Mrs Georgiadou said she wanted to get as many people as possible to sign it - but she wasn't hoping for a government response.
"Democracy is ruled by society for society, not the majority for the majority," she said.
"I want it to prove it is no longer the will of the people. It was three years ago but the government has become infamous for changing their mind - so why can't the people?
"People should ask themselves, who is it that wants Brexit? It will help Putin, it will help Trump… but will it help us? I doubt it," she continued.
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Since the success of her petition, Mrs Georgiadou has faced criticism over posts she allegedly made on social media, using threatening language about the prime minister. She said she had no memory of the posts.
She said:  "It must have been a cut and paste job. The dates were all wrong."
"My friends thought it was funny. They have made photos of me trying to hold up a rifle with my zimmer-frame... I don't own a zimmer-frame by the way - or a rifle."
Mrs Georgiadou says she cannot attend the march for another EU referendum in London on Saturday but would welcome tributes from the demonstrators.
"I want them to sing a song for me, 'March on, march on, with hope in your heart and you'll never walk alone'."

Brexit negotiations "have been difficult" and "no solution has been identified" to the Irish backstop, the European Commission has said.
It comes after the latest talks between UK ministers and EU Brexit negotiator Michel Barnier in Brussels.
Commission spokesman Margaritis Schinas said the talks had taken place in a "constructive atmosphere" but there had been no breakthrough.
The UK is pushing for legally-binding changes to the EU deal.
Mr Schinas was speaking after Mr Barnier briefed the European Commission's weekly meeting on the state of Brexit talks.
Speaking after talks with Mr Barnier, the UK's Attorney General Geoffrey Cox said: "Both sides have exchanged robust, strong views. We're now facing the real discussions. Talks will be resuming soon."
He added: "We're into the meat of the matter, we've put forward very reasonable proposals."
Downing Street echoed Mr Barnier's characterisation of the talks as "difficult", but said the negotiations were "ongoing".
"The EU continues to say that it wants this to be resolved and that it wants the UK to leave with a deal. Parliament has been clear that for this to happen, we require legally-binding changes which mean that the UK can't be trapped in the backstop indefinitely," said the PM's official spokesman.
"That is what we will continue to pursue."
The backstop is an insurance policy - designed to avoid a hard border "under all circumstances" - between Northern Ireland and the Irish Republic.
Prime Minister Theresa May is pinning her hopes on getting changes to it that will prevent the UK from being tied to EU customs rules if no permanent trade deal is agreed after Brexit.
She believes this would be enough to get MPs - who last month rejected her deal by an historic margin - to back her deal in a vote she has promised on or before 12 March.
But the EU has consistently refused to rewrite the deal it has struck with Mrs May, which is meant to ensure an orderly departure from the bloc on 29 March and pave the way for trade talks.
And Mr Barnier repeated that message to EU leaders, according to Mr Schinas.
"Discussions have been difficult and no solution has been identified to that is consistent with the withdrawal agreement, including the Northern Ireland protocol which, as you know, will not be reopened," he said at a press conference in Brussels.
BBC Brussels reporter Adam Fleming explained that EU sources said the UK side couldn't guarantee that whatever might end up being agreed in Brussels would even get through Parliament.
Mrs May is also hoping to attract votes from Labour MPs in Leave-voting areas of the UK, as she battles to get her deal through the Commons.
She is promising MPs a vote on any changes to workers' rights after Brexit.
No 10 said Parliament would be given a say over whether to adopt any new protections introduced on the continent and to stay aligned with EU standards.
Labour MPs have been seeking assurances the UK will not fall behind EU standards after Brexit.
But trade unions said the MPs should not be "taken in by blatant window dressing" and the assurances on workers' rights were "not worth the paper they are written on".
Meanwhile, Labour leader Jeremy Corbyn has met Conservative MPs who back a close, Norway-style relationship with the EU after Brexit.
He discussed the idea of a "Common Market 2.0" trade-focused model with former ministers Nick Boles and Sir Oliver Letwin.
Mr Boles said the goal was to reach a cross-party compromise to ensure the UK left the EU but in a manner which protected its economic interests.
The Labour spokesman said the meeting was to "discuss how to achieve a deal that would be good for jobs and could bring Leave and Remain voters together".
The meeting comes after Mr Corbyn and the main business organisations - the CBI, the Institute of Directors, the Federation of Small Businesses, the British Chambers of Commerce and Make UK - met on Tuesday to discuss Labour's Brexit plan based on a customs union with the EU.

There have been "fruitful" discussions on Irish issues at the Brexit talks, the EU's chief negotiator has said.
Michel Barnier also said there had been "genuine progress' on the Common Travel Area (CTA).
The CTA is a UK-Ireland arrangement allowing free movement of UK and Irish citizens between the Republic of Ireland, NI and the rest of the UK.
Mr Barnier was speaking in Brussels at the end of the third week of Brexit negotiations with the UK.
There has been slow progress on other major issues, including the size of the so-called Brexit bill the UK will have to pay.
Mr Barnier said negotiations were still "quite far" away from being in a position to begin talks on future trade arrangements.
UK Brexit secretary David Davis said he had a duty to tax payers to "rigorously interrogate" the EU's position on the bill.
But Mr Davis said the talks had been "constructive" overall.
He said there was a "high degree of convergence" on the CTA, and recognition of the need for joint work on other cross border issues.
The Brexit secretary urged the EU to be "more imaginative and flexible" in its approach.
Chancellor of the Exchequer Philip Hammond was in Dublin on Thursday, where he met the Irish Foreign Minister, Simon Coveney.
Mr Coveney said he had "urged" the chancellor to "listen to those who stand to be most negatively impacted by Brexit across these islands".
He said he had emphasised that the UK remaining in the Customs Union and the Single Market was the best way to avoid a hard border.
In article for the Irish Times, Mr Hammond said the UK government was determined "to avoid any physical infrastructure" along either side of the border.
"Our economies are already closely entwined. Our businesses operate across the land and sea borders, and so do our people," he wrote.

The government has distanced itself from a page of Brexit notes caught on camera in Westminster.
The handwritten notes, carried by an aide to Conservative MP Mark Field, included "what's the model? Have your cake and eat it" and "unlikely" in reference to the EU single market.
They were photographed after Mr Field and his aide left a meeting with the Brexit department at 9 Downing Street.
The government said the notes did not reflect its Brexit position.
"These individual notes do not belong to a government official or a special adviser. They do not reflect the government's position in relation to Brexit negotiations," a spokesman said.
The notes, held by Mr Field's chief of staff Julia Dockerill, were captured on a long-lens camera by photographer Steve Back.
"Difficult on article 50 implementation - Barnier wants to see what deal looks like first," they note, in an apparent reference to the lead EU negotiator Michel Barnier.
"Got to be done in parallel - 20 odd negotiations. Keep the two years. Won't provide more detail. We think it's unlikely we'll be offered single market," they also say.
Among the reaction from other EU members, Luxembourg PM Xavier Bettel said of the UK stance: "They want to have their cake, eat it, and get a smile from the baker, but not the other things... there are European values which cannot be separated. No cherry-picking."
The BBC's assistant political editor Norman Smith says the government's response, playing down the picture's significance, underlines just how "awkward" it is, because it does seem to be of a view held "within" the Brexit department.
"The real damage is that phrase 'what is the model? Have cake and eat it.' The damage is the way that will be read by other EU countries," he says.
It is not known who Mr Field - a vice-chairman of the Conservative Party and MP for the Cities of London and Westminster - was meeting, or if the page of scribbled notes being carried by his aide is definitely an account of talks at the department handling Britain's departure from the EU.
The notes appear to suggest that a transitional arrangement - which would allow the UK continued access to the single market after Brexit while it negotiates a new trade deal - is also unlikely.
"Transitional - loath to do it. Whitehall will hold onto it. We need to bring an end to negotiations," the paper reads.
The picture is enough to give Downing Street indigestion. But as the last shenanigans over a memo suggested, unless and until Number 10 is willing to share more details of their plans, or at least be clearer about the broad answers to the questions, every scrap or information will be pored over by journalists and interested parties, eager, if not downright desperate, for more information.
If there is a vacuum, others will fill it. Downing Street is well aware of this. And some of the Number 10 team don't think it's a sustainable situation. But in the absence of a traditionally functioning opposition, and look at today's polls which suggest a stonking lead for the Tories, this lack of information does not, at least, appear to be doing much wider harm.
The document also says it is "unlikely" the UK will remain in the single market, and that a transitional arrangement, immediately after Brexit, will not happen either.
It says a deal on manufacturing should be "relatively straightforward", but one on services will be "harder" to achieve.
And in what appears to be a reference to the negotiating team the government will encounter in Brussels, the document says: "Very French. Need fair process guaranteed."
The government has refused to reveal details of its Brexit negotiation strategy in advance, saying it will not offer a "running commentary".
Debate has focused on the level of access the UK could secure to the single market, and whether this would come at the price of greater immigration controls.
For Labour, shadow Brexit secretary Keir Starmer called for the government "to come clean, to end this unnecessary uncertainty and publish a clear plan for Brexit".
"These disclosures are significant because they suggest that the government is not even going to fight for the single market or customs union in the negotiations. If that is the case, there are huge implications for the economy, for businesses and for jobs in the UK," he said.
Lib Dem leader Tim Farron said: "If this is a strategy it is incoherent. We can't have our cake and eat it and there is no certainty on the single market. This picture shows the government doesn't have a plan or even a clue."

Theresa May has rejected claims she does not believe in Brexit - and insisted she would make a success of it "regardless of the outcome" of talks.
She told the BBC's Andrew Marr Show her plan for post-Brexit trade with the EU was not dead, despite it having been rejected by EU leaders.
And she urged the Tory party - in Birmingham for their annual conference - to "come together" and back it.
Boris Johnson has called her so-called Chequers plan "deranged".
In his latest broadside against her Brexit strategy, the former foreign secretary suggested he might be able to strike a better deal than her with Brussels.
He told the Sunday Times : "Unlike the prime minister, I fought for this, I believe in it, I think it's the right thing for our country and I think that what is happening now is, alas, not what people were promised in 2016."
Mr Johnson also set out domestic policy ideas, including building a bridge between Britain and Ireland and putting the HS2 scheme on hold to focus on a rail link in northern England.
Mrs May, who campaigned for Remain in the 2016 EU referendum, hit back at Mr Johnson in her Andrew Marr interview.
She said: "I do believe in Brexit. Crucially, I believe in delivering Brexit in a way that respects the vote and delivers on the vote of the British people while also protecting our union, protecting jobs and ensuring we make a success of Brexit for the future.
"That's why I want us to get a really good free trade deal with the European Union, which is what lies at the heart of the Chequers plan."
But she also said she was prepared for a "no deal" scenario, saying: "We will make a success of Brexit, regardless of the outcome of the negotiations."
The Labour Party has said it will back Mrs May in Parliament if she agrees to their plan for a customs union with the EU and a Brexit deal that guarantees workers' rights and protects jobs.
Mrs May said: "My message to the Labour Party is that they should stop playing politics with Brexit and start acting in the national interest.
"My message to my party is let's come together and get the best deal for Britain."
EU leaders have rejected her Chequers plan because they believe it would undermine the single market by allowing the UK to "cherry pick" bits of EU law it liked and ditch the rest.
Mrs May said: "We think we are putting forward a proposal that will maintain the integrity of the single market."
She said she wanted a more detailed response from the EU on their objections.
Later on Sunday, Foreign Secretary Jeremy Hunt hit back at the EU's negotiation stance in his speech to the party conference.
He said the EU seemed to want to "punish" the UK for leaving, and added: "If you turn the EU club into a prison, the desire to get out of it won't diminish, it will grow and we won't be the only prisoner that will want to escape."
Mr Hunt also addressed EU leaders directly, saying: "If you reject the hand of friendship offered by our prime minister, you turn your back on the partnership that has given Europe more security, more freedom, more prosperity, more opportunities than ever before in history."
In the main conference hall, pro-Brexit former CBI chief Sir Digby Jones gave a watching Mrs May a boost with a speech hailing her for standing up to the EU "bully boys" and attacking Mr Johnson as an "irrelevance".
By Chris Mason, BBC political correspondent, in Birmingham
Just like the Labour conference last week, the Conservatives are keen to show us they have plenty of songs on their playlist.
But just like the Labour conference last week, one record is louder than all the others and seems jammed on repeat: Brexit.
Autumn guarantees two things: leaves falling off trees and Conservative conferences in which there is a series of deftly choreographed Johnsonian interventions, before and during the main event.
Forty-eight hours on from his 4,000 or so words for the Daily Telegraph, one word from Mr Johnson is sufficient to grab a headline or two today: "deranged".
The big question of the next few days, beyond the Brexit noise: does the PM offer any indication, however vague, of the possibility of her shifting on her much criticised Brexit plan?
But former Brexit Secretary David Davis, who like Mr Johnson quit the cabinet over Mrs May's Brexit proposals, told Sky News the Chequers plan "will die" because "it's just wrong".
He said he expected a free trade deal to be struck along the lines of a Canada-style agreement, adding that "we are going to have a very scary few months" as talks with the EU entered their final stages, but that was "normal".
On the Andrew Marr Show, Mrs May also defended the "hostile environment" immigration policies she introduced as home secretary,  which led to people from the so-called Windrush generation losing their jobs, welfare benefits and right to remain in the UK.
She apologised for the fact that many long-standing UK residents of Caribbean origin had been caught by her Immigration Act, but declined to apologise for the policy itself.
Mrs May wants to use the Conservative conference to focus on domestic issues as well as Brexit, after Labour unveiled a string of new policies at its conference last week.
She has announced plans to tackle a big increase in rough sleeping, to be funded by a tax on foreign-owned homes.
The Prime Minister also revealed plans for a Festival of Great Britain and Northern Ireland to showcase the nation in January 2022 - months before the next scheduled general election.
And Health Secretary Matt Hancock said health officials would produce guidelines on the amount of time young people should spend on social media.

British passports will change from burgundy to blue after Britain leaves the EU, the Home Office has said.
Immigration Minister Brandon Lewis said he was delighted to return to the "iconic" blue and gold design which came into use almost 100 years ago.
The new passports will be issued to those renewing or applying for a passport from October 2019.
Burgundy passports were first issued in 1988. The EU has never compelled the UK to change the colour of its passport.
Former UKIP leader Nigel Farage responded to the announcement by tweeting "Happy Brexmas!"
He added: "In the 2016 referendum, we wanted our passports back. Now we've got them back!"
But Labour MP Mary Creagh tweeted: "No-one under 45 will have owned a blue passport, and most will think they're not worth £50 billion and crashing the economy."
Mr Lewis told BBC Radio 4's Today programme he knew many Remain voters who still had an "attachment" and "speak fondly" of the blue passport.
By Dominic Casciani, home affairs correspondent
Did Brussels force the UK to change the colour of its passport? No.
The European Union has never had the power to force the UK to change the colour of the British passport.
Dumping the blue for burgundy was a decision taken by the UK in the 1980s after the then EEC (European Economic Community) member states tried to harmonise designs to make life easier for travellers and border officials.
So this wasn't a decision forced on the UK by Brussels Eurocrats. Ministers could have ignored it.
Croatia retained its blue passport after it joined the EU in 2013.
In a similar vein, the EU has never had the power to order the UK to remove references to Her Majesty The Queen from the passport. It is still a British document, but with added EU wording to guarantee freedom of movement.
The only legal requirement to harmonise EU passports related to security standards, part of a global governmental effort to combat forgery.
If the EU wanted passports to change in any other way, the plans would need each government to agree.
Tory MP Andrew Rosindell, who campaigned to bring back the blue passport, tweeted: "A great Christmas present for those who care about our national identity - the fanatical Remainers hate it, but the restoration of our own British passport is a powerful symbol that Britain is Back!"
However, many other people have mocked the announcement on social media.
Simon Blackwell, a comedy writer, said: "Why do we need any colour passport? We should just be able to shout, "British! Less of your nonsense!" and stroll straight through."
According to the Passport Index, 76 countries have blue passports, including a number of former colonial and Commonwealth countries, such as Australia, the United States, Canada, India and Hong Kong.
Several Caribbean countries also have blue passports, including Jamaica, Antigua and Barbuda, Barbados and St Vincent and the Grenadines.
In Europe, people from Iceland and Bosnia and Herzegovina both carry blue passports, while it is also a popular colour in central and south America - Argentina, Brazil, Costa Rica, El Salvador, Uruguay and Venezuela are among those that have them.
Others include Israel, Iraq, Syria and North Korea.
Stig Abell, editor of the Times Literary Supplement, tweeted: "I've just spent the last 10 minutes screaming 'Take that you burgundy symbol of EU oppression' at my passport.
"It just stares insolently back, as if it is an inanimate and merely functional object and its colour doesn't matter."
The new passports will also have updated security features to protect against fraud, Mr Lewis said.
The Home Office said there was no need for British passport holders to do anything ahead of their current passport renewal date, adding that the changes would be introduced in phases.
When the UK leaves the EU in March 2019, burgundy passports will continue to be issued but with no reference to the European Union.
The blue passports will be issued later the same year, after a new contract for their production is negotiated.
"Leaving the EU gives us a unique opportunity to restore our national identity and forge a new path for ourselves in the world", Mr Lewis said.

The President of the European Council, Donald Tusk, has told the Taoiseach, Leo Varadkar, that Ireland's interests come first in the Brexit negotiations.
Speaking in Dublin, Mr Tusk said nothing must be done to risk the peace process or the Good Friday Agreement.
He said every EU leader he has met has expressed support for Ireland's position.
He called on the British government to produce a "realistic solution" to avoid a hard border on the island of Ireland.
Mr Tusk said: "If in London someone assumes that the negotiations will deal with other issues first before moving to the Irish issue, my response would be 'Ireland First'."
Responding to Theresa May's criticism of the draft Withdrawal Agreement which the Commission published on 28 February, Mr Tusk said: "We also have to be clear that any backsliding on the commitment made so far would create the risk to further progress in Brexit negotiations."
"Since my last visit to Dublin I have spoken to virtually every EU leader and everyone without exception declared... that among their priorities are protecting the peace process and avoiding a hard border. The EU stands by Ireland."
Mr Tusk began his comments with some light-hearted weather references saying: "I may be from the east but I am not a beast".
But the tone quickly became more serious as he reaffirmed the EU position on the negotiations:  "We also expect the UK to provide a specific and realistic solution to avoid a hard border. As long as the UK doesn't present such a solution, it is very difficult to imagine substantial progress in Brexit negotiations."
Mr Varadkar told the news conference: "I've always said that my preference is to avoid a hard border through a wider future relationship between the United Kingdom of Great Britain and Northern Ireland and the European Union.
"We're committed to playing our part in exploring this option, or alternative specific solutions, in a way that respects the structure of these negotiations and that will of course require further detailed progress to be put forward by the UK government.
"However we must have certainty that if a better option proves unachievable, the backstop of maintaining full alignment of Northern Ireland with those rules of the single market and customs union that apply in order to protect north-south co-operation and avoid a hard border."
Mr Tusk also referred to a recent speech by Chancellor of the Exchequer, Philip Hammond in which he called for financial services to be included in a future trade deal.
The EC president said: "Services are about common rules, common supervision and common enforcement, to ensure a level playing field, to ensure the integrity of the single market and ultimately also to ensure financial stability.
"This is why we cannot offer the same in services as we can offer in goods.  It's also why FTAs (free trade agreements) don't have detailed rules for financial services.
"We should all be clear that, also when it comes to financial services, life will be different after Brexit."
Responding to Mr Hammond's assertion that it was in the interest of both Britain and EU to ensure that UK-based financial services companies had easy access to the single market, Mr Tusk said: "I fully respect the Chancellor's competence in defining what is in the UK's interest. He must allow us to define what is in the EU's interest."
Democratic Unionist MEP Diane Dodds said Mr Tusk's comments suggest the EU will again hold up the trade talks if the December fall-back option of alignment is not legally translated.
"Far from putting 'Ireland first' this will generate further frustration among Republic of Ireland businesses dependent on access to their primary marketplace in the UK," she said.
"These include Irish agri-food firms which export around 40% of their produce to Great Britain and Northern Ireland."
SDLP leader Colum Eastwood said Mr Tusk's comments showed that "the EU is not messing about".
"It is crystal clear that the EU's commitment to protecting the interests of the island of Ireland is immovable," he said.

A majority of police forces in England and Wales saw record levels of hate crimes in the first full three months following the EU referendum, according to new analysis.
More than 14,000 hate crimes were recorded between July and September.
In 10 forces the number of suspected hate crimes increased by more than 50%, compared to the previous three months.
Police say their own monitoring suggests incidents have levelled out after the summer's spike.
Last October the Home Office published provisional figures which suggested the number of hate crimes in July 2016 had been 41% higher than 12 months earlier.
Those 5,468 reports indicated there had been a spike in reports - supporting anecdotal evidence across the country of an increased number of threatening, violent or abusive incidents.
The fresh data compiled by the Press Association comes from official statistics which include detailed figures for five core crimes which are deemed to be racially or religiously aggravated, ranging from assaults through to criminal damage.
In the three months to September 2016, 33 of the 44 forces in England and Wales saw their highest levels of hate crimes since comparable records began in 2012.
Dorset and Nottinghamshire saw the highest percentage increases in reports - 100% and 75% respectively - compared to the levels seen between March and the end of June. That previous period had included the referendum campaign itself and the week immediately after the vote.
The Metropolitan Police in London recorded the highest number of hates crimes, with 3,356 in that period, while Greater Manchester and West Yorkshire Police recorded 1,033 and 1,013 respectively.
South Yorkshire, Gloucestershire, Surrey and City of London Police posted falls in hate crime.
Assistant Chief Constable Mark Hamilton, the National Police Chiefs' Council's lead for hate crime, said: "We know that national and global events have the potential to trigger short-terms rises in hate crime and we saw this following the EU referendum last year.
"Police forces took a robust approach to these crimes and reporting returned to previously seen levels.
"These numbers are still far too high.  We have increased the central reporting and monitoring functions to enable us to recognise spikes earlier. This will be used to assess any threats that may arise and inform local police activity."
Analysis by Dominic Casciani, BBC home affairs correspondent
While the overall figure from this analysis comes to 14,300 hate crimes in three months, it can't confidently be claimed as a quarterly national record across the UK because of the complicated way that hate crimes are counted.
There's no doubt there was a spike after the Brexit vote, but the long-term picture won't become clear for months. And if 2016 turns out to be a record year, there still needs to be some caution about what the figures mean.
Sexual offences rose in recent years thanks to more people coming forward to report what had happened to them.
If there is a long-term rise in hate crime recorded by police, it may simply reflect that victims have more confidence that it is worth speaking to the police.
But David Isaac, chairman of the Equality and Human Rights Commission, warned that many people remained anxious.
"It must be sensible to prepare for any possible spikes during the Brexit process," he said.
"The triggering of Article 50 is the next major milestone and we must do all we can to discourage hate attacks and to support people who feel at risk."
Fizza Qureshi of Migrants' Rights Network, a campaign group that runs an online service encouraging people to report hate crimes  and have them recorded on a real-time map, said: "The experience of thousands of people in the UK of discrimination, hostility and at times violence is invisible to many people in Britain - but today's figures lay it bare for all to see."

Prime Minister Theresa May has been forced to quit. Parliament is deadlocked. Both the Conservative and Labour parties are deeply divided and deeply unpopular.
What's more, with days to go before there is a new occupant of No 10, no-one has identified a clear route to an agreement that will avoid an outcome pretty much everyone says they want to avoid - a costly and disruptive no-deal Brexit. So, how did the UK end up here?
For the past few months, the BBC's Panorama team has spoken to those with first-hand knowledge of the negotiations - in Brussels, Paris and Dublin as well as Westminster. We've interviewed at length, on and off the record, the men and women who tried and failed to make a Brexit deal that both the UK and the EU could agree to.
This is an account of 10 crucial mistakes, mishaps and misunderstandings that might explain why we haven't left yet.
George Bridges was a new minister in the Brexit department created from scratch in 2016 when Theresa May became prime minister - a job she only got because the UK voted to leave the EU.
At least Bridges had an office. Secretary of State David Davis's political advisers had to share a cupboard, while the department's top official had to change his office three times in one day. It was chaos.
Lord Bridges, who was a junior minister, assumed that the thinking about Brexit must be taking place somewhere else:
"I was very much under the view that there would be somewhere in No 10 a very small, very secret group, putting together an almighty chart, a big plan of how we were going to negotiate and crucially what our overall objectives were. So, the prime minister - rather like a Bond villain - would be sitting with her white cat on her lap with this big plan behind her. I'd love to say that that room existed. I never found it."
He wasn't the only one. In Brussels, top EU officials were waiting to see what the UK would propose.
"We thought they are so brilliant there will be, in some vault somewhere in Westminster, a Harry Potter type book with all the tricks and all the things in it to do."
Frans Timmermans, first vice president of the European Commission, was shocked by what he saw and heard. Or rather what he didn't:
"I thought, 'Oh my God, they haven't got a plan…they haven't got a plan… it's like Lance Corporal Jones'. It was, 'Don't panic, don't panic,' running around like idiots."
The truth is there was no plan for Brexit when the UK voted to leave. David Cameron had no Plan B when he called the EU referendum. One senior official says he stopped civil servants preparing one as he was fearful it might leak.
The main Leave campaign, led by Boris Johnson and Michael Gove, had decided not to produce a Plan A. They knew the choices that would have to be made would split their coalition of support.
Theresa May came to office without a plan. Indeed, she barely mentioned Brexit in her speech in Downing Street.
Speaking to the BBC, former French President Francois Hollande says he told his fellow EU leaders straight after the referendum that the UK would have to pay a price:
"Brexit might lead to a slippery slope where others, and particularly those under the sway of populists, might decide to follow what the British have just been doing."
EU leaders sensed that populism was on the march. Brexit was followed by the election of Donald Trump.
When the new US president called the other President Donald - Donald Tusk, the president of the European Council - he asked a question with a hint of menace: "Who's next?"
With elections due in France and the Netherlands in 2017, this was no mere taunt. The leader of the French National Front, Marine Le Pen, was campaigning for "Frexit". Polls suggested victory was likely for the Dutch far right leader Geert Wilders. Hungary, Austria and Italy were already governed by politicians who were highly critical of the EU.
There were tears in the office of Jean-Claude Juncker, the president of the European Commission, when he and his officials heard that the UK had voted to leave.
Juncker's right hand man was a formidable German lawyer called Martin Selmayr, thought by many to be the most important man in Brussels. Giving his first British broadcast interview to Panorama, he says:
"I think the most important thing at this moment in time was to preserve the unity of the other 27 member states - to make sure that in the process that followed, all 27 saw eye to eye …[and] to use this moment not to further weaken the [European] Union, not the beginning of the end, but the start of a new beginning for the European project," says Selmayr.
When Selmayr met the British minister he knew best, David Lidington,  who'd been Minister for Europe for many years and who would go on to become Theresa May's de facto deputy - he spelt out what this would mean. Lidington recalls this conversation:
"He said to me, 'Look David, there's not going to be the traditional EU late into the night, into the wee small hours, horse trading on this. It'll be the Commission that your side talks to. We are not going to give your prime minister the chance to try and pick us off."
The UK was no longer to be treated like a member of the club, in which it could seek to build alliances and divide and rule the 27 countries still inside. It would be treated as if it had already left.
Negotiations would take place not with representatives of every country but with a team led by one man - a suave silver-haired Frenchman called Michel Barnier. In his first British broadcast interview since the negotiations began, he told Panorama:
"Everybody will have to pay a price - EU and UK - because there is no added value to Brexit. Brexit is a negative negotiation. It is a lose-lose game for everybody."
Philip Hammond didn't like what he was hearing. Theresa May was delivering her first speech as prime minister to the Conservative Party Conference in 2016, and her new chancellor of the Exchequer was sitting in the audience.
"I was trying to keep my face dead straight, conscious that there were cameras on me," he says.
May began by saying that "Brexit means Brexit and we're going to make a success of it". That came as no surprise to Hammond. He'd heard her use the phrase many times before.
But then the prime minister continued: "Our laws will be made not in Brussels but in Westminster. The authority of EU law in Britain will end." That meant that the UK would have to leave the single market. It could not stay as close as possible to the EU economically - like Norway or Switzerland.
Hammond says that he had not been consulted about the speech or the policy:
"I didn't know. I think the prime minister felt that as a former remainer she needed to demonstrate her credentials by presenting quite an extreme version of Brexit. Some of the things that were being said were likely to have quite an impact outside the hall."
Senior EU figures were watching and concluded that the prime minister had outlined a series of undeliverable red lines.
The man who'd written the speech was May's powerful chief of staff Nick Timothy. A passionate leaver, he had also dreamed up "Brexit means Brexit" - a phrase that was much less empty than it seemed.
"I plead guilty to that phrase. It was one of the most irritating in British politics.
"Funnily enough it actually meant three different things. Firstly, that she understood that having been a remainer when the country voted to leave she would deliver on that mandate.
"It was [also] a warning to others - I think in particular in Parliament who were already showing signs of not really accepting the result - that Brexit must mean Brexit. Then at a third level that Brexit must meaningfully mean Brexit and couldn't be a kind of shadow membership."
Click here to watch Panorama: Britain's Brexit Crisis on BBC One, 18 July at 21:00
In the same speech, May announced that she would soon begin the formal process of leaving the EU by triggering Article 50. Hammond believes this was a mistake, given that there had been no real debate in the government, let alone the country, about what Brexit should mean.
"With the benefit of hindsight, I can now see that that was wrong," he says. "The real issue is debating with ourselves what kind of Brexit Britain wants.  And we should have done that before we triggered the process."
The chancellor says there was always going to be a tension between protecting the economy and "taking back control" of policies like immigration. It was a tension that was never fully resolved.
"... She hoped to improve her position and make it easier to deliver what people voted for in the referendum but actually the result made that job even more difficult."
Gavin Barwell lost his seat as a Conservative MP when Theresa May called a general election in June 2017. He was hired as her new chief of staff, replacing Nick Timothy - the man blamed by many for her decision to go to the polls. The election  left her with no majority in the House of Commons.
"Those first few weeks were a pretty traumatic experience," says Barwell. "That was apparent from the first day I walked into No 10."
The US President Lyndon B Johnson said: "The first rule of politics - you have to be able to count."
In other words, leaders need to be sure that they have more people backing their policies than opposing them.
The votes of Tory MPs alone would not now give May a majority. She turned to Northern Ireland's Democratic Unionist Party (DUP) for support. What she didn't do - until it was far too late - was to try to woo opposition MPs.  That was what Ted Heath had done before he took Britain into the Common Market in 1973.
Incidentally, it was not just May's closest advisers and cabinet ministers who helped convince her to call an election. Allies of Jean-Claude Juncker, a former prime minister himself, admit that while he would never have advised her to call an election, he did tell her that having her own mandate would help her.
Juncker warned that a tiny majority in a House of Commons that was less enthusiastic about Brexit than the British public would cause real problems when she eventually needed MPs to ratify a Brexit deal with the EU.
"...The UK chose itself the date for leaving in March 2019. This is why every time I just recall the clock is ticking. Be careful eh?"
 Again and again, Michel Barnier reminded British ministers that they would have just two years to reach agreement. It was clearly stated in Article 50 of the Lisbon Treaty that set the rules for how a country could leave the EU.  It allowed Brussels to use time against the UK.
 Senior figures in government have told me that the UK side misunderstood Barnier's real role. He was the public face of the negotiations and the politician who would keep the leaders of the EU's 27 countries on side.
Barnier's deputies did the real negotiating, alongside Martin Selmayr - the man whose nickname in Brussels is "the Monster" - who really decided what could and could not be agreed by the EU.
Selmayr explains the thinking behind the process for the Brexit negotiations, that would give the EU control not just of the timetable but also the agenda and the order [or sequencing] of the talks.
"Brexit will always be a sad event because it's a divorce. First of all you separate the assets… the rights and duties that are stemming from 40 years of a very long and intense and close relationship. Then you see if you remain friends afterwards or if you can remain close friends afterwards."
In 2017, Brexit Secretary David Davis promised a long hot summer when he would fight the idea that the UK would have to agree the Brexit bill it owed - which would run into tens of billions of pounds - before any talks could begin on a future trading relationship with the EU.
In the event the fight never occurred. He claims that he was overruled by May:
"She felt pressurised, unconfident, maybe even insecure after the general election outcome. She gave away the fact that we were going to meet everything they wanted - money and citizens' rights and so on - and get nothing back in return."
David Davis never persuaded the rest of the cabinet, let alone the prime minister herself, to make the threat summed up in another of her oft-repeated phrases - "no deal is better than a bad deal" - appear credible.
"The Treasury in particular would always argue you can't frighten the horses," he says. "Don't talk about it publicly, don't say what needs to be done, don't do the public preparation."
Davis complains that the chancellor was so nervous of spooking business that he stopped the Brexit department sending out letters to tens of thousands of small businesses telling them to prepare for a no-deal Brexit.
Hammond counters that he was trying to reassure business to stay in the country and to keep investing, so the last thing he wanted was anything that would have the appearance of no deal.
"There was a tension at the beginning. We didn't want to send business a message that we're going to crash out of the EU and see businesses perhaps relocating - taking jobs out of the United Kingdom."
The official projections were clear. A no-deal Brexit would lead to 10% tariffs on car exports, and 40% tariffs on the sale of lamb, says Hammond, as well as potential chaos at Dover with the French being able to "dial up and dial down" the queues at will to make a political point.
Hammond was not alone. One of the top officials handling Brexit told ministers that threatening no deal was like taking the pin out of a grenade and holding it next to your own head.
When I asked Michel Barnier if May or her ministers had ever made a no deal threat behind closed doors, he replied emphatically, "No", before adding, "I think that the UK side, which is well informed and competent and knows the way we work on the EU side, knew from the very beginning that we've never been impressed by such a threat. It's not useful to use it."
Selmayr agreed. "I don't think it's ever a reality for anybody who is in a responsible position. It has consequences. It ruins your relationship for the future and I don't think anybody responsible on the UK side or the EU side has an interest in that," he said.
In fact, when I asked Selmayr if he thought the UK was prepared for that eventuality, he said he was "very certain" it was not.
"We have seen what has been prepared on our side of the border for a hard Brexit," he said. "We don't see the same level of preparation on the other side of the border.
"... That would be in many ways a symbol of the past of tragedy, of emotion, of terrorism, of murder."
It was not just in Brussels that Brexit was seen as a threat.
In Dublin, Simon Coveney - who is now Ireland's Tanaiste, or deputy head of government - says he feared that there would be a return to a hard Irish border unless the issue was addressed right at the beginning of the negotiations.
Other senior figures in the Irish government have told the BBC that they were concerned that Ireland could be "dragged out" of the EU by its bigger, richer neighbour. That is why the backstop - the issue which came to dog Brexit - was born.
After Brexit, the border between Northern Ireland and the Irish Republic would be the only land border between the EU and the UK. If peace was to continue, everyone agreed that there should be no border controls. However, the EU's desire to protect its single market would mean there had to be checks on certain goods such as farm animals and chemicals that crossed the border.
The argument went that a post-Brexit Britain might do a trade deal with Donald Trump's US and could agree to allow the import of chlorine-washed chicken or hormone-treated meat. Without a border, those banned goods could move from north to south and into the EU, undercutting European food standards and representing cheap and unfair competition to their farmers.
Controls designed to enforce EU rules could become a target for paramilitaries and encourage smuggling which for years was key to the financing of terrorism.
If the UK followed EU rules and regulations, this wouldn't be a problem but Ireland and the EU demanded a guarantee - or a backstop - that whatever trade deal was eventually signed between the two sides there could never be a hard border.
Brexiteers saw this as a trap designed to keep the UK bound to EU rules and in a customs union. Talking to the BBC, the former Brexit Secretary Dominic Raab, sums up their fears:
"The idea that you could leave the EU, be successful and demonstrate that the EU perhaps wasn't all it was cut out to be was for them the thing that made [the EU]    the most nervous. And the obvious answer to that was to try and lock the United Kingdom in to as many EU rules as possible without any say over them and without any means to escape from that regime, and that's the conundrum of the backstop."
Raab's predecessor David Davis agrees with this position:
"They needed a lever which put us in the wrong and them in the right, I think that's the way they saw it. [With] the Irish border there's a strong political, moral, sentimental argument... based on fiction really, but nevertheless that's how it's used."
In other words the backstop was as much about trade as it was about peace. It was as much about French determination to protect the single market as it was about Irish worries about a new source of conflict. One of May's closest allies told us it was the "operationalisation by Brussels of a French idea dressed in a green jersey".
So why did the prime minister sign up to it? Because the clock was ticking and because she'd agreed to the EU's sequencing of the talks. No backstop meant no progress to talking about trade.
What's more, Theresa May was desperate to get agreement to the Treasury's top priority, which was the demand from big business for an extra two years to adapt to Brexit - the so-called transition period.
Davis blames No 10 for agreeing to the backstop. "They signed up to the backstop because they were desperate to make progress. They basically had a loss of nerve."
When we put to Martin Selmayr that the deal was "swallow what you don't much like on Ireland, and get more time", he replies: "Absolutely."
"Let's get the UK involved with France and Germany. Let's see how the dust settles and let's talk about whether we can come to a new deal for Europe."
Britain's de facto deputy prime minister David Lidington reveals to Panorama that he was made that startling offer by Martin Selmayr. It followed a summit of world leaders at which EU heads found themselves on the same side as Theresa May in a series of arguments with President Trump.
Selmayr explains why the offer was made:
"All the other European leaders were left behind when he [Trump] took the helicopter and they looked each other in the eyes and also at Theresa May and they thought, 'At least we all agree with each other, we are the last bastion of the rules-based international system.' I think that led to many thinking, 'Well, if she comes back tomorrow and has thought again, we wouldn't mind'."
Donald Tusk once joked in public about the idea that Brexit could be reversed saying, "Who knows? You may say I'm a dreamer, but I'm not the only one." However, this is the first time it has been confirmed that an approach and an offer was made by the European Commission to put Brexit on ice.
The offer was rejected and some in the EU came to the view it would be better if the UK left - and left quickly. However, the scale of opposition Theresa May faced in Parliament meant others continued to believe and hope that there would be another referendum and Brexit would not happen. This made them less likely to compromise.
"The two big parties have been trying to outmanoeuvre each other on Brexit, and for a long time Brexit has been used by the opposition party as a way of trying to trigger a general election. For me, as somebody who loves Britain, who's lived there, who's studied there, who has family there, I think it's a tragedy quite frankly, that in the face of this huge decision that the British people have made, that the political system has not been able to unite behind a middle-ground position and unite the country."
Simon Coveney is scathing about the failure of the British Parliament and political system to achieve consensus on Brexit. It's a stark contrast with the unity which has been on show in Dublin.
He blames the opposition Labour Party as well as the Tories. The government's Chief Whip, Julian Smith, says that he has lost a lot of sleep as a result of trying - and failing - to get a deal through the House of Commons.
"I think that there was definitely a shift from some Brexiteers who, if you'd asked them three years ago, would they be happy with the prime minister's deal, they'd have bitten your arm off. They then, during the course of the last year, became, I think, increasingly concerned about different elements of it, seeing some form of threat behind many aspects of it, and there was a kind of purification process - they sort of wanted everything on day one."
The Tories were hopelessly divided over what sort of Brexit deal to pursue. When May finally proposed her "Chequers plan" she did it without ensuring that she had the support of David Davis, her Brexit secretary .
Her allies believe that if Davis had been offered another job, he would have taken it rather than quitting the Cabinet altogether. They believe that Boris Johnson might then have stayed in the government.  As it was he became the figurehead for those wanting to "chuck Chequers" and, eventually, to chuck Theresa May as well.
The chief whip also blames the Speaker for blocking Brexit.  John Bercow ruled that the government could not bring back its withdrawal agreement to the Commons after it had been defeated twice. By this time, even hardliners like Boris Johnson and Jacob Rees-Mogg were prepared to vote with the government. No 10 insiders claim that they had the basis of an agreement which could have got DUP support as well but the vote was never held.
"Parliament is and has been deadlocked for one simple reason," says Julian Smith. "Large groups of MPs have been prepared to gamble that they could force the outcome they wanted - a harder Brexit or another referendum or a general election - rather than backing Theresa May's deal."
"If the only goal of the EU is this market obviously you could think that the German car industry could force the German government to comply with the demands coming out of London, but for Germany the EU is much, much more than a market. It's their destiny, it's not revisiting the horrors of history so even the car industry itself understands that this is fundamentally more important than selling cars to the United Kingdom."
EU leaders such as Frans Timmermans believe that British politicians do not understand the idealism and the history which underlies the European project. He says that "continental Europeans" do not see the EU in the same way as the United Kingdom - "as a market".
Brexiteers like Boris Johnson don't dispute the history but they do doubt that the leaders of any country would willingly harm their own economies. He has said in public that EU countries will want to sell us their cars or cheese or even Prosecco.
Did that claim infuriate Timmermans?
"Yes it did, also, perhaps I'm being a bit harsh but it's about time we became a bit harsh also because I'm not sure he [Johnson] was being genuine, I always have the impression he's playing games."
David Lidington - a lifelong pro-European - agrees that the EU has always seen itself as a political project but says it takes two to create a misunderstanding. He says that EU leaders have too often dismissed British demands as driven purely by short-term political pressures rather than principle:
"They thought Tories were simply pandering to UKIP or the DUP and never understood that Euroscepticism, a desire for sovereignty, support for the Union were real forces that any political leader and party would have to address."
Those misunderstandings have dogged the Brexit negotiations as both sides have miscalculated how the other side will react.
What has not been tested yet is whether the credible threat of no deal, a refusal to compromise on the Irish border and a willingness to withhold the £39bn divorce bill which Britain has agreed to pay will improve or destroy the chances of getting a deal.
We're about to find out.
Additional research and reporting by Britain's Brexit Crisis producer Max Stern

Donald Tusk does a good turn in press conferences, delighting headline writers by channelling song lyrics, making dramatic pauses. He, like his European Council colleagues, is a pro.
Even when he is saying something positive about the Brexit negotiations, he manages to convey his personal sadness about the fact the UK has decided to leave with a rather hang dog expression.
Today therefore, don't be surprised that the headlines out of his press conference to mark the publication of the EU's negotiating guidelines for our future trade relationship with them after Brexit are tough for the UK, his expressions hard reading for the government, and the guidelines themselves showing big gaps between the two sides as, to use his phrase today, we are "drifting apart".
The guidelines include, therefore, what the EU side would see as a reality check for the UK. In Brussels' view, there are, as one insider put it, "some vestiges of la la land" in the UK's position.
Today's paper demonstrates how sceptical the EU 27 is, for example, about the UK's hope to choose to stay in some European agencies.
Again, Mr Tusk has said that the UK's overall hope to pick and choose bits of the European apparatus is a non-starter. But before the next formal round of negotiations have begun it would be a genuine shock if he were to say anything else.
On the UK side, the EU has what one insider suggested were "significant' cojones", to suggest for example that the EU retains fishing rights in UK waters. And while not exactly jumping for joy, nor is the government in meltdown over the EU's opening gambit.
The details of the guidelines are here, complete with Donald Tusk's warnings.
But is this a giant two fingers to Theresa May's entire approach that really changes things for the negotiations? Have they today completely torn up the Mansion House speech?
There are significant differences of course, and I'm not suggesting for one second that the way forward is clear. But no one in government will be hugely surprised by the publication today, nor do they believe that it is time to run up the white flag.
In fact, the two sides notionally agree that they are both looking for an ambitious trade deal. Having repeatedly ruled out staying in the Single Market or the Customs Union, that is what the prime minister says she wants. And the EU has said it is willing to talk on the basis of there being no tariffs or quotas either.
Back in the depths of the referendum campaign, that would have seemed like quite a prize. And crucially, the draft guidelines hold out a small promise of room for manoeuvre, saying "if the UK positions were to evolve, the EU would be prepared to reconsider its offer".
In the coming months that may prove the most important paragraph of all. If the UK is willing to compromise, well the EU might have a rethink too.
The document may well be a reminder that it's the UK that will have to do most of the budging, but the draft guidelines do suggestion there is at least a conversation to be had.

A petition on Parliament's website calling for Brexit to be cancelled has now passed more than 5.7m signatures.
The petition to revoke the Article 50 withdrawal process has gained more than one million signatures since Saturday's march calling for a new EU referendum.
Theresa May has stressed that the UK had already decided to leave the EU in the biggest ever democratic exercise.
But European Council chief Donald Tusk has said revoking Brexit was an option if MPs again rejected the PM's deal.
The UK has to decide its next move by 12 April after the EU agreed a plan to delay Brexit beyond 29 March.
The prime minister hopes to bring the agreement she has negotiated with the EU back to the Commons for the third time but MPs want other options to be considered as well - and on Monday backed a series of votes to find out the kind of Brexit deal they would support.
In December, the European Court of Justice ruled that the UK can unilaterally revoke Article 50 of the Treaty of the European Union, the clause which allows a country to leave the bloc.
This means the UK can decide to stay in the EU without the consent of the 27 other member states.
Lib Dem MP Layla Moran has said the petition could "give oxygen" to the campaign for another Brexit referendum, a so-called People's Vote.
However, speaking on Thursday night after the petition reached the two-million mark, Mrs May said the public had already had their say on EU membership.
"They voted in 2016, they voted to leave. I think the time is now to deliver for the British people, the time is now to make the decision," she said.
People signing petitions on the Parliament website are asked to tick a box saying they are a British citizen or UK resident and to confirm their name, email address and postcode to sign.
The petition was started in February and quickly passed the 100,000-signature threshold needed for it to be debated in Parliament. It began to attract thousands of more signatures last week and at one stage caused the petition website to crash.
It reached four million signatures on Saturday, as hundreds of thousands of people marched in central London, making it the most popular to have been submitted to the parliament website.
A petition for a second EU referendum in June 2016 attracted more than four million signatures and was debated in the Commons - but thousands of signatures were removed after it was discovered to have been hijacked by automated bots.
In January, MPs debated whether the UK should leave the EU without a deal, after a petition calling for that got 137,731 signatures.

The UK will be unable to buy privileged access to the single market after it leaves the EU, says one of the top UK officials to have worked in Brussels.
Jonathan Faull, who retired last week, said that access to the single market "is not something that's on sale".
He also warned the UK should not assume it can  broker a deal with Angela Merkel if she wins re-election as German chancellor.
Theresa May plans to trigger the Brexit negotiations by the end of March.
But Mr Faull said that Britain has one important card to play in the EU negotiations - co-operation on European defence.
The warnings by Mr Faull, who served in the European Commission for 38 years, come as the government scrambles to assemble its Brexit negotiating team in the wake of the resignation of the UK's EU ambassador, Sir Ivan Rogers.
He is to be replaced by Sir Tim Barrow, a former UK ambassador to Moscow.
In his interview with BBC Newsnight, Mr Faull cast doubt about an idea, which is being promoted by senior Whitehall officials, that the UK could pay for privileged access to the EU's single market.
This would be designed to circumvent the rules of the single market whose members, including Norway which is outside the EU, have to accept the free movement of people and the jurisdiction of the European Court of Justice.
David Davis, the Brexit secretary, confirmed last month that the government was considering the idea.
Mr Faull said: "Can you buy access to the single market? It's not something that's on sale in that way. I find that rather extraordinary."
The former European Commission official pointed out that Norway is bound by two core rules of the EU - accepting the free movement of people and abiding by the European Court of Justice.
Theresa May has indicated that she would like to have some access to the single market. But the prime minister is to confirm in a speech later this month that the UK will have two fundamental red lines in its Brexit negotiations - control of its borders and freedom from the ECJ.
Mr Faull suggested that if the UK cannot accept the fundamental rules of the single market it would be regarded as a foreign country: "I don't think it is a question of buying your way somehow into the single market."
"You're a member of the single market as a member of the EU or the EEA. Or you're a foreign country outside it, and you conclude agreements with the EU - if you want to and it wants to - regarding the way in which your goods, services, capital and people move around.
"Or you don't and you have one or two international rules which apply and that's it, that's a choice to be made by both sides."
Newsnight was speaking to Mr Faull as part of a profile of Michel Barnier, the former French foreign minister who is the EU's chief Brexit negotiator.
Downing Street expects Barnier to adopt a hardline stance once the Brexit negotiations are formally under way when Theresa May triggers Article 50 of the Lisbon Treaty.
But in private, ministers believe that Angela Merkel will take a more benign approach if she wins re-election as German chancellor later this year.
Mr Faull warns that Theresa May's government could be in danger of repeating the mistake of David Cameron who believed that Mrs Merkel would come to his rescue. Mr Faull was the senior European Commission official involved in the Cameron negotiations.
"I think it would be a mistake to see the EU institutions as somehow wholly different from the 27 countries. These are all actors that will be working together on this," he said.
"I think one should look perhaps at the experience of the negotiations which took place before the referendum. where perhaps some similar thoughts were expressed and turned out not to be fully realised."
Mr Faull's remarks were endorsed by Lord Patten of Barnes. The former European commissioner told Newsnight: "There's an awful lot in the British press about what we'll get from them, what we'll negotiate from them. And I think it overlooks the fact - and I'm not making a 'why we should remain' point - the fact is they'll decide."
"They'll decide and we must hope that we can get as decent a deal as possible. But it's ultimately going to be decided in Paris and Berlin and some of the other member states."
But Mr Faull said that Mr Barnier will be well disposed to the UK in one key area - co-operation on defence led by France and the UK, Europe's two largest defence powers.
He said: "Michel Barnier has done a lot of work in recent years on defence and strategy issues and he believes the UK is absolutely crucial to the defence and security of Europe, the continent."
"And Franco-British cooperation in defence and security matters is extremely important and he will want - and I think all Europeans will want - a way to be found for that to continue."
"But that's more complicated if you're outside the EU, because part of the mechanisms used for this purpose are today EU mechanisms - so all of that will have to be looked into."
Nicholas Watt is political editor for BBC Newsnight

Airbus has warned it could leave the UK if it exits the European Union single market and customs union without a transition deal.
The European planemaker said the warning was not part of "project fear", but was a "dawning reality".
Airbus employs 14,000 people at 25 sites in the UK - around half in Wales.
The UK government said it was confident of getting a good deal for all industries, but the Welsh government said it was "extremely worrying".
In its Brexit "risk assessment" published on Thursday, Airbus said if the UK left the EU next year without a deal - meaning it left both the single market and customs union immediately and without any agreed transition - it would "lead to severe disruption and interruption of UK production".
"This scenario would force Airbus to reconsider its investments in the UK, and its long-term footprint in the country," it added.
The company, which makes wings for the A320, A330/A340, A350 and A380 passenger planes in the UK, also said the current planned transition period, due to end in December 2020, was too short for it to make changes to its supply chain.
As a result, it would "refrain from extending" its UK supplier base. It said it currently had more than 4,000 suppliers in the UK.
The customs union brings together the EU's 28 members in a duty-free area, in which they pay the same rate of duty on non-EU goods
Prime Minister Theresa May has ruled out staying in the customs union. The UK is due to leave the EU on 29 March 2019.
The UK government is considering two other options: a customs partnership that would remove the need for new customs checks at the border; and a "highly streamlined" customs arrangement that would minimise customs checks rather than getting rid of them altogether.
Michel Barnier, the EU's Brexit negotiator, has said that both options are unrealistic.
A spokesperson for Prime Minister Theresa May said: "We are confident that we are going to get a good deal, one that ensures that trade is as free and frictionless as possible, including for the aerospace sector,"
A Welsh government spokesperson said: "We have repeatedly warned that the UK cannot take the huge economic risk of cutting ourselves adrift from the single market and customs union. Particularly in the case of manufacturing sectors, which in Wales are so important in providing high-paid, high-skilled jobs."
Simon Jack, business editor
It has been a source of exasperation for some cabinet members that although many companies have privately expressed concern - even alarm - at the progress of the Brexit negotiations, they have been reluctant to make their fears public, and have even dialled down the shrillness of their warnings when meeting the prime minister in person.
Airbus' decision to warn that future investment in their operations in the UK are under review, while not exactly welcome, is therefore considered by some in government as an honest and helpful declaration of what's at stake for UK workers and the wider economy.
Prominent Brexit supporter Sir Bernard Jenkin described Airbus' comments as the kind of "speculation" seen before, during and after the referendum from large companies. But Airbus' UK boss, Katherine Bennett, told the BBC, "this is not project fear, this is dawning reality".
Tom Williams, chief operating officer of Airbus Commercial Aircraft, said in "any scenario", Brexit had "severe negative consequences" for the UK aerospace industry and Airbus in particular.
Without a deal, he said Airbus believed the impact on its UK operations could be "significant".
"Put simply, a no-deal scenario directly threatens Airbus' future in the UK."
Airbus's main civil aircraft business is based in a suburb of the French city of Toulouse. Apart from France and the UK, it has production and manufacturing facilities in Germany, Spain, China and the US.
Mr Williams told the BBC's Today programme that Airbus was currently working on developing the "next generation" of aircraft wings in the UK.
"We are seriously considering whether we should continue that development or whether we should find alternative solutions," he added.
Conservative MP Stephen Crabb said the warning from Airbus should be a "wake-up call".
Mr Crabb tweeted: "The enormous Airbus factory in North Wales is one of the jewels in the crown of UK manufacturing. This is a wake-up call. A pragmatic, sensible Brexit that protects trade & jobs is vital."
And shadow Brexit secretary Sir Keir Starmer tweeted: "If proof was needed that the PM's Brexit red lines need to be abandoned (and fast), this is it."
Liberal Democrat leader Sir Vince Cable described the Airbus warning as "the 'Oh my God' moment where something real is happening".
He added: "Airbus are making absolutely clear that if there is a risk of a hard Brexit, they will have to stockpile parts. They can't take the risk.
"A hundred and ten thousand jobs depend on this company.  About one-and-a-half billion in tax revenue that will not go into the NHS.
"We're now beginning to get serious about what Brexit means."

"The last call"... "we cannot wait any more"... "huge and serious" gaps.
European leaders can repeat the same message, louder and louder.
But this EU summit's instructions to Theresa May may as well have been shouted into an empty cupboard.
Because they know what she knows - that the past 24 hours of Brexit conversations are not nearly as important as the next seven days of discussions at home between Number 10 and the rest of the government.
And after more than two years, this time next week ministers should be nearing the conclusion of their country retreat at Chequers.
It's there that the prime minister hopes to find resolution in her team on a more detailed offer to the rest of the EU - easing, if not removing, all the contradictions in the Tories' positions.
Any pretence that the cabinet agrees is long gone.
The government's promised publication of their choices within days, which if comprehensive and detailed as promised, will mark a big step forward, and in theory allow progress towards a final deal.
But if the eventual Brexit white paper is flimsy - still a list of tentative options - patience in Brussels may finally run out.
Sources suggest that if there is no clarity from the UK next week, all that will be available to Britain is a simple free trade deal.
For many months, Theresa May has held the ring while inside her party brawls over Brexit have raged.
If she can't end the fight, by picking a winning side or forcing a persuasive compromise, the EU may call time.
In the next seven days the prime minister has hurdles she must clear to secure her future.

The prospect of Brexit happening without any deal being reached between the UK and the EU is "unthinkable", Home Secretary Amber Rudd has said.
Ms Rudd was responding to a question about the impact on security of nothing being agreed before the UK leaves.
"We will make sure there is something between them and us to maintain our security," she assured MPs.
Earlier Brexit Secretary David Davis defended keeping the "no deal" option open in the on-going negotiations.
After five rounds of Brexit negotiations, the EU has described the talks as in "deadlock" and there has been an increased debate about the possibility of the UK leaving without a deal in place.
One of the UK's aims is for a new security treaty with the EU, and Ms Rudd told the Commons Home Affairs Committee contingency plans were being made in case this was not in place by the UK's departure in March 2019.
Asked whether, if there was "no deal of any form", Britain would be as safe and secure as it currently is, she replied: "I think it is unthinkable there would be no deal.
"It is so much in their interests as well as ours - in their communities', families', tourists' interests to have something in place."
Ms Rudd also said it was "unthinkable" EU citizens would be asked to leave the UK after Brexit, but was unable to offer guarantees while negotiations continue.
Mr Davis was asked about a "no deal" scenario as he updated MPs on Monday's dinner between Theresa May and EU officials.
Reaching agreement with the EU is "by far and away the best option" he said, adding: "The maintenance of the option of no deal is for both negotiating reasons and sensible security - any government doing its job properly will do that."
International Trade Secretary Liam Fox said there was no reason to fear the impact on the economy of no deal being agreed, saying it "would not be the Armageddon that people project".
He told the BBC: "I think that we need to concentrate on the realities, get rid of the hyperbole around the debate and focus on the fact that if we can get a good agreement with the EU, both Britain and the EU would be better off for it."
A UK-EU free trade deal cannot be discussed until the EU deems sufficient progress has been made on other matters and gives the green light.
In his statement to MPs, Mr Davis said the UK was "reaching the limits of what we can achieve" in Brexit talks without moving on to talk about trade.
He urged EU leaders to give counterpart Michel Barnier the green light at this week's EU summit to begin trade talks.
Mr Barnier said he wanted to speed up talks but "it takes two to accelerate".
This was a reference to comments made by Mrs May after her dinner with the EU's chief negotiator, in which she said the two sides had agreed on the need to "accelerate" the process.
Speaking on Tuesday, Mr Barnier said a "constructive dynamic" was needed over the next two months but "there was a lot of work to do" and issues must be tackled in the "right order".
"At the moment we are still not yet at the first step which is securing citizen rights, guaranteeing the long term success of the good Friday agreement and finalising the accounts," he said.
The talks - which were held as EU member states prepare to assess progress so far on Thursday - were said to be "constructive and friendly" but the UK's financial settlement with the EU continues to be a sticking point and the EU will not discuss trade until this has been settled.
Along with the UK's "divorce bill", the EU is insisting agreement be reached on citizens' rights and what happens on the Northern Ireland border before agreeing to open talks on the free trade deal Mrs May's government wants to strike.
In his Commons statement, Mr Davis urged the EU to give Mr Barnier a mandate to start discussing its future relations with the UK, including trade and defence, telling MPs he was "ready to move the negotiations on".
He suggested the UK was "reaching the limits of what we can achieve without consideration of the future relationship".
"Our aim remains to provide as much certainty to business and citizens on both sides. To fully provide that certainty, we must be able to talk about the future."
On citizens' rights, he said key issues such as the rules on family reunion, the right to return, the onward movement of British expats in Europe and the right of EU residents to export benefits had still to be settled.
Announcing that EU citizens who currently have permanent residence in the UK would not have to go through the full process of re-applying before Brexit, he said the UK had consistently "gone further and provided more certainty" on their status than the EU had done.
While the UK had "some way to secure the new partnership with the EU", he was "confident we are on the right path".
Speaking in the Commons earlier on Tuesday, Foreign Secretary Boris Johnson said he thought a reported bill of £100bn was too high and urged the EU to "get serious" and agree to settle the citizens' rights question.
For Labour, shadow Brexit secretary Sir Keir Starmer said EU and UK citizens were still no wiser over their future while it "appeared the deadlock over the financial settlement is such that the two sides are barely talking".
"Nobody should underestimate the seriousness of the situation we find ourselves in. At the first hurdle, the government has failed to hit a very important target."
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Home Secretary Amber Rudd has hit back at Tory Brexiteers over attacks on the civil service and claims of disunity.
Ms Rudd said backbencher Jacob Rees-Mogg was "wrong" to accuse the Treasury of "fiddling the figures" with forecasts showing the UK would be worse off outside the EU.
The leaked forecast that sparked the row was a cross-departmental "tool" to "help inform the debate", she said.
And she said ministers were more united over Brexit than critics claim.
Speaking on the BBC's Andrew Marr show, she said she was "not intimidated" by Brexiteers' warnings over the customs union and that the UK government would not "surrender too quickly" in its battle for a "bespoke" trade deal with the EU.
Negotiations are taking place between the UK and the EU ahead of the UK's scheduled exit in March 2019.
Ahead of a week of key meetings, Theresa May is facing growing calls to set out in detail what she wants to secure - in particular how closely-bound the UK will be to the EU after it leaves.
Writing in the Sunday Telegraph,  Bernard Jenkin, a Conservative MP who was a key Leave campaigner, accused the government of being "vague" and "divided" on the issue.
But Ms Rudd told Andrew Marr she had "a surprise for the Brexiteers", that the key Brexit committee of ministers was "more united than they think".
The cabinet agrees on the need for "frictionless trade", the ability to strike international trade deals and avoid a hard border in Ireland, she said.
And on the key point of the customs union - which currently prevents the UK from striking international trade deals - she suggested "a form of customs agreement" would be needed.
Last week International Trade Secretary Liam Fox said it was "very difficult" to see how staying in a customs union would allow the UK to have an "independent trade policy" after Brexit.
BBC political correspondent Susana Mendonca
The accusations of cabinet divisions and disunity have kept coming from Brexit-supporting MPs over the past week. Now the home secretary has pushed back, saying the cabinet is "more united than they think".
If that is the case, the cabinet will be expected to demonstrate some of that unity this week when discussions between Theresa May, David Davis and EU negotiator Michel Barnier are bound to throw up some bones of contention - the transition deal being the main one. Will the cabinet be singing from the same hymn sheet on that? And what about the customs union, another thorny issue that key ministers have very different views on?
To silence its detractors, the cabinet will have to demonstrate this week it is neither "vague" nor "divided" - but whatever approach it comes up with is likely to lead to divisions with those who think they are going too far or not far enough.
The role of the civil service has been thrust into the limelight in recent days by a leaked analysis predicting an economic hit to the UK after Brexit.
Ms Rudd said the report did not "model everything" and predicted the UK economy would "absolutely grow" after Brexit, but said putting up trade barriers would have "consequences".
Describing the civil service as the envy of the world, she added: "We have to have these forecasts before making decisions."
She said she had been "surprised" at Mr Rees-Mogg's remarks and added that ministerial Brexit colleague Steve Baker - who has clashed with Whitehall unions and apologised to Parliament - had had an "interesting week".
Mr Baker's apology followed a Commons exchange after which he was accused of not challenging Mr Rees-Mogg's suggestion of Treasury bias against Brexit.
On the BBC's Sunday Politics, Conservative Party Chairman Brandon Lewis echoed Ms Rudd in saying Mr Rees-Mogg was wrong and defending Whitehall.
Former top civil servants have also hit back at critics.
Speaking on ITV's Peston on Sunday, ex-cabinet secretary Lord O'Donnell said claims officials were distorting figures were "crazy".
People who do not like their analysis tend to shoot the "messenger", he said.
"We look at the evidence and we go where it is.
"Of course if you are selling snake oil, you don't like the idea of experts testing your products."
His predecessor Andrew Turnbull, who was cabinet secretary under Tony Blair, told the Observer that attacks on the civil service were similar to tactics used by German nationalists between the two world wars.
BBC business reporter Rob Young
Customs union members each apply the same tariff to goods bought from outside the EU. Goods from inside the EU are not subject to tariffs.
Theresa May says Britain is leaving the customs union - so what will replace it?
For a lot of firms, customs rules are just as important as a trade deal. Brexit could disrupt many supply chains, if businesses buy parts from Germany or Italy, for example. Many exporters want a new customs deal with the EU to reduce the need for border checks - limiting queues and paperwork. But this could restrict Britain's ability to strike international trade deals outside the EU.
Some worry this undermines one of the key potential benefits of Brexit.
Customs are also key to the future border with Ireland. No wonder this is one of the thorniest issues arising from Brexit.
The UK and the EU do not currently agree on whether EU citizens moving to the UK during the planned two-year transition period after Brexit should get the same long-term rights as those who arrive before the UK leaves.
Defending the UK's position, Ms Rudd said it was "right to have a distinction between before March 2019 and afterwards".
Chancellor Philip Hammond has been the focus of much of the criticism from Brexiteers in the Conservative Party, and in his Telegraph article Mr Jenkin suggested Mr Hammond was not toeing the party line.
"If ministers are vague or divided, life for officials becomes impossible, as we can see now. Ministerial collective responsibility really matters," he said.
He added: "If the prime minister sticks to one policy and the chancellor keeps advocating another, what are officials meant to do?"
Earlier this month, Mr Hammond suggested the UK's relationship with the EU would change only "very modestly" after Brexit.
But Mr Jenkin urged the prime minister to stick to her position and ensure, among other things, Britain leaves the single market and customs union.
He wrote: "She can only command a majority in Parliament on her present policy.
"Her MPs will back her, because we are overwhelmingly at one with the majority of the British people who now want a clean Brexit and an end to the present uncertainty."

Amber Rudd has quit Boris Johnson's cabinet, with an outspoken attack on the government's approach to Brexit.
The ex-work and pensions secretary said the government was having no "formal negotiations" with the EU about a new deal, only "conversations".
Instead, 80-90% of Brexit work was spent preparing for an "inferior" no-deal option, she said.
But Chancellor Sajid Javid said ministers were "straining every sinew" to get a deal with the EU.
He told the BBC's Andrew Marr Show a "tremendous amount of effort" had gone into securing a revised deal.
Mr Javid added that preparations for a no-deal scenario would "concentrate minds" in Europe regarding working towards a new agreement.
Downing Street says environment minister Therese Coffey will replace Ms Rudd as work and pensions secretary.
BBC political correspondent Jonathan Blake said the prime minister spent Sunday meeting his closest advisers at the government's countryside residence Chevening House, in Kent, "perhaps planning the next move".
Ms Rudd told the Sunday Times she would be considering whether to stand as an independent Conservative should there be an general election.
In her resignation letter to the prime minister, Ms Rudd said: "I joined your cabinet in good faith: accepting that no-deal had to be on the table, because it was the means by which we would have the best chance of achieving a new deal to leave on 31 October.
"However, I no longer believe leaving with a deal is the government's main objective."
She called the PM's decision to expel 21 MPs from the parliamentary Conservative party an "act of political vandalism", after her former colleagues rebelled last week over a bill designed to avoid a no-deal Brexit.
"If we become a party which has no place for the type of moderates that I am, the centre-right Conservatives, then we will not win [a general election]," she said.
by John Pienaar, BBC deputy political editor
Amber Rudd's resignation was symptomatic of a deeper struggle going on inside the government and inside the Conservative Party.
Whatever anyone says, a number of ministers are considered to be privately unhappy with the government's strategy and contemplating the possibility of resigning in the wake of Amber Rudd's resignation.
The former chancellor, Philip Hammond, was saying this weekend that usurpers were turning the Tory party into an extreme right-wing sect.
He was clearly referring to people like the prime minister's famously abrasive, divisive adviser, Dominic Cummings.
But there's no sign of the inner circle in No 10 relenting or repenting - just the opposite.
One minister said to me today: "Look at the opinion polls. Tories well ahead - it's working." Losing colleagues, to him, was collateral damage.
Ms Rudd, the MP for Hastings and Rye, who supported Remain in the 2016 referendum, has resigned the Tory whip - meaning she will remain an MP but no longer sit as part of the Conservative party in Parliament.
She told the BBC there was "very little evidence" the government would get a new Brexit deal, and she had only received a "one-page summary" of efforts to get an agreement when she asked for details earlier this week.
She said "proper discussions about policy" had not been taking place, suggesting senior ministers had limited involvement in the PM's decisions.
Cabinet ministers had also not been shown legal advice to the prime minister about his decision to prorogue - or suspend - Parliament from next week until 14 October, Ms Rudd said.
Asked who was running the country, if not the cabinet, she replied: "If I knew that, I would perhaps have had further conversations with the prime minister, or them."
However, Mr Javid said there had been "progress" in talks with the EU about making changes to former PM Theresa May's Brexit deal, which was rejected three times by the House of Commons.
He said the government has "many new ideas" for proposals to break the deadlock over the contentious backstop plan in the deal aiming to preserve seamless border on the island of Ireland.
However he said it would be "madness" to talk through the details of the government's proposals openly.
"Anyone who understands how negotiation works, you would not discuss those in public," he added.
Former Foreign Secretary Jeremy Hunt said Ms Rudd's departure was "desperately sad news", describing her as "one of the most principled and capable ministers I've worked with".
Former Chancellor Philip Hammond tweeted that the Conservative Party had been "taken over by unelected advisors, entryists and usurpers".
Shadow Brexit secretary Sir Keir Starmer tweeted that her departure showed Mr Johnson's government was "falling apart".
Labour Party chair Ian Lavery said the resignation was a sign that "no one trusts" Mr Johnson. "The prime minister has run out of authority in record time and his Brexit plan has been exposed as a sham," he said.
SNP Westminster leader Ian Blackford called on the prime minister to resign, arguing he had "no support or credibility left".
But Foreign Secretary Dominic Raab said Mr Johnson had made clear to all his cabinet ministers they needed to support his policy of leaving the EU by 31 October, in all circumstances.
"We all accepted that, and I think the prime minister was right to restore some discipline - and I think he's right to expect it from his top team," he told Sky News.
In other developments:
Monday
Wednesday:
Thursday:

It's not a snub.
Or a rule-breaker.
Or a witches' cauldron around which anti-UK tactics will be plotted.
Theresa May doesn't invite the European Union to her Brexit strategy discussions - as you might expect - and the EU doesn't invite her to theirs, for the very same reasons.
As a full member (still) of the EU, the UK prime minister is included - as she must be - in today's formal summit of all 28 EU leaders.
Mrs May will be present for discussions on migration, Aleppo, Ukraine trade and Russia sanctions.
But once that is over and summit press conferences have been held, EU leaders will meet without the UK for an "informal dinner" where the menu reads: Brexit from hors d'oeuvres to dessert.
The timing of this dinner is a diary convenience.
Getting 27 world leaders round one table isn't easy, especially when a number of them are fighting for political survival at home.
So, while together in Brussels anyway for the summit, Chancellor Angela Merkel, President Francois Hollande et al agreed to stay a bit longer to talk Article 50, the by-now long-awaited triggering by the UK of formal Brexit talks, that Mrs May promises early next year.
Dinner tonight, my sources tell me, will be all about procedure.
The EU27 (as the leaders minus the UK now call themselves) will formally re-confirm the European Commission as the lead Brexit negotiator for the whole European Union.
Make no mistake, in such a complex and politically important process, Germany, France and other EU countries will keep a very close eye on the Commission but they know it is the only EU institution with the manpower, the expertise (it leads all EU trade negotiations) and a legal mandate (as so-called guardian of EU Treaties) for detailed negotiations.
So much for Brexit procedure; as for content over tonight's nibbles, my sources insist there's little to discuss until the UK government makes a firm commitment to the kind of Brexit it wants.
UK Brexit Secretary, David Davis, for example, just came up with four possible scenarios as regards the European Customs Union.
But EU leaders are clearly nervous.
Brexit has become a political football as populist movements gather strength across Europe.
Many leaders are also irritated with the perceived arrogance of the UK government - whether it's the foreign secretary insisting that EU Single Market rules will be bent for the UK or the Brexit Secretary suggesting an interim trade deal might be accepted out of kindness to the EU, rather than the other way round, which is the perspective of Brussels.
Over and again I'm told: we never wanted the UK to leave. It chose to go. We now need this over and done with so Brexit no longer hangs over all EU affairs.
EU governments insist they want an end deal that's good for everyone. They're keen to keep Britain close. But they do expect the UK to respect EU law. That means, as we've heard: no access to the Single Market if the UK won't accept the right of EU citizens to apply live and work in the UK.
On this point, EU countries and the Commission sing from the same hymn sheet.
They all benefit from the Single Market and they worry about weakening it.
But, desperate as they are to insist that theirs is a fully united front, there will undoubtedly be Brexit bickering amongst tonight's dinner guests.
One high-level source described Article 50 to me as "the mother of all complexities".
Some European Prime Ministers (particularly from the Baltic States and central Europe) worry the Commission will be too hard line. They want open talk of a transition deal and believe Article 50 proceedings should be about the future EU-UK relationship, not just the divorce.
Many EU leaders chatting about Brexit tonight know they're unlikely to see the process through.
Elections are fast-approaching in France, the Netherlands and Germany. Possibly in Italy too.
Today the BBC revealed a memo to the government by a high level British civil servant warning Brexit could take years and even then be voted down by an EU country or institution.
Something the EU warned about from the start.
Still, a Brussels source said to me it'll be far speedier if hard-line Brexiteers win the day and the UK reverts to WTO trade rules.
No transition deal needed then, he said.
Another Brussels voice believed Russia sanctions discussions at today's EU summit would show Theresa May that she has more in common with the EU than she realises.
The year 2017 is going to be a lot about Russia, my contact insisted.
"Prime Minister May will find us a lot more Russia-reliable than the soon-to-be US president, Donald Trump."
"Though the UK never appreciated its EU relationship as 'special'," he noted (not without a note of bitterness).

This didn't seem a comfortable moment for Dominic Raab.
The Brexit secretary campaigned for Leave, and is a true believer in the cause. Yet here he was, setting out plans to cope with a British failure to reach the kind of deal Brexiteers once claimed would be easy to accomplish.
Again and again, the Brexit department's guidance refers to the "unlikely event" of Brexit without an EU deal - but Dominic Raab conceded it could happen.
The risk was real. The International Trade Secretary, Liam Fox, has suggested that outcome is more likely than not. The Brexit secretary may disagree on the level of risk, but could not deny that it would lead to higher costs and a fresh burden of red tape on businesses, scientific and medical research and individuals.
In today's first tranche of advisory papers on how to handle a no-deal Brexit, we learned card payments in Europe could cost more, as the EU cap on charges disappeared. That would add to the holiday and travel expenses of millions of Brits.
There was no guarantee yet of Brits and other UK dwellers on the continent having the same access to bank accounts and pension payments. Again Mr Raab was looking on the bright side. Why would the EU refuse to co-operate and risk piling identical burdens on Europeans in Britain.
The list went on. And on. Medicines were being stockpiled - though that didn't rule out the possibility of shortages.
And on the potential effect on UK firms involved in trade with the EU, the message was no less striking for being an inevitable consequence of quitting the EU single market and operating under the rule of the World Trade Organisation in the absence of a free trade agreement. Exporters would face an entirely new system of customs duties and safety declarations at a stroke. Consultants would need to be consulted. Software bought. Contracts rewritten.
Yes, farmers who receive EU subsidies could count on those payments being continued by a newly liberated Department for the Environment, Food and Rural Affairs. Whether the same farmers would be entirely happy with the new schedule of tariffs on agricultural imports and exports is another matter, and not discussed today.
The list of new home-grown rules and regulatory agencies was huge. Mr Raab's hope was that the EU would co-operate with and recognise this new sprawling network of agencies and authorities, not for Britain's sake, but in its own interests. Maybe. But who knows?
The minister hoped and believed an agreement was still the most likely outcome. The two sides, he said, were "within sight" of a deal. Some close to the process might consider that an optimistic assessment. Theresa May's Chequers plan - a single market for goods but not services among other things - seems to have fallen rather flat in Brussels.
Dover is, after all, "within sight" of Calais. The political distance may turn out to be unbridgeable. So far, there's no sign of Brussels weakening on its negotiating "red lines". Today's "no-deal" plans may seem extensive, and there is much more to come.
To Dominic Raab the idea that everything will work out in the end seems plain common sense. The potential disruption and costs former Remainers and Brexit sceptics see as national self-harm, Brexiteers see as a few bumps in the road en route to a brighter future.
Dominic Raab may be a more comfortable colleague for the prime minister to deal with than his predecessor, David Davis, but he is a true believer nonetheless. You could call his conviction a product of faith. Or, if you prefer, call it wishful thinking.

EU leaders who gathered in Brussels put on a united front to back Theresa May's argument that the withdrawal agreement they endorsed was the "best and only" Brexit deal available.
But there was no sense of celebration, and there were plenty of signs of how tough negotiations on the future EU-UK relationship are likely to be.
Alongside the withdrawal agreement, and the political declaration on future ties, the remaining 27 EU leaders published a separate statement (without the UK) that vowed to protect their own interests, on a range of issues from fishing to fair competition to the rights of citizens.
"The European Council," it said, "will demonstrate particular vigilance as regards safeguarding the rights and interests of citizens, the necessity to maintain ambitious level playing field conditions, and to protect fishing enterprises and coastal communities."
It emphasised in particular that a fisheries agreement that builds on "existing reciprocal access and quota shares" is a matter of priority.
The statement was a clear sign that the UK will not have things all its own way, when it comes to balancing the competing demands of access to EU markets for UK fish produce, and access to UK fishing waters for EU boats.
Several EU leaders highlighted fishing as a particularly sensitive issue. German Chancellor Angela Merkel said talks on fisheries were "undoubtedly going to be an area where negotiations are going to be tough".
But the bluntest warning came from the French President Emmanuel Macron, who suggested that if the UK was unwilling to compromise in negotiations on fishing, which would need to make rapid progress, then talks on a wider trade deal would be slow.
"We as 27 have a clear position on fair competition, on fish, and on the subject of the EU's regulatory autonomy, and that forms part of our position for the future relationship talks," he said.
The president implied that without sufficient progress on trade, the backstop plan to avoid a hard border in Ireland would have to be implemented, including a temporary customs union for the whole of the UK.
"It is a lever because it is in our mutual interest to have this future relationship," Mr Macron said.
"I can't imagine that the desire of Theresa May or her supporters is to remain for the long term in a customs union, but (instead) to define a proper future relationship that resolves this problem."
It is a warning that the prime minister could have done without, as she seeks to appeal to the British public for support for her deal in advance of a vote in Parliament next month.
But it is also a reminder - if any were needed - that other countries have domestic political concerns that will have to be taken into account.
If anything, the negotiations on the future relationship - which can only begin formally after the UK has left the EU - will be even harder than the 18 months of negotiations that produced the withdrawal agreement which has just been endorsed.

Andrea Leadsom has said that the EU may be prepared to grant the UK a "couple of extra weeks" beyond the 29 March deadline to finalise preparations for Brexit.
The Commons leader said that in light of the UK's strong relationship with its "EU friends", the UK could be allowed more time for an approved deal to pass all its parliamentary stages.
But Ms Leadsom accused the EU of being in denial about the unease in the UK over the Northern Ireland backstop.
In a rebuke of Amber Rudd and Philip Hammond, the Commons leader called on the cabinet to rally behind Theresa May and accept that the UK will leave the EU without a deal if MPs reject her deal.
In an interview with BBC Newsnight, Ms Leadsom said she had "grave concerns" about a bill, proposed by Labour MP Yvette Cooper, which could extend Article 50 by nine months.
But she said that the EU could agree to allow the UK to remain in the EU for a few weeks longer than the March deadline. This could happen if a deal has been reached, but more time is needed for parliament to approve its Brexit legislation.
A Downing Street spokesman said: "There is no change to our position. We are not considering an extension to article 50 and are committed to doing whatever it takes to have the statute books ready for when we leave the EU on March 29th this year."
Ms Leadsom, who is in charge of timetabling government business in the Commons, said: "We can get the legislation through and I think we do, in spite of everything, have a very strong relationship with our EU friends and neighbours and I am absolutely certain that if we needed a couple of extra weeks or something then that would be feasible."
In answer to the suggestion that this would amount to an extension of Article 50, which is due to conclude on 29 March, she said: "It doesn't necessarily mean that. I think we would want to think carefully about it. But as things stand I do feel that we can get, with the support of both Houses - the House of Commons and the House of Lords - with goodwill and a determination we can still get the legislation through in good time."
In the interview, Ms Leadsom highlighted tensions when she was asked about cabinet discipline, after the warnings from Ms Rudd and Mr Hammond about the dangers of a no deal Brexit.
"I'm totally aligned to the prime minister," she said. "I believe that is where collective responsibility should lie.
"So number one, the legal default is we leave the EU on 29 March without a deal, unless there is a deal in place. That hasn't changed. That is the prime minister's view and that's my view.
"Of course, it is also very important that we continue to prepare for all eventualities because we do need to make sure that in all circumstances the UK can continue to thrive and do well in a post EU environment.
"I do encourage my colleagues in cabinet to get behind that sentiment and to make sure that we are all on the same page. We are now in the really final days."
Ms Leadsom was highly critical of the the EU for failing to understand the deep unease in the UK over the Northern Ireland backstop.
In the most contentious area of the deal, the UK and the EU have agreed to avoid a hard border between Northern Ireland and Ireland by binding the former closely to EU rules.
This would apply after the transition period if the UK and the EU have failed to negotiate a future relationship by then.
"Keeping the UK in an unlimited, in time terms, backstop that we can't unilaterally exit from under any circumstances is a real problem for many," she said.
"Resolve that and [many Conservative MPs and the DUP] can support the prime minister's deal.
"The EU need to be listening very carefully to that. They are slightly in denial saying that that is not the issue. It very much is the issue.
"So I am hoping the European Commissioners will look very closely at the backstop and think of a way through this, because the legal default is that we leave the EU on 29 March without a deal unless we can agree a deal."
Ms Leadsom was speaking to Newsnight during a visit to Manchester to highlight her work chairing a cross-government group on early years intervention.
You can watch Newsnight on BBC 2 weekdays 22:30 or on iPlayer. Subscribe to the programme on YouTube or follow them on Twitter.

Speaker John Bercow has described the abuse and harassment of MPs outside Parliament as "a type of fascism" and called for a change of policing policy.
He said recent incidents, including Tory MP Anna Soubry being verbally abused on Monday, were "intolerable".
At least 115 MPs have called on police to improve their response to abusive protesters outside Parliament.
The Metropolitan Police has said it is ready to "deal robustly" with any instances of criminal harassment.
Deputy Assistant Commissioner Laurence Taylor said the force was assessing whether any crimes had been committed, following a third-party report of a public order offence on College Green, opposite the Houses of Parliament.
He said Scotland Yard will be "enhancing the policing presence" in the run-up to next week's vote on Theresa May's Brexit deal.
Revised advice was issued to MPs by Parliament security on Tuesday.
Meanwhile, a man has been arrested on suspicion of trespassing after he tried to get into Parliament.
Armed officers arrested him at about 19:20 GMT on Tuesday after he got through Carriage Gates, at the entrance to the Houses of Parliament. He was taken to a police station, the Metropolitan Police said.
The incident is not being treated as terror-related.
The BBC has no plans to stop broadcasting from College Green but does not intend to report from there every day.
A BBC spokeswoman said: "We are working closely with authorities and other broadcasters to ensure the safety of our reporters and interviewees at all times."
Ms Soubry was shouted at - including being called a liar and a Nazi - during live TV interviews on BBC News and Sky.
The former minister - a supporter of a fresh Brexit referendum - was later called "scum" and jostled as she tried to re-enter the Palace of Westminster.
She criticised police for not intervening and called for the protesters to be prosecuted under public order laws.
Section 5 of the 1986 Public Order Act means that "threatening or abusive words or behaviour, or disorderly behaviour" might be deemed a criminal offence.
But Article 10 (right to freedom of expression) and Article 11 (right to freedom of peaceful assembly and to freedom of association) of the European Convention on Human Rights contain the rights to peaceful protest.
College Green is regularly used by media to interview politicians, as well as being a popular site for protesters to gather.
Ms Soubry told the BBC she had "no problem with people protesting", saying this was a "very small group of far-right extremists who just want to undermine democracy".
The MP for Broxtowe said: "There is a very clear distinction between peaceful, lawful protest and robust debate - holding MPs to account, and it can be face to face - and some of the scenes we have seen in the last six weeks here at Parliament."
The cross-party group of MPs who have signed the letter - which includes those both for and against Brexit - said many of the concerns had been "repeatedly raised" with officers and senior policing staff.
"We write to express our serious concerns about the deteriorating public order and security situation in and around the exterior of the Parliamentary estate including College Green," the letter, co-ordinated by Labour MP Stephen Doughty, read.
"After months of peaceful and calm protests by groups representing a range of political views on Brexit, an ugly element of individuals with strong far-right and extreme right connections - which your officers are well aware of - have increasingly engaged in intimidatory and potentially criminal acts targeting Members of Parliament, journalists, activists and members of the public."
The letter said there appeared to be a "lack of co-ordination in the response from the police and appropriate authorities".
Sky News presenter Kay Burley said the "increasingly vile, aggressive and intimidating" abuse had forced her to change her own route to Parliament and she now had to have security protection.
She told BBC Radio 5 Live she had been interviewed three times by the police about the situation, but the protesters knew their rights and what they could and couldn't get away with.
But she added: "How far does it have to escalate before the police have to take it seriously?"
Labour's Mary Creagh said the "really vile, misogynistic thuggery" that had been seen was not an isolated incident.
She pointed to the murder of MP Jo Cox, who was killed in her West Yorkshire constituency by right-wing extremist Thomas Mair in June 2016.
Commons Speaker John Bercow said he was "concerned" about a "pattern of protest" targeting female MPs and journalists and called it a "type of fascism".
In his letter to the Met Police chief on Tuesday, he said he recognised it was "a difficult job striking the balance between allowing peaceful protests and intervening when things turn sour".
But he added: "It's one thing demonstrating from a distance with placards, or calling out slogans - and another, where the protester invades the personal space of a member, subjects him or her to a tirade of menacing, racist, sexist and misogynistic abuse, and follows them back to their place of work."
Labour MP Jess Phillips, who has previously spoken out against online abuse, told the BBC's Victoria Derbyshire programme that some protesters were "organised right-wing groups" trying to "scare our politicians into making decisions based on fringe views".
"People deserve to be safe at work," the Birmingham Yardley MP said. "I didn't come here to be bullied by far-right bullies, far-left bullies, or anyone, we came here to do what we felt was best."
Also on Monday, political commentator Owen Jones published a video on Twitter that he had recorded while being followed and shouted at by a group of protesters outside Parliament.
Last month, a video emerged of prominent Brexiteer Michael Gove being accosted by a protester dressed as Santa as he walked to Parliament.
Mr Bercow said he was aware of protests in recent weeks around the Palace of Westminster "involving aggressive and threatening behaviour towards members by assorted groups that have donned the yellow vests seen in France" - a reference to last year's "gilet jaune" anti-government demonstrations.
By Dominic Casciani, BBC home affairs correspondent
A recognisable figure in the group that surrounded Anna Soubry on Monday is online far-right campaigner James Goddard.
He says there can be no peace while Islam exists in the West and that the establishment is riven with paedophiles. He told police outside Parliament they were "fair game" and "if you want a war, we will give you a war".
Mr Goddard emerged as a DIY far-right campaigner last year as he began to gather followers after campaigning in support of the then-jailed anti-Islam activist, Stephen Lennon aka Tommy Robinson.
Before the incident at Parliament involving Ms Soubry, he'd been helping to organise France-style "yellow vest" protests - including attempts to block bridges in London.
Mr Goddard relies on donations from his followers - he frequently runs crowdfunding appeals for his campaigns.
On Tuesday evening, Facebook confirmed it has closed his account.
"We will not tolerate hate speech on Facebook which creates an environment of intimidation and which may provoke real-world violence," said a spokesman. Minutes later, his separate Paypal crowdfunding page disappeared too.
No 10 said the incident was "unacceptable" and MPs "should be free to do their jobs without any form of intimidation".
The BBC and other broadcasters have set up temporary studios on College Green ahead of the Commons vote on Mrs May's Brexit deal on 15 January.
The BBC's assistant political editor Norman Smith said some MPs had expressed unease privately about being interviewed there, given the frequency and vehemence of the protests.

Thousands of protesters have taken to the streets of central London in a march against Brexit and Conservative Party leadership hopeful Boris Johnson.
The pro-European March for Change is holding a "No to Boris, Yes to Europe" event, and includes a blimp depicting him.
Campaigners are asking for Mr Johnson to "stop the Brexit chaos".
Either he or Jeremy Hunt will be named as Theresa May's replacement as prime minister next week.
Former foreign secretary Mr Johnson, who has declined to comment on the march, is seen as the frontrunner in the contest.
He said the UK would leave the European Union by 31 October "come what may" under his tenure, while Mr Hunt said he expected this to happen by Christmas.
Mr Johnson has claimed Brexit "done right" could "cement and intensify" the union between the UK nations.
The balloon depicting Mr Johnson has "£350m" emblazed on its front, symbolising the leave campaign's pledge of money towards the NHS during the 2016 referendum.
The March for Change organisers said: "We won't put up with a hard Brexit PM being imposed on the country and hurtling us towards the cliff edge."
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As so often, the cabinet managed to agree on what they don't like - the EU's version of the backstop - but they had a harder time agreeing what they do all like.
And even after more than two hours of talks, there is, as things stand, no "fully formed" UK proposal to get the Brexit talks going again.
There is no miraculous solution that can show the EU that promising a customs union to the whole of the UK can have a time limit that fits with their principles.
Donald Tusk has demanded new facts on Wednesday.
But as Theresa May prepares to go to Brussels, there's no sign of them. And there is no deal on the table right now that would definitely get through Parliament.
What to do then when there isn't agreement? Delay of course!
One insider says the government has no choice but to play it long, in the hope that the passage of time will concentrate minds.
Indications from ministers are that the government is now realistically looking to the deal not being done (if it is) until December. (Meaningful vote with your Christmas turkey anyone?)
One cabinet minister told me the PM was trying to manage expectations, telling colleagues today "not to be downhearted" if there was no summit in November.
And there have been suggestions too for ages that the EU would be ready to offer an extension to the whole process.
It's not clear, however, what facts more time would change. Remember a lot of smart people have been trying to find a way to answer all the conundrums for months and months and months.
Officials on both sides thought they were moving towards a possible arrangement of paragraphs last week but the politics here meant it couldn't be done.
And without new facts, will Theresa May be able to buy herself more time? The first call on that will be made in the next 48 hours by the EU.
The worst case scenario for No 10 is that EU leaders are so fed up with the UK position and what they see as the lack of reality, that on Thursday they formally say they will hold a no-deal summit in November.
That would switch them on to a track that would be hard to get off once in motion. One EU source expressed disbelief that Theresa May thought she could turn up on Wednesday with nothing new. It was simply crazy, in their view, to suggest that the ball can be lobbed back into the EU court.
The best case, and it seems right now unlikely, dream scenario is for the EU to say that, after all, there is a deal in reach, so let's get a date in the diary for the sign-off next month.
What seems more likely is a holding position. EU leaders could give some kind of vague noises that both sides still want to pursue negotiations, so that the talks can get going again.
One Brussels source said that while it is "time for choices", they could give the prime minister space and time to build a majority at home for  a deal.
But her party might not. Even if the EU gives her another few weeks to keep going, another few weeks to find a solution, if this summit goes visibly badly, it is not clear that her backbenchers and the Democratic Unionists will back Theresa May to carry on.
It's becoming increasingly common around Westminster to hear MPs say, "I simply can't see a way through."

Is there a conspiracy between so called "disaster capitalists" who have made big financial bets which will come good if the UK leaves the EU without a deal - and a government that is determined to leave on 31 October - do or die?
There has been a lot speculation, that er… speculators who help fund the Conservative Party are set to win big on their bets against the pound and UK assets if the UK leaves the EU without a deal.
The current strain of this theory runs something like this - you Conservatives deliver a no-deal Brexit from which we will profit and we promise to bankroll the party in the coming election and beyond.
There are always plenty of fans of compelling and dramatic narratives like this - but they don't usually include the former chancellor of the exchequer and the former permanent secretary to the treasury - Nick (now Lord) Macpherson.
Philip Hammond said: "Johnson is backed by speculators who have bet billions on a hard Brexit - and there is only one option that works for them: a crash-out no-deal that sends the currency tumbling and inflation soaring."
Lord Macpherson then backed him in the following tweet.
Boris Johnson's own sister Rachel, when trying to explain her brother's do or die approach to leaving on 31 October, said one explanation could be influence "from people who have invested billions shorting the pound and the country in the hope of a no deal Brexit".
What should we make of the clear implication/insinuation that Boris Johnson is being influenced by financial gamblers who stand to make a packet out of no deal?
What we know to be true is that Tory party finances which had begun to struggle under Theresa May are reported to have bounced back under Boris Johnson.
John McDonnell claimed in the House of Commons that backers of no deal had donated £726,000 this year alone - some from hedge funds.
But most of it was not from hedge funds and to put the sums in context, in the first six months of the year, donations to the Tory party totalled more than £9m.
Party officials say the recent uptick in donations is because Johnson is better at shaking the hat - not because he's agreed to seek no deal to enrich a small minority of donors.
The claim that these no deal-backing hedge funds are betting against British companies that will falter come 1 November is also hard to find evidence for. The way most hedge funds work is that they take two positions - one long, one short.
For example, if you think, say, Barclays will do better than, say, Metro Bank over the next few months or years, you back Barclays and you bet against Metro. You make money as long as Barclays goes up more than Metro OR - if they both fall - that Barclays falls less than Metro Bank.
This is not a bet against British banks - it's a bet on two companies' relative performance.
As for the currency, companies of all types make bets against the pound for different reasons. The main reason is as a form of insurance. If I am a US-based multinational that makes, say, 30% of my money in sterling, that contribution will be hit if the pound falls (as most expect will happen after a no-deal Brexit). By taking a bet against sterling, that hit will be offset by the return on that bet and my income will be insured.
But there are hedge funds who place out-and-out bets on currencies. One of them is run by Crispin Odey who made £300m when the pound plunged following the UK referendum result in 2016. He is a no-deal backer, doesn't deny he will prosper if that happens, and contributed £10,000 towards Boris Johnson's campaign.
He described claims that he was trying to influence Johnson as nonsense, insisting he had absolutely no influence over Johnson.
Another hedge fund boss who wished to remain anonymous said the idea that a small group of financiers was pulling the strings to achieve a no deal was ridiculous. Not least, he said, because it would be "bonkers" to bet that a currency that was already at a 30-year low against the rest of the world would go that much lower.
"Most hedge funds are waiting for the moment to buy," he told me, adding that he was certain that Johnson was sincere in his wish for a deal.
They would say that wouldn't they, I hear you say. But it's also worth remembering that for every person who has bet against the pound, there is someone who has taken the other side of that bet. These are usually big international investment banks, the bosses and partners of which often make political donations of their own.
Hedge funds make money by betting the market is wrong - that the price of something is not reflecting what is really going on. It's no secret that many pollsters are hired by hedge funds to conduct political research on which they bet. Paying for better information is not the same as nobbling the result.
The general unease about speculators getting involved in politics is understandable.
As one bank chairman told me: "When hedge fund owners start backing individuals or parties we should worry. It creates at best a perception of conflict of interest. At worst a genuine conflict."
The widespread acceptance of this current conspiracy theory demonstrates that this rings true for many. But, as yet, there has not been enough evidence produced that a few shadowy financiers are pulling the strings of a no-deal Brexit puppet.

The deal the UK government was set to agree with the European Union on Monday came as "a big shock" to the DUP, its leader Arlene Foster has said.
She was speaking to Republic of Ireland national broadcaster RTÉ.
Talks in Brussels halted because the DUP, which props up the Tory minority government, rejected a proposal about the future of the Irish border.
Mrs Foster said the DUP saw the text of the deal on Monday morning, despite asking to see it for five weeks.
"Once we saw the text, we knew it was not going to be acceptable," she said.
Talks between Prime Minister Theresa May and European Commission President Jean-Claude Juncker broke up without agreement on Monday.
The crucial sticking point was over how closely aligned Northern Ireland's regulations will be with those in the Republic of Ireland, and the rest of the EU, in order to avoid a "hard" border.
Mrs Foster said her party could not sign up to anything that would allow a border to develop in the Irish Sea and that its red line was any situation where Northern Ireland was different from the rest of the UK.
Ms Foster also said that the British negotiating team indicated to her that it was the Irish government that prevented the DUP from being shown a copy of the text.
However, the Irish government has rejected Ms Foster's claim and said it had "no role whatsoever in the negotiations conducted by the British government".
"It therefore had no involvement in any decision on which documents should go to the DUP," the Irish government said.
Ms Foster also said that she told Mrs May the DUP would not support Brexit legislation in the House of Commons unless the text presented on Monday was changed.
She said that she had a very open conversation with Mrs May after she had made the DUP position clear in a press conference on Monday afternoon.
She said she told Mrs May that "it could have been dealt with differently".
She said the DUP now wishes to look at the text, make it clear what they cannot agree with and try to work through to move on to Phase Two of the talks.
"Nobody wants a hard border on the island of Ireland," she added.
Taoiseach (Irish prime minister) Leo Varadkar  told the Dáil (Irish parliament) that "the ball is now in London's court".
He said that he accepted that Mrs May was negotiating in good faith but had difficulties.
Earlier on Tuesday, DUP deputy leader Nigel Dodds said the Irish government was risking Anglo-Irish relations and co-operation in Northern Ireland with a "reckless and dangerous" attitude to Brexit talks.
Mr Dodds accused the Irish government of "flexing their muscles".
Speaking in the House of Commons Brexit Secretary David Davis told MPs that Northern Ireland would not be "left behind".
He emphatically denied a suggestion that Northern Ireland would remain in the single market and the customs union after Brexit.
The Labour Party described the government's approach to Brexit talks as "embarrassing".
However, Mr Dodds accused the Irish government of a "noticeable change in tone and aggression" since Mr Varadkar and Irish Foreign Minister Simon Coveney came to power.
by Mark Devenport, BBC News NI political editor
"Rubbish" - the response from a senior DUP source when I put it to them that the party had been kept in the loop about Theresa May's Brexit deal, but got cold feet when the likes of Nicola Sturgeon, Carwyn Jones and Sadiq Khan started demanding the same special treatment for Scotland, Wales and London.
Something doesn't add up.
Last Thursday, DUP leader Arlene Foster declared that her party was "in constant contact on these issues with the government".
Was that via face-to-face meetings of the two parties' "co-ordination committee", or just via telephone conversations? If the latter, the line must have been very crackly.
Mr Dodds added it was clear that the European Union has given a veto to the Irish government and that they were "flexing their muscles and using their current position to try and gain wins for them".
"I don't argue with their desire to advance their interests but they're doing so in a reckless and dangerous way that is putting at risk years of good Anglo-Irish relations and good co-operation within Northern Ireland."
He added: "What matters are the words that are used in text and in international treaties and agreements and it's vitally important that text translates accurately to what are the general principles of political agreement."
The prime minister needs the support of the DUP, which is Northern Ireland's largest party and has 10 MPs at Westminster, because she does not have a majority to win votes in the House of Commons.
Meanwhile, Shadow Brexit Secretary Keir Starmer claimed in the House of Commons that the Conservatives' agreement with the DUP at Westminster was a "coalition of chaos" and said "the DUP tail is wagging the Tory dog."
But Mr Davis said "the suggestion that we might depart the European Union to leave one part of the United Kingdom behind and still inside the single market and the customs union - that is emphatically not something that the UK government is considering".
"So when the first minister of Wales complains about it or the first minister of Scotland uses it as a reason to start banging the tattered drum of independence or the Mayor of London says it justifies a hard border on the M25, I say they are making a foolish mistake.
"No UK government would allow such a thing let alone a Conservative and Unionist government."

Universities and Science Minister Chris Skidmore has said that the UK will not implement the EU Copyright Directive after the country leaves the EU.
Several companies have criticised the law, which would hold them accountable for not removing copyrighted content uploaded by users, if it is passed.
EU member states have until 7 June 2021 to implement the new reforms, but the UK will have left the EU by then.
The UK was among 19 nations that initially supported the law.
That was in its final European Council vote in April 2019.
Copyright is the legal right that allows an artist to protect how their original work is used.
The EU Copyright Directive that covers how "online content-sharing services" should deal with copyright-protected content, such as television programmes and movies.
It refers to services that primarily exist to give the public access to "protected works or other protected subject-matter uploaded by its users", such as Soundcloud, Dailymotion and YouTube.
It was Article 13 which prompted fears over the future of memes and GIFs - stills, animated or short video clips that go viral - since they mainly rely on copyrighted scenes from TV and film.
Critics claimed Article 13 would make it nearly impossible to upload even the tiniest part of a copyrighted work to Facebook, YouTube, or any other site.
However, specific tweaks to the law in 2019 made memes safe "for purposes of quotation, criticism, review, caricature, parody and pastiche".
Prime Minister Boris Johnson criticised the law in March, claiming that it was "terrible for the internet".
Google had campaigned fiercely against the changes, arguing they would "harm Europe's creative and digital industries" and "change the web as we know it".
YouTube boss Susan Wojcicki had also warned that users in the EU could be cut off from the video platform.
Kathy Berry, a professional support lawyer at Linklaters, welcomed the government's stance on the law, claiming it will "allow the UK to agree to more tech-friendly copyright provisions in free trade deals with other countries".
The law sparked suggestions from its biggest critics that it would end up "killing memes and parodies," despite it permitting the sharing of memes and GIFs.

The Welsh Assembly does not have a legal right to be consulted by UK ministers triggering Brexit, the Supreme Court has ruled.
Senior judges said that the UK government cannot start Article 50 without consulting MPs.
They said assembly members have no veto over the process to leave the EU.
But the Welsh Government's chief legal officer Mick Antoniw called the ruling "a victory" in upholding the sovereignty of Parliament.
Welsh ministers had argued that the assembly should be consulted on starting Brexit. They had intervened in the UK government appeal against an earlier High Court ruling.
Counsel General Mr Antoniw told the assembly on Tuesday that AMs are likely to vote on Brexit, despite the ruling, although he said it was not a veto.
Giving the judgement on Tuesday, President of the Supreme Court Lord Neuberger said: "On the devolution issues, the court unanimously rules that UK ministers are not legally compelled to consult the devolved legislatures before triggering Article 50.
"The devolution statutes were enacted on the assumption that the UK would be a member of the EU, but they do not require it.
"Relations with the EU are a matter for the UK government."
The ruling said the assembly and other devolved legislatures had no veto.
But it did say withdrawal from the EU will change the powers of the governments and assemblies in Wales, Scotland and Northern Ireland.
The Welsh Government had argued that if MPs did not vote on Article 50, which was the UK government's original intention, it would undermine the basis for devolution.
Welsh ministers had also argued that this plan would have short-circuited a convention which requires Welsh assembly members to vote on legislation which affects the Welsh devolution settlement.
The Sewel Convention is an arrangement between the UK and Welsh governments where if any new laws come in that affect devolution, they have to be approved by AMs by a vote.
But the Supreme Court ruling sets out that Sewel is a political convention and not a legal one, and so is not a legally enforceable obligation.
The assembly research service states the court is not giving the UK government and Parliament license to ignore Sewel, but it cannot decide disputes about whether it had been applied correctly.
Mr Antoniw, Welsh Government's senior legal advisor and am AM, told BBC Wales the ruling was "certainly a victory in terms of upholding the sovereignty of Parliament".
"We've never argued for a veto, and the court made that point, but what it does do is stress the importance of the Sewel Convention in terms of engagement."
Earlier, speaking to BBC Radio Wales before the judgement, Mr Antoniw defended the £84,000 cost of the Welsh Government's intervention, saying: "The voice of Wales within the UK constitution is priceless."
Plaid Cymru spokesman for external affairs Steffan Lewis said the party would still seek to table a vote in the assembly on the triggering of Article 50.
"It is a simple matter of democracy that the devolved legislatures should have a role in commencing the process of leaving the EU," he said.
UKIP MEP and independent AM Nathan Gill said the Brexit white paper published by the Welsh Government on Monday "will make it into the Guinness Book of Records for having the shortest shelf life ever, 24 hours".
"Because it's now been made obsolete," he claimed.
But Mr Gill - a member of the committee advising First Minister Carwyn Jones on Brexit - said the Supreme Court judgement in favour of parliament was "no surprise".
An UKIP assembly group spokesman said it welcomed the judgement on Article 50 and Parliament, and that any attempt to block Brexit would trigger an immediate general election: "We say bring it on."
"It would be absurd for Wales, Scotland, Northern Ireland to have a veto over triggering Article 50," he said.
The Welsh Conservatives' Europe spokesman Mark Isherwood, said: "The Welsh Government's tortuous arguments were an expensive sideshow.
"It would have been better if every effort had been focused on delivering a Welsh Government paper on Brexit before the UK government announced its negotiating strategy."
Welsh Liberal Democrat leader Mark Williams welcomed the ruling, saying it showed the sovereignty of parliament was paramount, and that his party will vote against Article 50.
Several Labour MPs have indicated they will disobey any order by party leader Jeremy Corbyn to vote in favour of Article 50.
Pontypridd MP Owen Smith, who backed Remain, suggested there ought to be a fresh referendum on the terms of leaving the EU, fearing the UK was set for the "hardest of hard Brexits" by leaving the single market and the customs union.
"The right thing to do then is to allow the British people once more in an ultra-democratic moment to confirm whether they really want the hard, hard Brexit they are likely to get," he said.

Labour will not support any Brexit deal negotiated by the government unless it meets the party's "six tests", the shadow Brexit secretary has said.
Any deal must include a strong relationship with the EU and the same benefits the UK currently has from the single market, Sir Keir Starmer said.
The UK should "honour our obligations" regarding any "divorce bill", he added.
The government will trigger Article 50 on Wednesday, kick-starting talks aimed at agreeing a Brexit deal with the EU.
The government will then publish its Great Repeal Bill on Thursday. It will propose giving ministers the powers to change some aspects of European laws when they have been incorporated into UK legislation, without needing the approval of Parliament.
Triggering Article 50 begins a two-year negotiation process to attempt to reach a deal before Britain officially leaves the EU in March 2019.
If no deal is agreed, it would mean World Trade Organization rules would be imposed - less favourable terms than trading within the single market.
Outlining Labour's demands in a speech in London, Sir Keir said the prime minister "should be under no illusion" and added that Labour would not support a deal "that fails to reflect core British values and the six tests I have set out today".
"All of us want the best for Britain. But the stakes are high and the prime minister's approach so far does not bode well," he said.
The BBC's assistant political editor Norman Smith said some of the tests were akin to "motherhood and apple pie" and could be met quite easily.
But he said Labour were setting the bar quite high in calling for the UK to retain the "exact same benefits" as currently afforded by membership of the single market and the customs union.
In demanding this, Sir Keir said Labour was only seeking the same objective that Brexit Secretary David Davis had set himself in Parliament.
"The government can't turn around and say this is unachievable because it was David Davis... who said that," he said.
Another key demand is for "fair management of migration in the interests of the economy and communities".
Sir Keir said he accepted that the EU principle of freedom of movement "has to go" but he insisted a future immigration policy must be one of managed migration which works for businesses and communities.
One of the tests calls for "a strong collaborative future relationship with the EU". He said it was important to state that because "some of the pure Brexiteers actually want us to crash out [without a deal], either at the Article 50 stage in two years or before that".
"This is the worst of all possible outcomes," he added, saying there would be greater certainty if Theresa May agreed to transitional arrangements from 29 March 2019 until a treaty setting out future relations was finally signed.
Responding to Sir Keir's intervention, Conservative MP Maria Caulfield said Labour were divided over the UK's future outside of the EU and merely "sniping from the sidelines".
"They can't even agree on whether they want to control immigration, and have today failed to make ending uncontrolled free movement one of their tests for supporting a deal with the EU," she said.
No 10 said it wanted the "greatest possible access" to the single market.
European Commission President Jean-Claude Juncker suggested last week that the UK may have to pay up to £50bn for privileged access to the single market and customs union.
Asked about this on Sunday, Home Secretary Amber Rudd said business wanted the "widest possible access" to the single market but how much this would cost would form part of the negotiations.
She also dismissed a "no deal" scenario outlined by EU Brexit negotiator Michel Barnier - with truck queues at Dover, disruption to air traffic and a suspension in the movement of nuclear materials to the UK - as "apocalyptic".
"I think it's fair to say I don't recognise that description... he would say that wouldn't he?" she said.
It has been reported the Great Repeal Bill will include proposals for the government to be given a "new time-limited correcting power" which would allow changes to be made through so-called Henry VIII clauses - without needing the approval of Parliament.
The government says it needs the power to make "technical" changes quickly as a lot of EU law will not work properly without changes being made but Labour leader Jeremy Corbyn says he will not allow Parliament to be "overridden" and ministers to issue a "series of diktats".
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If you walk down Whitehall in central London, you cannot escape reminders of wars fought and empires run from this small district on the north bank of the Thames. There are memorials to the fallen, statues of field marshals and even a Turkish cannon captured in some long-forgotten conflict.
Yet the civil service that once gloried in its global administrative stretch is now the smallest it has been since World War Two. And with the government launching the British state on its greatest administrative, economic and legal reform since it committed the nation to total war in 1939, there is a simple question: is Whitehall up for Brexit?
"It's been a scramble but the ducks are in a row," one Cabinet minister told me confidently.
For the scale of the challenge is immense.
Thousands of civil servants to be mobilised and retasked, thousands of laws and regulations to be rewritten or rejected and thousands of people trained and employed to do the many things currently carried out by the European Union.
This endeavour is not only about the two years of initial negotiations with 27 EU member states that will shortly begin, it is also about the mammoth preparations the UK must make for leaving the EU whatever the outcome of the negotiations.
"The challenge of Brexit has few, if any, parallels in its complexity," says Sir Jeremy Heywood, the Cabinet Secretary. "Its full implications and impact on the political, economic and social life of the country... will probably only become clear from the perspective of future decades."
Perhaps the greatest challenge the civil service has faced was its utter lack of preparation for the British people voting out in the referendum last June. They were expressly forbidden from drawing up any plans by David Cameron's administration and have been playing catch up ever since.
Ministers say the civil service has responded well, creating two new government departments from a standing start. The Department for Exiting the EU (DExEU) has something north of 320 staff, the Department for International Trade, several thousand.
Both departments, along with the Foreign Office, have been given an extra £400m by the Treasury over the next four years to pay for their work on Brexit. There were some initial turf wars but officials now say there is greater singularity of purpose.
Much work has been done analysing options, quantifying markets and assessing laws. Huge volumes of paper have been landing on DExEU desks looking at the impact of Brexit on every aspect of the economy.
The aim is to allow David Davis, the Secretary of State for Exiting the EU, to draw up an a la carte menu for the prime minister, setting out potential options and costs so that she can navigate the negotiations ahead.
For there is no doubt that these will be Theresa May's negotiations. The main negotiating team will include Mr Davis, his permanent secretary, Olly Robbins, and Sir Tim Barrow, the UK permanent representative to the EU.
Below them will be civil servants from all affected government departments, summoned in to work on specific "chapters" of the negotiations, on everything from fish to agriculture to financial services. They will be the team dealing with the European Commission negotiators on an almost daily basis.
Yet above them will be Mrs May who will have to drive the talks and make the big calls. But such is the size of the task that even the prime minister will struggle to retain her usual iron grip.
One minister told me: "This is the first big test to see if she can delegate. This is so big that No 10 cannot control it, they cannot be on top of all the detail."
Not all are so sanguine about the preparedness of Whitehall. The National Audit Office says in a new report that, while 1,000 new roles have been created in the civil service to deal with Brexit, a third remain unfilled and most of the new appointees have simply been transferred from other parts of government.
And the Institute for Government warns that departments such as the Home Office and the Department for Environment, Food and Rural Affairs are underfunded, cannot afford more staff and will be forced to drop non-Brexit work.
Other insiders warn that, although much work has been done setting out options, less thought has been devoted to how the negotiations will progress themselves and how the government should organise itself. Officials talk of not knowing precisely for what they are preparing because Downing Street refuses to reveal its negotiating plans.
The process, inevitably, will begin with negotiations about the negotiations. Who will talk to whom, about what and in what order? The UK government wants to discuss its divorce from the EU at the same time as its future trade relationship. The EU says the two issues must remain separate.
Then will come the exit agreement itself. Much will be visceral and hard-fought. Protecting the rights of EU nationals in the UK and vice versa sounds easy as both sides say they want this to be resolved early on and want to keep the status quo. But the hugely complex detail will be hard to agree.
Yet sorting that out might be easy compared to agreeing how much money, if any, the UK will owe the EU when it leaves. The government says nothing, the EU is hinting at £50bn. And all this is before any negotiations about any future trade arrangement between the UK and the EU and any transitional process that may be needed.
While this will generate a huge amount of work for some in the civil service, many other officials will be focused instead on preparing the UK for leaving the EU come what may.
Much of this will focus on Westminster. There is the Great Repeal Bill to be written and passed through Parliament to ensure that all EU law is transferred automatically into UK law the moment we leave. The aim is to ensure there is no legal chaos and to allow Parliament all the time it needs gradually to unstitch the UK from four decades of EU legislation.
This will be a massive piece of legislative work that will require officials to re-examine huge swathes of UK law. They will have to decide which bits of EU law to return to Westminster and which bits are devolved, a tricky issue in light of Holyrood's demand for a second independence referendum. The Institute for Government warns there might be a need for further 15 separate Brexit Bills.
In the short term, there are a huge number of separate parliamentary inquiries into Brexit - 55 in all - being carried out by various committees of MPs and peers. Ministers have to reply to each one within 60 days and officials are struggling to meet that deadline.
Then there is the process of the UK re-establishing its status at the World Trade Organization (WTO), something that will be needed even if we get a new trade deal with the EU.
The government hopes to transfer its current EU tariff rates into a new UK-specific schedule of trade commitments. But such a "copy and paste" arrangement will be complicated and will almost certainly face challenge from other WTO members. UK diplomats in Geneva, where the WTO is based, have a hard job of reassurance ahead of them.
And then there is also the process of creating new organisations that will fill the gaps in our national life left as the EU tide ebbs from our shores. Officials will need to set up new customs and immigration systems, neither of which will be simple or easy.
So, as the phoney war ends with the triggering of Article 50, Whitehall is facing perhaps its greatest challenge in a generation.

The UK should be able to unilaterally cancel its withdrawal from the EU, according to a top European law officer.
The non-binding opinion was delivered by an advocate general of the European Court of Justice.
A group of Scottish politicians has asked the court whether the UK can call off Brexit without the consent of other member states.
The Court of Justice (ECJ) will deliver its final ruling at a later date.
The advice from advocate general Manuel Campos Sanchez-Bordona comes as the House of Commons begins five days of debates on Prime Minister Theresa May's proposed Brexit deal, with a vote due to be held next Tuesday.
In a written statement, the ECJ said Mr Campos Sanchez-Bordona's opinion was that if a country decided to leave the EU, it should also have the power to change its mind during the two-year exit process specified in Article 50 of the EU treaty.
And it should be able to do so without needing the consent of the other 27 member states - contrary to what the EU itself has argued.
While the advocate general's opinions are not binding, the court tends to follow them in the majority of its final rulings.
The anti-Brexit politicians and campaigners who have brought the case hope it will give MPs an extra option when considering whether to approve Mrs May's draft deal or not, because it could keep alive the prospect of calling off Brexit - potentially through another referendum.
The ECJ statement said the advocate general had proposed that the Court of Justice should "declare that Article 50 allows the unilateral revocation of the notification of the intention to withdraw from the EU".
It added: "That possibility continues to exist until such time as the withdrawal agreement is formally concluded."
The UK is due to leave the EU on 29 March next year, but the deal negotiated with the EU has to be backed by a majority MPs if it is to come into force.
Welcoming the advocate general's opinion, SNP MEP Alyn Smith, one of those who brought the case, said it showed that "we now have a roadmap out of the Brexit shambles".
He said parliament was not necessarily facing a choice between accepting Mrs May's deal or leaving the EU with no deal, and that "there are other options, and we can stop the clock."
A cross-party group of politicians and campaigners including Green MSPs Andy Wightman and Ross Greer, MEP Alyn Smith and MP Joanna Cherry of the SNP, and Labour MEPs David Martin and Catherine Stihler brought the case together with lawyer Jolyon Maugham QC, director of the Good Law Project.
They initially took it to the Court of Session in Edinburgh, which ultimately agreed to pass it to the ECJ.
Two attempts by the UK government to appeal against the referral to the European court were rejected, and the case was opposed by the government and the EU institutions in a hearing before all 27 ECJ judges last week.
Hubert Legal, the chief lawyer for the European Council, argued that allowing unilateral withdrawal could create "endless uncertainty" by allowing countries to announce they are leaving the EU in an attempt to secure better membership terms, before cancelling their withdrawal.
The UK government's lawyers argued that the case was purely hypothetical as "the UK does not intend to revoke its notification", and ECJ judges should therefore refuse to rule on it.
They added that the politicians behind the case wanted to use it as "political ammunition to be used in, and to pressure, the UK parliament".
The advocate general's opinion that the UK has the right to unilaterally withdraw Article 50 notification of its intention to leave the EU flies in the face of what the UK government and the EU want.
Although the Advocate General's opinion is non-binding, the ECJ follow his opinions in the majority of cases.
The whole issue of revocation remains hypothetical at present because the government has made it clear there is no possibility of seeking to revoke the notice to leave the EU.
However, the statement raises the question of how the UK might revoke notification.
It would almost certainly need to be done by an act of parliament. If it was done by ministers alone using prerogative powers it would frustrate the will of parliament as expressed in the European Union (Withdrawal) Act 2018.
It should be noted that the statement and the case concerns revocation of notice to leave, and not a delay or extension of the two-year period provided for under Article 50.
That period can be extended, but only with the agreement of all of the other 27 EU states. Whereas extension of the Article 50 period could become a political necessity, revocation of Article 50 remains something of an academic point at present. However, that would change if there was a second referendum in which the British people voted to remain in the EU.

Prime Minister Theresa May is to officially notify the European Union next Wednesday that the UK is leaving.
Downing Street said she would write a letter to the European Council, adding that it hoped negotiations on the terms of exit and future relations could then begin as quickly as possible.
An EU spokesman said it was "ready and waiting" for the letter.
Mrs May's spokesman also rejected reports an early election may be held, saying: "It's not going to happen."
Under the Article 50 process, talks on the terms of exit and future relations are not allowed until the UK formally tells the EU it is leaving.
If all goes according to the two year negotiations allowed for in the official timetable, Brexit should happen in March 2019.
A No 10 spokesman said the UK's Ambassador to the EU, Sir Tim Barrow, informed the European Council, headed by President Donald Tusk, earlier on Monday of the date that Article 50 would be triggered.
Mrs May is expected to make a statement to the House of Commons on Wednesday shortly after invoking Article 50, setting out her aims.
A spokesman said the government wants negotiations to start as soon as possible but added that they "fully appreciate it is right that the other 27 EU states have time to agree their position".
The BBC's Ben Wright said he expected the Article 50 letter to be short, possibly extending to two pages at most, and for Mrs May to use it to publicly reiterate her general objectives - such as leaving the single market but reaching a mutually beneficial agreement on trade and other issues.
Speaking in Swansea on Monday, during the first of a series of visits around the UK before she triggers Article 50, Mrs May said she was intent on "delivering on Brexit and getting the right deal".
Last year's referendum result, she added, "was not just about leaving the EU" but was a vote for a "change in the way the country works".
"Part of that is building a strong economy and ensuring that the benefits of economic growth and prosperity are felt across every part of the UK."
Brexit Secretary David Davis said the UK was now "on the threshold of the most important negotiation for this country for a generation".
"The government is clear in its aims," he said. "A deal that works for every nation and region of the UK and indeed for all of Europe - a new, positive partnership between the UK and our friends and allies in the European Union."
In response to the news, Mr Tusk tweeted: "Within 48 hours of the UK triggering Article 50, I will present the draft Brexit guidelines to the EU27 Member States."
Mr Tusk has previously said he expects to call an extraordinary summit of the 27 other members within four to six weeks, to draw up a mandate for the European Commission's chief negotiator, Michel Barnier. Under this scenario, talks are likely to begin in earnest in May.
Sir Tim Barrow, the UK's most senior representative at the EU, said the 27 had had plenty of time to prepare for this moment and he expected them to set out their stall "pretty quickly".
"Our mandate is clear, it is to get on with it," he told MPs on the European Scrutiny Committee. "There is a timetable that everyone has bought into it."
Mrs May said last year that she intended to notify the EU of the UK's intention to leave by the end of March. The move was approved by Parliament two weeks ago when peers and MPs passed unchanged a bill giving the prime minister the authority to set the process in motion.
EU leaders have said they want to conclude the talks within 18 months to allow the terms of the UK's exit to be ratified by the UK Parliament and the European Parliament, as well as approved by the necessary majority of EU states.
Mrs May has said MPs and peers will have a vote on the deal she negotiates but she has insisted the UK will leave anyway even if Parliament rejects it. The government has said it expects to secure a positive outcome but made clear there is a chance of there being no formal agreement with Mrs May saying no deal was better than a bad deal.
Ahead of Mrs May naming the date European Commission President Jean-Claude Juncker was quoted in German newspaper Bild saying the UK may have to abandon hopes of getting a trade deal if it did not agree to the term offered by the EU.
These terms may include a £50bn "divorce bill" and Mr Juncker said Brexit could bring the remaining 27 members closer together: "They will all see from the UK's example that leaving the EU is a bad idea."
Labour's Keir Starmer said the opposition would hold the government to account throughout the process, claiming the prime minister had failed to provide certainty about her plans or prepare for the "clear dangers" of not reaching a deal at all.
The Scottish National Party's Europe spokesperson at Westminster, Stephen Gethins, said: "Today's announcement... shatters beyond repair any notion or position that the Prime Minister is seeking a UK-wide agreement.
"For nine months since the EU referendum, there has been no attempt by the UK government to seek a meaningful discussion or agreement with the devolved administrations."
Lib Dem leader Tim Farron, who has called for the public to have their say on the terms of exit in a further referendum, said Mrs May's decision to rule out membership of the single market before negotiations began was proof she was pursuing an "extreme and divisive" Brexit.
"Leaving the single market was not on the ballot paper in the referendum, it is a political choice made by Theresa May," he said.
Later this week, EU leaders will gather in Rome to mark the 60th anniversary of the Treaties of Rome, which established the European Economic Community - the initial forerunner to the EU. Mrs May is not attending the event.

Conservative donor Lord Ashcroft says he believes Boris Johnson's Brexit interventions might help Theresa May in her negotiations with the EU.
The former deputy chairman said the PM could tell Brussels: "This is the type of difficulty I have in bringing people into line."
Mr Johnson, the foreign secretary, has been accused of undermining Mrs May by setting out his own vision of Brexit.
But Lord Ashcroft said he could not "see much harm" in his recent comments.
Speaking to BBC political editor Laura Kuenssberg at the Conservative Party conference in Manchester, the tycoon said: "Everyone wants the best deal for Britain in EU negotiations - the issue is that everyone has a different view on how they should proceed.
"But it is a complex set of negotiations and I don't believe that a deal will be struck until much nearer the time and there's a lot of play acting going on and positioning.
"I don't see much harm in what Boris has put forward, I don't see it's highly inconsistent. At the same time Theresa can use that as a strength in the EU negotiations by saying 'this is the type of difference I have in bringing people into line'."
After the Conservatives lost their Commons majority in June's general election, much of the talk at conference is about how to address the challenge posed by Jeremy Corbyn and Labour.
Lord Ashcroft said the party needed to "reassemble" and "get its act together", adding that there would be different "nuances" from ministers throughout the Brexit process.
In his latest comments on Brexit, Mr Johnson wrote in The Sun that Mrs May's planned transition phase must not last "a second more" than two years.
The foreign secretary also set out his plan for Brexit in a Daily Telegraph article last month.
This sparked accusations of "backseat driving" and prompted Mrs May to say the government was "driven from the front".

Austrian chancellor Sebastian Kurz has told Theresa May it is "important to avoid a hard Brexit", after talks with the UK prime minister.
Mrs May is in Salzburg as part of a mission by UK ministers to sell their post-Brexit trade proposals.
Mr Kurz said he viewed Brexit "negatively" but felt negotiations were going "quite well".
Mrs May then held talks with Czech PM Andrej Babis before heading off on her summer holidays.
Speaking at a brief joint press conference, Mr Kurz, who has just assumed the EU presidency for six months, said: "The Brexit decision is a decision we see very negatively.
"But, of course, it has been taken by the British people so now we have to find a way to deal with it, and from our point of view it is important to avoid a hard Brexit."
He said he hoped the UK's talks with EU chief negotiator Michel Barnier would be successful and a "solution" could be found by October.
The BBC understands that Mr Kurz has indicated he supports the idea of EU leaders holding formal Brexit talks at a summit in Salzburg in September.
Mrs May hailed the strength of the UK's relationship with Austria, adding: "We are delivering on a vote of the British people, they chose to leave the EU and we will deliver that."
Later, Mrs May pitched her idea for a post-Brexit free trade area to her Czech counterpart Andrej Babis.
A Downing Street spokesman said: "She highlighted that a UK-EU free trade area would maintain frictionless trade that would enable businesses across Europe to maintain their vital integrated supply chains.
"They agreed it was important to find a solution and that negotiations should continue at pace."
Both the EU and UK say a deal can be done by October - five months before the UK is due to leave the European Union - but have also said preparations are being made in case negotiations end in no deal.
Mr Barnier has already rejected a key element of her proposal for post-Brexit trade with the EU.
International Trade Secretary Liam Fox has accused the EU of pushing the UK towards a "no deal" scenario because they "keep saying no to everything".
Mr Fox, who is on a trade mission to San Francisco, told Business Insider the UK should leave without a deal if talks break down, rather than requesting an extension of the Article 50 process to continue negotiations, as some have suggested.
"To attempt to extend our membership even longer, many voters would regard as a complete betrayal by the political class, and I think they would be right," he added.
Mrs May's trip to Austria is one of several being made to Europe by British government ministers over the summer to promote her plan, detailed in the Brexit White Paper, to European leaders.
Foreign Secretary Jeremy Hunt met his German counterpart in Berlin on Monday and the UK chancellor, home secretary, business secretary and the minister for the Cabinet Office are also meeting counterparts across Europe over the summer.
Following talks in Austria, Mrs May will head to Italy with her husband, Philip, for a week before returning to the UK to work.
She is also due to attend a World War One memorial event marking the centenary of the battle of Amiens, which began on 8 August 1918, before heading off for two weeks' holiday in Switzerland.
Analysis by BBC Diplomatic Correspondent James Robbins
Salzburg in high summer is packed with tourists and music lovers enjoying the annual festival.
Theresa May went to the opera on Friday night, but only after her talks with Mr Kurz and Mr Babis.
The prime minister is hoping to persuade them to urge others in the EU27 to relax their common position - particularly by accepting her proposals for continuing free movement of products after Brexit.
But there's no sign either Austria or the Czech Republic is willing to budge. Eurosceptic feeling may be strong among their populations, but neither leader is contemplating following Britain out of the Union.
Instead, both governments believe Mrs May is still cherry-picking and that Britain must blink first to avoid what they call a catastrophic crash-out they are convinced would hurt the UK far more than the EU.
Mozart's The Magic Flute, in the city of his birth, should have been something of a relief for Mrs May.
The UK's Brexit White Paper, drawn up after agreement with the cabinet at Chequers, proposes close ties in some areas, such as the trade in goods, but Mrs May says it will end free movement of people and the jurisdiction of the European Court, and allow the UK to strike trade deals with other nations.
It would involve the UK collecting some EU tariffs - in a bid to ensure frictionless trade in goods and to avoid a hard border in Northern Ireland - under its proposed Facilitated Customs Arrangement for goods and agri-foods.
The plan sparked two UK cabinet resignations - former Brexit Secretary David Davis and former Foreign Secretary Boris Johnson.
Mr Barnier said on Thursday that the EU "will not delegate the application of its customs policy and rules and VAT and excises duty collection to a non-member who would not be subject to the EU's governance structures".
Any customs arrangement or union "must respect this principle", he said.

At a time of great uncertainty the new chancellor chose to display caution.
Despite long wanting to get his hands on the nation's purse strings, Philip Hammond was not tempted into grand gestures.
There were modest giveaways for those "just about managing" in order to keep true to Theresa May's promise of a Government for all; a reduction in the rate benefits are withdrawn for those working, a ban on letting fees and a boost to the minimum wage - much briefed in advance to perhaps gain some headlines before gloomy forecasts became the story.
There was a shift away from his predecessor's focus on deficit reduction within a set timeframe - instead Mr Hammond said he would deliver a surplus as soon as possible, announcing investment in housing and roads, money for research and development - the focus on boosting productivity.
But this was still a Chancellor keen to limit spending in order to secure stability.
Brexit has made the future unpredictable.
Philip Hammond may have more insight that most into the Government's planned approach to leaving the EU, but he still wanted to ensure he had enough in his back pocket to withstand any shocks that may come.
And with vast increases in borrowing and reduced growth predicted, Mr Hammond limited the giveaways and changed the economic rules to give himself the flexibility to respond.
This was a careful balancing act, an attempt to follow through on promised support for those in society who need it most while keeping the nation's books in order.
At the same time, this was an attempt to recognise the potential economic turbulence Brexit could bring without invoking the ire of backbench Eurosceptics with an overly negative outlook.
Mr Hammond was careful to speak of opportunities as well as challenges, describing a "great nation", resilient and strong.
By his own admission there was no grand "rabbit in the hat". Mr Hammond wasn't out to steal the show, but rather prove he can be the steady hand on the tiller in choppy economic waters.
But for Labour, this was an opportunity to seize on a chink in the government's economic armour, with the Shadow Chancellor John McDonnell saying the much-hailed long term economic plan had been an "abject failure".

Chancellor Philip Hammond has called economic forecasts in the Autumn Statement one of a "range of outcomes" after some pro-Brexit MPs criticised them for being too pessimistic.
The Office for Budget Responsibility (OBR) forecast more government borrowing and reductions in economic growth after the referendum.
Ex-minister Iain Duncan Smith accused the OBR of "utter doom and gloom".
But Mr Chancellor Hammond said it was good to prepare for a "rainy day".
He added that the government was investing to boost infrastructure and economic productivity and there was a "downward path in borrowing".
BBC economics editor Kamal Ahmed said the chancellor "hopes that the forecasts do prove very gloomy" and he was "setting a bottom line from which he hopes the government can clamber upwards".
During Wednesday's Autumn Statement, Mr Hammond's first since becoming chancellor, he told MPs the UK's deficit would no longer be cleared by 2020.
And the OBR estimated the government would have to borrow £122bn more than forecast in March's Budget, with the referendum result accounting for £58.7bn of this.
The Brexit vote meant potential growth in the current Parliament would be 2.4% lower than forecast in March, according to the OBR who also admitted producing a forecast was "far from straightforward", as it had not been given any extra information from the government about its negotiation plans.
It said: "We have made a judgement - consistent with most external studies - that over the time horizon of our forecast any likely Brexit outcome would lead to lower trade flows, lower investment and lower net inward migration than we would otherwise have seen, and hence lower potential output."
The organisation said the economy would be affected by future choices that the government makes about regulatory and other policies and it "could move in either a growth-enhancing or a growth-impeding direction".
Asked about the OBR's predictions, the former Work and Pensions Secretary and Leave campaigner Mr Duncan Smith told the Daily Telegraph it was "another utter doom and gloom scenario" from the organisation.
The Economists for Brexit group predicted more "humiliating U-turns" from the OBR, saying it had  "assumed a pessimistic outlook for the UK economy outside the EU, based on bad economic policy-making".
Conservative MP John Redwood, who also supported Brexit, added: "Their [GDP growth] forecast probably is too low, their borrowing forecast is far too high, and we'll get good access to the single market once we're out of the EU."
But Downing Street dismissed the criticism, saying the OBR's role was to "provide transparency and credibility".
She added: "They are an independent forecaster. We won't get into second guessing them."
In his statement, Mr Hammond promised to invest £23bn on "innovation and infrastructure" over the next five years, with more money for roads, broadband and regional development.
He told BBC Radio 4's Today programme: "There's a downward path in borrowing. We need to keep the downward path on borrowing... But we also need to invest in our economy, to generate the revenue that will drive down the debt."
Describing economic forecasting as "not a precise science", Mr Hammond said of the OBR's forecast: "We should think of it as one of the possible range of outcomes we need to plan for."
He added: "We have a very strong foundation on which to build."
Mr Hammond also said: "We should have a plan which both invests in our economy and puts a little aside for the possibility of a slightly more rainy day next year or the year after."
Uncertainty was "not just about" Brexit but the change of US government when Donald Trump takes office and the growth rate of the Chinese economy, he added.
Labour said the Autumn Statement offered no hope for the future after six "wasted" years.
Among Mr Hammond's announcements were:
The speech also triggered questions about the future of the so-called "triple lock" protection for state pensions, while campaigners criticised the lack of extra funding for social care.
The triple-lock guarantees that state pensions rise by the same as average earnings, the consumer price index, or 2.5%, whichever is the highest.
Mr Hammond said the government would meet this pledge, adding: "But as we look ahead to the next Parliament, we will need to ensure we tackle the challenges of rising longevity and fiscal sustainability."
Former work and pensions secretary Stephen Crabb backed a review of the mechanism after 2020.
He told the BBC: "The fiscal impact of the triple lock is not something anyone can dismiss lightly and if we are serious about ensuring that our welfare system remains affordable in the very long term then my own view is that the triple lock has served its purpose and probably needs to get amended, to ensure that we don't have to keep going back to working age families and squeezing the same people's incomes time and again."
Meanwhile health and social care leaders have condemned the statement for a "missed opportunity" to announce new investment.
For Labour, shadow chancellor John McDonnell told BBC One's Breakfast that although he welcomed the government "moving on investment policy" there had been "mismanagement of the economy over the last six years".
"I find it extremely worrying that they've used the last six years with austerity measures and instead of investing they've been cutting, and as a result of that they're unprepared and ill-equipped for Brexit."
The SNP said Mr Hammond had offered little on Brexit, which it called the "elephant in the room".
Liberal Democrat leader Tim Farron said: "The government's mishandling of Brexit is hitting those on lower and middle incomes the hardest."
He added that "rhetoric" about helping those "just about managing" had not resulted in action, creating "surprising and massive disappointment".
But UKIP said billions were being wasted by the government "delaying" the UK's exit from the EU.
Plaid Cymru said there was little in the statement to help rebuild the Welsh economy and close the wage gap with England.
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The outlook for wages is "dreadful" with the squeeze on pay lasting for more than 10 years, independent economists have said.
The Institute for Fiscal Studies (IFS) said workers would earn less in real wages in 2021 than they did in 2008.
Other analysis shows the biggest losers between now and 2020 will be lower income families, with the poorest third likely to see incomes drop.
Chancellor Philip Hammond said millions of new jobs had been created.
Defending his Autumn Statement plans, the chancellor told Radio 4's Today programme that the government had brought job growth. It was investing for the future, preparing for a "rainy day", and government borrowing was on a "downward path", he added.
In its analysis of the Autumn Statement, the independent think tank, the IFS, said workers would earn less in real wages in 2021 than they did in 2008.
"This has, for sure, been the worst decade for living standards certainly since the last war and probably since the 1920s," said Paul Johnson, director of the IFS.
"We have seen no increase in average incomes so far and it does not look like we are going to get much of an increase over the next four or five years either."
The "outlook for living standards and for the public finances has deteriorated pretty sharply over the last nine months", he added.
Real average earnings - which factor in the rising cost of living - were forecast to rise by less than 5% between now and 2021. That forecast is 3.7% lower than was projected in March.
"Half of the wage growth projected for the next five years back in March is not now projected to happen. On these projections real wages will, remarkably, still be below their 2008 levels in 2021," Mr Johnson said.
"One cannot stress enough how dreadful that is - more than a decade without real earnings growth. We have certainly not seen a period remotely like it in the last 70 years."
The biggest impact on income in recent years, according to the IFS, has been felt by younger workers. Those aged 60 and over, in contrast, have seen living standards rise.
The squeeze on living standards could be worse during this Parliament than between 2010 and 2015, suggests the Resolution Foundation think tank. which campaigns for people on low and middle incomes.
Lower growth in pay, an accelerating rise in the cost of living, and welfare changes such as a freeze on working age benefits all combined to show that incomes on average would only grow by 0.2% a year, it said.
This compares to a rise of 0.5% during the coalition government years - a period of austerity in the aftermath of the financial crisis.
"Taking all this together we can look at the outlook for family incomes in the coming years, and it paints a grim picture," the think tank said.
Significantly, given the government's focus on "just about managing" families, the data shows that lower income families will be worse off.
The Foundation said the poorest 10% would see an income hit of more than 3% by 2020 as a result of tax and welfare policies.
"While top earners were hit the hardest following the financial crisis, the big difference looking forward is that the biggest losers are lower income families, with the entire bottom third of the income distribution set to see incomes fall in the years ahead," the Foundation said.
The Treasury's own analysis, published alongside the Autumn Statement, shows that the poorest 30% of households will see a negative impact on incomes from tax, welfare and public spending measures by 2019-20.
Primarily, this is a result of the main working age benefits and tax credits being frozen in cash terms for four years from April 2016. That includes entitlements such as jobseeker's allowance and income support.
That income freeze is forecast to coincide with an acceleration in inflation, pushing up the cost of living.
The chancellor offered some help to the lowest paid with changes to Universal Credit - the new umbrella benefit gradually being introduced across the UK.
Mr Hammond announced a reduction in the rate at which the benefit is withdrawn from people when they start work.
The Resolution Foundation report said this would have relatively little impact on family finances.
"When set against all other policy changes announced since the 2015 election, the Autumn Statement only undoes 7% of the hit from benefit cuts to the bottom half of the income distribution," it said.
Middle-income families will see some rises in income, but by no more than 1%, the Treasury documents show. The richest 10% will see the biggest hit to incomes.
More broadly, the IFS said that the OBR had forecast that national income in 2020-21 would be £30bn lower than projected in March - the equivalent to £1,000 per household.
Among Mr Hammond's announcements were:
The IFS said that Mr Hammond had clearly put whatever money he had into long-term plans.
"The clear prioritisation by Mr Hammond to direct most of what largesse he felt able to afford to paying for additional investment spending - roads, housing, research and development - to support the economy in the long run, rather than to pay to support the incomes of the "just-about-managing", or indeed public services, in the short run," Mr Johnson said.
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UK aviation regulator the CAA sought a joint no-deal transition plan with its EU counterpart but was rebuffed, correspondence seen by the BBC reveals.
The letters show the European Aviation Safety Agency (EASA) rejected a British call for a plan in July.
With months to go before the UK could drop out of the EU without a deal, the two bodies are yet to begin formal discussions.
EASA said technical talks could not pre-empt political agreement on Brexit.
In a letter to EASA in June, CAA chief executive Richard Moriarty said a "joint transition plan" was necessary to help assure people of "the on-going integrity of the aviation framework in any future scenario".
It said: "My team is standing by to support these discussions."
In response, EASA executive director Patrick Ky said he understood the request to limit disruption and safety risks.
But he added: "It remains the case that without sufficient clarity on both the outcome of the withdrawal process and the future UK legal framework such discussions would currently be premature."
If the UK leaves the EU without reaching a deal, the EU would not recognise certificates, approvals and licences issued by the CAA.
This could stop new aviation parts made in the UK - like wings constructed by Airbus - being put on EU planes.
British pilots with UK licences flying EU-registered aircraft would need to get second licences from another EU state or transfer their licences there.
The UK wants to participate in EASA after Brexit. Failing that, officials seek a deal where the EU and UK aviation authorities recognise each other's standards.
EASA has recently offered some UK aviation businesses the chance to be approved as "third county" suppliers to the EU, which means they could carry on doing business in the EU.
But not all areas of aviation are covered.
Although there are international agreements, there is no aviation equivalent of the World Trade Organization that would allow flights to continue seamlessly after a no-deal Brexit.
In a statement to BBC Radio 4's Today programme, EASA said Brexit negotiations were ongoing and added: "The outcome of those negotiations cannot be pre-empted, but until more clarity is gained of the terms of UK's withdrawal, discussion about technical details would not be useful since the framework for which we need to prepare is not known.
"Such technical-level discussions cannot pre-empt the overall political agreement, which is the subject of the withdrawal negotiations.
"Once the future framework is clearer, we will be open to engaging also in technical discussions."
The CAA said the UK would recognise safety licences and approvals issued by EASA and it urged EASA to recognise its own after Brexit.
A spokesman said: "We call upon the European Commission to allow EASA to hold discussions with us about the detailed technical arrangements that would apply in a no-deal scenario.
"We are ready to start these talks immediately."

A High Court ruling that Parliament - not the government alone - can trigger Article 50 threatens to delay Theresa May's timetable for leaving the EU, but could it spell the end for Brexit altogether?
Downing Street says it is confident that the Supreme Court will overrule the High Court and allow ministers, rather than MPs, to decide when to begin the formal process of leaving the EU.
But there is no evidence that government lawyers have yet amassed new arguments that might persuade the highest court in the land that the three eminent judges reached the wrong conclusion on Thursday.
So if that ruling stands, then the relevant secretary of state, David Davis - in charge of the process of exiting the EU -  has said his presumption is that an Act of Parliament would be required before triggering Article 50 of the Lisbon Treaty. No 10 has said that's the 'logical conclusion' of the ruling, too.
Incidentally a former Conservative leader - Iain Duncan Smith - disagrees, and believes a straightforward vote of MPs would satisfy the courts.
But let's assume government ministers are right.
Could the mere act of consulting largely pro-Remain MPs scupper Brexit?
Well, no.
Although the former chancellor Ken Clarke and the former Lib Dem leader Nick Clegg have told the BBC that they are prepared to vote against invoking Article 50, enough Remainers are saying they would respect the result of the referendum and vote to start the process of leaving the EU. The government would not lose this vote.
More likely is delay - rather than destruction - of Brexit.
But the opportunities for delay depend in part on the form any legislation would take.
Some pro-Brexit politicians are urging the government to come up with a simple one-line bill triggering Article 50.
The shorter and simpler the legislation, the more difficult it would be for Remainers to put forward elaborate amendments attempting to tie the government's hands in subsequent negotiations with the EU.
The former attorney general Dominic Grieve reckons that amendments could still be permitted, so long as they were addressed to the narrow substance of the bill.
This could allow, for example, an amendment to hold a second referendum on the final deal negotiated by the government, given that those negotiations were triggered by the Article 50 process - the option favoured by the former Labour leadership contender Owen Smith.
Even assuming that all amendments were defeated or ruled out of order, any legislation at all carries a risk for the government.
That's because it needs to be approved not just by the Commons but by the Lords.
And many pro-Remain unelected peers might be less squeamish than MPs about voting against Article 50.
If - and it's a big if - that were to happen, then the government would have to use the Parliament Acts to overrule them. Peers cannot stop legislation outright - they can simply force a rethink.
That would delay the process by about a year - scuppering not Brexit itself, but Theresa May's promise to start the process by the end of March 2017.
It might also extend our membership of the EU until just after the next general election, in the spring of 2020.
Some pro-Brexit Conservatives are already urging the prime minister to call an early election under these circumstances, on a platform of standing up for "the people" against "the peers".
With the party's lead in the polls, they calculate that this would strengthen the government's mandate.
But, given the complications and potential consequences of yesterday's ruling, you can understand why minsters are keeping their fingers firmly crossed that the Supreme Court will overturn it.

The EU must back Theresa May's Brexit plan or risk the UK leaving without a deal, the most senior member of the UK PM's cabinet has said.
Cabinet Office Minister David Lidington said the European Commission's proposals remained unacceptable.
And he appealed for compromise from the EU side in Brexit talks.
The EU's chief negotiator Michel Barnier said the EU was ready to offer the UK an unprecedented deal but it must not weaken the single market.
Speaking to a French business conference, Mr Lidington, who is Mrs May's de facto second-in-command, suggested there were only two choices on the table as Brexit talks entered a critical phase.
"With exactly seven months until the end of Article 50 process and less than two months ahead of the October European Council, we face the choice between the pragmatic proposals we are discussing now with the European Commission, or the risk of there being no deal.
"The alternative models do not meet the level of ambition or the outcome we all want to see delivered.
"So, we need the EU to engage with us on our positive vision of the future relationship."
His message was softened from a version of the speech released to journalists beforehand, which had simply warned of "no deal".
Mr Lidington was branded "arrogant" by the People's Vote campaign for another EU referendum, which added: "Good deal, bad deal or no deal, Brexit is a big deal and it must be for the people to decide."
It came as Brexit Secretary Dominic Raab denied reports Michel Barnier has turned down UK requests for extended meetings in Brussels.
Mr Raab was said by The Guardian to have been frustrated by the EU chief negotiator's alleged failure to make himself available for talks.
But Mr Raab told a Lords Committee he had a "good professional and personal rapport" with Mr Barnier.
And he would be holding a "long" meeting with him on Friday.
Mr Raab vowed to increase the pace and frequency of talks with Mr Barnier when he took over in July from David Davis, who quit as Brexit Secretary in protest at Theresa May's white paper on trade with the EU when Britain leaves.
"I'm confident that a deal is within our sights," Mr Raab told the Lords EU Committee. "We're bringing ambition, pragmatism, energy and if, and I expect it will be, and if it is matched, we get a deal."
He added: "Firstly, in relation to whatever tittle tattle may appear in whatever newspaper, I shall be over in Brussels tomorrow (Thursday) evening for a long, substantive meeting on Friday, I hope that gives you the facts directly with Michel Barnier."
Britain is on course to leave the EU on 29 March.
Both sides are hoping to agree a divorce deal and a statement on future trading relations by the next EU summit on 17 October - but Mr Raab suggested that deadline could slip, saying there was a "possibility that it may creep beyond" that date.
On the £39bn Brexit "divorce bill", Mr Raab said a no-deal scenario could affect arrangements over payments to the EU.
"I don't think it could be safely assumed on anyone's side that the financial settlement as has been agreed by the withdrawal agreement would then just be paid in precisely the same shape or speed or rate if there was no deal."
And he rejected claims by pro-EU Labour peer Lord Liddle that any deal document was likely to be "vacuous" and "opaque", saying he expected it to contain a "degree of detail" and some "clear choices".
Theresa May's chief Brexit advisor Olly Robbins will no longer have to face questions from MPs or peers, Mr Raab told the committee, which was holding a special meeting during Parliament's summer recess.
The two men were grilled by MPs in a joint appearance before the Commons Brexit committee in July.
But Mr Raab told the Lords EU committee that in future it would be ministers only - and not civil servants - that "come and be accountable" to Parliamentary committees over Brexit.
Meanwhile Mr Barnier, speaking Berlin, said the EU was "prepared to offer Britain a partnership such as there never has been with any other third country".
But, he added, it would not permit anything that weakened the single market.
"We respect Britain's red lines scrupulously. In return, they must respect what we are. Single market means single market ... There is no single market a la carte," he told reporters.
The pound rose 0.6%, to around $1.2950, after the EU chief negotiator's comments.

It's going to be quite a baptism of fire for the UK's new Brexit secretary on his first visit to Brussels in the new job.
He'll hardly have a foot through the door at the European Commission before he's faced with a barrage of questions. The EU wants clarity on the UK's negotiating position: is it based on Theresa May's Chequers cabinet agreement or the subsequent parliamentary amendments? Will the UK position change again in a few days or a week's time?
The EU's chief Brexit negotiator Michel Barnier then has another message he's hell-bent on delivering. Work with us, he will say to Dominic Raab, to finish the UK's exit deal - the so-called Withdrawal Agreement - otherwise the chances are rising of the UK crashing out of the EU without a deal come March next year.
Now coincidence of coincidences, just as Mr Raab arrives in town, the European Commission will publish a paper instructing EU governments to do more to prepare for the possibility of a no-deal Brexit which - it warns - would have a considerable impact on European businesses and citizens.
The paper mentions amongst other things the potential immediate impact on EU borders - with goods and people from the UK subject to customs checks. It predicts the aviation industry could be severely disrupted- with EU-UK airline and passenger rights agreements no longer valid. It advises that personal data transfers to the UK would be subject to new limitations and that the City of London would no longer have financial passporting rights.
The paper also alerts pharmaceutical companies to the fact that the testing of European medicines could no longer to be carried out in the UK in the case of a no-deal Brexit and it informs that the UK would have to be removed from EU databases.
Contrary to some UK media reports which suggest that the Commission's "preparedness paper" as it's known is being published now as a result of the political turmoil and uncertainty in Westminster, this is something the Commission has been working on for months. The Commission likes to say it began its preparedness research when the UK government began the mantra of "no deal is better than a bad deal" though that, I think, is questionable.
I've seen a draft of the preparedness paper but have been told it is a work in progress and will only be finalised on Thursday morning, just in time for Mr Raab's Brussels arrival.
As one senior EU diplomat put it to me: "When it comes to Brexit, there are no innocent timings."
Having had a lot of background chats with senior European officials of late, I can say with certainty that the Commission paper is not simply a scaremongering exercise.
There is genuine concern in Brussels that:
The EU thinks a Brexit no-deal scenario would be a bureaucratic, practical and financial nightmare for Europe.
So expect Mr Barnier to adopt encouraging tones with Mr Raab, reminding him that the Withdrawal Agreement is already 80% signed off between the EU and UK.
However, the 20% left is challenging to say the least - covering flashpoints like data protection, UK military bases in Cyprus and who should police the withdrawal agreement and subsequent almost two-year transition period.
On the Irish border backstop - where both the EU and UK have undertaken to avoid the re-introduction of a hard border between Northern Ireland and the Ireland whatever their post-Brexit relationship looks like - the Commission, I'm told, is working on rewording the protocol in the declared hope that will make it easier for team Theresa May to sign up to.
Former EU trade official Peter Guilford told me this week he believes the Brussels rumours that Brexit talks will go down to the wire this autumn and it would only be when the Commission "saw the whites of UK negotiators' eyes" that they would start making their own compromises instead of always hammering the UK for them.
But EU diplomats wonder: can Theresa May hang on till then?

The UK must come forward with proposals aimed at avoiding a hard border in Ireland, the EU's chief Brexit negotiator has said.
Michel Barnier said it is, so far, unclear what the UK is willing to commit to in Northern Ireland.
That echoes the position of the Irish government.
It wants the UK to give more commitments before the Brexit talks can begin considering a trade deal.
The prime minister has repeatedly said that the "unique circumstances" of Northern Ireland will require a "specific" solution.
During a speech in Brussels, Mr Barnier focused on the issue of what EU rules may continue to apply in Northern Ireland after Brexit.
He said: "There are over one hundred areas of cross-border co-operation on the island of Ireland.
"Such co-operation depends, in many cases, on the application of common rules and common regulatory space."
He added that the UK has said it would continue to apply some EU rules on its territory after Brexit but it is "unclear what rules will apply in Northern Ireland after Brexit".
UK ministers and unionist politicians have said they will not accept an arrangement which will "endanger the integrity of the UK single market".
However, Mr Barnier said Northern Ireland already has specific rules in some areas that are different to the rest of the UK.
He pointed to the "all-island" single electricity market, or specific regulations for plant health for the whole island of Ireland.
The DUP has criticised Mr Barnier's comments, describing them as an attempt to "bully the UK government toward support for a Brexit border scenario which would weaken Northern Ireland's constitutional position and devastate the local economy".
MEP Diane Dodds said any Brexit deal must reflect the fact that Great Britain is, by far, Northern Ireland's most important marketplace.
"We will not be cut off from the rest of UK either by associate membership of the EU or by regulatory divergence from Great Britain," she said.
"The DUP will exert our influence to ensure this is the case."
On Friday, Prime Minister Theresa May was told she had two weeks to makes progress on the border and the Brexit bill if the EU is to agree to begin Brexit trade talks before the end of the year.
EU Council President Donald Tusk said he was "ready" to move onto the next phase of Brexit talks, covering future relations with the UK.
But he said the UK must show much more progress on the "divorce bill" and the Irish border by early next month.
Mrs May said "good progress" was being made but more needed to be done.

There can be no Brexit withdrawal agreement without a "backstop" option for the Irish border, the EU's chief Brexit negotiator has said.
Michel Barnier said the Republic of Ireland has the full support of all EU member states and all EU institutions.
The backstop would involve NI, or the UK as a whole, aligning with the EU rules required to support North-South cooperation and an all-island economy.
Mr Barnier was speaking at the start of a two-day visit to Ireland.
The UK has accepted the need for a backstop to be written into the Brexit withdrawal agreement.
But it has not agreed what EU rules it should cover.
At the beginning of the all-island Brexit forum in Dundalk, County Louth, Mr Barnier said he knows that the so-called backstop has been the subject of "heated discussions in the UK".
"To be clear: without a backstop, there can be no withdrawal agreement," said Mr Barnier. "This is an EU issue, not only an Irish issue."
It almost became Brexit bingo - as journalists lost count of how many times Mr Barnier referenced the "backstop" option for the Irish border.
The backstop would mean that in the absence of any other solution, Northern Ireland, or the UK as a whole, would align with EU rules required to support north-south cooperation and an all-island economy.
While in principle the UK signed up to this option, precise detail on it has yet to appear.
Mr Barnier's three points were:
In brief - the backstop was agreed - so let's get on with it.
Mr Barnier also denied claims from Arlene Foster, the leader of the Democratic Unionist Party (DUP), that he has been "aggressive" towards Northern Ireland unionists in the Brexit talks.
The DUP leader said earlier that Mr Barnier did not understand the dispute and was not an "honest broker".
In response, the EU's chief Brexit negotiator said he was not ready to engage in "polemics" with Mrs Foster.
Mr Barnier's visit comes amid rising tensions over the future UK-Ireland border.
He told a press conference in Dundalk at the beginning of the all-island Brexit forum that his "door is open" to Mrs Foster and the DUP.
He said he had not approached the negotiations in a "spirit of revenge".
He added that he regretted the UK had voted to leave the EU, and said he was determined to work with the UK to find a solution to the Irish border issue.
The all-island Brexit forum is being hosted by the Taoiseach (Irish prime minister) Leo Varadkar and his deputy, Simon Coveney.
On Sunday, Mr Barnier said the UK was contradicting itself over its Irish border policy.
But Mrs Foster said she believes Mr Barnier does not understand the dispute and is "not an honest broker".
In return, he said that Mrs Foster needed to respect that his role was to negotiate on behalf of the EU and not to act as a mediator.
Meanwhile the Taoiseach again there needed to be "meaningful progress" on the border issue by the June EU summit.
Mr Varadkar said otherwise it would be difficult to get the withdrawal agreement in place by October.
In December, the UK and EU reached a political agreement in which the UK committed to protecting north-south cooperation on the island of Ireland.
It also guaranteed there would be no hard border, including physical infrastructure or related checks and controls.
However, the EU's proposed backstop solution to avoid a hard border - keeping Northern Ireland in the customs union after Brexit - continues to be at odds with what the UK government and the DUP say they would accept.
Mrs Foster told BBC political editor Laura Kuenssberg the DUP would not accept Northern Ireland being treated differently to the rest of the UK.
She said: "Michel Barnier's trying to present himself as someone who cares deeply about Northern Ireland and if that is the case he needs to hear the fact that we are part of the United Kingdom [and] will remain part of the United Kingdom constitutionally, politically and economically.
"Therefore his proposal of us being in an all-Ireland regulatory scenario with a border down the Irish Sea simply does not work.
"It does not work constitutionally, politically and it certainly does not work from an economic perspective."
Mrs Foster added: "We've tried to get him to understand the unionist position for the people of Northern Ireland but he hasn't really responded and I'm disappointed about that.
"I don't think he does understand the wider unionist culture of Northern Ireland."
The DUP is also expressing annoyance that Mr Varadkar is visiting Northern Ireland later without giving notice.
Mr Barnier is due to meet Mr Varadkar on Monday and will also speak to business leaders on both sides of the Irish border during his trip.

Michel Barnier has clarified remarks he is reported to have made about Brexit.
The EU negotiator was quoted as saying he saw the process as an opportunity to "teach" the British people and others what leaving the single market means.
Mr Barnier said he actually told a meeting it "was an occasion of great explanation for everyone in the EU".
The BBC understands he was talking in Italy about explaining the benefits of the single market to a broad European audience, not just specifically the UK.
The latest round of negotiations over the UK's exit from the EU concluded last week, with the two sides due to officially meet again later this month.
The UK, which is keen to move on from issues directly related to its withdrawal to talk about its future relationship with the EU, has said it would like to "intensify" the pace of talks, with Downing Street saying it is open to holding negotiations on a rolling basis.
There has been unconfirmed speculation that Prime Minister Theresa May is to make a major speech on Brexit later this month in the run-up to the Conservative Party conference.
Speaking at a conference in Italy on Saturday, Mr Barnier said he did not want to punish the UK for voting to leave the EU in last year's referendum.
But he reportedly warned that "there are extremely serious consequences of leaving the single market and it hasn't been explained to the British people".
"We intend to teach people… what leaving the single market means," he reportedly told the Ambrosetti forum.
Responding to the remarks, a No 10 spokesman said "the British people have heard those arguments."
Mr Barnier tweeted on Monday that what he had said was that Brexit was an "occasion to explain single market benefits in all countries, including my own".
He added "we do not want to "educate" or "teach lessons".
The former French minister, who met the Irish Republic's Foreign Minister Simon Coveney for talks on Monday, later reiterated these comments when speaking to a BBC reporter outside the European Parliament.
Amid growing tensions between the two sides about the progress of talks and the priority given to different issues, a senior EU official has said talks about the UK's financial obligations after Brexit are going backwards.
Gunther Oettinger, the European Commissioner responsible for the EU budget, said "the Brits have to accept that their obligations are going beyond March 2019".
"In July we had been thinking 'yes, they are on the way to accept it'. Now in the last few days they are coming back," he told a technology conference in Brussels.
BBC Brussels reporter Adam Fleming said Mr Oettinger had told him he believed that progress made on the issue in the July round of talks had been reversed during last week's session.
A source at the Department for Exiting the EU said it did not recognise this description and that there had been a robust debate about money.
Last week British officials gave a three-hour long presentation on the legal basis of the EU's request for a Brexit financial settlement.

The UK has until the end of 2020 to change its mind about leaving Europe's single market, the European Union's chief Brexit negotiator has said.
Michel Barnier said that if the UK changed its "red lines" during the post-Brexit transition period, the EU would also change its position.
Theresa May says the UK will quit the EU single market and customs union.
She says this is needed to ensure the UK has the power to control borders and do trade deals with other countries.
The UK is set to leave the EU in March 2019, at which point the transition phase - which the UK government calls the implementation phase - will begin. This will last until 31 December 2020, when the final arrangements agreed between the two sides will kick in.
Negotiations are under way between the two sides, but the UK has already said it plans to leave the single market, which provides for frictionless trade across borders and involves the free movement of people between member states.
In an interview with reporters from several European newspapers, Mr Barnier said the UK would not leave the single market and customs union until 31 December, and until this date, "everything is possible".
"If the UK wanted to change its red lines, we would therefore change ours," he said.
Mr Barnier added that he was not expecting this to happen, but that the EU would not be dogmatic.
He suggested the UK could follow a similar model to Norway, which has access to the single market in return for a financial contribution, accepting EU law and allowing the free movement of people.
This is one of those moments where Michel Barnier says things he has said before but in a way that is revealing about how the rest of the Brexit process will unfold.
The EU doesn't think the future relationship with the UK will be finalised by the date of its departure on 29 March 2019.
Which means that during the transition/implementation phase the UK could change its mind - quite significantly - about what it wants and then negotiate on that basis.
It also suggests that the EU wants the document sketching out the shape of the future relationship which will be agreed during the next phase of talks this year to be very, very open - not the detailed blueprint the British government seeks.
On the current trajectory, the UK will be out of the EU in 2019 but the arguments about whether it should remain in the customs union and the single market could carry on right up until a deal on the future relationship is sealed.
The UK government says it wants a comprehensive, bespoke free trade trade deal with the EU to replace its single market membership.
It wants to agree this by the Autumn in time for a "withdrawal agreement" to be ratified by the UK and EU Parliaments by March. But the EU has suggested only a "political declaration" will be possible by this deadline.
On Tuesday, the European Council's president said Brexit makes him "furious".
Speaking in Dublin, Donald Tusk said the UK's departure from the EU was "one of the saddest moments in twenty-first century European history".

They seek it here, they seek it there - but the centrepiece of the government's Brexit legislation, the EU (Withdrawal) Bill, seems to have gone into hiding.
Most Westminster observers expected the Commons to embark on eight days of detailed debate, in Committee of the Whole House, pretty much as soon as their conference recess was over.
Eyebrows were raised when it was not on this week's agenda - and they shot skywards when it was not put on the agenda for next week.
It is not a postponement, because the committee stage has never been scheduled, but something seems to be afoot.
What might it be? Challenged in Commons business questions by the SNP's Pete Wishart, Leader of the House Andrea Leadsom noted that MPs had proposed more than 300 amendments and 54 new clauses to the Bill and these were being studied by ministers.
And there is little doubt that some of these pose a real threat to the government's tenuous Commons majority.
The threat-in-chief is posed by amendments from the Conservative former attorney general, Dominic Grieve, to limit ministers' powers to re-write the law in the process of enacting Brexit.
Remember, this Bill is designed to allow the government to reprocess four decades of accumulated EU law into British law, so that the UK has functional legislation on all kinds of crucial areas, come Brexit Day.
The powers are pretty sweeping, because the Bill provides a toolkit to build an edifice which has not yet been designed - and Mr Grieve's amendments express the qualms of some MPs (including those of many strong Brexiteers) about their extent. He is the man most likely to amend.
I suspect the government is already whispering to him, behind the scenes, to produce an appropriate compromise, probably with the helpful endorsement of the Commons Procedure Select Committee behind it.
Was that the PM's bag-carrier, Seema Kennedy, I spotted in the public galler, when Mr Grieve set out his stall in evidence to the Procedure Committee on Wednesday?
If ministers can craft a compromise amendment, via ProcCom, face can be saved and division averted.
But with plenty more amendments still raining down, Mr Grieve is not the only threat. A recent addition is an amendment co-signed by the Nottinghamshire axis of Conservative ex-chancellor Ken Clarke and Labour's arch-Europhile, Chris Leslie.
This is a cunning production which takes the PM's commitment to a transition from full EU membership to Brexit, made in her Florence speech, and seeks to put it on the face of the Bill.
It follows her words precisely. But the killer point is that, if there's no transition, then a fresh act would be required to trigger Brexit day. In other words, if no transition, then they must come back and ask Parliament "what next?"
Now the government is not legislating against the clock as it was on the Article 50 Bill, when it was racing to get the measure through Commons and Lords before the end of the last Parliamentary year.
But its schedule is clearly slipping a little.
Next week is to be devoted to a little humdrum legislation, an opposition day debate and backbench business - that leaves seven debating weeks before Parliament embarks on its Christmas recess.
Take out one week to debate the Budget, and another for the November mini-half term (when a lot of select committee visits have been scheduled) and you have six weeks in which to cram the promised eight committee stage days devoted to the Bill, and the minimum of two days needed for report stage and third reading. Not impossible - but it does make for a packed Parliamentary programme, with little room for anything else.
There is rising speculation that the continuing delay in getting going reflects ministerial indecision about how to handle the amendments to the Bill - although another theory is that the government is waiting until next week's European summit is done, in the hope that it can firm up the terms of a possible transitional arrangement.
But the heat is on.

John Bercow has vowed "creativity" in Parliament if Boris Johnson ignores a law designed to stop a no-deal Brexit.
The Commons Speaker also said in a speech that the only possible Brexit was one backed by MPs.
A new law, passed before the suspension of Parliament, forces the PM to seek a delay until 31 January 2020, unless a deal or no-deal exit is approved by MPs by 19 October.
The PM has said he would rather be "dead in a ditch" than ask for a delay.
Responding to Mr Bercow's comments, Tory Brexiter MP Sir Bernard Jenkin said the role of the Speaker had become "irretrievably politicised and radicalised".
Meanwhile, Downing Street has announced Mr Johnson will travel to Luxembourg on Monday to hold talks with European Commission President Jean-Claude Juncker, and the country's prime minister Xavier Bettel.
Delivering a lecture in London, Mr Bercow said: "Not obeying the law must surely be a non-starter. Period."
He said it would be a "terrible example to set to the rest of society".
"The only form of Brexit which we will have, whenever that might be, will be a Brexit that the House of Commons has explicitly endorsed," he said.
"Surely, in 2019, in modern Britain, in a parliamentary democracy, we - parliamentarians, legislators - cannot in all conscience be conducting a debate as to whether adherence to the law is or isn't required."
He called it "astonishing" that "anyone has even entertained the notion".
If the government comes close to disobeying the law, Mr Bercow said that Parliament "would want to cut off such a possibility and do so forcefully".
"If that demands additional procedural creativity in order to come to pass, it is a racing certainty that this will happen, and that neither the limitations of the existing rule book nor the ticking of the clock will stop it doing so," he added.
The new law could force a Brexit delay beyond the current 31 October deadline by requiring the prime minister to request an extension to the UK's EU membership.
This would be done by making him write to EU leaders to prolong talks under Article 50 - the part of the EU's Lisbon Treaty which sets out what happens when a country decides that it wants to leave the EU.
The law forcing the PM to seek a delay unless MPs vote for a deal or no deal received royal assent on Monday, the final day that MPs sat in this session.
Parliament was suspended - or prorogued - in the early hours of Tuesday and is not scheduled to return until 14 October.
Foreign Secretary Dominic Raab has said the government would abide by the law, but would "test to the limit" what it requires of ministers.
Mr Bercow said: "One should no more refuse to request an extension of Article 50 because of what one might regard as the noble end of departing from the EU as soon as possible, than one could possibly excuse robbing a bank on the basis that the cash stolen would be donated to a charitable cause immediately afterwards."
Sir Bernard, who chairs the constitutional affairs select committee in Parliament, said the Commons should "adapt itself" to a new role for the Speaker.
He accused Mr Bercow of launching a "personal attack" on the prime minister, insisting this would have been "unthinkable 10 or 15 years ago".
The current position allows the occupant "unregulated and untrammelled power", he told BBC Radio 4's Today programme.
"It's a kind of majoritarian dictatorship position," he added.
Another Leave-voting Conservative MP, Michael Fabricant, said Mr Bercow had brought the office of Speaker into disrepute:
However, shadow chancellor John McDonnell said Mr Bercow was simply "exercising his proper role, which is to protect the right of Parliament".
He said a "sizeable number" of MPs across all political parties were against allowing the PM to "push us into a no-deal Brexit".
Such an outcome would be "against the will of Parliament, and I actually think against the will of the people as well," he added.
On Thursday, Mr Johnson insisted the UK "will be ready" to leave the EU by the current deadline without an agreement "if we have to".
In response to the publication of the government's Yellowhammer document, an assessment of a reasonable worst-case scenario in the event of a no-deal Brexit, Mr Johnson reiterated it was "the worst-case scenario".
"In reality we will certainly be ready for a no-deal Brexit if we have to do it and I stress again that's not where we intend to end up," Mr Johnson said.
Mr Bercow has announced he will stand down as Commons Speaker and MP at the next election or on 31 October, whichever comes first.
The House of Commons has confirmed an election to choose his successor will take place on Monday 4 November.
The Speaker's warning came as the EU's chief Brexit negotiator told political leaders in the European Parliament on Thursday that he could not say whether contacts with the UK government would result in a deal by mid-October.
Michel Barnier, in a speech to MEPs, suggested that negotiating a new withdrawal agreement remained uncertain despite discussions between Mr Johnson's team and the EU.
"I cannot tell you objectively whether contacts with the government of Mr Johnson will be able to reach an agreement by mid-October," he said.
"While we have previously reached an agreement, as far as we can speak, we have no reason to be optimistic."
He added: "We will see in the coming weeks if the British are able to make concrete proposals in writing that are legally operational."

The chancellor confirmed to MPs what has been widely known in Westminster for a long time.
Regular readers will know that from time to time I have ranted on about it here.
But Philip Hammond told MPs on Wednesday afternoon that indeed, it is the case that the cabinet has not yet had its big bonanza conversation about the "end state", when the prime minister will have to put her cards on the table finally, and explain the kind of relationship she wants with the EU after we leave, and after the transition period.
She will then have to try to persuade her cabinet colleagues to back her view.
It is a conversation that she has delayed for months, holding it back because she knows the cabinet is divided, and bringing them together could be extremely hard.
It boils down to this. Ministers like Boris Johnson and Michael Gove believe that Britain's future lies in striking out on our own, out of reach of most of the tentacles of the EU's institutions.
It is an over-simplification, but to explain the difference, you can point to the deal that Canada did with the EU, a free trade agreement essentially, where there is co-operation and collaboration to make it easy for business.
But there is nothing like the current situation - whether that's on immigration, rules for industry or the legal system. There is a strong and significant faction inside the Tory party that agrees with them and are extremely well organised and willing to make trouble if they see that possibility being undermined.
That's what explains the co-ordinated cage-rattling by Brexiteers since the first phase deal fell apart on Monday afternoon.
But there are others in Theresa May's team who think the best thing for business, and the best thing for the country is to mirror the EU's arrangements as far as we possibly can. The idea is that even though we will have left the EU, we preserve as much of our trading relationship as possible, even if that means continuing to be bound by many of the EU's rules and routines in all but name.
Again, it's a generalisation, but a relationship like Norway and the EU where they have very close ties (but not much influence) gives you a rough idea. Theresa May always says that she wants a "bespoke deal", but you can get a sense of the two different kinds of options here.
The technical term in Whitehall for the competing visions is "high or low alignment".
While the government disputes that it is only a choice of one or the other, politically in the Tory party it is a question of two "sides". And so far, the prime minister has avoided coming down completely on one side or another. Talk to ministers on different sides privately and they both seem to think Theresa May agrees with them, although they can't be completely sure..
There are intensely strong feelings in both camps, and so far, Theresa May's way of broadly avoiding arguments has been not to have the discussion.
Essentially what could be an enormous row, that might even end up with some members of the Cabinet resigning, has been postponed, rather than resolved.
But the crisis over the DUP has tightened the valve on what's a political pressure cooker. Because, to use the jargon, that dispute is essentially about 'alignment'.
The problem of Northern Ireland is the DUP's deep discomfort that Northern Ireland could be more closely aligned to the rest of the EU, and Dublin, than the rest of the UK. Basically, they don't want to be pulled more tightly to Dublin than to Westminster. It is its own deeply important, and sensitive, issue.
But it has forced the question of alignment more generally out into the open. And it's the first time the truce on the issue has been tested. How closely 'aligned' should  the UK really be outside the EU?
The prime minister had to make a call over the weekend to get to a potential deal to move on to the next phase of the Brexit talks.
But the way that deal held out the possibility of "high alignment", was simply not acceptable to many people in her party, as well as the DUP.
So now, the time is coming, and coming soon, when she will have to answer the question she's avoided answering in detail for many months. And the discussion she has been postponing in Cabinet for over a year.
There's a good reason. It's been to keep a lid on the ideological disputes that she knows exists.
On Wednesday afternoon Number 10 confirmed officially that the cabinet would have the discussion before Christmas. Her allies point again and again to the clues that she has given in her big interventions in the debate - whether the Lancaster House speech or her address in Florence.
On the question of alignment, sources in the Department for Exiting the European Union say that she made her position plain with this simple passage.
"There will be areas which do affect our economic relations where we and our European friends may have different goals; or where we share the same goals but want to achieve them through different means.
"And there will be areas where we want to achieve the same goals in the same ways, because it makes sense for our economies."
But the carefully constructed phrases she has put forward in her major speeches about Brexit have been, in a sense, sophisticated sticking plasters.
They have set out generalities, not specifics, and whether the implications were misunderstood or just ignored at the time, the reality of having to make actual decisions as the negotiations progress mean that sooner or later, she will have to rip them off.

Commons authorities have cast doubt on the idea that public donations could pay for the cost of making Big Ben chime when the UK leaves the EU.
Big Ben has been largely silent since refurbishment of its tower began.
But Boris Johnson has suggested crowdfunding could cover the costs of getting the bell working on 31 January.
The House of Commons Commission has said the estimated cost of up to £500,000 cannot be justified and using donations would be "unprecedented".
An amendment to the PM's Brexit bill, which would have required it to chime on Brexit day at 23:00 GMT, failed last week.
But on Tuesday, Mr Johnson told BBC Breakfast: "We're working up a plan so people can bung a bob for a Big Ben bong, because there are some people who want to."
The commission said ongoing work to the Palace of Westminster's Elizabeth Tower meant getting the chimes working again now would cost between £350,000 and £500,000.
The body - a group of MPs and officials responsible for the day-to-day running of Parliament - later issued a second statement raising concerns about any type of crowdfunding.
Any fundraising would have to be "consistent with principles of propriety and proper oversight of public expenditure", it said.
It added that the Commons had a "well-established" process by which it approved spending which allowed it to "preserve its constitutional position in relation to government".
When the restoration work started in 2017, it was agreed that Big Ben should sound for Remembrance Sunday, Armistice Day and New Year's Eve.
According to the commission, this arrangement was made so the project team could plan its works around the dates well in advance.
The House of Commons Commission's estimate for the cost of sounding Big Ben on Brexit day is made up of two separate parts:
The commission says the floor in the belfry has been removed and there would be a significant cost to put in and then remove a temporary floor.
As well as the floor, the £120,000 figure also includes the cost of installing and dismantling the temporary mechanism (an electric bell hammer) to sound the bell.
Commons Speaker Sir Lindsay Hoyle said: "The Commission believes it is important to weigh up the costs this would involve if Big Ben is to chime on 31 January.
"You are talking about £50,000 a bong. We also have to bear in mind that the only people who will hear it will be those who live near or are visiting Westminster."
However, Brexit Party leader Nigel Farage questioned the £500,000 figure, and accused the commission of "obstruction".
In an article for the Telegraph, he wrote: "It tolled on New Year's Eve, on Remembrance Sunday and on Armistice Day.
"Did this cost £500,000 on each occasion? I would love to know the answer."
Brexiteer Mark Francois, one of the Tory MPs behind the failed amendment, has said it would be "inconceivable" if Big Ben did not sound to mark the occasion.
But Labour MP David Lammy said £500,000 was a "huge amount of money to waste on jingoism".
The PM's official spokesman said there was not a "specific government fund" to meet the costs of getting Big Ben to chime on Brexit day.
But he added: "If the public wants Big Ben to bong and the money is raised, then that is great.
"We will make sure that - whatever happens in regard to Big Ben's bongs - January 31 is properly marked."

Incoming UK PM Boris Johnson faces "challenging" times, the EU has warned, as it reacted to his election as new Conservative leader.
Mr Johnson has the immediate task of guiding the UK out of the EU ahead of a 31 October deadline.
He says he wants to renegotiate an agreement with the EU, ditching large parts of the deal outgoing PM Theresa May struck last year.
But EU leaders have said the withdrawal agreement is not up for renegotiation.
The European Commission's newly elected President, Ursula von der Leyen, has however said she is willing to grant the UK another extension to Brexit talks, if London comes up with good reasons.
Congratulating Mr Johnson, Mrs von der Leyen said: "There are many different and difficult topics to tackle together. There are challenging times ahead of us. I think it is very important to build up a strong and a good working relation because we have the duty to deliver something that is good for people in Europe and in the United Kingdom."
The EU's Brexit negotiator, Michel Barnier, is due to meet MEPs on the European Parliament's Brexit Steering Group in an extraordinary meeting on Wednesday to respond to Mr Johnson's election.
US President Donald Trump meanwhile congratulated Mr Johnson on his victory, tweeting:
Later, he said: "We have a really good man is going to be the prime minister of the UK now, Boris Johnson. A good man. He's tough and he's smart. They're saying 'Britain Trump'. They call him 'Britain Trump' and people are saying that's a good thing. They like me over there.
"That's what they wanted. That's what they need... He'll get it done. Boris is good. He's going to do a good job."
In the often divisive Brexit world of "them and us", it is easy to forget that, beyond Brexit, EU leaders still see the UK as a close partner and ally.
Tuesday's messages of congratulation to Boris Johnson from across Europe were a timely reminder.
Whatever happens with Brexit, France, Germany, Poland et al still very much hope to work closely with the UK on international issues like Russia sanctions, Iran and human rights protection.
But EU leaders' welcoming tone does not signal a willingness to accept whatever Prime Minister Johnson might demand in terms of changes to the Brexit deal.
He's right when he says a no-deal Brexit is bad for Brussels, but he overestimates EU wiggle room. Amendments will only be forthcoming if EU leaders deem them workable and are convinced the new prime minister commands a majority in parliament to get the Brexit deal through once and for all.
In Germany, Chancellor Angela Merkel congratulated Mr Johnson, saying she would keep pursuing a "strong friendship" with London.
"I congratulate Boris Johnson and look forward to good co-operation. Our countries should continue to share a strong friendship in the future."
In a statement, her CDU party said they expect Mr Johnson "to pursue a responsible policy in Britain's interest. Responsible means - even for a Brexit hardliner - to prevent an unregulated Brexit at all costs".
German industry chiefs have also warned of the dangers of no-deal Brexit. Joachim Lang, CEO of the Association of German Industry, said: "Threats from London to leave the EU with no deal are harmful and will come back like a boomerang. They exacerbate damages that have already affected the economy."
Mr Johnson has pledged the UK will leave the EU on 31 October "do or die", accepting that a no-deal exit will happen if a new agreement cannot be reached by then.
France's President Emmanuel Macron praised outgoing Prime Minister Theresa May's "courage and dignity" and the fact that she had never "blocked the workings of the European Union".
On the new man in charge, he said: "I am looking forward to working with him, not only on European topics and the ongoing Brexit negotiations, but also on important international topics... such as Iran and international security."
Italy's Interior Minister and leader of the Lega (League) party, Matteo Salvini, tweeted: "Good job #BorisJohnson. The fact that on the left they depict him as 'more dangerous than the Lega' makes me like even him more."
The EU's chief Brexit negotiator Michel Barnier tweeted:
The deputy prime minister and foreign minister of Ireland, Simon Coveney, tweeted:

Boris Johnson has said he "won't be deterred by anybody" from leaving the EU on 31 October.
The prime minister said he was "cautiously optimistic" of getting a Brexit deal, but the UK would leave by the deadline "whatever happens".
EU chief Brexit negotiator Michel Barnier said he did not have "reasons to be optimistic" over getting a deal.
Mr Johnson will meet him and European Commission President Jean-Claude Juncker on Monday for talks.
During the PM's speech, at the Convention of the North in Rotherham, South Yorkshire, he was heckled by an audience member who told him to "get back to Parliament" and "sort out the mess that you have created".
Earlier this week Parliament passed a law forcing Mr Johnson to ask for an extension to Brexit.
He will have to write to the EU on 19 October to ask for an extra three months, unless he returns with a deal - then approved by MPs - or gets the Commons to back a no-deal Brexit.
But despite the new law, Mr Johnson said he would rather be "dead in a ditch" than ask for an extension.
The Speaker of the Commons, John Bercow, vowed to act with "creativity" if Mr Johnson ignored the law, saying it would be a "terrible example to set to the rest of society".
MPs managed to pass the law before Parliament was suspended - or prorogued - in the early hours of Tuesday morning until 14 October.
Mr Johnson said the government had made the move so it could hold a Queen's Speech and put forward its new domestic policy agenda.
But opposition MPs claim it was to stop scrutiny in Parliament of his Brexit plans.
Earlier this week, a Scottish court ruled the prorogation was unlawful as it was motivated by an "improper purpose of stymieing Parliament".
The government is appealing against the decision and a ruling will be made by the Supreme Court in London on Tuesday.
Answering questions after his speech, Mr Johnson said: "We are working incredibly hard to get a deal. There is the rough shape of the deal to be done.
"I have been to talk to various other EU leaders, particularly in Germany, in France and in Ireland, where we made a good deal of progress.
"I'm seeing [Mr Juncker and Mr Barnier] on Monday and we will talk about the ideas that we've been working on and we will see where we get."
He added: "I would say I'm cautiously optimistic."
MPs are still demanding Parliament be recalled to scrutinise a number of Brexit-related issues, including the release of so-called "Yellowhammer" papers - a government assessment of a reasonable worst-case scenario in the event of the UK leaving the EU without a deal.
But Mr Johnson said that "whatever the shenanigans that may be going on at Westminster", the government would "get on with delivering our agenda and preparing to take this country out of the EU on 31 October".
He added that there would still be "ample time" for MPs to scrutinise any deal reached with the EU, adding that he "very much hoped" to agree one at the EU summit on 17 and 18 October.
The Times newspaper reported that a Brexit deal could be on the horizon as the Northern Irish Democratic Unionists (DUP) - the party which has a confidence and supply deal with the Conservatives - had reportedly agreed to "shift its red lines" over the backstop.
The backstop is the policy in the existing withdrawal agreement - negotiated between former Prime Minister Theresa May and the EU - aimed at preventing a hard border returning to the island of Ireland, but it has proved controversial with a number of pro-Brexit MPs.
However, the reports were rejected by the DUP's leader Arlene Foster, who tweeted: "Anonymous sources lead to nonsense stories."
A UK spokesman in Brussels revealed the negotiating team had "presented some ideas" on an all-island Sanitary and Phyto-Sanitary solution - essentially keeping Northern Ireland aligned with EU regulations on animal and food health.
But the DUP has said it would not support any arrangement that could see Northern Ireland treated differently than the rest of the UK after Brexit.

Downing Street has hit back at Boris Johnson over his criticism of Theresa May's approach to Brexit, saying she is providing "serious leadership" and "a serious plan".
Mr Johnson has written in the Daily Telegraph that the approach agreed at Chequers "means disaster" for Britain.
The ex-foreign secretary said the PM's plan would hand the EU "victory".
But Mrs May's official spokesman said: "There's no new ideas in this article to respond to."
Downing Street said the prime minister's blueprint for future relations with the EU, hammered out with cabinet members at her country residence in July, was deliverable and could win the support of the House of Commons.
And former home secretary Amber Rudd told the BBC's Politics Live: "Once again, it's a case of leap before you look - there's absolutely no proposal here."
Ms Rudd said the Chequers plan represented "the best shot we have of Brexit that's going to work for the UK".
Mr Johnson resigned from the government in July in protest at the deal agreed by the cabinet at Chequers, the prime minister's country residence, as the UK's preferred way forward in negotiations with Brussels.
Other Tory MPs have also criticised the package, and the EU's chief negotiator, Michel Barnier, says he is "strongly opposed" to the proposals.
Mrs May's plan would see the UK agreeing a "common rulebook" with the EU for trading in goods, in an attempt to maintain frictionless trade at the border.
Critics argue this would leave the UK tied to EU rules after it leaves on 29 March 2019, and prevent Britain from striking its own trade deals in years to come.
If the UK and the EU do reach a deal, MPs will then have to approve it.
In his first intervention on the EU debate since quitting the government, Mr Johnson compared negotiations between Brexit Secretary Dominic Raab and Mr Barnier to a wrestling match.
He wrote: "The whole thing is about as pre-ordained as a bout between Giant Haystacks and Big Daddy; and in this case, I am afraid, the inevitable outcome is a victory for the EU, with the UK lying flat on the canvas and 12 stars circling symbolically over our semi-conscious head."
Mr Johnson said negotiations based on the Chequers plan had so far seen the EU take "every important trick", adding: "The UK has agreed to hand over £40bn of taxpayers' money for two-thirds of diddly squat."
He said by using the strategy - defended by Mrs May in the Sunday Telegraph over the weekend - the UK had "gone into battle with the white flag fluttering over our leading tank".
If it continued on the same path, Mr Johnson added, the government would "throw away most of the advantages of Brexit".
Mr Johnson also accused some members of the government of using the issue of the border between Ireland and Northern Ireland to "stop a proper Brexit", but added: "They have been rumbled."
The "scandal" around the border problem was "not that we have failed, but that we have not even tried", he added.
Mr Johnson argued that a hard border would not be needed after Brexit - because people did not need to be checked due to the Common Travel Area and that any checks on goods could be done away from the border.
In response, Mrs May's official spokesman said: "What we need at this time is serious leadership with a serious plan and that's exactly what the country has with this prime minister and this Brexit plan.
"She is a serious prime minister and she has put forward serious proposals."
But Tory Brexiteer Jacob Rees-Mogg, one of a group of MPs to meet Mr Barnier on Monday, suggested the EU negotiator agreed with him that the Chequers plan was "absolute rubbish" and he preferred the option of a looser arrangement based on Canada's trade agreement with the EU.
"Interestingly, Eurosceptics and Mr Barnier are in greater agreement than Eurosceptics and the government and between Mr Barnier and the government," Mr Rees-Mogg said. "It's very encouraging."
Labour's shadow foreign secretary Emily Thornberry told Politics Live that if Mrs May gave in Brexiteers, "she's going to end up coming back to Parliament with something that's not acceptable to Parliament... so then what happens?"
She added: "To hear some members of the Conservative Party play fast and loose with the [Northern Ireland] peace settlement is disgusting."
Scotland's First Minister Nicola Sturgeon described Mr Johnson as a "charlatan" who must share in responsibility for the "disaster" of Brexit.
Downing Street also rejected a proposal from former Conservative minister Nick Boles for the UK to stay in the European Economic Area to allow time for a new trade deal to be negotiated.
Mr Boles said the PM's plan, as it stands, has "close to zero" chance of winning support from Parliament while former education secretary Justine Greening told Radio 4's World at One that it was "more unpopular with the British public than the poll tax" and Theresa May should consign it to history.
"She should now accept it has not worked and look for alternative routes through," she said.
On Sunday, the prime minister wrote that she was "confident" a "good deal" could be reached on Brexit.
But she said it was right for the government to prepare for a no-deal scenario - even though this would create "real challenges for both the UK and the EU" in some sectors.

Tory leadership rivals Boris Johnson and Jeremy Hunt are at loggerheads over how the UK should leave the EU.
Both contenders for prime minister claim they can renegotiate a Brexit deal that the EU says is closed.
Mr Johnson said the UK must leave on 31 October "deal or no deal" but Mr Hunt called this a "fake deadline" that could trigger a general election if Parliament rejects a no-deal Brexit.
The winner of the contest will take over from Theresa May on 24 July.
The two men will face more questions from the public on Wednesday in a digital hustings, streamed on the Conservative Party's Facebook and Twitter accounts.
In an interview with Talk Radio, Mr Johnson insisted he would take the UK out of the EU by Halloween "come what may, do or die" and has challenged his opponent to make the same commitment.
Mr Hunt said he was prepared to leave without a deal, but not if there was a "prospect of a better deal".
During a phone-in on BBC Radio 2's Jeremy Vine Show, the Mr Hunt agreed with a caller who said the EU was "treating us like dirt", adding: "I don't think they've shown respect for us at all."
He has secured the backing of Scottish Conservative leader Ruth Davidson - who supported Sajid Javid and then Michael Gove in previous rounds - because she said he had "put the Union first".
A no-deal exit would see the UK leave the customs union and single market overnight and start trading with the EU on World Trade Organisation rules.
Opponents say it would cause huge disruption at the borders and be catastrophic to many firms reliant on trade with the continent - supporters say any negative effects would be manageable.
The EU has repeatedly insisted it will not re-open negotiations on the withdrawal agreement drawn up between Brussels and Theresa May - rejected three times by MPs.
On Wednesday, a European Commission spokeswoman confirmed that remained the bloc's position even if the only alternative was a no-deal exit.
Earlier, former Brexit secretary Dominic Raab, who is backing Mr Johnson, said Mr Hunt had shown "weakness" and "naivety" by entertaining the possibility of another extension.
He told BBC Radio 4's Today programme it would be the "EU's choice" to see the UK leave without an agreement, adding: "There is nothing stopping us getting a deal by October, if there's the political will."
He predicted "vanishingly few" Tory MPs would vote to bring down a government pursuing a no-deal exit in a vote of no confidence - even though Defence Minister Tobias Ellwood has said "a dozen or so" Conservatives could support such a move.
It comes as International Trade Secretary Liam Fox - who is backing Mr Hunt - again criticised Mr Johnson's claim that the UK could continue tariff-free trade with the EU in the event of a no-deal Brexit.
Mr Johnson has argued that a provision under the General Agreement on Tariffs and Trade - known as GATT 24 - could be used to avoid tariffs for up to 10 years.
But Mr Fox said this would require the agreement of the EU, which Brussels has made clear it would not give.
On Tuesday, Mr Johnson conceded that his plan would require the approval of the rest of the EU, but insisted it was still "an option".
Boris Johnson and Jeremy Hunt say they are serious about pushing for a no-deal Brexit if they are unable to negotiate a better withdrawal agreement with Brussels.
Yet the EU seems unfazed. Why, when we know EU leaders want to avoid a no-deal Brexit?
Part of the reason, at least, is time.
It's summer. European capitals are sweltering under a heatwave with government ministers counting the days until they hit the beach or find some cool mountain air.
The day the Brexit extension runs out - 31 October - seems an eternity away in political terms.
Also, just as Messrs Johnson and Hunt do not accept the EU's word when it says the Withdrawal Agreement cannot and will not be re-negotiated, EU leaders do not take them at their word when they threaten no deal by the end of October.
Former leadership candidate Rory Stewart, who is backing Mr Hunt, said the problem with Mr Johnson's plan was that he was just telling people "what they want to hear".
The international development secretary told the Today programme Mr Johnson was "pretending he has a magic solution" which was "not going to damage them at all", but the reality was he was going to let people down.
He also said he would definitely vote against a Tory government to stop a no-deal Brexit, but would stop short of backing a no confidence vote.
Mr Johnson continues to face scrutiny about Friday's row with his girlfriend Carrie Symonds, which prompted neighbours to call the police.
After days of criticism that he was hiding away, Mr Johnson undertook a series of media and public appearances on Tuesday - but declined to answer questions about the argument.
On Tuesday Mr Hunt told the BBC the next prime minister should be someone who is "trustworthy" and the ability to negotiate a new Brexit deal was about "personality", but stopped short of directly criticising his rival.
The day before, Mr Johnson told the BBC anyone questioning his character was "talking absolute nonsense".

Boris Johnson has criticised the UK government's Brexit talks strategy, saying it lacks "guts" and suggested Donald Trump could do a better job.
The foreign secretary also took a swipe at Chancellor Philip Hammond, calling the Treasury "the heart of Remain", in comments to a private dinner.
He said the Brexit talks were heading for "meltdown" and Leave supporters may not get the deal they expected.
Theresa May said Mr Johnson "had strong views on Brexit but so do I".
Speaking in Canada, where she is attending the G7 summit, the prime minister refused to be drawn on whether the foreign secretary was undermining her, a day after a row with her Brexit Secretary David Davis.
She said the process of leaving the EU was "complex" but her focus was on getting the right deal for Britain and people should judge her on her record in the negotiations so far.
In a recording, obtained by Buzzfeed, Mr Johnson warns the UK could remain "locked in orbit around the EU" and claimed the Irish border issue - one of the main sticking points in talks with Brussels - had been allowed to dictate "the whole of our agenda".
"It's so small and there are so few firms that actually use that border regularly, it's just beyond belief that we're allowing the tail to wag the dog in this way," he said.
The foreign secretary was apparently speaking to around 20 people in a private room after an Institute of Directors reception on Wednesday night.
It follows a day of wrangling over the government's "backstop" plan in the event of no customs deal being agreed before Brexit.
Theresa May was forced to agree to a cut-off date of December 2021 for any interim arrangements after Brexit Secretary David Davis threatened to resign.
But speaking to reporters on route to the G7 summit in Canada, she twice refused to give a "cast-iron guarantee" that the end date would not slip beyond that.
And speaking in Brussels, the EU's chief negotiator Michel Barnier said the proposal could only apply to Northern Ireland, not the UK as a whole, and questioned whether temporary arrangements were acceptable, telling journalists "backstop means backstop".
In the leaked comments, Mr Johnson said the prime minister was "going to go into a phase where we are much more combative with Brussels".
He added: "You've got to face the fact there may now be a meltdown. OK? I don't want anybody to panic during the meltdown. No panic. Pro bono publico, no bloody panic. It's going to be all right in the end."
Brexit will be "irreversible" and will happen, Mr Johnson said, but the "risk is that it will not be the one we want".
He added: "Unless you make the change, unless you have the guts to go for the independent policy, you're never going to get the economic benefits of Brexit. You'll never get the political benefits of Brexit."
He was said to have described concerns over the border between Northern Ireland and the Irish Republic as "pure millennium bug stuff" and suggested Chancellor Philip Hammond's department was "basically the heart of Remain".
Speaking about the Treasury, he added: "They don't want any disruption of the economy. So they're sacrificing all the medium and long-term gains out of fear of short-term disruption."
In response, Mr Hammond said his "advice to colleagues" was to engage with the EU as his experience was "a collaborative approach is generally more productive than a confrontational approach".
But Brexit-supporting MPs backed Mr Johnson, Peter Bone saying Mrs May "probably agrees with him as well".
The talks, he said, were "being held back by Remain officials who are driving this thing" - suggesting they should all be removed and Brexit Secretary David Davis given a "free hand".
No 10 said there was "rigorous debate" about Brexit but its focus was on delivering the deal the public wanted.
Scotland's First Minister Nicola Sturgeon said Mr Johnson was "simply not fit for the high office he holds" while Irish leader Leo Varadkar said "when I want to know what the view of the British government is, I listen to the prime minister".
Labour MP Rupa Huq, who campaigns against a "hard" Brexit, said Mr Johnson had been "very dismissive" of the risks to Northern Ireland, treating it - in her words - as a "small country that nobody bothers about".
Mr Johnson was the keynote speaker at Conservative Way Forward's summer reception and took questions for more than an hour, according to Buzzfeed.
Asked about Donald Trump, he reportedly said he was "increasingly admiring" of the US President and was "more and more convinced that there is method in his madness".
"Imagine Trump doing Brexit," he added.
"He'd go in bloody hard... There'd be all sorts of breakdowns, all sorts of chaos. Everyone would think he'd gone mad. But actually you might get somewhere. It's a very, very good thought."

Boris Johnson has refused to deny claims he used an expletive when asked about business concerns about Brexit.
The foreign secretary is reported to have used the swear word at a diplomatic gathering last week.
Asked about this in the Commons, he said he may have "expressed scepticism about some of the views of those who profess to speak up for business".
Theresa May said it was right the government listened to business voices about the terms of the UK's exit.
This story contains language some may find offensive.
Airbus, BMW and Siemens have warned about the impact on their UK-based operations if the UK leaves the EU next March without any agreement.
Their warnings have prompted different responses from ministers.
Business Secretary Greg Clark has said the UK must "take and act on the advice of business" but Health Secretary Jeremy Hunt said a warning from Airbus that it could cease operations entirely in the UK, threatening thousands of jobs, was "completely inappropriate".
Asked about corporate concerns over a so-called hard Brexit, at an event for EU diplomats in London last week, Mr Johnson is reported to have replied: "Fuck business."
Mr Johnson, who was reportedly speaking at the time to Rudolf Huygelen, Belgium's ambassador to the EU, was also overheard saying he and others would fight Theresa May's soft Brexit "and win".
The foreign secretary, who was a key figure in the Leave campaign, was pressed on the issue in Parliament by Labour MP Owen Smith, who asked him if the comments were correct and, if so, whether they could be "remotely justified".
"I don't think anybody could doubt the passionate support of this government for business," Mr Johnson said.
"It may be that I have, from time to time, expressed scepticism about some of the views of those who profess to speak up for business."
Mr Johnson's comments about Brexit have frequently proved controversial. He was recorded telling Tory donors last month that the UK's strategy lacked "guts" and suggested US President Donald Trump could do a better job.
The latest remark has angered some Tory MPs, with former Science Minister George Freeman telling BBC Radio 4's World at One programme that the reported comments were not "helpful, responsible or statesmanlike".
The prime minister, who will travel to Brussels on Thursday for a summit of EU leaders, told a chief executives summit hosted by the Times she wanted business to be able to speak to the government.
"It's right that we listen to the voice of business," she said.
"Business is at the heart of how we are going to develop this country," she said. "We want to ensure we are listening to the business voice because business provides the backbone of our economy."
MPs who favour a clean break with the EU after Brexit, in March 29 2019, have called on Mrs May to walk away from negotiations if the EU does not show willingness to begin trade talks immediately.

Boris Johnson has admitted he would need EU co-operation to avoid a hard Irish border or the possibility of crippling tariffs on trade in the event of a no-deal Brexit.
In an exclusive interview with the BBC, the favourite to be the next PM said: "It's not just up to us."
But he said he did "not believe for a moment" the UK would leave without a deal, although he was willing to do so.
Asked about a row he'd had with his partner, he said it was "simply unfair" to involve "loved ones" in the debate.
Reports of the argument on Friday with his girlfriend, Carrie Symonds, dominated headlines over the weekend after the police were called to their address in London.
The interview comes after Sky News said it would have to cancel a head-to-head debate on Tuesday between the two leadership contenders as Mr Johnson had "so far declined" to take part.
Work and Pensions Secretary Amber Rudd told Radio 4's Today programme she found Mr Johnson's decision to ignore live TV debates "very odd" and urged him "to reconsider".
Following days of criticism that he has been avoiding media scrutiny, Mr Johnson has given a number of other interviews, including with LBC and Talk Radio.
On LBC, he was repeatedly challenged on his personal life and a photograph which showed him and his partner. Asked whether his campaign was behind the release of the picture, Mr Johnson refused to answer.
He told Talk Radio's political editor Ross Kempsell he would "not rest" until the UK had left the EU, insisting Brexit would happen on 31 October "come what may... do or die".
Meanwhile, the other candidate, Jeremy Hunt has promised to boost defence spending by £15bn over the next five years if he becomes prime minister.
In his interview with BBC political editor Laura Kuenssberg, Mr Johnson said the existing deal negotiated by Theresa May "is dead".
He insisted it was possible to broker a new deal with the EU before the end of October because the political landscape had changed in the UK and on the continent.
"I think actually that politics has changed so much since 29 March," he said, referring to the original Brexit deadline.
"I think on both sides of the Channel there's a really different understanding of what is needed."
At the moment, the UK is due to leave the EU on 31 October after the PM's Brexit deal was rejected three times by Parliament, and the EU has previously said the withdrawal agreement reached with the UK cannot be reopened.
Mr Johnson said he would be able to persuade Brussels to resolve the Irish border issue - a key sticking point - despite repeated warnings from EU leaders that that was impossible.
He said there were "abundant, abundant technical fixes" that could be made to avoid border checks.
When challenged that these did not exist yet, Mr Johnson replied: "Well, they do actually... in very large measure they do, you have trusted trader schemes, all sorts of schemes that you could put into place."
But, he admitted, there was "no single magic bullet" to solve the issue.
Mr Johnson's really controversial gamble is to say he could do a new trade deal with EU leaders before the end of October.
And he says he would be able to do that before resolving the most controversial conundrum - how you fix the dilemma over the Irish border.
He clearly believes he has the political skill to pull that off. He and his supporters would say that is a plan.
But it is a plan that is full of ifs and buts - either heroic or foolhardy assumptions to imagine that EU leaders and Parliament would be ready to back his vision - and back it by Halloween - on an extremely tight deadline.
The political pressure is on, not just to get it done quickly, but done in a way that does not harm our relations with the rest of the world and the livelihoods of people living in this country.
In terms of the controversies over his personal life, it is absolutely clear even now - when he is on the threshold of No 10 - that Boris Johnson thinks there are questions he simply does not have to answer.
And for a politician about whose character many people have their doubts, that is going to follow him around unless and until he is willing to give more.
Mr Johnson said if he was elected he would start new talks as soon as he reached Downing Street to discuss a free trade agreement.
He also said he hoped the EU would be willing to grant a period of time where the status quo was maintained for a deal to be finalised after Brexit.
He called this "an implementation period", but accepted this was not the same as the implementation period in the current draft treaty agreed with the EU.
Mr Johnson committed to passing new laws as soon as possible in order to guarantee the rights of EU citizens living in the UK.
The former foreign secretary also suggested EU leaders might change their attitude to renegotiation because they had Brexit Party MEPs they did not want in their Parliament, and wanted to get the £39bn that had been promised as part of the so-called divorce bill.
And he said MPs could be more willing to back a revised deal because - after disappointing local and European elections last month - they realised both Labour and the Conservatives would face "real danger of extinction" if Brexit were to be stalled again.
Mr Johnson refused again to give more detail of what happened at his home in the early hours of Friday.
"I do not talk about stuff involving my family, my loved ones," he said.
"And there's a very good reason for that. That is that, if you do, you drag them into things that really is... not fair on them."
Instead of his private life, he said the public actually want to know "what is going on with this guy?"
"Does he, when it comes to trust, when it comes to character, all those things, does he deliver what he says he's going to deliver?"
Despite widespread criticisms from his fellow Conservatives that he cannot be trusted, Mr Johnson said anyone questioning his character was "talking absolute nonsense".
He also refused to respond to accusations from rival Jeremy Hunt that he was being a "coward" for avoiding more head-to-head TV debates, promising that if elected he would "govern from the centre right" because the centre "is where you win".
Ms Rudd, who is supporting Mr Hunt, said Mr Johnson was making a mistake by shying away from the debates and said he needed to "go further" in explaining his Brexit plan.
"This is an incredibly difficult situation and Boris needs to explain how he will deal with both sides of the Conservative Party that have concerns and try and break the impasse with the European Union.
"Enthusiasm and optimism is not sufficient."
Responding to claims that a dozen Tory MPs would be prepared to bring down a government heading to a no-deal Brexit, she said: "I think that's about right. I think it's slightly less than that, but it's certainly more than two."
Correction 7th August 2019: An earlier version of this article referred to crippling tariffs on trade in the event of a no-deal Brexit and has been amended to make clear that Boris Johnson was asked about this as a possibility.

Boris Johnson says the government is "working together" and that he will not be resigning after criticism of his intervention on Brexit.
The foreign secretary has been accused of undermining Theresa May with a 4,000-word article setting out his own post-EU vision.
But he told journalists the government was "a nest of singing birds".
Mr Johnson - along with other ministers - is due to attend the PM's Brexit speech in Florence on Friday.
Asked about his article, Mrs May said she was "getting on with the job" of delivering Brexit.
Earlier the foreign secretary was accused by ex-chancellor Ken Clarke of making a pitch for a future Tory leadership election with his article.
Mr Clarke said that "in normal circumstances" Mr Johnson would have been sacked. Some reports have claimed Mr Johnson will resign if his blueprint for Brexit is not followed.
But speaking in New York, the foreign secretary said "of course not" when asked whether he was going to quit, and predicted the government would "deliver a fantastic Brexit".
Asked whether there was a cabinet split on Europe, Mr Johnson said: "No, we are a government working together.
"We are a nest of singing birds."
Mr Johnson and Mrs May are both attending the United Nations General Assembly in New York.
Asked repeatedly about Mr Johnson and reports of cabinet disunity over Brexit, the PM stressed that the government was united in trying to get the best possible deal.
"What I think the majority of the British public want to see is what we're doing, which is getting on with the job of those negotiations with the European Union and getting on with the job of the best deal for the UK," she told the BBC.
Responding to questions about the so-called divorce bill for the UK to pay on leaving the EU, she said the UK was a "law-abiding nation" and would "stand by our obligations" as well as carrying on contributing to programmes it wants to be a part of after Brexit.
Mr Johnson's article said the UK should not pay for access to the EU single market.
The continuing fallout from the article - published in Saturday's Telegraph - led, on Monday, to Mrs May having to rebut claims that Mr Johnson was trying to become a "back-seat driver" in her cabinet.
The PM, who is due to set out her vision for Brexit in a speech in Florence on Friday, declared: "This government is driven from the front."
Speaking on BBC Radio 4's Today programme, Mr Clarke said that in her speech Mrs May had to set out "for the first time, really" what the UK can "can realistically achieve in negotiations".
That must include "free access to the European market and no new barriers for our trade," he argued, and how best "to avoid economic damage to the country".
"Alongside that, personal publicity and campaigning by the foreign secretary is actually just an irrelevant nuisance."
Mr Clarke said: "Sounding off personally in this way is totally unhelpful and he shouldn't exploit the fact she hasn't got a majority in Parliament.
"He knows perfectly well that normally the foreign secretary would be sacked for doing that - and she, unfortunately, after the general election, is not in the position easily to sack him - which he should stop exploiting."
He also attacked Mr Johnson for repeating "one of the more simplistic and dishonest arguments of the hardline Leavers" in his article - a reference to "taking back control" of £350m a week after Brexit.
The foreign secretary said on Monday that his article was meant to be an "opening drum roll" for the PM's speech.
"Because I was involved in that Brexit campaign, people want to know where we are going," he added.
Mrs May attempted to avoid a public row with her foreign secretary, telling reporters travelling with her on a trade mission to Canada: "Boris is Boris."
Former foreign secretary, Lord Hague, writing in the Daily Telegraph, warned that disunity over Brexit could hand power to Jeremy Corbyn's Labour Party.
He wrote: "It is putting it a bit too politely to say, in the wake of Boris Johnson's article in this newspaper on Saturday, that the approach of senior ministers to the Brexit negotiations appears to lack co-ordination.
"More bluntly, it is now 15 months since the referendum, and high time that all members of the government were able to express themselves on this subject in the same way as each other, putting forward the same points, as part of an agreed plan."

Boris Johnson has likened the challenge of avoiding a hard border in Northern Ireland to the boundaries between different boroughs of London.
The foreign secretary said it was a "very relevant comparison" because money was "invisibly" taken from people travelling between Camden and Westminster when he was London mayor.
London's congestion zone charge does not involve manual checks.
Labour said his comments were "typically facile and tactless".
The Irish opposition Fianna Fail party said it was "extraordinary" to suggest the two borders were the same, while the SDLP said: "Trivialising the very serious concerns relating to Ireland displays a dangerous ignorance that must be challenged."
The future of the Irish border after Brexit has been a key sticking point in talks so far.
The UK plans to leave the EU's customs union but wants to avoid border posts and physical checks between Northern Ireland and the Republic.
Mr Johnson, a former London mayor, told BBC Radio 4's Today programme there were "all sorts of things you can do" to achieve this.
"We think that we can have very efficient facilitation systems to make sure that there's no need for a hard border, excessive checks at the frontier between Northern Ireland and the Republic," he said.
"There's no border between Islington or Camden and Westminster... but when I was mayor of London we anaesthetically and invisibly took hundreds of millions of pounds from the accounts of people travelling between those two boroughs without any need for border checks whatever."
He added: "It's a very relevant comparison because there's all sorts of scope for pre-booking, electronic checks, all sorts of things that you can do to obviate the need for a hard border to allow us to come out of the customs union, take back control of our trade policy and do trade deals."
Analysis by the BBC's Mark Devenport
How literally should we take the Foreign Secretary's analogy? The collection of the London congestion charge relies on a network of automatic number plate recognition cameras which identifies motorists moving around the city.
However back in August last year, when the UK released a position paper on Northern Ireland after Brexit, government officials briefed journalists that a pledge to "avoid any physical border infrastructure in either the United Kingdom or Ireland, for any purpose (including customs or agri-food checks)" effectively ruled out plans for the installation of cameras near the border, or set back from it.
Instead the clear suggestion was that any technological fix would be more likely to involve firms becoming "authorised economic operators" and filling out customs forms from the comfort of the desks in their office HQs.
The BBC has asked for clarification of whether government policy has shifted on this point. But in the absence of a more detailed response we may note that Downing Street has told lobby correspondents that Mr Johnson "was not offering a technical solution" to the border issue.
Instead, the prime minister's spokesman clarified, "the foreign secretary was making a comparison to demonstrate our overall approach that the 110 million people crossing the border will continue living their lives as before, travelling freely just as Londoners cross boroughs every day".
That defence is not likely to appease Mr Johnson's critics, but it seems fair to say he was trying to get out of a tight spot during a wide ranging Today programme interview, rather than seeking to unveil a wholly new approach to the one set out in last year's position paper.
Labour's shadow Northern Ireland secretary Owen Smith dismissed the comments as "ludicrous".
And he accused Mr Johnson of "glibly dismissing the concerns of thousand of families and businesses who live and work along the border", adding that his remark "insults the intelligence of all who are worrying about how to resolve the border question after Brexit".
Irish MEP Mairead McGuinness, vice president of the European Parliament, also questioned the analogy. "The UK is a different country than the Republic of Ireland ... and therefore the comparison doesn't quite fit," she told BBC2's Daily Politics.
The foreign secretary's comments have also sparked a wave of reaction on Twitter:
But former Conservative leader Iain Duncan Smith backed Mr Johnson.
"What Boris was saying was there are various ways in which you can manage things, like money transfers, checks on cars, checks on lorries - the technology now exists and is being used and is being developed around the world," he told BBC Radio 4's The World at One.
And DUP MP Sammy Wilson said a virtual border already exists.
"There's a different tax regime in Northern Ireland than the Irish Republic - VAT, excise duty is different - yet billions of pounds worth of goods cross that border, taxes are paid and not a lorry is stopped to check the goods because through virtual methods, through IT, through electronic invoicing, those taxes are collected by both the Irish government and the British government," he said.
The first draft of a legally-binding agreement between the UK and the EU, due to be published on Wednesday, is expected to address the issue of Northern Ireland.
The Dublin government says the option of Northern Ireland staying in full regulatory alignment with the European Union after Brexit should be included as a "backstop" - but this is opposed by some Conservative MPs and the Democratic Unionist Party.
Meanwhile former World Trade Organisation chief Pascal Lamy argued that whatever Brexit option was chosen "will necessitate a border" between Northern Ireland and the Republic, because checks will have to be carried out on goods and people.
Instead he suggested to the Commons Brexit committee a "Macau option" for Northern Ireland.
"You should think about giving to Northern Ireland the same autonomous trade capacity that China has given to Macau, which doesn't mean that Macau doesn't belong to China," he said.

The prime minister has said it is "up to the EU, this is their call" if the UK leaves the EU without a deal.
Boris Johnson made his first visit to Wales as PM on Tuesday, seeking support from farmers for his Brexit plans.
He held talks with Wales' First Minister Mark Drakeford, who said there was a "deeply concerning lack of detail" from the new prime minister.
Mr Johnson said: "We're not aiming for a no-deal Brexit, we don't think that's where we'll end up."
"This is very much up to our friends and partners across the channel," he added.
A Welsh farmer called on Mr Johnson to stop "playing Russian roulette" with the lamb industry over the threat of a no-deal Brexit.
It followed the Farmers' Union of Wales president warning of "civil unrest" in rural areas if no agreement is struck.
Earlier, the prime minister had his first phone call with Irish leader Leo Varadkar since taking office.
The visit to Wales came as the Conservatives fight to hold Brecon and Radnorshire in a by-election on Thursday.
Mr Johnson visited a chicken farm in St Brides Wentlooge, near Newport, before travelling to online retailer BVG Group in Brecon.
He later attended a meeting in the Welsh Assembly with Mark Drakeford, where he was booed by a group of protesters on arrival.
In a news conference afterwards, Mr Drakeford said they had an "engaged discussion" on Brexit.
The Welsh Labour leader said he pressed Mr Johnson to explain the path to a deal with the EU but did not get a "clear sense" from him of what the plan would be.
Mr Drakeford said he emphasised the "catastrophic effect" a no-deal Brexit would have on the Welsh economy, and said the PM provided assurances of support for manufacturing and agriculture in such a scenario.
"But asked to describe the nature of that support, I'm afraid that there is a deeply concerning lack of detail that is available to people whose livelihood is on the line," Mr Drakeford said.
The first minister said the PM told him there would be many new opportunities for Welsh agriculture and businesses, but he had "no sense again" there was detailed thinking behind what "otherwise becomes vacuous optimism".
Mr Drakeford said he warned Mr Johnson "the future of the UK is more at risk today than at any other point in his political lifetime", and said he had put ideas to him on how the Union could be "reinvented".
A Downing Street spokeswoman said the two spoke about the importance of the union and support for farmers in Wales.
She added: "The PM set out how the UK will be leaving the EU on October 31st, come what may, and said he would seek to work with the Welsh Government and other devolved administrations, to make sure communities across the UK are ready to maximise on the opportunities that Brexit will bring."
Many Welsh farmers are heavily reliant on free trade with the EU. If the UK leaves without a deal many would face significant tariffs on their exports to EU countries.
The prime minister did not give any television interviews to Welsh broadcasters on Tuesday.
However, during the farm visit, he told reporters the agriculture sector will "have the support they need" in the event of no-deal.
"We will make sure that they have the support that they need, if there are markets that are going to be tricky that we help them to find new markets, we have interventions that aim to support them and their incomes," Mr Johnson said.
"The most important point is that we don't want tariffs and we don't envisage they will be necessary.
"And I think common sense would dictate it would be better and massively in the interests of our EU friends to have a zero-tariff, zero-quota regime of the kind we currently have."
Mr Johnson suggested funds for "export refunds" would be made available for the Welsh Government to administer.
Asked how the system would work, given agriculture is devolved, he said: "It will be up to the Welsh Government to administer it. We will make sure the funds are available."
A Welsh Government source said they were surprised by the nature of the announcement.
The farming industry is worth more than £6bn to the Welsh economy and supports 14,000 businesses, 45,000 jobs and about 25,000 farmers.
Welsh lamb will face at least 40% tariffs in a no-deal scenario, prompting a sheep farmer to call for Mr Johnson "to stop playing Russian roulette with the industry as he appears to be doing at the moment".
"If we do go out with a no deal, it will be absolutely catastrophic even if it is just for a few months," Helen Roberts, who is also development officer for the National Sheep Association in Wales, told Radio 4's Today programme.
She said her members would protest against a no-deal Brexit, adding: "I think it's time to come and stand up for ourselves, and be counted."
On Monday, the prime minister said there was "every chance" a Brexit deal with the EU could be struck, but the existing agreement with the EU has "got to go".
However senior minister Michael Gove, who has been put in charge of preparing for no deal, has said the UK government was working on the assumption the UK would leave the EU without an agreement.
Ahead of his meeting with Mr Johnson, Mr Drakeford tweeted Brexit "will decimate our agricultural and manufacturing sectors and risks ripping the Union apart".
"The PM must stop playing fast and loose with our country," he said.
Earlier on Tuesday, Welsh Secretary Alun Cairns suggested new global markets, including in Japan, will be available to sheep meat producers.
Mr Cairns told the BBC: "We are now looking to the growth that will come from right around the world, 90% of global growth will come from outside of the EU,
"But we don't want to close our back on the European market either and that's why working hard to get a deal is important, but of course there needs to be a shift in attitude and a positive response to the cause that we're making."
Plaid Cymru Westminster leader Liz Saville Roberts pointed out via Twitter the Japanese market had been opened up to Welsh lamb by the EU-Japan trade deal.
Mr Cairns added farmers "can be guaranteed that the same money will be available to ensure that we are protecting this sector".
By Felicity Evans, BBC Wales political editor
It is clear there was no meeting of minds between Mark Drakeford and Boris Johnson.
As well as having "fundamentally different views" on Brexit, the two leaders are very different characters.
The first minister is a details man - after Brexit he wants to know what support will be on offer to Welsh manufacturing and agriculture, when it'll be available and how long for.
But the prime minister paints in bold colours, and he knows that despite concerns over the impact of a no-deal exit in Wales, voters here chose to leave the EU in 2016.
This is the first of many meetings between the two leaders - whether they can find common ground remains to be seen.

Boris Johnson has given key cabinet roles to leading Brexiteers after becoming the UK's new prime minister.
Dominic Raab and Priti Patel return to government as foreign secretary and home secretary respectively.
Sajid Javid has been named as the new chancellor as more than half of Theresa May's old cabinet, including leadership rival Jeremy Hunt, quit or were sacked.
Earlier, Mr Johnson said the Brexit "doomsters and gloomsters" were wrong and the UK would leave on 31 October.
Speaking outside No 10, he said the UK would meet that deadline "no ifs, no buts", adding: "The buck stops with me."
Mr Johnson then turned his attention to a radical overhaul of the government, with 17 of Mrs May's former senior ministers being axed or stepping down.
Announcing his departure, Foreign Secretary Mr Hunt said he had been offered an alternative role but had turned it down.
Defence Secretary Penny Mordaunt, a leading Brexiteer who is popular across the party, was the most surprising departure. She has been replaced by Ben Wallace, a former soldier and longstanding ally of Mr Johnson's.
Another prominent Brexiteer, International Trade Secretary Liam Fox, was also ousted, along with Business Secretary Greg Clark - a vocal opponent of a no-deal Brexit.
All three supported Mr Hunt in the Tory leadership contest.
Education Secretary Damian Hinds, Northern Ireland Secretary Karen Bradley, Immigration Minister Caroline Nokes, Culture Secretary Jeremy Wright and Communities Secretary James Brokenshire have also gone, along with Chris Grayling, whose record as Transport Secretary was much criticised.
Scottish Secretary David Mundell, who has left his position after four years, joked whether there would be "room" on the backbenches after all the dismissals.
This comes on top of the earlier resignations of four leading ministers, including Chancellor Philip Hammond, Justice Secretary David Gauke and Cabinet Office minister David Lidington.
Conservative MP Nigel Evans described the changes as a "summer's day massacre".
The BBC's chief political correspondent Vicki Young said the sackings suggested Mr Johnson wasn't looking to build bridges across the party.
Instead, she said, he was focused above all else on assembling the team he thought would bring about the results he needed, even if that was controversial.
As the upheaval in government was happening, hundreds of people gathered outside the gates of Downing Street in protest against Mr Johnson's appointment.
Former Home Secretary Sajid Javid - a banker before entering politics - has been given the key role of chancellor, having thrown his weight behind Boris Johnson after being eliminated from the leadership race himself.
Priti Patel - who quit as international development secretary in 2017 after holding unauthorised meetings with Israeli officials - succeeds Mr Javid at the Home Office, where she said she would focus on keeping the UK country safe and fighting "the scourge of crime".
Dominic Raab is a former Brexit secretary, but quit over Mrs May's handling of the process.
He said he was "hugely humbled" by his appointment and said the UK needed to "bring finality" to Brexit so it could focus on the other big challenges.
Other figures involved in the Vote Leave referendum campaign have also been rewarded.
Michael Gove leaves behind his environment brief to become Chancellor of the Duchy of Lancaster, a more senior ministerial role but one without a specific portfolio.
Meanwhile, Jacob Rees-Mogg becomes leader of the House of Commons - his first government role.
Liz Truss moves from second in command at the Treasury to head the Department for International trade while Steve Barclay has been re-appointed as Brexit Secretary.
Health Secretary Matt Hancock and Work and Pensions Secretary Amber Rudd are among the few ministers who backed Remain who have kept their jobs. Ms Rudd also takes on the women and equalities brief.
Meanwhile, there is a speedy return to office for Gavin Williamson as education secretary.
He was sacked as defence secretary less than three months ago after No 10 concluded he was responsible for the leaking of unauthorised information from a National Security Council meeting - which he denied.
Mr Johnson's team has promised a record number of women in the cabinet. Nicky Morgan, Theresa Villiers and Andrea Leadsom have all returned to top jobs, taking on the culture, environment and business briefs respectively.
There are also promotions for Robert Buckland (justice) and Alok Sharma (international development) while former party chairman Grant Shapps, a key member of Boris Johnson's leadership campaign team, makes a comeback at transport.
Former Chief Whip Julian Smith is the new Northern Ireland Secretary, while Dumfries and Galloway MP Alister Jack, who was only elected to Parliament last year, is expected to become Scottish Secretary. Alun Cairns remains as Welsh Secretary.
Earlier, in a 13-minute speech outside Downing Street, Mr Johnson listed a wide range of domestic ambitions, chiefly a promise to sort out care for the elderly "once and for all".
Reforms to the social care sector have eluded previous governments because of their cost and complexity.
"We will fix it once and for all with a clear plan we have prepared to give every older person the dignity and security they deserve," he insisted.
Mr Johnson also pledged to improve infrastructure, recruit 20,000 new police officers and "level up" school spending. He promised reforms to ensure the £20bn in extra funding earmarked for the NHS "really gets to the front line".
And he pledged to boost the UK's biotech and space science sectors, change the tax rules to provide incentives for investment, and do more to promote the welfare of animals.
Setting out his priorities for office, the former London mayor hit out at the "pessimists" who did not believe Brexit could be delivered and called for an end to three years of indecision.
"The people who bet against Britain are going to lose their shirts because we are going to restore trust in our democracy," he said.
"The time has come to act, to take decisions and change this country for the better."
He said he had "every confidence" the UK would leave the EU in 99 days time with a deal, but preparations for the "remote possibility" of a no-deal Brexit would be accelerated.
Mr Johnson vowed to bring all four nations of the United Kingdom - or what he described as the "awesome foursome" - together in the task of strengthening a post-Brexit country.
"Though I am today building a great team of men and women, I will take personal responsibility for the change I want to see," he concluded.
"Never mind the backstop, the buck stops here."
Labour's Sir Keir Starmer said Mr Johnson's speech was "all rhetoric". New Lib Dem leader Jo Swinson said she would welcome a cross-party push to find a solution on social care, but attacked Mr Johnson's "bluster and bravado" over Brexit.
Mr Johnson took over after Theresa May handed in her resignation to the Queen.
Earlier, as she relinquished power after three years, Mrs May said being prime minister had been "the greatest honour" and wished her successor well.
During his journey to Buckingham Palace, Mr Johnson's car was briefly held up by protesters from Greenpeace, who formed a human chain across The Mall.

Boris Johnson has restored the whip to 10 of the 21 Tory MPs who rebelled against him over Brexit last month.
The rebels were expelled from the parliamentary Conservative Party after backing efforts to pass legislation to block a no-deal Brexit.
Ex-ministers including Ed Vaizey and Margot James are among those to be welcomed back.
Former Tory chancellors Philip Hammond and Ken Clarke are among those who remain outside the party.
The move to readmit the rebels came shortly before MPs backed the prime minister's plan to hold an early general election on Thursday, 12 December.
Those who have had the whip restored are now eligible to stand as Conservative candidates at the election if new candidates have not since been chosen.
Some of those who have been welcomed back, including Sir Nicholas and former minister Alistair Burt, have previously said they would be retiring.
As well as Sir Nicholas, grandson of Sir Winston Churchill, those readmitted into the party include Greg Clark, who served as a cabinet minister under Theresa May.
Caroline Nokes, Richard Benyon, Stephen Hammond, Steve Brine and Richard Harrington complete the list of those to have been given the whip back.
Ex-chancellors Philip Hammond and Ken Clarke, and former justice secretary David Gauke, are among those not to have had the whip restored.
Sir Oliver Letwin, Justine Greening, Dominic Grieve, Rory Stewart, Guto Bebb, Anne Milton and Antoinette Sandbach also remain as independents.

Boris Johnson has pledged to "hold out the hand" and "go the extra thousand miles" to strike a new Brexit deal.
During a visit to Scotland, the prime minister said the existing withdrawal agreement negotiated with European leaders was "dead" and had "got to go".
However, he said there was "every chance we can get a deal".
But Scotland's First Minister, Nicola Sturgeon, said Mr Johnson had set the UK on an "almost inevitable path to a no-deal Brexit".
Preparations for leaving the European Union without a withdrawal deal are being ramped up, with Mr Johnson saying the UK must leave the EU by 31 October.
While in Scotland he met Ms Sturgeon and Scottish Conservative leader Ruth Davidson - both of whom have positioned themselves against a no-deal exit.
Two committees have been set up as the UK government intensifies preparations for a possible no-deal exit, including a "daily operations committee" of senior ministers.
Meanwhile, the pound has sunk to a 28-month low against the dollar, apparently due to concerns about Brexit.
Speaking at the Faslane naval base near Glasgow, Mr Johnson said his "assumption is that we can get a new deal", but said it was "responsible for any government to prepare for no deal if we absolutely have to".
He said: "I don't want the UK to be aloof or hanging back, I want us to engage, to hold out the hand, to go the extra thousand miles, and what we want to do is make it absolutely clear that the backstop is no good, it's dead, it's got to go.
"The withdrawal agreement is dead, it's got to go. But there is scope for us to do a new deal.
"We will make it very clear to our friends - we're talking to the Irish today - what the limits are and what we want to do.
"We're very confident that with goodwill on both sides, two mature political entities, the UK and EU, can get this thing done."
Meanwhile, the prime minister's chief Brexit negotiator, David Frost, has urged his EU counterparts not to "underestimate" Mr Johnson or his commitment to the 31 October deadline.
Mr Johnson has faced scrutiny over his Brexit strategy from colleagues and opponents alike during his visit to Scotland.
Ms Davidson has previously said Mr Johnson has her "full support" in his efforts to secure a withdrawal agreement with the EU, but that she will not support a no-deal Brexit.
After a meeting at Holyrood, the Scottish Tory leader said the pair had discussed their "shared determination to strengthen the Union", adding Mr Johnson had "made clear the government's preference is to leave the EU with a deal".
Mr Johnson, meanwhile, said he was Ms Davidson's "number one fan".
Analysis by BBC Scotland editor Sarah Smith
Boris Johnson's toughest meeting might not have been with Scottish First Minister Nicola Sturgeon, but rather Scottish Conservative leader Ruth Davidson.
Ms Davidson made no secret of the fact that she did not want Mr Johnson as PM. And in the few days since he took charge relations have already gone further south.
He ignored his Scottish leader's advice not to sack the Scottish Secretary David Mundell and replace him with the pro-Brexit MP Alister Jack. He then further snubbed the Scottish contingent of parliamentarians when he put an MP who sits for an English seat into the Scotland office as a minister.
Ms Davidson has said publicly that she would not support a no-deal exit from the EU and that as leader of the Scottish party she does not have to sign up to any loyalty pledge to support a no deal.
She believes the PM would have sacked her if he could. But he can't - and she will take full advantage of her ability to speak out.
Ms Sturgeon - who hosted Mr Johnson at her official Bute House residence - has also pledged to fight against a no-deal exit, saying it would cost 100,000 jobs and "plunge the economy into recession".
Speaking after what she described as a "very lively exchange" with Mr Johnson, she also said she believed he was really pursuing a no-deal Brexit.
"He says he wants to get a deal, but what is not clear to me is how he intends to get from the very hard-line, fixed position that he's taken to a position where a deal is possible, if the EU also sticks to the very consistent position it has taken," she said.
"That makes me think that whatever Boris Johnson is saying about his preference being to strike a deal, in reality he is pursuing a no-deal Brexit."
She added that she had made clear to Mr Johnson her opposition to Brexit and no-deal and that the people of Scotland should be able to "choose their own future".
A No 10 spokesman said the PM told Ms Sturgeon he "was a passionate believer in the power of the Union" and "would work tirelessly to strengthen the United Kingdom and improve the lives of people right across Scotland".
Mr Johnson said his preference was to negotiate a new deal that abolished the backstop - but the UK would be leaving the EU on 31 October "come what may", the spokesman added.
Mr Johnson also used his trip to Scotland to announce funding for projects to boost the economy in Scotland, Wales and Northern Ireland.
However Scottish Finance Secretary Derek Mackay claimed the £300m "isn't new funding" and was already under negotiation before Mr Johnson became prime minister.
Welsh Labour also hit out at the funding plans, calling them "very thin stuff" which would not make up for a "chronic lack of investment".
The UK government, however, insisted the money was new, with Scottish Secretary Alister Jack saying city deals would help "create jobs and boost local economies".
The growth deal plan comes after Mr Johnson announced a £3.6bn towns fund over the weekend, which will initially support 100 places in England.
As part of his visit to Scotland, the prime minister also announced plans for a new Office for Veterans' Affairs within the UK government, to coordinate medical treatment and training and "ensure no veteran is disadvantaged because of their service".
The prime minister also plans to go to Wales to meet members of its farming community and Northern Ireland to discuss ongoing efforts to restore devolution at Stormont.
Who is in charge of what?

The government's final Brexit proposals will include customs checks on the island of Ireland.
The BBC's Laura Kuenssberg said Boris Johnson's plans will see Northern Ireland "in a different relationship with the EU to the rest of the UK".
Boris Johnson is addressing the Tory conference before submitting the new proposals to the EU.
The European Commission said they will "examine it objectively" and "listen carefully to the UK".
The Commission's president, Jean-Claude Juncker will talk to the PM on the phone later, while negotiating teams will meet in Brussels.
In his first speech at the event as prime minister, he will call it a "fair and reasonable" Brexit compromise, and say only by leaving the EU on 31 October can the UK "move on".
Mr Johnson will also claim the public will no longer be "taken for fools" by those who want to delay or block the process.
Tory Chairman James Cleverly said the UK had been "flexible and pragmatic", and now the EU must be the same.
On the eve of his speech, Mr Johnson told a conference fringe meeting in Manchester, hosted by the DUP, that he hoped to reach a deal with the EU over the course of "the next few days".
The government has insisted it will not negotiate a further delay beyond the Halloween deadline, saying this would be unnecessary and costly for the UK.
However, under the terms of a law passed by Parliament last month, the PM faces having to request another extension unless MPs back the terms of withdrawal by 19 October - two days after a summit of European leaders.
On Tuesday, Mr Johnson dismissed leaked reports that customs posts could be set up on either side of the border between Northern Ireland and the Republic of Ireland.
He said suggestions the UK wanted "clearance zones" for goods as part of a package of alternative arrangements to replace the Irish backstop were wide of the mark.
While he conceded some customs checks would be needed as the UK leaves the EU's customs union and single market, he said technology could keep them to an "absolute minimum".
The issue of the Irish border - and how to keep it free from border checks when it becomes the frontier between the UK and the EU - has been a key sticking point in Brexit negotiations.
Mr Johnson says the solution reached by the EU and Theresa May, the backstop, is "anti-democratic" and "inconsistent with the sovereignty of the UK", claiming it offered no means for the UK to unilaterally exit and no say for the people of Northern Ireland over the rules that would apply there.
BBC political editor Laura Kuenssberg said the new offer from Mr Johnson included some new customs checks on the island of Ireland, and would leave Northern Ireland in a different relationship with the EU to the rest of the UK in some ways.
She said the plans were "based on the notion of consent", giving more powers to Northern Ireland's devolved Parliament - the Stormont Assembly - to shape its future relationship with the EU - despite the fact the assembly is approaching 1,000 days without sitting.
The proposals also suggest a time period for when the relationship between Northern Ireland and the EU could move on.
But the full and precise details of Mr Johnson's plan twill not be clear until after the prime minister's speech at conference.
Speaking to BBC Radio 4's Today programme earlier, Mr Cleverly appeared to put the ball in the EU's court.
"We have been in negotiating for some while," he said. "The UK has been flexible, but a negotiation means both parties need to be flexible.
"What we need to see now is the EU be flexible - and if they can be pragmatic and flexible, we can leave with a deal on 31 October. But we are going to leave on 31 October whatever."
Irish Fine Gael senator Neale Richmond told Today that the PM's plans were a "big move" from the withdrawal agreement made by Theresa May.
Mr Richmond said, under the plan, Northern Ireland would leave the customs union and "come out of the single market in all areas, apart from agri-food products and industrial products, and indeed it only stays in those areas for four years".
This, he added, would require "additional checks" on the island of Ireland - something he described as "extremely disappointing".
Laura Kuenssberg said there was a "real expectation and belief" in No 10 that "this is now the crunch point".
She said: "This is the moment…where the EU will have to respond and say [either] there is something that is a basis of a deal here, or not.
"And what Boris Johnson is trying to suggest is if the answer is not, then for him, that means no-deal."
The EU needs to see the precise details of Boris Johnson's proposals, but the direction of travel that has been coming through is different.
The very idea of customs check between Ireland and Northern Ireland, the promise of the use of technologies to ease the process that haven't yet been tried and tested, or don't even exist yet…that is a big no-no for the EU.
The bloc will look at the proposals carefully. They need to try as they do want a deal, and also they need to be seen to be trying.
But it is fundamentally misunderstanding the EU if the prime minister thinks at this stage the 26 EU leaders will turn round on the Irish prime minister and say: "Listen, you are going to have to accept this because we just want to have a deal."
It is also fundamentally misunderstanding the German Chancellor Angela Merkel, her attachment to EU unity and the integrity of the single market.
And also it is misunderstanding that the EU sees this in a bigger picture. If suddenly now they were to back down to all of the prime minister's demands how would that look to other trade partners across the globe.
So EU leaders will be very careful not to rubbish the prime minister's ideas, to talk about them as a basis for an agreement, but if it is take it or leave it, they will be leaving at this point.
BBC assistant political editor Norman Smith said it was particularly important Mr Johnson secured the support of the Democratic Unionist Party's 10 MPs.
He said: "I think it is very clear this deal is not going to fly unless Boris Johnson can bring the DUP along with him... one way or another he has to make sure they're on board."
BBC Northern Ireland political editor Mark Devenport said sources from the DUP were supportive of the proposals and had been kept informed during their development.
However, the party's leader, Arlene Foster, declined to say whether she had seen the PM's proposals.
She told the BBC: "What we are doing with this prime minister is working very closely with him and we will continue to work closely with him over the next couple of hours and days.
"I hope we do get a deal that is acceptable to the European Union and one that is good for the whole of the United Kingdom."
Speaking in Manchester, Mr Johnson will suggest voters are "desperate" for the country to focus on other priorities and will contrast his determination to leave on 31 October with the "years of uncertainty" that he says would result from a Labour government promising another referendum.
"What people want, what Leavers want, what Remainers want, what the whole world wants - is to move on," he is expected to say.
"I am afraid that after three-and-a-half years people are beginning to feel that they are being taken for fools.
"They are beginning to suspect that there are forces in this country that simply don't want Brexit delivered at all.
"And if they turn out to be right in that suspicion then I believe there will be grave consequences for trust in democracy.
"Let's get Brexit done on October 31 so in 2020 our country can move on."
Mr Johnson's conference speech is set to clash with Prime Minister's Questions, which is taking place at 12.00 BST.
Normally the Commons goes into recess for the Tory conference, but MPs voted against this amid the bitter fallout from the government's unlawful prorogation of Parliament.
Foreign Secretary Dominic Raab will deputise for the prime minister, facing the shadow home secretary Diane Abbott over the despatch box.
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Boris Johnson has secured the highest number of votes in the first MPs' ballot to select the Conservative Party leader and next prime minister.
Three contenders - Mark Harper, Andrea Leadsom and Esther McVey - were knocked out in the secret ballot of Tory MPs.
Mr Johnson received 114 votes, significantly more than his nearest rival Jeremy Hunt, who came second with 43. Michael Gove was third with 37.
Seven candidates progress to the next round of voting next week.
The two who prove most popular after the last MPs' ballot will go to Conservative Party members in a final vote later this month.
The winner of the contest to succeed Theresa May is expected to be announced in the week of 22 July.
Sources close to Health Secretary Matt Hancock told the BBC's Laura Kuenssberg he was "mulling over" whether to withdraw from the contest after coming sixth with 20 votes.
Home Secretary Sajid Javid, who came fifth with 23 votes, is understood to be staying in the race for now. Some have suggested his candidacy - with support from Mr Hancock - could take on Mr Hunt to become second in the ballot.
Mr Johnson, a former foreign secretary who served for eight years as London mayor, said he was "delighted" to win but warned that his campaign still had "a long way to go".
Foreign Secretary Mr Hunt said: "Boris did well today but what the result shows is, when it comes to the members' stage, I'm the man to take him on."
Environment Secretary Mr Gove said it was "all to play for" and he was "very much looking forward" to candidates' TV debates on Channel 4 on Sunday and on BBC One next Tuesday.
All 313 Conservative MPs voted in the first ballot, including Mrs May, who refused to say whom she had backed.
The fourth-placed candidate, former Brexit secretary Dominic Raab, said he was "proud and honoured" and he had a "good base to build on".
Mr Javid said: "I look forward to continuing to share my positive vision and my plan for uniting the country."
Mr Hancock thanked his supporters, saying it was "terrific to have more votes from colleagues than I could have hoped for".
And International Development Secretary Rory Stewart, the seventh-placed candidate, told the BBC's Politics Live he was "completely over the Moon" to have got through the first vote.
He said he had had only six declared votes ahead of the poll, but "more than three times that" had voted for him in the secret ballot.
The margin of success took his fellow candidates by surprise - but not the core of Boris Johnson's team.
After many, many weeks of private campaigning, introducing Boris Johnson to the world of the spreadsheet, this morning one of his organisers wrote the number 114 and sealed it in an envelope.
At lunchtime, the announcement revealed the controversial former foreign secretary had indeed received exactly that number.
That is not just a marker of the level of Mr Johnson's support but for the sometimes clownish politician, whose reputation has risen and fallen and then risen again, it's a sign that it is different this time.
Justice Secretary David Gauke said Mr Stewart was now the main challenger to Mr Johnson, saying: "He's really in with a chance and the momentum is with Rory."
But Defence Secretary Penny Mordaunt, who is supporting Mr Hunt's campaign, said the foreign secretary was "attractive to many sides of the party because he's a serious individual".
And schools minister Nick Gibb told BBC Radio 4's World at One that Mr Gove was now "best placed as a Brexiteer to challenge the front runner" Mr Johnson in the final.
Further ballots are scheduled to take place on 18, 19 and 20 June to whittle down the contenders until only two are left.
The final pair will then be put to a vote of members of the wider Conservative Party from 22 June, with the winner expected to be announced about four weeks later.
After being knocked out of the contest, Mr Harper, a former government chief whip, said he continued "to believe we need a credible plan that delivers Brexit" in order to "restore trust".
Mrs Leadsom's campaign team said they were "disappointed" but "wish all the other candidates well".
And Ms McVey, who gained nine votes, coming last in the first round of MPs' ballots, said she was "extremely grateful" to those who had supported her.
Televised candidates' debates are scheduled to take place, but not all the remaining seven have confirmed they are taking part.
Work and Pensions Secretary Amber Rudd, who is backing Mr Hunt, urged them to appear, saying the Conservative Party "needs to remember that we're not just choosing a leader, we're choosing a prime minister and the public need to see them".
And former Brexit secretary David Davis, who is backing Mr Raab, said it was "very important" for the public to hear from the contenders.
Mr Johnson has previously been criticised by some of his rivals for not taking part in media interviews during the campaign.
The leadership race has so far been dominated by Brexit and arguments over whether a deal can be renegotiated with the EU by 31 October, and whether talking up a no-deal Brexit is a plausible promise.
On Tuesday 18 June BBC One will host a live election debate between the Conservative MPs still in the race.
If you would like to ask the candidates a question live on air, use the form below. It should be open to all of them, not a specific politician.
Tory leadership rivals face first party vote
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Boris Johnson has been elected new Conservative leader in a ballot of party members and will become the next UK prime minister.
He beat Jeremy Hunt comfortably, winning 92,153 votes to his rival's 46,656.
The former London mayor takes over from Theresa May on Wednesday.
In his victory speech, Mr Johnson promised he would "deliver Brexit, unite the country and defeat Jeremy Corbyn".
Speaking at the Queen Elizabeth II centre in London, he said: "We are going to energise the country.
"We are going to get Brexit done on 31 October and take advantage of all the opportunities it will bring with a new spirit of can do.
"We are once again going to believe in ourselves, and like some slumbering giant we are going to rise and ping off the guy ropes of self doubt and negativity."
Mr Johnson thanked his predecessor, saying it had been "a privilege to serve in her cabinet". He was Mrs May's foreign secretary until resigning over Brexit.
The outgoing PM - who is standing down after a revolt by Conservative MPs over her Brexit policy - congratulated her successor, promising him her "full support from the backbenches".
Foreign Secretary Mr Hunt said he was "very disappointed", but Mr Johnson would do "a great job". He said he had "total, unshakeable confidence in our country" and that was a valuable quality at such a challenging time.
Mr Hunt added: "It was always going to be uphill for us because I was someone who voted Remain and I think lots of party members felt that this was a moment when you just had to have someone who voted for Brexit in the referendum.
"In retrospect, that was a hurdle we were never able to overcome."
Donald Trump told an event in Washington "a really good man is going to be the prime minister of the UK now," and Mr Johnson would "get it done", referring to Brexit.
The president added: "They call him Britain Trump. That's a good thing."
Almost 160,000 Conservative members were eligible to vote in the contest and turnout was 87.4%.
Mr Johnson's share of the vote - 66.4% - was slightly lower than that garnered by David Cameron in the 2005 Tory leadership election (67.6%).
The former London mayor and ex-foreign secretary spoke to staff at Conservative Party HQ after his victory was announced.
He was then given a rousing reception by Tory MPs at a meeting in Parliament, where he urged them to "unite, unite, unite and win".
The BBC's Nick Eardley, who was outside the room, said such gatherings had been gloomy and downbeat for many months, but this one was full of laughter.
One MP told our correspondent: "The BoJo show is up and running." Another said: "The cloud has been lifted."
Mr Johnson will begin announcing his new cabinet on Wednesday, but it has already been confirmed that Mark Spencer, MP for Sherwood in Nottinghamshire, will become chief whip - the person responsible for enforcing party discipline in the Commons.
A number of senior figures have already said they will not serve under Mr Johnson, though, citing their opposition to his stance on Brexit.
He has pledged the UK will leave the EU on 31 October "do or die", accepting that a no-deal exit will happen if a new agreement cannot be reached by then.
Education Minister Anne Milton tweeted her resignation just half an hour before the leadership result was due to be revealed, insisting the UK "must leave the EU in a responsible manner".
And International Development Secretary Rory Stewart confirmed he would be returning to the backbenches, where he would be spending more time "serving Cumbria" and "walking".
David Gauke, another vocal opponent of a no-deal Brexit, announced he was resigning as justice secretary.
They join the likes of Chancellor Philip Hammond, Foreign Office minister Sir Alan Duncan and Culture Minister Margot James who have all said they disagree too strongly with Mr Johnson's Brexit strategy to work closely with him.
Boris Johnson will become our next prime minister.
A sentence that might thrill you. A sentence that might horrify you. A sentence that 12 months ago even his most die-hard fans would have found hard to believe.
But it's not a sentence, unusually maybe for politics, that won't bother you either way.
Because whatever you think of Boris Johnson, he is a politician that is hard to ignore.
With a personality, and perhaps an ego, of a scale that few of his colleagues can match. This is the man who even as a child wanted to be "world king".
Now, he is the Tory king, and the Brexiteers are the court.
Read Laura's blog here
The EU Commission's Brexit negotiator, Michel Barnier, said he was looking forward to working with Mr Johnson "to facilitate the ratification of the withdrawal agreement and achieve an orderly Brexit".
The new Tory leader has previously said the agreement Mrs May reached with the EU was "dead", having been rejected three times by MPs.
Guy Verhofstadt, the European Parliament's chief Brexit co-ordinator, said the parliament would hold an extraordinary meeting on Wednesday in response to Mr Johnson's election.
Jeremy Corbyn reacted to the result by tweeting that Mr Johnson had "won the support of fewer than 100,000 unrepresentative Conservative Party members".
"The people of our country should decide who becomes the prime minister in a general election," he added.
Speaking to the BBC later, Mr Corbyn said Labour planned to table a motion of no confidence in Mr Johnson. Asked when that would be, he replied: "It will be an interesting surprise for you all."
Wednesday 12:00 BST onwards: Theresa May takes part in her last Prime Minister's Questions. After lunch she will make a short farewell speech outside No. 10 before travelling to see the Queen to tender her resignation.
Boris Johnson will then arrive for an audience at Buckingham Palace where he will be invited to form a government.
After that he will make a speech in Downing Street before entering the building for the first time as prime minister.
Later, he will begin announcing his most senior cabinet appointments, such as chancellor, home secretary and foreign secretary, and will make and take his first calls from other world leaders.
Thursday: Mr Johnson is expected to make a statement to Parliament about his Brexit strategy and take questions from MPs. Parliament will break up for its summer recess later.
The new PM will also continue announcing his new cabinet.
Newly-elected Lib Dem leader Jo Swinson said Mr Johnson had "shown time and time again that he isn't fit to be the prime minister of our country".
First Minister of Scotland Nicola Sturgeon congratulated Mr Johnson, but said she had "profound concerns" about him becoming prime minister.
The new leader also received congratulations from Arlene Foster, the leader of Northern Ireland's Democratic Unionist Party, whose support has kept the Conservatives in government since the 2017 general election.
She said the pact - known as a confidence and supply agreement - continued and would be reviewed over the coming weeks "to explore the policy priorities of both parties".
Leader of the Scottish Conservatives Ruth Davidson, who backed Mr Hunt in the campaign, also sent her congratulations, adding that the new PM had "an enormous task ahead of him".
In the often divisive Brexit world of "them and us" it's easy to forget that, beyond Brexit, EU leaders still see the UK as a close partner and ally. Today's messages of congratulation to Boris Johnson from across Europe were a timely reminder.
Whatever happens with Brexit, France, Germany, Poland et al still very much hope to work closely with the UK on international issues like Russia sanctions, Iran, and human rights protection.
But EU leaders' welcoming tone does not signal a willingness to accept whatever Prime Minister Johnson might demand in terms of changes to the Brexit deal.
He's right when he says a no-deal Brexit is bad for Brussels, but he overestimates EU wiggle room. Amendments will only be forthcoming if EU leaders deem them workable and are convinced the new prime minister commands a majority in Parliament to get an agreement through once and for all.

The European Union is "open but not convinced" by the UK PM's new proposals for a Brexit deal with the EU, the president of the European Council says.
Donald Tusk was among several leading EU voices to express doubt over Boris Johnson's withdrawal agreement plan.
The plan would keep Northern Ireland in the EU single market for goods but see it leave the customs union.
But what happens to the border between Northern Ireland and Ireland remains a central sticking point.
Irish PM Leo Varadkar said the new plans for the withdrawal agreement were welcome, but "fall short in a number of aspects".
It comes as UK PM Boris Johnson's Europe adviser, David Frost, is to hold another round of talks in Brussels in a bid to break the Brexit deadlock.
The EU's chief negotiator, Michel Barnier, has told European diplomats he still has plenty of questions about the British proposal to replace the backstop - the measure designed to prevent a hard border on the island of Ireland after Brexit.
He has said he will be in a better position to judge possible future negotiations with the UK once he has spoken to Mr Frost.
On Thursday, Mr Johnson said he had made a "genuine attempt to bridge the chasm" with EU officials before time runs out to reach a deal for the 31 October deadline for the UK to leave the EU.
The UK government says it is aiming to reach a final agreement at an EU summit on 17 October.
EU leaders face a delicate political dance, uncertain if Mr Johnson is open for deeper negotiations or is focusing his attention on a possible election campaign, the BBC's Europe editor Katya Adler says.
Whatever happens, she adds, the EU will be reluctant to be seen slamming the door in the face of the UK.
Meanwhile, Scotland's highest civil court is to consider whether Mr Johnson could be jailed if he ignores legislation aimed at preventing no-deal.
The so-called Benn Act requires the government to ask the EU for an extension to the Brexit deadline if it fails to either pass a deal in Parliament, or get MPs to approve no-deal, by 19 October.
However, Mr Johnson has repeatedly insisted he would not ask for a delay as the law requires him to, describing the legislation as a "surrender bill".
Downing Street hopes its new plan will replace the controversial Irish backstop provision that has proved the biggest obstacle to the existing withdrawal agreement.
The backstop was meant to keep a free-flowing border on the island of Ireland but critics - including Mr Johnson - fear it could trap the UK in EU trading rules indefinitely.
Mr Johnson's latest plan seeks to address this with the following:
The new UK proposals envisage two borders - one between Northern Ireland and Ireland, and a second between Northern Ireland and the rest of the UK, says the BBC's Europe editor Katya Adler.
EU negotiators say they have already identified problems with the plans, including the continuing failure to avoid a hard border on the island of Ireland and the threat to the single market.
Donald Tusk reacted in a tweet, after speaking to Taoiseach (Irish prime minister) Leo Varadkar, who is seen as key to agreeing to a withdrawal deal.
For his part, Mr Varadkar voiced concerns over the customs proposals, questioning how Northern Ireland and Ireland could operate under different customs systems without the need for physical checkpoints.
He also questioned the plan to give Northern Ireland's Assembly a veto over entering into a "regulatory zone" with the EU, without the involvement of Ireland or the EU.
The UK has made some progress but "further work is needed", European Commission chief Jean-Claude Juncker said.
Accepting the current proposals would not meet the objectives of the backstop including preventing a hard border, he added.
Meanwhile, the European parliament's Brexit co-ordinator, Guy Verhofstadt, called the plans "unworkable".
In an interview with the BBC, Mr Verhofstadt said the plan represented "a repackaging of old ideas".
Earlier, the European parliament's Brexit committee said the plan didn't match "even remotely" what had already been agreed.

Boris Johnson has faced a double defeat in the Commons after MPs turned down his motion for a general election.
Earlier, MPs backed a bill aimed at blocking a no-deal Brexit if the PM hadn't agreed a plan with the EU ahead of the 31 October deadline.
Mr Johnson said the bill "scuppered" negotiations and the only way forward now was an election.
But Labour leader Jeremy Corbyn accused the PM of "playing a disingenuous game" to force a no-deal Brexit.
He said his party would back an election after the bill had been passed, but not before.
Both the SNP and the Liberal Democrats also criticised the prime minister's motion as a plot to make sure the UK left the EU without a deal.
But supporters of Mr Johnson hit back at opposition members who had been calling for a general election for two years.
Mr Johnson wanted MPs to agree to an early general election on 15 October, saying the bill - which forces him to ask for an extension to the Brexit deadline if no deal had been agreed - left him unable to negotiate a deal.
He needed two thirds of all MPs to vote in favour under the Fixed Term Parliaments Act, but the result only saw 298 vote for the motion and 56 against - 136 short of the number he needed.
Labour sources told the BBC the party abstained on the vote, although three MPs appeared to have voted for it and 28 against.
The SNP also abstained.
The bill to block no deal passed all its stages in the Commons in one day, with the support of most opposition parties and 21 Tory rebels, as they tried to push it through ahead of Parliament being suspended next week.
It will now go to the Lords for approval.
Peers are debating a business motion on how to move forward with the bill - but pro-Brexit peers have laid down over 100 amendments to derail its progress.
Speaking after the vote, the PM attacked Mr Corbyn, claiming he was "the first leader of the opposition in the democratic history of our country to refuse the invitation to an election".
He said he "urged [Mr Corbyn's] colleagues to reflect on the unsustainability of this position overnight and in the course of the next few days."
Earlier, the Labour leader said Mr Johnson's offer of an election was "a bit like an offer of an apple to Snow White from the Wicked Queen... offering the poison of a no deal".
He added: "Let this bill [to block a no deal] pass and gain Royal Assent, then we will back an election so we do not crash out."
One senior MP told the BBC's political editor Laura Kuenssberg that Mr Corbyn had said he would not allow Mr Johnson to have an election before 31 October.
The leader of the SNP in Westminster, Ian Blackford, said the debate about an early election was only going ahead because the PM had lost the vote against the bill.
He added: "[Mr Johnson] must accept the will of this House, accept the bill that Parliament has passed, accept your duty as prime minister and go to the European Council on 17 October and negotiate the extension you have been instructed to deliver."
Leader of the Liberal Democrats, Jo Swinson, praised the cross-party work on the bill as "putting the national interest first", but condemned Mr Johnson's reaction.
"I am intrigued that as a result of this vote... the prime minister's response is this somehow messes up his plan," she added.
"If he is seriously saying the extent of his plan was to try to bully the EU and only get a good deal by threatening [to] leave without a deal... it is not very well thought through."
But Tory MP Nigel Evans criticised the opposition, telling the Commons: "They have been given an opportunity [for an election] and they are running scared - not just from the prime minister, not just from a general election, but from the people of this country who in 2016 said they wanted to leave the EU."
Earlier, shadow Brexit secretary Sir Keir Starmer told Labour MPs the leadership would not back an election until a Brexit delay had been agreed with the EU - making the 15 October proposal impossible.
But the First Minister of Scotland and leader of the SNP, Nicola Sturgeon, tweeted that the opposition parties must "seek to force [an] election" after the bill becomes law but before Parliament is suspended.
She added: "It's starting to feel like Labour doesn't want an election at all and leaving this PM in place knowing he'll try every trick in book to get what he wants would be irresponsible."
The bill says the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK's departure date to 31 January 2020 - and, unusually, the bill actually includes the wording of the letter he would have to write.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal. During that time, MPs - not the government - will have the opportunity to reject the EU's date.
The bill also requires ministers to report to the House of Commons over the next few months. potentially providing more opportunities to take control of the timetable.
Be aware though, this could all change over the next few days because MPs and peers have the power to pass amendments to any law.
Meanwhile, the fallout from No 10's decision to withdraw the party whip from 21 Tory rebels who backed the bill to block no deal has continued to face criticism from others in the party.
A group of around 80 Conservatives have written to the prime minister, calling on him to re-instate the whip to the "principled, hard-working and dedicated" MPs.
In a statement on behalf of the "One Nation Caucus", former minister and Tory MP Damian Green said: "Removing the whip from valued colleagues who have served their country and party with distinction damages our hope of winning the next general election."

Prime Minister Boris Johnson has taken the step of writing to all of the MPs who sit in the House of Commons, outlining his plans to ask for a suspension of Parliament in the first half of September. The move will limit the number of parliamentary days available for opponents of a no-deal Brexit to try to block that possibility.
Dear colleague,
I hope that you had an enjoyable and productive summer recess, with the opportunity for some rest ahead of the return of the House.
I wanted to take this opportunity to update you on the Government's plans for its business in Parliament.
As you know, for some time parliamentary business has been sparse.
The current session has lasted more than 340 days and needs to be brought to a close - in almost 400 years only the 2010-12 session comes close, at 250 days.
Bills have been introduced, which, while worthy in their own right, have at times seemed more about filling time in both the Commons and the Lords, while key Brexit legislation has been held back to ensure it could still be considered for carry-over into a second session.
This cannot continue.
I therefore intend to bring forward a new bold and ambitious domestic legislative agenda for the renewal of our country after Brexit.
There will be a significant Brexit legislative programme to get through but that should be no excuse for a lack of ambition!
We will help the NHS, fight violent crime, invest in infrastructure and science and cut the cost of living.
This morning I spoke to Her Majesty The Queen to request an end to the current parliamentary session in the second sitting week in September, before commencing the second session of this Parliament with a Queen's speech on Monday 14 October.
A central feature of the legislative programme will be the Government's number one legislative priority, if a new deal is forthcoming at EU Council, to introduce a Withdrawal Agreement Bill and move at pace to secure its passage before 31 October.
I fully recognise that the debate on the Queen's Speech will be an opportunity for Members of Parliament to express their view on this Government's legislative agenda and its approach to, and the result of, the European Council on 17-18 October.
It is right that you should have the chance to do so, in a clear and unambiguous manner.
I also believe it is vitally important that the key votes associated with the Queen's Speech and any deal with the EU fall at a time when parliamentarians are best placed to judge the Government's programme.
Parliament will have the opportunity to debate the Government's overall programme, and approach to Brexit, in the run up to EU Council, and then vote on this on 21 and 22 October, once we know the outcome of the Council.
Should I succeed in agreeing a deal with the EU, Parliament will then have the opportunity to pass the Bill required for ratification of the deal ahead of 31 October.
Finally, I want to reiterate to colleagues that these weeks leading up to the European Council on 17/18 October are vitally important for the sake of my negotiations with the EU.
Member States are watching what Parliament does with great interest and it is only by showing unity and resolve that we stand a chance of securing a new deal that can be passed by Parliament.
In the meantime, the Government will take the responsible approach of continuing its preparations for leaving the EU, with or without a deal.
The Leader of the Commons will update the House in the normal fashion with regard to business for the final week.
For now, I can confirm that on Monday 9 September both Houses will debate the motions on the first reports relating to the Northern Ireland (Executive Formation etc) Act 2019 (NIEFA).
Following these debates we will begin preparation to end the Parliamentary session ahead of a Queen's Speech.
The Business Managers in both Houses will shortly engage with their opposite numbers, and MPs more widely, on plans for passing a deal should one be forthcoming.
Decisions will also need to be taken about carrying over some of the bills currently before the House, and we will look to work constructively with the Opposition on this front.
If agreement cannot be reached we will look to reintroduce the bills in the next session, and details on this will be set out in the Queen's Speech.
As always my door is open to all colleagues should you wish to discuss this or any other matter.
Yours sincerely,
Boris Johnson

These are the decisions of a prime minister in a hurry.
One who is aware that he's up against the clock.
One who has to pull off - within a few months - what his predecessor could not manage over years.
The team surrounding Boris Johnson has been put together with one goal in mind - to help him keep the promise he's made, to see the country leave the European Union in good time.
Number 10 believes it shows strength of purpose - a new administration determined and willing to take decisions after years of drift and disappointment.
Brexit believers have the top roles. But it is not a cabinet made up purely of the most burning Eurosceptics.
Most of those around the table backed Theresa May's ill-fated deal, so they weren't part of the last stand. They are, in the main, pragmatists not purists - and with prominent former Remainers in there too.
It is perhaps a discernible step to the right - a team that could ready itself to fight a different kind of election, maybe soon, although that's not the intention.
Don't doubt though the scale of the change - one senior Tory described the wholesale clear out as a warped takeover. Another named the new cabinet a Rocky Horror Show.
It's a set of decisions put together to prioritise the task at hand, not to soothe nerves in those who doubt the new prime minister.
But the approach is vintage Johnson - delivered in haste, easy to revile, but a bold statement of intent that's impossible to ignore.

Boris Johnson has delivered his first speech in Downing Street after becoming the UK's new prime minister.
You can read the full text of his speech below.
Good afternoon.
I have just been to see Her Majesty the Queen who has invited me to form a government and I have accepted.
I pay tribute to the fortitude and patience of my predecessor and her deep sense of public service.
But in spite of all her efforts, it has become clear that there are pessimists at home and abroad who think that after three years of indecision, that this country has become a prisoner to the old arguments of 2016 and that in this home of democracy we are incapable of honouring a basic democratic mandate.
And so I am standing before you today to tell you, the British people, that those critics are wrong.
The doubters, the doomsters, the gloomsters - they are going to get it wrong again.
The people who bet against Britain are going to lose their shirts, because we are going to restore trust in our democracy and we are going to fulfil the repeated promises of Parliament to the people and come out of the EU on October 31, no ifs or buts.
And we will do a new deal, a better deal that will maximise the opportunities of Brexit while allowing us to develop a new and exciting partnership with the rest of Europe, based on free trade and mutual support.
I have every confidence that in 99 days' time we will have cracked it. But you know what - we aren't going to wait 99 days, because the British people have had enough of waiting.
The time has come to act, to take decisions, to give strong leadership and to change this country for the better.
And though the Queen has just honoured me with this extraordinary office of state my job is to serve you, the people.
Because if there is one point we politicians need to remember, it is that the people are our bosses.
My job is to make your streets safer - and we are going to begin with another 20,000 police on the streets and we start recruiting forthwith.
My job is to make sure you don't have to wait 3 weeks to see your GP - and we start work this week, with 20 new hospital upgrades, and ensuring that money for the NHS really does get to the front line.
My job is to protect you or your parents or grandparents from the fear of having to sell your home to pay for the costs of care.
And so I am announcing now - on the steps of Downing Street - that we will fix the crisis in social care once and for all with a clear plan we have prepared to give every older person the dignity and security they deserve.
My job is to make sure your kids get a superb education, wherever they are in the country - and that's why we have already announced that we are going to level up per pupil funding in primary and secondary schools.
And that is the work that begins immediately behind that black door.
And though I am today building a great team of men and women, I will take personal responsibility for the change I want to see.
Never mind the backstop - the buck stops here.
And I will tell you something else about my job. It is to be prime minister of the whole United Kingdom.
And that means uniting our country, answering at last the plea of the forgotten people and the left-behind towns by physically and literally renewing the ties that bind us together.
So that with safer streets and better education and fantastic new road and rail infrastructure and full fibre broadband we level up across Britain with higher wages, and a higher living wage, and higher productivity.
We close the opportunity gap, giving millions of young people the chance to own their own homes and giving business the confidence to invest across the UK.
Because it is time we unleashed the productive power not just of London and the South East, but of every corner of England, Scotland, Wales and Northern Ireland.
The awesome foursome that are incarnated in that red, white, and blue flag - who together are so much more than the sum of their parts, and whose brand and political personality is admired and even loved around the world.
For our inventiveness, for our humour, for our universities, our scientists, our armed forces, our diplomacy for the equalities on which we insist - whether race or gender or LGBT or the right of every girl in the world to 12 years of quality education - and for the values we stand for around the world
Everyone knows the values that flag represents.
It stands for freedom and free speech and habeas corpus and the rule of law, and above all it stands for democracy.
And that is why we will come out of the EU on October 31.
Because in the end, Brexit was a fundamental decision by the British people that they wanted their laws made by people that they can elect and they can remove from office.
And we must now respect that decision, and create a new partnership with our European friends -  as warm and as close and as affectionate as possible.
And the first step is to repeat unequivocally our guarantee to the 3.2 million EU nationals now living and working among us, and I say directly to you - thank you for your contribution to our society.
Thank you for your patience, and I can assure you that under this government you will get the absolute certainty of the rights to live and remain.
And next I say to our friends in Ireland, and in Brussels and around the EU: I am convinced that we can do a deal without checks at the Irish border, because we refuse under any circumstances to have such checks and yet without that anti-democratic backstop.
And it is of course vital at the same time that we prepare for the remote possibility that Brussels refuses any further to negotiate, and we are forced to come out with no deal, not because we want that outcome - of course not - but because it is only common sense to prepare.
And let me stress that there is a vital sense in which those preparations cannot be wasted, and that is because under any circumstances we will need to get ready at some point in the near future to come out of the EU customs union and out of regulatory control, fully determined at last to take advantage of Brexit.
Because that is the course on which this country is now set.
With high hearts and growing confidence, we will now accelerate the work of getting ready.
And the ports will be ready and the banks will be ready, and the factories will be ready, and business will be ready, and the hospitals will be ready, and our amazing food and farming sector will be ready and waiting to continue selling ever more, not just here but around the world.
And don't forget that in the event of a no deal outcome, we will have the extra lubrication of the £39 billion, and whatever deal we do we will prepare this autumn for an economic package to boost British business and to lengthen this country's lead as the number one destination in this continent for overseas investment.
And to all those who continue to prophesy disaster, I say yes - there will be difficulties, though I believe that with energy and application they will be far less serious than some have claimed.
But if there is one thing that has really sapped the confidence of business over the last three years, it is not the decisions we have taken - it is our refusal to take decisions.
And to all those who say we cannot be ready, I say do not underestimate this country.
Do not underestimate our powers of organisation and our determination, because we know the enormous strengths of this economy in life sciences, in tech, in academia, in music, the arts, culture, financial services.
It is here in Britain that we are using gene therapy, for the first time, to treat the most common form of blindness.
Here in Britain that we are leading the world in the battery technology that will help cut CO2 and tackle climate change and produce green jobs for the next generation.
And as we prepare for a post-Brexit future, it is time we looked not at the risks but at the opportunities that are upon us.
So let us begin work now to create free ports that will drive growth and thousands of high-skilled jobs in left-behind areas.
Let's start now to liberate the UK's extraordinary bioscience sector from anti-genetic modification rules, and let's develop the blight-resistant crops that will feed the world.
Let's get going now on our own position navigation and timing satellite and earth observation systems - UK assets orbiting in space, with all the long term strategic and commercial benefits for this country.
Let's change the tax rules to provide extra incentives to invest in capital and research.
And let's promote the welfare of animals that has always been so close to the hearts of the British people.
And yes, let's start now on those free trade deals - because it is free trade that has done more than anything else to lift billions out of poverty.
All this and more we can do now and only now, at this extraordinary moment in our history.
And after three years of unfounded self-doubt, it is time to change the record.
To recover our natural and historic role as an enterprising, outward-looking and truly global Britain, generous in temper and engaged with the world.
No one in the last few centuries has succeeded in betting against the pluck and nerve and ambition of this country.
They will not succeed today.
We in this government will work flat out to give this country the leadership it deserves, and that work begins now.
Thank you very much.

Boris Johnson has said the row over the border in Northern Ireland is being used to frustrate Brexit.
The foreign secretary insisted there were "very good solutions" to avoid the need for a hard border.
There is a stand-off on the issue with the EU publishing a legal draft of its Brexit withdrawal agreement.
An option for Northern Ireland to follow EU rules to avoid a "hard border" - if an alternative arrangement is not agreed - has sparked a row.
The Democratic Unionist Party, which offers vital support in key votes to the Tory government, says details of the draft treaty have "fundamentally breached" an agreement reached in Brussels late last year.
Conservative Brexiteers say it is "completely unacceptable" and would effectively annex Northern Ireland.
The European Union's chief negotiator, Michel Barnier, unveiling the draft agreement, described this Northern Ireland border option as a "backstop" if no other proposals are found. And a former EU commissioner said it was down to the UK to come up with a solution, warning that "at a high pace we are heading to the cliff edge".
BBC assistant political editor Norman Smith said it was shaping up to become "the big Brexit bust-up" with both sides of the argument refusing to budge.
Mr Johnson faced criticisism on Tuesday for suggesting in a BBC interview the issue of the border could be managed as easily as London's congestion charging zone.
Speaking to Sky News on Wednesday, he said: "What is going on at the moment is that the issue of the Northern Irish border is being used quite a lot politically to try and keep the UK in the customs union - effectively the single market - so we cannot really leave the EU. That is what is going on."
"If the EU or Dublin believes the UK government will be signing up to a border in the Irish Sea, they are deluded," said senior DUP member Sir Jeffrey Donaldson.
Mr Donaldson argued the draft divorce treaty would also undermine the constitutional status of Northern Ireland in the Belfast Agreement.
That 1998 treaty - also known as the Good Friday Agreement - between the British and Irish governments and most political parties in Northern Ireland decided how the region would be governed and brought an end to 30 years of sectarian conflict.
Former Brexit minister David Jones told BBC Radio 4's Today programme the EU was proposing that Northern Ireland stay in the customs union, and subject to the jurisdiction of the European Court of Justice.
"That effectively amounts to an annexure of Northern Ireland by the European Union," he said, adding: "I think that it would be pretty catastrophic and I think that the European Union in actually proposing this is behaving wholly irresponsibly."
But former EU trade commissioner Karel de Gucht said: "If you have another solution then please come up with it."
All of the UK's proposals so far have been "mutually incompatible", he added.
And Irish Prime Minister Leo Varadkar told RTE that in order to avoid the backstop being triggered,  "it is up to the UK to bring proposals to the table to make that possible".
He added: "It's not OK for people, whether pro-Brexit politicians in Britain, people or parties in Northern Ireland, to just say 'no' now."
The draft document aims to encapsulate - in legally binding language - agreements already reached on Ireland, citizens' rights and the UK's so-called "divorce bill".
It mandates that during the Brexit transition, which it says should last only until the end of 2020, the UK must continue to comply with all existing EU legislation. It would however lose all voting rights and decision-making power, including on any rules adopted by the 27 remaining member states.
EU negotiator Michel Barnier has said the document will not contain any surprises because it translates the political pledges made by both sides in the talks so far.
"The clock is ticking; time is short," Mr Barnier said at a news conference on Tuesday. "I am concerned."
Theresa May wants trade to be frictionless across the Irish border after Brexit.
But there is plenty of political friction as every potential solution seems to bring a new problem.
In a leaked letter designed to demonstrate that there would be no need for new infrastructure between Northern Ireland and the Republic, Boris Johnson used a potentially toxic phrase: "even IF there is a hard border".
This allowed critics to suggest that a regime of border checks which would be anathema to republicans, nationalists and the Irish government was being contemplated.
Downing Street swiftly reiterated its commitment to no hard border.
But one of the solutions - indeed, the most detailed option - being put forward by the EU would keep Northern Ireland aligned with EU regulations.
The DUP's Jeffrey Donaldson has said the government cannot sign up to what would in effect be a border in the Irish Sea.
And with rebellions threatened by some of her own backbenchers, Mrs May is likely to need the DUP's MPs to deliver the Brexit she's promising.
The prime minister's office has categorically dismissed any prospect of a return to a "hard border" in Ireland as a consequence of Brexit.
The statement on Tuesday evening followed the leak of a letter to the prime minister from Mr Johnson, in which he appeared to contemplate the possibility of future customs border checks, after the UK, including Northern Ireland leaves the EU customs union.
The leaked letter, obtained by Sky News, quoted Mr Johnson telling the prime minister the return of a hard border on the island of Ireland would continue to leave 95% of traffic to pass unchecked.
Following the letter's emergence, Labour called for Mr Johnson - one of the leading Brexiteers in the cabinet - to be dismissed "before he can do any more damage".
A spokesman for Mr Johnson said the letter was "designed to outline how a highly facilitated border would work and help to make a successful Brexit".
"It shows how we could manage a border without infrastructure or related checks and controls while protecting UK, Northern Ireland, Irish and EU interests."

Boris Johnson says there should be "no doubt" the only alternative to the Brexit proposals he will put to Brussels later is no-deal.
Addressing his party conference in Manchester, the PM said his plan would be a "compromise by the UK", but he hoped the EU would "understand that and compromise in their turn".
The European Commission said they will "examine [the proposals] objectively".
The Irish PM said he had not seen the plans but was "not encouraged".
Leo Varadker told the Irish Parliament: "What we are hearing is not encouraging and would not be the basis for agreement."
The UK is set to leave the EU on 31 October.
The government has insisted it will not negotiate a further delay beyond the Halloween deadline, saying this would be unnecessary and costly for the UK.
However, under the terms of a law passed by Parliament last month, the PM faces having to request another extension unless MPs back the terms of withdrawal by 19 October - two days after a summit of European leaders.
The European Commission's President Jean-Claude Juncker and Mr Johnson will speak on the phone later, and the two sides' negotiating teams will also meet.
In his speech, Mr Johnson said no-deal was not an outcome the government was seeking, but "it is an outcome for which we are ready".
On the eve of his speech, Mr Johnson told a conference fringe meeting, hosted by the DUP, that he hoped to reach a deal with the EU over the course of "the next few days".
The issue of the Irish border - and how to keep it free from border checks when it becomes the frontier between the UK and the EU - has been a key sticking point in Brexit negotiations.
Mr Johnson has said the solution reached by the EU and Theresa May, the backstop, is "anti-democratic" and "inconsistent with the sovereignty of the UK", claiming it offered no means for the UK to unilaterally exit and no say for the people of Northern Ireland over the rules that would apply there.
The PM used his speech to confirm parts of his offer to the EU.
He said that "under no circumstances" would there be checks at or near the border in Northern Ireland and the proposals would respect the peace process and the Good Friday agreement.
It included promising "a process of renewable democratic consent" for the Stormont Assembly on its relationship with the EU going forward.
He also referred to the use of technological solutions to ensure there was no hard border on the island of Ireland.
He said he did not want a deal to be out of reach "because of what is essentially a technical discussion of the exact nature of future customs checks when that technology is improving the whole time".
Mr Johnson also said he would "protect the existing regulatory arrangements for farmers and other businesses on both sides of the border".
He added: "At the same time we will allow the UK - whole and entire - to withdraw from the EU, with control of our own trade policy from the start."
The PM said this would "protect the union".
Echoing the main slogan of the conference, Mr Johnson said: "Let's get Brexit done on 31 October…to answer the cry of those 17.4 million who voted for Brexit [and] for those millions who may have voted Remain, but are first and foremost democrats and accept the result of the referendum."
He said the Tories were "not an anti-European party" and the UK is "not an anti-European country".
The PM added: "We love Europe. We are European.
"But after 45 years of really dramatic constitutional change, we must have a new relationship with the EU."
This speech was hugely important for Boris Johnson's Brexit deal.
Be in no doubt that amongst those listening most closely, most intently, will be leaders in other European capitals, trying to gauge whether Mr Johnson is serious about a Brexit deal or whether he is paving the way for no-deal and looking to blame the EU.
This was actually a rather surprising speech because there was none of the aggressive, combative language that we had been expecting - none of the in your face, take it or leave it final offer that we were told would form the guts of his argument.
Instead, it seemed Mr Johnson went out of his way to adopt a rather more emollient approach, saying how much he loved Europe, how the Tory Party wasn't an anti-European party and how Britain wasn't an anti-European country.
What that meant was that Mr Johnson didn't endeavour to bring the house down in the conference hall. He didn't go for the easy Brussels bashing, and for the wider viewers in this country, there were no brand new policy announcements.
You sense Mr Johnson has calculated for the next few hours and days that the really crucial audience in terms of his premiership, and for his future, is not here in Manchester - it's in capitals around the EU.
Before Mr Johnson's speech, a European Commission spokeswoman said they would examine the proposals objectively, adding: "We will listen carefully to the UK."
She said the EU wanted to agree a deal with the UK, saying "an orderly withdrawal is far more preferable than a 'no-deal' scenario".
But the spokeswoman also reminded the UK of its "well-known criteria",  saying: "In order for there to be a deal, we must have a legally operational solution that meets all the objectives of the backstop.
"[That means] preventing a hard border, preserving North-South cooperation and the all-island economy, and protecting the EU's Single Market and Ireland's place in it."
Leo Varadker said he would work until the last moment to secure an agreement, but he added: "We will not do so at any cost, and we are ready for no-deal if that's what the British decide to do."
The BBC's Europe editor, Katya Adler said the bloc wanted to do a deal and needed to be seen to try.
But she added it was "fundamentally misunderstanding the EU" if the prime minister believed the other 26 EU leaders will turn round to Ireland and say they have to accept the proposals just they want to have a deal.
There were huge rounds of applause for Mr Johnson from within the conference hall, showing support from his party.
After the speech, one member said the PM was "exactly what we need", while another said she had been "inspired", adding: "We are so fed up with nothing happening, but we feel like something will happen now because we think he will deliver."
Leaving the hall, Tory MP Mims Davies described her leader as "bombastic Boris", saying: "That [speech] was a message to the country, a message to our party and a message to the EU - we are ready to get on with this."
But the PM's plan has been branded as "extreme" and "doomed to failure" by the SNP's Westminster leader, Ian Blackford, who said his strategy was leading towards a no-deal.
Shadow chancellor John McDonnell said the prime minister's speech was "absolute bluster" and he described it as a "cynical manipulation to get a no-deal".
Mr McDonnell also that any Brexit deal or no-deal should be put to the people to make the final decision.
The director general of the CBI, Dame Carolyn Fairbairn, praised the PM's "optimistic vision for the UK".
But she said his plan "relies on a good Brexit deal".
"The UK is at a crossroads," she said. "[And] the no-deal turning ends in a very different place: a swamp that will slow the UK's every step for years to come."
The PM also used the opportunity to criticise Parliament, saying it "refuses to deliver Brexit, refuses to do anything constructive and refuses to have an election".
He said: "I am afraid that after three and a half years people are beginning to feel that they are being taken for fools."
Mr Johnson said the Tories were "the party of the NHS" because of their belief in capitalism, adding: "We understand the vital symmetry at the heart of the modern British economy between a dynamic enterprise culture and great public services precisely because we are the party of capitalism."
He praised London as its former mayor, but pledged to "unlock talent in every corner of the UK", and ensure safety with his existing policies of 20,000 additional police officers and tackling county lines gangs.
And he repeated more policy announcements from the conference on infrastructure, education, law and order.
Mr Johnson concluded: "Let's get on with sensible moderate one nation but tax-cutting Tory government and, figuratively if not literally, let us send Jeremy Corbyn into orbit where he belongs.
"Let's get Brexit done [and] let's bring our country together."
Mr Johnson's conference speech clashed with Prime Minister's Questions.
Normally the Commons goes into recess for the Tory conference, but MPs voted against this amid the bitter fallout from the government's unlawful prorogation of Parliament.
Foreign Secretary Dominic Raab deputised for the prime minister, facing the shadow home secretary Diane Abbott over the despatch box.
He told MPs the government will present its written Brexit proposals to them later.
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Boris Johnson has told the BBC that Britain should reject any EU demands for a £50bn "exit bill" and follow the example of former PM Margaret Thatcher.
It has been reported that EU negotiator Michel Barnier has said the UK must continue to pay into the EU until 2020.
Mr Johnson said it was "not reasonable" for the UK to "continue to make vast budget payments" once it left the EU.
He cited Mrs Thatcher's success at the 1984 Fontainebleau Summit, when she threatened to halt payments to the EU.
Laura Kuenssberg: Thatcher to inspire UK 'Brexit bill' talks?
Poland fails to stop Tusk EU re-election
"I think we have illustrious precedent in this matter, and you will doubtless recall the 1984 Fontainebleau Summit in which Mrs Thatcher said she wanted her money back, and I think that is exactly what we will get," he told BBC political editor Laura Kuenssberg in BBC Two's Brexit: Britain's Biggest Deal.
"It is not reasonable, I don't think, for the UK having left the EU to continue to make vast budget payments, I think everybody understands that and that's the reality."
The UK won the rebate in 1984, after then prime minister Margaret Thatcher threatened to halt payments to the EU budget.
At the time the UK was then the third poorest member of the Community but was on course to become the biggest net contributor to the EU budget.
Asked about Mr Johnson's comments, Mrs May said "there was only ever one Margaret Thatcher" and insisted the British people did not vote for Brexit to keep paying "huge sums" into the EU budget.
The Daily Telegraph has reported that Mr Barnier raised the idea that the UK may have to pay 60bn euros (£52bn) to cover the UK's share of outstanding pension liabilities, loan guarantees and spending on UK-based projects until 2020 - even if it leaves the EU by 2019.
Irish premier Enda Kenny suggested he may back demands for the UK to pay a "divorce bill" when it leaves the EU, telling reporters at the summit on Thursday: "When you sign on for a contract, you commit yourself to participation.
"And obviously the extent of that level of money will be determined. Mr Barnier is the lead negotiator for the European Union and obviously Britain will have a say.
"But that no more than any other problem will have to be faced, it will have to be dealt with and it will be dealt with."
Meanwhile, in London, ministers have cleared time for MPs to vote on reversing Lords Brexit bill amendments.
Commons Leader David Lidington announced that the bill will be debated by MPs on Monday, 13 March.
Ministers hope to overturn peers' calls for a "meaningful" parliamentary vote on the final terms of the UK's withdrawal from the EU.
They also want to reverse a Lords defeat on the issue of guaranteeing the rights of EU citizens in the UK.
At the summit, the 28 EU leaders discussed migration, security and economic growth, but the meeting began with a vote backing former Polish prime minister Donald Tusk remaining European Council president - a move opposed by Poland's government.
Polish Prime Minister Beata Szydlo had accused predecessor Mr Tusk of interfering in the country's domestic affairs.
The president is elected by the European Council by a qualified majority, which means that no single country can veto it.
At the summit, Mrs May called for more action to counter "Russian disinformation" and "raise the visibility" of Western commitment in the western Balkans, where Moscow faces allegations of helping to plot a coup attempt in Montenegro.
She is leaving the summit on Thursday.
The other 27 leaders are expected to use Friday's informal meeting to discuss the next summit in Rome on 25 March, which will celebrate the EU's 60th anniversary.
A government source suggested Mrs May, who plans to trigger Article 50 this month - the mechanism that kick-starts the UK's departure from the EU - will not be attending the Rome summit.

It is fair to say it has been a confusing day, but what do we actually know tonight?
No 10 have prepared a proposal for a "Temporary Customs Arrangement", where the UK would retain close ties to the EU for an indeterminate period after the end of the transition period - past 2020 - in case none of their hoped for customs fixes come to pass.
They believed they had the support of senior ministers to publish it on Thursday, even without explicit and detailed discussions of the written paper itself in the inner Brexit cabinet, let alone the full gathering of senior ministers.
It became clear, however, and rather surprisingly to the outside observer, that the man in government who is meant to be in charge of the Brexit process was not completely on-board.
So the brakes have been slammed on publishing the paper until meetings and discussions between senior ministers tomorrow.
No 10 is trying to find a way of satisfying Brexit Secretary David Davis, who is not just concerned about the lack of time limit in this particular proposal, but also Downing Street's refusal so far to publish his hoped for Brexit blueprint before the end of this month, and a lack of decision about the government's preferred long term option on customs.
Again, therefore, No 10 has had to row back because it either didn't fully understand the level of unhappiness inside cabinet, or because they were aware of it but believed they could push on regardless - because the imperative of cracking on with the Brexit process is more important than political sensitivities at home.
Brexiteers on the Tory benches would have been likely to erupt at the current proposal with no end date. So, if David Davis' desires can be as one source suggested "managed" tomorrow, his fury may have avoided a wider revolt.
But Theresa May's internal critics believe this is yet another product of her reluctance to face down those in her party who want to impose their vision on her achingly slow journey to compromise.
Again, the government stumbles when trying to resolve its own internal contradictions, before being able to confront the EU 27.
This latest saga may yet be solved in the next 24 hours. But it is not impossible to imagine that it may not, with a potential, if perhaps not yet likely, resignation of David Davis.
And again, the irony is that the UK is tying itself in knots over a position that the EU is likely to reject.

The Liberal Democrats have won the Brecon and Radnorshire by-election, leaving new PM Boris Johnson with a working majority in Parliament of one.
Jane Dodds overturned an 8,038 majority to beat Conservative Chris Davies by 1,425 votes.
Mr Davies stood again after being unseated by a petition following his conviction for a false expenses claim.
It was the first electoral test for Mr Johnson just eight days after becoming prime minister.
It was also the quickest by-election defeat for any new prime minister since World War Two.
Now, with the thinnest majority, he will have to rely heavily on the support of his own MPs and his confidence-and-supply partners the DUP to get any legislation passed in key votes.
It was a bad night for Labour, whose vote share dropped by 12.4% as it was beaten into fourth place by the Brexit Party.
The result means the Lib Dems now have 13 MPs.
Ms Dodds, who is the Welsh Liberal Democrat leader, said: "My very first act as your new MP when I get to Westminster will be to find Mr Boris Johnson, wherever he's hiding, and tell him to stop playing with the future of our community and rule out a no-deal Brexit."
Mr Davies congratulated Ms Dodds saying "I wish her well for the future" and paid tribute to his family saying they had "a difficult time over the past few months".
The turnout was 59.6%, down from 74.6% at the general election, but it is the highest for a by-election since Winchester in 1997.
Neither Plaid Cymru nor the Greens fielded candidates, to try to maximise the Remain vote.
Tory party chairman James Cleverly told BBC Radio 4's Today programme it was a "very close result in a by-election in which the Lib Dems were expected to romp home comfortably".
In a message to Conservative MPs concerned about the government's Brexit policy he said the new prime minister had received a "clear mandate from parliamentarians" and an "even more thumping victory in the leadership election".
"I do think it's incumbent on all Conservatives to support the prime minister in what has been a long-standing Conservative policy," he said.
But recently-elected Liberal Democrat leader Jo Swinson said: "Boris Johnson's shrinking majority makes it clear that he has no mandate to crash us out of the EU."
She denied the party had "played" the system by striking a deal with Plaid Cymru and the Greens.
"I want to have a different voting system but we're working within the system that we have," she said.
Celebrating victory later on Friday morning with party activists, Ms Swinson said the Lib Dems were "winning again" and she would "fight to keep our country in the European Union".
Ms Dodds, 55, lives in the neighbouring mid Wales constituency of Montgomeryshire and is a child-protection social worker.
The Lib Dems have held the rural seat for all but nine of the last 34 years and lost at the 2015 general election.
Plaid Cymru leader Adam Price said the "spirit of co-operation" between the pro-Remain parties had led to Ms Dodds's election, as he called for another EU referendum.
"But if the prime minister is intent on a general election, he should know that Plaid Cymru and the other pro-Remain parties are committed to cooperating so that we beat Brexit once and for all," he said.
Wales Green Party leader Anthony Slaughter said its decision to withdraw from the by-election was "absolutely vindicated" by the result.
"The people of Brecon and Radnorshire have taken the opportunity to cut Boris Johnson's majority in Westminster to a highly unstable one, reducing further the risk of a disastrous crash-out Brexit," he said.
Labour leader Jeremy Corbyn called the result "disappointing".
He added: "The Liberal Democrats won it after doing a deal with Plaid Cymru and the Greens.
"I think that a lot of voters were determined to get rid of the Conservative, and they voted accordingly. So we were squeezed, but it's a place we have not held for a very long time. The area has changed a bit."
Prof Laura McAllister, from Cardiff University's Wales Governance Centre, said the result should not be read as a "resounding victory" for Remain.
She pointed out that the three Brexit-supporting parties had 2-3,000 votes more than the Remain alliance.
But she added: "There are always nuanced undercurrents to this. The reality is Brexit isn't the only issue people were voting on.
"People were probably voting on rural and local issues. We can never categorically say this was about Brexit."
Sir John Curtice, professor of politics at Strathclyde University, said the Conservatives were enjoying a "Boris bounce" and the result was encouraging for the party despite the loss.
But he added: "In an early general election, at the moment at least, the Conservatives would be at risk of losing."
He said the Lib Dems could pick up 40 or 50 seats, which would make winning a large overall majority "rather more difficult for the Conservatives".
By Jonathan Blake, BBC political correspondent
As the ballots were counted, the candidates looked on - neither the Tories nor the Liberal Democrats dared to claim victory or concede defeat.
One thing was certain, the result when it came would be close.
But a win is a win and the Lib Dems will shout this from the rooftops as proof they can cut through with an anti-Brexit message.
The Remain alliance proved to be a winning formula, as Plaid Cymru and the Green Party stood aside to give the Lib Dems a clear run against the Tories.
If the Brexit Party hadn't been standing, the Conservatives might have clinched it.
Labour will look hard at its disastrous result and wonder what might have been with a clearer message on Brexit.
And for the Tories, the people of Brecon and Radnorshire have delivered an unwelcome verdict on their former MP and the new prime minister.
Boris Johnson's hands were already tied in parliament and the ropes around his wrists have just been pulled a little tighter.
At one stage Labour feared it might lose its deposit and blamed voters switching tactically to the Lib Dems.
A Welsh Labour spokesman said: "We always knew this was going to be a difficult night for us, but we're proud of our positive campaign in Brecon and Radnorshire."
"One thing is clear - voters have rejected Boris Johnson and his divisive, out-of-touch UK Tory government."
Political analyst Prof Roger Awan-Scully, from Cardiff University, said: "Labour need to look very closely at this result. Everything points to not just tactical voting for the Lib Dems but also dissatisfaction with Jeremy Corbyn and [First Minister] Mark Drakeford."
The Brexit Party's Des Parkinson, a retired police chief superintendent, who finished third, said: "If you look at the actual total of the vote, the Brexiteers won.
"It shows where the votes are but the prime minister has to deliver a clear Brexit... if he doesn't, then his government is in dire trouble."
The Monster Raving Loony Party pushed the UKIP candidate into sixth place.
Voters have also given their thoughts on the result.
Farmer Trevor Walters voted for Mr Davies and said the Tories might have won, had the Brexit Party not stood, but called the speculation over a Brexit no-deal fallout "scaremongering".
He added: "We're not going to be left in the lurch. I don't think for one second that'll happen. Something will be done to sweeten the blow of all that and get us engaged with a proper trade deal."
Independent book shop owner Emma Corfield-Walters, who backed the Lib Dems, said: "None of us know what's going to happen in the future.
"I think we're all entirely confused on the Brexit issue and I think this result shows us."

Hospitals are likely to experience delays to cancer testing and treatment regardless of the result of next week's Brexit vote, BBC Newsnight has learned.
The Royal College of Radiologists has told doctors to prepare for possible delays for some drugs used to detect cancer if there is a no-deal Brexit.
It says clinicians should reduce their workload in the days after 29 March, when the UK is due to leave the EU.
The government said it had "robust" plans for however the UK leaves the EU.
MPs will vote on Prime Minister Theresa May's Brexit withdrawal agreement by 12 March.
If Parliament does not vote in favour of her deal and there is no extension of Article 50 - the two-year process for leaving the EU - the UK will leave with no withdrawal agreement, known as a no-deal Brexit.
The five-page guidance to doctors from the Royal College of Radiologists (RCR), seen by Newsnight, warns that some radiopharmaceutical suppliers "anticipate there may be some delay to their delivery times".
It advises clinicians to: "Keep [your] workload lighter for the first week following a no-deal Brexit, in order to see more clearly what the impact is likely to be."
It adds: "In the weeks leading up to Brexit you should consider how to prioritise requests based on clinical need, should supplies be compromised."
The guidance refers to the radioisotopes commonly used in the diagnosis and treatment of some cancers.
These cannot be stockpiled in advance because of the rapid decay of their radioactivity and "a one-day delay to delivery would reduce available activity by approximately 20%", according to the guidance from the RCR.
A spokesman for the RCR told Newsnight the organisation now believed it was "inevitable" that uncertainty over Brexit would cause delays to some cancer tests and treatments.
Dr Richard Graham said: "Of course, now there will inevitably be delays to treatment as a result of the Brexit process because we need to start booking our lists for the post-Brexit date.
"We will need to book clinics less heavily so that we've got more wriggle room if we don't have the radioisotopes in order to diagnose and treat the patients."
Dr Graham said the RCR had met with the Department of Health and Social Care several months ago "when they were very optimistic that there would be a deal" and that the guidance would not be necessary.
"But unfortunately now it looks like no deal really is a tangible possibility, so it's vital that we get this guidance out now so patients treatment and diagnosis is disrupted at the bare minimum."
Dr Graham said it would have been "much easier" for medics if they had known that a no-deal Brexit was not going to happen.
"But of course we understand that might be a negotiating strategy to get the best deal for the country.
"Putting patients' health at risk for the sake of getting a good Brexit deal is a difficult priority to balance."
The Department of Health and Social Care has asked radiopharmaceutical suppliers to use air freight in the event of a no-deal Brexit, as that is expected to cause road disruption.
But the guidance states that "some companies feel their plans will ensure no delays but others anticipate there may be some delay to their delivery times".
And on one specific type of treatment, known as radionuclide therapy, it states that "only one supplier has been confident it will be able to deliver therapy doses on particular required days".
The radiologists' warning that it is now too late to escape some disruption - even if Mrs May secures majority Parliamentary support for her withdrawal agreement - follows similar statements from other sectors.
UK-based financial firms have already had to establish offices elsewhere in the EU in case they suddenly find themselves unable to service European clients from 29 March.
And surveys show that stockpiling by manufacturing firms is at the highest level on record due to the fear of a no-deal Brexit.
A Department of Health and Social Care spokesperson said: "Leaving the EU with a deal remains the government's top priority.
"As a responsible government we have robust contingency plans in place so patients can continue to have access to medicines, including medical radioisotopes, whatever the EU Exit outcome.
"We have worked with the pharmaceutical industry to ensure that planes are contracted to bring in medical radioisotopes under the appropriate specialist conditions and suppliers are working closely with the NHS to minimise any potential impact of changes to delivery times."

European Council President Donald Tusk has said he will appeal to EU leaders "to be open to a long extension" of the Brexit deadline, if the UK needs to rethink its strategy and get consensus.
His intervention came as UK MPs voted to seek a delay of the 29 March deadline to leave the EU.
EU leaders meet in Brussels on 21 March and they would have the final say.
Prime Minister Theresa May has said that if her Brexit deal is not approved a longer extension may be necessary.
After two resounding defeats in the House of Commons, she will make another attempt by 20 March to push through her Withdrawal Agreement with the EU.
MPs backed a government motion on Thursday to extend the two-year deadline to 30 June if the Mrs May's deal is passed next week, while noting that a longer extension would be necessary if it is rejected.
All 27 other EU nations would have to agree to an extension, and Mr Tusk, who is the bloc's summit chairman, will hold talks with several leaders ahead of next week's Brussels meeting.
While European Commission President Jean-Claude Juncker has insisted that any postponement "should be complete before the European elections" at the end of May, Mr Tusk made clear a longer delay was on the cards.
While he did not specify the length of the delay, officials suggested it would have to be at least a year if the UK prime minister's deal was rejected a third time.
Mr Tusk said earlier this year that the EU's hearts were still open to the UK if it changed its mind about Brexit. He provoked an angry reaction from pro-Brexit supporters when he said there was a "special place in hell" for those who had promoted Brexit "without even a sketch of a plan of how to carry it out safely".
So at this crucial point, what do Europe's leaders think about extending Article 50, the two-year treaty provision that the UK invoked on 29 March 2017?
Jenny Hill in Berlin
"A lot of the trust is gone." Among business and political figures in Berlin, there's growing frustration, even anger, at developments in Britain.
Nevertheless, Germany is likely to do all it can to help facilitate the orderly Brexit which Angela Merkel insists is still possible.
The German chancellor won't be drawn publicly on whether she would support an extension to Article 50, but it's widely accepted here that she and her government would be willing do so.
There are those who believe that support should be conditional upon Britain's ability to outline its reasons and expectations before such an extension is granted. And there are significant concerns about the impact of a longer extension upon the EU elections but Germany's interests lie in avoiding a no-deal Brexit – and the damage that could wreak on the German economy.
Its government will do what it can to achieve that aim.
Dr Norbert Roettgen, who chairs the foreign affairs committee, urged Britain and the EU to take their time.
"Everything is hectic, hysterical, unclear. Let's slow down and try to get a clear head," he said. "The world will not end if we all take time for a breather, focus on important points."
"If we try to rush a result now it will definitely go wrong."
Hugh Schofield in Paris
As a "frontline" country which effectively shares a border with the UK – thanks to the Channel Tunnel –  France has more to fear than most from a no-deal Brexit.
Yet when it comes to granting London more time, President Emmanuel Macron is expected to insist on conditions.
He will not approve an extension if it simply means putting off the pain.
A "technical" extension of a few weeks would be an easy matter, according to Elvire Fabry of the Jacques Delors Institute in Paris.
Even if the House of Commons had approved Theresa May's plan on Tuesday, such an extension would probably have been inevitable, and automatically approved at the EU summit next week.
"But a longer extension poses all sorts of problems. No-one is comfortable with the idea of the UK taking part in the EU elections in May. It would be a most unwelcome distraction," Ms Fabry said.
"So for a longer extension there would have to be a very clear and precise objective written in - for example new elections in the UK or a new referendum."
She said that Brussels "was pretty favourable" to the idea – but in the last few days things had changed.
"No-one over here is saying, 'let's just get it over with and have a No Deal.' That fatigue seems to be gaining ground in the UK, but not in Europe."
"Here everyone is exhausted and impatient – but we feel there is nothing much more we can do. It's the Brits who have to sort this out among themselves."
Adam Easton in Warsaw
"The British people have decided the UK should leave, it should be concluded. Otherwise it would be a humiliation."
That's how one MEP from the governing party, Ryszard Legutko, put it, adding: "A second referendum or too long an extension would also be a humiliation".
Top officials are a little more gentle.
Poland's foreign minister, Jacek Czaputowicz, has said the UK may need a little more time.
"We are watching what is happening in the UK - the votes, there are certain expectations about how they will end. Maybe we will need to… extend this period a bit, maybe a little more time is needed for reflection," he told reporters in the Polish parliament.
"From our point of view a no-deal Brexit is the worst solution."
For Warsaw, securing the rights of the estimated one million Poles living in the UK has always been and remains the number one priority, and the two governments are in "constant contact".
But Poland is hoping for a deal and a smooth transition period. That's because the UK is Poland's third-largest sales market.
Anna Holligan in Rotterdam
Dutch Foreign Minister Stef Blok has told the BBC his country would look "with benevolence" at any request to extend Article 50. But "without a clear goal an extension won't solve anything", he warned.
The mantra "hope for the best, prepare for the worst" underpins the Dutch approach, and Mr Blok was at an event showcasing the government's preparations for a no-deal exit.
"I'm looking forward to any solution that will solve the problem, but that has to come from London now."
The Dutch never wanted the UK to leave the EU but respected its choice. Now they view any possible extension a little like tearing off a sticking plaster. Ideally it should be done rapidly to get the pain over with.
"We're living in the reality Brexit has dealt us", says foreign trade minister Sigrid Kaag, gesturing towards a stream of trucks trundling on to a ferry bound for the UK port of Felixstowe.
"(The Netherlands) is your natural gateway to Europe. With a stable government. We're not sitting idle, we're not panicking, we're getting ready for any eventuality."
James Reynolds in Rome
Italy would support an extension of Article 50 on two conditions:
Italy believes that the UK government is genuine when it says it doesn't want No Deal, a senior Italian official, who asked not to be named, told the BBC.
But, at the same time, Italy is not shy about preparing for No Deal. In the next few days, the government is hoping to pass a package of laws aimed at addressing its priorities : citizens' rights, financial stability, help for businesses.
Next week, the Rome government expects to roll out a series of information sessions in ports around the country to explain how No Deal would work.

The international border between Northern Ireland and the Republic of Ireland is about 310 miles long with, depending on how many tracks you include, as many as 275 crossing points.
In reality, the entire border is a crossing point because, apart from road signs changing from miles per hour to kilometres per hour, there is no physical infrastructure to see.
The concern is that all that could change when the UK leaves the European Union, and Ireland stays as an EU member state.
Part of the concern is political. The 1998 Good Friday Agreement, the basic building block of peace in Northern Ireland, removed security checkpoints from the border and helped make it all but invisible. Customs checks could undermine much of that progress.
Like many peace deals, the Good Friday Agreement is a masterpiece of creative ambiguity, allowing different people to take different things from different parts of the text.
Shared membership of the European Union made that much easier to achieve. Ireland wants a clear written commitment that the agreement will be respected in all its parts.
The other concern of course is economic. The economies of Northern Ireland and the Republic are completely interconnected. Huge amounts of goods and services cross the border every day without checks of any kind.
Brexit negotiators are currently looking through more than 140 areas of north-south co-operation, involving everything from the single electricity market to environmental protection.
It is also estimated that at least 30,000 people cross the border every day for work. The movement of people is governed by the Common Travel Area between the UK and Ireland, which predates the EU.
Both sides are determined that the Common Travel Area will remain in place, but that in itself doesn't resolve the challenge of a hard border re-emerging.
Because the UK has announced that it is leaving the EU single market and the customs union. That immediately turns the internal border in Ireland into an external border for the single market and the customs union - with all the potential checks that implies.
At the moment, all rules and regulations, north and south, are exactly the same - on food safety, on animal welfare… you name it.
Again, it's a relationship based in large part on agreements covered by joint membership of the EU. As soon as that changes, border checks may have to begin again.
That's why the Irish government wants a written guarantee from the UK that Northern Ireland will continue to follow EU rules - so goods can continue to move freely across the border.
"It seems essential to us," said the Irish Foreign Minister Simon Coveney earlier this month, "that there is no emergence of regulatory divergence from the rules of the internal market or the customs unions which are necessary for meaningful north-south co-operation, or an all-Ireland economy that is consistent with the Good Friday Agreement."
In other words, both Ireland and the rest of the EU are suggesting that Northern Ireland should stay within the customs union and the single market.
Yes. It would - in effect - push the customs border out into the Irish Sea... an internal customs border, if you like, between Northern Ireland and Great Britain.
Would that be acceptable to the UK government, or to its Unionist political allies in Northern Ireland, the DUP? In a word, no.
"We respect the European Union desire to protect the legal order of the single market and customs union," the UK's Brexit Secretary David Davis said in Brussels recently.
"But that cannot come at a cost to the constitutional and economic integrity of the United Kingdom."
If it did that then, under World Trade Organization rules, it would have to do the same for the rest of the world. The UK economy would be swamped with cheap imports.
The EU would impose checks anyway which might allow the UK government to shift the blame on to Brussels. But that would be a pretty futile gesture.
If it was easy, it would already have been done.
The EU argues that the UK's red lines on Ireland - no border on the one hand, and UK exit from the single market and the customs union on the other - are fundamentally incompatible.
The British government has spoken of technological fixes such as pre-screening of goods, and trusted trader schemes.
The EU says such things could speed up border transit, but it would be nowhere near enough to avoid the return of some border checks.
Alternatively, Irish officials argue that there are already cases of rules and regulations being different in Northern Ireland than in the rest of the UK, and they point to other examples such as Hong Kong in China where there are different regulatory arrangements within sovereign states.
Intense negotiations are taking place to try to come up with a solution that would ensure a) no divergence of regulations in key areas; and b) the creation of some form of customs partnership on the island of Ireland, which doesn't threaten the constitutional order of the UK.
But if a fix emerges that seems to turn Northern Ireland into a back door route into the single market, then other EU countries will cry foul.
So even if all parties agree in the next two weeks that "sufficient progress" on Ireland has been made, there will be a long way to go before any kind of lasting solution emerges.
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The pavement cafes and bars were packed last Sunday as Brussels basked in an unseasonably warm weekend.
Among the drinkers were diplomats from the EU member states who had been kept in the dark ever since negotiators from the European Commission and UK had entered an intense and secret period of talks, jokingly known as "the tunnel".
"You can have a couple but not too many," advised one official close to the talks, hinting that movement was imminent.
After more than a week of radio silence, the rest of the European machine believed that a provisional agreement on the Brexit divorce treaty was just hours away.
The aperitifs were abandoned after the UK announced that Brexit Secretary Dominic Raab would be in Brussels for face-to-face talks with his opposite number Michel Barnier.
Ambassadors from the 27 other member states were told to prepare for an early-evening briefing. Diplomats said the mood music was good.
But British sources warned the situation was not as positive as it appeared and there were still serious outstanding issues, particularly with the so-called "backstop" - the back-up plan to avoid to a hard border on the island of Ireland that could see Northern Ireland staying in the EU's customs union.
A tweet from Michel Barnier changed the mood.
Negotiations would be "paused" until EU leaders gathered for a Brexit-themed dinner on Wednesday. Both sides sounded seriously depressed.
The Politico website then claimed that officials had reached a deal at a technical level that "collapsed" when the Brexit Secretary became involved.
It made British civil servants desperate to prove that the prime minister's European adviser, Olly Robbins, had not drafted his own deal that had angered his political masters.
By Monday morning, Downing Street had coined a new phrase to explain the stumbling block: the "backstop to the backstop".
It was a way to rebrand the EU's insistence that Northern Ireland should stay in the customs union in the event no other solutions were found to avoid the need to reintroduce a border.
Theresa May reminded the House of Commons of her alternative of a UK-wide customs arrangement with the EU, which had been tabled in the summer as a "Temporary Customs Arrangement".
Previously described as a "bridge" between the post-Brexit transition (or "implementation") phase, it was now "our backstop".
Brussels noted with approval that the prime minister had talked about a process for deciding when it should come to an end instead of a date - a formula that was "event-driven" rather than time-specific.
It was also much closer to the phrase agreed with the EU that any backstop would be in place "unless and until" another solution is found.
And it would be legal for the EU to commit to during the Brexit process whereas a permanent customs solution was not, confirmed a European official who quoted the European treaties.
Meanwhile, it was suggested privately that the two sides had found a way to address the other half of the Irish border problem: keeping Northern Ireland aligned with the rules of the single market needed to avoid checks on the Irish border, but not necessarily avoiding them between Northern Ireland and Great Britain.
Theresa May also suggested that more progress had been made than people realised in the talks on the future relationship, including on financial services.
The day before EU leaders were to meet, Michel Barnier travelled to Luxembourg to update European affairs ministers.
He made a passing reference to the idea of extending the post-Brexit transition phase but gave few details. The UK seemed relaxed about the story despite the fact it would dominate the rest of the week.
Then came the first of a three-day marathon of seven separate summits in Brussels.
Every EU leader spoke from the same script on Brexit: there was no decisive progress but they wanted to carry on talking.
"Do no harm and avoid anyone feeling offended when they leave," was the slogan.
Theresa May was given a 15-minute slot in which to make her case. A diplomat said she spoke so quickly it was as if she had a plane to catch.
The other leaders dined on pan-fried mushrooms, turbot and sorbet without the prime minister.
Inside the room Irish Taoiseach Leo Varadkar brandished a copy of an Irish newspaper, with a front page devoted to a murder during the Troubles to demonstrate Ireland's emotional case alongside its economic one.
Outside the room, European officials stuck to their concept of a Northern Ireland-only backstop but said they were prepared to "camouflage" it to make it as palatable as possible to the British.
One compared it to a child being distracted from a bowl of spinach by filling the table with more appetising food.
A potential extension of the transition period was part of this effort.
It was a possibility that Mrs May was "cautiously" open to, an official confirmed. The president of the European Parliament, Antonio Tajani, said the same.
Dinner ended with the leaders saying there would be no planning for a Brexit summit in November, but leaving the door open to one if the negotiations made progress.
Talk of no deal - often perceived as a hostile act - was kept to a minimum.
And officials reassured British journalists that a late-night drink featuring Angela Merkel, Emmanuel Macron and others - but not Theresa May - was a celebration of the Luxembourgish election results rather than a "screw you" to the UK.
"You guys are so paranoid," said an ambassador.
Disaster had been avoided but the transition proposal had created a domestic political nightmare for the prime minister.
Downing Street was now trying to play the proposal down: "Just an idea…. it'll never be used."
Their focus was getting a legally binding reference to a UK-wide customs arrangement into the paperwork that would comprise the final Brexit deal, and they were exasperated that media coverage of the summit was dominated by the transition issue.
Then there was confusion when European Council President Donald Tusk said during a press conference that the 27 leaders had not discussed the concept, and yet European Commission President Jean-Claude Juncker said it would "probably" end up happening.
"Chaotic and un-coordinated" is the way one European diplomat described the Brexit component of the summit.
He blamed too little planning, a lack of precision from the European Commission and not enough co-ordination among the member states.
As the EU's multiple summits came to an end, Theresa May's fellow leaders suggested that the negotiations could not restart until the prime minister acknowledged that the Withdrawal Agreement had to contain an option for the backstop that might apply to Northern Ireland but not the rest of the UK.
The UK would also have to accept that its aspiration of truly friction-less trade could only be achieved by staying in the EU's customs union and sticking to the rules of the single market.
In other words: there are some tasty goodies on offer, but Britain will only be invited back to the table when it is prepared to eat its greens.
Listen to Adam Fleming and the rest of the BBC's Brexitcast team for the lowdown from Brussels and Westminster

Theresa May faces a battle to get a key piece of Brexit legislation through Parliament, opponents have warned.
Shadow Brexit Secretary Sir Keir Starmer said it was "highly likely" Labour would seek to amend the Repeal Bill, which aims to convert EU legislation into British law.
The SNP, Lib Dems and Green MP Caroline Lucas will also press for changes.
The bill, described by the PM as an "essential step" to EU withdrawal - was the centrepiece of the Queen's Speech.
It will repeal the 1972 European Communities Act, which took Britain into the EU and meant that European law took precedence over laws passed in the British parliament.
It starts its Parliamentary journey next week but it is not likely be debated on the floor of the Commons until the autumn, with some predicting fireworks as MPs on all sides bid to change Mrs May's approach to Brexit in a series of votes.
Last month, 49 Labour MPs defied party leader Jeremy Corbyn by backing a Queen's Speech amendment calling for Britain to stay in the single market and customs union after Brexit.
Conservative backbenchers opposed to what they regard as a "hard Brexit" are also reported to be plotting to force changes to the Repeal Bill.
Labour rebels are understood to be planning to join forces with Tory rebels, the Lib Dems and the SNP to force changes to the Repeal Bill, and future pieces of Brexit legislation.
The Labour leadership backs an exit from the single market but wants to protect EU safeguards on employment rights and the environment - and is concerned these could be scrapped or watered down by the Repeal Bill.
Speaking to BBC Radio 4's Today programme, Sir Keir said the Labour leadership was likely to table amendments that would seek to curb the power of government ministers to amend or scrap EU laws without MPs' scrutiny.
He said: "I think it's highly likely we will want to table that push amendment dealing with the scope of power given to the executive but also to concentrate on issues such as enforcement of rights and protections."
Green Party co-leader Caroline Lucas told the programme she was also preparing to amend the Bill, while the SNP's Stephen Gethins said his party "had a responsibility" to work with others over the terms.
Former Brexit minister David Jones, who lost his frontbench role in the post-election reshuffle, said Labour should back the government over the Bill after promising to deliver Brexit in its manifesto.
Pressed on the scale of the challenge, he told the Today programme: "Clearly there is huge pressure, though, having said that, I have no doubt that we will be able to do it."
Of 27 Bills and draft Bills in the Queen's Speech, eight were devoted to leaving the EU.
In addition to the Repeal Bill, there were separate pieces of legislation on  on customs, trade, immigration, fisheries, agriculture, nuclear safeguards and the international sanctions regime.

David Davis, who has been leading UK negotiations to leave the EU, has quit his role as Brexit Secretary
He told the BBC that he was no longer the best person to deliver the PM's Brexit plan - agreed by the cabinet on Friday - as he did not "believe" in it.
He said the "career-ending" decision was a personal one but he felt the UK was "giving away too much and too easily" to the EU in the negotiations.
Mrs May said she did not agree but thanked him for his work.
The resignation is a blow to Mrs May as she seeks to win over Eurosceptic MPs to her proposed Brexit vision, which would form the basis of the UK's position in on-going talks with the EU.
Dominic Raab, who campaigned for Leave during the UK's 2016 EU referendum, has been promoted from housing minister to take over from Mr Davis.
The UK is due to leave the European Union on 29 March 2019, but the two sides have yet to agree how trade will work between the UK and the EU afterwards.
There have been differences within the Conservative Party over how far the UK should prioritise the economy by compromising on issues such as leaving the remit of the European Court of Justice and ending free movement of people.
Mrs May's Conservative Party only has a majority in Parliament with the support in key votes of the 10 MPs from Northern Ireland's Democratic Unionist Party, so any split raises questions about whether her plan could survive a Commons vote - and has also led to renewed questions about whether she will face a challenge to her position.
In a sign of how delicately positioned the numbers are on Brexit strategy it has emerged that the government has taken the unusual step of arranging a briefing for opposition Labour MPs on the detail of the Brexit plan agreed on Friday.
In his resignation letter, Mr Davis told Mrs May that "the current trend of policy and tactics" was making it "look less and less likely" that the UK would leave the customs union and single market.
He said he was "unpersuaded" that the government's negotiating approach "will not just lead to further demands for concessions" from Brussels.
Mr Davis, who was appointed Brexit Secretary in 2016, said: "The general direction of policy will leave us in at best a weak negotiating position, and possibly an inescapable one."
In her reply, Mrs May said: "I do not agree with your characterisation of the policy we agreed at cabinet on Friday."
She said she was "sorry" he was leaving but would "like to thank you warmly for everything you have done... to shape our departure from the EU".
Mr Davis told BBC Radio 4's Today programme that he had objected to Theresa May's plan at the Chequers meeting, telling cabinet colleagues at the outset that he was "the odd man out".
He said it was "not tenable" for him to stay in post and try to persuade Tory MPs to back the policy when he did not think it was "workable".
"The best person to do this is someone who really believes in it, not me."
He said he feared the EU would seek to further water down the UK's plans and his resignation would make it easier for the UK to resist attempts to extract further concessions.
Mr Davis told BBC political editor Laura Kuenssberg that he had been compromising for two years and that the latest plan was "a compromise too far".
But Mr Davis insisted he continued to back Theresa May, saying that if he "wanted to bring her down", the time would have been after she failed to win last year's general election outright.
A leadership contest now would be "the wrong thing to do", adding: "I won't throw my hat into the ring."
Eurosceptic MP Steve Baker has also resigned. He played a leading role in the Brexit campaign in the run up to the 2016 referendum. He was promoted to the Department for Exiting the EU as a parliamentary under-secretary in June last year.
Conservative MP Peter Bone hailed Mr Davis's resignation as a "principled and brave decision", adding: "The PM's proposals for a Brexit in name only are not acceptable."
Labour Party chairman Ian Lavery said: "This is absolute chaos and Theresa May has no authority left."
By BBC political editor Laura Kuenssberg
After many months of rumours that he would pull the plug, David Davis has actually quit as Brexit Secretary.
His unhappiness in government has been no secret for some time, but after the prime minister's Chequers agreement with cabinet ministers to pursue closer ties with the EU than he desired, he found his position untenable.
After a visit to Downing Street on Sunday he concluded that he had no choice but to walk.
The move, while not completely surprising, throws doubt on to how secure the government's Brexit strategy is.
Read Laura's full blog here
Mrs May is due to address MPs on Monday afternoon and is expected to tell MPs that the strategy agreed by the cabinet at Chequers on Friday is the "right Brexit" for Britain.
Brexiteer MP Jacob Rees-Mogg said it would be "very difficult" for Mrs May's plans to win the backing of MPs without Mr Davis.
He told BBC 5 Live: "These proposals will have to come to the House of Commons in legislation and the question is 'will they command support from Conservative MPs?'
"And I think without David Davis there, without his imprimatur, it will be very difficult for them to get the support of Conservative MPs and therefore the prime minister would be well advised to reconsider them."
BBC political editor Laura Kuenssberg said she understands Mr Davis was "furious" after a meeting at No 10 earlier on Sunday and "concluded he could not stay in post".
The resignation came as people awaited the verdicts of senior figures from the Brexit side of the 2016 referendum.  There has yet been no on the record comment from Foreign Secretary Boris Johnson, while Environment Secretary Michael Gove told the BBC on Sunday he was urging Tory MPs to support Mrs May.
One of the leading pro-Remain Conservative MPs Anna Soubry did not refer directly to Mr Davis's resignation, but tweeted it was "not the time for egos, grandstanding and blind ideology".
The director-general of the CBI, Carolyn Fairbairn, said the resignation was "a blow", adding that business had welcomed the agreement of ministers on Friday.
Meanwhile, some Remain-supporting politicians said the resignation was evidence of the need for a second referendum.
Lord Adonis, a prominent backer of a second vote, tweeted: "People's Vote to put Brexit out of its misery a big step closer after DD's resignation. Now the Brexiteers holding Mrs May hostage are falling out, there isn't a majority for any withdrawal treaty in Parliament."
The Liberal Democrats called on people to sign a petition for a vote on the proposed deal, adding: "The resignation of David Davis is yet more evidence of the chaos of this Tory Brexit. You deserve the final say".
Nigel Farage congratulated Mr Davis for quitting and called for Mrs May to be replaced as prime minister, accusing her of being "duplicitous" and claiming her response "shows she is controlled by the civil service".

MPs are trying to influence the Brexit process in a number of ways, as Theresa May continues her bid to get the EU to change the deal.
The prime minister has asked MPs to approve a motion on Thursday simply acknowledging that process is ongoing and restating their support for the approach.
Several MPs tabled amendments setting out alternative plans and Commons Speaker John Bercow has selected three to be put to a Commons vote.
Even if they won the backing of a majority of MPs, the proposals would not be binding on the government. However, they could put pressure on Mrs May to change course.
She has adopted proposals from two successful backbench amendments tabled in January.
One asked her to seek alternatives to the "backstop", which aims to prevent the return of customs checkpoints on the Irish border in the event that no trade deal has come into force. The other rejected leaving the EU without a formal exit deal.
The selected proposals are below. Use our guide to Brexit jargon or follow the links for further explanation.
Required the government to either give MPs a vote on the withdrawal agreement and political declaration on future UK-EU relations by 27 February, or make a statement saying there is no longer an agreement in principle with Brussels and so allow MPs to vote on - and amend - its planned next steps.
Labour Leader Jeremy Corbyn's amendment was defeated by 322 votes to 306, giving the government a majority of 16.
Sought to postpone the Brexit date by at least three months.
This had the backing of Liberal Democrats, as well as the SNP contingent.
However, most Labour MPs abstained and so the amendment was defeated by 93 votes to 315.
Instructed the government to publish within seven days "the most recent official briefing document relating to business and trade on the implications of a no-deal Brexit presented to cabinet".
This had the backing of some mostly Remain-supporting Labour and Conservative backbenchers.
But Ms Soubry withdrew the amendment after Brexit Minister Chris Heaton-Harris indicated that Cabinet Office Minister David Lidington would meet her and would be publishing the relevant information.
Ms Soubry welcomed the move but said she reserved the right to lay the amendment again at end of February if the government did not publish the documents.

Prime Minister Theresa May has laughed off journalists' questions about going to war with Spain following the Gibraltar Brexit row.
Mrs May said her approach to negotiations was "definitely jaw jaw".
On Sunday ex-Tory leader Lord Howard said the PM would defend Gibraltar in the same way as Margaret Thatcher defended the Falklands in the 1982 war.
Spain's foreign minister said his government was "surprised by the tone of comments coming out of Britain".
"It seems someone is losing their cool," Alfonso Dastis told a conference in Madrid.
The current row was sparked by draft Brexit negotiating guidelines published by the EU last Friday saying any decisions affecting Gibraltar would be run past Spain.
The guidelines said: "After the United Kingdom leaves the Union, no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without the agreement between the Kingdom of Spain and the United Kingdom."
Speaking to reporters on a flight to Jordan, Mrs May was asked if - borrowing from a phase used by Winston Churchill - Britain's approach should be described as "jaw jaw, not war war".
"It's definitely jaw jaw," replied the PM, who laughed when asked to rule out a war with Spain.
"What we are doing, with all EU countries in the EU is sitting down and talking to them," she said.
"We're going to be talking to them about getting the best possible deal for the UK and for those countries - Spain included."
Mrs May said British policy on Gibraltar had not, and would not, change.
Gibraltar: key facts
Gibraltar's chief minister Fabian Picardo said: "Gibraltar is not a bargaining chip in these negotiations. Gibraltar belongs to the Gibraltarians and we want to stay British."
Mr Picardo urged European Council President Donald Tusk to remove the reference to Gibraltar.
"Mr Tusk, who has been given to using the analogies of the divorce and divorce petition, is behaving like a cuckolded husband who is taking it out on the children," he said.
The EU's guidelines followed a letter from Mrs May formally triggering Brexit talks, which did not mention Gibraltar directly.
Lord Howard raised the spectre of military action, saying that 35 years ago, "another woman prime minister sent a taskforce halfway across the world to protect another small group of British people against another Spanish-speaking country.
"And I'm absolutely clear that our current woman prime minister will show the same resolve in relation to Gibraltar as her predecessor did."
After Argentina invaded the Falklands in 1982, Margaret Thatcher sent a task force to reclaim the islands, in the South Atlantic.
An estimated 655 Argentine and 255 British servicemen lost their lives in the fighting that followed.
Former Labour foreign secretary Jack Straw, whose 2002 referendum asking Gibraltarians if they wanted Britain to share sovereignty with Spain was rejected by 99% to 1%, dismissed the threat of military action as "frankly absurd and reeks of 19th century jingoism", adding that Britain leaving the EU would result in "all sorts of problems" popping up.
"For the Spanish, Gibraltar is an affront to their sense of national identity and their sense of sovereignty - it's a bit like having a part of Dover owned by Spain," he told BBC Radio 4's Today programme.
Mr Straw said while Britain was in the EU "we held equal cards with Spain", but once it left, the situation would be reversed, with the 27 EU nations "holding the cards".
Lib Dem leader Tim Farron said of Lord Howard's comments: "In only a few days the Conservative right are turning long-term allies into potential enemies."
But Brexit Secretary David Davis, in Spain for meetings with members of its government, said Lord Howard was expressing the "resolve" of the UK in supporting the sovereignty of Gibraltar. He made it clear any talk of Falklands style taskforces "wasn't going to happen".
Former Labour minister Lord Foulkes used House of Lords' question time to ask why Gibraltar had not been mentioned in Mrs May's letter to the EU last week, which triggered the start of Brexit negotiations.
Foreign Office Minister Baroness Anelay of St John's replied, saying the government took the matter "so seriously" it did not want to mention just one aspect of the negotiations in a letter that set out general principles which all applied to Gibraltar.
Spain has long contested Britain's 300 year-rule of Gibraltar, which has a population of about 30,000.

Lots of things can be true at the same time, even though they seem to contradict each other. It happens a lot in politics as, if you read my ramblings here often, you'll know I've said before.
This time, lots of seemingly contradicting strands are combining to create a situation that is potentially dangerous for Theresa May, and not very helpful for the UK's case in the Brexit negotiations.
Yes, it is true that a powerful group of Brexiteers believe that they have been told by No 10, that any effort to water down the government's position on the Customs Union would be treated as a vote of confidence, to bring rebel Remainers to heel.
This is in the context not of this week's vote, which would not have any power to force a change of heart, but a vote that will have that authority next month.
It is also true that those potential rebel Remainers believe they have been assured by the government that they would NOT turn a vote on the customs union into a vote of confidence. They think they can try to shift Theresa May's position without collapsing the government, indeed they say the chatter about a confidence vote is a 'ruse' by the Brexiteers.
Downing Street says publicly that no such decision has been made. It's not surprising that in uncharted territory they don't want to be bound to one position now over a vote that's not for another month.
But it is also true that No 10 cannot sustain a situation where the two opposing sides in the Tory party who are in perma-campaign mode, are continually told the opposite. It is not possible to drive left and right at the same time.
It is also true that the government's public position has been clear for ages - to leave the customs union and pursue two separate potential models, the 'hybrid' and the 'max fac' . If you want to But it is also true that some Cabinet ministers believe that only the second option is remotely viable. Even in No 10 senior figures accept that they are nowhere near being able to prove to the EU that the hybrid model would work.
Even the Brexit Secretary himself, David Davis, questioned its credibility almost as soon as it was published, saying it was "blue sky thinking". Many months on, at least in public, there doesn't seem to be much evidence that would change his or other Brexiteer ministers' views.
That's why there are whispers, as on the front of today's Times, that he and others might try to force the PM to ditch it.
It's also the case that there has not been enough progress towards sorting out the Irish border question. Whether the UK should call the EU's bluff as some Brexiteers suggest, or accept what others see as inevitable and change position, is a different question. For as long as the question is open, the border question is a proxy for the whole debate about the world after Brexit.
Should we mirror the existing arrangements we have to minimise disruption, or go for a more radical break?
The most important truth is that with a divided party and no majority, it's massively difficult for Theresa May to settle that question.
Her survival so far has hinged on only inching forward, but pressure is building through the proxy of the arguments about the customs union, to take a bolder next step.

Is the DUP about to do a 180 and support checks in the Irish Sea as part of a Brexit deal?
Political u-turns aren't unheard of, after all.
But in this case, it seems a good way off.
Newspaper reports that the DUP has privately shifted its red lines on the backstop were quickly - and publicly - panned by senior party figures.
But is that the full story?
It's important to set out what the DUP has said it will accept, and how its tone has changed in recent days, causing a whiff of hope about a potential deal.
The party has always made protecting the union its main priority, delivering Brexit second - and in the early stages of the negotiations insisted there could be no deal that allowed any splits to develop between Northern Ireland and Great Britain.
It had, however, said it could accept certain regulatory differences that didn't damage trade with Great Britain or undermine the Union.
The Northern Ireland Assembly would also need to have oversight of the process.
While continuing to oppose the backstop, the party has softened its language, saying it would be open to all-island "arrangements" on food standards and animal health, which could partially remove the need for some checks at the land border.
That would mean Northern Ireland continuing to follow some EU rules and accepting new checks on some goods coming in from Great Britain
They haven't set out precisely what the arrangements could look like - don't expect them to either.
The Times story hinted the DUP could accept EU rules in other areas too - which is perhaps why the party has pushed back so hard.
If the DUP is going to to back anything that even slightly resembles NI only accepting EU rules, they will need to be able to sell it.
Their ideas are being talked about by the prime minister as well.
Boris Johnson has found himself boxed in by Parliament, and by demanding the backstop disappear, he has few options left when it comes to getting a deal by his Halloween deadline.
So is a compromise of sorts coming down the tracks?
There have certainly been warmer words this week from some in Brussels, with Ireland's EU commissioner Phil Hogan saying he believed there is "movement on both sides".
But we still don't know quite how the landing zone for a last-minute deal will look.
Will the DUP and Boris Johnson, despite their protestations, go further than all-island "arrangements" and move towards a Northern Ireland-specific solution?
What will the EU be prepared to sign up to?
If Stormont has the power to refuse to accept new EU regulations on food standards that would fall short of guaranteeing no hard border in the future.
Could Stormont have a consultative role on those EU issues which would apply in Northern Ireland?
Bear in mind that would require Stormont to get back up and running first, but there is a theory that if a deal is reached, there would be a two-year transition period which could allow some breathing space for devolution to be restored in order for Stormont to play its part.
There's also the question of trust: The DUP say they do not believe Boris Johnson will turn his back on them and sign up to anything they disagree with.
Others aren't so sure.
Cynics might say stories in the national press that the DUP is softening are an attempt by someone to bounce the party into accepting something else.
Right now, political tactics are being deployed on all sides.
No-one wants to be seen to budge too much.
Despite what the key players will all say publicly, they know someone will have to give more, and accept more.
Behind the scenes, what is being discussed could be very different - as pressure is applied for an agreement to take shape.
Boris Johnson has said he really wants to leave the EU with a deal on 31 October.
It may now be a question of who can shout louder at him about what that deal should look like, in the seemingly short time that's left.

Boris Johnson has hit the pause button on his Brexit legislation after MPs rejected his plan to get it through the Commons in three days.
MPs backed his Withdrawal Agreement Bill - but minutes later voted against the timetable, leaving it "in limbo".
After the vote, EU Council President Donald Tusk said he would recommend EU leaders backed an extension to the 31 October Brexit deadline.
But a No 10 source said if a delay was granted, the PM would seek an election.
On Saturday, Mr Johnson complied with a law demanding he write to the EU to ask for a three-month extension, but did not sign the letter.
Following the result in the Commons, he said it was Parliament and not the government that had requested an extension.
Mr Johnson said he would reiterate his pledge to EU leaders, telling them it was still his policy to leave by the end of October.
But Commons leader Jacob Rees-Mogg told MPs it was "very hard" to see how the necessary laws could be passed to leave with a deal by the deadline.
A spokesman from the European Commission said: "[The Commission] takes note of tonight's result and expects the UK government to inform us about the next steps."
But Mr Tusk tweeted he would "recommend the EU27 accept the UK request for an extension" in order to "avoid a no-deal Brexit".
The BBC's Europe editor Katya Adler said: "[The] temptation amongst most I speak to tonight in EU circles is to grant the 31 Jan extension."
And the BBC's political editor Laura Kuenssberg said that meant the government's plan to seek an election was "looking likely".
However, an EU source told BBC Brussels reporter Adam Fleming the bloc was considering a "flextension" - an extension with a maximum end date, but the flexibility for the UK to leave early if a deal is ratified.
Following Tuesday's Commons votes, a Downing Street source said Parliament "blew its last chance".
They added: "If Parliament's delay is agreed by Brussels, then the only way the country can move on is with an election."
Labour leader Jeremy Corbyn said Mr Johnson was "the author of his own misfortune".
He told the Commons that MPs had "refused to be bounced into debating a hugely significantly piece of legislation in just two days, with barely any notice or an analysis of the economic impact of this bill".
But Mr Corbyn offered to enter discussions over a "sensible" timetable for the PM's deal to go through Parliament.
The SNP's leader, Ian Blackford, said it was "another humiliating defeat" for the PM, and MPs had "spoken with a very clear voice to tell the PM he is not on".
Liberal Democrat leader Jo Swinson called on Mr Johnson to "end the brinkmanship and replace it with some statesmanship" in order to secure an extension with the EU.
Boris Johnson agreed his new plan with EU leaders last week, but has repeatedly pledged to leave the bloc by the end of October, with or without a deal.
This is despite him having to ask for an extension to Brexit on Saturday after MPs backed an amendment attempting to block a no-deal.
The bill that would turn his plan into law - the Withdrawal Agreement Bill - was published on Monday evening, and he urged MPs to back a three-day timetable to push it through the Commons ahead of the Halloween deadline.
The PM told Parliament if it "decides to delay everything until January or possibly longer", he would seek an election - but he did not say what the government would do if the EU offered a shorter extension.
MPs did approve the bill on its first hurdle through the Commons - called the second reading - by 329 votes to 299.
But in a vote straight after, they rejected the so-called programme motion, in other words the planned timetable to get the bill through Parliament, by 14 votes after a number of MPs criticised the pace of the legislation.
Mr Johnson told the Commons: "I will speak to EU member states about their intentions [but] until they have reached a decision - until we reach a decision, I will say - we will pause this legislation."
In the meantime, however, he said the government would "take the only responsible course and accelerate our preparations for a no deal outcome".
The PM added: "Let me be clear. Our policy remains that we should not delay [and] that we should leave the EU on 31 October."
If an election were to be triggered this week, the earliest it could take place would be Thursday 28 November, as the law requires 25 days between an election being called in Parliament and polling day.
But Mr Johnson cannot force an election himself and would need the backing of Parliament.
MPs had been due to debate the bill over Wednesday and Thursday, but will now return to discussing the contents of the Queen's Speech - which put forward the government's domestic agenda for the new session of Parliament.
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The government's Brexit bill will enable more British judges to depart from previous rulings of the EU's top court, Downing Street says.
The PM's spokesman said the Withdrawal Agreement Bill would expand this power to courts below the Supreme Court.
He added this would ensure judges at lower courts would not be "inadvertently" tied to the rulings "for years to come".
But others warned the move would cause legal uncertainty.
MPs are set for an initial vote on the withdrawal bill on Friday, after the Conservatives won an 80-seat majority at last week's general election.
Previous rulings of the European Court of Justice (ECJ) are set to be incorporated into the case law followed by British courts after Brexit.
The provision is contained in a separate EU withdrawal law passed in June last year under the premiership of Theresa May.
Previously, only the Supreme Court and the High Court of Justiciary in Scotland would be allowed to depart from these rulings.
Prime Minister Boris Johnson's spokesman said enabling lower courts to do the same was an "important change" to ensure they do not face a "legal bottleneck".
"We will take back control of our laws and disentangle ourselves from the EU's legal order just as was promised to the British people," he said.
There is no real detail in the government's pledge - but it marks a potentially really significant development.
It means that UK civil courts below the Supreme Court, for example the Court of Appeal, High Court, county courts, and tribunals such as the Employment Appeal Tribunal could depart from ECJ rulings in areas such as workers' rights.
Take for instance the right to paid holidays. The ECJ has interpreted this right more generously than the UK courts: for example, on the inclusion of overtime in holiday pay, and currently its interpretation binds the UK courts.
Following the 11 month transition period after Brexit, the way is open, for example, for an employer to take a case to one of the UK's lower civil courts and invite a judge to apply a more restrictive interpretation to the right to paid holidays.
This would create plenty of work for lawyers, but it opens a can of worms and could affect many workers.
The government's move was welcomed by former Tory leader Iain Duncan Smith, a leading figure in the pro-Brexit European Research Group.
"This is a critical pledge that puts sovereign rights back in the hands of the UK government and of course the British people," he said.
However, crossbench peer Lord Pannick QC, who acted for businesswoman Gina Millar in two cases against the government over its handling of Brexit, cautioned against the measure.
He told the Times, which first reported on the move, that allowing lower courts to depart from ECJ rulings would "cause very considerable legal uncertainty".
The government is hoping to get its Brexit deal through Parliament in the new year, enabling the UK to leave the EU by the end of January.
If passed, the UK would then follow EU rules during an 11-month transition period due to conclude at the end of December 2020.
MPs in the previous Parliament gave initial backing to the PM's Brexit bill but rejected his plan to fast-track the legislation through Parliament in three days in order to leave the EU by the then Brexit deadline of 31 October.
The government has already said the amended version of the withdrawal bill that will come back before MPs on Friday will include a new clause to rule out any extension to the transition period beyond the end of next year.

The UK has two weeks to clarify key issues or make concessions if progress is to be made in Brexit talks, the bloc's chief negotiator has said.
Michel Barnier was speaking after meeting the Brexit secretary for talks on citizens' rights, the Irish border, and the UK's "divorce bill".
David Davis said it was time for both sides "to work to find solutions".
Before the talks, Theresa May said she wanted the UK's exit date set in law, and warned MPs not to block Brexit.
Speaking at a press conference in Brussels, Mr Barnier suggested Britain would have to clarify its position in the next fortnight on what it would pay to settle its obligations to the EU if the talks were to have achieved "sufficient progress" ahead of December's European Council meeting.
"It is just a matter of settling accounts as in any separation," Mr Barnier said.
Mr Barnier also said both sides had to work towards an "objective interpretation" of Prime Minister Theresa May's pledge that no member of the EU would lose out financially as a result of the Brexit vote.
The Brexit secretary insisted good progress was being made across the board, and that the negotiations had narrowed to a "few outstanding, albeit important, issues".
Mr Davis and Mr Barnier agreed there had been progress on the issue of settled status for EU citizens in the UK after Brexit.
Mr Barnier said the UK had provided "useful clarifications" on guaranteeing rights, although more work needed to be done on some points including rights of families and exporting welfare payments.
For the UK's part, Mr Davis said, the government had "listened carefully" to concerns and that there would be a "streamlined and straightforward" process for EU nationals to obtain settled status.
But Mr Davis rejected a suggestion that Northern Ireland could remain within the European customs union.
He was responding to a European Commission paper, which proposed that Northern Ireland may have to remain a member of the EU's single market or customs union, if a so-called "hard border" with the Irish Republic is to be avoided.
Saying there had been "frank discussions" with Mr Barnier and his negotiators on the issue of the Irish border, Mr Davis insisted there could be "no new border" inside the UK.
"We respect the European Union desire to protect the legal order of the single market and the customs union, but that cannot come at cost to the constitutional and economic integrity of the United Kingdom," Mr Davis told reporters in Brussels.
"We recognise the need for specific solutions for the unique circumstances of Northern Ireland.  But let me be clear - this cannot amount to creating a new border inside our United Kingdom," he added.
Mr Barnier said the "unique situation" on the island of Ireland required "technical and regulatory solutions necessary to prevent a hard border".
By Adam Fleming, BBC Europe correspondent
Michel Barnier usually says at post-negotiation press conferences that the clock is ticking.
He didn't this time: he gave a specific timeframe. He wants the UK to provide more clarity in the next two weeks on its positions on the rights of EU citizens who wish to remain after Brexit, the plans for the Irish border and principles for calculating Britain's financial obligations.
Although the EU doesn't want a precise figure, it wants the UK to clarify what it's willing to pay to live up to the financial commitments made as a member.
On Ireland, both sides have pledged to protect the peace process but the EU has suggested that might require Northern Ireland sticking to European rules on customs and the single market - rules that the rest of Britain might not follow in future. David Davis rejected that.
UK sources agree it looks like they've been set a deadline but they feel it is a logical reading of the EU's timetable, under which their officials have to begin preparations for the next summit of EU leaders in December fairly soon.
Looking ahead to December's EU summit, Mr Davis pledged the UK was "ready and willing" to engage with Brussels "as often and as quickly as needed".
"But we need to see flexibility, imagination and willingness to make progress on both sides if these negotiations are to succeed and we are able to realise our new deep and special partnership," he said.
Friday's update came as Prime Minister Theresa May announced she wanted the date the UK leaves the EU - 29 March 2019 - enshrined in law.
The prime minister said the decision to put the specific time of Brexit "on the front page" of the Brexit bill showed the government was determined to see the process through.
"Let no-one doubt our determination or question our resolve, Brexit is happening," she wrote.
The draft legislation has already passed its second reading, and now faces several attempts to amend it at the next part of its parliamentary journey - the committee stage.
Mrs May said the government would listen to MPs if they had ideas for improving the bill, but warned against attempts to halt the process.
"We will not tolerate attempts from any quarter to use the process of amendments to this bill as a mechanism to try to block the democratic wishes of the British people by attempting to slow down or stop our departure from the European Union."

European Council President Donald Tusk has said a compromise with the UK over Brexit is "still possible", after Theresa May warned she was prepared to walk away from talks.
In a statement, Mr Tusk said he was a "true admirer" of the PM.
But he defended the EU's approach and said it was in fact Mrs May who had been "tough" and "uncompromising".
Mrs May on Friday demanded more respect from Brussels after EU leaders rejected a major part of her Brexit plan.
She had tried to sell her blueprint, which was agreed by ministers at Chequers, to EU countries at a summit in Salzburg, Austria, this week.
But the EU said the new economic partnership she had put forward "will not work" and risked "undermining the single market".
The UK is due to leave the EU on 29 March 2019 - but the two sides are trying to reach a deal by November so it can be ratified in time.
Mr Tusk issued a statement on Friday evening, hours after Mrs May delivered her own speech in Downing Street in which she said the EU's rejection of her plan without offering an alternative was "unacceptable".
Mr Tusk said EU leaders at the summit had treated her proposals with "all seriousness" and said they were a "step in the right direction".
Britain had known about the EU's reservations over the Chequers plan for weeks, he added.
Mr Tusk said: "While understanding the logic of the negotiations, I remain convinced that a compromise, good for all, is still possible.
"I say these words as a close friend of the UK and a true admirer of PM May."
Mrs May's statement dominates many of Saturday's front pages.
The Express calls her speech her "finest hour" and says she was right to demand respect from the EU and the Daily Mail says Mrs May "confronted the arrogance of the EU elite with unyielding, level-headed reason" and describes the EU's behaviour in Salzburg as "shabby".
The Sun describes it as Mrs May's "Brexit fightback" while the i draws a comparison to Margaret Thatcher with a headline that reads: "May tells EU: I'm not for turning".
But the Daily Telegraph says the prime minister is facing a showdown with her cabinet next week when ministers will call for a "Plan B" alternative to the Chequers proposals.
Italian MEP Roberto Gualtieri, who sits on the European Parliament's Brexit Steering Group, also expressed optimism that a solution will be reached.
He told BBC Newsnight: "I think that no deal is not an option. We are sure that the rationality will prevail."
In her televised statement on Friday, Mrs May said talks had reached an "impasse" and could only be unblocked with "serious engagement" from the EU side.
"Throughout this process, I have treated the EU with nothing but respect," she said. "The UK expects the same, a good relationship at the end of this process depends on it.
"At this late stage in the negotiations, it is not acceptable to simply reject the other side's proposals without a detailed explanation and counter proposals."
The pound's fall against the dollar and the euro deepened following Mrs May's statement.
Some Brexiteer MPs praised her for her comments. Jacob Rees-Mogg welcomed the "strong and forthright" speech but said she should abandon her Chequers plan and come forward with a Canada-style free trade agreement.
Conservative MP Andrew Bridgen - who previously called for a no-confidence vote on Mrs May - said she needed to "chuck" the Chequers plan.
"I think it could be a very, very rough ride for the prime minister when she finally realises how unpopular her Chequers proposals are, not only within the EU, but within the membership of the Conservative Party out in the constituencies," Mr Bridgen told BBC Newsnight. "It' s a grim time really.
In her speech on Friday, the PM said both sides were still "a long way apart" on two big issues: the post-Brexit economic relationship between the UK and EU, and the "backstop" for the Irish border, if there is a delay in implementing that relationship.
Both the UK and the EU want to avoid a hard border - physical infrastructure like cameras or guard posts - between Northern Ireland and the Irish Republic but cannot agree on how.
The two options being offered by the EU for the long-term relationship - for the UK to stay in the European Economic Area and customs union or a basic free trade agreement - were not acceptable, Mrs May said.
Mrs May says her plan for the UK and EU to share a "common rulebook" for goods, but not services, is the only credible way to avoid a hard border.
Arlene Foster, leader of Northern Ireland's DUP, who Mrs May relies on for a Commons majority in key votes, said the prime minister was "right to stand firm in the face of disrespectful, intransigent and disgraceful behaviour by the European Union".
Labour leader Jeremy Corbyn said the prime minister's negotiating strategy "has been a disaster" and said "political games from both the EU and our government need to end" to avoid a no-deal scenario.
Labour wants to see the UK join a customs union with the EU after Brexit, but remain outside of the single market.

Conservative MPs should back Theresa May's deal this week or risk losing Brexit altogether, Foreign Secretary Jeremy Hunt has warned.
There was "wind in the sails" of those opposing Brexit and the consequences for the party will be "devastating", if it is not delivered, he said.
MPs will vote again on the deal on Tuesday, after rejecting it in January.
Labour's John McDonnell said it looked like the PM had failed to secure any changes and it would be rejected again.
The UK is due to leave on 29 March, although Parliament has yet to agree the terms of withdrawal.
MPs will vote for a second time on Tuesday on the withdrawal deal Mrs May has negotiated with the European Union - after rejecting it by a historic margin in January.
If they reject it again, they will get a vote on leaving without a deal, and if that fails, on delaying the exit date.
Many Conservative Brexiteers voted against the deal in January over concerns about the backstop - a controversial insurance policy designed to prevent physical checks on the border between Northern Ireland and the Republic of Ireland.
But there have been few visible signs of progress over the issue in continuing talks between EU and UK officials.
Mr Hunt told BBC One's Andrew Marr Show some MPs wanted to "kill" the deal, in order to delay Brexit, with the ultimate aim of getting another referendum on the issue.
"Within three weeks, those people could have two of those three things," he said, adding that Labour's position made the third more likely.
He said: "We are in very perilous waters, and people who want to make sure that we really do deliver this result need to remember that if it fails... they are going to say: 'There was a party that promised to deliver Brexit, we put them into No 10 and they failed', and the consequences for us as a party, would be devastating."
He added: "We have an opportunity now to leave on March 29, or shortly thereafter. And it's very important that we grasp that opportunity because there is wind in the sails of people trying to stop Brexit."
If Parliament approves Mrs May's withdrawal agreement next week and the UK leaves the EU on 29 March, it will begin a transition period, when the two sides will attempt to agree a comprehensive trade deal.
If a trade deal is not agreed by the end of the transition period, the "backstop" plan is designed to maintain an open border on the island of Ireland.
It would keep the UK in a "single customs territory" with the EU, and leave Northern Ireland in the EU's single market for goods.
But some MPs fear that - in its current form - the backstop may leave the UK tied to the EU indefinitely.
On Friday, Mrs May urged the EU to help her get the deal through by resolving concerns about the backstop.
But Shadow Chancellor John McDonnell told the BBC: "It looks as though she's bringing back the same deal so it looks as though we will have the same result and it will be thrown out."
He said the party's priority this week would be to stop Theresa May "driving through some sort of Brexit deal that will damage our economy and undermine jobs" and if that meant a delay to allow for a discussion about the deal Labour backs instead "so be it".
He also denied that Labour's support for keeping the option of another referendum open had been put on the backburner, adding: "If Parliament can't agree, if we have to break the logjam, yes, we will keep the option available of going back to the people."
And he said he believed that Labour's alternative Brexit deal could be agreed with the EU "within a matter of weeks" but said any delay requested should be "as long as is necessary".
Labour's policy is to seek a permanent customs union with the EU after Brexit, which would allow the UK "a say" in future trade deals. Mr McDonnell said the EU had "looked positively" on the proposal.
On Friday, the EU said it would give "legal force" to assurances it has already made about the withdrawal deal and its chief negotiator Michel Barnier tweeted that the UK would be free to leave a proposed single customs territory with the EU - provided Northern Ireland remained within it.
The leader of the House of Commons, Andrea Leadsom, said she was deeply disappointed by the EU's proposal, which has already been rejected by the UK government.
The Brexit Secretary it was "not the time to rerun old arguments".

Allowing the UK to unilaterally halt the Brexit process could lead to "disaster", judges at Europe's top court have been warned.
The European Court of Justice is deliberating on whether the UK can call off its withdrawal from the EU without permission from member states.
But lawyers acting for the EU said allowing countries to do so could create "endless uncertainty".
The case has been brought by a group of Scottish politicians who oppose Brexit.
They hope it will give clear guidance to the UK Parliament about the options open to it as MPs vote on the prime minister's Brexit deal - and that it will result in "no Brexit" being an alternative to either "no deal" or Mrs May's deal.
The UK government says it has no intention of calling off Brexit, and says the politicians bringing the case are using it as "ammunition" in their campaign to halt the withdrawal process.
The court also heard from lawyers representing the Council of the European Union and from the European Commission, who both argue that revoking Article 50 is possible - but that it would require unanimous agreement from the other 27 member states.
They are concerned that the case could set a precedent where other countries would be able to formally notify their intention to leave and then seek better terms from the remaining EU countries, before cancelling their withdrawal.
Analysis by Adam Fleming, BBC News in Luxembourg
There were two emotions on display in the ECJ's gold-encrusted courtroom: hope and fear. The UK government was worried that anything said about Brexit by European judges could be used as ammunition in the battle to bring down Theresa May's deal.
The EU fretted about Article 50 being re-written in a way that meant a country could announce it was leaving then change its mind again and again, creating a state of permanent anxiety. Or worse, using it as a tactic to secure a better deal at the EU's expense.
The campaigners who brought the case were just glad that the concept of Brexit being reversed had a very public airing so close to the vote on the deal by MPs.
Hubert Legal, the chief lawyer for the European Council, argued that allowing unilateral withdrawal could therefore lead to "disaster", of which "the main victim could be the European project altogether".
This was echoed by lawyers for the European Commission, who said states could act in an "abusive" manner by stopping and restarting the countdown clock, creating "endless uncertainty" - which the two-year time limit built into Article 50 was designed to guard against.
A four-hour hearing on Tuesday morning saw the full court of 27 judges consider the arguments in the case.
The court has said it will aim to decide "quickly" on the case, but has not yet set a date for doing so.
The case is being considered against the backdrop of Prime Minister Theresa May fighting to sell her draft Brexit deal to MPs, ahead of a vote in the Commons in December.
The UK will leave the EU on 29 March under the terms of "Article 50", a two-year notification of withdrawal which MPs triggered in March last year.
The case has been brought by a cross-party group of Scottish politicians including Green MSPs Andy Wightman and Ross Greer, MEP Alyn Smith and MP Joanna Cherry of the SNP, and Labour MEPs David Martin and Catherine Stihler.
They say it could give MPs an extra option when considering whether to approve the draft deal or not, because it could keep alive the prospect of calling off Brexit
Mr Wightman said the question was "vital", saying that "the chaos around Brexit shows no sign of being resolved" and that the UK parliament "must be fully informed of all of its options".
Aidan O'Neill QC, who is representing the Scottish politicians, told the court that European lawyers were inviting the judges to act "unconstitutionally and in contravention of the rule of law by reinterpreting the treaties".
He said: "It cannot be in the interest of the union as a whole to force a member state to leave the union against the wishes of the people.
"The union's wider interest lies with member states remaining in the EU when their peoples wish to do so."
The UK government has opposed the case being heard from the outset, but failed to prevent it going before judges in Luxembourg after a series of appeals.
The UK government's position is that the court has "long refused for very good reasons" to answer hypothetical questions which could interfere with domestic politics. They argue that because "the UK does not intend to revoke its notification", the question of whether it can do so unilaterally is a hypothetical one.
Ms Cherry raised the case and the issue of revoking Article 50 with Mrs May in the Commons on Monday, prompting the prime minister to say that "it is not going to happen because it is not government policy".
Advocate General Lord Keen, who is representing the UK government, argued in court that the case was being used as "ammunition" by opponents of Brexit, and said the judges should find it inadmissable.

Gina Miller is the businesswoman and campaigner who has twice led legal challenges against the government and won.
Her first victory came in September 2017, when the Supreme Court ruled in favour of giving MPs a say over triggering Article 50 - the legal mechanism taking the UK out of the EU.
Her second came on Tuesday, when the Supreme Court ruled that Boris Johnson's decision to suspend Parliament was unlawful.
Her success in the courts has come at a price - she has become a hate figure for many Brexit supporters and has had to employ round-the-clock security after threats to her life.
She says she does not want to block Brexit, but is standing up for Parliamentary democracy.
Speaking outside the Supreme Court after the ruling on Tuesday, she said: "Today is not a win for any individual or cause, it's a win for Parliamentary sovereignty, the separation of powers and the independence of our British courts.
"Crucially, this ruling confirms that we are a nation governed by the rule of law."
Mrs Miller is not officially aligned to any political party, having spurned the advances of the Liberal Democrats, who rapturously received a speech she gave at their 2018 party conference.
A 54-year-old investment manager and philanthropist, Mrs Miller was born in Guyana and educated in Britain.
She went first to an exclusive all-girls private boarding school, Roedean, on the outskirts of Brighton, at the age of 10, then to Moira House Girls' School, in Eastbourne, East Sussex.
Afterwards, she studied law at the University of East London, but left before completing her degree.
Mrs Miller went on to start a successful marketing consultancy business with clients including private medical specialists in Harley Street in London.
In 2009, she used the money she had made in marketing to co-found an investment firm supporting smaller charities.
"I realised then it was my money, I could do what I wanted with it and so I used that money to get involved in social justice," Mrs Miller told Unfiltered with James O'Brien last year.
And in 2012, the businesswoman began the True and Fair Campaign, which campaigned for greater transparency in the City of London's fund management industry.
According to an interview with the Financial Times in 2016, this led some in the industry to label her the "black widow spider".
Speaking about a time she asked three men at an industry party why they were staring at her, she told the paper: "One of them replied that I was a disgrace and that my lobbying efforts would bring down the entire City."
Mrs Miller launched her first Brexit legal case with London-based Spanish hairdresser Deir Tozetti Dos Santos and the People's Challenge group, set up by Grahame Pigney - a UK citizen who lives in France.
Backed by a crowd-funding campaign, they argued the government could not invoke Article 50 of the Lisbon Treaty - starting the formal process of the UK leaving the EU - without seeking approval from Parliament.
Mrs Miller argued only Parliament could make a decision leading to the loss of her "rights" under EU law.
But she stressed the challenge was not an attempt to overturn the referendum decision, telling BBC Radio 4's Today programme: "We are all leavers now."
In November 2016, three High Court judges ruled Parliament had to vote on when the process could begin.
Speaking after her victory, Mrs Miller told the BBC the case was about scrutinising the details of Brexit, such as "how we leave, how they're going to negotiate, the directions of travel the government will take".
And she said the legal challenge was about more than Brexit, arguing that it was "verging on dictatorship" for a prime minister to be able to take away people's rights without Parliament's consent.
The government appealed, and the case went to the Supreme Court the following December, but the 11 judges rejected it by a majority of eight to three.
Following the successful legal challenge, Mrs Miller suffered online abuse, including rape and death threats against her and her family.
She told James O'Brien: "It has changed the way we live our lives, and the conversations we have with the children".
"We use humour a lot because that's the only way to get through it", she told him.
In July 2017, an aristocrat who wrote a Facebook post offering £5,000 to anyone who ran over Mrs Miller was sentenced to 12 weeks in prison.
Describing the businesswoman as a "boat jumper", Rhodri Colwyn Philipps - the 4th Viscount St Davids - wrote: "If this is what we should expect from immigrants, send them back to their stinking jungles."
The peer claimed the comments were "satire" and a "joke".
But the judge, who said the post effectively put a "bounty" on Mrs Miller's head, found him guilty of two charges of making menacing communications.
Later that year, Mrs Miller was named as Britain's most influential black person.
"It's amazing to get an accolade when what I've done has solicited a huge amount of abuse," she said on receiving her title.
"To have somebody acknowledge me is extraordinarily kind and counters a lot of what I still get on a daily basis."
Despite the backlash, Mrs Miller went on to launch a second challenge against the government to "defend Parliamentary sovereignty".
After Mr Johnson announced in August that he would suspend Parliament for five weeks, Mrs Miller challenged the legality of the decision at the High Court.
She argued that Parliament would be "silenced" for an "exceptional" length of time in the critical period before the 31 October Brexit deadline.
She initially lost her case, but in Scotland, a separate legal challenge succeeded, with judges taking the view that the suspension was unlawful.
The UK government appealed to the Supreme Court against the Scottish judgement, and the two cases were then heard together.
The court unanimously ruled in favour of Mrs Miller's appeal and against the government's.
Judges said it was wrong to stop MPs carrying out duties in the run-up to the Brexit deadline on 31 October.
After the ruling Mrs Miller told reporters the ruling showed the government "will push the law, they will push the constitution and they will even bend it to get their own way".

We asked for your questions and received more than 1,100 responses within five hours. Below are some answers to our most frequently asked questions.
The court ruling does not mean the end of Brexit.
The case was about the government's right to trigger the formal two-year process of leaving the EU without there being a vote in Parliament.
The government is going to appeal against the decision, but, as things stand, the ruling means MPs and lords will have to give their go-ahead before Prime Minister Theresa May starts her negotiations on the UK's exit from the European Union.
Theoretically, they could decide not to give the go-ahead - but, in practice, that is seen as highly unlikely given that a majority of people who voted in the June referendum voted for the UK to leave the EU.
Legal affairs commentator Joshua Rozenberg said the decision had been based on the argument the government could not use its executive powers because it would mean effectively overturning an act of Parliament.
Triggering Article 50 would eventually lead to the UK leaving the EU, which effectively takes away rights granted by Parliament, such as the right to free movement in Europe.
The High Court ruling effectively defined the limits of government power by reiterating that Parliament is sovereign - it can create laws and only Parliament can take them away.
We do not know yet, but it may try to repeat the argument that its prerogative powers allow it to trigger Article 50 because that in itself does not mean an immediate change to UK citizens' EU rights.
Paragraph 13 of the ruling essentially states that a parliamentary motion is not enough to satisfy the terms of Brexit.
UK membership is bound not in prerogative power, but in the 1972 EU Communities Act, and therefore needs primary legislation to be taken away.
Brexit Secretary David Davis said: "The judges have laid out what we can't do and not exactly what we can do, but we are presuming it requires an act of Parliament."
The EU referendum was advisory - as was discussed in the court ruling on Thursday.
It points to the "basic constitutional principles of parliamentary sovereignty and representative parliamentary democracy" in the UK, which "led to the conclusion that a referendum on any topic can only be advisory for the lawmakers in Parliament unless very clear language to the contrary is used in the referendum legislation in question".
"No such language is used in the 2015 Referendum Act," it adds.
Possibly, but it would be surprising if it was, according to Joshua Rozenberg, because the case is about the UK's constitutional requirements, not EU law.
The lead claimant in the case is investment manager and philanthropist Gina Miller, who launched the case alongside London-based hairdresser Deir Dos Santos and a group called the People's Challenge Group, which is backed by a crowdfunding campaign. You can Article 50 of the Lisbon Treaty is usually considered to be the only legal way to leave the EU. It states that a country that decides to leave the EU has two years to negotiate "arrangements for its withdrawal, taking account of the framework for its future relationship with the union". This will involve unravelling UK-EU treaty obligations; such as contributions to EU budgets, and holding talks on future trade relations. However some have suggested that the UK could leave the EU by other means - by amending EU treaties or repealing UK legislation. Douglas Carswell, then a Conservative MP and now UKIP, tried to introduce a European Communities Act 1972 Repeal Bill in 2012.
Although negotiations over international treaties are normally powers reserved to the UK Parliament at Westminster, because leaving the EU could involve the removal of people's rights under EU law, the devolved administrations want to have their say in the Article 50 process.
Ever since devolution to Scotland, Wales and Northern Ireland began in 1999, Westminster normally seeks the agreement of the devolved parliaments and assemblies if it is legislating on devolved matters. While Westminster debates a bill, legislative consent motions are passed in Wales, Scotland and Northern Ireland. Political difficulties could arise should they choose to vote on legislative consent motions relating to any bill to enact Article 50.
On Friday the Welsh Assembly's senior legal adviser, Mick Antoniw, said he would seek to make representations to the Supreme Court during the government's appeal about the potential impact on Wales. SNP MPs may decide to vote against triggering Article 50 at Westminster - Scotland's First Minister Nicola Sturgeon said they would "vote in line with the wishes and the interests of the Scottish people", potentially delaying the process.
A High Court case in Belfast last week saw a cross-party group of MLAs attempt to prevent Article 50 being triggered without a Parliamentary vote or a vote in the Northern Ireland Assembly. That case was rejected but those behind it are taking it to the Supreme Court.
Much depends on whether the government wins its appeal to the Supreme Court and, if not, to what extent new legislation about triggering Article 50 is delayed by questions and amendments in Parliament.
Theresa May announced the Great Repeal Bill - which would abolish the 1972 European Communities Act and transpose all relevant EU law on to the UK statute book after the UK leaves the EU - on the day she said she wanted to trigger Article 50 by the end of March 2017. The High Court ruling that the government cannot enact Article 50 without the backing of Parliament could delay that timetable.
Many British expats were annoyed at not being allowed to vote in the EU referendum and there are moves by the government to scrap, by 2020, a rule that says Brits who have not lived in the UK for 15 years cannot vote in UK elections.
However, this ruling does not stop the 23 June vote to leave coming into force, nor does it mean a second referendum, so expats who wanted to vote to remain in the EU are unlikely to be able to vote on the issue again.
Even if there were a second vote on the issue, the government's "votes for life" proposal refers to UK parliamentary elections and says the "franchise for referendums will continue to be held on a case-by-case basis" - so it is not clear whether, in the event of a hypothetical second vote on Brexit, expats would get a vote anyway.
This has not yet been put to the test as no country has triggered Article 50 before and there seems to be some confusion. The Scottish cross-bench peer who wrote it, Lord Kerr, told the BBC this week he believed it was "not irrevocable" and, even if the process had begun, a member state could still choose to remain in the EU. However the High Court ruling states that it was "common ground" between both sides that Article 50 "cannot be withdrawn once it is given".
Once Article 50 is triggered, the UK has up to two years to negotiate a deal with the EU. But what if it runs out of time?
Robyn Munro, from the Institute for Government, says there are three options: 1) the UK could get an extension on the negotiating period if all EU members agree, 2) the UK could try for an "interim deal" while negotiations continue after two years - perhaps with some access to the single market but losing its influence in the EU and 3) the UK could leave without any agreement, and treaties would cease to apply. This would mean falling back on WTO rules for trade but there would be much uncertainty over other areas such as the rights of UK citizens who live and work in the EU, EU citizens in the UK and whether UK airlines would have the right to fly into EU airspace.

In a crisis there can be opportunity.
This is now a crisis - the rules that traditionally have preserved governments are out of the window.
The prime minister has been defeated again. Her authority - if not all gone - is in shreds.
But for Number 10 there's an opportunity too, because MPs will soon be presented with a new choice - back the PM's deal, which has already been defeated twice, or accept the chance of a delay to Brexit.
This isn't the choice of a government that's in control. But the tactic is to make the best of chaos.
To use nerves among Brexiteers to shove them towards accepting Theresa May's deal in the absence of another solution with no other agreed alternative - yet.
The prime minister is beginning another day not sure of where it will end.
MPs are bristling to push their own different solutions - none of which she or Parliament as a whole, let alone the public, is ready to accept.
Yet even if this pandemonium strangely leads the way to order, to a smooth departure from the European Union, there's a different question: could a functioning administration ever again exist under the present cast?

A new plan for post-Brexit customs arrangements will be a "significant step forward", a Downing Street source has promised.
The proposal, to be presented to ministers on Friday, will offer "the best of both worlds" - an independent trade policy and friction-free trade, the source added.
But no details have yet been revealed about how it will work.
Ministers have so far failed to agree what type of customs model to pursue.
Friday's Chequers summit, which will be followed by a White Paper setting out more details, is aimed at finalising the UK's preferred path which can then be put to the EU.
BBC political editor Laura Kuenssberg said some ministers appeared not to have been involved in drawing up the new proposal, which is being called a "third way" after two previous proposals divided opinion.
Earlier, government divisions were underlined when Foreign Secretary Boris Johnson intervened in defence of Eurosceptic backbencher Jacob Rees-Mogg, who had been accused by two other foreign office ministers of "threatening" Theresa May over Brexit.
The UK is due to leave the EU on 29 March 2019, and negotiations are taking place on what the future relationship between the UK and the EU will look like.
Key things that have yet to be agreed are how the two sides will trade with each other in years to come - and how to avoid new border checks between Northern Ireland and the Republic, which is a member of the EU.
Before reaching agreement with the EU, Mrs May needs to resolve splits within her cabinet on the shape of Brexit.
BBC political editor Laura Kuenssberg
The immediate problem with the "new plan" is whether or not it really exists.
Because while Number 10 says it does, ask other people in government and they are not quite so sure. Ministers who you might have thought would be aware of the detail like - oh, you might imagine - the Brexit secretary had not agreed the lines, before Number 10 made their intervention.
And it's said tonight that the reason he has not been involved in agreeing the "new plan" is because it does not actually exist yet. The customs decision expected in some parts of government therefore is what has been anticipated for some time as "max fac plus" - a souped up version of the proposal that originally won the day in the Brexit subcommittee what feels like a lifetime ago - with, you assume, a long lead-in time while the technology is made to work.
Baffled? Quite possibly so. But it's perhaps only safe to say that four days before ministers are expected to actually make some final decisions, all is not precisely as you might have expected.
Read the rest of Laura's blog
Earlier, she urged the EU to consider her blueprint for future relations "seriously" as she updated MPs on last week's Brussels summit.
Pressed to give more detail of her plans as she took questions in the Commons, Mrs May said she hoped her vision for the UK's future relations would address the "real differences" on the issue of the Irish border.
"The EU and its member states will want to consider our proposals seriously," she said.
"We both need to show flexibility to build the deep relationship after we have left that is in the interests of both our peoples."
Labour leader Jeremy Corbyn said the cabinet was irrevocably split between different Tory factions.
But Mrs May rejected calls to "pick a side" between Remainers and Brexiteers, saying: "I have picked the side of the British people and these are the ones for whom I will deliver."
She is also due to have talks in Berlin with German Chancellor Angela Merkel ahead of the Chequers meeting.
The BBC's Brussels reporter Adam Fleming
Sources in both the European Council and the European Commission deny they have seen a draft of the UK's Brexit White Paper.
Officials in Brussels predict it will mostly be a compilation of existing British positions - "a best of" is how one described it.
Theresa May "hinted" at the publication of the document when she addressed EU leaders at their summit last week but she did not elaborate on its contents.
Ministers from the remaining 27 member states are planning to respond to the White Paper at a meeting of the General Affairs Council on 20 July.
EU officials expect to be going through the document until the end of July.
The government has so far talked publicly about two potential customs options.
One, a customs partnership, would mean the UK applies the EU's own tariffs and rules of origin to all goods arriving in the country and then hands over what was owed for goods that subsequently end up in the EU.
The other, known as maximum facilitation or max-fac, aimed to employ new technology to remove the need for physical customs checks where possible.
It is understood both options have been deemed practically or politically undeliverable and a third option is on the table, believed to involve "alignment" with the EU in regulations covering trade in goods but a looser relationship for services.
Writing in the Daily Telegraph earlier, Mr Rees-Mogg said he and other members of the 60-strong group of Eurosceptic Tory MPs he leads, known as the European Research Group, would reject a deal that did not amount to a clean break with the EU.
Mr Rees-Mogg said a deal which restricted the UK's ability to make trade agreements with other nations or control migration could not be accepted and Mrs May "must stick to her righteous cause and deliver what she has said she would".
But, speaking in the Commons, pro-EU MP Anna Soubry said the public were tired of what she said were continual "fudges" on key questions and urged Mrs May to stamp her authority once and for all.
And her colleague Nicky Morgan said Mrs May "would not be thanked for the mess we will end up in" if the government did not prioritise the needs of the economy in a "pragmatic, sensible, flexible" Brexit.
The Democratic Unionist Party, whose support Theresa May needs to have a majority in key Commons votes, said it would not support any deal which did not give the UK full control over its borders.
"We don't give blank cheques to anybody," its Westminster leader Nigel Dodds said after meeting the PM for an hour in Downing Street.
"We want to see a proper Brexit which fulfils the referendum result but we have been very clear that it has to be on the basis of the whole of the UK leaving the EU as one."
He accused Dublin and other European capitals of trying to "bully" the UK and using the issue of the Northern Irish border to "create an outcome which is to their liking", adding "they won't succeed in that".

The EU has finally announced its informal approval of a new Brexit extension: a full three months, running until 31 January, as suggested in the UK prime minister's extension request.
But what an excruciatingly long and confusing political dance to get there. And the dance is not over yet.
To become a formal offer, the Brexit extension still needs to be accepted by Prime Minister Boris Johnson. This is EU law and an unavoidable part of the procedure. But how uncomfortable for the prime minister who sought to distance himself as much as possible from the extension, previously promising that he would rather die in a ditch than request one.
The EU is also attaching some extra wording to the extension. Brussels wants the UK to realise that this is a "flextension": the UK does not need to stay in the full three months; instead, it can leave as soon as its parliament and the European Parliament have ratified the new Brexit deal. The extension text cites 1 December and 1 January as possible "early out" dates.
The EU extension text also reminds the UK that, until it leaves, it remains a fully paid-up member of the EU, including all the rights and obligations that go along with membership.
A new European Commission starts work in roughly a month's time. The new Commission President, Ursula von der Leyen, is insisting the UK nominate a new commissioner so as not to undermine the legal workings of the EU as long as the UK remains in it.
Mr Johnson is obliged by UK law to accept the new Brexit delay. But EU leaders take nothing for granted anymore. Under EU law, a no-deal Brexit is still possible as of midnight Central European Time (23:00 GMT) on Thursday.
Now, if and when the prime minister despatches his ambassador to the EU to submit a letter of UK acceptance of the extension, then Brussels says it still needs another 24 hours. This is because the text was agreed at EU ambassador level. It still needs to be signed off by the "grands fromages" - leaders in all EU capitals.
And why did it take the EU so long to make a decision? Early last week, there were confident assertions being made in Brussels that the UK's three-month extension request would be approved.
Yet what followed was a seemingly shambolic make-it-up-as-you-go-along EU timetable, where "announcement day" moved from last Thursday to Friday to this Tuesday, Wednesday and now Monday.
What initially slowed EU leaders down last week was France, the one EU country deeply opposed to the three-month extension. President Emmanuel Macron agreed with Boris Johnson that a shorter, sharper extension would better focus the minds of MPs in Westminster on the newly negotiated Brexit deal.
After more than three years of Brexit confusion and indecision in Parliament, France feared a longer extension would give MPs the space to keep chasing their tails instead of coming to conclusions.
UK political discourse at the end of last week also interfered with the EU's decision-making process. Government and opposition MPs kept deferring questions about holding a general election, saying: "We'll decide when we hear from the EU about the length of the extension they're going to grant."
EU leaders did not want their decision about a Brexit delay to be politicised. Since a vote was scheduled in Westminster on Monday on Boris Johnson's push to hold a December general election, Brussels said it would announce its extension decision after that.
But two key issues moved ahead of time over the weekend, meaning that, in the end, the EU felt emboldened to make its announcement ahead of the Westminster vote:
And after the extension has been signed off this week, Brussels will watch from the sidelines, arms folded, as the next moves are decided in Westminster.
Hope runs deep in the EU that Brexit will now finally be decided by UK politicians and voters, but there is a lingering sense of doubt here too.
Based on more than three years of false dawns in the process, the EU knows there is a distinct possibility, come January, that the spectre of yet another Brexit extension could rise once again.

A commemorative 50p coin marking the UK's departure from the EU has been unveiled by Chancellor Sajid Javid.
The coins bear the inscription "Peace, prosperity and friendship with all nations" and the date of 31 January.
Mr Javid had first ordered production of the coins in advance of the UK's original 31 October departure date.
But the Brexit delay meant about a million coins had to be melted down and the metal put aside until a new exit date was confirmed.
About three million Brexit coins will enter circulation around the UK from Friday, with a further seven million to be added later in the year.
Mr Javid, who is Master of the Mint, was given the first batch of coins and will present one to Prime Minister Boris Johnson this week.
As part of the launch of the coin, the Royal Mint will open the doors of its south Wales HQ for 24 hours on 31 January (from 00:01 to 23.59) to let people strike their own commemorative Brexit coins.
Mr Javid said: "Leaving the European Union is a turning point in our history and this coin marks the beginning of this new chapter."
The European Parliament is expected to approve the Withdrawal Agreement on Wednesday, after the PM this week signed the treaty paving the way for the UK to leave on 31 January.

It's not even 24 hours since the PM called the general election she said she wouldn't call.
It's the opposite of Gordon Brown's "election that never was", rather the "election that wasn't meant to be".
Much will be written about her motivations for the U-turn, the change of heart that led her to this point. The long-term view of her motivation will in time be coloured by the eventual result of course.
But as the unofficial day one of this campaign draws to a close, some things are clear.
For months there has been a pretty straightforward balance sheet of advantages and disadvantages to holding an early poll. Theresa May believed it tipped to holding firm.
There were plenty of reasons for going early - most temptingly making the most of Labour's weakness to grab dozens of seats.
It would free Theresa May from the strictures of the 2015 manifesto - she's already proved she doesn't feel much constrained by that - which no one who remains in government had involvement in putting together.
It would give her her own mandate, even though PMs are not directly elected. It would draw a line between her leadership and David Cameron's, once and for all.
And with a likely majority, IF the polls are correct, it would make it easier for her to get her Brexit plans through Parliament, give her more freedom to pursue her other - some controversial - plans like reintroducing grammars, and strengthen her hand with EU leaders as she gets down to negotiations.
Going early could also minimise the potential fallout over the Tory expenses saga - a bad hangover from the 2015 election.
In the negative column:
Until only a few days ago it was those arguments that held sway.
Theresa May has shown time and again that she is willing to change her mind when the facts change.
For example, she and her chancellor dropped a major plank of his Budget in only a week when they saw resistance, and the government junked a review of the powers of the House of Lords.
Her public argument for calling an election - that it was resistance from the opposition and the Lords over Brexit - does not quite tell the full story.
Parliament has been tricky for the PM, but certainly not impossible.
Notwithstanding that, nor the factors that have created strong political arguments for taking the plunge in the last couple of months, senior government sources point to a specific factor that changed the prime minister's calculation.
The end of the likely tortuous Article 50 negotiations is a hard deadline set for March 2019.
Under the Fixed Term Parliaments Act, that's when the Tories would be starting to prepare for a general election the following year, with what one cabinet minister described as certain "political needs".
In other words, the government would be exposed to hardball from the EU because ministers would be desperate to avoid accepting anything that would be politically unpopular, or hold the Brexit process up, at the start of a crucial election cycle.
As one insider put it: "We'd be vulnerable to the rest of the EU in 2019 because they know we'd have to move fast."
Ministers say that's the central reason for Mrs May's change of heart because "if there was an election in three years, we'd be up against the clock".
By holding the election now, Theresa May hopes she gains a fresh start on the political clock on Brexit, even though the Article 50 process still has a deadline of only two years.
This gives what was described as "flexibility over the logistics of Brexit… we don't have to pretend we can do it all in two years".
That's not to say for a second this means departure from the EU will be held up. The Article 50 process will proceed, the government says, exactly as planned.
But, if the Tories win, an early election may have bought ministers some valuable breathing space to work out what the UK really looks like outside the EU.
They'll have, in theory, three years after exit for things to settle down before the public get another chance to have their say.
That timetabling question was not her only reason, as outlined above.
But after the EU's initial brush off after the Article 50 letter, that argument became more compelling.
The PM's conclusion was that the best way of her going into those negotiations in as strong a position as possible, was by taking advantage of the window between the French and German elections before the EU gets down to proper business.
A hypothetically bigger majority of course also acts to neutralise the cruelly dubbed "Remoaners" in her own party, and the far larger, and much more powerful, group of ardent Leavers who have been able to exert a lot of pressure.
But while the polls suggest an early election could make many of her political problems disappear, polls prove nothing.
Politics in 2017, as we've discussed again and again, is unpredictable and taking bets is a fool's game. The reasons Theresa May hung back from an early election haven't disappeared.
PS: Westminster's guessing game has been who knew, and when.
No one will confirm officially on the record. For what it's worth, sources tell me that David Davis and Philip Hammond were the only ministers who were extensively consulted.
Both Boris Johnson and Amber Rudd were told before Tuesday morning's cabinet meeting. But there were ministers around the cabinet table who had no idea and who were, it's said, visibly shocked when Mrs May told them.
The cabinet was kept in the cabinet room during the announcement, and watched it on TV.
The mood was apparently very enthusiastic, with one moment of huge laughter when the wifi link that was playing her announcement on the screen in the street just outside broke down and the PM suddenly went to black.
Apparently the glitch was sorted within a few seconds, but her colleagues will hope the PM is better at running an election campaign than sorting out the Number 10 broadband.

Chancellor Philip Hammond has insisted that the prime minister's Brexit deal is better than remaining in the EU.
He said the deal respected the result of the 2016 referendum and offered "the best compromise possible".
European Council President Donald Tusk has recommended that the EU approve the deal at a summit on Sunday.
It comes after Spain, which threatened to miss the summit, was reassured over objections it had raised about Gibraltar.
Spanish Prime Minister Pedro Sanchez has now received enough reassurances from the UK government over the issue.
Mrs May flies into Brussels later to hold talks with top EU officials, ahead of the summit.
The UK is scheduled to depart the EU on 29 March 2019.
The terms of the UK's withdrawal have been under negotiation since June 2016 following a referendum in which 51.9% voted to leave the EU.
Even if the EU approves the deal, it still has to be passed by the UK Parliament, with many MPs having stated their opposition.
Arlene Foster, the leader of Northern Ireland's Democratic Unionist Party (DUP), has already stated the party will not back the Brexit deal - and is expected to reiterate her position at this weekend's annual conference in Belfast.
She will say the withdrawal agreement contains arrangements that are not in Northern Ireland's long-term economic or strategic interests.
Mrs May relies on the DUP, whose 10 MPs help the minority Conservative government to pass legislation.
The DUP has threatened to look again at the agreement with the Conservatives if the Brexit deal gets through Parliament.
DUP Chief Whip Jeffrey Donaldson denied the party would walk away from its agreement - but told the BBC the party was "very unhappy" with the withdrawal agreement.
Philip Hammond told Today he was hopeful of a solution with the DUP.
The deal on offer was the "best way of Britain leaving the EU with the minimum negative impact on the economy," he said.
The chancellor said the deal was better than remaining in the EU because it honoured the referendum result and offered "the best compromise possible... satisfying both sides" of the Brexit argument.
"If we want this country to be successful in the future, we have got to bring it back together after this process," he said.
By Leila Nathoo, BBC political correspondent
Ministers' hard sell of the Brexit deal continues - this morning it was Philip Hammond's turn.
He's been trying to reassure the DUP over their concerns about the Irish border - but he also had a message for MPs thinking of voting against the deal in the Commons.
Don't - or chaos will be unleashed.
Warnings about the economic consequences of a Parliamentary rejection will remind some of what was dubbed 'Project Fear' during the referendum campaign.
The chancellor's suggestion that there is no alternative can be seen as a dismissal of those critics - the DUP, Tory Brexiteers - who think there is still a chance of renegotiation.
Meanwhile, former Northern Ireland secretary Theresa Villiers - a Leave campaigner in 2016 - has said she will vote against the withdrawal agreement.
"I do not believe it is in the national interest," she told Today.
She said "every effort should continue to be made to try and reach a better agreement" but failing that, Theresa May "should walk away".
But Mr Hammond warned that a no-deal Brexit would unleash "economic chaos".
"If the meaningful vote [in Parliament] is lost we are in uncharted territory," he said.
On Saturday, Mrs May will meet the president of the European Commission, Jean-Claude Juncker, and European Council President Donald Tusk for talks.
Then on Sunday, EU leaders will meet for the special Brexit summit. They will be asked to approve two key Brexit documents:
There is no formal vote on Sunday but the EU expects to proceed after reaching a consensus.
Spain raised last-minute objections to how the issue of Gibraltar - a British Overseas Territory with 30,000 residents - had been handled in the Brexit talks so far.
Spain has long-held ambitions to bring the territory back under Spanish rule, and there's growing concern about how their economic ties with the territory will be affected by Brexit.
Although one country on its own cannot stop the withdrawal agreement being approved, there is "no way the EU can rubber-stamp a text when an existing member is so strongly opposed", said BBC News Europe editor Katya Adler.
France, Denmark and the Netherlands had raised concerns over what the political declaration said about fishing rights in UK waters - but this issue is understood to have been resolved.
If the EU signs off the withdrawal deal, Mrs May will then need to persuade MPs in her own Parliament to back it.
A vote in Parliament is expected to happen in December.
Labour, the SNP the Liberal Democrats, the DUP and Plaid Cymru have all said they will vote against the government's deal, as well as many Conservatives.
On Friday, the PM said the UK should not hope for a "better deal" from the EU if MPs reject her Brexit agreement.
But she declined to say whether the UK would be better off outside the EU, saying only it would be "different".
Meanwhile, the Telegraph said it has seen leaked Cabinet papers which suggest the PM is planning to "reframe the Brexit debate around migration" - by planning restrictions on low-skilled migrants coming to the UK - in a bid to attract the support of Brexiteers.
Yes. After the 2017 general election, Mrs May's Conservative Party got 318 seats - four short of the number she needed to rule with a majority government.
The DUP formed a confidence and supply agreement with the Tories, promising that its 10 MPs would vote with the government, and therefore enable it to win key votes in Parliament.
The DUP opposes the Brexit deal because of the "backstop" - the last resort back-up plan to make sure a hard border between Northern Ireland and the Republic of Ireland never happens.
It will only come into effect if the UK and EU fail to agree a long-term trade deal. But the backstop would mean that Northern Ireland - but not the rest of the UK - would still follow some EU rules on things such as food products.

International Trade Secretary Liam Fox has refused to back Chancellor Philip Hammond's warning that a "no-deal" Brexit could damage the economy.
Speaking on the BBC's Andrew Marr show, he said: "This idea that we can predict what our borrowing would be 15 years in advance is just a bit hard to swallow."
Treasury analysis estimates that by 2033 borrowing would be around £80bn a year higher under a "no-deal" scenario.
It also forecasts no deal could mean a 7.7% hit to GDP over the next 15 years.
Asked by Andrew Marr whether he accepted the figures, Mr Fox said: "Can you think back in all your time in politics where the Treasury have made predictions that were correct 15 years out. I can't.
"They didn't predict the financial crisis. No-one could."
Pressed on whether he agreed with the chancellor, Mr Fox said: "I don't believe that it's possible to have a 15-year time horizon on predictions of GDP."
"So the answer's no," said Marr.
Divisions have deepened within the party in recent months as Brexiteers accuse Mr Hammond - who is seen to be pushing for a softer version of Brexit - of embarking on "another instalment of dodgy project fear".
Meanwhile, there is growing pressure on the prime minister to win support for her Brexit plan, known as the Chequers agreement.
The plan would see the UK agreeing a "common rulebook" with the EU for trading in goods, in an attempt to maintain friction-less trade at the border.
But critics say it will leave the UK tied to EU rules and prevent Britain from striking its own trade deals in years to come.
In his interview, Mr Fox said he was behind the Chequers plan and and could not imagine many things worse than remaining in the EU.
By Susana Mendonca, BBC political correspondent
The prime minister may be promising to stand firm on no second referendum but that is not stopping opponents in her own party from gearing up to take down her Chequers plan for Brexit.
International Trade Secretary Liam Fox - who's stayed inside the PM's camp - has warned that there's no point in trying to unseat Theresa May because "changing the leader doesn't change the party arithmetic".
While David Davis, who resigned over Chequers, has suggested that the prime minister limited his influence over the negotiation process. He said while he was the Brexit secretary, whether he "controlled events" was "another matter".
Mr Davis has never been one to shy away from making his views known and now that he is on the outside of the tent - he will join the chorus of Brexiteers doing exactly that, as Mrs May heads into the final stretch before she does or does not get a deal on Brexit.
In an article for the Sunday Telegraph, Theresa May has insisted she would not be forced into watering down her Brexit plan during negotiations with the EU.
The PM wrote that she would "not be pushed" into compromises that were not in the "national interest".
But David Davis, the former Brexit secretary who resigned over the Chequers agreement, said the caveat - "except in the national interest" - was an "incredible open sesame to all".
Also interviewed on the Marr show, he admitted he would vote against Mrs May's plan in any Commons vote, saying it would be "almost worse" than staying in the EU.
Another Conservative MP, Nick Boles - a former minister who backed Remain - said the Chequers policy had "failed" and he could no longer support it.
Also writing in the Sunday Telegraph, he said the EU was treating the plan as "an opening bid", and the UK was facing "the humiliation of a deal dictated by Brussels".
In his interview, David Davis said concerns over maintaining a soft border between Northern Ireland border and the Republic had been "heavily overemphasised" in the past.
"This is a much more straightforward issue to deal with if we choose to, if we put the political will behind it, we and the Irish Republic, the two together," he said.
However he said he did agree with Mrs May that a second referendum should not take place.
In her article, she said it would be a "gross betrayal of our democracy and... trust" to "give in" to those calling for another vote.
Her objection to it comes as a movement pressing for another referendum - the People's Vote - continues to gather high profile backers, including Sir Patrick Stewart and BBC football anchor Gary Lineker - as well as donations.
One supporter, Labour MP Chuka Umunna, said the impetus had shifted toward a public vote over the summer and it would be a "betrayal of democracy" for Mrs May "to force a bad deal - or no deal - on Britain without giving the public the chance to have a final say".

The Democratic Unionist Party's (DUP) bottom line has always been that any new Brexit arrangements should not separate Northern Ireland from the rest of the UK, economically or constitutionally.
Under the Stormont assembly's cross-community voting rules, contentious measures require a majority of both unionists and nationalists in order to pass.
The DUP had hoped to secure an upfront Stormont vote to approve the new arrangements.
But it's understood that the current proposals would give Stormont a say four years after the end of the transition period - that would mean 2024.
A straightforward numerical majority would keep the special arrangements in place for another four years.
Alternatively, if the arrangements get cross-community consent - in other words, if they're passed by most nationalists and most unionists - they would remain in place for eight years.
But a vote couldn't happen if the assembly wasn't operating.
Shortly afterwards, an election left unionism without a numerical majority in the Stormont chamber for the first time in the history of Northern Ireland.
So for the DUP, the issue of consent - and a fear that Dublin and Brussels would have too big an influence on trading rules - goes to the heart of the party's concerns that Northern Ireland's place in the UK would be weakened.
Several rounds of talks to restore the Stormont Executive haven't succeeded - and few, if any, hold out hope that devolution is returning in the coming weeks.
Her tweet - "No border and no veto" - shows how the complexities of Stormont politics have become increasingly bound up with the UK-EU negotiations.
The technical talk about Brexit and the border focuses on trade, goods regulations, and potential tariffs.
But for politicians in Belfast and Dublin, the significance of those issues is generated by deeper issues - such as identity, nationality, and peacebuilding.

Meetings, on their own, are not a Plan B. Conversations, are not by themselves, compromises.
To get any deal done where there are such clashing views all around, it requires give and take. It feels like a political lifetime since there has been a fundamental dispute in the cabinet, in the Tory party and across Parliament. Theresa May has stubbornly, although understandably, tried to plot a middle course.
But that has failed so spectacularly at this stage. Ultimately she may well be left with the same dilemma of which way to tack.
It's clear, wide open, in public, that the cabinet is at odds with each other. Just listen to David Gauke and Liam Fox on whether a customs union could be a compromise for example.
The answer for her is not suddenly going to emerge from a unified tier of her top team. There are perhaps five or six of the cabinet who would be happy to see that kind of relationship as a way to bring Labour on board.
But there is a group of around the same size who would rather see what they describe as a "managed no deal".
You may well wonder if that isn't a contradiction in terms.
But the principle would be that the UK would pay the divorce bill already agreed and over a two-year period construct a series of side deals on specific issues, rather than try to come up with a whole new comprehensive plan.
There are already intense arguments about whether that's remotely realistic. But the overall point is that the prime minister cannot just therefore look to her top colleagues for an immediate solution.
Before she decides which way to tack, or how far to budge, she may need to ask herself if the talks she wants to hold with other political parties are occasions when she is really open to ideas - or just ways of managing the political situation.
One cabinet minister involved in the talks suggested that many MPs still needed to understand how the agreement they have reached with the EU worked. And that as "project reality" dawned, there could still be a way through of salvaging Mrs May's deal in something like its current form.
And certainly there wasn't much in the PM's lectern statement to suggest she is suddenly ready to move very much. One former minister described it as "still flicking the V at the 48% - she's deluded, she never changes her mind and cannot conceive that others might".
If all that the prime minister intends to do is massage a few egos with these talks, it seems unlikely that she'll find a quick route to success. And Labour may well stay outside the process.
Many members of the public might be furious that Labour leader Jeremy Corbyn won't play nice during a time of crisis. He's always said he believes in dialogue, but when it really matters, he says no. But inside the Labour movement there are others who might accuse of him of helping to make Brexit happen if he takes part. Like so many facets of this process, it's not a straightforward political calculation.
But across Parliament, for a very long time now, even some MPs who were on the prime minister's side to start with have been intensely frustrated that she hasn't listened. It will take a lot more than a cup of tea in Downing Street to bring her many critics on board.

The UK and European Commission have reached an agreement that should allow them to move Brexit talks on to the next stage.
Here are some of the key lines in the agreement document.
So here's the first linguistic somersault. This agreement is designed to lock in the progress made so far, and allow technical experts to continue to work on it during the second phase of talks.
But EU negotiations always work on the principle that nothing is agreed until everything is agreed, and that raises the prospect that if the second phase runs into trouble, then what has been agreed so far could, in theory, unravel.
That is certainly not the intention on either side, but it underscores that the negotiating process still has a very long way to run - and the hardest part is still to come.
The separation agreement on citizens' rights will not fall under the direct jurisdiction of the European Court of Justice (officially called the CJEU but commonly referred to as the ECJ) which was the initial demand from the European Union.
But the ECJ will continue to play a role, because this agreement says UK courts will have to pay "due regard" to its decisions on an indefinite basis.
And for eight years after Brexit, there will be a mechanism for UK courts to refer questions of interpretation directly to the ECJ.
It is a compromise, but the sort of compromise that some supporters of Brexit will find hard to stomach.
This detail on citizens' rights is important.
The agreement will apply to anyone taking up residence before the UK leaves the EU, so people could still take the decision to move next year, or even in early 2019, and they would be fully protected by it. That option will remain open for new arrivals until the day the UK leaves - currently presumed to be 29 March 2019.
In fact the European Commission argues that the "specified date" should be considerably later. In an official communication to the European Council it argues that during a transition all EU citizens should have all their rights upheld. In other words, it says, the "specified date" should not be the actual date of withdrawal, but the final day of a transition period (potentially two years later or even longer).
There are also a lot of technical details hidden in the weeds of the agreement that remain to be negotiated, and that's why some groups representing citizens who are caught up in this dilemma are far from happy.
The reaction of the European Parliament, which has taken a tough line on citizens' rights, will be important because it has to ratify the final agreement.
This is the key phrase in the long section setting out how the border between Northern Ireland and the Republic of Ireland will operate after the UK leaves the EU.
The preference on both sides is for an ambitious free trade agreement, which will address many of the concerns that have been raised (although questions of customs duties would still have to be addressed).
As a backstop though, the UK has guaranteed that it will maintain "full alignment" with the EU's single market and customs rules that govern cross-border trade.
It is a form of words that everyone can (just about) live with for now, but there is plenty of tough negotiating ahead.
It's not entirely clear how full alignment could be maintained without Northern Ireland staying in the single market and the customs union, especially as there is no such thing as partial membership. It is another sign that the competing demands that have been discussed this week have been sidestepped, but not fully resolved.
This sentence about the financial settlement is a bureaucratic masterpiece, and suggests that plenty of detail still needs to be sorted out behind the scenes.
For months, the money appeared to be the most intractable issue in the withdrawal negotiations, but money is easier to finesse than borders or courts.
A method for calculating the bill has been agreed, but the calculation of an exact UK share will depend on exchange rates, on interest rates, on the number of financial commitments that never turn into payments, and more.
The question of how and when payments will be made still needs to resolved, but it will be a schedule lasting for many years to come, and it is highly unlikely that anyone will ever be able to give an exact figure for the size of the divorce bill.
UK sources say it will be up to £40bn, but some EU sources expect it to be higher than that. No-one can say for sure, and both sides want to keep it that way.
Update 11 December 2017: This piece was amended to take account of the European Commission's view on the specified date for EU citizens' rights.
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Tory rebels "could collapse the government" if they vote against a Brexit deal negotiated with the EU, a leading rebel has said.
Dominic Grieve said he wakes up "in a cold sweat" thinking about what could happen if a final deal is rejected.
But he suggested rebels would not back down in a current row with ministers about how much of a say MPs should get.
The EU Withdrawal Bill returns to the Lords and Commons this week, with further rebellions expected.
Last week the government avoided a defeat on the bill after agreeing to hold further talks with rebels.
They want a bigger role for Parliament, should a final Brexit deal be rejected by MPs, or if no deal is reached - the so-called "meaningful vote".
Former Attorney General Mr Grieve told BBC One's Sunday Politics that he thought they had agreed MPs could have an "advisory" vote, that would not order the government to do anything, but would help people to "keep calm" during what would be a "critical situation".
But after two days of talks, Mr Grieve said a government amendment drawn up to avert a rebellion was changed at the last minute and was now "valueless".
He implied rebels would vote against it this week: "I'm absolutely sure that the group is quite determined that the meaningful vote pledge, which was given to us, has got to be fulfilled."
He added: "The alternative is that we've all got to sign up to a slavery clause now, saying whatever the government does, when it comes to January, however potentially catastrophic it might be for my constituents and my country, I'm signing in blood now that I will follow over the edge of a cliff, and that I can tell you, I am not prepared to do."
The government's amendment to the EU (Withdrawal) Bill sets out what must happen in the event of three scenarios: If MPs vote down the UK-EU Brexit deal, if Theresa May announces before 21 January 2019 that no deal has been reached, or if 21st January passes with no deal being struck.
Under these circumstances, a minister must make a statement in Parliament setting out their next steps and give MPs an opportunity to vote.
However, the vote would be on "a motion in neutral terms", merely stating that the House has considered the statement.
Rebels had originally wanted the amendment to say that the government must seek the approval of Parliament for its course of action - and that ministers must be directed by MPs and peers.
When it was put to him that voting against any Brexit deal at "the 11th hour" of negotiations could cause the government to collapse, he replied:  "We could collapse the government and I can assure you, I wake up at 2am in a cold sweat thinking about the problems that we have put on our shoulders."
Last week another Conservative MP, Tom Tugendhat, told Sky News there was "going to be a new government" if MPs rejected the government's Brexit deal.
Solicitor General Robert Buckland said that "however well intentioned" Mr Grieve's plan had been, his worry was that "it actually plays badly in the most important negotiation, which is over in Brussels".
It would imply to the EU, he said, that "there's a third party in this relationship" - Parliament - which could "trump whatever the UK government say".
He said ministers would stick with the new amendment for Monday, adding: "Let's see what the Lords make of it. Of course we have Tuesday to consider matters ahead of the Wednesday vote."
Earlier the prime minister defended her handling of the row.
She told BBC One's Andrew Marr Show she had met Tory rebels and "undertook to consider their concerns".
She admitted there had been "a debate" about what a "meaningful" vote for Parliament meant: "I've listened carefully to the concerns, I've put an amendment down which I think balances this issue of the role of Parliament together with the need for us to ensure we don't overturn the decision of the British people."
But she said Parliament "cannot tie the hands of government in negotiations".
The main purposes of the EU Withdrawal Bill are to end the supremacy of EU law in the UK, and transfer existing EU law into UK law so the same rules and regulations apply on the day after Brexit.
But as it passes through Parliament, MPs and peers have been trying to change it, in some cases adding bits on that would change the government's Brexit strategy.
The government says the whole row is about a "hypothetical" scenario and they are "confident we will agree a good deal with the EU which Parliament will support".

As MPs begin five days of debate on Theresa May's Brexit deal it looks like the prime minister faces the exact situation she called an election last year to try and avoid.
Whether it is the decision on whether the government is in contempt of Parliament (in other words, in lots of embarrassing trouble for ignoring the demand to publish the full Brexit legal advice), or MPs asking for the right to tell ministers what to do if there is a second attempt by the government to get Theresa May's Brexit compromise deal through the Commons (the attempt by Dominic Grieve today, that could take 'no deal' off the table for good), or what seems now, the likely rejection of  Theresa May's agreement with the EU next week, those manoeuvres, those sub-plots in the Brexit drama, amount to one central thing - slowly but surely, Parliament grasping the levers of power - one might even say, taking back control.
To use the posh term, it is the legislature trying to take over the executive, and this is what chills some spines in No 10. With MPs on the Tory benches as well as the opposition looking for ever more arcane ways of tying ministers up in knots, there is a sense whatever happens next Tuesday, what we are seeing is the gumming up of the government, maybe for good.
For many MPs of course, this is a moment, if not to hang out the bunting, to take heart from Parliament's influence, to be reassured about its role, its ability not just to scrutinise legislation, but to make things happen, or more pertinently, to stop them taking place.
But remember, as one government insider put it this morning, "there are no numbers FOR anything" - in essence the idea that the Commons would be able to come together to agree anything quickly on behalf of the country seems optimistic in the extreme.
They'd be able to agree that they should prevent a disorderly 'no deal' exit. The prominent Labour MP, Hilary Benn, is making a formal attempt to guarantee just that.
But beyond that? If the government's plan falls, some MPs will certainly push for another referendum - but a majority for that seems out of reach for now. Some, and there is cross-party support, would try to argue for a Norway-style deal with close economic ties to the EU. There might, just about, be a majority for that.
But that model would not see the UK have total control of its immigration policy. For many, but of course not all, Leave voters, that was the priority in the referendum. It's potentially therefore deeply problematic to go for such an arrangement.
If voters partly voted Leave to demand more say over immigration, what message does Westminster send back to the electorate if they carve up a deal that simply does not do that?
Of course MPs absolutely ought to be voting for what they believe is best, at this huge moment. Some of them may be spooked by the idea of turmoil, or at least on-going confusion.
Many more are poised to make their objections count.
But don't kid yourself that if Parliament takes charge of the process that the situation will become any clearer fast.
By calling the election last year, this kind of Parliamentary mess was exactly what the prime minister was trying to avoid. She had a tiny majority then, and this would have been a hard fight in any case.
But that historic gamble, that she tried and failed, has made this perhaps harder than she could have imagined. With no majority, even tiny numbers of MPs can make a huge amount of noise.

The request for delay is an answer to one question.
When confronted with the possibility of taking the UK out of the EU without a formal deal in place or slamming on the brakes, which way would the prime minister jump?
Would she choose a pure plan - pursuing Brexit over the risk of instability?
Or would Theresa May heed the voices of warning, rather than those in her own party arguing that any short-term pain would be worth long-term gain, and ask for delay, despite the embarrassment of doing so, and the frustration of those who wanted her to keep the promise of leaving on time?
Mrs May kept many in Westminster guessing for a long time.
But her meetings in Europe, her plea on Tuesday, are evidence of the decision she finally took - that almost any entreaties to European leaders are worth it to avoid opening Pandora's Box. Pausing again brings embarrassment and angers many on her own side, but it's a lesser evil than departing with no deal.
If the prime minister is granted a strings-attached delay later, the next question is perhaps as big.
What will she do with the extra time she's been granted? Will it even be up to her?
Cross-party talks with the Labour Party are serious - both sides in the room are taking part in good faith and expect more negotiations on Thursday.
But the more talking they do, the more the scale of the task to bring them together reveals itself.
Forget a quick solution from this joint process, and don't bank on one happening at all.
The divisions may simply be too great - the moment when it might have worked perhaps has passed.
If that fails, then the answer may pass again, back to Parliament - MPs confronted again with the power to choose from a wide array of different choices - with the ability, if not yet the common purpose to choose a version of Brexit for all of us.
And of course, if a long delay is agreed it could push hungry Tories who want a change of leadership again into action.
But the obvious response to another question is crystal clear - who is in charge for today?
It's the EU leaders who will determine the date and nature of this delay - not the country that voted in an effort to pull back control.

The Brexit process has turned into a "nightmare", the prime minister of Luxembourg has said after holding talks with UK PM Boris Johnson.
Xavier Bettel said Mr Johnson had failed to put forward any serious plans to allow a deal by 31 October.
But Mr Johnson, who cancelled his press conference because of the noise from protesters, said "there's been a lot of work" and "papers have been shared".
He urged the EU to make "movement" in its opposition to scrap the backstop.
Mr Johnson said his joint press conference was cancelled over fears the two leaders would have been "drowned out" by pro-EU protesters.
"I don't think it would have been fair to the prime minister of Luxembourg," he said.
"I think there was clearly going to be a lot of noise and I think our points might have been drowned out."
Political editor Laura Kuenssberg said that Number 10 had asked for the press conference to be held inside, according to sources.
Mr Bettel, who conducted the planned press conference alone, said the "only solution" was the existing withdrawal agreement.
He said there were "no concrete proposals at the moment on the table" from the UK and said the EU "needs more than just words".
"We need written proposals and the time is ticking so stop speaking and act," he said.
"But we won't accept any agreement that goes against a single market, who will be against the Good Friday Agreement."
Away from the crowds, Mr Johnson said the EU must make "movement" in its opposition to scrap the Irish backstop, but insisted there was "just the right amount of time" to get a deal done.
When asked what concrete proposals he had made, Mr Johnson said "there's been a lot of work" and "papers have been shared".
"We've got to manage this carefully. Yes, we've got a good chance of a deal. Yes, I can see the shape of it. Everybody could see roughly what could be done," he said.
He reiterated that the UK will come out of the EU on 31 October "deal or no deal".
As soon as we arrived at the office of the prime minister of Luxembourg it became obvious a planned outdoor news conference could not go ahead.
The anti-Brexit protesters in the square numbered fewer than a hundred but their music and megaphones made it sound like a lot more and they occasionally used language you wouldn't want to hear on the news.
Behind the scenes the British and Luxembourgish delegations grappled with a diplomatic dilemma - move the event inside but exclude the majority of the journalists? Gamble that the demonstrators could pipe down for a bit? Silence the host to save the guest's blushes?
The end result saw Mr Johnson do a short interview at the ambassador's residence to be shared with everyone while Mr Bettel took to the stage next to an empty podium.
He used the moment in the spotlight to deliver an impassioned speech, made all the more dramatic by the fact he's famed as one of the EU's most smiley, mild-mannered leaders.
Earlier, both Mr Johnson and Mr Juncker - who met for the first time since the PM took office in July - agreed the discussions between the UK and EU "needed to intensify" and meetings "would soon take place on a daily basis".
But regardless of the outcome, No 10 said the PM would take the UK out of the EU on 31 October.
Downing Street also said Mr Johnson confirmed his commitment to the Good Friday Agreement - the peace deal brokered in Northern Ireland - and still had a "determination to reach a deal with the backstop removed, that UK parliamentarians could support".
Mr Johnson has called the Irish backstop "undemocratic" and said it needed to be removed from any deal with the EU.
A Downing Street spokesperson said Mr Johnson also reiterated he would not request an extension and would take the UK out of the EU on 31 October.
The EU has said it is willing to look at alternatives, but that an insurance policy like the backstop must be in place.
The backstop is the controversial policy in the existing withdrawal agreement, rejected three times by MPs, which would require the UK to follow the EU's customs rules to ensure there are no physical checks on the border between Northern Ireland and the Republic.
Last week MPs passed a law that would force the prime minister to ask the EU for an extension to the 31 October deadline if a deal was not agreed by 19 October.
But the prime minister's official spokesman said: "The position of the PM is that we comply with the law, but that we are leaving on 31 October whatever the outcome."
They also confirmed that the current date set for a transition period - the time for the UK and EU to negotiate their future relationship after officially leaving - of December 2020 would not be extended.
Over the weekend Mr Johnson told a newspaper that the UK would break out of its "manacles" like cartoon character The Incredible Hulk - with or without a deal.
The BBC's political editor Laura Kuenssberg said the issue of whether the UK had the legal right to leave on 31 October - come what may - could end up in court.
Reports have suggested Mr Johnson is considering a plan to keep Northern Ireland more closely aligned to the EU after Brexit, as an alternative to the current Irish backstop.
The Democratic Unionist Party - which supports the Conservatives in Parliament - has rejected any plan that would see Northern Ireland treated differently to the rest of the UK.
The PM's spokesman would not give details, but said the government had "put forward workable solutions in a number of areas".
Writing in Monday's Daily Telegraph, Mr Johnson said he believed he could strike a deal with the EU within weeks and was working "flat out to achieve one".
"If we can make enough progress in the next few days, I intend to go to that crucial summit... and finalise an agreement that will protect the interests of business and citizens on both sides of the channel, and on both sides of the border in Ireland," he wrote.
Many MPs have also questioned how serious the government is about getting a deal, such as former justice secretary David Gauke who said "detailed proposals" had yet to be put forward.
"It still remains the case the UK government has not produced detailed proposals as to how it wants to replace the Irish backstop," he told Radio 4's Today.
Foreign Secretary Dominic Raab said the PM would stress he wanted a deal, but there had to be "some finality" to it.
He said claims from the EU side that the UK was dragging its feet were part of the "tactical posturing that goes on in any negotiation".
He told Today the UK had been clear the "anti-democratic backstop" had to be removed from the current withdrawal agreement, and the outline of future trading relationship set out in the political declaration had to be much more ambitious.
"The EU knows our position. Lots of the detail has been talked through at technical and political level," he said. "The framework is very clear.
"But of course the nature of these negotiations is that there will be a tendency to rubbish things we put forward in order to exact further demands. We are not going to get involved in that."
Monday:  Boris Johnson meets European Commission President Jean-Claude Juncker for Brexit talks in Luxembourg
Tuesday: The Supreme Court begins to consider the legality of Mr Johnson's decision to suspend parliament until 14 October
Wednesday: The European Parliament to debate Brexit

Their offices are full of boxes, they're living in hotels and don't ask them when they're having their leaving drinks. How have the UK's MEPs been coping with the ever-changing Brexit situation?
It's the last day of the European Parliament in Strasbourg before the elections in May, but there's not much last-minute packing for the UK group of MEPs - they've been ready to go for nearly a month.
When the UK voted to leave the EU, the country's representatives in the European Parliament expected to be out of a job on 29 March. Instead they have watched two deadlines pass by as MPs in Westminster failed to agree on the withdrawal deal.
Now a new Brexit date of 31 October means the UK is likely to take part in European elections on 23 May and some MEPs are eyeing an unexpected return to Europe.
But job prospects there could be short-lived. Whenever the UK breaks the Brexit deadlock, they could be sent home. And if the prime minister succeeds in winning support for a deal before polling day, elections could be called off altogether.
MEPs are used to a nomadic life, dividing their time between parliament sessions in Brussels and Strasbourg, as well as their home constituencies in the UK. But many of them feel recent months have taken an already unstable situation to extremes.
Catherine Bearder, Liberal Democrat MEP, says: "Life is never certain as a politician, but this is beyond anything I've ever seen before."
The 70-year-old had been planning a quiet retirement - "painting, gardening, doing yoga" - but said she is back on an election footing now, determined to fight to keep the UK's place at the European table.
For Nathan Gill, a former UKIP and independent MEP who has now joined the newly launched Brexit Party, the delays have been a blow to the cause he spent the last 15 years of his life on.
Speaking from an office filled with packing boxes, he says: "It's unbelievable, it's disgraceful."
He says he was forced to leave his Brussels apartment and move into a hotel after his lease ended. Later he got turfed out of there too.
As UK Prime Minister Theresa May sought the latest extension to Brexit and an emergency EU summit rolled into town, prices rose so much that Mr Gill had to temporarily decamp to Antwerp, some 25 miles (41km) away.
Every country in the EU elects representatives to the parliament, which meets in Strasbourg and Brussels. The UK has 73 MEPs, representing each of its 12 regions for five-year terms.
Their job is to debate and to help decide on EU laws, as well as scrutinising the work of EU institutions.
The last election saw 19 Conservatives elected, 20 from Labour and 24 from UKIP - although 19 UKIP MEPs have since left the party and one was expelled.
The Greens have three MEPs, the SNP has two and there is one each from the Liberal Democrats, Democratic Unionist Party, Sinn Fein, the Ulster Unionist Party and Plaid Cymru.
Labour's David Martin is the UK's longest-serving MEP, first elected in 1984.
The Brexit Party is not the only new party planning to contest these European elections. Change UK - formed by former Labour and Tory MPs, initially under the name The Independent Group - says it had 3,700 people applying to be candidates.
MEPs themselves will receive a transitional allowance when their term ends, equivalent to a month's salary for every year they have served. But across the political spectrum, they are united in feeling that staff have been treated badly.
Each MEP has a budget to hire assistants, with up to three in Brussels as well as staff in their home region. Information about the future for these staff members is scarce and always changing, MEPs say.
Contracts could not be extended until Brexit extensions were officially confirmed by the European Council, usually at the last minute as negotiations went to the wire.
For some staff, the last-minute deadline extensions meant losing redundancy pay as they had already accepted jobs elsewhere. Others who remain are sleeping on sofas as their apartment leases run out.
"It's very brutal from a staff point of view," says Conservative MEP Daniel Dalton. "You're in one day and out the other and your staff are out with you."
Green MEP Jean Lambert says staff had to be made redundant and offices closed as the original Brexit deadline loomed in March. But the party kept in place a contingency plan in case the UK took part in European elections.
"We've got a plan A and a plan B, which is more than the government has," she says - although she plans to retire as an elected representative.
If the UK does elect MEPs, what will they do in a potentially short-lived return to Brussels and Strasbourg?
Some Brexiteer politicians such as Nathan Gill warn that they plan to make the EU nations "regret" the UK MEPs' return.
Mr Gill says the Brexit Party hopes to work with other anti-EU and anti-euro parties across the continent, such as the far-right Alternative for Germany (AfD) and Italy's anti-immigration League party, to cause disruption.
"We want them to realise they should have just let us go," he says. "They don't need this thorn in their side."
But Conservative MEP Mr Dalton, who backs the government's Brexit withdrawal agreement, says it would be "completely counter-productive".
He says British politicians have often failed to understand that the EU Parliament is based on compromise, so the adversarial politics of Westminster fall flat. "All it does is annoy people," he says. "They're much more likely to get more stubborn."
UKIP MEP Stuart Agnew is another who has postponed retirement to take part in the elections, if they happen. He says he was surprised that Westminster MPs had let the Brexit deadlock get to this point.
"I would have lost a bet. I thought they would have banged heads together, that the Conservatives wouldn't want European elections and neither would Labour. I was wrong," he says.
Other MEPs have made firm decisions not to stand again but have still been left bewildered by recent weeks.
David Martin, Labour MEP, says he intends to do academic lecturing on the EU and trade policy, but had been struggling to agree a start date.
"The Brexit negotiations will be a really good case study in how not to negotiate with the European Union," he says.
He has also been puzzling over a unique issue of etiquette: when should Brexiting MEPs say their goodbyes?
As Mr Martin puts it: "You don't want to have a farewell dinner and say goodbye to everyone, and still be there the next day."

Hundreds of thousands of people have marched in central London calling for another EU referendum, as MPs search for a way out of the Brexit impasse.
Organisers of the "Put It To The People" campaign say more than a million people joined the march before rallying in front of Parliament.
Protesters carrying EU flags and placards called for any Brexit deal be put to another public vote.
On Thursday, European leaders agreed to delay the UK's departure from the EU.
PM Theresa May is coming under pressure to quit after saying she might not put her Brexit deal to a third vote by MPs.
Speakers at the rally included Labour's deputy leader Tom Watson, Scotland's First Minister Nicola Sturgeon, London Mayor Sadiq Khan, former Tory turned independent MP Anna Soubry and former attorney general Dominic Grieve.
Crowds were told the initial count showed more than a million people had turned up - putting it on a par with the biggest march of the century, the Stop the War march in 2003.
There was no independent verification of the numbers but BBC correspondent Richard Lister, who was at the scene, said it was a "very densely packed" protest and people were still arriving in Parliament Square five hours after the march began.
He said: "The organisers say it was one million-strong, it's very hard to verify those kinds of claims but this was a very significant march, well into the hundreds of thousands."
Labour's Tom Watson told the crowd in Parliament Square that Mrs May's deal was a "lousy" one - whether you voted Leave or Remain.
He said he had this message for her: "I can only vote for a deal if you let the people vote on it too. Prime Minister, you've lost control of this process, you're plunging the country into chaos, let the people take control."
Ms Sturgeon said now was "the moment of maximum opportunity" to avoid a no-deal Brexit.
By Katie Wright, BBC News, in Park Lane
The streets around Park Lane were teeming with people hours ahead of the march's scheduled 1pm start, having come from all corners of the country - and some from further beyond.
The blue and yellow of the EU was splashed all over the ever-expanding crowd, which was full of groups of families, friends, colleagues and political groups.
Many people came draped in flags and carried homemade signs, featuring slogans ranging from playful - "Never gonna give EU up" - to political - "Forget the Ides of March - beware the Brexit of May". And then there were the plain angry - "Brexit is treason".
One member of the crowd, German-born vet Chris Reichmann, described it as a "carnival" atmosphere - with "lots of different nationalities" but "really British in a way".
And it was noisy, with some of London's most recognisable streets overflowing with people marching steadily to a soundtrack of beating drums, whistles and blaring horns.
Occasionally the hordes would erupt into spontaneous cheering, as well as chants of "What do we want? People's vote. When do we want it? Now!"
Game Of Thrones star Lena Headey, Strictly Come Dancing presenter Claudia Winkleman and Neil Tennant of the Pet Shop Boys were among the famous names to take to the streets.
Sadiq Khan joined demonstrators at the front of the march as it began, holding up a "Put it to the People" banner.
He was flanked by Liberal Democrat leader Vince Cable, who tweeted that there was a "huge turnout of people here from all walks of life".
But veteran Conservative MP John Redwood told the BBC: "We know that 16 million people wanted to stay in the EU, and some of those would still like to stay in the EU, and within that quite a few would like to have another go and have another referendum - but it was always a minority."
The prime minister wrote to all MPs on Friday saying she will ditch plans to put the deal to another so-called meaningful vote on her withdrawal deal if not enough MPs support it.
Unless her deal is passed by MPs, the UK will have to come up with an alternative plan or else face leaving without a deal on 12 April.
Downing Street sources have denied reports in the Times newspaper that discussions are under way about a timetable for the prime minister to step down.
Meanwhile, a record-breaking online petition on Parliament's website calling for Brexit to be cancelled by revoking Article 50 has attracted more than four million signatures.
As the number of signatures on the petition continued to climb, its creator Margaret Georgiadou said she had "received three death threats over the phone", and a "torrent of abuse" via her Facebook account.
Liberal Democrat MP Layla Moran said the petition could "give oxygen" to the campaign for another Brexit referendum.
The march comes as the pro-Brexit March to Leave, which started in Sunderland a week ago, continues towards London.
Former Ukip leader Nigel Farage re-joined the March to Leave in Linby, near Nottingham, on Saturday morning telling around 200 Brexit supporters that Mrs May had reduced the nation "to a state of humiliation".
Speaking from the top of an open-top bus, Mr Farage said those gathering for the People's Vote march in London were not the majority, before leading the marchers through the village.

Sir Vince Cable - the likely next Lib Dem leader - says he is "beginning to think Brexit may never happen".
He said "enormous" divisions in the Labour and the Tory parties and a "deteriorating" economy would make people think again.
"People will realise that we didn't vote to be poorer, and I think the whole question of continued membership will once again arise," he said.
He was speaking on the BBC's Andrew Marr show.
His comments were dismissed by leading Eurosceptic Conservative MP Owen Paterson, who said Sir Vince was just "chucking buckets of water around" and ignoring the "huge vote" in favour of leaving in the referendum and at the general election, where the two main parties backed Brexit.
"Vince Cable's party went down in votes, as did the other little parties who want to stay in the European Union," he told the BBC's Sunday Politics.
He added: "I am afraid Vince is behind history. We are going to leave. We are on target."
Sir Vince conceded that the Lib Dem policy on a second referendum on the terms of a Brexit deal "didn't really cut through in the general election".
But he said it could offer voters "a way out when it becomes clear the Brexit is potentially disastrous".
The former business secretary looks set to be crowned Lib Dem leader. He is the only candidate following the resignation of Tim Farron.
Sir Vince told the BBC he wants to work with Labour and Tory MPs to block what he regards as Theresa May's "hard Brexit" policy.
"A lot of people are keeping their heads down," he said, and "we'll see what happens" when MPs returned from their summer break.
But he added: "I'm beginning to think that Brexit may never happen.
"The problems are so enormous, the divisions within the two major parties are so enormous. I can see a scenario in which this doesn't happen."
MPs are set to vote on the Repeal Bill, a key piece of Brexit legislation, in the autumn.
Sir Vince has said he wants to form a cross-party coalition including like-minded Tory and Labour MPs to oppose Britain's exit from the single market - the official policy of both the Conservative and Labour parties.
He said Labour MPs who disagreed with their leader's position were welcome in his party, and predicted Labour's divisions on the issue would get worse.
"Jeremy Corbyn had a good election, for sure, but there is an element of a 'bubble' about it," he told Andrew Marr.
"He managed to attract large numbers of people on the basis that he was leading opposition to Brexit.
"Actually he is very pro-Brexit, and hard Brexit, and I think when that becomes apparent, the divisions in the Labour Party will become more real and the opportunity for us to move into that space will be substantial."
Sir Vince has come under fire for saying Theresa May's comment, in her 2016 Conservative Party conference speech, that "if you believe you're a citizen of the world, you're a citizen of nowhere," was like something out of Adolf Hitler's Mein Kampf.
Quizzed by Andrew Marr on this, Sir Vince said he had got the wrong dictator: "I got my literary reference wrong - I think it was Stalin who talked about 'rootless cosmopolitans'."
Sir Vince, who won back his Twickenham seat at the general election, is not expected to face a challenger for the Lib Dem leadership but he said would still produce a manifesto. He suggested he would back income tax rises to pay for improvements to health and social care.

Donald Tusk has insisted the EU "does not want to build a wall", but Brexit means "we will be drifting apart".
The EU Council president said Theresa May wanted to "demonstrate at any price that Brexit could be a success", but that was not the EU's objective.
He was unveiling draft guidelines for the EU side of Brexit trade talks.
Mr Tusk said the EU wanted an "ambitious and advanced" free trade deal - and continued access to UK waters for EU fishing vessels.
"Our agreement will not make trade between the UK and EU frictionless or smoother," he said.
"It will make it more complicated and costly than today for all of us. This is the essence of Brexit."
He said it would be the first time in history that a free trade agreement would "loosen, not strengthen, economic ties".
The draft European Council guidelines call for zero-tariff trade in goods - where the EU has a surplus.
The document also says access for services will be limited by the fact that the UK will be outside the EU and will no longer share a common regulatory and judiciary framework.
The draft guidelines repeat EU warnings that there can be "no cherry-picking" of participation in the single market for particular sectors of industry.
The BBC's Reality Check correspondent Chris Morris said the "narrow negotiating mandate set out in these guidelines suggests that the EU doesn't think it will be much more ambitious than other free trade agreements it has negotiated - Canada is the most obvious example".
Mr Tusk said he wanted continued security and research cooperation and to ensure flights were not grounded.
But he added: "No member state is free to pick only those sectors of the internal market they like, or to accept the role of the ECJ only when it suits their interest."
The draft guidelines also say that the EU will "preserve its autonomy as regards its decision-making, which excludes participation of the United Kingdom as a third-country to EU Institutions, agencies or bodies".
Mrs May acknowledged in her Mansion House speech on Brexit on Friday that neither side would get everything they want from negotiations.
But she also stressed that the UK wanted a bespoke trade deal, rather than an "off-the-shelf" model.
"The fact is that every free trade agreement has varying market access depending on the respective interests of the countries involved," she said.
"If this is cherry-picking, then every trade arrangement is cherry-picking."
She also said: "We will also want to explore with the EU, the terms on which the UK could remain part of EU agencies."
This appears to be in conflict with the EU draft guidelines, although BBC Research has found several examples of non-EU members participating - as a member or observer - in EU agencies and bodies, such as the European Environment Agency and the European Medicines Agency.
The EU says it wants to maintain "existing reciprocal access to fishing waters" - a leading concern of the fishing industry in countries bordering the North Sea.
In her Mansion House speech, Mrs May said: "The UK will regain control over our domestic fisheries management rules and access to our waters."
She added that the UK would want to "work together to manage shared stocks in a sustainable way and to agree reciprocal access to waters and a fairer allocation of fishing opportunities for the UK fishing industry".
Brexit Secretary David Davis - quizzed on Tuesday by Brexiteer Labour MP Kate Hoey - insisted the government would not betray UK fishing communities by "trading away fishing rights" for "other things".
Asked about the EU's demand to keep access as it is now, Chancellor Philip Hammond said the UK was "open to discussing with our EU partners about the appropriate arrangements for reciprocal access for our fishermen to EU waters and for EU fishermen to our waters".
Campaign group Fishing for Leave urged the government not to "cave in" to the EU demands, saying: "Nowhere else is access to fisheries included as negotiating collateral for a free trade agreement."
Financial services are not mentioned specifically in the EU draft guidelines, but it is shaping up to be a major sticking point.
UK Chancellor Philip Hammond has told European leaders that it is in the "mutual interest" of both the UK and the EU to include financial services in a free trade agreement.
"Given the shape of the British economy and our trade balance with the EU 27, it's hard to see how any deal that did not include services could look like a fair and balanced settlement," he said in a speech.
"Not only is it possible to include financial services in a trade deal, but this is very much in our mutual interest to do so."
But Donald Tusk appeared to reject the UK proposals. The EU says the UK will be treated like any other "third country" after Brexit.
Asked about the EU guidelines, which also warn of the "negative economic consequences" of Brexit, Mr Hammond said: "It does not surprise me remotely that what they have set out this morning is a very tough position. That's what any competent, skilled and experienced negotiator would do."
EU deal 'must include financial services'
Donald Tusk unveiled his guidelines in a picture-perfect castle in the hills outside Luxembourg.
A nice change to the usual venues in Brussels but the same tough message from the EU that the UK's red lines limit what it can get from the final Brexit deal.
The best that's on offer is a free trade agreement on goods with no tariffs, and access to the European markets for the UK service sector - but under EU rules and with no specific mention of financial services.
I asked a sad-sounding Donald Tusk if his offer came anywhere close to what the prime minister had asked for in her Mansion House speech. His pause was epically long, which suggested he knows it is not.
His document is also pretty gloomy, with a spine-chilling warning about the economic costs to the UK.
But there is also a big offer tucked away in a later paragraph - there are other options available if the government is prepared to compromise on its red lines.
The leaders of the remaining 27 EU states must approve the plans at a Brussels summit on 22 March, setting the template for chief negotiator Michel Barnier for talks with the UK about their future relationship.
The UK is due to leave the EU at the end of March 2019, and both sides have said they would like a deal on their future relationship to be agreed by this autumn to allow time for parliaments to approve the deal before Brexit happens.
The European Parliament has stressed that its preferred option is for the UK to continue to be a member of the single market and customs union after Brexit, in a draft resolution, leaked to the Politico website.
The parliament does not have a formal role in the Brexit negotiations but does have a veto on the final deal.
The European Parliament document, which may be changed before it is adopted, says non-EU members - even if very closely aligned to the bloc - cannot expect the same rights and benefits as EU members.
It also warns that the UK's current "red lines" in Brexit talks "would lead to customs checks and verification which would affect global supply chains and manufacturing processes, even if tariff barriers can be avoided".
It says a "deep and comprehensive" trade deal, of the kind envisioned by Theresa May, must entail "a binding interpretation role" for the European Court of Justice.
MPs in Westminster are, meanwhile, debating a call by Plaid Cymru - who have four MPs in Wales - for UK nationals to be allowed to keep their EU citizenship after Brexit.
Plaid said EU citizenship would give holders the right to travel, live, study and work anywhere in the EU even after the UK leaves next year.
A UK government spokesman said only citizens of EU member states could hold EU citizenship.

A Brexit minister has apologised in Parliament for comments he made about the independence of the civil service.
Steve Baker said he had been told Treasury officials were deliberately trying to influence policy in favour of staying in the EU customs union.
Charles Grant, an EU policy expert said to have been the source of the claims, has since denied telling Mr Baker this.
Mr Baker told MPs he now accepted this and insisted that he had the "highest regard" for the civil service.
In a short speech in the Commons before proceedings began on Friday, Mr Baker said he wanted to set the record straight.
"As I explained yesterday (Thursday) I considered what I understood to be the suggestion being put to me as implausible because of the long standing and well regarded impartiality of the civil service," he said.
After Mr Baker's claims emerged on Thursday, Mr Grant, the Centre for European Reform think tank chief, issued a statement.
He said he recalled telling the minister at an event at the Conservative Party conference that he was aware of Treasury research showing the economic costs of leaving the customs union outweighed the benefits of striking free trade deals.
But he added: "I did not say or imply that the Treasury had deliberately developed a model to show that all non-customs union options were bad, with the intention to influence policy."
An audio recording of Mr Grant's lunch at the Tory conference has since been published online.
In his apology, Mr Baker said: "In the context of that audio I accept that I should have corrected or dismissed the premise of my Hon Friend's question.
"I have apologised to Charles Grant who is an honest and trustworthy man.
"As I have put on record many times I have the highest regard for our hard-working civil servants. I am grateful for this early opportunity to correct the record, and I apologise to the House."
Downing Street said it was "the right thing to do" for Mr Baker to have made a "heartfelt" apology for his comments, adding: "We consider this matter closed."
Theresa May's spokesman said the prime minister had not personally spoken to Mr Baker about the row but No 10 officials did have a word with him after the recording of Mr Grant's lunch emerged.
The row was sparked by Commons exchanges on Thursday at Brexit questions.
Prominent Brexiteer Jacob Rees-Mogg asked Mr Baker to confirm if he had heard Mr Grant that "officials in the Treasury have deliberately developed a model to show that all options other than staying in the customs union were bad and that officials intended to use this to influence policy".
In response, Mr Baker said he was "sorry to say" that Mr Rees-Mogg's account was "essentially correct", adding: "At the time I considered it implausible because my direct experience is that civil servants are extraordinarily careful to uphold the impartiality of the civil service."
Mr Baker, a leading backbench Eurosceptic before his promotion to a ministerial post, was challenged by opposition MPs as he delivered his answer to Mr Rees-Mogg, prompting him to add: "I didn't say it was correct. I said the account that was put to me is correct.
"It was put to me, I considered it an extraordinary allegation, I still consider it an extraordinary allegation."
Following Mr Baker's apology, Mr Rees-Mogg is continuing to insist that the Treasury has questions to answer over its stance on the customs union.
Theresa May has ruled out staying in the customs union - which allows tariff-free trade between its members but prevents them from negotiating their own trade deals - but has not excluded the possibility of some form of customs partnership with the EU after Brexit.

The Brexit vote must not be frustrated and the government needs to maintain an "absolute" focus on delivering it, Theresa May has said.
In a speech to Tory activists the PM said, as her negotiations with the EU reach their final stages, the "worst thing we could do is lose our focus".
It came as three pro-EU cabinet members warned they could vote to delay Brexit to prevent a "disastrous" no-deal.
But Mrs May said there must be no party "purges" over MPs with differing views.
Ahead of crucial votes in the Commons next week, Greg Clark, Amber Rudd and David Gauke told the Daily Mail they would be prepared to defy the prime minister and vote for a delay.
The intervention led to calls for their resignations by Tory Brexiteers.
The UK remains on course to leave the European Union on 29 March.
However, the government has repeatedly refused to rule out the possibility of the UK leaving without a formal deal, in the event that Mrs May cannot get MPs to approve the deal she negotiated with Brussels in time.
Mrs May's speech to the National Conservative Convention in Oxford on Saturday evening came as MPs prepare for a series of votes on Wednesday which could see Parliament take control of the Brexit process.
Delegates at the convention overwhelmingly backed a symbolic motion saying Brexit should not be delayed, and leaving without an agreement should remain an option.
Mr Clark, the business secretary, along with Ms Rudd, the work and pensions secretary, and the justice secretary, Mr Gauke, had earlier said they would be prepared to defy Mrs May and vote for a delay to Brexit.
They argued there  "simply will not be time to agree a deal and complete all the necessary legislation" unless a deal is approved in the coming days.
An amendment tabled by former Tory minister Sir Oliver Letwin and Labour's Yvette Cooper would give Parliament the opportunity to delay Brexit and prevent a no-deal situation if there is no agreement with the EU by the middle of March.
But Mrs May told activists: "Our focus to deliver Brexit must be absolute.
"We must not, and I will not, frustrate what was the largest democratic exercise in this country's history. In the very final stages of this process, the worst thing we could do is lose our focus."
Mrs May also said there should be no moves to deselect MPs because of their views on Brexit.
The resignations of three pro-Remain Tory MPs - Anna Soubry, Heidi Allen and Sarah Wollaston - to join a group of Labour defectors in the new Independent Group reduced the Tories working majority in Parliament to eight.
Mrs May said: "No-one gets more frustrated than I do when people vote against the whip, particularly given the tight Parliamentary arithmetic that we face.
"But we are not a party of purges and retribution. We called a referendum and let people express their views - so we should not be seeking to deselect any of our MPs because of their views on Brexit.
"Our party is rightly a broad church - on that and other issues."
Mrs May is expected to hold talks with European Council president Donald Tusk and other key EU figures in Egypt later during a summit between leaders of EU and Arab league countries.
But Downing Street has played down hopes of a breakthrough on her Brexit deal being reached in Sharm el- Sheikh.
The summit is the first between leaders of EU and Arab league countries and will focus on tackling concerns over security and migration, and boosting trade.

Some of the biggest names in science are pleading for a deal on Brexit to avoid damaging British and European research.
A letter to Theresa May and Jean-Claude-Juncker has been signed by 29 Nobel Laureates and six winners of the prestigious Fields medal.
Science needs "the flow of people and ideas across borders", it says.
It comes as a survey found that many scientists are considering leaving the UK.
Sir Paul Nurse, one of the signatories and a Nobel prize-winner for research into breast cancer, said: "The message is, 'take science seriously'."
Science can help tackle global challenges like treating disease, generating clean energy and guaranteeing food supplies, the letter says - but to do that it needs to bring together the most talented researchers.
And it says Britain and the EU "must now strive to ensure that as little harm as possible is done to research".
Funding and freedom of movement are the two big concerns.
Over the years of Britain's membership of the EU, leading scientists say that the UK has been extremely successful at landing European grants.
Britain's overall financial contributions have been larger than the sums received but the UK's top scientific academy, the Royal Society, calculates that British science as a sector has gained financially.
"...it receives a greater amount of EU funding for research and development than the proportion of its contribution analyses suggests is earmarked for this," it says.
Members states pay their national contributions into a central pot which is then divided between the different spending programmes.
The UK Office of National Statistics (ONS) reports an "indicative" figure for the UK's contribution to EU research and development of €5.4bn over the period 2007-2013.
During this time, it says, the UK received €8.8bn in direct EU funding for research, development and innovation activities.
Sir Paul reckons that without a deal, British science could lose about £1bn a year.
There had been hopes that Britain could rapidly negotiate a new science relationship with the EU, with an associate status like that of Switzerland, in which contributions are made and grants received. But that has not happened so far.
The other worry is that without freedom of movement, the brightest scientific talent may be put off by the bureaucracy of having to apply for a visa.
In an internal survey, staff at the Francis Crick Institute in London were asked for their views on Brexit - the Crick is the largest biomedical research centre under one roof in Europe.
Of the roughly 1,000 scientists on the staff, 40% are from EU countries and a priority was to find out what they might do after Brexit.
78% of the EU scientists said they were "less likely" to stay in the UK.
51% of all the institute's scientists - including those from Britain - said they were less likely to stay.
45% of lab heads said Brexit had already affected their work - either recruiting new scientists, being excluded from EU programmes or facing increased costs after the fall in the pound.
97% of those who responded said a no-deal Brexit would be bad for UK science.
One manager of a lab at the institute, Val Maciulyte from Lithuania, told me the "uncertainty" of the Brexit process meant she was considering moving after seven years in Britain.
"I think that definitely makes me think of other places than the UK, I'm thinking about other options in Europe, in central Europe, or even maybe going back to Lithuania," she said.
Jasmin Zohren, a post-doctoral researcher from Germany, said it was difficult to plan because "no one knows what is going to happen" but she wants to live in a country that is in the EU, despite "loving London".
She said: "I'm currently funded by the EU - also for my PhD which I did in the UK - and I know that lots of this money will not arrive in the UK any more. And of course that's a big concern."
A senior scientist, Monica Rodrigo from Spain, said that the uncertainty was having an impact on everyone.
"I think the biggest thing is the level of stress that people are having because it's not only affecting your professional life but it's affecting other things," she said.
"Even if you're a British scientist it's affecting how you carry on your life and what you're going to do in the future - are you going to stay where there's limited funding or go somewhere else?"
I put it to Sir Paul that even without a deal, British science would be strong enough to cope.
"We will of course survive, we will of course receive funding from the government and we will keep going," he says.
"But at the moment Britain is at the top of the tree; we are considered widely around the world to be the best and we are in danger of losing that top position if we don't get this right."
A government spokesman said: "The UK plays a vital role in making Europe a pioneering base for research, and values the contribution that international researchers make to the UK.
"This will not change when we leave the EU.
"We will seek an ambitious relationship on science and innovation with our EU partners, exploring future UK participation in mutually beneficial research programmes, and will continue to support science, research and innovation through our modern industrial strategy.
 "We have a proud record of welcoming the world's brightest scientists and researchers to work and study here, and after we leave the EU we will have an immigration system to support this."

The UK's Brexit negotiations have not begun well amid "differences" inside the cabinet, a former head of the diplomatic service has said.
Sir Simon Fraser, chief mandarin at the Foreign Office until 2015, said the UK side had been "a bit absent" from formal negotiations in Brussels.
Sir Simon, who now advises businesses on Brexit, said he was concerned the UK had not put forward a clear position.
Downing Street said it disagreed strongly with his comments.
The government is expected to publish "position papers" on key issues soon.
Speaking to BBC Radio 4's Westminster Hour, Sir Simon, who campaigned for Remain ahead of last year's referendum, said he feared divisions within the cabinet were preventing the government from presenting a united front.
"The negotiations have only just begun, I don't think they have begun particularly promisingly, frankly, on the British side," he said.
"We haven't put forward a lot because, as we know, there are differences within the cabinet about the sort of Brexit that we are heading for and until those differences are further resolved I think it's very difficult for us to have a clear position."
He added: "I think so far we haven't put much on the table apart from something on the status of nationals, so we are a bit absent from the formal negotiation."
He called on the government to publish further details about its views on issues, including future customs arrangements and the Northern Irish border in the coming weeks.
"I think we need to demonstrate that we are ready to engage on the substance so that people can understand what is really at stake here and what the options are."
Downing Street rejected Sir Simon's analysis.
"The last two months, we have had a constructive start to the negotiations. We have covered a significant amount of important ground," the prime minister's spokesman said.
"As the secretary of state for exiting the European Union said at the end of the last negotiating round, important progress has been made in understanding one another's positions on key issues."
Last month, Brexit Secretary David Davis said he was confident negotiations would continue as planned after reports Brussels may delay trade talks because of a lack of progress on the "divorce" settlement.
At the weekend, the Sunday Telegraph claimed UK negotiators are now prepared to pay up to £36bn to the EU to settle the so-called Brexit divorce bill.
Downing Street said it did not recognise this figure.
Conservative MP Peter Bone said it would be "totally bizarre" for the UK to give the EU any money, let alone £36bn, adding that such a fee was unlikely to get through Parliament.
Another Eurosceptic MP, Jacob Rees-Mogg, said there was "no logic" to the figure that was being reported.
Responding to Sir Simon's comments, Liberal Democrat Brexit spokesman Tom Brake said: "This government is in the middle of the single biggest economic and diplomatic negotiation in our history.
"Yet while the clock is running down, key cabinet members are still squabbling over what type of Brexit to pursue."
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The EU's chief negotiator said there would be "substantial" consequences from Brexit after the first round of talks with the UK.
Michel Barnier said he was "not in the frame of mind to make concessions or ask for concessions".
UK Brexit Secretary David Davis said talks got off to a "promising start".
The UK appears to have conceded to the EU's preferred order for the talks which will mean trade negotiations do not begin immediately.
Mr Davis and Mr Barnier gave a joint press conference after day one of the talks in Brussels.
The initial focus will be on expat rights, a financial settlement and "other separation issues".
Discussions aimed at preserving the Good Friday Agreement and common travel area in Ireland will also begin, although Mr Davis suggested these issues may not be settled until the end of the process, when the UK's trade relationship with the EU is settled.
The UK had wanted talks on its future relationship with the EU to be considered from the outset, but Mr Barnier said this would only happen once the European Council decided "sufficient progress has been made" on the other issues.
Mr Davis - who had predicted this would be the "row of the summer" - denied suggestions the agreed timetable showed Britain's "weakness" and insisted it was "completely consistent" with the government's aim of parallel trade and exit talks.
"It's not when it starts it's how it finishes that matters," he said.
Asked whether he had made any concessions to the UK in return, Mr Barnier said the UK had decided to leave the EU - not the other way around, and each side had to "assume our responsibility and the consequences of our decisions".
"I am not in a frame of mind to make concessions, or ask for concessions," he said.
"It's not about punishment, it is not about revenge.
"Basically, we are implementing the decision taken by the United Kingdom to leave the European Union, and unravel 43 years of patiently-built relations.
"I will do all I can to put emotion to one side and stick to the facts, the figures, and the legal basis, and work with the United Kingdom to find an agreement in that frame of mind."
Laura Kuennsberg, BBC political editor
It's often compared to a divorce - the UK wanted to talk about who gets the house and the CD collection at the same time as settling who pays for the kids' weddings in 20 years' time.
The EU on the other hand have been firm all along that the future arrangements could only be discussed once the terms of the initial split have been agreed.
The debate was called "parallelism versus sequentialism" and from this afternoon's press conference and the announcement of the procedure it is clear that the UK has lost.
Ministers believed they would be able to persuade the EU - the failure to do so has been described as a "total cave-in".
The discussion was even predicted by Mr Davis as likely to be the "row of the summer". The row won't happen because it seems the UK has already given in.
Mr Barnier said a "fair deal" was possible "and far better than no deal". He promised to work with, not against, the UK.
"We must lift the uncertainty caused by Brexit," he said.
The two men - who exchanged gifts at the start of the talks - set out the structure for the initial negotiations. There will be one week of negotiations every month.
Working groups of "senior experts" will be set up to focus on the three main areas.
On citizens' rights, which the UK has said should be an immediate priority, Mr Davis said there was "much common ground".
The UK is set to leave the EU by the end of March 2019, following last year's referendum vote.
Prior to the start of talks, Mr Davis gave his counterpart a first edition of a mountaineering book - a French-language version of Regards vers Annapurna - while Mr Barnier reciprocated with a traditional, hand-carved walking stick from Savoie, complete with leather wrist strap.
Who's who in the UK delegation?
After holding talks with Theresa May in Downing Street, new Irish prime minister Leo Varadkar said there must be no return to a hard border between Northern Ireland and the Republic of Ireland and economic borders must be "invisible".
While he said he regretted Mrs May's decision to leave the single market and customs union, he said the two had a shared objective to minimise disruption to trade after the UK's exit.
Earlier former Marks and Spencer chairman Lord Rose, who chaired the Stronger In campaign last year, told BBC Radio 4's Today programme that he was reassured that economic considerations were "top of the pile" but ministers needed to be realistic with the public.
Speaking on the same programme, JD Wetherspoon founder Tim Martin - one of the leading pro-Leave business voices - said negotiators had to be open to possible compromises but also prepared to walk away and to default to World Trade Organization rules if necessary.
"I don't think many people feel that staying in the single market and customs union and being subject to EU laws is Brexit.
"I think Brexit is parliamentary sovereignty and an assertion of democracy. Outside that, I think there is a quite a lot of scope," Mr Martin said.
For Labour, shadow Brexit secretary Sir Keir Starmer said there was "real confusion" about the government's mandate after the general election result.

The UK's offer on Brexit must be acceptable to the Republic of Ireland before the negotiations can move on, the president of the European Council, Donald Tusk, has said.
Mr Tusk was speaking after talks with the Irish prime minister in Dublin on Friday.
He said: "The UK's future lies - in some ways - in Dublin".
The European Union has said "sufficient progress" must be made on the Irish border before negotiations can move on.
"The Irish request is the EU's request," Mr Tusk said.
"I realise that for some British politicians this may be hard to understand.
"But such is the logic behind the fact that Ireland is the EU member while the UK is leaving.
"This is why the key to the UK's future lies - in some ways - in Dublin, at least as long as Brexit negotiations continue."
In a press conference with Taoiseach (Irish prime minister) Leo Varadkar, Mr Tusk said that the UK's decision to leave the EU had created "uncertainty for millions of people".
"The border between Ireland and Northern Ireland is no longer a symbol of division, it is a symbol of cooperation and we cannot allow Brexit to destroy this achievement of the Good Friday Agreement," he said.
By BBC Political Correspondent Adam Fleming
There is a lively debate about whether the Irish government has a veto over the decision - to be taken at the summit of EU leaders on 14 and 15 December - about whether Brexit talks can move to the next phase.
Call it what you like, but now Donald Tusk has told us for sure that the rest of the EU will do what Ireland decides.
There was a put-down for British politicians who may find it "hard to understand" why this is important.
But there was some comfort for the British government: Donald Tusk shares their view that the issue of the border can only be solved when there is more clarity about the UK's future relationship with the EU.
And Mr Tusk ended by saying "the key to the UK's future lies - in some ways - in Dublin." Is this a hint that the Irish government's suggestion that Northern Ireland remain in the EU's single market and customs union is the answer for the whole of the UK?
Or is it just a reminder that Dublin is first among equals among the remaining 27 members of the EU?
"The UK started Brexit and now it is their responsibility to propose a credible commitment to do what is necessary to avoid a hard border.
"As you know, I asked Prime Minister May to put a final offer on the table by the 4th of December so that we can assess whether sufficient progress can be made at the upcoming European Council.
"Let me say very clearly. If the UK offer is unacceptable for Ireland, it will also be unacceptable for the EU."
The taoiseach thanked Mr Tusk for the solidarity demonstrated by all EU partners and called the EU "a family which sticks together".
He said he was optimistic that a deal could be achieved by Monday.
However, he said any UK offer must indicate how a hard border can be avoided and avoid the risk of regulatory divergence.
On Thursday, the DUP's Sammy Wilson said any attempt to "placate Dublin and the EU" could mean a withdrawal of DUP support at Westminster.
He was responding to reports of a possible strategy to deal with the Irish border after Brexit.
The story suggested that British and EU officials could be about to seek separate customs measures for Northern Ireland after the UK leaves the European Union.
The DUP struck a deal with Prime Minister Theresa May's government in June, agreeing to support Tory policies at Westminster, in return for an extra £1bn in government spending for Northern Ireland.

A former top trade adviser to US President Trump has told the BBC "there is a level of panic" around Brexit "that is not justified".
Stephen Vaughn, who served as acting trade representative before becoming general counsel on trade, stressed the UK has "enormous leverage" in a potential trade deal with the US.
On a deal's likelihood, he said the Trump administration is "ready to go".
The UK will be able to strike its own trade deals only after leaving the EU.
As a member of President Trump's negotiating team, Mr Vaughn had a key role in the talks with Canada and China, before leaving the administration in April.
In reference to a potential UK deal, he compared the situation with US-Canada negotiations: "No one would say, 'Canada has to join the US in a union or Canada will get steamrolled by the US'."
"You have an enormous amount of leverage, and we'll see how you use it," he added, speaking in his first broadcast interview since leaving the Office of the US Trade Representative.
On US preparations for a potential deal with the UK, he said that Robert Lighthizer, the current US Trade Representative, had done all the preparations needed.
However, he acknowledged that agreeing a deal could take "months or years".
The US Trade Representative, sometimes shortened to USTR, is the president's top adviser on international trade. The team negotiates directly with foreign governments to create trade agreements and participate in global trade policy organisations.
Concerns have been raised over the impact of a deal on life in the UK, including whether US drugmakers would demand the ability to sell to the NHS.
Another key export for the US is agricultural products, but the fact farming methods in the US don't fall under the EU regulations has led some to worry about food standards.
Mr Vaughn emphasised that the US would like a deal to involve the expansion of farm exports, saying he doesn't think it's "something people should be afraid of".
The trade expert, who now works in the private sector, also played an active role in the Trump administration's trade war with China.
He said that a key aspect of those talks was to make sure the two sides comprehended each other: "You really just want to make sure everybody is understanding the issues and what is at stake."
He added that the talks are very "serious" and there is no "yelling and screaming".
Mr Vaughn stressed that the US is concerned about various Chinese practices and that it wants to see Chinese businesses become more "market-oriented".
He went on to defend the use of tariffs against China: "You're trying to figure out, how do you get leverage on the other people?", he explained, adding that Mr Trump is not satisfied with the status quo he inherited.
On the impact of tariffs, he rejected the idea that the measures may be having a negative effect on US business.
"When you look at the actual data, we have by far the largest economy in the G7 and our manufacturing sector continues to grow," he argued.
US business groups have called for a rethink on tariffs, including the National Retail Federation, which has complained about the administration "doubling down on a flawed tariff strategy".
The former top adviser to President Trump, Gary Cohn, has also warned that the tariffs are backfiring.
Speaking in an earlier interview with the BBC, Mr Cohn criticised the approach the Trump administration is taking against China, saying: "I think everyone loses in a trade war."
Mr Cohn, who served as director of the National Economic Council in the Trump administration, announcing he was resigning after Mr Trump decided to impose import tariffs on steel and aluminium.
Mr Vaughn became the acting USTR on Trump's inauguration day in January 2017, staying on until Mr Lighthizer was confirmed in May 2017. He served as Mr Lighthizer's general counsel until the end of April 2019.
Before entering the White House, he was a partner at US law firm King & Spalding, a role to which he has returned.
On his departure, a statement by Mr Lighthizer read: "Stephen has played a central role in shaping and implementing the President's trade policies."

Theresa May has renewed her efforts to sell her draft Brexit withdrawal agreement - arguing it will stop EU migrants "jumping the queue".
She said migration would become skills-based, with Europeans no longer prioritised over "engineers from Sydney or software developers from Delhi".
The PM also insisted to business leaders at the CBI that the withdrawal deal had been "agreed in full".
Nicola Sturgeon said the PM's remarks on EU free movement were "offensive".
The Scottish First Minister said for the prime minister to use such language to describe reciprocal arrangements entered into freely by the UK - allowing EU nationals to live and work in the UK and vice-versa - was "really disgraceful".
Meanwhile, the DUP, which is opposed to the Irish border backstop proposal in the withdrawal agreement, abstained on amendments to the Finance Bill in the Commons on Monday evening.
It also supported one amendment proposed by the Labour Party.
The DUP has a so-called confidence-and-supply arrangement to support the Conservative Party, which does not have a majority in the House of Commons, which was secured with a controversial £1bn funding deal for Northern Ireland.
The party's Brexit spokesman, Sammy Wilson, told BBC's Newsnight the abstentions were made because the government had broken a fundamental agreement to deliver Brexit for the people of the UK "as a whole" and to not "separate Northern Ireland constitutionally or economically from the United Kingdom".
The move was designed to send a political message back, he said.
"'Look, we've got an agreement with you, but you've got to keep your side of the bargain, otherwise we don't feel obliged to keep ours.'"
A senior DUP source stressed, however, that this was not the end of the confidence-and-supply agreement between the Conservatives and the DUP.
Also on Monday evening, the government said it would publish an economic analysis comparing the costs and benefits of its Brexit deal with those of the UK staying in the EU.
A cross-party group of MPs had proposed an amendment to the Bill calling on ministers to publish the forecasts.
The government said MPs would be given the analysis before the meaningful vote on the final deal. It will look at a no-deal scenario, a free trade agreement and the government's proposed deal.
The prime minister's appeal to business leaders came as Tory MPs continue to press for late changes to the deal.
Ministers from the remaining 27 EU countries have met in Brussels to work on the political declaration setting out their future relationship with the UK - a meeting which revealed Spanish concern at the wording's impact on Gibraltar's future.
Meanwhile, Labour leader Jeremy Corbyn, whose party is set to reject Mrs May's deal, told the CBI business lobby group's conference that Brexit can be a "catalyst for economic transformation" in the UK.
There has been widespread criticism of the draft 585-page withdrawal agreement - and the short paper setting out what the UK and EU's future relationship could look like - which are set to be finalised and signed off at an EU summit this weekend.
Two of the prime minister's cabinet ministers resigned over the proposed deal, while others are believed to be trying to change its wording.
Speculation continues over whether the number of Tory MPs submitting letters of no-confidence in Mrs May will reach the 48 required to trigger a confidence vote on her leadership of the Conservative Party.
Mrs May told the CBI's annual conference in London that her plan would provide a fair immigration system that would help young people in the UK get jobs and training.
"It will no longer be the case that EU nationals, regardless of the skills or experience they have to offer, can jump the queue ahead of engineers from Sydney or software developers from Delhi.
"Instead of a system based on where a person is from, we will have one that is built around the talents and skills a person has to offer."
She also said she was not willing to reopen discussions with Brussels over the withdrawal agreement, saying "the core elements of that deal are already in place".
She said that she expected to hammer out a framework for a future trade relationship in Brussels this week, before signing off the deal on Sunday.
CBI president John Allan urged MPs to back Mrs May's deal - despite it not being "perfect" - and warned of the consequences for businesses if the UK were to simply crash out of the EU.
The Labour leader said Mrs May's "botched" deal "breaches the prime minister's own red lines" and "makes no mention of retaining frictionless trade".
Mr Corbyn suggested the EU would consider re-writing the draft agreement "at the 11th hour" if MPs rejected the proposals.
He also suggested the UK's exit from the EU should be a catalyst for far-reaching economic and social change and a "radical programme of investment" in infrastructure, education and skills.
The draft document sets out the terms of the UK's departure, including how much money will be paid to the EU, details of the transition period, and citizens' rights.
The transition period - currently due to last until 31 December 2020 - will mean the UK is officially out of the EU, but still abiding by most of its rules. During this time, the two sides hope to negotiate a permanent trade deal.
The UK and the EU want to avoid a hard Northern Ireland border whatever happens, so they agreed to a "backstop" - described as an insurance policy by Mrs May - aimed at achieving this if the sides cannot agree a trade deal that avoids a physically visible border.
The backstop would mean Northern Ireland would stay more closely aligned to some EU rules, which critics say is unacceptable. And the whole of the UK would be in a single custom territory - effectively keeping the whole of the UK in the EU customs union.
The critics say that during the transition period, the UK will still abide by most of the EU's rules but have no power over setting them - and there is no system for the UK being able to leave any backstop deal without the EU's agreement, so it could become a permanent arrangement.
When asked whether the transition period could last until the end of 2022, Business Secretary Greg Clark told BBC Radio 4's Today programme: "It would be at our request and that would be a maximum period."
He said it could be extended for a matter of "weeks or months", and added: "If we were six weeks away from concluding a future economic partnership and agreeing that, then it may make sense to extend the transition period."
Later, Mrs May told the CBI conference that it was "important" to be out of the implementation period before the next general election - which is due in June 2022.
Environment Secretary Michael Gove, one of the five cabinet ministers who were believed to be trying to change the wording of the deal, said on Monday that the prime minister "has my full support" and she is doing a "very good job".
"I hope people will get behind her as she endeavours to get the very, very best deal for Britain," he said.
But former Foreign Secretary Boris Johnson used his column in Monday's Daily Telegraph to renew his criticism of the draft agreement, describing it as a "585-page fig-leaf [that] does nothing to cover the embarrassment of our total defeat".
And former Tory leader Lord Howard told BBC Radio 4's Today programme that a vote of confidence would be a distraction.
Guy Verhofstadt, the European Parliament's Brexit co-ordinator, said any suggestions EU nationals had been given preferential treatment were wrong since they were merely "exercising rights which provided freedom and opportunities".
Michel Barnier, the EU's chief Brexit negotiator, called on all parties to "remain calm" and focus on the future agreement.
Speaking at a press conference in Brussels after meeting the 27 other EU member states, he said the withdrawal deal was "fair and balanced" but made clear a transition period extension could not be indefinite, "it has to be a fixed period of time".
During Monday's meeting, the Spanish government raised concerns about two articles in the withdrawal agreement (184 and 3), saying that taken together they add up to Gibraltar remaining permanently as UK territory.
The BBC's Brussels reporter Adam Fleming says most member states, along with the European Commission and the European Council, do not agree with Madrid's reading of the text and are seeking to provide reassurance.

Former Conservative Deputy Prime Minister Lord Heseltine has been sacked as a government adviser after rebelling over Brexit in the House of Lords.
Lord Heseltine backed the demand for a parliamentary vote on the final deal to be written into Brexit legislation.
He learned hours later on Tuesday that he had been fired from five government advisory roles he had held.
He said he accepted Number 10's right to sack him but "sometimes there are issues which transcend party politics".
Asked what he thought his sacking said about the current government, he told BBC Radio 4's Today: "I have never met Theresa May so I can't make a judgement. She's doing very well in the polls... the public approve of what she's doing."
Lord Heseltine, who campaigned to remain in the EU, told the Lords that the UK was facing "the most momentous peacetime decision of our time".
The peer said he was having dinner with his wife when he got a call from the chief whip, and went to the Lords to be told he was being sacked.
Lord Heseltine told the BBC the prime minister was "exercising her perfectly legitimate right to get rid of opposition in any way she finds appropriate".
"Whether it's a wise thing to do is a matter for her not for me," he said.
"I have been hugely proud of the work I have done for David Cameron and now for this prime minister, and if they don't want me to go on they must sack me."
He said it was a "great disappointment" for him as "for six years I have had the incredible privilege of working inside the Whitehall machine with civil servants helping ministers to make decisions".
Lord Heseltine continued: "I did write a newspaper article the other day setting out exactly what I intended to do so I think they could have told me this would be the price, but let me make it quite clear; I would still have voted as I did tonight.
"Sometimes in politics there are issues which transcend party politics; in the end you have to be your own person. I believe our interests are intertwined with Europe. I am not prepared to change.
"Every Conservative prime minister I worked for has told me, including this prime minister before the referendum, that we were essentially seeking British self-interest in Europe.
"It's not perfect but it's much better than anything that happened before the Second World War."
The 83-year-old - who dramatically walked out of Mrs Thatcher's cabinet during a row over Westland helicopters in 1986 - served as a minister in both her and John Major's Conservative governments in the 1980s and 1990s.
Who is Lord Heseltine?
Nicknamed "Tarzan" because of his combative manner and long blond hair, renowned by the press as a Conservative "big beast", Michael Heseltine has been a major figure on the UK political scene for decades.
Having made a fortune in publishing, he was an MP from 1966 to 2001.
After Margaret Thatcher came to power in 1979, the ambitious and politically centrist Heseltine became environment secretary and then defence secretary.
But he and his boss had a huge fall-out in 1986, over a complex dispute involving the future of Westland helicopters. He quit and walked out in the middle of a cabinet meeting.
Heseltine remained on the backbenches until, in 1990, with Thatcher apparently losing popularity among the public and her own party, he launched a leadership bid. He didn't win but inflicted enough of a blow on the PM's prestige for her to resign.
John Major won the next contest, but Heseltine, an ardent Europhile, returned to the cabinet, rising to deputy prime minister in the last two years of Major's premiership, a period beset with Conservative disputes over the UK's relationship with the EU.
Heseltine retired as an MP and entered the Lords, where he continued occasionally to speak out on issues dear to his heart - including putting the Remain case during the EU referendum campaign - and also returned to publishing.
Lord Heseltine was brought in by former Prime Minister David Cameron to advise the government on a range of projects, including schemes in east London and Swansea.
He told Today that his roles were taking up three to four days a week.
A Downing Street spokesman said he understood Mrs May had in fact met Lord Heseltine, although he did not confirm whether this was before or after she became prime minister.
In a statement, the government said it had "a clearly stated and consistent position" that the Brexit bill should be passed without amendment.
The chief whip in the Lords asked Lord Heseltine to stand down because he voted against the government's official position, it said, adding: "The government would like to warmly thank Lord Heseltine for his service."
Former Tory chief whip Mark Harper said it was "quite reasonable" to sack Lord Heseltine for opposing government policy.
Brexit Secretary David Davis has said some in the Lords are seeking to "frustrate" Brexit but it was the government's intention to ensure that did not happen.
When the bill returns to the Commons next week ministers will have some persuading to do to reverse the Lords changes, but Theresa May remains on course to trigger Article 50 and begin Brexit negotiations before the end of this month.
Peers voted by 366 votes to 268 in favour of an amendment to the bill to have a "meaningful" parliamentary vote on the final terms of the Brexit deal.
It was the second defeat for the bill in the Lords - the previous one was on the issue of guaranteeing the rights of EU citizens.
After a three-hour debate on Tuesday, the turnout for the vote was the largest in the Lords since 1831, according to Parliament's website.
As well as Lord Heseltine, 12 other Tory peers defied the government to vote in favour of the amendment, including former ministers Lord Deben and Viscount Hailsham.
Mrs May has said she wants to trigger Article 50 by the end of March but the Commons is unlikely to have an opportunity to consider the changes made by the Lords until the middle of next week because four days have been set aside for debate on the Budget.

The government has seen off an attempt to add conditions to its Brexit bill as a Conservative rebellion was avoided.
MPs rejected a bid by Labour's Chris Leslie to force the government to consult Parliament on the deal struck with the EU before it is finalised.
It came after ministers pledged that a "meaningful" vote would be offered.
Labour and some Tories had pushed for MPs to have a decisive say on the final terms, but the 326 to 293 vote meant the bill remained unchanged.
Seven Conservatives rebelled, while six Labour MPs voted with the government.
Several other attempts to amend the draft legislation, which if passed will authorise the prime minister to formally begin Brexit negotiations under Article 50 of the Lisbon Treaty, were also rejected during more than seven hours of debate.
More amendments will be considered on Wednesday before MPs hold a final vote on whether to back the bill.
Theresa May has already promised Parliament will get a say on the final deal, but critics, including some Conservatives, said they wanted more than the "take it or leave it" vote being offered.
Any possibility of a major Conservative rebellion appeared to be halted by comments from Brexit Minister David Jones.
Mr Jones said MPs would get a say on the final draft Brexit agreement before it was voted upon by the European Parliament.
"This will be a meaningful vote," he told MPs.
"It will be the choice of leaving the EU with a negotiated deal or not."
However, some MPs questioned whether any concessions had in fact been offered, with Downing Street playing down claims the government's position had changed.
Asked what would happen if Parliament rejected the Brexit deal or if there was no agreement with the EU to vote upon, Mr Jones said that in each scenario the UK would still leave the EU but "fall back on other arrangements".
This would effectively see the UK default to World Trade Organization trade rules, involving potential tariffs on exports and imports.
Opponents of Brexit have said this would cause real damage to British business, but supporters say the UK can live with the consequences if necessary as the UK would then be free to negotiate its own trade arrangements.
Mr Jones said the government wanted to avoid a situation in which ministers were  sent back to the negotiating table to hammer out a better deal.
This, he said, would be hard given the two-year limit for talks and would also be "the surest way of undermining our negotiating position and delivering a worse deal".
Former chancellor Ken Clarke - the only Tory to vote against kickstarting the Brexit process last week - said Parliament should have the opportunity to shape the final deal, while former SNP leader Alex Salmond said MPs should have a genuine choice without the "Sword of Damocles" hanging over them.
Labour's Chuka Umunna said the choice facing MPs was "unacceptable", ex-Lib Dem leader Nick Clegg described it as a "symbolic handout" while Green Party leader Caroline Lucas said MPs were being "duped".
But Labour's font bench claimed the move as a "significant victory" in response to its repeated demands for a "meaningful" vote at the end of the two-year negotiation process.
The party withdrew its proposed amendment before Mr Leslie's was defeated.
Conservatives Mr Clarke, Bob Neill, Andrew Tyrie, Claire Perry, Anna Soubry, Antoinette Sandbach and Heidi Allen, defied their party whip.
Ms Perry told MPs the tone of the debate "sometimes borders on the hysterical", before adding: "I feel like sometimes I am sitting along with colleagues who are like jihadis in their support for a hard Brexit."
Teasing her colleagues, she said: "No Brexit is hard enough - 'begone you evil Europeans, we never want you to darken our doors again'. People say: 'Steady on, Claire', but I am afraid I heard speeches last week exactly making that point."
On the Labour benches, Frank Field, Ronnie Campbell, Kate Hoey, Kelvin Hopkins, Graham Stringer and Gisela Stuart voted with the government.
Labour leader Jeremy Corbyn, who backed the Remain side in last year's EU referendum, has ordered his MPs to support the government's bill, whether his party's amendments are accepted or not, in the third reading vote expected on Wednesday.
Mr Corbyn argues that it would be undemocratic to ignore the will of the people, as expressed in last June's EU referendum.
Shadow business secretary Clive Lewis has vowed to oppose the bill unless Labour amendments are passed in the Commons.
Frontbench members of parties are generally expected to resign from their post if they ignore a three-line whip.

Another Brexit referendum will become a "plausible" way forward if there is deadlock in Parliament, Work and Pensions Secretary Amber Rudd has said.
She told ITV's Peston show while she did not personally support another vote, the case for one would grow if MPs could not agree another solution.
She said she hoped MPs would back Theresa May's deal with the EU next month but it would be "very difficult".
The PM says the UK must be ready to leave without a deal if it is rejected.
Mrs May has repeatedly ruled out holding another referendum, saying it was the government's duty to implement the result of the 2016 Brexit vote.
A Downing Street source said the government was "very clear we are 100% opposed" to another referendum.
The UK is due to leave the EU on 29 March 2019 but an agreement on the terms of its withdrawal and a declaration on future relations will only come into force if the UK and EU Parliaments approve it.
The Commons vote was due to be held earlier this month but the PM postponed it once it became clear it would be defeated by a large margin.
She has since sought to gain further assurances from EU leaders to allay MPs' concerns.
Ms Rudd told Robert Peston she could not be sure MPs would back the deal. She suggested arguments for another referendum would come into play if they did not and if they rejected other options.
"I have said I don't want a People's Vote or referendum in general but if parliament absolutely failed to reach a consensus I could see there would be a plausible argument for it," she said.
"Parliament has to reach a majority on how it is going to leave the EU. If it fails to do so, I can see the argument for taking it back to the people again as much as it would distress many of my colleagues."
If Mrs May's deal is rejected, the default position is for the UK to leave in March unless the government seeks to extend the Article 50 negotiating process or Parliament intervenes to stop it happening.
Ms Rudd, who has likened the idea of a no-deal exit to a car crash, said it was imperative that MPs "find a way of getting a deal through Parliament".
To that end, she said she backed the idea of testing the will of Parliament through a series of "indicative" votes on "Plan B" options should MPs reject the PM's agreement.
"It would flush out where... the majority is," she said. "So people who hold onto the idea of one option or another would see there is no majority and so they will need to move to their next preference.
"We will hopefully be able to find where the compromise and the consensus is."
Speaking on the same programme, Labour's shadow education secretary Angela Rayner said talk of another referendum was "hypothetical" at this stage and would represent a "failure" by Parliament.
She accused the prime minister of trying to scare MPs into backing her deal by delaying the vote on it to the latest possible date.
Earlier on Wednesday, the European Commission announced a series of temporary measures designed to reduce the economic impact if the UK was to leave without a comprehensive legally-binding agreement.
But it made clear that it could not counter all the problems it expects.
The Republic of Ireland has given more details of its own no-deal contingency planning, saying the risk of the UK leaving without an agreement was "very real".
It warns of potentially "severe macroeconomic, trade and sectoral impacts" for Ireland as well as "significant gaps" in policing and judicial co-operation.
In such a scenario, it said its priorities would be to uphold the Common Travel Area between the UK and Ireland, ensure there is no return of physical checks on the border between the Republic and Northern Ireland and ensure the "best possible outcome" in terms of trade.
The UK has allocated a further £2bn in funding to government departments to prepare for the possibility and has urged businesses to put their own no-deal plans in motion.

The woman who brought the successful legal challenge against the government over Brexit has accused prominent politicians of behaving "despicably".
Gina Miller told the BBC they had "exacerbated" worries during and after the EU vote and failed to defend her and others with "legitimate concerns" about the process in the face of abuse.
She insists she did not bring her case to thwart the UK's exit from the EU.
But she said some politicians were in "la la land" about what lay in store.
The investment manager was speaking to the BBC's political editor Laura Kuenssberg after the Supreme Court upheld her challenge to the government's approach.
By a margin of eight to three, the justices ruled that Parliament must give its consent before Theresa May can start official talks on the terms of the UK's exit.
Ministers say it was right for the court to decide and they will comply with the ruling.
Mrs Miller, who voted to remain in the EU, said she felt vindicated but that her goal all along had been to give a voice to the millions of people with a stake in the process and help deliver "the best Brexit we can get".
"This is about right and wrong, it's wrong that a government think they are above the law. It's right that I can bring this case," she said.
The 51-year old, who was born in Guyana but educated in Britain, suggested the EU referendum had created a climate of fear in which anyone asking questions about Brexit was seen as unpatriotic and "branded as traitors".
"There's this sense that if you ask a question about Brexit then you're not representing Britain," she said. "Asking questions about Brexit is the most patriotic thing you can do."
She added: "People voted because of legitimate concerns. Politicians have behaved despicably because they have exacerbated those anxieties."
Asked if Theresa May and her ministers had behaved "despicably", Ms Miller said it was "wrong of them not to stand up earlier when the judges were being vilified".
"I think it was wrong of them to not actually speak up sooner about abuse for not just myself but for other people who live in the UK."
Mrs Miller, who says she has been subjected to constant abuse including death threats, said she felt her "family and safety have been put in jeopardy".
"The idea that as a woman I had no right to speak out and I'm not bright enough to speak out. And as an ethnic woman I have no place in society. That's worrying."
She said she was still concerned that politicians were "twisting the truth" when it came to the UK's future outside the EU and Mrs May and her ministers needed to "be honest" with the public about what was achievable from the negotiations.
"Even now, some of the things I hear about what is possible, as we progress Brexit, it's as though they are living in some sort of la la land because it's pure fantasy."
She added: "There are 27 other member states on the other side of the table who are not just going to give us what we want. They are not going to give us cherry picking".

The Lord Chancellor has backed the independence of the UK's judiciary but stopped short of condemning attacks on senior judges over the Brexit ruling.
The Bar Council had demanded Liz Truss respond to criticism from some MPs and newspapers over the decision that MPs should vote on triggering Article 50.
The Daily Mail branded judges "Enemies of the people"; the Daily Express said it was "the day democracy died".
Ms Truss said the "impartiality" of the courts was "respected the world over".
On Thursday, the High Court ruled Parliament should vote on when the government can trigger Article 50, beginning the formal process of the UK leaving the EU.
Three judges found that the government could not start the formal process by using the royal prerogative alone, and would need the backing of both the Commons and the Lords.
The government is seeking to overturn the decision at the Supreme Court - the UK's highest court of appeal - next month.
Following fierce criticism of the ruling, the Bar Council of England and Wales - the professional body representing barristers called for Ms Truss to defend the judges "as a matter of urgency".
But its chairwoman Chantal-Aimee Doerries QC said she would have expected the Lord Chancellor - who is responsible for courts, prisons, probation and constitutional affairs - to make a clearer statement on the "unprecedented" attack which  "undermines the rule of law in this country".
She said the court was entitled to rule on the case and she was "surprised by the backlash" because the judges were "doing their job".
The Criminal Bar Association later passed a resolution backing the Bar Council's demands.
In her statement, Ms Truss, who is also justice secretary, said: "The independence of the judiciary is the foundation upon which our rule of law is built and our judiciary is rightly respected the world over for its independence and impartiality.
"In relation to the case heard in the High Court, the government has made it clear it will appeal to the Supreme Court. Legal process must be followed."
By Ben Wright, BBC News political correspondent
It could not be called a comprehensive response.
Having declined all requests for an interview, the Lord Chancellor Liz Truss put out a three-line statement saying the judiciary was independent and impartial.
Considering the vitriol of some press reaction to the High Court judges decision - "enemies of the people" according to the Daily Mail - and the demands for a defence of the judiciary from Labour and prominent Tory MPs, the government's response was the bare minimum.
We know ministers are angry about the ruling and are appealing to the Supreme Court.
But given a chance to say newspapers and politicians should be very wary about attacking the judiciary the Lord Chancellor demurred.
Nor did she say the courts did have the jurisdiction to rule on this dispute.
However, it be a very brave (or foolish?) minister to criticise the press for writing what they like about Brexit. And many voters will share the anger of some newspapers about the decision of the court.
Shadow justice secretary Richard Burgon, who had earlier said Ms Truss's silence was "embarrassing", called her statement "too little, much too late" and said she had failed to "adequately stand up to attacks on [the] judiciary".
He said "pressure from the legal profession, professional bodies, politicians and the public has paid off" and Ms Truss had "finally made at least some progress on this issue".
But he added: "All Liz Truss has done is recite the well-known principle of the independence of the judiciary...
"The last few days mean that much of the legal community now has no confidence in the Lord Chancellor to fulfil her statutory duty to protect the independence of the British judiciary."
Writing on Twitter, Lib Dem leader Tim Farron described the response from Ms Truss as a "weak statement from a weak cabinet minister".
Earlier, Tory MP and former Attorney-General, Dominic Grieve, has compared coverage in one UK newspaper to the Nazi party's newspaper.
He told BBC Radio 5 live: "Newspapers in a free society can do what they like.
"But if you did decide to behave immoderately and whip up frenzied hatred you can do that in a free society if you set about it, and newspapers like the Daily Mail are no different from the Voelkischer Beobachter in Nazi Germany if they run headlines of that type."
Daily Mail columnist Stephen Glover defended his newspaper's stance, saying he did not believe the judges would "feel frightened or worried" by the criticism.
He said they had made a "decisive intervention" in the political process, and "must expect some comeback".
UKIP MP Douglas Carswell is among those who have attacked the judges, calling them "politicians without accountability".
Meanwhile, Gina Miller, the investment manager and philanthropist who led the legal campaign, has said she plans to report online trolls to police after receiving rape and death threats.
"I am really cross at the politicians and the media who are whipping this up because they are the ones inciting racism and violence and acrimony," she said.
The Archbishop of Canterbury, Justin Welby, also commented on the row, writing in a tweet: "Horrified by trolling of judges & those going to court; British values call for honest but good disagreeing, need reconciliation not abuse".
He added independent judges were "fundamental to our values" and it was "wrong to attack them for declaring the law",
Prime Minister Theresa May has said she is "confident" the government will win its Supreme Court appeal and is committed to triggering Article 50 by March 2017.

The European Court of Justice has ruled the UK can cancel Brexit without the permission of the other 27 EU members.
The ECJ judges ruled this could be done without altering the terms of Britain's membership.
A group of anti-Brexit politicians argued the UK should be able to unilaterally halt Brexit, but they were opposed by the government and EU.
The decision came as Theresa May announced a Commons vote on whether to approve her deal would be postponed.
MPs had been widely expected on Tuesday to reject the EU withdrawal agreement negotiated by Mrs May.
But she pre-empted their decision, saying the vote would be deferred to a later date so she could seek "further assurances" from EU leaders about the application of the Irish border backstop.
In a subsequent statement to MPs, Brexit Secretary Steve Barclay said the government noted the ECJ ruling but insisted "our policy has not changed".
He said the UK would be leaving the EU on 29 March 2019, under the terms of the EU's Article 50 process, and had "absolutely no intention" of overturning the 2016 Brexit vote.
"The government's firm and long held policy is that we will not revoke the Article 50 notice," he said.
The case was brought by a cross-party group of Scottish politicians and the Good Law Project who wanted to know whether the UK could revoke the decision to leave the EU without getting approval from the other member states.
They believed that if the ruling went in their favour, it could pave the way for an alternative option to Brexit, such as another referendum.
Both the UK government and the EU had been against it going to the ECJ.
The EU warned that it would set a dangerous precedent by encouraging other countries to announce they were leaving in an attempt to secure better membership terms, before cancelling their withdrawal.
The UK government's lawyers also argued that the case was purely hypothetical as "the UK does not intend to revoke its notification" and those politicians behind it wanted to use the case as "political ammunition to be used in, and to pressure, the UK Parliament".
The ECJ ruled that the UK can unilaterally revoke its withdrawal from the EU, broadly following the non-binding opinion given last week by a senior ECJ official - the advocate general.
The statement from the court said the ability for a member state to change its mind after telling the EU it wanted to leave would last as long as a withdrawal agreement had not been entered into, or for the two-year period after it had notified the bloc it was leaving.
If that two-year period gets extended, then a member state could change its mind during that extra time too.
The court said the UK would be able to stay on the same terms it has now, so it would not be forced to join the euro or the Schengen area - where there are no passport controls between countries.
But the decision to stay must "follow a democratic process".
The member state would then have to write to the EU to notify them of the "unequivocal and unconditional" decision.
The ECJ said it made the ruling to "clarify the options open to MPs" ahead of voting on Mrs May's deal.
The politicians involved hope the victory will increase the chances of Brexit being called off completely, potentially through another referendum.
Scottish Green MSP Ross Greer - one of the politicians who launched the case - said: "This is a massive moment at the start of a vital week, pointing to a clear way out of the Brexit mess."
And the SNP's Alyn Smith, who was also involved in the case, said: "A bright light has switched on above an exit sign."
Jolyon Maugham QC, director of the Good Law Project which took the case to the court, said that the ruling was "arguably the most important case in modern domestic legal history".
"It is up to MPs to remember what they came into politics for and find the moral courage to put the country's interests before private ambition," he added.
Scotland's First Minister Nicola Sturgeon - who backed Remain - said the ruling meant it was "now open to the House of Commons" to extend Article 50 to allow time for another vote.
And Lib Dem Brexit spokesman Tom Brake tweeted that it was the "best news possible" and said it was now "full steam ahead for a People's Vote".
Environment Secretary Michael Gove, a prominent Brexiteer, told BBC Radio 4's Today programme those calling for a second vote were "people who never accepted that first vote, who didn't accept that democratic mandate and who want to overturn it".
"We don't want to stay in the EU. We voted very clearly, 17.4 million people sent a clear message that we want to leave the European Union, and that means also leaving the jurisdiction of the European Court of Justice," he added.
"So, this case is all very well, but it doesn't alter the referendum vote or the clear intention of the government to make sure that we leave on 29 March."
Foreign Secretary Jeremy Hunt told the BBC people would be "shocked and very angry" if any government delayed leaving the EU and it was "certainly not the intention of the government".
Brexiteer Tory Jacob Rees-Mogg hailed the decision as the right one, but told LBC radio: "I think this government would find it very difficult to remain the government if it went away from what it said in its manifesto and the referendum result."
A spokeswoman for the European Commission said it would "take note" of the judgement, but there was an "agreement on the table".
"As President [Jean-Claude] Juncker said, this deal is the best and only deal possible. We will not renegotiate," he said.
"Our position has therefore not changed and as far as we are concerned the United Kingdom is leaving the European Union on the 29 March 2019."
BBC Brussels correspondent Adam Fleming said the ruling made staying in the EU "a real, viable option" and that may "sway a few MPs" in the way they vote.
But he said "a lot would have to change in British politics" to see the UK remain in the EU, with Mrs May and the government having to change its mind to make it a "political reality".

Dundee will not be able to compete in the European Capital of Culture 2023 competition due to Brexit, the European Commission has confirmed.
Five UK cities were bidding to host the title, with the winner expected to be announced next week.
A letter from the European Commission to the Department of Digital, Culture, Media and Sport (DCMS) said UK participation "would not be possible".
It said the UK's selection process should "immediately be discontinued".
Dundee's bid team were due to make their final presentation to the competition judges next week.
BBC Scotland understands that the DCMS only received the Commission's letter on Wednesday.
A Dundee 2023 spokesman said that the team was "hugely disappointed" at the European Commission's late decision.
He said: "The timing is disrespectful not only to the citizens of Dundee, but to people from all five bidding cities who have devoted so much time, effort and energy so far in this competition.
"It's a sad irony that one of the key drivers of our bid was a desire to further enhance our cultural links with Europe."
The UK's five final bid proposals were submitted at the end of October.
They were Dundee, Nottingham, Leeds, Milton Keynes, and a joint proposal from Belfast, Londonderry and Strabane.
Dundee's 80-page bid document was understood to include 110 new projects across the city.
Scotland's culture secretary Fiona Hyslop said: "It is now deeply concerning that the amount of time, effort and expense Dundee have put into scoping out their bid could be wasted thanks to the Brexit policy of the UK government .
"We are in urgent contact with the UK government and Dundee to understand the potential implications of this situation and to establish what action the UK Government is going to take to address it."
The DCMS said it "disagreed" with the European Commission's stance and was "deeply disappointed" that the Commission had waited until the UK cities had submitted their bids before "communicating this new position to us".
The UK government said previously that the title was "part of our plan for a dynamic, outward-looking and global Britain" post-Brexit.
However, it had warned bidders that the contest "may be subject to the outcome of those exit negotiations".
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Welsh politicians have clashed over Theresa May's announcement that the UK should leave the EU single market.
In a speech, the prime minister said staying in the single market would mean "not leaving the EU at all".
First Minister Carwyn Jones said he would still push for "full and unfettered access" to the single market, while Plaid Cymru MP Jonathan Edwards warned of an "extreme Brexit".
But Welsh Tory leader Andrew RT Davies denied it would damage the economy.
In a long-awaited speech, Mrs May said Parliament would get a vote on the final deal agreed between the UK and the European Union.
She promised an end to "vast contributions" to the EU, and said the devolved administrations would be "fully engaged" in the process of negotiating Brexit.
"I should equally be clear that no decisions currently taken by the devolved administrations will be removed from them," Mrs May.
First Minister Carwyn Jones told AMs that the prime minister spoke to him on the phone before her speech.
"Some of it was welcome ... the tone was better", he said during First Minister's Questions.
But as well as giving the Houses of Parliament a vote on the final Brexit deal, Mr Jones said the Senedd would need one too, as many of the terms would cover policy areas devolved to Wales.
He added: "There will be nothing to stop this Assembly from implementing European directives if it wishes to.  There is no ban on doing that."
Mr Jones said he would continue to make the case to have "full and unfettered access" to the EU single market, despite Mrs May's insistence that the UK would leave.
"What we have to avoid in the next few months and years is anything that impairs the ability of businesses to export from Wales, and therefore makes it more difficult for them to employ people," he said.
Labour's Shadow Welsh Secretary Jo Stevens added:  "With the PM set on a damaging hard Brexit, I'm fearful Wales will be left behind and made to suffer the terrible consequences of this incompetent Tory government."
Welsh Secretary Alun Cairns said Brexit gave the UK the opportunity to become "global leaders in free trade".
"There are new opportunities out there, the UK economy is exceptionally strong and both Wales and Welsh businesses are set to benefit from that", he said.
Mr Cairns added that he supported leaving the single market, saying the British people "won't accept and can't accept" the free movement of people.
Andrew RT Davies, who leads the Conservatives in the assembly, denied what he called a "clean Brexit" would be damaging to the Welsh economy.
"This was a hugely welcome speech from the prime minister, providing clarity and certainty ahead of the triggering of Article 50," he said.
"The onus now, in many ways, moves on to the EU itself and leaders on the continent will need to determine for themselves if they want to be part of a new trading agreement with the fifth largest economy in the world."
Mr Edwards, Plaid Cymru spokesman on leaving the EU, said:  "The Prime Minister has put the British State on track for an 'extreme Brexit', isolating Wales and the other UK countries from the rest of the world.
"The Prime Minister has put appeasing her deluded right-wing politicians before protecting the economy and surely the Labour Party must now join Plaid Cymru in voting against triggering Article 50.
"The people voted to leave the EU, not the single market or the customs union.
"Nobody voted to make themselves redundant or give themselves a pay cut. For Wales - a country whose economy is heavily dependent on its exports - isolating ourselves from the single market will be disastrous."
He added that "The serious and disproportionate impact this will have on Wales' economy and devolved functions means that Wales' Parliament must also be asked to endorse the terms of the agreement before it goes ahead, not just Westminster."
UKIP's MEP for Wales Nathan Gill welcomed the speech, saying: "Remaining a member of the single market was never an option as it amounted to no Brexit at all.
"Too many of the 'elite' in media and politics are trying to re-live the referendum, rather than respecting the will of the people and moving forward.
"It's clear to me that the best deal for both Wales and the UK would be a free trade deal between the UK and EU, allowing British companies the freedom to trade with and operate in the single market, and let European businesses do the same here.
"It would also bring back control over immigration and end the supremacy of European courts."
While the prime minister said no decisions currently taken by the Welsh Assembly would be removed after Brexit, the Welsh Government is keen to take control of two major issues currently decided at EU level - farming subsidies and economic aid to Wales' poorest areas.
Asked by UKIP AM Mark Reckless about the repatriation of powers from Brussels, the first minister said:  "If you look at agriculture, we take the decisions on agriculture. If you look at fisheries, we take the decisions on fisheries.
"There is no question of there being some kind of UK-wide agriculture policy that's not devolved on the basis of what the Prime Minister said today.  That's quite clear to me."
He said the people of Wales would not want to see "Brussels bureaucrats replaced with Whitehall bureaucrats."

The government has said it will release information from Brexit impact studies, after Labour won a vote effectively forcing their hand.
Ministers had argued that releasing the economic impact studies would undermine their Brexit negotiating position.
But Commons Leader Andrea Leadsom agreed that Wednesday's vote was "binding" and told MPs: "The information will be forthcoming."
Brexit Secretary David Davis said ministers would be "as open as we can".
He said he was already talking to Hilary Benn, the Labour chairman of the Committee for Exiting the European Union, about "how we handle the confidentiality of the documentation we'll hand over".
The government has been under pressure to release the studies, which show the potential impact of leaving the EU on 58 economic sectors.
On Monday it published the list of sectors that have been looked at, ranging from aerospace and aviation to tourism and legal services. But it had argued that releasing them would undermine its negotiating position.
But on Wednesday Labour used an arcane parliamentary procedure to get the documents released.
It involved tabling a motion that "an humble address be presented to Her Majesty" requiring that the reports "be laid before this House and that the impact assessments arising from those analyses be provided to the Committee on Exiting the European Union".
The government chose not to oppose the motion and it was not initially clear whether it would be binding.
Speaker John Bercow told MPs on Wednesday that this type of motion had "traditionally been regarded as binding or effective" and made clear that the government should respond quickly to the vote.
Brexit Secretary Mr Davis told MPs that discussions were under way with Mr Benn about releasing the the documents but added: "These documents are not some sort of grand plan, they're data about the regulations and the markets of individual sectors which inform our negotiation.
"Of course we will be as open as we can be with the select committee, I fully intend to."
In a letter to Mr Davis, Mr Benn asked him to confirm in writing what arrangements he was making to provide his committee with the impact assessments.
He added that he hoped it would be done "much sooner" than the 12 weeks the government had previously indicated it would take to respond to opposition day debate motions.
Earlier Commons Leader Ms Leadsom was asked when the studies would be released. She replied: "It is absolutely accepted that the motion passed by the House yesterday is binding and that the information will be forthcoming.
"But, as I think as has been made very clear, it is the case that it is difficult to balance the conflicting obligation to protect the public interest through not disclosing information that could harm the national interest and the public interest whilst at the same time ensuring that the resolution of the House passed yesterday is adhered to."

Theresa May and EU Commission President Jean-Claude Juncker have agreed to "accelerate" Brexit negotiations - but there was no sign of a breakthrough after their working dinner.
A joint statement said the Brussels talks - which came before EU member states meet to assess progress - were "constructive and friendly".
The UK's financial settlement with the EU continues to be a sticking point.
The EU will not discuss trade until this has been settled.
Mrs May has also spoken to the French and German leaders ahead of the European Council summit.
The EU's chief negotiator Michel Barnier and his UK opposite number, Brexit Secretary David Davis, also joined the working dinner.
"The prime minister and the president of the European Commission reviewed the progress made in the Article 50 negotiations so far and agreed that these efforts should accelerate over the months to come," the statement read.
"The working dinner took place in a constructive and friendly atmosphere."
By Laura Kuenssberg, BBC political editor
Accelerate, accelerate, accelerate, accelerate.
OK, in theory, if I am driving a car at four miles per hour and I speed up to eight miles per hour, technically I am accelerating.
I may still be basically crawling along. I still may be late - very, very late - for my eventual destination. But, by the very action of pressing the pedal and going faster, I am actually speeding up.
If anyone accuses me of going nowhere, or slowing down - well, look at my speedometer. I am going faster and I have evidence that you are wrong!
That is why, in the next few days, don't be surprised if every Tory politician you see, hear, or read about is using that word (at least those loyal to the government) to claim that there is progress in the Brexit talks, just days after the chief negotiator on the EU side declared a deadlock.
BBC Europe correspondent Kevin Connolly said the joint statement released after the dinner was "a masterpiece of uncommunicative communication".
He said: "It recorded formally that Brexit negotiations are taking place between the EU 27 and the UK - a statement of the obvious that may hint at Brussels' displeasure with British attempts to talk directly to individual member states as well."
He added: "The gnomic communique was perhaps an attempt to avoid a repeat of the fallout from the last bilateral dinner in Downing Street in April after which the EU side was reported to have described the British as 'delusional' and even disparaged the food."
Along with the UK's "divorce bill", the EU is insisting agreement be reached on citizens' rights and what happens on the Northern Irish border before agreeing to open talks on the free trade deal Mrs May's government wants to strike.
Last week an internal draft document suggested the EU was going to begin preparing for the possibility of trade talks beginning in December - provided the UK does more to bridge the gap on these key negotiating points.
Speaking on BBC Radio 4's Today programme, Michael Fuchs, the vice chairman of Angela Merkels's Christian Democratic Union party, agreed it was "absolutely necessary" to accelerate the talks, given the two-year timeframe for departure set out by the EU treaties.
But he suggested Foreign Secretary Boris Johnson was thwarting Mrs May's attempts to reach a deal on the financial issue.
"I know there are internal problems, whatever she is offering, Boris Johnson is saying it's too much," he said.
"I don't know what his influence (is), it seems to be pretty strong because otherwise she would come up with other proposals I guess and the problem is she has internal trouble in the Tories."
Speaking in the House of Commons, Mr Johnson said he thought a reported bill of £100bn was too high, accusing Labour of being willing to "cough up" such a sum.
He said the government was united on its Brexit strategy and urged the EU to "get serious" and agree to settle the citizens' rights question.
Meanwhile, a new report suggests that leaving the EU without a trade deal would lead to a significant rise in living costs for millions of people.
Research by the Resolution Foundation and trade experts at Sussex University calculates that the average household would pay an extra £260 a year for imported goods.
For three million households - those who consume the most imported goods - that figure would nearly double to £500 a year.
The report says that without a Brexit deal, European goods would incur the same tariffs as those imposed on other World Trade Organisation countries, increasing levies on dairy products by 45% and meat products by 37%.
But a government spokesperson said ministers were optimistic about achieving an agreement with the EU that would allow for frictionless trade in goods and services.
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Brexit Secretary David Davis has called on both sides in the negotiations on the UK's departure from the European Union to "get down to business".
Mr Davis was in Brussels to launch the second round of formal talks.
He said his priority was to "lift the uncertainty" for EU citizens living in the UK and Britons living in the EU.
The EU says there must be substantial progress on this - and on a financial settlement and the issue of the Irish border - before trade talks can begin.
Appearing alongside EU chief negotiator Michel Barnier, Mr Davis said there had been a good start to the process and it was time to get to the "substance of the matter".
Mr Barnier said the negotiators would "now delve into the heart of the matter".
Talks will cover citizens' rights, finance, Northern Ireland and Euratom, with separate negotiating teams set up for each issue.
A UK government source told the BBC that 98 British officials were in Brussels for the negotiations.
Mr Davis spent two to three hours in the EU quarter, meeting Mr Barnier for between 45 minutes and a hour before returning to London.
The two men are expected to give an update on progress made at a press conference on Thursday.
Earlier this month, Theresa May's offer to give the three million EU citizens in the UK "settled status" after Brexit was immediately dismissed by European Council President Donald Tusk as "below our expectations".
And Mr Barnier has said there were still major differences between the EU and UK on the subject.
Speaking at a separate European Council meeting in Brussels, Foreign Secretary Boris Johnson insisted the UK had made a "very fair, serious offer".
By Kevin Connolly, BBC Europe correspondent
The call to "get down to business" from David Davis is meant to signal that the Brexit talks are entering a serious phase after an opening session of pleasantries and procedural discussions.
That might raise eyebrows on the European side where there's a perception that Britain dithered for months after the Brexit referendum before getting down to talks.
The UK says it's prioritising the issue of mutual citizens rights after its opening proposals received a lukewarm response in Brussels.
The atmosphere around this second round of talks may have been improved a little by a government acknowledgement that the UK has obligations to the EU which will survive withdrawal and which need to be resolved.
Mr Johnson has said that Brussels can "go whistle" if it expected the UK to pay an "extortionate" bill as part of the separation.
The government's official position, confirmed in a Parliamentary statement last week, is that it will "work with the EU to determine a fair settlement of the UK's rights and obligations as a departing member state, in accordance with the law and in the spirit of our continuing partnership".
The EU has insisted that citizen rights - along with the "divorce payment" and border issues - must be dealt with before future UK-EU trade can be discussed.
Sir Keir Starmer, Labour's shadow Brexit secretary, criticised Mr Davis for spending "only a few minutes in Brussels before heading back to Whitehall".
"There is no agreed cabinet position on vital Brexit issues, the negotiating team is not prepared and the Prime Minister has lost her authority," he said, calling for engagement "with the substance of talks".
The Liberal Democrats' Brexit spokesperson, Tom Brake, said Mr Davis' brief visit to Brussels - and a lack of briefing papers on the UK side of the table in when the negotiators posed for a photograph - was proof that government preparation for the negotiations was lacking.
"He didn't have any position papers with him because this government has no agreed Brexit position," he said.
Lord O'Donnell, the UK's former top civil servant, suggested the chances of a smooth Brexit were at risk.

Sandwiches would be one of the first victims of a breakdown in the food supply chain in the event of a disorderly no-deal Brexit, according to a senior grocery executive.
"If you look at the ingredients - a bit of lettuce, tomato, maybe avocado, chicken with a bit of mayonnaise - all prepared fresh and kept chilled, sandwiches would be some of the most vulnerable products if food supply chains were interrupted."
The space between two pieces of bread is perhaps unlikely new territory for Brexit contingency planning but it reflects an area of serious concern that government ministers have been quizzed over this week.
Although they have said they hope and expect a deal to be done - they are making emergency preparations for the potential interruption to vital supplies like fresh food now that they have said planning for "no deal" is being stepped up.
Responses from Brexit Secretary Dominic Raab have been slightly evasive on this issue. When asked by MPs whether the government was stockpiling food he said: "It would be wrong to describe it as the government doing stockpiling but we will look at this issue in the round and make sure that there is adequate food supply."
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Publishers warn Brexit could hit exports
BMW joins Airbus in Brexit warning
This has led to images being conjured of massive warehouses being filled with emergency rations to see the nation through as if on a war footing. So, if the government isn't stockpiling food, is anyone else? Is it even necessary?
Food retailers are understandably reluctant to talk openly about empty shelves but this is what I've learned.
First - every major food retailer I've spoken to is quite clear they have NOT been approached by government to start redirecting any food to some sort of emergency reserve.
"It wouldn't work anyway," said one. "Fifty percent of the food we eat is either fresh or chilled - that includes ready meals - so warehousing wouldn't help".
There is another problem according to another.
"There simply isn't any spare slack in the supply chain to do this. There are no slightly-under-packed lorries or empty warehouses available to do this at scale. To suggest it could even be done if required is incredibly naive."
Most agree there is a real potential threat.
The Beast from the East was essentially two days of snow and it resulted in empty shelves starting to appear in some supermarkets. "Crashing out of the EU without a deal could potentially see the ports overwhelmed, with gridlock that could take days to work through and that would be a massive problem."
So neither the government, nor industry, is stockpiling food - but that does not mean that food retailers aren't making contingency plans.
Most of them get a lot of fresh food from the southern hemisphere in winter and the northern hemisphere from spring onwards - some are looking at extending their southern hemisphere sourcing longer into the spring.
That makes sense according to Lord (Mark) Price, former boss of Waitrose and trade minister. "In late March/early April you would be switching from southern to northern hemisphere providers for some produce so it would make sense to stretch that."
Lord Price downplays the chances of shortages of food availability but concedes that prices would probably rise. "If you are suddenly operating on WTO rules (which impose tariffs on most agricultural products) then clearly there are going to be price increases in some goods and the extra demand for supplies from outside the EU will also push up prices."
There is another option to solve a potential food shortage - and one that some grocery executives think will be exercised if the UK looks like it could run out of food. "The soundings we are getting from government is that if we are facing disaster, we could simply extend Article 50 (the two-year Brexit stopwatch that started running when it was triggered in March 2017), said one.
Staying in the EU for a bit longer would keep the chiller cabinet full of sandwiches - but it would doubtless raise the political temperature.

An executive at Airbus says that work on the Galileo sat-nav system will have to be moved out of the UK if the company wins a key contract.
Galileo has become something of a political football in Brexit talks.
The EU says it would have to stop the UK from accessing the encrypted part of the network when it leaves next year.
Colin Paynter, the company's UK managing director, said that EU rules required Airbus to transfer all work to its factories in France and Germany.
Mr Paynter was speaking at a Commons committee hearing on Exiting the European Union on Wednesday.
The system was conceived to give Europe its own satellite-navigation capability - independent of US GPS - for use in positioning and timing applications, such as in finance, telecommunications, the utilities, and to support the emergency services and the military.
The UK has played a key role in the programme, and Airbus is currently bidding for the renewal of a contract covering the Galileo ground control segment - potentially worth about 200 million euros. This work is currently run out of Portsmouth.
About 100 people are currently employed by Airbus on these services. Most would likely have to move to where the work is, but it's possible some could be reallocated to other projects.
"One of the conditions in that bid documentation from the European Space Agency is that all work has to be led by an EU-based company by March '19," Mr Paynter told the committee.
"Effectively that means that for Airbus to bid and win that work, we will effectively novate (move) all of the work from the UK to our factories in France and Germany on day one of that contract."
Asked by Committee chair Hilary Benn MP whether the Brexit transition period could mitigate this condition, Mr Paynter replied: "No, because this area of Galileo - and many areas of Galileo - is classed as a security-sensitive procurement. I believe that isn't covered in the transitional arrangements."
The UK's access to Galileo's encrypted service, which would be required for military and security uses of the system, would be blocked by the EU after Brexit.
This warning prompted the Business Secretary Greg Clark to announce that the government would look into options for developing its own satellite-navigation system.
Asked by Labour MP Pat McFadden whether developing a British sat-nav system was feasible, Mr Paynter replied: "I think the key thing for me is, it's not up to industry to determine whether there's a requirement or need for an independent UK system... I would say that, in terms of feasibility, I think after such a long and deep involvement with the Galileo programme as UK industry, we have all the skills and capabilities needed to support that programme should it come out."
But Dr Bleddyn Bowen, who researches space and defence at the University of Leicester, told the committee: "Technically, yes, it's feasible - Britain could do it. But it will cost a lot of money and it will run over budget."
He added: "You need to look at the other GNSSs - global navigation satellite systems - that have been built. The Americans are currently building their third generation of GPS satellites, which have become notorious for cost overruns and delays because they're encountering new technological problems as they improve the system.
"Britain has just built the satellites for the Galileo system. That means Britain has to build a new satellite-navigation system - not the same one. That will mean new technological developments and innovations as well, which will cause delays."
According to one estimate, the UK has paid about 1.4 billion euros into the 12-14 billion-euro Galileo programme since 2005.
Estimates for the cost of an indigenous system in the range of £3-5bn were probably right, Mr Paynter said. That was money Dr Bowen told the committee could be better spent elsewhere, filling missing capability gaps in the British space programme.
Follow Paul on Twitter.

A post-Brexit UK-EU trade deal might take 10 years to finalise and still fail, the UK's top diplomat in Brussels has privately told the government.
The BBC understands Sir Ivan Rogers warned ministers that the European consensus was that a deal might not be done until the early to mid-2020s.
He also cautioned that an agreement could be rejected ultimately by other EU members' national parliaments.
PM Theresa May said she wanted Brexit to be "smooth and orderly".
In October, Sir Ivan, who conducted David Cameron's negotiation over the UK's relationship with the EU, advised ministers that the view of the 27 other countries was that a free trade agreement could take as long as a decade.
He said that even once concluded, the deal might not survive the process of ratification, which involves every country having to approve the deal in its own parliament.
It is also understood he suggested that the expectation among European leaders was that a free trade deal, rather than continued membership of the single market, was the likely option for the UK after Brexit.
Sir Ivan's private advice contrasts with ministers publicly insisting a deal can be done in the two years allowed by the triggering of Article 50 - the formal start of the process of leaving the EU.
Downing Street said he was relaying other EU members' views, rather than his own or the British government's.
A spokesman said: "It is wrong to suggest this was advice from our ambassador to the EU. Like all ambassadors, part of his role is to report the views of others."
Just how long will it take?
The government is intent on persuading us Brexit can be done smoothly, and to time.
So the suggestion that the UK's most senior diplomat in Brussels has privately told the government that a final trade deal with the rest of the EU might not be done for 10 years, and might ultimately fail, may give rise to more nerves.
EU leaders are meeting in Brussels - and will discuss Brexit negotiations at an end of summit dinner, without UK Prime Minister Theresa May being present.
Arriving in Brussels, Mrs May was asked about the 10-year claim, but concentrated her answer on the subject of immigration, which is what the EU leaders are focusing on during a chunk of their one-day summit.
She added that a smooth UK exit from the EU was "not just in our interests, it's in the interests of the the rest of Europe as well".
International Trade Minister Mark Garnier told the Commons Sir Ivan's views were "words from interlocutors" rather than a strict definition of how long talks will take.
Dominic Raab, a former minister and a Leave campaigner, told BBC Radio 4's Today programme that Sir Ivan was "scarred by his own pessimistic advice in the past".
"It's reasonable to set out the worst case scenario for a five to 10 year period to iron out a trade deal," he said.
"The key thing is whether we maintain barrier-free trade in the meantime in which case frankly there's no problem - we leave the EU in two years we complete the free trade agreement afterwards."
Former cabinet secretary Sir Gus O'Donnell predicted negotiating a final deal would take "at least five years".
"We certainly won't have come to any final arrangements in two years' time," he told BBC Radio 4's The Westminster Hour.
"We might well get to a point where we can symbolically leave but all sorts of details will still remain to be sorted out."
Remain-backing former Labour minister and European commissioner Lord Mandelson predicted "between five and 10 years" was the most likely timescale, telling a committee of MPs that after a deal is reached on the UK's exit terms, talks on trade arrangements would be harder and take longer.
Downing Street said Thursday's meeting showed the EU was facing up to the reality that the UK was leaving.
It is expected that the other members will discuss who will the lead the EU's negotiating team in Brexit talks.
This is expected to be former EU Commissioner Michel Barnier, who is in charge of the European Commission's Brexit team.
In other Brexit developments, the House of Lords EU financial affairs sub-committee has warned that financial services firms could quit the City of London unless there are transitional arrangements, or a "Brexit bridge" to prevent them moving to New York, Dublin, Frankfurt of Paris.
And European Parliament president Martin Schulz reiterated there would be no negotiation until the UK had officially notified the EU of its departure.
Addressing the 28 EU leaders, he added: "The UK and the EU are, and will remain, closely connected and there are too many lives on the line for an erratic, quick and total separation."
He urged leaders to work towards Brexit "in a spirit of loyal co-operation", adding: "We cannot allow the Brexit process to become an emotional affair, nor should we turn it into a legal maze from which exit is extremely difficult.
"We must not feed populists' unfounded claims that the EU is the master of all evil.  We must also use this moment to concretely reflect on what we want the EU to be in the future and to provide it with the necessary tools."

Detailed plans on the UK's post-Brexit future will not be published until after this month's EU summit.
Theresa May will summon senior ministers to an away day at Chequers in July to settle details of the white paper and find a common way forward.
With ministers aiming to complete the negotiations by October, many expected the plans to be released earlier.
Labour leader Jeremy Corbyn accused the Tories of "botching Brexit and risking jobs".
The announcement comes after Boris Johnson said the UK's Brexit strategy lacks "guts".
The white paper has been called the government's "most significant publication on the EU since the referendum".
Speaking at the G7 summit in Canada, the prime minister said: "There's going to be a lot of activity in the negotiations over the coming weeks.
One only has to look back at the turbulent week just passed to see the challenge Theresa May will face in uniting her bickering Cabinet at her away day.
It took several meetings with the Brexit Secretary David Davis on Wednesday to quell suggestions he'd resign in frustration with the current status of proposals.
Then a recording of the Foreign Secretary Boris Johnson emerged, undermining both the Prime Minister with claims the Brexit talks weren't going well, and also the pro-EU Chancellor Philip Hammond with a claim his Treasury Department was "the heart of remain."
The latter was more than just a limp lettuce leaf based gag (hearts of Romaine/heart of remain - ouch!) - it underlined the serious divisions now being so publicly displayed between senior ministers that would normally be hidden behind the closed doors of the cabinet.
Theresa May might hope taking them all away for a lock-in at Chequers will finally unite all factions behind a set of White Paper proposals - but this week suggests it won't be easy.
"I'll be going to the June European Council where we'll be talking about finalising the withdrawal agreement, but also pressing on the future relationship.
"After that, I'll be bringing my ministers together for an away day at Chequers to finalise the white paper we're going to be publishing.
"And then before Parliament breaks for the summer, we'll be bringing the Trade and Customs Bill back to the House of Commons.
"Throughout all of that time, the negotiations will be continuing."
In response, Mr Corbyn said that Parliament should take control and set negotiating priorities because the "divided and chaotic government" had failed.
"The government promised a 'detailed, ambitious and precise' Brexit White Paper this month setting out their negotiating priorities. Once again it's been postponed," he said,
"The Tories are botching Brexit and risking jobs and our economy in the process."
This week's events have once again highlighted the gulf of opinion in the cabinet over Brexit.
On Thursday, Mrs May was forced to agree to an "expected end date" of December 2021 for any interim arrangements after Brexit Secretary David Davis threatened to resign over the wording of the UK's proposed temporary customs agreement - the so-called backstop.
The proposal would see the UK match EU trade tariffs temporarily in order to avoid a hard Irish border post-Brexit.
That row was followed by comments from the Foreign Secretary Boris Johnson - recorded at a private dinner - where he warned of a Brexit meltdown, and said issues around the Irish border were mistakenly being allowed to dominate proceedings.
Mr Johnson also branded the Treasury - and, by implication, Chancellor Philip Hammond, "the heart of remain".
Responding to his comments, Mrs May said: "The foreign secretary has strong views on Brexit, but so do I. That's why I'm getting on with delivering Brexit."
But on Friday EU chief negotiator Michel Barnier criticised Mrs May's proposals for a customs arrangement.
He stressed that he was not rejecting the UK prime minister's ideas - but said any "backstop" to prevent a hard Irish border could not be time-limited.
Mr Barnier said the UK paper "raises more questions than it answers" but would be examined "objectively".
Mrs May told the BBC: "This is a negotiation, Michel Barnier has said exactly that point.
"We have put a proposal on the table, on this backstop relating to Northern Ireland, we will now sit down and negotiate it with the European Union."

Any "transitional deal" in the period after Brexit must end by June 2022, the time of the next general election, Philip Hammond has said.
But the chancellor said there must be "business as usual, life as normal" for Britons as the UK left the EU.
"Many things would look similar" the day after Brexit - on 29 March 2019 - as the UK moved gradually towards a new relationship with the EU, he said.
The EU has said it is too soon to discuss a transitional deal.
A European Commission spokesman said: "We are about to discuss the specifics of separation and once this is done to the satisfaction of everyone, we may move to the second step."
The UK is due to leave the EU at the end of March 2019 but there has been increasing talk of a "transitional" or "implementation" stage to smooth the process, before a new long-term relationship with the EU comes into force.
This could mean a period during which some EU rules would continue to apply to the UK after it has technically left the bloc. Newspaper reports have suggested these could include the free movement of people, something that was seen as a key issue in the vote to leave the EU.
Mr Hammond also appeared to acknowledge that it could mean new trade deals with non-EU countries could not be signed during that period.
The chancellor told BBC Radio 4's Today programme the length of any transitional deal would "be driven by technical considerations".
Beneath the surface, Chancellor Philip Hammond had been arguing for a transitional arrangement to avoid choppy waters in 2019. There is no longer any dissent in the ranks - that concept has been agreed by the Cabinet.
In return, the chancellor has acceded to demands by ministers who voted to leave the EU that any transitional phase must be completed by the scheduled date of the next general election - June 2022.
But have other disagreements so far escaped the political sonar?
On Thursday, immigration minister Brandon Lewis said it was a "simple matter of fact" that EU free movement rules would not apply after 2019.
Mr Hammond said this was correct because freedom of movement was an EU concept and the UK would leave the customs union and single market on 29 March 2019.
But he said the question that needed answering was what happened next, so that British people and businesses could "get on with their lives" without "massive disruption".
He said he hoped that, in the immediate aftermath, goods would "continue to flow across the border between the UK and the EU in much the same way as they do now".
On whether EU citizens would continue to be free to enter the UK, he said it would be "some time before we are able to introduce full migration controls between the UK and the European Union".
"That's not a matter of political choice, it's a matter of fact. We have to put in place quite a lot of new infrastructure, we will need a lot of new people, we will need new IT systems... This is going to take a while to deliver."
He said Britons wanted to know they would still be able to "go about their business" after March 2019, from buying European goods to going off on holiday, adding: "The government's job is to make sure that our economy can go on functioning normally, that people can go about their businesses as usual... that is our focus."
Some of Mr Hammond's colleagues who campaigned for a Leave vote have accepted that an "implementation period" after Brexit is likely.
The Conservative MP and Leave campaigner Nigel Evans said any transition period should end as soon as the UK had arrangements in place, saying: "This is not going to be seen as a ruse whereby some people who might have liked us to remain in the European Union can see this as an opportunity to keep us half in.
"That's not going to happen. We are, in all but one or two transitional arrangements, going to have left the European Union by March 2019."
Shadow Brexit secretary Sir Keir Starmer said Labour had been calling for "appropriate transitional arrangements" which the chancellor "now appears to accept".
"However, in light of the clear divisions this week within the Cabinet, I hope the chancellor was not merely speaking in a personal capacity," he said.
"I also hope that this is the final burial of the flawed proposition that 'no deal' is a viable option."
Lib Dem leader Sir Vince Cable said a transition period was only "kicking the can down the road".
"All the problems associated with a hard Brexit, leaving the single market, leaving the customs union, they will simply be confronted two years later."
Meanwhile, Malta's PM Joseph Muscat has said he is "starting to believe that Brexit will not happen", according to the Guardian.

It could take a further two years for Britain to fully leave the EU and start negotiating new trade deals with other countries, Liam Fox has said.
The international trade secretary told the BBC there could be a two-year "implementation phase" after the UK officially left the EU, in March 2019.
He had "no ideological barrier" to a phase to help business adjust, he said.
Mr Fox denied he was planning for a situation in which the UK left the EU without a deal.
It follows reports of cabinet divisions over Brexit, with Chancellor Philip Hammond saying last month that no deal with the EU "would be a very, very bad outcome".
If the UK leaves the EU without a trade agreement it could default to World Trade Organisation rules, potentially facing tariffs on goods and services traded with the EU.
Mr Fox said the UK could "of course survive with no deal" but he wanted a "full and comprehensive deal" with the EU.
He also said "the free trade agreement that we will have to come to with the European Union should be one of the easiest in human history" because the UK already met EU standards.
Some MPs have called for the UK to remain in the EU's single market and customs union after Brexit. Some non-EU European countries, such as Norway, are members of the single market.
Mr Fox said that he did not "have a problem" with a transitional Brexit deal, which he described as an "implementation phase" but insisted: "You can not leave the European Union and be in the single market and the customs union."
Speaking after a speech in Geneva, where he is meeting the WTO's director general, Mr Fox implied that such a phase could last two years.
Earlier this month, Mr Fox told Bloomberg TV he would be "very happy" with a transitional phase lasting "a few months".
He told the BBC: "We're going to leave [the EU] in March 2019.
"But if we can do it in a way that minimises or avoids any disruption to business, that provides them with the greatest amount of certainty and stability, then that's clearly a sensible thing to do.
"And if we have an implementation phase between us leaving the European Union and moving to whatever new arrangement and relationship we have with the EU,  I don't have any problem with that, for me there's no ideological barrier to that."
Mr Fox said he had been waiting to leave the EU "for a very long time, another two years, say, wouldn't be too much to ask".
And he said the UK would want to be able to "negotiate and conclude" trade deals outside the EU after March 2019 - but that was something that would be subject to negotiation.
BBC political editor Laura Kuenssberg said Mr Fox's apparent acceptance of "some kind of transition" indicated "a change in tone from Brexiteers" since the general election.
Lib Dem Brexit spokesman Tom Brake said: "I think the penny has finally dropped even with Liam Fox, that what the Brexiteers had presented as a simple, straightforward process that could be completed within a couple of years, now they realise that there's probably going to be a couple of years on top of that, and even that may be an underestimate."
Mr Fox's Labour shadow, Barry Gardiner, said any trade deal with the EU would have a political dimension.
Mr Gardiner said: "Liam Fox seems to be saying it makes economic sense for the EU to give us a good deal and we already have the basis for that, so why don't they just say, 'Right, we'll keep it as it is.'?
"But of course that ignores the fact that the European Union too has its own political objectives, and they are about ever-closer union of the remaining 27 and ensuring that nobody of those 27 feels that they too might get a better deal outside of Europe than inside."
Mr Fox also said earlier that the UK would take up an independent seat on the World Trade Organisation after Brexit and he believed that talks with the WTO indicated that "we will simply replicate our current obligations under the European Union as we move into the United Kingdom as an independent member".

Slowly but surely, like a submarine emerging from murky waters, the government's position on what happens immediately after Brexit is becoming clearer. And the speed of our withdrawal can now be measured, too.
Beneath the surface, Chancellor Philip Hammond had been arguing for a transitional arrangement to avoid choppy waters in 2019. There is no longer any dissent in the ranks - that concept has been agreed by the cabinet.
In return the chancellor has acceded to demands by ministers who voted to leave the EU that any transitional phase must be completed by the scheduled date of the next general election - June 2022.
But have other disagreements so far escaped the political sonar?
Mr Hammond privately believes a new trade deal with the EU simply can't be struck by the time of Brexit, in March 2019. So he would be prepared to leave things much as they are for a time.
While technically the UK would leave the single market and customs union, initially at least extremely similar arrangements would be put in place while a final free trade deal was completed. Then there would be a period where the new arrangements would be phased in.
That is why he uses phrases such as "transitional phase" or "transitional period". And on the record, he has said he wants to ensure things feel like "business as usual" to the British people, the day after the UK leaves.
But others in cabinet, not least Brexit Secretary David Davis, are much more confident that the essentials of any new trading arrangements with the EU could be hammered out by 2019.
So all that's needed isn't so much a "transitional phase" of further negotiation but an "implementation period" that puts any new arrangements in place.
For example, everyone recognises that, outside of the customs union, new staff and IT systems would be required to deliver the new regime and that simply couldn't be done the day after Brexit.
And there are further potential disagreements which could threaten the current esprit de corps - how long would the free movement of labour last after Brexit?
While, technically, free movement ends with EU membership, the government has already agreed there will be a "grace period" when EU citizens can still come to work here freely, so long as they register with the authorities.
A similar system operates in many EU countries now - and they call it "free movement".
The chancellor and Home Secretary Amber Rudd stress that it will take time to better police our borders, and to wean some companies off any over-reliance on migrant labour.
So the exact length of the grace period may yet end up in a graceless political dispute.
Terms of future trade could also cause conflict. Mr Hammond signalled his willingness to put any new trading arrangements with other countries on hold until after the transition.
Frankly the EU would probably demand this but it's hard to see Liam Fox, the international trade secretary, accept any ban on negotiating - rather than implementing - new deals until a transitional phase ends.
Then there is the thorny issue of which body supervises the trading rules between the UK and EU during a period of transition - would the European Court of Justice (ECJ) still have a role?
Mr Hammond has floated the idea of a tribunal, similar to the arrangements in place in European Economic Area countries such as Norway, to settle any disputes.
But if the EU insists on the ECJ, cabinet unity may yet fray. This might even torpedo any hope of a transitional arrangement that the British government could accept.
So while on the surface it may look like the course of HMS Brexit appears clearer, still waters run deep.

Airbus has warned that it could move wing-building out of the UK in the future if there is a no-deal Brexit.
The planemaker's chief executive, Tom Enders, said Airbus "will have to make potentially very harmful decisions for the UK" in the event of no deal.
He said it was a "disgrace" that firms could still not plan for Brexit.
His remarks were welcomed by Business Minister Richard Harrington, who said Airbus was correct to warn of the dangers of a no-deal scenario.
"Crashing out is a disaster for business," Mr Harrington told a meeting at the German embassy on Thursday morning.
"Airbus is correct to say it publicly about and I'm delighted they have done so," he added.
In all, Airbus employs 14,000 people in the UK.
That includes 6,000 jobs at its main wings factory at Broughton in Wales, as well as 3,000 at Filton, near Bristol, where wings are designed and supported.
Mr Enders said: "Please don't listen to the Brexiteers' madness which asserts that, because we have huge plants here, we will not move and we will always be here. They are wrong."
Responding to Airbus's statement, a government spokesperson said: "The UK is a world leader in aerospace. We are the home of the jet engine, the wing factory of the world and are world-renowned for our skills and capabilities in the most technically-advanced parts of aerospace manufacturing.
"It remains our top priority to leave the EU with a good deal; a deal that is good for business, will protect jobs and prosperity, and provide the certainty that business needs."
Airbus's latest intervention follows announcements by two other companies that they were moving their headquarters out of the UK.
Sony said it would transfer its European HQ from the UK to the Netherlands to avoid disruptions caused by Brexit.
And appliance maker Dyson announced it was moving its headquarters to Singapore, from Malmesbury in Wiltshire, although it said the decision had nothing to do with Brexit.
However, another firm, Japanese technology company Fujitsu, told the BBC it had "zero intention" of moving its operations out of London.
Duncan Tait, Fujitsu's European boss, said it had "a thriving business in the UK", adding: "We're recruiting people every week."
Mr Enders said that while the world's second-largest aerospace group could not "pick up and move our large UK factories to other parts of the world immediately", Airbus could be "forced to redirect future investments in the event of a no-deal Brexit".
"And make no mistake, there are plenty of countries out there who would love to build the wings for Airbus aircraft," he added.
"Brexit is threatening to destroy a century of development based on education, research and human capital."
Katherine Bennett, senior vice-president of Airbus in the UK, reinforced Mr Enders' message.
She told the BBC that a no-deal Brexit would be "catastrophic" for her business, with "chaos at the borders" that would hold up delivery of vital components.
This is not the first time that Airbus has warned of the consequences for its business of a no-deal Brexit.
Last year, it issued a risk assessment saying that if the UK left the EU without a withdrawal deal, it "would force Airbus to reconsider its investments in the UK and its long-term footprint in the country".
However, Mr Enders' latest remarks suggest that the firm has toughened its stance since then.
MPs are putting forward alternative plans to Theresa May's Brexit plan after it was voted down by Parliament last week.
The UK is due to leave the EU on 29 March this year.
by Theo Leggett, BBC business correspondent
The gloves are off. That's the clear message from Airbus' pugnacious chief executive, Tom Enders.
Opposition to Brexit from Airbus is not new. The company warned of the potential dangers to its business even before the referendum had taken place.
Since then, the rhetoric has been steadily ramped up. Last year, the company published a "Brexit Risk Assessment", in which it warned that leaving without a deal would be "catastrophic" for its business.
We've had warnings about the risk to future investment before, but now the threat is much more explicit and the language is much more forthright. The failure to come up with a clear plan is a "disgrace". Other countries would "love" to build the aircraft wings currently made at Broughton.
There's even a warning not to listen to "the Brexiteers' madness". The time for diplomacy, it seems, is past.
So what's changed? The company clearly believes that the risk of "no deal" is growing, thanks to the impasse in the House of Commons.
And as a business which relies on the rapid transfer of parts from the UK to assembly lines in France and Germany, it is very exposed to any delays in shipments - or problems getting new safety certification.
Meanwhile, Tom Enders is due to leave his job in April. So perhaps he's in a very good position to talk tough, without worrying whom he's upsetting in the process.

Voting to leave the European Union was a "bad decision" for the UK, the Irish foreign minister has said.
Charlie Flanagan said Brexit could be "painful" for the UK and his country, which he added should not be "placed in a position of more disadvantage".
He also urged negotiators to keep the Common Travel Area between Northern Ireland and the Republic.
The comments come after Prime Minister Theresa May met European Council President Donald Tusk in London.
Mr Flanagan told BBC's Newsnight it was "absolutely essential" there was no return to a hard border on the island of Ireland - which is expected to be a key element of Brexit negotiations between the UK and EU.
"The Good Friday Agreement remains the foundation stone of our peace, and anything adverse to that agreement will not be acceptable," he said.
However, despite his criticism of the decision to leave, the Irish minister said he believed there was no intent to punish Britain among EU members, adding that the relationship between the UK and the Republic of Ireland was its "warmest ever".
He said: "I believe [Brexit] was a bad decision, but of course as a democrat I fully respect and recognise the will and wishes of the British people. We've got to deal with that now.
"The Article 50 process has commenced, and I believe it's essential now that we get through the negotiations in such a way that the end result can be as close as possible a relationship between the European Union and the United Kingdom, albeit with the UK gone."
On Friday, Mrs May and Mr Tusk met at 10 Downing Street for the first time since Article 50 was triggered, with Gibraltar at the heart of the talks.
In its draft negotiating guidelines, published last week, the EU said decisions affecting Gibraltar - a UK overseas territory - would have to be taken with the agreement of the Spanish government.
This led to former Conservative leader Lord Howard saying the prime minister would defend Gibraltar in the same way Margaret Thatcher defended the Falkland Islands.
Mrs May laughed off the prospect of war with Spain, but after her meeting with Mr Tusk, a Number 10 spokesman said she had been clear she was determined to achieve the "best possible deal" for Gibraltar as well as the UK.
"The PM also made clear that... there would be no negotiation on the sovereignty of Gibraltar without the consent of its people," he added.
EU sources told the Press Association it had been a "good and friendly" meeting.
One source added: "They agreed to stay in regular contact throughout the Brexit process to keep a constructive approach and seek to lower tensions that may arise, also when talks on some issues like Gibraltar inevitably will become difficult."

MPs have overwhelmingly agreed to let the government begin the UK's departure from the EU as they voted for the Brexit bill.
The draft legislation was approved by 494 votes to 122, and now moves to the House of Lords.
Shadow business secretary Clive Lewis was one of 52 Labour MPs to defy party orders to back the bill and he resigned from the front bench.
PM Theresa May wants to trigger formal Brexit talks by the end of March.
She will do this by invoking Article 50 of the Lisbon Treaty, but requires Parliament's permission before doing so.
Mr Lewis, who earlier said he was undecided on whether to support the European Union (Notification of Withdrawal) Bill, announced his resignation as MPs began voting for the final time.
He said he "cannot, in all good conscience, vote for something I believe will ultimately harm the city I have the honour to represent, love and call home".
Leader Jeremy Corbyn said he understood the difficulties the vote presented some of his MPs but said they had been ordered to back the Article 50 because the party would not "block Brexit".
Shadow home secretary Diane Abbott, who missed last week's initial vote on the bill, backed it this time.
She told the BBC she had "a lot of misgivings about the idea of a Tory Brexit" and predicted the UK would "come to regret it", but added: "I'm a loyal member of the shadow cabinet and I'm loyal to Jeremy Corbyn."
The Labour rebellion was five MPs up on last week's vote, while former Chancellor Ken Clarke was again the only Conservative to vote against the two-clause bill.
During the voting, SNP MPs were reprimanded by deputy speaker Lindsay Hoyle after they started singing Ode to Joy, the European Union anthem.
Afterwards, Brexit Secretary David Davis hailed the "historic vote", adding: "It is now time for everyone, whichever way they voted in the referendum, to unite to make a success of the important task at hand for our country."
Peers will now consider the draft legislation, and a government source told BBC political editor Laura Kuenssberg: "If the Lords don't want to face an overwhelming public call to be abolished they must get on and protect democracy and pass this bill."
Earlier the bill survived several attempts to change its wording and add extra conditions.
These included Labour MP Harriet Harman's bid to protect the residence rights of EU citizens in the UK, which was outvoted by 332 votes to 290, with three Conservative MPs rebelling.
A Liberal Democrat bid for a referendum on the terms of the UK leaving the EU was defeated by 340 votes to 33.
Afterwards, Mr Corbyn tweeted: "Real fight starts now. Over next two years Labour will use every opportunity to ensure Brexit protects jobs, living standards and the economy."
But Scottish First Minister Nicola Sturgeon accused him of giving the Conservatives a "blank cheque".
She tweeted: "You didn't win a single concession but still voted for the bill. Pathetic."
The bill will be debated in the House of Lords after it returns from recess on 20 February.
Liberal Democrat leader Tim Farron vowed the party's peers would seek to amend the bill in the Lords, including another attempt to ensure a referendum on the final Brexit deal.

European Council President Donald Tusk has hinted that the UK should stay in the EU, after the prime minister's Brexit deal was rejected in parliament.
"If a deal is impossible, and no-one wants no deal, then who will finally have the courage to say what the only positive solution is?" he tweeted.
MPs voted by 432 votes to 202 to reject the deal, which sets out the terms of Britain's exit from the EU on 29 March.
Other EU officials and politicians reacted with dismay to the result.
It was the largest defeat for a sitting government in history, with 118 of the votes against coming from Prime Minister Theresa May's own Conservative Party.
It has cast more doubt on the Brexit process, and the leader of the opposition Labour Party, Jeremy Corbyn, has tabled a vote of no confidence in the government.
As well as Mr Tusk's tweet, there has been plenty of comment on Tuesday's vote from across Europe. Here are the key quotes:
European Commission President Jean-Claude Juncker warned that time was running out for the UK to strike a deal.
"I urge the United Kingdom to clarify its intentions as soon as possible. Time is almost up," he said shortly after the result was announced.
"The risk of a disorderly withdrawal of the United Kingdom has increased with this evening's vote," he added.
The EU's chief Brexit negotiator Michel Barnier said he "profoundly" regretted the vote.
"An orderly withdrawal will remain our absolute priority in the coming weeks," he told the European Parliament in Strasbourg.
He added that there would be a favourable response if Mrs May were prepared to rethink her position on issues like the single market and customs union.
Chancellor Angela Merkel said there was still time to negotiate but "we're now waiting on what the prime minister proposes".
Finance Minister and Vice Chancellor Olaf Scholz said Tuesday was a "bitter day for Europe".
"We are well prepared, but a hard Brexit would be the least attractive choice, for the EU and [UK]," he said.
Annegret Kramp-Karrenbauer, the leader of the ruling Christian Democrat Union party, echoed this view.
"A hard Brexit will be the worst of all options," she said.
"The pressure is mainly on them," French President Emmanuel Macron said of the UK.
He said a transition period was essential because a no-deal Brexit would be damaging.
"We will have to negotiate a transition period with them because the British cannot afford to no longer have planes taking off or landing at home," he said.
Later a presidential source said France was stepping up preparations for a "no-deal" Brexit.
Prime Minister Leo Varadkar said that the Republic was also now preparing for a no-deal Brexit but would work hard to avoid it because it "would not protect the peace in Northern Ireland".
But he said the ball was now in the UK government's court to find a solution.
"We understand the PM will now consult with other parties and other political leaders on an agreed way forward we welcome that," he said.
"The onus is on Westminster to come up with solutions that they can support but they must be solutions that the European Union and Ireland can accept."
Meanwhile Foreign Minister Simon Coveney ruled out any alternative to the agreement reached with the UK over the Irish border.
"We're not going to allow physical border infrastructure to reappear," he told national broadcaster RTE.

The government has survived an attempt by pro-EU Conservative MPs to change its post-Brexit trade strategy.
The MPs wanted the UK to join a customs union if it does not agree a free-trade deal with the EU.
But the government, which says a customs union would stop it striking new trade deals, won by 307 to 301.
Ahead of the vote, Tory MPs were told a defeat would lead to a vote of no confidence in the government, sources told the BBC's John Pienaar.
The government did, however, lose a separate vote on its Trade Bill on the regulation of medicines after Brexit.
MPs backed an amendment by 305 votes to 301 that would keep the UK in the European medicines regulatory network.
There were 12 Tory rebels in both the customs and medicines votes - but the government's total was boosted by four Labour MPs in the customs vote.
The customs union allows for tariff-free trading between members with a common tariff set for imports from the rest of the world.
The UK is due to leave the EU on 29 March 2019 but the two sides have yet to agree how their final trading relationship will work.
The Commons has been debating two pieces of legislation - on customs and trade - and there have been several attempts to change them by both pro-Brexit and pro-EU MPs.
The latest key vote was on customs, with a debate sparked by Tory MP Stephen Hammond's amendment to the Trade Bill.
It stated that if a free trade area had not been negotiated by 21 January, ministers must change tack and start discussions on joining a customs union.
Labour backs the idea of a customs union with the EU after Brexit - but the government says this would mean the UK is unable to strike its own international trade deals.
During the debate on the Trade Bill, a minister tried to persuade Mr Hammond and his supporters to back down, promising to deal with the "essence" of their concerns when the bill goes to the House of Lords.
Although this was rejected by Mr Hammond, the government won the vote and the bill was later approved by the House of Commons.
The 12 MPs that voted against the government on customs and trade were: Heidi Allan, Guto Bebb, Ken Clarke, Jonathan Djanogly, Dominic Grieve, Stephen Hammond, Philip Lee, Nicky Morgan, Bob Neill, Antoinette Sandbach, Anna Soubry and Sarah Wollaston.
On the other side, four Labour MPs voted with the government: Frank Field, Kate Hoey, John Mann, and Graham Stringer.
Lib Dem leader Sir Vince Cable and his predecessor Tim Farron - who were criticised after missing Monday night's knife-edge Brexit votes - were back at Westminster and voted against the government.
But a former Lib Dem minister, Jo Swinson, complained that Tory MP Brandon Lewis participated in the votes despite having agreed to abstain.
Ms Swinson, a Remain supporter who has recently given birth and was unable to vote, tweeted Mr Lewis did not keep to their arrangement to balance out her effective abstention - known as "pairing" - and accused the government of "desperate stuff".
They didn't escape defeat for long.
Having squeaked through last night the government was beaten for only the second time ever in the Commons on key Brexit legislation.
And guess what, it was on a vote they didn't expect to lose - Dr Phillip Lee, who quit the government to speak out on Brexit, put forward his own amendment to protect the links between the UK and the European Medicines Agency to ensure the smooth flow of medicines and new drugs for British patients after Brexit.
And he had enough to support to win it, just. An embarrassment for the government certainly.
It is another reminder of how difficult it is for Theresa May to get her way in the House of Commons where she doesn't have her own majority.
It is serious. A defeat is a problem. But it wasn't a complete disaster tonight for two reasons.
First, the amendment isn't a million miles away from the government's own policy. While not straightforward, the vote hasn't forced a screeching U-turn.
The more important reason is that the vote that followed, on keeping the UK in a customs union, went the other way.
Read Laura's blog
The vote on medicine regulation was only the government's second defeat on Brexit in the House of Commons.
MPs voted for the UK to take "all necessary steps" to participate in the regulatory network operated by the European Medicines Agency after it leaves the EU.
The agency, which evaluates and supervises medicines and helps national authorities authorise the sale of drugs across the EU, is currently based in London but is moving to Amsterdam after Brexit.
There have been warnings that Brexit may cause delays in UK patients getting new drugs.
The government says it is "seeking participation" in the agency after Brexit and would make an "appropriate financial contribution" in return.
But it has not agreed to take "all necessary steps" to secure this.
Responding to the defeat, the government said: "We will now reflect on this amendment and seek to revisit in the Lords."

Michael Gove has warned of the rise of identity politics in Britain, but insisted the Brexit campaign which he helped lead did not fan its flames.
The Tory minister said elements on the left and right wanted to pit groups against each other in a "conflict for recognition, rights and resources".
But he rejected claims Leave voters were also examples of "identitarians".
He told an event in London that Brexit was motivated by a desire to "restore faith in our democratic institutions".
Addressing a conference on the future of the United Kingdom, the environment secretary said the tendency to look at "political questions through the prism of identity" posed a challenge not just to the constitutional order which he said had, for the most part, served the UK so well for hundreds of years but to the concept of individual rights.
"The identitarians want to move away from the liberal principles of equal treatment for all, colour blindness and respect for individual rights," he told the event, hosted by the Policy Exchange think tank.
"Instead they embrace a politics which divides society in contending groups and demands people define themselves by their group membership rather than as autonomous individuals."
On the left of politics, he said this was characterised by an "insistence that an individual should check their privilege before speaking and pipe down if they don't fit in or avoid cultural appropriation - in other words know their place in the world if they want to get a hearing".
Despite the "effective eclipse of UKIP" as a political force, he said the manifestation of identity politics on the right of the political spectrum in the UK and further afield was "equally concerning".
"You hear it when there is an appeal to defend men's rights which is an attempt to make gender a cause of conflict, not an aspect of character," he said.
"Or when some politicians claim our borders should be closed to people because of their faith or religion."
In contrast, he said unionism as a political tradition, while needing to be rejuvenated and kept relevant, was underpinned by principles and institutions which offered a "warm home" to "so many from a distinct and diverse background".
Through its allegiances to "Magna Cartas, Bills of Rights, Great Reform Acts and Golden Jubilees, not tribal, cultural, sexual and divisive totems" - unionism stood in direct opposition to identity politics, he added.
Accusing the SNP of "playing with" identity politics for its own electoral benefit and using Brexit as just one of many "grievances", he said Scottish nationalism "conflates truly progressive politics with superior virtue that can apparently only really come from living north of the border".
But Mr Gove came under fire from former Conservative MP and Lib Dem MSP Keith Raffan who said the Brexit vote, opposed by 62% of those who voted in Scotland, had put a "totally avoidable" strain on the union, as demonstrated by the Scottish Parliament's recent refusal to give its consent to the EU Withdrawal Bill.
Vote Leave's campaign claims about Turkish immigration were "far worse" than anything the SNP had ever come up with, he suggested.
"Haven't you played with identity politics when the Leave campaign stated that 80 million Turks could decamp to England - dog-whistle politics of the nastiest kind," he asked Mr Gove.
The environment secretary, who is Scottish, said he "respectfully disagreed" with claims the Brexit vote was driven by xenophobia or a nostalgia for a return to the the time when Britain was an imperial power.
"People wanted to make sure they had control of their borders, of our taxes, of our laws and all of that was part of a broad campaign to restore faith in our democratic institutions," he said.
Asked directly whether Leave supporters were identitarians, Mr Gove said the "answer to that question is no".
Speaking at the same event, Conservative Party chairman Brandon Lewis said English identity should be celebrated more openly as part of the UK projecting an "outward-looking" face to the world after Brexit.
But former Labour cabinet minister Jim Murphy said that while he remained a passionate believer in the union, he feared David Cameron's efforts to make the Conservatives a truly national party had "dissipated" in favour of them embracing a narrower English nationalism.
And the SNP's Pete Wishart poured scorn on the whole idea of an "unionism convention" as well as Mr Gove's claim that the UK had become "more welcoming" to immigrants since the Brexit vote. He tweeted:

MPs have again failed to agree on proposals for the next steps in the Brexit process.
The Commons voted on four alternatives to Theresa May's withdrawal deal, but none gained a majority. One Tory MP resigned the whip in frustration.
Mrs May will now hold a crucial cabinet meeting to decide what to do and whether to put her deal to MPs again.
The UK has until 12 April to either seek a longer extension from the EU or decide to leave without a deal.
The so-called indicative votes on Monday night were not legally binding, so the government would not have been forced to adopt the proposals. But they had been billed as the moment when Parliament might finally compromise.
Mrs May's plan for the UK's departure has been rejected by MPs three times.
As a result of that failure, she was forced to ask the EU to agree to postpone Brexit from the original date of 29 March.
Meanwhile, Parliament took control of the process away from the government in order to hold a series of votes designed to find an alternative way forward.
Last week, eight options were put to MPs, but none was able to command a majority, and on Monday night, a whittled down four were rejected too. They were:
Those pushing for a customs union argued that their option was defeated by the narrowest margin, only three votes.
It would see the UK remain in the same system of tariffs - taxes - on goods as the rest of the EU - potentially simplifying the issue of the Northern Ireland border, but preventing the UK from striking independent trade deals with other countries.
Those in favour of another EU referendum pointed out that the motion calling for that option received the most votes in favour, totalling 280.
Following the failure of his own motion, Common Market 2.0, Conservative former minister Nick Boles resigned from the party.
The MP for Grantham and Stamford said he could "no longer sit for this party", adding: "I have done everything I can to find a compromise."
As he left the Commons, MPs were heard shouting, "don't go Nick", while some MPs from other parties applauded him.
He later tweeted that he would remain an MP and sit in the Commons as "an Independent Progressive Conservative".
Brexit Secretary Stephen Barclay said the "only option" left now was to find a way forward that allows the UK to leave the EU with a deal - and the only deal available was the prime minister's.
If that could be done this week, he added, the UK could avoid having to take part in elections to the European Parliament in May.
Health Secretary Matt Hancock agreed it was time for Mrs May's deal to be passed.
But Labour leader Jeremy Corbyn said that while it was "disappointing" that none of the proposals secured a majority, he said he wanted to remind the Commons that Mrs May's deal had been "overwhelmingly rejected".
He urged MPs to hold a third round of indicative votes on Wednesday in the hope that a majority could yet be found for a way forward.
For months, Parliament has been saying "Let us have a say, let us find the way forward," but in the end they couldn't quite do it. Parliament doesn't know what it wants and we still have lots of different tribes and factions who aren't willing to make peace.
That means that by the day, two things are becoming more likely. One, leaving the EU without a deal. And two, a general election, because we're at an impasse.
One person who doesn't think that would be a good idea is former foreign secretary and Brexiteer Boris Johnson.
He told me going to the polls would "solve nothing" and would "just infuriate people". He also said that only somebody who "really believes in Brexit" should be in charge once Theresa May steps down. I wonder who that could be...
Hear more from Laura and the gang in Brexitcast.
Liberal Democrat Norman Lamb told BBC Look East he was "ashamed to be a member of this Parliament" and hit out at MPs in his own party - five of whom voted against a customs union and four of whom voted against Common Market 2.0.
He said the Commons was "playing with fire and will unleash dark forces unless we learn to compromise".
But prominent Brexiteer Steve Baker said he was "glad the House of Commons has concluded nothing".
He said the prime minister must now go back to the EU and persuade them to rewrite the withdrawal deal - something they have so far refused to do - otherwise the choice was between no deal or no Brexit.
Senior figures in the EU, though, showed their frustration at the latest moves in Westminster.
European Parliament Brexit coordinator Guy Verhofstadt tweeted that by voting down all the options, a "hard Brexit becomes nearly inevitable".
BBC Europe editor Kayta Adler said the mood in Brussels was one of disbelief - that the UK still does not seem to know what it wants.
She said EU leaders were also questioning the logic of arguing over things like a customs union or Common Market option at this stage, because right now, the UK has only three options as they see it - no deal, no Brexit or Theresa May's deal - and anything else is a matter for future talks once the UK has actually left.

It was only yesterday that the Brexit Secretary, David Davis, told MPs it just might all be a bit tricky to have a White Paper, a formal document outlining the government's plans for Brexit, and stick to the timetable they want to pursue.
Rebel Remainers though were "delighted", that, stealing Jeremy Corbyn's thunder, a planted question from a loyal Tory MP at PMQs today produced in fact a promise from the Prime Minister that, after all, there will be a White Paper.
It is a climbdown, no question, a last-minute change of heart.
Late last night Brexiteers were being assured there would be no bending, no delay to the government's plans and no giving in to the Remainers.
Even early this morning, government sources were privately suggesting that they were quite happy to have the white paper option up their sleeve, but there were no immediate plans to make that promise.
Then voila, at 1205 GMT, the pledge of a white paper suddenly emerged. As one senior Tory joked, "welcome to the vacillation of the next two years".
It may be being described as a "massive, unplanned" concession but it doesn't seriously hurt the government.
First off, it shows goodwill to the rebel Tory Remainers, many of whom feel their Eurosceptic rivals have had the upper hand of late. Schmoozing matters round these parts.
It takes one of the potential arguments that could have gathered pace off the table, before the Article 50 bill is even published. And, rightly or wrongly, no one expects a white paper will contain anything new that the prime minister has not yet already said.
It's largely a victory for the Remainers about process, rather than substance.
For her critics this is evidence of weakness, that's she has been pushed into changing her mind.
But it doesn't need to change the government's timetable, and today's embarrassment of a climbdown might be worth the goodwill that Number 10 will get in return.

Tony Blair has warned Jeremy Corbyn that Brexit will make it harder for Labour to deliver its promises if it wins power.
The former prime minister said Mr Corbyn would be in "exactly the same position" as the Tories  - distracted by Brexit and short of money.
Speaking to the BBC's John Pienaar, he defended his call for a second EU referendum.
Labour has backed Brexit and ruled out a second referendum if it wins power.
One member of Labour's shadow cabinet told the BBC Mr Blair's intervention was "utterly unhelpful".
"Lots of Labour voters voted for Brexit and this to them sounds like the metropolitan elite ignoring them," he said.
"The whole Tony Blair project was about being on the right side of public opinion. And now look at this. Are you telling me the Tony Blair of 1994 would have said this?"
Britain is due to leave the EU on 29 March 2019, but Mr Blair said it would be too late to change course by then.
He has repeatedly argued that people are entitled to change their mind - either through another referendum or a general election - once the terms of its departure are clear.
And he urged the current Labour leadership to adopt the same stance.
The former prime minister said he was "committed" to seeing a Labour government elected, but added a "qualification" - which was that "it's going to be extremely difficult in my view for Labour to deliver on its promises if it puts itself in exactly the same position as the Tory government's going to be on Brexit - because it will find it has less money to deal with the country's problems, that it's distracted by dealing with Brexit rather than the health service, jobs and living standards."
The UK would "face a very challenging situation" if it was leaving the EU under a Corbyn government, he added.
Mr Blair said that if people voted again for Brexit, he would not push for a third poll - "that concludes the argument", he said.
But he said that he would not support either of what he saw as the two most likely outcomes of negotiations - a Canada-style free trade deal or the UK being aligned with the EU but having no influence over key decisions.
Shadow Brexit secretary Sir Keir Starmer says Labour will push for a deal that would preserve as many of the benefits of the single market and customs union as possible, as well as protecting workers' rights and the environment.
But Mr Blair believes this is a "confusing" strategy and is not "credible".
"Far better to fight for the right for the country to re-think, demand that we know the full details of the new relationship before we quit the old one, go to the high ground on opposing Brexit and go after the Tories for their failures to tackle the country's real challenges.
"Make Brexit the Tory Brexit. Make them own it 100%. Show people why Brexit isn't, and never was, the answer."
Mr Blair - a longstanding critic of Labour leader Jeremy Corbyn - has ditched his business interests to take a more active role in British politics through his Institute for Global Change think tank.
He has previously attacked Mr Corbyn's stance on Brexit - prompting the Labour leader to say Mr Blair should respect the result of the 2016 EU referendum.
Richard Tice, co-chairman of the pro-Brexit Leave Means Leave campaign, said Mr Blair "and his elite gang" were "still determined to stop Brexit" and will lead the UK "to the very bad deal which we had in the single market and the customs union".
In Mr Blair's latest article published on his institute's website, he offered this advice to Jeremy Corbyn and his team: "At every PMQs nail each myth of the Brexit campaign, say why the Tory divisions are weakening our country, something only credible if we are opposed to Brexit, not advocating a different Brexit, and challenge the whole farce head on of a prime minister leading our nation in a direction which even today she can't bring herself to say she would vote for.
"If we do leave Europe, the governing mind will have been that of the Tory right.
"But, if Labour continues to go along with Brexit and insists on leaving the single market, the handmaiden of Brexit will have been the timidity of Labour."
Mr Blair's comments came as his institute issued a document highlighting developments in the UK since the Brexit vote, including a downgrade in economic forecasts.

"Are you trying to provoke the UK government?" was my question today to Michel Barnier, the EU's chief Brexit negotiator.
His favourite maxim is "stay calm and keep negotiating" but, I put it to him, he was surely well aware of the explosive reaction that would probably follow in the UK after seeing the European Commission's protocol on the Irish border.
So was this an EU ruse to rouse the UK government into focusing on and speeding up negotiations? After all, Mr Barnier never tires of pointing out that the time to negotiate is running out.
No, he told me. His aim was not to provoke or to create shockwaves. He wanted to make these negotiations a success. But, he added, he had long warned the UK that leaving the EU would have serious consequences.
The commission's proposal for Northern Ireland appeared today as part of its draft UK withdrawal agreement.
This is the European Commission's interpretation - in legally binding language - of the agreements it believes have so far been reached with the UK government. They include the so-called Brexit Bill and the rights of EU citizens in the UK and UK citizens in the EU after Brexit, and separately outline issues the commission still wants to be negotiated.
No final agreement has yet been reached on the Irish border conundrum and the fudged compromise settled on just before Christmas became painfully exposed on Wednesday.
Both the EU and the UK say they are committed to safeguarding the Good Friday Agreement and avoiding the re-introduction of a hard border between Northern Ireland and the Irish Republic.
The UK believes this can be done as part of an eventual far-reaching free trade agreement with the EU and with the help of smart technology.
These are known as options A and B on Ireland.
The EU has insisted - and the UK agreed back in December - on an option C as a fallback plan.
This would see full regulatory alignment between Northern Ireland and the EU in areas necessary to maintain North-South cross border co-operation.
In the absence to date of any concrete detail from the UK on how options A or B would work, the European Commission has gone to town in this draft withdrawal agreement on option C - including Northern Ireland staying in an EU customs union and in relevant parts of the single market, all under the jurisdiction of the European Court of Justice.
Michel Barnier insisted it was the EU's duty to ensure the integrity of the Good Friday Peace Agreement after Brexit, but you couldn't have crossed more UK lines if you'd tried.
And, right on cue, all the main actors delivered the lines you would expect.
Theresa May rejected the commission's text, vigorously defending the territorial integrity of the UK. She is mindful of course of the strong opinion of Northern Ireland's Democratic Unionist Party (DUP), which she relies on for support in the UK parliament.
Michel Barnier, meanwhile, defended the position of EU member state Ireland.
But before you go away, head in hands, thinking: we're in another deep Brexit crisis - we are actually slap back in the middle of a negotiation.
There were strong words but no-one slammed any doors today.
The commission's draft text will now be debated and possibly amended by the 27 EU member states before then being presented to the UK government for negotiation.
In the next stage of this drama Donald Tusk, the President of the European Council, heads to London to see the prime minister ahead of her Brexit speech on Friday.
The EU says it will be listening closely.
And as a parting shot on Wednesday - in an apparent spirit of compromise even if on a separate Brexit subject - the UK has offered a step towards more rights for EU citizens coming to the UK during the transition.
Still, as one EU diplomat pointed out to me soberly, be under no illusion, the Irish question still has the potential to bring the whole Brexit deal tumbling down.

Downing Street has reassured fans of Strictly Come Dancing that the show is not at risk from Brexit, following claims by Sir Vince Cable.
Sir Vince - who appeared on the the Strictly Christmas special in 2010 - said a "cack-handed" immigration policy could stop dancers from the EU appearing on the show.
The Lib Dem leader made the comments after a meeting with Michel Barnier.
He made the case for a second referendum to the EU negotiator.
Many of the professional dancers on Strictly Come Dancing come from EU countries.
"As British society falls apart it could pose a risk to Strictly,"  Sir Vince, who has said he wants to halt Brexit, told The Telegraph.
"If we have a cack-handed immigration policy like what we have for non-EU citizens, all kinds of perverse decisions could be made,"
But a Downing Street spokesperson said: "I think Strictly will be fine."
The government has faced calls from dance companies, the Musicians' Union and other arts organisations to protect the free movement of performers when the UK leaves the EU in March.
Launched by the BBC in 2004, Strictly Come Dancing has become a firm Saturday night favourite and is currently in its 16th series.

Brexit's fate is "in the hands of our British friends" after EU leaders agreed to delay the departure date by at least two weeks, says Donald Tusk.
If MPs approve Theresa May's withdrawal deal next week, Brexit would be delayed from 29 March until 22 May.
But if they do not, the UK has until 12 April to come up with a new plan.
European Council President Mr Tusk said that until 12 April, "anything is possible" including a much longer delay or cancelling Brexit altogether.
Speaking in Brussels on Friday, he said he was "really happy" the 27 EU leaders had reached a unanimous decision to extend the two-year Article 50 process, under which the UK was due to leave the EU next Friday.
"It means that until 12 April, anything is possible: a deal, a long extension if the United Kingdom decided to rethink its strategy, or revoking Article 50, which is a prerogative of the UK government.
"The fate of Brexit is in the hands of our British friends. As the EU, we are prepared for the worst, but hope for the best. As you know, hope dies last."
According to the final summit conclusions, the UK is expected to "indicate a way forward" before 12 April, if MPs do not approve the withdrawal deal negotiated with the EU, which would then be considered by the European Council.
Theresa May has been granted a little breathing space. The EU has allowed a few more days to try to get her deal through the House of Commons.
But it's not the timetable that she chose.
And as things stand, the expectation that the compromise deal will get through is low.
And, more to the point, the government does not believe that it can hold off another attempt by a powerful cross-party group of MPs who are resolved to put Parliament forcibly in charge of the process to find alternatives.
Ministers are therefore today not just wondering about how to manage one last heave for the prime minister's deal, but what they should do next, when - odds on - the whole issue is in the hands of the Commons, not Number 10.
Read Laura's blog
The UK must decide by then whether it will be taking part in European Parliamentary elections from 23-26 May - if it does not, then a long delay would become "impossible", Mr Tusk said.
On Friday, Mrs May's deputy David Lidington met opposition parties to discuss how MPs could vote on alternatives to the government's Brexit plan next week.
These could include options such as holding another referendum, leaving with no deal or pursuing a closer economic arrangement such as the "Common Market 2.0" plan.
MPs are expected to vote on Mrs May's deal for a third time next week, despite Commons Speaker John Bercow ruling that it could not be brought back for another vote without "substantial" changes.
But in a letter to all MPs on Friday evening, Mrs May said it was possible a third vote on the deal may not take place "if it appears there is not sufficient support to bring the deal back next week".
The prime minister offered to talk to MPs over the coming days "as Parliament prepares to take momentous decisions".
She also referred to her televised address on Wednesday, in which she blamed the delay to Brexit on MPs.
Mrs May acknowledged that "a number of colleagues had raised concerns" about her words and it had not been her intention to make a their "difficult job... any more difficult".
Earlier, Business Secretary Greg Clark told the BBC that if they do not back Mrs May's deal, then the government would give Parliament the means to express their views on a series of other options.
He said this meant an attempt by a cross-party group to enable MPs to take control of Commons business, so they can get indicative votes, would not be necessary.
But he said the government's ambition should be to try to build as big a consensus as possible on Brexit, rather than simply "getting it over the line" with a slim majority of one or two votes.
29 March: Current Brexit date in UK law
12 April: If MPs do not approve the withdrawal deal next week - "all options will remain open" until this date. The UK must propose a way forward before this date for consideration by EU leaders
22 May: If MPs do approve the deal next week, Brexit will be delayed until this date
23-26 May: European Parliamentary elections are held across member states
Mrs May has ruled out revoking Article 50, which would cancel Brexit, and has said it would be wrong to ask Britons to vote for candidates for the elections to the European Parliament, due to be held from 23-26 May, three years after they voted to leave the EU.
Her official spokesman said: "There is now a clear point of decision. If we are able to have a successful vote next week then we can pass the necessary legislation for ratifying the agreement and we can, as a country, be outside the European Union two months today."
For now, the UK's departure date is still written in to law as next Friday, 29 March.
But Mrs May is expected to change that by tabling legislation next week and getting it through the Commons and the Lords.
The withdrawal deal sets out the terms of the UK's departure from the bloc, including the "divorce bill", the transition period, citizens' rights and the controversial "backstop" arrangements, aimed at preventing a return to border checks between Northern Ireland and the Republic of Ireland.
But it must be approved by UK MPs, who have already rejected it twice by large margins.
The Irish premier Leo Varadkar said the choices were now obvious: "It's this agreement, no deal, or the parliament taking indicative votes for a much closer long-term relationship with the EU."
But Nigel Dodds, deputy leader of the DUP - whose votes Mrs May relies on to support her minority government - said the prime minister had "missed an opportunity" to propose changes to the withdrawal agreement to help get it through the Commons.
"The prime minister has now agreed with the EU to kick the can down the road for another two weeks and humiliatingly revoke her oft-stated pledge that the UK would leave the EU on 29 March," he said.
"Nothing has changed as far as the withdrawal agreement is concerned."

"The ball is in the government's court" when it comes to a way forward with Brexit, Labour's Sir Keir Starmer says.
Talks between Labour and the government began last week, with Theresa May saying only a cross-party pact would see MPs agree a deal in Parliament.
But the shadow Brexit secretary said Mrs May's team had "not changed its position" on her existing plan.
The PM will meet German Chancellor Angela Merkel and French President Emmanuel Macron on Tuesday.
Mrs May's spokesman said she was also making calls to other European leaders from Downing Street on Monday afternoon.
She is due at an emergency summit in Brussels on Wednesday, where EU leaders will expect to hear fresh plans ahead of the UK's scheduled exit date - Friday at 23:00 BST.
Meanwhile, peers are continuing to examine a bill brought by senior Labour MP Yvette Cooper, which aims to force the PM to request a Brexit extension rather than leave the EU without a deal.
Despite communications over the weekend, there were no further talks with Labour scheduled for Monday.
However, Sir Keir - who is part of Labour's negotiating team - added: "I have no doubt things will develop today."
BBC political editor Laura Kuenssberg said the party was now "expecting [an] updated proposal" from the government, and more formal talks could take place this afternoon.
Foreign Secretary Jeremy Hunt said Mrs May was leaving "no stone unturned" to try and resolve Brexit, while Culture Secretary Jeremy Wright told BBC Radio 4's Today programme that all sides needed to be "prepared to compromise" to "fulfil the primary objective" of leaving the EU.
But shadow transport secretary Andy McDonald told BBC's Radio 4's Today programme that talks between the parties had "not been entirely productive".
Several Conservatives have also strongly criticised the move, with the former Foreign Secretary Boris Johnson using his column in Monday's Daily Telegraph to warn that Tory MPs would not allow Mrs May to "surrender" to Mr Corbyn.
The EU's chief Brexit negotiator, Michel Barnier, is in Dublin for talks with the Irish Taoiseach Leo Varadkar.
The pair are expected to discuss developments in London, as well as ongoing planning for a possible no-deal scenario.
On Sunday, Mrs May tweeted a video message, explaining her decision to negotiate with Labour, saying: "People didn't vote on party lines when it came to the Brexit referendum.
"And I think members of the public want to see their politicians working together more often."
If no compromise can be reached with Labour, Mrs May has committed to putting a series of Brexit options to the Commons and being bound by the result.
Sir Keir said the talks had been taking place "in good faith" and that "both sides... have approached this in the spirit of trying to find a way forward".
But he added: "At the moment we are waiting to see what the government is putting on the table as a proposal.
"All they have done so far is indicate various things but not to change the political declaration [the non-legally binding document setting out the UK's future relationship with the EU] so the ball is in the government's court.
"We need to see what they come back with and when we do we will take a collective position on that."
Rebecca Long-Bailey, who is also a member of Labour's negotiating team, described the mood as "positive and hopeful" - but she told the BBC's Andrew Marr show the government's proposals "have not been compliant with the definition of a customs union", which is her party's key demand.
That would allow tariff-free trade in goods with the EU but limit the UK from striking its own deals. Leaving the arrangement was a Conservative manifesto commitment.
However, Solicitor General Robert Buckland told BBC Radio 4's Westminster Hour that "something approximating a customs arrangement or customs union" was the most likely outcome of the talks.
"In this particular hung Parliament none of us can get perfection, we need to compromise," he added.
Ms Long-Bailey also suggested Labour could be prepared to cancel Brexit by revoking Article 50 - the legal mechanism through which Brexit is taking place - if the UK was heading towards a no-deal scenario on Friday.
Although 12 April remains, in law, the date the UK will leave the EU, Mrs May has already requested that be rescheduled until the end of June.
BBC political correspondent Vicki Young said if EU leaders did not think she had a credible plan to get Parliament behind a deal, they might refuse or insist on a much lengthier extension to the Brexit process.
This outcome is opposed by some Tory Brexiteers as it would mean the UK having to take part in European Parliamentary elections.
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PM Theresa May has struck a last-minute deal with the EU in a bid to move Brexit talks on to the next phase.
There will be no "hard border" with Ireland; and the rights of EU citizens in the UK and UK citizens in the EU will be protected.
The so-called "divorce bill" will amount to between £35bn and £39bn, Downing Street sources say.
The European Commission president said it was a "breakthrough" and he was confident EU leaders will approve it.
They are due to meet next Thursday for a European Council summit and need to give their backing to the deal if the next phase of negotiations are to begin.
Talks can then move onto a transition deal to cover a period of up to two years after Brexit, and the "framework for the future relationship" - preliminary discussions about a future trade deal, although the EU says a deal can only be finalised once the UK has left the EU.
A final withdrawal treaty and transition deal will have to be ratified by the EU nations and the UK Parliament, before the UK leaves in March 2019.
Northern Ireland's Democratic Unionist Party, whose opposition on Monday led to talks breaking down,  said there was still "more work to be done" on the border issue and how it votes on the final deal "will depend on its contents". Mrs May depends on the party's support to win key votes in Westminster.
The pound was trading at a six-month high against the euro as news broke of the draft agreement.
The UK government and the EU want to maintain the free flow of goods, without border checks that they fear could threaten a return to The Troubles, but the DUP does not want Northern Ireland to be treated differently to the rest of the UK after Brexit.
The joint EU-UK document says any future deal must protect "North-South co-operation" and hold to the UK's "guarantee of avoiding a hard border".
The agreement also says "no new regulatory barriers" will be allowed between Northern Ireland and the rest of the UK, and that Northern Ireland's businesses will continue to have "unfettered access" to the UK internal market - a passage thought to have been added to meet DUP concerns.
But it also sets out a fallback position if the UK fails to agree a trade deal. This could prove controversial because it says there will continue to be "full alignment" between the EU and Northern Ireland on some elements of cross-border trade, as set out in the Good Friday Agreement.
The DUP would have preferred this not to be in the agreement, says the BBC's Chris Morris, and there could be some hard negotiating to do further down the line.
Agreement has been reached on what happens to the three million EU citizens living in the UK and more than a million UK citizens in EU states after Brexit.
EU citizens currently in the UK would be allowed to continue living and working there - and those already in the country who do not yet have permanent residency would be able to acquire it after Brexit.
Freedom of movement could continue for two years after March 2019, although the UK says new arrivals will have to register.
The plan is that UK citizens in living in an EU country would get the same rights, although they would not retain them if they moved to another EU country.
For eight years after Brexit, UK courts will be able to refer cases involving EU nationals to the European Court of Justice for interpretation.
But the campaign group the 3million, which represents EU citizens in the UK, said there was "still no clarity around the registration criteria for these rights" and said of the eight years: "Our rights should not have an expiry date".
A figure is not mentioned in the text of the agreement but Downing Street sources says it will be between £35bn and £39bn.  It will be paid over four years and the precise figure is unlikely to be known for some time.
EU Brexit negotiator Michel Barnier said the EU had agreed to drop the cost of relocating UK-based EU agencies from the final divorce bill.
The prime minister said it would be "fair to the British taxpayer" and would mean the UK in future "will be able to invest more in our priorities at home, such as housing, schools and the NHS".
Technically a future trade deal cannot be signed while the UK remains a member of the EU but "preliminary and preparatory discussions" can begin.
But the EU's chief Brexit negotiator Michel Barnier has said the withdrawal treaty and transition deal need to be ready by October 2018 - in order that they can be ratified by March 2019, before the "real negotiation" begins on the future relationship.
Mr Barnier suggested on Friday that the only option for a future trade arrangement was a Canada-style deal, rather than a one based on Norway, which retains free movement and unrestricted access to the single market but pays into the EU budget.
The European Council wants the UK to remain a "member" of the EU's customs union and single market and to remain under the full jurisdiction of the European Court of Justice during the transition period, according to a leaked document.
The DUP, whose opposition on Monday led to talks breaking down, say there have been six "substantial changes" to the text.
Party leader Arlene Foster said they would mean there was "no red line down the Irish Sea" - meaning no customs barrier between Northern Ireland and the rest of the UK.
But BBC Northern Ireland economics editor John Campbell says there is a lot of hard negotiating to come and compromises to be made.
Another interpretation of the deal is that that it still leaves the door open for a special status for Northern Ireland, he adds.
What does Brexit deal mean for NI?
The prime minister made her decisions on Thursday night while the No 10 Downing Street Christmas party carried on.
It isn't celebration on Friday though for her government, but relief.
Theresa May's cabinet colleagues heaped praise on her, with Environment Secretary Michael Gove saying it was a "significant personal political achievement" for Mrs May while Foreign Secretary Boris Johnson tweeted: "Congratulations to PM for her determination in getting today's deal."
But Labour's Brexit spokesman Sir Keir Starmer said Mrs May should "seriously reflect on her approach to the negotiations so far".
He added: "Despite being two months later than originally planned, it is encouraging that the European Commission has recommended sufficient progress in the Brexit negotiations."
European press relieved at Brexit 'white smoke'
DUP Leader Arlene Foster said it meant that Northern Ireland would "not be separated constitutionally, politically, economically or regulatory from the rest of the United Kingdom" and "in all circumstances the United Kingdom will continue to ensure the same unfettered access for Northern Ireland's businesses to the whole of the UK internal market".
Scotland's First Minister Nicola Sturgeon tweeted: "Move to phase 2 of talks is good - but the devil is in the detail and things now get really tough."
Lib Dem leader Vince Cable, who backs a referendum on the final deal, said "it reduces the risk of a catastrophic no-deal Brexit" but questioned if it would last or be "torn apart by Theresa May's own MPs".
Former UKIP leader Nigel Farage told the BBC the estimated bill was "way more than we need to pay" and he was unhappy that the European Court of Justice would continue to have a role for up to eight years. "The whole thing is humiliating. We have collapsed at every level."

A plan that keeps the UK in the EU's single market may be backed by Labour leader Jeremy Corbyn, a Welsh MP has indicated.
After Prime Minister Theresa May's withdrawal agreement was defeated twice, MPs will look at other options.
Aberavon's Stephen Kinnock said "Common Market 2.0" puts "flesh on the bones of Labour's formal policy position".
The UK was due to leave the EU on 29 March but after MPs failed to agree on the terms, it has been pushed back.
Meanwhile, Conservative MPs David TC Davies and Robert Buckland have said brokering a deal this week must be a priority.
On Wednesday, MPs are expected to be allowed a vote on a range of Brexit options, in an attempt to achieve majority support for one way forward.
These include cancelling Brexit, holding another referendum - which is favoured by many Labour MPs, and leaving without a deal.
Mr Kinnock has for a long time made calls for the UK to remain as closely aligned to the EU as possible.
He told Sunday Politics Wales the "Common Market 2.0" plan would see a relationship similar to what Norway enjoys with the EU, with access to the single market.
But opponents have said this would leave the UK too closely aligned with the EU's rules such as making financial contributions and an element of freedom of movement.
Mr Kinnock said he had held very "constructive and productive" discussions with Jeremy Corbyn and Labour's Brexit spokesman Keir Starmer.
"I believe that this is a real opportunity to re-set our relationship with the European Union and to have one based on democratic consent," he said.
"We don't want to be part of that deeper, more political union but we want the Common Market, we want that strong market-based relationship."
Meanwhile, solicitor general Robert Buckland said people were "fed up of uncertainty".
"The Europeans are running out of patience. They've spent a lot of time on this," the Llanelli-born, Conservative South Swindon MP told BBC Radio Wales' Sunday Supplement programme.
"They had to wipe out a large part of their agenda. They wanted to talk about China and other issues to do with the internet.
"They've spent a lot of time on Brexit. They want this over."
He said he wanted the votes of MPs on options to be "tempered in the light of that reality".
"They (the EU) have made it clear - the way out is the withdrawal agreement," Mr Buckland added, in a plea for MPs to get behind Mrs May's twice-defeated deal.
And Monmouth MP David TC Davies said Theresa May had to do "whatever it takes" to get a Brexit deal agreed this week - even if it means standing down.

David Davis has warned against "putting politics above prosperity" in Britain's post-Brexit relationship with the EU.
In a speech in Berlin, the UK's Brexit Secretary outlined his hopes for a deal that "allows for the freest possible trade in goods and services".
He also said he thought it "incredibly unlikely" there would be no deal.
The EU says negotiations cannot move on to trade until questions about the UK "divorce bill", citizens' rights and Northern Ireland are resolved.
BBC political editor Laura Kuenssberg said Mr Davis's speech was delivered politely but implied "pretty significant frustrations on the UK side with the EU's attitude".
In a question and answer session following the speech, a German interviewer got a round of applause for suggesting the UK government looked to be "in chaos".
Mr Davis replied: "One of the issues in modern politics is that all governments have periods of turbulence.
"This is a period of turbulence, it will pass."
In his speech to an economic conference organised by the German newspaper Süddeutsche Zeitung, he said trade between Germany and the UK was worth 176bn euros a year or "more than a thousand euros to every man, woman and child in each of our countries".
He said the "close economic ties" with the EU "should continue, if not strengthen" after Brexit, and he warned: "Putting politics above prosperity is never a smart choice".
The UK was seeking a "deep and comprehensive free trade agreement" of a scope the EU had never seen before as well as "continued close co-operation in highly regulated areas such as transport, energy and data", he said.
Britain would use an independent trade policy to lead a "race to the top on quality and standards" rather than engage in a "race to the bottom" that would mean lower standards, he told the audience.
He said the EU and UK needed to "think creatively" about their post-Brexit relationship but stressed the need for a "time limited transition period" to implement the new arrangements.
"And that would mean access to the UK and European markets would continue on current terms. Keeping both the rights of a European Union member and the obligations of one, such as the role of the European Court of Justice.
"That also means staying in all the EU regulators and agencies during that limited period. Which would be about two years."
He added that tariff-free trade should be maintained and there must be an "effective dispute mechanism" for any disputes that may arise, that should be neither the UK courts, nor the European Court of Justice.
"It must be appropriate for both sides so that it can give business the confidence it needs that this partnership will endure."
In a question and answer session following his speech, Mr Davis laughed off a question about whether the UK would be prepared to pay 60bn euros to settle its financial obligations.
He said the UK's aim was that "nobody will have to pay more ... nobody will receive less" but would not give a figure that the UK would be prepared to pay.
Asked if he thought the Brexit negotiations would end in "no deal", he said: "I think that's incredibly unlikely."
While the UK government has not put a figure on the amount it is prepared to pay to settle the UK's obligations but it has been estimated at 20bn euros (about £18bn).
The Sun newspaper reported on Thursday that the prime minister was preparing to offer an additional £20bn to the EU to clear the way for talks about a transitional and future trade deal. Downing Street described that as "yet more speculation".
EU sources told the BBC last week that the UK had only two weeks left to make progress on the so-called withdrawal issues, including the amount the UK will pay as it leaves and Mr Davis's EU counterpart Michel Barnier said "time is pressing" to get agreement on the bill.

European Council President Donald Tusk has quoted lyrics from John Lennon's Imagine to suggest the door remains open to the UK staying in the EU.
Ahead of a Brussels summit he said of that prospect: "You may say I'm a dreamer, but I'm not the only one."
Theresa May, who has said the UK will honour the referendum vote to leave, was due to outline her plans for the issue of expats' rights to EU leaders.
Speaking at the summit she hailed the "constructive" start to Brexit talks.
The gathering of 28 EU member states' leaders comes the day after measures to enable Brexit dominated the Queen's Speech. Mrs May's Conservatives are still trying to secure the Commons support needed to pass their programme.
Mrs May told reporters as she arrived: "I'm going to be setting out some of the UK's plans particularly on how we propose to protect the rights of EU citizens and UK citizens as we leave.
"That's been an important issue. We've wanted it to be one of the early issues to be considered in the negotiations. That is now the case. That work is starting."
She also said she would be raising other important issues, including how European leaders could work together to stop the spread of extremism online and ensure there was no "safe space" online for terrorists.
Brexit negotiations began on Monday.
Speaking before the summit, Mr Tusk said: "It is a most difficult process, for which the EU is well prepared. You can hear different predictions coming from different people about the possible outcome of these negotiations - hard Brexit, soft Brexit or no deal.
"Some of my British friends have even asked me whether Brexit could be reversed and whether I could imagine an outcome where the UK stays part of the EU.
"I told them that, in fact, the European Union was built on dreams that seemed impossible to achieve. So, who knows. You may say I'm a dreamer, but I'm not the only one."
His comments were raised at a press conference in Brussels later with President of the European Commission, Jean Claude Juncker, who said: "In Europe, I never have illusions because I don't want to lose them."
But Mr Tusk said: "I still have dreams. Politics without dreams - it would be a nightmare."
"If you had my experience from my part of Europe you would know that miracles do happen and some of my political dreams have come true... but at the same time I am a realist, this is why first of all we should start our negotiations as effectively as possible and the final decision... this is a decision for Britain and UK citizens."
Earlier Chancellor Philip Hammond told BBC Radio 4's Today he wanted an early agreement on the principle of a "transitional" period to reassure business there would not be a "cliff edge" when the UK leaves the EU at the end of March 2019.
He also denied that a series of controversial Conservative manifesto commitments had been dumped in the wake of the disappointing election result.
He told Today that the manifesto was for a five-year period, but the Queen's Speech programme had been for the first two years, which are dominated by the process of Brexit.
Both the UK and the rest of the EU say they want to come to an arrangement to secure the status of about 3.2 million EU nationals living in the UK, and 900,000 Britons overseas, but nothing has been decided so far.
UK opposition parties have urged the government to make a unilateral guarantee to the EU migrants - but ministers have insisted a reciprocal deal is needed to ensure British expats are protected.
Mrs May will not be present when the leaders of the remaining 27 EU states hold a brief discussion about Brexit after her presentation. They are expected to consider the relocation of the two EU agencies governing medicine and banking which are currently based in London.
Of the 27 bills in the Queen's Speech, eight related to Brexit and its impact on immigration, trade and sectors such as fisheries and farming.
At the centre was the so-called Repeal Bill, which will copy over all EU laws into UK law, with Parliament then deciding which bits to retain.
With MPs voting on the speech next week, the Conservatives are hoping an  arrangement with Northern Ireland's Democratic Unionist Party will be in place to support their minority government.
But despite both sides saying they were confident of a deal being agreed, sources suggested to the BBC the DUP were "getting to the limits" of what they were requesting in return for supporting the Tories - with the chances of a plausible long-term deal, rather than a short-term bargain to get the Queen's Speech through, diminishing.
As well as clearing the Commons, Brexit legislation will also have to navigate the House of Lords, where the Tories also do not have a majority.
Another potential obstacle could emerge if the approval of the Scottish Parliament is needed for the Repeal Bill.
Speaking in the Commons after the Queen's Speech, Mrs May said there was a "possibility" the bill, which is needed to stop EU law applying in the UK, could require Holyrood's consent.
At the two-day summit, where the agenda is formally dominated by immigration, security and the economy, Mrs May will also brief her counterparts on the UK's commitment to a new £75m plan designed to stem the flow of illegal migrants from Africa to Europe.

Foreign Secretary Jeremy Hunt says "extra time" may be needed to finalise legislation for Brexit.
Mr Hunt said a possible delay in the UK's departure from the EU beyond the 29 March deadline depended on the progress made in the coming weeks.
The PM is seeking "alternative arrangements" to the backstop, but the EU says it will not renegotiate.
Parliament's February break has been cancelled, which No 10 said showed all steps were being taken to avoid delay.
The UK is due to leave the European Union at 23:00 on 29 March. The backstop is an "insurance" policy to stop the return of checks on goods and people along the Northern Ireland border.
Earlier this month, Commons Leader Andrea Leadsom said that the EU may be prepared to grant the UK a "couple of extra weeks" beyond the 29 March deadline to finalise preparations for Brexit.
And BBC political editor Laura Kuenssberg said there had been "growing chatter" about a potential delay and a potential extension to Article 50 - the mechanism by which the UK leaves the EU.
Labour leader Jeremy Corbyn said the government "has had two-and-a-half years to negotiate and has failed to do so".
But the prime minister's official spokesman said the government remained committed to leaving the EU on 29 March.
"The fact that recess won't be taking place shows you that we are taking all available steps to make sure that 29 March is our exit date," the spokesman said.
Downing Street was also discussing the possibility of Parliament sitting for extra hours in the run up to Brexit, the spokesman said.
Transport Secretary Chris Grayling said the government was "not talking about extensions" to Brexit at the moment, saying the focus should be "getting on with the job of completing the deal".
Mr Hunt told BBC Radio 4's Today programme: "It is true that if we ended up approving the deal in the days before the 29 March, then we might need some extra time to pass critical legislation.
"But if we are able to make progress sooner, then that might not be necessary. We can't know at this stage exactly which of those scenarios would happen."
Theresa May has been talking to a variety of MPs and EU leaders, including President of the European Council Donald Tusk and the Irish Taoiseach, Leo Varadkar, after MPs voted on Tuesday for her to make changes to the backstop.
Mr Hunt said it was a "challenging situation" and the government was "not ruling out" any  potential solutions to the Irish border issue.
He said the commitment to the Good Friday Agreement - which protects against the return of a hard border between Northern Ireland and the Republic of Ireland - would need to be demonstrated.
The EU's concerns that the UK could "access the single market by the back door" would also need to be alleviated, he said.
"If we can overcome those two issues, which I think we can, then we will be able to have substantive discussions," he said.
The backstop was one of the main reasons Mrs May's Brexit deal was voted down in Parliament by a record margin earlier in January because critics say a different status for Northern Ireland could threaten the existence of the UK and fear that the backstop could become permanent.
Alternatives to the backstop that the prime minister has said she wants to discuss with EU leaders include:
She also wants to discuss a time limit on the backstop and a "unilateral exit" mechanism - both options ruled out by the EU in the past.
The EU's chief negotiator, Michel Barnier said on Wednesday that the Irish backstop was "part and parcel" of the UK's Brexit deal and would not be renegotiated.
Several Conservative MPs have been spotted going to meetings in Downing Street, including former Brexit minister Steve Baker, Iain Duncan Smith, Mrs May's close ally Damian Green and Nicky Morgan.
Ms Morgan, a former education secretary, said she was there to discuss a plan known as the "Malthouse Compromise".
Engineered by both Leavers and Remainers, the proposal includes extending the transition period for a year and protecting EU citizens' rights, instead of using the backstop.
Union officials have also been meeting with government officials in the Cabinet Office to discuss Mrs May's Brexit plan.
A Trades Union Congress spokesman said the prime minister's deal came "nowhere close" to offering the safeguards desired for working people.
"The strongest possible protection for workers' rights would come from sticking by single market and customs union rules," he said.
When asked about a Times article that said Mrs May was preparing to entice Labour MPs to vote for her deal with money for constituencies, Labour MP John Mann said a group of 10 met the prime minister two weeks ago.
Mr Mann, who was also spotted in Downing Street on Thursday, told the BBC the group asked for "a significant amount of money" for poorer areas, "so that we can actually move forward as we leave the EU".
But he said he had voted for the deal already, "so I can't be bribed".
"There's no expectation, this isn't transactional politics. We're asking for money for areas that have not had their fair share in the past," he said.
Meanwhile, Mrs Leadsom told MPs that "in light of the significant decisions taken by the House this week" she was giving the House notice that "there are currently no plans to bring forward a motion to agree dates for the February recess".
Parliament had been due to rise for recess on Thursday, 14 February and return on Monday, 25 February.
Mrs Leadsom said she realised it was short notice, but said their constituents "would expect that the House is able to continue to make progress at this important time".
Labour leader Jeremy Corbyn accused the government of running down the clock on Brexit.
He said: "We delayed the parliamentary vote from 11 December until January - and then lost by the biggest majority ever against a government.
"Now we're going back to Brussels but we are very unclear about what we're going back to Brussels to do and when I asked the prime minister about this yesterday, she was incredibly vague.
"It is possible that there will have to be an extension in order to get an agreement because we cannot leave the EU on March 29 without an agreement. Crashing out would mean problems of transport, problems of medicine supply, problems of supply to the food processing industry that does just in time deliveries - and that simply is not acceptable.
"This government has had two-and-a-half years to negotiate and has failed to do so."

Labour has said leaked government papers "confirm its worst fears" about plans to dilute workers' rights after Brexit.
The documents, revealed by the Financial Times, say that the drafting of commitments on workers' rights and the environment in the Brexit deal "leaves room for interpretation".
Labour said it is a "blueprint" for ending "vital rights and protections".
But Business Minister Kwesi Kwarteng said the claims are "way exaggerated".
The leaked paper suggests that the government believes there is considerable scope to diverge from the EU on employment rights and other regulations after Brexit, despite its pledge to maintain a "level playing field" in Boris Johnson's latest deal.
In Mr Johnson's Brexit deal, references to a level playing field - the idea that the UK and EU countries keep their rules and standards close to prevent one trying to gain a competitive advantage - were removed from the legally binding withdrawal agreement.
Instead, they were put into the non-binding "political declaration", which describes the potential future relationship between the UK and EU.
According to the FT, the leaked document says the UK's and EU's interpretation of the "level playing field" pledge will be "very different", and the text represents a "much more open starting point" for negotiations over a future trade deal.
Purportedly drafted by the Brexit department, the paper appears to contradict promises by the prime minister on Wednesday that the UK is committed to the "highest possible standards" for the environment and rights at work.
It comes as EU leaders consider their decision on a new deadline for Brexit, having agreed to an extension in principle after the UK government admitted it could not meet its 31 October deadline.
The document will fuel fears among some in the EU that Boris Johnson is planning to shape Britain into a Singapore-style economy, with low taxes and light regulation, which could compete against Europe by potentially downgrading rights.
Suggestions that workers' rights could be diluted will also raise concerns among Labour MPs, 19 of whom voted for the Withdrawal Agreement Bill to progress in the House of Commons.
Labour shadow Brexit minister Jenny Chapman said the documents "confirm our worst fears".
She said: "Boris Johnson's Brexit is a blueprint for a deregulated economy, which will see vital rights and protections torn up."
The Brexit department said it did not recognise the document, however.
And Business Minister Kwesi Kwarteng told the BBC the claims were "completely mad" after the government had worked to win the support of Labour MPs.
"It wouldn't make any sense at all to dilute workers' rights in building that coalition to land the bill," he said.
"We have said we will be better than our word. We have said our ambition on securing workers' rights will be stronger than the provision of the bill."
Environmental groups have also raised concerns after the document was leaked, calling on ministers to introduce legal guarantees on current standards in the Environment Bill, which is due to be debated for the first time in the Commons on Monday.
Benjamin Halfpenny from Greener UK, a coalition of groups including the RSPB, Friends of the Earth and the National Trust, said: "The government has had plenty of opportunities to put a commitment to existing standards into law, but has thus far not done so.
"Such a commitment would not prevent future governments from going further on things like water quality and chemical safety, just stop them going backwards."
A Brexit department spokesman said the government "has no intention of lowering the standards of workers' rights or environmental protection after we leave the EU".
He said the UK already exceeds the minimum standards in areas such as maternity leave, shared parental leave and greenhouse gas emissions targets.

Labour's deputy leader Tom Watson has described another Brexit referendum as "the least worst option" and urged his party to throw its weight behind one.
Speaking to the BBC, he said Labour should then fight for Remain, even though "we might lose some votes".
Jeremy Corbyn has resisted calls to fully endorse another public vote, only calling for it in some circumstances.
But Mr Watson said Labour would pay "a very high electoral price" if it did not have "a clear position" on Brexit.
The nuanced position was blamed for Labour's performance at the European elections - it came third behind The Brexit Party and the Liberal Democrats, with its share of the vote falling to 14%.
Afterwards, several senior figures criticised a lack of clarity on Brexit, and last week, MPs expressed their frustration at a heated meeting of the Parliamentary Labour Party.
The PLP is still split, though, with some MPs in Leave-supporting areas warning against backing a further public vote.
The shadow cabinet was due to meet on Monday to discuss Brexit, but the meeting has been postponed.
Mr Watson - who has repeatedly put pressure on Mr Corbyn to back a further referendum - told the BBC's political editor Laura Kuenssberg he believed it was now the only choice available.
Theresa May's Brexit deal with the EU has been rejected by Parliament three times and the UK currently has until 31 October to come up with another way to leave.
"Sometimes in politics your choices are the least worst option," Mr Watson said. "It is my honestly held view that Parliament will not be able to get a deal on Brexit and therefore the only choice, reluctantly, is to ask the people to take another look at it."
When asked if he would leave the Labour Party if things did not change, he replied, "I'm never going to leave the Labour Party," but added "sometimes I wonder whether the Labour Party is leaving me."
Earlier, in a speech to the Centre for European Reform, the deputy leader said Labour must be honest about the EU's strengths.
"Pro-European is who we are and who we have always been. Our members are Remain. Our values are Remain. Our hearts are Remain."
He told the BBC Labour "might lost some votes if we change position", but added: "I think it's incumbent on us to give an honest account of ourselves and make the case for why we've changed our position."
Mr Watson is calling for a one-off meeting or ballot of members to be held to vote on a shift in policy - warning Labour could not afford to wait until its party conference in late September.
But as he gave his speech, Labour chairman Ian Lavery - who is against another referendum - tweeted that "ignoring Leave voters" was not a sensible move.
Labour MP John Mann warned adopting an overtly Remain position would lead to Labour losing the next general election "by a significant amount".
He said if Labour "turned its back" on voters in the North who voted Leave, "then Tom Watson won't be deputy, Jeremy Corbyn won't be prime minister."
Labour MP Kerry McCarthy said she would commend Mr Watson for "speaking out", but shadow ministers needed to "meet urgently for a proper discussion on Brexit".
"We need to be clear where Labour stands, and if [the] shadow cabinet can't agree, put it to the members," Ms McCarthy posted on Twitter.
Mr Watson has received support from a number of colleagues, including Jess Phillips and Anna Turley.
Another MP, Siobhain McDonagh, tweeted: "I have had my differences with Tom Watson over the years but this video is brilliant and his argument is bang on! So many Labour members will be cheering him on!"
Laura Kuenssberg says plenty of Labour MPs are worried because they represent constituencies with Leave voters, but there is no question the balance in the party is on the other side.
"There are plenty of senior people - including those absolutely loyal to Jeremy Corbyn - who think it is time for the leadership to make a clearer statement arguing for another referendum and for Britain to stay in EU," she says.
"Some of those think it is vital to do before the summer and they predict we may end up with an election in the autumn with the Tories arguing for Leave and Labour arguing for Remain."
However, Mr Watson said all strands of opinion within the party are entitled to be heard.
He also argued that the "core" EU values of internationalism, solidarity and freedom are also the values of Labour.
"Some people have begun to equate support for Europe with class identity - I don't think that's right or helpful," he said.
"The majority of Labour people are supportive of Europe and that support is not dictated by social class."

Negotiators from the UK and EU are having what has been described as "intense technical discussions" in an attempt to agree a new Brexit deal.
About a dozen British officials, including the UK's EU adviser David Frost, are taking part in the talks at the EU Commission in Brussels.
The meetings are expected to continue through the weekend.
But European Council President Donald Tusk has suggested there is only the slightest chance of an agreement.
The UK is due to leave the EU at 23:00 GMT on 31 October and a European leaders' summit next Thursday and Friday is seen as the last chance to agree a deal before that deadline.
Prime Minister Boris Johnson's revised proposals - designed to avoid concerns about hard border on the island of Ireland after Brexit - were criticised by EU leaders at the start of last week.
However, on Thursday, Mr Johnson and the Irish prime minister Leo Varadkar held talks and said they could "see a pathway to a possible deal".
BBC Europe reporter Gavin Lee said there is no scheduled timetable for the discussions in Brussels and neither the UK or EU are offering any detail yet on the apparent common ground that has been found on the Irish border.
Our correspondent said the first public announcement on the talks may come on Monday, after the EU's 27 ambassadors have been updated on the progress so far.
Meanwhile, shadow Brexit secretary Sir Keir Starmer says Labour would take action through the courts if Mr Johnson tries to push through a no-deal Brexit.
Addressing the Co-operative Party conference in Glasgow, Sir Keir said if the PM did not secure a deal at the EU summit on 17 and 18 October, he must comply with the so-called Benn Act passed by MPs in September, which requires him to seek a further delay.
"If he doesn't, we'll enforce the law - in the courts and in Parliament. Whatever it takes, we will prevent a no-deal Brexit," he said.
This weekend's talks in Brussels follow a meeting on Friday between Brexit Secretary Steve Barclay and EU chief negotiator Michel Barnier, described by both sides as "constructive".
In a statement issued later, the European Commission said: "The EU and the UK have agreed to intensify discussions over the coming days."
Speaking on BBC Radio 4's Today programme, Culture Secretary Nicky Morgan reiterated that "lots of details" needed to be worked out between both parties but said the "mood music" on negotiations "seems positive".
She added that "speculation doesn't really help" and politicians needed to "stand back and give those negotiations and discussions the best chance of succeeding".
On Friday, Mr Tusk said he had received "promising signals" from the Irish PM, before adding: "Of course there is no guarantee of success and time is practically up, but even the slightest chance must be used".
Mr Johnson also acknowledged there was not "a done deal", saying: "The best thing we can do now is let our negotiators get on with it."
Support from Democratic Unionist Party MPs could be crucial to get a deal through Parliament.
But DUP leader Arlene Foster said: "Anything that traps Northern Ireland in the EU... will not have our support."
Brexiteer Sir John Redwood believes Mr Johnson should "table a free trade agreement" which would "unlock" most of the issues around borders and immigration.
He added: "I think the border issue is greatly exaggerated, because it is in the interest of the European Union and Ireland to exaggerate it."
Ms Morgan was asked on the Today programme about reports of Downing Street briefings that the Tories could contest a general election on a no-deal Brexit ticket, if an agreement cannot be reached.
The Loughborough MP - who voted Remain - did not say whether she would contest an election on such a ticket, but said reports that Mr Johnson is preparing to fight a general election on a no deal platform are "wide of the mark".
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Special sitting of Parliament and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

The UK and EU say key issues remain unresolved following unscheduled Brexit talks in Brussels.
Brexit Secretary Dominic Raab and EU chief negotiator Michel Barnier met for more than an hour ahead of a crunch EU leaders' summit this week.
Mr Barnier tweeted that issues, such as how to avoid a hard border with Ireland, were "still open".
A UK government spokesman said UK and EU negotiators "have made real progress in a number of key areas".
"However there remain a number of unresolved issues relating to the backstop," he added.
BBC political editor Laura Kuenssberg said talks had "made progress" in the last few days - and dismissed reports of a row between Mr Raab and Mr Barnier - but added it was "clear the two sides are stuck" on how the Irish backstop might work.
No further talks are planned before Mr Barnier and Theresa May's summit on Wednesday, she added.
The meeting comes as domestic political pressure on Mrs May increases amid threats of potential cabinet resignations.
In a letter to the prime minister, Scottish Secretary David Mundell and Scots Tory leader Ruth Davidson said they would not accept Northern Ireland being treated differently from the rest of the UK in any Brexit deal.
It follows reports that other top ministers have been considering their positions over the weekend ahead of a meeting of the cabinet on Tuesday at which ministers could be asked to give their consent to any agreement.
By BBC political editor Laura Kuenssberg
While there may have been a sense in Brussels that Mrs May was moving towards them, if anything the politics at home have become more fraught.
Thursday's cabinet meeting ramped up concerns and gave Brexiteers another excuse to rattle their sabres.
The DUP continues its warnings that it'd sink the administration rather than see the deal it fears done. Several cabinet ministers are thinking about whether they can go on.
And, more to the point, different groups of Tory MPs with gripes about other policies are scenting opportunity as the government is so vulnerable.
Any move for the PM has become both harder, and more urgent.
Her party won't accept a proposal to keep the UK essentially in the customs union. Parliament is likely to block no deal. The EU won't accept her Chequers plan.
Even loyal ministers are deeply worried - "She is like a chess player who only has the king left - all she can do is move one square at a time until she is check-mated."
The Raab-Barnier meeting came amid conflicting signals as to whether the two sides were nearing a deal on the terms of the UK's exit next March.
Diplomats from the remaining 27 EU member states were summoned for an update on the process at 17.30 BST, prompting feverish speculation that a deal had been done.
The BBC's Brussels reporter Adam Fleming said that while Mr Raab's visit had an air of drama, it was standard practice in the talks for civil servants to hand over to politicians at key points like this.
Rather than a "victory lap" by Mr Raab, he said the UK's statement that "face-to-face talks were necessary to resolve several big issues" should be taken at face value, and Northern Ireland remained a "sticking point".
The issue of the border between Northern Ireland and the Republic of Ireland, which will become the UK's border with the EU, is one of the last remaining obstacles to achieving a divorce deal with Brussels.
Wrangling is continuing over the nature of a "backstop" to keep the border open if a wider UK-EU trade arrangement cannot resolve it.
The EU's version, which would see just Northern Ireland remain aligned with Brussels' rules, has been called unacceptable by Mrs May and her Democratic Unionist allies.
And many Conservative MPs are unhappy with the UK government's proposed alternative, which would see the UK temporarily remain in a customs union until the Irish border question is resolved, either through technological solutions or as part of a wider trade agreement.
Brexiteers fear this will leave the UK in indefinite limbo, bound by the EU's rules and limited in the trade deals it can negotiate with other countries.
Writing in the Sunday Times, former Brexit Secretary David Davis urged ministers to "exert their collective authority" and reject the plans at a cabinet meeting on Tuesday.
But Foreign Secretary Jeremy Hunt, who has been hosting other European foreign ministers at his Chevening residence, said such calls were "wrong" when "last-minute" talks were going on and Mrs May was "battling for Britain".
"The reason that's wrong is there is no-one who is going to be able to negotiate the right deal for Britain better than Theresa May. This is the time to stand rock solid behind Theresa May."
In their letter to the PM, Mr Mundell and Ms Davidson indicated they would not tolerate a situation in which Northern Ireland remained in the customs union and single market, while the rest of the UK was outside it.
They said the integrity of the UK "remains the single most important issue for us" and cannot be undermined by any withdrawal agreement with the EU.
A source close to Ms Davidson said the issue was a "red line" for her, while a source close to Mr Mundell told the BBC: "If you find yourself not agreeing with government policy" resigning would be the "logical outcome".
Health Secretary Matt Hancock, in an interview with the BBC's Andrew Marr show, insisted there were "different ways" to ensure any customs commitments were "credibly time-limited".
And Scottish First Minister and SNP leader Nicola Sturgeon, who wants Scotland to remain in the EU, has questioned whether Mr Mundell and Ms Davidson had "the gumption" to resign.

Donald Tusk has issued a "last call" to the UK to "lay the cards on the table" if a Brexit deal is to be done in time.
The European Council president said the "most difficult" issues were unresolved and "quick progress" was needed if agreement was to be reached by October.
Talks continue over the terms of the UK's withdrawal from the EU in March next year. What happens to the Irish border remains a sticking point.
The UK says both sides want to see a "faster pace" in talks.
But Prime Minister Theresa May has been unable to say much new at this summit - the last one before October - because she has yet to get her cabinet to agree on a blueprint for the UK's future relationship with the EU.
They are due to meet at Chequers next Friday, in what has been billed as a make-or-break meeting. Mrs May has said the UK will then publish a White Paper setting out "in more detail what strong partnership the United Kingdom wants to see with the European Union in the future".
Chancellor Angela Merkel said Mrs May would "come to Germany and we will have a longer debate on this", once the proposals were published.
At the close of the summit, Mr Tusk told reporters there was a "great deal of work ahead" on Brexit and the "most difficult tasks are still unresolved".
"Quick progress" was needed if a deal was to be reached at the next summit.
"This is the last call to lay the cards on the table," he said.
By the BBC's political editor Laura Kuenssberg
European leaders can repeat the same message, louder and louder.
But this EU summit's instructions to Theresa May may as well have been shouted into an empty cupboard.
Because they know what she knows - that the past 24 hours of Brexit conversations are not nearly as important as the next seven days of discussions at home between Number 10 and the rest of the government.
And after more than two years, this time next week ministers should be nearing the conclusion of their country retreat at Chequers.
It's there that the prime minister hopes to find resolution in her team on a more detailed offer to the rest of the EU - easing, if not removing, all the contradictions in the Tories' positions.
He was one of a string of EU chiefs demanding more clarity from the UK prime minister, who left the summit before the 27 other EU leaders discussed Brexit together on Friday.
European Commission President Jean-Claude Juncker said the British had to "make clear their position" adding: "We cannot go on to live with a split cabinet. They have to say what they want and we will respond to that."
EU chief Brexit negotiator Michel Barnier warned: "The time is very short" and that while progress had been made, "huge and serious divergence remains, in particular on Ireland and Northern Ireland".
He also said he hoped to see "workable and realistic" proposals from the UK on what the future relationship between the UK and EU should look like.
He said he was "ready to invite the UK delegation to come back to Brussels next Monday" to continue working on a deal.
BBC political editor Laura Kuenssberg said she understood that UK officials had already informed the EU Commission they would not hold talks on Monday and the "mini row over diaries" revealed "how tetchy things are".
European leaders at the summit welcomed progress on the legal text of the withdrawal agreement but noted that "important aspects still need to be agreed" including the territorial application of the deal "notably as regards Gibraltar".  Talks between Spain and the UK over Gibraltar, including access to its airport and the exchange of tax information, continue.
They also expressed concern that "no substantial progress has yet been achieved on agreeing a backstop solution for Ireland/Northern Ireland", if a deal on customs arrangements is not agreed by December 2020. when the transition period is due to end.
And they called on member states and EU institutions "to step up their work on preparedness at all levels and for all outcomes" - the European Commission president has said the EU must prepare for the possibility that no Brexit deal will be reached.
Mrs May's own cabinet is divided over what the UK's customs arrangements after December 2020 should look like, when the transition period agreed with the EU is due to end.
And there are disagreements over the future movement of goods and people across the border between Northern Ireland and the Republic of Ireland.
But asked if he believed Mrs May could resolve the differences, Mr Juncker told the BBC he knew the prime minister and: "yes ... she will".
On Thursday, Mrs May said a strong future partnership with the EU was in everyone's interests.
"I think both sides are keen to continue that work at a faster pace than we have done up till now and certainly we would welcome that," she said.
She added that the UK would publish a White Paper setting out "in more detail [the] strong partnership the United Kingdom wants to see with the European Union in the future".
But she urged fellow EU leaders to tell their negotiators the UK should be allowed to continue to take part in schemes like the Prum mechanism for sharing DNA profiles, the Second Generation Schengen Information System - a database of "real time" alerts about certain individuals - and the European Criminal Records Information System.
Without UK participation in such schemes, she suggested their collective ability to fight terrorism would be reduced.
Mrs May's Europe adviser Olly Robbins and Brexit Secretary David Davis were due to appear in front of the UK's Brexit select committee next week but it is understood that the appearance has been delayed until after the publication of the White Paper.
Former Brexit minister Lord Bridges, who backed Remain in the EU referendum, told the Evening Standard there was a risk negotiations could become a "rout", if the cabinet could not compromise, first with each other, then with Europe.
"If nothing changes, there's a danger the UK will have to agree to a withdrawal treaty full of meaningless waffle on our future relationship with the EU," warned Lord Bridges.
"With so little leverage in the next phase, the negotiations would become a rout. Worse, uncertainty will drag on, damaging our economy."

Theresa May says she has secured "legally binding" changes to her Brexit deal, a day ahead of MPs voting on it.
But European Commission President Jean-Claude Juncker warned if the deal was voted down there was "no third chance".
They spoke at a joint press conference in Strasbourg after a late meeting.
Labour leader Jeremy Corbyn said the prime minister's negotiations had "failed" and the announcements did not contain "anything approaching the changes" she had promised Parliament.
Cabinet Office Minister David Lidington announced the changes to the Commons shortly before the press conference, saying they would mean the EU "cannot try to trap the UK in the [Irish] backstop indefinitely".
Mrs May confirmed she would be opening the debate on Tuesday ahead of a so-called "meaningful vote" on her deal, which must be agreed by Parliament to come into force.
Last time her deal was put to Parliament in January, she suffered an historic loss as it was voted down by a margin of 230.
The PM also said her attorney general, Geoffrey Cox, would publish his legal advice on the changes to the deal before the vote.
By BBC political editor Laura Kuenssberg
Monday morning government blues have been replaced by Tuesday morning nervous hopes.
The government does not suddenly expect its Brexit deal to be ushered through at speed, cheered on by well-wishers.
It does, however, believe that Monday night's double act in Strasbourg by Theresa May and Jean Claude Juncker puts it, to quote one cabinet minister, "back in the races".
The extra assurances wrought from weeks of talks with the EU will move some of the prime minister's objectors from the "no" column to the "yes".
Read Laura's blog here.
Mrs May flew out to the European Parliament late on Monday with her Brexit Secretary Steve Barclay for last-ditch talks ahead of the vote.
In the discussions with Mr Juncker and the EU's chief Brexit negotiator Michel Barnier, two documents were agreed by all parties, which Mr Lidington said would "strengthen and improve" both the withdrawal agreement from the EU and the political declaration on the future relationship.
The first is a "joint legally binding instrument" on the withdrawal agreement.
Mrs May said it could be used to start a "formal dispute" against the EU if it tried to keep the UK tied into the backstop - the safety net designed to maintain an open border on the island of Ireland - indefinitely.
The backstop has been criticised by some who believe it will keep the UK tied to the EU indefinitely, but the bloc has said "if used [it] will apply temporarily".
The second is a "joint statement" adding to the political declaration - the statement in the deal about the UK and EU's future relationship - to commit to replacing the backstop with alternative arrangements by December 2020.
Another document will also be put forward by the government, known as a "unilateral declaration".
The PM said this would outline the UK's position that there was nothing to prevent it from leaving the backstop arrangement if discussions on a future relationship with the EU break down and there is no prospect on an agreement.
Mrs May said: "MPs were clear that legal changes were needed to the backstop. Today we have secured legal changes.
"Now is the time to come together to back this improved Brexit deal and deliver on the instruction of the British people."
Mr Juncker also warned MPs that they would be putting everything at risk if they voted down the deal.
"In politics sometimes you get a second chance," he said.
"It is what we do with that second chance that counts. There will be no third chance."
He added: "Let us speak crystal clear about the choice - it is this deal or Brexit might not happen at all."
Labour leader Mr Corbyn urged MPs to vote against the deal when it returns to the Commons on Tuesday.
"Since her Brexit deal was so overwhelmingly rejected, the prime minister has recklessly run down the clock, failed to effectively negotiate with the EU and refused to find common ground for a deal Parliament could support," he added.
The Conservatives' partner in Parliament, the DUP, have been outspoken critics of the deal - especially the backstop.
After the announcement, a spokesman said: "These publications need careful analysis. We will be taking appropriate advice, scrutinising the text line by line and forming our own judgement."

Did anything change? Not that much.
But for Downing Street, this has not been a pointless stop-off in the almost never-ending Brexit adventure.
Because, while there hasn't been a breakthrough, the EU has agreed to more talks, which at least opens up the possibility of discussing the changes to the troubled backstop that has caused such political difficulty.
It might not sound like much, but "we can talk", is at least a different message to "this is over" .
In the perception war, which is, of course, part of this whole battle, Theresa May didn't leave Brussels with nothing.
And in these torrid times, given the last summit before Christmas, (remember, nebulous?) going home with a process, if not a promise, counts for something.
That does not, for the avoidance of doubt, remotely make the prime minister's next steps easy.
The EU's suggestion that a compromise with Labour might sound tempting and practical. It's also a step forward for some Tory MPs who are pushing for a softer compromise.
But as we've discussed here so many times, moving to a softer Brexit could result in the downfall of the government, it could be that simple.
David Lidington and Keir Starmer might sit down to talk within days, but there are evidently costs for both of the main Westminster parties if they work together to get this deal through.
On the EU side, where so many governments are coalitions, the idea of cross-party working has an inevitable logic. But at this stage, straightforwardly, that is not the government's chosen way out.
As things stand, the Opposition wants to find compromise and the European Union wants to talk.
Sounds good? It doesn't work like that.
Because the interpretation of the political reality in most of the government, is that Theresa May won't shift to meet Labour, not yet.
And Brussels won't move yet to meet her.
And as the clock runs down, the pressure on the prime minister goes up and up with no obvious way out.
But making a big switch simply carries too many political risks, at this stage.
Just keeping going doesn't sound like a cunning political strategy but perhaps, right now, it's the only and best plan.

The chancellor has warned manufacturers that "there will not be alignment" with the EU after Brexit and insists firms must "adjust" to new regulations.
Speaking to the Financial Times, Sajid Javid admitted not all businesses would benefit from Brexit.
The Food and Drink Federation said it sounded like the "death knell" for frictionless trade with the EU and was likely to cause food prices to rise.
Mr Javid declined to specify which EU rules he wanted to drop.
The automotive, food and drink and pharmaceutical industries all warned the government last year that moving away from key EU rules would be damaging.
But Mr Javid told the paper: "There will be an impact on business one way or the other, some will benefit, some won't."
He said Japan's car industry was an example of a manufacturing sector which found success without following EU rules.
Asked how differing regulations between the UK and EU may impact industries such as automotive and pharmaceuticals, he said: "We're also talking about companies that have known since 2016 that we are leaving the EU.
"Admittedly, they didn't know the exact terms."
Tim Rycroft, chief operating officer of the Food and Drink Federation, told BBC Radio 4's Today programme that "it sounds awfully like the death knell for the concept of frictionless trade with the EU".
He said it probably meant that food prices would rise when the transition period finishes at the end of this year.
Mr Rycroft acknowledged that some other industries might benefit from UK-specific trade rules. But he said: "We also have to make sure the government clearly understands what the consequences will be for industries like ours if they go ahead and change our trading terms."
The Confederation of British Industry (CBI) said it welcomed the chancellor's "ambitious" vision but said government should not feel it has an "obligation" to depart from EU rules.
Carolyn Fairbairn, CBI director-general, said for many companies, "particularly in some of the most deprived regions of the UK", keeping the same rules would support jobs and maintain competitiveness.
The Society of Motor Manufacturers and Traders said the automotive industry in the UK and EU was "uniquely integrated" and its priority was to avoid "expensive tariffs and other 'behind the border' barriers".
It said it was vital to have "early sight" of the government's plans so companies could evaluate their impact.
The government has not yet agreed a future trading relationship with the EU - it plans to do so in the 11-month transition period which begins after the UK leaves the bloc on 31 January.
During the transition period the UK will continue to follow EU rules and contribute to its budget.
The chancellor also said he wanted to double the UK's annual economic growth to between 2.7 and 2.8%.
However, the outgoing governor of the Bank of England, Mark Carney, told the Financial Times last week he thought the UK's trend growth rate was much lower, at between 1 and 1.5%.
Mr Javid said the extra growth would come from spending on skills and infrastructure in the Midlands and the north of England - even if they did not offer as much "bang for the buck" as projects in other parts of the country.
Historically low interest rates, which allow the government to borrow money relatively cheaply, were "almost a signal to me from the market - from investors - that here's the cash, use it to do something productive", Mr Javid said.
He pledged to rewrite Treasury investment rules, which have tended to favour government investment in places with high economic growth and high productivity.
Mr Javid said the rules had helped to "entrench" inequality and insisted weaker parts of the country would have first call on the new money.
In November, the Bank of England said a weaker global economy and its new assumptions about Brexit would knock 1% off UK growth over the next three years compared with its previous August forecast.

A government source has told the BBC there will be "no deal tonight", as officials continue to work on the technical details in Brussels.
The UK and EU had been hoping to sign off a revised Brexit deal before Thursday's crunch EU council meeting.
Boris Johnson has been trying to get Tory Brexiteers and the DUP to back his revised plan for Northern Ireland.
The new draft Brexit deal has a mechanism enabling Northern Ireland to approve or reject the border plans.
This would give the Stormont Assembly the chance to vote on Brexit arrangements four years after the transition period ends in 2020.
The EU believes this replaces the controversial Northern Ireland backstop with arrangements that are sustainable over time and are democratically supported, as requested by the UK.
The backstop was designed to avoid a hard border on the island of Ireland after Brexit and involved the UK potentially retaining a very close relationship with the EU - staying in the customs union - for an indefinite period.
The legal text of the draft still has to be approved by the British government.
BBC political editor Laura Kuenssberg said she understood the issues between the UK, EU and Ireland were "pretty much sorted", but that DUP sources were warning there were still gaps between proposals and what the party could support.
The Democratic Unionist Party has propped up the Conservative government since the 2017 general election and their support could be vital if Parliament is to approve any agreement Mr Johnson secures.
Earlier, the PM likened the Brexit talks to climbing Everest, saying the summit was "not far" but still surrounded by "cloud".
He will travel to Brussels to attend the EU Council summit on Thursday.
The UK is due to leave the EU at 23:00 GMT on 31 October and Mr Johnson has repeatedly insisted this will happen, regardless of whether there is a deal or not.
The EU's chief negotiator Michel Barnier has, meanwhile, been briefing EU ambassadors, ahead of Thursday's summit - the meeting was originally due to take place at lunch time but was put back twice.
Asked afterwards, whether there was a deal, Mr Barnier said: "We are working, we are working."
The issue of the Irish border - and how to handle the flow of goods and people across it once it becomes the border between the UK and the EU after Brexit - has long been a sticking point in the negotiations.
The border is also a matter of great political, security and diplomatic sensitivity in Ireland.
Mr Johnson's proposals for a new Brexit deal hinge on getting rid of the backstop - the solution to border issues agreed by Theresa May which proved unpalatable to many MPs.
However, his plans would see Northern Ireland treated differently from the rest of the UK - something the DUP, among others, has great concerns about.
The DUP has, in particular, been demanding assurances around the so-called consent mechanism - the idea the prime minister came up with to give communities in Northern Ireland a regular say over whatever comes into effect.
A source told Newsnight's political editor Nick Watt the thinking in Number 10 was that "the DUP never want to own a solution - at some point you have to call their bluff. You just have to hope they will sulkily acquiesce."
The party's leader, Arlene Foster, held talks in Downing Street on Tuesday night and Wednesday morning.
As well as the DUP, Mr Johnson is also trying to secure support from Tory Brexiteers, most of whom are part of the European Research Group.
Chairman Steve Baker told reporters after a meeting in Downing Street on Wednesday evening his group "hope [to] be with the prime minister, but there are thousands of people out there who are counting on us not to let them down and we are not going to".
"We are just really wishing the prime minister well and hoping he has total success. We know there will be compromises, but we will be looking at this deal in minute detail with a view to supporting it, but until we see that text, we can't say."
As Wednesday draws to a close, a deal is still, DBP - difficult but possible, in case you haven't caught the lingo by now.
I hear from both sides of the Channel that the issues between the UK, Ireland and the EU are pretty much ironed out.
A schedule is in place for EU leaders to be able to sign off a deal tomorrow, discussing it as the first item on the agenda at the summit if the ink is dry.
The government has in place its plan to ask MPs to approve the hypothetical deal in Parliament on Saturday.
Despite all the obstacles, all the warnings about the tightness of the timetable, it is not yet too late.
Boris Johnson faces another deadline on Saturday - the date set out in the so-called Benn Act, which was passed last month by MPs seeking to avoid a no-deal Brexit.
If MPs have not approved a deal - or voted for leaving the EU without one - by Saturday, then Mr Johnson must send a letter to the EU requesting an extension to 31 January 2020.
The prime minister's official spokesman has confirmed the government will table a motion for Parliament to sit this Saturday from 09:00 to 14:00 BST.
That motion would be considered on Thursday.
However, this does not mean the House of Commons will definitely sit on Saturday - the government could table the motion but not push it to a vote.
The expectation on the EU side is that a new Brexit deal text is pretty much ready.
They are now just waiting to hear from the UK side whether it can be signed off.
Even if this text is ready, though, even if it can be signed off by EU leaders, the EU will not yet be breathing a sigh of relief because they have been here before.
Theresa May signed a Brexit deal with the EU and it went on to be rejected multiple times by House of Commons.
The fear is, if a new Brexit text meets the same fate, the UK government will come back to Brussels asking for more concessions.

Contingency plans in case the UK has to leave the EU with no deal in place are "well under way", a minister has said.
Dominic Raab said while the UK had to "strive for the very best outcome" from Brexit negotiations, it had to "prepare for all eventualities".
The Sunday Telegraph claimed there were plans to "unlock" billions of pounds in the new year to prepare for a "no deal" Brexit, if talks make no progress.
Six months of Brexit negotiations have not led to a significant breakthrough.
Last month Prime Minister Theresa May used a speech in Florence to set out proposals for a two-year transition period after the UK leaves the EU in March 2019, in a bid to ease the deadlock.
Talks had stalled over key issues including EU citizens' rights, a financial settlement and on the Northern Ireland border.
UK Brexit Secretary David Davis has since said "decisive steps forward" have been made - although EU Brexit negotiator Michel Barnier has said there are still "big gaps" between the two sides on some issues.
The Sunday Telegraph reported that, if no further progress is made, Mrs May has decided to commit billions in the new year to spend on things like new technology to speed up customs checks, in case there is no trade deal and the UK has to revert to World Trade Organisation tariffs with the EU.
Appearing on the BBC's Sunday Politics, Justice Minister Mr Raab was asked why there was no visible sign of preparations for no deal - such as the recruitment of more customs officers and more infrastructure at ports.
He said: "This planning goes on, it's right that it does because of the prime minister's clear point of view that we need to search and hope for the best, strive for the very best outcome from these negotiations, but prepare for all eventualities.
"What we don't do is run around advertising it demonstrably. Why? Because we want to send the right, positive tone to our EU partners.
"So we don't go talking about what happens if we end up with no deal, but quietly, assiduously, those preparations will be in place."
He added that the government wanted to see "the best deal I think in terms of trade, security, co-operation" but added: "Those contingency plans are well under way."
Labour's Shadow Foreign Secretary Emily Thornberry told the programme that after Brexit, Britain "should stay as close as we can" to the EU because it is "good for our economy".
"We need to leave the European Union but it is good for our economy - they're our biggest market - that we stay as close as we can.
"And the problem that the British country has is that a good half of the Tory party wants to go sailing off into the mid-Atlantic with no deal at all and that would be disastrous for our country."
EU leaders are due to decide at October's meeting of the European Council whether enough progress has been made on key issues to move on to the UK's post-Brexit relationship with the EU.
Meanwhile two Conservative MEPs who voted to block moves towards trade talks between the UK and European Union have had the party whip removed.
South West MEP Julie Girling and South East MEP Richard Ashworth were suspended from the Conservative Party after supporting a resolution in Strasbourg declaring that "sufficient progress" had not been made in talks to move on to discussions about the future relationship.
In a letter, European Parliament Chief Whip Dan Dalton said: "Given the seriousness of this issue, and your failure to discuss your intention to vote against the agreed position of the Conservative delegation in advance, I am therefore writing to inform you that I am suspending the Conservative whip from you until further notice."
Julie Girling told her local newspaper she had not voted to block trade talks but to "focus the minds of negotiators" and "drive more effective negotiations".
Mr Ashworth reportedly said he was confused by the suspension: "The vote was not about disrupting Brexit and the negotiations. We were asked a technical question about how much progress had been made and the answer for me was not enough."
The fourth round of Brexit negotiations began on 25 September, with the UK due to leave the EU in March 2019.

Donald Tusk has poured cold water on hopes of a Brexit breakthrough at Wednesday's EU summit, saying the Irish border was still a sticking point.
The European Council president said he had "no grounds for optimism" it would be solved at the summit.
And he called on Theresa May to come up with "concrete proposals" to break the "impasse".
The prime minister told her cabinet a deal was within reach if the government "stand together and stand firm".
Asked if she would be coming forward with "concrete proposals" at the summit, Mrs May's official spokesman said: "The prime minister set out her position yesterday (Monday). She looks forward to a face-to-face discussion with him tomorrow.
"There are many areas where we have made progress. More progress is needed on the backstop."
The "backstop" is a fall back plan for avoiding a hard border in Ireland if the two sides can't strike a trade deal in time - but they can't agree on how long it should last and what form it should take.
No new proposals are expected to be tabled or discussed this week and discussions are likely to continue at official level only.
Mrs May had already put forward a "workable solution", Downing Street said.
Speaking at a press conference in Brussels, Mr Tusk said: "As I see it, the only source of hope for a deal for now is the goodwill and determination on both sides.
"However, for a breakthrough to take place besides goodwill we need new facts.
"Tomorrow (Wednesday), I am going to ask Prime Minister May whether she has concrete proposals on how to break the impasse."
He urged Mrs May to present "something creative enough" to break the deadlock.
He said EU leaders would discuss how to step up preparations for a "no-deal scenario", but stressed that did not mean they were not also making "every effort to reach the best agreement possible for all sides".
Both sides in Brexit talks were hoping that a deal on the UK's withdrawal from the EU, including the Irish border question, would be agreed by mid-November in time for it to be ratified by EU members and for MPs at Westminster to vote on it.
The UK and the EU had hoped that enough progress would be made at Wednesday's EU council meeting to call a special summit in November to finalise the terms of the UK's exit.
Asked if the November summit would still go ahead, Mr Tusk said: "It's for the leaders to decide whether we need an extraordinary summit in November or not.
"Logistically, we are ready, but we need the feeling that we are close to a real breakthrough. The clock is ticking."
Downing Street said Mrs May has told cabinet ministers not to be "downhearted" if the European Council does not set a date for a November summit, amid growing expectation in government that any final agreement may be pushed back to December.
The prime minister told a cabinet meeting on Tuesday morning she could not agree to any deal with the EU which created a new border between Northern Ireland and the rest of the UK - or one which locked the UK into a customs union with the EU indefinitely.
She says this would be the consequence of the proposals currently on the table from the EU.
The cabinet had discussed a "mechanism" that would avoid an indefinite customs union if a full trade deal cannot be agreed by the end of the 21-month transition period that is due to kick in after the UK leaves on 29 March - the so-called "backstop" plan.
But it was "not a decision-making cabinet", Downing Street said.
However, the EU is considering a proposal for a UK-wide temporary customs arrangement, Mrs May's spokesman added.
The prime minister told ministers progress had been made in Brexit talks on the "future framework" for trade and although there would be challenging moments ahead a deal with Brussels was within reach, Downing Street said.
"I am convinced that if we as a government stand together and stand firm we will achieve this," she said.
Mrs May used Tuesday's cabinet to rally support for her position among senior ministers, amid reports eight of them had met on Monday to discuss their concerns about it.
Downing Street said none of the eight - Dominic Raab, Jeremy Hunt, Michael Gove, Penny Mordaunt, Chris Grayling, Liz Truss, Andrea Leadsom and Geoffrey Cox - had threatened to quit at Tuesday's cabinet meeting and it was clear that she had strong support.
The EU's chief Brexit negotiator Michel Barnier, who is travelling to Luxembourg to brief EU leaders ahead of Wednesday's summit, said he hoped a deal with Britain was possible "in the coming weeks".
"We are still not there.
"There are still several issues which remain unresolved, including that of Ireland, and therefore what I understand is that more time is required to find this comprehensive deal and to reach this decisive progress which we need in order to finalise these negotiations on the orderly exit of the United Kingdom."

Unless the UK's withdrawal agreement with Brussels is reopened and the backstop abolished there is no prospect of a deal, Downing Street has said.
The strong statement came after the EU pushed back against Boris Johnson's proposal to implement "alternative arrangements" for the UK-Irish border.
Mr Johnson has said the backstop is "anti-democratic" and must be scrapped.
European Council President Donald Tusk said it was "an insurance to avoid a hard border on the island of Ireland".
Meanwhile, the government has announced UK officials will stop attending most EU meetings from 1 September.
The Department for Exiting the European Union said it would "unshackle" them from discussions "about the future of the Union after the UK has left" and allow them to focus on "our immediate national priorities".
Later this week Mr Johnson will meet German Chancellor Angela Merkel and French President Emmanuel Macron for the first time since entering No 10.
Ahead of that, in a letter to European Council President Tusk, he called for the backstop to be removed from the withdrawal agreement reached between the EU and his predecessor, Theresa May, arguing it risked undermining the Northern Irish peace process.
Mr Johnson said the reaction to his demand for the backstop to be scrapped had been "a bit negative" but "we will get there".
He said he would enter Brexit talks with EU leaders with "a lot of oomph".
Mr Johnson added: "I think there is a real sense now that something needs to be done with this backstop. We can't get it through Parliament as it is."
He reiterated his view that EU countries were less likely to make concessions to the UK "as long as they think there's a possibility that Parliament will block Brexit".
The border is a matter of great political, security and diplomatic sensitivity, and both the UK and EU agree that whatever happens after Brexit there should be no new physical checks or infrastructure at the frontier.
The backstop is a position of last resort to guarantee that, but if implemented, it would see Northern Ireland stay aligned to some rules of the EU single market.
It would also involve a temporary single customs territory, effectively keeping the whole of the UK in the EU customs union.
Mrs May's withdrawal agreement has been voted down three times by MPs.
A series of voices from the European side rejected Mr Johnson's assertions.
Mr Tusk said those opposing the backstop without "realistic alternatives" supported re-establishing a hard border.
This was the reality "even if they do not admit it", he added.
The European Commission said Mr Johnson's letter did not contain a "legally operational solution" to prevent a hard Irish border.
"It does not set out what any alternative arrangements could be," a spokeswoman said, and "recognises that there is no guarantee such arrangements would be in place by the end of the transitional period".
Guy Verhofstadt, Brexit spokesman for the European Parliament, said the backstop was "a vital insurance policy... supported by the people of the island of Ireland".
And speaking in Iceland, Chancellor Merkel said: "Once we have a practical solution to ensure that the Good Friday Agreement continues to apply, then we don't need the backstop of course."
A Downing Street spokesperson insisted the UK government was "ready to negotiate, in good faith, an alternative to the backstop, with provisions to ensure that the Irish border issues are dealt with where they should always have been: in the negotiations on the future agreement between the UK and the EU".
The question is whether Boris Johnson's letter to the EU is intended as the start of negotiations - or designed to be the end of them.
He's suggested the only way to get a deal is to take the backstop out. Not to time limit it, or modify it, but to bin it.
But if he has a fully-fledged, different plan up his sleeve, why he isn't spelling out more detail of those "alternative arrangements"?
And why can't Downing Street say what additional reassurances would be available to the Irish government in the absence of a backstop, if trade talks falter?
The lack of detail on Plan B has made some critics in his own party wonder if his Plan A is simply to make an offer the EU can't accept and then blame them for no deal.
But No 10 insists he'd do a deal quickly if the EU was more flexible. In other words, Brussels would be expected to blink first as the prospect of no deal approaches.
So far, though, the EU is staring him out.
Labour leader Jeremy Corbyn said it was unclear what the prime minister thought he was negotiating.
"He needs to recognise that by just holding the threat of a no-deal Brexit on 31 October towards the European Union isn't going to bring about a change, it's going to make things much worse," he said.
"He created this arbitrary date by his behaviour during the Tory Party leadership campaign. He needs to wise up and stop the nonsense of 31 October and start talking seriously."

Parliament has a "clear choice" to stand up for the UK against a draft Brexit deal or allow it to break up the union and make the UK a "vassal" state, DUP MP Nigel Dodds has said.
The Irish border has been the main sticking point in the talks.
The UK and EU have agreed to a "backstop", which would see NI stay aligned to some EU rules if another solution cannot be found.
Mr Dodds told MPs the prime minister had broken promises made to his party.
Several cabinet ministers have resigned, saying the deal presents a threat to the integrity of the union.
Mr Dodds was among MPs criticising the prime minister in the House of Commons amid a backlash over her plan.
The DUP's 10 MPs prop up the Conservative government to ensure it has a majority to pass key legislation in the Commons.
Mr Dodds said he could take Mrs May through the list of promises she made about the future of Northern Ireland but that would be a "waste of time because she clearly doesn't listen".
He put it to MPs: "The choice is now clear, we stand up for the United Kingdom, the whole of the United Kingdom, the integrity of the United Kingdom or we vote for a vassal state with the break-up of the UK."
But the prime minister said it was wrong to imply that she had not considered the interests of the people of Northern Ireland.
The real spat among politicians is over the UK and EU's agreement on the Northern Ireland backstop.
It would see Northern Ireland staying aligned to some rules of the EU single market, if another solution cannot be found by the end of the transition period in December 2020.
That means that goods coming into Northern Ireland would need to be checked to see if they meet EU standards.
It would also involve a temporary single custom territory effectively keeping the whole of the UK in the EU customs union - until both the EU and UK agree that it is no longer necessary.
Mrs May has said there was no deal on the table that did not involve signing up to the backstop - but that it is only an insurance policy.
"I know there are some who said I should simply rip up the UK's commitment to the backstop but this would have been an entirely irresponsible course of action," she said.
Labour has also said it will not approve the plan, with party leader Jeremy Corbyn saying the backstop proposal would create a "de facto border in the Irish Sea".
Mr Corbyn said it locked "Britain into a deal which it cannot leave without the agreement of the EU".
Yes, four resignations by junior and cabinet ministers before 10:30 GMT on Thursday, including the Brexit Secretary, Dominic Raab.
The DUP's deputy leader, Nigel Dodds, tweeted thanks to Mr Raab and others for "standing up for the union".
Karen Bradley has denied accusations that the political fall-out over the draft Brexit plan is a "car crash" and said the deal was "good for the union".
She was speaking in Belfast after meeting a number of business leaders to discuss what has been agreed by EU and UK negotiators.
"Nobody said it would be easy," said Mrs Bradley, adding that the majority of the cabinet is still behind the deal.
She gave Mrs May her full support, and said: "This is a woman who gets things done."
The Northern Ireland Secretary also appealed for "cool heads".
"The people of Northern Ireland when they see this deal will see it is a good deal for the whole of the UK and Northern Ireland, and I hope they tell their politicians that," she added.
Asked about whether there are question marks over the future of the government's confidence and supply deal with the DUP, Mrs Bradley said that was a "matter for the parties' chief whips".
Mrs May has faced a huge backlash from the Democratic Unionist Party (DUP), amid suggestions of moves within the Conservative Party to force a no-confidence vote.
DUP MP Jim Shannon said his party had been "betrayed" by the prime minister.
He told BBC NI's Good Morning Ulster programme that his party feels Theresa May has broken her commitments to them and is "up for an election".
Stephen Farry, the deputy leader of Alliance said it is important that the business community speaks out more loudly in the coming days, as the deal offers them the best of both worlds.
You can But Ulster Unionist leader, Robin Swann, said the draft deal had been "a monumental error of judgement on behalf of the DUP", which would have a devastating long-term impact.
The Irish Foreign Minister, Simon Coveney, has said people "should not talk down" the chances of a Brexit deal getting through Parliament.
Mr Coveney told Irish national broadcaster RTÉ that the deal is "the only one on the table".
An emergency EU summit is now due to take place on 25 November to agree the draft text.
After that, Mrs May needs to get MPs to vote for it. The BBC's political editor Laura Kuenssberg said that could take place in early December.
There have been a number of calls by senior Conservatives for the prime minister to go and there could yet be more resignations from the cabinet.
Former chairman of the Northern Ireland Affairs Committee Laurence Robertson said he has written a letter of no confidence in the prime minister to the Conservative Party 's 1922 committee.
If 48 letters are submitted then Theresa May would face a no-confidence vote within the Conservative Party.

MPs, celebrities and business leaders have launched a campaign calling for a public vote on the final Brexit deal between the UK and the European Union.
The People's Vote - which held a rally in Camden, north London, on Sunday - aims to unite anti-Brexit groups.
Organisers said some 1,200 people were at the event, including MPs from all leading parties. Pro-Brexit campaigners also gathered outside.
Both the Conservatives and Labour have ruled out a second referendum.
Actor Sir Patrick Stewart, who played Charles Xavier in the X-Men films based on the comic books, said the famous character would have voted Remain.
He told the rally: "Unity, common cause, wellbeing of society and debate were paramount to the belief of this fictional character.
 "Our country's future is at stake and we will not stand idly by.
 "That is why I support a people's vote on the final deal."
Britain voted to leave the EU by 51.9% to 48.1% in June 2016.
The UK will formally cease to be an EU member in March 2019, and the two sides hope to reach a final deal on the terms of its exit by October - in time for it to be ratified by UK and European parliaments.
Speaking to the BBC at the event, Labour peer Lord Adonis said: "People want a say... it was a vote in the dark two years ago.
"No-one had any idea what the consequences of Brexit were going to be."
And Green Party co-leader Caroline Lucas told attendees that Brexit was "not inevitable", adding: "We'll do everything we can in Parliament for a people's vote. This issue is far too important to leave to the politicians."
Conservative MP Anna Soubry told the crowd the UK was about to embark on a course that would "make you and your grandchildren... less prosperous than you are now".
"I think the best and right thing to do is to put it back to the people and say you can have a vote on this deal," she said.
Chuka Umunna, MP for Streatham, said: "We need more Conservative members of Parliament to be as brave as Anna and many others who defied the whip and put their country before their party."
Lib Dem Layla Moran said: "Whether you voted to Leave or Remain... there is nothing more democratic than allowing the people to accept or reject a deal that will affect our country for decades to come."
Meanwhile, pro-Brexit demonstrators also turned up at the launch, and Conservative MP Nadine Dorries argued there was no public appetite for a second referendum.
Appearing alongside Mr Umunna on ITV's Peston on Sunday, she said: "A second referendum, Chukka, which is what you're really campaigning for, is never going to happen. The public don't want it."
Earlier, actor Sir Patrick told the BBC's Andrew Marr Show that the "terms and conditions" of Brexit were "quite unlike" how they were presented during the run up to the 2016 referendum.
Sir Patrick also said he was motivated by "history and emotion" to want to stay in the EU.
"I'm a war baby and growing up a lot of the world was not good. So the day we joined was one of the most exciting days of my adulthood," he added.
Also speaking on the Andrew Marr Show, Foreign Secretary Boris Johnson responded to the campaign, noting that the people's vote had already taken place:
"They voted with a substantial majority to leave the EU. We're now trying to deliver on that mandate from the people."
Mr Johnson addressed the remarks made by Sir Patrick, who also played the role of Captain Jean-Luc Picard in Star Trek: The Next Generation.
"I think we'll get a great result and we'll be able to have, not only a gigantic free trade deal with our friends and partners across the Channel, but we'll be able to boldly go to areas we perhaps neglected over the past five years."

The EU could be ready to drop some of its "red lines" from the Brexit deal it struck with the UK to "help" save it, Chancellor Philip Hammond has said.
He did not believe the EU would scrap the backstop plan to keep the border open between Northern Ireland and Ireland.
But some EU leaders were "looking at what they can do" to change it.
Andrea Leadsom has, meanwhile, said the EU would delay Brexit for a "couple of weeks" to help get a deal through.
She told the BBC's Newsnight that due to our "very strong relationship" with the EU, a short extension would be "feasible".
But Downing Street said: "There is no change to our position.
"We are not considering an extension to Article 50 and are committed to doing whatever it takes to have the statute books ready for when we leave the EU on 29 March this year."
The UK is set to leave the EU on that date, with or without a deal.
Theresa May is battling to get her plan through Parliament, despite the fact it suffered an historic defeat in the Commons last week - losing by 432 votes to 202.
A major part of the loss was because of the controversial backstop, which is the fallback position for after Brexit to ensure a hard border is not introduced.
Without a hard border, there will be no checks on people or goods passing between the two countries - as it is now.
Critics claim the backstop plan separates Northern Ireland from the rest of the UK by keeping it more closely aligned to EU rules. But its backers say it will prevent political tensions rising along the border.
Downing Street said it was continuing conversations with MPs to address a range of concerns about the backstop ahead of the plan returning to the Commons on Tuesday - including with hard-line Brexiteers in the Tory Party and the DUP, which supports the government in Parliament but voted against her deal.
Both sets of MPs have said they will not vote for the PM's deal while the backstop is part of it.
No 10 admitted they were "not there yet" with a new proposal to take to Brussels, but said there was a clear message from the EU that they wanted the UK to leave with a deal and, in order to do so, there will have to be some changes.
Some backbench MPs are trying to make the deal more palatable by removing, replacing or time-limiting the backstop, while others are trying to force ministers to delay Britain's departure from the EU for up to a year if MPs can't agree on a deal by 26 February, to prevent a no-deal Brexit.
Speaking to BBC Radio 4's Today programme from Davos earlier, Mr Hammond said leaving with a withdrawal agreement was the "only credible and sustainable way" forward and warned of "very significant disruption" for the UK economy if the country left the EU without a deal.
But he claimed some European politicians were "thinking very hard about where the European Union has drawn its red lines [and] whether they really need to be in the place where they have been drawn".
He added: "What I am hearing from European politicians and commentators is that they do take this issue very seriously, they understand the challenge that we have got at home and generally - not all of them, but many of them - want to help.
"They are not prepared to compromise on the fundamental principles that the EU has set out, but they certainly are looking at whether there is anything they can do without compromising those principles."
French finance minister Bruno Le Maire said it was up to the British government to find a way out of the situation, not EU member states.
He told Today that the backstop issue was "done" and the EU had "nothing to give" on the Brexit deal apart from "clarifications".
Mr Hammond said the French had "always been the hardest in this debate" and talking to other European politicians would offer "a more balanced view".
By Chris Mason, BBC political correspondent
Speak to people from the government in private, and some will tell you they think minds are moving on their own side.
They hope some Brexiteers are open to compromise; willing to climb down, if only they can be provided with a ladder.
And now the chancellor has said in public that perhaps the EU is willing to budge at least a bit too.
On Tuesday, MPs will get a chance to express their views on a range of possible options, which could, depending on how the day plays out, hand the prime minister numerical evidence that Parliament may be able to support a variation of her Brexit deal - if the EU is willing to compromise too.
Publicly, the EU is saying what it has always said - the withdrawal agreement is finished and it isn't being re-opened.
So, the big question will be, is anything Parliament could potentially coalesce around and vote through also palatable to the EU?
We are not likely to get any indication of that until at least the middle of next week.
In an interview with BBC's Newsnight, Mrs Leadsom said she believed the government could still get Mrs May's deal through Parliament before 29 March.
But, she added: "In spite of everything, we have a very strong relationship with our EU friends and neighbours and I am absolutely certain that if we needed a couple of extra weeks or something then that would be feasible.
"We would want to think carefully about it, but as things stand, I do feel that we can get, with the support of both houses - the House of Commons and the House of Lords - with goodwill and a determination, we can still get the legislation through in time."
The deputy leader of the DUP, Nigel Dodds, said he had been "encouraged" by a change in tone from Europe - namely a speech by the EU's chief negotiator, Michel Barnier, who said on Wednesday that they would "have to find an operational way" of carrying out checks without putting a hard border between Ireland and Northern Ireland.
Mr Dodds called it a "new and more realistic approach" and "a long way from the dramatic language EU spokespeople were using this time last year".
But Mark Francois, a Tory MP and vice chairman of the pro-Leave European Research Group, said: "The only thing that we would contemplate is if the entire backstop is removed from the [deal]."
"They'd have to take it out lock, stock and barrel. I don't know whether the EU would be prepared to do that, but if they're not, then we're not going to support it."
On Thursday, the German boss of Airbus, Tom Enders criticised Brexiteer "madness" and said his company might have to make "potentially very harmful decisions for the UK" in the event of it leaving the EU with no deal.
Airbus currently employs 14,000 workers in the UK and every wing on its commercial aircraft is currently made here.
In a video message, Mr Enders said: “Please don’t listen to the Brexiteers’ madness which asserts that ‘because we have huge plants here we will not move and we will always be here’. They are wrong.”
But Mr Francois hit back in a live interview on BBC News, tearing up Mr Enders' words and saying: "My father, Reginald Francois, was a D-Day veteran. He never submitted to bullying by any German and neither will his son."

Ireland is not alone in Brexit negotiations and will remain backed by all member states, European Commission President Jean-Claude Juncker has said.
Mr Juncker was speaking in Dublin on Thursday.
He is in Ireland for a two-day visit as the impasse between the EU and the UK over the Irish border continues.
This week the EU warned that more work was needed on how to deal with the 300-mile frontier post-Brexit.
Mr Juncker started his visit with a meeting with Taoiseach (Irish prime minister) Leo Varadkar and Irish Foreign Minister Simon Coveney at Government Buildings in Dublin.
After the meeting, Mr Juncker made clear that a resolution to the border issue was crucial to the withdrawal treaty.
"This is not a bilateral question between Ireland the United Kingdom - this is an issue between the UK and the European Union," he said.
"We want to make it clear again and again that Ireland is not alone.
"We have Ireland backed by 26 member states and the commission - this will not change.
"I am strongly against any temptation to isolate Ireland and not to conclude the deal on Ireland.
"Ireland has to be part of the deal."
Mr Junker will receive an honorary doctorate from the National University of Ireland and attend an official dinner hosted by Mr Varadkar in Dublin Castle later on Thursday.
He will also address a joint sitting of both houses of the Irish parliament, the Oireachtas.
On Friday, he will meet Irish President Michael D Higgins and visit the home of the Gaelic Athletic Association (GAA), Croke Park, and the GAA museum.
He will also watch a demonstration of Gaelic football and hurling.

Senior Conservatives have signalled they are not prepared to support a no-deal Brexit as they inflicted a defeat on the government in Parliament.
MPs backed an amendment to the Finance Bill, which would limit the scope for tax changes following a no deal unless authorised by MPs, by 303 to 296 votes.
Twenty Tories rebelled and, while its practical effect will be limited, Labour said it was an "important step".
But Brexiteers said the UK would leave the EU on 29 March, come what may.
Before the vote, No 10 said a defeat would be "inconvenient rather than significant", with experts pointing out there were other mechanisms available to government to raise money.
Former cabinet ministers Michael Fallon, Justine Greening, Dominic Grieve, Ken Clarke and Sir Oliver Letwin were among the 20 Conservative MPs who defied the government by backing a cross-party amendment tabled by Yvette Cooper.
Sir Oliver, a government loyalist who has never previously rebelled over Brexit, said he wanted to send a message to opponents of Theresa May's Brexit deal, to be voted on next week.
"I want to make it abundantly clear to my honourable friends who are voting against the prime minister's deal, which I shall be supporting, that the majority in this House will not allow a no-deal exit to occur on the 29 March.
"I will continue to do so right up to the end of March, in the hope that we can put pay to this disastrous proposal."
Mr Corbyn hailed the development as an "important step" towards preventing a no-deal Brexit.
The Labour leader tweeted: "It shows that there is no majority in Parliament, the cabinet or the country for crashing out of the EU without an agreement."
By Vicki Young, BBC chief political correspondent
Downing Street was saying earlier that this would not be catastrophic if it was voted through, as it was a minor issue when it came to tax powers if there was a no-deal scenario.
What this is about is Parliament saying to the government "we can control this process" if it comes to it.
Opponents of a no-deal Brexit will say this shows they have the numbers to stop the government going down that path, although that will be argued against by the Brexiteers.
It also shows the difficulty that Theresa May has when it comes to legislation because she does not have a working majority.
Her arrangement with the DUP meant she was supposed to have a majority but if there are enough Conservative MPs willing to go against their own government, that disappears.
The prime minister could try to turn this around and say to the Brexiteers "you are jeopardising Brexit from happening at all" because there is not a majority for a no-deal Brexit in the Commons.
If you are trying to look for a bright side for the government, that is probably it.
The setback, the government's sixth Commons defeat since July 2017, comes as MPs prepare to resume debate on Wednesday on the PM's proposed Brexit deal, culminating in a vote next week.
It also comes at the end of a day in which senior ministers spoke out about the risks of exiting the EU without any agreement on the terms of withdrawal.
Work and Pensions Secretary Amber Rudd told the cabinet that the public would take a "dim view" of government if it settled for a disorderly Brexit and suggested it would make the UK less safe.
And Business Secretary Greg Clark said such an outcome "could not be contemplated".
The Commons amendment is designed to make a no-deal exit harder by limiting the Treasury's ability to raise certain taxes after the UK left, without the explicit consent of Parliament.
The technical changes to a crucial piece of government legislation were intended to demonstrate to ministers the strength of opposition to a no-deal Brexit in the Commons.
Ms Cooper said although it would not block a no-deal exit, it "set a precedent" and showed MPs would not allow the UK "to just drift into it by accident".
Lib Dem leader Sir Vince Cable said the vote was largely symbolic from an administrative point of view, as the powers being taken away from ministers were limited.
But he said it sent a potent message that Tory MPs would "revolt" if the government changed its policy and embraced no deal as its desired outcome.
Treasury minister Robert Jenrick said the government "neither wanted nor expected" a no-deal exit but defended "prudent preparation to provide our taxpayers with the certainty they deserve" and said all the defeat would do would be to make the UK "somewhat less prepared".
Many Tory Brexiteers believe a no-deal exit, which would see the UK trade with the EU on the basis of World Trade Organization rules, is nothing to be feared.
Former Tory leader Iain Duncan Smith said "scare stories" that it would lead to planes being grounded and ports being gridlocked must be put to bed.
Tuesday's vote, he told Sky News, did not alter the fact that MPs had already passed legislation last year specifying that the UK would leave on 29 March.
"We have legislated to leave the EU, with or without a deal. That is what people voted for."
By the BBC's Reality Check correspondent Chris Morris
There's a big problem facing members of Parliament who want to avoid a no-deal Brexit.
They can't just show there is a majority in the House of Commons against no deal - they need to prove there is a majority in favour of an alternative outcome.
That's because leaving the EU - with or without a deal - is currently the default.
What we're likely to see over the next couple of months is what some are calling "guerrilla warfare by amendment" in the House of Commons.
The trade bill is likely to be another target - it would be needed in the event of no deal, to try to keep the UK trading on the same terms as it has now with the rest of the world.
The idea behind all this parliamentary manoeuvring is to demonstrate that there is a clear majority in the House of Commons against no deal.
But none of it, taken in isolation, will prevent the Article 50 clock ticking away until it stops at the end of March.

MPs have voted on a series of amendments designed to change the direction of Brexit.
Commons Speaker John Bercow selected seven amendments to be debated and voted on.
Here are the amendments, and the results, in the order in which they took place.
Instructed the government to rule out a "disastrous no deal" scenario (this option was supported by some Brexiteers but many MPs feared it would cause chaos at ports and disruption for businesses) and allowed Parliament to consider - and vote on - options including:
Forced the government to make time for MPs to discuss a range of alternatives to the prime minister's Brexit plan on six full days in the Commons before 26 March.
MPs would have been able to table amendments to be voted on at the end of the debate, which could have included alternative Brexit options such as Labour's plan, a second referendum, no deal and the Norway-style relationship preferred by some MPs.
This had the backing of some Labour backbenchers, as well as the SNP's Philippa Whitford, Lib Dem Tom Brake, Plaid Cymru's Jonathan Edwards and Caroline Lucas, of the Greens.
Attempted to rule out the UK leaving the EU without a formal deal by allowing Parliament time to pass a new law.
The bill to bring in the new law would have required Theresa May to seek to postpone Brexit day (currently 29 March) until 31 December, if MPs did not approve her deal by 26 February.
The prime minister would have had to do this by asking the EU to agree to extend the two-year limit on Article 50 - the mechanism paving the way for the UK to leave the EU.
It had the backing of senior Conservative backbenchers such as Nicky Morgan and Oliver Letwin, former Lib Dem health minister Norman Lamb and Plaid Cymru's Ben Lake.
The Labour leadership had also decided to get behind this amendment and ordered Labour MPs to vote for it.
But Labour Leader Jeremy Corbyn said he backed limiting any extension to a "short window" of three months to allow time for renegotiation.
Required the government to ask the EU to postpone Brexit day (without specifying for how long).
Seeks to prevent a "no-deal" Brexit by adding to the PM's motion that Parliament "rejects the United Kingdom leaving the European Union without a Withdrawal Agreement and a Framework for the Future Relationship".
The two MPs are in neighbouring constituencies and have raised concerns over local manufacturing supply chains.
Calls for Parliament to require the backstop to be replaced with "alternative arrangements to avoid a hard border" but otherwise supports the prime minister's deal.
Theresa May ordered Conservative MPs to vote for this amendment.
Some Conservative rebels, who voted against the prime minister two weeks ago, said it was too vague and did not address their other concerns about her deal.
Others, such as former Foreign Secretary Boris Johnson, said they would support it if Mrs May indicated that she would press the EU to re-open the withdrawal agreement to make changes to the backstop that would be legally binding - something she has told MPs that she will do.
Northern Ireland's DUP, which keeps Mrs May in power, also indicated they would back the Brady amendment.
Neither of the Spelman nor the Brady amendments are binding on the government, although support for them puts political pressure on Theresa May to follow their direction.
Theresa May has already said she will return to Brussels to reopen negotiations on legally-binding alternatives to the "backstop".

There will be a hunt for a new idea.
Some magic new solution that might - maybe, possibly - provide a sudden surprise solution to Brexit's conundrums, in the way exhausted pilgrims might fall jubilantly on the Holy grail proclaiming, at last, that its jewels are beyond compare and a world changing treasure is now in their heroic clutches.
And yes, it is absolutely the case that different technical solutions will be explored again - whether they be ways of carving out potential technological solutions to managing the Irish border or additional paragraphs of legal language that could be constructed to suit all sides.
And, of course, in the next fortnight the government - and everyone in Westminster and in Brussels - will spend a lot of energy trying to work out which other possible ways of fixing the acute problem with the backstop could be done.
Fundamentally though, our politicians have been staring at the same problem for more than two years.
I'm reminded of how many months ago, during one of the other frenzies over how to "solve" the border issue, one official told me that, essentially, all that could really be done was to put the same words in a different order.
The next fortnight's efforts will be a bit more complex than that, but they may prove the old adage: "There is no such thing as an original idea."
Different ways of moving different promises or verbiage around, but a bold brand new solution no one's already thought of? Don't hold your breath.
But the facts of the situation in their most simple way are the same.
The UK is on course to leave the EU. That means the border on the island of Ireland becomes a border between a separate country and an enormous free trade area.
Everyone promises they don't want to have anything like a traditional border - but no one can agree on how to avoid that.
There is only one thing now that is certain to change, and that is the power of time.
The hope may be misplaced, but the hope nonetheless on the UK side is that as the clock ticks down with no solution, eventually, the fear of the consequences of the UK leaving without a deal will concentrate minds.
And the pressure of the approach of a deadline could in turn shift the politics.
Because it is the desire of EU leaders to avoid the worst that will either salvage Theresa May's deal, or not.
Her political drive to get this over the line will determine how radical or tough she is prepared to be.
And for different EU leaders, their own calculations - which are, of course, driven by politics in their home countries, as well as the role of the EU - will shape whether they are willing to flex at all.
Technical and legal rules and agreements are, of course, vitally important in all of this.
But if there was an easy solution in policy and precedent, it perhaps would have been found by now.
It feels like we are now entering into a final staring match, where politics - not policy - will decide who has to look away.
The problem, as ever, for Theresa May is that she is one against 27 others.

The UK could pursue alternative options if Theresa May's Brexit plan is rejected by MPs, Work and Pensions Secretary Amber Rudd has acknowledged.
She is the first cabinet minister to publicly float the possibility of "plausible" alternatives.
Mrs Rudd told BBC Radio 4's Today programme she still supported the PM's plan  - but "anything could happen" if it did not get through on Tuesday.
She said it could be "chaotic" if Mrs May's deal is rejected.
Mrs Rudd said a so-called "Norway plus" option or another referendum would both be possibilities in such a situation.
A Norway plus arrangement would see the UK remaining in the European Economic Area (EEA) and joining a customs union with the EU.
However the UK would have to accept free movement of people - breaching a previous "red line" laid down by the PM.
Ms Rudd described it as a "plausible", but not a "desirable" option for a Plan B. She also said she was not certain it could be done.
Norway is not a member of the EU but it is part of the EEA.  While a cross-party group of MPs back a similar status for the UK - the government would need to apply to join Norway and three other countries in the European Free Trade Association.
Ms Rudd said the deal Mrs May reached with the EU last month was the "best option".
"What we need is a compromise deal - that's what the prime minister has proposed," she said.
Asked why she had previously refused to speculate on possible alternatives to Mrs May's agreement, Ms Rudd said: "We are getting closer to the vote.
"People are saying why they are not going to vote for it and I'm just pointing out if you don't vote for it, these are the other things that could happen. Are you sure you want them more?"
By Matt Cole, BBC political correspondent
Far and wide this week - ministers have travelled the UK selling the idea of Theresa May's Brexit plan.
The message has been a simple one - there is no alternative.
Until this morning - when the Work and Pensions Secretary Amber Rudd opened the door to a Plan B...  and what might happen if MPs vote down the deal.
To be clear, Mrs Rudd says she still backs - and will vote for - the PM's plan. But she has now become the first voice from within the cabinet to entertain a notion of what happens next if the vote is lost.
What is more, politicians know how their words are weighed. The work and pensions secretary will have been aware that people would interpret raising the prospect of a Norway Plus relationship with the EU as her signalling her support.
Some will find it easy to believe that her declaration that such an arrangement would be "plausible" is none other than an early shot in the looming battle of the Plan Bs.
For there to be a plan B though, plan A must first be voted down.
And despite Mrs Rudd's protestations of faith that the deal's not dead, it's looking highly likely it will be killed off on Tuesday.
Ms Rudd told Today a lot of people had a "perfect vision" of what they think Brexit should look like, "and that perfect is not available".
"I would urge my colleagues to think about, first of all, why people voted to leave the European Union, what their interpretation is of that; and, secondly, what the alternatives are," she said.
She added: "If it doesn't get through, anything could happen...  and none of them are as good as the current arrangement."
Ms Rudd said she hoped an amendment to Tuesday's vote, tabled by former Northern Ireland minister Sir Hugo Swire in an attempt to win over Eurosceptic MPs, "will give some of my colleagues reassurance".
Many MPs have expressed concerns about the so-called backstop arrangement, aimed at preventing a "hard border" between Northern Ireland and the Republic of Ireland if no trade deal is ready before the end of the post-Brexit transition period, in December 2020.
The amendment would enable Parliament to approve a decision to trigger the backstop and put a one-year time limit on it.
On Saturday, Colchester MP Will Quince became the latest Conservative to resign from the government over the backstop question.
Mr Quince stepped down as a ministerial aide to Defence Secretary Gavin Williamson, telling the Sunday Telegraph he could not support a backstop without an end date.
For what could happen after the vote, read here.
You can read a more detailed explanation of the Norway model here.

Cabinet minister Amber Rudd has told the BBC she is "committed to making sure we avoid" a no deal Brexit and would not rule out resigning over it.
The work and pensions secretary said she was "going to wait and see" whether the prime minister allowed MPs a free vote on potential options next week.
Labour MP Yvette Cooper has tabled an amendment to delay Brexit if no deal is reached by the end of February.
MPs heavily rejected the deal Theresa May agreed with the EU last week.
The UK is due to leave the EU at 23:00 GMT on 29 March and the prime minister has faced repeated calls to rule out the prospect of leaving without a deal, if no agreement can be reached.
She says it is not within the government's power to rule it out - but various backbench MPs will try to move amendments to postpone Brexit if no agreement can be reached, when the Commons votes on a way forward next Tuesday.
Ms Rudd returned to the cabinet in November, less than seven months after quitting as home secretary in April 2018 over the Windrush scandal.
She told the BBC's Newsnight that she wanted MPs to get a free vote on the various amendments - but would not say if she would resign her ministerial post to back an amendment from Labour's Yvette Cooper.
The amendment would give time for a bill to suspend the Article 50 process for leaving the EU to the end of the year, if a new deal has not been agreed with Brussels by the end of February.
Ms Rudd said the "best outcome" was for MPs to support Mrs May's deal and "every day in Parliament we hear about MPs who voted against the withdrawal agreement who are reconsidering".
Pressed on whether she would quit to block no deal, she said: "I think it's too early for anyone to make those sort of commitments because at the moment there is a lot of change going on.
"I have called for a free vote for the amendments on Tuesday and we'll see what position the government takes."
Meanwhile, Chancellor Philip Hammond told an audience of business people on Thursday: "In the 2016 referendum, a promise was made to the majority who voted for Brexit - that they were voting for a more prosperous future.
"Not leaving would be seen as a betrayal of that referendum decision.
"But leaving without a deal would undermine our future prosperity, and would equally represent a betrayal of the promises that were made."
The chancellor, who like Ms Rudd campaigned for a Remain vote during the 2016 EU referendum, said: "The only sustainable solution is a negotiated settlement with the EU."
Labour's shadow chancellor John McDonnell said: "The chancellor must now surely consider his position in the government.
"Philip Hammond's comments today demonstrate he has acknowledged the damage a no-deal Brexit would do to our economy, jobs and living standards.
"If the prime minister fails to listen to his warnings and continues to refuse to take no deal off the table there is no other option, he must resign."
It comes as aerospace giant Airbus warns that it could move its wing-building operations out of the UK if no Brexit deal is reached.
Jaguar Land Rover also announced it would extend its annual April shutdown in car production, because of uncertainties around Brexit.
And Business Minister Richard Harrington also spoke out against a no-deal Brexit on Thursday saying: "Crashing out is a disaster for business… Airbus is correct to say it publicly and I'm delighted they have done so."
Later Airbus senior vice president Katherine Bennett was asked on Sky News whether the government had put the company up to issue warnings about the consequences of a no-deal Brexit.
She said: "No, the government didn't. The government have been talking to us and other industry representatives all the time, of course, and we've given them lots of information about the potential impacts.
"But they did say 'could you make sure that you make clear the potential impact of a no deal?', and we are happy to do that because no deal is potentially going to be catastrophic for us."
Theresa May met union leaders on Thursday as she continues to seek support for her Brexit deal, ahead of a crucial Commons vote on Tuesday. Last week the withdrawal deal negotiated with the EU was rejected by MPs by a historic margin -  432 votes to 202.
The prime minister is hoping to tweak her deal to address concerns about the "backstop" among her own backbenchers and Northern Ireland's Democratic Unionist Party, which she relies on to keep her in power, ahead of another vote on her proposed way forward next Tuesday.
The backstop is the "insurance policy" in the withdrawal deal, intended to ensure that whatever else happens, there will be no return to a visible border between Northern Ireland and the Irish Republic after the UK leaves the EU. But it has proved controversial with many MPs on her own side who argue it keeps Northern Ireland too closely aligned with the EU, and that the UK could be permanently trapped in the arrangement.
A guide to MPs' Brexit amendments
However as well as Yvette Cooper's amendment, her Labour colleague, Rachel Reeves, has also tabled an amendment to extend Article 50. Other amendments would ask the government to consider a range of options over six full days in Parliament before the March deadline, to set up a "Citizens' Assembly" to give the public more say or to insist on "an expiry date to the backstop".
Plans by a group of Tory and Labour MPs to table an amendment on another EU referendum have been dropped, after they admitted they didn't have sufficient backing from MPs, although the Lib Dems will be tabling an amendment calling for a "People's Vote".
It will be up to Speaker John Bercow to select amendments to put to the vote.

Tory MPs have been urged to rally round Theresa May ahead of a series of crucial parliamentary votes on Brexit.
Former home secretary Amber Rudd and ex-leader Iain Duncan Smith called for "discipline" and "unity of purpose".
Writing in Sunday's Telegraph, they said the EU Withdrawal Bill was key to delivering Brexit and any defeats would help Labour "frustrate" the process.
But ex-chancellor Ken Clarke said Theresa May was being "undermined" by her ministers and had to be "rescued".
Labour are urging Tory rebels to side with them in the Commons on Tuesday and Wednesday as ministers try to overturn more than a dozen amendments made by the House of Lords.
If enough Tory MPs decide to vote with Labour and other opposition parties, the government could be defeated on several key votes, including on amendments intended to keep the UK in a customs union with the EU and to give Parliament a decisive say over the final Brexit deal.
Labour's Sir Keir Starmer told the BBC's Andrew Marr that while it would be difficult for Tory MPs to rebel, they had a "real chance to change the course of the Brexit negotiations".
But in a show of unity, Ms Rudd - a leading Remain supporter in the 2016 referendum - and Mr Duncan Smith, a vocal Brexiteer, said Labour would be quick to exploit any government setback.
"Jeremy Corbyn will do everything he can to stop us," they wrote. "That includes cynically trying to frustrate the Brexit process for his own political ends."
In the joint article, the pair say the withdrawal bill is "not about competing visions of the future but about ensuring legal certainty at our point of departure".
Urging colleagues "to demonstrate discipline and unity of purpose", they said "we cannot allow ourselves to become divided and risk losing the precious chance to go on implementing policies that transform lives".
Housing minister Dominic Raab said he was "reasonably confident" the government, which will have the support of a handful of pro-Brexit Labour MPs and the 10 Democratic Unionist MPs, would prevail.
Passing the withdrawal bill would be a "turning point" in the Brexit process, he told the BBC's Sunday Politics, as it would be the basis for a "smooth transition" after the UK leaves.
Potential rebels had to think "very seriously" before defying the government, he added.
Are rebels prepared to strike?
By Susana Mendonca, BBC political correspondent
With its small Commons majority, just a few backbench Tories siding with the opposition could lead to defeats for the government this week.
What isn't clear is whether those backbenchers unhappy with the government's approach on the EU Withdrawal Bill will go as far as to strike the kind of blow that could destabilise a prime minister who's already struggling to keep her Cabinet together after a week of threats of resignations.
The fact that two such high-profile polar opposites on Brexit - Remainer Amber Rudd and Brexiteer Iain Duncan Smith - have joined forces to urge their colleagues to vote with the government is a sign of just how worried some on both sides on the Conservative Brexit debate are about the prospect of Theresa May being weakened in EU negotiations, or even toppled.
"Better the devil you know" is a phrase that comes to mind - as neither side wants to end up with a PM who leans more towards the type of Brexit they don't want.
There are Tory backbenchers like Ken Clarke who think the only way to tame the more vociferous Brexiteers on the frontbench is for backbenchers to inflict a blow that they cannot ignore.
So there will some rebels this week despite the warnings to toe the line - but will there be enough of them?
The prime minister, who will address all Tory MPs on Monday, has accused peers of going "far beyond" their role with their amendments to the withdrawal bill.
But former Chancellor Ken Clarke rejected suggestions Mrs May could be forced out if she was defeated - saying she would comfortably win any vote of confidence among Conservative MPs.
"We need to rescue the prime minister from this terrible treatment she is getting from key members of her cabinet," he told Sunday Politics.
He suggested Foreign Secretary Boris Johnson, who criticised the government's strategy last week, and Brexit Secretary David Davis, who reportedly came close to resigning, were using "Donald Trump methods" to undermine the prime minister.
The veteran europhile said MPs must take "control" of the Brexit process and he would back efforts to strengthen the terms of the "meaningful vote" that Parliament has been promised on the final deal.
"I know we have got to back the prime minister but kicking the can down the road for another month is hopeless," he said.
Speaking earlier to the BBC's Andrew Marr show, Cabinet Office minister David Lidington accepted the parliamentary arithmetic was "difficult" but urged MPs to "get behind" the PM.
But confirming the SNP would vote against the government on all the amendments, Scottish First Minister Nicola Sturgeon said the EU Withdrawal Bill as it stood was "unacceptable".

Commons leader Andrea Leadsom has questioned Speaker John Bercow's impartiality over Brexit.
It followed his criticism of the government's decision to cancel Tuesday's crunch vote on Brexit.
Mr Bercow said that doing so was being "deeply discourteous" to MPs.
A spokeswoman for Mr Bercow hit back at the criticism, saying he had "never allowed his personal views to influence" his chairing of debates and statements in the Commons.
Mrs Leadsom told BBC Radio 4's Today: "He's made his views on Brexit on the record, and the problem with that of course is that the chair's impartiality is absolutely essential."
She was asked whether she believed Mr Bercow's position - chairing debates in the House of Commons - was "tainted", she replied: "He's made his views known on Brexit... it's a matter for him but nevertheless it's a challenge and all colleagues need to form their own view of that."
Last year the Daily Telegraph reported on a video where the Speaker told students: "Personally I voted to Remain. I thought it was better to stay in the European Union than not."
There have been questions over Mr Bercow's neutrality on other issues in the past, including voicing his opposition to the US President speaking in Parliament in February 2017.
There have been reports the Speaker would stand down in the summer of 2019, although he has not commented publicly on the claims, which have been attributed to his 'friends'.
Mr Bercow's stance, in trying to persuade the government to hold a vote on whether to cancel the planned vote on the Brexit deal, was backed by a number of MPs on Monday.
Their current jobs mean they have to work together, and there has been previous friction between Mr Bercow and Mrs Leadsom:
The role of the Commons leader is to organise government business in the House, to chair the Parliamentary Business and Legislation Committee, and update MPs each Thursday on business for the following week.
The Speaker's main job is to chair debates in the Commons, and to keep MPs in order, as seen during Prime Minister's Questions on Wednesdays.
The office holder - an MP who remains politically neutral - can direct MPs to withdraw remarks or be quiet, suspend a sitting of the House, or suspend MPs after 'naming' them for their behaviour.
He can also play a key role when there are disputes over Parliamentary rules and procedure - something which has been increasingly the case during the Brexit process.
Asked for Mrs May's opinion on the impartiality of the speaker, following Mrs Leadsom's comments, Theresa May's official spokesman said: "That's not a question I've ever discussed directly with the prime minister.
"What I would say is that established convention is that the speaker must remain politically impartial at all times. It is for the House to determine if this is not the case."
When asked whether Mrs May believed Mr Bercow should stand aside during the remaining Brexit debate and allow a deputy to take the chair, the PM's spokesman said: "It's for the House to determine these matters."
The Speaker's spokeswoman said: "Impartiality has been the watchword for John Bercow's Speakership. He is fair to all sides - both government and opposition - and to different points of view within and between parties."
She added: "Many would observe that his passionate view that all voices should be heard has led to statements and question times running on longer than anticipated."
During her Today interview, Mrs Leadsom was also asked about Theresa May's handling of the Brexit negotiations, and the decision to scrap the vote on her Brexit deal because she knew it would be defeated.
Questioned about how long Mrs May would remain as prime minister, her former leadership rival said: 'I'm not speculating about the future."
She added: "The prime minister is absolutely doing the right thing; going back to the EU and seeking reassurances, in the form of legally binding reassurances, that provide parliament with the democratic capability of preventing the UK being caught in a backstop."
On Tuesday, Mrs May is holding talks abroad with Dutch PM Mark Rutte, Germany's Angela Merkel and European Commission President Jean-Claude Juncker.

German Chancellor Angela Merkel has said she will fight for an "orderly Brexit" until "the very last hour".
Mrs Merkel said that current events were in a "state of flux", adding that European Union leaders would try to react to whatever the UK proposed.
The UK is due to leave the EU in 10 days' time, with or without a deal.
Prime Minister Theresa May is writing to European Council President Donald Tusk to ask for an extension. She will meet EU leaders later this week.
Mrs May's proposed Brexit deal has already been rejected twice by MPs at Westminster.
The Speaker of the House of Commons, John Bercow, has ruled that Mrs May cannot bring it back for a third vote without "substantial" changes.
Mrs Merkel refused to be drawn on whether she would now support an extension. Addressing a conference in Berlin, she said:
"I will fight for an orderly Brexit on 29 March until the very last hour.
"We don't have that much time left... I must say that I'm not in a position to speculate on what I will do on Thursday because it depends on what Theresa May will tell us."
An aide to French President Emmanuel Macron also said any possible request for an extension would not be automatically accepted.
"An extension is not for certain", the aide said.
"First point: is there a plan, a strategy, to justify an extension?"
Also on Tuesday, EU chief negotiator Michel Barnier told reporters that if Mrs May requested an extension, it would be for EU leaders to "assess the reason and the usefulness" for such a request.
"EU leaders will need a concrete plan for the UK in order to be able to make an informed decision and key questions will be: does an extension increase the chances for the ratification of the Withdrawal Agreement?" he said.
Meanwhile, the European Council has adopted a series of contingency measures in the event of the UK leaving the EU without a deal.
The measures are aimed at limiting "the most severe damage caused by a disorderly Brexit", and set out proposals for transport, fisheries, education and social security.
They include ways to minimise disruption to UK students studying in the EU and EU students studying in the UK under the Erasmus+ programme.
By Adam Fleming, BBC News
The EU27 are feeling their way towards ground rules for an extension to the Brexit process. It cannot be an opportunity for the UK to renegotiate the divorce treaty.
Britain will have to take part in the European Parliament elections if an extension extends beyond the summer.
Will the UK have to sign up to a good behaviour clause where it promises not to use its veto over the EU's long-term budget as leverage to get a better deal? And it all has to be for a good reason, like pursuing a different future relationship or for an election or a referendum.
The EU may also ask the prime minister for more proof that Westminster will accept a delay.
This has prompted speculation about the concept of an extension being approved at this week's summit of EU leaders, followed by a parliamentary vote, followed by - wait for it - another summit on the eve of 29 March, which would be billed as the last chance to avoid No Deal.

So what next?
By the landslide standards of previous Brexit votes, this was a narrow defeat for the government.
And they may calculate that they can reel in a few more ex-Tory rebels add a few Labour MPs from Leave seats, and muster a modest majority for Boris Johnson's Brexit deal, in a further vote next week, even without the support of the Northern Ireland DUP.
In an ill-tempered series of points of order after today's votes, Jacob Rees-Mogg indicated that the government would now seek to hold a further "meaningful vote" to win Commons approval for the deal, paving the way for a Withdrawal Agreement Bill to put it into law.
Ah, argued a number of opposition MPs, wouldn't that amount to putting the same issue to the vote twice?
Remember that the Speaker prevented the government from staging a third vote on Theresa May's deal, on the principle that it was out of order for ministers to keep asking the same question again and again, until they got the answer they wanted.
The Speaker, John Bercow, did not give a definitive ruling, saying that he would ponder the matter and take advice.
LIVE: Latest reaction to Johnson's letter >
ANALYSIS: Chances of agreement still strong, says Laura Kuenssberg >
UPSUM: What happened on Saturday? >
EXPLAINED: How another delay would work >
If he allows the vote, Labour MPs in pro-Brexit seats will be under massive pressure.
They would much rather go straight to a Withdrawal Agreement Bill, where they can tinker with the detail to their heart's content - possibly allying with dissident Tories to write a customs union into it.
And for the government, putting down a bill without the support of the DUP would be fraught with danger.
An early indicator will be whether the government can win the programme motion necessary to ensure the Bill gets through in quick time.
Meanwhile, opposition MPs were keen to know whether the PM would follow the terms of the "Benn Act" and write to the EU, to request a further extension of UK membership.
His enigmatic reply that he was not prepared to "negotiate" an extension did not, it seems to me, exclude the possibility of sending the required letter.
There was a very interesting discussion of what might then happen in Lord Pannick's speech to Saturday's sitting of the House of Lords.
He suggested that a flat refusal to send the required letter should provoke the resignation of the Lord Chancellor and the Attorney General, but that the Benn Act did not preclude the prime minister from saying to EU leaders he didn't want an extension - there was a very thin line, and the result could be "a very interesting case in the Supreme Court".
Meanwhile, the Parliamentary programme for next week, including that new "meaningful vote" and dicey-looking votes on the Queen's Speech, will have to be rejigged.
With no government majority, and its DUP allies looking very disenchanted, the chances of an amendment being passed are high - spelling further trouble.
Once, such a defeat would have automatically triggered the resignation of the government, but in the era of the Fixed Term Parliaments Act it is unclear what the implications would now be.
One educated guess, from Sir Bernard Jenkin, the senior Conservative who chairs the Public Administration and Constitutional Affairs Committee, is that the prime minister would be within his rights to demand a formal no-confidence vote in the terms set down in the Fixed-Term Parliament Act - and remain in office unless and until such a vote was passed.
It's going to be an interesting week.
I promised a blog on what's coming up in Parliament next week, and indeed, it is more than half written; the trouble is, as outlined above, the agenda for next week will have to be reshaped. So I will hold off publishing it until I know more. Apologies.

When the party of government is conducting something akin to a political civil - or perhaps that should be uncivil - war, the main party of opposition will seem united by comparison.
Certainly Theresa May's deal has succeeded in bringing her opponents together to denounce it.
But according to the former Labour Prime Minister Tony Blair, the position of both frontbenches on Brexit is "weird".
He believes Theresa May is wasting time seeking to resuscitate a deal that he has pronounced as dead.
And there is the spectacle of the current Labour leader holding back from tabling a confidence motion in a government he wants to remove.
More about that later…
Tony Blair now puts the likelihood of a new referendum at "above the 50% mark". He revealed that he had been speaking to Labour MPs who represent Leave areas in recent weeks.
He's been trying to reassure them that giving people a final say wouldn't  lead to Brexit-backing voters call time on their parliamentary careers.
His argument is that a referendum would be framed as a regretful consequence of a gridlocked parliament. But their fears are not the only, indeed, not the main, barrier to gaining a new referendum.
Labour's official policy is to call for a general election. And, if that doesn't happen, to keep all options on the table - including campaigning for a "public vote".
This just about kept the party united at its annual conference in the autumn, But now the strains are beginning to show.
Again there is unity around calling on Theresa May to bring her deal to Parliament next week rather than waiting until January.
Beyond that, the parliamentary party's apparent solidity begins to fracture.
MPs who back  Tony Blair's position on a referendum  - such as Chuka Umunna - have called on Jeremy Corbyn to table a motion of no confidence in the government.
The calculation is that it would fail because the DUP (on this issue at least) would back the Conservatives.
That would then tick the policy box - Labour has asked for an election, hasn't got it, and now it can move on to at the very least discussing the option of a new referendum.
But because it wouldn't succeed in bringing the government down, Jeremy Corbyn is unlikely to table a formal vote of confidence next week.
He is also not enthusiastic about confronting the prospect of a new referendum as a consequence.
Instead, we may well see a non-binding censure motion being tabled if Theresa May indeed delays the vote on her deal.
So, political damage could be inflicted on the Prime Minister without it rebounding and causing a problem for the Opposition leadership.
But as Tony Blair's  former spin doctor Alastair Campbell - a leading advocate for a new referendum - warned his fellow campaigners: "it may be time to face up to the fact that Labour under Jeremy Corbyn will do everything to make sure a People's Vote won't happen".
Certainly - from a different perspective - that is Labour leaver Kate Hoey's view of Jeremy Corbyn's position too. She and he were both Eurosceptic rebels through the Blair and Brown years.
And while the option of a "public vote" is Labour policy, I understand behind the scenes in the shadow cabinet the issue is proving highly contentious.
I am told that party chairman Ian Lavery and shadow justice secretary Richard Burgon have been arguing strongly against committing the party to a referendum - even further down the line.
Jon Trickett and - perhaps unsurprisingly, given his public statements - the shadow international trade secretary Barry Gardiner take a similar view.
The shadow education secretary Angela Rayner was never seen as a staunch opponent of the idea but did suggest another referendum could be seen as "undermining democracy" on BBC's Question Time.
The shadow Brexit secretary Sir Keir Starmer said at Labour's conference - without clearing it with his party leader - that Remain should be an option if there were a new referendum.
But I am told privately he has been quite cautious about when to commit to a new vote - and whether it could be won.
The shadow chancellor John McDonnell's relatively warm language towards the referendum option in recent weeks - even agreeing that under certain circumstances it could become "inevitable" - has led to tensions with the leader's office.
Many younger activists in Momentum - the movement John McDonnell and ally Jon Lansman set up  - support the position of "remain and reform" the EU and the left-wing Another Europe Is Possible - along with unions such as the GMB and TSSA - want a new vote.
There are those in Labour's ranks who think there is a "third way" between rejecting the May deal and signing up to a new vote.
The chair of the Commons Brexit committee, Hilary Benn, favours a 'Norway Plus' option - staying economically close to the EU but outside its political structures.
He wants Parliament to be able to vote on this option but I am told that Jeremy Corbyn does not want to embrace this policy, which would involve staying inside the single market.
Tony Blair's prediction is this: He doesn't necessarily think that the current Labour leadership will ever embrace a new popular vote.
But if Parliament rejects every other option, he believes Labour MPs will be faced with a stark choice between extending Article 50 and backing a new referendum, or leaving with no deal.
Under these circumstances, he argues, an "overwhelming" number of Labour MPs would opt for a new vote - and could cite party policy as cover.
Hilary Benn isn't so sure. He also thinks there is a danger that Parliament rejects all options - including his favourite, Norway.
But that this wouldn't necessarily lead to a new referendum. "All of the options have real and genuine difficulties," he told Radio 4's 'Political Thinking' podcast.
"All of the options have real and genuine difficulties. It may be that the prime minister decides 'well, I'm taking my deal to the country.'"
Well that, in its own way, really would be a People's Vote.

Jeremy Corbyn says he will ask his MPs to vote for the Article 50 Brexit process to begin, if the government is forced to seek Parliament's approval.
He said it was "very clear" his party accepted the referendum result.
Some shadow cabinet members are reportedly considering voting against triggering the UK's EU exit negotiations.
The Supreme Court will announce next Tuesday whether the government needs to seek Parliament's approval.
Ministers say they already have enough powers under the Royal Prerogative to go ahead with Brexit.
But campaigners argue that starting Brexit in this way would be undemocratic and unconstitutional.
In June's referendum, 51.9% of voters backed leaving the EU, while 48.1% supported remaining in the 28-nation group.
Mr Corbyn said: "It's very clear the referendum made a decision that Britain is to leave the European Union. It was not to destroy jobs and living standards or communities, but it was to leave the European Union and have a different relationship in the future.
"I have made it very clear that the Labour Party accepts and respects the decision of the British people. We will not block Article 50."
Asked if that meant he would be imposing a three-line whip - the strongest available sanction - on Labour MPs, requiring them to back Article 50, he said: "It means that all Labour MPs will be asked to vote in that direction next week or whenever the vote comes up."
The Guardian reports that four shadow cabinet ministers and several junior Labour spokespeople were considering defying Mr Corbyn and voting against Article 50 being invoked.
The Supreme Court's decision on whether a vote needs to take place follows a government appeal against a High Court ruling last autumn that MPs and peers should have to vote give their approval.
Following Mr Corbyn's comments, Green Party co-leader Caroline  Lucas said he was "trying to deny Labour MPs the chance to make their own principled choice on one of the most important decisions of the UK's recent history".
And Liberal Democrat leader Tim Farron said Mr Corbyn was "actively helping" the government in its plans to leave the European single market, "at a huge cost to jobs and prosperity".

I'm afraid, yes, it's back to the backstop.
As you'll know, unless it's your first time reading here, the arrangement to guard against going back to the borders of the past in Northern Ireland is at the root of the Tory rebels' complaints about the government's deal.
And frankly, all along it's been the most fundamental Brexit conundrum, with added nightmare political points because Theresa May relies on the Northern Irish unionist DUP.
Number 10's thinking, therefore, has been for many weeks now, solve the backstop and you might go some way to getting their deal through the Commons.
That's still been the stuff of horrors, however, because the EU and Ireland have been stuck together like glue, with both of them absolutely adamant that you can't mess with the backstop - it can't come out of the agreement and even though there's the odd voice like the Polish foreign minister yesterday, trying to be helpful, Brussels' message has been, there is no budging.
But a tiny gap might just have emerged from an unlikely source, the Irish leader Leo Varadkar himself.
Speaking in Dublin this afternoon he was talking in familiar terms about how a hard border wasn't acceptable and couldn't be allowed to happen.
That's why, he repeated forcefully, the backstop was required.
For a reminder of how it's meant to work, you can read my colleague's explanations here.
But he went on to say that if the UK was on the verge of leaving without a formal agreed deal, (remember, if there is no deal, then there is no backstop), then there would be an obligation to find a way, some kind of separate arrangements to protect trade and the peace process.
Note, he was not saying this was what he was hoping or planning for.
And he maintained the backstop was the best way of doing this.
But it matters because some in Westminster, including at the cabinet table, who believe that a separate arrangement to sort out this aspect of the troubled withdrawal agreement, could be a way out of the parliamentary gridlock.
In other words, take this tangle out of the deal, so that MPs can vote for the agreement with its most controversial bit removed, and fix the specific problems of the backstop in a different process.
That is not what Mr Varadkar was advocating.
And when such an idea has been floated previously, only a few days ago, it got short shrift.
But when all camps are so dug into their positions, any hint or word that vaguely raises the prospect of a way through, matters.
An Irish government source told me that if we end up in that kind of situation, the EU would still absolutely have to be involved in such talks - the border in Ireland would become one between the EU and UK and Brussels would have to be at the heart of any discussions.
But as the weeks march on, and the prospect of the turmoil of leaving without an arrangement comes closer, politicians might just feel the pressure in a way that makes the impossible become at least a possibility.

Sir Vince Cable has denied suggesting older Brexit voters were racist.
In a speech at his party's spring conference, the Lib Dem leader said too many older people who voted Leave longed for a world where "faces were white" and were "driven by nostalgia".
Tory MPs have labelled the comments as "wrong" and "unwise".
But Sir Vince called it a "simple truth of the matter" that the majority of the older generation voted Leave while younger people favoured Remain.
In his speech on Sunday, Sir Vince said a "nostalgia for a world where passports were blue, faces were white and the map was coloured imperial pink" had driven some older voters to Brexit.
"And it was their votes on one wet day in June which crushed the hopes and aspirations of young people for years to come," he added.
Asked on BBC Radio 4's Today programme whether he was suggesting older Brexit voters were racist, Sir Vince said: "I didn't suggest that at all."
But he repeated his claim that "nostalgia for that world" was a factor in how people had voted.
"Why else has so much fuss been made about the change in the colour of the passport?" he added.
Conservative MPs have criticised the Lib Dem leader over his speech.
Housing, Communities and Local Government Secretary Sajid Javid said: "Sir Vince should be trying to bring country together, not seeking to tear it apart."
Tory party chair Brandon Lewis said his comments were "rude" and "offensive".
Conservative MEP Daniel Hannan said "calling 17.4 million people racists is unfair and unwise" and the deputy chairman of the Conservatives, James Cleverly, said "not liking brown faces" was not the reason he voted Brexit.
The Lib Dems are campaigning for a second referendum on the final Brexit deal, which the government opposes.
Sir Vince told his audience in Southport: "I've myself been on a journey. I confess that my own initial reaction to the referendum was to think maybe there was little choice but to pursue Brexit.
"I thought, you know, the public had voted to be poorer - well, that was their right.
"What changed my mind was the evidence that Brexit had overwhelmingly been the choice of the older generation.
"75% of under 25s voted to remain. But 70% of over 65s voted for Brexit," he said.
Sir Vince also took a swipe at his own party's lack of diversity - it has had a lower proportion of non-white MPs and candidates than Labour or the Conservatives in recent years.
"Looking around the auditorium, we are very, very white," he told the party faithful.
"We must prioritise making our party more ethnically diverse."

Boris Johnson has met Emmanuel Macron in Paris for Brexit talks, with the French president saying the UK's vote to quit the EU must be respected.
But he added that the Ireland-Northern Ireland backstop plan was "indispensable" to preserving political stability and the single market.
The backstop, opposed by Mr Johnson, aims to prevent a hard border on the island of Ireland after Brexit.
Mr Johnson said that with "energy and creativity we can find a way forward".
On Wednesday German Chancellor Angela Merkel said the onus was on the UK to find a workable plan.
UK Prime Minister Mr Johnson insists the backstop must be ditched if a no-deal exit from the EU on 31 October is to be avoided.
He argues that it could leave the UK tied to the EU indefinitely, contrary to the result of the 2016 referendum, in which almost 52% of voters opted to leave.
But the EU has repeatedly said the withdrawal deal negotiated by former PM Theresa May, which includes the backstop, cannot be renegotiated.
However, it has previously said it would be willing to "improve" the political declaration - the document that sets out the UK's future relationship with the EU.
The handshake between the PM and the president was warm and long-lasting. But it was the words that mattered.
President Macron said that, while he had been portrayed as the "hard boy" of the EU, he was simply being clear about where he stood.
He described the backstop both as an "indispensable guarantee" of "stability in Ireland" and the means of protecting the integrity of the European single market.
But the expectation that he'd refuse point-blank to renegotiate the Brexit deal didn't materialise.
Instead, he simply warned that any withdrawal agreement that the two sides might reach in the next month wouldn't be very different from the existing one. And he asked for more "visibility" from the UK on its alternative proposals.
It would seem that both Mr Macron and Angela Merkel are determined not to shut the door entirely in Boris Johnson's face, and perhaps equally determined not to be blamed for no deal.
Speaking after he greeted Mr Johnson at Paris's Elysee Palace, Mr Macron said he was "very confident" that the UK and EU would be able to find a solution within 30 days - a timetable suggested by Mrs Merkel - "if there is a good will on both sides".
He said it would not be possible to find a new withdrawal agreement "very different from the existing one" within that time, but added that an answer could be reached "without reshuffling" the current deal.
Mr Macron also denied that he was the "hard boy in the band", following suggestions that he would be tougher on the UK than his German counterpart.
Standing beside Mr Macron, Mr Johnson said he had been "powerfully encouraged" by his conversations with Mrs Merkel in Berlin on Wednesday.
He emphasised his desire for a deal with the EU but added that it was "vital for trust in politics" that the UK left the EU on 31 October.
He also said that "under no circumstances" would the UK put checks or controls on the Ireland-UK border.
The two leaders ate lunch, drank coffee and walked through the Elysee gardens together during their talks, which lasted just under two hours. Mr Johnson then left to fly back to the UK.
If implemented, the backstop would see Northern Ireland staying aligned to some rules of the EU single market, should the UK and the EU not agree a trade deal after Brexit.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
These arrangements would apply until both the EU and UK agreed they were no longer necessary.
Mrs Merkel has argued that the withdrawal agreement does not need to be reopened if a practical solution to the backstop crisis can be found.
Brexit is due to happen on 31 October, with no deal being the default option. The prime minister has said he wants to leave the EU with a deal, but that the UK would be ready if none is reached.
Mr Johnson will attend the G7 summit on Saturday in Biarritz, France, alongside other leaders including US President Donald Trump.
Asked about Mr Macron's comments, Labour leader Jeremy Corbyn said he agreed there should not be a hard border on the island of Ireland.
He described the Irish peace process as "an enormous step forward" which "cannot be negotiated away by Boris Johnson".
Mr Corbyn has cancelled a trip to Ghana, urging MPs to meet him next week to discuss ways to prevent a no-deal Brexit.
He has proposed that MPs should help him defeat the government in a no-confidence motion and install him as a caretaker prime minister.
If he wins the vote, he plans to delay Brexit, call a snap election and campaign for another referendum.
The Liberal Democrats, SNP, Change UK, Plaid Cymru and the Green Party have agreed to the meeting with Mr Corbyn. But Conservative MP Dame Caroline Spelman and independent MP Nick Boles have said they will not attend.
Mr Boles, who quit the Conservatives in April over the party's approach to Brexit, said the Labour leader should prioritise a change in the law to delay leaving the EU ahead of a no-confidence vote.

The EU's chief negotiator Michel Barnier says the Irish backstop is "part and parcel" of the UK's Brexit deal and will not be renegotiated.
Speaking at the European Parliament, Mr Barnier said it was a "realistic solution" to preventing a hard border.
British MPs voted earlier this month against the deal agreed by the UK and EU during 18 months of negotiations.
Instead, on Tuesday, they voted for PM Theresa May to seek "alternative arrangements" to the backstop.
The UK is due to leave the European Union at 23:00 GMT on 29 March. The backstop is an "insurance" policy to stop the return of checks on goods and people along the Northern Ireland border.
As it stands, the backstop would effectively keep the UK inside the EU's customs union, but with Northern Ireland also conforming to some rules of the single market.
It was one of the main reasons Mrs May's Brexit deal was voted down in Parliament by an historic margin earlier in January as critics say a different status for Northern Ireland could threaten the existence of the UK and fear that the backstop could become permanent.
Mrs May has said there are several possible alternatives to the backstop that she wanted to discuss with EU leaders.
These include a "trusted trader" scheme to avoid physical checks on goods flowing through the border, "mutual recognition" of rules with the EU and "technological" solutions.
However, Business Secretary Greg Clark told ITV's Peston programme that he did not think "those technical possibilities are there yet".
Mrs May also wants to discuss a time limit on the backstop and a "unilateral exit" mechanism - both options ruled out by the EU in the past.
The message from the EU though was the backstop remained an integral part of the withdrawal agreement - the so-called "divorce deal" agreeing the terms of the UK's exit from the EU.
Mr Barnier said: "Calmly and clearly, I will say right here and now - with this withdrawal agreement proposed for ratification - we need this backstop as it is.
"Rejecting the backstop as it stands today boils down to rejecting the solution which has been found with the British, but the problem remains."
Mrs May had a 45-minute phone call with the President of the European Council, Donald Tusk, on Wednesday evening, described as "open and frank" by one source.
They told BBC Brussels correspondent Adam Fleming that the PM had explained the result of the votes, but Mr Tusk reiterated the withdrawal agreement was not up for renegotiation.
The source also said Mrs May was told the EU could not keep guessing what might work, so it was up to the UK to provide solutions that could get a majority in the Commons.
The Irish Taoiseach, Leo Varadkar, also spoke to Mrs May and said the latest developments had "reinforced the need for a backstop which is legally robust and workable in practice".
Earlier, his deputy, Simon Coveney, gave a warning over Mrs May's future plans for the backstop, saying that anyone who allowed the "borders and divisions of the past" to return would be "judged harshly in history".
He added: "There are some things that are more important than economic relationships and this is one of them."
President of the European Commission Jean-Claude Juncker said he believed Mrs May's "personal commitment" to avoid "slipping back to darker times past", but he said the "safety net" of the backstop was necessary to prevent it.
He added: "We have no desire to use this safety net, [but] no safety net can be truly safe if it can just be removed at any time."
But UK MEP Nigel Farage attacked the EU, claiming it had pushed Mrs May into the backstop in the first place.
The former UKIP leader told the European Parliament: "I accept [Mrs May] made a dreadful mistake by signing up to the backstop, [but] you summoned her at 04:15 in the morning, she left Downing Street, she went to meet the ultimatum you set her.
"She signed up to something that has proved to be a disaster. She signed up to something that no country, unless it had been defeated in war, would have signed up to.
"We now realise that mistake and the House of Commons, the country is overall looking for a deal."
And Conservative MEP Ashley Fox said the backstop would create a hard border, rather than prevent one, unless it was amended.
At the same time as the European Parliament was discussing Brexit, Mrs May and Labour leader Jeremy Corbyn were holding their long-awaited meeting on the issue, following an earlier clash at Prime Minister's Questions.
In the Commons Mr Corbyn repeatedly urged Mrs May to rule out a no-deal Brexit after a majority of MPs voted against the prospect in another vote on Tuesday.
But Mrs May said: "You cannot just vote to reject no deal, you have to support a deal."
Their later meeting, away from the cameras, was "very cordial", according to a Labour spokesperson.
"There was a useful exchange of views. We made the case for our plan. There was a detailed exchange of views on a customs union and single market relationship."
The pair agreed to meet again soon, the spokesperson added.
The European Parliament's Brexit coordinator, Guy Verhofstadt, echoed his colleagues by criticising the UK for not being clear about what they wanted from the deal.
He said the two years had been "exhausting" on both sides of the Channel, and called for Mrs May and Mr Corbyn to work together - "not only eating biscuits and drinking tea" - to come to a cross-party solution and to stop "using and abusing Brexit to get rid of each other".
Mr Juncker said the votes in the Commons on Tuesday increased the risk of a "disorderly" Brexit, but he still believed there could be a deal done between the EU and UK, adding: "We will work day and night to make it happen, and to ensure we are ready in case it does not."

EU officials have poured cold water on alternative proposals for the Brexit backstop by a former British European Commission official.
Sir Jonathan Faull had suggested the EU and UK could maintain their own customs and regulatory regimes while using their laws to protect each others' markets.
He also proposed creating "trade centres" away from the Irish border.
This would mean goods would not have to be checked at the frontier.
One senior EU source told BBC News NI the proposals were "inadequate and not anywhere near the landing zone".
Speaking on the BBC's Today programme, Sir Jonathan said: "The idea is that whatever controls are necessary are done away from the border, leaving the border free and open."
The backstop is a position of last resort to prevent the hardening of the Irish border in the absence of other solutions.
It would see Northern Ireland staying aligned to some rules of the EU single market and the whole of the UK, forming a "temporary single customs territory" with the EU.
The prime minister says the backstop cannot form part of any Brexit deal.
At the centre of the Faull plan is the concept of "dual autonomy" - meaning the EU and UK would maintain their own customs and regulatory regimes but use their laws to protect each others' markets.
The paper states: "Under this proposal it will be a violation of UK law backed up by severe penalties knowingly to export, through the frontier between the North and the Republic, goods which do not comply with the regulatory standards of the EU."
In effect, UK public law would be backing not only the regulatory standards for goods on the UK market, but also goods destined for export to the EU through the frontier with the Republic.
The paper also suggests the establishment of "trade centres" in the UK and Northern Ireland, where goods destined for the EU would be subject to customs clearance and regulatory checks.
However, that would seem to fall well short of the Irish government's position that any solution must not introduce new checks on the island of Ireland - even away from the border.
It points to the 2017 Joint Report of the EU and UK, a interim deal, in which there was a commitment to avoid a hard border, "including any physical infrastructure or related checks and controls".
Speaking to the BBC, John McGrane from the British Irish Chamber of Commerce suggested the paper did not fully address the issue of EU law on food standards.
Strict EU rules stipulate that food products entering from a non-member state must be subject to checks at the point of entry into the EU.
Mr McGrane said: "This is not like different VAT rates, animals and animal products have to be checked at the point of import, it's a matter of human health protection."

The EU's chief negotiator has ruled out allowing the UK to collect customs duties on its behalf, a key UK proposal for post-Brexit trade.
Michel Barnier said the UK wanted to "take back control" of its money, law and borders - but so did the EU.
The EU would not delegate "excises duty collection to a non-member", he said.
Both he and UK Brexit Secretary Dominic Raab said progress had been made but "obstacles" remained before reaching a deal in October.
Mr Raab said: "We have agreed to meet again in mid-August and then to continue weekly discussions to clear away all the obstacles that line our path, to a strong deal in October - one that works for both sides."
He replaced David Davis, who quit as Brexit secretary in protest at Theresa May's plans for a future economic relationship between the UK and EU, as set out in the White Paper.
That set out in more detail the government's proposed customs system, the Facilitated Customs Arrangement for goods and agri-foods. The UK's plan involves it collecting some EU tariffs - in a bid to ensure frictionless trade in goods and to avoid a hard border in Northern Ireland.
Michel Barnier wants the UK to make a choice.
If it wants to have frictionless trade with the EU's single market then it will have to join a customs union, or something like it, which will mean applying the EU's tariffs and reducing the scope for doing free trade deals with others.
If it wants more freedom, it will have to agree arrangements with the EU that will reduce friction but not eliminate it altogether.
It's an old tune that sounds different after the publication of the UK's White Paper, which was supposed to have solved this dilemma.
It also sounds like the UK will propose a revamped version of its idea for avoiding a hard border between the Republic of Ireland and Northern Ireland but the two sides are still divided on whether that should have a time-limit or not.
Lost among all of this will be the nugget of good news: Big strides have been made on security co-operation after Brexit.
But Mr Barnier said retaining control of the money, law and borders also applied to the EU's customs policy.
"The EU cannot and the EU will not delegate the application of its customs policy and rules and VAT and excises duty collection to a non-member who would not be subject to the EU's governance structures," he said.
Any customs arrangement or union "must respect this principle", he said.
BBC assistant political editor Norman Smith said Mr Barnier appeared to have delivered a significant blow to Mrs May's controversial proposals, which have already been criticised by pro-Brexit Tory MPs.
Speaking after talks with Mr Raab, Mr Barnier said that Theresa May's Brexit White Paper plan was a "real step forward".
He highlighted agreement on security measures and said both sides wanted a wide-ranging free trade deal.
But he added: "To be frank, we are not at the end of the road yet."
While UK proposals on security marked "a real step forward" and he welcomed the acknowledgement that the European Court of Justice was the only arbiter of EU law, he added: "In contrast, on our future economic relationship, it comes as no surprise that finding common ground between the EU27 and the UK is more difficult."
Brexit Secretary Mr Raab said the UK proposals had been designed "to respect the result of the referendum, and the core principles of the EU".
"We have considered the innovative approaches the EU has taken in the past with other third countries - when the political will has been there," he said.
"In sum, the UK has set out our plans in detail. Those plans are ambitious, principled and pragmatic. I am committed to injecting new energy into these talks, along with Michel."
Turning to Mr Barnier, he said: "Michel, we have work to do."
The UK is due to leave the EU on 29 March 2019 but has yet to agree how its final relationship with the bloc will work.
The SNP's Angus MacNeil tweeted that the press conference spelt the end for the prime minister's Chequers plan:
Labour MP Ben Bradshaw, who is part of the People's Vote campaign for a vote on any final Brexit deal, said: "The White Paper is dead. It has expired. It has ceased to be."
For the Liberal Democrats, Christine Jardine said the prime minister's White Paper was "struggling to survive" .

The UK failed to show solidarity with a Europe reeling from terror attacks when it voted for Brexit in 2016, the EU's chief negotiator has suggested.
The UK "chose to be on their own again" when the need to act together against groups such as Islamic State had never been "so strong", Michel Barnier said.
In Berlin, he said the UK must now leave bodies such as Europol but could still participate in EU-led operations.
No 10 said it intended to still play a "full part" in Europe's security.
Speaking on a visit to Iraq, Theresa May said the UK was playing a leading role in training its army to fight so-called Islamic State and also depriving the militant group of outlets for its propaganda.
There are 1,400 British military and civilian personnel in Iraq, who have helped train and equip 25,000 Iraqi and Kurdish fighters since the UK's combat role ended in 2009.
After meeting British troops near Baghdad, she insisted the UK's defence budget was rising and the UK's capabilities would be continually reviewed.
The UK, which has long-established bilateral defence relations with countries such as France, has said it wants security and intelligence co-operation to continue after Brexit and be bolstered by a new treaty.
But Mr Barnier, a former French foreign minister, said it was clear it would not be business as usual in defence and security as in other matters once the UK had left in March 2019.
In a speech to a German security conference, he said that while the UK would remain a diplomatic and military power by virtue of its membership of Nato and the UN Security Council, it would no longer be involved in European decision-making in defence matters and would "lose some levers for wielding influence".
Reflecting on the "great shock" caused by the Leave vote in the June 2016 referendum, he said it had come "after a series of of attacks on European soil, committed by young people who grew up in Europe, in our countries".
A series of attacks in Paris in November 2015 killed 130 people, while a bombing at Brussels airport and on the city's Metro system in April 2016 left 32 people dead.
The Leave vote, Mr Barnier said, had come "six months after the French minister of defence issued a call for solidarity to all his European counterparts to join forces to fight the terrorism of [the so-called Islamic State]".
"Never had the need to be together, to protect ourselves together, to act together been so strong, so manifest," he said.
"Yet rather than stay shoulder to shoulder with the union, the British chose to be on their own again."
The UK, which has suffered a string of terror attacks in 2017, has been at the forefront of the fight against IS - carrying out air strikes against the militants in Iraq and Syria.
Mr Barnier's comments drew an immediate response from Brexit supporters.
In his speech, Mr Barnier also made clear the EU was taking on greater responsibility for Europe's defence and although the UK still had an important contribution to make, Brexit would leave it on the outside.
The UK, he said, would no longer be able to:
This, he said, was the "logical consequence of the sovereign choice made by the British".
But insisting there must be no "horse-trading" over security in the Brexit negotiations, he said common interests and values dictated the UK and EU would continue to work together, with the UK participating in selective EU operations on a voluntarily basis.
Cooperation, he added, was also vital in areas such as:
"The construction of a 'Europe of Defence' has begun," he said.
"Obviously, we will not wait for the United Kingdom to implement it, but when the time comes we will be ready to cooperate with the United Kingdom.
"This partnership will be in our best interests, since it is what the European citizens expect and it will contribute to the stability and security of our continent and our neighbourhood."
Negotiations on the UK's future relations with the EU, including on defence, have yet to begin.
But Downing Street said: "We've been clear that we want to play a full part in the security of the EU and Europe after we leave, and we think that's in the interests of both Britain and the European Union."

A campaign for another EU referendum - this time on the final Brexit deal - has been launched in London.
Chairman Lord Malloch-Brown, a former Labour minister, said it was "time for the truth" about what leaving the EU would mean.
The group, backed by billionaire George Soros, hopes to build support for a referendum on the deal over the summer.
The prime minister's spokesman said: "There isn't going to be a second referendum."
Best for Britain is targeting Labour MPs, but also needs at least 10 Conservative "rebels" if it is to win a vote in Parliament on an amendment calling for a new referendum - which is opposed by both the Conservative and Labour front benches.
If successful, the group says a "people's vote" on whether to accept the final deal - which would include the option of remaining in the EU - could be held before Brexit in March 2019.
Lord Malloch-Brown, a former UN deputy secretary general, said the "chronic uncertainty" surrounding Brexit talks was harming business and it was "time to settle this once and for all".
He said the campaign would accept the outcome of any referendum but it was "time for the truth and nothing but the truth" on Brexit, rather than "false facts" on the side of buses and "project fear".
Best for Britain says it will be campaigning in 70 "key" constituencies over the summer to urge MPs to back its plan and says it will be "talking to people on the doorstep about how Brexit is affecting them".
Pro-Brexit campaign group Leave.EU have attacked Lord Malloch-Brown as a "puppet for George Soros" and chief "Remoaner," while another group, Leave Means Leave, has launched a fundraising drive among supporters to "secure the swift, clean Brexit you all voted for".
Lord Malloch-Brown denied Best for Britain was a "puppet" of a foreign donor because it took 20% of its funding from Mr Soros - and he insisted he was not embarrassed to take the Hungarian-American tycoon's money.
"Like him, I am very proud of a career spent in international human rights, promoting democracy and trying to secure healthy democratic cultures in countries everywhere.
"I never expected to be doing it back home, but I'm pleased to be doing so."

A Tory ex-minister is trying to put a block on the EU's controversial proposals for a "backstop" to guarantee no hard Irish border after Brexit.
Steve Baker has put down amendments to the Northern Ireland bill, which is to be discussed in Parliament next week.
He wants to make it a legal requirement to get the Stormont Assembly's approval for any plan to treat Northern Ireland differently from the rest of the UK.
But the devolved government has not sat since power-sharing collapsed in 2017.
The bill aims to give its civil servants greater flexibility in making decisions, in the absence of government.
However, it has drawn the attention of those arguing over plans for the UK's future trading relationship with the EU.
Both the EU and UK are signed up to the need for a "backstop" - effectively an insurance policy to avoid the introduction of checks on the border between Northern Ireland and the Irish Republic - which is an EU member - after Brexit.
During the "transition period" after the UK leaves the EU in March 2019 until 31 December 2020, the UK's relationship with the EU will stay largely the same - something designed to smooth the path to a future permanent relationship between them.
But if there is a gap between the transition period ending, and the "future relationship" coming into force, the backstop would ensure no hard border in the meantime.
The EU and UK are agreed there can be no return to a hard border - but disagree over how the backstop should operate.
The government has proposed a backstop which would effectively keep the whole of the UK in the EU customs union for a limited period, until a comprehensive agreement is reached.
Under the EU's idea of a contingency plan, Northern Ireland would remain in the EU's customs union, large parts of the single market and the EU VAT system - something the UK says is unacceptable as it would create a new border down the Irish Sea, between Northern Ireland and the rest of the UK.
Mr Baker, the Tory MP for Wycombe and deputy chairman of the Conservative pro-Brexit European Research Group of Tory MPs. said his amendments would ensure that "emergency powers" could not be used to implement measures in the absence of an assembly.
"Northern Ireland is an integral part of the UK."
"Creating barriers between Northern Ireland and Great Britain, creating a separate regulatory regime or imposing EU laws on Northern Ireland via emergency legislation does not respect Northern Ireland's status in the UK."
BBC political correspondent Jessica Parker said it was unclear what level of support there was for the amendments.
"But negotiators may not welcome any attempt to impose legal limits on the talks which are already at an impasse," she added.
A government statement said the Northern Ireland bill is intended to provide civil servants with the "certainty and clarity" they needed to deliver public services.
"It enables key appointments that cannot currently be made in the absence of Northern Ireland ministers to be made during the period before an executive is next formed," the statement added.
"The bill also creates the necessary time and space to restart political talks with the aim of restoring devolved government as soon as possible."

Boris Johnson has met Labour leader Jeremy Corbyn amid uncertainty over what happens next with Brexit.
The meeting comes after MPs rejected the PM's plan to fast-track a bill to implement his deal through Parliament.
During PMQs, Mr Johnson said MPs had "willed the end but not the means" and it was now the EU's decision whether to grant an extension beyond 31 October.
Mr Corbyn told the Commons MPs must "have the necessary time to improve on this worse-than-terrible treaty".
The BBC's political editor Laura Kuenssberg says she understands nothing was agreed at the meeting on Wednesday morning.
Labour was keen to discuss a different timetable for the Brexit bill, while the PM wanted to know what Mr Corbyn would do if the EU refused to grant an extension, she added.
A Labour Party spokesperson said: "Jeremy Corbyn reiterated Labour's offer to the prime minister to agree a reasonable timetable to debate, scrutinise and amend the Withdrawal Agreement Bill, and restated that Labour will support a general election when the threat of a no-deal crash-out is off the table."
No 10 said there had been "no meeting of minds" between the two men and no further talks were currently planned.
The PM announced that he would pause the progress of the Withdrawal Agreement Bill (WAB) on Tuesday after MPs rejected a plan to pass it in just three days.
EU leaders, meanwhile, are considering whether to grant a delay to the Brexit deadline and what length it should be.
Laura Kuenssberg said a decision was not expected until Friday, leaving Westminster "still in limbo".
Mr Johnson was forced by law to send a letter to Brussels requesting a three-month extension, and No 10 had indicated he would push for a general election if the EU agreed.
His official spokesman said Mr Johnson had spoken to European Council President Donald Tusk and German Chancellor Angela Merkel on Wednesday and stressed to both his continued opposition to a delay.
The 27 EU ambassadors have had a first, informal discussion about a Brexit extension, BBC News Brussels reporter Adam Fleming says.
The ambassadors all agreed on the need to extend the deadline, to avoid a no-deal outcome - but the duration of this possible extension remains under discussion.
In the meantime, President Tusk's consultations with EU leaders will continue.
The EU is in no hurry to settle its attitude towards another Brexit extension because it's under no immediate pressure of time - the current extension runs until midnight on 31 October. The instinct of the European Council is to take the time it needs to reach agreement, even if that's seen as frustrating in Downing Street.
Donald Tusk as President of the Council acts as a kind of convener for the 27 heads of government - each has to be consulted at least once by phone so the process takes a little time even when the matter is straightforward.
The council works by unanimity so whatever it eventually decides will have to be acceptable to all 27 and it's true that there are differences of emphasis - there's a view in Paris, for example, that a shorter extension might concentrate minds in London.
The EU has its own limits to consider as well. First, it doesn't want to look as though it's pressuring Parliament into any particular course of action.
Second, it's clear the EU will never want to look as though it's forcing the UK out of the Brexit door or be the cause of a no-deal Brexit - for that reason, whatever the frustrations, an offer will come.
The attraction of 31 January is that it's a kind of "off-the-shelf" arrangement enshrined in the letter written by Boris Johnson to the European Council at the behest of Parliament.
At Prime Minister's Questions, Mr Johnson said it was "remarkable" that MPs backed the Withdrawal Agreement Bill at its first Commons hurdle, but a "great shame" that MPs did not back his proposed timetable for it.
He said it was "peculiar" that Mr Corbyn appeared to want him to bring back the bill when Labour MPs were told to vote against it on Tuesday.
In reply, the Labour leader said it was Mr Johnson who had "decided to delay his own withdrawal bill" when he made the decision to pause it.
He listed a number of concerns his party had with it, for example around workers' rights, and said Labour had made it clear it wanted to see a customs union built into the deal.
Mr Corbyn also accused Mr Johnson of trying "to prevent genuine democratic scrutiny and debate", adding: "Does the prime minister accept that Parliament should have the necessary time to improve on this worse-than-terrible treaty?"
Mr Johnson rejected criticism that the deal was a threat to the integrity of the United Kingdom, and repeatedly insisted it had been "approved by Parliament" on Tuesday night.
Tuesday's vote on the bill - so-called "second reading" - was only the first stage of Parliamentary scrutiny.
Detailed dissection by MPs at the committee stage would come next - along with attempts to amend the bill - followed by further votes in the House. If it was eventually approved by the Commons a similar process of scrutiny would be carried out by peers in the Lords.
The SNP has indicated it wants an extension to allow for a general election, while the Liberal Democrats say the PM needs to get an extension to allow a further referendum. Both parties would rather the UK revoked Article 50 and stopped the Brexit process.
SNP Westminster leader Ian Blackford urged the prime minister to confirm that the legislation would not be passed unless consent was given by the Scottish Parliament.
But Mr Johnson said the Scottish Parliament had no role in approving the Brexit bill and suggested Mr Blackford "have a word with other opposition parties" to trigger a general election "to settle the matter".
In a statement responding to Mr Johnson's and Mr Corbyn's earlier meeting, Ms Swinson said it was "more clear proof" that the Labour leader wanted to deliver Brexit, after 19 Labour MPs supported the bill's second reading.
"It seems that Jeremy Corbyn has thrown Boris Johnson another lifeline this morning, as six white men met to discuss pushing through a Brexit deal which will wreck our country," she said.
Under the Fixed-term Parliaments Act, the prime minister needs to have the backing of two-thirds of MPs to hold a snap poll. This has been rejected twice by MPs.
Another route to an election is a one-line bill, that requires only a simple majority, but any such bill is likely to incur a host of amendments, for example, giving 16 and 17-year-olds the right to vote.
There is also the option of a vote of no confidence in the government, and Mr Johnson could even call one himself.
But Parliamentary rules state that if it passes, the Commons has 14 days to form an alternative administration, so the PM would run the risk of being forced out of Downing Street if opposition parties can unite around a different leader.
If an election were to be triggered this week, the earliest it could take place would be Thursday 28 November, as the law requires 25 days between an election being called in Parliament and polling day.
The fact that talks took place between Jeremy Corbyn and Boris Johnson suggests that No 10 may not be totally wedded to the idea of a winter general election. Pressed in the Commons the PM did not close the door to bringing back his deal.
And there are those in government who are deeply wary of a winter election. Why? Bluntly, because it is so blooming cold.
No-one is going to thank him if they have to tramp off to the polling station in the bleak midwinter. There's a fear that older voters would be the most likely not to turn up - yet those may be the ones who were keenest to back Brexit.
Then there is the nativity play problem. Many school halls, which are used for polling stations, have been booked up for Christmas activities - and woe betide Mr Johnson if he forces those to be cancelled.

Prime Minister Boris Johnson and his Irish counterpart Leo Varadkar agree they can "see a pathway to a possible deal" after talks, Downing Street says.
The leaders spoke for over two hours, including a one-to-one discussion during a walk in the grounds of Thornton Manor in north-west England.
Mr Varadkar said Thursday's "positive" meeting was "sufficient to allow negotiations to resume in Brussels".
Brexit Secretary Stephen Barclay will meet the EU's Michel Barnier on Friday.
On Wednesday, EU leaders accused the UK of proposing untested ideas, adding that progress had been limited.
A crunch EU summit next week on 17 and 18 October is seen as the last chance for the UK and EU to agree a deal ahead of 31 October deadline.
After the meeting, Mr Varadkar told reporters the talks were at a "very sensitive stage" but were "very positive and very promising".
He said he was now "convinced" the UK wants an agreement, saying: "I do see a pathway towards an agreement in the coming weeks."
However, issues remain over "consent and democracy" and ensuring there is no customs border, Mr Varadkar said.
The Brexit proposals from Mr Johnson include a provision for the consent of Northern Ireland's politicians to be sought every four years - meaning the arrangement could, in theory, continue indefinitely.
"It remains our position that there can't be a hard border between north and south," Mr Varadkar added.
"No one's cracking open the champagne… don't even pour a pint of warm Guinness," joked one of the few people familiar with what actually happened on Thursday after talks between Boris Johnson and Leo Varadkar.
Nothing that happened in the privacy of a country house wedding venue on the Wirral means there will be a deal with the EU in the next seven days.
Nothing has made the obstacles in the way of reaching an agreement magically disappear.
But something has changed today.
After days of various EU players publicly scorning the UK's proposals, explaining the objections and lamenting the weaknesses, there is a tangible willingness, on the bloc's side at least, to see seriously if they can work.
We've discussed here so many times why Ireland's attitude matters so much, so the very public positivity from Mr Varadkar - his "maybe", instead of "no" to Mr Johnson's proposals - is extremely important.
There is hardly any detail out there of the compromises or concessions that might be actually in play to make a deal work.
Don't give too much credence to even the best informed speculation that's already whirring online as to how it could happen.
A joint statement said the prime minister and Taoiseach (Irish leader) had a "detailed and constructive discussion".
"Both continue to believe that a deal is in everybody's interest," the statement said. "They agreed that they could see a pathway to a possible deal."
The talks concentrated on "the challenges of customs and consent", Downing Street said.
"They agreed to reflect further on their discussions and that officials would continue to engage intensively on them."
Mr Johnson put forward fresh proposals for a Brexit deal last week, but Mr Varadkar had previously said "big gaps" remained between the UK and the EU.
Cabinet minister Michael Gove, who has responsibility for the UK's no-deal preparations, said: "I have to prepare for every eventuality but I'm hopeful following the good conversation that they had that we can make good progress in the days ahead."
Northern Ireland Secretary Julian Smith told BBC Northern Ireland's The View he was "delighted to see the positivity that came out of the meeting".
He said the "mood music and developments are really, really positive".
Under Mr Johnson's proposals, which he calls a "broad landing zone" for a new deal with the EU:
The prime minister has insisted the UK will leave the EU with or without a deal at the end of the month.
That is despite the so-called Benn Act - passed by MPs last month - demanding he request a delay to the Article 50 deadline from the EU until January 2020 if a deal has not been agreed before 19 October.
On Wednesday, Business Secretary Andrea Leadsom suggested the PM was gearing up to bypass legal obstacles to a no-deal Brexit by sending one letter requesting an extension and, in the same instance, submitting a second memo telling European leaders he does not want one.
Asked on ITV's Peston programme whether the idea of sending two letters to the EU was a possible loophole, Ms Leadsom replied: "Absolutely."
In a speech in Northampton, Labour leader Jeremy Corbyn reiterated that his party would agree to a general election as soon as no-deal has been taken "off the table", as the PM "can't be trusted not to break the law".
He also accused Mr Johnson of "using the Queen" to deliver a "pre-election Tory party political broadcast" at next week's state opening of Parliament.
He told party supporters that the government had "no obvious means" of getting new laws passed, and holding a Queen's Speech before an election was a "cynical stunt."
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Special sitting of Parliament and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

The UK's statistics watchdog has stood by its criticism of Boris Johnson in a growing row over the possible financial windfall the NHS may get from Brexit.
Sir David Norgrove said he was "disappointed" the foreign secretary had revived Vote Leave's pledge of £350m a week extra for the NHS.
Mr Johnson hit back at "a wilful distortion of the text of my article", asking for the claim to be withdrawn.
The mention of £350m came in a Daily Telegraph piece by Mr Johnson.
In it, he wrote: "Once we have settled our accounts, we will take back control of roughly £350 million per week.
"It would be a fine thing, as many of us have pointed out, if a lot of that money went on the NHS."
The article, in which he also said he opposed paying the EU to secure temporary access to the single market during a transitional phase after the UK's departure, divided Tory MPs.
Some claimed it undermined Theresa May's leadership ahead of a crucial speech later this week and amounted to a leadership challenge.
Home Secretary Amber Rudd accused her cabinet colleague of being a Brexit "back-seat driver", telling the BBC that while it was fine for Mr Johnson to show his enthusiasm for Brexit, he should remember he was not "driving the car".
Defence Minister Tobias Ellwood criticised what he called "party discord", tweeting: "We are not witnessing our finest hour-at a testing time when poise, purpose and unity are called for."
But a leading figure in last year's Brexit campaign, Environment Secretary Michael Gove, urged people to focus on what Mr Johnson had written, "not the headlines".
"Debate should be forward looking on how to make most of life outside EU - not refighting referendum", he added on Twitter.
By Chris Mason, BBC political correspondent
This is an extraordinary row.
A senior cabinet minister and the most senior civil servant responsible for official statistics, engaged in a public slanging match on a Sunday afternoon.
At lunchtime, Sir David's letter, accusing the foreign secretary of "a clear misuse of official statistics."
Then the first counter attack: a spokesman for Mr Johnson claimed that Sir David was actually complaining about the headlines provoked by the foreign secretary's article.
No he wasn't, responded a spokeswoman for the UK Statistics Authority.
And then Mr Johnson's formal written reply to Sir David accusing him of "a complete misrepresentation of what I said" and asking him "to withdraw it."
Who will people trust the most? The civil servant or the politician?
That is your call.
The chair of the UK Statistics Authority wrote on Sunday to Mr Johnson setting out his concerns about the £350m figure.
The authority, which is an independent statutory body, previously criticised use of the figure - which was displayed on the side of a campaign bus - during the 2016 referendum campaign.
Sir David wrote in the letter: "I am surprised and disappointed that you have chosen to repeat the figure of £350 million per week, in connection with the amount that might be available for extra public spending when we leave the European Union".
The watchdog said the article "confused" the size of the UK's annual gross and net contributions to the EU's budget.
His letter continued: "It also assumes that payments currently made to the UK by the EU, including for example for the support of agriculture and scientific research, will not be paid by the UK government when we leave. It is a clear misuse of official statistics."
In Mr Johnson's reply, he wrote: "I must say that I was surprised and disappointed by your letter of today, since it was based on what appeared to be a wilful distortion of the text of my article.
"You say that I claim that there would be £350 million that 'might be available for extra public spending' when we leave the EU.
"This is a complete misrepresentation of what I said and I would like you to withdraw it."
He continued: "Once we leave the EU we will take back control of all such UK-funded spending, and, although of course I have no doubt that we will continue to spend significantly on UK priorities such as agriculture and research, that spending will be done under UK control.
"As for the rebate - whose value you did not know - it only forms part of the EU's financing arrangements with the agreement of all other EU member states.
"We do not control it ourselves."
Labour MP Yvette Cooper said Mr Johnson "just thinks it's OK to repeatedly lie".
Lib Dem leader Sir Vince Cable said the foreign secretary's credibility was "shot to pieces".
Several Tory MPs have praised Mr Johnson's vision of what can be achieved after the UK leaves and said his objectives are largely in tune with those of the government.
Writing in the Telegraph, backbencher Jacob Rees-Mogg said the article was "tremendous" and had "magnificently rejected" the "depressing view" that Britain could not cope without the protection of the European Union.
Speaking on the Andrew Marr Show, Ms Rudd said she did not believe it was a prelude to a leadership challenge.
"I know what an irrepressible enthusiast (Johnson) is about Brexit, and what he's done is set it out there, I think it's absolutely fine, I would expect nothing less from Boris," she said.
But she added: "I don't want him managing the Brexit process, what we have got is Theresa May managing the process, driving the car.
"I am going to make sure, as far as I and the rest of the cabinet is concerned, we help her do that."
Several prominent Leave campaigners have distanced themselves from the £350m figure in the wake of the referendum result although others have continued to insist it is legitimate.
The prime minister is due to make a major speech on Brexit in Florence, amid speculation she is prepared to announce some kind of deal on transitional trade payments.
First she is due to meet Mr Johnson in New York, where the foreign secretary is expected to be in the audience when she addresses the United Nations General Assembly on Wednesday.

Tory rebels and opposition MPs have defeated the government in the first stage of their attempt to pass a law designed to prevent a no-deal Brexit.
The Commons voted 328 to 301 to take control of the agenda, meaning they can bring forward a bill seeking to delay the UK's exit date.
In response, Boris Johnson said he would bring forward a motion for an early general election.
Jeremy Corbyn said the bill should be passed before an election was held.
In total, 21 Tory MPs, including a number of ex-cabinet ministers, joined opposition parties to defeat the government.
After the vote, Downing Street said those Tory MPs who rebelled would have the whip removed, effectively expelling them from the parliamentary party.
No 10 had hoped the threat of expulsion - and an election - would bring would-be rebels into line.
The longest-serving of the Tory rebels, ex-chancellor Ken Clarke, told BBC Newsnight he was still "a mainstream Conservative" but he didn't recognise his party any more.
The "knockabout character" of the prime minister had "the most right-wing cabinet a Conservative government has ever produced", he said.
The prime minister said the MPs' bill would "hand control" of Brexit negotiations to the EU and bring "more dither, more delay, more confusion".
He told MPs he had no choice but to press ahead with efforts to call an October election, adding: "The people of this country will have to choose."
The result means the MPs will be able to take control of Commons business on Wednesday.
That will give them the chance to introduce a cross-party bill which would force the prime minister to ask for Brexit to be delayed until 31 January, unless MPs approve a new deal, or vote in favour of a no-deal exit, by 19 October.
The BBC understands the government intends to hold an election on 15 October, two days before a crucial EU summit in Brussels.
To call an election under the Fixed-term Parliaments Act, Mr Johnson would need support from Labour as he requires the backing of two-thirds of the UK's 650 MPs.
But Mr Corbyn said the legislation backed by opposition MPs and Tory rebels should pass before any election was held, to "take no deal off the table".
He added: "There is no majority to leave without a deal within the country".
Shadow justice secretary Richard Burgon said he did not trust Boris Johnson not to call an election for mid-October and then change the date afterwards.
He said the prime minister could "change the date so that during the general election campaign we crash out of the European Union with a no deal".
"We want it bolting down that a no-deal Brexit can't occur, and once that's done, we want a general election as soon as possible," he told the BBC.
The BBC's chief political correspondent, Vicki Young, said the government was framing the situation as the Labour leader trying to block Brexit, and that would be its argument going into a general election.
It's hard to know where to start sometimes.
The pace and gravity of events in Westminster this week is both monumental and dizzying.
A prime minister has lost his wafer of a majority.
But some close to the prime minister believe that from this crisis comes an opportunity - to close the unfinished business of the referendum result in 2016, with the Tory party at last being the bearers of a crystal-clear message on Brexit.
It's a measure of how upside down the political norms are - that the prime minister losing his first vote in office is considered by some of his allies as a benefit.
SNP Westminster leader Ian Blackford said he was "delighted" that MPs had expressed a "very clear view" in favour of a law to block no deal.
"Boris Johnson and his government must respect the right of parliamentarians to represent the interests of their constituents," he said.
"Yes, there must be an election, but an election follows on from securing an extension to the [Brexit deadline]."

The prime minister has ruled out a Northern Ireland-only backstop.
During a Facebook live on Wednesday afternoon Boris Johnson said the UK "will not accept" it.
Earlier, DUP leader Arlene Foster said a Northern Ireland-only backstop was anti-democratic, but believed the prime minister "is in the space of trying to find a deal".
There had been speculation the government is re-considering the idea of a so-called Stormont lock to break the impasse.
It would create a formal mechanism for consulting and seeking the approval of Northern Ireland's devolved administration in the backstop, allowing the Stormont parties a say before any divergence between NI and GB would happen, after Brexit.
However the Stormont institutions collapsed in 2017, after a row between the power-sharing parties.
Parliament is currently suspended for five weeks. When sitting, the prime minister answers questions from other MPs on Wednesdays.
During the live stream on Wednesday Mr Johnson said: "The backstop is going to be removed, I very much hope. I insist, it's the only way to get a deal.
"We will not accept either a Northern Ireland only backstop, that simply doesn't work for the UK.
"We've got to come out whole and entire and solve the problems of the Northern Irish border and I'm certain that we can do that. And we're working flat out to do that".
However, speaking earlier on BBC Radio Ulster, Mrs Foster said: "It's not just the DUP that rejects the backstop, it's a much wider coalition that rejects the backstop.
"What we need to do now is reject the backstop, move on and find a deal that works.
"That's what I'm focused on and I think it's what the prime minister is focused on as well."
The backstop is the insurance policy to maintain an open border between Northern Ireland and the Republic of Ireland after Brexit, until a wider solution is found.
Mrs Foster, who met the prime minister on Tuesday, said the government was "exploring" an all-island food standards zone as part of a solution to replace the backstop.
She denied the DUP's influence with the prime minister had waned after he lost his parliamentary majority.
The DUP had been propping up the Conservatives in a confidence-and-supply pact since June 2017, with the votes of its 10 MPs giving the government a majority to get legislation passed in Parliament.
However, last week Mr Johnson lost his majority after 21 Conservative rebels had the whip removed for voting against the party on Brexit legislation.
It means he no longer requires the DUP's votes, but Mrs Foster said her party had a "much wider bond" with Mr Johnson than just the political arrangement.
She said she believed the prime minister was true to his word in ruling out a Northern Ireland-only backstop.
There are suggestions that the government is contemplating such a proposal in order to ensure the UK leaves the EU with a deal by 31 October, but Mrs Foster said that was not true.
She also dismissed suggestions that a solution could end up being the backstop by another name, adding: "It's not just a case of tampering with words."
On Tuesday, the former Taoiseach (Irish PM) Bertie Ahern said consent from Northern Ireland's unionist parties was "essential" if a deal was to be reached.
Her party had engaged in talks with the DUP for many years and this would continue, she added.
But she warned: "There is simply no meeting of minds on the matter of Brexit."
The prime minister has insisted he will not seek an extension to the Brexit deadline if there is no agreement with the EU.
In Dublin on Monday, Mr Johnson said he had an "abundance of proposals" to replace the backstop.
The idea of a NI-only backstop was first suggested early in the Brexit negotiations.
Former PM Theresa May rejected it in 2018 because she relied on the votes of the 10 DUP MPs in Parliament.
The Irish government has said it is willing to look at a "Northern-Ireland specific solution".
On Tuesday, Ireland's EU Commissioner Phil Hogan told RTÉ that there was "movement" on both sides of the Brexit negotiations.

The prime minister has suggested he is open to an all-Ireland food standards zone as part of a solution to replace the Brexit backstop.
Food standards are one of the most difficult border issues.
That is due to strict EU rules that say products from a non-member state must be checked at the point of entry.
If Northern Ireland was to align with the Republic of Ireland, it would effectively continue to follow EU rules.
That would mean that some food products coming from elsewhere in the UK would be subject to new checks and controls at Northern Ireland ports.
It came as Boris Johnson faced MPs in the Commons ahead of a showdown over Brexit.
In a blow to the prime minister, Tory rebels and opposition MPs defeated the government in the first stage of their attempt to pass a law designed to prevent a no-deal Brexit.
Mr Johnson has said he will visit Dublin on Monday to meet Taoiseach Leo Varadkar.
The prime minister said he wants to discuss the issue with the EU, and during the meeting with Mr Varadkar next week.
By John Campbell, BBC News NI economics and business editor
Would an all-island food standards zone be the backstop by another name?
Not quite.
The backstop would involve Northern Ireland following a range of single market rules beyond food and agriculture.
There's also the question of consent by unionist parties in Northern Ireland.
The prime minister said an all-island arrangement would have to "clearly enjoy the consent of all parties and institutions with an interest".
That suggests unionists would have to be convinced that the governance of such an arrangement would give them a greater say than have under the current backstop.
And remember, the backstop is only supposed to be temporary.
Would this food standards zone be intended as a permanent arrangement, just like the existing all-island animal health zone?
Mr Johnson said he recognises that "for reasons of geography and economics, agrifood is increasingly managed on a common basis across the island".
He told the Commons: "We are ready to find ways forward that recognises this reality, provided it clearly enjoys the consent of all parties and institutions with an interest."
That suggests any arrangement would need to have the support of the Democratic Unionist Party (DUP) and other unionists.
DUP deputy leader Nigel Dodds told BBC Newsline that the party would be "willing to sit down and look at what Boris is looking at and what can be done".
"We want to get a deal provided it's within the parameters of ensuring that it's not economically and constitutionally injurious to the union of Great Britain and Northern Ireland," he added.
The island of Ireland is already a single zone for animal health, which means all livestock coming into Northern Ireland from Great Britain is checked on entry.
If it was also to be a single zone for food standards, it would mean that some products coming from elsewhere in the UK would be subject to new checks and controls at Northern Ireland ports.
Earlier this week, a leaked government document suggested an all-Ireland food standards zone is being considered as part of a solution to replace the Brexit backstop.
The document states that alignment of standards between Northern Ireland and the Republic of Ireland is seen as "one of the most practical, deliverable and negotiable facilitations".
However, it cautions that such an arrangement comes with many of the same political challenges as the backstop.
In relation to the document, a government spokesperson declined to comment.
"We have been clear that we stand ready to negotiate in good faith an alternative to the backstop, with provisions to ensure that the Irish border issues are dealt with where they should always have been, in the negotiations on the future agreement between the UK and the EU," the spokesperson said.
"We have likewise always said that these issues will require a package of measures addressing different customs and regulatory aspects, rather than just one single solution."
The backstop is a position of last resort to prevent the hardening of the Irish border in the absence of other solutions.
It would see Northern Ireland staying aligned to some rules of the EU single market and the whole of the UK forming a "temporary single customs territory" with the EU.
The prime minister has said the backstop cannot form part of any Brexit deal.
Meanwhile, DUP MP Sir Jeffrey Donaldson said there was now an inevitability about a general election in the coming weeks after Mr Johnson's government lost its working majority.
On Tuesday night, the Commons voted 328 to 301 to take control of the agenda, meaning they can bring forward a bill seeking to delay the UK's exit date.
In response, the prime minister said he would bring forward a motion for an early general election.
"If the general election is forced because of Brexit, then inevitably Brexit is going to be front and centre in the election," Sir Jeffrey said.

Boris Johnson has said he can see "a way forward" to reaching a deal with the EU in "all our interests" before Brexit is due to happen on 31 October.
But the prime minister warned the cabinet there was still a "significant amount of work" to do, as EU and UK officials continue to hold talks.
Parliament will meet on Saturday and vote on any deal achieved by Mr Johnson at a Brussels summit this week.
Labour said it would "wait and see" but would oppose anything "damaging".
The European Commission echoed the prime minister, saying: "A lot of work remains to be done."
Shadow business secretary Rebecca Long-Bailey told BBC One's Andrew Marr Show: "We don't think the Tories have moved too far on their deal."
SNP leader Nicola Sturgeon told the same programme: "We will not vote for the kind of deal specified by Boris Johnson."
Talks in Brussels between UK and EU officials - described as "intense technical discussions" - continued on Sunday and will re-start on Monday.
House of Commons Leader Jacob Rees-Mogg, a leading Brexiteer, told Sky News that "compromise" would be inevitable during negotiations.
He added: "I trust Boris Johnson to ensure the relationship the United Kingdom has with the European Union is one where we are not a vassal state."
Mr Rees-Mogg also said he might have to "eat my words" and support a plan close to the one put forward by former Prime Minister Theresa May, which MPs rejected three times.
By Nick Eardley, BBC political correspondent
Is there going to be a deal then?
Forgive me a politician's answer, but the truth is nobody knows for sure. Not yet.
Both sides are being tight-lipped on the exact discussions happening behind closed doors in Brussels.
Indeed the cabinet was given very little detail about what exactly is being discussed.
Some might see that as a positive sign; nobody is going public on the concerns they have.
That doesn't mean they don't have them, but it suggests there is serious work going in to try to solve them.
I'm told Boris Johnson sounded genuinely confident in the cabinet conference call that a deal can be done.
Others in Westminster are filling up the coldest water they can find to pour all over reports a deal could be coming.
One opposition source told me they have war-gamed six potential outcomes for this mammoth political week.
They didn't give any of them more than a 50% chance.
Michel Barnier, the EU's chief Brexit negotiator, is expected to update ambassadors from the bloc's 27 member countries on Tuesday.
The summit in Brussels on Thursday and Friday is seen as the final chance to get a Brexit deal agreed ahead of the deadline of 23:00 GMT on 31 October.
A Downing Street spokesperson said: "The prime minister updated cabinet on the current progress being made in ongoing Brexit negotiations, reiterating that a pathway to a deal could be seen but that there is still a significant amount of work to get there and we must remain prepared to leave on 31 October."
The spokesman said Mr Johnson believed a deal could "respect the Good Friday Agreement", signed in 1998 in an effort to end the Troubles in Northern Ireland.
It could also "get rid of" the backstop - the plan to prevent the return of a hard border between Northern Ireland and the Irish Republic - which the government says threatens the future of the UK.
Liberal Democrat leader Jo Swinson told Sky News that any agreement reached by Mr Johnson should "be put to the public so they can have the final say".
But asked whether more MPs would be likely to support a deal, if the Commons first voted in favour of putting it to a referendum, Labour leader Jeremy Corbyn said: "I think many in Parliament, not necessarily Labour MPs - others - might be inclined to support it because they don't really agree with the deal.
"I would caution them on this."
Asked about Labour's stance, Home Secretary Priti Patel replied: "They are clearly playing politics. The British public want to ensure that we get Brexit done."
Mr Johnson's revised proposals - designed to avoid concerns about the backstop - were criticised by EU leaders at the start of last week.
However, on Thursday, Mr Johnson and Irish Prime Minister Leo Varadkar held talks and said they could "see a pathway to a possible deal".
The Benn Act, passed by Parliament last month, requires Mr Johnson to ask EU leaders for a delay to Brexit if a deal has not been reached and agreed to by MPs by 19 October.
The first Queen's Speech of Mr Johnson's premiership, delivered during the State Opening of Parliament on Monday, will see the government highlight its priorities, including on Brexit.
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Special sitting of Parliament and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

The UK is on the verge of making a historic mistake if it does not "junk the backstop", Boris Johnson has said.
He told the DUP conference the EU had made NI an "indispensable bargaining chip" in the Brexit negotiations.
DUP leader Arlene Foster said a Brexit deal that includes the backstop plan is "not in the national interest".
There has been political opposition among unionists to the government's plan because of the backstop, which aims to avoid a hard Irish border.
It would see only Northern Ireland stay aligned to some EU rules if it took effect.
European Council President Donald Tusk has recommended that the EU approve the Brexit deal at a summit on Sunday.
The DUP is concerned that the backstop could threaten the integrity of the union and place a trade border down the Irish Sea.
Mr Johnson is one of two senior Conservative MPs to appear at the conference this weekend, after Chancellor Philip Hammond spoke on Friday night.
"We must agree that neither side will introduce a hard border in Northern Ireland," he said.
The former foreign secretary said the UK had an "absolute duty to get this right" and that there is still time to work for a better deal.
"In the words of that great Northern Irish singer Van Morrison, it is time we all moved from the dark end of the street to the bright side of the road," he added, to applause.
He said he hoped the DUP and Conservatives could continue working together, "backing our union against all those who would seek to divide us".
by Jayne McCormack, BBC News NI political reporter
What do Star Wars, sardines and the Titanic all have in common?
Answer: They all somehow ended up getting a mention in Boris Johnson's speech at the DUP conference (yes, really).
It certainly wasn't a normal party conference, but these are unusual times. There was standing room only as the politician, who often brings a rock star flavour to events, took to the stage.
That being said, while much of what he said received roars of applause, my colleague Gareth Gordon noticed one woman asleep in the front row.
But even getting Mr Johnson to appear at the conference will be seen as a victory for the DUP, in its attempt to resist the government's path for Brexit. Before party leader Arlene Foster was announced to the stage, one DUP councillor described her as "a lady who's not for turning".
But with Theresa May also holding firm against the DUP's opposition to the backstop so far, soon enough someone's going to have to give.
Mr Johnson also suggested the creation of a secretary of state for "no deal" on World Trade Organisation terms, "with real powers across Whitehall to make things happen".
"I do not believe that we will exit without a deal - that is totally unnecessary - but it is only responsible of government to make the proper preparations," he added.
Mrs Foster told her party's conference that the prime minister had not been able to guarantee that the backstop would not have to be used.
The government has said it is looking at alternative arrangements to ensure the backstop is a last resort.
But, Mrs Foster said there were "many contradictions" in the draft withdrawal agreement.
She said she understood the position of many in the business community, who have urged DUP MPs to back the deal.
But she added that the party could not wish away proposals that it believes are not in the best interests of Northern Ireland's economy or interests.
"The choice is not between this deal and no deal, despite what the government spin machine may say," she said.
Ahead of the party conference, Mrs Foster warned that if the deal gets passed in parliament, her party may have to revisit its confidence-and-supply pact with the Conservatives.
The DUP holds the balance of power at Westminster, as the government relies on the votes of its 10 MPs to have a working majority in parliament.
It signed a confidence and supply pact with the Conservatives in June 2017 and negotiated an extra £1bn in spending for Northern Ireland - but the rift between the parties over the Brexit plan has put the arrangement under significant pressure.
On Saturday, she said "the DUP had never been afraid to say yes when it is right to do so, nor to say no when required".
Earlier, the DUP's deputy leader Nigel Dodds said the party would "stand firm in the face of inevitable onslaught" in opposing the government's Brexit plan.
Mr Dodds told the party's conference: "Prime minister - bin the backstop."
Mr Dodds told the conference that the union is "non-negotiable".
He described Theresa May's draft plan as portraying a "pitiful and pathetic place for the United Kingdom".
The government has insisted that it will not renegotiate the current plan, and has urged MPs to back it or risk a no deal scenario.
Mr Dodds added that the DUP wanted to leave the EU with a deal, but "not a deal at any price".
On Friday, the Chancellor, Philip Hammond, told the BBC that the government is looking at ways to provide extra assurances to the DUP over the Irish border backstop.
He was speaking during a visit to an integrated school in Moira, County Down.
The government of Gibraltar is also represented at the DUP conference.
Gibraltar has become involved in the Brexit debate as Spain sought written assurances from the UK that it would be directly consulted over its future trade negotiations with the EU which relate to Gibraltar, a British Overseas Territory.
Donald Tusk recommended that the EU approve the Brexit deal after Spanish PM Pedro Sanchez received assurances from the UK government over Gibraltar, and dropped his threat to boycott the summit.
On Saturday, the government of Gibraltar said the territory "will not fold" over Brexit and staunchly supports the union.
Housing and equality minister Samantha Sacramento told the DUP conference Gibraltar would "not be bullied".
The chief minister of Gibraltar, Fabian Picardo, was due to attend but could not make it because of the ongoing Brexit negotiations.
Gibraltar voted overwhelmingly (96%) to remain in the EU.

Boris Johnson has said the chances of a Brexit deal are "touch and go" - having previously said the odds of a no-deal Brexit were "a million to one".
In a BBC interview at the G7 summit in France, he said it "all depends on our EU friends and partners".
When pressed on the chances, he said: "I think it's going to be touch and go. But the important thing is to get ready to come out without a deal."
Donald Tusk told the PM the EU is open to alternatives to the backstop.
BBC Europe editor Katya Adler said the European Council president and Mr Johnson held talks on Sunday, which were in a "genuinely positive atmosphere".
But she said Mr Tusk repeated the EU's position that any alternatives to the Irish backstop would have to be "realistic" and "immediately operational".
An EU official added the meeting had "mainly restated known positions" and Brussels had been hoping for "new elements to unblock the situation".
The two men clashed on Saturday over who would be "Mr No Deal" - the person to blame in the case of a no-deal Brexit.
Mr Johnson has previously said the UK must leave on 31 October "deal or no deal", but that the chances of a no-deal Brexit happening are a "million to one".
Asked if people would still be able to get their medicine if there was a no-deal Brexit, the prime minister told the BBC: "That is certainly a guarantee that we can make."
But he added: "I do not want at this stage to say there won't be unforeseen difficulties."
Speaking at the G7 summit on Sunday, he reiterated his desire to scrap the backstop from the current withdrawal agreement, saying it could keep the UK "locked in" EU rules, if a trade deal is not agreed after Brexit.
He said: "I think in the last few days there has been a dawning realisation in Brussels and other European capitals what the shape of the problem is for the UK."
Mr Johnson said he was an "optimist" and thought the EU would understand there is an "opportunity to do a deal".
The PM also said if there is no deal, the UK would keep a "very substantial" part of the £39bn Theresa May had agreed to pay the EU in her withdrawal agreement.
The G7 summit - a get-together of most of the leaders of the world's largest economies - comes with just over two months until the UK is scheduled to leave the EU at the end of October.
Mrs May struck a withdrawal agreement with the EU - the so-called "divorce deal" - but British MPs rejected the deal three times.
Mr Johnson wants to remove the Irish backstop from the deal but the EU has consistently ruled this out, saying it will not renegotiate the agreement.
If implemented, the backstop - a last resort should the UK and the EU not agree a trade deal after Brexit - would see Northern Ireland staying aligned to some rules of the EU single market.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
This week German Chancellor Angela Merkel suggested there could be an alternative to the backstop but the onus was on the UK to find it.
But the next day French President Emmanuel Macron said the backstop was "indispensable" to preserving political stability and the single market.
Also on Sunday, the PM met President Donald Trump to discuss a trade deal between the UK and the US.
Mr Johnson said the US's aim to strike a deal within a year was "going to be tight", adding: "These [Americans] are tough guys."
Meanwhile, former chancellor Philip Hammond has written to the PM about the leaked Operation Yellowhammer documents on preparations for a no-deal Brexit.
He said it was now apparent the document was dated August 2019, and therefore could not have been leaked by a minister from Mrs May's government.

Boris Johnson has signed the Brexit withdrawal agreement in Downing Street.
The prime minister hailed a "fantastic moment" for the country after he put his name to the historic agreement, which paves the way for the UK's exit from the European Union next Friday.
He said he hoped it would "bring to an end far too many years of argument and division".
Earlier on Friday, European leaders signed the document in Brussels, before it was transported to London by train.
The signings mark another step in the ratification process, following Parliament's approval of the Brexit bill earlier this week. The European Parliament will vote on the agreement on 29 January.
Downing Street officials said the PM marked the document with a Parker fountain pen, as is traditional for ceremonial signings in No 10.
It was witnessed by EU and Foreign Office officials, including the PM's Chief Negotiator David Frost, and Downing Street staff.
"The signing is a fantastic moment, which finally delivers the result of the 2016 referendum and brings to an end far too many years of argument and division," Mr Johnson said.
"We can now move forward as one country - with a government focused upon delivering better public services, greater opportunity and unleashing the potential of every corner of our brilliant UK, while building a strong new relationship with the EU as friends and sovereign equals."
Earlier on Friday, the document crossed the channel on a Eurostar train, having been signed in Brussels by the European Council's president Charles Michel and the European Commission president Ursula von der Leyen.
The UK will keep a copy of the agreement while the original will return to Brussels, where it will be stored in an archive along with other historic international agreements.
Next week's European Parliament vote is seen as all but a formality, after it was backed by the parliament's constitutional affairs committee on Thursday.
Mrs von der Leyen and other senior EU figures are sceptical about the UK government's plan to negotiate a comprehensive deal on future relations before the end of 2020. They believe the timetable for that is too tight.
But Prime Minister Boris Johnson is upbeat, insisting the UK can now move forward after years of wrangling over Brexit.
Mr Michel, the former Belgian Prime Minister who chairs EU summits, said in a tweet: "Things will inevitably change but our friendship will remain. We start a new chapter as partners and allies."

The PM has said he will give MPs more time to debate his Brexit deal, if they agree to a 12 December election.
Boris Johnson told the BBC he expected the EU to grant an extension to his 31 October deadline, even though he "really" did not want one.
But Jeremy Corbyn said he would not support an election until a no-deal Brexit is "off the table".
EU leaders could give their verdict on delaying Brexit for up to three months on Friday.
Commons leader Jacob Rees-Mogg told MPs the government would on Monday table a motion calling for a general election.
Under the 2011 Fixed-Term Parliament Act, two-thirds of MPs must vote for a general election before one can be held.
In a letter to Labour leader Mr Corbyn, Mr Johnson said his "preferred option" was a short Brexit postponement "say to 15 or 30 November".
But Mr Corbyn said: "Take no-deal off the table and we absolutely support a general election.
"I've been calling for an election ever since the last one because this country needs one to deal with all the social injustice issues - but no-deal must be taken off the table.
"The EU will decide whether there is an extension tomorrow... and then we can decide."
Mr Johnson wrote that, in that case, he would try to get his deal through Parliament again, with Labour's support.
The prime minister added that he "assumes" Mr Corbyn "will cooperate with me to get our new Brexit deal ratified, so we leave with a new deal rather than no deal".
If, as widely expected, the EU's Brexit delay is to the end of January, Mr Johnson said he will hold a Commons vote next week on a 12 December election.
If Labour agrees to this, the government said it will try to get its deal through before Parliament is dissolved for the campaign on 6 November.
Treasury sources told the BBC that the Budget would not now be delivered on 6 November as scheduled.
The prime minister told BBC political editor Laura Kuenssberg: "I'm afraid it looks as though our EU friends are going to respond to Parliament's request by having an extension, which I really don't want at all.
"So, the way to get this done, the way to get Brexit done, is, I think, to be reasonable with Parliament and say if they genuinely want more time to study this excellent deal, they can have it but they have to agree to a general election on 12 December."
Asked what he would do if Labour refused to vote for an election, he said: "We would campaign day after day for the people of this country to be released from subjection to a Parliament that has outlived its usefulness."
The prime minister has repeatedly insisted the UK will leave the EU on 31 October, with or without a deal.
But he was forced to send a letter to the EU requesting an extension, under legislation passed by MPs last month.
MPs voted on Tuesday to back the first stage of the Withdrawal Agreement Bill, putting the deal the PM agreed with Brussels into law - but rejected Mr Johnson's plan to push it through the Commons in three days.
The BBC's Europe editor Katya Adler says EU leaders are set to decide on Friday whether to grant the UK a three-month Brexit extension - although the decision could be delayed to Monday.
Most EU nations back it but France "is digging its heels in", she adds.
So there could be an emergency summit in Brussels on Monday to allow leaders to reach agreement face-to-face.
Boris Johnson cannot be remotely sure Labour and the smaller parties will let him have his way. The SNP and the Lib Dems are both tempted to go for an election as soon as a three month delay is agreed.
The Labour Party's official position has always been that they would agree to an election, in fact officially they are chomping at the bit, like the other parties, as long as a delay is agreed.
One senior member of the shadow cabinet predicted they would not be able to withstand the pressure if the Lib Dems and the SNP said yes.
Jeremy Corbyn himself, and certainly one group in his camp, are understood to be very tempted too. But, just as in 2017, lots of Labour MPs are horrified at the idea, partly because of Labour's standing in the polls.
But also, there are senior shadow cabinet ministers who believe the smart thing would be to leave the PM in his purgatory, twisting, unable to get his bill through, unable to get to an election.
In short, the position is fluid, and Labour is having words with itself tonight.
Read the full article

The High Court has thrown out an attempt to prosecute Boris Johnson over claims he lied during the 2016 referendum campaign by saying the UK gave the EU £350m a week.
The Tory leadership hopeful challenged a summons to attend court on three claims of misconduct in public office.
His lawyers said he denied acting improperly or dishonestly.
Marcus Ball, the campaigner who brought the private prosecution, said the matter was "not over".
He crowdfunded more than £300,000 to bring the case.
Mr Johnson, a former Foreign Secretary, was handed a summons to attend Westminster Magistrates' Court on 29 May.
But at a High Court hearing in London, Lady Justice Rafferty and Mr Justice Supperstone overturned this decision.
Addressing Mr Johnson's barrister, Adrian Darbishire QC, Lady Justice Rafferty said: "We are persuaded, Mr Darbishire, so you succeed, and the relief that we grant is the quashing of the summonses."
Reasons for the High Court's ruling will be given at a later date.
Mr Ball's lawyers first lodged an application in February to summons Mr Johnson, claiming that, while an MP and mayor of London, he had deliberately misled the public during the 2016 EU referendum campaign, and had repeated the statement during the 2017 general election.
The £350m figure was used by the pro-Brexit Vote Leave group throughout the referendum. It also appeared on the side of the campaign bus, which urged the UK to "fund our NHS instead".
Mr Darbishire said the attempt to prosecute Mr Johnson was "politically motivated and vexatious".
BBC legal affairs correspondent Clive Coleman said Mr Johnson's lawyers had sought to say the district judge who issued the summons got the law wrong.
The Uxbridge and South Ruislip MP's legal team argued that the offence of misconduct in public office was about the secret abuse of power and there was nothing secret about Mr Johnson's claim, which they said had been challenged during the campaign.
Mr Johnson did not appear at the High Court hearing and a spokesman said he would not be commenting on the case.
In a statement, his lawyers said they were "disappointed" by the district judge's decision and now "pleased" that the High Court had "rectified that decision so quickly".
Speaking outside court, Mr Ball said he had spent more than the £300,000 he raised on the case, leaving him in "massive debt".
In a statement, he later added that he would "keep fighting".

Prime Minister Boris Johnson has written to European Council President Donald Tusk, calling for the Irish backstop to be scrapped. BBC Northern Ireland's economic and business editor, John Campbell, and the Reality Check team have been looking at some of the key passages and what they mean.
Boris Johnson's focus here is the backstop. That's the insurance policy - agreed by Theresa May and the European Union (EU) - to avoid a hard Irish border.
It would come into effect after Brexit if the UK and the EU failed to reach a trade deal that would keep the border between Northern Ireland and the Republic of Ireland as open as it is now.
It would keep:
Mr Johnson identifies two problems with this.
First, the UK could not unilaterally bring the backstop to an end, unless it could be proven that the EU was acting in bad faith. In March, the attorney general, Geoffrey Cox, concluded if the UK and EU negotiated in good faith but still could not reach an agreement on their long-term relationship, the UK would have "no internationally lawful means" of leaving the backstop without EU agreement.
Secondly, there is the issue of EU single market rules continuing to apply in Northern Ireland. Those rules are set in Brussels, rather than Belfast, meaning Northern Ireland voters would have no direct influence. However, the EU can point to a specialised committee of UK and EU representatives that would be set up to oversee the implementation of the backstop and review cross-border cooperation. Reporting to that committee would be a working group to act as a forum for consultation. And taken together, these arrangements could be interpreted as giving the UK a decision-shaping role in regard to EU rules covered by the backstop.
Theresa May accepted a backstop was needed to protect the Good Friday agreement.
Widely seen as marking the effective end of Northern Ireland's Troubles, the agreement established:
But Mr Johnson takes a sharply different view from his predecessor. He has accepted the argument, advanced in a series of papers and articles by Lord Trimble and other senior unionists, that the backstop would breach one of the central principles of the Good Friday agreement - there should be no change in Northern Ireland's constitutional status without the consent of a majority of voters.
Nationalists, on the other hand, say this principle applies to a vote on a united Ireland only.
The border policy most favoured by Brexit supporters, "alternative arrangements" refers to a package of technical and administrative solutions to keep the border open without the UK having to stick closely to EU rules and regulations.
The EU has committed to exploring alternative arrangements - but only once a withdrawal agreement containing the backstop has been passed.
The UK government, meanwhile, has appointed a panel of experts to advise on alternative arrangements - but it has not yet published a report.
Separately, a group led by two Conservative MPs has published an alternative arrangements plan.
It suggested the widespread use of trusted-traders schemes for cross-border businesses, which would minimise the need for any checking of goods.
It also said any customs checks could happen "inland" at warehouses or company premises, using mobile inspection teams.
And use of customs brokers is proposed for small businesses, with the very smallest being exempt from any new procedures.
However, this plan was dismissed by Northern Ireland business groups as unrealistic and lacking credibility.
Mr Johnson repeats the long-standing UK commitment not to have infrastructure at the border.
But in the EU's view the UK has already made a commitment that goes beyond this.
In the joint report of 2017 (effectively an interim deal), the UK committed to no physical infrastructure or "related checks and controls".
For the EU, this means no new checks and controls anywhere on the island of Ireland, be it at facilities away from the border or at company premises.
But Brexit supporters think this commitment went too far and should have been limited to no checks at the border itself. And the wording of his letter suggests Mr Johnson agrees.
Like the rest of the UK Northern Ireland uses the pound, while across the border the euro is the currency.
But the UK and Ireland are currently part of a single EU VAT area.
This means that when a UK product is exported to another EU country, VAT is paid where the product is consumed.
But if the UK left the EU, VAT liabilities would have to be assessed by customs officials at borders - unless some new arrangement is in place.
One solution would be for the UK to have continued access to the EU's VAT Information Exchange System (VIES).
However, that would be an unprecedented arrangement - not even Norway, which has a major VAT deal with the EU, has full access to the VIES.
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A UK minister has attended a European Union meeting for the final time before the country leaves the bloc on Friday.
Speaking after the General Affairs Council meeting in Brussels, Foreign Office Minister Chris Pincher said the UK was "looking forward to the next chapter" in its relations with the EU.
The UK and the EU's 27 remaining countries would "continue to defend shared values" after Brexit, he said.
The European Parliament will hold its vote on the Brexit deal on Wednesday.
It comes after the withdrawal agreement was formally signed by Boris Johnson and EU leaders last week.
Topics discussed at Tuesday's meeting included Croatia's six-month stint in charge of the EU presidency, which officially begins this month.
As he arrived for the meeting, Mr Pincher told reporters: "I'm here to reassert to my EU friends and colleagues that, though we are leaving the EU, we are not leaving Europe.
"Our shared history, our shared values, our commitment to security and prosperity continue as equals - sovereign equals."
He wished his counterparts "the best for the future".
He later tweeted a number of pictures of him talking to his European counterparts.
Outlining Croatia's EU presidency plans, European Affairs Minister Andreja Metelko-Zgombić said ministers were "sad to see a member state leave".
But she added that Brexit should be seen as the "new starting point for building a close relationship and partnership" with the UK in the future.
"The distance between Dover and Calais will not increase over the night on Friday," she told reporters ahead of the meeting.
"We will remain very close geographically, and we should give ourselves the means to achieve a loyal and balanced relationship".
The UK's departure on Friday will be followed by an 11-month transition period, during which the UK will continue to follow EU rules.
The moment is set to be officially marked in London with a light show in Downing Street and a speech from the prime minister.
A special 50p coin will also enter circulation to mark the occasion.

Theresa May's Brexit speech was broadly welcomed by UK business and finance for adding clarity.
But the widespread reaction was that it's the final detail of the EU exit terms that matter, not laying out the direction of travel. Here are some responses from business leaders.
"In business, what you achieve in a negotiation - not what you bid for - is what really matters. The Brexit process is no different. While businesses now have a clearer sense of the prime minister's top-line priorities, they will come away from her speech knowing little more about the likely outcome of the Brexit negotiations than they did yesterday.
"The simple fact is that businesses all across the UK are carrying on. Directly-affected companies are being pragmatic, and are preparing for a range of possible outcomes. Away from Westminster, many businesses are ignoring the Brexit 'noise' completely, and say there needs to be a far bigger focus on getting the basics right here at home."
"Nearly half of managers (49%) believe that Brexit will have a negative impact on economic growth, so it's imperative that we act now if we want UK business to remain dynamic and resilient.
"With the prime minister signalling today that the UK will make a clean break from the EU, it is inevitable that the number of foreign workers coming to the UK will fall after Brexit, so we need to invest heavily in home grown talent now to ensure that we have the skilled workers capable of plugging the gaps."
"I am very encouraged by the vision set out by the prime minister today. The UK voted to leave the European Union and she is determined to make this happen in a way that restores our sovereignty but which ensures the UK becomes a global leader in free trade.
"British business now needs to get behind the government as it sets out to secure the best deal for our country's future. As the prime minister said, we are leaving the EU but we are not leaving Europe - it will remain an important market for British business but we need to be able to trade freely with the rest of the world as well."
"While we have got some more certainty about where the government is heading on this, for us it doesn't make a difference, we are still going to go ahead with our plans to open a subsidiary [inside the EU].
"What we need is the licensing and the regulatory ability to be able to provide insurance to the EU customers that we have. Without access to the single market we are not going to be able to continue to do that for some of our business from London as we have done, traditionally, for many years."
"The Prime Minister has provided important clarity ahead of the triggering of Article 50 and the start of formal Brexit negotiations. ADS will continue to support government as it seeks to secure an ambitious agreement with our EU partners that delivers barrier-free access to trade, skills and simplified regulatory regimes.
"Securing the best deal for the UK and our EU partners will take time and it is essential that there are transitional arrangements in place to avoid disrupting closely integrated supply chains and damaging the UK's global competitiveness."
"Today the prime minister changed the landscape. Ruling out membership of the Single Market has reduced options for maintaining a barrier-free trading relationship between the UK and the EU. But businesses will welcome the greater clarity and the ambition to create a more prosperous, open and global Britain, with the freest possible trade between the UK and the EU.
"The pressure is now on to deliver these objectives and achieve a smooth and orderly exit. Businesses want to make a success of Brexit but will be concerned about falling back on damaging WTO rules."
"We strongly welcome Theresa May's announcement that the UK will leave the Single Market and will not participate in the customs union in its current form. Leaving this protectionist union is the only way for the UK to maximise the economic benefits of leaving the EU, which, through the right policies, we estimate will deliver a 4% GDP Brexit dividend and will lead to consumer prices falling by 8%.
"In order to deliver this maximum economic benefit, it is crucial that the UK achieves a position of tariff free trade across the world as swiftly as possible, whilst avoiding a tit-for-tat tariff war with the EU which will harm consumers and postpone Brexit's economic benefits."
"In order for the government to lay the foundations of a globally competitive Britain, it must bring forward a clear and far-reaching industrial strategy that will enable businesses to seize the many expected opportunities the prime minister believes will arise after we leave the EU.
"In the end it's the detail of the final agreement that will matter and it is important that this will be open to parliamentary scrutiny. Parliament and business will want to see a very clear, evidence-based plan to ensure the UK economy avoids collateral damage arising from our departure."
"The recognition by the prime minister of the importance of single market arrangements for the automotive sector is critical. We need government to deliver a deal which includes participation in the customs union to help safeguard EU trade, trade that is tariff-free and avoids the non-tariff and regulatory barriers that would jeopardise investment, growth and consumer choice.
"Achieving this will not be easy and we must, at all costs, avoid a cliff-edge and reversion to WTO tariffs, which would threaten the viability of the industry."
"This is an aggressive move by the UK, showing little regard for our trading relationship and for relations with other EU member states. Theresa May has signalled a change to the UK business model, away from a collective European rules-based approach, towards a more nationalistic, isolated stance.
"This is likely to lead to a protracted and unwelcome period of uncertainty and instability for business. Ireland is uniquely exposed to the risks given out deep economic ties with the UK."

More than 70 business leaders have signed a letter to the Sunday Times calling for a public vote on the UK's Brexit deal.
The chief executive of Waterstones and former Sainsbury's boss Justin King are among those saying a "destructive hard Brexit" will damage the UK economy.
A group called Business for a People's Vote will launch on Thursday.
A Downing Street source told the BBC the Prime Minister was clear that there would be no new referendum.
The letter was coordinated by The People's Vote campaign, which wants a ballot on whether to accept the terms of the UK's departure from the European Union.
Richard Reed, co-founder of Innocent Drinks and Martha Lane Fox, the founder of Lastminute.com - who both campaigned for Remain - signed the letter, as did Lord Myners, the former chairman of Marks and Spencer.
It reads: "The business community was promised that, if the country voted to leave, there would continue to be frictionless trade with the EU and the certainty about future relations that we need to invest for the long term.
"Despite the Prime Minister's best efforts, the proposals being discussed by the government and the European Commission fall far short of this.
"The uncertainty over the past two years has already led to a slump in investment."
The letter concludes: "We are now facing either a blindfold or a destructive hard Brexit.
"Given that neither was on the ballot in 2016, we believe the ultimate choice should be handed back to the public with a People's Vote."
Waterstones chief executive James Daunt told the BBC: "All the paper we use is imported. We rely on just-in-time methods and now there are multiple uncertainties."
Prime Minister Theresa May has said asking the public to vote again would be a betrayal of the public's trust.
The Downing Street source told the BBC: "The Prime Minister has been clear - no second referendum.
"We had a people's vote, it was in June 2016."

The UK risks losing jobs and investment without an urgent Brexit transition deal, Britain's five biggest business lobby groups have warned.
In a joint letter being sent to Brexit Secretary David Davis, the groups including the CBI and Institute of Directors, say time is running out.
The head of the CBI said firms wanted an agreement on the transition period by the end of the year.
A government spokesman said the talks were "making real, tangible progress".
The other lobby groups backing the letter are the British Chambers of Commerce, the Federation of Small Businesses, and the EEF manufacturers' body.
CBI director-general Carolyn Fairbairn told the BBC: "One of the big messages from firms is 'get on with it' on both sides.
"This is real, this is urgent and a transition agreement by the end of the year would help enormously to keep investment and jobs in the country," she said.
Theresa May has suggested a transition period of about two years, with the UK and EU trading on broadly similar terms to now and payments to Brussels to meet Britain's budget commitments.
But although EU negotiators have agreed to start preliminary work on a future relationship, they still want more concessions on the UK's so-called "divorce payment" before starting talks on trade and transition.
The five business bodies - which together represent firms employing millions of people - are calling for more urgency, with less than a year and a half left until the UK leaves the European Union.
Concern about the loss of UK jobs and investment was underlined last week when the boss of investment banking giant Goldman Sachs, Lloyd Blankfein, tweeted that he will be "spending a lot more time" in Frankfurt.
Earlier this month, the deputy governor of the Bank of England, Sam Woods, warned that the UK and the EU must agree a transition deal by Christmas or companies would start triggering contingency plans.
And in a survey released on Monday, the EEF said that Brexit uncertainty was holding back the plans of manufacturing firms to invest in new plants and machinery.
Mr Davis is holding Brexit talks in Paris on Monday after France appeared to emerge as the most hardline EU member state when it comes to the divorce bill.
The prime minister is also due to update the Commons on the progress made during last week's summit of EU leaders in Brussels.
It is thought that Mrs May will say that negotiations are "deeply technical", but she has not forgotten that the lives of millions of people are at the heart of the process.
A spokesman for the Department for Exiting the European Union said the prime minister proposed a strictly time-limited implementation period in her Florence speech.
He said: "We are making real and tangible progress in a number of vital areas in negotiations. However, many of the issues that remain are linked to the discussions we need to have on our future relationship.
"That is why we are pleased that the EU has now agreed to start internal preparatory discussions on the framework for transitional arrangements as well as our future partnership."

Firms that rely on EU workers have warned of the "catastrophic" impact of proposals to slash unskilled migration on the day Britain leaves the EU.
Under the draft plan, leaked to the Guardian, firms would have to recruit locally unless they could prove an "economic need" to employ EU citizens.
They could face a skills tax to boost training of UK workers if they still chose to employ unskilled EU staff.
But business groups say a "sudden" cut could cause "massive disruption".
The National Farmers' Union claimed the "entire food supply chain" could be threatened.
NFU deputy president Minette Batters said: "We are calling for an urgent and clear commitment from government to ensure that farmers and growers have access to sufficient numbers of permanent and seasonal workers post-Brexit.
"And we need clarity on the new rules for EU nationals living and working in the UK well before free movement ends in March 2019."
The leaked Home Office document has not been signed off by ministers, who will set out their post-Brexit migration plans later this year.
But Defence Secretary Michael Fallon said: "The public voted to leave the European Union. That means freedom of movement has to end."
He said "people with the right skills" would still be "welcome".
But he added: "Equally we have to make sure that British companies are also prepared to train up British workers.
Analysis
BBC political editor Laura Kuenssberg
The prime minister has at least two big reasons for wanting to get this right.
For Theresa May, the referendum result was a clear instruction from the British people that they wanted to reduce the levels of immigration. Politically, therefore, she believes it's a demand she has to meet.
And as home secretary for six years, when the government continually flunked its own immigration target, the new system that will control immigration is finally, perhaps, a chance to meet her own long-missed goal.
So Wednesday's mega-leak from the Home Office of the potential design of the post Brexit system is significant. "The public are very clear, they want to see immigration not stopped but brought properly under control."
His message was echoed by Theresa May at Prime Minister's Questions, who told MPs immigration had to be cut to ease the strain on public services, adding that it "often hits those at the lower end of the income scale hardest in depressing their wages".
The EU has not issued an official response to the leaked document. Unnamed sources have told The Times the EU would block access to the single market during the transition period the UK wants after Brexit if it presses ahead with the proposals.
Michael Fallon said the government would take the views of business into account when drawing up its migration policy.
But business groups have hit back at his suggestion that they are using cheap foreign labour rather than training up British workers.
The British Hospitality Association said: "If these proposals are implemented it could be catastrophic for the UK hospitality industry and for those who enjoy the hospitality it brings."
The BHA claims 75% of waiters, 25% of chefs and 37% of housekeepers in the UK are EU nationals and at least 60,000 new EU workers are needed every year to fill vacancies.
The organisation said it would take 10 years to train up enough British workers to plug the gap and some businesses would fail in the meantime, "taking UK jobs with them".
Ian Wright, director general of the Food and Drink Federation, said: "If this does represent the government's thinking it shows a deep lack of understanding of the vital contribution that EU migrant workers make - at all skill levels - across the food chain."
A trade body representing Britain's manufacturers, the EEF described the leaked proposals as a "mixed bag".
"On the highly skilled side, the system described is one we can work with, after some changes," a spokesman said, but it had "grave concerns" about low-skilled workers, "with many UK manufacturers telling us that they simply don't get jobs applications from prospective UK workers".
The Home Office document obtained by the Guardian, entitled the Border, Immigration and Citizenship System After the UK Leaves the EU, is marked extremely sensitive and dated August 2017.
Among the ideas in it are:
"The government will take a view on the economic and social needs of the country as regards EU migration, rather than leaving this decision entirely to those wishing to come here and employers," the document states.
Low-skilled migrants would be offered residency for a maximum of two years while those in "high-skilled occupations" would be granted permits to work for a longer period of three to five years.
EU citizens coming as tourists, on short-term business trips or visits to friends and family would be able to enter the UK without needing permission, under the draft proposals.
Those staying longer would need to register for a residence permit by showing proof of employment, study or self-sufficiency. Applicants' fingerprints could also be taken.
The document says the new regime would only come fully into force at the end of a transition period, which could last up to three years.
The proposals would not affect EU nationals already living and working in the UK - the government says they should be given the right to apply for "settled status" after five years of being lawful residents, although agreement on this has yet to be reached in Brexit talks.
The leaked document says: "Put plainly, this means that, to be considered valuable to the country as a whole, immigration should benefit not just the migrants themselves but also make existing residents better off."
Sources have told the BBC that the proposals have been updated six times since the leaked document was written in August and although the broad principles in it are correct, it has yet to be discussed by the cabinet.
Lord Green, of the Migration Watch pressure group, said: "These proposals rightly focus on low-skilled migration and by doing so could reduce net migration from the EU by 100,000 a year over time."
UKIP also welcomed the proposals, saying they should be implemented "without fudging" - but Labour MP Yvette Cooper said they appeared to fly in the face of Home Secretary Amber Rudd's commitment earlier this summer to consult on a post-Brexit immigration system.
The TUC said the "back of the envelope plans" would "create an underground economy, encouraging bad bosses to exploit migrants and undercut decent employers offering good jobs".
Lib Dem leader Sir Vince Cable claimed Theresa May had suppressed "up to nine reports" showing immigration did not hit the wages or jobs of existing UK workers when she was home secretary - claims denied by Downing Street.
Italy's minister for European Affairs, Sandro Gozi, has described the proposals as "very restrictive and unacceptable".
He told the BBC News Channel that it was "the wrong direction in our analysis" and "we won't be ready to negotiate along those lines".

The cabinet has decided to "ramp up" preparations for a no-deal Brexit amid uncertainty over the fate of Theresa May's proposed EU exit deal.
It allocated to ministries £2bn set aside in case the UK leaves on 29 March without MPs having accepted any deal.
Letters will be sent to 140,000 firms updating them on what they should do while 3,500 troops will be put on standby to help government departments.
Lib Dem leader Sir Vince Cable said it amounted to "psychological warfare".
With 101 days left until Brexit and many MPs still opposed to the government's withdrawal agreement, which MPs will vote on in mid-January, ministers met for a longer-than-normal two and a half hour meeting.
They agreed that businesses should activate their own no deal contingency plans, as they think appropriate.
Updated Revenue and Customs information packs will be sent to firms later this week, setting out what changes could be needed at the border.
Consumers are being advised to familiarise themselves with advice published this summer, in areas ranging from booking flights to using credit cards, with more details promised in the coming weeks.
The Treasury said £480m of the £2bn of preparation funding would go to the Home Office, helping it to employ more Border Force officers and boost national security.
Defra would receive £410m, allowing it to focus on ensuring the trade in fish, food products and chemicals remains uninterrupted.
HMRC, which is being allocated £375m, plans to hire more than 3,000 new staff to handle increases in customs activities, as well as investing in new technology at borders.
The next largest allocations will be £190m for the Department for Business and £128m for the Department for International Trade.
Separately, Defence Secretary Gavin Williamson has told MPs that 3,500 military personnel, including logisticians and engineers as well as infantry units, were ready to be deployed if needed.
About 10% of the force would be reservists who will receive their call up papers in the middle of January so that if needed they would be ready in March.
In other developments:
Brexit Secretary Stephen Barclay said the cabinet had agreed that "preparing for a no deal will be an operational priority within government but our overall priority is to secure a deal".
He said no-deal planning "needs to be much more of a priority for businesses" and there would be a "significant increase" in the guidance issued to them over the next 14 weeks, as Brexit day approaches.
E-mails will be sent out to 80,000 of those businesses most like to be affected over the next few days.
In the autumn of 2017, The Treasury earmarked £3bn for no-deal planning between 2018 and 2020.
In March, Chancellor Philip Hammond said half of that had been allocated to 20 government departments, with the Home Office, transport, the environment and business among the largest recipients.
At Tuesday's cabinet meeting ministers approved the second tranche - plus an under-spend from the current year - to go to departments for the 2019/20 year, with the priority areas being borders, security and international trade.
Health Secretary Matt Hancock has already ordered full "no deal" planning across the National Health Service, he told the BBC's Newsnight on Monday.
But Guy Verhofstadt, the European Parliament's Brexit negotiator, criticised UK ministers, who he said were "glorifying" the prospect of leaving without a comprehensive deal in the hope individual agreements could be reached in areas like transport and livestock movements.
And Labour said a no-deal exit was "not viable" and it would work with other parties to stop it.
"It is testament to the prime minister's failure in these negotiations that the government is now spending billions of pounds of taxpayers' money to prepare for a no-deal Brexit that is rejected by Parliament and many of those sat around the Cabinet table," said shadow Brexit minister Jenny Chapman.
And the Lib Dems, who are campaigning for another referendum, said the government was "attempting to scare" MPs, businesses and the public with the threat of a no-deal.
"Theresa May is irresponsibly trying to run down the clock so that the only option is to support her discredited deal," Sir Vince Cable said.
MPs will vote on the prime minister's Brexit deal, which sets out the terms of Britain's exit from the EU and includes a declaration on the outline of the future relations, in the middle of January.
The deal will only come into force if both the UK and European parliaments approve it.
The BBC understands Mrs May is planning to use the Commons vote as a "moment of reckoning" for the Brexit process.
Sources have told the BBC that Downing Street will not stand in the way of MPs who seek to amend the government's motion on the Brexit deal to put forward potential alternatives.
The prime minister was previously thought to be against this idea.
Meanwhile, Jeremy Corbyn is under pressure to push for a further vote of no-confidence in the government as a whole.
On Monday night, the Labour leader tabled a motion calling on MPs to declare they have no confidence in the prime minister because she failed to have a vote on her Brexit deal straight away.
No 10 has refused to make time for the motion and Commons Speaker John Bercow confirmed on Tuesday that there were under no obligation to do so.
Other parties - the SNP, Lib Dems, Plaid Cymru and the Greens - have called on Mr Corbyn to push for a no-confidence vote against the government as a whole.
Unlike a vote aimed at the prime minister, the government would have to allow a vote on this motion and, if successful, it could force a general election.
Northern Ireland's DUP, whose votes the Conservative government has relied on in big votes since the June 2017 election, said they would not support Labour.
Mrs May also appeared to have the support of pro-Brexit backbench critics who last week failed in a bid to oust her as Tory leader.
One of them, Jacob Rees-Mogg, said he would never vote against Mrs May or a Conservative government. He said on Tuesday evening that he had a "civilised and courteous" meeting with the PM, and that the government was "prudent" to engage in no-deal planning.

The cabinet has reached a "collective" agreement on the basis of the UK's future relationship with the EU after Brexit, Theresa May has said.
Ministers have signed up to a plan to create a free trade area for industrial and agricultural goods with the bloc, based on a "common rule book".
They also supported what could amount to a "combined customs territory".
The BBC's Laura Kuenssberg said the plan, agreed after a 12-hour meeting, would "anger many Tory Brexiteers".
Our political editor said the prime minister had "picked a side" by opting for a closer relationship with the EU than many colleagues desired - and she now had to sell it to her party and the other European leaders.
No 10, she added, hoped the new commitments would unlock the next phase of talks with the rest of the EU but it was not yet clear how many, or what kind, of objections were raised.
Downing Street said the proposals marked a "substantial evolution" in the UK's position and would resolve outstanding concerns about the future of the border between Northern Ireland and the Irish Republic.
"This is a proposal that I believe will be good for the UK and good for the EU, and I look forward to it being received positively," Mrs May told the BBC.
One pro-Brexit cabinet minister told the BBC there was "no point" pushing for a vote as "we were well and truly outnumbered by 20 to seven".
Nicholas Watt, political editor of BBC Newsnight, said the minister also warned that "it will be a problem" if there is any attempt to "water down plans even further" should the EU reject the UK's proposals.
The UK said it now wanted to accelerate the negotiations in an effort to secure an agreement by October, but also warned it will step up preparations for leaving on 29 March 2019 without a deal.
The EU's negotiator Michel Barnier, who earlier suggested the EU would be willing to shift its position if the UK relaxed some of its "red lines", tweeted his reaction:
The prime minister had gathered her 26 cabinet ministers together at her country residence to try and resolve differences over the shape of the UK's relations with the EU and break the current deadlock with the EU.
The main details of the Chequers statement are as follows:
Mrs May said this was an "important step" in the process of negotiating the UK's smooth exit from the EU.
"Of course we still have work to do with the EU in ensuring that we get to that end point in October. But this is good we have come today, following our detailed discussions, to a positive future for the UK," she said.
She said the proposals, to be formally published in a white paper next week, would give the UK the freedom to strike trade deals with other countries while maintaining regulatory, environmental and consumer standards.
In a letter sent to all Conservative MPs, she said she had allowed colleagues to express their views while policy was developed but "agreement on this proposal marks the point where this is no longer the case and collective responsibility is fully restored".
There is no mention in the document of either the single market or the customs union, which the UK has committed to leave after the end of a transition period in December 2020.
Under plans for a free trade zone, the UK would be committed legally to following EU law for a large part of the economy, including manufacturing and farming.
While Parliament would retain the right to diverge from EU regulations in these areas, the document makes clear that "choosing not to pass the relevant legislation would have consequences for market access, security co-operation or the frictionless border".
The document also commits the government to step up preparedness for a no-deal scenario, as one of a range of possible outcomes, "given the short period remaining before the necessary conclusion of negotiations".
The CBI employers group welcomed the proposals for a free trade area in goods which it said would provide a "confidence boost" to business.
Shadow international trade secretary Barry Gardiner said there was "a danger that this is a lowest common denominator plan" designed to hold the cabinet together, rather than "secure the strong negotiating position that we need with the EU".
He told BBC Radio 4's Today programme: "Once upon a time we were told 'Brexit means Brexit', now we are told it means maintaining a common rulebook for all goods, a joint institutional framework for interpreting the agreement and the UK and EU forming this combined customs territory.
"That looks very much like regulatory alignment, the ECJ (European Court of Justice) and half a customs union to me."
Transport Secretary Chris Grayling, who backed Brexit in the referendum, said the deal would end free movement of people and would end the remit of the European Court of Justice in the UK - saying that UK judges always pay regards to other countries' courts, such as Canada or Hong Kong.
He added, on BBC Radio 4's Today programme, that the cabinet had agreed to step up preparations for the UK leaving the EU without a Brexit deal.
Fellow cabinet Brexiteer Andrea Leadsom also tweeted her backing for the deal:
Leading Tory backbench Brexiteer, Jacob Rees-Mogg told the same programme that it was difficult to say whether or not the agreement was meeting the party's manifesto commitments on Brexit because he had seen only a three page summary rather than the full 100-plus page document.
He said it was "possible", when the detail emerged, that the proposal could be "worse than no deal".
And Sir Vince Cable, leader of the Liberal Democrats, said it could be the case that "Brexiteers have signed up to it knowing perfectly well that it is not going to pass the European Union and they'll then be able to blame Europe for the fact that it won't work".
Pro-Brexit campaign group Leave Means Leave said it would represent a "bad deal for the UK" which would "only slide further as the EU takes more and more".
Former UKIP leader Nigel Farage said the plan amounted to a "sell-out to global corporates" and would do nothing for the 90% of British firms which do not export to Europe.
Veteran Eurosceptic Tory MP Sir Bill Cash said he was "deeply disappointed to say the least" about the plans, which he suggested could contradict the terms of the EU Withdrawal Act passed by MPs last month.

The cabinet has backed a draft withdrawal agreement between the UK and the EU, Theresa May has said.
The prime minister was speaking after what she said was a "long, detailed and impassioned debate" in a five-hour cabinet meeting.
She said it was a "decisive step" in the progress of Brexit, and would allow the agreement to be finalised.
The EU's chief negotiator said it was in both sides' interests.
But leading Brexiteer Jacob Rees-Mogg described it as a "rotten deal".
BBC political editor Laura Kuenssberg said the cabinet was "certainly not unanimous", with nine ministers speaking out against the deal.
In her statement outside Downing Street, Mrs May said the agreed package was "the result of thousands of hours of hard negotiation with EU officials".
She believed that "this decisive choice is in the best interests of the entire UK", adding: "When you strip away the detail, the choice before us is clear.
"This deal, which delivers on the vote of the referendum, which brings back control of our money, laws and borders, ends free movement, protects jobs, security and our Union; or leave with no deal, or no Brexit at all."
The 585-page draft withdrawal agreement has now been published, alongside a shorter statement setting out what the UK and EU's future relations will look like.
The withdrawal agreement covers so-called "divorce" issues. It includes a commitment to protect the rights of EU nationals in the UK and Britons living in the EU to continue living, working and studying.
There is also a planned 21-month transition period after the UK leaves the EU in March 2019, and a "financial settlement" from the UK, thought to be between £35bn and £39bn.
The most contentious part of the negotiations is a "backstop", which aims to guarantee that physical checks will not be reintroduced at the border with the Irish Republic, in the event this is not settled by a UK-EU trade deal.
Both sides have resolved to ensure the backstop is not necessary by coming up with alternative arrangements.
Speaking at a press conference, EU negotiator Michel Barnier said if this is not possible by July 2020, the transition period could be extended - and if it is still not settled by the end of the transition, the backstop would "kick in".
This would involve a joint UK-EU "single customs territory", so customs checks are not needed on the border.
Northern Ireland would stay aligned to the EU single market rules that are "essential for the avoidance of a hard border", Mr Barnier added, saying the backstop plan was based on the UK's proposal.
Labour leader Jeremy Corbyn said he did not think the agreement was in the national interest because it "doesn't meet the needs of all parts of Britain".
Labour would reveal during Thursday morning's Commons statement whether it will vote against the agreement, he said.
Some Tory MPs are angry, claiming it could mean the UK is tied to EU rules for years to come.
Earlier a senior Conservative told the BBC there could be a move to a vote of no-confidence in Mrs May, perhaps as soon as Thursday,
Meanwhile Mr Rees-Mogg, who has written to MPs urging them to oppose the proposals, told BBC Radio 5 Live it was "a pretty rotten deal", keeping the UK in the EU's customs union and "splitting up" the UK.
Despite winning the backing of her cabinet, the prime minister faces a battle to get the completed deal through Parliament.
Northern Ireland's Democratic Unionist Party - which gives the government the support it needs to win key votes - has joined opposition parties in criticising it.
Senior DUP figures spent an hour in Theresa May's office after the publication of the draft text.
Scotland's First Minister Nicola Sturgeon said: "This proposed deal would be a bad one for Scotland, taking us out of a single market eight times the size of the UK market alone and posing a huge threat to jobs, investment and living standards."
Theresa May is sure to face some hostile questioning when she faces MPs' questions on Thursday.
Meanwhile, the EU has said "decisive progress" has now been made in the negotiations.
This was the test required before it would call a special summit to agree the withdrawal plans, possibly later this month.
After that, the government faces a crunch vote in Parliament where MPs will be asked to approve the plans.
The UK is set to leave the EU on 29 March 2019 - at which point, if the withdrawal agreement has been ratified, the transition period begins.
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Cabinet ministers are meeting at Chequers in a bid to thrash out an agreement on the shape of the UK's future relationship with the EU.
Theresa May has said they have "a duty" to reach agreement on Friday, amid splits over how closely the UK should stick to EU rules after Brexit.
She is expected to propose keeping the UK aligned with the EU on trading rules for goods but not services.
An ex-minister warned that would mean "something less than the full Brexit".
If ministers reach an agreement, the EU can then choose to accept or reject their proposals.
Speaking on Friday, the EU's Brexit negotiator Michel Barnier said it was "ready to adapt our offer should the UK's red lines change" but insisted there could be no "unravelling" of the single market.
Ministers are expected to be at Chequers, a 16th Century house in Buckinghamshire which is the PM's country residence, until about 22.00 GMT. They had to hand in their phones and any smartwatches on arrival.
Cabinet Office Minister David Lidington said the proposal would include a common rulebook on some sectors - like industrial goods and agricultural goods - for "practical" supply chain reasons.
He told BBC Radio 4's Today programme: "I'm pretty confident we will end up with a concrete position which everybody is able to sign up to."
But Brexiteer ministers are understood to be unhappy. Seven cabinet ministers met at the Foreign Office on Thursday evening to discuss the proposal.
There have also been suggestions that the prime minister's proposal would make a US trade deal more difficult. No 10 says it is "categorically untrue that we will not be able to strike a trade deal with the US".
David Jones, a former minister at the Department for Exiting the EU, said Mrs May's proposal looked set to breach her "red lines" on leaving the customs union, single market and jurisdiction of the European Court of Justice.
BBC Political Editor Laura Kuenssberg
If this was easy, Theresa May would not need the cloistered environment of Chequers to get her cabinet to agree. She would not need the tranquil quiet of the Buckinghamshire countryside to broker peace.
She is vulnerable because her plan is hardly Brexit to some of those who campaigned to leave.
Vulnerable in her party because her authority is in short supply and there is intense disagreement. Vulnerable then in Parliament because without a majority, a small faction can wreak havoc on either side.
Ahead of the meeting, Mrs May said the cabinet had "a great opportunity - and a duty. To set an ambitious course to enhance our prosperity and security outside the European Union - and to build a country that genuinely works for everyone".
Labour's Sir Keir Starmer said a workable agreement that could be taken to the EU was needed and "simply a truce in the cabinet was not good enough for Britain".
Scottish First Minister Nicola Sturgeon said time was running out for the UK and the worst outcome would be ministers emerging "arm in arm, saying they've agreed, because that means there's another helping of fudge being served up and what is being put forward is likely to be rejected by Europe".
Meanwhile sources close to David Cameron confirmed the former PM met Boris Johnson on Thursday and discussed Brexit.
But they said there was "no grand view" on the negotiations and disputed reports Mr Cameron had agreed that Theresa May's plan was the "worst of all worlds".
There have been differing views within the cabinet about how closely the UK should stick to EU rules after Brexit, and what compromises should be made to achieve "as frictionless as possible" trade.
The aim is to agree a UK proposal on how future relations should work on Friday, the details of which would then be published in a White Paper net week.
That would then be the subject of negotiations with the EU - which might have different ideas.
Ministers have yet to agree what they want to replace the UK's membership of the EU's customs union, which allows for tariff-free trading between members.
One of the key issues is the need to avoid new border checks between Northern Ireland and the Republic of Ireland when the UK is outside the customs union.
The EU and UK say there can be no return to a hard border. But Eurosceptic MPs say tying the UK to the EU after it leaves will prevent it from striking its own trade deals with other countries.
Meanwhile 46 other Conservative MPs have urged Mrs May to listen to businesses and target a deal which enables "frictionless trade to continue".
The "facilitated customs arrangement" is understood to be a proposal for a post-Brexit customs agreement which would allow the UK the freedom to set its own tariffs on goods arriving into the country.
Technology would be used to determine where the goods will ultimately end up - and therefore whether UK or EU tariffs should be paid.
It would keep the UK aligned to EU regulations in some sectors- such as industrial and agricultural goods - but Parliament would be able to decide where to deviate.
The 120-page plan is also understood to propose an end to the free movement of people but to say the UK would have to accept the jurisdiction of the European Court of Justice in some areas.
Details of how the plan would work in practice have yet to be published. But Downing Street says it is confident the arrangement would be partly in place by the end of the proposed transition period in December 2020 - with the system being fully operational by the next general election, due in 2022.
It is not clear whether the EU will agree to it.
The UK is due to leave the European Union at 23:00 GMT on 29 March 2019.
But to allow time for parliaments in the UK and the EU to approve whatever deal is agreed, the aim is for the framework for future relations to be agreed this autumn.
But the UK government has not, as yet, settled on what its post-Brexit relationship with the EU should look like.
EU leaders last week told Mrs May it was time to "lay the cards on the table" if a Brexit deal was to be done on time.
Businesses, including Jaguar Land Rover, Airbus and BMW, have also been stepping up the pressure on the government to provide more detail.

"We're still blathering about the state of the party, not the country."
"It's like the last days of Rome." "It's chaos."
On the outside, the government is poised to send a letter to the European Union ahead of talks in Brussels at some point tomorrow, with the final draft likely to be completed in the morning by the prime minister and her team of advisers.
The letter will spell out the kind of delay the government is seeking to the Brexit process.
The delay, and the next steps in our departure, were the subject of a 90-minute discussion at cabinet this morning.
But ministers and advisers on the inside have a rather different view of what's going on.
The cabinet is still split, with some ministers who believe that a long delay is needed.
So, as one outlined today that the "best thing for the country is for someone else to grab control of the order paper and move to a customs union" - translated, push for a long pause on Brexit so that Parliament can wrangle its way to a softer Brexit.
Others, like the leader of the House, who sources say argued the case with force today, believe that the government should ask for a short delay, then ramp up to leave without a formal arrangement with the EU, having had more time to prepare.
One minister who was in the room suggested the prime minister gave the impression that she would ask the EU for an extension to the end of June, with the option of (you guessed it) a "backstop" option of a delay of up to two years.
But another minister said they left the meeting with the view that there had, in fact, been no judgement really made at all.
Another insider was boiling with frustration that, in their view, yet again, Theresa May was failing to express what she actually wants to do clearly, and allowing the Tory Party, and of course Parliament - and more importantly the rest of the country - twist in the wind while she grinds on.
There is also, as ever, a less theological group of ministers who are trying to help manage the competing factions, although some of their colleagues on the backbenches believe they are just passive passengers.
Just in case you needed reminding, delaying Brexit at all goes against the promise that Mrs May made so many times.
And how long for is of course a question of massive significance to the country, and also, may have a bearing on whether the government has a real chance of finally ramming its EU compromise deal through Parliament before too long.
It is still possible that could happen, and when it does, happen rather fast.
But the latest cabinet nightmare over the delay tests almost to destruction the notion that this administration finds it almost impossible to reach meaningful conclusions on Brexit, so profound are the divisions inside.
Officially, Downing Street sources denied there was any firm conclusion of timelines, although the prime minister has said on many occasions she wants it done as soon as possible and has mentioned the short "technical" extension of 30 June many times.
They say there has been no final decision.
For Mrs May's growing number of critics in her own government, that is exactly the point.

The government says "progress needs to be made urgently" on Brexit talks with Labour - but that arranging time with the opposition has been "difficult".
Senior figures from both sides have been trying to break the deadlock by agreeing a Brexit deal MPs can support.
No 10 said talks had "been difficult in some areas", including "timetabling".
But Labour leader Jeremy Corbyn said the government "really needs to move on" and change its Brexit agreement to solve the impasse.
He said: "We cannot go on hearing this tired old mantra that the Brexit agreement has to be adhered to."
The deal Theresa May negotiated with the EU has been rejected twice by Parliament, with the withdrawal agreement - the terms on how the UK leaves the bloc, rather than its future relationship with it - defeated a further time.
Weeks of talks resumed between the two parties in Westminster on Tuesday afternoon following the Easter break.
Mrs May's de facto deputy David Lidington was expected to lead for the government.
Shadow Brexit secretary Keir Starmer, shadow chancellor John McDonnell, shadow business secretary Rebecca Long-Bailey and shadow environment secretary Sue Hayman took part on behalf of Labour.
Ahead of the meeting, Sir Keir said "fundamental issues" remained between his party and ministers on a number of key issues.
Some Tory MPs are angry the discussions with Labour are even taking place.
Leading backbencher Nigel Evans called on Mrs May to step down as prime minister "as soon as possible", adding that the PM "had been reaching out to the Labour Party and Jeremy Corbyn, when she should have been reaching out to the people".
Talks between Labour and the government seem to be faltering on two fronts - timing and substance.
Both sides say there has been serious engagement.
But the prime minister wants the talks concluded urgently to give her a chance of cancelling the UK's participation in the European parliamentary elections.
That means getting a deal through Parliament by 22 May.
If it looks like an agreement can't be reached with the opposition quickly, Theresa May wants them jointly to sign up to a series of parliamentary votes that both sides would regard as binding, to try to break the impasse.
But Labour doesn't appear willing to be rushed.
And the main opposition party says Mrs May still needs to erase her red line on a customs union if she is to make progress.
Sources say the issue was discussed at the cabinet today - but, while no votes were taken, there didn't seem to be a majority in favour of doing so.
As things stand, the Brexit deadlock continues - and the European election campaigns are getting under way.
Senior members of the influential 1922 committee of Tory MPs are meeting in Parliament.
Under current party rules, MPs cannot call another no-confidence vote in the prime minister until December - but the committee is expected to discuss whether steps should be taken to try to change that.
The group's joint executive secretary Mr Evans told BBC Radio 4's Today programme the calls for the prime minister to quit had become "a clamour".
"The only way we're going to break this impasse properly is if we have fresh leadership of the Conservative Party," he said.
But prisons minister Rory Stewart said Mrs May was doing a "good job" and deserved "praise not blame".
"It's nothing to do with the individual, it's that people disagree deeply about Brexit," he added.
The comments came after it emerged that Mrs May faces a no-confidence challenge from Tory campaigners.
More than 70 local association chiefs have called for an extraordinary general meeting to discuss her leadership and a non-binding vote is to be held at the National Conservative Convention EGM in May.
If the grass-roots Tory vote showed a lack of confidence - it could put greater pressure on the 1922 Committee to find some way of forcibly removing the PM from office.
That pressure could increase further if the Tories poll badly in local and European elections on 2 and 23 May respectively.
The UK has been given an extension to the Brexit process until 31 October.
Change UK has launched its European election campaign in Bristol, while Nigel Farage's Brexit Party has unveiled more of its candidates in London.

British expats who want Brexit to be halted because of "corrupt practices" during the 2016 referendum have had their case heard in the High Court.
The UK in EU Challenge group says the result should be quashed because of "misconduct" by pro-Leave campaigners.
Mr Justice Ouseley's decision is expected on either Monday or Tuesday.
An earlier attempt to challenge the result was rejected on the grounds that it had not been proven that any wrongdoing affected the vote's outcome.
The case is being brought against the government by four British citizens living on the European continent, Susan Wilson, Elinore Gayson, Carole-Anne Richards and John Shaw.
They say the Article 50 process, by which the UK is leaving the EU, should be halted due to breaches of spending limits and other irregularities by leave-supporting groups during the referendum.
Lawyers for the group say the infractions, which resulted in Vote Leave and Leave.EU being fined £61,000 and £70,000 respectively by the Electoral Commission earlier this year, cast doubt on the legitimacy of the result under the terms of the 1983 Representation of The People Act.
Speaking after the hearing, Susan Wilson said she was hopeful of success.
"We also maintain our firm belief that the referendum result cannot be considered the 'will of the people'," she said.
"The Leave campaign's fraudulent behaviour has been proven by the Electoral Commission and we are continually frustrated that the government fails to acknowledge the impact of this illegality and continues to defend its position."
The campaigners' written arguments were dismissed at a preliminary hearing in September, when Mr Justice Supperstone ruled that the electoral watchdog, in punishing the two leave campaigns, had not established that the referendum result had been "procured by fraud".
Friday's oral hearing enabled the group to make their case in person.
If he decides to grant a judicial review, the campaigners have asked for it be expedited, saying it is a "matter of urgency" the matter is dealt with before the UK's scheduled departure on 29 March 2019.
Government lawyers say Theresa May did not act unlawfully when she triggered Article 50 in March 2017, since that although the Electoral Commission investigations were a matter of public record at the time, their findings that campaign violations had occurred were not known until over a year later.
They also argue there is no evidence of a "causal effect" between breaches of campaign rules and the outcome of the referendum - which saw a 51.9% to 48.1% vote in favour of leaving the EU.
The prime minister has said the referendum was the biggest democratic exercise in UK history, with more than 33 million people taking part, and it is her duty to implement the peoples' wishes.
The official remain campaign, Britain Stronger in Europe, was fined £1,250 last year for not declaring certain invoices correctly while the Liberal Democrats, which backed staying in the EU, were fined £18,000 for not providing acceptable invoices or receipts for 80 payments.
In a separate case, the European Court of Justice will rule on Monday whether the UK has the right to unilaterally rescind Article 50 without the say-so of the EU's 27 other members.

Theresa May's deal has not just been defeated - her plan for her main mission as leader of the country has been crushed by an alliance of her critics who don't even agree amongst themselves.
Now she has another ordeal - an official vote of no confidence in her government being mounted by the opposition party.
That is a legal attempt to push the government to collapse into a general election.
On the runes tonight, it seems unlikely that it will force her into that, but she can't be absolutely sure.
One of the reasons No 10 has found themselves in this desperate position is because their judgements have been the wrong ones on so many occasions so far.
She promised MPs tonight that if she survives the confidence vote, then there will be an attempt to listen to what MPs really want - an effort, at this very late stage, to find common cause in Parliament.
But her team has been quick tonight to suggest that, while she is promising to listen, she has no inkling at this stage of dropping her own firm commitments - making it clear that she wants to stick to setting an independent trade policy, which so far shuts down a chance of moving to a Labour-friendly customs union.
It doesn't sound tonight like she has any enthusiasm for junking her deal. Indeed, a source that was on a conference call with business leaders - hosted by the chancellor and other cabinet ministers - was told they could not renegotiate the Withdrawal Agreement.
The plan instead was for a "shake down" of MPs in the next few days to find out what they would tolerate in terms of promises for the longer term future relationship.
As we've discussed here before, the Cabinet doesn't even have a clear view itself on how she should proceed.
Today, the leader of the House of Commons told me it would be Brussels that has to move. But some others are crystal clear that the PM will have to soften her offer, because that's what Parliament will tolerate.
History was made tonight with the scale of this defeat - a higher figure than the wildest of numbers that were gossiped about before the vote.
But the prime minister's dilemma is a more serious version of the same it's always been.
She has no majority of her own in Parliament to make her middle way through stick. And her many critics don't agree on the direction she should take - a more dramatic break with the EU, or a tighter, softer version.
Those two fundamental and clashing positions have always threatened to pull her and the government apart.
Even the PM's allies would acknowledge that the government has made plenty of mistakes.
But that widespread disagreement across the spectrum is Mrs May's nightmare that, right now, is a bad dream without end.

Now the Brexit deal has been signed off in Brussels, attention turns to Westminster.
MPs will get their say on whether they approve of the deal or not. Several days of debate will be followed by what's known as the "meaningful vote". This is expected to take place in the week beginning 10 December.
Any attempt to work out the parliamentary arithmetic can only be an estimate so all numbers should be treated with caution. As things stand, though, there seems to be a majority against the proposed deal.
Theresa May relies on the 10 Democratic Unionist Party MPs for her majority in the House of Commons. Their opposition to the proposed deal alone could make winning the vote tricky but the prime minister's problems don't end there.
Some 57 Conservative MPs have signed up to the StandUp4Brexit campaign which argues that the proposed deal leaves the UK too close to the EU. (That includes Charlie Elphicke who is currently suspended from the party but generally votes with the government.)
Added to those are the seven pro-Brexit MPs who resigned from government or party jobs on 15 November. And several more who have publicly stated they are opposed to the deal.
Then there are, perhaps, a further dozen or so Conservative MPs from the Remain wing of the party who support the People's Vote campaign for another referendum or would like a closer relationship with the EU.
All in all, there are around 80-90 Tories currently set to defy the government.
Some of them have only said they can't support the deal which, perhaps, suggests, they might abstain when it comes to the crucial vote. But others are more hardline.
On the other side of the calculation, there are a handful of pro-Brexit Labour MPs who might back the deal. And a further group who could vote for it to stop the possible alternative of a "no deal" Brexit.
There's also one Liberal Democrat MP, Stephen Lloyd, who says he'll vote in favour of the deal to fulfil a pledge he made to his constituents.
As things stand, though, this group isn't big enough to outweigh the DUP and Conservative rebels.
Things can change of course. Mrs May will hope to persuade some of the rebels and more opposition MPs. But she has a long way to go.

Sir Oliver Letwin told BBC News on Wednesday morning: "I think it should be possible to forge an arrangement in which we do have frictionless trade in a customs union, for the time being at least."
At the moment, the UK has frictionless trade with other European Union (EU) countries because the EU is both a single market and a customs union.
The customs union means that once goods have cleared customs in one country and the commonly agreed tariffs (charges on imports) have been paid, they can be shipped to others in the union without further tariffs being imposed.
The single-market part means that there is free movement of goods, services, capital and people and all the members follow the same rules, regulations and standards.
Having just one or the other does not give you frictionless trade.
Turkey, for example, has a customs union with the EU, covering most manufactured goods, but is not part of the single market.
The border between Turkey and Bulgaria is far from frictionless. Documentation is needed to cross the border, including things such as export licences, invoices and transport permits.
A report prepared for the European Commission in 2014 suggested a waiting time of about three hours for lorries travelling from Turkey to Bulgaria - but, anecdotally, lorry drivers say they sometimes have to wait for more than 24 hours, in queues several kilometres long.
Norway is part of the single market but not part of the EU or its customs union.
That means that goods exported from Norway into the EU must meet rules of origin requirements, to demonstrate that they do not contain more than the maximum permitted level of parts and components from elsewhere.
Norway's border with Sweden, for example, is one of the most frictionless in the world between two countries that do not have a customs union - but it still takes about 20 minutes on average for a lorry to pass through its main border crossing, at Svinesund.
Sir Oliver told BBC Reality Check: "I am of course assuming that the Chequers arrangement for a single market in goods is also part of the deal, as both Mr Corbyn and Mrs May will wish it to be."
While Theresa May's Chequers agreement did indeed suggest a common rulebook on goods, the political declaration that sets out the starting point for the negotiations on a future relationship says that trade in goods should be "as close as possible", which is not the same as being frictionless.


Major suppliers to care homes and hospitals are stockpiling food to offset the potential disruption of a no-deal Brexit.
Apetito and Bidfood, who between them supply thousands of care providers, said they were holding extra inventory in case of supply chain problems.
Both said they were prepared but Apetito said it feared others were not.
"We are in a strong position," said Apetito UK boss Paul Freeston.
"But some firms would not be able to build up big stocks," like his firm, he said. "Or if they are doing fresh produce they would have to stop. A Hard Brexit could cause them significant economic difficulties."
Apetito provides pre-made meals to more than 400 hospitals and 450 care homes, as well as 100,000 vulnerable people in their homes.
Mr Freeston said it was spending £5m in building its inventory ahead of Brexit - doubling the raw materials it holds from four to eight weeks' of stock and pre-made meals from five to six weeks'.
But if the disruption lasted much longer than 12 to 16 weeks, the firm would have "very real difficulties", because it supplies specialist food for elderly people and those with critical conditions.
But if there are backlogs at UK ports in the event of a no-deal, "the quality of food could suffer and our product range would really narrow", Mr Freeston said.
The other worry is that if the UK suddenly started trading on World Trade Organisation terms with the EU, the cost of raw materials could jump - and Britain imports about a third of its food from the bloc.
The concerns are shared by Bidfood, which supplies the kitchens of 4,000 care homes and 950 hospitals across the UK, as well as schools and prisons.
Jim Gouldie, its supply chain and technical services director, said the firm had "looked carefully" at products needed by sectors with a "duty of care" and invested in additional warehousing.
Meanwhile Anglia Crown, which manufactures meals for 100 hospital sites, told the BBC it was worried about prices rising after Brexit. A spokeswoman said the company was agreeing prices for "as many commodities as possible, especially any bought in from Europe".
Despite the warnings, the National Care Association said most of the care homes it represents are prepared for any no-deal disruption and have enough food stocks in place - even if that means relying on dried or canned food to carry them through.
But boss Nadra Ahmed is worried that any price shocks to suppliers could end up being passed on to providers.
"Care providers are struggling with funding and recruitment issues already so any increases will increase the challenges they face."
The Hospital Caterers Association (HCA), which represents hospital catering companies, says most of his members have been preparing for Brexit for some time. And while he is not overly worried about a no deal, he does expect some short term volatility after Brexit.
"A number are making arrangements to increase their stock holding - either on site or by securing commitments from their long-established suppliers," he says.
"But this clearly is not possible for perishable goods. It is imperative that we ensure continuity of supply to minimise any potential disruption to patients' menus."
A government spokesperson said: "Our priority is to make sure that patients continue to receive the same high standard of care.
"We are working closely with the NHS, Defra and healthcare providers to ensure the uninterrupted supply of food and specialised nutritional products to patients, as part of our preparations for a no-deal EU Exit."

Justice Secretary David Gauke has become the second cabinet minister to suggest Parliament could be given free votes on some Brexit-related issues.
He told the BBC MPs should be able to vote according to their personal views when the next Brexit motion is debated on Tuesday, "to resolve things".
Mr Gauke also reiterated he would consider his position if the government opted for a no deal EU withdrawal.
Work and Pensions Secretary Amber Rudd has adopted a similar stance.
She told the BBC this week that she is "committed to making sure we avoid" a no deal Brexit and would not rule out resigning over it.
But she said allowing a free vote could help establish what Brexit solution could command a majority among MPs.
Speaking on BBC Radio 4's Any Questions, Mr Gauke - who like Ms Rudd backed Remain in the referendum - warned that the way the UK leaves the EU should not be "railroaded through" without Parliament giving consent.
Asked whether he backed MPs being given a free vote - even if it potentially led to an extension of Article 50 - Mr Gauke said: "I think there is a case for free votes in this area to resolve things.
"As far as Tuesday is concerned... we need to see what all the amendments are going to be, to see whether Tuesday is a crunch point or not."
On Tuesday, the House of Commons will see MPs vote on Mrs May's next steps for Brexit.
Some groups of MPs have also tabled amendments to her motion to try and change the course of Brexit - including attempts to stop a no-deal Brexit and to extend the deadline for leaving the EU.
Meanwhile, Ireland's minister for European affairs Helen McEntee has said Ireland is not "trying to be awkward" in the row over the controversial backstop in the Brexit deal.
The backstop is a last resort measure to ensure an open border between the Republic of Ireland and Northern Ireland.
It would only be used if the UK and EU cannot agree a permanent trade deal by the time the Brexit transition period finishes at the end of 2020.
Speaking to BBC Radio 4's Today programme, Ms McEntee said Mrs May's red lines on Brexit have made a backstop "absolutely necessary".
She explained: "The UK have said we're leaving the single market, we're leaving the customs union, and for us that makes it more difficult to avoid a border."
The minister added: "The onus by the UK has been shifted back on Ireland that we should compromise, that we are the ones that are trying to be awkward or difficult.
"We did not vote for Brexit. We don't believe in it.
"But we are protecting a peace process. There is an obligation on the UK to ensure the Good Friday Agreement is protected."
The UK is due to leave the EU at 23:00 GMT on 29 March, and the prime minister has faced repeated calls to rule out the prospect of leaving without a deal if no agreement can be reached.
Theresa May is continuing to seek support for her Brexit deal ahead of a crucial Commons vote on Tuesday.
On 15 January, the withdrawal deal she negotiated with the EU was rejected by MPs by a historic margin - 432 votes to 202.
Tuesday's vote will see MPs debate and vote on her next steps for Brexit.
Opposition and backbench MPs have been tabling amendments to her motion in a bid to force the government to change direction.
These include attempts to stop a no deal Brexit and to extend the deadline for leaving the EU.
On Friday, Commons Leader Andrea Leadsom said cabinet ministers should back the prime minister's stance of leaving the option of a no deal on the table.
She also suggested the EU may be prepared to grant the UK a "couple of extra weeks" beyond the 29 March deadline to finalise preparations for Brexit.
However, Ms Leadsom said she had "grave concerns" about a bill, proposed by Labour MP Yvette Cooper, which could extend Article 50 - which triggers the UK's withdrawal from the EU - by nine months.
Mr Gauke agreed with a suggestion that leaving without a deal could be "pretty disastrous" for the UK, saying it would have a "significant impact" on jobs.
He said: "If there is a conscious choice, 'Right, that's it, we're going no deal', that would be something I would find extremely difficult."

German Chancellor Angela Merkel says some British people have "illusions" about discussing the UK's future ties with the EU at the same time as nailing down the UK's Brexit terms.
An EU-UK deal can only be discussed once the exit issues - such as UK payments to the EU budget - are resolved, Mrs Merkel told German MPs.
The UK initiated the formal procedure to leave the EU on 29 March.
It sets a two-year deadline for completion of the exit negotiations.
EU leaders are to meet on Saturday to adopt their joint negotiating position on Brexit. They are working on the basis of draft guidelines issued on 31 March.
Official talks will not begin until after the UK general election on 8 June.
UK Prime Minister Theresa May called the early election, saying she needed to strengthen her hand in Brexit negotiations.
The EU wants the terms of the UK's exit to be decided before any discussion of a future trade relationship, while Mrs May wants the two issues to be dealt with simultaneously.
The German chancellor told German MPs it would be "a waste of time" to maintain illusions that the two sets of negotiations could be held simultaneously.
EU Trade Commissioner Cecilia Malmstrom said the EU would "for sure" reach a free trade deal with the UK after Brexit.
But Mrs Merkel warned that it would be a different relationship, saying: "A third country - which is what the UK will be - cannot and will not have the same rights as an EU member state.
"All 27 EU countries and the EU institutions agree about that," she told the Bundestag, Germany's lower house of parliament.
Angela Merkel's priorities are clear: to preserve the integrity of the EU and to secure the rights of its citizens living in the UK.
Her speech today may have sounded tough. In truth she is simply repeating what she's said all along: Britain cannot expect to cherry-pick in these negotiations. EU unity matters here, so she's sticking - more or less - to the Brussels script.
Germany is likely to take a moderately softer stance than, say, France. Sources here indicate there might be, for example, some wriggle room over the figure of the Brexit bill. There is little appetite for a punitive approach - Germany, of course, has an eye to its economic relationship with Britain. Nevertheless even the business lobby here (including the head of the association of Germany's all powerful automotive industry) acknowledge that the EU's interests must come first.
It's also worth noting that Brexit is also not the central focus for Berlin. There is a degree of frustration among politicians who are already preoccupied - not only with other challenges facing Europe, including migration, terror, conflict - but with their own looming general election.
Mrs Merkel said the immediate Brexit priorities to decide on were the rights of EU citizens in the UK and Britons in continental Europe and Britain's ongoing financial obligations.
"We can only do an agreement on the future relationship with Britain when all questions about its exit have been cleared up satisfactorily," she said.
"The sooner the UK government is ready for constructive solutions, the sooner we can meet its wish to talk about the future relationship. But first we need to know how the UK government envisages that relationship. It can only be done in that sequence."
EU officials estimate that the UK faces a bill of €60bn (£51bn; $65bn) because of EU budget rules. UK politicians have said the government will not pay a sum of that size.
Mrs Merkel stressed the need to protect the interests of some 100,000 Germans living in the UK.
But she went on to say "we are also ready to make a fair offer to British citizens in Germany and the rest of Europe.
"They are an important part of our community and should remain so."
Mrs Merkel noted the difficulty of unpicking 44 years' worth of EU legislation that counts the UK as a member state.
The people who will negotiate Brexit
Experts have warned that it usually takes the EU many years to negotiate free trade deals with non-EU countries. The EU-Canada deal, Ceta, was concluded after eight years of talks.

The UK government insists Theresa May's Brexit proposal is a "workable, credible" deal, despite being rejected by EU leaders at a summit in Salzburg.
Minister James Brokenshire said "tough words" were to be expected near the end of negotiations but the government was "resolute" in its bid to get a deal.
He said the so-called Chequers plan "does deliver" and it was now for the EU to "be specific" about its concerns.
The UK is due to leave the EU on 29 March 2019.
Prime Minister Theresa May says her plan for the UK and EU to share a "common rulebook" for goods, but not services, is the only credible way to avoid a hard border between Northern Ireland and the Republic of Ireland.
But it is opposed by some within her own party who argue it would compromise the UK's sovereignty, and got a cool reception at this week's EU summit in Salzburg, Austria. Mrs May described her talks there with European Council President Donald Tusk as "frank".
In a news conference, Mr Tusk said that while there were some "positive elements" in the Chequers plan, EU leaders had agreed that the proposals needed to be redrawn: "The suggested framework for economic co-operation will not work, not least because it is undermining the single market."
He followed it up by posting a photograph on Instagram of he and Mrs May looking at cakes with the caption: "A piece of cake, perhaps? Sorry, no cherries."
The EU has argued that the UK cannot "cherry-pick" elements from its rulebook.
On Friday, Communities Secretary Mr Brokenshire, a former Northern Ireland Secretary, told BBC Radio 4's Today programme: "The Chequers deal is a workable, credible deal to meet our ambitions.
"They [the EU] have said that it's about the integrity of the single market and we believe the Chequers deal responds to that, and it's for the EU to engage with what's on the table."
But former cabinet minister Iain Duncan Smith, who campaigned for Brexit, questioned why the UK had gone for a plan which "was so obviously not going to cut the mustard with the EU".
He added that the EU had "behaved appallingly" towards Mrs May and he described Mr Tusk's Instagram photograph as "quite insulting".
The UK and EU are trying to reach a deal in time and want to avoid a hard border - physical infrastructure like cameras or guard posts - between Northern Ireland and the Irish Republic but cannot agree on how.
The EU insists on its own "legally binding Irish backstop" - what it describes as an insurance policy to prevent a hard border, if no other solution can be found.
By BBC political editor Laura Kuenssberg
Theresa May and her government have been trying to pursue a middle way, to find a stance between the basic options - a close "Norway style", or free trade deal roughly like Canada.
It feels that the search for something else has been in vain.
Sources on the EU side express irritation at the UK's approach, at what they see as the strident tone the prime minister took in the last 48 hours.
The European Council is not the same as Prime Minister's Questions, it's suggested.
But to kick out publicly as they did in Salzburg certainly runs the risk of pushing Mrs May too far.
It suggests Northern Ireland should stay aligned with the EU in key areas, in effect staying in the customs union and single market. But the UK says this is unacceptable as it would split Northern Ireland from the rest of the UK.
Transport Secretary Chris Grayling told BBC Newsnight: "At the moment what the European Union is asking in and around Northern Ireland is simply impossible for any UK government to accept. And actually if they stick with that position, there will be no deal."
Mrs May has said the UK will come forward "shortly" with new proposals on the so-called "backstop" arrangements, but also insisted Chequers was the "only serious and credible proposition" for an overall deal.
Scotland's First Minister Nicola Sturgeon tweeted: "Now that the EU has explicitly rejected it, the Chequers pretence has to stop.
"At the very least, single market/customs union membership must be back on the table and the Article 50 clock [the time-limited process taking Britain out of the EU] must be stopped to avoid a cliff edge."
Shadow Brexit secretary Sir Keir Starmer told the BBC that if the negotiations ended without a deal, it "would be catastrophic for our economy, plunging it into real crisis".
"Really, the next few weeks should be all about how does the prime minister avoid that," he told the BBC.
"She needs to accept that we need a customs union and a strong single market deal, both for the Northern Ireland border and for our economy."
Leading Conservative Remainer Dominic Grieve said he believed a deal would be offered but one that would be "very difficult" for the UK to accept - "which is why we are going to have to reconsider what we are doing".
He said the EU could only show limited flexibility towards a non-member: "We are asking for something that the EU, as an international treaty organisation, cannot readily give us."
Mr Tusk said on Thursday that October would be the "moment of truth" for reaching a deal, and that "if the conditions are there" an additional summit would be held in November to "formalise" it.
Meanwhile, pro-European Scottish politicians seeking a ruling on whether Brexit can be halted have been given permission to take their case to Europe's highest court.
The cross-party group of politicians argue that Article 50 can be revoked if MPs vote to do so.
They won an appeal at the Court of Session in Edinburgh, Scotland's highest court, and the European Court of Justice will be asked to give a definitive ruling.

My deal or no deal! An agreement or Armageddon! Compromise or catastrophe!
This is not of course a subject to be flippant about. And it is easy to see why the government has moved already to presenting the next couple of months of fraught activity in Westminster as already being a decision for MPs - back Theresa May whatever she brings back from Brussels or take a reckless roll of the dice.
There is nothing funny about the forecasts of what could happen if there is no deal.
Number 10 believes that will be the rub, the reality of the situation. But while they might wish they were at the closing stage where those arguments will play, they are not there yet.
There are still forces at play that could shape the outcome of the deal, before the Tory whips can start counting up the votes.
First - some Brexiteers are absolutely serious and organised about trying to force Theresa May to shift her plans. They are already making a lot of political noise.
They will demand much of the oxygen at the Tory conference and could make life for the government extremely hard on what one described as 'any or all' votes in the run-up to the Brexit deal.
It doesn't seem necessarily clear to me why the PM would be able to hold off all their demands this time, when on many previous occasions she has had to budge a little.
In turn, some former Remainers plan to use other legislation coming back to Parliament to have another go at softening the government's position.
There is a putative plan for another amendment to leave the country in the European economic area, starting with changing the Trade Bill in the House of Lords.
One MP involved told me: "Some MPs talk about opposing no deal but what does that really mean? There has to be a fallback plan and this amendment could lead the way to finding a solution."
It doesn't mean that those former Remainers will be successful this time around, but it doesn't mean they won't give it a good try.
Add to that the increasing visibility of those campaigning for a second referendum. They know such a vote could only really come out of the turmoil of a no-deal scenario. But they are trying, extremely hard, to shift the terms of the debate.
Lastly and most importantly, Theresa May's plan is a set of proposals for negotiation.
While we may see friendlier rhetoric this week at an EU leaders' shindig in Salzburg, they are never going to accept her compromise in one big chunk.
There will be a process of push and shove, there will have to be some more compromise. The final terms could make the calculations for MPs very different. Even some government ministers privately say they can't be sure they will back the PM until that much later stage.
In the end Number 10 may well be right - they could get their way in Parliament, pushing through a historic deal not by making a persuasive case for its merits but by talking up the risks of saying no.
Common sense? Or just scare tactics? That's the call MPs may have to face.

Brexiteers have attacked Philip Hammond for reiterating a warning that a "no-deal" Brexit could damage the economy.
The chancellor's warning was published in a letter, hours after the government laid out plans for a "no-deal" Brexit.
Conservative MP Marcus Fysh accused Mr Hammond of embarking on "another instalment of dodgy project fear".
Meanwhile, the World Trade Organization head has told the BBC no deal "would not be the end of the world... but it's not going to be a walk in the park".
In a letter published on the Treasury website, Mr Hammond repeated the findings of the Treasury's provisional Brexit analysis released earlier this year.
That analysis includes a warning that a "no-deal" Brexit could mean a 7.7% hit to GDP over the next 15 years, compared with the "status quo baseline".
Writing to Nicky Morgan, chairwoman of the treasury committee, he said that under a "no-deal" scenario chemicals, food and drink, clothing, manufacturing, cars and retail would be the sectors "most affected negatively in the long run".
He added that the largest negative impacts would be felt "in the north-east [of England] and Northern Ireland".
The letter also said Treasury analysis estimated borrowing would be around £80bn a year higher under a "no-deal" scenario by 2033.
Mr Hammond added that this analysis was now "undergoing a process of refinement" and emphasised that a "no-deal" Brexit was not the government's preferred option and that it was "confident of a agreeing a good deal".
The timing of the letter was criticised, coming so soon after Brexit Secretary Dominic Raab sought to play down the risk of no deal - describing the impact as a "potential short-term disruption".
Prominent Brexiteer Jacob Rees-Mogg, who has written to all Tory local associations urging them to reject the PM's Chequers deal, said leaving on WTO terms was not "as absurdly frightening as the chancellor of the exchequer thinks it may be".
"As a dog returneth to his vomit, so a fool returneth to his folly," he said.
"The naysayers in the Treasury have consistently wanted to paint a bleak picture because they are frightened of taking responsibility for managing the economy without the crutch of the EU. It is a sign of their weakness.
"What Mr Hammond is doing is a reminder of why no-one believes the politicised forecasts of the Treasury. The Treasury is desperate to stop Brexit. Everything the Treasury does has to be read in this light."
But Tory MP Sarah Wollaston, who backs a new referendum on the outcome of the Brexit negotiations, said Mr Hammond's comments were timely and they complemented, rather than contradicted, the no-deal analysis.
She told BBC Radio 4's Today that Mr Rees-Mogg, who chairs the European Research Group (ERG) of Tory MPs, held too much sway in the party and the "ERG tail is wagging the Conservative dog".
Cabinet Office minister David Lidington said there was "nothing new" in the chancellor's comments, telling Today that it was "clear" that leaving the EU without an agreement was "not a desirable outcome".
Asked whether he agreed with his colleague Liam Fox, who claimed earlier this month the odds were 60:40 in favour of a "no-deal" exit, Mr Lidington said he was not a betting man but the odds of a deal were "good".
"We have to do the emergency 'no-deal' planning but it is not in our interests we end up in that position."
Shadow Brexit secretary Sir Keir Starmer said: "A 'no-deal' Brexit has never been viable and would represent a complete failure of the government's negotiating strategy."
Roberto Azevedo, the director-general of the WTO, said there would be an impact from a "no-deal" Brexit, with the possibility of trade "barriers" at the borders and tariffs between the UK and the EU almost certain.
"The EU cannot discriminate amongst the WTO members, so the UK will have to be treated as all the other members, and the other members pay tariffs so the UK will have to pay tariffs as well," he said.
He was also asked whether the UK could unilaterally remove its trade tariffs.
"Technically, yes," he replied. "But not only to the EU, to everybody, so you cannot pick and choose to whom you lower your tariffs.
"If you decide that a particular product, let's say glasses, that they go down to zero, that's perfectly right, any member of the WTO can do that. But that zero applies to everyone else."

The government and Labour have held further talks aimed at breaking the deadlock in Parliament over Brexit.
Shadow Chancellor John McDonnell said discussions with cabinet ministers David Lidington and Michael Gove had been "positive" and "constructive".
He added that a timetable was being worked out for more meetings over the next seven to 10 days.
EU leaders have agreed to delay the UK's departure date from 12 April to 31 October, to avoid a no-deal Brexit.
But Prime Minister Theresa May has said the UK can still leave before 22 May, if Parliament backs the withdrawal agreement she reached with the EU.
This would avoid the UK having to take part in European Parliament elections, currently scheduled for 23 May.
The UK was originally due to leave the EU on 29 March, but its departure date has been delayed twice, after the Commons rejected the withdrawal deal negotiated with the EU by large margins.
The meeting between Mr McDonnell, members of Jeremy Corbyn's staff and Mr Gove and Mr Lidington lasted just over an hour.
Asked if the government had moved on its "red lines", Mr McDonnell told reporters: "I'm not going into the detail of it.
"We are trying to be as constructive as we possibly can on all sides... but we will see by the end of next week how far we have got."
BBC political correspondent Iain Watson has been told that the Conservative and Labour delegations have discussed some of the fine detail of the potential changes to the "political declaration" - the non-legally binding part of the Brexit deal, which sets out a blueprint for future relations between the EU and UK.
But he said the two sides were still some way apart on customs arrangements.
Labour wants a new permanent customs union with the EU, which would allow tariff-free trade in goods.
The government has repeatedly ruled out remaining in the EU's customs union, arguing it would prevent the UK from setting its own trade policy.
Under EU rules, the UK will have to hold European Parliament elections in May, or face leaving on 1 June without a deal.
Speaking to the BBC on Friday, Chancellor Philip Hammond said: "Clearly nobody wants to fight the European elections.
"It feels like a pointless exercise and the only way we can avoid that is by getting a deal agreed and done quickly, and if we can do that by 22 May, we can avoid fighting the European parliamentary elections.
"In any case we want to ensure any British MEPs that are elected never have to take their seats in the European Parliament by ensuring this is all done well before the new European Parliament convenes."
Meanwhile, the government says it will "continue to make all necessary preparations" for a no-deal Brexit.
A government source said "plans will evolve and adapt", but would not stop while the chance of leaving the EU without an agreement remained.
The source said that a leaked message which reportedly referred to the "winding down" of no-deal preparation related only to Operation Yellowhammer - the contingency planning programme based on worst-case scenarios - and not no-deal planning in general.
But the government has confirmed it is stopping Operation Brock - the contraflow put on the London-bound carriageway of the M20 in Kent - "in light of the reduced threat of disruption to services across the English Channel in the coming weeks".

Jeremy Corbyn has met other opposition party leaders to discuss ways of averting a no-deal Brexit.
The Labour leader had outlined a plan to become caretaker PM after defeating the government in a no-confidence vote.
But in his invitation letter, he pledged to discuss "all tactics available" to stop the UK leaving the EU on 31 October without a deal.
Tory Party chairman James Cleverly said Mr Corbyn was offering "chaos, delay and uncertainty".
The SNP, Liberal Democrats, Change UK, Plaid Cymru and Green Party all accepted the invitation to meet Mr Corbyn and discuss his proposals.
The Labour leader also invited five Conservative MPs opposed to a no-deal exit, but none said they would be attending.
One of them, former Attorney General Dominic Grieve, said he was not able to make it, but was willing to meet Mr Corbyn at another time.
Brexit Party leader Nigel Farage criticised those attending, saying they were "very out of touch with public opinion" and leaving the EU without an agreement was now "the only acceptable deal".
Mr Corbyn has said if he wins a no-confidence vote, he will delay Brexit, call a snap election and campaign for another referendum.
The Liberal Democrats, and some potential Tory allies opposed to a no-deal exit, have indicated they won't back a plan that leads to him in No 10.
Ahead of the meeting, Lib Dem leader Jo Swinson told BBC Breakfast a plan involving Mr Corbyn as interim leader was less likely to succeed.
Shadow Brexit secretary Sir Keir Starmer said Tuesday's meeting would be "a pretty frank discussion" about the options available.
"Today is about, can we get a unified approach that we agree? There'll have to be give and take, but we must have a plan that everybody can coalesce around and that we implement as soon as we can next week," he told BBC Radio 4's Today programme.
As well as Mr Corbyn's no-confidence plan, MPs will also discuss taking legislative measures to block a potential no-deal, Sir Keir said.
"I think they're direct, I think they're effective. I want something with a legal edge."
MPs previously passed a law in April to force former PM Theresa May to request an extension of the UK's EU membership beyond the original Brexit deadline of 29 March.
Repeating that approach would require them to first take control of the parliamentary timetable to make time for the law to be debated.
Speaking on Tuesday, SNP Westminster leader Ian Blackford said one way to do that would be to amend a motion debated as part of an emergency debate in the Commons.
Emergency debate motions - topical matters added to business at short notice - are normally considered unamendable, meaning Speaker John Bercow may have to give a ruling that one is.
If successful, Mr Blackford told the BBC, this strategy would allow MPs to pass a law compelling the prime minister to seek a Brexit delay at a summit of EU leaders in mid-October.
Ahead of the meeting, Change UK leader Anna Soubry said passing legislation was the "immediate solution" for avoiding a no-deal exit.
On Monday, PM Boris Johnson said he was "marginally more optimistic" about striking a new Brexit deal with the EU.
Asked at the end of the G7 summit in France about the possibility of MPs thwarting plans to leave the EU at the end of October, Mr Johnson said: "I think it's the job of everybody in Parliament to get this thing done.
"I think it's what the people want, I also think, by the way, it's what our friends and partners on the other side of the Channel want - they want it over."
Mr Johnson says he wants to leave with an agreement, but the UK must leave the EU by the latest deadline of 31 October "do or die".
Although Boris Johnson only has the most emaciated of majorities, the opposition seems to be divided on tactics and outcome.
Mr Corbyn wants to be a caretaker prime minister, he wants to call a general election and campaign for another referendum. But Jo Swinson wants to know, does he really want to stop Brexit? Or whether, in a referendum, he would have a Labour version of leave on the ballot paper?
More crucially, she says the only way for Mr Corbyn to become caretaker leader is to win a vote of no confidence against Mr Johnson. And if Tory rebels won't support Mr Corbyn, she wants to know if he would stand aside for a veteran parliamentarian such as Ken Clarke or Harriet Harman.
Already her attitude has been described as petulant by a senior Labour frontbencher so that doesn't necessarily augur well for today's talks.
The most likely outcome is that MPs will try to seize the parliamentary agenda and legislate against a no deal, but that in itself isn't a watertight solution.
There are two weapons in Mr Johnson's armoury. He has ruled out suspending Parliament in September, but hasn't ruled it out entirely ahead of the 31 October deadline. If he does that, that stops them trying to block no deal at the last minute.
On the other hand, if MPs tell him 'you're going to have to legislate to extend Brexit,' he can say 'I refuse to do it' and call an election.
Writing in the Independent, Mr Corbyn pledged to discuss all options with other party leaders to "stop this no-deal disaster in its tracks".
He said: "[No-deal Brexit] won't return sovereignty, it will put us at the mercy of Trump and the big US corporations dying to get their teeth into our NHS, sound the death knell for our steel industry and strip back our food standards and animal welfare protections."
Green Party MP Caroline Lucas, who attended Tuesday's meeting, tweeted: "Boris Johnson's intentions are clear: suspending Parliament, a crash out Brexit and blaming MPs for the chaos".
"We will not be bullied. We will not surrender parliamentary sovereignty to the right wing cabal in No 10. MPs must unite to stop this abuse of executive power."
Former Tory MP Nick Boles - who rejected Mr Corbyn's invitation to talks - tweeted that he would not "countenance" a no-deal exit, or "any undemocratic steps to frustrate the will of Parliament".
Meanwhile, MPs from different parties are later expected to sign a declaration pledging to set up an alternative assembly if the PM prorogues - or suspends - Parliament.
Mr Johnson says he has no plans to do this, but has not ruled out such a move to make sure the UK leaves the EU by the end of October.
Responding to Mr Corbyn's newspaper article, Mr Cleverly said: "The alternative to delivering Brexit is Jeremy Corbyn in Downing Street, a man who would wreck the economy, break up our Union, is soft on crime and won't stand up for Britain."
He insisted only Mr Johnson and the Conservatives could provide the leadership needed to deliver Brexit by 31 October, "whatever the circumstances".

Jeremy Corbyn says he told Theresa May "don't bring no deal back to Parliament" in their long-awaited face-to-face meeting on Brexit.
The Labour leader said it was "not acceptable" for the PM to keep the no-deal option on the table after MPs voted against it on Tuesday.
After the meeting, Mrs May tweeted: "The only way to avoid No Deal is to vote for a deal."
MPs will vote on the deal again after she seeks to renegotiate with the EU.
Mr Corbyn said it was a "serious" meeting and Mrs May had "listened".
He had refused to meet Mrs May unless she agreed to rule out a no-deal Brexit, but changed his mind after MPs voted against the idea of leaving the EU on 29 March without a deal on Tuesday evening.
In her tweet, Mrs May said she had been "pleased" to meet Mr Corbyn and had stressed the importance of the UK doing its own trade deals after Brexit.
A Labour spokesperson said the two would meet again "soon" after the 45 minutes of "cordial" talks in the prime minister's Commons office.
Mr Corbyn said: "I set out the Labour case for a comprehensive customs union with the European Union, in order to protect jobs and trade.
"She certainly understood the point that we were making."
He added: "The last words I said to her were 'don't bring no deal back to Parliament' because it's not acceptable - it's not a sensible or serious way of going forward."
He said he was suspicious the government was trying to "run down the clock", and if that appeared to be the case when Parliament discussed Brexit again next month, Labour would "look at all the options on the table at that time".
Asked if Labour would support or table a motion to try and extend Article 50, which would delay the date of Brexit, Mr Corbyn said: "That is a question for 13 February."
He added that it was quite possible the prime minister would return to Parliament next month "with nothing".
Asked if he had a problem with Irish backstop, which Mrs May is seeking to renegotiate with the EU, he said: "I have a problem where the agreement is one-sided."
The two party leaders earlier clashed over Brexit at a noisy Prime Minister's Questions in the Commons.
During the exchange, Mr Corbyn said the prime minister may have succeeded in "temporarily uniting her very divided party" in Tuesday's votes on amendments to her plan, but she had to make "more important compromises" to "unite the country".
Mrs May said Mr Corbyn was a "fine one to talk about coming together", when he had only now agreed to meet her.
She said the majority of MPs had identified the Irish backstop as the main sticking point preventing them from backing her deal, whereas Mr Corbyn's Brexit proposals had been rejected.
"He has no plan for Brexit, no good plan for our economy and no plan for our country," she told MPs.
MPs voted 317 to 301 in favour of changing the backstop plan - the section of Mrs May's deal with the EU designed to avoid the return of Northern Ireland border checks.
Five amendments, including Labour MP Yvette Cooper's bid to delay Brexit if Mrs May does not get her deal through Parliament and Mr Corbyn's own amendment, were defeated on Tuesday.
Mr Corbyn asked Mrs May whether, if she did not agree a deal with Brussels that MPs would support, she would back Labour's proposals for a "a strong single market, comprehensive customs union and the guaranteeing of rights and protections rather than the alternative she has been threatening - to crash out with no-deal".
Mrs May told him: "You cannot just vote to reject no deal, you have to support a deal."
It was a message she repeated to Labour MP Jack Dromey, who together with Tory MP Caroline Spelman got MPs to back a non-binding amendment rejecting a no-deal Brexit on Tuesday.
Later in the session, Nigel Dodds, leader of the Northern Ireland's Democratic Unionist Party at Westminster, described remarks by the  Irish Foreign Minister Simon Coveney on the UK's approach to Brexit as "highly reckless and extremely dangerous".
Mr Coveney likened the UK's negotiating stance to "either you give me what I want or I'm jumping out the window".
Mr Dodds said that kind of rhetoric needed "to be toned down".
Mrs May said she will speak to Irish premier Leo Varadkar later on Wednesday.
"It is important for us to work with the Irish government on the arrangements that will be in place in the future," she added.
But ahead of the call, Mr Varadkar told the Irish Parliament that the EU stood by the withdrawal agreement and renegotiation was not on the table.
At the moment, the UK is due to leave the European Union at 23:00 GMT on 29 March, with or without a deal.
The UK and the EU negotiated their withdrawal agreement deal over the past 18 months but it needs to be backed by MPs for it to come into force. Earlier this month, MPs voted against the plan Mrs May had proposed by 432 votes to 202.
Mrs May said that, after taking Tuesday's votes into account and talking to the EU, any revised deal would be brought back to the Commons "as soon as possible" for a second "meaningful vote".

Brexit is a "complete mess" and the country "cannot go on like this", Jeremy Corbyn has said in his new year's message to the country.
The Labour leader said Theresa May had let down down both Leave and Remain voters by trying to "drive a bad deal" through Parliament over the UK's exit.
Meanwhile, Lib Dem leader Sir Vince Cable has urged those seeking another referendum to "keep fighting".
No 10 said there was "still work to do" on building support for the PM's deal.
Downing Street said the prime minister had spoken to European leaders over the festive period as she seeks to address the concerns of many Tory MPs about the withdrawal agreement.
MPs are due to vote on the deal in the Commons in mid-January.
The UK is due to leave the EU on 29 March 2019 but there is uncertainty as to what will happen if MPs reject the UK's withdrawal agreement.
The opposition is seeking to force a general election by voting down the deal and calling a vote of no confidence in the government.
Mr Corbyn, who has said Labour would seek to re-open negotiations with Brussels to pursue a better outcome, said the Conservatives had "plunged the country into crisis".
He accused the government of "trying to drive through a bad deal and letting people down all across the country whether they voted leave or remain".
Only Labour, he claimed, was capable of uniting the UK, with policies to tackle inequality and job insecurity.
"Eight years of damaging Tory failure has left us with a divided country where millions are struggling to make ends meet," he said. "We cannot go on like this.
"Labour is ready to deliver a radical alternative to rebuild and transform our country. We will stand up to the powerful few so the wealth you create is shared fairly not hoarded by a privileged elite.
"We will work to create a society where the talent of everyone is unleashed. That is how we will unite our country."
In his end-of-year message, Sir Vince Cable has insisted Brexit can be stopped as he urged fellow supporters of another referendum on the UK's future in Europe to "keep fighting".
"The history books will look back on the coming three months as critical," he said.
"Are we going to make a terrible mistake, leaving behind our influence in Europe's most successful peace project and the world's biggest marketplace?
"Or are the British people, in the final hours, going to be given a chance to re-consider, in light of all the facts which have come to the surface in the last two years?"
Meanwhile, Scottish First minister Nicola Sturgeon has sought to assure EU migrants that they would always be welcome in Scotland.
"Our reputation for being an open, warm-hearted, hospitable country has never been more important," the SNP leader said in her Hogmanay message.
"I want to make that especially clear to the hundreds of thousands of nationals from other EU countries, who have done us the honour of choosing Scotland as their home.
"I know that this is a deeply uncertain time for you. But I also want you to know that your contribution to our national life - to our economy, communities and society - is hugely valued."
Mrs May is seeking further "political and legal" assurances from EU leaders over how long the controversial backstop plan to avoid physical checks on the Irish border would last, amid concerns it would tie the UK indefinitely to EU rules.
A No 10 spokesperson said the prime minister had "been in contact with European leaders and that will continue in the lead up to the vote".
"Her focus is certainly on getting the assurances that MPs want ahead of that vote taking place," he added.
"There is still work to do and talks will continue."

Down is up. Up is down. Black is white. And white is black. Friend is foe. Foe is friend. Stop me now, or else I'll go on forever.
But the point is this - the prime minister has had a terrible day today as the government made history in two excruciating ways.
Ministers were found to be in contempt of Parliament - a very serious telling off - and the government had a hat trick of defeats - the first time since the 1970s that's happened.
As you'd expect too, MP after MP after MP rose after Theresa May's remarks to slam her deal as Tory divisions were played out on the green benches, with harsh words exchanged.
But in this topsy-turvy world, the overall outcome of the day for Mrs May's big test a week tonight might have been not all bad.
The amendment from Tory Remain rebel Dominic Grieve is, on the face of it, a strait jacket for Mrs May - a way that MPs can more easily push the government around.
So far, so disaster. Except it could actually peel off some rebels on both sides... possibly.
Former Remain rebels now have a possible route to get what they want if the PM's plan is rejected, as there is a possible - I emphasise the possible - way to get a vote with a majority for a Norway-style agreement or, less likely, a push for another referendum.
That won't go unnoticed by Brexiteers too, who may feel (some of them at least) that Mrs May's deal might be their best bet in that case, rather than risk that softer, squidgier Brexit.
It's possible therefore that today's shenanigans have made it less likely that the prime minister will face a terrible defeat next week because a few wobbly rebels on both sides might come in line.
It's also worth noting the involvement of several former, normally loyal, cabinet ministers such as Sir Oliver Letwin.
He has often been used as a fixer by the chief whip, whispers suggest. It's perfectly possible that his moves today are completely unrelated.
But also not impossible that somehow today's result has been influenced by conversations about finding the prime minister a softer landing.
Suggestions there was any kind of collusion were described as something that's too rude to write here. But nothing much happens around here at the moment without motive and suspicion being questioned.

Freedom of movement, access to healthcare abroad, voting rights - some fundamental aspects of British life in the EU must be clarified before Brexit happens.
A Luxembourg liberal MEP, Charles Goerens, has proposed offering British citizens the option of retaining their EU citizenship for a fee. This "associate EU citizenship" idea could be part of the Brexit negotiations but it raises all sorts of legal questions.
The EU treaties say EU citizenship "does not replace national citizenship" but "is additional to it". So EU citizenship cannot be acquired by giving up UK citizenship.
Once the UK leaves the EU, British citizens will lose their EU citizenship. And once Prime Minister Theresa May triggers the Article 50 withdrawal process, which she aims to do before next April, there will be just two years to resolve citizenship issues.
Citizens' rights have to be part of the Article 50 negotiations because about 1.2 million UK citizens live in other EU countries and three million EU nationals live in the UK. They need to know what, if any, reciprocal rights they will continue to enjoy after Brexit.
Important decisions about jobs, homes, pensions and healthcare could depend on those safeguards.
EU citizenship is described in Article 20 of the Treaty on the Functioning of the European Union and includes the rights to:
Beyond those rights, EU law also provides many social protections for EU citizens in the areas of healthcare, work and pensions.
An EU citizen can access another EU country's social security system, provided he or she has paid social insurance back home. An example is the EHIC health card - a passport to emergency treatment abroad.
The reciprocal rights are called "EU social security coordination". The rules are complex, as social provision varies greatly from country to country.
Mr Goerens proposes that UK citizens could pay an annual, individual membership fee directly into the EU budget to retain their EU citizenship after Brexit. He did not suggest any figure for that fee.
An associate citizen would retain freedom of movement in the EU, the right to reside in another EU country under existing rules and the right to vote in European elections.
The European Parliament will vote on the proposal next month - it is Amendment 882 in a long report on possible future EU treaty changes.
It has generated much interest on social media and Mr Goerens says many British MEPs have expressed support.
But even if MEPs back the proposal, it still has a long way to go.
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The need for treaty change makes this initiative very hard to achieve by the likely 2019 deadline for Brexit.
It could only become law after a treaty change because it would change the nature of EU citizenship.
But aggrieved pro-EU Britons may welcome the fact that Belgian MEP Guy Verhofstadt has backed the proposal.
Mr Verhofstadt, an influential liberal, will be the European Parliament's lead negotiator on Brexit.
EU leaders will inevitably have to change the treaties in the next few years because the UK's role will have to be deleted or amended in EU texts.
However, a change to the nature of EU citizenship would require full ratification by all 28 member states - and that could not be done quickly, Prof Catherine Barnard, an expert on EU law, told the BBC.
But the proposal, she said, at least showed a willingness in the EU to "find creative ways to help the 48% who voted to Remain [in the EU]".
Camino Mortera-Martinez, an EU justice expert at the Centre for European Reform, said there was "no appetite for treaty change in Brussels at the moment".
Next year politicians in the Netherlands, France and Germany will focus on general elections. They will want to avoid EU treaty changes, which are notoriously time-consuming and difficult. It took nearly nine years to draft and enact the Lisbon Treaty.
Empowering MEPs to continue representing some UK citizens after Brexit would be another big legal hurdle.
Prof Barnard questioned how an MEP could represent an area where "half the constituents are not even associate EU citizens". "That is a non-starter," she said.
If British "associate EU citizens" were to have continued freedom of movement, the UK would have to offer the EU something in return, both experts argue.
But that is very problematic. The Brexit vote on 23 June made curbing immigration from the EU a top priority for Mrs May's government. Freedom of movement will be one of the thorniest issues.
It would also be hard to get agreement on a fee for EU citizenship, Prof Barnard said. For example Spain, hosting many elderly Britons who use its healthcare system, might demand a high fee.
If it took the form of a new EU tax, it would require extra bureaucrats to collect and allocate the income.
The European Court of Justice would have to oversee associate citizenship - another thorny issue, because the whole idea of Brexit is for the UK to "take back control". So how could an EU court retain jurisdiction over UK citizens?
And it could be discriminatory to offer associate EU citizenship only to UK citizens. Many Serbs and Turks might also demand it, as they would like to join the EU.

The Commons vote on Tuesday will not be delayed, the Brexit Secretary has said, amid growing calls for the PM to go back to Brussels to renegotiate.
Stephen Barclay also said Theresa May could stay in post if, as expected, MPs reject her Brexit plan.
The PM has warned Tory rebels it could lead to a general election, and there was a "very real risk of no Brexit".
Boris Johnson said the PM could stay on if she lost but must renegotiate the deal with Brussels.
The withdrawal deal negotiated between the UK and EU has been endorsed by EU leaders but must also be backed by Parliament.
But the government is widely expected to lose the vote with Labour, the Liberal Democrats, the DUP, the SNP and dozens of Conservative MPs saying they cannot support the deal.
European Council President Donald Tusk tweeted on Sunday it would be "an important week for the fate of Brexit", after a phone call with Theresa May.
Despite newspaper speculation it could be called off, Brexit Secretary Stephen Barclay said: "The vote is going ahead and that's because it's a good deal and it's the only deal".
He warned against suggesting negotiations could be reopened: "The French, the Spanish and others will turn round, if we seek to reopen the negotiation, and ask for more."
And he insisted that Theresa May could remain prime minister, even if her deal is heavily defeated by MPs: "Yes, the prime minister is fighting for us and will continue in post."
Mr Johnson, who quit the cabinet over Mrs May's Brexit strategy, told the BBC he did not want a "no-deal" Brexit or another referendum, but it was not right to say there were no other alternatives.
He said the Northern Ireland "backstop" - effectively an insurance policy to prevent a hard border if no free trade deal is struck in time - put the UK in a "diabolical negotiating position".
MPs could give Mrs May "a powerful mandate to change that backstop" by voting it down on Tuesday, he said.
The border issue should instead be covered in negotiations over a future trading relationship with Europe, he said, and the UK should "incentivise" the EU by withholding "at least half" of the UK's agreed £39bn "divorce" payment, until a free trade is signed at the end of 2020.
He dismissed suggestions he had already offered other Tory MPs jobs if they backed a future leadership bid by him as "nonsense" and said the public wanted to see a plan "to get out of this mess" rather than "stuff about leadership elections and personalities" - although he did not rule out challenging Mrs May for the leadership.
And the former foreign secretary, a key figure in the 2016 campaign to leave the EU, said: "Don't underestimate the deep sense of personal responsibility I feel for Brexit and what's happened.
"It breaks my heart to think that after all we fought for... that we should consign ourselves to a future in which the EU effectively rules us in many respects and yet we have no say around the table in Brussels."
By BBC political correspondent Nick Eardley
Some Conservatives are urging Theresa May to defer Tuesday's vote, fearing a humiliating defeat which would destabilise the government.
They hope more clarity or compromise on the backstop issue can be provided - and some wavering Tories won over.
But others point out that no acceptable compromise has been found so far - and question whether one will be found now.
They also point out that Brussels has shown little enthusiasm for revisiting the backstop. Indeed there are some who believe only a strong rejection of Theresa May's deal will encourage the EU to rethink.
The Brexit Secretary said the vote would go ahead. With some still seeking to persuade the prime minister, it cannot be completely certain the vote will go ahead until Monday.
If the deal is rejected, it is unclear what happens next. Mrs May told the Mail on Sunday it would mean "grave uncertainty for the nation with a very real risk of no Brexit or leaving the European Union with no deal".
Protesters calling for another referendum to decide the issue were joined by politicians from across the political spectrum at a rally on Sunday, including Tory peer Lord Heseltine, Green MP Caroline Lucas, and Labour MP Rosena Allin-Khan.
Conservative former minister Philip Lee told the rally in east London: "I think a People's Vote is the best hope that we have of reuniting our country after this sorry episode."
Ms Lucas said the message to Mrs May was: "We don't want your vision of a mean-minded little Britain, with our borders closed and our horizons narrowed."
And Dr Allin-Khan said: "The promises made in 2016 are so far removed from the reality of the 585-page Withdrawal Agreement that it's time to take the Brexit decision back to the people."
She was careful to say that the vote should only take place if there was not a general election - it is Labour Party policy to call for an election and, only if that does not happen, to keep "all options" open, including a referendum.
But Labour Leader Jeremy Corbyn told ITV News that he would "have a discussion" with Rosena Allin-Khan, who is a shadow minister, about her appearance at the rally: "She's entitled to her point of view. I would rather she and every other Labour MP spent today and tomorrow and Tuesday concentrating solely on making sure we defeat this deal."
And former Tory leader Iain Duncan Smith said there was "a very large chunk of people who would feel utterly betrayed" if another referendum was called.
A UKIP-organised "Brexit Betrayal" march also took place in London, amid controversy over leader Gerard Batten's decision to appoint controversial activist Tommy Robinson as an adviser.
On Saturday, Work and Pensions Secretary Amber Rudd suggested a so-called "Norway Plus" option - which would see the UK remaining in the European Economic Area and joining a customs union with the EU - could be another possibility, if the deal was rejected.
But Mr Barclay told the BBC: "I don't think it honours the referendum result" - saying it would not give the UK control over immigration.
Esther McVey, who quit the cabinet over the deal, also said Mrs May should "immediately" renegotiate with Brussels, if MPs reject her deal.
Asked if she would consider a leadership bid, she told Sky News it was not about "personalities" and she would back the PM if she renegotiated the deal.
But she did not rule it out, saying she'd give it "serious consideration" if she were asked to stand.
Justice Minister Rory Stewart told the BBC that the government "should come back again" to Parliament if it loses Tuesday's vote, potentially with some "small adjustment" to the deal but suggested some MPs were using the backstop "as an excuse" to reject it.
Shadow Business Secretary Rebecca Long-Bailey would not confirm that Labour would immediately put down a motion of no confidence in the prime minister.
She said: "We will have to see what happens on Tuesday... we will have to make an assessment at the time and we will be in discussions with other political parties across the House to assess the best thing to do."
She added that the PM should call a general election, having lost a key proposal, but added "alternatively she could offer to renegotiate around a deal that would provide consensus in Parliament".

A cross-party group of MPs will use next month's landmark Brexit vote to try to ensure the UK cannot leave the EU without a deal.
They want to amend the "meaningful vote" motion to rule out "no deal".
The BBC understands Conservative, Labour, SNP, Liberal Democrat, Plaid Cymru and Green politicians are involved.
MPs are due to vote on the prime minister's Brexit agreement with the EU on 11 December.
Theresa May has repeatedly said voting the deal down would risk a "no-deal" Brexit.
But amendments being discussed in Westminster would seek to rule that out. Several sources told the BBC they think such an amendment is the only one that could command a majority.
It would not be legally binding, but a source said if MPs back the amendment it would be a clear "expression of parliamentary opinion".
Another source says it would "knock out" leaving the EU without a deal as a realistic option.
A third source said there was a "growing consensus" against a "no-deal" Brexit.
Up to six amendments will be voted on when MPs pass judgement on the prime minister's Brexit deal.
One has already been tabled by chairman of the Brexit select committee, Hilary Benn, which would rule out no deal and allow MPs to give the government instruction on how to act. That has been backed by Conservatives Dominic Grieve and Sarah Wollaston, as well as Labour's Meg Hillier, Yvette Cooper and Rachel Reeves.
Separately Labour's front bench has tabled an amendment saying that the party cannot support the agreement, as it fails to provide for a customs union and "strong single market" deal. It also says it opposes a no deal withdrawal, and "resolves to pursue every option" that prevents such a scenario.
There is also likely to be a front bench amendment from the SNP. Some in Parliament think they are unlikely to pass but they hope a cross-party effort will be seen as less partisan and will have more chance of achieving a majority.
The amendments will be selected by Commons Speaker John Bercow, on 11 December - the last of five days of debate on the Brexit agreement.

A cross-party Brexit deal will not get through Parliament unless it is subject to a fresh public vote, shadow Brexit secretary Sir Keir Starmer says.
Talks between Labour and ministers over leaving the EU have been going on for a month with little sign of progress.
Sir Keir told the Guardian that without a new referendum up to 150 Labour MPs would vote against any agreement made.
Environment Secretary Michael Gove suggested Labour needed more time to come to terms with the idea of a deal.
"For some in the Labour Party it will be a significant step to accept supporting Brexit and to come behind the prime minister's approach," he told the BBC.
After talks broke up on Monday evening, a Labour spokesperson said the shadow cabinet would be updated on what had been discussed.
The BBC's Iain Watson said: "It sounds like the plug has not been pulled on these yet, but it doesn't sound as if there's substantial progress to report."
A Downing Street spokesperson said: "In preparation for an update to cabinet tomorrow, today's meeting took stock across the range of issues discussed in talks over the last few weeks".
"We continue to seek to agree a way forward in order to secure our orderly withdrawal from the EU."
The UK was due to leave the EU on 29 March but the deadline was pushed back to 31 October after MPs rejected Theresa May's proposed deal three times.
Talks between the government and Labour aimed at finding a way to end the impasse resumed on Monday, with pressure growing on both sides to show progress or pull out.
No 10 said there was a "clear desire" to get on with the process. Asked if there was a deadline, a spokesman said: "Let's see where we get to this evening."
If there is no agreement, Theresa May has said she will return to Parliament and ask MPs to vote again on a range of possible options.
Parliament failed to unite behind a way forward in a series of "indicative votes" in March, but the PM says the government would now be prepared to accept whatever commanded a majority, so long as Labour did too.
Sir Keir said he would not be afraid to end the talks as soon as this week if the PM did not budge on her so-called red lines - positions that she feels cannot be changed in the Brexit deal.
He suggested a referendum on the final deal had become a red line of its own for many Labour MPs, saying "A significant number, probably 120 if not 150, would not back a deal if it hasn't got a confirmatory vote."
Labour's stated policy is that it supports a further referendum on Brexit under certain circumstances.
It has rejected the idea of campaigning for one in any event but will demand a public vote if it cannot get changes to the government's deal or an election.
Labour's Stephen Kinnock, who backs the UK leaving but retaining the closest possible economic links with the EU, said it would be a "real shame" if the talks were "torpedoed" by his party's insistence on another referendum.
"If you try to insert a second referendum into these talks they won't get through because the Conservatives will not whip their MPs to support it," he told Radio 4's World At One.
However, Labour's deputy leader, Tom Watson, said another public vote was the only "way out" of the current stalemate.
Asked whether Labour wanted to leave or remain in the EU, he told Radio 4's Today: "We are a remain and reform party," but "when it comes to a deal people can form their own view."
In a speech later marking the 25th anniversary of former Labour leader John Smith's death, Mr Watson reflected on Mr Smith's pro-Europeanism and said he would have backed a "People's Vote".
Asked if a deadline should be set for the talks, Mr Gove said the government needed time to properly "understand and explore" Labour's position.
While another referendum would be a "bad idea" he said, Mr Gove declined to rule out any of Labour's main proposals, such as some form of customs union with the EU.
The reality is these talks have been genuine, but very difficult.
Neither side wanted to pull the plug before the local elections 10 days or so ago.
But now, as time goes on, it may well be we are reaching the moment where they have to throw up their hands and say: "We just can't do it."
Jeremy Corbyn and Theresa May are both on lonely tightropes trying to get across the other side of this slow-moving crisis. I think they would both like it to be over with, maybe with a cross-party deal.
But the prime minister doesn't want to put a huge compromise on the table, she doesn't want another referendum. Jeremy Corbyn doesn't want to help out the government unless he can get genuine changes.
If neither of them feel they can really budge, well, the talks are not going to be able to succeed, and the government will then have to try to move on to votes in Parliament, the next part of the process.
June 2017 - Labour's general election manifesto accepts referendum result
March 2018 - Shadow Northern Ireland secretary Owen Smith sacked for supporting second referendum on final deal
September - Labour agrees if a general election cannot be achieved it "must support all options… including a public vote"
18 November - Labour leader Jeremy Corbyn says a new referendum is "an option for the future" but "not an option for today"
28 November - Shadow chancellor John McDonnell says Labour will "inevitably" back a second referendum if unable to secure general election
16 January 2019 - 71 Labour MPs say they support a public vote
6 February - Mr Corbyn writes a letter to Mrs May outlining five changes with no mention of a "People's Vote"
28 February - Labour says it will back a public vote after its proposed Brexit deal is rejected
14 March - Five Labour MPs quit party roles to oppose a further referendum
27 March - The party backs a confirmatory public vote in Parliament's indicative votes on a way forward for Brexit
30 April - Party agrees to demand a public vote if it cannot get changes to the government's deal or an election, as it decides wording to EU election manifesto

The government and Labour are "testing out" each other's ideas as they try to resolve the Brexit deadlock, cabinet minister David Lidington has said.
He told the BBC they had a "fair bit in common" over future customs objectives but further compromise was needed.
While there was no deadline, he said the sides would "take stock" in 10 days and the process could not drag out.
But former Conservative leader Iain Duncan Smith said the process was a "recipe for disaster" for his party.
He called for Prime Minister Theresa May to make way for a new Conservative leader next month - but Mr Lidington insisted replacing the prime minister would "not change the arithmetic in Parliament".
Talks between the government and Labour are set to continue over the Easter parliamentary recess in the hope of finding a Brexit agreement that will be acceptable to MPs.
A series of working groups in key areas, such as environmental standards, security and workers' rights, have been set up to try and find common ground.
The EU has insisted the terms of the UK's withdrawal, rejected three times by MPs, cannot be renegotiated - but there is scope to strengthen the political declaration, a document setting out the parameters of the UK's future relations with the EU, ahead of the new Brexit deadline of 31 October.
Mr Lidington, who is regarded as Mrs May's de facto deputy, said he had not set a deadline for the talks to produce a result but the public wanted Parliament to resolve their differences quickly.
"I don't think the question can be allowed to drag out for much longer," he said.
Asked whether the government could drop its opposition to a customs union with the EU, as demanded by Labour, Mr Lidington said both sides had well-known "public positions".
He suggested the two sides were considering whether there was a "mechanism" to deliver the benefits of a customs union, such as tariff and quota-free trade with the EU, while also enabling the UK to have an independent trade policy and input into EU agreements affecting the UK.
"What we have found in terms of objectives… there is a fair bit that both parties would have in common," he said. "If we are going to find an agreement there needs to be movement on both sides.
"I don't want to compromise what is at the moment a space where we are testing with the opposition, and they are testing with us, particular ways in which we could move forward."
But Mr Duncan Smith warned against his party embracing Labour's Brexit policy, telling Sky's Sophy Ridge on Sunday that he had "real concerns with some of my colleagues going out lauding Jeremy Corbyn".
"We need to be very clear in the course of this that we don't end up letting Jeremy Corbyn dictate to us that we stay in a customs union, or we have some kind of second referendum, or stay aligned with the European single market - all of that given to us by Jeremy Corbyn is a recipe for disaster."
He said there was real grassroots anger at the prospect of the Conservatives having to fight European elections at the end of May and the prime minister should leave Downing Street this summer irrespective of whether the withdrawal agreement had been approved or not.
"She said she would go as and when the agreement was ratified, which was looking at around about May, June. I think those dates still stand," he said.
But Labour's shadow transport Secretary Andy McDonald said the talks would "count for nothing" if the Conservatives changed leader and a hard Brexiteer took over from Mrs May.
Meanwhile, Jeremy Corbyn has been warned Labour will "haemorrhage" votes in the EU election unless the party explicitly backs a further referendum.
MEP Richard Corbett, leader of the party in the EU Parliament, told the Observer Labour risked losing out to parties committed to a public vote.
"If Labour does not re-confirm its support for a confirmatory public vote on any Brexit deal in its manifesto, then it will haemorrhage votes to parties who do have a clear message," he said.
"If on the other hand we do offer clarity and a confirmatory ballot we could do very well."
Labour's current policy is to keep all options on the table - including pressing for a further EU referendum.
Labour MP David Lammy told the BBC's Andrew Marr Show that the current "rows would continue" unless the public had the final say on the issue.
Several members of the shadow cabinet and many backbenchers, particularly in Leave-supporting areas, are opposed to the idea.

If Brexit looks like a political nightmare for Theresa May, it's because it is one; a nightmare she volunteered to endure the day she chose to run for PM.
"It goes with the territory," she told a colleague who offered sympathy recently.
Now she has the job of designing the kind of Brexit her most vocal, and occasionally threatening, Brexiteer Tory colleagues are demanding, then somehow selling it to Parliament, where most MPs and even more peers never liked Brexit at all and seem determined to make that mission impossible.
Search for the government's detailed blueprint for Brexit, a future trade deal and, more urgently, the customs union, and it becomes clear there isn't one.
How could there be?
Brexiteers want out. Full stop.
Or, it's hinted, they'll take Theresa May's scalp.
Most MPs and peers want to stay as close to the customs union as possible, for as long as possible.
There's no way to please them all.
And now, I'm told there's an embryonic, maybe desperate, idea being very quietly discussed among Whitehall mandarins, including UK Brexit negotiators, and privately, a number of ministers and business leaders in the loop: one which hard-line Brexiteers will hate more than most.
Sir Stephen Wall, Britain's former ambassador to the EU and former adviser to Downing Street said he'd heard the proposal amounted to, somehow, trying to stay in a customs deal by another name.
"I'm certainly picking up the idea (of) staying in the customs union," he told me in an interview for BBC Radio Four's World at One.
"Obviously through the transition we would anyway, but potentially beyond the transition... while we seek trade deals," he told me.
"One of the things this process has demonstrated so far - is that positions that we started off with have changed over time, as people have come to grips with the reality and the consequences, and if you're Theresa May you're having to think about the costs to the United Kingdom and how to minimise that cost in economic terms.
"So the idea of thinking about something slightly more long term...is very much there."
Sir Stephen understood the discussion was "in Theresa May's mind", but he didn't know what she'd finally decide.
Sadly, for him and others who share his view, I'm told the prime minister meant what she said when she told Brexiteer Tory MPs they'd get the kind of Brexit they want.
Quite apart from the political minefield at Westminster, it would be hard to persuade Brussels to let Britain stay in some variety of customs deal - whether you call it that or not - while striking outside trade deals, or trying to.
Somehow reaching agreement on migration, something well short of the free movement the EU wants and regaining control of British borders would be another enormous obstacle.
It would be easy, though, compared to persuading Brexiteers it's OK to stay in any customs arrangement.
The prime minister, I'm told, is also every bit as bullish as her Brexit Secretary, David Davis, about the possibility of completing a comprehensive "bespoke" trade agreement with the EU by the end of the Brexit transition period.
Some senior officials privately believe it would take years to strike such an agreement.
The former civil servant who until recently ran the Department of International Trade, Sir Martin Donnelly, told me he believed it would take "five, six, seven years" at least.
That raised the prospect of Britain reaching the end of its transition time with no deal, a new so called "cliff edge".
But in Downing Street they're having none of it. One senior figure argues that European political leaders were often more "can do" - and that would make a difference.
Time's running painfully short.
There's still a huge barrier to a final deal. It sits on the Irish border.
Dublin and Brussels want a British pledge there'll be no hard border on the island of Ireland when the UK leaves the EU even if that means staying a full member of customs union, or creating a new customs border with mainland Britain. It's a Unionists' taboo.
The former Taeseach, Bertie Ahern puts it bluntly.
There'll be no deal unless Theresa May gives ground, he said, and he didn't baulk at the term "fudge".
"Politics and negotiation is about compromise," he said.
"I hope, and I think it's possible, that whatever the name is on it - I know the UK government would have a difficulty saying the 'customs union' is still fully in place - I wouldn't get myself hung up on that - but whatever name you put on it, I think hopefully what will happen, and I think it's a good idea for everybody, if we have a customs union that is not dissimilar from what is presently there.
"That will be a good thing for the EU, a good thing for the UK government for other reasons, but it will solve the Irish question."
The EU summit is just weeks away.
The hope in Team May is that it will be possible to put off the final reckoning until later, probably October when Parliament gives its verdict on the outline Brexit agreement.
Rarely has delay been so vital to forming a plan to redefine Britain and its place in the world.
It may simply be a mark of Carolyn Fairbairn's optimistic outlook, but the Director General of the CBI believes it may yet be possible to win the argument and avoid the kind of customs barriers she believes would be, in her words, disastrous for British business.
"We are very much hoping that's where we end up because businesses across the country - we've talked to thousands of businesses in the last year - the importance of frictionless trade, being able to move goods backwards and forwards without tariffs and rules of origin, and delays abroad, is absolutely fundamental. So we are hoping for a result on this that delivers. We don't care what it's called - but a customs union outcome".
"Forget it" say the Brexiteers, who see all talk of staying in or close to the customs union - any part of the EU - as an act of denial by the remain establishment.
But what if Parliament disagrees - wants a softer Brexit than they can bear?
Tory MP Bernard Jenkin spoke for many of his Brexiteer colleagues when he told me the "remainers" were simply in denial about the fact their predictions of economic harm from the Brexit referendum had failed to materialise.
What if Parliament disagreed?
"Does Parliament really want to pick a fight with the British people," he wondered.
Well, a good many MPs and peers would be perfectly happy to defy Mr Jenkin, and defeat Mrs May for the sake of kicking a "hard Brexit" into touch.
If that also means kicking the prime minister into touch, as far as a lot of her political opponents are concerned, so much the better.
As it is, Theresa May's thinking and the thinking of her Brexiteer colleagues seems to coincide.
It seems the latest, or any, soft Brexit plan won't fly.
If the government's defeated in Parliament, where does that leave Brexit, and Mrs May's premiership?
Well, I don't have a clue. And I'm quite sure no-one at Westminster, in Downing Street or in Brussels has the faintest idea either.
With more wrangling ahead in Cabinet, much more in Brussels and what may be a final reckoning at Westminster in the autumn, it's understandable the government has no detailed plan for the final shape of Brexit.
But with the UK's place in the world being redefined in real time, that doesn't make the situation any more comfortable.

DUP leader Arlene Foster has said her party will "not be able to support" Theresa May's latest proposals aimed at resolving the Brexit deadlock.
The party accused the PM of breaking promises over plans to avoid a hard border between Northern Ireland and the Republic of Ireland.
The plans were revealed in a letter from Theresa May to Mrs Foster, leaked to the Times.
Downing Street reiterated the PM's commitment to avoiding a hard border.
Mrs May relies on the support of the DUP's 10 MPs in key votes because she does not have a majority in the House of Commons.
Agreeing a backstop - a contingency plan designed to keep an open border between Northern Ireland and the Republic of Ireland until the UK and European Union settle their future relationship - remains the main obstacle in the way of a wider deal between the two sides.
Mrs May describes it in her letter to the DUP as "an insurance policy that no-one in the UK or the EU wants or expects to use".
The DUP leader said the party could not back the deal if it came before Parliament and said the PM "needs to reflect" on that.
Mrs Foster told the BBC that a response to a letter sent to the PM last week "unfortunately does say that she's in a position where she's considering regulatory alignment".
"We would not be able to support this if it came to parliament in the form that it is in the letter," said the DUP leader.
"Now there are stages to go through before it comes to parliament. She still has to have a cabinet meeting in relation to this matter and we believe that there is a chance for her to reflect on the fact that we will not be able to support it in its current form.
Mrs Foster added: "I believe that not only would we not be able to support what she has sent to us but that there are many others that wouldn't be able to support it in her own party as well."
If sufficient progress is made on the issue in the next few days, it is thought a special cabinet meeting could be held early next week for ministers to approve the draft agreement on the terms of the UK's exit.
A Downing Street spokesman said: "The government will not agree anything that brings about a hard border on the island of Ireland."
The UK and EU have failed, so far, to reach agreement on how to ensure there are no border checks between Northern Ireland and the Republic of Ireland, if a free trade deal is not in place by the end of the post-Brexit "transition period" in December 2020. This is known as the "backstop".
The EU's proposal, to keep Northern Ireland in its customs union and single market, is unacceptable to the UK because it would mean Northern Ireland having different regulations to the rest of the UK.
But the UK's proposal, which would effectively keep the whole of the UK in the EU customs union for a limited period after Brexit, includes an "expected" end date of 2021 - something which is unacceptable to the EU, which says any "backstop" must apply "unless and until" it is no longer needed.
It says its Northern Ireland-only proposal should remain in place, in case the issue of the Irish border was not sorted out by that end date.
The BBC's John Campbell said what was upsetting the DUP in Mrs May's letter was the issue of single market regulations, not customs.
He said the letter suggested the unique circumstances of Northern Ireland may require alignment with EU single market regulations "in some scenarios" adding that any such alignment would have to be "carefully circumscribed to what is strictly necessary to avoid any hard border".
The DUP has interpreted the wording of her letter to mean that the EU's proposal will be in the Brexit divorce deal, despite Mrs May's insistence it will never come into effect.
BBC political correspondent Iain Watson said the row came down to an issue of trust between Mrs May and her DUP allies, who were suspicious she might sign up to a deal with the EU they did not agree with.
Chancellor Philip Hammond said: "We have always said that we can't accept the [EU] commission proposal for a Northern Ireland-specific solution."
Irish PM Leo Varadkar told a press conference: "The most important thing to me is the objective, and that is to give everyone in Northern Ireland the assurance that a hard border will not develop between north and south, no matter what else may happen in the years ahead.
"That is why we are seeking one that is legally operative and one that gives us that guarantee that is necessary."

The DUP has accused the government of preparing for a Brexit U-turn after the chancellor suggested another referendum would be a "credible proposition".
The DUP has also insisted that it does not support the UK joining a customs union with the EU.
On Wednesday, chief whip Sir Jeffrey Donaldson hinted the DUP might be open to a customs union.
But on Thursday, he criticised "halfway houses" and "staging posts", saying it was not the Brexit people voted for.
Meanwhile, his DUP colleague Sammy Wilson hit out at Chancellor Philip Hammond for suggesting another referendum would be a "credible proposition", before signing off on a deal.
Speaking in the Commons on Thursday, Mr Wilson said: "Are we beginning to see yet the start of another U-turn by a government which has abandoned all of its promises to go forward with a no deal, to have no border down the Irish Sea and to ensure we leave the EU on 29th March?"
Labour has called for a permanent customs union with the EU and is in talks with the government about reaching a compromise.
In a statement on Thursday, Sir Jeffrey called on Prime Minister Theresa May to press the EU for changes to the withdrawal agreement, rather than "subcontract" the negotiations to Labour leader Jeremy Corbyn.
"Whilst the prime minister and her government may consider other options as halfway houses or staging posts, that is not the Brexit which people voted for," he said.
"We will work in Parliament for the referendum result to be properly respected."
The DUP MP added: "It is late in the day, but it is still possible to secure a deal which implements the referendum result and enables the United Kingdom to take back control of its trade, money, laws and borders."
Late on Wednesday, MPs voted by a majority of one to force the prime minister to ask for an extension to the Brexit process, in a bid to avoid any no-deal scenario.
Earlier that evening, Sir Jeffrey said his party would have preferred a form of Brexit that enables the UK to negotiate new trade agreements with other countries.
"That's part of the reason for Brexit and maybe a customs union might be a temporary staging post towards that objective," he told BBC Newsline.
"We will wait to see what the prime minister brings before Parliament but we are very clear, we want a Brexit that delivers for all of the United Kingdom and that keeps the United Kingdom together - that is our objective."
MPs have been debating legislation which would require Mrs May to seek an extension to Article 50 and give the Commons the power to approve or amend whatever was agreed.
Wednesday's knife-edge parliamentary vote to ask the EU for a longer Brexit extension was on a bill brought by Labour's Yvette Cooper.
It was fast-tracked through all Commons stages - a process that can take months - in one day and is now going through the Lords.
It will still be up to the EU to decide whether to grant an extension.
Meanwhile, Attorney General Geoffrey Cox said it was an "article of faith" that the UK must leave the EU to honour the referendum result.
He told the BBC a customs union was "not desirable" but if that was the only way of leaving the EU, he would take it.
The comments come a day after Mrs May said that she will ask the EU for a further extension to Brexit.
Talks between the prime minister and Jeremy Corbyn on Wednesday were said to be "constructive".
It is understood that each party has appointed a negotiating team, and they are meeting before a full day of discussions on Thursday.
Mr Corbyn had said he was "very happy" to meet Mrs May, and would ensure plans for a customs union and protection of workers' rights were on the table.
The DUP has supported the government in a confidence-and-supply pact since June 2017, after a snap general election.
But it is at odds with the prime minister and her Brexit deal, because of the Irish border backstop in the withdrawal agreement.
The party opposes the plan because if it took effect, it would lead to trade differences between Northern Ireland and Great Britain, which the DUP said poses a risk to the integrity of the union.
The UK is still scheduled to leave the EU on 12 April, unless the EU agrees to another extension.
But it is likely to demand that the UK takes part in European elections, which are due to take place on 23 May.
However, Mrs May said she wanted any further extension to be "as short as possible" - before 22 May so the UK does not have to take part in the elections.
Both the UK and EU have continued preparations for a no deal, in the event that a breakthrough cannot be reached in time.

The DUP has endorsed Boris Johnson's offer to the European Union.
It includes the creation of an all-island regulatory zone for agriculture, food and all manufactured goods.
DUP leader Arlene Foster said it was a serious and sensible way forward which "allows the people of Northern Ireland a role which they didn't have".
However, the Irish prime minister said the proposals "do not fully meet the agreed objectives of the backstop" - the mechanism they seek to replace.
After speaking with Boris Johnson on Wednesday evening, Taoiseach Leo Varadkar indicated "he would study them in further detail and would consult with the EU institutions, including the Task Force and our EU partners".
The two prime ministers agreed to talk again next week.
The backstop, agreed in Theresa May's withdrawal agreement, is meant to keep a free-flowing border on the island of Ireland, but critics fear it could trap the UK in EU trading rules indefinitely.
The government plan, outlined in a seven-page document published on Wednesday, would see Northern Ireland stay in the European single market for goods, but leave the customs union - resulting in new customs checks.
The Northern Ireland Assembly would get to approve the arrangements first and vote every four years on keeping them.
Speaking in Belfast after returning from the Conservative Party conference Mrs Foster said it gives the people of Northern Ireland "the consent that they didn't have in terms of the anti-democratic nature of the backstop".
"This is a serious and sensible way forward to have engagement with the European Union in a way that allows us all in the United Kingdom to leave the EU," she added.
The UK proposal is that a revived Stormont Assembly and Executive would have to give their consent for the trade arrangements to come into force before the end of a transition period, which is due to last until 2021.
That consent would then have to be renewed every four years.
Under Assembly cross-community voting rules this would give both unionists and nationalists a veto over aligning with the EU.
If the Assembly withheld its consent, Northern Ireland would revert to the trade regulations which apply elsewhere in the UK.
If the arrangements are approved by the Assembly and Executive, Northern Ireland would adopt EU trade regulations.
However, under the UK proposal it would remain within the UK customs territory meaning there will be a requirement for some customs checks on goods moving across the border.
The European Commission said it will "examine [the proposals] objectively".
In his speech to the Conservative Party conference on Wednesday, Mr Johnson described his plan as a "compromise for both sides" which would "protect the union".
His offer is for an "all-island regulatory zone", which would mean Northern Ireland would have to follow EU rules for goods.
There would be additional checks on goods moving from Great Britain to Northern Ireland, but the UK would not apply further checks on goods entering Northern Ireland from Ireland.
Checks relating to the single market are about product standards, to ensure goods comply with EU regulations.
However, Northern Ireland would leave the EU customs union with the rest of the UK, so there would have to be new customs checks between North and South.
Those checks would look at customs documents and the payment of tariffs, which allow goods to cross the border in the first place.
The government proposals suggest the vast majority of checks could be carried out electronically - but thinks a small number of physical checks would have to take place, either at business premises or at points on the supply chain.
Vice President Michelle O'Neill said that the EU must not accept the proposals as they "failed to meet the objectives of the Irish backstop".
She said: "While a no-deal Brexit was avoided in March and April, there is no optimism that this will be the case come 31 October.
"This is catastrophic for citizens and for business."
In his speech to the Conservative Party conference on Wednesday, Mr Johnson described his plan as a "compromise for both sides" which would "protect the union".
SDLP leader Colum Eastwood said the proposals were "dead on arrival".
He has called on the leaders of the UK's biggest parties to vote Mr Johnson out of office.
Alliance leader and MEP Naomi Long said: "This proposal is in many ways the worst of both worlds, as we've gone from having no new borders to having two."
Ulster Unionist leader Robin Swann claimed the PM's proposals would see Northern Ireland left in a "perpetual cycle of uncertainty".
He said: "The prime minister and the DUP are fooling no-one with these proposals. This new protocol should be deeply concerning for all those who have the long term economic and constitutional welfare of Northern Ireland and its people at heart.
"Northern Ireland would become a hybrid part of the UK with a border up the Irish Sea."

The DUP has held out the prospect of supporting a customs union as talks continue between Theresa May and Jeremy Corbyn to break the Brexit deadlock.
Sir Jeffrey Donaldson made the suggestion to BBC News NI on Wednesday evening.
It came as the Tory and Labour leaders agreed a "programme of work" to try to find a way forward to put to MPs.
Earlier, the DUP called the prime minister's handling of the overall Brexit negotiations "lamentable".
Late on Wednesday, MPs voted by a majority of one to force the prime minister to ask for an extension to the Brexit process, in a bid to avoid any no-deal scenario.
Earlier on Wednesday evening, Sir Jeffrey said his party would have preferred a form of Brexit that enables the UK to negotiate new trade agreements with other countries.
"That's part of the reason for Brexit and maybe a customs union might be a temporary staging post towards that objective," he told BBC Newsline.
"We will wait to see what the prime minister brings before Parliament but we are very clear, we want a Brexit that delivers for all of the United Kingdom and that keeps the United Kingdom together - that is our objective."
The DUP MP earlier told BBC Radio Ulster that regardless of what emerges in the coming days, the DUP's stance on the union was "un-persuadable" and they remained in an "influential position" because of the government's fragile working majority in Parliament.
MPs have been debating legislation which would require Mrs May to seek an extension to Article 50 and give the Commons the power to approve or amend whatever was agreed.
Wednesday's knife-edge parliamentary vote to ask the EU for a longer Brexit extension was on a bill brought by Labour's Yvette Cooper.
It was fast-tracked through all Commons stages - a process that can take months - in one day and is now going through the Lords.
It will still be up to the EU to decide whether to grant an extension.
If the UK joined a customs union with the EU, this would lessen the need for the Irish border backstop, but would not remove it altogether.
On its own, a customs union would unequivocally not eliminate the potential for border checks in Ireland.
Customs are not the only things which could be enforced at the border - checks on food products to see if they meet EU standards would still remain an outstanding issue.
That is a matter that only some sort of continued single market access would grant.
On Monday, the DUP voted against an indicative vote proposing a customs union, but it was not binding.
If Mrs May and Mr Corbyn cannot agree a compromise, the government will put forward its own series of indicative votes - which will be binding - and could include Mrs May's own deal versus a series of other options.
Supporting one union to secure another. Might this be the new DUP tactic?
First, Nigel Dodds said he would rather remain in the EU than risk the union.
Now the party whip is saying a customs union "could be a temporary staging  post" to the "preferred form of Brexit".
On the same day, the Attorney General Geoffrey Cox suggested he, too, could live with a customs union if it helped deliver Brexit.
For the DUP, it's about preserving the union first, delivering Brexit second.
But supporting a customs union in the political declaration, which is not legally binding, may just be a negotiating tactic.
And as a "staging post" it may disappear when Theresa May's replacement takes over the negotiation.
Meanwhile, Attorney General Geoffrey Cox said it was an "article of faith" that the UK must leave the EU to honour the referendum result.
He told the BBC a customs union was "not desirable" but if that was the only way of leaving the EU, he would take it.
The comments come a day after Mrs May said that she will ask the EU for a further extension to Brexit.
Talks between the prime minister and Jeremy Corbyn on Wednesday were said to be "constructive".
It is understood that each party has appointed a negotiating team, and they are meeting before a full day of discussions on Thursday.
Mr Corbyn had said he was "very happy" to meet Mrs May, and would ensure plans for a customs union and protection of workers' rights were on the table.
The DUP has supported the government in a confidence-and-supply pact since June 2017, after a snap general election.
But it is at odds with the prime minister and her Brexit deal, because of the Irish border backstop in the withdrawal agreement.
The party opposes the plan because if it took effect, it would lead to trade differences between Northern Ireland and Great Britain, which the DUP said poses a risk to the integrity of the union.
The UK is still scheduled to leave the EU on 12 April, unless the EU agrees to another extension.
But it is likely to demand that the UK takes part in European elections, which are due to take place on 23 May.
However, Mrs May said she wanted any further extension to be "as short as possible" - before 22 May so the UK does not have to take part in the elections.
Both the UK and EU have continued preparations for a no deal, in the event that a breakthrough cannot be reached in time.

The DUP would have to revisit its confidence and supply deal with the Tories if Theresa May's Brexit deal passes through parliament, Arlene Foster has said.
The DUP leader said her agreement with the Conservatives had been intended to provide the UK with national stability and to deliver on Brexit.
She was speaking on Radio Ulster's Inside Politics programme.
The DUP is holding its annual conference this weekend.
"If this is not going to deliver on Brexit then of course that brings us to the situation of looking again at the confidence and supply deal.
"But we are not there yet," she said.
The DUP leader insisted the government should "ditch the Irish backstop" and recognise that, in practice, nobody will implement a hard border on the island of Ireland.
She argued that the prospect of such a hard border has taken on a "mythical status" in the Brexit negotiations.
Mrs Foster argued that the EU Withdrawal Agreement as it stands will not get the support of parliament.
Instead of "wasting time" on the agreement, she said Mrs May should try to secure a better deal.
The chancellor, Philip Hammond, is one of two Conservative MPs to attend the DUP party conference in Belfast this weekend.
Mr Hammond spoke at a dinner on Friday night.
Earlier, he told the BBC that the government is looking at ways to provide extra assurances to the DUP over the Irish border backstop.
He was speaking during a visit to an integrated school in Moira, County Down.
Mr Hammond said the government has a number of choices through the "parliamentary process", which include extending the implementation period to avoid having to use the backstop.
"I would much prefer to see us extending the implementation period and I am sure my DUP colleagues would take the same view," he said.
"So we need to look at how we can provide reassurance about how we will use the options that the agreement gives us."
Boris Johnson will give a speech to the conference on Saturday afternoon.
Mrs Foster said the reference to the potential use of technology to monitor cross-border trade in the latest EU-UK Political Declaration does not change her party's objections to Mrs May's Withdrawal Agreement.
She said it would have been much better if both the EU and the UK had explored potential technological solutions to maintaining smooth cross-border trade in the summer of last year, when unionists previously championed the idea.
Mrs  Foster said the withdrawal agreement will be legally binding and have the status of an international treaty, so it remains important to the DUP that nothing contained in it damages the UK constitutionally or economically.
Inside Politics is on BBC Radio Ulster on Friday at 18:05 GMT and Saturday at 13:35 GMT.

Northern Ireland's Democratic Unionist Party is planning to vote against the Budget if Theresa May breaches the party's Brexit red lines, Newsnight has learnt.
The party would end its parliamentary support for the prime minister if she agrees a deal at next week's EU summit that led to additional checks between Northern Ireland and the rest of the UK.
The loss of the DUP, which won ten seats at the last election, would raise severe doubts about the government's ability to pass the Budget which is due to be delivered on 29 October.
Losing a budget vote has traditionally been seen as a withdrawal of confidence in the government. One former Tory cabinet minister told Newsnight: "The DUP should be putting the fear of God into Downing St."
The DUP is growing alarmed because it fears Downing St is edging towards a deal with the EU that may lead to additional regulatory checks on goods travelling between Great Britain and Northern Ireland.
Michel Barnier, the EU's chief negotiator, has called for such checks to avoid creating a hard border between Northern Ireland and the Irish Republic. This would be achieved by aligning Northern Ireland with the rules of the single market.
The prime minister has strongly rejected the Barnier plan. But senior DUP sources fear that Downing St may agree to some form of regulatory checks.
One DUP source told Newsnight: "If we are not happy with what happens next week [in Brussels] we won't be bounced into anything. If she doesn't take our concerns on board, we will take the view that Theresa May is not the leader to take us through to a safe Brexit."
The DUP was concerned after Mr Barnier reportedly told the party in Brussels this week that Great Britain is entitled to sign a traditional free trade deal with the EU. But Northern Ireland would have to be separate and subject to the rules of the single market to avoid a hard border on the island of Ireland.
The prime minister has consistently said that no UK prime minister would agree to hiving off Northern Ireland from the rest of the UK. Mel Stride, the financial secretary to the Treasury, insisted that there has been no change in government policy.
Asked about the BBC report that the DUP might vote down the budget, he told Radio 4's The World at One: "I'm not going to speculate on something that just isn't going to happen. We are extremely clear that there will be no border down the Irish Sea."
But the DUP fears that a two-part Brexit deal is emerging that would breach its "nuclear" red line. That is its code for pulling the plug on Theresa May even if that led to Jeremy Corbyn becoming prime minister.
The DUP believe the government's possible Brexit deal would lead to:
You can watch Newsnight on BBC 2 weekdays 22:30 or on Iplayer. Subscribe to the programme on YouTube or follow them on Twitter.

It is painful to watch the prime minister "pleading" with EU leaders to grant another extension to the Brexit date, Arlene Foster has said.
The DUP leader told the BBC she found it "humiliating that we are having to go and beg so that we can leave".
On Wednesday, a special EU summit will take place as leaders consider Theresa May's request.
The UK is still scheduled to leave the EU on 12 April, unless a delay is agreed.
Mrs May is meeting German and French leaders on Tuesday afternoon, in a bid to seek support to postpone the Brexit date again.
The prime minister met Angela Merkel in Berlin, and will meet Emmanuel Macron in Paris, as she urges both to back her request to delay Brexit again until 30 June.
After the talks, Ms Merkel said a delay that runs to the end of the year or the start of 2020 was a possibility.
But Mrs Foster criticised the Prime Minister saying she "needed to be strong, she needed to show leadership, and I'm sorry to say that hasn't been evident in this past couple of months".
However, when pressed on the future of the confidence-and-supply pact her party shares with the government, Mrs Foster said who leads the Conservatives is not a matter for the DUP.
She insisted that the DUP would work in the interests of unionism and would work with whoever was prime minister, but she said it was disappointing that the Irish border backstop still had not been dealt with.
"She is the leader of a party that said they would deliver on Brexit and at the moment she is failing to do that," she added.
Meanwhile, the Taoiseach (Irish prime minister) Leo Varadkar has said he is "confident" an extension will be agreed at the EU summit.
Leo Varadkar said the discussions would focus on the length of any extension and the conditions applied to it, such as shaping a new Common Agricultural Policy (CAP) and electing the next president of the European Commission - and whether the UK could be involved in these decisions.
He said many EU countries were concerned that Brexit was "taking up so much of the EU agenda".
Mr Varadkar added that the Irish government had no objection to a long extension, but he did not want to see that leading to the re-opening of the Withdrawal Agreement.
He said there were certain dates in the text that would expire if the extension was too lengthy, that could lead to the agreement having to be amended.

The Democratic Unionist Party has said there are "still issues to be discussed" with the government as Theresa May continues to try to win support for her Brexit deal.
Mrs May is expected to bring her withdrawal agreement back to the Commons next week for a third vote.
It comes after MPs this week rejected her deal and voted to delay Brexit.
The DUP, which has twice voted against the agreement, said it remained in discussions with the government.
It has been reported by the Spectator magazine that there is a "better than 50:50 chance" the party will support the deal next week.
A DUP spokesman denied reports that extra money for Northern Ireland had been part of the talks, despite the involvement of Chancellor Philip Hammond in discussions on Friday.
The party has previously voted against the deal over concerns around the Northern Ireland backstop - an insurance policy to maintain an open border in Ireland.
The 10 votes provided by the DUP, which props up the government, are thought to be key to the prime minister securing her deal.
A DUP party spokesman said: "We are in discussions with the government to ensure Northern Ireland is not separated out from the rest of the United Kingdom as we leave the European Union. Contrary to some reports, we are not discussing cash.
"There are still issues to be addressed in our discussions."
If the deal fails to gain support, having already been defeated in the Commons by large margins twice, Mrs May has warned a longer extension may be needed, and the UK may have to take part in European elections.
Latvian foreign minister Edgars Rinkevics suggested a delay of up to two years could be required if MPs continue to reject Mrs May's withdrawal agreement.
"Number one priority would be the deal that is reached is passed," he told BBC Radio 4's Today programme.
"If it is not the case, what we need is clear vision from the UK government how much time UK needs to come up with new proposals, new ideas how we proceed.
"In that case it's not a couple of months, I believe then we are talking about maybe one or two years."
Former Cabinet minister Esther McVey, who resigned over the Brexit agreement, suggested fellow Brexiteers could back Mrs May's "rubbish" deal next week to make sure the UK leaves the EU.
She told BBC Radio 4's Political Thinking With Nick Robinson podcast: "The element now is that people will have to take a bad deal rather than no deal."
Meanwhile, shadow chancellor John McDonnell said "quite a number" of MPs would be prepared to support a compromise deal, with the guarantee the deal goes back to the people for a final say on Brexit.
Speaking before an event in Gravesend, Kent, Mr McDonnell said politicians would move "heaven and earth" to prevent the UK from leaving the EU without a deal.
But any final say should not be on the deal Mrs May has agreed, "because it's not credible", he said.
Earlier, Tory MP Nick Boles resigned from his local Conservative association after clashing with the group over Brexit.
Mr Boles, who has spoken out against leaving the EU with no deal, said a "division had opened up" between him and the local association.
Local activists had wanted to deselect him as their candidate in the next general election because of his stance on Brexit.
Chief Whip Julian Smith said Mr Boles was a "valued member of the Conservative parliamentary party, which I hope will continue to benefit from his ideas and drive".
Separately, pro-Brexit marchers, led by former UKIP leader Nigel Farage, have begun a two-week journey from Sunderland to London.
About 100 people assembled to start the march. They were joined by counter-protesters, including those from anti-Brexit campaign Led by Donkeys.
Mr Farage aims to walk 100 miles of the 270-mile March to Leave, which is due to arrive in the capital on 29 March.

The Democratic Unionist Party (DUP) has voted for a proposal that could delay Brexit until all necessary UK laws are passed in Parliament.
MPs voted by 322 to 306 to pass the so-called Letwin amendment to the government's Brexit deal, inflicting a blow on the prime minster's strategy.
The DUP backs Brexit, but does not support the prime minister's revised proposals for Northern Ireland.
It is not clear when Number 10 will now hold a meaningful vote on its deal.
MPs met on Saturday for a rare sitting, with the government hoping to hold a vote on its Brexit deal - but that vote was pulled after they voted for the Letwin amendment.
Independent unionist MP for North Down, Lady Hermon, backed it as well.
It withholds approval of the deal until the legislation to enact it - known as the Withdrawal Agreement Bill (WAB) -  is safely passed: a move that automatically triggers the "Benn Act" to force the prime minister to request a further postponement of Brexit until 31 January.
 A Downing Street source told the BBC Boris Johnson would send a letter to the EU by 00:00 BST to request a Brexit delay but he will not sign it,
The request will be accompanied by a second letter, signed by Mr Johnson, which will say he believes that a delay would be a mistake, the source said.
The prime minister has vowed to bring in legislation on Monday to implement the deal he struck with Brussels this week.
DUP East Antrim MP Sammy Wilson said voting against the government was "the only way" to ensure there was proper scrutiny of the deal.
"We were doing the people of Northern Ireland a favour as well by ensuring that their interests are properly represented," he added.
He said the DUP would now seek changes to the deal, in order address concerns the party has, and suggested the party would vote against the WAB if revisions were not made.
By Jayne McCormack, BBC News NI Political Reporter
Boris Johnson just got a taste of what Theresa May faced from the DUP when she was prime minister.
The party's 10 votes, as well as Lady Hermon's, were decisive in inflicting defeat on the government.
But in less than a year since Mr Johnson gave the keynote speech at the DUP conference, he has seriously fractured the Conservative Party's relationship with Northern Ireland unionism.
The DUP had conceded on regulatory checks in the Irish Sea; in return expecting Mr Johnson to make other commitments to them.
But he didn't.
So the DUP are reminding the PM that, for now at least, they still hold the balance of power in Parliament when it comes to such huge votes.
The DUP is opposed to the consent mechanism in the Brexit deal, which would give the Northern Ireland Assembly a say on whether to continue following EU customs rules.
It would take place by a simply majority vote: pro-EU parties have a narrow majority at Stormont and there would be no unionist veto, as demanded by the DUP.
Earlier Mr Dodds had told Boris Johnson he needed to respect the concerns of unionists - but the prime minister dismissed suggestions that his deal breached the principle of consent.
Under the terms of the Good Friday Agreement, votes on contentious matters should be backed by a majority of unionists and nationalists.
"In all frankness I do think it a pity that it is thought necessary for one side or the other of the debate in Northern Ireland to have a veto on those arrangements," he told MPs.
He argued that the Brexit referendum had taken place on a straight majority basis, adding: "I think that principle should be applied elsewhere, I see no reason why it should not apply in Northern Ireland as well."
Independent unionist MP for North Down, Lady Hermon, has not confirmed whether she will support the government's plan.
She told Mr Johnson there is "anger" in Northern Ireland's unionist community over his deal - but the PM said he is committed to the constitutional position of Northern Ireland, calling it "inviolable".
Meanwhile, in a statement released after the vote, Taoiseach (Irish Prime Minister) Leo Varadkar said that the European Union and United Kingdom had made a withdrawal agreement last Thursday that defends Ireland's interests.
"To date, no request for an extension has been made by the UK government. Should that happen, President Tusk will consult with all 27 heads of state and government on whether or not we will grant one. An extension can only be granted by unanimity," he said.
"Today's antics and bluster will not allay the fears of Irish workers, business or agri foods  producers and our border communities," she said.
The new Brexit deal would involve Stormont giving ongoing consent to any special arrangements for Northern Ireland via a straight majority, instead of on a cross-community basis.
Northern Ireland would continue to follow EU rules on food safety and product standards and would also leave the EU customs union.
But EU customs procedures would still apply on goods coming into Northern Ireland from Great Britain in order to avoid checks at the border.
Stormont would have to approve those arrangements on an ongoing basis.
Approval would involve a straight-forward majority, which would keep the special arrangements in place for four years.
Alternatively, if the arrangements are approved by a majority of nationalists and a majority of unionists, they would remain in place for eight years.
If the Northern Ireland Assembly voted to end the arrangements there would be a two-year notice period, during which the UK and the EU would have to agree ways to protect the peace process and avoid a hard border.
If a vote was not held - by choice or because the assembly was not sitting - then the government has committed to finding an "alternative process".

The withdrawal agreement approved by the UK and EU leaders is "worse than no deal", DUP deputy leader Nigel Dodds has said.
The DUP, which props up the government, has repeatedly said it will vote against it in Parliament.
There has been political opposition to the plan because of the backstop, which aims to avoid a hard Irish border.
A number of business and farming groups in NI have also urged the DUP to support the deal and provide certainty.
Speaking to BBC 5 Live's Pienaar's Politics, Mr Dodds said his party's "one red line" had been ignored by the government.
The agreement on the backstop would see only Northern Ireland stay aligned to some EU rules, if it took effect.
The DUP is concerned that the backstop could threaten the integrity of the union and place a trade border down the Irish Sea.
"What Theresa may has succeeded in doing is putting a proposition on the table which is worse than no deal and worse than staying in the EU, whatever else is put on the table," said the North Belfast MP.
"The government is going to spend the next fortnight engaged in all sorts of project fear initiatives in order to try to get MPs to vote for something that is clearly unsatisfactory."
The DUP has repeatedly said it will vote against the deal, as it stands, when it comes to Parliament to be ratified in a few weeks' time.
Mr Dodds said his party would not be "bought off", he said, adding that "there is absolutely no way this deal can go through on the basis of side offers."
"The DUP has been very clear all along - we have core beliefs and principles and we're sticking by those," he said.
"It is the least worst option - there is no good Brexit."
"It must be clear that under no scenario will there be a hardening of the border in Ireland or the abandonment of the Good Friday Agreement, which we must all work to fully implement and defend," she added.
Earlier, DUP leader Arlene Foster said her party is "disappointed" with Theresa May and the government's decision to press ahead with the Brexit deal.
Mrs Foster said the the agreement "goes against everything" the DUP had been promised.
Speaking on The Andrew Marr Show on Sunday, Arlene Foster said: "We're disappointed with the way this has progressed.
"She (Theresa May) is a unionist, but this deal goes against everything she has said about all of that."
Mrs Foster said there is still time to negotiate for a "better deal".
"We should use the time now to look for a third way. I recognise we are negotiating with a fatigue, there comes a time when everybody is tired and just wants to get on with it but we shouldn't accept the outcome for the sake of it," she added.
Several newspapers have reported that the DUP is involved in discussions with several cabinet ministers about a secret "Brexit plan B", if Mrs May's deal does not get passed in the Commons.
Mrs Foster did not explicitly deny the report, but said her party was having "conversations right across government" about the deal.
She also said she did not see any circumstances right now where Mrs May's deal would have enough support to get through parliament.
The DUP holds the balance of power at Westminster, as the government relies on the votes of its 10 MPs to have a working majority in parliament.
It signed a confidence and supply pact with the Conservatives in June 2017 and negotiated an extra £1bn in spending for Northern Ireland - but the rift between the parties over the Brexit plan has put the arrangement under significant pressure.
Mrs Foster has already said if the government's deal gets passed in the Commons, the DUP will have to review the confidence and supply pact.
"We'll review it at that point in time: things are fluid, things change - we'll have to see where we are," she added.
The government has insisted that it will not renegotiate the current plan, and has urged MPs to back it or risk a no deal scenario.

Westminster seems more peaceful tonight.
Maybe I should just stop there. It is Friday night after all, and after the Big Dipper ride of the last few days, maybe for Number 10, and maybe for you, that's enough to be going on with for now.
But Number 10 knows they'd be kidding themselves to imagine that the danger has gone. We simply won't know, probably until Monday, whether there are enough Tory MPs willing to put their names to letters calling for her to go to trigger a vote on confidence in her that might - in theory - force her from office.
It is possible that by the start of next week Theresa May finds herself with a vote that could unseat her.
If she doesn't, or even if she does but then wins such a vote, here's the problem.
More than 20 MPs have put their names out there publicly calling on her to go and screaming protests at her Brexit deal. They might not get their confidence vote. Even if they do, they might not get enough support to oust her.
But it seems impossible for those who have put their names out there to vote for the Brexit deal in a few weeks time.
With the DUP bristling with rage about the deal and how it was arrived at, and very little sign of a cavalry of Labour MPs riding to the rescue, the number of public protests from those Tory MPs makes it seem like Theresa May's agreement is doomed.
In that regard, how on earth does the government plan to get it through? Can they?
There are two factors that Number 10 hopes will come through for them. First off, they hope that once the deal is done officially with the EU, next Sunday (25 November), then the dynamic will change.
Something along the lines of the leaked plan to sell the deal that we saw last week can get going, and when it does, expect it to rev up fast and loud.
As we've discussed before plenty of times, the government machine will crank up fast and furiously to get MPs to back the deal - or else.
And they also hope that more Labour MPs than currently expected will back them in the end. That's not just because they could choose a deal rather than open Pandora's box.
But it's also because there's a belief in Number 10 that Labour's fellow politicians on the left around Europe will make it clear that frankly, this deal is the best the UK will get, and that a hypothetical Labour government couldn't and wouldn't do any better.
Is that realistic, when the opposition party have the temptation of doing maximum damage to the government of the day? Let's see.
For some of the government's critics, it's simply deluded to imagine they will be able to turn this debate around.
The draft deal, only 48 hours after it was published, has been roundly attacked. There are many more MPs on the record now than are needed to defeat the agreement in Parliament.
But it is impossible to be in the minds of the MPs contemplating turning in a letter calling for May to quit over the weekend.
And harder still to be in the minds of those who will have an agonising choice if the deal makes it to the Commons in a few weeks time.
It is calmer in Westminster tonight, but it is messy, and the danger hasn't gone away.

MPs will vote on Theresa May's Brexit deal on Tuesday, 15 January, government sources have confirmed.
The Commons vote was called off last month by the PM, who was facing defeat, but sources have told the BBC the vote will not be delayed again.
It is also understood the government will set out further reassurances on the controversial backstop.
Meanwhile, more than 200 MPs have signed a letter to Theresa May, urging her to rule out a no-deal Brexit.
It comes as a major exercise involving more than 100 lorries is being carried out in Kent to test out how to manage traffic queues near the Channel ports in the event of a no-deal Brexit.
The PM's deal - which covers the terms of the UK's divorce and the framework of future relations with the EU - has already been agreed with EU leaders. But it needs to pass a vote by MPs before it is accepted.
The UK is due to leave the EU on 29 March 2019 whether the deal is passed by MPs or not.
Mrs May's deal is facing opposition from many of her own MPs, as well as Labour and other opposition parties including the Remain-supporting Liberal Democrats.
The DUP - which Mrs May's Conservative Party relies on for a majority in Parliament - has said it will not back the deal.
But Brexit minister Kwasi Kwarteng dismissed suggestions that the government had accepted it would lose next week's vote and was planning on returning to Brussels.
"The plan is to win the vote on Tuesday, or whenever it comes," Mr Kwarteng told BBC Radio 4's Today programme.
He said a week was "a very long time in politics" and he was "very hopeful" the deal would be voted through.
BBC assistant political editor Norman Smith said reassurances on the Irish backstop were likely to include proposals to minimise any regulatory differences between Northern Ireland and the rest of the UK.
Plans to give Stormont a role in deciding whether the backstop should come into force were also likely.
There could be further possible safeguards for Parliament, with MPs perhaps being given a vote before the UK enters the backstop and the right to notify Brussels of the UK's intention to quit the backstop within a specified time period, our correspondent added.
Government sources also said they hope to set out further reassurances from the EU that the backstop is only temporary.
Meanwhile, writing in Daily Telegraph, ex-foreign secretary Boris Johnson said the option of leaving the EU with no deal is "closest to what people actually voted for" in the 2016 EU referendum.
And Tory MP Damian Green - also an ex-cabinet minister - said the onus was on the MPs to say what deal they would support.
Tory Dame Caroline Spelman, who organised the MPs' letter with Labour MP Jack Dromey, said "crashing out" of the EU without a deal would cause job losses.
Dame Caroline - a Remain supporter who was environment secretary for two years when David Cameron was prime minister - told BBC Radio 4's Westminster Hour programme that 209 MPs had signed the letter.
Asked if the prime minister "gets it", Dame Caroline said: "Yes, I definitely think she gets it. She wouldn't have invited us to come in and see her if she didn't."
Dame Caroline said the signatories to her letter included Brexit and Remain supporters - but the letter did not bind them to supporting the PM's withdrawal deal.
Instead, Dame Caroline said, it creates a "platform" which would "stabilise the economy and give reassurance to manufacturing".
"We are united on one thing - we want to protect jobs and livelihoods by making sure we don't crash out without a deal," she said.
The MPs have been invited to meet the prime minister on Tuesday.
Many Conservative MPs continue to believe the deal does not represent the Brexit the country voted for, and some are actively calling for Britain to leave with no deal.
If the UK leaves the EU without a deal, it would automatically fall back on World Trade Organization rules - which would apply automatically to trade between the UK and EU.
Writing in the Telegraph on Monday, Brexiteer Mr Johnson said of all the options suggested, the no-deal option is "gaining in popularity" and dismissed the warnings against it which he said were "downright apocalyptic".
Mr Johnson said he wants Mrs May to remove the backstop from the withdrawal agreement, "to give real legal protection to the UK".
"Failing that, we should approach the challenge of leaving on WTO terms in a way that is realistic and sensible," he said.
On Sunday, Tory MP Peter Bone told Sky News the best way to "get on" with Brexit was to leave without a deal - which would be "absolutely OK".
He said support for leaving without a deal was "hardening".
But speaking on Sunday, Mrs May warned that if Parliament rejects her Brexit deal, the country faces "uncharted territory".
The UK's exit in March was "in danger" if MPs did not vote for it, she added.
As well as the invite to all signatories of the letter to Downing Street, Mrs May has also invited all Tory MPs to drinks receptions on Monday and Wednesday.
BBC Radio 4's Westminster Hour is broadcast at 22:00 GMT on Sunday and can be listened to here.

David Davis said he can "live with" a transition period of under two years if that helps to secure an early deal.
The Brexit secretary said the EU and UK will establish a joint committee during the transition period to guarantee a "duty of good faith" by both sides.
He said that outlines of the transition phase would reassure Brexit supporters.
Mr Davis will travel to Brussels on Sunday for a meeting on Monday with the EU's chief negotiator Michel Barnier.
Prime Minister Theresa May has called for an implementation period of "around two years" after the UK leaves the EU on 29 March next year.
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In an interview with BBC Newsnight, Mr Davis said he was prepared to accept the EU demand that the transition should come to end earlier - in December 2020 - to ensure the transition is concluded at the same time as the EU's seven-year budget cycle.
The Brexit secretary said his main priority was to secure agreement on the implementation period at next week's EU summit in Brussels.
He told Newsnight: "That is more important to me than a few months either way. So I'm not bothered too much about the question of whether it is Christmas 2020 or Easter 2021."
Asked whether he could live with the transition ending in December 2020, he said: "I would live with that. We are still in the middle of a negotiation. Frankly what I would not do is delay the decision [on an implementation period] in order to get a month or two more."
Mr Davis said that the UK's decision to accept the EU's transition timetable will be balanced by the establishment of a new joint committee to ensure both sides observer a "duty of good faith" during the transition.
He downplayed concerns, voiced by the prominent Tory Brexit supporter Jacob Rees-Mogg, that the UK would be a "vassal state" during the transition. He said most EU laws take two years to pass - three months longer than the proposed transition timetable.
Mr Davis said: "It is not going to be a big material issue. But we want to have in place, and we will have in place, is a joint committee which will oversee any issues like this that come up and a duty of good faith, good faith on both sides so neither side is disadvantaged. So we won't fall into Mr Rees-Mogg's interesting definition of our position."
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The Brexit secretary was interviewed by Newsnight during a day in which he travelled to Copenhagen and Prague to shore up support for the UK in the Brexit negotiations.
Britain believes that the remaining 27 member states, who have been united behind Brussels in the first phase of negotiations, may have their own concerns which could be helpful to the UK in the final phase of negotiations.
Mr Davis, who has been criticised by the European Commission for visiting EU capitals rather than negotiating in person in Brussels, announced he would meet Michel Barnier in Brussels on Monday.
He said: "On all of these [strands in the negotiations] we started discussions with the Commission in Downing Street about four weeks or so ago.  Since then a team, my team, have been working flat out. Principally in Brussels, and that will continue through this weekend, and I shall join them on Sunday and we'll have another meeting with Michel on Monday."

Cabinet ministers should "exert their collective authority" and rebel against Theresa May's proposed Brexit deal, ex-Brexit Secretary David Davis has said.
The prime minister has suggested a temporary arrangement for the whole UK to remain in the customs union while the Irish border issue is resolved.
Brexiteers fear this may be indefinite, limiting the ability to do trade deals.
But Health Secretary Matt Hancock said there were "different ways" to ensure any commitments were time-limited.
Asked whether any deal would include a date at which the UK would no longer be bound by the rules of the customs union, he told the BBC's Andrew Marr show, "I certainly hope so".
"There are different ways you can make sure something is credibly time-limited and that is what I want to see ", he said.
There was "absolutely no reason" for cabinet ministers to quit over the issue, he suggested, urging them to "pull behind" Mrs May ahead of a crucial summit of EU leaders on Wednesday.
The current Brexit Secretary, Dominic Raab, went to Brussels on Sunday afternoon to meet with the EU's chief negotiator Michel Barnier ahead of the event.
A Department for Exiting the European Union spokesman said: "With several big issues still to resolve, including the Northern Ireland backstop, it was jointly agreed that face-to-face talks were necessary."
Wednesday's summit will signal whether or not a deal is likely to be struck in the run-up to the UK's scheduled exit on 29 March 2019.
But writing in the Sunday Times, Mr Davis said the PM's plan was unacceptable.
"This is one of the most fundamental decisions that government has taken in modern times," he added.
And Labour, on whom Theresa May may have to rely to win a Parliamentary vote on the deal later this year, said it would not support "any fudge cooked up with Brussels".
"The government are playing chicken on this," Shadow foreign secretary Emily Thornberry told the BBC's Andrew Marr show, claiming a choice between no deal and a "bit of Theresa May nonsense" was unacceptable.
"We say no... We are not agreeing to build half a bridge when we do not know where it is going."
Mr Davis resigned from his post in July - days after Mrs May's so-called Chequers deal was agreed by cabinet - saying he did not believe in the plan.
The issue of the border between Northern Ireland and the Republic of Ireland, which will become the UK's border with the EU, is one of the last remaining obstacles to achieving a divorce deal with Brussels.
Wrangling is continuing over the nature of a "backstop" to keep the border open if a wider UK-EU trade arrangement cannot resolve it.
The EU's version, which would see just Northern Ireland remain aligned with Brussels' rules, has been called unacceptable by Mrs May and her Democratic Unionist allies.
Mr Davis said the government's negotiating strategy had "fundamental flaws", arising from its "unwise decision" to let the EU dictate the principle of the backstop in December, when the two sides agreed a wider settlement on citizens rights and the so-called divorce bill.
By Helen Catt, BBC political correspondent
That David Davis is no fan of Theresa May's Brexit plan is not surprising.
That he's choosing to ratchet up the pressure with a public call to rebellion aimed at her most senior ministers is perhaps more so.
The former Brexit secretary's own resignation from the cabinet in July did not alter the prime minister's course.
But time to reach a deal with the EU is now considerably shorter, and there have been reports that other senior Conservatives have concerns about the back-up plan for the Irish border too.
The key question is perhaps not so much whom his article might persuade, but whether or not it reflects what some in the cabinet may already be thinking.
Former Tory leader Iain Duncan Smith said it had been a mistake for the prime minister to allow herself to get "boxed in" over the issue of Northern Ireland.
Asked on Sky News' Sophy Ridge show whether he backed calls for a Cabinet rebellion, Mr Duncan Smith said, "when you no longer agree on a fundamental issue, then it's probably time that you found yourself on the back benches".
Negotiations have continued this weekend between the UK and the EU ahead of Wednesday's meeting.
On Saturday evening, German newspaper Suddeutsche Zeitung reported a deal had already been reached between Mrs May and the EU, and would be announced on Monday.
But a No 10 source told the BBC the report was "100%, categorically untrue" and negotiations were ongoing.
Elsewhere, DUP leader Arlene Foster warned the prime minister on Saturday not to accept a "dodgy" deal with the EU.
Mrs Foster said Mrs May should not back a plan that would "effectively cut Northern Ireland adrift". According to a leaked email reported in the Observer, Mrs Foster is preparing for a no-deal Brexit.
The boss of clothing firm Next has suggested leaving the EU without an over-arching deal would not be a disaster for the retail sector and urged ministers to step up their preparations.
Lord Wolfson, a Conservative peer, told Andrew Marr it need not result in delays at the UK's ports as firms could complete new customs declarations online or at their warehouses while tariffs on EU imports could be set at zero to ensure prices do not go up.
But more than three-quarters of NHS trusts have made no preparations for Brexit whatsoever - according to documents obtained by the People's Vote campaign under Freedom of Information requests.
The group also commissioned a YouGov poll of the UK's doctors and nurses, who - according to the poll - now back another referendum by a margin of three to one.

A European odyssey, which has taken David Davis to more than half of the EU's capital cities this year, is drawing to a close.
This weekend Mr Davis will swap the grandeur of chancelleries across Europe for the more functional surroundings of the EU quarter in Brussels.
The UK Brexit secretary will meet his EU counterpart Michel Barnier in Brussels on Monday.
It will be his first visit to the EU capital this year.
In an interview with BBC Newsnight the Brexit secretary said he was "reasonably confident" the UK will reach agreement on one key area at the heart of the negotiations: a transition phase after the UK leaves the EU in March 2019.
The UK has given ground by accepting the EU call for the transition to end in December 2020.
Prime Minister Theresa May had suggested a slightly longer transition of "around two years". This concession by the UK is balanced by an agreement that the UK and EU will establish a joint committee to ensure both sides observe a "duty of good faith" during the transition.
An agreement on a transition phase will create space for Mr Davis and Mr Barnier to move to the next stage: agreeing the outlines of a future trading relationship that will kick in once the transition phase ends.
The move to the second phase of negotiations will not, however, be straightforward.
The EU is deeply frustrated that further steps have not been taken to resolve the dilemma over the Irish border. Britain says the Irish border, one of the main issues in phase one, cannot be finally resolved until the nature of the UK's future relationship with the EU has been agreed, at least in outline.
Britain believes that in the first phase of the negotiations, Mr Barnier achieved remarkable unity among EU member states because they each had an interest in agreeing the starter issues: the UK's financial settlement and the rights of EU citizens in the UK.
In the next phase, which will focus on trade and security, member states may have their own interests to champion.
The Brexit secretary believes that his tour of EU capitals will prove invaluable in the second phase of negotiations.
The UK will be able to "change tack" in some areas to address particular concerns of some member states who might, in turn, lend Britain a helping hand in the negotiations.
During his European odyssey, the Davis visits have followed a routine pattern.
After flying in on an RAF plane, he bounds up to each capital's foreign ministry, greets the relevant minister like an old friend, cracks jokes and then settles down to hear the concerns of that country about Brexit.
On his first appointment in Copenhagen on Wednesday, Mr Davis joked to Anders Samuelsen, the Danish foreign minister, about how he has earned a reputation as a Jekyll and Hyde figure.
Mr Davis laughed about how he, a former SAS Reservist who has no need for a coat even in chilly northern Europe, had suffered the humiliation of having his travel plans disrupted by temperatures plummeting to the "minus 20" zone in neighbouring Sweden.
In a Newsnight interview on the final leg of his tour in the Czech capital Prague, the Brexit secretary denied he had been playing "divide and rule" as he flies from capital to capital.
"One of the things I have always said is people like to think negotiations are a sort of battle of machismo. Actually the best negotiations are the ones which find the best outcome for both sides. This is really that," he said.
In Prague, he heard from Martin Stropnický, the foreign minister, how keen the Czech Republic is to protect and enhance billions of pounds in exports to the UK. That will be down to the future trading negotiations, which will be based on EU guidelines that are due to be approved at next week's summit.
Mr Davis is relaxed about the draft guidelines, which raise the prospect of tariff-free trade in goods but also suggest a much harsher regime for services because of the UK's decision not to be bound by the rules of the single market.
The Brexit secretary said the guidelines are broad enough to allow a full-scale negotiation.
"Everybody is interested in having a deal, a deal that actually allows as much trade to continue on the same basis as possible. Of course it will be a tough negotiation. They all are. But I am confident we are going to get there.
"That is the thing that when people look back in 20 or 30 years' time that is the thing they are going to remember most: what was the basis upon which we continued the relationship after we left? It won't be the short term things, it will be that."
In Denmark and in the Czech Republic, a former Warsaw Pact country, Mr Davis found strong support for the UK over Russia. He insisted that the UK's departure from the EU would not make it more difficult to secure such support in the future.
The UK Brexit secretary said: "I don't think they looked at a treaty before they decided what their opinion was. They heard what had happened, they saw what the prime minister said in the House of Commons and they made a judgment.
"They didn't say: 'Am I treaty bound to do this or that?' [On] defence and security, we are a big player."
As he clocks up the (RAF) air miles to win over friends, the Brexit secretary appears to have abandoned his old image as a Westminster bruiser from central casting.
Sitting in a grand reception room of the British embassy in Prague, with its panoramic views of the former seat of Holy Roman Emperors, he is a model of diplomacy, telling Newsnight: "One of my tasks is, we start as friends and allies of all 27 member states. We will stay friends and allies during this process. And after we have left the EU, we will still be friends and allies."

Brexit Secretary David Davis is confident negotiations will continue as planned after reports that Brussels may delay trade talks because of a lack of progress on the "divorce" settlement.
EU chief negotiator Michel Barnier had wanted progress on the exit payment, citizens' rights and the Northern Ireland border issue by October.
The Daily Telegraph has reported this could now slip back to December.
But the Brexit department says next-stage talks are on course for October.
A spokesman for the Department for Exiting the EU said: "Negotiations to leave the EU are under way and we have already made good progress on a number of issues.
"As the secretary of state said, it is important that both sides demonstrate a dynamic and flexible approach to these negotiations.
"Government officials are working at pace and we are confident we will have made sufficient progress by October to advance the talks to the next phase.
"On the financial settlement, we have been clear that we recognise the UK has obligations to the EU and that the EU also has obligations to the UK."
The upbeat assessment followed a report in the Telegraph which said Mr Barnier had told a private meeting of ambassadors that the next phase of negotiations would be delayed by two months because of the wrangle over how much the UK owes the bloc.
The report said Mr Barnier had claimed the EU would not talk about trade or the UK's future relationship with Brussels until "sufficient progress" had been made on the other "divorce" issues.
European Commission spokeswoman Mina Andreeva would not be drawn on what was said at the meeting with ambassadors.
At a press briefing in Brussels she said Mr Barnier had publicly acknowledged that "so far limited progress has been achieved in the negotiations" but EU officials were ready to work on the issues over the summer if the UK side provided further updates.
She said European Commission president Jean-Claude Juncker was committed to engaging with the UK.
"President Juncker has asked, specifically, the task force on Article 50 to be ready every day throughout the coming weeks, throughout the month of August, to engage with our British counterparts should the UK wish to substantiate their position on some of the cases where it has not happened yet," she said.
"The commission stands ready - we are ready to work - and I cannot speculate beyond that on any timetable because that will depend on the pace of the progress being made."

Justice Secretary David Gauke has said he would be "very surprised" if the prime minister was prepared to back a no-deal Brexit, if her deal fails.
Mr Gauke also said he would find it "very difficult" to stay in cabinet, if that became government policy.
Cabinet splits have emerged over what should happen if the PM's withdrawal deal is rejected by MPs next month.
Andrea Leadsom has suggested a "managed no deal" Brexit while Amber Rudd said a new referendum was "plausible".
Mr Gauke supported Remain in the 2016 referendum.
Labour MP Chuka Umunna, who campaigns for another EU referendum, said the justice secretary had "effectively admitted that all the talk of leaving the EU without a deal is nonsense and a false threat designed to scare MPs into voting for the government's Brexit plan".
He added: "At a time when our schools, hospitals and police are desperately underfunded, the £4.2bn being spent preparing for Brexit would be far better spent on our public services."
The UK is due to leave the EU on 29 March 2019 but an agreement on the terms of its withdrawal and a declaration on future relations will only come into force if the UK and EU Parliaments approve it.
The Commons vote was due to be held earlier this month but Theresa May postponed it, once it became clear it would be defeated by a large margin.
MPs are due to start debating the deal again on Wednesday 9 January.
If Mrs May's deal is rejected, the default position is for the UK to leave in March unless the government seeks to extend the Article 50 negotiating process or Parliament intervenes to stop it happening.
Mr Gauke, who was interviewed on the BBC's Political Thinking with Nick Robinson podcast, was asked about comments he reportedly made at a cabinet meeting on Tuesday, in which he dismissed the idea of a "managed no deal" Brexit as a "unicorn".
He told the BBC: "I think making a conscious decision to proceed with no deal would not be the responsible course of action and I think we would have to look at what other choices were available to us."
Asked if he would remain in the cabinet, he said: "I think it would be very difficult for me in those circumstances."
He said there was a risk of an "accidental no deal" and that "the best way of stopping no deal is to back the prime minister's deal, in my view".
But Mr Gauke said: "I think if it came down to the government saying, consciously, we will just have to do that, I don't think there would be a lot of support for it. I would be very surprised if the prime minister would be prepared to go down that route."
Mrs May has suggested the choice facing MPs is one between her deal, no deal or potentially, no Brexit at all. She has refused to rule out a "no deal" Brexit - under pressure from many MPs to do so.
On Thursday, Commons Leader Andrea Leadsom told the BBC a "managed" no deal did not have to mean no withdrawal agreement at all.
The Leave campaigner said it could be a stripped-down agreement incorporating some of the EU's no-deal preparations.
"What I am looking at is trying to find an alternative so that in the event that we cannot agree to this deal there could be a further deal that looks at a more minimalist approach but enables us to leave with some kind of implementation period.
"That avoids a cliff edge, that avoids uncertainty for businesses and travellers and so on."

The EU's Brexit negotiator Michel Barnier has called for a "moment of clarity" from the UK as talks resumed.
At the start of a fourth round of talks, Mr Barnier said the process had been going six months and progress on key separation issues was essential.
For the UK, David Davis said Theresa May had shown "leadership and flexibility" in her Florence speech and given reassurances on financial issues.
There were "no excuses for standing in the way of progress", he insisted.
The new round of negotiations is the first chance for the EU team to respond to Mrs May's speech in Italy last week, in which she said the UK wanted a two-year transition period and would honour its financial obligations.
The prime minister aimed to restore momentum to a process that was widely reported to be stalling.
Speaking in Brussels, Mr Barnier said he was "keen and eager" for the UK to translate the "constructive" sentiments in Mrs May's speech into firm negotiating positions on issues such as citizens' rights, the Irish border and financial issues, including the UK's so-called divorce bill.
Remarking that it had been six months since the UK triggered Article 50, he said progress on these three fronts was essential to allow talks to move on to the future of the bilateral trade relationship, as the UK would like.
"We are six months into the process," he said. "We are getting closer to the UK's withdrawal. I think this moment should be a moment of clarity."
Mr Davis said he hoped for progress on all fronts but made clear any agreement on financial matters could only be reached in the context of the UK's future partnership with the EU.
"The UK is absolutely committed to work through the detail. We are laying out concrete proposals and there are no excuses for standing in the way of progress."
In her speech on Friday, Mrs May offered to continue paying into the EU for a two-year transition after the UK leaves in 2019 to ensure the bloc is not left with a budget black hole.
The prime minister sought to reassure member states that they would not lose out financially during the current EU budget period, which runs to 2020.
She also confirmed there would be no restrictions on EU citizens coming to the UK during the transition period, but after Brexit they would be registered as they arrived.
Mr Davis has insisted that Mrs May's speech was not influenced by a 4,000-word article by Foreign Secretary Boris Johnson, in the run-up to the event, setting out his own vision for Brexit.
Meanwhile, the UK and Scottish governments have held a fresh round of talks on Brexit in London.
Scotland's Deputy First Minister John Swinney and Brexit minister Mike Russell met First Secretary of State Damian Green to discuss concerns about the EU Withdrawal Bill.
And Mrs May has held talks in Downing Street with Irish premier Leo Varadkar, in her first meeting with an EU leader since the Florence speech.
Mr Varadkar said his counterpart's proposal for a post-Brexit transitional period was a step in the right direction but it was too early to say whether the UK had made sufficient progress in general.

The UK's attorney general says Brexit negotiations will continue as EU officials call for "acceptable" ideas by Friday to break the impasse.
Geoffrey Cox said plans to solve the deadlock over the Irish backstop were "as clear as day", with just days until MPs vote on the Brexit deal.
Commons Leader Andrea Leadsom confirmed the vote will be held on 12 March.
Chancellor Philip Hammond has warned Brexiteers to vote for the deal or face delay to the UK's exit from the EU.
The backstop is an insurance policy designed to prevent physical checks on the border between Northern Ireland and the Republic of Ireland.
Mr Cox, who was in Brussels on Tuesday to push for further changes to the Brexit deal, said talks will "almost certainly" continue through the weekend.
He said there had been "careful discussions" with the EU and stressed it was government policy to seek the legal changes to the backstop.
"We are discussing text with the European Union," he said.
"I am surprised to hear the comments that have emerged over the last 48 hours that the proposals are not clear; they are as clear as day, and we are continuing to discuss them."
Earlier Mr Hammond refused to be drawn on how he would vote if Mrs May's deal is defeated.
"If the prime minister's deal does not get approved on Tuesday then it is likely that the House of Commons will vote to extend the Article 50 procedure, to not leave the European Union without a deal, and where we go thereafter is highly uncertain," he told BBC Radio 4's Today programme.
"For those people who are passionate about ensuring that we leave the European Union on time it surely must be something that they need to think very, very carefully about now because they run the risk of us moving away from their preferred course of action if we don't get this deal through."
In the Commons, Mr Cox also noted that his proposals to change the backstop had been referred to in some quarters as "Cox's codpiece" - using a term to describe a pouch attached to a man's breeches worn in the 15th and 16th Century.
"What I am concerned to ensure is that what's inside the codpiece is in full working order," he quipped.
But Brexiteer Mark Francois, who is a member of the Eurosceptic group of Conservative MPs, the ERG, said Mr Cox had taken charge of the negotiations and would "effectively be examining his own codpiece in the Commons".
He questioned how Mr Cox could provide objective advice when he was "in effect marking his own homework".
Mr Cox replied that "the law is the law", and that he will judge documents relating to the backstop "entirely and impartially".
What we heard from the chancellor this morning was that he was clear about the uncertainties ahead - and rather unclear (cagey, in fact) about how he might vote when it came to decision-time about a no-deal.
There was an explicit warning to Brexiteers: vote for the prime minister's deal because otherwise, it's delay and a soft Brexit.
As one minister expressed to me yesterday, they believe the vote does have a chance of getting through because Brexiteers will realise - just in time - that it's either the PM's deal next week, or what this minister described as "soft, softer, then meltdown".
But across government, the mood is not optimistic about what's going to happen next week and most ministers are expecting a defeat.
French Europe minister Nathalie Loiseau reiterated the EU's position that the withdrawal agreement cannot be reopened and said the deal was the "best possible solution" with the controversial Irish backstop a "last resort solution".
She said: "We don't like the backstop, we don't want to have to implement it, and if we have to, we don't want to stay in the backstop.
"We all agree that it should be temporary."
Meanwhile, former Labour Prime Minister Gordon Brown has told the BBC he is calling for the UK to seek an extension to the Article 50 process, under which the UK is due to leave the European Union on 29 March.
Mr Brown suggested a year-long extension would allow further consultation with the British people. Any extension would require the unanimous agreement of the EU.
He suggested citizens' assemblies could be used - as they were in Ireland ahead of a referendum on abortion - to consult people further on the issues in the absence of any clear majority for a way forward.
"Parliament has proved itself incapable of solving this problem," he said.
"I respect the job that legislators try to do but the country is fed up that Parliament hasn't found an answer. I think the only way that we can get unity in this country is by involving the people in trying to find the solution."
In the Commons, Andrea Leadsom said in the "deeply regrettable case" that the deal is rejected, she will make another statement on Tuesday, to allocate time for the promised votes on leaving without a deal or deferring the UK's exit from the EU beyond the scheduled date of 29 March.
Mrs May is pinning her hopes on getting changes to the backstop that will prevent the UK from being tied to EU customs rules if no permanent trade deal is agreed after Brexit.
Critics say that - if the backstop were used - it would keep the UK tied to the EU indefinitely.
Conservative backbencher Theresa Villiers, a Brexiteer who voted against the withdrawal deal in January, told BBC Radio 4's World at One: "As things look at the moment, I don't see that there is a new revised deal coming back from the European Union which implements significant enough changes to the draft withdrawal agreement to change the result [of the Commons vote on the deal]."
Negotiations between British ministers and the EU officials over the past 24 hours have been described as "difficult", with the EU insisting there has been no breakthrough.
Diplomats from the 28 member states were told on Wednesday that Mrs May could meet European Commission President Jean-Claude Juncker on Monday if progress was made.
But the BBC's Europe reporter Adam Fleming said talk of a deadline for new proposals and a weekend of negotiations was "a notional timetable" and that more flexibility could be possible.

A No 10 source has said a Brexit deal is "essentially impossible" after a call between the PM and Angela Merkel.
Boris Johnson and the German chancellor spoke earlier about the proposals he had put forward to the EU - but the source said she made clear a deal based on them was "overwhelmingly unlikely".
Mrs Merkel's office said it would not comment on "private" conversations.
But the BBC's Adam Fleming said there was "scepticism" within the EU that Mrs Merkel would have used such language.
And the EU's top official warned the UK against a "stupid blame game".
President of the European Council Donald Tusk sent a public tweet to Mr Johnson, telling him "the future of Europe and the UK" was at stake.
With efforts to get a deal by the end of the month on an apparent knife edge, Mr Johnson and his Irish counterpart Leo Varadkar have said they hope to meet later in the week.
But Mr Varadkar told an interviewer on Tuesday evening he thought it would be "very difficult" to secure an agreement by next week.
He said the UK had "repudiated" the deal negotiated previously with Theresa May's government and had "sort of put half of that now back on the table, and are saying that's a concession. And of course it isn't, really".
And following talks in Downing Street, the president of the European Parliament said there had been "no progress" and MEPs would not agree to a compromise deal "at any price".
David Sassoli said the UK's new proposed customs arrangements for Northern Ireland were a "long way from something to which the Parliament could agree".
Amid frantic diplomatic manoeuvring in European capitals, details of a call earlier on Tuesday between the UK and German leaders have reignited tensions across the continent.
The No 10 source suggested Mrs Merkel told her counterpart the only way to break the deadlock was for Northern Ireland to stay in the customs union and for it to permanently accept EU single market rules on trade in goods.
This, the source said, marked a shift in Germany's approach and made a negotiated deal "essentially impossible".
The prime minister's official spokesman said the conversation had been "frank" but denied the negotiations were all but over.
Norbert Rottgen, an ally of the chancellor who is chair of the Bundestag's Foreign Affairs Committee, said there was "no new German position".
He tweeted that a deal based on the UK's latest proposals had "been unrealistic from the beginning and yet the EU has been willing to engage".
The BBC's Europe editor Katya Adler said it was "no secret" Berlin found the UK's proposed new customs solution for Northern Ireland problematic.
While Berlin had not given up hope, she said the chances of a no-deal exit were rising again as the nature of the UK's proposals made any compromise very difficult.
Under Mr Johnson's proposals, which he calls a "broad landing zone" for a new deal with the EU:
The UK's chief negotiator, David Frost, is continuing to meet EU counterparts in Brussels, but the No 10 source said Tuesday morning's phone call had been a "clarifying moment", adding: "Talks in Brussels are close to breaking down."
They said the UK was not willing to move away from the principle of providing a consent mechanism for Northern Ireland, or the plan for leaving the customs union, and if the EU did not accept those principles, "that will be that" and the plan moving forward would be an "obstructive" strategy towards Brussels.
They also accused the EU of being "willing to torpedo the Good Friday agreement" - the peace process agreed in Northern Ireland in the 1990s - by refusing to accept Mr Johnson's proposals.
Hands up if all this stuff about "spokesman" and "sources" is driving you bonkers? Here's the in-brief explanation of how it works at Westminster.
The prime minister has an official spokesman. They work for the government, not the political party that is in government. They give two briefings a day to reporters when Parliament is sitting and they are on the record. That is to say we report what is said and we report who said it - although by convention we don't actually name the spokesman.
There are two reasons for this: they are speaking on behalf of the PM, not themselves. And sometimes a deputy does the briefing instead.
In addition to the official spokesman, there are other people in Downing Street who will talk to journalists. For some, that is their specific job. For others, it is not.
These people will always talk to us off the record - so we can quote them, but not name them, or do anything that risks identifying them.
Journalists always prefer on the record quotes, but in politics as in life, people are often more candid in private, and so we can get a greater sense of what is going on in return for respecting the terms on which the information has been given to us.
Updating MPs on contingency planning for a no-deal exit, minister Michael Gove said there was still "every chance" of a deal but the EU must engage with the UK's plans.
"In setting out these proposals, we've moved - it is now time for the EU to move too," he said.
Ireland's Tánaiste (Deputy Prime Minister), Simon Coveney, said a deal was still possible but "not any at cost" - and the UK must accept it had "responsibilities" on the island of Ireland.
The UK and Irish leaders spoke on the phone for 40 minutes on Tuesday, after which No 10 said both sides "strongly reiterated" their desire to reach a deal.
But Labour's shadow Brexit secretary Sir Keir Starmer told MPs the government was "intent on collapsing the talks and engaging in a reckless blame game".
"The stark reality is the government put forward proposals that were designed to fail," he said, adding that it was "beneath contempt" that, according to a Downing Street source reported by the Spectator, the UK could withdraw security co-operation from other EU countries if it were forced to remain beyond 31 October.
The PM has insisted the UK will leave the EU on that date, with or without a deal.
That is despite legislation passed by MPs last month, known as the Benn Act, which requires Mr Johnson to write to the EU requesting a further delay if no deal is signed off by Parliament by 19 October - unless MPs agree to a no-deal Brexit.
No-one really wants to comment directly on this phone call - certainly not Berlin - but talking to EU officials and diplomats in Brussels, there is considerable scepticism.
That's because the words attributed to Angela Merkel do not reflect the EU's agreed language.
For one, Mrs Merkel and the EU have repeatedly said they will keep talking to the last second and will not pull the plug before that.
And secondly, the No 10 source claims the EU wants to keep Northern Ireland permanently "trapped" in the customs union - Brussels insists it doesn't want that at all, it just wants the option for Northern Ireland stay inside temporarily until something else is worked out.
So as I say, scepticism. It could be a misinterpretation or it could be a deliberate bit of spin, because we're now entering into a blame game about whose fault it is that progress isn't being made.
The key focus of the new UK plans is to replace the so-called backstop - the policy negotiated by Theresa May and the EU to prevent a hard border returning to the island of Ireland - which has long been a sticking point.
After presenting them, government sources hoped the sides might be able to enter an intense 10-day period of talks almost immediately, but a number of senior EU figures, including Irish Taoiseach Leo Varadkar, warned they did not form the basis for deeper negotiations - even if they believed a deal could still be done.
Mr Varadkar has warned the Johnson plan could actually undermine that principle by giving one party in Northern Ireland a veto over what happens to the country as a whole.
Tuesday 8 October - Last working day in the House of Commons before it is will be prorogued - suspended - ahead of a Queen's Speech to begin a new parliamentary session.
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

The deal is done, the pound has been climbing; forget the snow, only sunshine and clear skies ahead for Brexit.
The two hardy political mountaineers have scaled the heights. David Davis and Michel Barnier, representing the UK and the EU, have agreed in principle to the transition deal, or implementation period (whatever you want to call it) - a period of 21 months where the two sides can work out the finer details of the relationship that will evolve over many, many years.
The sighs of relief from No 10 will be so loud they'll be heard in Brussels. The government has something they can say is an agreement, which means progress, and they hope it's an insurance policy against business pulling up stumps and abandoning the UK as the uncertainty around Brexit threatens their ability to make plans.
"Hang on," I rightly hear you say. It is not, that simple.
Yes, the EU and the UK have hammered out a political agreement on what happens as soon as we leave the European Union next year. The short answer is, as the prime minister conceded back in Florence in September, not very much.
And during that period the UK will pay significant amounts of cash for the status quo. But there are three big questions about what has been agreed.
First: As ministers have been perfectly well aware for a long time, there have had to be compromises to get this far. The EU has bent in some areas true, but the UK has done more of the budging. As we reported a few weeks ago for example,  the UK's original hope to make big changes to EU immigration during the transition period, has gone.  The UK has agreed the EU's preferred date of finishing the implementation period at the end of 2020, rather than spring 2021. And in the next few hours the text of today's Brussels statements will be scoured to see where else the big concessions have come.
Second: What is left to resolve? The answer is, a lot. The original plan for the first phase of the talks was to resolve citizens' rights, Ireland and the divorce bill. Well, the cash and citizens' rights are done. That is of course, an achievement of its own. But there is no sign of agreement on the Irish issue, and the UK has had to agree that the controversial backstop remains to solve the problem if everything goes wrong.  And this stage is, remember, only about how we leave - the divorce proceedings not the final agreement that will determine how the UK does business with the EU in the decades to come. This is an important step that is highly likely to be rubber stamped later this week, but it ain't over.
Lastly: How politically acceptable are the fudges agreed so far at home? David Davis has got his "joint committee" that will police the implementation agreement. No 10 hopes this will ease concerns that the UK will essentially have to abide by the EU rules without much of a say - to use the terrible jargon, to be a "rule-taker not a rule-maker". But it is not certain that guarantee will be enough on the Tory backbenches to end claims that the transition will leave us a "vassal state".  And on fishing for example, there is disappointment already that the government has agreed to concede some sovereignty on UK waters during the implementation period that might give rise to demands for a tougher approach in the next part of the negotiations. Don't be surprised for one moment if there are plenty of Brexiteer mutterings that "nothing is agreed, until everything is agreed".
Today though the government will trumpet the fact they have come this far.
Expect ministers to hail the agreement on transition as evidence that Brexit is on track, and to big-up what they see as achievements in the talks - the UK will be able to sign and ratify trade agreements in the transition period for example, to be ready to come into force at midnight on 31 December 2020.
But the agreement has been possible because some of the hard bits have been parked. This a long, a very very long, game.

A legal challenge over Prime Minister Boris Johnson's decision to suspend Parliament has been rejected in the High Court.
The case was brought by businesswoman Gina Miller, who argued the move was "an unlawful abuse of power".
Rejecting Ms Miller's case, Lord Chief Justice Lord Burnett said she could immediately appeal because of the important points of law at stake.
The appeal is expected to be heard at the Supreme Court on 17 September.
Ms Miller said she was "very disappointed with the judgment".
She added: "We feel it is absolutely vital that Parliament should be sitting. We are therefore pleased that the judges have given us permission to appeal to the Supreme Court, which we will be doing, and they feel that our case has the merit to be handed up."
A similar legal challenge was rejected at Edinburgh's Court of Session earlier this week.
Following an appeal, judges at Scotland's highest civil court said on Friday a decision would not be made before Wednesday.
The prime minister announced on 28 August he wanted to shut down Parliament, a process known as proroguing, for five weeks ahead of a Queen's Speech on 14 October.
His political opponents argued at the time that Mr Johnson's aim was to avoid parliamentary scrutiny and to stop them passing legislation that would prevent the UK leaving the European Union without a deal on 31 October.
The UK government insisted this was not the case and said the aim of proroguing Parliament was to allow Mr Johnson to set out his legislative plans in the Queen's Speech while still allowing sufficient time for MPs to debate Brexit.
A bill designed to prevent a no-deal Brexit has since been passed by MPs and is expected to gain royal assent before the shutdown next week.
In 2017, Gina Miller won a case which stopped ministers triggering the Article 50 process - by which the UK leaves the EU - without a vote in Parliament.
The latest case brought by Ms Miller was supported by a number of other parties, including former prime minister Sir John Major.
During the hearing, Lord Pannick QC said prorogation breached the legal principle of Parliamentary sovereignty.
He said the PM's decision was "extraordinary" - both because of the "exceptional length" of the suspension and because Parliament would be "silenced" during the critical period leading up to the 31 October deadline.
Mr Johnson's lawyers argued prorogation was a political, not a legal, matter.
Rejecting the case, Lord Burnett said: "We have concluded that, whilst we should grant permission to apply for judicial review, the claim must be dismissed."
The three judges are expected to give their reasons for dismissing the case in writing next week.
We don't know why Gina Miller lost, but we have an idea of what will be before the Supreme Court.
Ms Miller's team accepts Boris Johnson can ask the Queen to shut down Parliament.
But they argued an exceptional five-week prorogation was an abuse of his executive powers.
The problem in challenging that in court is that judges are there to enforce the law.
The government argues that the law is silent on how long a prorogation should be and that it doesn't help the court judge whether Parliament actually wants to sit, or what would constitute "sufficient" time for considering Brexit - or indeed whether the entire affair is simply a giant political argument that's no business of M'Lords and Ladies at all.
And that's why the case is heading to the Supreme Court.
In Scotland, a group of politicians are attempting to overturn a court ruling made on Wednesday that Mr Johnson's plan to shut down parliament ahead of Brexit is, in fact, legal.
Lord Doherty, sitting at the Court of Session, said the prime minister had not broken any laws by asking the Queen for a five-week suspension as it was for Parliament and the electorate to judge the prime minister's actions - not the courts.
The group of more than 70 largely pro-Remain politicians, headed by SNP MP Joanna Cherry, argues that Mr Johnson is exceeding his powers and attempting to undermine democracy by avoiding parliamentary scrutiny before the UK leaves the EU on 31 October.
On Friday, Lord Carloway said the court had some extremely complex issues to decide, and it hoped to be in a position to give its judgment on Wednesday.
In Belfast, a campaigner for victims of the Troubles brought a case on Friday arguing that a no-deal exit from the EU could jeopardise the Northern Ireland peace process.
The lawyers of Raymond McCord - whose son was murdered by the loyalist Ulster Volunteer Force in 1997 - argued no-deal would endanger the Good Friday Agreement and that suspending Parliament is unconstitutional.
The hearing at the High Court in Belfast was adjourned until Monday.
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She didn't budge. And she was never going to.
After her embarrassment yesterday at the hands of EU leaders, with restive backbenchers at her back, Theresa May was never going to use this highly unusual appearance in Downing Street and dramatically reverse out of her position.
Simply, to back down less than 24 hours later would have looked weak.
And the prime minister has invested huge amounts of time, effort, and political capital into her Chequers plan.
Ministers never believed that it would be the precise form of the final agreement.
But Number 10 believed that in good faith, they had put something credible on the table for discussion.
She has already lost two cabinet ministers over the compromise, and endured weeks of attacks from different wings of her party.
So one, albeit, highly embarrassing diplomatic bust-up was not going to force her to back down.
Her anger was visible though today, explaining again why she believes the two familiar post-Brexit trade options, Norway and Canada, cannot, and will not work for the UK.
And she called for respect from the EU: "Throughout this process I have treated the EU with nothing but respect, the UK expects the same".
A stern tone, strong words.
And in going further on citizens' rights too, perhaps Mrs May has sought to take the high ground, in contrast to what some in the UK are seeing as the EU's poor behaviour yesterday.
But while there is no remote sign from the PM today that she is about to compromise, forces in the EU and in her own party are intent on forcing her to do so.
Her problem is that they want to push her in different directions.
Rhetoric doesn't change the fact that few of the players involved outside Number 10 believe that the suggestions the prime minister has put forward can be the ones that ultimately will win the day.

As Westminster waits and the prime minister calls for an official EU decision to be made, France is acting as a spoke in the wheels. Much as it did back in spring when leaders debated the April Brexit extension.
A consensus is forming amongst most EU countries, including powerful Germany, to grant the three-month delay outlined in Boris Johnson's letter to Brussels requesting a new Brexit extension. They hope to formally announce this on Friday. Ambassadors representing the 27 EU leaders are expected to meet mid-morning in Brussels.
But France worries a 12-week extension could encourage more UK indecisiveness or a general election which may prove inconclusive on Brexit.
President Emmanuel Macron favours a short, sharp Brexit delay; encouraging MPs and the UK government to concentrate on ratifying the newly-negotiated Brexit deal.
Mr Macron is fed up with the more than three-year EU focus on Brexit and the ever-present threat of a no-deal scenario. He'd rather shift attention to reforming the EU itself, to the benefit (he believes) of the countries remaining in it.
Of course, the French president knows Brexit won't be over if and when the UK leaves. Brexit Chapter Two, the negotiations on a comprehensive EU-UK trade deal will likely be lengthy and complex, but they will largely be the competence of the European Commission, landing far more rarely on EU leaders' in-trays.
But will President Macron really veto the three-month extension Germany and others favour? He has already angered a number in the EU of late by putting his foot down on widening the bloc to include two new member states.
If he refuses to agree with an EU majority over the new Brexit extension, then Mr Macron will be using up exactly the kind of good will/openness to consensus decision-making that he needs if he wants to make headway on his EU reform agenda.
Is the length of the Brexit extension really worth that to him?
It could well be that Mr Macron is using the days before the extension decision is formally announced to stamp his feet that:
a)    The UK should not take Brexit extensions for granted and
b)    That the extension time should be used for something concrete.
There is an active EU debate right now (as there was prior to the last Brexit extension being granted) over whether to attach specific conditions. For example, to say that the EU will only grant the extension if the UK begins a new parliamentary timetable aimed at ratifying the Brexit deal or if it holds a general election.
But while it's easy for EU politicians to make assertions like that, it's far more complex to formally put these conditions into writing. It risks looking like Brussels meddling in the domestic politics of a sovereign EU country. So, as with the previous extension, there are unlikely to be formal take-it-or-leave-it conditions attached.
And why are the majority of EU leaders in favour of approving the UK-requested three-month extension? Well, they believe it:
a)    Prevents the EU having to agonise over two extensions in quick succession. A short one to see if the Brexit deal can be ratified in the UK parliament and, if not, then a second extension soon after, to allow the UK to hold elections or a referendum.
b)    Most EU leaders think opting for the extension time asked for by UK (the three months mentioned in the PM's request letter and in the Benn Act compelling him to write that letter) is the most neutral thing Brussels can do, considering the heated political climate in the UK.
Germany, for example, worries that offering more than three months could be viewed in the UK as the EU "trying to keep the UK in as long as possible" while opting for a shorter time could be regarded as an attempt to meddle in UK parliamentary procedure by "forcing" MPs hands over the ratification of the Brexit deal or even as the EU "throwing the UK out".
That explains the EU majority preference for three months but, as with the last Brexit delay, Brussels dubs this a 'flextension'. The UK would not be compelled to remain in the EU for the full extra 12 weeks. It would leave as soon as the UK parliament and the European parliament ratified the Brexit deal.
However, watching the ongoing divisions in Parliament - inside Boris Johnson's Conservative party over whether to prioritise elections vs getting the Brexit deal ratified and also the splits in the Labour party to back, or not to back calling a general election, EU figures mutter in private, that they half expect to be asked for yet another Brexit extension come January.

What just happened? "Simples", the prime minister said (yes, actually seeming to quote a meerkat from a TV advert, welcome to 2019 everyone).
But, if you are finding it not quite so "simples" to work out what's changed in Westminster today, I don't blame you.
Something has changed and, at the same time, not that much has.
No 10 believed that they were going to lose a vote in the Commons on Wednesday on a plan put forward by Labour's Yvette Cooper.
Under that plan, the government would have been forced to put the brakes on Brexit if their compromise deal with the EU was rejected again by Parliament next month.
And, on top of that, it would have given MPs more say over what happens next, designed with the specific aim of giving Parliament a breathing space to pursue consensus for a softer Brexit - a closer relationship with the EU than the PM has agreed.
Add to that pressure, a fair number of ministers were willing to resign if Theresa May didn't say, "OK, if the choice is leaving without a deal, or delaying, I'll delay".
Remember, that's a question that she has avoided for months and months and months, because she regards the promise to leave as planned on 29 March as a solemn one she made to the electorate.
And also, because she believed that being willing to walk away without a deal has been an important element of her negotiating stance.
As the law stands too, the default is that we leave, whatever happens.
But if MPs were going to force her to rule out leaving on time without a deal by trying to change the law, the choice for the prime minister this week was: let the Commons inflict the defeat tomorrow or at least take the decision herself and try to stay in control of events.
One cabinet source disappointed with the decision described it as an "unhappy, but maybe necessary" choice.
What the Cabinet has therefore agreed to do - with one of those threatening to resign saying "it does the trick for now" - is set out a real showdown in the middle of next month.
By 12 March - probably on 12 March, depending what goes on with the negotiations in Brussels - MPs will have another chance to vote on the PM's deal with the EU.
Remember, last month it was kicked out with a thumping defeat.
If the government loses that vote again, the next day, MPs will vote explicitly on whether we should leave the EU without a formal deal or not.
The overwhelming expectation is that MPs collectively would say no to departure without a deal.
If they did reject that idea, there would be another vote on 14 March. This time it would be on whether or not to extend the process for a short time - to delay Brexit for another couple of months while the government keeps trying to untangle the mess.
This is not the same as the prime minister saying that she wants to delay Brexit. She is still insisting that she wants her deal to go through, stick to the timetable and leave at the end of March.
But it is, after many months of promising that we'd leave as planned, the first time she has had to acknowledge it might run very late.
And because Parliament would almost inevitably reject leaving without a deal at the end of March, it changes the choice for MPs in the next fortnight.
No 10 has tried to make the case that MPs will have to choose between the PM's deal, or no deal. Now it's a choice between her deal, no deal, or delay.
Her move today does not change the law and make it impossible for us to leave without a deal at any point.
There's also a really fundamental question about what an extension would actually achieve, when the government, the EU and MPs have been staring at the same set of problems for more than two years and haven't found a happy solution.
The government won't say today what choice they would recommend at the end of March, or what they would do at the end of that extension - leaving with no formal arrangement in place at that point is still a possibility.
But today's move does definitely mean one thing -  it is now extremely unlikely that we will leave at the end of March without a deal, that much at least is "simples".

Former Chancellor George Osborne has said delaying the UK's exit from the EU is now the "most likely" option.
The UK has to choose between no deal - which he compared to Russian roulette - or no Brexit for now, he told the BBC.
But Theresa May says the best option is to approve her withdrawal agreement, which MPs rejected last week.
And International Trade Secretary Liam Fox told the BBC that if MPs blocked Brexit it could have "calamitous" and "unforeseen consequences".
Under current law, the UK will exit the EU on 29 March, whether or not a deal has been struck. The decision to leave was taken by 52% to 48% in a referendum in June 2016. Mr Osborne, now a newspaper editor, was chancellor and a key Remain campaigner at the time.
Speaking to BBC business editor Simon Jack in Davos, Mr Osborne said that the prospect of no deal meant "the gun is held to the British economy's head".
"Russian roulette is a game which you should never play because there's a one-in-six chance that the bullet goes into your head," he said.
Mr Osborne, who was sacked by Mrs May when she became prime minister after the referendum, said his successor Philip Hammond had "sensibly" told businesses that leaving without a deal was not a possibility.
"But we now need to hear it from the British prime minister," he said.
Mr Osborne said that although there might be a majority in Parliament to prevent no deal, it was not clear how MPs would achieve it.
Shadow chancellor John McDonnell told the BBC's Newsnight that it was "highly likely" the party would back an amendment put forward by Labour MP Yvette Cooper, with support from MPs in other parties.
It would give time for a bill to suspend the Article 50 process for leaving the EU if a new deal has not been agreed with Brussels by the end of February.
"I think it's increasingly likely already that we'll have to take that option because the government has run the clock down," Mr McDonnell said.
It is one of several alternative plans by MPs that will be put forward when Mrs May returns to the Commons on 29 January to set out her own proposed next steps.
Among the MPs' plans are to consider a range of options over six full days in Parliament before the March deadline or hold a representative "Citizens' Assembly" to give the public more say.
Another proposal seeks to win over some opponents of the prime minister's deal by insisting on "an expiry date to the backstop", the "insurance policy" intended to avoid a hard border on the island of Ireland.
The backstop is opposed by some Conservative MPs and Northern Ireland's Democratic Unionist Party because it could mean keeping the UK in a customs union with the EU indefinitely and having different rules for different parts of the UK.
But the Taoiseach (Irish prime minister) Leo Varadkar said he could not give up the formal guarantee of the backstop "for a promise that it will be all right on the night".
The European Commission also warned that it was "obvious" that a no-deal Brexit would mean a hard border in Ireland.
Scottish First Minister Nicola Sturgeon, who is meeting Mrs May for talks on Wednesday, said she supports seeking an extension to the Brexit deadline.
Meanwhile, Dyson, the company founded by vocal Brexit advocate Sir James Dyson, has announced it is moving headquarters to Singapore.
However, chief executive Jim Rowan said the decision was prompted by growing opportunities in Asia rather than by Brexit.

Theresa May has been granted an extra two weeks to come up with a Brexit solution after talks with EU leaders.
The UK's departure date had originally been set for 29 March.
If Mrs May can get her withdrawal deal through Parliament next week, that date will be pushed back to 22 May to give time to pass the necessary legislation.
If the prime minister can't get the deal through, the UK will have to propose a way forward by 12 April for EU leaders to consider.
European Council President Donald Tusk said all Brexit options would remain open until then.
"The UK government will still have a choice between a deal, no deal, a long extension or revoking Article 50," he said.
"The 12 April is a key date in terms of the UK deciding whether to hold European Parliament elections.
"If it has not decided to do so by then, the option of long extension will automatically become impossible."
Mrs May ruled out revoking Article 50, which would cancel Brexit, and she also said "it would be wrong" to ask Britons to vote for candidates for the elections to the European Parliament, due to be held from 23-26 May, three years after they voted to leave the EU.
The UK's departure date is still written in to law as next Friday, 29 March.
29 March: Current Brexit date in UK law
12 April: If MPs do not approve the withdrawal deal next week - "all options will remain open" until this date. The UK must propose a way forward before this date for consideration by EU leaders.
22 May: If MPs do approve the deal next week, Brexit will be delayed until this date
23-26 May: European Parliamentary elections are held across member states
Mrs May is expected to table secondary legislation - that has to go through the Commons and the Lords by next Friday - to remove 29 March from UK law.
But Downing Street sources say an agreement with the EU to extend the Brexit deadline would be a piece of international law and would take precedence even if Parliament rejected it.
Mrs May said MPs had a "clear choice".
Speaking on Thursday, after waiting for the 27 other EU countries to make their decision at a summit in Brussels, the prime minister said she would now be "working hard to build support for getting the deal through".
The withdrawal deal, negotiated over two years between the UK and EU, sets out the terms of the UK's departure from the bloc, including the "divorce bill", the transition period, citizens' rights and the controversial "backstop" arrangements, aimed at preventing a return to border checks between Northern Ireland and the Republic of Ireland.
But it must be approved by UK MPs, who have already rejected it twice by large margins.
MPs are expected to vote for a third time on it next week, despite Commons Speaker John Bercow saying what is put forward must be substantially different to be voted on.
Theresa May has been granted a little breathing space. The EU has allowed a few more days to try to get her deal through the House of Commons.
But it's not the timetable that she chose.
And as things stand, the expectation that the compromise deal will get through is low.
And, more to the point, the government does not believe that it can hold off another attempt by a powerful cross-party group of MPs who are resolved to put Parliament forcibly in charge of the process to find alternatives.
Ministers are therefore today not just wondering about how to manage one last heave for the prime minister's deal, but what they should do next, when - odds on - the whole issue is in the hands of the Commons, not Number 10.
Read Laura's blog
Senior Labour MP Hilary Benn has also said that he will table an amendment on Monday, enabling MPs to hold a series of "indicative votes" on Wednesday on alternatives to Mrs May's plan. He said these could include a free trade agreement, a customs union and a referendum.
He told the BBC the EU's decision was "a case of crisis delayed, not crisis ended" as it still looked unlikely that Mrs May's deal would be approved.
"We cannot have a no-deal Brexit in three weeks' time," he said.
The government is also exploring with opposition parties the idea of holding "indicative" votes on alternatives to its own Brexit policy, in an effort to retain some control over the process.
Plaid Cymru's leader at Westminster, Liz Saville Roberts, who has been taking part in the talks, said: "The government is now openly exploring a process to allow Parliament to take control - an effective admission that they have lost all authority.
"We will be continuing to push for a People's Vote as a way out of this Brexit mess."
At a news conference on Thursday night, Mrs May also struck a conciliatory tone when she referred to her speech from Downing Street the previous evening, which had sparked an angry reaction from MPs after she blamed them for the Brexit deadlock.
"Last night I expressed my frustration and I know that MPs are frustrated too," she said. "They have difficult jobs to do."
Speaking to Nick Robinson's Political Thinking podcast, Business Secretary Greg Clark said that speech "clearly wasn't a great success".
"I don't think it was helpful in resolving the matter. But, listen, none of us is infallible and even prime ministers sometimes don't get the tone quite right," he said.
It comes after a petition calling for Article 50 to be revoked passed three million signatures. A march demanding another referendum is also planned for Saturday in central London.
In her briefing to journalists, Mrs May dismissed calls to revoke Article 50 - the process by which the UK leaves the EU - which would mean Brexit is cancelled.
Mrs May said people had voted to leave and were told their decision would be respected.

Labour has finally pulled the plug on the Brexit talks with the government, at the end of a week in which they appeared to be on life support.
So is it, as some suggest, time to read the last rites on Theresa May's Withdrawal Agreement Bill?
Let's be clear - it will be challenging, to say the least, for the legislation to get through the Commons.
But reports of its demise may well have been exaggerated. It may not go down to immediate defeat. And this is why.
A leaked memo from the government side, not agreed by Labour or the cabinet, contained a wheeze that could have been attractive to both leaderships.
Even before the Withdrawal Agreement Bill makes its appearance, the memo suggested there could be a "free vote" in Parliament on another referendum.
This is rather different from what the shadow Brexit secretary, Sir Keir Starmer, was suggesting - that there ought to be a "confirmatory" vote, as part of a package, on any agreed deal.
The leaders of both the main parties aren't keen on another public vote, to say the least. So a stand-alone Commons vote on the issue, divorced from the deal, would be more likely to go down to defeat - as it has on previous occasions.
Jeremy Corbyn could say to People's Vote supporters in his ranks: "Oh, I did try for a referendum, but oops, it didn't work - so now let's just leave with the best possible deal."
But it would seem that this approach has been scuppered by Labour's wider negotiating team and, presumably, by the cabinet. I have had a strong steer that this proposal in the leaked government memo won't go ahead in this form.
But this might not be the setback it seems for the prime minister because supporters of another referendum may have no option but to vote initially for her bill.
There will be a vote at what's called, in parliamentary speak, second reading in the first week in June. If the prime minister is defeated at this point, it's basically the end of the road for her deal and her premiership.
But if MPs vote for the bill at second reading, they then get an opportunity to change it - and that would include an amendment on another referendum.
So it's not impossible that some people who hate Theresa May's deal give it their temporary backing so they can discuss improving it, or putting it to a public vote.
Talks with Labour are over - but efforts to win over individual Labour MPs are not. Note the wording of Downing Street's statement that "complete agreement" hasn't been reached.
So expect to see some incentives in - or around - the Brexit bill for opposition MPs to back the government. For example, a commitment to stay in step with the EU on workers' rights and environmental protection.
Allies of Sir Keir have blamed the breakdown of the talks on the PM's inability to get a customs union compromise past her cabinet.
But if she keeps Conservative MPs on board in the legislation by eschewing a customs union but delivers a "comprehensive" (trust me, this word is important to some Labour MPs) temporary arrangement to last until the next election, some soft opposition to her deal may crumble.
Then there is the argument put forward by the former Conservative minister Nick Boles, echoed off the record by some in Downing Street.
If the prime minister's bill gets shot down in flames there is no other readily available vehicle to prevent the default option of no deal. Indeed, No 10 insiders expect to see "vociferous" arguments for no deal if Theresa May's legislation falls.
Some unions, such as the GMB and Unison, favour another referendum. But the leadership of Unite, which is closest to Mr Corbyn, essentially favours leaving with a deal - and Labour MPs will be made well aware of this.
So even if Labour formally opposes the bill at second reading, there could be a sizeable rebellion from those former Remainers representing Leave areas - safe in the knowledge that they wouldn't exactly be upsetting some powerful forces in the party.
And the MPs who support what's called Common Market 2.0 could be crucial to the outcome. These are, broadly speaking, Labour MPs who are neither Corbynistas nor in favour of another referendum - such as Lucy Powell and Stephen Kinnock - and they are very keen to avoid no deal.
However, if the Labour whip is to oppose, expect it to be rigorously enforced irrespective of the views of the party leader's office. So Mrs May's immediate fate may still be in the hands of opposition MPs
The forthcoming leadership contest may firm up opposition to Theresa May's bill on the Conservative benches
By putting the Withdrawal Agreement Bill out of its misery almost as soon as it appears, the prime minister's critics know she will vacate office sooner rather than later.
But some candidates will be keener for her to get Brexit over the line, even with a less than optimal deal, so they don't immediately get bogged down with difficult votes. It would also allow them to make their pitch based on the future relationship with the EU.
So could some of their supporters - irrespective of their public criticism of the deal - quietly vote to get it over the line?
Set against all this, there is plenty of analysis in the public domain which will tell you how impossible it is for a deal to go through.
But right now, No 10 might well see "highly improbable" as grounds for optimism. Hope dies last, does it not?

Brexit Secretary Dominic Raab says he quit the cabinet over "fatal flaws" in the draft Brexit agreement with the EU.
And he told the BBC the UK should be ready to risk a no-deal Brexit in the face of EU "blackmail".
Another cabinet minister, Esther McVey, also quit alongside junior ministers Suella Braverman and Shailesh Vara.
PM Theresa May faced nearly three hours of largely hostile questions in the Commons and could potentially face a vote of no confidence from Tory MPs.
BBC political editor Laura Kuenssberg said a source had told her Michael Gove has been offered the job of Brexit Secretary and he was understood to be considering it, but to be asking for assurances that he could pursue a different kind of deal.
Leading backbench Brexiteer Jacob Rees-Mogg has submitted a letter of no confidence in her to Sir Graham Brady, chairman of the Tories' backbench 1922 Committee.
A vote will be triggered if 48 Tory MPs write letters to Sir Graham. It is understood 48 letters have not yet been received.
Mr Rees-Mogg told reporters that the negotiations had "given way on all the key points" adding: "The deal risks Brexit because it is not a proper Brexit."
He denied being involved in a coup against the PM, saying he was "working through the procedures of the Conservative Party" which was "entirely constitutional".
Mr Rees-Mogg said he did not have any leadership ambitions of his own but listed Brexiteers Boris Johnson, David Davis, Dominic Raab, Esther McVey and Penny Mordaunt as among those who would be "very capable of leading a proper Brexit".
Downing Street said Mrs May would fight any no-confidence vote.
Asked by Labour MP Mike Gapes if it was time she "stood aside for someone else who could take this country forward in a united way", Mrs May replied: "No."
Chief whip Julian Smith said the prime minister "will not be bullied" into changing course.
And Foreign Office minister Sir Alan Duncan described Mr Rees-Mogg's comments as "deeply destructive" and warned Conservative MPs: "If this government is undermined further, we could destroy the government, we could significantly damage and even destroy the Conservative Party, all of which would be happening in the middle of an unconcluded set of Brexit negotiations."
He added: "We have a massive responsibility to exercise our judgement in a climate of what has to be compromise."
The day after Theresa May announced that she had secured the backing of her cabinet for the withdrawal agreement, she told MPs it was not a final agreement, but brought the UK "close to a Brexit deal".
But she was met with laughter and shouts of "resign" as she said it would allow the UK to leave the EU "in a smooth and orderly way" on 29 March
The prime minister told MPs the agreement would deliver the Brexit people voted for and allow the UK to take back control of its "money, laws and borders".
But Labour Leader Jeremy Corbyn said: "This is not the deal the country was promised and Parliament cannot - and I believe will not - accept a false choice between this bad deal and no deal."
Dominic Raab - a Leave supporter promoted to the cabinet to replace David Davis who quit in protest at Mrs May's Brexit plans in July - is the most high-profile minister to quit the government.
He was closely involved in drafting the 585-page document, which sets out the terms of Britain's departure from the EU.
He told the BBC's political editor Laura Kuenssberg: "I've been fighting for a good Brexit deal but the terms proposed to the cabinet yesterday [Wednesday], I think, had two major and fatal flaws.
"The first is that the terms being offered by the EU threaten the integrity of the United Kingdom and the second is that they would lead to an indefinite if not permanent situation where we're locked into a regime with no say over the rules being applied, with no exit mechanism.
"I think that would be damaging for the economy but devastating for public trust in our democracy."
He said Theresa May needed a Brexit secretary who "will pursue the deal that she wants to put to the country with conviction".
"I don't feel I can do that in good conscience," he added.
He said he held Mrs May in "high esteem" but said: "I do think we need to change course on Brexit".
And he said the government should be willing to risk a no-deal Brexit in the face of what he described as the EU's "blackmail".
The alternative for the prime minister was her inevitable defeat in the Commons, he argued.
Asked if he would put himself forward for leader, if the government falls apart, he did not rule it out but said it would be "irresponsible" to be talking about that now.
In her resignation letter, Work and Pensions Secretary Esther McVey told Mrs May the agreement does not "honour the result of the referendum, indeed it does not meet the tests you set from the outset of your premiership".
"We have gone from 'no deal is better than a bad deal' to any deal is better than no deal," she added.
Anne-Marie Trevelyan, a ministerial aide at the education department, has also quit, as has Ranil Jayawardena, a ministerial aide at the justice department.
Northern Ireland minister Shailesh Vara was the first to resign over Mrs May's agreement on Thursday morning, saying, it "leaves the UK in a halfway house with no time limit on when we will finally be a sovereign nation". Brexit minister Suella Braverman also quit.
And Rehman Chisti quit as vice chairman of the Conservative Party - partly over the withdrawal agreement.
Labour leader Jeremy Corbyn said: "After two years of bungled negotiations, the government has produced a botched deal that breaches the prime minister's own red lines and does not meet our six tests.
"The government is in chaos. Their deal risks leaving the country in an indefinite halfway house without a real say."
The SNP's leader at Westminster Ian Blackford said Mrs May was "trying to sell us a deal that is already dead in the water" and expressed outrage that Scotland was not mentioned once in the draft withdrawal agreement.
But the controversial part relates to what will happen to the Irish border.
The agreement includes a "backstop" - a kind of safety net to ensure there is no hard border whatever the outcome of future trade talks between the UK and the EU.
If there is no trade deal in place by the end of the transition period, the backstop will mean that Northern Ireland would stay aligned to some EU rules on things such as food products and goods standards.
It would also involve a temporary single customs territory, effectively keeping the whole of the UK in the EU customs union.
Brexiteers do not like the prospect of potentially being tied to EU customs rules for years or even, as some fear, indefinitely.
And Northern Ireland's Democratic Unionist Party has said it will not tolerate anything that creates a new border down the Irish Sea and they will not vote for the agreement.
Setting out details of the arrangements for a possible "backstop", Mrs May said: "I do not pretend that this has been a comfortable process, or that either we or the EU are entirely happy with some of the arrangements which have been included in it."
But she added that "while some people might pretend otherwise, there is no deal which delivers the Brexit the British people voted for which does not involve this insurance policy".
She insisted it was a last resort and would be time-limited.
Much will depend on whether Mrs May faces a vote of no-confidence in her leadership. If she does, all bets are off.
If not, European Council President Donald Tusk has announced an emergency meeting of EU leaders in Brussels on 25 November, at which the withdrawal agreement and a political declaration on future relations would be finalised and formalised.
The BBC's Brussels correspondent Adam Fleming said the UK and the EU will have to agree an ultimate end date for the post-Brexit transition period by the end of next week.
The transition period is due to end in 2020 and can be extended once by mutual agreement.
The text of the draft withdrawal agreement currently says the end date is "20XX".
A senior EU official said the negotiators will have to fill in a specific year by the 25 November summit.
Ultimately any deal would be put to MPs. Tory backbencher Mark Francois told Mrs May earlier that with Labour, the SNP, the Lib Dems and scores of Tory MPs planning to vote against it, it is "mathematically impossible to get this deal through the House of Commons".

European Council President Donald Tusk and Prime Minister Boris Johnson have clashed over who would be to blame in the case of a no-deal Brexit.
Mr Tusk said Mr Johnson risked being remembered as "Mr No Deal" - but the PM responded by saying it was Mr Tusk who would become "Mr No-Deal Brexit".
The pair are due to meet for talks at the G7 summit in France on Sunday.
Mr Tusk added the EU was "willing to listen" to the PM's ideas for Brexit - as long as they are "realistic".
But speaking at his press conference in Biarritz, Mr Tusk said he would "not co-operate on [a] no-deal".
Since becoming PM, Mr Johnson has said the UK will leave the EU on 31 October.
Mr Johnson has repeatedly stated he would prefer to leave the EU with a deal, but insists the backstop - the insurance policy designed to avoid a hard border on the island of Ireland - must be removed from the withdrawal agreement.
"I've made it absolutely clear I don't want no deal and that we've got to get rid of the backstop from the treaty and if Mr Tusk doesn't want to go down as Mr No-Deal Brexit I hope that point will be borne in mind too," he said.
Earlier in the day, Mr Tusk had used the same moniker when talking about Mr Johnson.
"I still hope Prime Minister Johnson will not like to go down in history as Mr No Deal," he said.
"The EU has always been open to co-operation. One thing I will not co-operate on is a no deal.
"We are willing to listen to ideas that are operational, realistic and acceptable to all EU member states."
Analysis by BBC diplomatic correspondent James Landale
When Boris Johnson met President Emmanuel Macron and Chancellor Angela Merkel this week, he got a relatively positive response.
Both leaders indicated they were willing to listen to any ideas the prime minister may have to avoid a no-deal Brexit.
But Mr Johnson's meeting with Donald Tusk at the G7 summit on Sunday may now prove more problematic.
The spat between both men - both of them warning they could go down in history as Mr No Deal - shows that both sides are engaged in a blame game.
Neither side wishes to be seen as the intransigent partner in a negotiation that leads to no deal.
Mr Macron and Ms Merkel were implicit in this, while Mr Tusk was explicit, prompting an equally blunt response from Mr Johnson.
It is, of course, still possible that some political space may be carved out to allow for a compromise at the last minute. But all the signs still point towards a no-deal Brexit at the end of October.
The G7 summit - a get-together of most of the leaders of the world's largest economies - comes with just over two months until the UK is scheduled to leave the EU at the end of October.
Mr Johnson wants to renegotiate the Irish backstop - a key Brexit sticking point - but the EU has consistently ruled this out.
Speaking on Saturday, Mr Johnson said: "We've made it very clear we won't be instituting any kind of checks or controls at the Northern Irish border. We don't think such controls are necessary.
"There are a large range of alternative arrangements - these we will be discussing in the coming weeks."
If implemented, the backstop - a last resort should the UK and the EU not agree a trade deal after Brexit - would see Northern Ireland staying aligned to some rules of the EU single market.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
At a news conference on Wednesday with Mr Johnson, German Chancellor Merkel suggested an alternative to the backstop might be achievable, adding that the onus was on the UK.
But the next day French President Macron said the backstop was "indispensable" to preserving political stability and the single market.
After visiting his counterparts in Paris and Berlin this week, Mr Johnson said there was "new mood music", but reaching a new deal would not be "a cinch".
He has insisted the UK will leave the EU on 31 October, whether or not a new deal is reached.
Mr Johnson will also meet with US President Donald Trump, who arrived in France around Saturday lunchtime.
Asked if he would be telling Mr Trump not to escalate the US-China trade war, Mr Johnson said: "You bet."
He added one of his priorities for the summit was "the state of global trade".

European Council president Donald Tusk has said not enough progress has been made to move to the next phase of Brexit talks in Brussels.
He said Theresa May's "realistic" speech on Friday showed the UK's "philosophy of having a cake and eating it is finally coming to an end".
But he said "there is not sufficient progress yet".
Mrs May had hoped her offer of a two-year transition period after Brexit would unblock talks in Brussels.
Emerging from Downing Street after talks with Mrs May, Mr Tusk said: "I feel cautiously optimistic about the constructive and more realistic tone in the prime minister's speech in Florence and of our discussion today.
"This shows that the philosophy of having a cake and eating it, is finally at an end. At least I hope so. That's good news.
"But of course no-one will ever tell me that Brexit is a good thing because as I have always said, in fact, Brexit is only about damage control.
"And I didn't change my opinion.  I feel now we will discuss our future relations with the UK once there is so-called sufficient progress.
"The two sides are working and we will work hard at it. But if you ask me and if today member states ask me, I would say there is no sufficient progress yet. But we will work on it."
His words come a month before the European Council will decide whether sufficient progress has been made to begin trade talks, as the UK wants.
Hesitant, understated, but with a very clear message.
In fact, so quietly spoken those of us listening here, crouched beneath the cameras, a metre from his shoes, could barely hear his words.
Two pieces of imagery have been frequently leaned on in updates on the Brexit negotiations.
The EU has a love of noisy timepieces; all those references to ticking clocks.
And the desire of some in the UK to have our cake and eat it crops up quite a bit too.
Mr Tusk's "hope" that the references to gorging on confectionery are over stood out.
But so too did his blunt assessment that more has to be achieved before the talks move on to the future relationship.
So, for the prime minister, did her Florence speech do the business?
From her perspective, it looks like it has worked a bit, but not yet enough.
The council says it first wants more detail on citizen's rights, a financial settlement and the Irish border before turning to the kind of trade deal the UK will have with the EU after it leaves.
Brexit Secretary David Davis, who is taking part in the fourth round of Brexit talks in Brussels, said that Mrs May had shown "leadership and flexibility" in her Florence speech and given reassurances on financial issues.
There were "no excuses for standing in the way of progress", he insisted.
But the EU's Brexit negotiator Michel Barnier called for a "moment of clarity" from the UK.
Speaking in Brussels, Mr Barnier said he was "keen and eager" for the UK to translate the "constructive" sentiments in Mrs May's speech into firm negotiating positions on issues such as citizens' rights, the Irish border and financial issues, including the UK's so-called divorce bill.
Remarking that it had been six months since the UK triggered Article 50, he said progress on these three fronts was essential to allow talks to move on to the future of the bilateral trade relationship, as the UK would like.
"We are six months into the process," he said. "We are getting closer to the UK's withdrawal. I think this moment should be a moment of clarity."
Speaking ahead of her meeting with Mr Tusk, Mrs May said that "by being creative" the UK and the EU can maintain cooperation and partnership when the UK leaves the EU.
And she said that "things have moved on" in terms of the discussions and negotiations in the Brexit talks.

European Council president Donald Tusk says the EU should consider offering the UK a "flexible" delay to Brexit of up to a year, with the option of leaving earlier if a deal is ratified.
He said there was "little reason to believe" a Brexit deal would be approved by the extension deadline UK PM Theresa May has requested - 30 June.
Writing to EU leaders, he said any delay should have conditions attached.
It is up to EU members to vote on the proposals at a summit on Wednesday.
A draft EU document circulated to diplomats ahead of the emergency summit also proposes an extension but leaves the date of the proposed new deadline blank.
The BBC's Brussels correspondent Adam Fleming said the document referred to an extension lasting "only as long as is necessary and, in any event, no longer than XX.XX.XXXX and ending earlier if the withdrawal agreement is ratified".
The UK is currently due to leave the EU at 23:00 BST on Friday.
So far, UK MPs have rejected the withdrawal agreement Mrs May reached with other European leaders last year, so she is now asking for the leaving date to be extended.
Meanwhile, Mrs May has been meeting French President Emmanuel Macron in Paris and German Chancellor Angela Merkel in Berlin for talks ahead of the summit.
Afterwards, Ms Merkel said a delay that ran until the end of this year or the start of 2020 was a possibility.
Mr Tusk said granting the 30 June extension that Mrs May is seeking "would increase the risk of a rolling series of short extensions and emergency summits, creating new cliff-edge dates".
And if the European Council did not agree on an extension at all, "there would be a risk of an accidental no-deal Brexit", he said.
"One possibility would be a flexible extension, which would last only as long as necessary and no longer than one year, as beyond that date we will need to decide unanimously on some key European projects."
Mr Tusk said the EU would need to agree on a number of conditions to be attached to any proposed extension, including that there would be no re-opening of negotiations on the withdrawal agreement.
He said the UK should be treated "with the highest respect" and "neither side should be allowed to feel humiliated".
BBC Europe editor Katya Adler said the EU's draft conclusions "should be taken with a big pinch of salt" as EU leaders could "rip up the conclusions and start again" on Wednesday.
She said the fact that the length of delay had been left blank in the conclusions shows EU leaders were still divided on the issue.
Downing Street said Mrs May had discussed the UK's request for an extension of Article 50 - the process by which the UK leaves the EU - until 30 June, with the option to make it shorter if a deal is ratified earlier, with both Ms Merkel and Mr Macron.
The prime minister and Chancellor Merkel agreed on the importance of ensuring Britain's orderly withdrawal, a statement said.
Mrs May and Mr Macron also discussed next month's European Parliamentary elections, with the prime minister saying the government was "working very hard" to avoid the need for the UK to take part as it is supposed to if it is still a member of the EU on 23 May.
Following a meeting of the EU's General Affairs Council in Luxembourg, diplomats said "slightly more than a handful" of member states spoke in favour of delaying Article 50 until 30 June but the majority were in favour of a longer extension.
EU leaders are curious to hear the prime minister's Plan B. They hope there is one, although they're not convinced.
They want to know, if they say, "Yes," to another Brexit extension, what it will be used for.
And they suspect Theresa May wants them to do her dirty work for her.
EU diplomatic sources I have spoken to suggest the prime minister may have officially asked the EU for a short new extension (until 30 June) as that was politically easier for her back home, whereas she believed and hoped (the theory goes) that EU leaders will insist instead on a flexible long extension that she actually needs.
The bottom line is: EU leaders are extremely unlikely to refuse to further extend the Brexit process.
Meanwhile, the latest round of talks between Labour and the Conservatives aimed at breaking the impasse in Parliament have finished for the day with both sides expressing hope there would be progress.
They are hoping to reach compromise changes to the Brexit deal agreed by Mrs May that could be accepted by the Commons, with Labour pushing for the inclusion of a customs union.
That would allow tariff-free trade in goods with the EU but limit the UK from striking its own deals. Leaving the arrangement was a Conservative manifesto commitment.
Environment Secretary Michael Gove said the talks had been "open and constructive" but the sides differed on a "number of areas".
Labour's shadow business secretary Rebecca Long Bailey said they were "hopeful progress will be made".
Further talks will be held on Thursday.
On Tuesday afternoon, MPs also approved a government motion for Mrs May to ask the EU to delay Brexit until June 30, required after a bill from Labour's Yvette Cooper became law.
If Labour and the government cannot agree on a way forward, Mrs May has promised to put a series of Brexit options to the Commons to vote on - with the government to be bound by the result.
These options could include holding another referendum on any Brexit deal agreed by Parliament.

European Council President Donald Tusk has recommended that the EU approve the Brexit deal at a summit on Sunday.
It comes after Spanish PM Pedro Sanchez received assurances from the UK government over Gibraltar, and dropped his threat to boycott the summit.
He said he had received the written guarantees he needed over Spain's role in the future of the British territory.
UK Prime Minister Theresa May has arrived in Brussels and held talks with top EU officials, ahead of the summit.
Meanwhile, former UK Foreign Secretary Boris Johnson said the UK would become a "satellite state" under the deal.
The UK is scheduled to leave the EU on 29 March 2019.
The terms of the UK's withdrawal have been under negotiation since June 2016 following a referendum in which 51.9% voted to leave the EU.
Even if the EU approves the deal, it still has to be passed by the UK Parliament, with many MPs having stated their opposition.
Spain had raised last-minute objections ahead of the summit about how the issue of Gibraltar had been handled in the Brexit talks so far.
But EU leaders secured a compromise with the Spanish prime minister, who said that Europe and the UK "had accepted the conditions set down by Spain" and so would "vote in favour of Brexit".
Mr Tusk, who represents EU leaders on the world stage, said he recommended "that we approve on Sunday the outcome of the Brexit negotiations" in a letter to members of the European Council.
He added: "No-one has reasons to be happy. But at least at this critical time, the EU 27 has passed the test of unity and solidarity."
Mrs May met the president of the European Commission, Jean-Claude Juncker, and Mr Tusk for talks on Saturday evening.
Then on Sunday, EU leaders will meet for the special Brexit summit. They will be asked to approve two key Brexit documents:
There is no formal vote on Sunday but the EU expects to proceed after reaching a consensus.
If the EU signs off the withdrawal deal, Mrs May will then need to persuade MPs in the UK Parliament to back it.
A vote is expected in December. Labour, the Liberal Democrats, the SNP and the DUP have all said they will vote against the government's deal, as well as many Conservatives.
BBC News political correspondent Ben Wright has said Mrs May "faces an incredibly hard job" getting the deal passed by MPs.
Spain threatened to derail the Brexit deal over concerns about its role in future trade arrangements involving Gibraltar - a British Overseas Territory with 30,000 residents.
But the UK published a letter it had sent to Spain reassuring it over the withdrawal agreement.
After holding emergency talks with Mr Tusk and Mr Juncker, the Spanish prime minister dropped his threat.
Mr Sanchez said: "Gibraltar is excluded from the general negotiation of the European Union with the United Kingdom.
"This gives the chance to Spain to have direct negotiations with the United Kingdom over Gibraltar."
Spain's foreign minister Josep Borrell said the assurance was "the most important" development since the Treaty of Utrecht in 1713, which ceded Gibraltar to Britain.
But BBC Europe correspondent Kevin Connolly said that the UK's letter does not contain anything substantially different from the withdrawal agreement.
He said there was a suspicion that Spanish ministers were "showboating a little for the domestic electorate" on the eve of elections in Andalusia, in the south of Spain, where Gibraltar is a significant issue.
Theresa May said discussions with Spain have been "constructive and sensible" but that the UK's position on Gibraltar will not change.
She said: "I'm proud that Gibraltar is British and I will always stand by Gibraltar."
Gibraltar's chief minister Fabian Picardo also played down Spain's claims about the UK's guarantees.
He said: "What you have heard from the Spanish prime minister was not a reflection of any new position, however much he tried to present it as such."
The former foreign secretary told Northern Ireland's Democratic Unionist Party (DUP) conference that the UK was on the verge of "making a historic mistake".
Mr Johnson said the UK had an "absolute duty to get this right" and there was still time to work for a better deal.
Mrs May relies on the support of the DUP's 10 MPs in key votes because she does not have a majority in the House of Commons.
The DUP has threatened to look again at the agreement with the Conservatives if the Brexit deal gets through Parliament.
But Mr Johnson said it was "absolutely vital that we keep this partnership going" to avoid Labour coming to power.
The DUP opposes the Brexit deal because of the "backstop" - the back-up plan to make sure a hard border between Northern Ireland and the Republic of Ireland never happens.
It will only come into effect if the UK and EU fail to agree a long-term trade deal. But the backstop would mean that Northern Ireland - but not the rest of the UK - would still follow some EU rules on things such as food products.
DUP leader Arlene Foster told her party conference that the prime minister had not been able to guarantee that the backstop would not have to be used.
She urged the government to secure a better deal for Northern Ireland, adding: "The choice is not between this deal and no deal, despite what the government spin machine may say."
Chancellor Philip Hammond insisted that the prime minister's Brexit deal is better than remaining in the EU.
He said the deal respected the result of the 2016 referendum and offered "the best compromise possible".
He added that he was hopeful of a solution with the DUP.
On Friday, the PM said the UK should not hope for a "better deal" from the EU if MPs reject her Brexit agreement.
But Mrs May declined to say whether the UK would be better off outside the EU, saying only it would be "different".

The EU will "not be intimidated" by threats about the UK leaving with no deal, Donald Tusk has said.
He said suggestions the UK would be better off leaving with no deal, rather than with a bad deal, "increasingly take the form of a threat".
The European Council president told the European Parliament that in the Brexit talks "a no deal scenario would be bad for everyone but above all for the UK".
He said the "goal is a smooth divorce" with the UK and EU as "good friends"
He told the last meeting of the European Parliament before the UK triggers Article 50 that it was "carefully preparing" for Brexit and "it is our wish to make this process constructive and conducted in an orderly manner".
But he warned: "However, the claims, increasingly taking the form of threats that no agreement will be good for the UK, and bad for the EU, need to be addressed.
"I want to be clear that a 'no deal scenario' would be bad for everyone, but above all for the UK, because it would leave a number of issues unresolved.
"We will not be intimidated by threats - and I can assure you they simply will not work.
"Our goal is to have a smooth divorce and a good framework for the future - and it is good to know that Prime Minister Theresa May shares this view."
Mr Tusk also stressed that he would "do everything in my power to make sure that the EU and the UK will be close friends in the future", adding that "Britain will be dearly missed as an EU member state".
"At the same time, I would like to stress again that the EU's door will always remain open for our British friends," he said.
In Westminster meanwhile, Brexit Secretary David Davis told the Commons Exiting the European Union committee he had yet to "quantify" the impact of leaving the EU without a deal.
"I have a fairly clear view of how it will work out, I just haven't quantified it yet. We will get a quantification later on, but it is quite plain how it will work out," he said.
Mr Davis told the MPs it was right to assume leaving the EU without a deal would involve trade tariffs.
Pressed on whether this would be a good thing, he said: "At this stage, until we have worked out all the mitigation procedures, we could not quantify the outcome."
He said this would not be as good as the free trade deal the government was seeking with the EU, but was "not as frightening" as some people think.
The Brexit secretary said it was "very important" that the negotiations are "as far as possible amicable".
"There will be times when the negotiations will get tough I am sure, but tough does not mean spiteful, angry, whatever you want to choose," he said.
Mr Davis said EU nations should be allowed a "considerable amount of slack" because they are disappointed the UK is leaving.
But Labour's shadow Brexit secretary Sir Keir Starmer claimed Mr Davis's comments proved the government had "made no assessment of the economic impact of the prime minister failing to secure a deal".
"What's clear, from the CBI and others, is that there is no result that would be worse for the British economy than leaving with no deal," he said.
"No deal would be the worst possible deal. The government should rule out this dangerous and counter-productive threat before Article 50 is triggered."
The Lib Dems said the government's position on no deal being reached was "the equivalent of driving towards a cliff-edge with a blindfold on".
Scotland's First Minister Nicola Sturgeon says she wants to ask the UK government for permission to hold a second referendum on Scottish independence to protect the nation's interests in the wake of the UK opting to leave the EU.
She said the Brexit vote has left Scotland at a crossroads, with an independence referendum needed to allow the country to choose which path to take.
Mr Davis said the government had promised to seek an agreement with Scotland on its Brexit strategy.
"If one side doesn't want to agree there is no way 'seek to agree' can turn to 'agree'," he added.
The minister also said he expected the European Union (Notification of Withdrawal) Bill, which cleared the Commons and the Lords earlier this week, to receive Royal Assent and become law on Thursday.
The new law will give Theresa May the power to invoke Article 50 of the Lisbon Treaty and trigger formal Brexit negotiations - a move she is expected to make by the end of March.

The green light to begin talks about a post-Brexit trade deal won't come until December at the earliest, the European Council president has suggested.
Donald Tusk warned that if the current "slow pace" of negotiations continues the UK and the EU "will have to think about where we are heading".
The UK has been hoping EU leaders will decide next week that enough progress has been made to open trade talks.
Brexit Secretary David Davis is in Brussels as negotiations continue.
He held a working lunch with EU lead negotiator Michel Barnier, which the French politician said had been "good" and "constructive".
In an LBC interview, Theresa May - who voted Remain last year - would not say how she would vote if another referendum was held.
"I don't answer hypothetical questions," the PM said.
On the negotiations, she said the two sides were "very close" to a deal on citizens' rights.
But she said she was not able to guarantee the rights of all EU citizens currently living in the UK, since if the UK and the EU were not able to reach a wider deal on the terms of exit, this would impact on welfare payments and other issues.
She rejected suggestions the UK was playing catch-up, saying its negotiators were "exceptionally well prepared" and the reason there would be a pause in talks on Wednesday was the EU had not scheduled them.
The UK is hoping the EU will agree to move on from the initial phase of talks, covering the financial settlement, Northern Ireland and citizens' rights, to discussing future issues like trade.
A decision on whether to agree this will be taken at a European Council summit on 19 October.
But Mr Tusk all but ruled this out in a speech in Brussels, saying: "We are negotiating in good faith, and we still hope that the so-called 'sufficient progress' will be possible by December.
"However, if it turns out that the talks continue at a slow pace, and that `sufficient progress' hasn't been reached, then - together with our UK friends - we will have to think about where we are heading."
The UK is set to leave the European Union at the end of March 2019.
Both EU and UK teams have said the ball is in the other side's court this week - implying that it is the other side that has to make the next concession.
Asked by the BBC whose court he thought "the ball is in", Mr Barnier warned that "Brexit is not a game".
This week's fifth round of talks came as ministers sought to ease disquiet among Brexit-backing MPs about the UK's strategy for a two year "transition" period between being a full EU member and the UK's eventual post-Brexit relations with the EU.
Downing Street said it wanted the process to be "as smooth as possible".
After Mrs May briefed her cabinet on Tuesday, a No 10 spokesman said the government hoped to negotiate a deal with the EU on the terms of exit but was prepared for all eventualities - a reference to what some believe is the growing likelihood of a "no deal" scenario.
Mr Tusk said the EU side was not preparing for such a scenario.
Taking questions from MPs on Monday, Mrs May also confirmed that the UK could remain subject to the rulings of the European Court of Justice during a planned two-year transition period after Britain leaves the EU in March 2019.
This was criticised by some pro-Leave campaigners, with backbencher Jacob Rees-Mogg telling the BBC he was "troubled" by the PM's statement.
"If we're remaining under the jurisdiction of the ECJ then we haven't left the European Union or the date of departure is being delayed," he said.
Foreign Secretary Boris Johnson and Environment Secretary Michael Gove - two key figures in last year's Leave campaign - both issued statements backing Mrs May's comments.
BBC assistant political editor Norman Smith said their intervention underlined the government's nervousness about the reaction of Tory Brexiteers over the European Court of Justice's jurisdiction - which for many of them is a "red line".
Mr Johnson, who has been accused of undermining the PM with his recent interventions on Brexit strategy, issued a statement backing her "powerful vision".
On Twitter, Environment Secretary Mr Gove said: "Strong statement from PM on Brexit - let's be pragmatic over implementation to secure maximum freedom to diverge from EU in end state."
Asked on Tuesday about the role of the ECJ during a transitional phase, No 10 said business should only have to adjust to one set of changes following the UK's departure.
But it reiterated the PM's hope that a new dispute resolution system could be devised as quickly as possible to assume the ECJ's functions and settle the matter once and for all.

They weren't off-the-cuff remarks, but a planned outburst.
The softly-spoken politician who holds the authority of all EU countries has just completely condemned a chunk of the British cabinet, wondering aloud: "What that special place in hell looks like for those who promoted Brexit, without even a sketch of a plan how to carry it out safely".
Sure, for a long time the EU has been frustrated with how the UK has approached all of this.
And sure, plenty of voters in the UK are annoyed too at how politicians have been handling these negotiations.
But it is quite something for Donald Tusk to have gone in like this, studs up, even though he sometimes reminisces about his time as a football hooligan in his youth.
Be clear, he was not intending to talk about voters who wanted to Leave, but politicians who were involved in the campaign.
He also had pretty stern remarks for those who'd been on the other side of the argument, accusing those who still want the UK to stay in the EU of having "no political force, and no effective leadership".
Mr Tusk will be all too aware that he will provoke tempers at home, even laughing about it as he left the stage with the Taoiseach, the Irish leader, Leo Varadkar.
But if you strip away the planned flash of temper, also in his remarks was an invitation to the prime minister to come forward with a different version of the backstop - a "believable guarantee", a promise that a "common solution is possible".
That is, on the face of it, in tone at least, more of an opening to the UK to put something new on the table than we have seen from the EU side.
Certainly, Theresa May's most pressing job is to put something that could work on the table in Belfast, and in Brussels, and to do it fast.
But don't forget, also at her back, she has Brexiteers whom she needs to manage, whose expectations she needs to contain, whose votes she desperately needs.
And at a time when cool tempers and compromise are absolutely needed, Mr Tusk's remarks are likely to whip up the mood instead.

Theresa May has hailed the draft agreement on post-Brexit relations as "right for the whole of the UK" and insisted a deal "is within our grasp".
The political declaration - outlining how UK-EU trade, security and other issues will work - has been "agreed in principle", the European Council says.
London and Brussels have already agreed the draft terms of the UK's exit from the EU on 29 March 2019.
The prime minister told MPs it would deliver the Brexit people voted for.
The political declaration is a separate document to the 585-page withdrawal agreement, published last week, which covers the UK's £39bn "divorce bill", citizens' rights after Brexit and the thorny issue of the Northern Ireland "backstop" - how to avoid the need for a manned border on the island of Ireland.
The withdrawal agreement is legally-binding - the political declaration is not.
It sets out broad aspirations for the kind of relationship the UK and the EU will have after Brexit. Some of the wording of it is non-committal and allows both sides to keep their options open.
"The negotiations (on the political declaration) are now at a critical moment and all our efforts must be focused on working with our European partners to bring this process to a final conclusion in the interests of all our people," said the PM.
"The British people want Brexit to be settled, they want a good deal that sets us on a course for a brighter future, and they want us to come together as a country and to move on to focus on the big issues at home, like our NHS.
"The deal that will enable us to do this is now within our grasp. In these crucial 72 hours ahead, I will do everything possible to deliver it for the British people."
But Labour Leader Jeremy Corbyn described the agreement as "26 pages of waffle" which "could have been written two years ago".
"This is the blindfold Brexit we all feared - a leap in the dark. It falls short of Labour's six tests," he added. "What on earth have the government been doing for the past two years?"
Lib Dem leader Sir Vince Cable, who is campaigning for another referendum, described it as an "agreement to have an agreement" that was "full of worryingly vague aspirations".
Tensions remain over some parts of the withdrawal agreement.
Spain's prime minister, Pedro Sanchez, has said his government is "annoyed" that the divorce agreement does not specify that Gibraltar's future must be decided directly by officials in Madrid and London - and France is understood to have sought amendments to the wording on fishing rights in UK waters.
On Thursday evening, he said further changes must be made to the withdrawal agreement:  "After my conversation with Theresa May, our positions remain far away."
Mrs May said she had spoken to Mr Sanchez and was "confident that on Sunday we will be able to agree a deal for the whole of the United Kingdom family including Gibraltar" - and that the UK's sovereignty over the territory was not under threat.
If all goes as planned, the UK and the EU will use the political declaration as the basis for a trade agreement, to be hammered out during a 21-month transition period that is due to kick-in after Brexit happens on 29 March, during which the UK will continue to be a member of the EU single market and customs union.
The draft document says: "The future relationship will be based on a balance of rights and obligations, taking into account the principles of each party.
"This balance must ensure the autonomy of the union's decision-making and be consistent with the union's principles, in particular with respect to the integrity of the single market and the customs union and the indivisibility of the four freedoms.
"It must also ensure the sovereignty of the United Kingdom and the protection of its internal market, while respecting the result of the 2016 referendum including with regard to the development of its independent trade policy and the ending of free movement of people between the Union and the United Kingdom."
In the Commons, Mrs May faced calls from Brexiteer Conservative MPs, including former Foreign Secretary Boris Johnson, and Jeffrey Donaldson of the DUP, who have threatened to vote down the deal, to ditch the Northern Ireland "backstop" and come forward with the alternatives set out in the political declaration instead.
Opponents of Brexit were also critical of the new document.
Conservative MP Philip Lee, who quit the government in protest at its handling of Brexit, said it "reads like a letter to Santa", while Labour's Chuka Umunna, a leading supporter of the People's Vote campaign for a new referendum, said it was "entirely aspirational and doesn't finalise anything".
Conservatives Sir Nicholas Soames and Nick Herbert were among a handful of MPs to speak out in favour of Mrs May's deal during the debate.
Scottish Conservative MPs are also concerned that the declaration will not protect the interests of the UK fishing industry.
But the government insists the UK's "red lines" on fishing have been protected, and the text acknowledges the UK will be "an independent coastal state" with the rights and responsibilities that entails.
A government source said the EU had wanted "existing reciprocal access to fishing waters and resources [to] be maintained" but this had been rejected.
The SNP's leader at Westminster, Ian Blackford, said Scotland's fishing rights had been "thrown overboard like they were discarded fish", adding, "so much for taking back control, more like trading away Scotland's interests".
And Sammy Wilson, Brexit spokesman for the DUP, which has been in a confidence-and-supply agreement with the government, said the "non-binding aspirational agreement" had been drafted to "help the prime minister, rather than mitigate the very damaging and dangerous draft withdrawal agreement".
Several EU countries have raised concerns about Mrs May's planned meeting with Mr Juncker on Saturday night, saying that it should not lead to any changes in the text.
Germany has reiterated that Angela Merkel would not attend Sunday's meeting if the text has not been agreed in advance.
Separately, EU diplomats have said the Spanish government "sees the making of a compromise" on the issue of Gibraltar.

The EU is unlikely to accept the UK's latest proposal for avoiding a "hard border" on the island of Ireland after Brexit, the Irish government has said.
Theresa May has said 80% of firms would face no new customs checks between Northern Ireland and the Irish Republic and others would be simplified.
But Irish Foreign Minister Simon Coveney said he was not sure it would adequately protect the EU's market.
The proposal, he said, was a "starting point" for talks not a solution.
The British prime minister has ruled out the return of physical infrastructure on the border between Northern Ireland and the Irish Republic after the UK leaves the EU on 29 March 2019, insisting that this commitment was "absolutely clear".
But Dublin and Brussels remain to be convinced that this can be avoided after the UK leaves the EU's customs union, unless Northern Ireland continues to abide by its rules and those of the single market.
The "backstop" option agreed by the two sides in December is for Northern Ireland to remain fully aligned with the rules of the customs union - which eliminates tariffs between its members - and the single market, in areas of existing North-South co-operation.
This is unacceptable to the Democratic Unionist Party, which Theresa May relies on for votes in the House of Commons, and to many Conservatives MPs who say it would create a new border in the Irish Sea and amount to Northern Ireland being "annexed".
But Mr Coveney told the BBC's Andrew Marr show this remained the default outcome unless both sides could agree other workable solutions to keep goods and people crossing over a "largely invisible" border.
"Our responsibility is to work positively with Britain to explore solutions but if we can't agree solutions then what we have, of course, is the backstop which is a commitment by the British government to maintain full alignment with the rules of customs union and the single market," he said.
Asked about Theresa May's proposal, in a major speech on Friday, to waive customs checks for 80% of firms doing business across the border, he said it could not be taken for granted.
"This is the mistake that is made in Britain all the time," he said.
"When someone definitively says something will be the case from the British government, people assume that is the negotiated outcome. Of course it is not.
"I am not sure the EU will be able to support a situation whereby 80% of companies that trade north-south and south-north will actually protect the integrity of the EU single market," he said.
"While of course we will explore and look at all the proposed British solutions, they are essentially a starting point in negotiations not an end point." he said.
Mr Coveney said Dublin wanted to avoid a hard border with Northern Ireland as much as London did.
But he insisted that for a single market to function "if goods move from one customs union to another there needs to be some checks" unless some mechanism was negotiated to prevent them.
In Friday's speech, Mrs May said the vast majority of north-south trade was carried out by small and medium-sized business whose economic contribution was not "systemically significant" to the EU market but which would be most affected by custom checks and other red tape.
"We would allow them to continue to operate as they do currently, with no new restrictions," she said.
The DUP said the "sensible" idea should be the basis for negotiations currently going on in Brussels.
Speaking on Sunday, Mrs May said she was pleased that Irish PM Leo Varadkar agreed to sit down alongside the European Commission and UK to look at her proposals in more detail.
"We've got proposals as to how we're going to achieve that, now we're going to be able to sit down and talk with others about how we're going to do that," she told Andrew Marr.
But Scottish First Minister Nicola Sturgeon, who wants the whole of the UK to remain in the customs union, said the PM was relying on "technological solutions that perhaps do not even exist".
"One of the most shameful features of the whole Brexit process has been the negligent way that the interests of Ireland have just been cast aside," she told ITV's Peston on Sunday.

The EU has defended its right to make plans for a "no-deal" Brexit, amid UK fears firms may lose out as a result.
David Davis has reportedly complained about EU guidance stating the UK would become a "third country" in 2019 with no reference to a possible trade deal.
In a letter to Theresa May, obtained by the FT, the Brexit secretary warned UK firms may have to relocate to Europe or risk seeing contracts terminated.
But the EU said the UK had first raised the possibility of there being no deal.
A spokeswoman rejected suggestions that Britain was being treated differently to other EU members and that its rights were being abused.
The UK is due to leave the EU on 29 March 2019.
The second phase of Brexit negotiations, covering transitional arrangements after the UK leaves and economic and security co-operation in the future, are due to begin soon.
Prime Minister Theresa May has said it is right to plan for all scenarios, including no deal, but she is confident the two sides will reach an agreement on their post-Brexit relations in time for the UK's departure.
But British concerns about the EU's own preparations for Brexit have surfaced with Mr Davis suggesting they are "frequently damaging to UK interests".
In a letter to Mrs May last month, extracts of which have been seen by the Financial Times, he warned it was potentially discriminatory of EU agencies to have issued guidance to businesses stating that the UK would become a "third country" outside the EU without any reference to a future trade deal sought by both sides.
Warning the EU's current stance amounted to "potential breaches of the UK's rights as a member state", he said he would urge the European Commission's Brexit taskforce to withdraw the statements made so far, in light of the agreement reached in December to begin trade negotiations.
A Number 10 spokesman said it did not comment on leaks, but the EU insisted its contingency planning was not a breach of the UK's rights as a full member until the date of its departure.
"We are surprised that the UK is surprised that we are preparing for a scenario announced by the UK government itself," the commission's chief spokeswoman said.
"After all, it was Theresa May herself who said in her Lancaster House speech in January 2017, and repeated in her Florence speech in September, that 'no deal for Britain is better than a bad deal for Britain, it is right that the government should prepare for every eventuality'.
"So we take these words by the prime minister very seriously, and it is therefore only natural that in this house we also prepare for every eventuality."
Scottish First Minister Nicola Sturgeon, who favours the UK remaining in the single market and customs union, said Mr Davis's words were "extraordinary" given the government had set aside £3.7bn to prepare the UK for the possibility of leaving without an agreement.
And Labour MP Pat McFadden, who supports the Open Britain campaign for close ties with the EU, said the EU's actions should "come as no surprise" as the UK was "implicitly threatening a no-deal scenario" itself.
Meanwhile, the SNP, Liberal Democrats, Green Party and Plaid Cymru accused Labour of an "abdication of responsibility" for declining to join them in backing single market membership after Brexit.
Following a cross-party meeting in Parliament, they criticised Jeremy Corbyn's pursuit of a "jobs-first" Brexit, arguing it was impossible without backing single market membership, as some Labour MPs are urging.
In response, Labour sources said the single market was "not a membership club that can be joined" and the party's goal was to retain the benefits of the single market through the negotiation.

The UK's freedom to determine its own rules on immigration, trade and fishing in a transition period after Brexit may be further restricted, according to revised EU guidelines on a transition.
Draft EU documents would see full freedom of movement extended until the start of 2021.
The UK would also need "authorisation" to stick with existing EU trade deals.
The BBC's Adam Fleming said the guidelines appeared to be aiming for a "business as usual" transition period".
The UK is scheduled to leave the EU on 29 March 2019 but to minimise the disruption to people and businesses the idea is to smooth the way to post-Brexit relations over 18 months to two years - which is referred to as a transitional or implementation period.
But many Conservative MPs, and some ministers, are concerned about the effects that an effective "stand-still agreement" for about two years would have in terms of entrenching the role of the European Court of Justice and curbing the UK's room for manoeuvre in negotiating trade deals.
The other 27 EU countries will meet later this month to finalise their guidelines for Michel Barnier, the EU's Brexit negotiator, ahead of the start of formal talks.
According to a draft copy of the guidelines, reported by the FT and the Guardian, the EU is seeking to tighten the conditions which will apply to the UK during the transitional period which the EU proposes will last up to 31 December 2020.
Among areas where the language has been toughened, the text stipulates that provisions on citizens' rights, agreed as part of a first-stage deal in December, will not kick in until the end of the transition period.
The FT said this meant the UK would not be able to deny work permits to any aspiring EU migrants pending the introduction of new immigration rules.
It also states that the UK will need the EU's permission to roll over international trade agreements with non-EU countries that the UK currently benefits from as an EU member.
On fishing, it proposes that existing quota rules will remain the same during the transition phase, and that any changes arising from "specific consultations" must be in "full respect" of EU law.
Businesses based in, and trading with, the UK want details of a transition agreement to be agreed as soon as possible so they can plan for the future and avoid having to deal with two sets of regulatory changes, a position backed by the Treasury.
But British ministers have also insisted that free movement will end when the UK leaves and that European workers coming to the UK after 29 March 2019 will have to register.
The FT said some UK diplomats believed the revisions were potentially beneficial as, on trade, they referred to the UK striking its own deals while remaining "bound by the obligations" stemming from existing agreements.
Speaking in a debate in the European Parliament, leading MEP Guy Verhofstadt said the rights of EU and British citizens - including on free movement - should continue to apply until the transition period ends.
"It is very important that in these negotiating directives... the new system for EU citizens living in Britain is only coming into place after the transition," he said.
There should be, he argued, "no question" of trying to "make it difficult for EU citizens to obtain their permit to reside in Britain".
Meanwhile, the president of the European Council Donald Tusk urged "more clarity" from the UK about what kind of relationship it wanted with the EU.
"The hardest work is still ahead of us and time is limited," he said, adding that Brexit would happen "unless there is a change of heart amongst our British friends".
British ministers have hit out at the "relative silence" from the EU about its own aspirations for a post-Brexit relationship while there are also concerns that the EU's decision to publish guidance to its agencies about what to do in the result of no Brexit deal being reached risks discriminating against British firms.

The EU is to begin preparing for its post-Brexit trade negotiations with the UK, while refusing to discuss the matter with the British government.
An internal draft document suggests the 27 EU countries should discuss trade among themselves while officials in Brussels prepare the details.
The draft text could yet be revised.
EU Commission chief Jean-Claude Juncker said a lack of compromise over the UK's financial commitments was impeding progress - saying "they have to pay".
Speaking in Luxembourg, Mr Juncker used the analogy of someone covering the bill after ordering 28 beers at a bar to explain the EU's position - and added that the Brexit negotiating process was taking longer than expected.
He also dismissed the wrangling over citizens' rights - another sticking point - as "nonsense", calling on the UK to adopt a "common sense" approach and say "things will stay as they are" after Brexit.
Downing Street said "good progress" was being made in the talks.
As the fifth round of talks ended in Brussels on Thursday, the EU's chief negotiator, Michel Barnier, said there was "deadlock" over the UK's Brexit bill.
He said there had not been enough progress to move to the next stage of post-Brexit trade talks - as the UK had hoped -  but added that he hoped for "decisive progress" by the time of the December summit of the European Council.
The draft paper submitted to the 27 EU states by European Council president Donald Tusk, suggests free trade talks could open in December - should Prime Minister Theresa May improve her offer on what the UK pays when it leaves.
The BBC's Europe correspondent Adam Fleming said the paper contained "something for everyone" - with the reference to trade talks accompanied by a call for the UK to do more to bridge the gap on the key negotiating points.
The document calls for talks - about a transition period and the future relationship - to move to the next phase "as soon as possible".
The draft conclusions - to be put to EU leaders next Friday - also call for more concessions from the UK on its financial obligations and the rights of European nationals who wish to stay after Brexit.
The paper confirms Mr Barnier's assessment, that there has not been "sufficient progress" on three key elements of a withdrawal treaty for leaders to agree to open the trade talks now.
But it says the leaders would welcome developments on these key issues: the rights of three million EU citizens in the UK, protecting peace in Northern Ireland from the effect of a new border and Britain's outstanding "financial obligations".
The council would then pledge to "reassess the state of progress" at their December summit.
Bernd Kolmel, chairman of Germany's Eurosceptic Liberal Conservative Reformers, told BBC Radio 4's Today programme there appeared to have been little progress between the first and fifth round of talks - something he described as a "disaster".
He called on the EU to expand the talks to include its future relationships and trade with the UK.
Anders Vistisen, a Danish Eurosceptic MEP and vice-chair of the EU Parliament's foreign affairs committee, agreed, adding: "The most integral thing is the future relationship. If we are making a bad trade deal for Britain we are also hurting ourselves."
The document states that in order "to be fully ready", EU leaders would ask Mr Barnier and his officials to start preparing now for a transition - albeit without actually starting to talk to the UK about it.
"The European Council invites the Council (Article 50) together with the Union negotiator to start internal preparatory discussions," the draft reads.
A Downing Street spokeswoman would not comment on the draft EU document but said Theresa May "has been clear all along that we need to reach a settlement", adding that UK would honour its financial commitments.
Meanwhile, a crucial plank of the government's Brexit legislation faces a raft of attempted amendments by MPs as ministers seek to steer it through Parliament.
The EU (Withdrawal) Bill will end the supremacy of EU law in the UK and incorporate existing Brussels legislation onto the UK statute book.
Commons Leader Andrea Leadsom said going through the proposed changes was "taking a bit of time" as she confirmed there would be no debate on the bill next week.
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The EU "will not be rushed" on a trade deal with the UK after Brexit, according to Ireland's deputy PM.
Boris Johnson says a deal can be agreed by the end of 2020 and has included a pledge in his Brexit bill not to extend any transition period to secure one.
But Simon Coveney says it is "probably going to take longer than a year".
Security Minister Brandon Lewis defended Mr Johnson's deadline, saying he had a "strong record of getting things done".
After the UK leaves the EU on 31 January, it will enter an 11-month transition period, where it will largely follow EU rules but will not have any representation in the bloc's institutions.
This period will come to an end on 31 December and Mr Johnson has ruled out extending it any further if a deal on the future relationship between the UK and EU has not been agreed.
The promise is included in the prime minister's Brexit bill, which was voted through by MPs earlier this week and will now head to the House of Lords before becoming law.
But opposition parties have raised concerns about the hard deadline, saying it creates another way of the UK leaving without a deal.
Speaking on the BBC's Andrew Marr programme, Mr Coveney said he accepted the UK was leaving the EU at the end of January, and he hoped for the future deal to "achieve the closest possible relationship" between the two sides.
But he warned there was "no way of the UK... maintaining the same relationship we have today while outside the European Union," adding: "That is the reality of Brexit, I'm afraid."
Mr Coveney said Mr Johnson had "set a very ambitious timetable" in his bill.
"Just because a British parliament decides that British law says something doesn't mean that law applies to the other 27 countries of the European Union," he added.
"The European Union will approach this on the basis of getting the best deal possible, a fair and balanced deal, to ensure the UK and the EU can interact as friends in the future.
"But the EU will not be rushed on this just because Britain passes law."
The deputy prime minister (Tanaiste) said the EU had "constantly warned [Mr Johnson's] timeframe is ambitious, if not unrealistic".
"From an EU perspective, we will try to approach all of these really important and sensitive areas with a sense of partnership and friendship.
"But at the same time, they are complex... [and] in my view, it is probably going to take longer than a year. But we will have to wait and see."
Government minister Mr Lewis admitted the negotiations would be difficult, but he disagreed with Mr Coveney's assessment of the timetable.
"I think we can do it," he told Andrew Marr. "I think it can be done, not just because both parties… are committed to doing it, and want to do it, but we are a country that has already got a known pattern of work with the EU.
"Therefore getting a holistic agreement in the next 12 months is achievable".
Mr Coveney's comments followed a speech by new European Commission President Ursula von der Leyen earlier this week, saying it would be "impossible" to reach a comprehensive trade deal by the end of 2020.
She warned that without an extension to the transition period beyond 2020 "you cannot expect to agree every single aspect of our new partnership". She called the deadline "very tight".
Mrs von der Leyen, a former German defence minister, took over from Jean-Claude Juncker at the start of December. She met Mr Johnson for talks in London last week.

EU leaders have approved guidelines for the negotiation of future relations with the UK after Brexit.
The text on trade, security and other issues was agreed in "less than half a minute", clearing the way for the next phase of Brexit talks to get under way.
The UK is due to leave in March 2019 and negotiators have said they want a deal in place by the end of the year.
Prime Minister Theresa May said she believed there was a new "spirit of co-operation and opportunity".
The formal adoption of the guidelines, although widely expected, is seen as another key step as the Brexit process gathers momentum.
The guidelines give chief negotiator Michel Barnier the mandate to talk directly to the UK about the future relationship with a view to reaching a broad political agreement by October to allow the EU and UK parliaments time to consider it.
European Council President Donald Tusk said the "positive momentum" should be used to settle outstanding issues like avoiding a hard border in Northern Ireland.
EU leaders will decide in June whether the "Irish question" has been resolved and will look into a "common declaration on our future", he added.
Mrs May, who was not present when her colleagues met to discuss Brexit, said she believed there was a "new dynamic" in the negotiations.
"I believe we are approaching this with a spirit of co-operation, a spirit of opportunity for the future as well, and we will now be sitting down and determining those workable solutions for Northern Ireland, but also for our future security partnership and economic partnership," she said.
"I believe it is in the best interest of both the UK and the EU that we get a deal that actually is in the interests of both."
By the BBC's Europe reporter Adam Fleming
The remaining 27 leaders have also endorsed an agreement reached earlier this week on a 21-month transition period between March 2019, when the UK officially leaves, and the end of 2020.
During that period, the UK will be able to negotiate, sign and ratify its own trade deals, while EU citizens arriving in the UK will enjoy the same rights and guarantees as those who arrive before Brexit.
A solution to avoid a hard border on the island of Ireland has yet to be agreed, with the EU insisting on a "backstop" option of Northern Ireland, in effect, remaining in the customs union.
Irish Prime Minister Leo Varadkar said he wanted an agreement that keeps the UK "as close as possible" to the EU in order to protect trade and jobs.
But Labour, which supports staying in the customs union, said the UK and EU were a "very long way away" from achieving this at the moment and the PM needed to "finally drop her reckless red lines".
Meanwhile, EU leaders are calling for reciprocal access to UK fishing waters and stocks to be maintained after the end of the transition period.
Asked whether he thought the UK would agree to this, European Commission President Jean-Claude Juncker told BBC Scotland this was the EU's "working basis".
"We are in ongoing discussions with the UK - to try and bring them (to) where we are and they are trying to bring us (to) where they are," he said.
The UK has already agreed to abide by the rules of the Common Fisheries Policy during the transition, sparking anger among fishing groups which want full sovereignty over UK waters upon Brexit.

EU ambassadors have agreed to delay Brexit, but will not make a decision on a new deadline date until next week.
The European Commission said work on this would "continue in the coming days".
The talks came after Chancellor Sajid Javid admitted the government's deadline to deliver Brexit next Thursday "can't be met".
Boris Johnson said he was waiting for the EU to decide "what they want to do".
MPs are expected on Monday to consider the prime minister's call for an early general election.
Mr Johnson says he wants to hold one on 12 December, if the EU offers a Brexit delay until 31 January.
But the chances of enough MPs backing the motion - which requires the support of two-thirds of the House of Commons - appear uncertain, with Labour not committing to how it plans to vote.
Leader Jeremy Corbyn said he was only prepared to agree to an election once the PM had completely ruled out "to my satisfaction" the possibility of a no-deal Brexit.
"My position is we've got to get no-deal taken off the table first," he told ITV's This Morning programme.
"Providing the prime minister comes to Parliament on Monday and makes it absolutely clear he is going to make sure that there is no crash out - because his deal includes the possibility of a no-deal exit... if he comes on Monday and says that, then OK," he added.
Mr Johnson has said his "preferred option" is a short Brexit postponement to "say to 15 or 30 November".
Following the Brussels meeting, he again urged Mr Corbyn to vote for a snap poll, calling on him to "man up" and agree to his election proposal.
"Nobody will believe that the Labour Party is really going to allow Brexit to happen unless there is a deadline of an election on 12 December," he said.
On Thursday, the government had appeared to threaten a halt to all but essential Commons business if Parliament refused to vote for an election.
However, on Friday a Downing Street spokesperson said that this would only apply to Brexit legislation, and that otherwise the prime minister would continue pursuing his "dynamic and ambitious" domestic agenda "with full vigour" even if MPs do not vote for an election.
By BBC parliamentary correspondent Mark D'Arcy
For many MPs, scrutiny of the detail of legislation is an empty ritual, during which they sign Christmas cards or answer letters, rather than engaging with the process. Others will detect problems which might be critical to their constituents and local interests.
Ram the Withdrawal Agreement Bill through the Commons in 36 hours, runs the argument, and there would be little chance to address them, while a more leisurely process could head off any number of problems once the bill becomes law.
But don't ignore the raw electoral strategy that lurks millimetres below the surface of this argument. The Conservatives are seeking to frame the Brexit battle as "the people versus Parliament".
But plenty of Labour MPs say they're simply not prepared to vote for an election at a time and on the ground of the prime minister's choosing.
They want the Conservatives to go into an election with their Brexit Party flank unsecured, and with their internal divisions over Brexit festering visibly.
Read the full article
European Commission spokeswoman Mina Andreeva said: "What I can tell you is that the EU 27 have agreed to the principle of an extension and work will now continue in the coming days."
She added that they intended to take a decision without holding an emergency summit.
A source close to French President Emmanuel Macron said he did not believe a Brexit extension was justified unless the UK provided a reason for it.
"We must show the British that it is up to them to clarify the situation and that an extension is not a given," the source said.
BBC Brussels correspondent Adam Fleming said a decision on the length of the extension was expected on Monday, but that the announcement could be delayed until Tuesday if the ambassadors struggled to agree a date.
He said there is pressure to avoid a last-minute summit on 30 October, in which leaders would have to prevent the UK leaving without a deal the next day.
Earlier, Mr Javid told BBC Breakfast the government had to "accept we won't be able to leave on 31 October".
He added that ministers "had done everything possible" to leave the EU by the end of the month, but "everyone expects an extension".
Mr Johnson was compelled by a law passed by MPs - known as the Benn Act - to send a letter to the bloc requesting a delay until 31 January 2020.
Before sending the letter on Saturday, he had repeatedly promised the UK would leave the EU on Halloween.

Billions of euros of British taxpayers' money could remain locked into an EU bank for more than thirty years after Brexit, the UK has been warned.
Alexander Stubb, vice president of the European Investment Bank - in which the UK is a 16% shareholder - said it would not be fully repaid until 2054.
He described Brexit as a "travesty" but denied the move was a punishment.
"The EIB has leveraged the economy of the UK many, many fold over the years," he told BBC Radio 4's Today.
The UK has 3.5bn euros (£3.1bn) of capital at the bank and a House of Lords report said the UK's investment could be worth 10.1bn (£8.9bn) euros taking into account reserves and profits.
Established in 1958, the EIB uses capital provided by EU countries to make loans at low rates, often for major infrastructure projects.
All 28 EU nations are shareholders in the Luxembourg-based bank, with the UK being the largest alongside Germany, France and Italy.
Mr Stubb, a former prime minister of Finland, told the BBC that the UK's money could be tied up for decades in after it leaves the EU in 2019.
"Everyone on both sides of the negotiating table agree that we have to pay back the 3.5 billion euro, basically in cash, and that will happen over a long period, up until 2054, because that's when the loans are amortised."
He insisted that no-one in the bank wanted to "punish" the UK for leaving and actually wanted to "alleviate the pain" of Brexit.
"I have a British heart pumping, I am married to a Brit, my children have dual nationality and I think Brexit is one of the biggest travesties that we have seen in the modern era," he said.
"So I will do everything in my power to alleviate the pain, but the economic facts are just such that there are no winners in Brexit - apart from perhaps a few lawyers. Unfortunately, we will see this in the coming years."
The BBC's Ross Hawkins said Today had heard how delays in authorising new loans while the UK remains part of the EU could see fewer social homes built.
One housing association, Stonewater, said it may build around 300 fewer homes because its application for £100m to build new properties had ground to a halt.
Its executive director John Bruton told the programme: "The Bank has been waiting for assurances from the UK government before the application can be progressed."

Again and again throughout this Brexit process I've been struck by the chasm in thinking between leading UK politicians and the viewpoint of EU leaders.
But the current state of affairs is particularly surreal.
As the UK's political class twists and turns itself into a spitting Brexit frenzy and the pound fluctuates hysterically on the currency markets, the EU has popped on its blinkers, clapped its hands firmly over its metaphorical ears and is resolutely continuing preparations for a special summit of EU leaders to sign a Brexit deal that many in the UK believe/hope could yet end up in the bin.
So far, nothing - none of the screaming headlines back in the UK - is managing to distract the EU from its focus.
This, first and foremost, is because Theresa May stands firmly behind the Brexit deal. And Europeans view her as the UK's chief Brexit negotiator.
UK cabinet ministers - even Brexit secretaries - can come and go, but as long as the prime minister remains on board, EU leaders believe the seal-the-deal Brexit summit will go ahead.
There is also zero - really, truly, honestly, not just saying it - zero-intention or appetite in Europe to start renegotiating the withdrawal deal with the UK.
For Europe's leaders, the document is the result of 19 months of intense and tense negotiations working towards something (Brexit) that none of them wants and which has already sucked up an enormous amount of time, energy and money across the European capitals in preparation.
Of course, the EU would rather the UK changed its mind and stayed in the club. But if it is leaving then this, they say, is the deal on the table.
The EU's chief Brexit negotiator, Michel Barnier, told EU ambassadors on Friday that the European Union should not start a last minute bargaining process.
The EU should protect its principles, he said: meaning standing by the backstop guarantee on the Irish border.
Brussels wants to close this chapter and move on.
But remember: we're talking about the divorce deal here. Not the future EU-UK trade deal.
Sure, EU and UK negotiators are hammering out a document this weekend to outline the kind of relationship they intend to have with one another after Brexit but - spoiler alert - when it comes to the chapter on future economic relations, expect their text to be suitably vague.
And, anyway, this document unlike the Brexit withdrawal agreement is not legally binding.
Detailed negotiations on the new EU-UK trade deal will only begin after Brexit day and the UK is legally, if not politically, free to choose - and change - the kind of economic relationship it wants with the bloc: very close à la EEA (European Economic Area),or a more arm's-length deal like Canada has.
But, since it takes two to tango in negotiations, each choice has consequences under EU law.
More from Katya:Volatile UK politics could bin Brexit deal, worries EU
A Canada-like free-trade agreement can never - whatever David Davis and others promised - offer frictionless trade. And it would lead to a customs border on the island of Ireland unless a separate arrangement is agreed for Northern Ireland.
Whereas being a member of the EEA would mean the UK accepting freedom of movement and paying into the EU budget.
But the by-now hugely controversial EU-UK customs relationship outlined in the Brexit withdrawal treaty need never come about.
It is an on-paper insurance policy to avoid a hard border between Northern Ireland and the Republic of Ireland since, as already discussed, no-one knows right now what the future economic relationship will look like between the EU and the UK.
The reason it is a UK-wide customs arrangement is because Theresa May, not the EU, wanted it to be.
And, if a new trade deal is ready between the two sides before the end of the transition period - the end of 2020 - then the "backstop" customs partnership would be superseded.
If it isn't ready, the UK government could ask the EU to extend the transition period instead, though that of course has consequences too: ongoing freedom of movement, payments into the EU budget etc.
The options don't look appetising perhaps but, as I have said, if the UK parliament now rejects the Brexit withdrawal deal, hoping to renegotiate a "better" (i.e more successfully cake-and-eat-it) deal, then the EU doesn't want to know.
But they would likely "freeze" the Article 50 process if the UK were to hold a general election or a second referendum.
Out of self-interest, of course.
Firstly, because the EU wants to avoid a costly, chaotic no-deal scenario and, secondly, because as France's Emmanuel Macron has said so often, they will keep the door open until the last moment in case the UK should change its mind about leaving.
But, deep down, Europeans think a nationwide change of heart is unlikely and that the Brexit deal will in the end be signed.
Which is why, in stark contrast to the UK media obsession with the current political turmoil, Brexit is far, far down the running order of evening news programmes across Europe.

Senior Europeans have called on Foreign Secretary Jeremy Hunt to apologise for likening the EU to the Soviet Union.
Mr Hunt's comment, during his Tory conference speech, was about efforts to stop members leaving the bloc.
Brexit coordinator Guy Verhofstadt was among MEPs calling for an apology. Some described the comments as "a new level of populism" and far-right language.
Mr Hunt said he was pointing out the EU negotiators' approach was not consistent with European values.
Three serving EU ambassadors to London publicly criticised the foreign secretary on Monday, saying the comparison was both wrong and insulting to those who had lived through years of Soviet rule.
But UKIP leader Nigel Farage said Mr Hunt was "using my language".
Relations between the UK and the EU were already on edge after European leaders publicly criticised Theresa May's plan for future co-operation after Brexit at a summit in Austria last month.
British ministers had accused the EU of not showing the UK due respect after the PM's plans were mocked on social media during the Salzburg meeting.
Then, on Sunday, Mr Hunt provoked a diplomatic row after accusing the EU of seeking to punish the UK in order to "keep the club together".
His speech recalled a visit to Latvia earlier this summer and the role that the UK and others played in helping it transition from Soviet rule to becoming a modern democracy and market economy.
"What happened to the confidence and ideals of the European dream?" he asked. "The EU was set up to protect freedom. It was the Soviet Union that stopped people leaving."
In response, Baiba Braze, the Latvian ambassador to the UK, said the comparison was misguided as the Soviets "killed, deported, exiled and imprisoned hundreds of thousands of Latvia's inhabitants after the illegal occupation in 1940, and ruined lives of three generations, while the EU has brought prosperity, equality, growth, respect".
Her Estonian counterpart, Tiina Intelmann, joined in the criticism, tweeting:
The Swedish ambassador Torbjorn Sohlstrom said the UK rightly deserved respect but the comments were wide of the mark.
The remarks have also raised eyebrows among former senior British diplomats.
Lord Ricketts, who led the Foreign Office between 2006 and 2010, said the only punishment that the UK would suffer from Brexit was "self-inflicted".
"This rubbish is unworthy of a British foreign secretary," he said. "The EU isn't a Soviet-style prison. Its legal order has brought peace and prosperity after a century of war."
And his successor, Sir Simon Fraser, suggested it was a "shocking failure of judgement" by Mr Hunt, who succeeded Boris Johnson in the role in July.
A European Commission spokesman added: "I would say respectfully that we would all benefit - and in particular foreign affairs ministers - from opening a history book from time to time."

What's so striking about this draft Brexit deal the UK media and politicians are all abuzz about, is the marked lack of excitement and/or hysteria in EU circles.
Contrary to the UK narrative, this is not viewed in Brussels as the back-against-the-wall, make-or-break moment.
There's still some time to keep negotiating. EU-UK technical talks are, in fact, ongoing as neither all the "i"s, nor all the "t"s of a deal have yet been dotted or crossed.
The thinking here is: if the UK cabinet or certain EU member states strongly object to specific parts of the draft document (as long as they don't rip up the whole thing), then negotiators can go back to the drawing board.
As I've mentioned before, the EU is clearly more relaxed about timing - as long as a deal is signed before March - than Theresa May at this stage.
You get the feeling that the current sense of pressure and urgency is designed to help the UK prime minister at home.
Storm clouds surrounded her once again last weekend, with cabinet minister Jo Johnson resigning and mutterings of potential mutiny from Brexiteer and Remainer conservative MPs, never mind the Labour Party and the DUP plotting over the eventual Brexit parliamentary vote.
It looked (once again) like the whole thing could unravel on the UK side.
Brussels has repeatedly told Mrs May that - as long as they could agree on the details of a deal amongst themselves - the EU would help her present it however she wished in order to help her sell the package back home.
I think now is one of those moments, which would explain why Brussels kept so silent on Tuesday night - such a politically sensitive night in the UK.
One of my high-level EU contacts even sent me an emoji with a closed zip instead of a mouth - to indicate that he couldn't talk.
These are hours for Downing Street to spin.
This is not to say that the EU is completely chilled about the appearance of a draft Brexit deal - played down to me by a Brussels contact as a "mutual understanding" between EU and UK negotiators.
That's a reminder that this is a technical draft - not yet a political agreement.
While all eyes on Wednesday will be on Number 10 Downing Street and the reaction of the UK cabinet, the governments of all 27 EU countries and the European parliament also want to get their eyes and their mitts on all 500 pages of the document ASAP.
Of key interest to them: the compromise wording over the backstop, that insurance policy for the Irish border.
They, and Ireland in particular, will be relieved to see something Brexiteers will not like at all - that the EU will decide alongside the UK if and when the backstop arrangements need to kick in and also when they can be terminated and superseded by a new EU-UK trade deal.
They will also note that the all-UK customs union with the EU outlined as part of the backstop will be deeper with Northern Ireland than with the rest of the UK. This will be hard for the DUP to swallow.
More important to EU heavyweights France and Germany - and others that trade closely with the UK like Ireland, Denmark and the Netherlands - will be to examine the small print of the backstop customs union to ensure the UK would have no competitive advantage over them.
I've spoken to diplomats who worry the European Commission was in such a hurry to get this draft Brexit deal document ready to Theresa May's timetable, that the priorities of some EU member states may have been overlooked.
France, Denmark, the Netherlands and Spain for example won't be happy that fishing rights in UK waters do not seem to appear in the text.
European capitals want a minimum of seven to 10 days to pore over the draft with a fine-tooth comb.
So, could there still be a special Brexit deal summit called this month as Theresa May so hopes?
It's not impossible - 25 November is being spoken about as a potential date.
Later on Wednesday as the UK cabinet meets in London, the 27 EU ambassadors will gather in Brussels.
To be discussed: the draft Brexit deal, the possibility of a November summit and - as a clear indication of the current uncertainty - ongoing contingency plans for a no-deal Brexit.

Europe's leaders feel they have already lost far too much political time on Brexit.
Again today, Prime Minister Theresa May heads to Paris and Berlin for talks with Emmanuel Macron and Angela Merkel - this after a number of phone calls on Monday with other EU leaders - with little up her sleeve or in her pocket to share with them.
But far from showing impatience (OK, Berlin and Paris would have been happy with a call rather than a more time-consuming visit), EU leaders have welcomed being in contact with Mrs May ahead of Wednesday's Brexit summit.
She doesn't have a great track record for "getting the tone right on the night" at EU gatherings. And with a no-deal Brexit looming this Friday, the EU thinks this is no time for misunderstandings.
There is little European expectation that cross-party talks with opposition leader Jeremy Corbyn will come to fruition this week - if ever.
So, EU leaders are curious to hear the prime minister's Plan B. They hope there is one, although they're not convinced.
They want to know, if they say yes to another Brexit extension, what it will be used for.
And they suspect Theresa May wants them to do her dirty work for her. EU diplomatic sources I have spoken to suggest the prime minister may have officially asked the EU for a short new extension (until 30 June) as that was politically easier for her back home, whereas she believed and hoped (the theory goes) that EU leaders would insist instead on a flexible long extension that she actually needs.
The bottom line is: EU leaders are extremely unlikely to refuse to further extend the Brexit process.
France's Emmanuel Macron has been built up in the press (and he has done much to encourage this image) as the Brexit villain who could veto an extension and force no deal on Friday.
But, while possible, it is unlikely. There is no EU appetite for a chaotic Brexit. And while President Macron relishes playing bad cop, he alone will not want to be responsible for the effects of no deal in Calais and on the Irish border.
The first is bad for France, the other for Ireland (Mr Macron spoke of his solidarity with Ireland while in Dublin only last week) and for the EU as a whole - with a threat to the integrity of the single market along the border between Ireland and Northern Ireland after a no-deal Brexit.
Rather than vetoing an extension altogether, Mr Macron is more likely to push for tough conditions to any new Brexit delay, These are:
It's hard to see how the two last conditions could be made legally enforceable. But demanding "tough conditions" has as much to do with Mr Macron putting on his Defender of Europe hat for a wide audience, as anything else.
Aside from extension conditions, EU leaders are still split over how long any new Brexit delay could or should be.
Some feel a short extension would keep up the pressure on MPs to finally come to a Brexit conclusion. Others favour a longer extension - nine months to a year but with the UK able to duck out early after parliament ratifies a Brexit deal (the so-called "flextension").
Bear in mind, EU leaders are beginning to lose credibility at home for allowing the Brexit can to be constantly kicked down the road. Uncertainty is costly for European businesses too.
The Belgian prime minister has asked an inner core of countries most affected by Brexit - including Germany, Ireland, the Netherlands and France - to meet a couple of hours before the summit on Wednesday starts to try to iron out some of their differences ahead of time.

EU leaders have agreed to move Brexit talks on to the second phase but called for "further clarity" from the UK about the future relationship it wants.
The first issue to be discussed, early next year, will be the details of an expected two-year transition period after the UK's exit in March 2019.
Talks on trade and security co-operation are set to follow in March.
Theresa May hailed an "important step" on the road but Germany's Angela Merkel said it would get "even tougher".
Donald Tusk, the president of the European Council, broke the news that the 27 EU leaders were happy to move on to phase two after they met in Brussels.
He congratulated Mrs May on reaching this stage and said the EU would begin internal preparations for the next phase right now as well as "exploratory contacts with the UK to get more clarity on their vision".
While securing a deal in time for the UK's exit in March 2019 was realistic, he suggested that the next phase would be "more challenging and more demanding".
Mrs May said the two sides would begin discussions on future relations straight away and hoped for "rapid progress" on a transitional phase to "give certainty" to business.
"This is an important step on the road to delivering the smooth and orderly Brexit that people voted for in June 2016," she said.
"The UK and EU have shown what can be achieved with commitment and perseverance on both sides."
Labour's international trade spokesman, Barry Gardiner, welcomed the move forward, but said it would be a "real problem" for business if the EU didn't start talking trade for a further three months.
He also said his party would not put a time limit on a post-Brexit transition phase, as the expected two-year period would be "extremely tight".
The EU has published its guidelines for phase two of the negotiations, with discussions on future economic co-operation not likely to begin until March.
The three-page document says the UK will remain under the jurisdiction of the European Court of Justice and be required to permit freedom of movement during any transition period.
And agreements on the Irish border, the so-called divorce bill and the rights of EU and UK citizens, agreed by Mrs May last Friday, must be "respected in full and translated faithfully into legal terms as quickly as possible".
The document says: "As the UK will continue to participate in the customs union and the single market during the transition, it will have to continue to comply with EU trade policy."
While the EU is willing to engage in "preliminary and preparatory discussions" on trade as part of building a "close partnership" after the UK's departure, this means any formal agreement "can only be finalised and concluded once the UK has become a third country".
By the BBC's political editor Laura Kuenssberg
After the six months she has had, Theresa May might be entitled to breathe a sigh of relief, as the European Council officially declared that the first phase of our long goodbye from the European Union is over.
Stand back from the daily dramas and perhaps it was always bound to happen.
Both sides are committed to getting an agreement.
The EU and the UK both want a deal to be done, and while there has, inevitably, been grumpiness on both sides, they have, in the main, dealt with each other in good faith.
The document "calls on the UK to provide further clarity on its position on the framework for the future relationship".
But in a passage added during the past week, it invites the EU's Brexit negotiator Michel Barnier to "continue internal preparatory discussions" on future relations rather than having to wait until March to do so.
Sources have told the BBC that the government is highly likely to accept an amendment to the EU Withdrawal Bill next week to see off another potential Commons defeat for Theresa May.
Conservative rebels have been concerned about plans to put the Brexit date and time - 11pm on 29 March 2019 - into law.
Backbenchers, including former minister Oliver Letwin, have tabled an amendment, suggesting a change to the legislation.
Ministers are likely to accept their plan, which is a change that some of the potential rebels have been asking for, the BBC understands.
Senior sources are confident they can see off a defeat, after No 10 said there were no plans to take the date out of the bill.
Responding to the reports, Shadow Brexit secretary Sir Keir Starmer wrote on Twitter: "After a car-crash defeat on Brexit vote, rumours that PM will now U-turn on gimmick exit day amendment: forced to get a Tory MP to amend her own amendment before its put to the vote!"
European Commission President Jean-Claude Juncker said the EU's initial priority was to "formalise the agreement" that had already been reached before moving forward, adding "the second phase will be significantly harder and the first was very difficult".
Praising Mrs May as a "tough, smart and polite" negotiator, he said he was "entirely convinced" that the final agreement reached would be approved by the UK and European Parliaments.
Giving his response, French President Emmanuel Macron said that in moving forward the EU had maintained its unity, protected the integrity of the single market and ensured "compliance with our own rules".
Mrs May is set to discuss her vision of the "end state" for the UK outside the EU at a cabinet meeting on Tuesday, having suffered her first Commons Brexit defeat earlier this week.

EU leaders have pulled apart the UK's Brexit proposals, accusing Boris Johnson of putting forward untested ideas to solve the Irish border crisis.
Chief negotiator Michel Barnier said the EU needed workable solutions "today not tomorrow".
European Commission President Jean-Claude Juncker told MEPs that while he would "not exclude" a deal in the coming days, progress had been limited.
Mr Johnson has said he remains "cautiously optimistic" about a deal.
He will meet his Irish counterpart, Leo Varadkar, on Thursday to try and break the deadlock, while continuing to insist the UK will leave on 31 October with or without an agreement.
In Westminster, meanwhile, a group of Conservative MPs has been demanding assurances from the PM that he will not take the party into the next general election - whenever it comes - on a straightforward promise to leave with no deal.
And earlier, it emerged MPs would be called to Parliament for a special Saturday sitting on 19 October - the day after a crunch EU summit, which is seen as the last chance for a deal ahead of the Halloween deadline.
The UK put forward fresh proposals for a Brexit deal last week, but so far the reaction from the EU has not been encouraging.
Updating MEPs on the state of talks, Mr Barnier said he believed "with goodwill" on both sides there could be an agreement in the run-up to the summit.
But he said "to put things very frankly and to try to be objective, we are not really in a position where we are able to find an agreement".
As it stood, he said, the UK was proposing replacing an "operable, practical and legal solution" to avoid a hard Irish border with "one that is simply a temporary solution".
Mr Barnier said the UK's suggested alternative to the Irish backstop - which would see customs checks conducted away from the border at business premises or electronically - "had not been tested" and was "largely based" on exemptions for small businesses and technology that "has yet to be developed".
"We need operational real controls, credible controls, we are talking about the credibility of the single market here - its credulity to consumers, to companies, and to third counties that we have agreements with."
Mr Barnier also questioned the viability of the UK's proposals to give the Northern Ireland Assembly a veto over whether it aligned with EU single market rules for goods from 2021 onwards and whether to diverge from them in the future.
However, he did confirm the two sides were looking at "a more important role" for the Northern Irish political institutions.
Under Mr Johnson's proposals, which he calls a "broad landing zone" for a new deal with the EU:
Mr Juncker, meanwhile, took a swipe at the UK in the wake of a political row over the details of Tuesday's phone call between Mr Johnson and German Chancellor Angela Merkel.
Following the call, a No 10 source claimed the German leader had said a deal based on the UK's proposals was "overwhelmingly unlikely" and made new demands which made an agreement "essentially impossible".
"We remain in discussion with the UK," Mr Juncker said. "Personally I don't exclude a deal. I do not accept this blame game that started in London."
During a sometimes bad-tempered debate in the European Parliament, former Belgian prime minister Guy Verhofstadt, accused Mr Johnson of treating those seeking to prevent a no-deal Brexit as "traitors, collaborators and surrenderers".
"The reason this is happening is very simple. It is a blame game. A blame game against everybody - against the EU, against Ireland, against Mrs Merkel, against the British judicial system, against Labour, against the Lib Dems, even against Mrs May," he said.
"The only person who is not being blamed is Mr Johnson apparently. All the rest are part of the problem."
Lib Dem MEP Jane Brophy urged the EU to give the UK as long an extension as possible to allow time for a general election and a referendum.
But Brexit Party leader Nigel Farage suggested Brussels was no longer negotiating in "good faith" and the UK was fed up with being "talked down to and insulted" by EU leaders.
"You are not looking for solutions. You are looking to put obstacles in our way."
Mr Farage also suggested a no-deal Brexit would be a "winning ticket" at a future general election - a prospect which has reportedly caused some disquiet among Conservative MPs.
At a meeting on Wednesday afternoon with a group of One Nation Tories - led by ex-minister Damian Green - the PM was told that dozens of his MPs would not be willing to support a straightforward manifesto promise to leave without a deal if there was a snap election before the end of the year.
Mr Johnson sought to reassure them he was still very much focused on getting a deal.
But the BBC's Laura Kuenssberg said while no decision had been taken, she understood a future manifesto could include a promise to leave with an agreement if possible, alongside a vow to leave anyway "within days or weeks" if the Tories won a Commons majority and there was no chance of a deal.
The prime minister has said he is determined the UK will leave the EU on 31 October, despite legislation, known as the Benn Act, which requires him to write to Brussels requesting a further delay if a deal is not signed off by Parliament by 19 October - or unless MPs agree to a no-deal Brexit.
Scottish judges decided on Wednesday to delay a decision on whether to sign the letter if Mr Johnson refused to do so, saying instead they would wait until the political debate had "played out".
Elsewhere, there was anger among some Brexiteers after European Parliament President David Sassoli met Commons Speaker John Bercow in London.
A statement after the meeting from Mr Sassoli said they both "fully agreed on the important role that our parliaments play in the Brexit process" and the European institution would support any request from the UK for an extension.
Mr Farage said it was "disgraceful" the pair had "agreed to work to prevent a no-deal Brexit".
Conservative MP Marcus Fysh said it was "so far beyond his (Mr Bercow's) constitutional role" and accused him of "colluding with a foreign power".

EU leaders have dismissed talk of renegotiating the draft Brexit deal and warned the UK's political situation could make a "no-deal" more likely.
German Chancellor Angela Merkel said there was "no question" of reopening talks as a document was "on the table".
Meanwhile French PM Edouard Philippe said there was a need to prepare for a no-deal because of UK "uncertainty".
The EU has set out a series of meetings leading up to 25 November when it plans to approve the Brexit agreement.
However leaders admit that there is still much ground to cover after the UK Prime Minister Theresa May won backing on Wednesday from her cabinet for the 585-page draft agreement.
"We still have a long road ahead of us on both sides," the EU's chief Brexit negotiator Michel Barnier said.
On Thursday, Mrs Merkel said she was pleased that progress had been made.
But following news of resignations from Mrs May's cabinet, including the UK's Brexit Secretary Dominic Raab, she said it was possible that Britain may still leave without a deal.
She also said that there was no appetite for further talks on possible amendments to the current agreement.
"We have a document on the table that Britain and the EU 27 have agreed to, so for me there is no question at the moment whether we negotiate further," she said.
Mr Philippe appeared to echo her sentiment over UK political uncertainty.
"It will escape no-one that the current political situation in Britain could fuel uncertainty... over the ratification of the accord," he said.
The European Parliament's Brexit chief Guy Verhofstadt said the deal had been hammered out after two years of "intense negotiations" and he hoped UK MPs would accept that "there is not a lot of room [for] manoeuvre to say, 'OK, let's start again'".
French Finance Minister Bruno Le Maire said the deal was "good news for the French economy" but also issued caution, saying the UK must be made to respect all EU rules.
Analysis by BBC Europe editor, Katya Adler
The EU knows there is a very real possibility the Brexit deal could be voted down by the UK Parliament in a few weeks' time.
I put the question to Michel Barnier on Wednesday night at his press conference - but, skilled politician that he is, he refused to engage.
Brussels is very keen indeed not to give the impression that the EU might change or come up with a "better" Brexit deal text if this one ends up being rejected in the House of Commons.
Mr Barnier quoted Theresa May as saying that this is a deal in the UK's interest.
Finland's Prime Minister Juha Sipila tweeted to say that while Wednesday's developments were important, "decisions on both sides are still needed for a final agreement".
Austrian Chancellor Sebastian Kurz said he was "very pleased" and "optimistic", adding: "We are pinning our hopes on it."
Speaking on Thursday alongside EU Council head Donald Tusk, Mr Barnier said the agreement was fair and balanced, took into account the UK's needs and laid the ground for an "ambitious new partnership".
Mr Tusk praised Mr Barnier's work and said the agreement had "secured the interests of the 27 member states and EU as a whole".
He laid out the timetable for the days ahead.
Mr Tusk said: "Since the very beginning, we have had no doubt that Brexit is a lose-lose situation, and that our negotiations are only about damage control."
Addressing the UK, he added: "As much as I am sad to see you leave, I will do everything to make this farewell the least painful possible, for you and for us."
Mr Barnier later took the document to the European Parliament. Its president, Antonio Tajani, said MEPs would vote on the deal in early 2019.
If the agreement is approved by both sides, a 21-month transition period will kick in, during which a trade deal and the thorny issue of how to ensure there is no physical border between Northern Ireland - part of the UK - and the Republic of Ireland will need to be worked out.
A smooth border-free exchange underpins the peace deal that ended the Northern Ireland conflict.

EU leaders head into this weekend with a heavy heart. They know, in theory, that all Brexit options remain on the table and they haven't entirely given up hope of a negotiated UK departure, but there is little trust here that the prime minister or Parliament will manage to pull it off.
Despite all the drama, the money and time spent by EU leaders on Brexit over the last two years (summits, dedicated governmental departments, no-deal planning), all the hard, hard graft put in by the EU and UK negotiating teams, Europe's leaders are asking themselves what there is to show for it all.
Ongoing Brexit divisions in parliament, in government and in Theresa May's cabinet were on screaming technicolour display again last week.
EU leaders used to use the threat of a no-deal Brexit as a negotiating tactic (as did the UK). They now believe it to be a very real prospect.
That has led to a number of countries - notably France - questioning the logic of delaying Brexit for much longer.
They wonder if the UK will ever unite around a Brexit Way Forward -  be it a softer Brexit, no deal or no Brexit.
Would a Brexit extension, allowing for a general election or a second referendum, really settle the issue, they ask?
Or will the EU and UK end up in a no deal scenario anyway, after countless extra months of agonising (and costly) uncertainty?
France's President Macron - suffering from sagging popularity ratings at home - is hell-bent on breathing life in to the European project.
He is far from excited at the idea of having a recalcitrant UK - with 8.5 toes already out of the club - overshadowing proceedings for the immediate future.
In the next few months, the EU holds decisive elections for the European parliament, where populist nationalists are predicted to make a strong showing. New European Commission and European Council presidents will need to be chosen and the next EU budget should be  decided this autumn. The French president is not alone in worrying that an in-the-process-of leaving UK could throw a spanner in the works if it so chose.
This is not to say that the answer will be no if the prime minister comes to the emergency Brexit summit of EU leaders on 10 April, asking for a longer delay.
But there is a lively debate right now in EU circles about the virtue of granting the UK (by law all EU countries must come to a unanimous decision) a longer Brexit delay vs no deal in April or May. Of course no deal would be costly for the EU too, but for some, it's beginning to look like the best of a bunch of bad options.
Treating a no-deal Brexit as a looming, very real possibility, rather than a distant, highly unlikely prospect, is making the EU take a long, hard look at its own no-deal planning.
At every opportunity, in press statements and tweets, EU leaders boast that they are fully prepared- but that is not entirely true.
Some countries and businesses are better prepared than others, but there are two hot potato political issues that - up until now - EU leaders have shied away from confronting.
No longer.
Spain is now being told to stop trying to score points - however small - over Gibraltar. Madrid's insistence on describing the Rock as a UK colony has held up finalising a document ensuring EU-wide, visa-free travel for UK citizens throughout the EU in case of no deal.
But the EU's main no deal planning concern is the Irish border.
Leaders are beginning to lean on Dublin now to finesse its plans for the border with Northern Ireland in case of a no deal Brexit. The Irish government has kept plans vague until now because the idea of border checks is politically so sensitive on the island. But Brussels believes checks and some physical infrastructure will be needed, even if it's away from the border itself.
Germany's Angela Merkel is scheduled to fly to Dublin next week.
Whatever happens with Brexit, she and other European leaders want to make sure their single market will be protected.

EU leaders have urged Theresa May to do more to break the deadlock in the Brexit negotiations as they gather at a crunch Brussels summit.
Dutch PM Mark Rutte said "a lot more clarity" on the UK's financial offer was needed before talks could progress.
German Chancellor Angela Merkel said there were "encouraging" signs but that progress so far was "not sufficient" to open trade talks.
However, Mrs Merkel suggested this could happen in December.
Mrs May, who has called for "urgency" in reaching agreement on the issue of citizens' rights, will address EU leaders at the summit later.
At a meeting on Friday, at which the UK will not be present, the 27 leaders are expected to conclude officially that "insufficient progress" has been made on the first topics for discussion to move onto the second phase of trade discussions.
These topics are citizens' rights, the UK's financial obligation and the border in Northern Ireland.
The UK prime minister spoke of her desire for a future partnership with the EU as she arrived in Brussels, but added: "We'll also be looking at the concrete progress that has been made in our exit negotiations and setting out ambitious plans for the weeks ahead.
"I particularly, for example, want to see an urgency in reaching an agreement on citizens' rights."
Speaking to the BBC, Mr Rutte said he welcomed the PM's recent speech in Florence, where she set out what she has described as a "bold and ambitious agenda".
But he said she needed to make "absolutely clear" what she was offering to do in relationship to the UK's financial obligations towards the EU.
"Maybe it's not possible now to name a number but at least to come up with a methodology, a system, a complete proposal to solve this issue," he said.
"As long as that is not happening I don't see how we can move forward."
Analysis by Europe correspondent Kevin Connolly
The October summit was always the first date in the EU calendar on which a gathering of the 27 heads of government could declare themselves satisfied with the Brexit divorce negotiations and agree to start talking about trade.
It's been clear for weeks that they won't do that - but they will offer the UK some encouragement by starting internal discussions about future trade with the UK - ready for any breakthrough at the next summit in December.
Theresa May isn't expected to make any big new proposal in her after-dinner remarks but to underline the quality of the financial offer made in her speech in Florence - worth around £20bn.
The EU side wants more though - more money as well as further movement on citizens rights and the Irish border.
There are almost as many predictions about what happens next as there are diplomats in Brussels; one has suggested that the prospects of a December breakthrough are no better than fifty-fifty but an official close to the talks said the signal on Brexit from this summit would be fundamentally positive.
Before leaving for Brussels, Mrs May used a Facebook post to offer further assurances to the three million or so nationals of other EU countries living in the UK and uncertain about their future after Brexit.
In the open letter, which was also mailed to 100,000 EU nationals, she said those who already had permanent residence would be able to "swap this" for settled status in as hassle-free a way as possible.
The process of applying for permanent residency, for which EU nationals are eligible after five years, has long been criticised as cumbersome and overly bureaucratic. At one point, it involved filling out an 85-page form.
In simplifying it, Mrs May said she was committed to putting "people first" in the negotiations and expected British nationals living on the continent to be treated in the same way.
"I know both sides will consider each other's proposals with an open mind and with flexibility and creativity on both sides, I am confident we can conclude discussions on citizens' rights in the coming weeks," she said.
Nicolas Hatton, of the 3million pressure group formed to fight for the rights of EU nationals in the UK, described the PM's statement as "very positive", but said its timing was "a bit more dubious".
"We should have received that letter maybe 12 months ago so we would not have felt so anxious about our future" he said, adding: "I think the letter was actually addressed to EU leaders."
Meanwhile a group of pro-Brexit Tory and Labour politicians - including former Chancellor Lord Lawson, former Conservative minister Owen Paterson and Labour MP Kate Hoey - is urging Mrs May to walk away from negotiations this week if the EU does not accommodate the UK's wishes.
In the event of no progress at Thursday's meeting, the letter, organised by the Leave Means Leave campaign, says Mrs May should formally declare the UK is working on the assumption it will be reverting to World Trade Organisation (WTO) rules on 30 March 2019.
Mr Paterson told the Today programme the UK should not be "terrified" of leaving the EU without a deal in place, saying this appeared "inevitable at the moment" due to the EU's "complete obsession with money" - the so-called Brexit divorce bill.
But Labour's Brexit spokesman, Sir Keir Starmer, said it would be "irresponsible" to threaten to walk away with the talks only at "phase one".
He added that Labour was not "duty bound" to support any deal the PM secures with Brussels.
Sir Keir and Labour leader Jeremy Corbyn are also in Brussels for their own talks with EU officials.

EU leaders have gathered in Brussels for a meeting where they are expected to rubber stamp the Brexit transition deal and clear the way for trade talks.
Theresa May said she looked forward to it being endorsed so they could "move on swiftly" to talks about the future UK-EU relationship, including trade.
The EU's Donald Tusk said he had recommended EU leaders welcome the 21-month period "in practice".
But the PM is under pressure not to concede any further on UK fishing.
Arriving in Brussels she said: "I'm looking forward to talking about Brexit. We made considerable progress through the agreement on the implementation period, which will bring certainty to businesses and people.
"I look forward to the European Council endorsing that agreement and moving on swiftly to talk about the future partnership that we all want to build together."
The UK is set to leave the 27-nation bloc on 29 March 2019, but earlier this week Brexit Secretary David Davis and EU chief negotiator Michel Barnier struck a deal that would allow for a transition period - which the UK government describes as an implementation period - until December 2020.
Under the terms of that joint legal text, the UK will be able to negotiate, sign and ratify its own trade deals, while EU citizens arriving in the UK will enjoy the same rights and guarantees as those who arrive before Brexit.
To the dismay of some of her Conservative MPs, the UK will effectively remain in the Common Fisheries Policy until the end of 2020, while a solution to avoid a hard border on the island of Ireland has yet to be agreed, with the EU insisting on a "backstop" option of Northern Ireland effectively remaining in the customs union and parts of the single market.
The prime minister told the Commons that for the first time in 40 years, Britain would be able to "forge our own way by negotiation our own trade agreements".
However, she faces warnings that the deal could be scuppered by her own MPs unless she tears up "unacceptable" proposals for fishing.
Some 14 of the PM's backbench parliamentary allies - 13 Conservatives and one DUP MP - have signed a joint letter denouncing the draft deal agreed by the government earlier this week.
One of those, the DUP's Brexit spokesman Sammy Wilson, said Scottish, Northern Irish and English MPs with coastal communities had laid down a "marker" with the prime minister.
He said she needed to make "it quite clear that after the transition period we will have total control of our waters and we'll no long allow the EU to plunder our fishing grounds".
BBC political editor Laura Kuenssberg said the fishing issue "doesn't feel like an enormous problem" at this moment but "the prime minister doesn't have a majority on her own and if enough of the DUP and enough of those new Scottish MPs really do threaten trouble further down the tracks, she may have no choice but to listen".
Meanwhile, Mr Tusk took to Twitter to urge the other 27 EU leaders to welcome, in principle, the agreement on transition and other matters at a session expected to take place on Friday.
"In practice, the transition phase will allow to delay [sic] all the negative consequences of Brexit by another 21 months," he wrote.
He told reporters he was "absolutely sure" the two sides would find a last solution to prevent the return of physical checks on the border between Northern Ireland and the Republic of Ireland.
The Irish government has insisted the UK has provided a "cast-iron guarantee" that will ensure no physical infrastructure, checks or controls at the border after withdrawal.
A written declaration issued by the European Council on the eve of the summit called for "intensified efforts on the remaining withdrawal issues, as well as issues related to the territorial application of the Withdrawal Agreement, notably as regards Gibraltar, and reiterates that nothing is agreed until everything is agreed".
There have been complications over the British overseas territory, which will leave the EU on the same day as the UK, in the run-up to Thursday's meeting.
At the UK's request, Gibraltar was specifically mentioned in the transition text but Spain, which maintains a long-standing sovereignty claim, subsequently sought reassurances that its interests would be protected.
Also on Friday, the EU is set to adopt guidelines for its negotiations over its future permanent post-Brexit relationship with the UK.

The heads of the European Commission and Council - Ursula von der Leyen and Charles Michel - have signed the Withdrawal Agreement, ahead of the UK's exit from the EU on 31 January.
The Queen approved it on Thursday, and next Wednesday the European Parliament is expected to vote for it too.
The UK has agreed to abide by EU rules during a transition period until the end of the year. By 2021 the UK aims to have agreed a deal on future ties.
Brexit ends 46 years in the EU club.
After the document was signed in Brussels it was taken to Downing Street by EU and UK officials, for signing by UK Prime Minister Boris Johnson, due later on Friday. The agreement will then travel back to Brussels, and a copy of it will remain in London.
Next week's European Parliament vote is seen as all but a formality, after it was backed by the parliament's constitutional affairs committee on Thursday.
Mrs von der Leyen and other senior EU figures are sceptical about the UK government's plan to negotiate a comprehensive deal on future relations before the end of 2020. They believe the timetable for that is too tight.
But Prime Minister Boris Johnson is upbeat, insisting the UK can now move forward after years of wrangling over Brexit.
Charles Michel, the former Belgian Prime Minister who chairs EU summits, said in a tweet "things will inevitably change but our friendship will remain.
"We start a new chapter as partners and allies."
The EU Commission official who spent more than three years negotiating Brexit - Michel Barnier - stood behind the two EU leaders at the low-key signing ceremony.
Earlier Mr Johnson said "at times it felt like we would never cross the Brexit finish line, but we've done it.
"Now we can put the rancour and division of the past three years behind us and focus on delivering a bright, exciting future - with better hospitals and schools, safer streets and opportunity spread to every corner of our country."
MPs overruled an attempt by the House of Lords to secure additional rights, including for unaccompanied child refugees, in the Withdrawal Agreement.

The EU's 27 other leaders have met without the UK's Theresa May to discuss their Brexit negotiation plans.
They met informally at the European Council summit in Brussels amid tensions over the handling of talks.
Downing Street said Mrs May had not sought to be present at that meeting and it showed the EU was facing up to the reality that the UK was leaving.
It comes as the UK government plays down a suggestion that negotiating a UK-EU trade deal could take 10 years.
The BBC understands the UK's senior diplomat in the EU warned ministers that the European consensus was that a deal might not be done until the early to mid-2020s.
Arriving in Brussels, Mrs May was asked about the 10-year claim, but concentrated her answer on the subject of immigration, which is what the EU leaders have focused on during a chunk of their one-day summit.
She added that a smooth UK exit from the EU was "not just in our interests, it's in the interests of the the rest of Europe as well".
Despite her absence from the later, informal meeting, Downing Street said Mrs May would play a full role in talks on other issues such as Syria.
This was echoed by European Parliament president Martin Schulz, who told the 28 leaders the UK would still enjoy the "rights and benefits" of EU membership while still fulfilling its "duties".
At the summit, the leaders discussed controlling mass migration into Europe, the EU's relationship with Ukraine, co-operation with Nato and economic matters.
Speaking afterwards, Mrs May said they had also discussed "the appalling situation in Syria".
"We heard from the mayor of eastern Aleppo, he had one plea for us - to allow the safe evacuation of the people in the city," she said.
"President Assad and his backers - Russia and Iran - bear responsibility for the tragedy in Aleppo, they must now allow the United Nations to ensure the safe evacuation of the civilians who are left there.
"The UK is going to provide a further £20m of practical support for those who are most vulnerable. The mayor of eastern Aleppo said to us: 'We can't bring back those we have lost, but we can save those who remain.' And that is what we must now do."
The UK is to send a further 40 officials to Greece to try to speed up asylum claims from Iraqis, Afghans and Eritreans arriving there, in an effort to deter others from coming.
There are already 70 UK caseworkers "experienced" in dealing with the return of asylum-seekers taking part in the trial scheme.
The UK is pressing for more EU-wide action to tackle economic migration at its source, working with countries such as Libya and Egypt to help control their borders.
Mrs May has also held bilateral meetings with the leaders of Latvia and Lithuania as well as the president of the European Parliament, Martin Schulz.
One of the issues to be discussed by the 27 non-UK EU leaders is who will lead their negotiating team, amid tensions between the different EU institutions.
It is expected to be former EU Commissioner Michel Barnier who is in charge of the European Commission's Brexit team.
Former Belgian prime minister Guy Verhofstadt, who is leading the European Parliament's Brexit taskforce, claimed it could start separate negotiations with the UK unless EU leaders take "its role seriously".
He warned the European Commission not to "sideline" the Parliament.
Mrs May spoke to the new Italian prime minister Paolo Gentiloni on Wednesday. She has already held face-to-face talks with 23 EU leaders to brief them on the UK's intentions after June's referendum vote to leave the EU.
The prime minister also spoke to Donald Tusk, the president of the European Council, who confirmed she would update the rest of the EU on the UK's preparations.
A senior EU official said that, by the end of the summit, the 27 would be "procedurally prepared" for the negotiations and there was a consensus that although the process would be led by the Commission, it would be "controlled" by the member states.
It said the 27 were sticking to the principle of "no negotiation without notification", meaning talks could only begin once the UK triggered Article 50.

Low-skilled migration will fall when the UK ends EU free movement access after Brexit, Theresa May has promised.
The prime minister said high-skilled workers would be prioritised with no preferential treatment for people from the EU compared with those from the rest of the world.
But she said a future trade deal with the EU could include an agreement on "mobility" of each other's workers.
Business groups expressed alarm about a crackdown on low-skilled workers.
The Confederation of British Industry said it would make a shortage of care, construction and hospitality workers worse, adding: "Restricting access to the workers the UK needs is self-defeating."
The British Retail Consortium said the policy should be based on the economy's needs rather an "arbitrarily" drawing a line based on salaries or skills.
And Labour said the government was making a "dubious distinction" between low and high-skilled workers - saying care workers were technically "low-skilled" but were "vital to our society".
As it stands, EU freedom of movement allows people from the European Economic Area - all EU countries, as well as Norway, Iceland and Liechtenstein - plus Switzerland, to travel and work in the UK without visas, regardless of skills.
For the rest of the world, specific categories of visas are needed to come and work or study in the UK, including one for "skilled workers" - who usually have to earn at least £30,000 and have a job offer.
Currently, no "Tier 3" - low-skilled labour - visas are being given out. The UK defines low skilled roles as ones which do not require post-16 education or more than a short period of on-the-job training.
The post-Brexit immigration plans follow a recommendation by the Migration Advisory Committee, which was also backed by Labour.
The cabinet agreed to the committee's recommendations last week, and a White Paper setting out the details is promised in the autumn.
Under the proposals:
"The new skills-based system will make sure low-skilled immigration is brought down and set the UK on the path to reduce immigration to sustainable levels, as we promised," Mrs May said.
Speaking on BBC Radio 4's Today programme, she said free movement would end "once and for all" once the UK leaves the EU.
Asked whether exemptions would be made for industries requiring high levels of unskilled labour, she said the plan would recognise "the further needs of the economy" but that there would not be "lots of exemptions" for different sectors.
And asked whether tourists would face extra bureaucracy when they visit EU countries, she said she hoped this would be dealt with in the course of the negotiations with the EU.
The new system would aim to bring net migration to "sustainable levels", she promised - which she has defined as being below 100,000, a target the Tories set years ago but have never met.
The EU's view
The European Parliament's Brexit co-ordinator Guy Verhofstadt said the EU would not accept a UK immigration system that discriminated based on skills and job type - and that's the centre-piece of Mrs May's proposal.
But it is not clear the extent to which the two sides will ever negotiate over this issue: the Brexit talks so far have been about the rights of people who have already moved and the negotiations about a future trade deal are likely to be about tourists, students and businesspeople - known in the jargon as "mobility" rather than immigration.
In typical fastidious fashion Michel Barnier's team has already thought about all of this, giving a presentation to diplomats in February which said that UK migrants to the EU would be treated like citizens from anywhere else after Brexit.
In a BBC Breakfast TV interview which also covered broader Brexit policy, Mrs May brushed off suggestions that there would have to be a general election or a referendum on any deal struck with the EU:
The government has already announced the rights of EU citizens already living and working in the UK would be safeguarded after Brexit.
Speaking at the Conservative Party conference in Birmingham, Home Secretary Sajid Javid told them: "Deal or no deal, we want you to stay. We need you to stay. You can stay."
Mr Javid said the UK had an "incredible opportunity" to set out an immigration system "without being constrained by the EU".
The new rules would be "based on merit", he said, promising a system that "That judges people not by where they are from, but on what they can do".
In his conference speech, Mr Javid also said he would raise the standard of English required for people wanting to become British citizens and reform the official 'Life in the UK' test to make it better reflect British values.
Guy Verhofstadt, the European Parliament's Brexit coordinator, said the EU would not accept a system "based on discrimination of skills and nationality".
British Retail Consortium chief executive Helen Dickinson told the BBC it did not make sense to have separate rules for low and high-skilled workers.
"We shouldn't be thinking about it like that, we should be thinking about what it is the economy needs and, from a retail industry point of view, what it is that we as consumers need in our day-to-day lives in buying the products that we are taking for granted," she said.
CBI director general Carolyn Fairbairn said the latest proposals had "taken a wrong turn".
"By dismissing the importance of low skilled workers to the UK economy, the government risks harming businesses and living standards now and in the future."
Former Conservative Party leader Iain Duncan Smith predicted the UK benefits system would remain a "massive pull factor" for unskilled workers coming from the EU to compete with Britons.
Asked about the warnings of shortages in sectors like care homes if this was cut, he said investment in new technology to monitor people in their own homes was needed to reduce dependency on cheap labour.
Alp Mehmet, of the Migration Watch UK campaign group, claimed the proposals were "not likely" to cut net migration because EU migration would be replaced with arrivals from the rest of the world.
"That's taking your foot off the brake and frankly slipping onto the accelerator," he said.

The EU's top Brexit negotiator has said there are still major differences between the EU and UK on the rights of EU citizens living in Britain.
"The British position does not allow those persons concerned to continue to live their lives as they do today," Michel Barnier said.
Mr Barnier said the European Court of Justice (ECJ) must have jurisdiction to guarantee citizens' rights.
He also said it was essential that the UK recognise its financial obligations.
If Britain did not accept it had some financial obligations, there would be no basis to discuss other issues, he said.
Ahead of the second round of talks next week, Mr Barnier said the EU had made its stance on the issues clear and was waiting on Britain to do the same.
"Our team is ready," he said. " I'm ready. I'm very prepared and willing to work on this very quickly - night and day, the weekend."
"We want EU citizens in Britain to have the same rights as British citizens who live in the EU," he told a news conference.
That would require the ECJ to be the "ultimate guarantor" of those rights, he said, because Britain could simply change its laws later, creating uncertainty.
UK law also imposes restrictions in areas such as reuniting families across borders, he said - something which was not applied to UK citizens living in Spain, for example.
Adam Fleming, BBC News, Brussels
Michel Barnier's message to the UK was: it's time to get a move on, to provide more clarity about the British position on a range of issues.
"As soon as possible," was his request, with the EU's chief negotiator joking that he was willing to work over the weekend and on Friday, which is a bank holiday in his native France.
The biggest sticking point appears to be the EU's insistence that Britain settles its outstanding financial obligations. Asked about Boris Johnson's suggestion on Tuesday that the EU could "go whistle", he joked that the only sound he could hear was a clock ticking.
There was copious evidence of the Barnier charm - but he was happy to turn on the menace, repeating several times that the UK would have to face the "consequences" of its choice to depart the EU.
Trying to sound eminently reasonable, he denied that his demand for a financial payment was a "ransom" or a "punishment."
Mr Barnier also said that those rights - along with the "divorce payment" and border issues - must be dealt with before future UK-EU trade could be discussed.
The financial payment the EU says will be owed to cover the UK's commitments is also a key point for Mr Barnier. Estimates have put the amount at anywhere from €60bn to €100bn (£53-89bn).
Asked about UK Foreign Secretary Boris Johnson's comment that the EU could "go whistle" over the demand, Mr Barnier replied: "I'm not hearing any whistling. Just the clock ticking."
He denied that the EU was holding the UK government to ransom, and said it was simply a matter of "trust".
"It is not an exit bill, it is not a ransom - we won't ask for anything else than what the UK has committed to as a member," he said.
Mr Barnier also announced he would meet other key politicians on Thursday who were not part of Theresa May's government - including opposition leader Jeremy Corbyn, representatives from the House of Lords, and the first ministers of Scotland and Wales.
"I have always made clear that I will listen to different points on view in the British debate," he said.
"Of course, I will only negotiate with the UK government," he added.

The UK will have to reach a Brexit deal by October 2018, according to the EU's chief negotiator for Brexit.
Michel Barnier told reporters that "time will be short" for negotiations because the proposed deal needed to be ratified as part of the two year process set to be triggered in March.
He said the UK could not "cherry pick" on issues such as the single market.
Earlier, UK Prime Minister Theresa May told the BBC she was aiming for a "red, white and blue Brexit" for the UK.
Speaking at a press conference in Brussels, Mr Barnier said a taskforce of 30 people had been set up to make sure the EU would "be ready" when Article 50 was called.
"Time will be short," he said. "It is clear the period for actual negotiations will be shorter than two years.
"At the beginning, the two years included the time for the council to set guidelines and to authorise negotiations. At the end, the agreement must of course be approved by the Council and European Parliament. Finally the UK will have to approve the agreement - all within the two year period.
"All in all there will be less than 18 months to negotiate. That is short. Should the UK notify by the end of March as Prime Minister Theresa May said she would, it is safe to say negotiations could start a few weeks later and an Article 50 deal reached by October 2018."
Mr Barnier, making his first public speech on the issue, was appointed to the post of chief Brexit negotiator on 1 October this year by European Commission President Jean-Claude Juncker, who said he "wanted an experienced politician for this difficult job".
The chief negotiator said he had spent time speaking to European member governments and said the Brexit negotiations had been informed by four main principles.
These included the "determination for unity" and a pledge to not start negotiations before being officially notified by the UK of its desire to leave, via the triggering of Article 50.
He also said: "Being a member of EU comes with rights and benefits. Third countries (non members as the UK will be after Brexit) can never have the same rights and benefits since they are not subject to the same obligations.
"The single market and its four freedoms (which includes freedom of movement) are indivisible. Cherry picking is not an option."
The BBC's Europe correspondent Damian Grammaticas asked Mr Barnier if the UK "paying in" to stay in the single market was a possibility after Brexit Secretary David Davis said last week the government "would consider it".
"There is access to the single market, but this is accompanied by predetermined, very specific contribution to the EU budget," said the chief negotiator.
"That is one of the models that already exists and that is one of the closest models there is to the EU without being a member."
But Mr Barnier added there were various options and until Article 50 had been called, there was little more he could say.
"It is up to the UK to tell us what they have in mind, then it is up to us at the 27 [member states] to say what we are prepared to conceive of."
Mr Barnier said he "didn't like to speculate very much" on what the future relationship between the EU and the UK would be, but it was time to "keep calm and negotiate".
"The sooner, the better," he added. "We all have a common interest in not prolonging the lack of certainty and we for our part need to concentrate on the European agenda on this new page that we will be writing in the history in the construction of the EU.
"There will be rebalancing but my conviction remains the same. Europe has to be the bedrock on which European citizens can lean in order to push ahead and construct the EU further for their safety, security, defence and prosperity."
"It is much better to show solidarity than to stand alone."
Analysis - Damian Grammaticas, BBC Europe correspondent
The EU appears to be signalling loud and clear what is on offer to the UK - and what isn't.
This isn't the EU playing hardball. That's to misread the EU's cues. And it isn't new. EU leaders have reiterated the same principles ever since the UK referendum.
From their point of view, their position is logical and consistent. EU leaders believe they have built the world's most integrated single market. They don't want to unpick parts of it for one nation that is leaving. Preserving their union is their priority.
So, Michel Barnier made clear that the UK cannot expect better terms outside the EU than inside. UK talk of getting a special deal that privileges the car industry or the City of London may not to be acceptable to the EU. As for paying to get access to the Single Market, that's possible Mr Barnier hinted - if, like Norway, you accept the EU's rules.
But 'cherry-picking' won't happen, he said. Importantly too, he indicated, a Brexit deal will cover the exit terms.
The UK's future relationship with the EU will, in all likelihood, have to be settled later, once the UK is out of the EU and has the status of a third country. It's not about driving a hard bargain. The EU is signalling it has its rules and principles, and isn't offering to change them.
Downing Street said it was sticking to its timetable despite the speech from Mr Barnier.
The prime minister's official spokesman said: "In terms of how long the negotiations actually take place, clearly that is a matter that will resolve itself as a result of the negotiations."
He said that the position of the rest of the EU on the timetable was a "matter for them".
But on the 18-month timetable, he said: "It is the first I have heard of it."
Mrs May said getting the right deal for British people would benefit the EU.
Speaking to the BBC's deputy political editor John Pienaar - before Mr Barnier's comments - on her two-day trip to Bahrain, Theresa May said: "People talk about the sort of Brexit that there is going to be. Is it hard or soft? Is it grey or white?
"Actually we want a red, white and blue Brexit; that is the right Brexit for the UK, the right deal for the UK. I believe that a deal that is right for the UK will also be a deal that is right for the EU."
On the issue of revealing more of those plans to Parliament, the prime minister said she still wanted "to keep some cards close to my chest".
But Mrs May said regardless of the outcome of this week's Supreme Court case - on whether the government can trigger Article 50 alone or need parliamentary approval - she would "deliver on the vote of the British people."
Hilary Benn, chairman of the Brexit Select Committee and Labour MP, believes talk of an 18-month time limit will add extra pressure.
He told BBC News: "It means there is going to be a very short time from the triggering of Article 50 to negotiate the divorce arrangements and crucially what our new relationship with Europe is going to be once we have left, when it comes to trade and the single market.
"What I think he has said reinforces the argument that I have been making that we are going to need transitional arrangements [around the negotiations]."
Mr Barnier said a short term agreement "could have some point" in helping move towards a final deal.
But Boris Johnson said 18 months is "ample time" for the UK to negotiate with the EU.
Speaking as he arrived at a NATO meeting of foreign ministers in Brussels, the Foreign Secretary said: "With a fair wind and everybody acting in a positive and compromising mood, as I'm sure they will, we can get a great deal for the UK and for the rest of Europe".
When in charge of regional policy, Mr Barnier said he worked on a programme supporting Northern Ireland and the Good Friday agreement.
When asked by The Irish Times whether he would dismiss the idea of a hard border being put in place post-Brexit, he would not commit either way.
"The UK decision to leave the EU will have consequences, in particular perhaps for what are the EU's external borders today," he said.
"All I can say at this moment in time is I am personally extremely aware of this particular topic. We will throughout these negotiations with the UK and of course with Ireland, do our utmost to uphold the success of the Good Friday Agreement and of course retain the dialogue there."
A former EU commissioner, Mr Barnier led the EU's banking reforms and was dubbed "the most dangerous man in Europe" by some in the financial services industry.
But after he championed capping bankers' bonuses, he won respect as a tough but even-handed negotiator.
Mr Barnier has refused to take part in any pre-negotiations before Article 50 is triggered, but he did meet Brexit Secretary David Davis for coffee last month.
Speaking in November in Brussels, he said: "Don't ask me to tell you what will be at the end of the road, we haven't begun to walk yet."

The meeting comes as the EU negotiator unveiled a draft Brexit agreement on Wednesday morning.
The document proposes a "common regulatory area" on the island of Ireland if solutions cannot be found for the post-Brexit border.
The Prime Minister Theresa May has rejected the proposal.
She said that it threatens the "constitutional integrity" of the United Kingdom.
Unionist politicians have strongly rejected the idea but the Taoiseach (Irish prime minister) Leo Varardkar said it was now up to proponents of Brexit to come up with solutions to ensure that there is no hard border between Northern Ireland and the Republic of Ireland after the UK leaves the EU.
The DUP leader Arlene Foster tweeted that the draft text was "constitutionally unacceptable and would be economically catastrophic for Northern Ireland".
The Ulster Unionist leader Robin Swan said the draft proposal was "a complete non-starter for Unionists".
He described the draft agreement as "nothing short of a move by the EU to annex Northern Ireland".
"No British Government could accept this.
"It demonstrates complete and utter contempt for Northern Ireland's constitutional position and also for the Belfast Agreement," he added.
The TUV leader Jim Allister said the draft treaty "seeks to subvert the integrity of the United Kingdom by demanding that Northern Ireland is hived off under EU jurisdiction into its customs union, which, of necessity then requires border checks between Northern Ireland and Great Britain".
However the SDLP Brexit spokesperson Claire Hanna said her party "welcomes the EU's cast iron commitment to protecting the Good Friday Agreement and preventing a border in Ireland".
"Despite some utterances on the airwaves from some, there is nothing surprising in this draft withdrawal agreement today - this is essentially what was agreed by the UK and the EU in December.
"The UK Government and the Brexiteers have a choice, they either go for alignment with the Customs Union and the Single Market to protect these islands - or they support the EU on the common regulatory area," she added.
She accused the British government and Brexiteers of debating Brexit "with zero regard for the impact on Ireland".
"And now," she said, "they want to conclude their debate, and make their exit by putting the Good Friday Agreement through the shedder.
"The Tory-DUP axis is satisfied to treat the welfare of the people of this island as collateral damage so long as they can achieve their 'little Englander' Brexit," she added.
She called on the Taoiseach Leo Varadkar to convene the British-Irish Intergovernmental Conference.
In reply to Ms McDonald, Taoiseach Leo Varardkar said that the UK government had made a commitment that there would be no border between the Republic and Northern Ireland.
"This is the last resort as Prime Minister May describes it, there are alternative solutions," he said.
He said his government and the UK government shared the preferred option of avoiding a hard border in Ireland as well as between the island of Ireland and Great Britain.
"I do not want a border between Letterkenny and Derry any more than I want a border between Larne and Stranraer."
He said that it was now up to "hard-line Brexiteers" and some politicians in Northern Ireland to come up with alternatives saying "just saying no and being angry isn't enough".
"It is up to them now to come up with alternative solutions... in a legal form that can be enforced."

The EU has rejected calls for an agreement to protect UK and EU expats' rights, if there is a no-deal Brexit.
Tory MP Alberto Costa quit his government job to table an amendment calling for the protections.
It was backed by the government in votes on Wednesday, with Mr Costa urging the PM to write to EU chiefs to demand an agreement on rights.
But the European Commission said it would "not negotiate mini deals" as it would imply negotiations had failed.
Theresa May's withdrawal deal includes pledges to protect the rights of UK citizens in EU states and EU citizens in the UK after Brexit.
But MPs have so far rejected Mrs May's deal  - raising the prospect of the UK leaving the EU without a deal on 29 March.
Mr Costa's amendment called for the PM to write to the President of the European Council, Donald Tusk, to seek to guarantee the rights of EU nationals even under a no-deal Brexit.
He had to resign from his unpaid government role as a parliamentary private secretary to Scotland Secretary David Mundell, due to the convention that MPs serving in government should not amend government motions.
The amendment gained support from 141 MPs from different parties, and was accepted by the government.  The amendment was approved unanimously by MPs, without a vote.
Speaking in the Commons , Mr Costa said he had "been a loyal Conservative member. I have never rebelled and have scarcely spoken out of turn".
But, he told MPs that EU citizens' rights "should have been dealt with at the outset of the United Kingdom's decision to leave the EU".
And he has accused the UK government of using citizens' rights as a "bargaining chip" in talks with Brussels.
Responding to Mr Costa's amendment, European Commission spokesperson, Mina Andreeva, said "the best way to protect the rights of these 4.5 million people concerned is through the withdrawal agreement.
"We will not negotiate mini deals, because negotiating such mini deals outside the withdrawal agreement would imply that the negotiations have failed.
"The Commission has consistently made clear that rights of EU citizens in the United Kingdom and UK nationals in the EU are our top priority, they should not pay the price for Brexit."
The Commission has urged EU member states to take a "generous approach" to UK citizens living abroad, she added.
Theresa May has said EU citizens in the UK will be able to stay even if there is no deal done on Brexit.
EU nationals with a right to permanent residence, which is granted after they have lived in the UK for five years, should not see their rights affected after Brexit.
But there is uncertainty about what no deal would mean for Britons living in France, Spain, Germany and elsewhere.
The priority for most will be to register as residents, but the rules - including deadlines for paperwork - vary from country to country.
Mrs May has promised MPs a meaningful vote on her deal by 12 March - just 17 days before the UK is set to leave the EU.
She has also committed to giving MPs a vote on delaying Brexit, if they reject both her deal and no-deal.

The government's bid to extract the UK from EU law in time for Brexit has passed its first parliamentary test.
MPs backed the EU Withdrawal Bill by 326 votes to 290 despite critics warning that it represented a "power grab" by ministers.
The bill, which will end the supremacy of EU law in the UK, now moves onto its next parliamentary stage.
Ministers sought to reassure MPs by considering calls for safeguards over their use of new powers.
Prime Minister Theresa May welcomed the Commons vote in the early hours of Tuesday morning, saying the bill offered "certainty and clarity" - but Labour described it as an "affront to parliamentary democracy".
Seven Labour MPs defied Jeremy Corbyn's order to oppose the bill - Ronnie Campbell, Frank Field, Kate Hoey, Kelvin Hopkins, John Mann, Dennis Skinner and Graham Stringer. No Conservatives voted against it.
Having cleared the second reading stage, the bill will now face more attempts to change it with MPs, including several senior Conservative backbenchers, publishing a proposed 157 amendments, covering 59 pages.
Previously referred to as the Great Repeal Bill, the EU Withdrawal Bill overturns the 1972 European Communities Act which took the UK into the then European Economic Community.
It will also convert all existing EU laws into UK law, to ensure there are no gaps in legislation on Brexit day.
Critics' concerns centre on ministers giving themselves the power to make changes to laws during this process without consulting MPs.
The government says it needs to be able to make minor technical changes to ensure a smooth transition, but fears were raised that ministers were getting sweeping powers to avoid parliamentary scrutiny.
More than 100 MPs had their say during the two-day second reading debate.
Labour, which denounced the "vague offers" of concessions, mostly voted against the bill.
Shadow Brexit secretary Sir Keir Starmer said the bill was a "naked power grab" by the government, adding that "this is a deeply disappointing result".
He said: "Labour will seek to amend and remove the worst aspects from the bill but the flaws are so fundamental it's hard to see how this could ever be made fit for purpose."
Lib Dem Brexit spokesman Tom Brake said MPs who backed the bill should feel "ashamed".
"This is a dark day for the mother of parliaments," he added.
Summing up the Commons debate, Justice Secretary David Lidington had said some criticism had been "exaggerated up to and beyond the point of hyperbole".
He said the bill would "enable us to have a coherent and functioning statute book" on the day the UK leaves the EU.
BBC political editor Laura Kuenssberg said Conservative MPs concerned about the legislation had already tabled a number of amendments to "remove the excesses of the bill" and to "make considerable improvements".
These include limiting the use of delegated powers, giving Parliament the "final say" on the EU withdrawal agreement and restoring the EU Charter of Fundamental Rights.
One MP told the BBC: "We hope MPs from all parties who share our concerns and aims to make the bill fit for the purpose of delivering a smooth Brexit will add their names."
SNP MPs, who also voted against the bill, said powers over devolved issues would be seized by Westminster as they were returned from Brussels.
But Mr Lidington denied this, predicting it would result in a "significant increase" in the powers exercised by the devolved administrations.
The bill will now receive line-by-line scrutiny in its committee stage.
MPs voted in favour of the government's proposed timetable for debating legislation - by 318 votes to 301 - guaranteeing 64 hours of debate over eight days.
But Mr Lidington said the government was "willing to consider" extending the allocated time.
The Bill's committee stage will take place when MPs return to parliament after their party conferences.

The European Commission says it has started to implement its preparations for a no-deal Brexit - in case the UK leaves the EU without a plan.
It has announced temporary measures to try to reduce the impact, but says it cannot counter all the problems it expects.
As PM Theresa May's proposed exit plan flounders in Parliament, both sides are preparing for what they see as the worst-case situation.
The UK has allocated £2bn ($2.5bn) in funding to government departments.
The European Commission's measures are designed to limit disruption in certain key areas, such as finance and transport, if Brexit goes ahead in March without a deal.
"These measures will not - and cannot - mitigate the overall impact of a 'no-deal' scenario," it said in a statement.
"This is an exercise in damage limitation," added commissioner Valdis Dombrovskis in a news conference, saying a contingency plan was necessary "given the continued uncertainty in the UK".
The commission's 14 measures cover legislation that will aim to ensure some continuity.
They address eight sectors, taking in issues such as transport and customs, data protection, animal health and plants, climate policy and key financial products.
Among other things, the measures would temporarily allow:
The commission has also urged its 27 remaining member states to take a "generous" approach to the residency rights of UK citizens in the EU following a no-deal Brexit, "provided that this approach is reciprocated by the UK".
The Commission says these measures should not compare with EU membership, or the transition period on offer in the Withdrawal Agreement - which the UK Parliament has yet to vote on.
Brussels says the arrangements will be strictly time-limited, and will be ended without any consultation with the UK.
And it warns that the following will occur from the date of a disorderly UK exit from the EU:
BBC Europe editor Katya Adler says Brussels will be keen to point out that these proposals are not in the UK's favour.
They are to protect EU member states from the more catastrophic aspects of Brexit if no deal is reached, our correspondent explains.
Visas will not be required for UK citizens to spend short periods in EU countries, the commission said.
For stays of over 90 days, a residence permit or a long-stay visa will be required.
Member states have been told to take all necessary legislative and administrative measures so that temporary residence documents can be issued by the withdrawal date.
UK citizens who have lived in an EU state for a period of more than five years must be granted, subject to certain conditions, long-term resident status, the commission said.
This demonstrates where the EU has a limited remit. The proposals on UK citizens living in EU countries rely on the governments concerned because it involves areas of national - not European - power.
However, a pressure group representing Britons living in the EU27 is far from happy:
A senior EU official said the only way of properly looking after citizens was via the withdrawal agreement agreed between the UK government and the EU.
By Adam Fleming, Brussels correspondent
The EU has been slightly more generous than expected in its planning for a no-deal Brexit.
Its proposal that British truckers can carry on trucking in the EU for nine months before they have to apply for scarce international permits will be welcomed by the industry.
Some of the measures will also be in place for longer than previously suggested. For example, the bare-bones aviation legislation will last until March 2020, not December 2019.
Some of the measures recognising the UK's financial regulations as equivalent to the EU's will continue for up to two years.
Brussels isn't doing this out of the goodness of its heart. This is the product of calculation of what is in its interests and which vulnerabilities need to be protected.
And the European Commission is clearly concerned about countries doing their own deals with the UK, hence a plea not to.
But the message from Brussels is clear: the deal that's on offer is way, way, way better than no deal at all.
The European Commission's initial guidance on the issue was published in November.
It committed to publishing its draft version by the end of 2018, allowing for eight weeks of consultation, as required by EU treaties.
The issue is heating up because Mrs May's proposed deal, which was agreed with the EU, has so far failed to gain enough support in the UK Parliament, which will vote on it next month.
The deadline for leaving is now 100 days away.
On Tuesday, the cabinet said it had decided to "ramp up" preparations for a no-deal Brexit.
The government has sent letters to 140,000 firms urging them to plan ahead, while 3,500 troops will be put on standby to maintain essential services.
It will also distribute 100-page information packs to businesses on Friday.
The UK is due to leave the EU on 29 March, two years after triggering an EU mechanism known as Article 50, which covers departure from the bloc.

The EU has said it is now up to MPs to decide the next steps for Brexit and it remains "committed" to agreeing a deal in time for the UK to leave this month.
Officials said they had offered fresh assurances on the issue of the Irish backstop ahead of Tuesday's second vote by MPs on Theresa May's deal.
It was "now for the Commons to take an important set of decisions", they said.
Labour and Tory MPs have told the PM she must honour her commitment to put her deal to the vote again on Tuesday.
Amid speculation the vote could be postponed or downgraded, No 10 confirmed it remained the plan to go ahead with another "meaningful vote", with the motion to be debated to be published later on Monday.
Downing Street said the PM's focus was "getting on with the work required to allow MPs to support the deal and to bring this stage of the process to an end".
The BBC's political editor Laura Kuenssberg said the prime minister was "likely" to head to Strasbourg later - where the European Parliament is based.
This was reiterated by Irish Foreign Minister Simon Coveney, who told a press conference he "understands" Mrs May is travelling to the city later.
But neither No 10 or the European Commission have confirmed this, with a spokesperson for the latter saying: "We keep talking and working."
The spokesperson did confirm, however, that the European Commission President Jean-Claude Juncker and Mrs May had spoken by phone on Monday.
The UK is due to leave the EU on 29 March but MPs rejected the withdrawal deal on offer in January and demanded major changes.
BBC Brussels reporter Adam Fleming said the mood was "bleak" in Brussels after the EU's chief Brexit negotiator, Michel Barnier, briefed EU ambassadors on the state of play earlier.
Adam Fleming said the member states were told that the UK had rejected the EU's proposed solutions on the backstop because "they wouldn't get the support of the Cabinet".
"There is a widely held view that the UK has not been negotiating in good faith over the last few days," he said, adding that at least one diplomat had mentioned planning for a "post-Theresa May government".
The government has been seeking changes to the Irish backstop, the safety net designed to maintain an open border on the island of Ireland, and only to be used as a last resort.
But the details of it were a sticking point for many MPs when they voted her deal down in January. They worry that - in its current form - the backstop may leave the UK tied to the EU indefinitely.
In a statement, the Commission said it had put forward proposals to try and reassure MPs the backstop "if used will apply temporarily".
A spokesman said the EU was willing to meet UK negotiators at any time.
He added: "We are committed to using our best endeavours to find a subsequent agreement that replaces the backstop... We are committed to ratifying this deal before 29 March."
Earlier, Mr Barnier said that talks about the UK's withdrawal from the bloc were now between the British government and MPs.
The BBC's political editor Laura Kuenssberg said the chances of Parliament approving Mrs May's deal appeared "very remote" at this stage.
She said it was still possible that the UK would come back with some new assurances from the EU over the backstop which could "get the numbers down" and limit the scale of any defeat.
Mark Francois, a member of the European Research Group of Brexit-backing Tory MPs, said unless "something amazing" materialised, the outcome of Tuesday's vote would be similar to that in January - when the government lost by a record 230 votes.
Former Labour cabinet minister Yvette Cooper said Mrs May "had given...her word" to MPs that this week's votes would happen.
Ms Cooper, who has spearheaded parliamentary efforts to rule out a no-deal exit, called for talks on the withdrawal deal and the UK's exit to be put on hold while the PM tried to build a consensus in Parliament and the country.
"The stakes are far too high to assume she has this under control," she said. "If she won't find a way forward, Parliament has a responsibility to do so instead."
There will be an urgent question from Labour in the Commons later, asking Mrs May for an update on the progress made in achieving legal changes to the withdrawal agreement and the timetable for its approval.
Shadow Brexit secretary Sir Keir Starmer said it was "imperative" that Mrs May responded, rather than sending a junior minister.
As things stand, the chances of Theresa May getting approval in the Commons tomorrow for her Brexit compromise, reversing a defeat of more than 200 votes, are very remote.
That said, it is quite possible to get those numbers down. Despite the fact the talks are stuttering with Brussels, it is still likely there will be some kind of piece of paper that emerges from the Berlaymont building - those edifices in Brussels where negotiators have been locked for the past few days.
There is likely to be some kind of reassurance on paper out of those talks, probably at some point later today.
The political point though is this: It is very unlikely - very unlikely - that it's going to be enough to get the kind of revision to the deal that could comfortably reverse the defeat for the prime minister.
That's why some MPs are starting to say, as they did last time, it is unwise for her to keep marching into gunfire to do again what no prime minister had done in recent memory - to go into a crucial vote all but knowing you are going to lose, and lose badly.
And that's why things are so risky this week.

Theresa May's bid to make her Brexit deal more acceptable to MPs has suffered a blow after EU leaders said it was "not open for renegotiation".
She wanted legal assurances on the Irish backstop and had warned the deal itself was "at risk" over the issue.
But European Commission president Jean-Claude Juncker said there could be clarifications but no renegotiation.
Labour says MPs must vote on the deal next week and it was "unacceptable" for it to be pushed back to January.
"This is becoming a farce," said Shadow Brexit Secretary Sir Keir Starmer.
"The prime minister pulled this important vote last week on the basis that she was going to get meaningful changes to her Brexit deal, She has obviously not."
On Thursday evening, Mr Juncker urged the UK to set out more clearly what it wants, adding that the European Commission will publish information on 19 December on its preparations, should the UK leave the EU without a deal in place.
"Our UK friends need to say what they want, instead of asking us to say what we want, and so we would like within a few weeks our UK friends to set out their expectations for us, because this debate is sometimes nebulous and imprecise and I would like clarifications," he said.
Pooled video footage from the summit on Friday showed Mrs May and Mr Juncker engaged in what appeared to be a tense exchange, following his comments.
The Democratic Unionist Party, on whom Theresa May relies for her Commons majority, said the EU's response was unsurprising and Mrs May must not "roll over as has happened previously".
"The EU are doing what they always do," said the party's leader Arlene Foster. "The key question is whether the prime minister will stand up to them."
But Cabinet minister David Lidington described the meeting as a "welcome first step" in showing that the EU was committed "to negotiate a trade deal with the UK speedily".
Mrs May travelled to Brussels to make a special plea to EU leaders after delaying Tuesday's Commons vote on the deal, in anticipation of a heavy defeat.
She then went on to win a confidence vote brought by her own MPs but vowed to listen to the concerns of the 37% of Tory MPs who voted against her and was hoping to address their concerns about the controversial "backstop" plan in the withdrawal agreement.
Critics say the backstop - aimed at preventing a hard border in Northern Ireland - would keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
Conservative MPs have demanded changes to make it clear that it could not last forever, and the UK could terminate the arrangement on its own.
If this meeting was meant to provide Theresa May with the beginnings of an escape route from her Brexit conundrum, the signs are nothing less than awful.
At one of her most vulnerable political moments, Number 10 was hopeful at least of an indication of a potential solution to the most intense of a long list of Brexit problems - the controversial so-called backstop, designed to guarantee there would be no hard Irish border.
But right now, that's simply not on offer.
EU leaders made it plain that their warnings - that their divorce deal with Britain was not up for negotiation - were real.
In comments released by Downing Street on Thursday, Mrs May urged EU leaders to help her "get this deal over the line" and said she firmly believed it could get through the Commons, saying: "There is a majority in my Parliament who want to leave with a deal so with the right assurances this deal can be passed. Indeed, it is the only deal capable of getting through my Parliament," she said.
Mrs May urged EU leaders to work with her to "change the perception" of the controversial backstop plan.
But European Council president Donald Tusk said the withdrawal agreement was "not open for renegotiation" although he stressed the backstop was "an insurance policy", saying it was the EU's "firm determination" to work "speedily" on alternative arrangements.
BBC Brussels reporter Adam Fleming said the fact that the EU said it would use its "best endeavours" to get a future trade deal that would get rid of the need for a backstop - even if the backstop came into force - was seen as important by British officials who said it meant the UK could go to an independent arbitration panel if they felt the EU was dragging its feet.
But he said Ireland had requested that the European Council conclusions be toughened up and a paragraph which suggested further work would be done to reassure the UK was removed because "there was no support" for it.
Downing Street has confirmed MPs will not now vote on Mrs May's deal before Christmas, and said the vote would happen "as soon as possible in January".
Conservative Brexiteer Mark Francois told the BBC: "It is as plain as a pikestaff that this will never get through the House of Commons... the prime minister, I'm afraid, is completely boxed in."
The Labour former PM Tony Blair told the BBC he believed a majority of MPs in the Commons would back another referendum on Brexit, if Parliament could not agree on another way forward:
"I think that will happen if it is clear that there is no majority for any one form of Brexit," he told Radio 4's Today.
"We have had 30 months of negotiation and let's be clear - we are in crisis mode on this."

The EU will only agree to a short delay to Brexit if MPs approve the current withdrawal agreement next week, Theresa May has been told.
EU Council President Donald Tusk said an extension, requested by the prime minister on Wednesday, was possible.
Mrs May has written to Mr Tusk requesting a Brexit delay to 30 June, saying she needed more time to get her deal agreed by MPs and passed into law.
The PM will be making a statement from Downing Street at 20:15 GMT.
Mr Tusk said he believed all 27 other EU members, who must sign off on the extension, would agree but it depended on a "positive" vote in the House of Commons.
The length of any extension was open for discussion, he told reporters in Brussels.
The UK is due to leave the EU next Friday, on 29 March.
While a delay until 30 June "had its merits", Mr Tusk also suggested there were "political and legal" questions about delaying Brexit beyond 23 May - when European elections will be held.
While the current withdrawal agreement could not be changed, he suggested additional legal assurances the EU gave Mrs May in Strasbourg last week could be formalised to help get the backing of MPs.
Mr Tusk spoke to Mrs May before his statement.
Meanwhile, an emergency debate took place in Parliament on Wednesday afternoon, with Labour pressing for further detail about the PM's intentions and demanding that any delay is long enough to allow MPs to "break the impasse and find a way forward".
The prime minister is meeting MPs from opposition parties to discuss her letter.
But ahead of the meeting, the SNP's Westminster leader Ian Blackford, Lib Dem leader Vince Cable MP, Plaid Cymru's Westminster leader Liz Saville Roberts and the Green Party MP Caroline Lucas released a joint statement, calling for a longer extension and for Parliament to sit continuously "until it can reach a decision".
At a highly charged Prime Minister's Questions earlier, Mrs May said MPs had "indulged themselves on Europe for too long" and voters "deserved better".
She said she had rejected calls for a longer delay to Brexit because she wanted to avoid the UK taking part in European elections in May, which she said would be "unacceptable" three years after voting to leave the EU.
"It would be a failure to deliver on the referendum decision this House said it would deliver," she told the Commons.
But she added: "As prime minister I could not consider a further delay beyond 30 June."
This was seen by some as an indication that Mrs May would resign rather than seek a further delay.
Labour leader Jeremy Corbyn accused her of leading the UK into "crisis, chaos and division".
"We are still legally due to leave the European Union in nine days' time," he told Mrs May at PMQs.
"Months of running down the clock and a concerted campaign of blackmail, bullying and bribery has failed to convince the House or the country that her deal is anything but a damaging national failure and should be rejected."
He urged the prime minister to meet him later on Wednesday to discuss a "compromise to get through this crisis", a plea ignored by the PM.
The Labour leader will travel to Brussels on Thursday to meet the EU's chief negotiator Michel Barnier. He is also expected to hold talks with several EU 27 leaders.
In her letter to Mr Tusk, the prime minister says she had wanted to hold a Commons vote on her withdrawal agreement this week but had been prevented from doing so by Commons Speaker John Bercow.
But she adds: "It remains my intention to bring the deal back to the House."
If the motion is passed, more time will be needed for Parliament to ratify the deal, she says. There is no mention in the letter of a longer delay, as some had been expecting.
Mrs May, who has been meeting groups of cabinet ministers on Wednesday afternoon, told MPs that an extension beyond 30 June would not "take no-deal off the table" if an agreement had still not been reached.
She has repeatedly insisted the UK would leave the EU on 29 March and she told MPs it had always been her preferred option, but with a withdrawal deal to ensure it was an "orderly" exit.
But she was forced to seek a delay after MPs twice rejected the withdrawal deal she has agreed with the EU by massive margins and voted to reject a no-deal Brexit.
Her plan to hold a third vote on the deal this week were blocked by the Speaker, John Bercow, who said it would break longstanding conventions preventing MPs from being repeatedly asked the same question.
MPs from across the political spectrum lined up to attack Mrs May over her announcement at prime minister's questions.
The SNP's Pete Wishart, who wants another EU referendum, accused her of "caving in to Brexiteers".
He urged her to "develop a backbone and stand up to those who would take this nation to disaster".
Yvette Cooper - one of a string of Labour MPs to call for "indicative votes" on different alternatives to Mrs May's Brexit deal - accused the PM of harming the national interest, adding: "I beg this prime minister to think again."
Mrs May said Commons votes had already been held on different Brexit options and the "one positive thing" that had been agreed was to rule out a no-deal departure on 29 March.
Conservative Brexiteer Peter Bone warned Mrs May she will be "betraying" the public if she continues to seek to delay Brexit.
"If you continue to apply for an extension to Article 50 you will be betraying the British people. If you don't, you will be honouring their instruction.
"Prime minister, it is entirely down to you. History will judge you at this moment. Prime minister, which is it to be?"
Mrs May replied: "I am saying that I think we should look again at being able to leave with a negotiated deal, but in order to do that we need time for this Parliament to ratify a deal, and in order to do that we need an extension until 30 June."

The EU has cast doubt on claims its chief negotiator described the government's Brexit plan as "dead in the water".
Labour MP Stephen Kinnock attributed the remarks - which he said were in French - to Michel Barnier after a meeting in Brussels.
EU Commission spokesman Margaritis Schinas urged journalists to wait for a transcript to be published.
The Chequers plan contains some "positive elements", he added.
The UK is leaving the EU on 29 March 2019, and negotiations are taking place between the two sides.
Brexit Secretary Dominic Raab has been meeting Mr Barnier for more negotiations as the two sides seek to reach an agreement before a summit in October.
In July the government set out how it wants to trade with the EU - and avoid new border checks in Northern Ireland - after a summit at Chequers, the prime minister's country residence.
But the plans have been criticised by Brexiteers and the government faces a battle to persuade Parliament to approve them, even if the EU agrees.
On Monday Mr Barnier met members of the UK's Brexit Committee, which contains both pro and anti-EU MPs.
After the meeting, Tory Brexiteer Jacob Rees-Mogg said Mr Barnier had agreed with him that the Chequers plan was "complete rubbish" and on Wednesday Mr Kinnock told Mr Raab the EU negotiator said the package was "dead in the water".
Challenged by Brexit Secretary Dominic Raab as to the exact wording used by Mr Barnier, Mr Kinnock switched to French, saying he had said: "Les propositions sont mortes" (the proposals are dead).
The committee is expected to publish a transcript of the meeting in the coming days.
Asked about the comments, Mr Schinas said Mr Barnier had been "very clear" in expressing the EU's position.
"I don't think that people present in the room and beyond the room have any doubt on what we said on Chequers - we identified where there were positive elements and we discussed also the possibility for further discussions to address issues that still create problems," he said.
Mr Schinas said the private meeting provided "the perfect recipe for everybody coming out of there and saying what one or the other understood Michel saying".
He added: "Let's wait for the transcript and then let's check the sort of things that are reported of what Michel Barnier said against what he actually really said."
Meanwhile, a paper with details of planning for a no-deal Brexit has been caught on camera in Whitehall.
It reveals government departments are expected to make cuts in other spending to prepare for the possibility of no deal being reached.
Codenamed Operation Yellowhammer, it appears to be run by the Civil Contingencies Secretariat, which is responsible for emergency planning.
The government says a deal with the EU is the most likely outcome.
But it is also making contingency plans for leaving without one, and recently published a series of papers detailing preparations and offering advice.
The document, captured by photographer Steve Back, was being carried by Treasury Minister John Glen as he left the Cabinet Office.
Downing Street said civil contingencies planning happened routinely in advance of significant events, and that the yellowhammer name had been generated at random.
Asked about the document during a visit to Strathclyde University, Chancellor Philip Hammond - who has previously warned about the economic impact of no deal being reached - said departments had the funding needed to plan for such a scenario.
He added: "In no deal circumstances we would have to refocus government priorities so that government was concentrated on the circumstances that we found ourselves in.
"Let me reiterate again that is not the outcome we are expecting and it's not the outcome we're seeking."
Analysis by BBC political editor Laura Kuenssberg
As an intellectual exercise, none of this brief excerpt is completely surprising.
But it demonstrates the political reality that in government there is concern about what might happen to the financial system, what might happen to transport, air and rail, but still a message to government departments they should try to find cash to spend on 'no deal' preparations from existing budgets, rather than the big cash pot that's been allocated so far.
Read Laura's blog on the leaked paper

A summit of EU member states to discuss Brexit is be held on 29 April, a month after the UK triggers Article 50.
The meeting will be used to agree the guidelines for the EU's negotiating team headed by Michel Barnier.
European Council president Donald Tusk said the priority would be giving "clarity" to EU residents, business and member states about the talks ahead.
Prime Minister Theresa May will officially notify the EU of the UK's intention to leave on 29 March.
She told her cabinet on Tuesday that triggering Article 50 would be an "historic event" and the start of a "bold new chapter... as a prosperous open and global nation".
The letter which she will send to Mr Tusk, will be "one of the most important documents in the country's recent history" and it will set the tone for a new relationship with the EU, she told her senior team of ministers.
April's meeting, which the UK will not attend, will be held just days after the first round of voting in the French presidential election.
Mrs May has said she hopes that talks will get under way as soon as possible although it is thought that they will not begin in earnest until after April's meeting and the final outcome of the French contest is known on 7 May.
In a statement, Mr Tusk said he regretted but respected the UK's decision to leave the EU and wanted the "process of divorce" to be as "painless as possible" for the European Union.
A majority of Leave and Remain voters want Theresa May to secure restrictions on immigration from EU countries in Brexit talks, new research suggests.
The survey - by pollster Professor John Curtice - suggested 82% of Leave voters want EU migrants to be treated the same as those from outside the EU.
More than half of the Remain voters surveyed - 58% - agreed.
The National Centre for Social Research Survey of 2,322 people was carried out in February and early March.
It suggested 88% of those who voted to come out of the EU in last June's referendum wanted to maintain free trade with the EU, with 91% of Remain supporters backing that policy.
Other findings include:
"Our main priority for the negotiations must be to create as much certainty and clarity as possible for all citizens, companies and member states that will be negatively affected by Brexit, as well as our important partners and friends around the world like Japan," he said.
British ministers have said the EU's draft guidelines, which are expected to be published within 48 hours of Article 50 being triggered, will be a "very important" moment of "choreography" in the Brexit process.
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Once talks start, they are expected to focus initially on the rights of EU nationals living in the UK and Britons living on the continent as well as what, if any, payments the UK will have to make to the EU's budget to cover current and future liabilities.
Mr Barnier, a former European Commission official, has called for talks to be completed by October 2018 to give time for any agreement to be ratified before the UK leaves, expected on March 29 2019 under the two-year Article 50 process.
Within days of April's meeting, he is expected to make recommendations to EU leaders on how the talks should be structured to achieve this.
Investment bank Goldman Sachs is to move some jobs away from London and expand its European presence, a senior executive said on Tuesday.
The US bank's European chief executive, Richard Gnodde, said it would begin the process before the UK leaves the European Union but said the numbers involved were "in the hundreds of people as opposed to anything greater than that".
Another senior executive at the bank said last week that London would remain a significant financial hub after Brexit.

The EU says much work still needs to be done on Brexit, despite agreeing a draft withdrawal document with the UK.
"We still have a long road ahead of us on both sides," chief negotiator Michel Barnier said.
The EU has set out a series of meetings leading to one on 25 November where it plans to approve the Brexit agreement.
UK Prime Minister Theresa May has won the backing of her cabinet but faces a tough task getting the agreement approved by Parliament.
A sign of that came on Thursday morning when Mr Barnier's UK counterpart, Brexit Secretary Dominic Raab, resigned saying he could not "in good conscience" support the agreement. He was one of four ministers to quit.
Mrs May later defended the deal in the House of Commons, telling MPs it delivered on the Brexit referendum and provided for an orderly withdrawal.
Mr Barnier was speaking on Thursday morning alongside EU Council head Donald Tusk as the chief negotiator formally handed over the 585-page draft withdrawal agreement.
Mr Barnier said the agreement was fair and balanced, took into account the UK's needs and laid the ground for an "ambitious new partnership".
Mr Tusk praised Mr Barnier's work and said the agreement had "secured the interests of the 27 member states and EU as a whole".
He laid out the timetable for the days ahead.
Mr Tusk said: "Since the very beginning, we have had no doubt that Brexit is a lose-lose situation, and that our negotiations are only about damage control."
Addressing the UK, he added: "As much as I am sad to see you leave, I will do everything to make this farewell the least painful possible, for you and for us."
Mr Barnier later took the document to the European Parliament. Its president, Antonio Tajani, said MEPs would vote on the deal in early 2019.
If the agreement is approved by both sides, a 21-month transition period will kick in, during which a trade deal and the thorny issue of how to ensure there is no physical border between Northern Ireland - part of the UK - and the Republic of Ireland will need to be worked out.
A smooth border-free exchange underpins the peace deal that ended the Northern Ireland conflict.
The draft withdrawal agreement covers so-called "divorce" issues as the UK prepares to leave the EU. It includes a "financial settlement" from the UK, thought to be about £39bn (€45bn; $50bn).
Speaking at a press briefing in Brussels on Wednesday, Mr Barnier addressed one of the major concerns of the divorce, the Irish "hard border" issue.
He said that to avoid the need for physical checks on goods or infrastructure at the border between Northern Ireland and the Republic of Ireland, the EU would work with the UK to agree a trade deal. However if talks fail, the so-called "backstop" measure would be used.
Both sides have resolved to ensure the backstop is not necessary by coming up with alternative arrangements.
"If we are not ready by 2020, we can extend the provision so we have more time, and if we are still not there with the future agreement after this, the backstop agreement would kick in," he said.
"There will be a UK-wide single customs territory which Northern Ireland will remain in, and Northern Ireland will remain aligned to the rules of a single market essential for avoiding a border including on agriculture policy."
The draft withdrawal agreement states that the transition period may be extended by mutual consent.
Mr Barnier said that any extension would by a one-off, "by a limited period and by joint agreement".
During the transition, the UK will be out of the EU. It will have no voting rights but will continue to abide by the majority of its rules.
There are also special protocols in place for Gibraltar and Cyprus to enable people there "to continue to live as they do today", Mr Barnier added.
Spain has longstanding claims to the British Overseas Territory of Gibraltar and the deal sets out bilateral co-operation on customs, policing, trade, taxation and citizens' rights.
The UK has sovereign military bases in Cyprus. EU law will continue to apply at the bases, with the deal securing the rights of the 11,000 Cypriot civilians working there.
Analysis by BBC Europe editor, Katya Adler
The EU knows there is a very real possibility the Brexit deal could be voted down by the UK Parliament in a few weeks' time.
I put the question to Michel Barnier on Wednesday night at his press conference - but, skilled politician that he is, he refused to engage.
Brussels is very keen indeed not to give the impression that the EU might change or come up with a "better" Brexit deal text if this one ends up being rejected in the House of Commons.
Mr Barnier quoted Theresa May as saying that this is a deal in the UK's interest.
German Chancellor Angela Merkel on Thursday welcomed the draft agreement, saying: "I am very happy that, after lengthy and not always easy negotiations, a proposal could be reached."
The European Parliament's Brexit chief Guy Verhofstadt said the deal had been hammered out after two years of "intense negotiations" and he hoped UK MPs would accept that "there is not a lot of room [for] manoeuvre to say, 'OK, let's start again'".
French Finance Minister Bruno Le Maire said the deal was "good news for the French economy" but also issued caution, saying the UK must be made to respect all EU rules.
Finland's Prime Minister Juha Sipila tweeted to say that while Wednesday's developments were important, "decisions on both sides are still needed for a final agreement".
Austrian Chancellor Sebastian Kurz said he was "very pleased", adding: "The result is a good one."

European Council President Donald Tusk is proposing to offer the UK a 12-month "flexible" extension to its Brexit date, according to a senior EU source.
His plan, which would need to be agreed by EU leaders at a summit next week, would allow the UK to leave sooner if Parliament ratifies a deal.
The UK's Conservatives and Labour Party are set to continue Brexit talks later.
Theresa May has written to Mr Tusk with the UK's request for a further delay to Brexit until 30 June.
The UK is due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by MPs.
Downing Street said "technical" talks between Labour and the Conservatives on Thursday had been "productive" and would continue on Friday.
Attorney General Geoffrey Cox has told the BBC that if they fail, the delay is "likely to be a long one".
Prime Minister Theresa May has said a further postponement to the Brexit date is needed if the UK is to avoid leaving the EU without a deal, a scenario both EU leaders and many British MPs believe would create problems for businesses and cause difficulties at ports.
On Wednesday, MPs voted - by a majority of one - in favour of a backbench bill which would force Mrs May to ask the EU for a further extension.
However, the PM wants to keep any delay as short as possible.
To do that, she and Labour leader Jeremy Corbyn would need to agree a proposal for MPs to vote on before 10 April, when EU leaders are expected to consider any extension request at an emergency summit.
If they cannot, Mrs May has said a number of options would be put to MPs "to determine which course to pursue".
Mr Cox told the BBC's Political Thinking podcast that particular scenario would involve accepting whatever postponement the EU offered, which was likely to be "longer than just a few weeks or months".
But Conservative Brexiteer Sir Bernard Jenkin said the EU was "toying" with the UK and the PM was under no obligation to accept the terms of any extension, even if mandated to by MPs.
"The government just wants cover," he told BBC Radio 4's Today. "They want an excuse to do what they are going to do anyway, which is to take us into some kind of extension. The British people don't want that."
But he said an extension of a year or so would be better than leaving on the terms agreed by the PM, accusing her of being "pretty dishonest" about her willingness to countenance a no-deal exit.
Europe's leaders have been split over whether, and how, to grant any extension.
However, BBC Europe editor Katya Adler has been told by a senior EU official that Mr Tusk "believes he's come up with an answer", after several hours of meetings in preparation for the summit.
But his proposal would have to be agreed unanimously by EU leaders next week. The prime minister wrote to Mr Tusk to request the extension ahead of Wednesday's meeting.
You could almost hear the sound of collective eye-rolling across 27 European capitals after Theresa May requested a Brexit extension-time (till 30th June) that Brussels has already repeatedly rejected.
Most EU leaders are leaning toward a longer Brexit delay to avoid being constantly approached by the PM for a rolling series of short extensions... with the threat of a no-deal Brexit always just around the corner.
Donald Tusk, the president of the European Council, believes he has hit on a compromise solution: his "flextension", which would last a year with the UK able to walk away from it as soon as Parliament ratifies the Brexit deal.
But EU leaders are not yet singing from the same hymn sheet on this. Expect closed-door political fireworks, although it's unclear whether it'll be a modest display or an all-out extravaganza - at their emergency Brexit summit next week. Under EU law, they have to hammer out a unanimous position.
The EU has previously said that the UK must decide by 12 April whether it will stand candidates in May's European Parliamentary elections, or else the option of a long extension to Brexit would become impossible.
Talks between Conservative ministers and Labour lasted nearly five hours on Thursday.
Mr Corbyn has written to his MPs saying discussions included customs arrangements, single market alignment, internal security, the need for legal underpinning to any agreements and a "confirmatory" vote.
The main item of business in the last frantic 24 hours has been the cross-party talks between the Conservatives and the Labour Party.
From both sides, it sounds like they are serious and genuine, and negotiators got into the guts of both their positions and technical details on Thursday.
Remember, behind the scenes there isn't as much difference between the two sides' versions of Brexit as the hue and cry of Parliament implies.
But the political, not the policy, distance between the two is plainly enormous.
Shadow Treasury minister Clive Lewis told the BBC the party would not be talking to the government if a "confirmatory referendum" was not an option.
But 25 Labour MPs - including a number representing Leave-voting seats - have written to Mr Corbyn, saying another referendum should not be included in any compromise Brexit deal.
Asked whether another referendum on any final deal was a credible option, Mr Cox said: "A good deal of persuasion might be needed to satisfy the government that a second referendum would be appropriate. But of course we will consider any suggestion that's made."
If the talks fail, the government faces an additional obstacle in the form of a backbench bill which would force the PM to seek a new delay.
Passed by MPs by one vote on Wednesday, the bill is being scrutinised by the House of Lords, who will next consider the draft legislation on Monday.
Ministers have argued it could increase "the risk of an accidental no-deal" in the event the EU agreed to an extension but argued for a different date than one specified by MPs.
That would mean Mrs May having to bring the issue back to the Commons on 11 April, when European leaders would have returned home, the prime minister's spokesman said.
After a meeting with Irish Prime Minister Leo Varadkar in Dublin, German Chancellor Angela Merkel said her country still hoped for an "orderly Brexit".
"We will do everything in order to prevent... Britain crashing out of the European Union," she said.
"But we have to do this together with Britain and with their position that they will present to us."

Jeremy Corbyn's letter setting out his party's demands for supporting a Brexit deal has been welcomed by the European Parliament's Brexit co-ordinator.
Guy Verhofstadt said "the broadest possible majority" was needed for a Brexit deal in the UK.
An EU source said European Council President Donald Tusk said the letter was a "promising way" out of the impasse, in talks with the PM.
But Mr Corbyn's stance has upset Labour supporters of another referendum.
MP Owen Smith has said he and "lots of other people" were considering their future in the party as a result.
The UK is due to leave the EU on 29 March when the two-year limit on withdrawal negotiations under the Article 50 process expires.
But Prime Minister Theresa May is struggling to get the withdrawal deal she has negotiated with the EU through Parliament - MPs rejected it by a historic margin last month.
Mr Corbyn wrote to her on Wednesday spelling out his party's five demands for supporting a deal. These included a "permanent and comprehensive UK-wide customs union" aligned with the EU's customs rules, but with an agreement "that includes a UK say on future EU trade deals".
The letter does not mention previous demands that any deal must deliver the "exact same benefits" that membership of the single market and customs union currently does - effectively scrapping the party's "six tests" that had been its Brexit policy.
Mrs May has been in Brussels holding talks with Mr Tusk, Mr Verhofstadt, European Parliament President Antonio Tajani and European Commission President Jean-Claude Juncker.
Mr Verhofstadt told a press conference: "We can't have an agreement with uncertainty in the UK based on majorities of six, seven, eight or nine votes in the House of Commons.
"A cross-party co-operation is the way forward and I think I can say that we welcome also the letter that Jeremy Corbyn has written today to Mrs May to offer such a cross-party exit.
"It's important now that this leads to a position in the UK that has the broadest possible majority, so that we can conclude these negotiations."
However, it was criticised by Labour members of the People's Vote campaign for another EU referendum, who said Mr Corbyn had gone back on a commitment to back a public vote, if he cannot force a general election.
Mr Smith, who challenged Mr Corbyn for the Labour leadership in 2016, told BBC Radio 5 Live: "At the moment, I may be asked by the Labour Party to row in behind a policy decision that they know, and the government knows, is going to make the people I represent poorer and - more fundamentally actually - is at odds with the internationalist, social democratic values I believe in."
Another pro-EU Labour MP, Chuka Umunna, said: "This is not opposition, it is the facilitation of a deal which will make this country poorer."
But Labour's Stephen Kinnock, who backs the "Norway Plus" model of a close economic partnership with the EU, welcomed Mr Corbyn's letter, tweeting: "This can break the deadlock."
And the Conservative former cabinet minister Sir Oliver Letwin, who also favours a Norway-style agreement, said it could be the basis of a cross-party deal.
Labour shadow Brexit secretary Sir Keir Starmer told the BBC: "What this letter does is to set out in clear terms that the prime minister needs to abandon her Brexit red lines.
"It does not rule out the option of a second referendum - a public vote - and Jeremy Corbyn will be writing to members today to remind them about that."
A senior No 10 source said the government was "looking at those proposals but there are obviously very considerable points of difference that exist between us.
"The PM continues to believe an independent trade policy is one of the key advantages of Brexit."

There is "a lot of uncertainty" about the UK's capacity to patrol fishing waters after a no-deal Brexit, a government memo mistakenly emailed to the BBC has revealed.
The memo, from the Department for the Environment, Food and Rural Affairs, says there are just 12 ships "to monitor a space three times the size of the surface area of the UK".
Meanwhile Michael Gove has said there will be a government support fund to help British businesses in the event of a no-deal Brexit.
The UK is due to leave the EU on 31 October. A "divorce" deal - which sets out how the UK leaves - has not been agreed and Prime Minister Boris Johnson has pledged to leave whether one is reached or not.
In the event of leaving without a deal, the UK would become an independent coastal state and leave the Common Fisheries Policy, which states the EU's shared rules about how much fish countries can catch and where.
But ministers said they are confident security will be enforced after Brexit.
Defra's internal email mentioned a number of media stories, including one being worked on by a freelance journalist for the Independent.
According to the memo, the story planned to look at the preparation being made to deter EU fishermen from UK waters in the case of a no-deal Brexit, and also whether the UK will enforce the exclusion of foreign vessels.
The note reads: "While our public position on this wider issue is already clear and widely communicated, in that post-Brexit we will be an independent coastal state with control of our waters, both policy and MoD have indicated we are not on an overly strong footing to get ahead of the potential claims that could arise from this story.
"At this stage, there is a lot of uncertainty about the sufficiency of enforcement in a no-deal because we have 12 vessels that need to monitor a space three times the size of the surface area of the UK."
Admiral Lord West, a Labour peer and former First Sea Lord, said the email appeared to show the UK has "insufficient assets to patrol and look after our exclusive economic zone for fisheries, and also our territorial seas".
"This will be thrown into stark relief if we should cease to have an agreement with the EU on fisheries."
He added: "This is something a number of us have been saying for some time now, but it has always been denied by Defra and the government."
However, Barrie Deas, the CEO of the National Federation of Fisherman's Organisations (NFFO), said any EU vessel would be "foolish" to fish in UK waters - even without a deal in place.
He told BBC Radio 4's Today programme: "Under international law, the UK would automatically become an independent coastal state with the rights and responsibilities of that status and there is an obligation under the UN Law of the Sea for countries that share stocks to co-operate.
"So I think there will be a fisheries agreement post-Brexit between the UK and the EU, but on a different basis from the Common Fisheries Policy."
A government spokesperson confirmed an internal email concerned with the "veracity and details of media enquiries" had been "inadvertently sent outside of Defra".
They said: "Britain is leaving the EU on 31 October with or without a deal.
"We are confident that we will have the ships and the expertise we need to properly enforce security in UK waters."
Mr Gove, the cabinet minister in charge of preparations for a possible no-deal Brexit, spoke openly for the first time about a government support fund for British businesses during a visit to Northern Ireland on Friday.
The support package, known as Operation Kingfisher, will help companies deal with any "bumps in the road" that might occur as a result of a no-deal Brexit.
BBC political correspondent Jessica Parker said the plans predate Boris Johnson's premiership but few details have so far been revealed - including how much money will be made available and where the cash would come from.
According to the Times, the government has compiled a list of companies it believes could be most exposed financially if the UK leaves the EU without a deal and may need of help. It is said to include a number of firms in the construction and manufacturing sectors.

Brexit negotiations with the EU are heading for a "no deal" scenario, Labour's Emily Thornberry has warned.
Shadow foreign secretary Ms Thornberry said the PM's failure to control her party was causing "intransigence" on the UK side, which was a "serious threat to Britain" and its interests.
But International Trade Secretary Liam Fox said a failure to agree a deal was "not exactly a nightmare scenario".
The UK was preparing "mitigation" measures for such an outcome, he said.
Meanwhile, the Spanish foreign minister said the lives of UK expats in Spain would not be "disrupted" - even if no Brexit deal is agreed.
Theresa May will update MPs on Monday on the progress made at last week's Brussels summit, where EU leaders agreed to begin scoping work on future trade talks while asking for more concessions from the UK on the opening phase of negotiations.
These talks, covering the UK's "divorce bill", the rights of expats after Brexit and the border in Northern Ireland, have failed to reach agreement so far - leading to a focus on what happens if nothing is put in place by the time the UK leaves the European Union in March 2019.
Speaking on the BBC's Andrew Marr Show, Ms Thornberry said: "I think what we may be seeing is the Europeans trying to make it clear that it is not their fault that there are these difficulties - the intransigence does not come from their side, it comes from Theresa May's side.
"And in the end I think the reality is the intransigence is on Theresa May's side, because she doesn't have the strength or the authority to be able to control her backbenchers, let alone her cabinet. And I think we are heading for no deal, and I think that that is a serious threat to Britain and it is not in Britain's interests for that to happen.
"We will stop that."
Labour is seeking to work with Tory rebels to amend a key plank of Brexit legislation - the EU Withdrawal Bill - so that Parliament has the power to reject whatever the outcome of the negotiations turns out to be.
Following last week's summit, European Council President Donald Tusk said that although not enough progress had been made to begin trade talks, reports of deadlock may have been exaggerated.
French President Emmanuel Macron said there was still much work to be done on the financial commitment before trade talks can begin, adding: "We are not halfway there."
Speaking on ITV's Peston on Sunday, Mr Fox said a final figure for the UK's financial settlement with the EU cannot come "until we know what the final package looks like", later in the negotiation process.
He also dismissed President Macron's suggestion that "secondary players" in the UK were "bluffing" about the possibility of a no deal outcome, saying this was "completely wrong".
Mr Fox, who is responsible for striking global trade deals after Brexit, said he would prefer a "comprehensive" arrangement to be agreed - but was "not scared" of what would happen if this was not possible.
And he said trade talks would only be complicated if the "European elite" tried to "punish Britain for having the audacity to use our legal rights to leave the European Union".
He said he hoped "economic sense" would prevail, as opposed to the "near-theological" pursuit of closer EU integration.
When she addresses MPs on Monday, Mrs May is expected to reaffirm her commitment to EU nationals living in the UK, saying she will "put people first" in the "deeply technical" talks.
Speaking on the Marr show, Spanish Foreign Minister Alfonso Dastis said expats would be allowed to continue living in Spain even if no Brexit deal was reached.
"I do hope that there will be a deal," he said.
"If there is no deal we will make sure that the lives of ordinary people who are in Spain, the UK people, is not disrupted.
"As you know, the relationship between the UK and Spain is a very close one in terms of economic relations and also social exchanges.
"Over 17 million Brits come to Spain every year and many of them live here or retire here, and we want to keep it that way as much as possible."

Members of the European Parliament have overwhelmingly backed the terms of the UK's departure from the EU.
MEPs ratified the Brexit Withdrawal Agreement by 621 votes to 49 following an emotional debate in Brussels.
After the vote, MEPs marked the UK's exit by singing Auld Lang Syne.
Several British MEPs said they hoped the UK would return one day although Eurosceptics, including the Brexit Party's Nigel Farage, used their final speeches to tear into the EU.
The UK is due to leave the bloc at 23:00 GMT on Friday.
Ratification of the withdrawal agreement, agreed by the UK and EU in October, was not in doubt after it easily cleared its committee stage last week.
Signing the letter confirming the EU's consent, the Parliament's president, David Sassoli, said the two sides must heed the words of the late Labour MP Jo Cox when approaching their future relationship and recognise "there is more that unites us than divides us."
"You are leaving the EU but you will always be part of Europe…It is very hard to say goodbye. That is why, like my colleagues, I will say arrivederci."
Wednesday's session saw those on either side of the Brexit debate, including the UK's 73 MEPs, celebrate or lament the end of British EU membership.
Some MEPs marked the occasion with songs - others wore "always united" scarves.
The Parliament's Brexit spokesman, Guy Verhofstadt, said it was "sad to see a country leaving that has twice given its blood to liberate Europe".
He added that British MEPs had brought "wit, charm, and intelligence" as well as "stubbornness", and would be missed.
President of the European Commission Ursula von der Leyen said ratification of the withdrawal deal was "only a first step" towards a new partnership between the EU and the UK.
The two should "join forces" in areas such as climate change, she said, and seek a close partnership following the UK's exit on Friday.
"We will always love you and we will not be far," she told the UK in closing.
The EU's Brexit negotiator Michel Barnier also wished the UK well, saying the bloc would approach talks on the future relationship with "patience" and "objectivity" while defending its members' interests.
On the other side, though, Conservative MEP and prominent Eurosceptic Daniel Hannan said opinion in Britain turned against the bloc when it became clear "the aspiration was to have the EU as a quasi-state".
"If at any stage Britain had been able to have a trade-only relationship that would have been enough," he went on, but added: "You are losing a bad tenant and gaining a good neighbour."
Mr Farage - who has been campaigning for the UK's exit since before he was first elected to the Brussels Parliament in 1999 - used his final speech to excoriate the EU.
"I want Brexit to start a debate right across Europe - what do we want from Europe?" he said, arguing that "trade, friendship, co-operation and reciprocity" between nations could be achieved without "all of these institutions and all of this power".
He and his fellow Brexit Party MEPs waved Union flags before walking out of the chamber en masse.
A tearful Molly Scott Cato was applauded and hugged by her colleagues after she spoke of her "grief and regret" at Brexit and the hope she would return to the European Parliament "one day".
"While now is not the time to campaign to rejoin the EU, we must keep the dream alive," the Green Party MEP said.
Belgian MEP Philippe Lamberts said the EU must learn lessons from the UK's decision to leave.
He said the bloc had to "regain the hearts and minds of European citizens" by focusing on what it could do for the many, not the few.
Earlier, the S&D coalition, which houses Labour's 10 MEPs, displayed a sign aimed at departing British members, which read: "It's not goodbye, it's au revoir."
On Tuesday evening, several MEPs in the Green group also held a ceremony to mark the UK's departure.
While Brexit Party MEPs spoke of their joy and relief at leaving, others shared messages of sadness on social media as they prepared to vote for the last time.
The Green Party's Alexandra Phillips tweeted: "I'm devastated to be leaving the best job in the world. I get to make real change every day while being surrounded by 27 different languages and cultures."
Liberal Democrats shared pictures of gifts from the pro-European Renew Europe group.
After the UK leaves, there will be an 11-month transition period in which the two sides hope to negotiate their future economic relationship.
Trade talks are expected to begin in earnest in early March. The European Parliament will also get a say in ratifying any future trade deal.
The UK has insisted talks should not extend beyond 31 December 2020 when a transition period - which will see the UK follow EU rules - comes to an end.
President Sassoli told CNN on Tuesday that the timetable for a deal was tight.
He said the UK's exit would be "painful" for the bloc but building a new partnership based upon friendly co-operation and mutual interests was now essential.

Eurostar trains and electricity supplies in Northern Ireland face possible disruption if the UK exits the EU without a deal, the government says.
The latest batch of contingency papers for a no-deal Brexit warn rail services could be suspended without specific agreements with France and Belgium.
The Single Electricity Market on the island of Ireland may cease to operate, hitting consumers on both sides.
Brexit Secretary Dominic Raab said the UK was prepared for all eventualities.
Ministers have insisted they are striving for a negotiated agreement ahead of the UK's exit on 29 March 2019.
But they are continuing to provide information to the public and businesses about the consequences if this does not happen.
The latest tranche of documents, the fourth to be published so far, state that in the event of a no-deal exit, some train operators will have to apply for new licences, certificates and authorisations from an EU rail regulator to continue services.
Operators such as Eurostar, which currently only hold a UK licence, would be affected unless individual agreements are struck with countries on the continent.
The operator runs about 40 direct services a day, via the Channel Tunnel, from London to Paris, Brussels, Amsterdam, Rotterdam and other destinations.
Mr Raab said people should not hold off buying rail tickets as the UK would work with its French, Belgian and Dutch counterparts to ensure they were able to travel and goods could be moved.
But Labour said this would "not reassure anyone" as "ministers have barely scratched the surface of what would need to be done in the event of the UK crashing out of the EU without a deal".
In a separate development, the M26 in Kent is being shut overnight while work is done to see if it can be used as a "parking lot" for lorries, in the event of a no-deal Brexit, prompting complaints from road hauliers.
The Lib Dems said a no-deal would be a "catastrophe" but people should not be "scared" into settling for what it said was Theresa May's flawed proposed agreement with the EU.
Talks on the terms of the UK's exit are nearing a crunch point, with both sides pushing for an agreement by the middle of November at the latest.
Documents released on Friday warn of the potential fallout to the electricity market in Northern Ireland if the current Single Electricity Market arrangements that apply on a north-south basis cannot be continued.
The Department for Exiting the EU said it was keen to work with Dublin and Brussels to reach an agreement on maintaining existing arrangements whatever the outcome of the negotiations, including no deal.
But it warned that there was a risk Northern Ireland would become separated from the Republic of Ireland, in energy terms, and that this would make the market "less efficient".
In such a situation, it said regulators may have to use "fall-back arrangements" to ensure power is transmitted between Britain and Northern Ireland and to maintain the necessary generating capacity.
Mr Raab said the Single Electricity Market was the product of bilateral co-operation between London and Dublin and he hoped this would continue. Even if it did not, he said the UK would be prepared.
"We have got interconnectors and the regulatory measures that the government can take to make sure that Northern Ireland maintains the energy supply it needs."
On consumer rights, British subscribers to Netflix, Spotify and other online entertainment could see their access to content limited when they travel to the EU's 27 remaining member states, depending on what local rights deals and portability agreements are struck.
There would be no change for package holidaymakers unless their booking is with an EU-based firm and completed outside the UK - when they might not be protected from the firm going bust.
In the event of a no-deal exit, the transportation of horses to the continent could also be disrupted.
Unless the EU agrees to grant the UK "third country status" on the day it leaves, no horses will be allowed to travel to the continent - a potentially huge blow to the racing industry.
The government said it was confident the UK meets the animal health requirements to secure an immediate listing as a third country, making it subject to the same rules as countries like Australia and New Zealand.
But, it added "in the event the UK is not a listed country equine movement to the EU could not take place".
The documents also state that the UK wants to maintain the benefits of the 40 free trade agreements with more than 70 countries that it is party to from being an EU member.
Other subjects covered in Friday's documents include:
Previous no-deal papers have warned of the risks of UK flights to the continent being grounded and Britons visiting the EU facing extra credit card charges.

The UK will be a "laughing stock" in Europe if it cannot police its fishing waters after Brexit, former First Sea Lord Admiral Lord West has said.
He claimed there were few vessels to enforce new regulations for UK inshore fishing waters after it leaves the EU.
And the ex-Falklands veteran, who was once a Labour security minister, said he was "stunned" at the government's "amazing complacency" over the issue.
But minister Lord Gardiner insisted a vessel monitoring system was in place.
Lord West raised the issue just days after the government announced it is to withdraw from the London Fisheries Convention - the deal which allows foreign fisherman access to British waters.
Lord Gardiner, a rural affairs minister, said the Marine Management Organisation would supervise the UK's "exclusive economic zone", which stretches from six to 200 nautical miles - while the Association of Inshore Fisheries and Conservation Authorities would cover up to six nautical miles.
But he added that as the UK leaves the EU a review will be needed to reflect on the level of fisheries enforcement required.
That response prompted Lord West to say: "This simple sailor is absolutely stunned by the answer, which shows amazing complacency.
"The bottom line is we have very, very few vessels involved in this. They are not properly centrally coordinated. We've already seen a number of the countries involved saying 'well to hell with what you're saying, we're coming there anyway'.
"We will be made a laughing stock if we apply some rules and cannot enforce them."
Lord West urged ministers to establish "a centralised command system to actually control the various assets we have", adding that "far too few of them seem to be able to focus on things like someone fishing illegally in the six to 12 mile zones".
He said more ships and boats needed to be built "to ensure we can actually enforce it".
The minister said he would like Lord West, who served in the Royal Navy between 1965 and 2006, to go with him to Newcastle to see a new digital vessel monitoring system that can pinpoint "every vessel that's at sea within our waters".
He said there were three offshore patrol vessels in operation, with a further five new river offshore patrol vessels being built that will be used for fisheries protection.
But Labour's rural affairs spokeswoman Baroness Jones of Whitchurch argued that "fish stocks can't be managed unilaterally", adding "there has to be some cooperation with neighbouring countries".
"Fish shoals can sometimes move for hundreds of miles, and indeed our own fishermen fish up to the north of Russia and southern Portugal," she said.
"There's no point in making a unilateral declaration."
But Lord Gardiner said not only would the government be negotiating "with our partners and friends in Europe so we have a sustainable fishing industry" but post-Brexit the UK will "have the ability to decide who fishes in our waters".
He said the chief executive of National Federation of Fishermen's Organisations had welcomed the UK's decision to give notice to the London Fisheries Convention as "an important part of establishing the UK as an independent coastal state with sovereignty over its own exclusive economic zone".
He said fishing is worth £1.3bn to the UK economy, employs 34,600 people and has 6,000 fishing vessels. Each year, 708,000 tonnes of fish are landed, worth £775m.
The government would be "very conscious" of the interests of the coastal and fishing communities of the UK, he added.

Britons living in Spain will not have their lives "disrupted" after Brexit - even if there is no UK-EU deal, the Spanish foreign minister says.
The two sides are yet to reach an agreement about how the rights of expats will be protected after Brexit.
Theresa May has called for "urgency" from the EU side in finding a solution.
And speaking on the BBC's Andrew Marr Show, Alfonso Dastis sought to reassure more than 300,000 Britons living in Spain.
"I do hope that there will be a deal," the minister said.
"If there is no deal we will make sure that the lives of ordinary people who are in Spain, the UK people, is not disrupted.
"As you know, the relationship between the UK and Spain is a very close one in terms of economic relations and also social exchanges.
"Over 17 million Brits come to Spain every year and many of them live here or retire here and we want to keep it that way as much as possible."
According to the Office for National Statistics, Spain is host to the largest number of British citizens living in the EU (308,805), and just over a third (101,045) are aged 65 and over.
Citizens' rights are one of the first subjects being negotiated in the first round of Brexit talks - which have moved so slowly there has been increased talk of no deal at all being reached between the two sides.
The role of the European Court of Justice in guaranteeing the rights of EU nationals in the UK has been a sticking point. The EU argues this must continue, but ministers say the EU court will no longer have jurisdiction in the UK after Brexit.
Ahead of last week's Brussels summit, Mrs May said the two sides were "in touching distance" of finding an agreement.
On Monday she is expected to tell MPs she will "put people first" in the "complicated and deeply technical" negotiations.

Any agreement to allow an extended Brexit transition should be instead of - not as well as - a "backstop" to avoid the return to border checks in Ireland, the Brexit secretary has said.
The 21-month transition is currently expected to end on 31 December 2020 - but an extension was floated during last week's EU summit.
The idea angered Leave-supporting MPs.
But Dominic Raab says it should be instead of a backstop - the nature of which is also controversial.
It comes after hundreds of thousands of protesters marched through London on Saturday, calling for a referendum on the outcome of the Brexit negotiations.
Meanwhile, negotiators are at loggerheads over how best to avoid checks coming in on the Irish border after the UK leaves the EU.
The UK and EU are agreed on the need for a "transition period" - which Theresa May calls an implementation period - designed to smooth the path between the UK leaving the EU on 29 March next year, and a new permanent relationship with the bloc, including a new trading agreement, coming into force.
During that period, which ends on 31 December 2020, the UK's relationship would remain largely the same as at present.
But in case there is a gap between that period ending, and a long-term UK-EU relationship coming into force, the EU has proposed that Northern Ireland remain in the EU customs union for a period to avoid the need for customs checks on the border with the Irish Republic.
The UK government is opposed to this, because it would mean that Northern Ireland had a different set of rules to the rest of the UK - it argues it would effectively create a new border down the Irish Sea.
Prime Minister Theresa May's alternative backstop proposal is that the whole of the UK would temporarily stay in the customs union.
Mrs May suggested last week that the period could be extended by "a matter of months" if it helped to avoid a "hard border" with the Irish Republic.
However, this angered some pro-Brexit campaigners, who said it would leave Brussels with too much power in negotiations.
Writing in the Sunday Telegraph, Mr Raab said there should be no "indefinite limbo" inside the EU's customs union.
But he added: "The prime minister has rightly refused to rule out considering different approaches - including extending the implementation period for a limited period of a few months, as an alternative to the backstop.
"But we won't sacrifice Northern Ireland, and we must have finality to any backstop - whether through a time-limit or a mechanism that enables the UK to leave, in case the EU doesn't live up to its promise to get the future relationship in place swiftly."
It comes as a former Brexit minister is trying to put a legal barrier in the way of the EU's backstop plan by requiring the approval of the Stormont Assembly.
Northern Ireland's devolved government has not sat since power-sharing collapsed in January 2017.
And on Saturday, an estimated 700,000 people marched through central London to demand a referendum on the final Brexit deal.
Mayor of London Sadiq Khan - who started the march - was among those who addressed a rally in Parliament Square, along with representatives from the main political parties.
Celebrity speakers included Steve Coogan, Delia Smith and Deborah Meaden.
At the same time, former UKIP leader Nigel Farage led a pro-Brexit rally in Harrogate, North Yorkshire.
He said: "The evidence suggests about a third of those that voted remain now say we're democrats and think the government should simply get on with it.
"And that's our message - get on with it, fulfil your promises to us, you said if we voted to leave it would happen, it needs to."

UK companies are likely to speed up plans for a no-deal Brexit in response to Tuesday's votes in Parliament, the head of the CBI has told the BBC.
Carolyn Fairbairn said a plan to renegotiate the UK's withdrawal deal "feels like a real throw of the dice".
"I don't think there will be a single business this morning who is stopping or halting their no-deal planning," she said in response to the idea.
"I fear they may even be accelerating it," she added.
Other business groups endorsed the CBI's view that Parliament's opposition to a no-deal Brexit was welcome, while a Northern Ireland business group said there was "despair" that commitments to protect its members' interests could be removed.
Theresa May is expected to seek further talks with EU leaders in the coming days after MPs voted 317 to 301 in favour of replacing the backstop - the insurance policy designed to avoid a hard border in Ireland in the event of no deal.
The backstop is the main objection that Brexiteers in the Conservative party have to the deal negotiated by Mrs May, which was heavily rejected by MPs earlier this month in the largest defeat for a sitting government in history.
The EU has already said it will not change the legal text of the deal.
Ms Fairbairn said the reaction of businesses to the outcome of Tuesday's voting would be one of "rising frustration and concern".
She said Parliament had shown that there was "a consensus against no-deal", but added: "It does nothing to take no-deal off the table and it does feel like hope rather than strategy."
The CBI head said businesses in Northern Ireland were "incredibly concerned" about the turn that events were taking, adding: "The backstop is there for a purpose."
One day, technology might be able to solve the Irish border problem, she said, but until that was possible, there had to be "other arrangements in place".
Ms Fairbairn said many small and medium-sized businesses had done nothing to prepare for the "shock" of a "cliff-edge" departure from the EU on 29 March.
"I think the kind of concerns that people have around disruption are absolutely right," she said. "No deal is just not manageable at this stage."
Stephen Kelly, chief executive of Manufacturing Northern Ireland, told the BBC that firms there were "in despair and really confused" about what was going on.
He said more than 90% of the organisation's members supported the withdrawal agreement, including the backstop, and they felt "let down" by Tuesday's events in Parliament.
He added: "A deal that doesn't work for Northern Ireland isn't a deal."
Other business groups expressed opposition to a no-deal Brexit.
Stephen Phipson, chief executive of the EEF, the manufacturers' organisation, called on Mrs May to "confirm that she will not allow us to slide over the no-deal cliff".
Mike Cherry, chairman of the Federation of Small Businesses, said MPs had "at least made some movement on breaking the Brexit deadlock".
Dr Adam Marshall, director general of the British Chambers of Commerce, said: "Neither government nor many businesses are ready for a no-deal exit in two months' time, and it must not be allowed to happen by default."
Stephen Martin, director general of the Institute of Directors, said: "While it is something that MPs have managed to form a majority in any vote, the path ahead is still far from clear."

The first applications from EU nationals wanting to stay in the UK after Brexit are being submitted.
A group of university students and NHS workers in the north-west of England are taking part in a trial to test the system before it opens later this year.
The three million or so EU residents in the UK have until the end of June 2021 to register for "settled status".
Ministers, who insist the process will be simple, say the pilot will allow for "necessary adjustments" to be made.
The UK is due to leave the EU on 29 March 2019.
The government has said it wants EU nationals living in the country to be able to stay, with Brexit Secretary Dominic Raab saying last week that this applied whether there was an agreement on the terms of exit or not.
Ministers have said they aim to keep paperwork to a minimum, saying the form that has to be filled in online or via smartphone app will contain only a handful of questions and take a matter of minutes to complete.
Up to 4,000 people, including students from Liverpool universities and staff from 12 NHS trusts, will be the first to have a go during the pilot. They are being guided through the application process by Home Office officials.
Applicants have to provide proof of identity, declare any criminal convictions and upload a photograph - while officials will check employment data and run security checks.
The process - which will cost £65 for adults and £32.50 for children under the age of 16 - will operate on the basis of a presumption that applications will be accepted.
While stopping short of guaranteeing their future, Mr Raab said last week that it was "inconceivable" that non-UK citizens would be asked to leave whatever the outcome of current negotiations with the EU.
Immigration minister Caroline Nokes said the pilot was another step in making it easy for EU nationals to obtain settled status - enabling them to live and work in the UK on the same terms as now.
"From today, we are inviting a small group of EU citizens to make an application to secure their status," she said. "We will use their feedback to make any necessary adjustments ahead of the scheme being fully opened."
The scheme is due to fully open on 30 March, 2019, with settled status granted to EU nationals who have lived in the UK for five years - unless they have serious criminal convictions or for security reasons.
Those who are resident in the UK by 31 December 2020 but who have not lived in the UK for five years will get pre-settled status which allows them to live and work in the UK until they reach the five year mark and can claim settled status.

 Twenty-seven European Union leaders meeting in Brussels formally endorsed the bloc's guidelines on negotiating Brexit on 29 April. Like the draft guidelines issued in March, the approved version is a plan for how the EU wants to manage negotiations with the UK, and says that talks on a trade deal will only start after the brass tacks of separation have been agreed. But a few changes were made to the document between the draft and final version.
Read the full guidelines, here.
Here, the BBC's Reality Check correspondent Chris Morris teases out the key sentences and explains their significance.
The European Council will monitor progress closely and determine when sufficient progress has been achieved to allow negotiations to proceed to the next phase.
What's the significance? This is about whether and when initial talks on separation, or "divorce" arrangements, can move on to discussion of a future trade deal. The UK wanted to talk about trade straight away but the EU is ruling that out. Donald Tusk, the European Council President, said it would be up to the other 27 countries to determine what "sufficient progress" actually means. It could happen in the autumn, he suggested - but this is the EU asserting its control over the process.
...there will be no separate negotiations between individual member states and the United Kingdom…
What's the significance? Will the UK try to divide and rule by exploiting differences of opinion between different member states as the talks progress? This sentence suggests the European Council is well aware of that possibility, and intends to get legally binding language written into negotiating directives to prevent it happening. There is a distinction, of course, between formal "negotiations" and what you might call "informal contacts" - so the UK will try to talk separately to other countries anyway.
The people who will negotiate Brexit
A single financial settlement - including issues resulting from the MFF [Multiannual Financial Framework] as well as those related to the European Investment Bank (EIB), the European Development Fund (EDF) and the European Central Bank (ECB) - should ensure that the Union and the United Kingdom both respect the obligations resulting from the whole period of the UK membership in the Union. The settlement should cover all commitments as well as liabilities, including contingent liabilities.
What's the significance?
There is more detail here than in the initial draft about the level of EU expectation when it comes to a financial settlement with the UK. It means the EU expects the UK to fulfil all the obligations it has made in the past, including for bills that will not be paid until after the UK has left the Union. This is confirmation that reaching agreement on how to calculate this financial settlement will be one of the biggest challenges of the initial phase of negotiations.
Any future free trade agreement…must ensure a level playing field in terms of competition and state aid, and must encompass safeguards against unfair competitive advantages…"
Translation: Don't be tempted to undercut the single market by trying to gain a competitive advantage at our expense. You won't get the deep and comprehensive free trade agreement you want if that happens.
"Preserving the integrity of the single market excludes participation based on a sector-by-sector approach."
What's the significance? There had been suggestions in the UK that specific sectors like the car industry could be given some kind of special access to the single market. This sentence rules that out altogether. For the EU it is a non-starter.
Such guarantees must be effective, enforceable, non-discriminatory and comprehensive, including the right to acquire permanent residence after a continuous period of five years of legal residence. Citizens should be able to exercise their rights through smooth and simple administrative procedures.
This reflects concern among EU member states that the UK is underestimating the technical difficulties of reaching an agreement on the issue of citizens' rights. There have to be legal guarantees, one senior official said, not just a gentlemen's agreement. And, at the moment of course, the ultimate legal authority for EU citizens is the European Court of Justice. That makes this a tricky political problem in the UK, not least because some of these issues will still be relevant decades into the future. The EU is also concerned that the UK Home Office is placing and will continue to place bureaucratic obstacles  in the path of EU citizens trying to secure their future - this is a warning shot across British bows.
Any future framework should safeguard financial stability in the Union and respect its regulatory and supervisory regime and standards and their application.
This has been added after pressure from the French and others who are concerned that the UK might be tempted to undercut EU standards in the financial services sector. The language here reinforces the view that the EU will not tolerate the UK trying to gain a competitive advantage through a much looser regulatory regime.

France's president mixed up his English when he said in error that UK visitors would need French visas if there was a no-deal Brexit, aides say.
Emmanuel Macron had meant to say that British people would not need visas in such circumstances.
The confusion came as Mr Macron was speaking to the media in English at the end of an EU summit in Brussels.
UK citizens currently enjoy visa-free travel in the EU, but that could change with Brexit. The UK is set to leave the 28-nation bloc on 29 March 2019.
The BBC's Gavin Lee raised the visa issue with President Macron at Thursday's news conference, after leaders had failed to achieve a breakthrough on Brexit.
By Gavin Lee, BBC News, Brussels
The mix-up came after I asked President Macron whether newspaper reports of UK citizens needing visas for work or holidays in the event of a no-deal was true.
The president's response was that "we will not stop visas, it is fake news, as some other leaders would say", and he went on to say "we will definitely deliver visas for people".
His team now say it was a case of a "second language" slip-up, and that President Macron meant to say "we will not start visas for British people".
They say they would aim for a deal which allows for a "special status" agreement for workers and tourists for both countries, that avoids the need for any "official visa system".
In the event of a no-deal Brexit, Mr Macron said, measures would be taken to cover flights, ferries and businesses as well.
A draft law has been tabled in the upper house of the French parliament that will let the government set new rules for Britons visiting France after Brexit. The draft suggests they will be treated as "third country" visitors - a similar category to Americans or Chinese. The preamble of the bill raises the possibility that visas may be imposed.
But, in the event of a no-deal Brexit, the bill also gives the government the power to adapt or suspend the need for visas and residence permits for UK citizens.
A deal remains elusive mainly because of wrangling over the future Northern Ireland border. Brexit risks reinstating physical controls at the border, which were scrapped under the Northern Ireland peace settlement.
The current Brexit plan is for a transition period of 21 months from the end of March, to smooth the UK's path to a future relationship outside the EU.
UK Prime Minister Theresa May said that transition could be extended "for a few months", if needed. But some Brexit campaigners have reacted angrily to the suggestion.
"I do prefer a deal and I want a deal, but I will never favour a bad deal," Mr Macron said on Thursday.
"In case of no deal our responsibility is to ensure that the life of our people will not be so far impacted."
Mr Macron described the "dynamic" of the Brexit negotiations as "positive because there is a willingness on the British side to find a solution".
He said "now it's for Prime Minister May to propose a solution, but we will not compromise on the key elements of the mandate we gave to [EU negotiator] Michel Barnier".
The French president also denied suggestions that the UK prime minister had been snubbed late on Wednesday, when four EU leaders went out for a drink in the Grand Place in the centre of Brussels.
He told the BBC that Theresa May had left the summit earlier, and said she would certainly be invited in future.
"I am always happy and open to share a drink with the different leaders, so obviously Theresa May will be very much welcome," he said.

Former French Foreign Minister Michel Barnier has been appointed by the European Commission to negotiate with Britain over Brexit.
Announcing the appointment, European Commission President Jean-Claude Juncker said he "wanted an experienced politician for this difficult job".
Mr Barnier will take up his post on 1 October.
A former EU commissioner, Mr Barnier led the EU's banking reforms - a move unpopular in London's finance district.
In a tweet, Mr Barnier said he was honoured to be appointed to the role.
Mr Barnier will work with his British opposite number, Brexit minister David Davis, who was at the forefront of the campaign to leave the EU.
Negotiations will only begin when Article 50 is triggered.
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Mr Barnier is known as a tough negotiator.
As European commissioner for financial services between 2010 and 2014, he spearheaded the overhaul of EU banking laws in the aftermath of the 2008 financial crisis.
These included a swathe of measures, which included capping banker bonuses and a crackdown on short selling - some of which were objected to by the City of London.
Comments on social media by British political editors have already declared the appointment an 'act of war'.
The BBC's chief correspondent Gavin Hewitt points out that Mr Barnier will come with a French, as well as a Brussels, brief:
European Council President Donald Tusk, who chairs EU summits, had previously appointed Belgian EU official Didier Seeuws to oversee preparations for the Brexit negotiations.
It was not immediately clear what the relationship between Mr Barnier and Mr Seeuws would be.

French officials have rejected suggestions they could resort to a "go-slow" policy at the port of Calais if there is no Brexit deal.
The UK's Brexit Secretary Dominic Raab warned on Thursday of major disruption in a "worse case scenario", which might force firms to use other ports.
But Xavier Bertrand, president of the Hauts-de-France region, said ensuring "fluidity" of trade was essential.
Another official said closing Calais would be an "economic suicide mission".
There has been widespread concern about the impact of longer border checks at Calais if the UK leaves the EU on 29 March 2019 without a deal.
Transport Secretary Chris Grayling met the mayor of Calais, Natacha Bouchart, on Thursday to discuss French and British preparations for such an eventuality amid claims that businesses may be forced to use Dutch and Belgian ports instead to transport goods.
Responding to a question in the House of Commons about no-deal planning on Thursday, Mr Raab appeared to suggest the French could choose to create additional delays.
"We also need to prepare for the worst case scenario where the authorities at Calais are deliberately directing a go-slow approach  by supporting a diversion of the flow to more amenable ports in other countries," he said.
Responding on Twitter, Mr Bertrand said closing the port of Calais or the Channel Tunnel to cross-channel traffic in the event of a no-deal Brexit "was not envisaged".
"Who could believe such a thing? We have to do everything to guarantee fluidity," he wrote.
And Jean-Paul Mulot, who represents Hauts-de-France, France's northern-most region, in the UK said that while there might be delays if the event of a no-deal, it was in France's interest to minimise these.
Brexit-backing MPs, including Dover's Charlie Elphicke, have said talks of gridlock at channel ports are being used politically by opponents of the UK leaving.
At present, the UK's membership of the EU single market and the customs union allows for the free movement of goods, people and services around Europe.
But the UK government has said it is leaving both of these arrangements as part of Brexit.
The UK and the EU are in negotiations on how their final relationship will work but have yet to reach a deal on key issues.
Both sides say they still want to agree a deal before the UK leaves the EU on 29 March 2019, but are also making plans for what happens without one.
This week the National Audit Office warned that queues and delays were likely at border crossings under a no-deal Brexit, saying exporters did not have time to prepare for new rules.
A "transition" period to cushion the UK's exit from the EU is planned to last until December 2020 - but this is dependent on the two sides reaching agreement on outstanding issues like the Irish border.

A fresh legal challenge to Brexit has been blocked by the High Court.
A group of campaigners who want Britain to stay in the EU single market argued that Parliament must approve the UK's exit from the European Economic Area.
But the judges refused to give the green light for the challenge, saying the judicial review was "premature".
The Supreme Court ruled last month that Parliament must have its say before the government can trigger Article 50 and begin official talks on leaving the EU.
Parliament is in the process of considering legislation which would give Theresa May the authority to notify the EU of the UK's intention to leave by the end of March.
MPs overwhelmingly backed the bill on second reading on Wednesday.
The latest legal challenge was brought by supporters of a so-called "soft Brexit" - which would see the UK remain a member of the EU's internal market.
They include Peter Wilding, chairman of the pro-Europe pressure group British Influence, and lobbyist Adrian Yalland.
The government claimed the case was unarguable since the existing EEA agreement would automatically cease to exist once the UK left the EU.
Under the terms of the EEA, which first came into legal force in 1994, the EU's 28 members and three other signatories are bound to accept the free movement of people, services, goods and capital across their borders.
Dismissing the case, Lord Justice Lloyd Jones and Mr Justice Lewis said the government had not made a decision "as to the mechanism by which the EEA agreement would cease to apply within the UK".
As a result, they said it was not clear at this stage what issues, if any, would fall within the jurisdiction of the courts.
In a joint statement, Mr Wilding and Mr Yalland suggested the government had "used procedure" to thwart them.
They said they would not rule out bringing further proceedings to give all those who would be directly affected by Brexit some form of legal certainty about their rights.
"It is intolerable that those who depend upon their EEA rights to trade with the EEA, or those who are married to EEA citizens, or are EEA citizens resident in the UK, are being used as a negotiating pawn by a government who can choose to act unilaterally to clarify our legal position, but will not," they said.
"The government must stop playing poker with our rights and stop taking liberties with our freedoms."
But a government spokesman welcomed Friday's decision.
"As the prime minister has said, we will not be a member of the single market and we will be seeking a broad new partnership with the EU including a bold and ambitious free trade agreement," he said.
Former UKIP leader Nigel Farage said the ruling was "good news".

The UK and the EU will remain the "best of friends" but they will "not be as close as before" after Brexit, the new European Commission president has said.
Speaking ahead of talks with the PM, Ursula von der Leyen warned it would be "impossible" to reach a comprehensive trade deal by the end of 2020.
She said if the deadline was not extended it was not a case of "all or nothing", but of priorities.
Boris Johnson has insisted a deal is possible by December 2020.
After their meeting in No 10, a Downing Street spokesman said talks had been "positive", but the PM had been "clear" the process of negotiation would not be extended.
After its 31 January exit, the UK will enter into an 11-month transition period in which it will largely follow EU rules but will not have any representation in the bloc's institutions. This period will come to an end on 31 December.
Only when the UK leaves the EU can the two sides begin talks on their future economic relationship.
Mr Johnson told Mrs von der Leyen he "wanted a positive new UK and EU partnership, based on friendly co-operation, our shared history, interests and values", as well as a "broad free trade agreement covering goods and services, and cooperation in other areas".
He also said the UK was ready to start negotiations "as soon as possible" after 31 January.
Speaking at the London School of Economics earlier in the day, Mrs von der Leyen said the EU was "ready to negotiate a truly ambitions partnership with UK" but she warned of "tough" talks ahead.
"We will go as far as we can, but the truth is that our partnership cannot and will not be the same as before and it cannot and will not be as close as before because with every choice comes a consequences with every decision comes a trade off."
Mrs von der Leyen, a former German defence minister, took over from Jean-Claude Juncker at the start of December. She was a student at the LSE in the 1970s.
She also attended the same school as Mr Johnson in Belgium - something the prime minister highlighted as they posed for photos in Number 10.
Mrs von der Leyen said she hoped the new trading relationship would be based on "zero tariffs, zero quotas, zero dumping".
But she said: "Without the free movement of people you cannot have the free movement of capital and services.
"The more divergence there is the more distant the partnership will be."
Mrs von der Leyen also warned that without an extension of the transition period beyond 2020  "you cannot expect to agree every single aspect of our new partnership".
She called the deadline "very tight".
Opposition MPs have warned that trade deals typically take years to conclude and the UK risks defaulting to World Trade Organisation rules at the start of 2021, potentially leading to damaging tariffs for some industries.
But Brexit Secretary Stephen Barclay told BBC Breakfast the UK and EU had agreed in the political declaration to do a trade deal by the end of this year and he was "confident" they would do that.
The meeting between Boris Johnson and new European Commission President Ursula von der Leyen is significant in that it's their first face-to-face in their new roles - but today does not mark the start of post-Brexit trade talks.
EU law dictates that trade talks can't start until the UK legally leaves the bloc. Then EU countries must agree a mandate for the EU Commission to negotiate a comprehensive trade agreement on their behalf.
This mandate then has to be formally signed off at minister level by representatives of all EU countries.
All this means, the EU says, is trade talks will start at the beginning of March.
When UK ministers complain that's too long to wait, the EU response is that the UK always pushed for bigger role for national governments in EU decision-making to make it more democratic.
Expect red-line drawing with smiles today between the prime minister and Mrs von der Leyen - presented as "friends telling each other truths".
The EU position is that the prime minister's timetable to get an "ambitious, comprehensive" trade deal agreed and ratified by December is unrealistic.
However, the prime minister will counter this with "truths" of his own, including that negotiations have to be done by December because he won't extend the transition period.
Legislation implementing the terms of Mr Johnson's Brexit deal continues to move through the Commons, with the government easily winning all three votes on the Withdrawal Agreement Bill on Tuesday.
The bill will enshrine in law the terms of the transition period, first negotiated by Mr Johnson's predecessor Theresa May, as well as agreements on citizens' rights, customs arrangements in Northern Ireland and the UK's financial settlement.
Attempts by Northern Ireland parties to amend the bill to ensure "unfettered access" for businesses there to the rest of the UK market failed to pass on Wednesday afternoon.
MPs also rejected an attempt by Labour to reinstate child refugee protection rights in the Brexit bill.

An appeal to raise £500,000 by the weekend has been launched to ensure Big Ben chimes when the UK leaves the EU at 23:00 GMT on 31 January.
The famous bell has only rung a few times since renovations began in 2017.
The PM's spokesman highlighted "potential difficulties" in using money raised from public donations.
But the Brexit Party's Richard Tice said it would be "pretty feeble if we can't organise for a bell to chime at this historic moment".
StandUp4Brexit, the organisation behind the crowdfunder, says if it does not reach the target, the money will be donated to veterans' charity Help For Heroes.
More than £155,000 had been raised by Friday morning, with one of the largest single contributions coming from Tory MP Mark Francois, who donated £1,000.
Business Secretary Andrea Leadsom has said she donated £10.
Appealing for contributions, the group writes: "However you may have voted in the referendum, this unique moment is unlikely ever to be repeated...
"If you would like to see it marked by the chiming of the most iconic timepiece in the world, please donate now."
The House of Commons Commission has estimated that getting the bell to ring during renovation works on the Palace of Westminster's Elizabeth Tower, which houses it, would cost between £350,000 and £500,000.
The body - a group of MPs and officials responsible for the day-to-day running of Parliament - said this was because of the costs of bringing back the chiming mechanism and installing a temporary floor, and delays to the conservation work.
On Wednesday the commission said the estimated costs could not be justified, and appeared to cast doubt on the idea that public donations should cover them.
In a statement, the body said using donations for the works would be an "unprecedented approach".
"Any novel form of funding would need to be consistent with principles of propriety and proper oversight of public expenditure," it added.
On Thursday, the PM's spokesman said: "The House of Commons authorities have set out that there may be potential difficulties in accepting money from public donations.
"I think the PM's focus is on the events which he and the government are planning to mark 31 January. It's a significant moment in our history and we want to ensure that's properly recorded."
On Tuesday, Commons Speaker Sir Lindsay Hoyle said there was a need to "weigh up the costs" involved in making Big Ben chime for Brexit.
"You are talking about £50,000 a bong," he added.
"We also have to bear in mind that the only people who will hear it will be those who live near or are visiting Westminster."
But Brexit Party chairman Richard Tice told the BBC's Today programme he did not believe the figure was correct, pointing out that the bell rang on New Year's Eve.
He also suggested that "bureaucrats in the Houses of Parliament" might stop the money being used, on the grounds that it would not be public money.
He added that if the target was not reached, a recording of Big Ben's chimes would be played through a loudspeaker at a Brexit event organised by Leave Means Leave group in London's Parliament Square.
The event gained "provisional authorisation" from the Office of the London Mayor on Wednesday.
Responding to the call for donations, Commons leader Jacob Rees-Mogg told the Commons: "One shouldn't look a gift horse in the mouth."
"If people wish to pay for things, that should be considered as part of their public spiritedness, rather than thinking everything should fall on the hard-pressed taxpayer."

The GMB has become the largest union to date to back a referendum on the outcome of the Brexit negotiations, urging Labour to "follow suit".
General Secretary Tim Roache told the BBC "false promises" had been made during the 2016 referendum and it was time to "let the people decide".
But he said that the vote should be on the terms of exit, not on whether Brexit would actually happen, which he said had already been decided.
The UK is to leave on 29 March 2019.
The cross-party People's Vote campaign, which is backed by the Lib Dems and Greens as well as many Labour MPs, has said a referendum must be held on the outcome of the negotiations with the EU, including the option to remain in the bloc.
GMB said it had consulted its 620,000 members before its executive committee chose to endorse the idea of a new referendum.
While it respected the outcome of the 2016 Brexit vote, it said the reality facing the British public was very different from what they voted for.
"People voted for change," Mr Roache said. "They voted to take back control. They did not vote for economic chaos or to put jobs and hard-won rights on the line."
"In trade union terms if we negotiate a pay deal for our members we put that deal back to the members and they decide whether that's acceptable or not.
"We have no faith given what's happened in the last few months in this government delivering a Brexit deal that works for working people.
"If the government are comfortable with that, well let's let the people decide then."
A number of unions, including the TSSA and Royal College of Nursing, have backed a further referendum although Unite, the country's largest, has so far stopped short of doing so.
In July, it said it was "open to the possibility" of another EU referendum "depending on political circumstances" and its priority was planning for a general election.
The Labour leadership has said that a new referendum is not party policy but senior figures have suggested no options should be taken off the table as the negotiations enter a crucial phase and Prime Minister Theresa May attempts to negotiate a deal next month.
Mrs May has insisted there will be no new vote under any circumstances and her Chequers plan for Brexit delivers on the result of the 2016 referendum.
Updating MPs on negotiations on Tuesday, Brexit Secretary Dominic Raab said "dangling" the prospect of another vote at this stage would invite the EU to give the UK "the very worst terms".

As Brexiteer Conservatives go, George Eustice sits in the mainstream.
Unlike more hardline colleagues, the now former fisheries minister has actually been willing to contemplate a Brexit which leaves the UK quite close the European Union; a relationship with the EU comparable to Norway's, at least for a while.
He resigned today not because he's opposed to the prime minister's vision of Brexit; the deal she's trying to strike in Brussels and get through the Commons.
He supported that vision and he still does.
He resigned because he believes Mrs May's been manoeuvred into putting Brexit itself in doubt.
For George Eustice the breaking point was allowing MPs to vote on whether to rule out a no-deal Brexit, he's one of many Brexiteers who are convinced the danger of a disruptive exit might add to the pressure on the EU to make concessions.
And he's especially upset about Mrs May promising a vote on whether to delay Brexit beyond 29 March, if only for a short time.
The prime minister was driven to volunteer those concessions by the fear of being defeated in the Commons this week, and having to concede them anyway.
Her de-facto deputy David Lidington, and Chief Whip Julian Smith, warned Mrs May plainly that she had no choice.
A core of ministers, senior, junior and their parliamentary aides, were willing to sacrifice their jobs if necessary to bring about that defeat.
She gave in, and hated doing so.
But the fear of George Eustice - shared by other Brexiteers is that once Brexit is delayed, the government loses control.
Brussels would be in a position to dictate terms. A short delay could become a long one. Brexit could be delayed for months, years, indefinitely.
Theresa May has promised MPs a chance to give their verdict on her deal - and to set down their own preferences for Brexit whether she's managed to strike one or not - on or before 12 March.
There's still no new deal, no way of being sure whether she'll finally win support after so many setbacks.
And Mrs May's still hoping Brexiteer ministers back her, for fear of losing control, maybe losing Brexit altogether.
George Eustice's resignation is a demonstration of the anger and frustration of Brexiteer Tories at being placed in such a painfully uncomfortable position.

Gibraltar has accused Spain of manipulating the European Council for its own political interests.
A draft document on the EU's Brexit strategy said no agreement on the EU's future relationship with the UK would apply to Gibraltar without the consent of Spain, giving it a potential veto.
But Gibraltar's chief minister Fabian Picardo said this was "unacceptable".
Conservative MPs in the UK have warned that the sovereignty of the UK overseas territory is non-negotiable.
MP Jack Lopresti said Spain was using Brexit as "a fig leaf for trouble making", while fellow Tory Bob Neill tweeted "no sell out".
Foreign Secretary Boris Johnson spoke to Mr Picardo as the UK government attempted to reassure Gibraltar and said: "As ever, the UK remains implacable and rock-like in our support for Gibraltar."
An EU source told the BBC the inclusion of the Gibraltar issue in the document had come after lobbying from Spain.
Spain has long contested Britain's 300 year-rule of Gibraltar.
Gibraltarians, who number about 30,000, rejected by 99% to 1% the idea of the UK sharing sovereignty with Spain, in a vote in 2002.
However, Spain has continued to press its territorial claim.
Following last June's EU referendum - in which Gibraltar voted by 96% to 4% to remain in the EU - Spain's then foreign minister suggested shared sovereignty could allow Gibraltarians to maintain some of the benefits of EU membership and enable Spain to "plant its flag" there.
But Alfonso Dastis, his successor, said in January that Spain would not put Gibraltar at the centre of the negotiations and it would be free to leave the EU if it wished.
Gibraltar: key facts
In its draft Brexit negotiating guidelines, the European Council identified future arrangements for Gibraltar as one of its 26 core principles.
It wrote: "After the UK leaves the union, no agreement between the EU and the UK may apply to the territory of Gibraltar without agreement between Spain and the UK."
Brussels officials were quoted by the Guardian as saying the EU was standing up for its members interests.
"That means Spain now," a senior EU official told the newspaper.
"Any extension of the deal [after withdrawal] to Gibraltar... will require the support of Spain. [The text] recognises that there are two parties to this dispute."
But Mr Picardo said: "This draft suggests that Spain is trying to get away with mortgaging the future relationship between the EU and Gibraltar to its usual obsession with our homeland.
"This is a disgraceful attempt by Spain to manipulate the European Council for its own, narrow, political interests.
"Brexit is already complicated enough without Spain trying to complicate it further."
Mr Lopresti, chairman of the UK's All-Party Parliamentary Group on Gibraltar, said there was no question of any negotiation over Gibraltar's future.
He will raise the matter with the secretary general of Nato, of which the UK and Spain are both members.
He said: "It is shameful that the EU have attempted to allow Spain an effective veto over the future of British sovereign territory, flying in the face of the will of the people of Gibraltar."
Mr Neill, chairman of the Commons Justice Select Committee, which examines relations between the UK and its overseas territories, tweeted: "Gibraltar's friends in the UK will be watching this very carefully. There will be no sell-out."
Labour MP Mary Creagh, a supporter of the Open Britain campaign group, said Gibraltarians risked being treated as "pawns" in the Brexit process.
"The Rock depends on free movement of labour from Spain, and on its place in the single market to support its vital services industries," she said.
"'Brextremists' should be ashamed that their actions have destabilised the situation in Gibraltar."
Lord Boswell, chairman of the House of Lords EU Committee, said it was "unfortunate" that the prime minister's Article 50 letter made no mention of Gibraltar and said this meant "the door has been opened for the EU to present it as a disputed territory".
"The reality is that any agreement on the future UK-EU relationship is likely to require the unanimous agreement of all 27 remaining member states, including Spain, as well as the UK," he said.
Gibraltar's government has ruled out any dilution of sovereignty in return for continued access to the European single market or other benefits attached to EU membership.
Key issues in post-Brexit negotiations relating to Gibraltar are likely to be border controls - thousands of workers commute in and out of the territory from the Spanish mainland every day - and airport landing rights.

Michael Gove has said the PM must be given "flexibility" to negotiate a Brexit deal and he would not stop her if it meant paying more to the EU.
"I would not block the prime minister in doing what she believed was right," he told BBC One's Andrew Marr Show.
The so-called divorce bill has been one of the main sticking points in Brexit negotiations so far.
Theresa May has said the UK will honour commitments made but has not put a final figure on what will be paid.
But there have been reports that some Brexiteers are prepared for the UK to pay more than the 20bn euros (about £18bn) that has previously been suggested.
The money is among issues that must be resolved before the EU will agree to move on to talking about a transitional deal and future trade deal.
Last week, the EU's chief Brexit negotiator Michel Barnier said the UK had two weeks to clarify what it would pay to settle its accounts, if the talks were to make "sufficient progress" before the next big EU leaders' meeting in December.
On Sunday, he told French newspaper Le Journal du Dimanche he was making plans for the possible failure of talks, adding: "It's not my (preferred) option... but it's a possibility. Everyone needs to plan for it, member states and businesses alike. We too are preparing for it technically."
Leave campaigner and entrepreneur James Dyson, also interviewed on the Marr programme, said it was "quite outrageous" for the EU to demand "billions and billions" before agreeing to negotiate on a future deal.
"I would walk away. I think that's the only way to deal with them," he said.
But Environment Secretary Mr Gove, who headed up the successful Vote Leave campaign during the EU referendum, said: "I can understand James's point of view but on this occasion, respectfully, disagree with him.
"I think it's far better for us to be engaged in these negotiations."
Asked if he would block the prime minister if securing a deal meant the UK had to offer more money, he said: "I certainly would not. I would not block the prime minister in doing what she believed was right."
"We have to make sure that when we are negotiating on money or anything else that we both respect Britain's interests but also make sure, as the prime minister has said, that no EU country is out of pocket as a result of the decisions that we have made."
"My view is the prime minister and [Brexit Secretary] David Davis should be given the flexibility that they need in order to secure that good deal."
Asked about a Mail on Sunday story reporting that both Mr Gove and Mr Johnson had written to the prime minister expressing their "worry" that "in some parts of government the current preparations are not proceeding with anything like sufficient energy".
He told the BBC: "As a departmental minister I have a responsibility .. to make sure that we are ready for any eventuality."
He stressed the cabinet wanted to achieve a "good Brexit deal" but added: "We are also making sure that whatever may happen in these negotiations, that Britain can make the best of them."

Leading Brexiteers in the cabinet have rallied behind Theresa May amid attempts to unseat her by Tory MPs.
Michael Gove said he "absolutely" had confidence in Mrs May as he confirmed he would not be following several other ministers out of the door.
And Liam Fox urged MPs to support the PM's draft Brexit agreement, saying a "deal was better than no deal".
The PM has named health minister Steve Barclay as her new Brexit Secretary following Dominic Raab's exit.
The 46-year old former banking executive backed Leave in the 2016 referendum and has never rebelled against the Tory whip during his eight years in the Parliament.
A mini-reshuffle has also seen Amber Rudd confirmed as the new work and pensions secretary after Esther McVey's resignation on Thursday.
The BBC understands Leader of the House Andrea Leadsom could oversee a meeting over the weekend of pro-Brexit cabinet members who have concerns about the deal.
Mr Gove and Mr Fox are expected be present, along with International Development Secretary Penny Mordaunt and Transport Secretary Chris Grayling.
The news came as more Conservatives expressed unhappiness with Mrs May's leadership and urged a confidence vote.
The BBC's political editor Laura Kuenssberg said about 20 Tories have, so far, publicly stated they have submitted letters of no confidence in the PM over her handling of Brexit.
This is some way short of the 48 needed to trigger a vote under Conservative Party rules.
One of those to do so, ex-minister Mark Francois, said the draft agreement negotiated by Mrs May with the EU was "truly awful" and the prime minister "just doesn't listen" to concerns within her party.
Ex-Brexit minister Steve Baker told the BBC's Politics Live that although he could not be sure of the number of letters submitted, he believed it was "close" to 48 and a contest was "imminent".
If this happened, he suggested the European Research Group of Brexiteer Tory MPs, headed by Jacob Rees-Mogg, would "collectively agree" which single candidate was best-placed to deliver the Brexit they wanted and back them.
But Cabinet Office minister David Lidington said Mrs May would win any contest "decisively" and "deserved to" since there was "no plausible alternative" to her approach.
Rumours had been rife that Mr Gove, a key figure in the 2016 Leave campaign, would follow fellow Brexiteers out of the cabinet in protest at the EU withdrawal agreement.
But the environment secretary, who reportedly rejected an offer to make him Brexit secretary after Dominic Raab's exit, told reporters on Friday he was focused on working in cabinet to get "the right deal in the future".
Asked if he had confidence in the PM, Mr Gove said: "I absolutely do."
He added: "I'm also looking forward to continuing to work with all my government colleagues and all my colleagues in parliament in order to make sure that we get the best future for Britain."
International Trade Secretary Liam Fox told an event in Bristol: "We are not elected to do what we want to do, but to do what is in the national interest."
Speaking in public for the first time since the withdrawal agreement was signed off by cabinet, Mr Fox said he hopes MPs "will take a rational and reasonable view" of the deal.
He added: "I hope across parliament we recognise that a deal is better than no deal, and businesses require certainty - it's in our national interest to provide certainty as soon as possible."
By BBC Assistant Political Editor Norman Smith
Michael Gove is not resigning because he thinks that even at this very late hour, he is the person who can make Theresa May change course with Brexit.
This is a huge relief for Theresa May, who meanwhile has been carrying on with business as usual by trying to sell her deal.
Theresa May has made it absolutely clear that she is going nowhere.
Senior placed Tory MPs are saying they have reached the magic 48 letters needed for a vote of confidence against Theresa May, but Sir Graham Brady - chairman of the 1922 committee - is giving precious little away.
A Conservative party leadership challenge is most definitely looming, if not this morning or this afternoon, by the weekend.
Michael Gove is a bit of a man of mystery, but if he doesn't take the Brexit Secretary role, it begs the question of who would take that job.
Mr Gove's decision to stay was a boost for Mrs May, who followed up a defiant Downing Street press conference on Thursday with a live phone-in on Friday morning on LBC radio, during which two callers said she should stand aside.
She compared herself to her cricketing hero Geoffrey Boycott who she said had "kept at the crease and carried on".
Ex-Culture Secretary John Whittingdale is among the latest Tory MP to demand a vote of confidence in the PM while a number of MPs, including Mr Francois and Adam Holloway, publicly tweeted copies of their letter.
But this prompted a blistering response from veteran Conservative MP Nicholas Soames.
Ambassadors from EU member states also met in Brussels on Friday morning to discuss the agreement.
The bloc's chief negotiator, Michel Barnier, paid tribute to Mrs May, but said that the EU had to protect its principles even if there were political problems in the UK.
BBC Brussels reporter Adam Fleming said the consensus from the meeting was that the EU should keep calm and not provoke the situation in the UK.
The government unveiled its long-awaited draft withdrawal agreement on Wednesday, which sets out the terms of the UK's departure from the EU, over 585 pages.
But Mrs May is facing opposition from across the political spectrum to the draft deal, which must be approved by Parliament, with critics saying it will leave the UK indefinitely tied to the EU.
It is also understood that a group of cabinet ministers are also considering whether to try to force Mrs May to make some changes to the withdrawal deal.

Michael Gove has confirmed that some foreign trawlers will still have access to UK waters after Brexit.
Mr Gove, the UK environment secretary, said British fishermen would not have the capacity to land all of the fish in British territorial waters.
And he said that some access would therefore be granted to vessels from other countries.
He was speaking during a fact-finding mission to Denmark, which was largely focused on the Danish food industry.
The Danish fishing industry is currently highly-dependent on fish caught in UK territorial waters.
The meeting was attended by Niels Wichmann, chief executive of the Danish Fishermen organisation, who told BBC Scotland that there was no suggestion from Mr Gove that Denmark would receive preferential treatment.
And he said Mr Gove "did not say numerous countries, he just said other countries" would be granted access.
Mr Wichmann added: "The thing is he was just being realistic and he was saying that we need, within the Brexit negotiations phase, to find out where the final goal is, the final solution to the fisheries.
"The fisheries will be outside the common fisheries policy and we need a transitional period. In that transitional period we will have to have access from other countries."
Mr Wichmann also said that the Danes were seeking a deal that would effectively mean "business as usual" with regard to access to UK fisheries after Brexit.
Mr Gove's remarks in Denmark follow an appearance on the BBC's Andrew Marr show last month, when he said no foreign boats would be allowed to fish within six to 12 miles of the UK coast.
But he said the UK would become an "independent coastal state" after leaving the EU, which would allow it to extend control of its waters up to 200 miles from its coastline.
Mr Gove said this would allow the UK to "take control" of its waters, and then negotiate with other countries to allow them access to British fisheries.
He also described the EU's common fisheries policy as an environmental disaster, and said the government wanted to change that, upon Brexit, to ensure sustainable fish stocks in future.
The common fisheries policy has been extremely unpopular among Scottish fishermen, who are said to have overwhelmingly backed Brexit.
Anger has generally been focused on quotas for fishing catches and on other European fleets being given equal access to fishing grounds in Scottish waters.
Responding to Mr Gove's remarks, Bertie Armstrong of the Scottish Fishermen's Federation said: "It is clear from our meetings with the government that control over our waters will be in our hands after Brexit.
"We will be out of the Common Fisheries Policy and we will decide who fishes where and for what. Our position is straightforward: we must have first call on quota."
But the SNP claimed that the "startling revelations on the Tories' true position over fisheries post-Brexit" showed that "you cannot trust the Tories to stand up for rural Scotland's interests".
SNP MSP Stewart Stevenson said: "Michael Gove must immediately make absolutely clear what the UK government's real position on the future of fisheries is.
"He could start by confirming that devolved powers over fisheries will transfer to Scotland so that we can get on with developing our own management policies which put Scottish fishing interests, offshore and onshore, first."
A spokesman for the UK's Department of Environment, Food and Rural Affairs said: "Leaving the EU means we will take back control of our territorial waters, and for the first time in 50 years we will be able to grant fishing access for other countries on our terms.
"We will allocate quotas on the basis of what is scientifically sustainable, making sure we have a healthy marine environment and profitable fishing industry."

If MPs don't back Theresa May's Brexit deal there could be another EU referendum, Michael Gove has said.
The leading cabinet Brexiteer said Mrs May's deal was not perfect - but if MPs did not vote it through on 11 December there was a risk of "no Brexit at all".
He told the BBC's Andrew Marr show there may now be a Commons majority for another referendum.
Labour has said it will attempt to topple Mrs May and force a general election if MPs reject her deal.
If that fails, they will then seek support in the Commons for another referendum.
Michael Gove insisted Mrs May could still win the vote on 11 December despite dozens of her own MPs being against her EU deal.
The environment secretary told the BBC that winning the Commons vote would be "challenging".
But although Mrs May's deal was not perfect, "we have got to recognise that if we don't vote for this, the alternatives are no deal or no Brexit".
"There is a real risk if we don't vote for this deal there may be a majority in the House of Commons for a second referendum," said Mr Gove, a leading figure in the 2016 Leave campaign.
Asked if Mrs May would have to stand down as PM if she lost the vote on her deal in nine days' time, he said: "Absolutely not."
He claimed there was a "strong movement behind the prime minister" among the public.
Labour has said it will table a no confidence motion in the government if MPs vote down the deal in a bid to topple Mrs May and force a general election.
Shadow Brexit secretary Sir Keir Starmer said: "If the prime minister has lost a vote of that significance then there has to be a question of confidence in the government.
"I think it's inevitable that we would seek to move that," he added.
Under the Fixed Term Parliament Act, if the government loses a vote on a motion of no confidence it has 14 days to pass a second confidence motion, or Parliament is dissolved and a general election is called.
If Labour fails to force a general election it will seek support in the Commons for another EU referendum.
Conservative support for a further referendum is growing - science minister Sam Gyimah quit the government on Saturday to join the People's Vote campaign.
A cross-party group of 17 MPs, in a letter published in the Observer, has also called for Parliament to support another referendum at the earliest opportunity.
But a referendum can only be held if the government legislates for one and a majority of MPs vote for it.
The People's Vote campaign, which is backed by about 30 Labour MPs, a smaller number of Conservatives, the Lib Dems, the SNP, Plaid Cymru and the Greens, argue that the public must be given the final say on the terms of Britain's exit, now that they know what the deal is.
Following Michael Gove's comments on the Marr show, Lib Dem Brexit spokesman Tom Brake said: "The government has made a Horlicks out of Brexit and now one of its chief architects has admitted that the final say might go back to the people."
He said the Lib Dems and "many others" will "demand a People's Vote with an option to remain in the EU".
Labour's shadow international development secretary Barry Gardiner told Andrew Marr he thought "remain and no-deal" would have to be "on the table" in any referendum.
But Sir Keir Starmer told Sky News he would be "worried" about no-deal being on the ballot paper, as it would be "catastrophic" for the country.
Michael Gove claimed the Leave campaign would probably win a fresh referendum by an even larger margin but holding one would "damage faith in democracy and rip apart the social fabric" of the country.
Many Leave voters would see it is a "condescending" move by the political establishment, who would effectively be saying people were "too thick to make a decision" the first time around, he told Andrew Marr.
By Laura Kuenssberg, BBC political editor
Support for the prime minister's Brexit compromise seems to be shrinking, rather than growing.
If Theresa May acknowledges it in private, she certainly won't touch that notion in public.
The government claims the chances of Britain leaving the EU on 29 March without a deal are more likely if MPs reject Mrs May's deal.
Mr Gove said there would not be another Commons vote on the deal if MPs voted it down on 11 December - something Mrs May has previously refused to rule out.
There has been speculation the prime minister could return to Brussels to ask for the deal to be modified to reflect MPs' concerns before putting it to another Commons vote.
The EU has said the deal it has agreed with Mrs May is their final offer and it will not be renegotiated.
They argue the UK will be kept tied to the EU with no say in its rules until Brussels decides it can leave, under the terms of the Northern Irish "backstop".
Mrs May insists the backstop, which is designed to keep the Irish border open until the UK can agree a free trade deal with the EU, would be temporary.
However, her former Brexit secretary Dominic Raab told the Sunday Times the backstop would last indefinitely - for as long as it takes to negotiate a new UK-EU relationship - "unless the EU allows us to exit".
Michael Gove told Andrew Marr he was also uncomfortable about the "backstop" but it would be temporary.
This was because it would hand the UK economy a "competitive advantage" over the remaining 27 EU nations, he argued.
Opponents of Theresa May's Brexit deal believe the UK's chief law officer, Geoffrey Cox, has advised the government that the Northern Ireland "backstop" would continue indefinitely.
They think this is why the government is refusing to publish Mr Cox's legal advice on the EU withdrawal agreement in full - as it would make it even harder for her to convince MPs to back her deal.
The government insists such legal advice is always confidential - and that MPs will be able to question Mr Cox about it on Monday, when he makes a statement to the Commons. MPs will start five days of debate on the deal on Tuesday.
But Labour is spearheading a cross-party effort - including the government's partners the DUP - to force the legal advice to be published, ahead of the debate.
Sir Keir, a former director of public prosecutions, said the opposition parties would press for contempt of Parliament proceedings if MPs are not shown the advice.
If contempt proceedings were requested, it would be up to Commons Speaker John Bercow to decide whether a debate and vote should be held.

The government has not proposed any changes to the PM's Brexit deal during cross-party talks, says shadow Brexit secretary Sir Keir Starmer.
Meetings have been taking place between Tory and Labour politicians to find a proposal to put to the Commons before an emergency EU summit next week.
But Sir Keir said the government was not "countenancing any change" on the wording of the existing plan.
A Downing Street spokesman said: "We have made serious proposals."
The government was "prepared to pursue changes to the political declaration", a plan for the future relationship with the EU, to "deliver a deal that is acceptable to both sides", the spokesman said.
Sir Keir said the government's approach was "disappointing", and it would not consider any changes to the "actual wording" of the political declaration. "Compromise requires change," he said.
"We want the talks to continue and we've written in those terms to the government, but we do need change if we're going to compromise."
The UK is currently due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by MPs.
Theresa May has written to European Council President Donald Tusk to request an extension to 30 June.
But she says if the Commons agrees a deal in time, the UK should be able to leave before European parliamentary elections on 23 May.
By Jonathan Blake, BBC political correspondent
Both sides say they are serious about these talks, but there is little to show for that so far.
Perhaps that's no surprise.
After more than two years of negotiations with the EU and months of wrangling in parliament, the idea that the government could sit down with Labour and thrash out a deal that keeps both sides happy in a few days seems optimistic at best.
There appears to be disagreement over what the talks can achieve; changes to the political declaration on the UK's future relationship with the EU, or an additional document to what has already been agreed?
If a deal is done, it may or may not fly. Plenty of Tory MPs are uneasy about working with Labour and the closer ties to the EU it may lead to.
Many Labour MPs want a further referendum regardless of what is agreed - something Jeremy Corbyn has been luke warm on so far.
At this stage a deal looks doubtful. But this is Brexit and stranger things have happened.
Prisons minister Rory Stewart told BBC Radio 4's PM programme that there were "tensions" but there was "quite a lot of life" left in the talks with Labour.
"In truth the positions of the two parties are very, very close and where there's goodwill it should be possible to get this done and get it done relatively quickly," he said.
He insisted that "of course we are prepared to compromise" on the political declaration.
BBC political editor Laura Kuenssberg said: "The sense is that the government has only offered clarifications on what might be possible from the existing documents, rather than adjusting any of their actual proposals in the two documents."
She added that both sides agree the talks are not yet over, but there are no firm commitments for when further discussions might take place.
In case no agreement has been reached by 23 May, the prime minister has said the UK would prepare to field candidates in European parliamentary elections.
BBC Europe editor Katya Adler has been told by a senior EU source that European Council President Donald Tusk will propose a 12-month "flexible" extension to Brexit, with the option of cutting it short if the UK Parliament ratifies a deal.
But French President Emmanuel Macron's office said on Friday that it was "premature" to consider another delay.

The government is set to publish the first in a series of technical notices designed to prepare the UK for the possibility of a no-deal Brexit.
The notices will include advice for businesses, citizens and public bodies.
Brexit Secretary Dominic Raab said securing a deal was still "the most likely outcome" - but added making alternative arrangements was the "responsible" thing to do.
The European Union has already produced 68 technical notices of its own.
Between late August and the end of September, government departments are expected to publish around 70 technical notices.
Mr Raab - who travels to Brussels this week to continue negotiations with the EU - said the advice was necessary to "mitigate the risks and make sure the UK is ready to make a success of Brexit".
He added the government wanted to "clearly set out the steps that people, businesses and public services need to take in the unlikely event that we don't reach an agreement" with the EU.
Downing Street described the advice due on Thursday as "sensible, proportionate, and part of a common sense approach to ensure stability, whatever the outcome of talks".
The day will also see Mr Raab make a speech in Westminster to outline the government's plans for the possibility of leaving the EU without a deal in March next year.
Downing Street said it wanted to ensure "consumers and businesses are not harmed" by the possibility of no deal being agreed.

The government has prepared the legal text of an updated Brexit deal, government sources have told the BBC.
It is expected to make more of the plans public in the next few days, a senior government figure says.
The government has suggested creating "customs clearance zones" in Northern Ireland and Irish Republic, as part of the proposals put to the EU.
But Ireland's Deputy Prime Minister Simon Coveney said the plans were a "non-starter".
In a tweet, Mr Coveney said Northern Ireland and the Republic of Ireland "deserve better" than the proposals, which were originally reported by Irish state broadcaster RTE.
Proposals for reaching a Brexit deal had been expected ahead of a crucial EU summit on 17 October.
The UK is due to leave the EU on 31 October, and Prime Minister Boris Johnson says this will happen whether or not there is a new deal with Brussels.
Mr Johnson says that he would prefer leaving with a deal.
At the Conservative Party conference on Monday, he said: "I'm cautiously optimistic. We have made some pretty big moves, we are waiting to see whether our European friends will help us and whether we can find the right landing zone."
MPs have passed a law, known as the Benn Act, requiring Mr Johnson to seek an extension to the deadline from the bloc if he is unable to pass a deal in Parliament, or get MPs to approve a no-deal Brexit, by 19 October.
With the detailed proposals on the table, the UK side hopes that by the end of the week, both the EU and UK would be in a period of intense negotiations where both sides thrash out a final text.
But there is no certainty over whether the EU will accept the premise of the plans in order to move to the next phase of talks.
The biggest obstacle to a deal is the backstop - the plan to prevent a hard border between Northern Ireland and the Irish Republic.
The policy - agreed to by former PM Theresa May in her withdrawal deal with the EU, which was rejected three times by Parliament - is unacceptable to many Conservative MPs.
Since becoming prime minister, Mr Johnson has stressed to EU leaders the backstop would have to be replaced if any deal was to be passed by Parliament.
Mr Johnson has argued that the backstop would keep the UK too closely aligned with EU rules after Brexit.
The EU Commission has said it is willing to look at new proposals but these must achieve the same aims as the backstop - and be legally enforceable.
Sources involved in the negotiations with the EU say the checks proposed would not be at the Irish border, and suggestions there would be a series of checkpoints along the border are a misunderstanding.
The proposals were rejected by political parties in Dublin and non-unionist politicians in Belfast, with the SDLP's Colum Eastwood saying there would be "economic and security challenges that are unacceptable".
"Anything that causes there to be customs, tariffs, checks anywhere represents a hardening of the border," she told Radio 4's Today programme.
"[It] goes against all of the commitments that have been entered into by the British government at the get-go of this Brexit process to protect the Good Friday Agreement, to ensure no hardening of the border, to respect the Irish economy, Irish society - to do nothing that would in anyway threaten or destabilise the situation," she added.
Shadow Brexit secretary Sir Keir Starmer described the proposals as "utterly unworkable".
Talks have continued between the UK and EU, at a technical level. Brexit Secretary Stephen Barclay and the EU's chief negotiator, Michel Barnier met on Friday.
The BBC has learnt the proposals will accept the need for customs checks on the island of Ireland - but insist these checks, as the government previously pledged, would be conducted away from the border.
Customs formalities would be carried out mostly where goods originate or at their final destination.
The UK government maintains that any further customs inspections would be very limited - and these could be conducted either at new locations or at existing business premises.
The Irish broadcaster RTE had reported that a "string of customs posts perhaps five to 10 miles away from the frontier" had been floated by the UK.
However, government sources have denied that UK officials had proposed a series of inspection posts on either side of the Irish border.
Leader of the Liberal Democrats Jo Swinson told the Today programme the proposals showed Mr Johnson was "not serious" about getting a deal.
"He knows that this is going to be rejected," she said.
Ms Swinson also said cross-party talks continued about how to ensure the Benn Act was "watertight".
She raised concerns that although Mr Johnson has promised to respect the rule of law, he has also promised to deliver Brexit on 31 October, with or without a deal.
"Those two things can't simultaneously be true," she said.

The government is trying to "purge" Tory rebels who oppose it over Brexit, ex-Justice Secretary David Gauke says.
A senior source from the whips' office - which ensures MPs vote on party lines - said those who voted to block no deal would be expelled and deselected.
The threat came as opposition MPs prepared to introduce legislation in an effort to avoid no deal.
Mr Gauke said the PM was seeking to "re-align" and "transform" the Tories "in the direction of The Brexit Party".
The prime minister has said the UK must leave the EU on 31 October, with or without a deal, prompting a number of MPs to unite to try to prevent the UK leaving without an agreement.
Meanwhile, speaking ahead of a meeting of the shadow cabinet, where Labour will finalise plans aimed at stopping no deal, Jeremy Corbyn said an election would be "the democratic way forward".
MPs will this week seek to bring forward legislation against no deal in Parliament, with specific details expected to be outlined on Tuesday.
But in a warning to Tory MPs thinking of supporting such efforts, a senior whips' office source said anyone who failed to vote with the government would lose the whip - meaning they would effectively be expelled from the party - and would not be able to stand as a Conservative candidate in an election.
The source said if Tory MPs fail to vote with the government on Tuesday they will be "destroying" its negotiating position and "handing control of Parliament to Jeremy Corbyn".
There was a chance of reaching a revised Brexit deal on 17 October - the date of the next EU summit - they added, but "only because Brussels realises the prime minister is totally committed to leaving on 31 October".
The Conservatives have a majority of just one, which includes a pact with the Northern Irish DUP, so if any Tory MP is kicked out - has the whip withdrawn - the party will go into a minority government.
Mr Johnson had been due to meet Tory MPs pushing to rule out no deal on Monday, but a source close to the group said the prime minister called off the meeting with no explanation.
Mr Gauke told BBC Radio 4's Today programme: "I don't think there seems to be a huge effort to persuade people to support the government this week.
"They seem quite prepared for a rebellion and then to purge those who support the rebellion from the party."
He said the government was "almost goading people into voting against" it to pave the way for a general election.
He later told the BBC's Victoria Derbyshire he would be prepared to lose his job to vote against no deal, saying: "I have to put what I consider to be the national interest first."
Under the Fixed Term Parliament Act, the prime minister could call a general election if two thirds of all MPs vote for one.
One could also be held if a motion of no confidence was passed and no alternative government was confirmed within 14 days.
Conservative MPs who have been vocal about their opposition to a no-deal Brexit include those who were ministers in Theresa May's cabinet only weeks ago.
As well as ex-Justice Secretary David Gauke, the group also includes former Chancellor Philip Hammond and former International Development Secretary Rory Stewart.
Other senior Tories like Ken Clarke and Oliver Letwin, both former ministers, have also said they would defy the government to stop no deal.
Beyond them, there is a much larger group of MPs - several dozen - who have suggested they do not agree with a no-deal Brexit, but have been less vocal about what action they would take. They include the likes of Greg Clark, Claire Perry, Ed Vaizey, Guto Bebb and David Mundell.
Tory MP Antoinette Sandbach, who has also said she would be prepare to lose her job to oppose a no-deal Brexit, told BBC Breakfast she had not been contacted by the whips' office.
"The decision has been made without the government even seeing the legislation that we're likely to be voting on tomorrow, so it seems to me that this is a very deliberate attempt to try and purge the Conservative Party of moderate, sensible voices," she said.
Nick Boles, the independent MP who quit the Conservatives over Brexit, told BBC Radio 4's Today programme the party had been "taken over" by the "hard right".
"The Conservative Party has fallen prey to an almost religious obsession with the hardest form of Brexit, which is obviously a Brexit with no deal," he said.
He said this was made clear with the resignation of Scottish Tory leader Ruth Davidson last week, who he described as a "progressive, modern, liberal Conservative".
Boris Johnson was elected with a promise of sticking to his Brexit deadline, come hell or high water.
If MPs make that impossible this week, he may well choose instead to press the button on another campaign, and go to the country.
I understand calling an election, maybe even this week, is one of the options under consideration.
But his team is well aware that chunks of the electorate might be pretty cross about going to the polls again.
So cranking up the pressure on Tory rebels at the start of this crucial week could create a convenient group of bogeymen who could be chucked out of the party, and take the blame.
On Sunday, cabinet minister Michael Gove refused to guarantee Downing Street would abide by any legislation aimed at stopping no deal.
David Gauke has subsequently written to the attorney general - the government's senior law officer - demanding the government commits to following the rule of law.
Doing otherwise could "undermine the institutions and values we all hold dear", he wrote.
Privately, Mr Johnson's critics are warning they will seek a judicial review of the government's action should ministers choose to flout the will of Parliament by ignoring a no-deal law.
Education Secretary Gavin Williamson told the BBC it was "perfectly normal" for a government to take the time to see how any new legislation would impact Brexit negotiations, but insisted: "Every government stands by the law."
He said he did not believe any anti no-deal legislation would be passed by Parliament and hoped that Tory MPs would "rally round" the prime minister this week.
Meanwhile, former Prime Minister Tony Blair has warned a general election would be an "elephant trap" Labour must not fall into and Brexit must be "resolved" first.
But Labour leader Jeremy Corbyn said in a speech in Salford he did still want one.
"In that election Labour will give people the chance to take back control and have the final say in a public vote... including the option to Remain," he added.
He also called the prime minister's plans to shut down, or prorogue, Parliament "an attack on democracy that will be resisted".
Mr Johnson has said he asked for the suspension in order to hold a Queen's Speech - which sets out a list of laws the government hopes to get approved by Parliament - on 14 October.
But Labour says the suspension is to force through a no-deal Brexit.
Any new law has to pass all stages of both Houses of Parliament - this usually take weeks but could be done in as little as three days this week.
The bill could be challenged by the government and fall at any stage. It could fail to achieve enough support from either MPs or peers in votes held in the Houses.
This could be a tight timetable as there are as few as four sitting days before Parliament is suspended. This is due to happen between Monday, 9 September, and Thursday, 12 September, under plans announced by the prime minister.
Another hurdle for any bill could come in the Lords. Although opponents to no deal have a large majority, peers wanting to block legislation could talk until there is no time left.

Just hours ahead of UK Prime Minister Theresa May's touch-down here in Brussels, there is evidence - once again - of a yawning gulf between what's being hinted at by her office and the EU's reality.
Downing Street expects a revised Brexit deal in the offing, possibly ready for the House of Commons to vote on early next week. EU chief Brexit negotiator, Michel Barnier, is still talking about a "worrying political impasse".
Jean Claude Juncker, the president of the European Commission, says he expects no breakthrough during his meeting with Mrs May - but that is polite language compared to what I'm hearing behind the scenes.
Of course, it depends exactly what she asks for.
If the prime minister is looking for legally-binding assurances that the backstop mechanism to guarantee the Irish border will remain open after Brexit is not a trap or a permanent EU-UK post-Brexit solution, then EU diplomats tell me they could draw that up "anytime, 24/7".
That is, if Mrs May thinks it would be enough to get the Brexit deal through Parliament.
But few, if any, believe that would suffice for all MPs in the European Research Group, plus the DUP, to vote "yes" to the deal next week - never mind all the uncertainty in Parliament now caused by resignations from Labour and Theresa May's Conservative party.
And if the prime minister still wants backstop "assurances" to include a unilateral exit mechanism for the UK or a fixed, immovable end date, then she will meet an EU wall.
This is because the backstop is also a fallback mechanism for the EU to protect its single market.
The idea in Westminster that the EU will "blink in the end" rather than face a no-deal Brexit is correct, in that the EU is more flexible than it has previously indicated.
But the extent of its flexibility is grossly over-estimated by many MPs.
True, the EU has past form in budging at the last minute in high-stake negotiations like the Greek debt crisis - but only when it was deemed to be in the bloc's greater interest.
In the case of Greece, the EU decided to bend the rules to save, in the opinion of its leaders, the wider euro currency.
But watering down or abandoning the backstop mechanism altogether is thought to be damaging to the EU.
However much EU leaders want to avoid a no-deal Brexit, leaving exposed a 500km (310-mile) gap is thought to be far more costly for them in the long term. That is because of the risk of non-EU regulation goods being smuggled into the wider single market via Northern Ireland and the rest of the UK.
That perceived threat to the single market means the EU will not abandon or fundamentally weaken the backstop unless there is a watertight alternative in place.
Last week, a group of Dutch politicians came back from the UK lamenting what they described as the "lack of knowledge" and "lack of interest" amongst many in Westminster about how the EU works.
The lack-of-knowledge part is also being said in Brussels of the UK's Attorney General Geoffrey Cox, on whom so much Downing Street hope is now riding in order to try to get a deal though Parliament.
While the House of Commons has swirled in increasing turmoil over the last few weeks, little at all has changed in EU-UK talks.
The current impasse over the Brexit deal still comes down to the UK disliking the backstop mechanism.
EU countries dislike it too, by the way, and would rather never use it - but the EU is "only" offering legally-binding clarifications or assurances to express this - as well as ways to avoid triggering the backstop altogether.
One example of the latter would be the UK agreeing to a permanent customs union.
But Downing Street insists those ideas won't fly in the House of Commons.
EU officials believe any breakthrough, if found, will materialise next month. If not, the EU is getting ready to grant an extension to the UK's leaving process - Brexit is due to happen on 29 March. They realise, too, that MPs may call for that extension even earlier.
But the tone is noticeably hardening in Brussels.
EU officials say if no progress is made with the UK, regardless of any extension time, then they will use those extra months to deepen their planning to protect themselves from a no-deal Brexit.
Of course, to an extent, this is fighting talk, designed to increase the pressure on the UK.
So are the repeated declarations of EU unity over Brexit by Michel Barnier, the EU's chief Brexit negotiator, as he tours European capitals.
That said, I have been struck of late by a growing sense in the EU as time goes by that a no-deal Brexit – though highly undesirable – will be manageable for them, while still very damaging to UK.

The European Council has said that Brexit talks can enter the second phase following last week's agreement.
As a result it has published its guidelines for the next stage of talks.
Here are some of the key phrases from that document.
Don't forget that there are plenty of crucial details that still need to be resolved before negotiations on a withdrawal agreement come to an end.
That means the financial settlement, citizens' rights and of course, the Irish border.
Sufficient progress is not the end of the story, but the text also makes it clear that there will be a concerted effort to lock in what has been agreed so far - and that if the EU detects any reluctance or backsliding from the UK then that will have a negative effect on discussions about the future.
Theresa May has already agreed that a transition of about two years will take place under existing EU rules and regulations, but the EU's text makes crystal clear what it believes that means.
The UK will have to accept all EU law (that's what the acquis means) including new laws passed during the transition itself.
But it will no longer have a seat at the table when those laws are made. To put it brutally - the UK will, for a while, become a rule-taker rather than a rule-maker.
Both sides talk of a strictly time-limited transition period, so there doesn't appear to be much appetite at the moment for extending it.
Quite what happens if a future trade deal isn't ready by the end of the transition, a scenario many experts think is quite possible, will have to be debated in the future.
During the transition, the UK will have to accept the full jurisdiction of the European Court of Justice, and all four freedoms - including the freedom of movement of people.
The EU says the UK will remain in the single market and the customs union during a transition, while the UK insists that it will leave both on Brexit day.
This could become a semantic argument, because by accepting all rules and regulations - in other words, the status quo - the UK will remain in the single market and the customs union whether it likes it or not.
The British government has suggested that some things - like dispute resolution mechanisms - could change during the transition as agreement is made on future co-operation. But there's little appetite in the EU for that - in its view, you're either in or you're out.
The EU 27 stress that they want a close partnership with the UK in the future, but here they are setting out the limits of what they could mean.
The further away the UK wants to be from the rules and regulations of the single market the less access it will have - there is no such thing as partial membership.
This gets us back to the unresolved debate about what "full alignment" at the Irish border really means in practice.
The phrase "preserve a level playing field" is important too. The EU is anxious to ensure that the UK doesn't try to undercut the EU in any way by having looser regulations in certain key areas, and, if it does, then there will be consequences.
EU negotiators won't have the authority to start discussions with the UK on future relations (including trade and also things like security and foreign policy) until another set of guidelines is adopted in March 2018.
That gives the two sides not much more than six months to agree the text of a broad political declaration on the outlines of the future relationship.
The EU hopes to get that finalised by October 2018, but it emphasises that formal trade negotiations can only begin after the UK has left the EU.
Informal contacts on what the future might look like are probably taking place already, but the EU is still waiting for greater clarity from London about what exactly the UK government hopes to achieve in the long term.
The UK is trying to be as ambitious as possible about what can be done before Brexit actually happens. The EU, though, emphasises that trade talks will have to continue long after the UK has left.
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Any interim deal between the UK and the EU should not be allowed to become "eternal", according to a key figure in the negotiations.
Guy Verhofstadt, the European Parliament's chief Brexit negotiator, said any "transitional arrangement" should have a strict time limit.
A House of Lords report has warned of significant tariffs and other barriers to trade unless one is adopted.
And Chancellor Philip Hammond has said an interim arrangement may be needed.
But other ministers have reportedly expressed reservations in private and ex-UKIP leader Nigel Farage told the BBC he feared talk of interim deals was part of "backsliding" and attempts to "delay" the Brexit process.
The UK is scheduled to begin official negotiations on the terms of its exit from the EU by the end of March, when Prime Minister Theresa May has said she will trigger Article 50.
From that moment, the rules say that Britain will have  two years to agree a deal before it leaves the EU.
But getting an agreement on Britain's future trade with the EU may take much longer.
Ministers have hinted they could agree some kind of transitional process to avoid a shock to the economy, with Mr Hammond telling MPs on Monday that this could go some way to ensuring a "smoother transition".
Speaking on BBC Radio 4's The World at One, Mr Verhofstadt said a transitional deal was "certainly possible".
But he warned: "I have seen many times in politics that a so-called transitional agreement becomes an eternal, a definitive, agreement - that has to be avoided."
In a new report on the options for trade after Brexit, the House of Lords EU external affairs committee said the government should set out a clear plan at the start of negotiations, including specific proposals for what form any transitional deal could take.
The peers said that staying in the EU customs union - a move opposed by many Conservative MPs - could be an important element of such a deal.
And they warned that if there were no transition, the UK would have to rely on World Trade Organization rules for its trading arrangements, which would mean British firms facing significant tariffs and other barriers to trade.
BBC assistant political editor Norman Smith said Downing Street was insisting a transitional deal would not be part of a "softening up process" to prepare people for the UK being "entangled" with the EU for years to come.
He added that there was a "tension" between ministers who want to leave the EU first before negotiating, and those like Mr Hammond who think this would be "profoundly risky".
Former Conservative minister Anna Soubry told BBC Radio 4's Today programme a transitional arrangement would offer "real benefits", saying the alternative would involve the UK "dropping off the cliff edge".
She said she and her fellow Remain campaigners accepted the Brexit vote and that it was time for both sides to "come together".
Her fellow Conservative Peter Lilley was more cautious about the prospects of a transitional deal, saying that negotiating one could take as long as reaching a permanent agreement.
Mr Lilley said there was "no reason" the UK could not secure a free trade arrangement with the EU without having to continue with the free movement of people.
Brexit minister David Jones was asked about the possibility of a transitional arrangement as he arrived at an EU summit in Brussels.
"What we've always said is that we don't want to have a disruptive end to Britain's participation in the EU," he said, adding that a "smooth withdrawal" was the government's goal.
But the Leave Means Leave campaign said: "A transitional deal is absolutely unnecessary and poses a huge threat to the UK economy."
It said such an arrangement would involve the UK paying "extortionate sums of money to the EU" and would cause "serious uncertainty".
The government has committed itself to publishing some form of plan before it notifies the EU of its intention to leave but it is unclear how detailed this will be.
Business has expressed concerns about the impact of a "cliff-edge" departure from the EU, leading to speculation about temporary measures to soften the blow - including paying to retain tariff-free access to the single market.
In a speech at Bloomberg in London, shadow Brexit secretary Sir Keir Starmer said Labour could amend any bill giving the government authority to trigger Article 50 in order to avoid a so-called "hard Brexit" involving quitting the EU single market.
He insisted this could be done without delaying the Brexit process.
Sir Keir said Labour wanted to see tariff-free trade for UK businesses, no new "bureaucratic burdens", protection for the competitiveness of the services and manufacturing sectors and for workplace protections to be maintained.
He also said Labour should not fall into the "trap" of trying to "frustrate" Brexit, saying the stance adopted by the Liberal Democrats - who are promising a second referendum on the terms of the exit package - "cannot heal the rift in our society".
In response, the Conservatives said Labour supported the government's Brexit timetable in public, "but behind closed doors they talk about second referendums and now seek to attach conditions and tie the government's hands".

Chancellor Philip Hammond has said he is "optimistic" Brexit discussions between the government and Labour can reach "some form of agreement".
Mr Hammond said there were "no red lines" in the meetings.
But Labour leader Jeremy Corbyn said he was "waiting to see the red lines move" and had not "noticed any great change in the government's position".
Three days of talks ended on Friday without agreement and Labour said no more talks were planned this weekend.
Downing Street responded by saying it was prepared to pursue alterations to the deal and ready to hold further discussions with Labour over the weekend.
The talks have been taking place to try to find a proposal to put to MPs which could break the Brexit deadlock in the Commons before an emergency EU summit on Wednesday.
Speaking ahead of an EU finance ministers' meeting in Bucharest, Mr Hammond told reporters: "We are expecting to exchange some more text with the Labour Party today, so this is an ongoing process."
Mr Hammond said: "We should complete the process in Parliament... Some people in the Labour Party are making other suggestions to us. Of course, we have to be prepared to discuss them.
"Our approach to these discussions with Labour is we have no red lines. We will go into these talks with an open mind and discuss everything with them in a constructive fashion."
Speaking while campaigning for next month's local elections in Plymouth, Mr Corbyn suggested votes in Parliament were now the most likely way of providing a breakthrough on Brexit, saying his key priority was "to avoid crashing out of the EU with no deal".
Mr Corbyn told the BBC: "We have a party position on the future relationship with Europe... and we will responsibly discharge those duties, but we are determined to make sure there is no crashing out."
The prime minister has been unable to get Parliamentary backing for the withdrawal agreement she secured with the EU in November last year, which sets out the terms of the UK's departure.
Labour has said it wants fundamental changes to a document drawn up at the same time, known as the political declaration. It sets out ambitions for the future relationship between the UK and EU after Brexit - including on trade, regulations, security and fishing rights - but does not legally commit either party.
Shadow home secretary Ms Abbott told BBC Radio 4's Today programme that Labour had engaged in the talks "in good faith" and shadow Brexit minister Sir Keir Starmer had written to the government to say he wants them to continue.
She said there was concern that the government has made "no movement" on altering the political declaration and "that is key".
A Downing Street spokesman said after Friday's talks that "serious proposals" were made and it was "prepared to pursue changes to the political declaration in order to deliver a deal that is acceptable to both sides".
BBC political editor Laura Kuenssberg says there was a sense that the government has "only offered clarifications on what might be possible from the existing documents, rather than adjusting any of their actual proposals".
She added that both sides agreed the talks are not yet over, but there were no firm commitments for when further discussions might take place.
The UK is due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by the House of Commons.
Prime Minister Theresa May has written to European Council President Donald Tusk to request an extension to the Brexit process until 30 June but says if MPs agree a deal, the UK should be able to leave before European parliamentary elections are held on 23 May.
She says the UK would prepare to field candidates in May's European Parliament elections if MPs failed to back a deal.
But education minister Nadhim Zahawi told the Today programme it would be "a suicide note of the Conservative Party if we had to fight the European elections".
He added the elections would pose an "existential threat" to both the Conservatives and Labour if they "haven't been able to deliver Brexit".
Mr Zahawi suggested that if an agreement could not be found from the talks with Labour, MPs should be asked to find a compromise on a deal through a preferential voting system.
Any extension to the UK's departure would have to be unanimously approved by EU leaders.
A senior EU source told BBC Europe editor Katya Adler that Donald Tusk would propose a 12-month "flexible" extension, with the option of the UK leaving sooner once Parliament had ratified a deal.
French Europe minister Amelie de Montchalin said such a delay would require the UK to put forward a proposal with "clear and credible political backing".
"In the absence of such a plan, we would have to acknowledge that the UK chose to leave the EU in a disorderly manner," she added.
Irish Prime Minister Leo Varadkar told RTE it was unlikely that a UK request for a delay would be vetoed by any EU member nations as it could cause economic hardship in the bloc and "they wouldn't be forgiven for it".
But he said there was growing frustration from some nations which see Brexit as distracting from other things.

Philip Hammond has told business chiefs their Brexit fears can be resolved without staying in the customs union.
The chancellor rejected claims by the CBI president that continued membership was a "plan A" option "already out there" to minimise disruption to trade.
While the UK's post-Brexit customs options were "works in progress", he was sure a solution would be found.
Meanwhile, Boris Johnson has insisted the UK should leave the customs union "as fast as is reasonably possible".
Speaking on a trip to Argentina, the foreign secretary said the UK should establish its own trade policy outside existing customs arrangements "with all convenient speed".
The UK is leaving the EU in March 2019, which will be followed by a temporary transition phase until the end of 2020.
Most Brexiteers are against Theresa May's preferred option of a "customs partnership", under which the UK would collect tariffs set by the EU customs union on goods coming into the UK.
The alternative proposal would rely on technology and advance checks to minimise, rather than remove, customs checks. The EU has expressed doubts about whether either option would work.
Speaking at the employers' group's annual dinner, outgoing CBI president Paul Drechsler said the lack of political progress on the two proposals was a "hand-brake on our economy that can and must be released".
He urged ministers to be more pragmatic, telling Mr Hammond "there is already a solution out there that is our plan A, to choose to stay in a customs union with the EU, unless and until a better alternative can be found".
Mr Hammond said the government shared the CBI's desire to "minimise frictions and burdens, to avoid new barriers in Ireland and to grow British exports".
"But we do not agree that staying in the customs union is necessary to deliver them," he said.
Building on the two models under consideration, he said ministers were "confident we can develop a solution that will allow us to move forward while meeting your concerns".
Mr Johnson told Bloomberg that the UK needed to have its own trade and commercial policy, including its ability to set its own tariffs on goods from the rest of the world.
"The PM is the custodian of the plan which is to come out of the customs union, out of the single market and to get on with that project with all convenient speed," he said.
"That is what we're going to do. And what people like Argentina, Peru, Chile, outward looking free trading countries, what they want to hear from us is that we're getting on with it, with confidence and brio and zap and dynamism."
The UK has drawn up a "backstop" proposal in case customs arrangements have not been agreed by then, which would keep the UK aligned with the EU's customs union for a limited period.
Theresa May has insisted the plan, designed to avoid a hard border in Northern Ireland if the new arrangements are not ready in time. would only apply "in a very limited set of circumstances".
Mr Johnson, who is due to head to Chile on Wednesday on the final leg of his tour of South America, also suggested he would like to have a "Brexit plane" to help him travel the world and promote the government's vision of Global Britain.
While acknowledging that taxpayers would baulk at the cost of buying a jet for ministers, he said he thought the spending would be justified if it was not "exorbitant".

Chancellor Philip Hammond has signalled he would be prepared to vote against a no-deal Brexit in Parliament, claiming it could cost the UK up to £90bn.
Leaving the EU without a legal agreement would be the "wrong" policy and cause a huge "hit" to the public finances, he told MPs.
He said it was "highly unlikely" he would still be in his job after Theresa May stands down next month.
But he said it would be up to MPs to ensure no-deal "doesn't happen".
Shadow chancellor John McDonnell asked Mr Hammond at Treasury questions if he would join Labour in voting against no deal and opposing any attempt by a new prime minister to stop Parliament sitting in order to let a no-deal Brexit go ahead.
Meanwhile, the United Kingdom Warehousing Association has told BBC Newsnight that UK warehouses are "full", raising doubts about the ability of UK firms to stockpile goods ahead of a potential no-deal Brexit on 31 October.
Boris Johnson and Jeremy Hunt, the two men vying to succeed Mrs May, have both said they would be willing to take the UK out of the EU without a deal.
Mr Johnson has refused to rule out shutting down - proroguing - Parliament to push it through.
In reply to Mr McDonnell, the chancellor said: "I do agree with him, it would be wrong for a British government to pursue no deal as a policy and I believe it will be for the House of Commons, of which I will continue proudly to be a member, to ensure that doesn't happen."
In the event of no deal, the UK would immediately leave the EU with no agreement about the "divorce" process and leave both the single market and customs union - arrangements designed to help trade between members by eliminating checks and tariffs (taxes on imports).
The chancellor has been a long-term critic of a no-deal exit, making him something of a bogeyman among Brexiteers within his own party.
In recent days, Mr Hammond has questioned both leadership candidates' promises of greater spending and tax cuts if they make it to Downing Street.
He has insisted there is "no pot of money" sitting in the Treasury for extra spending or tax cuts and, in the event of a no-deal exit, all the £26bn "headroom" in the public finances would be absorbed by dealing with the economic upheaval.
"I have no doubt whatsoever that in a no deal exit we will need all of that money, and more, to respond to the immediate impacts of the disruption of a no deal exit," he told MPs.
"And that will mean there is no money available for either tax cuts or spending increases."
"But let me go further - the government's analysis suggests that in a disruptive no-deal exit there will be a hit to the Exchequer of about £90bn. That will also have to be factored in to future spending and tax decisions."
The Treasury has previously said a no-deal exit could lead to a £80bn spike in borrowing.
Speaking after Treasury questions, Mr McDonnell told reporters he felt the chancellor had been "ferocious" in his criticism of no deal and would be "influential" on the matter from the backbenches - if indeed that was where he found himself under a new Tory leader.
He said there was a "solid block" of Conservative MPs who would join Labour and other opposition parties in opposing a no-deal outcome.
Asked how Labour would prevent a no-deal Brexit, Mr McDonnell said the "window of opportunity was short" but the moral authority of Parliament would be in question if MPs repeatedly voted against it and yet the new prime minister went ahead anyway.
Meanwhile, the leadership contenders have been taking part in a hustings in Belfast where they were asked about their attitudes to no deal and their plans to solve the so-far intractable issue of the Irish border.
BBC assistant political editor Norman Smith said the difference between them was largely tonal - Mr Hunt has a tone of regret rather than enthusiasm when it comes to the prospect of no deal, while Mr Johnson seems almost keen to get to that point and the huge opportunities he sees in its aftermath.
Our correspondent also said the feeling in Team Johnson is that the desire among Tory MPs to fight a no deal may be fading.

Chancellor Philip Hammond has told the BBC's Andrew Marr Show that businesses are holding off from investing in the UK because of uncertainty about Brexit.
"It is absolutely clear businesses where they have discretion over investment, where they can hold off, are doing so - you can understand why.
"They are waiting for more clarity about what the future relationship with Europe will look like," he said.
The second round of Brexit negotiations take place in Brussels on Monday.
Mr Hammond's comments came as a Confederation of British Industry (CBI) survey suggested that 42% of UK firms believe Brexit has hurt their investment plans.
The CBI called on the government to quickly secure a future EU trade deal.
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Mr Hammond said that government ministers were becoming increasingly convinced of the need for transitional arrangements to reduce disruption as the UK leaves the EU.
"Five weeks ago the idea of a transition period was quite a new concept, I think now you would find that pretty much everybody around the cabinet table accepts that there will be some kind of transition," he said.
"We're into a real process now with the start of negotiations and I think you'll find the cabinet rallying around a position that maximises our negotiating leverage and gets the best possible deal for Britain."
He said a transitional arrangement was "right and sensible both for the UK and EU" and could potentially take a "couple of years".
Analysis: Joe Lynam, BBC business correspondent
When companies make a big investment, they tend to make a big splash about it. Press releases issued, stock exchanges advised and ministerial blessings acquired.
But when businesses decide NOT to invest in new staff, a new production line or even a new product, we rarely get to hear about it.  Companies pausing or cancelling investment  - for whatever reason - is counter-factual.
So surveys and anonymous polling are the next best way to gauge the corporate mood.
Although some Brexiteers regard the CBI as a pro-EU vassal, its survey showing two-fifths of companies pausing their investment plans because of Brexit is not an outlier. It chimes with similar reports from the British Chambers of Commerce, Deloitte and the Institute of Directors.
And who would blame firms for holding off? If their biggest market could soon be in or out of the Single Market, in or out of the Customs Union, and beholden or not to the ECJ, it does matter for their future investment plans.
Brexit minister David Davis is due in Brussels on Monday for the next round of talks with EU officials.
Ministers have talked of a transitional period after the UK leaves the EU to avoid a "cliff edge" scenario, but the length and precise arrangements have yet to be decided.
Speaking on the BBC's Sunday Politics show, International Trade Secretary Liam Fox said any transitional period should be "very time-limited", and should allow the UK to strike new trade deals - something it is unable to do as part of the EU's customs union.
Mr Fox accepted it was not clear whether the UK would have the power to finalise deals during this period.
Pressed on whether the UK could even negotiate during the transition, he said: "Well, I'd hope we'd be able to do that and I hope that's one of the conditions we would set."
He added: "It's certainly something I would want to see because otherwise it makes it much more difficult for us to take advantage of the opportunities that Brexit itself would produce."
Rain Newton-Smith, chief economist at the CBI business lobby group, said: "To help British business remain optimistic and keep uncertainty at bay, the government must work quickly to agree the terms of the [Brexit] transition and future trading arrangements.
"That's why the CBI has suggested staying in the single market and a customs union until a final deal comes into force.
"This is the simplest way of ensuring companies don't face a damaging cliff-edge and that trade flows can continue without disruption."
Labour says it would seek to preserve all the benefits of the single market and customs union if it was leading the negotiations.
Shadow business secretary Rebecca Long-Bailey told the Sunday Politics that Labour could seek to retain full membership of both bodies.
But she admitted it was "probably unlikely" a deal could be struck giving Labour control over laws and borders at the same time.
"If we could negotiate an agreement on remaining in the single market that dealt with all of those issues, then that would be fantastic," she said.
"Whether that's likely remains to be seen.
"We want to retain the benefits that we currently have within the customs union. We want to have our cake and eat it - as do most parties in Westminster - in terms of being able to negotiate our own trade deals."

Philip Hammond has warned the EU the UK will "go it alone" and build a new satellite navigation system if shut out of the Galileo project after Brexit.
The chancellor said the UK wanted to remain a "core member" of the EU-wide scheme, which it has helped pay for.
But if this was not possible, he said the UK would develop a rival scheme as access to the data satellites provided was vital for national security.
The issue has become an emerging dividing line in the Brexit talks.
The UK has demanded £1bn back from the EU if the bloc carries through on its plan to exclude Britain from Galileo, which was developed by the European Commission and the European Space Agency.
Brussels has cited legal issues about sharing sensitive information with a non-member state - but the UK has said the row could harm wider post-Brexit security co-operation and "risks being interpreted as a lack of trust in the United Kingdom".
Arriving for a meeting of European finance ministers on Friday, Mr Hammond - regarded as the cabinet's chief advocate of the closest possible links with the EU after Brexit - issued a stark warning.
"We need access to a satellite system of this kind, our plan has always been to work as a core member of the Galileo project, contributing financially and technical to the project," he said.
"If that proves impossible then Britain will have to go alone, possibly with partners outside Europe and the US to build a third, competing system. But for national security strategic reasons, we need access to a system and we'll ensure that we get it."
By BBC political correspondent Jonathan Blake
There is nothing like a common enemy to unite a divided group.
The EU's threat to freeze the UK out of its satellite navigation system has riled both Brexiteers and Remainers at the very top of government.
Philip Hammond, one of the most Brexit-sceptic figures in the cabinet, has talked of the UK "going it alone" with its own rival project.
In stark contrast, just the day before he'd spoken of "shared challenges" and "unshakeable commitments" between the UK and the EU.
If the line from Brussels that the UK is chasing a "fantasy" was designed to anger the other side it appears, at least in part, to have worked.
But it may also have helped galvanise UK officials' resolve to negotiate hard with the full backing of the cabinet.
Britain's aim of turning Galileo into a shared post-Brexit project is "a big ask" according to the EU, but that is different to saying it cannot or will not happen.
So it may also be the case that the government senses this is a fight it can win, and is upping the ante accordingly.
Labour seized on Mr Hammond's comments, suggesting they showed the government was willing to spend "billions of pounds" on an alternative space programme at a time of continuing austerity in public services.
"It's time the chancellor came down to Earth to prove he is on the same planet as the rest of us," said the shadow chancellor John McDonnell.
Amid growing tensions over post-Brexit security co-operation, a senior EU official on Thursday attacked the UK's "fantasy" approach to negotiations which they described as "let's just keep everything we have now".
Mr Hammond said such comments were "not particularly helpful" given the clock was ticking down to the UK's March 2019 exit and both sides needed to make significant progress by the next month's summit of European leaders.
"There are obviously a wide range of views on both sides but everybody that I've engaged with has been very constructive and very keen to find a way to move forward," he said.
The UK, which has one of Europe's largest military budgets and most sophisticated intelligence operations, has said it wants a separate defence and security treaty with the EU to enshrine existing co-operation.
On Friday, the UK published a paper making clear that agreement on the exchange of classified information was essential for future co-operation in a range of areas, such as common EU security and defence operations.
Among "ongoing commitments" that could be put in doubt include Operation Sophia, the Italian-led naval mission combating illegal migration in the Mediterranean which is being assisted by the Royal Navy and Operation Althea, a peacekeeping mission which upholds the 1995 Dayton Agreement in Bosnia-Herzegovina.
"Without access to documents of this kind, the UK would not be able to manage the risk of deployments and would not be able to commit personnel or assets," the document says.
The UK says it is in both sides' interest for it to maintain its "significant" role within the EU's Intelligence and Situation Centre and also points out that the UK's National Cyber Security Centre regularly shares intelligence with EU partners and helps attribute major attacks across the continent.
The UK wants a similar agreement to those the EU has with the US and Canada but says "existing networks" should be used to ensure no interruption in co-operation and that different security protocols should apply depending on how widely information is disseminated.

Philip Hammond's "no risk" approach to Brexit is causing problems for Theresa May, an ex-colleague has said.
Former Brexit Secretary David Davis told the BBC's Political Thinking podcast the chancellor was among those advising the prime minister "we can't take that risk and don't do that".
Mr Hammond has said no-one voted for Brexit to end up worse-off.
Meanwhile, leading Brexiteer Liam Fox has said getting MPs' support is vital and any deal can be "revised" later.
The UK is due to leave the EU on 29 March 2019. The negotiations have entered a crucial phase, with the two sides hoping to reach an agreement by the middle of November at the latest.
With the clock ticking, Mr Fox, the international trade secretary, has warned colleagues to focus on getting an agreement that can command the support of Parliament, where Mrs May has a slim majority and has already suffered several defeats over Brexit.
He and Mr Hammond are supporting the PM's Chequers plan for a free trade zone for goods, underpinned by a common rule book, unlike Mr Davis and Brexiteers outside government who say the plan should be ditched in favour of Canada-style free trade deal.
The chancellor is seen by Brexiteers as being too cautious and too ready to believe leading businesses' concerns about the economic impact of the UK leaving the EU without a deal and Treasury forecasts about the negative effect on economic growth and the public finances.
Mr Davis, who quit the cabinet in July in protest at the direction of Brexit policy, suggested that despite being an "old mate of mine", Mr Hammond was acting as a brake on the chances of getting the best possible deal.
Mr Davis told the BBC's Nick Robinson that the chancellor had been among ministers saying "we can't take this risk; we can't take that risk" which, he suggested, had made things more difficult for him, as a negotiator.
"Philip's an old mate of mine. But the truth is that you've got several ministers, not just him, in the background, issuing noises saying 'we don't mean this'. Well we bloody do!'".
However, on a trip to South Korea, Mr Fox said the "reality" facing all those who believed in Brexit was that any deal had to get through the Commons, where the PM relies on the Democratic Unionists for her majority.
"While I may be very sympathetic with those who take an ideologically purist position, we are also politicians whose job it is to deliver," he told Bloomberg.
"We must leave and we must leave on 29 March - not to deliver Brexit is the greatest political risk we could run.
"We should try and get as much of a final deal as we can get by 29 March but it is self-evident that if it is a bilateral treaty, it can be revised later on."
Brexiteers are divided on whether an imperfect deal can be improved after the UK's departure.
Environment Secretary Michael Gove has suggested it can be modified later, but former foreign secretary Boris Johnson has said this is "pie in the sky".
Ahead of the next summit of EU leaders later this month, the main sticking point to an agreement remains finding a solution to the issue of avoiding a hard border between Northern Ireland and the Republic of Ireland.
Both sides are under pressure to modify their so-called "backstop" proposals to prevent the return of physical checks at the border while protecting the EU's single market and the UK's internal market.
You can listen to the Political Thinking podcast with Nick Robinson

Conservative leadership candidate Matt Hancock has proposed an "Irish Border Council" as part of his Brexit plan.
Mr Hancock said it would aim to find a way to maintain a soft border and allow the UK to have an independent trade policy.
He said the council would be chaired by an independent figure, using the example of Senator George Mitchell's role in the NI peace process.
He added that he would also seek a time limit to the backstop.
The backstop is a position of last resort to maintain an open border on the island of Ireland.
It would see the whole of the UK stay in the EU's customs union and Northern Ireland stay in the single market for goods.
It would apply "unless and until" a deep trade deal or a technological solution, sufficient to keep the border as open is it is now, was agreed.
Mr Hancock claimed the EU has "previously mooted adding a time limit to the backstop".
The Irish government has always strongly resisted a time limit, saying it would undermine the point of the backstop.
Mr Hancock said his border council would involve all parties in Northern Ireland and have a role for the Irish government and EU.
He said it would aim to find a "long-term political, administrative and technological solution".
The proposal from Mr Hancock has a focus on technology, but he said any solution would require the political will and consent of communities on both sides of the border.
Meanwhile, another candidate - Sajid Javid - has said his Brexit plan also hinges on coming up with an alternative to the backstop.
Speaking on The Andrew Marr Show, he said: "I will focus on the one Brexit deal that has already got through Parliament. That was the withdrawal agreement with a change to the backstop."
He added: "[Ireland] is the tail that wags the dog on this and we need to make sure we can do more to build that goodwill in Ireland and build their confidence.
"What I would do is make a grand gesture to Ireland that we would cover all their costs - the upfront costs, the running costs - of a new digitised border.
"I think it could be done in a couple of years, but I think we could cover their costs."
Later Ireland's Europe Minister Helen McEntee reiterated Ireland's position.
She tweeted a clip of Mr Javid adding the comment: "The Withdrawal Agreement will not change. The backstop cannot change.
"Much of what was in the  Withdrawal Agreement was asked for by UK. They were not bystanders in the two years it took to negotiate.
"Bit of realism needed."

Outlining her plans for the UK leaving the EU, Theresa May said Brexit means leaving that union.
It currently allows tariff and paperwork-free trade between the UK and the Republic of Ireland.
But the prime minister said: "Full membership of the customs union prevents us from negotiating our own comprehensive trade deals."
She said she would now seek to negotiate a new customs deal with the EU, which would allow tariff-free trade to continue.
However, if a deal cannot be achieved it could lead to the return of some form of customs checks along the Irish border.
Posting on social media, Former Deputy First Minister Martin McGuiness said "a border of the future is coming at us".
What is a customs union and why does it matter?
A customs union is a form of trade agreement between two or more countries.
It means they decide not to impose tariffs (taxes on imports) on each other's goods and agree to impose common external tariffs on goods from countries outside their customs union.
Setting common external tariffs is what distinguishes a customs union from a free trade area.
The key argument for leaving the customs union is that it will allow the UK to negotiate its own trade agreements.
"Warm words, soft words from Theresa May mean nothing."
He added: "Her intentions to leave the Single European Market and her intentions to leave the customs union are going to have a detrimental impact on the economy in the north and across this island.
"It's clear today from Theresa May's Brexit statement that the views and opinions of the people of north have been completely ignored."
SDLP leader Colum Eastwood said "nowhere will be more damaged" by the plan outlined by Mrs May than Northern Ireland.
"If the British Government can negotiate special arrangements on the common travel area, they can negotiate special arrangements for trade and customs.
"No free trade customs access across the island means a hard Brexit in Ireland. It means a hard border."
DUP MP Sammy Wilson said the prime minister's statement would give the business community "more certainty".
"I further welcome that the prime minister has set out her plan for an ambitious Free Trade Agreement with the European Union, whilst here in Northern Ireland we will also maintain the Common Travel Area with the Republic," he said.
UUP economy spokesperson Steve Aiken said his party welcomed the prime minister's intention to retain the Common Travel Area between the UK and the Republic of Ireland.
He also said it was "deeply concerning" that "there is no one expressing the unique needs" of Northern Ireland after the dissolution of the Stormont assembly.
Alliance Party deputy leader Stephen Farry described Mrs May's speech as "catastrophic for Northern Ireland".
"Any departure from the customs union and the single market will necessitate a formal border either across the island of Ireland or down the Irish Sea."
He added: "A one-size-fits-all Brexit is just not practical. There are too many factors and circumstances particular to Northern Ireland.
"Yet, these have not yet been recognised and respected by the UK government."
Taoiseach (Irish prime minister) Enda Kenny said he welcomed the "clarity" brought by Mrs May's speech.
However, he was criticised by Micheál Martin, the leader of the Republic's main opposition party Fianna Fail, who said Mrs May may be speaking softly but was acting in her own national interest.
He said Mrs May wanted to have her cake and eat it in her approach to Brexit.
The British and Irish Chamber of Commerce said the prime minister's pledge on leaving the customs union and EU single market would be "alarming for businesses".
The Northern Ireland Independent Retail Trade Association (NIIRTA) said governments in London, Dublin and Belfast must "ensure that Brexit does not result in the hardening of the border and that no barriers whatsoever are placed on trade or workers across the EU".
A group that represents Irish business, IBEC, hit out at the speech on social media saying  "(The) UK's aggressive Brexit approach risks damaging UK-Irish relations."
During her speech earlier on Tuesday, the prime minister said maintaining the common travel area between the UK and Republic of Ireland would be a priority during Brexit negotiations.
She said: "No-one wants a return to the borders of the past.
"Our guiding principle must be to ensure that as we leave the European Union no new barriers to living or doing business within our own union are created.
"The United Kingdom will share a land border with the EU and maintaining that common travel area with the Republic of Ireland will be an important priority for the UK in the talks ahead."
In a statement, a spokesperson for the Irish government said that while the prime minister's comments may be seen as a warning of a "hard Brexit", Dublin has been preparing for all possible models of future UK-EU relations.
Mrs May also said she hopes that the "main parties" in Northern Ireland will form a government as soon as possible in the "spirit of unity".
She added that the UK government had received papers from Scotland and Wales on Brexit, but did not mention receiving any papers from Northern Ireland.
NI Secretary James Brokenshire was legally obliged to call for the 2 March vote on Monday after the executive collapsed over a botched green scheme.
Stormont was plunged into crisis after the resignation of Martin McGuinness as deputy first minister last week.

Did the prime minister just make it worse? It hardly seems that would have been possible.
Her agreement with the EU had been sharply kicked out several times by MPs. She'd promised that she would quit and get out of the way if that bought more support. Then she took the risk of talking to the political enemy to try to get a different deal.
But those measures failed - leaving her hope this time to dangle a bauble to each of Parliament's different Brexit tribes in the much more extensive plan of how she'd actually put our departure into law.
But even before she started talking, many MPs simply weren't listening.
After she finished, public rejections from almost all quarters started to pour in.
Of course, the vote itself on this bundle of measures won't be for at least a week - a lifetime in this hyper-speed world. A lot could change.
But the diplomatic way of describing the situation tonight? Compromising when no one else is interested in consensus is impossible.
The more brutal political interpretation - Theresa May's mishandling of this whole situation has, over many, many months, pulled her deeper and deeper down into a quagmire of her own creation.
An attempt at this stage to ask others for understanding to help her escape is just too late - far, far too late. Now some Conservative minds are turning to whether she can stay on to have this vote at all.

It's all about the money.
The UK and the EU have managed together to make a tiptoe forward in the Brexit talks.
But listening to EU leaders this afternoon it is abundantly clear that unless they change their minds, the UK is going to have to budge on the cash to make enough progress by December to be able to truly get on to the next phase of talks.
Certainly public money is tight in this administration, but frankly a hefty Brexit bill in exchange for a good deal would be the one big payment that the Chancellor Philip Hammond would be happy to sign off.
A move on the money is, therefore, primarily a political problem rather than anything to do with the actual funds.
There are whispers that Theresa May has privately reassured the other leaders that she is willing to put a lot more than the implicit 20 billion euros (£17.8bn) on the table as we leave.
Number 10 doesn't deny this, Mrs May didn't deny it when we asked her in the press conference today, nor did she reject the idea that the bill could be as high as 60 billion euros.
If she has actually given those private reassurances though, there's not much evidence the other EU leaders believe her or think it's enough.
But if she is to make that case more forcefully she has big political problems at home.
A much bigger payment is anathema to many Conservatives, and could frustrate swathes of voters who plumped for Brexit, in part on a promise that the country would get money back.
Number 10 is well aware of this.
One insider told me "it's all about the quantum," what "the party would swallow'.
Could a party with a powerful group of Brexiteers, including ministers who have gone on the record to say we shouldn't be shelling out much, really tolerate the prime minister calling for support to pay tens of billions?
This is not a question for now, but it has been logged for future reference inside Number 10.
Will there be a day when the prime minister decides to make a plain admission to the country, that the potential cost of leaving with no deal is a scarier prospect than having to cough up as much as 60 billion euros? About half what we spend on the NHS, but more than we spend on defence?
Or will she be pushed by those in her party who genuinely believe that is far better to cut our losses and walk out, than commit to an expensive deal.
Carrying her party and her European counterparts at the same time is Theresa May's fundamental challenge - on the face of it almost impossible.
And today's tiptoe forward is no guarantee that ultimately she will be able to go all the way.
PS There's lots of speculation that when the French President said the UK was not even "half way there" he was hinting that the bill could therefore be ultimately at least double 40 billion euros.
It wasn't really clear during the press conference that is what he meant, or whether he was using "half way there" to describe the state of the negotiations.
However, for ages in Westminster there has been an expectation that the eventual bill will be somewhere in that region, somewhere between 40 and 60, so it is not crazy to imagine that Macron's comments are further evidence that's the case.

Senior Tory Lord Heseltine has said he will rebel against the government when peers debate the bill giving Theresa May the authority to trigger Brexit.
He said he would support an opposition amendment in the House of Lords demanding MPs get a meaningful vote on the deal reached with the EU.
Writing in the Mail on Sunday, he denied this would be a "confrontation".
But Home Secretary Amber Rudd told ITV's Peston on Sunday programme: "I hope he will reconsider."
Last week peers gave an unopposed second reading to the European Union (Notification of Withdrawal) Bill, following a two-day debate involving more than 180 speakers.
MPs have already backed the proposed law, authorising Prime Minister Theresa May to inform the EU of the UK's intention to leave.
Opposition peers want to amend the bill at a later date to guarantee the rights of EU citizens in Britain and the role of Parliament in scrutinising the process.
As the government does not have a majority in the Lords, it is vulnerable to being outvoted if opposition peers - including Labour's 202 and the 102 Lib Dems - join forces.
Mrs May has said she wants to invoke Article 50 of the 2009 Lisbon Treaty - the formal two-year mechanism by which a member state must leave the EU - by the end of March, and the government has warned the House of Lords not to frustrate the process.
Lord Heseltine wrote in the Mail on Sunday: "The fightback starts here. My opponents will argue that the people have spoken, the [Brexit] mandate secured and the future cast. My experience stands against this argument."
He also wrote: "This is not a confrontation with the government. It is to ensure the Commons can exercise its authority over the defining issue of our time."
The former deputy prime minister, whose leadership challenge to Margaret Thatcher helped trigger her exit from Number 10 in 1990, campaigned for Remain in the run-up to the referendum.
He has been a long-standing supporter of the EU within the Conservative Party and backed the idea of the UK joining the single currency.
Ms Rudd said: "The fact is the House of Commons, which he was such a fantastic member of in his time, did pass it by a big majority
"I hope he will reconsider. There'll be plenty of opportunities to debate."
Labour backed the government in backing the bill in the Commons.
In a speech to the Scottish Labour Party conference in Perth, Labour leader Jeremy Corbyn said: "I accept that Brexit has unleashed uncertainty, instability and concern amongst many, many people. But we cannot simply wish away the result.
"Can you imagine the reaction from those 17 million people, including one million from Scotland, who voted to leave the European Union if we simply ignored them?"
However, Gina Miller, the investment manager who brought the successful legal challenge against the government, forcing the Article 50 issue to a vote in Parliament, accused the Commons of "cowardice" in giving the bill a "rubber stamp".
She told the Independent: "I am hoping the Lords actually do what they should be doing constitutionally, exercising their parliamentary sovereignty, being independent, scrutinising the government and looking to put in amendments."
Appearing on BBC One's Andrew Marr Show, she also said: "The will of the people does not negate the weight or wisdom of the Houses of Parliament."
But Conservative Party chairman Sir Patrick McLoughlin told the same programme: "The bill got an overwhelming majority, one of the biggest majorities a bill has got on its third reading in the House of Commons and it's gone to the House of Lords.
"The prime minister has said that there will be a vote once the negotiations are concluded. The prime minister won't conclude the negotiations if she thinks she's got a bad deal."
The Leader of the House of Commons, David Lidington, told BBC Radio 4's The Westminster Hour: "We'll listen, with respect as always, to the Lords when they debate the bill."
But he added that he hoped peers would not amend it, suggesting that to do so would go against the will of the people: "I still hope that the Lords will, at the end of the day, accept that this bill is in a particular position, unusual position, because of the referendum result."
Richard Tice, co-chairman of the pro-Brexit Leave Means Leave campaign, said: "It is of little surprise that Lord Heseltine - who has historically put the interests of the European Union ahead of those of Britain - will try to sabotage Article 50.
"Lord Heseltine's attempt to weaken the position of the prime minister ahead of negotiations with the EU is a truly unpatriotic act."

Leading German figures have written to the UK asking it to stay in the EU.
The letter, published in the Times, is signed by 31 people, including the leader of the Christian Democratic Union - and likely successor to Angela Merkel - Annegret Kramp-Karrenbauer and former Arsenal goalkeeper Jens Lehmann.
They cited post-work pints and pantomime as beloved British habits.
But the UK's role in post-war Europe is the focus of the signatories calling for Britain to stay.
"Without your great nation, this Continent would not be what it is today," they wrote.
The letter - also signed by the chief executive of Airbus, Thomas Enders, and punk singer Campino - said the UK had helped define the European Union as a community of "freedom and prosperity".
"After the horrors of the Second World War, Britain did not give up on us," it continued.
"It has welcomed Germany back as a sovereign nation and a European power.
"This we, as Germans, have not forgotten and we are grateful."
The signatories said that they "respect the choice" of British people who want to leave the EU and, if the country wants to leave for good, "it will always have friends in Germany and Europe".
But they said the choice was not irreversible and "our door will always remain open".
The letter concluded: "Britain has become part of who we are as Europeans and therefore we would miss Britain.
"We would miss the legendary British black humour and going to the pub after work hours to drink an ale. We would miss tea with milk and driving on the left-hand side of the road. And we would miss seeing the panto at Christmas.
"But more than anything else, we would miss the British people - our friends across the Channel.
"Therefore Britons should know, from the bottom of our hearts, we want them to stay."

The Brexit Secretary has said he understands Tory "jitters" about EU negotiations but urged MPs to hold their nerve as talks continue.
"The end is in sight in terms of a good deal, the prize we want," Dominic Raab said, asking them to "wait and see".
It comes amid newspaper speculation that Theresa May could face a vote of no confidence from Tory MPs.
On Saturday, protesters marched through London to call for a public vote on whatever Brexit deal is negotiated.
Some Tory MPs were angered last week by a suggestion that the post-Brexit "transition period" - designed to smooth the path between the UK leaving the EU in March 2019 and a future long-term relationship with Brussels - could be extended.
Ex-Tory leader and prominent Brexiteer Iain Duncan Smith said that would see the UK paying the EU "tens of billions" more and he said the negotiations "look more like a capitulation".
Moray MP Douglas Ross said Scotland's 13 Conservative MPs would not support a deal if the UK remained part of the Common Fisheries Policy beyond 2020.
And Tory backbencher Andrew Bridgen told the Mail on Sunday Theresa May was "drinking in the last chance saloon" and must attend a meeting of the 1922 committee of Conservative backbenchers this week.
Mr Raab told the BBC's Andrew Marr Show that he was "open minded" about the possibility of extending the transition period - which the government calls the implementation period - for about "three months or so" if needed, as long as it was clear how the UK would get out of it, to avoid "any sense that we are left indefinitely in a sort of customs union limbo".
He said: "I think it's understandable there are jitters on all sides of this debate and we need to hold our nerve. The end is in sight in terms of a good deal - the prize we want - a good deal with the EU and I think colleagues should wait and see what that looks like."
He added: "We won't want to bring something back which we aren't confident is a very good deal for the United Kingdom.  But now is the time to play for the team, I think that's the way we get the best deal for the EU and I also think that's what the country expects from us."
Asked if, realistically, the withdrawal agreement could still be being negotiated after November, he replied: "I think if it went any distance beyond that we would have a problem with implementing the deal, and it would almost be the worst-case scenario - we'd have a deal but couldn't implement it in time."
Meanwhile Brexit minister Suella Braverman has told the BBC's Pienaar's Politics that she supports the prime minister, but refused to say whether she would back her in a confidence vote.
She said: "I don't think there will be a vote of confidence in the prime minister and I am supporting the prime minister unequivocally and I want her to get on with the job to deliver Brexit and I know that she will be doing that."
The UK voted to leave the EU by a margin of 51.89% to 48.11% in a referendum in June 2016.
It is due to leave on 29 March 2019 but during the post-Brexit "transition period", set to run until 31 December 2020, the UK-EU relationship will stay largely the same.
If at the end of that period, a long-term "future relationship", including trade deal, is not ready, both sides have agreed on the need for provisions to ensure there is no need for customs checks - a "hard border" - between Northern Ireland and the Irish Republic, in the interim period.
This is called the "backstop" - but the two sides have yet to agree on what form it should take and how long it could last.
On Saturday, protesters took part in a huge march to London's Parliament Square to call for another referendum - this time on any final Brexit deal that is negotiated. Organisers say it attracted about 700,000 people.
Labour's shadow Brexit secretary Sir Keir Starmer said the march reflected "a much bigger group, both Leave and Remain [voters], who are utterly losing confidence in the prime minister's ability" to bring back a good deal.
Asked if Labour MPs would back Mrs May in Parliament, rather than risk a "no deal" exit from the EU, he said: "We do not accept this proposition it's that or no deal, and it's not just us. There's a huge majority in Parliament that will not accept that the alternative to Theresa May's deal, if there is one, is no deal."
He added: "I don't think anybody thinks this 30-year civil war in the Tory party on Europe is going to end before Christmas.
"What we're going to see is even if there's a deal, the Tory party will try to rip it up next year... They will not stop fighting about this.
"We've got to the very serious situation where people are saying 'Is this government actually capable of delivering because it's so divided?'."
There has been criticism of the language reported from unnamed Tory sources about Mrs May's future as Conservative leader about her entering the "killing zone" and telling her to "bring your own noose".
Scotland's First Minister Nicola Sturgeon tweeted:
Former cabinet minister Theresa Villiers, a Brexiteer, described the newspaper comments as "disturbing" while the Conservative peer Lord Lilley told BBC News the language was "unpleasant and objectionable": "On either side, that sort of language should not be used."

The European Union (EU) has agreed a Brexit delay until the end of October and preparations have started to take part in the European elections on 23 May.
Prime Minister Theresa May says if a deal gets through Parliament before that date, the UK will not participate. But it seems likely that the UK will still be in the EU at that point.
The European Parliament is directly elected by EU voters.
It is responsible, along with the Council of Ministers from member states, for making laws (proposed by the European Commission) and approving budgets.
It also plays a role in the EU's relations with other countries, including those wishing to join the bloc.
Its members represent the interests of different countries and different regions within the EU.
Every five years, EU countries go to the polls to elect members of the European Parliament (MEPs).
Each country is allocated a set number of seats, roughly depending on the size of its population. The smallest, Malta (population: around half a million) has six members sitting in the European Parliament while the largest, Germany (population: 82 million) has 96.
At the moment there are 751 MEPs in total and the UK has 73.
Candidates can stand as individuals or they can stand as representatives of one of the UK's political parties.
Once elected, they represent different regions of the country, again according to population. The north-east of England and Northern Ireland have three MEPs each while the south-east of England, including London, has 18.
While most UK MEPs are also members of a national party, once in the European Parliament they sit in one of eight political groups which include MEPs from across the EU who share the same political affiliation.
Member states can run elections to the European Parliament according to their own national laws and traditions, but they must stick to some common rules. MEPs must be elected using a system of proportional representation - so, for example, a party which gains a third of the votes wins a third of the seats.
Turnout in the UK for European Parliament elections is low both by EU standards and by the standards of other UK elections.
The last time they were held in 2014, 36% of those eligible to vote did so, compared with 43% in the EU as a whole.
That compares with 66% turnout at the following year's general election.
In 2016, 56% of the electorate voted in the Scottish Parliament elections, 45% in the Welsh Assembly and 54% in the Northern Ireland Assembly.
In local elections in England, turnout varies depending largely on what other elections are taking place on the same day, sometimes dipping as low as the European elections turnout and sometimes rising close to the level of general elections.
The last time European elections were held in 2014, the UK spent £109m on them.
The main costs were running the poll itself (securing polling stations and venues to run counts) and mailing out candidate information and polling cards.
The government has said that if the UK does not end up participating in the 2019 elections, it will reimburse local returning officers - the people responsible for running elections - for any expenses already paid.
The EU is planning to reduce the overall number of seats in the parliament from 751 to 705 when the UK leaves.
There will be a reallocation of 27 of the UK's seats to 14 other member states that are currently underrepresented. And the rest will be set aside with the possibility of being allocated to any new member states that join in the future.
The EU has already passed legislation to do this, but it does not take effect until the UK leaves.
The number of seats is capped in law at 751.
The European Commission had advised that as long as the UK made a decision to take part in the European elections by mid-April, this reallocation would be reversed.
But what if the UK elects MEPs and then passes a deal to leave the EU?
In that case, the UK MEPs would not take their seats, leaving vacancies.
The House of Commons Library says that extra MEPs could potentially be elected on "stand-by" in some member states but not take up their seats until the UK leaves the EU.
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It was an early-hour announcement that allowed many of the UK's business owners to finally get a few hours of restful sleep.
In Brussels on Thursday, the EU granted the UK a six-month extension, thus eliminating the immediate threat of a no-deal Brexit.
But for companies that have been preparing for a sudden exit, it was no more than a temporary reprieve.
"It's a bit of uncertainty that isn't helpful," says Andrew Graham. His 70-year-old company, Graham and Brown Wallpaper, has been stockpiling raw materials for months at its factory in Blackburn.
"Quite frankly, we could do with knowing where we're going," he told the BBC.
"An extension is better than a no deal, but actually we could do with getting the withdrawal deal through so that business can then plan for what it needs to do."
Joy Parkinson, who runs a Bury-based company selling natural beauty products, is more sanguine.
The Faith in Nature boss says Brexit is a hurdle, "but not insurmountable".
"We've been buying additional stock of the lovely fragrances we buy in from Europe, to make sure we were covered if there were issues around ports and blockages," she says.
"We were anticipating that some of our partners in European markets might have wanted to buy extra stock," Ms Parkinson explains, but that scenario never materialised.
"We've not overbought, so we've been fairly sensible and fairly pragmatic, we've not bought six months, 12 months of additional material, so we've managed the cash flow fairly pragmatically."
Nottingham florist and former Apprentice contestant Elizabeth McKenna has felt the impact of Brexit uncertainty much more strongly.
Her business, and her industry, are part of a finely tuned supply chain.
"We order and buy our flowers from Holland online," she explains. Orders need to be confirmed by 10:00 so as to meet auction deadlines in the Netherlands.
The flowers are then transported overnight via rail and ferries, and any delay could mean they arrive wilted or dead.
The initial Brexit date of 29 March, Ms McKenna explains, was just two days before her company's busiest day of the year - Mother's Day.
"That actually created an increase in commodity prices, because of the uncertainty with the exchange rate during that week which has directly affected profits within my industry.
"As far as trying to plan for what is going to happen with Brexit, we are a small industry... and we haven't had enough information to plan."
"Literally all that florists and people working at my level can do, as small independent businesses with 10 people, is wait and see what the government tells us."
Ms McKenna says small business have only received one or two Brexit-related letters from the likes of HMRC,
"We're essentially just saving money, cutting our costs where we can and are waiting to weather whatever is to come."
Other business have already had to absorb large additional costs.
Sloane's Hot Chocolate is made in a studio in Surrey - but sold in Waitrose, Harrods, and overseas to the US, Canada, Singapore, Dubai and Ireland.
It's one of many small businesses for which a further Brexit extension isn't merely a waiting period, but comes at a significant price.
Founder Brian Watt says the company's suffering began the day after the referendum in 2016, when the pound dropped sharply against the dollar.
This led to a 20% increase in the cost of its main ingredient - chocolate. The company chose not to pass that on to customers, instead eating into its profit margins.
Then, with a no-deal looming, Sloane's was told by one supplier that the price of their product would go up by 20% or 30%, forcing Mr Watt to stockpile.
"Whereas we would normally hold maybe one to two weeks supply of those items, we are now holding one to two months," he told the BBC, "because we would find it very difficult to pass on 20 to 30% price increases to our customers."
To help with the upfront costs of buying up supplies such as packaging, Sloane's had to secure a large overdraft from a bank.
But Mr Watt is stoic in the face of many more months of uncertainty.
"We basically made the decision that we are just going to get on with running our business," he says.

He did it, sort of. The prime minister has said he'll ask MPs to back an election in seven weeks time, just in time for Christmas.
The government's laying the motion tonight to hold the vote on Monday, trying to lay down the gauntlet to the opposition parties, who can keep him trapped in Number 10 if they like.
Remember this time last week there was delight in Downing Street that they had overcome expectations and agreed a deal with the EU.
But that euphoria fell away on that side of the argument, when MPs booted out the timetable to debate and pass all the new laws that would actually make Brexit happen.
For some of those objecting, it's a part of the ruse to stop our departure. But many others had what they considered entirely legitimate concerns about the speed with which he was trying to ram it through
Number 10's wheeze now is to dangle the offer of a few extra days of scrutiny to get it through, but only if MPs give in to Boris Johnson's other demand, backing to go to the ballot box soon after.
'Have the extra time you called for, but only if I get my ultimate prize' he's asking Parliament.
Downing Street knows full well however that opposition MPs are unlikely suddenly to swoon for this new timetable, it is hardly much extra time for scrutiny.
And while there are cabinet ministers who reckon it would be better to try as hard as possible with the bill, calmly and on a more conventional timetable, the dominant view in government is that there really is not a serious chance of the Brexit legislation getting through unmangled, so the only way, reluctantly for some, is to push the button for an election.
And this is where it gets very sticky for the government.
What happens next is partly dependent on exactly how the EU responds to the UK request for delay to Brexit.
That will become clear either on Friday or Monday. Although President Macron is understood to be on board for a short extension that would focus the minds, apparently texting as much to the prime minister on Thursday, the wider view in the EU is not expected to fall in line with that.
You can Precisely how they respond will shape the opposition parties' next moves. They might even, whisper it, come up with a fudge.
Boris Johnson cannot be remotely sure Labour and the smaller parties will let him have his way. The SNP and the Lib Dems are both tempted to go for an election as soon as a three month delay is agreed.
The Labour Party's official position has always been that they would agree to an election, in fact officially they are chomping at the bit, like the other parties, as long as a delay is agreed.
One senior member of the shadow cabinet predicted they would not be able to withstand the pressure if the Lib Dems and the SNP said yes.
Jeremy Corbyn himself, and certainly one group in his camp, are understood to be very tempted too. But, just as in 2017, lots of Labour MPs are horrified at the idea, partly because of Labour's standing in the polls.
But also, there are senior shadow cabinet ministers who believe the smart thing would be to leave the PM in his purgatory, twisting, unable to get his bill through, unable to get to an election.
In short, the position is fluid, and Labour is having words with itself tonight.
Plenty of Tory MPs worry that Labour will pursue precisely a delaying tactic - "like a boa constrictor they will slowly squeeze Boris until his novelty fun factor starts to grate".
If Boris Johnson therefore is totally and utterly stuck in a few days time, he in turn vows that he would raise the temperature even higher, to turn an already fraught and bizarre situation into something completely extraordinary, making MPs vote day after day after day on whether or not to have an election, and bringing forward no business to the House of Commons - the government going on a form of political strike.
The belief in Number 10 is that while it might be hellish getting there, in the end the logic moves towards the opposition allowing an election, in the end.
(There are also other ways you might remember to get there - a one line bill, a vote of no confidence - methods that Number 10 would also be willing to try, where they only need a majority of one vote, rather than two-thirds majority he needs under the election legislation.)
Either way, the opposition's final responses to the prime minister's gambit tonight are not final. They will wait to see exactly what the EU says.
What is obvious though is that the prime minister's 'do or die' Brexit deadline has disappeared. Whether his vow to get an election is one he is able to keep is also not in his control.
There will be no budget, there may not be an election, and there may not be Brexit any time soon, and depending what happens next there may not really be a government either in any traditional sense of the word.

Foreign Secretary Jeremy Hunt has warned the UK faces "Brexit paralysis" if MPs reject Theresa May's EU deal.
He said two Commons defeats this week showed Parliament was "committed one way or another to try to stop no-deal".
But that would risk "no Brexit", he argued, which would be a "breach of trust" with the public.
Tory rebel Dominic Grieve said it was the duty of MPs to "stop people committing national suicide" by going ahead with a no-deal Brexit.
He told a rally of supporters of another referendum in London that while the prime minister had done her best in negotiating the deal to honour the referendum result, while minimising the damage, the "unpleasant truth" was that "it can satisfy no-one".
"There is only one way out," he said.
"When the prime minister's deal is defeated, what else can we possibly offer to the British public which has any coherence at all but to go back and ask them to reconsider their decision?"
Mr Grieve, who tabled the amendment that led to a government defeat on Wednesday, has been at the forefront of cross-party efforts to ensure MPs have a say in what happens if Mrs May's deal is rejected.
The prime minister is widely expected to lose next Tuesday's vote on the withdrawal deal negotiated between the UK and the EU - with more than 100 Conservative MPs and the DUP, which usually support the Conservatives in Commons votes, among those set to vote against it.
Labour will also oppose the deal but leader Jeremy Corbyn has resisted growing calls from within his own party to get behind another EU referendum, insisting a general election is still his top priority if the deal is rejected.
"We're going to get smashed" - one government insider's apocalyptic prediction about one of the most important votes in recent political history.
As things stand, MPs are on course to kybosh Theresa May's long-argued-over Brexit deal, with a very heavy defeat.
Dozens of her own backbenchers have said publicly they will vote against it.
The opposition parties are adamant they will say "no" too.
Speaking to BBC Radio 4's Today programme, Mr Hunt said it was clear the Parliamentary arithmetic was "challenging".
LIVE: MPs continue Brexit debate
"We have a government that is committed to delivering Brexit, but it doesn't have a majority and we have seen this week that there is a Speaker who is willing to frustrate the government at every opportunity."
Commons Speaker John Bercow has been accused of bias by some Tory MPs over his decision to break with Parliamentary precedent by allowing a vote on Dominic Grieve's amendment to a government motion, which handed MPs more control over the Brexit process.
Mr Bercow said he was acting in the interests of MPs and had made an "honest judgement".
In a shift of tone, apparently aimed at winning over Brexiteers who are determined to vote Mrs May's deal down, Foreign Secretary Mr Hunt also warned that defeat for the government on Tuesday would not lead to them getting the kind of Brexit they wanted - and could lead to Britain staying in the EU.
"If this deal is rejected, ultimately what we may end up with is not a different type of Brexit but Brexit paralysis.
"And Brexit paralysis ultimately could lead to no Brexit.
"I'm saying this would be (an) incredibly damaging breach of trust and it would also be very bad for Britain's reputation abroad, having decided to leave the EU, if we in the end for whatever reasons found we weren't able to do it."
He acknowledged that MPs opposed to Brexit were flexing their muscles, telling Today: "After this week the idea that Parliament is going to do nothing at all is highly unlikely."
But he rejected the idea of holding a series of votes to find out what kind of Brexit MPs would support, as some have suggested, claiming there was no consensus for any alternative to Mrs May's plan.
"Everyone's had a crack at what they thought was their top outcome but we are all democrats and we have a responsibility to deliver the outcome the British people voted for."
The PM's deal was "not perfect" but it did "broadly deliver Brexit", despite arguments about the Irish backstop, he added, and urged MPs to "come together" to back it.
He was speaking as MPs prepared for the third of five days of debate on Mrs May's deal, with Home Secretary Sajid Javid opening proceedings.
If you feel like you ought to know more about Brexit...
Shadow Home Secretary Diane Abbott pointed to a warning from former MI6 chief Sir Richard Dearlove and former Armed Forces chief, Field Marshal Lord Guthrie that the deal negotiated with the EU would threaten national security.
She told MPs that Labour was "committed to honouring the referendum vote" but added: "This deal, as it stands, potentially abolishes the complex and highly-effective co-operation that has been established between this country and other members of the EU in the areas of freedom, justice and security."
The UK is set to leave the European Union on 29 March.

Theresa May has dismissed speculation she could be ousted as prime minister over her Brexit agreement, saying: "I am going to see this through."
Despite a series of ministers resigning and talk of a no-confidence vote, she vowed to get the deal signed off in Brussels and to put it to MPs.
"The course I have set out is the right one for our country," she said.
The BBC understands Michael Gove has rejected Mrs May's offer to become the new Brexit secretary.
BBC political editor Laura Kuenssberg said Environment Secretary Mr Gove had said he might accept - if he could try to make changes to the negotiated deal.
Sources said Mrs May made it clear that was not possible. He is now considering his position and contemplating resignation.
Other sources have told the BBC a wider group of ministers were discussing whether to try to force the PM to seek changes to the deal.
Earlier, Brexit Secretary Dominic Raab and Work and Pensions Secretary Esther McVey both quit in protest at the withdrawal agreement, along with two junior ministers.
And leading backbench Brexiteer Jacob Rees-Mogg submitted a letter of no confidence in Mrs May to Sir Graham Brady, chairman of the Tories' backbench 1922 Committee.
A vote will be triggered if 48 Tory MPs write letters to Sir Graham - it is understood 48 letters have not yet been received.
Mrs May spent nearly three hours fielding largely critical questions from MPs before holding a press conference in Downing Street to further answer her critics.
She acknowledged the agreement negotiated with the EU had entailed "difficult and sometimes uncomfortable decisions".
"I understand fully that there are some who are unhappy with those compromises but this deal delivers what people voted for and it is in the national interest," she said.
"We can only secure it, if we unite behind the agreement reached in cabinet yesterday.
"If we do not move forward with that agreement, nobody can know for sure the consequences that will follow.
"It will be to take a path of deep and grave uncertainty when the British people just want us to get on with it. They are looking to the Conservative Party to deliver."
Asked if she would carry on as prime minister if she won a no-confidence vote by a single vote, Mrs May said: "Leadership is about taking the right decisions, not the easy ones."
She said her job was to "bring back a deal that delivers on the vote of the British people".
She added: "I believe this is a deal which does deliver that, which is in the national interest and am I going to see this through? Yes."
The prime minister, a cricket fan, was asked if she would "resign as captain", but told journalists Geoffrey Boycott, famed for his batting marathons, was one of her sporting heroes: "And what do you know about Geoffrey Boycott? Geoffrey Boycott stuck to it and he got the runs in the end."
Amid suggestions she was struggling to fill the two cabinet posts vacated by Dominic Raab and Esther McVey earlier on Thursday, she joked: "I have had, actually, rather a busy day."
The BBC understands that Environment Secretary Michael Gove had been offered the job as Brexit Secretary but had asked for assurances that he could pursue a different kind of deal.
Mrs May said Mr Gove was doing "an excellent job at Defra" adding: "I haven't appointed a new Dexeu [Department for Exiting the European Union] secretary yet and I will be making appointments to the government in due course."
By BBC Political Editor Laura Kuenssberg
The government, for today at least, is at the mercy of events not in control.
Theresa May's vow to stay does not make her deep, deep problems disappear.
With her party in revolt, her colleagues departing - some determined to usher her out of office - we can't, and don't know yet, if Brexit can happen as planned, perhaps, if at all.
This could be a gale that's weathered in a few days, or a serious storm that sweeps the government away.
Read Laura's blog
Meanwhile German Chancellor Angela Merkel said there was no appetite for further talks on possible amendments to the current agreement: "We have a document on the table that Britain and the EU 27 have agreed to, so for me there is no question at the moment whether we negotiate further."
Despite a warning from Tory backbencher Mark Francois earlier that it would be "mathematically impossible to get this deal through the House of Commons", Mrs May said she believed, ultimately, her MPs would back it.
"I'm committed, as prime minister, to bringing the best deal back to the UK. I think MPs across my party who look at that deal will recognise the importance of delivering on the vote of the British people and recognise the importance of doing that in a way that does protect people's jobs, protect security and protect the unity of our United Kingdom."
But Liberal Democrat leader Sir Vince Cable suggested the prime minister was "in denial": "The facts haven't changed. There is no majority in Parliament for her deal, and she has rightly conceded that "No Brexit" is the real alternative to it."
He said it strengthened the case for another referendum "to break the deadlock and get the country out of this mess".
Earlier Labour Leader Jeremy Corbyn described the deal negotiated with the EU as "half-baked" and urged her to withdraw it.
He told MPs: "This is not the deal the country was promised and Parliament cannot - and I believe will not - accept a false choice between this bad deal and no deal."
But Northern Ireland Secretary Karen Bradley defended the prime minister, saying "there is no better person to do this job".
She said collective responsibility meant that ministers who could not support the deal were required to resign, but added: "The majority of the cabinet is behind it. The remaining members of the cabinet are absolutely behind this deal and what we need to do now is get behind the prime minister and get that deal sorted in the November (European) Council."

Prime Minister Theresa May has insisted she had to reach out to Labour in a bid to deliver Brexit or risk letting it "slip through our fingers".
The PM said there was a "stark choice" of either leaving the European Union with a deal or not leaving at all.
And shadow business secretary Rebecca Long-Bailey says if no-deal became an option Labour would consider "very, very strongly" voting to cancel Brexit.
Some Tories have criticised the PM for seeking Labour's help on her deal.
Commons Leader Andrea Leadsom said the Tories were working with Labour "through gritted teeth", adding that no deal would be better than cancelling Brexit.
MPs have rejected Mrs May's Brexit plan three times and last week's talks between the two parties were aimed at trying to find a proposal which could break the deadlock in the Commons before an emergency EU summit on Wednesday.
However, the three days of meetings stalled without agreement on Friday.
In a video message posted on Sunday, Mrs May said she could not see MPs accepting her deal "as things stand".
She added that she had been looking for "new ways" to get a deal through Parliament, but it would require "compromise on both sides".
"I think people voted to leave the EU, we have a duty as a Parliament to deliver that," she added.
Labour leader Jeremy Corbyn has said he was "waiting to see the red lines move" and had not "noticed any great change in the government's position".
He is coming under pressure from his MPs to demand a referendum on any deal he reaches with the government, with 80 signing a letter saying a public vote should be the "bottom line" in the negotiations.
In a statement issued on Saturday night, Mrs May said after doing "everything in my power" to persuade her party - and its backers in Northern Ireland's DUP - to approve the deal she agreed with the EU last year, she "had to take a new approach".
"We have no choice but to reach out across the House of Commons," the PM said, insisting the two main parties agreed on the need to protect jobs and end free movement.
"The referendum was not fought along party lines and people I speak to on the doorstep tell me they expect their politicians to work together when the national interest demands it."
Getting a majority of MPs to back a Brexit deal was the only way for the UK to leave the EU, Mrs May said.
"The longer this takes, the greater the risk of the UK never leaving at all."
Ms Long-Bailey, who was involved in Labour's meetings with the government, told BBC's Andrew Marr Show they were "very good-natured" and there had been "subsequent exchanges".
She said Labour was yet to see the compromise proposals needed to agree a deal but she was "hopeful that will change in the coming days and we are willing to continue the talks".
However, she added Labour would "keep all options in play to keep no deal off the table", including supporting a vote to revoke Article 50 - the legal mechanism through which Brexit is taking place.
Tory Brexiteers have reacted angrily to the prospect of Mrs May accepting Labour's demands, particularly for a customs union with the EU which would allow tariff-free trade in goods with the bloc but limit the UK from striking its own deals.
Ms Long-Bailey indicated Labour might be willing to be flexible over its support for a customs union but said the government proposals on the issue have "not been compliant with the definition of a customs union".
Interviewed on the Andrew Marr Show, Ms Leadsom reiterated her comments in the Sunday Telegraph that holding another referendum on the UK's departure would be the "ultimate betrayal".
She said that taking part in the European elections in the event of a Brexit delay would be "utterly unacceptable".
Ms Leadsom said: "Specifically provided we are leaving the European Union then it is important that we compromise, that's what this is about and it is through gritted teeth. But nevertheless the most important thing is to actually leave the EU," she said.
The Commons leader also told the BBC's Brexitcast there is the potential for bringing Mrs May's deal back before MPs this week.
The UK is due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by the House of Commons.
This week Mrs May is to ask Brussels for an extension to 30 June, with the possibility of an earlier departure if a deal is agreed.
Labour says it has had no indication the government will agree to its demand for changes to the political declaration - the section of Mrs May's Brexit deal which outlines the basis for future UK-EU relations.
The document declares mutual ambitions in areas such as trade, regulations, security and fishing rights - but does not legally commit either party.
Leaving the EU's customs union was a Conservative manifesto commitment, and former party whip Michael Fabricant predicted "open revolt" among Tories and Leave voters if MPs agreed to it.
However, Downing Street has described the prospect as "speculation".
Meanwhile, the Sunday Telegraph reported some activists were refusing to campaign for the party, while donations had "dried up".
And former Brexit Secretary Dominic Raab writes in the Mail on Sunday that Mrs May's approach "threatens to damage the Conservatives for years".
"There is now a danger that Brexit could be lost and that the government could fall - handing the keys to Downing Street to Corbyn," he says.
Tory MP Jacob Rees-Mogg said including Mr Corbyn in the Brexit process was a "mistake" as "he is not sympathetic to the government, obviously, and is a Remainer".
He told Sky News the reason Mrs May has not been able to secure the backing of all Conservative MPs was "her own creation" and because she failed to "deliver" a deal they could support.
Treasury Chief Secretary Liz Truss dismissed the idea of a long delay to Brexit, which could be ended if Parliament approved a deal.
Ms Truss told BBC Radio 5 Live's Pienaar's Politics a so-called flextension "sounds like purgatory", adding: "We haven't yet negotiated the free trade deal we need... So I think the British public are going to be pretty horrified if we go into more limbo than we've already had."
In a letter to Mr Corbyn, some Labour MPs have pointed out that - because the political declaration is not legally binding, and with Mrs May having promised to stand down - a future Tory PM could simply "rip up" any of her commitments.
Four shadow ministers were among 80 signatories of the Love Socialism Hate Brexit campaign letter pressing for a further public vote.
Any compromise deal agreed by Parliament will have "no legitimacy if it is not confirmed by the public", it argues.
However, Labour is split on the subject, with a letter signed by 25 Labour MPs on Thursday arguing the opposite.
They warned it would "divide the country further and add uncertainty for business" and could be "exploited by the far-right, damage the trust of many core Labour voters and reduce our chances of winning a general election".

Theresa May has bowed to pressure from a group of Tory MPs and ministers and agreed to give Parliament a vote on delaying the UK's departure from the EU on 29 March.
This will take place only if MPs reject her Brexit deal for a second time when they vote on it next Tuesday - and then also say no to the UK leaving the EU without a comprehensive, legally binding agreement, the so-called no-deal scenario.
With just 22 days to go, Parliament has yet to approve the terms of withdrawal negotiated with the EU.
MPs will have another "meaningful vote" on Theresa May's deal on 12 March and insisted that if MPs back her, the UK can still leave as planned just over two weeks later.
In the event of MPs backing a pause in the Brexit process, the PM has said she will seek the "shortest possible" delay, while also refusing to rule out the UK still leaving without a deal later in the year.
So if not 29 March, when could the UK actually end up leaving?
The first thing to point out is that any decision to delay the UK's departure by extending the Article 50 process would have to be agreed by both the UK and every other EU member.
The EU has sent out slightly mixed messages on the question, with some senior figures saying a delay would be sensible while others argue there would have to be a good reason for it.
But assuming the EU agrees to it, the first alternative Brexit date that has been touted is 18 April, which happens to be Maundy Thursday.
The thinking behind this is that it is also the last day in which the European Parliament can vote on issues before it breaks up ahead of May's Europe-wide elections - more about those later.
Members of the European Parliament (MEPs) also have to approve the deal although unlike MPs, who rejected the agreement by a margin of more than 200 votes, they have yet to consider it.
If the UK and EU run out of time to come up with a solution to address MPs' concerns about the current deal  - and EU leaders won't hold their next summit until 22 March - or if Mrs May loses MV2 by a narrow margin, there could be a short "technical" delay to allow everyone to regroup and make one last push to get it "over the line".
If the UK Parliament finally consents to the withdrawal agreement in late March or early April, it is thought that MEPs will soon follow suit - although expecting them to do so right at the last minute carries obvious risks.
And would this tight-ish timetable give the UK enough time to prepare for an orderly departure?
Irrespective of whether MPs agree to the deal, there are a number of other complicating factors.
First of all, MPs wrote the 29 March exit date into UK law when they passed the EU Withdrawal Bill last year. This would need to be superseded, although this is done relatively easily by way of a statutory instrument.
Furthermore, Mrs May has promised to enshrine the withdrawal agreement in domestic legislation by passing an Act of Parliament. It normally takes months for bills to pass through the Commons and Lords.
Although the PM has indicated the withdrawal and implementation bill could be fast-tracked, some MPs and peers may kick up a fuss saying two weeks does not leave enough time for proper scrutiny.
Thus 23 May or thereabouts has emerged as a possible new Brexit day. This, the thinking goes, would allow the UK two further months to fully prepare itself for leaving.
It would also see the UK leave before the outcome of May's European elections, due to take place between the 23 and 26 May, in which it will not play any part.
Simon Hart, a member of the Brexit Delivery Group of Tory MPs, has proposed tabling an amendment advocating a "strictly time-limited" delay until 23 May although this was withdrawn after Mrs May urged MPs not to "bind her hands".
If there are no signs of the two sides finding a solution to the thorny issue of the Irish backstop, then a slightly longer delay becomes a possibility.
Pushing back Brexit by about three months to the end of June would not be ideal for either side.
But it would be an admission that more time is needed for negotiations, particularly if the EU doesn't fancy, as has been reported, making further concessions that it can't be sure would be accepted by MPs.
Leaving on 23 June, on the third anniversary of the Brexit referendum, would be particularly sweet for many Brexiteers although the issue of ratification by the European Parliament would still be outstanding.
Newly elected MEPs from across Europe aren't due to take their seats until early July although they could conceivably convene a special session earlier or, possibly, approve the Brexit deal retrospectively.
There will be a big incentive to get the whole thing done and dusted before the end of July, both for political and more worldly reasons - no-one will want to see their summer holiday plans disrupted if at all possible.
Once you get past the end of July and the evenings start to draw in, that's when things get trickier.
The EU may be willing to grant one extension to the Brexit process but a series of rolling delays is reportedly not to its liking and a lengthier hiatus may only happen if there were a general election or another referendum.
That said, senior EU officials are reported to have mulled delaying Brexit until 2021 - in the hope the two sides will have negotiated their future relationship by then and this will sort out all the issues relating to the backstop.
But this is likely to be unacceptable to Conservative MPs, and millions of Leave voters, as it would mean the UK was still part of the EU more than five years after it voted to leave in 2016.
There is also the small matter of Europe's parliamentary elections. Could the UK remain in the EU for an indefinite period without sending representatives to Brussels and Strasbourg?
Theresa May has suggested this would not be viable but experts, such as the Institute for Government, have pointed out that there may be ways round this dilemma - in the short term anyway.
These could include the UK's existing MEPs being granted "observer status" with no voting rights or the UK sending national representatives, as Romania and Bulgaria did for four months after they joined in 2007.
Another potential option would be for the UK to re-elect its 73 MEPs - whose seats would otherwise be re-allocated - on an interim basis but to hold the polls at a different time from the rest of the EU.
But the cost of doing this would be controversial and would the Conservatives be willing to put up candidates when they were likely to be accused of betrayal by, among others, Nigel Farage's new Brexit party?

It will be "very difficult" for the UK and the EU to reach a Brexit agreement before the 31 October deadline, Irish leader Leo Varadkar has said.
He told Irish broadcaster RTE "big gaps" remained between the two sides.
Amid claims on Tuesday that talks were close to collapse, he also suggested the language around the discussions had turned toxic "in some quarters".
Mr Varadkar and Boris Johnson are expected to meet for further Brexit talks later this week.
The UK has said the EU needs to "move quickly" to stop it leaving without an agreement at the end of the month.
Taoiseach Leo Varadkar, who spoke with Mr Johnson by phone for about 45 minutes on Tuesday, said he would strive until the "last moment" to reach a deal with the UK, but "not at any cost" to his country, Northern Ireland and the rest of Europe.
He also downplayed the chances of any agreement being struck before the crucial summit of EU leaders on 17 October, during which next steps for Brexit are likely to be decided.
"I think it's going to be very difficult to secure an agreement by next week, quite frankly," Mr Varadkar said.
"Essentially, what the UK has done is repudiated the deal that we negotiated in good faith with prime minister [Theresa] May's government over two years and have sort of put half of that now back on the table, and are saying that's a concession. And of course it isn't really."
Mr Varadkar added that it was his job to hold the UK to commitments it had made since the 2016 referendum to prevent a hard border on the island of Ireland and uphold the Good Friday Agreement.
The Irish leader's comments came after a No 10 source claimed on Tuesday that Germany was now making it "essentially impossible" for the UK to leave the EU with a deal.
That assessment followed a "frank" phone call between Boris Johnson and German Chancellor Angela Merkel, during which they discussed Brexit proposals the UK prime minister put forward last week to the EU.
After the call, a No 10 source said Mrs Merkel had made clear a deal based on the prime minister's plans was "overwhelmingly unlikely" - though the BBC's Adam Fleming said there was "scepticism" within the EU that she would have used such language.
The No 10 source also suggested Mrs Merkel told her counterpart the only way to break the deadlock was for Northern Ireland to stay in the customs union and for it to permanently accept EU single market rules on trade in goods.
This, the source said, marked a shift in Germany's approach and made a negotiated deal "essentially impossible".
In response, the EU's top official, European Council President Donald Tusk, accused Mr Johnson of engaging in a "stupid blame game".
In a tweet to the prime minister, he added: "At stake is the future of Europe and the UK, as well as the security and interests of our people.
"You don't want a deal, you don't want an extension, you don't want to revoke, quo vadis (where are you going)?"
European Commission president Jean-Claude Juncker said that if negotiations fail, "the explanation will be found in the British camp (because) the original sin is found on the islands and not on the continent".
Speaking to the French Les Echos newspaper, he added: "A no-deal Brexit would lead to a collapse of the United Kingdom and a weakening of growth on the continent."
In his interview with RTE, Mr Varadkar was asked whether he was concerned the language around the talks was "getting toxic".
"I think it is, from some quarters, but you know I don't play dirty. You know, I don't think most EU leaders do either. We've been very straight up from when the referendum happened."
The prime minister also hosted European Parliament president David Sassoli in Downing Street on Tuesday, but the MEP left saying "no progress" had been made.
Mr Sassoli later told the BBC's Newsnight programme: "Angela Merkel's opinions must be taken seriously. We are all very worried because there are only a few days left.
"Because we understand that going out without an agreement leads to having a real problem, if not a real catastrophe."
Following the meeting, Downing Street said there was "little time" left to negotiate a new legally-binding withdrawal agreement, but Mr Johnson remained committed to doing all he could.
"We need to move quickly and work together to agree a deal," a No 10 spokesman said.
"He [the prime minister] reiterated that if we did not reach an agreement then the UK will leave without a deal on 31 October."
The PM's pledge comes despite legislation passed by MPs last month, known as the Benn Act, which requires Mr Johnson to write to the EU requesting a further delay if no deal is signed off by Parliament by 19 October - unless MPs agree to a no-deal Brexit.
While negotiations are continuing in Brussels, Mr Sassoli said a deal likely to command the support of MEPs was a "long way off".
Meanwhile, 19 Labour MPs have written to the European Commission president Mr Junker calling for a Brexit deal to be made with the government without any further delay.
Caroline Flint, who represents the leave-supporting constituency of Don Valley, told BBC Radio 4's Today programme the "uncertainty of Brexit has gone on too long" and the group did not think it was "impossible" to resolve the Irish border issue.
Tuesday 8 October - The House of Commons was prorogued - suspended - ahead of a Queen's Speech to begin a new parliamentary session.
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

The Irish prime minister has said he will support an extension of the Brexit deadline until 31 January 2020.
Taoiseach Leo Varadkar was speaking after talking to European Council President Donald Tusk on Wednesday.
The EU is yet to confirm how long it will approve another delay for, following the UK's request on Saturday.
Prime Minister Boris Johnson "paused" his Brexit bill on Tuesday after MPs rejected his plan to get it signed off in three days.
It is likely the EU will offer a so-called flextension - with the option that the UK could leave earlier than 31 January if a Brexit deal has been passed by then.
Speaking in the Dáil (Irish parliament), Mr Varadkar said EU leaders could hold an emergency meeting if Mr Tusk did not get consensus for an extension.
"My bags are always packed for Brussels and packed they are again," added the taoiseach.
On Tuesday evening, the Democratic Unionist Party's (DUP) 10 votes dealt a blow to the PM's plan to fast-track the bill through Parliament.
The party's chief whip Sir Jeffrey Donaldson said he believes the "penny has dropped" with the government that it needs the party's votes to pass Brexit legislation.
The votes of the DUP MPs and the independent North Down MP Lady Hermon meant the government lost by 14 votes.
Mr Johnson is awaiting the EU's verdict on approving another extension and Sir Jeffrey said the prime minister should use the time to talk to the party.
"I think he realises now that without the DUP on board getting his bill and his agreement through the House of Commons is going to be hugely challenging for him," he said.
"So I think the sensible thing for the government is to sit down with us and see if we can work this out."
Northern Ireland Affairs Committee chairman Simon Hoare said he was sorry the DUP did not support the withdrawal deal because it was the "best... that one can get as far as Northern Ireland is concerned".
But he added: "The DUP have played a hand of cards - I'm not entirely sure the hand of cards has played out as they anticipated it to be.
"What is now clear is that there is a cross-party alliance to deliver the Brexit deal negotiated by the prime minister and that did not require the DUP to vote for it."
MPs backed Mr Johnson's Withdrawal Agreement Bill on Tuesday but minutes later voted against the timetable, leaving it "in limbo".
The prime minister warned he would push for an election if MPs rejected his timetable and the EU granted a delay.
After the result in the Commons, Mr Johnson said it was Parliament, not the government, that had requested an extension.
DUP deputy leader Nigel Dodds denied reports that some of the party's MPs regretted not voting for the Brexit deal struck by previous prime minister Theresa May.
"Under Theresa May's deal Northern Ireland was part of the EU's customs arrangement, the customs union fully," Mr Dodds said on Wednesday.
"What she had tacked on was a customs partnership... that would then fall away and we would be having precisely the same problem we're having now.
"We foresaw this and that's why we opposed it."
He added: "We never trust anybody, except ourselves and our electorate and in that we've been proved absolutely right."
If an election were to be triggered this week, the earliest it could take place would be Thursday 28 November, as the law requires 25 days between an election being called in Parliament and polling day.
MPs had been due to debate the bill over Wednesday and Thursday but will now return to discussing the contents of the Queen's Speech, which put forward the government's domestic agenda for the new session of Parliament.

There can be no final decisions on the future of the Irish border until the UK and the EU have reached a trade agreement, Liam Fox has said.
The UK's international trade secretary also blamed the EU for Brexit delays.
The comments came after the Irish Republic's EU commissioner said Dublin could veto Brexit trade talks.
The EU has said "sufficient progress" has to be made on the Irish border before negotiations on a future relationship can begin.
Downing Street has said the whole of the UK will leave both the customs union and the single market when it leaves the EU in 2019.
"We don't want there to be a hard border but the UK is going to be leaving the customs union and the single market," Mr Fox told Sky News.
He added: "We can't come to a final answer to the Irish question until we get an idea of the end state. And until we get into discussions with the EU on the end state that will be very difficult - so the quicker we can do that the better, and we are still in a position where the EU doesn't want to do that."
Mr Fox accused the European Commission of having an "obsession" with ever-closer union between EU member states, which was delaying progress in Brexit talks.
Phil Hogan, the EU's agriculture commissioner, told the Observer that staying in the customs union would negate the need for a hard border - with customs posts and possible passport checks - on the island.
He said Dublin would "play tough to the end" over its threat to veto trade talks until it had guarantees over the border.
Shadow chancellor John McDonnell said he was "worried" by Mr Fox's comments, adding that Labour would not take continued membership of the single market and the customs union off the table.
"I think the one thing that we don't want to do is jeopardise any movement quickly, because we need movement to enable us to get into the proper trade negotiations," Mr McDonnell told ITV's Peston on Sunday.
"So I'm hoping that isn't a Downing Street-sanctioned statement that's he's made."
By Chris Mason, BBC political correspondent
It's 310 miles (499km) long - a squiggle on the map that meanders from Carlingford Lough in the east to Lough Foyle in the west.
The border between Northern Ireland and the Republic is the soon-to-be frontier between the UK and the European Union.
And right now it is the most troublesome frontier between Brexit negotiations stalling or progressing.
London and Dublin each say they are committed to maintaining an open border. But Ireland wonders how that will be possible.
Oh and one other thing to throw into the mix - after all the talk of how wobbly Theresa May's government is, so is Ireland's.
There could be a general election there before Christmas.
The EU has given Prime Minister Theresa May until 4 December to come up with further proposals on issues including the border, the Brexit divorce bill and citizens' rights, if European leaders are to agree to moving on to trade talks.
But Mr Hogan accused some in the British government of having what he called "blind faith" about securing a comprehensive free-trade deal after Brexit.
He said it was a "very simple fact" that "if the UK or Northern Ireland remained in the EU customs union, or better still the single market, there would be no border issue".
In these circumstances regulations on either side of the border would remain the same, and so a near-invisible border would be possible.
The Irish government has always insisted there must not be a hard border between the Republic and Northern Ireland, with Taoiseach Leo Varadkar saying he must have written assurance from the UK before Brexit talks can move on.
Irish Foreign Minister Simon Coveney has said the UK's desire for no hard border on the island of Ireland was "aspirational".
It comes as Ireland's deputy prime minister faces a motion of no confidence over her handling of a case involving a whistle-blower alleging corruption within the police.
The issue could see Prime Minister (Taoiseach) Leo Varadkar's coalition government fall and an election held before Christmas.
In her speech in Florence, this September, Mrs May restated that both the UK and EU would not accept any physical infrastructure at the border.
The Democratic Unionist Party said Northern Ireland and the rest of the UK must not be different.
Arlene Foster, the leader of the DUP, which is in a confidence-and-supply arrangement with the Conservative government, said she would not support "any suggestion that Northern Ireland, unlike the rest of the UK, will have to mirror European regulations".
Suggestions for alternate arrangements have included a new partnership that would "align" customs approaches between the UK and the EU, resulting in "no customs border at all between the UK and Ireland".

So many newspaper column inches have been devoted over the last week to a debate over whether or not Boris Johnson has managed to "win a victory" over his EU counterparts, getting them to "budge" over changing the Withdrawal Agreement.
You can in fact argue this both ways.
The "Yes-they've-budged" camp point to German Chancellor Angela Merkel and French President Emmanuel Macron now saying they will consider any new proposals from the UK on replacing the contentious Irish border backstop (if they are realistic and immediately operable).
This is a marked change from the EU's official position when Boris Johnson became UK Prime Minister: that the Brexit Withdrawal Agreement (containing the backstop) was signed, sealed and carved in stone.
The "No-the-EU-hasn't-really-budged" camp say EU leaders don't believe Boris Johnson has any realistic alternatives to the backstop up his sleeve, so they are trying to take the initiative in the blame game that would inevitably follow a no-deal Brexit by wanting to appear open.
The aim being that Angela Merkel, for example, could turn to German businesses that would lose out in a no-deal scenario and say: "Look, I tried my best. It's Boris Johnson who failed you."
EU figures who've been involved in Brexit negotiations are also keen to point out that being open to alternatives to the Irish backstop is not a change of position for Brussels. It's written into the existing Withdrawal Agreement.
And as for Angela Merkel's positive words to Boris Johnson about finding new solutions, the German media was quick to underline how often she has repeated over the last  few years that she would work "until the last minute to make a deal with the UK," as long as EU single market rules were respected.
Her attitude - in public at least - is unchanged.
Behind the scenes though, EU leaders have been readjusting their view of Boris Johnson somewhat.
During this summer's Conservative party leadership contest to replace Theresa May as prime minister, I heard Boris Johnson described in private conversations in EU circles as "a buffoon" and "a reckless populist willing to drive his country over the cliff-edge of a no-deal Brexit to satisfy his ambition to become prime minister".
I now notice a subtle tone change. In his one-to-one chats in Paris, Berlin and at the G7 with European Council President Donald Tusk, the prime minister has managed to persuade Brussels that:
a) He is serious in his threat to pursue a no-deal Brexit if no agreement with the EU can be found;
and b) He would actively prefer to get a deal through parliament if possible.
But this change in perception does not alter facts on the ground.
EU leaders still think a no-deal Brexit is the most likely option right now.
Time is running out - unless the prime minister were to do a last-minute U-turn and request a new Brexit extension after all.
EU politicians also speak of the numbers not adding up in parliament for Boris Johnson. A reason they give for not being willing to jump forward with a backstop compromise.
"There is little-to-no pressure from the rest of us in the EU on Dublin right now to find and accept a backstop compromise," one high-level EU diplomat told me.
"If we did introduce a time limit - or even if we got rid of the backstop altogether from the Withdrawal Agreement, as Boris Johnson says he wants us to do - what would be the point? The prime minister doesn't have the majority in parliament to guarantee the Brexit deal would then go through and we, the EU, would have sacrificed our principles, our reputation, exposed our single market on the island of Ireland and thrown member state Dublin under a bus voluntarily. We'd be worse off than if we just accept a no-deal Brexit is going to happen."
Boris Johnson's majority of one in parliament means EU leaders understand his focus is now domestic: shoring up his premiership by winning a general election, rather than agreeing a compromise deal with the EU.
Few in the EU are holding their breath that MPs will succeed in stopping a no-deal Brexit in the coming weeks - though if they did, Brussels would be delighted.
I notice rather that a number of European politicians are placing any hopes they have on Boris Johnson to avoid no deal. They speak of the prime minister's ambition to remain in the job and to go down in the history books in a positive way.
One European official remarked: "Johnson can see a no-deal Brexit is bad for his country but we're afraid he's boxed himself in with all his threats and promises at home."
EU leaders will now watch and wait for what early autumn brings in UK politics. The next scene in this Brexit drama will play out in Westminster, not Brussels.

The UK should "explore" allowing qualified free movement of workers from the EU after Brexit, Shadow Brexit Secretary Sir Keir Starmer has said.
In a potential softening of Labour's position, Sir Keir called for alignment with the EU's single market.
This could pave the way for EU migrants with jobs to be allowed to settle in the UK, subject to certain conditions and for Britain to accept EU rules restricting state aid.
The shadow cabinet minister made his remarks in an interview with Newsnight during a visit to Belfast after meeting nationalist parties.
He said Labour hoped to negotiate a future relationship with the EU involving a "comprehensive customs union and single market alignment".
This would avoid the need for a backstop, by guaranteeing no hard border in Northern Ireland.
Asked whether he could live with the Norway Plus plan, which would involve free movement of workers, Sir Keir said: "Well that would have to be explored and the precise detail of that."
The Norway Plus or the Common Market 2.0 plan - promoted by Labour MP Lucy Powell and Tory MP Nick Boles - would involve membership of a customs union and the free movement of workers, rather than EU rules allowing free movement of citizens.
Sir Keir said people would be willing to accept the movement of workers subject to restrictions: "If somebody is coming to do a job and it needs to be done and it has been advertised locally beforehand with nobody able to do it, then most people would say I accept that."
"Most people say that if you are coming to join your family that is something I can accept. Most people would say if somebody wants to come here and study and it is genuine then of course please come and study. In fact let's celebrate that," he added.
"So I actually think we get stuck on the freedom of movement discussion too early without saying what does a principled, effective and fair immigration policy look like?
"When we get into that debate we may find we can make better progress than we think."
Prime Minister Theresa May has maintained that free movement will end when the UK leaves the EU.
Sir Keir described free movement as one of two areas - along with staying aligned with the rules of the single market - that would be "sticking points" in negotiations with the EU under his plan.
"There is a negotiation to be had there. But I genuinely think that if 12, 18 months ago we had been clear, as the UK, to say we want a close economic relationship, we want these features - customs union, single market alignment - and the only sticking points now were how exactly do you stay aligned, what is the proposition about freedom of movement but we know what we are trying to achieve - we would be in a materially better place than we are now."
Sir Keir said he did not believe that EU state aid rules would be a problem because they do not "cut across" Labour's 2017 election manifesto.
He also said Labour would have no problems with observing a common playing field with the EU and upholding workplace and environmental rights that keep pace with EU.
Sinn Fein and the SDLP were alarmed last week when Jeremy Corbyn expressed unease at the Northern Ireland backstop which is strongly supported by nationalists.
The backstop is designed to avoid a hard border by tying Northern Ireland closely to the EU, if the UK and Brussels fail to agree a future relationship before the end of a 21-month transition period.
SDLP leader Colum Eastwood told Newsnight that Mr Corbyn was in danger of echoing the language of the DUP after the Labour leader warned that Britain could be tied into the backstop indefinitely.
Sir Keir reassured Sinn Fein and the SDLP that Labour remains committed to the backstop, as long as Theresa May maintains her red lines.
You can watch Newsnight on BBC 2 weekdays 22:30 or on iPlayer. Subscribe to the programme on YouTube or follow them on Twitter.

Theresa May is cautiously hopeful that her telephone diplomacy with EU leaders over the Christmas break could pay off over the next week.
After calls with Angela Merkel and Jean-Claude Juncker, the prime minister believes there is a growing mood in the EU to help the UK avoid a no-deal Brexit scenario.
Nothing is guaranteed, but there is an expectation in Whitehall that if the EU decides to help out, it would make helpful noises on the Northern Ireland backstop on the eve of the parliamentary vote on the prime minister's Brexit deal. The vote is due to take place on Tuesday or Wednesday next week.
The offer, if it comes, would be in writing. "The point is to have something with genuine meaning," one Whitehall source says.
As things stand, the prime minister is heading for a serious parliamentary defeat because she is confronted by two apparently immovable objects. They are: no appetite in the EU to make substantive changes to the Brexit deal, and opposition from the Democratic Unionist Party to parts of the deal regarding Northern Ireland.
But Whitehall is picking up signs of movement in the EU which would, in an ideal world for No 10, persuade the DUP to support the prime minister.
Downing St believes the DUP's influence goes way beyond its ten MPs. Officials regard the Unionists as "dominos" - get them on board and Brexiteer Tories will start to return to the fold, potentially winning over Labour MPs minded to support the prime minister if she is within shouting distance of victory.
The mood is slightly better in Downing St because the prime minister has been left with the clear impression from EU leaders that they are determined to avoid no-deal.
One Whitehall source said: "There is a genuine sense they want to avoid no-deal. How they will help us is the big unanswered question."
The hope is that next Monday or Tuesday - depending on the date of the parliamentary vote - the EU would issue a firm signal that the Northern Ireland backstop would not last indefinitely.
Under the backstop, which is designed to avoid a hard border between Northern Ireland and the Republic, Northern Ireland would be closely bound into the EU if the UK and the EU fail to agree a comprehensive new relationship by the end of the transition in December 2020.
The backstop is described as a temporary arrangement, but the EU is insisting it would last unless and until a replacement trade deal is agreed.
Over the holiday period the prime minister's chief EU negotiator Olly Robbins revived his idea of the UK and the EU setting a firm start date for the UK's future trade relationship with the EU, with December 2021 the strong preference. The UK believes the EU would find this idea easier to agree to than a firm end date to the backstop.
If the EU were to make a move then two possible scenarios could play out on the eve of the parliamentary vote:
If any such amendment were passed it could overcome the main difficulty the prime minister experienced at last month's EU summit. Many EU leaders said there was no point in making concessions when they would inevitably be rejected by Parliament.
If MPs indicated they were happy with the EU offer but need firmer legal assurances, that could provide the basis for an emergency EU summit to approve the offer. That would be a big step for the EU but there is no other way to provide a commitment with legal force.
In the end, the differences between the UK and the EU may prove to be irreconcilable. The EU wants to avoid a no-deal but it is adamant that the legally binding Withdrawal Agreement will not be reopened as long as Theresa May stands by her red lines, most notably on rejecting free movement of people. Brussels will also not agree to any wording that undermines the agreement.
The DUP is also highly suspicious of the government and the EU. Their strong opposition hardened when the government's legal advice said that in some circumstances Northern Ireland would have to treat Great Britain as a 'third country' - EU parlance for a foreign country.
Until the DUP have assurances that that scenario cannot happen - or at least would have a guarantee that it would only be temporary - it is all but impossible to see them coming on board.
You can watch Newsnight on BBC 2 weekdays 22:30 or on iPlayer. Subscribe to the programme on YouTube or follow them on Twitter.

Theresa May has urged MPs to back what she has described as a "new" Brexit deal - but what exactly is different in this updated withdrawal agreement?
The prime minister's "new Brexit deal" isn't all that new.
For a start, the withdrawal agreement itself - which includes the backstop plan for the Irish border - remains exactly the same.
That was always going to be the case. The EU has insisted that there will be no further negotiation on the text.
Instead, the government will seek changes to the accompanying political declaration, which focuses on the future relationship after Brexit.
But, as we've said many times before, it is not a legally binding document.
What Mrs May has offered for the first time is the prospect of a vote on holding a second referendum, and a vote on a temporary customs union.
But she says that will only be the case if MPs are willing to approve the withdrawal agreement bill in the House of Commons in the first week of June.
There are also promises on workers' rights and environmental protection - measures designed to appeal to Labour MPs. But similar promises, albeit in different form, have been made before.
As for Northern Ireland, the PM has said that the government would be under a legal obligation "to seek to conclude alternative arrangements" to the backstop by the end of 2020.
But note the word "seek" - it is an aspiration not a guarantee, and finding alternative arrangements, through the use of technology or other means, has so far proved very challenging.
Mrs May also spoke of a commitment, should the backstop have to come into force, to ensure that Great Britain will stay aligned with Northern Ireland to prevent new checks at the border.
Again, this is something that has been said before.
Nevertheless, the government is portraying this speech as a genuine effort to find compromise.
Others see it as a last roll of the dice.
The trouble is that Brexit has become a binary issue, and almost no-one in politics - whether they voted to leave or remain - seems to want to give up on their vision of how all this should be resolved.
That's why much of the initial reaction to the PM's speech from MPs, from all sides of the House of Commons, including her own backbenches, has ranged from lukewarm to openly hostile.
She will continue to warn that anyone voting against her latest plan risks losing Brexit altogether.
But the biggest problem for Mrs May is that there doesn't appear to be a majority in the Commons for any Brexit option.
That has been clear for many months now.
And nothing in this speech is likely to move the goalposts.
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If you'd listened only to question after question in the Commons on Monday afternoon, protesting loud and long at the prime minister's compromise, you might wonder why she just doesn't pack up and go home.
How on earth can Mrs May turn round the wave of resistance?
Has she finally met her impossible task?
In private, many MPs are even more caustic about this compromise deal getting through than they are in public - and that's saying something.
And among the number of the sceptics are plenty of ministers too.
Whether they are ministers who think the plan will fall and  are then willing to resign and then push for staying in the EU's single market and customs union...
....or whether they are Brexiteers in government who think Theresa May's made her own rotten luck by sticking too close to the EU...
...or even members of another group - those who look at the deal and think it's a grim, but realistic compromise, but then look at the numbers and think it just can't pass.
But while there might be fewer of them, there are still some brave souls in government who think there is a chance the deal can pass.
That's why the PM will be spending every day for the next fortnight determinedly arguing for the deal, and putting the case again and again. And then, yes, again: that in her view this deal is the only show in town.
And while MPs, certainly her supporters, might have grimaced at the torrent of criticism this afternoon, there is no sense at all at this stage that the prime minister has any intention of moving away from her position.
In fact, as the days get more desperate, in some of her public appearances and press conferences, she seems strangely more at ease, joking about forgetting journalists' names. Maybe, at long last, she has been able to settle on a simple Brexit message that she is actually comfortable with: in her view it's this deal or disaster.
And having manoeuvred herself into this position, she has no choice but to keep going. Her political fate rests on whether she can pass the deal. The stability of her government and, she would argue, the country too.
And everything about her track record tells us, as her colleagues privately confirm, the prime minister's style is to be stubborn and unbending; a weakness as well as a strength.
Along with what will undoubtedly be ruthless management of Tory MPs, No 10's plan is to relentlessly and publicly use the fear of the unknown - worries about political chaos - to bring colleagues into line.
It may work. It may well not. But Theresa May will not fail because she didn't try.
We know now the vote that will make history takes place on 11 December.
We may not know until that very moment which way it will go.

The "whole world" wants the UK to avoid a no-deal Brexit, Japan's PM has claimed, after talks with Theresa May.
Shinzo Abe pledged "total support" for the withdrawal agreement she has negotiated with the EU, which faces a crunch vote in the Commons on Tuesday.
Mrs May has been speaking to Labour MPs and union leaders in a bid to try to get her deal through the Commons, where scores of her own MPs oppose it.
It comes as Honda UK announced a six-day post Brexit shut down.
The Japanese-owned car giant said the move was to ensure it could adjust to "all possible outcomes caused by logistics and border issues".
Mrs May said leaving the EU provided "an unprecedented opportunity" for the countries to strengthen relations.
She and Mr Abe pledged to build on the trade agreement between Japan and the EU to secure an "ambitious bilateral arrangement" between Japan and the UK after Brexit.
Mr Abe said: "It is the strong will of Japan to further develop this strong partnership with the UK, to invest more into your country and to enjoy further economic growth with the UK.
"That is why we truly hope that a no-deal Brexit will be avoided, and in fact that is the whole wish of the whole world.
"Japan is in total support of the draft withdrawal agreement worked out between the EU and Prime Minister May, which provides for a transition to ensure legal stability for businesses that have invested into this country."
The UK is set to leave the European Union on 29 March.
The withdrawal agreement between the UK and EU - covering things like the "divorce bill", expat citizens' rights and a 20-month transition period - will only come into force if MPs back it in a vote.
A no-deal Brexit would see the UK leave without a withdrawal agreement and start trading with the EU on the basis of World Trade Organization rules, an outcome favoured by some Brexiteers.
The deal negotiated between the UK and EU looks set to be rejected by MPs next Tuesday, with 110 Conservative MPs having said they will oppose it, Labour set to vote against it and Labour Leader Jeremy Corbyn calling for a general election "at the earliest opportunity" - should it be voted down.
"A government that cannot get its business through the House of Commons is no government at all," he said.
"We're going to get smashed" - one government insider's apocalyptic prediction about one of the most important votes in recent political history.
As things stand, MPs are on course to kybosh Theresa May's long-argued-over Brexit deal, with a very heavy defeat.
Dozens of her own backbenchers have said publicly they will vote against it.
The opposition parties are adamant they will say "no" too.
Mrs May has been speaking to some Labour MPs and the leaders of two of the UK's biggest trade unions, Len McCluskey of Unite and Tim Roache of the GMB, in a bid to try to build support for the deal.
It has emerged that the government is considering backing an amendment from Labour Leave supporter John Mann, giving extra protections to workers and the environment, in a bid to win support.
Speaking alongside Prime Minister Abe, Mrs May repeated her call to MPs to support her plan in next Tuesday's crunch vote, saying: "The only way to avoid no deal is to have a deal and to agree a deal, and the deal that is on the table...the EU has made clear, is the only deal."
She said the deal allowed for a "more ambitious trading arrangement between the European Union and the United Kingdom than they have entered into with any other third country" which would also allow the UK to "strike good trade deals on our own with countries around the world, like Japan".
Labour MP Martin Whitfield, a supporter of the Best for Britain campaign for another referendum, said: "It is humiliating for the prime minster to be told to her face that the whole world wants to avoid a no-deal scenario, yet she still refuses to rule it out.
"Countries across the globe are looking at Britain in despair. Japan, like our other allies, understands the folly of a no-deal Brexit. Why doesn't Theresa May?"
Meanwhile, during the second of five days of debate on the deal, Conservative MP George Freeman has told MPs he will now vote for it "with a heavy heart", having previously said he could not support it.
He said it "wasn't perfect" but he would back it because "we are now in the dying stages and no deal is unconscionable".
Trade between the UK and Japan hit £28bn last year, and Japanese companies already employ 150,000 people in the UK.
During their meeting in Downing Street, Mrs May and Mr Abe also discussed a number of joint projects, including research around conditions such as dementia and heart failure, the increasing use of big data and artificial intelligence, and environmentally friendly growth.
They also made commitments on security - such as the UK deploying the Royal Navy warship HMS Montrose to the region to enforce sanctions against North Korea.
And as part of a cultural exchange, the National Gallery will send a major exhibition to Japan, including the Sunflowers painting by Vincent Van Gogh.
If you feel like you ought to know more about Brexit...

Top EU officials have expressed optimism that a Brexit deal can be struck by the end of the year.
Jean-Claude Juncker, the head of the European Commission, said the chance of the UK and the EU reaching a deal has increased in the last few days and could be agreed by November.
Meanwhile, European Council President Donald Tusk said an agreement was possible by the end of 2018.
But Irish PM Leo Varadkar said there is still "a fair bit of work to be done".
The UK is due to leave the EU on 29 March 2019.
However, there is still no agreement on some issues, including how to avoid new checks on the Irish border.
Both sides had hoped to finalise the so-called divorce agreement and agree a statement on their future economic co-operation by an EU summit in 11 days' time.
Speaking to the Austrian press on Friday and asked whether an agreement could be reached at the next meeting of European leaders on 17 October, Mr Juncker said: "We are not that far yet. But our will is unbroken to reach agreement with the British government."
He said a deal could be agreed by November.
"I have reason to think that the rapprochement potential between both sides has increased in recent days," Mr Juncker added.
He also reiterated his position that a no-deal scenario "would not be good" for either the UK or the EU.
Speaking on Saturday, European Council President Mr Tusk said: "We will try for it [agreeing a deal] in October... and I think there is a chance to have an accord by the end of the year."
Foreign Office minister Sir Alan Duncan also expressed optimism that a deal could be reached before December.
There were also reports from EU officials of a better atmosphere in talks over the Irish border.
The upbeat assessment of progress in negotiations prompted sterling to rise against the Euro and the US dollar.
But Mr Varadkar warned that the two sides had not crossed the finish line yet and the October summit was "a time to take stock".
He told reporters: "I would be hopeful at that point that there would be decisive progress allowing us to conclude an agreement by November.
"That remains to be seen yet. I think there is a fair bit of work to be done."
He added: "It's increasingly important that we conclude a deal sooner rather than later."
The BBC's Brussels correspondent Adam Fleming said officials still "seem to be pushing for the whole withdrawal agreement to basically be done" by the EU summit.
"Although, if we have learned anything from Brexit it's that the timetable is incredibly flexible, to use diplomatic language," he told BBC Radio 4's Today programme.
Downing Street distanced itself from suggestions - reported in the Daily Mail newspaper - that they were concerned Mr Juncker was trying to "bounce" the UK into agreeing a Brexit deal by mid-October.
Meanwhile, the Guardian reported senior Conservatives had been in private contact with a number of Labour MPs to persuade them to back Theresa May's Brexit deal.
Some Labour MPs who were mentioned in the article took to Twitter to refute the claims. Rachel Reeves tweeted: "All the Labour MPs listed work hard and fight Tories locally and nationally every day."
It comes weeks after the head of the European Council Donald Tusk said Theresa May's Brexit plans were unworkable.
Both sides had hoped to finalise the so-called divorce agreement and agree a statement on their future economic co-operation by the October summit.
But last month, the EU's chief negotiator Michel Barnier said that if both sides were "realistic" there could be an agreement by November, when a special one-off summit has been arranged.
The European Commission is also considering whether to publish an analysis of where the two sides agree on elements of their future relationship.
It could appear alongside the EU's latest contingency plans for a no-deal scenario, which will be released next week.
Speaking on BBC Radio 4's Any Questions, Sir Alan Duncan was also optimistic about the prospects of a deal.
"We are in the art of the possible here, and from what I see in government, I think that we will get a deal, be it in October or November at the two consecutive summits," he said.
Currently, thousands of people cross the border between Northern Ireland and the Republic of Ireland every day. Goods and services pass between the two areas easily without any restrictions.
As the UK and Ireland are currently part of the EU single market and customs union, products do not need to be inspected for customs and standards, but after Brexit, all that could change. The UK wants to leave both the single market and customs union.
Both the UK and EU have agreed they do not, in all circumstances, want a "hard border" - which means physical checks or installing infrastructure such as cameras or customs posts.
Both sides signed up to that promise in December 2017.
They hope they can achieve that anyway in a future agreement on a new trading relationship after Brexit.
But if there were to be a delay or a failure in reaching such an agreement, they have agreed there needs to be a "backstop" solution - which means a last resort plan - that would keep the Irish border open.
The trouble is the two sides can't agree on what the backstop text should say.
The EU's proposed backstop solution would see Northern Ireland stick to those rules of the customs union and single market that are required for cross-border co-operation to continue.
But the UK government is against this idea, saying it would effectively separate Northern Ireland from the rest of the UK and create a border in the Irish Sea.
Instead, it would like to see the UK as a whole remaining aligned with the EU customs union for a limited time. But the UK has now signalled that it is "open to looking at some of the options on regulatory checks".
Negotiators are yet to find a solution that is acceptable to both sides.

Jeremy Corbyn has said he is "looking at all the options" to prevent a no-deal Brexit after he met Tory MPs to discuss alternatives to the PM's deal if it rejected again by Parliament.
The Labour leader held talks with ex-Tory ministers Nick Boles and Sir Oliver Letwin, who favour a closer, Norway-style relationship with the EU.
He said he had discussed the so-called "Common Market 2.0 option" but would not commit to backing it at this stage.
The UK is due to leave on 29 March.
MPs will vote on whether to back Theresa May's Brexit deal on Tuesday.
They emphatically rejected the terms of withdrawal negotiated by the prime minister in January.
If they do so again, they will get to choose between leaving without a negotiated agreement or deferring the UK's exit date by an unspecified period.
Conservative MPs have been warned by the chief whip that if they vote down the deal and the negotiations are extended, they risk ending up with a "softer Brexit".
The Labour leadership wants the UK to remain in a customs union with the EU.
Many Labour MPs and some Conservatives back an even closer arrangement with the European Union - dubbed the "Common Market 2.0" plan - which would see the UK remain in the EU's single market by staying part of the European Economic Area.
Mr Corbyn said he had agreed to meet the Conservative MPs because he was adamantly opposed to a no-deal exit and he wanted to hear "what their ideas and options are".
"I am reaching out to all groups in Parliament to try and prevent a no-deal Brexit which I think would be very damaging," he said after the meeting. "We are looking at all the options."
While Labour wanted an agreement encompassing customs union, unhindered access to EU markets and legal protection of workers rights "what exact form that takes is subject to negotiation".
Asked if he would throw his weight behind the Boles-Letwin plan and oblige Labour MPs to vote for it, he said they were "quite a long way from that at this stage".
"We are obviously discussing it but our priority at the moment is preventing a no-deal exit".
In an article for the Mirror newspaper, Mr Corbyn said a close economic relationship was "the best Brexit compromise for both 17 million leave voters and 16 million remain voters".
While he respected the result of the 2016 Brexit referendum, he reiterated that Labour would back another EU referendum "to prevent a damaging Tory Brexit or a disastrous no deal outcome."

Jeremy Corbyn has met the EU's chief negotiator in Brussels to set out Labour's vision for Brexit.
Mr Corbyn told Michel Barnier he was "ready to take up the responsibility for Brexit negotiations" if there was a change in government.
The EU negotiator also held separate meetings with the first ministers of Wales and Scotland, Carwyn Jones and Nicola Sturgeon.
Mr Barnier has stressed he will only negotiate with the UK government.
The Conservatives said Mr Corbyn would "surrender", rather than negotiate with the EU if he was in charge.
Mr Corbyn presented Mr Barnier with an Arsenal football shirt and a copy of the Labour manifesto before the meeting, while Mr Barnier gave the Labour leader a vintage railway poster from his home region in the French alps.
Speaking afterwards, Mr Corbyn said he had told the EU negotiator that "under a Labour government, we will negotiate to make sure we have the trading relationship with Europe that protects industry, protects jobs and protects services".
He added: "We will also make sure Britain doesn't become some sort of low tax regime off the shore of Europe and we will not sign a trade treaty with the USA which is not only at variance with the Paris Climate Agreement but also damaging to living standards and working conditions in Britain."
A second formal round of Brexit negotiations is due to begin on Monday, and Mr Barnier has warned that significant issues remain between the UK and the EU on one of the first issues to be tackled, citizens' rights.
Labour says it would unilaterally guarantee EU nationals' rights and "extend the hand of partnership and friendship" to the rest of the bloc.
"In contrast to the Conservatives' megaphone diplomacy, we will conduct relations with our European neighbours respectfully and in the spirit of friendship," Mr Corbyn said.
"Our strong links with our European sister parties gives Labour an advantage in reaching an outcome that works for both sides."
His visit comes after Foreign Secretary Boris Johnson said the EU could "go whistle" if it wanted an "extortionate" divorce bill from the UK, prompting Mr Barnier to respond: "I'm not hearing any whistling, just the clock ticking."
Mr Jones said he would use his meeting to push for "full and unfettered access" to the EU single market and to avoid no deal being reached.
The Welsh first minister said he hoped to demonstrate to Mr Barnier that there were "parts of the UK that are prepared to engage constructively with the EU 27, rather than indulge in playing to the gallery".
Ms Sturgeon's spokesman said the meeting was "an opportunity to brief Mr Barnier on Scotland's priorities and seek to enhance our understanding of the current EU position as Brexit negotiations continue".
He added: "Our priority is protecting Scotland's vital interests, and building consensus against an extreme Brexit outside the single market, which would be potentially disastrous for jobs, investment and living standards.
"This is not about holding separate Scottish negotiations - we have always accepted that the EU will only negotiate with the UK, which is why we will continue to work hard to influence the UK position."
The Conservatives dismissed Mr Corbyn's trip to Brussels, saying Labour was "hopelessly divided" on key issues like immigration.
"Jeremy Corbyn wouldn't negotiate in Brexit talks, he would surrender. He has made clear Labour would accept any deal on offer - even if it was designed to punish Britain," Tory MP James Cleverly said.

Jeremy Corbyn has met the EU's chief Brexit negotiator in Brussels for what the Labour leader described as an "interesting, useful discussion".
Afterwards, Mr Corbyn said he was not negotiating with Michel Barnier, who he said had offered "no opinion" about Labour's vision for Brexit.
Labour has said it will oppose any deal Theresa May brings to Parliament if it fails to meet its "six tests".
Mr Barnier said he was "continuing to listen to all views on Brexit".
He tweeted:
Mr Corbyn was joined by shadow Brexit secretary Sir Keir Starmer for the talks, which come after Mr Corbyn told his party conference that he would back Theresa May if she proposed a "sensible" deal that kept the UK in a customs union with the EU.
The PM has repeatedly ruled this out.
Speaking after the meeting with Mr Barnier, Mr Corbyn said: "We've had an interesting, useful discussion with Mr Barnier. We have set out the views of the Labour Party surrounding Brexit following the conference speeches made by Keir Starmer and myself.
"We are obviously not negotiating. We are not in government, we are the opposition.
"But he was interested to know what our views are and the six tests we have laid down by which we will hold our government in future."
Asked if Mr Barnier had offered views on Labour's Brexit plan, Mr Corbyn said: "He made no opinion on this. It's not a negotiation, it's us informing him of what our views are and he telling us what the state of play was on the negotiations."
The Labour leader last met Mr Barnier, who is conducting the negotiations on behalf of the other 27 EU members, in July 2017.
EU officials said the timing of Thursday's meeting, coming just days before the start of the Conservative Party conference, was a coincidence and stressed that it was not part of the negotiations.
The meeting coincided with Mr Corbyn's trip to the Belgian capital to witness a square being renamed in honour of Jo Cox, the Labour MP who was murdered in June 2016.
Speaking ahead of his meeting with Mr Barnier, Mr Corbyn said he would urge EU officials "to do all they can to avoid a 'no-deal' outcome": "Crashing out of Europe with no deal risks being a national disaster."
Mrs May is under pressure to rethink her approach after European leaders warned key parts of her Chequers blueprint, which would keep the UK closely aligned with the EU in trade in goods, for future relations with the EU were not viable.
Up to 40 Tory Brexiteers have said they will oppose her plan if it comes to a vote in Parliament.
Home Secretary Sajid Javid said talk of a referendum on the outcome of the Brexit negotiations - which Labour has said must remain an option - was "deeply unhelpful" to getting the best deal for Britain.
But illustrating divisions within the Conservatives, his predecessor Amber Rudd told ITV's Peston that a new public vote was "absolutely" preferable to the UK leaving the EU next March without an agreement.
And backbencher Nadine Dorries said Mrs May should step down as she had become "handcuffed" to the Chequers deal and was not communicating the benefits of Brexit.
In his keynote leader's speech in Liverpool, Mr Corbyn said Labour would oppose a no-deal outcome and would also vote against any deal based on Chequers, as it would be extremely unlikely to meet the party's six tests, which include delivering the "exact same benefits" as members of the Single Market and Customs Union.
But he said if the PM brought home a deal that "includes a customs union and no hard border in Ireland", that protects jobs, people's rights at work and environmental and consumer standards, it would get his backing.
Mrs May has rejected staying in any form of customs union, saying it will prevent the UK from signing trade deals with other countries and setting its own tariffs.
Diplomats from the EU's 27 other members were briefed about the bloc's planning for a no-deal Brexit on Wednesday after a leaked document said the work had to intensify because of uncertainty about whether a final deal can be reached and approved by the UK and EU Parliaments.

Prime ministerial hopeful Jeremy Hunt has said he would consider withholding some of the UK's £39bn EU "divorce bill" in the event of a no-deal Brexit.
The foreign secretary told the Sunday Times he would not hand over "a penny more than is legally required of us".
His leadership rival Boris Johnson told Sky's Sophy Ridge he would "suspend" the money until the UK got a new deal.
He said he believed the EU would give ground to the UK as it had a "powerful incentive" to avoid a no-deal exit.
With less than a month to go before the new Tory leader is elected, the two contenders have also been setting out details of their proposed new Brexit negotiating teams amid reports that Olly Robins, Theresa May's chief negotiator, is planning to stand down this summer.
On the issue of the UK's "divorce bill", Mr Hunt told the Sunday Times "anyone who thinks I am going to write a blank cheque to the European Union is sorely mistaken".
"As a businessman I always paid my bills. That being said, if we leave without a deal I will not hand over a penny more than is legally required of us."
The Institute for Government (IFG) think tank previously said refusing to pay could lead the EU to launch a legal challenge.
But a House of Lords report into Brexit and the EU budget stated: "While the legal advice we have received differed, the stronger argument suggests that the UK will not be strictly obliged, as a matter of law, to render any payments at all after leaving."
BBC political correspondent Iain Watson says Mr Hunt knows that his voting to remain in the EU has not endeared him to some sections of the Conservative membership and is attempting to reassure them of his commitment to Brexit.
Earlier this month, Mr Johnson told the Sunday Times he would "retain" the financial settlement demanded by the EU until he had struck a deal more favourable than Theresa May's Withdrawal Agreement, which has been rejected three times by MPs.
In his Sky interview, Mr Johnson said the "drift and dither" of the past three years could not continue and he would take personal responsibility for "leading us out of this mess and getting Brexit done" by the revised deadline of 31 October.
Asked whether he would be willing to suspend Parliament to force through a no-deal exit, he said he did not "like the idea" and was "not remotely attracted to it".
But he said MPs "have got to understand it's their responsibility to get this thing done".
Mr Hunt and Mr Johnson are taking part in 15 hustings across the country as Conservative Party members decide on their party's next leader - and the next UK prime minister.
The 160,000 members will begin voting next week and the winner is expected to be announced on 23 July.
Mr Hunt's campaign team said he was in talks with the former Canadian prime minister, Stephen Harper, who he hopes could help to draw up plans for a deal similar to Canada's free trade agreement with the EU.
In response, Mr Harper tweeted that he was willing to help whoever won the contest.
Mr Johnson, who has already recruited Health Secretary Matt Hancock into his team, is thought to be drafting in Brexiteers such as Jacob Rees-Mogg as negotiators.
Mr Robbins, the civil servant who masterminded Theresa May's deal, is expected to step down shortly after the new prime minister enters office at the end of July.
He is the latest in a wave of civil servants to choose to quit rather than negotiate a new deal by within 100 days of either Mr Hunt or Mr Johnson becoming prime minister, to deliver Brexit by the delayed deadline of 31 October.
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Jeremy Hunt has told the EU it faces a "strategic choice" about whether to strike a mutually beneficial deal with the UK.
The foreign secretary is in Helsinki to discuss the UK's Brexit plan at the start of a three-day tour also taking in Latvia, Denmark and the Netherlands.
Mr Hunt said time was "at the point" to move negotiations forward, adding: "We need to take that opportunity."
The EU has said there are obstacles to meeting an October agreement deadline.
Last month, chief negotiator Michel Barnier ruled out allowing the UK to collect customs duties on the EU's behalf, a key UK proposal for post-Brexit trade.
Government ministers say they want to reach a deal with the EU covering issues like trade and border checks, but are also making contingency plans to prepare for leaving with no agreement in place.
Mr Hunt told reporters ahead of his meeting in Finland on Tuesday: "We want to safeguard our operational capacity as we leave the EU, and so we have put forward precise, credible proposals that ensure our ability to act is maintained.
"We are now at the point where the EU also faces strategic choices: with the option to move the negotiations forward and achieve a deal that works in our mutual interests.
"My simple message is that we need to take that opportunity."
The foreign secretary has previously warned of a "very real risk of a Brexit no deal by accident", if EU negotiators refused to change their approach.
Meanwhile, Germany Chancellor Angela Merkel called for a "reasonable, negotiated agreement" rather than an "unregulated Brexit".
Speaking at a 'town hall' event in the eastern city of Jena, she said the agreement should not be "static" and that if Britain wanted to continue benefiting from the EU in the future, "it must commit to re-accepting EU rules".
As well as promoting the proposals to the EU, the government is also trying to persuade Conservative MPs and members to back the package agreed at Chequers last month.
It prompted the resignation of key figures including Mr Hunt's predecessor, Boris Johnson, with some Tory Eurosceptics arguing the proposed trading relationship will leave the UK too closely tied to EU rules.

It is an "absolute priority" for the government to leave the EU by 23 May to avoid having to take part in European elections, Jeremy Hunt has said.
The foreign secretary said the public would find it "hugely disappointing" to be asked to send MEPs to Brussels.
Asked if it could be a disaster for the Tories, he told the BBC "in terms of polling it certainly looks that way".
Some local Tory activists have signalled they will not campaign and regard the polls as a "distraction".
Downing Street said that in order to avoid the need for elections, legislation implementing the Brexit withdrawal deal would have to be passed by Parliament by 22 May.
Last week, the EU agreed a new Brexit deadline of 31 October.
Talks between the government and Labour are set to continue over the Easter parliamentary recess in the hope of finding an agreement that will be acceptable to MPs.
A series of working groups in key areas, such as environmental standards, security and workers' rights, have been set up to try and find common ground.
Speaking on a visit to Japan, Mr Hunt said the talks with Labour had been "more constructive than people thought" but "we don't know if they are going to work".
If they did not lead anywhere, he suggested the government may "need to find a way to rebuild the DUP-Conservative coalition", which has come under real strain from Brexit.
The Democratic Unionists are supposed to support the government in key parliamentary votes to give it a majority in the House of Commons.
But they have refused to support the prime minister's withdrawal agreement over concerns with the controversial Irish backstop, which aims to avoid a hard border on the island of Ireland.
Mr Hunt told BBC Radio 4's Today programme that continuing Brexit "paralysis" would be "highly damaging" to the UK's global standing and international trading partners "are worried that we will become submerged in the mire of Brexit indecision".
While Japan and other major foreign investors were keen for the UK to "make up its mind" about Brexit, he suggested they would continue to keep faith with the UK even if it left without a deal.
"(Japan) has signed a deal with the EU and, in a no-deal situation, we hope that would roll over and apply for us, although no-deal, I think, is looking much less likely," he said.
"I think they are very keen to protect their trading relationship with the UK, but I think they are also wanting to talk to us about other things."
However, in February, the government released a statement saying it would not be able to replicate the EU's free trade deal with Japan after Brexit.
And Japan has not agreed to continuing existing trade terms in the event of no deal.
Mr Hunt downplayed talk of an imminent Conservative leadership contest, saying it would be a "sidetrack" from Brexit.
The foreign secretary, along with his predecessor Boris Johnson, are among a long list of potential candidates touted to succeed Mrs May when she stands down.
Asked whether the next leader could be someone, like himself, who campaigned to remain in the EU, Mr Hunt replied: "There is one very big difference between me and Boris, which is that I am foreign secretary and I have a very big job to do to try and get this deal over the line and that has to be my focus.
"I think that what matters is we have a cabinet that believes in Brexit."
On the first day of his trip to Japan, Mr Hunt met the country's prime minister Shinzo Abe and other political leaders.
He also took some time out of his political schedule to talk to pupils in a school in Tokyo. Mr Hunt is a fluent Japanese speaker, having taught English as a foreign language in Japan in his 20s.

Jeremy Hunt has said there is no possibility of the government backing a customs union with the EU after Brexit.
The health secretary said the UK wanted "frictionless trade" but would "find a different way" to achieve that.
Tory rebels are attempting to force the government to keep the option of a customs union with the EU on the table and have some cross-party support.
Theresa May will make a speech on the UK's future relationship with the EU next Friday.
And Labour Leader Jeremy Corbyn is set to outline Labour policy on a customs union on Monday, amid reports that his party's position on it is "evolving".
If he backs membership of a customs union, it could mean Mrs May faces a Commons showdown over the issue - with pro-European Conservative rebels joining forces with Labour MPs.
Conservative MP Anna Soubry says there is cross-party support for an amendment to the Trade Bill, currently going through Parliament, urging the government to pursue as a negotiating objective forming a customs union after Brexit.
A customs union means countries club together and agree to apply the same tariffs to goods from outside the union - but it does not allow members to strike their own trade deals.
Supporters of the UK being in a customs union argue it is vital to protect businesses - but opponents fear it would mean "Brexit in name only" and the UK should make its own arrangements.
Jeremy Hunt told BBC Radio 4's Today programme a customs union was "one way of getting frictionless trade but it is not the only way".
The government wanted to agree "frictionless trade by agreement between two sovereign bodies, the United Kingdom and the European Union", he said.
Asked if there was any possibility of the government coming round to the idea of a customs union with the EU after Brexit, he replied: "No".
The health secretary was not at the meeting of senior ministers at Chequers on Thursday but said a broad agreement had been reached ahead of a discussion by the whole cabinet and the prime minister's speech next Friday.
Despite "divergent views" there was a  "central common understanding is that there will be areas and sectors of industry where we agree to align our regulations with European regulations, such as the automotive industry.
"But it will be on a voluntary basis, we will as a sovereign power have the right to choose to diverge, and what we won't be doing is accepting changes in rules because the EU unilaterally chooses to make those changes," said Mr Hunt.
But pro-EU Labour backbencher Chuka Umunna - an ally of Anna Soubry - warned Theresa May her plan to leave the customs union could be defeated by MPs.
"If they are not going to change their position they are going to lose votes in the House of Commons, it's a straightforward as that."
Former prime minister Tony Blair said if there was an "impasse" in Parliament on the customs union issue, it made the case stronger for a referendum on the final Brexit deal - something dismissed by Labour Brexiteer Kate Hoey as "ridiculous".
He said a customs union would mitigate the problems of a "hard border" between Northern Ireland and the Republic of Ireland. In an article on his website, he attacked those politicians who, he said, were "prepared to sacrifice the Good Friday Agreement on the altar of Brexit and declare that the peace agreed in Northern Ireland is not, really, worth having anyway".
"This is irresponsibility that is frankly sickening," he said.
Mrs May will meet European Council President Donald Tusk in London on Thursday, the day before her speech.
Meanwhile the Times has reported that the prime minister is planning a U-turn over the right of EU citizens who arrive in the UK after Brexit, but during the "transition period", to remain in the country permanently.
Conservative Brexiteer Jacob Rees-Mogg told the BBC that would be "quite wrong": "I'd be astonished if Mrs May would make U-turn of that kind; she is a lady of great backbone and for her to kowtow to the European Union is, I think, unconscionable."

A "lot more work" is required to get MPs to back Theresa May's Brexit deal, Jeremy Hunt has said, amid uncertainty over whether it will be put to a vote for a third time this week.
The foreign secretary said there were "encouraging signs" that opponents of the deal were slowly coming round.
But he said another vote would only be held before Thursday's EU summit if ministers were "confident" of victory.
A number of Brexiteers have signalled they will continue to oppose the deal.
Former foreign secretary Boris Johnson called for further changes to the terms of withdrawal, which the EU has rejected, while 22 Tory MPs have written to the Daily Telegraph saying that leaving without any agreement - known as a no-deal exit - on 29 March would actually be a "good deal" for the UK.
Although the PM's plan is expected to be voted on for a third time in the coming days, the BBC's political editor Laura Kuenssberg said the situation remained highly unpredictable.
She said it was "eminently feasible" the PM would delay a vote until after Thursday's summit - at which European leaders will discuss a UK request to extend the Brexit process and delay the UK's departure.
Last week, MPs rejected Theresa May's deal for a second time - this time by 149 votes - and then backed plans to rule out leaving the EU without a deal.
They also voted in favour of an extension to the process - either until 30 June, if the deal is supported before 20 March; or a longer one that could include taking part in European elections if MPs reject her plan again.
All 27 EU member states would have to agree to an extension.
The possibility of Brexit being delayed or overturned in another referendum has seen some MPs reluctantly back Mrs May's deal.
A group of 15 Tory MPs from Leave-backing constituencies, including former Brexit Secretary David Davis, wrote a letter urging colleagues to back the deal to ensure Brexit goes ahead.
Speaking as he arrived in Brussels for a meeting of EU foreign ministers, Mr Hunt welcomed the fact "strong critics" of the deal were now prepared to support it in order to prevent the risk of "paralysis".
"I think there are some cautious signs of encouragement," he said. "But there is a lot more work to do...That is why we will be redoubling our efforts this week."
Asked if a third vote would definitely happen before Thursday's EU summit, he said he hoped it will but "we have to be confident we will get the numbers".
So far the number of Tories publicly switching positions falls far short of the 75 MPs Mrs May needs to switch sides.
Andrea Jenkyns told BBC News she was a "conviction politician...and would not be bullied into backing the deal" while Lee Rowley told Politics Live he could not support the deal as it stood as a "matter of principle".
Writing in his weekly Daily Telegraph column, Mr Johnson warned the UK would be "humiliated" if there was not a radical change of approach.
Jacob Rees-Mogg, chair of the European Research Group of Tory Brexiteers, said he was "waiting to see" whether the Democratic Unionists would swing round behind the deal before deciding which way to vote.
But he said he still believed leaving without any agreement was the "best option", telling LBC "it means... we will have restored our nation's independence".
Senior ministers have indicated the support of the DUP's 10 MPs, whose votes prop up the Conservative government, remains crucial.
No 10 confirmed negotiations with the DUP were continuing, including over the question of how the Northern Ireland Assembly could block any new regulatory barriers to trade with the rest of the UK.
DUP MLA Jim Wells told BBC Radio 4's Today the party still had a "huge difficulty" with the existing backstop arrangements - designed to prevent a hard border on the island of Ireland but which opponents say will separate Northern Ireland from the rest of the UK.
He said: "We could find ourselves locked in there forever in effect - and once you get in, you can never get out."
With UK politics mired in a fog of confusion, the only thing the EU can control this week is choreography at their leaders' summit.
Donald Tusk, European Council President and the representative of all 27 EU countries in Brussels, is visiting a number of capitals to try to co-ordinate a single EU response if or when Mrs May asks for an extension to Article 50.
On Monday, he's in Berlin and Paris - capitals of the EU superpowers, Germany and France. But when it comes to an extension, any of the EU's 27 leaders has a veto. The decision must be unanimous.
This conjures up horror visions in EU leaders' minds over being held to ransom by one of their ranks keen to use this leverage over Brexit to win a concession from Brussels over a separate issue.

Foreign Secretary Jeremy Hunt has warned Theresa May against agreeing a Brexit deal with Labour that involves a customs union with the EU.
Mr Hunt suggested that such an agreement would result in even fewer Tory MPs backing a deal in Parliament.
But Jeremy Corbyn insists his support is contingent on ministers accepting the need for a customs union.
Supporters say it would be better for businesses, but opponents feel it stops the UK setting its own trade policy.
Talks between Labour and the government have been taking place for a number of weeks after Mrs May's Brexit deal with the EU was effectively rejected for a third time by MPs.
Downing Street says further talks are being scheduled "in order to bring the process toward a conclusion" - and according to BBC Newsnight's political editor Nicholas Watt, a sense of urgency is growing.
Labour has previously complained that the government appeared unwilling to move on the possibility of a customs union.
But the PM's de facto deputy David Lidington said on Monday that the latest round of talks had been "productive", while Labour described them as "constructive".
All EU members - including the UK at present - are inside the customs union, meaning they do not have to pay taxes, called tariffs, to move goods and services between them.
This keeps cost down and avoids delays, but members have to operate as part of a bloc and cannot do their own trade deals with other countries around the world.
Labour is arguing for the UK to be part of a new form of customs union arrangement where the country could have "a say" in policy despite no longer being in the EU.
Critics say the EU would never agree to that, and in any case, the purpose of Brexit is to break free and remaining in a customs arrangement would go against that.
Leaving the customs union was also a Conservative manifesto commitment at the 2017 general election.
Mr Hunt told BBC Radio 4's Today programme: "If we were proposing - which I very much hope we don't - to sign up to the customs union, then I think there is a risk you would lose more Conservative MPs than you would gain Labour MPs."
However, he said he "definitely" thought the government could secure a deal that MPs would back.
Other cabinet ministers - including International Trade Secretary Liam Fox - have also recently signalled their unease at a customs union agreement.
Shadow chancellor John McDonnell tweeted that Mr Hunt's comment did "not inspire confidence that if a deal is agreed it would be successfully entrenched and last any longer than the next Tory leadership election".
Nick Boles, an independent MP who quit the Conservatives over the party's Brexit stance, also criticised Mr Hunt's comments as "ignorant and unhelpful", saying on Twitter that it revealed "naked opportunism" over the Conservative leadership.
Mrs May has said she will resign if her deal is passed through Parliament, leading to the prospect of an imminent leadership contest.
The prime minister is keen to get the Withdrawal Agreement Bill - legislation required to implement the withdrawal deal - through Parliament as soon as possible.
Ministers insist it is still their aim for that to happen by 22 May so the country does not have to take part in elections to the European Parliament a day later.

John Bercow has insisted MPs will have their say over whether the UK leaves the EU without a deal on 31 October.
The Speaker dismissed claims from some Brexiteers that because a no-deal exit is the default position in law, it will "inevitably" happen if no agreement is reached by then with Brussels.
Instead, he said there was "much debate to be had" and it was "unimaginable" that Parliament would be sidelined.
The October deadline was set after MPs repeatedly rejected Theresa May's plan.
The Commons has already voted to block a no-deal exit, but that vote was non-binding.
Mr Bercow's comments come as candidates for the Conservative leadership have been laying out their Brexit positions.
Several of them, including Boris Johnson and Dominic Raab, have said they would be willing to leave the EU on a no-deal basis. Others, though, like Jeremy Hunt and Rory Stewart, say that would be unacceptable.
The winner of the contest - not yet formally under way - is expected to be confirmed in July and will also become the UK's next prime minister.
Speaking at the Brookings Institution in Washington, US, Mr Bercow said: "There is a difference between a legal default position and what the interplay of different political forces in Parliament will facilitate.
"The idea that Parliament is going to be evacuated for the centre stage of debate on Brexit is simply unimaginable. The idea the House won't have its say is for the birds."
He continued: "The idea that there is an inevitability of a no-deal Brexit would be a quite wrong suggestion. There is no inevitability whatsoever about that."
Mr Bercow said there was still "a lot still to be said... and policy to be determined."
But he would not predict the outcome, and said Article 50 - the mechanism to leave the EU - was triggered under the last Parliament and "no Parliament can bind the hands of its successor".
"I believe passionately that Parliament must do what Parliament thinks is right," said Mr Bercow.
"MPs have a duty to do what they think is right in terms of voice and vote."

The shadow chancellor says Labour MPs will not be "bribed" into supporting Theresa May's Brexit deal in exchange for funding for their constituencies.
John McDonnell said any such offer would be "pork-barrel politics" and "dangerous for our democracy".
It follows reports that investment could be made in Leave-voting constituencies to secure MPs' votes.
A spokesman for the PM said this week any investment to tackle inequality could not be called "cash for votes".
The government is understood to be considering proposals from a group of Labour MPs in predominantly Leave-supporting constituencies to allocate more funds to their communities for big infrastructure projects.
It is thought the MPs have urged the prime minister to consider re-allocating the EU's regional aid budget away from big cities and local councils and to give the cash direct to smaller communities, often in former steel and coal mining areas.
On Thursday, Labour MP John Mann, who was one of only three Labour MPs to back Mrs May's Brexit deal, told her to "show us the money".
On a visit to Stoke-on-Trent on Saturday, however, Mr McDonnell rejected any link between votes and funding.
He said: "I can't see individual MPs, to be honest, selling their vote in parliament in this way and what most MPs I've spoken to are saying is if there is money to invest it should be invested anyway so just get on with it."
"Don't expect us to be bought and bribed in this way - that's a form of corrupt politics that we don't want to be introduced into our political system."
Mr McDonnell also criticised the government over its "supply and confidence" arrangement with the Democratic Unionist Party (DUP).
The DUP negotiated a deal for an extra £1bn in spending for Northern Ireland over two years in exchange for supporting Mrs May's minority Conservative government, following the snap election in 2017.
Mr McDonnell said: "It was something like £100m a vote they spent to get the DUP supporting them, so they already introduced that pork-barrel contractual politics.
"I think it degrades our political system and to try and extend it in this way, I think it's dangerous for our democracy."
His comments follow Labour Party chairman Ian Lavery saying that accepting any offer of funding "would be fool's gold".
Mr Mann, MP for Bassetlaw, a former coal mining area in Nottinghamshire, met cabinet office officials in Whitehall earlier this week.
Speaking afterwards, he told reporters: "I want to see, when we leave the European Union, significant investment in new technologies, new jobs, science and industry in areas like mine and all the other areas in the country like mine.
"This isn't transactional politics, this is about getting a national fund... the areas that voted Leave the most are the areas that have not had that investment."
Ministers are continuing to try to win support for the withdrawal deal Mrs May has negotiated with the EU, which was rejected by a historic margin in a Commons vote more than two weeks ago.
A spokesman for the prime minister this week confirmed ministers were looking at a programme of "national renewal" following Brexit to tackle inequality and rebuild communities, but that he "absolutely wouldn't characterise" the reported investment offer as "cash for votes".
This week, a backbench amendment to replace the Irish backstop with "alternative arrangements" in the deal, won the support of the Commons.
The PM says she will now return to Brussels in a bid to re-open negotiations.

Boris Johnson says he is "very confident" MPs will back the Brexit deal he has struck with the EU - despite the DUP's opposition to it.
The prime minister claimed he would win what is expected to be a knife-edge Commons vote on Saturday.
"This is our chance in the UK as democrats to get Brexit done, and come out on 31 October," he said.
The DUP is against concessions he made to the EU on customs checks at points of entry into Northern Ireland.
The party's deputy leader, Nigel Dodds, accused the prime minister of being "too eager by far to get a deal at any cost".
The PM must win support for his deal from Brexiters on his own side, as well as from 23 former Tory MPs who now sit as independents - including 21 whom he kicked out of the Tory parliamentary party last month after they rebelled against him in a bid to prevent a no-deal Brexit.
He must also convince Labour MPs concerned about protection for workers and the environment in the new deal.
Shadow Brexit secretary Sir Keir Starmer said Labour would oppose the deal, citing concerns it would allow the UK to move further away from EU regulations in the future.
He said the new agreement "paves the way for a decade of deregulation" and argued it would give the government "licence to slash" worker, environment and consumer protections.
Speaking in Brussels, Mr Johnson denied he would meet the same fate as his predecessor Theresa May, who repeatedly failed to get a Brexit deal through Parliament.
"I am very confident that when my colleagues in Parliament study this agreement that they will want to vote for it on Saturday and in succeeding days," he said at an EU summit in Brussels.
Appealing to the DUP, which the government relies on for support in key Commons votes, he insisted the UK could leave the EU "as one United Kingdom" and "decide our future together".
Mr Dodds earlier said he expected a "massive vote" against Mr Johnson's deal on Saturday in the House of Commons - and the DUP expected to "play a crucial role" in amending the legislation.
The new deal is largely the same as the one agreed by Theresa May last year - but it removes the controversial backstop clause, which critics say could have kept the UK tied indefinitely to EU customs rules.
Northern Ireland would now remain in the UK's customs union, but there would also be customs checks on some goods passing through en route to Ireland and the EU single market.
The DUP said: "This is not acceptable within the internal borders of the United Kingdom."
The party also objects to Northern Ireland potentially being part of a different VAT regime to the rest of the UK and is concerned about the deal violating the Good Friday Agreement's principle of consulting the nationalist and unionist communities on important issues.
European Commission President Jean-Claude Juncker caused a flurry earlier when he said there was no need for a Brexit extension as "we have a deal".
This was seen as a major boost for Mr Johnson, who has always insisted he would not go beyond 31 October - even if he was forced to ask for an extension under the terms of the so-called Benn Act, which kicks in on Saturday if MPs vote his deal down.
But Mr Juncker's EU colleagues were more cautious, with European Council President Donald Tusk saying he would "consult" member states about an extension if necessary.
At a joint press conference, Mr Tusk, Mr Juncker, EU chief negotiator Michel Barnier and Irish Taoiseach Leo Varadkar all expressed regret that the UK was leaving the EU.
Mr Tusk said: "On a more personal note, what I feel today, frankly speaking, is sadness, because in my heart I will always be a Remainer, and I hope that our British friends decide to return one day, our door will always be open."
The winning post for votes in the House of Commons is 320 if everyone turns up - seven Sinn Fein MPs don't sit and the Speaker and three deputies don't vote.
There are currently 287 voting Conservative MPs. The prime minister needs to limit any rebellion among them.
Then, if the DUP won't support his deal, he'll need the backing of 23 former Conservative MPs who are currently independents. Most will probably support the deal, but not all.
That's still not quite enough, though, so the PM will also need the backing of some Labour MPs and ex-Labour independents. In March, when MPs voted on Theresa May's deal for the third time, five Labour MPs backed it, plus two ex-Labour independents.
This time it's likely to be a bit higher than that because several MPs have said they would now back a deal.
All this still leaves the vote very close. And it's possible some MPs could abstain, making it even harder to predict the outcome.
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Labour has "run out of excuses" to oppose an early election, Boris Johnson has said, as MPs vote on whether to back his call for a December poll.
The PM said "nobody relished" going to the polls weeks before Christmas but this Parliament had "run its course" and was "incapable" of settling Brexit.
The PM has formally accepted the EU's offer of a Brexit extension until 31 January 2020 agreed earlier on Monday.
In a letter to EU officials, he said it was an "unwanted prolongation".
Urging the EU to rule out any further extension, he said there was time to ratify his Brexit deal but he feared the current Parliament would never do so "as long as it has the option of further delay".
The PM's acceptance means that the UK will not leave the EU on Thursday - despite a "do or die" promise he repeatedly made during this summer's Tory leadership campaign and since taking office in July.
EU Council President Donald Tusk said what was being offered was a "flextension" - meaning the UK could leave before the deadline if a deal was approved by Parliament.
It comes as MPs prepare to vote on the PM's proposals for an early general election on 12 December. The SNP and Lib Dems have also proposed an election - on 9 December. The vote is expected after 1900 GMT.
Speaking in the Commons, Mr Johnson said Labour was the only main opposition party resisting an early election, telling Mr Corbyn that he "can run but he cannot hide" from the electorate.
In response, Mr Corbyn said he backed an election but only after certain conditions were met - including legal confirmation of the extension and reassurances that students wouldn't be "disenfranchised" by the mid-December date because they had left for the Christmas holidays.
"The reason I am so cautious is that I do not trust the prime minister," he said. "Today he wants an election and his bill - not with our endorsement."
A No 10 source said the government would introduce a bill "almost identical" to the Lib Dem/SNP option on Tuesday if Labour voted their plan down later, and "we will have a pre-Christmas election anyway".
The SNP's Westminster leader Ian Blackford said it would only support a poll "on its terms" and suggested this could depend on 16 and 17-year olds and EU nationals being given the vote.
The UK was due to leave the EU on Thursday, but Mr Johnson was required to request an extension after Parliament failed to agree a Brexit deal.
The prime minister had repeatedly said the UK would leave on 31 October deadline with or without a deal, but the law - known as the Benn Act - requires him to accept the EU's extension offer.
The Lib Dem/SNP plan does not include a new timetable for his legislation - the Withdrawal Agreement Bill.
They want the 9 December because it would not leave enough time for the bill to become law before Parliament is dissolved - which must happen a minimum of 25 working days before an election.
The BBC's political editor, Laura Kuenssberg, said she understands the government has offered to fix the election date on 12 December, but a Lib Dem source told her they were holding firm to their date, adding: "If we are doing this, we are not doing it on the government's terms."
Labour MPs are expected to abstain in the Commons vote on a 12 December election.
It comes as government figures showed a surge in voter registrations, with nearly two million registering in the past eight weeks.
Over half of the applications - 58% - were from voters aged 34 or under, compared to just 7% for those over 65. The swell coincided with Mr Johnson's first proposal, in early September, for a snap election.
The EU has finally announced its informal approval of a new Brexit extension - but what an excruciatingly long and confusing political dance to get there. And the dance is not over yet.
To become a formal offer, the Brexit extension still needs to be accepted by UK PM Boris Johnson. This is EU law and an unavoidable part of the procedure.
But how uncomfortable for the prime minister who sought to distance himself as much as possible from the extension, previously promising that he would rather die in a ditch than request one.
The EU is also attaching some extra wording to the extension - including a reminder for the UK that, until it leaves, it remains a fully paid up member of the EU, including all the rights and obligations that go along with membership.
After the extension has been signed off this week, Brussels will watch, arms folded from the sidelines as the next moves are decided in Westminster.
The SNP and Lib Dems have broken with the Labour position on Brexit to push for an election on 9 December.
Their bill would tweak the 2011 Fixed-term Parliaments Act - the law which sets the time-frame for elections.
If passed, it would enable an election to take place with only a majority of one, rather than two-thirds of MPs.
It would also set the election date in stone and give PM no "wriggle room" to alter the date after MPs had voted, which he could theoretically do under the current legislation.
Lib Dem leader Jo Swinson said while her preference was for another referendum, there was not enough support in Parliament for this as things stood.
A general election, she told MPs, was the only way to stop Mr Johnson pushing through his Brexit deal in the coming weeks "on the back of Labour votes".
She said she would not insist for votes for 16-year olds as the price of her support. "The worst thing we can do for 16 and 17 year olds is to crash out without a deal"," she said.
"Leaving EU is the thing that will wreck their future."
The leader of The Independent Group for Change, former Conservative MP Anna Soubry, sent an email to her party's supporters accusing the SNP and Lib Dems of "turning their backs" on the People's Vote campaign.
The Independent Group for Change has five MPs.
Plaid Cymru, which has four MPs, said another referendum, rather than an election, was the "clearest way to end the Brexit chaos".

Labour would keep the UK in the EU single market and customs union for a transitional period after leaving the EU, the party has said.
Shadow Brexit secretary Sir Keir Starmer set out Labour's new position in the Observer.
The shift in policy would mean accepting the free movement of labour after leaving the EU in March 2019.
Sir Keir said the transition would be "as short as possible but as long as necessary".
Meanwhile, Brexit Secretary David Davis has urged the European Commission to have a flexible approach to talks.
Labour's leadership has been criticised by opponents for a lack of clarity on what deal Britain should seek immediately after leaving the EU.
Sir Keir said a transitional period was needed to avoid a "cliff edge" for the economy, so that goods and services could continue to flow between the EU and UK while negotiations on the permanent deal continued.
"Labour would seek a transitional deal that maintains the same basic terms that we currently enjoy with the EU," he wrote.
"That means we would seek to remain in a customs union with the EU and within the single market during this period.
"It means we would abide by the common rules of both."
He compared this with the government's preference for "bespoke" transitional arrangements after leaving the EU, which, Sir Keir said, were highly unlikely to be negotiated before March 2019.
He did not say how long the transitional period would be - only that it would be "as short as possible, but as long as is necessary".
By BBC political correspondent Jonathan Blake
A significant shift or simply the clarification of a confused picture?
Either way, Labour's plan for a transitional period after the UK leaves the EU only takes us so far.
Yes, we now know that a Labour government would keep the UK in the customs union and single market for some time after March 2019.
But how long for? And what happens after that?
Sir Keir has suggested continued membership of the customs union and single market with stricter controls on immigration.
That idea is likely to go down about as well as a flat beer in Brussels.
In the words of the EU's chief negotiator, "cherry picking is not an option".
Labour's plan will be music to the ears of its remain-voting supporters in London and beyond.
But to those in the party's heartlands, keen to see the back of Brussels, it may sound more like an alarm bell.
The customs union is the EU's tariff-free trading area, which imposes the same taxes on imports from certain countries outside the union.
The single market also includes the free movement of goods, services, capital and people.
"Those who campaigned to leave the EU are likely to be concerned that this could see unlimited  migration continue for some time after Brexit," said the BBC's political correspondent Iain Watson.
After the transitional period, Sir Keir said, the new relationship with the EU would "retain the benefits of the customs union and the single market", but how that would be achieved "is secondary to the outcome".
Remaining in a form of customs union with the EU was a "possible end destination" for Labour, he said, but that must be "subject to negotiations".
He said a final deal must address the "need for more effective management of migration".
Jeremy Corbyn's office confirmed that the proposals had been agreed with him and were official policy.
TUC general secretary Frances O'Grady said it was a "sensible and reasonable" approach to take, and would give working people "certainty" on their jobs and rights at work.
Labour MP Chuka Umunna, co-chairman of the all-party parliamentary group on EU relations, told BBC News the change in policy was "welcome" and urged Labour to commit to staying in the single market after the transition period.
However, a spokesman for Labour Leave, a pro-Brexit movement, warned the party risked losing the 37% of Labour voters who voted to leave the EU.
"Seven out of 10 Labour constituencies voted Leave. Single market membership is EU membership in all but name. Labour must honour the referendum," it tweeted.
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Liberal Democrat Brexit spokesman Tom Brake said it was "all spin and no principle".
Meanwhile, the SNP's Westminster leader, Ian Blackford, said Labour was simply delaying the UK's departure from the market, saying: "Labour still face a cliff edge, only later than the Tories."
Former-UKIP leader Nigel Farage tweeted that Mr Corbyn had "betrayed every Labour voter", having said he would support the UK leaving the single market during the general election campaign.
The government has also called for a transition period to help business adjust after Brexit.
But chancellor Philip Hammond and trade secretary Liam Fox said the UK would be "outside the single market and outside the customs union" during this period.
A paper subsequently published by the government said it could ask Brussels to establish a "temporary customs union" after March 2019.
But during this period, it would also expect to be able to negotiate its own international trade deals - something it cannot do as an EU customs union member.
Meanwhile, Brexit Secretary David Davis will meet the European Commission's chief negotiator Michel Barnier on Monday to formally open Brexit discussions.
The government said this week's negotiations were "likely to be technical in nature", ahead of more substantial talks in September.
It said both sides must be "flexible and willing to compromise" when it comes to solving areas where they disagree.

Labour MPs have been warned by their party not to accept money for their constituencies in return for supporting Theresa May's Brexit deal.
Labour chairman Ian Lavery said "taking such a bribe would be fool's gold" given the Tories' record on austerity.
John Mann has urged the PM to "show us the money" with "transformative investment" in areas that voted Leave.
But the Labour MP, who backed Theresa May's Brexit deal, denied it amounted to "transactional politics".
Writing on the Labour List website, Mr Lavery, the former general secretary of the National Union of Mineworkers and a close ally of Jeremy Corbyn, accused Mrs May of playing "divide and rule" over Brexit.
"If the prime minister wants to talk about ending austerity and protecting rights as we leave the EU, she should do so with the leader of the Labour Party and his team.
"Any Labour MP seriously considering discussions with the PM should remember her record and that of her party going back generations. Quite simply, taking such a bribe would be fool's gold."
The government is understood to be considering proposals from a group of Labour MPs in predominantly Leave-supporting constituencies, to allocate more funds to their communities for big infrastructure projects.
It is thought the MPs have urged the prime minister to consider re-allocating the EU's regional aid budget away from big cities and local councils and to give the cash direct to smaller communities, often in former steel and coal mining areas.
John Mann, MP for Bassetlaw, a former coal mining area in Nottinghamshire, met cabinet office officials in Whitehall on Thursday and told reporters: "I want to see, when we leave the European Union, significant investment in new technologies, new jobs, science and industry in areas like mine and all the other areas in the country like mine.
"This isn't transactional politics, this is about getting a national fund ... the areas that voted Leave the most are the areas that have not had that investment."
A couple of weeks ago, a Labour MP confessed quietly that they would vote for Theresa May's Brexit deal in the end.
But they wanted something to show for it, suggesting, half-teasingly, that they wanted the PFI debt of their local hospital paid off.
That MP was frustrated that the government had taken so long, as they saw it, to try to reach out to get them on board.
But they predicted that we would soon see what they described as "transactional politics", in a way that we haven't seen before in this country.
With Number 10 in a frantic hunt for support, maybe that time has arrived.
It comes as ministers continue to try to win support for the withdrawal deal Theresa May has negotiated with the EU, which was rejected by a historic margin in a Commons vote more than two weeks ago. Mr Mann was one of only three Labour MPs to back the deal.
Downing Street says that ministers are looking at a programme of "national renewal" following Brexit, to tackle inequality and rebuild communities but has denied any funding amounted to "cash for votes".
Asked if the government was trying to bribe Labour MPs, Chancellor Philip Hammond said: "No it doesn't work like that I'm afraid.
"What we are doing is looking at some of the drivers behind the Brexit vote.
"What was it that felt that made so many communities feel that they didn't have a stake in the way our economy was operating?
"And making sure we are investing in, for example, former coalfield communities to ensure they can keep up with the changes that are happening across the economy and that they too can share in our future prosperity."
But David Lammy, Labour MP for Tottenham, in north London, tweeted his response to headlines suggesting the PM was preparing to "woo Labour MPs with cash to back Brexit" saying: "Cowards and facilitators. History will be brutal."
And his colleague Chuka Umunna, who like Mr Lammy campaigns for another EU referendum, said on Twitter: "Government by bung is WRONG - whether involving DUP MPs or those from any other party.
"Funding should be based on the needs of the people not on the needs of an incompetent Tory PM to secure the votes of MPs for a deal which will make the UK poorer."
Asked about Mr Lammy's comments, the former Labour MP Frank Field, who now sits as an independent, said: "David would say that, he is in London. He isn't going to get any money and they are well provided for by the amount of rates they get in most areas and the wealth the business community brings to London."
The veteran MP for Birkenhead, on Merseyside, who backs Brexit, told BBC Newsnight Labour MPs representing Leave constituencies "should be fighting me to get to the front of the queue to get those funds".
He added: "That's how politics operates. The Tory party in government is very good at shoving money their way to their constituencies. I wish Labour were as effective."
But Anna Turley, MP for Redcar, a Teesside coastal town, which voted to leave the EU, told the same programme she found the idea "appalling".
"We have had nearly a decade now of austerity that has seen constituencies like mine absolutely hammered, £6bn has come out of public spending in the North by this government and if [there is] a programme or national renewal, I'm afraid it's too little too late."

Talks between Conservative and Labour teams have taken place for a second day, in a bid to end Brexit deadlock.
The discussions, which lasted 4.5 hours, were described as "detailed and productive" by the government.
Shadow Brexit Secretary Sir Keir Starmer said earlier that the idea of a "confirmatory" referendum on any Brexit deal would be discussed.
MPs backed a bill on Wednesday which would force the PM to seek a new delay to Brexit.
The House of Lords are debating it in general terms -  but detailed line-by-line scrutiny, when they will have the chance to propose changes to the bill, will not take place until Monday.
Leaving the cross-party talks, Sir Keir did not answer questions about what had been discussed, telling reporters: "We have had further discussions and we will be having further discussions with the government."
A Labour spokesman said the talks "are continuing and the teams are planning to meet again".
A Downing Street spokesman said: "Today both sets of negotiating teams met for four and a half hours of detailed and productive technical talks in the Cabinet Office, supported by the civil service."
The talks were attended on the Labour side by shadow Brexit secretary Sir Keir Starmer and shadow business secretary Rebecca Long-Bailey.
The government's negotiating team was senior cabinet minister David Lidington, Brexit Secretary Steve Barclay, chief whip Julian Smith, Business Secretary Greg Clark and Gavin Barwell - the prime minister's chief of staff.
Thursday's meeting followed discussions between Theresa May and Jeremy Corbyn on Wednesday.
The UK is due to leave the EU on 12 April, and as yet, no withdrawal deal is in place.
But ministers have warned that the backbench bill - put forward by Labour's Yvette Cooper - could increase "the risk of an accidental no-deal".
No 10 says Ms Cooper's bill, passed by the Commons with a majority of one vote on Wednesday, would deny the PM the power to agree a deal with EU leaders on April 10, as MPs would have to agree to any new Brexit date.
Any Brexit delay will require the unanimous backing of all 28 EU leaders at a summit next Wednesday.
If they agree - but suggest a different date to the one backed by MPs - the prime minister would have to bring it back to the Commons for further approval on Thursday 11 April.
"By April 11, the European Council will have concluded and the leaders will have returned to their member states. In the words of the secretary of state, the bill could increase the risk of an accidental no-deal exit," the prime minister's spokesman said.
The main item of business in the last frantic 24 hours has been the cross-party talks between the Conservatives and the Labour Party.
From both sides, it sounds like they are serious and genuine, and negotiators got into the guts of both their positions and technical details on Thursday.
Remember, behind the scenes there isn't as much difference between the two sides' versions of Brexit as the hue and cry of Parliament implies.
But the political, not the policy, distance between the two is plainly enormous.
The backbench bill, which was steered through the Commons in one day, will need the approval of the House of Lords if it is to become law.
Peers were expected to sit late into the night on Thursday as they hold their second reading debate on the bill.
The government's chief whip in the Lords, Lord Taylor said: "The proceedings on Monday the 8th should be concluded in a timely fashion to allow the House of Commons to consider any amendments made by this House."
It is the EU which decides whether to grant an extension, and German Chancellor Angela Merkel has met Irish Prime Minister Leo Varadkar for talks in Dublin.
Mr Varadkar said any further extension "must require and must have a credible and realistic way forward".
Mrs Merkel said she still hoped for an "orderly Brexit" adding: "I can say this from the German side - we will do everything in order to prevent a no-deal Brexit; Britain crashing out of the European Union.
"But we have to do this together with Britain and with their position that they will present to us."
Shadow Treasury minister Clive Lewis told BBC Radio 4's World at One that Labour would not be talking to the government if a "confirmatory referendum" wasn't an option.
But it has emerged that party chairman Ian Lavery offered to quit the shadow cabinet, after twice defying orders to vote in favour of another referendum.
And 25 Labour MPs - including former minister Caroline Flint and a number MPs for Leave-voting seats in the North and Midlands - have written to Jeremy Corbyn, saying another referendum should not be included in any compromise Brexit deal.
Meanwhile, Downing Street has announced a series of ministerial appointments, to replace ministers who quit over the government's Brexit strategy and Brexit votes.
Among them, party deputy chairman James Cleverly has been made a Brexit minister; Justin Tomlinson has been appointed as a minister in the Department for Work and Pensions; and Seema Kennedy has been made a health minister.

Labour should "unequivocally back Remain" in a fresh Brexit referendum and only then pursue power in a general election, its deputy has said.
Tom Watson said there was "no such thing as a good Brexit deal" and the 2016 Leave vote had been "invalidated".
Jeremy Corbyn said he did "not accept or agree with" his deputy's view.
"Our priority is to get a general election in order to give the people a chance to elect a government that cares for them," he said.
The Labour leader wants to hold another referendum once Labour has won power, in which voters would have the choice to remain in the EU alongside a "credible" Leave proposal.
However, he has said he would only choose a side once the shape of any revised Brexit deal negotiated by a Labour government became clear.
The BBC's political correspondent, Chris Mason, said Mr Watson was directly elected as deputy leader by party members, not appointed by Mr Corbyn, and so has a right to roam on policy other shadow cabinet ministers might not get away with it.
In a speech in London, Mr Watson said while an autumn general election seemed inevitable "that does not make it desirable".
"Elections should never be single issue campaigns," he argued, suggesting vital issues such as the future of the NHS, economic inequality and crime would be "drowned out" by the prime minister's "do or die" Brexit message.
"The only way to break the Brexit deadlock once and for all is a public vote in a referendum," he said. "A general election might well fail to solve this Brexit chaos."
In the event of another general election in the coming months, Mr Watson said Labour must be "crystal clear" about where it stands on Brexit if it wants to get a hearing for the rest of its domestic policy agenda.
"There is no such thing as a good Brexit deal, which is why I believe we should advocate for Remain. That is what the overwhelming majority of Labour Party members, MPs and trade unions believe."
Mr Watson will said that, though "very difficult", he and many others "respected the result of the 2016 referendum for a long time".
But, he added: "There eventually comes a point when circumstances are so changed, when so much new information has emerged that we didn't have in 2016, when so many people feel differently to how they felt then, that you have to say, no... the only proper way to proceed in such circumstances is to consult the people again."
The Liberal Democrats, who pushed Labour into third place in May's European elections with a strident anti-Brexit message, are pushing for Brexit to be stopped in its tracks by revoking Article 50 - the legal process for the UK's departure.
While stopping short of calling for that himself, Mr Watson said it was not too late for Labour to "win back" Remain voters.
"My experience on the doorstep tells me most of those who've deserted us over our Brexit policy did so with deep regret and would greatly prefer to come back," he added.
"They just want us to take an unequivocal position that whatever happens we'll fight to remain, and to sound like we mean it."
Former Labour leadership contender Owen Smith said Mr Watson was speaking for "the majority of Labour members and Labour voters", and that the party "should be clearing the Brexit issue off the table before we get to an election".
But another Labour MP, Gareth Snell - one of a group of MPs in the party wanting to bring back an amended version of Theresa May's original withdrawal agreement - said the "numbers simply don't exist" in Parliament to approve a further referendum.
He told Today: "The public have no appetite for a second referendum. The doors I knock every week… [voters] are not telling me they want to go back to the divisive referendum [but] they want a decision on this process to be taken as soon as possible."
Just 24 hours after Jeremy Corbyn hammered out a deal with the Labour-supporting unions, his deputy, Tom Watson, shattered any fragile unity.
Mr Watson and many Labour activists want a clearer commitment to campaign on a Remain platform - especially during a snap election.
So, apart from his own scepticism towards an EU that he believes needs reform, what is the thinking behind Jeremy Corbyn's position?
Well, it comes down to four things - psephology, party unity, politics and personal authority.
Unite's Len McCluskey dismissed Mr Watson's intervention, accusing him of "undermining" the leadership and suggesting his views "don't really matter".
The two men, who used to be close friends, fell out spectacularly in the aftermath of the Brexit referendum during an uprising by Labour MPs against Mr Corbyn's leadership.
The union leader suggested Mr Watson was "languishing on the fringes" of the party, adding: "It's sad. Now and again Tom pops up from where he has been hiding and comes up with something… which is normally to try and undermine his leader."
The Conservatives said Mr Watson had made it clear he wanted to "cancel" the 2016 Brexit referendum result.
Labour has voted twice against Boris Johnson's plans for a poll on 15 October.
The party's leadership has insisted it is eager for an election after the risk of a no-deal Brexit on 31 October has been ruled out.

Labour are backing a cross-party bid to ensure the UK cannot leave the EU without a deal.
Shadow Brexit secretary Sir Keir Starmer said the amendment to 11 December's Commons vote on the PM's Brexit deal had his "full support".
If MPs back the amendment it will not be binding but Theresa May would find it difficult to ignore.
And it could put Parliament in the driving seat if, as expected, MPs vote down the PM's Brexit deal.
Mrs May has repeatedly warned MPs that the only alternative to her Brexit deal is quitting the EU without a deal on 29 March.
The vast majority of Labour MPs are expected to vote against the deal on 11 December. However, a source has told the BBC there is a "growing consensus" among all MPs against a "no-deal" Brexit.
Labour leader Jeremy Corbyn told ITV's This Morning on Thursday that "nobody is going to allow no deal".
The amendment, tabled by Labour backbencher and chairman of the Brexit select committee, Hilary Benn, is understood to have support from Conservative, Labour, SNP, Liberal Democrat, Plaid Cymru and Green politicians.
Mr Benn argues it allows parliament to "take back control".
"For two years, she [Mrs May] said no deal is better than a bad deal," he told Radio 4's World at One.
"But frankly no deal all along has been the worst possible outcome and its really important that we close that off. Because we can't afford to fall over the edge of a cliff at the end of March."
Labour MP Yvette Cooper said the amendment would allow MPs to "properly debate and vote on the next steps, rather than just leaving it all" to the prime minister.
The BBC's Laura Kuenssberg says it supports what "some in Number 10 suspect - that is vote falls, Parliament essentially takes over from the executive".
Former Labour foreign secretary Jack Straw described the amendment as "a staging post" on the way to a further referendum.
Mr Straw, who was one of the Labour more Eurosceptic voices, says he believes there would be "a huge appetite" for a public vote.
By BBC political correspondent Chris Mason
Enter the four doctors.
A cross party quartet, pondering strategy, talking tactics.
They want another referendum - what campaigners call a People's Vote. So who are they?
Labour's Dr Paul Williams, Conservative GPs turned MPs Philip Lee and Sarah Wollaston, and the SNP's Dr Philippa Whitford.
Messages are zipping between them, trying to work out whether it is worth putting down an amendment to the big Brexit vote in Parliament, so MPs can express their support for another referendum.
I'm told they are in a "genuine dilemma" between wanting to articulate the views of those hundreds of thousands who marched through London calling for a "People's Vote" in October, but not wanting to "scupper the whole process" by failing to get the numbers and allowing opponents to say MPs don't back another referendum.
Senior figures in the People's Vote campaign emphasise that they must strike when their strength is at its greatest: after an expected government defeat on 11 December, when they hope Labour will, after failing to secure a general election, edge towards endorsing another referendum.
Up to six amendments will be voted on when MPs pass judgement on the prime minister's Brexit deal on 11 December.
Labour's front bench has tabled an amendment saying that the party cannot support the agreement, as it fails to provide for a customs union and "strong single market" deal. It also says it opposes a no deal withdrawal, and "resolves to pursue every option" that prevents such a scenario.
There is also likely to be a front bench amendment from the SNP. Some in Parliament think they are unlikely to pass but they hope a cross-party effort will be seen as less partisan and will have more chance of achieving a majority.
The amendments will be selected by Commons Speaker John Bercow, on 11 December - the last of five days of debate on the Brexit agreement.

Jeremy Corbyn has promised a further referendum on Brexit with a "credible Leave option" versus Remain if his party wins the next general election.
He said Labour was "ready" for the campaign, but its "priority" was to stop a no-deal Brexit.
Its manifesto will promise to reach a better Brexit deal, but is not expected to commit to either Leave or Remain.
Some senior party figures - close Corbyn allies - say they will campaign to stay in the EU in any circumstances.
They include shadow chancellor John McDonnell and shadow foreign secretary Emily Thornberry, who have both said remaining would be the best thing for the UK - even if the other option is a Labour-negotiated Brexit deal.
Union leaders want Leave on the ballot and met Mr Corbyn earlier to discuss the issue.
The BBCs political correspondent, Iain Watson, said senior Labour figures had been arguing that backing Remain would recover ground lost to the pro-EU Liberal Democrats in recent elections.
Pro-Remain Labour activists are also hoping the party's conference later this month will commit the leadership to backing Remain under all circumstances.
But, while Labour-affiliated unions - including Unite, who are one of the party's biggest backers - would rather stay in the EU than have no deal, they believe a Corbyn government should offer voters a choice in a referendum between a negotiated deal and Remain.
Speaking to the TUC conference in Brighton on Tuesday, he said: "Our priority is first to stop no-deal and then to trigger a general election.
"No one can trust the word of a prime minister who is threatening to break the law to force through no deal.
"So a general election is coming, but we won't allow Johnson to dictate the terms."
He added: "We're ready for that election. We're ready to unleash the biggest people-powered campaign we've ever seen.
"And in that election we will commit to a public vote with a credible option to leave and the option to remain."
The basis of Labour's election policy on Brexit became clear today.
Jeremy Corbyn agreed with Labour's significant funders - the affiliated trade unions - that if elected, the party would negotiate a new Brexit deal and put that to a referendum, along with the option to remain.
But the party will not say which option it would back during a general election.
So, during an imminent campaign, the leadership will be unable to tell voters if a future Labour government would advocate coming out or staying in the EU.
The Labour leader has rejected calls from senior figures in the party and grassroots activists to campaign explicitly to Remain during the election, amid fears votes and seats will be lost to the Lib Dems.
Today's union meeting was described as a senior Labour source as "decisive" in determining policy because the unions are formally represented on the committee which draws up the manifesto, so have huge influence over it.
Labour insiders hope to confine any disagreements on Brexit to a referendum, but sources admit the election campaign will be difficult to manage, as some shadow cabinet members have said they'd personally campaign to Remain even against a Labour deal.
In a wide-ranging speech, Mr Corbyn also promised to "put power in the hands of workers", pledging a future Labour government would enact "the biggest extension of rights for workers that our country has ever seen."
If elected, Labour would set up a specific government department for employment rights, he said, and give the brief to a dedicated cabinet minister.
Enforcement of rights would be boosted by a new agency with the power to enter workplaces and bring prosecutions on behalf of staff, he added.
Conservatives - 288 MPs
Prime Minister Boris Johnson has said he wants to leave the EU on 31 October "do or die". He says he wants to leave with a deal, but is willing to exit without one to ensure Brexit goes ahead by the current deadline.
SNP - 35 MPs
The SNP is pro-Remain and wants the UK to stay a member of the EU. It has been campaigning for another referendum on Brexit, and if it were to get one, would support Remain.
Liberal Democrats - 17 MPs
The Lib Dems also want to stay in the EU and have another referendum to achieve their goal - to revoke Article 50 (the law that sees the UK having to leave the bloc).
Democratic Unionist Party - 10 MPs
The DUP has a confidence and supply agreement with the Conservatives, giving them their support in the Commons. They are backing the PM's plans to leave the EU with or without a deal at the end of October.
The Independent Group for Change - 5 MPs
This party is made up of MPs who left the Conservatives and Labour because of their positions on Brexit (as well as allegations of anti-Semitism in the Labour Party). They back another referendum, or "People's Vote", and want the UK to remain in the EU.
Plaid Cymru - 4 MPs
The Welsh Party backs remaining in the EU, despite Wales voting out in the referendum. They want a further referendum and to Remain.
Green Party - 1 MP
The party's one MP, Caroline Lucas, has been a vocal campaigner for another referendum and believes the UK should stay in the EU.

Labour MPs who back staying in the EU single market have vowed to keep the pressure up on the government and their own leadership in the Brexit process.
Fifty Labour MPs defied Jeremy Corbyn's orders and backed single market membership in a vote on Thursday.
Three of them were subsequently sacked as frontbenchers.
The BBC understands the rebels think up to 90 Labour MPs back their cause and they could work with Tory MPs who also want a "soft Brexit" in future votes.
Prime Minister Theresa May and Labour leader Jeremy Corbyn both support leaving the EU's internal market as a way of bringing to an end the free movement of EU citizens into the UK.
Labour's manifesto called for the benefits of the single market and customs union to be retained after Brexit.
But some MPs believe this is virtually indistinguishable from the government's position, and want continued membership or access on equivalent terms, without which they say businesses will suffer and jobs will be lost.
Three shadow ministers - Ruth Cadbury, Catherine West and Andy Slaughter - were sacked by Mr Corbyn for defying his orders to abstain in a vote on an amendment to the Queen's Speech, tabled by Labour's Chuka Umunna, which pledged to remain in the single market and customs union.
Stephen Doughty, one of the 50 rebels, told the Guardian the fight was far from over.
"The key issue going forward is the extent to which Conservative MPs who have significant disquiet about the direction of Theresa May's hard Brexit are willing to put their money where their mouth is and stand up for membership of the single market and customs union and other issues in key legislation coming forward."
Another rebel MP told the BBC that there were up to 40 more colleagues who felt the same way but who had decided to sit on their hands in Thursday's vote because it was "premature" and Tory MPs were unlikely to have backed a vote that might have toppled the government.
They would instead "take smaller steps - one thing at a time" and seek to co-ordinating their efforts with the Lib Dems, SNP and likely Tory rebels.
Parliament will be asked to approve eight Brexit-related bills over the next two years, framing new policies on trade, customs procedures and immigration.
Another Labour MP, Wes Streeting, told Radio 4's World at One he was "surprised and disappointed" at Jeremy Corbyn's position, as he did not believe the party could "achieve its objectives of tariff-free, barrier-free access to the single market and a jobs first Brexit, outside of membership of the single market".
There has also been a backlash against Mr Umunna in the wake of the vote, with some senior figures suggesting he had caused unnecessary division at a time when Labour is on a high.
"I just felt that given we'd come out of the general election with such an unexpected result, and there's a real euphoria, to try and divide Labour MPs a week and a half in was a little disappointing," deputy leader Tom Watson said.
And Stephen Kinnock, who like many Labour MPs did not take part in the vote, said the decision to fire the rebels was "regrettable" but "had to be done".
Mr Umunna's amendment was defeated by 322 votes to 101 as most Labour MPs did not take part.
A separate amendment proposed by shadow chancellor John McDonnell - which called for Brexit to deliver the "exact same benefits" as the EU single market and customs union - was defeated by 323 to 297.
The UK is due to leave the EU on 29 March 2019, although negotiations on the terms of exit have just begun.

Labour has tabled a cross-party motion to try to stop a future prime minister pushing through a no-deal Brexit against the wishes of MPs.
The party is trying to force a vote to give MPs control of the timetable on 25 June and thereby the power to introduce legislation to avoid no deal.
Labour's Keir Starmer said it was a "safety valve", but Brexit Secretary Stephen Barclay criticised the plan.
Some Tory leadership hopefuls have said they would leave the EU without a deal.
Michael Gove said Labour's plans "must be resisted", as while he would prefer to agree a plan with the EU, "we must not rule out no deal."
For other candidates, including Rory Stewart and Mark Harper, the prospect of leaving without a deal is unacceptable.
However, neither man appears prepared to back the opposition motion. Mr Harper said his "instinct" was to oppose it while Mr Stewart - despite saying he was "wholly supportive" of the idea at his campaign launch in London - later tweeted that he would not be voting for it.
But Dominic Raab and Esther McVey have both said they would consider shutting down Parliament early - proroguing - in order to drive through no deal.
Leaving on a no-deal basis - without any agreement on the shape of the future relationship between the UK and EU - could lead to significant disruption.
The EU has previously said border checks would have to be brought in, affecting things like exports and travel and creating uncertainty around the rights of UK citizens living in the EU and vice-versa.
The government normally controls business in the Commons - but MPs have previously seized control to legislate in favour of extending the Brexit process.
Labour's shadow Brexit secretary Sir Keir said the motion was a "safety valve" designed to ensure Parliament "cannot be locked out of the Brexit process" in the coming months.
It would allow Parliament to push back against a new prime minister "foolish enough" to pursue a no-deal Brexit without MPs' consent.
That was especially important, Sir Keir argued, because the Tory leadership contest had "become an arms race to promise the most damaging form of Brexit".
Mr Barclay, though, said the motion was a "blind motion" because it did not specify the legislation that would be introduced under its terms.
Labour had previously accused ministers of backing a "blind Brexit" because the future relationship was not spelled out in the withdrawal agreement - but this motion was guilty of the same approach, he said.
He argued it would be a "fundamental change" to the way the House operated and therefore should be opposed.
The motion has cross-party backing, including from one Tory MP - Sir Oliver Letwin - who is supporting Michael Gove in the leadership contest.
It has been signed by Jeremy Corbyn, SNP Westminster leader Ian Blackford, Lib Dem leader Sir Vince Cable, Change UK leader Anna Soubry, Plaid Cymru Westminster leader Liz Saville-Roberts and former Green Party leader Caroline Lucas.
Due to the confidence and supply agreement with the Democratic Unionist Party, the Tories have a majority in Parliament of five.
That means it would take only three Conservatives to vote with the Labour motion for it to pass - if all opposition party MPs back it.
Another attempt to re-write the rules, another heave in the procedural tug of war, another day of drama in Parliament. But will it work?
It's not a straight vote for or against a no-deal Brexit - that would not change the fact that it is written in law and agreed with the EU that Brexit will happen on 31 October.
Think of this plan not as a knockout blow in a boxing match, but the first of a complicated sequence of moves in a chess game.
Labour want to pull off something similar to what happened in March, when MPs took control of parliamentary time to force the government to request an extension to the Brexit process from the EU.
Step one is seizing control of business in the House of Commons, and that's clearly the plan this time around.
Beyond that, the details aren't clear.
Compelling the new prime minister to ask the EU to delay Brexit further is the most likely option. But the answer of course, might be "no".
The default position in law is that the UK will leave the EU on 31 October - and if nothing changes, Brexit will happen regardless of whether there is a deal or not.
MPs wanting to stop a new PM leaving without a deal do however have a number of options at their disposal.
One would be to pass legislation requiring the government to seek an extension to the UK's membership. The EU would have to agree to an extension for it to be granted.
However, this would first require MPs to seize control of the parliamentary agenda, as Labour is attempting.
Another would be to use a vote of no confidence to bring down a government committed to pursuing a no-deal exit.
MPs could also use motions or political pressure to try and force the government into changing course.
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Labour MPs remain split over whether to back a further referendum on Brexit.
The party lost ground in the European elections, and some figures have called for a public vote to win back support, especially from Remainers.
Shadow home secretary Diane Abbott said another vote would be "the democratic thing to do" to move Brexit forward.
But Labour MPs representing Leave areas have warned against it, with Lisa Nandy saying it could be "the final breach of trust" with those voters.
The party agreed a policy at its last conference that if Parliament voted down the government's withdrawal deal with the EU - which it has effectively done three times - or talks ended in no-deal, there should be a general election.
But if it could not force one, conference agreed that the party "must support all options remaining on the table, including campaigning for a public vote".
It reiterated this position ahead of the European elections, but Labour's share of the vote fell to 14% and several senior figures criticised a lack of clarity.
Deputy leader Tom Watson said his party's Brexit stance had led to "electoral catastrophe", while former PM Tony Blair said it was not "possible to sit on the fence on Europe and appeal to both sides."
After the results, leader Jeremy Corbyn insisted his policy had been "very clear" all along - but he sent a letter to his MPs, saying it was "clear that the deadlock in Parliament can now only be broken by the issue going back to the people through a general election or a public vote".
On Tuesday, shadow home secretary Ms Abbott said Labour was "moving towards a clearer line".
She told BBC Radio 4's Today programme: "There is no inherent contradiction between respecting the result of the referendum and having a 'People's Vote' [or further referendum], not least because it's still not sure how a People's Vote would pan out.
"I've always argued that it's perfectly possible that Leave would win again, but we're supporting a People's Vote strongly now because it's the right thing to do and it's the democratic thing to do."
But Ms Nandy, the Labour MP for Wigan, told Today the European election results showed "very few people have changed their minds", and any shift in her area of the country was towards a no-deal Brexit - backed by Nigel Farage's Brexit Party, which secured 32% of the vote UK-wide.
She added: "There is a huge frustration amongst Labour voters who voted Leave in towns like mine to see leading figures from the Labour Party out calling for a second referendum before there's been any serious attempt to implement the result of the first."
Jeremy Corbyn put out a letter to Labour MPs on Monday night, in which he suggested if they couldn't get a general election then there should be a so-called "confirmatory referendum" on any Brexit deal.
But many Labour folk believe it's gone beyond that - that there's no prospect of a general election, there's no prospect of a deal, and they now need to campaign openly for a referendum and for Remain.
Mr Corbyn and some of his close allies like Unite leader Len McCluskey are very, very wary of doing that because of the impact it will have in northern, Leave-supporting Labour constituencies.
And also they warn if they were another referendum, it is quite possible that the electorate might say, "Well, we've already told you once, we'll tell you again - we want to leave but this time we want no deal."
And in that climate, it seems to me Mr Corbyn is just sort of hunkering down trying to say as little as possible.
We haven't got any sort of absolute clarity from him yet on where he stands, but I think it's only a matter of time, because I have no doubt he is going to be pressed and pressed on this.
Fellow backbencher Jo Platt, who represents Leigh - the neighbouring constituency to Ms Nandy - said the party "must provide answers" for voters, "not ask them to think again".
And Caroline Flint - Labour MP for Don Valley in South Yorkshire -  said another referendum was "seen by many Labour Leave areas as nothing more than a Stop Brexit mechanism".
Unite union leader and Corbyn ally Len McCluskey urged the party not to be "spooked" by the European election results and insisted another referendum "won't solve anything".
"I think [Jeremy] will repel all of those pressures coming from different sides, and he's already indicated he's going to take his time, speak to the members, the public, the unions, so we can work out a way that can take us forward," he said.
After Monday's election results, shadow chancellor John McDonnell - one of Mr Corbyn's closest political allies - told the BBC another referendum may be the only way forward.
Faced with the prospect of a "Brexiteer extremist" running the Conservative Party after the contest to replace Theresa May as leader, Mr McDonnell said Labour must back a fresh public vote to prevent a "catastrophic" no-deal scenario.
Wales' First Minister Mark Drakeford joined calls for a further referendum after Labour came third in the country, behind The Brexit Party and Plaid Cymru - making it the first time that Plaid had beaten Labour in a Wales-wide election, and only the second time it had lost such a poll in a century.
He told BBC Radio Wales: "We were doing our best to respect the result of the original referendum... I have now concluded that the only way we can try to guarantee a future for Wales that would not be a catastrophe is to put this decision back to the people in a referendum."
Scottish Labour leader Richard Leonard also said he was "more and more compelled" to believe that there should be another vote after his party lost both its seat at the European elections.

Labour's governing body has agreed to support a further referendum on Brexit under certain circumstances.
The National Executive Committee met to decide the wording of its manifesto for May's European elections.
It rejected the idea of campaigning for a referendum under all circumstances - as supported by deputy leader Tom Watson and many ordinary members.
But the party will demand a public vote if it cannot get changes to the government's deal or an election.
The National Executive Committee (NEC) oversees the overall direction of the party and is made up of representatives including shadow cabinet members, MPs, councillors and trade unions.
A Labour source said: "The NEC agreed the manifesto which will be fully in line with Labour's existing policy to support Labour's alternative plan and if we can't get the necessary changes to the government's deal, or a general election, to back the option of a public vote."
The decision was sufficiently nuanced, though, that MPs have interpreted it in different ways.
Wes Streeting, who favours another referendum, tweeted that the NEC had "made the right call and confirmed that a public vote will be in our manifesto for the European elections".
Fellow pro-referendum MP Bridget Phillipson said Labour had "done the bare minimum needed" and she could "only hope" it would be enough to win over voters who want another say on Brexit.
On the other side of the party, Gloria De Piero, who is against another vote, also welcomed the decision, arguing it meant the manifesto would "not contain a pledge" to hold a referendum - only keeping it as "an option" if a general election could not be engineered.
The UK will have to take part in European Parliamentary elections on 23 May unless a Brexit deal is accepted by MPs before then.
Labour agreed a policy at its last conference that if Parliament voted down the government's withdrawal deal with the EU - which it has effectively done three times - or talks ended in no-deal, there should be a general election.
But if it could not force one, conference agreed that the party "must support all options remaining on the table, including campaigning for a public vote".
Since then, though, Labour has entered into cross-party talks with the Conservatives to see if they can reach a consensus on how to get a Brexit deal through Parliament so that Britain can leave.
Many Labour members wanted the party to make its agreement to any deal conditional on it being put to a public vote - what Labour calls a "confirmatory ballot".
Labour have not yet made clear what their proposed referendum would be on, but a party briefing paper to MPs published earlier this year said it would need to have "a credible Leave option and Remain" on the ballot paper.
On the surface it doesn't look like Labour's position has changed - but it has a little bit.
Tom Watson, along with some trade unions and some party members, wanted a full-throated commitment to a referendum under all circumstances. What they have ended up with instead is a compromise or a fudge. Labour will call for a referendum if the Conservatives don't make changes to their Brexit deal.
Some pro-referendum MPs aren't too disappointed because they believe the Conservatives won't move far enough and that leaves the door open to a referendum in the end anyway.
Others, though, are disappointed because they think this is a way of avoiding a clear commitment in the run-up to the European elections.
In truth, it puts the ball back into the Tories' court when it comes to those cross-party Brexit talks.
Jeremy Corbyn is saying to Theresa May "if you can compromise with us, we can hold back the tide of demands in our own party for a referendum."
That's the bargain he's offering.
Speaking ahead of the NEC's decision, Tom Watson, the party's deputy leader, said "the context has changed" since the 2018 party conference and Labour should now throw its full support behind a second referendum "to heal the divide in the country".
Afterwards, he described the party's agreed manifesto as "very good" and insisted he was not "disappointed" with the outcome - although he said would say more when the document was published next week.
Manuel Cortes, secretary of the TSSA union which has a seat on the NEC, said he was disappointed that Labour had missed the opportunity to commit to giving voters another say.
The latest talks between the government and Labour on Monday were described as "positive" and "productive" by the two sides.
June 2017 - Labour's general election manifesto accepts referendum result
28 September 2018 - Labour agrees if a general election cannot be achieved it "must support all options… including campaigning for a public vote"
November 2018 - Shadow chancellor John McDonnell says Labour will "inevitably" back a second referendum if unable to secure general election
16 January 2019 - 71 Labour MPs say they support a public vote
6 February 2019 - Mr Corbyn writes a letter to Mrs May seeking five changes to her Brexit policy with no mention of a "People's Vote"
25 February 2019 - Labour says it will back a public vote if its proposed Brexit deal is rejected
14 March 2019 - Labour orders its MPs to abstain on an amendment calling for a second referendum
27 March 2019 - The party instructs its MPs to support Margaret Beckett's amendment which calls for a confirmatory public vote on any Brexit deal
30 April 2019 - NEC agrees that the European election manifesto will commit to a further referendum under certain circumstances

A shadow minister has quit Labour's front bench after being told to back legislation paving the way for the UK's departure from the EU.
Tulip Siddiq said she "cannot reconcile myself to the front-bench position".
Jeremy Corbyn has imposed a three-line whip on his MPs, telling them to back the newly-published bill.
The European Union (Notification of Withdrawal) Bill has been produced after the Supreme Court ruled legislation would be necessary.
In her resignation letter to Mr Corbyn, Ms Siddiq, who had been an early years minister, said: "Leaving the European Union presents enormous uncertainty for my constituents, with most believing that the disadvantages of leaving outweigh any potential benefits."
Despite reports he might rebel, Shadow Business Secretary Clive Lewis said on Thursday he would back the bill.
But he added: "Labour will seek to amend the Bill to prevent the government using Brexit to trash our rights, public services, jobs and living standards while cutting taxes for the wealthiest."
Labour MPs expected to vote against the bill at second reading include former leadership challenger Owen Smith, former culture secretary Ben Bradshaw and Cambridge MP Daniel Zeichner.
Mr Corbyn said Labour MPs would face a three-line whip to vote in favour of the bill.
He said he understood the "pressures and issues" members faced, but called on them to "unite" around "important issues" and "not to block Article 50 but to make sure it goes through next week".
Frontbench members of parties are generally expected to resign from their post if they decided to defy a three-line whip.
Prime Minister Theresa May has promised to begin the formal process of quitting the European Union, under Article 50 of the Lisbon Treaty, by the end of March.
The government was forced to draw up the legislation after losing an appeal at the Supreme Court on Tuesday, when judges ruled that Parliament must give permission to start the Brexit process.
The bill is due to be initially debated by MPs on Tuesday - in a sitting that may last until midnight - and clear the Commons on 8 February, after which it will move to the House of Lords.
As well as the bill, on Wednesday Prime Minister Theresa May announced the government would set out more details of its Brexit plans in a formal policy document.
In the House of Commons, MPs urged Mr Davis to commit to publishing the document, known as a White Paper, before the Article 50 bill legislation had passed through Parliament.
Mr Davis said the question involved "slightly separate issues".
The Article 50 bill, he said, was "about carrying out the will of the British people", adding that the White Paper would be published "as expeditiously as possible".
The Liberal Democrats have vowed to oppose Article 50 unless there is a guarantee of another referendum on the final Brexit deal that is agreed with Brussels, while the SNP has vowed to table 50 amendments to the legislation.
Taking questions from MPs, Mr Davis also said he disagreed with EU Commission chief negotiator Michel Barnier's view that trade talks would have to be handled separately from the Article 50 negotiations.
Such a "sequential approach" would be "not practical", he said, adding that he wanted all negotiations to be completed inside two years.

Jeremy Corbyn has challenged the next Tory leader to hold another referendum before taking Britain out of the EU, saying Labour will campaign for Remain.
Mr Corbyn says the party will take this position to stop "no deal or a damaging Tory Brexit".
But he does not say what he would do if he won a general election and was placed in charge of the Brexit process.
Some senior members of his team want him to take a pro-Remain stance in all circumstances.
In an interview with the BBC's John Pienaar, Mr Corbyn said Labour was now the "party of choice" when it came to Brexit.
He said he had done "what I think a leader should do... an awful lot of listening" - to party members, unions and the wider Labour movement - before coming to a revised position.
He said he would "make a case" to Parliament in September to get another referendum and in the meantime, Labour will "do everything we can to take no deal off the table or stop a damaging deal of the sort Hunt or Johnson propose".
Asked if he had changed his position because of pressure from colleagues, Mr Corbyn said: "Not a bit of it. I've been listening and I've enjoyed it."
Mr Corbyn said he could not say what Labour's position would be at a general election, but would decide it "very quickly", depending on the circumstances at the time, whenever one was called.
In a letter to members, he said Labour continued to believe the "compromise plan" set out for Brexit during cross-party talks with the government earlier this year was a "sensible alternative that could bring the country together".
This included a customs union, a strong single market relationship and the protection of environmental regulations and rights at work.
Mr Corbyn's statement followed a shadow cabinet meeting on Tuesday morning, and a meeting with trade union leaders on Monday.
The bosses of Labour's five-biggest affiliated unions called for the move the party has made - but also for it to hold a "confirmatory vote" on any new deal it negotiated if Labour won a general election.
The BBC's political correspondent Iain Watson said there was disagreement about the second part of the unions' stance in shadow cabinet, with deputy leader Tom Watson wanting a "straight Remain stance", meaning a decision on it was "kicked down the road".
The deputy leader is among leading figures who have argued that confusion over Labour's message on Brexit contributed to its poor performance in the recent European Parliament elections.
Mr Watson said he was "happy" with the new Brexit position "up to the election", but the party had "yet to cross that bridge" when it comes to its manifesto for the next election.
"Our members have been telling us for some time now that they want us to be a Remain party and that they want us to put the new deal to the people," he added.
"We're now going to campaign for that and I'm very proud that the shadow cabinet have now listened to their concerns."
Shadow Treasury minister Clive Lewis said if a snap election was called, Labour would try to renegotiate the Brexit deal agreed by Theresa May, despite saying it "very much looks like" Labour is now the party of Remain.
He told the BBC's Politics Live: "If we win that general election, we will come into power, and if we can renegotiate that deal - a Labour deal - we will, because that's what people asked for."
Some Labour MPs, including Brexit-backing John Mann and Emma Lewell-Buck, said the party could lose votes in Leave-supporting areas as a result of the policy.
Ms Lewell-Buck, who quit her shadow minister role in opposition to a further referendum, said she was "concerned" and had a "heavy heart" over the decision.
"But I am also very clear that I am representing my constituents and I will continue to do that no matter what because they are the people who put me where I am," she said.
By Nick Eardley, BBC political correspondent
There's always a "but", it seems, when it comes to Labour and Brexit. What the party is saying explicitly is that it'll try to force the new PM to hold another referendum and if that happens it will back Remain. But we don't know what Labour would do in the event of a general election.
The feeling among some Labour people is, "If you think it was hard to get here, trying to come to a manifesto position is going to be even harder," so they're just not going there yet.
Sometimes it feels Labour has been dragged kicking and screaming towards positions on Brexit, but it has at least got to a new one today. The question is whether it'll have to go further at some point.
Some on the Remain wing will be delighted with Jeremy Corbyn's shift, but others will feel there's more to do.
Former Labour MP Chris Leslie - who left the party to found Remain-backing Change UK - said Mr Corbyn's stance had "confirmed that if you vote Labour, you'll get Brexit".
He said the position "wasn't good enough", adding: "Brexit - whether a Labour Brexit or a Conservative Brexit - will cost people's jobs, put businesses in jeopardy, and diminish Britain in the eyes of our neighbours.
"Corbyn's refusal to be honest about that fact is a deep betrayal of the people Labour used to represent."
The Liberal Democrat's Brexit spokesperson, Tom Brake, said Labour "are still a party of Brexit".
He added: "Jeremy Corbyn can pretend all he likes that the Labour Party are finally moving towards backing the Liberal Democrat policy of a People's Vote, but it is clear it is still his intention to negotiate a damaging Brexit deal if he gets the keys to No 10."
But Miriam Mirwitch, chair of Young Labour, welcomed the move, adding: "This vital shift shows that Labour is a party centred around democracy that has listened to what it's members have wanted for some time: a People's Vote in which Labour campaigns to Remain."
June 2017 - Labour's general election manifesto accepts referendum result
28 September 2018 - Labour agrees if a general election cannot be achieved it "must support all options… including campaigning for a public vote"
November 2018 - Shadow chancellor John McDonnell says Labour will "inevitably" back a second referendum if unable to secure general election
16 January 2019 - 71 Labour MPs say they support a public vote
6 February 2019 - Mr Corbyn writes a letter to Mrs May seeking five changes to her Brexit policy with no mention of a "People's Vote"
25 February 2019 - Labour says it will back a public vote if its proposed Brexit deal is rejected
14 March 2019 - Labour orders its MPs to abstain on an amendment calling for a second referendum
27 March 2019 - The party instructs its MPs to support Margaret Beckett's amendment which calls for a confirmatory public vote on any Brexit deal
30 April 2019 - NEC agrees that the European election manifesto will commit to a further referendum under certain circumstances
9 July 2019 - Labour calls on the next PM to hold a referendum and pledges to campaign for Remain against "no deal or a damaging Tory Brexit"

Labour is redrafting European election leaflets after accusations of ignoring a pledge to hold a further Brexit referendum, the BBC has been told.
They will now refer to the party's preparations for a general election, with a referendum if necessary to avoid what it calls a "bad Tory deal".
Jeremy Corbyn says Labour's ruling body will make a decision on Tuesday about backing a public vote on any deal.
About 100 Labour MPs and MEPs want such a promise in the party manifesto.
They wrote to members of the national executive committee before it meets on Tuesday to decide on the manifesto.
Shadow Treasury ministers Clive Lewis and Anneliese Dodds and the shadow minister for disabled people Marsha de Cordova are among the frontbenchers backing the call for a confirmatory vote in any eventuality - not just to avoid a "bad deal".
Some Labour MPs are opposed to holding another EU referendum, however, with nine shadow cabinet members thought to be sceptical about such a move.
It had previously been reported that Labour's leaflets for the 23 May European Parliament elections do not mention pushing for another referendum.
Senior Labour backbencher Hilary Benn had questioned why no mention was made of a "confirmatory referendum" - despite the party twice supporting one in Commons votes.
The party's deputy leader Tom Watson has also argued for Labour to promise another referendum, if it is to counter the electoral challenge posed by Nigel Farage and his Brexit Party.
Labour agreed a policy at its last conference that if Parliament voted down the government's deal or talks end in no deal, there should be a general election.
But if it cannot force one, it added, the party "must support all options remaining on the table, including campaigning for a public vote".
Mr Corbyn said on Saturday: "The national executive will decide on Tuesday what will be in the European election manifesto and we will reflect the decisions made (at) last year's Labour Party conference - which were for a customs union, market access and rights protection within, with, the European Union.
"We would prefer to have a general election, but failing that if we get that agreement we are prepared to consider putting it to a confirmatory vote. That is a decision the national executive of the party will make."
Asked if the promise of a public confirmatory vote would be in election material, he added: "It's important that the party, which is a democratic party structure, makes those decisions. Sadly, or perhaps it's a good thing, I'm not a dictator of the Labour Party."
Analysis by Iain Watson, BBC political correspondent
When some of Labour's early European election literature was leaked, it provoked an internal row at a senior level.
Why? Because it made no mention of another referendum.
A letter from almost 100 MPs and MEPs calling for one has put additional pressure on the leadership.
With the agreement of a senior official in Jeremy Corbyn's office, the campaign literature is now to be rewritten.
There will be a mention of a confirmatory ballot/public vote (translation: a referendum) but only to avoid "a bad Tory deal".
This won't go far enough for those MPs calling for a referendum on any deal. That is, even if Mr Corbyn reaches agreement on a "soft" Brexit with Theresa May, a chunk of his Parliamentary party still want another referendum.
The issue will be hammered out when the ruling national executive meets on Tuesday to decide the manifesto for the European elections.
Some members will argue for no referendum, some will argue for one but with caveats, and others will press for a public vote under all circumstances.
Maybe the printing presses should be mothballed until Wednesday.
A letter, signed by some Labour MPs and MEPs, said: "Our members need to feel supported on doorsteps by a clear manifesto that marks us out as the only viable alternative to Nigel Farage's Brexit Party.
"We need a message of hope and solidarity, and we need to campaign for it without caveats. To motivate our supporters, and to do the right thing by our members and our policy, a clear commitment to a confirmatory public vote on any Brexit deal must be part of our European election manifesto.
"We understand the many different pressures and views within our movement, but without this clear commitment, we fear that our electoral coalition could fall apart."
Richard Corbett, leader of Labour's MEPs and a member of the NEC, told BBC Radio 4's Today programme: "The problem we face now is that Brexit is turning out to be so different from what was promised three years ago.
"Remember they said it would be easy - it's turning out to be rather complex. They said it would save loads of money that would all go to the NHS - it's turning out to be costly.
"They said it would not damage the economy - we are seeing firms move abroad, jobs lost, especially in manufacturing.
"Because it's so different, it's right that it should go back to the people for a final sign-off."

Leaving the European Union with no deal would have a "very adverse" effect on the UK, the justice secretary has said.
David Gauke said he hoped a deal would be struck within the next 10 days, but if not the government should "act responsibly".
But DUP deputy leader Nigel Dodds has insisted no deal was better than a bad deal.
Prime Minister Theresa May is seeking changes to the Withdrawal Agreement to help it achieve Parliamentary assent.
Mr Gauke warned on BBC Radio 4's Today programme of "very grave concerns" for the UK's economy, security and the union itself if the UK leaves without a deal.
"Leaving without a deal would have a very adverse effect, to put it mildly, on our economy, on our security and on the integrity of the union," he said.
The justice secretary said he hoped a deal will have been struck by 27 February, when the next round of Brexit votes are scheduled in the Commons.
But he continued: "If not, then we will have to act responsibly and make sure the economy is protected, our security is protected and the integrity of the union is protected.
"I have very grave concerns about the consequences of leaving without a deal."
Mr Gauke has previously suggested Brexit might have to be delayed.
But Mr Dodds told a meeting of party members in Omagh: "We want a Brexit deal, but we are very clear that a no deal is better than a bad deal."
The DUP deputy leader said changes were needed to the so-called Brexit backstop.
The backstop is an insurance policy designed to avoid a hard border between Northern Ireland and the Irish Republic - and the Tories rely on DUP votes to govern.
Mr Dodds said that there is "virtual unanimity in political unionism" that the current backstop imperils the UK.
Meanwhile, Business Minister Richard Harrington said he did not think Theresa May would let Britain leave the bloc without a deal.
He told BBC Radio 4's Week In Westminster: "When it comes to it, she will know the disaster that a hard Brexit would be for the British economy and I don't think she'll do it.
"No government can stand by and watch a country plummet earthwards because of a political dogma of a minority of a minority."
And Margot James became the latest cabinet member to threaten resignation over the possibility of no deal.
The digital minister told Channel 4 News: "I could not be part of a government that allowed this country to leave the European Union without a deal."
The prime minister is soon to return to Brussels to press for changes to the backstop. The EU has consistently ruled out amending the clause.

The government is facing a legal battle over whether the UK stays inside the single market after it has left the EU, the BBC has learned.
Lawyers say uncertainty over the UK's European Economic Area membership means ministers could be stopped from taking Britain out of the single market.
They will argue the UK will not leave the EEA automatically when it leaves the EU and Parliament should decide.
But the government said EEA membership ends when the UK leaves the EU.
The single market allows the tariff-free movement of goods, services, money and people within the EU.
The EEA, set up in the 1990s, extends those benefits to some non-EU members like Norway, Iceland and Liechtenstein.
Non-EU members are outside the Common Agricultural Policy and customs union, but get barrier-free trade with the single market in return for paying into some EU budgets and accepting the free movement of workers.
If the courts back the legal challenge and give Parliament the final say over EEA membership, then MPs could vote to ensure that Britain stays in the single market until a long-term trading relationship with the EU has been agreed.
The pro-single market think tank British Influence is writing to Brexit Secretary David Davis to inform him that it will seek a formal judicial review of the government's position.
The group warned that if the government did not get a clear legal opinion it could potentially end up acting outside the law.
All EU member states are in the European Economic Area and it had been assumed that when Britain leaves the EU it would automatically leave the EEA as well.
But some lawyers argue that leaving the EEA would not be automatic and would happen only if Britain formally withdraws by triggering Article 127 of the EEA agreement.
The legal question is focused on whether the UK is a member of the EEA in its own right or because it is a member of the EU.
If MPs do get to decide on Article 127, they could potentially overcome the government's small majority and keep Britain inside the single market after Brexit.
This would infuriate Brexiteers, but pro-EU campaigners say MPs would feel able to do this because people voted, they would argue, in the referendum to leave the EU and not the single market.
Paradoxically, though, the legal uncertainty over EEA membership could also end up being good news for the government.
If its negotiations with the EU went badly, and no deal looked likely, the UK could threaten to stay inside the EEA after Brexit. This would be politically hard for the government to sell as it would still involve EU workers moving freely within the UK. But it might be economically better than having to rely on World Trade Organisation rules which could involve high tariffs and barriers to trade.
The ability to stay on in the single market means Britain could force the EU into accepting a transitional period for the UK to avoid an economic cliff edge. This would be a useful stick for UK negotiators to have up as there appears to be no mechanism for the EEA to force out one of its members.
Professor George Yarrow, chairman of the Regulatory Policy Institute and emeritus professor at Hertford College, Oxford, said: "There is no provision in the EEA Agreement for UK membership to lapse if the UK withdraws from the EU.
"The only exit mechanism specified is Article 127, which would need to be triggered."
In other Brexit developments:
At the the very least this latest challenge could mean a lengthy legal process - potentially via the European Court of Justice - that could delay Brexit negotiations.
If the courts say Article 127 does need to be triggered, there is the question of whether an act of parliament would be needed for it to be authorised.
The government is already fighting in the courts to stop MPs getting the final say over triggering the Article 50 process.
Downing Street said the UK was only party to the EEA agreement through its EU membership and the government's position was clear that "once we leave the EU we will automatically leave the EEA".
The PM's official spokeswoman said Theresa May was focused on delivering the will of the British people with regard to Brexit and preparing for the upcoming negotiations.
Conservative MP and Brexiteer Dominic Raab said: "Rather than coming up with new legal wheezes to try and frustrate the will of the people, these lawyers should be working with us to make a success of Brexit.
"The public have spoken; we should respect the result and get on with it, not try to find new hurdles that undermine the democratic process."

MPs' opposition to a no-deal Brexit has hindered UK efforts to replicate an EU trade deal with Canada, says International Trade Secretary Liam Fox.
On Monday, Buzzfeed News reported that Canada was refusing to extend its existing deal with the EU to the UK if there is no Brexit agreement.
Mr Fox said "mixed signals" from Parliament had made it "very difficult" for ministers during talks.
But Labour said Mr Fox had been "stubborn and ideological".
The EU's deal with Canada, known as the Comprehensive Economic and Trade Agreement (Ceta) has been in force provisionally since September 2017.
Some 98% of all tariffs on goods traded between Canada and the EU have become duty free since then.
The UK hoped Canada would agree to "roll over" Ceta in the event of no deal in order to maintain continuity, but it appears those efforts have stalled.
Many MPs, including the chancellor, have insisted they will do everything possible to stop the UK leaving without a deal on 31 October, although both men vying to be the next prime minister say they would be prepared to accept it.
"Countries were negotiating with us on the basis that there would be potential of a no-deal exit," Mr Fox told MPs on the International Trade Committee on Wednesday.
He continued: "The progress was very advanced; in fact we reckoned above 99% of agreement.
"[But] the signals coming from our Parliament were conflicting.
"If Parliament continues to be inconsistent, it's very difficult for the government to maintain a consistent position in terms of negotiations."
He also said government plans to cut tariffs in the event of a no deal had made the Canadians think they would benefit if Ceta were not rolled over.
Around 87% of imports by value would be eligible for zero-tariff access under the temporary scheme.
But the international trade secretary said not agreeing to permanent post-Brexit arrangements would put Canadian exports at risk.
"My advice is still to the Canadian government to seek to make an agreement which covers us in all circumstances", he added.
Shadow international trade secretary Barry Gardiner said Canada would be at a "significant advantage" if the Ceta deal were not rolled over.
"The government's foolish approach will ensure that they do not have to offer trade preferences in return", he said.
"A no-deal Brexit means that our exporters face being shut out of core markets or having huge tariffs levied on their goods whilst importers into our market will not.
"Quite simply, it will be impossible to compete."
Cetais one of around 40 trade deals the UK is currently a part of due to its EU membership, which covers trade with more than 70 countries around the world.
The UK has so far agreed "continuity" deals with 11 countries and regions to maintain existing trade arrangements as far as possible after leaving the EU.
Last month it also signed an outline free trade agreement seeking to maintain trade arrangements with South Korea.

Any form of customs union with the EU after Brexit would be a "complete sellout" for the UK, International Trade Secretary Liam Fox has said.
The UK would find itself in a "worse position" than it is now, he said, if it left the existing arrangement but negotiated a similar new one.
Having to accept EU rules and limits on doing other deals would make the UK "less attractive", he said.
But his former top official has criticised the government's strategy.
Sir Martin Donnelly, who was permanent secretary in the Department for International Trade until last year, said any deals done after Brexit would not compensate for leaving the single market and the customs union.
Giving up access to the EU market and its existing trade agreements was "rather like rejecting a three course meal now in favour of the promise of a packet of crisps later", he said.
Sir Martin, who has previously warned about leaving the single market and has worked for the European Commission in the past, said that negotiating full access to the single market without accepting EU rules would require a "fairy godmother specialised in trade law".
Foreign Secretary Boris Johnson said he did "not agree for a moment" with Sir Martin's verdict, because the "real growth opportunities" were outside the EU.
Mr Johnson told BBC Radio 4's Today programme that a long-term customs union, as Labour has proposed, would lead to "colony status for the UK", which would not get a say in trade policy.
And Mr Fox hit back at Sir Martin as he took questions after his speech, saying it was "unsurprising that those who spend a lifetime working in the European Union see moving away from the European Union as being threatening".
He added: "The UK Brexit process is, as we've all discovered, a little more complex than a packet of Walkers."
The government has said it wants a customs agreement with the EU - which is the UK's single largest trading partner accounting for 43% of exports - but one that does not stop it from doing free trade deals with other countries.
Mr Fox, one of the most prominent Brexiteers in the cabinet, is the latest minister to set out his stall as part of the government's attempt to map out "the road to Brexit", which is due to happen in March 2019.
His speech came the day after Labour leader Jeremy Corbyn set out his approach to Brexit, saying he backed the UK being in a "new and comprehensive" customs union with the EU.
Mr Corbyn says a new customs union will help protect existing jobs and supply chains while giving the UK a say in future deals negotiated by the EU.
But Mr Fox rejected this, saying the UK would have to cede "considerable control" of its trade policy to Brussels in any customs union.
In his speech, at Bloomberg in London, Mr Fox said that changing economic and trade patterns meant the EU was a less significant partner than 15 years ago and the UK must have the freedom to exploit the "opportunities of the future", particularly in services and digital industries.
"As rule takers, without any say in how the rules were made, we would be in a worse position than we are today," he said. "It would be a complete sellout of Britain's national interests."
Citing Turkey's experience of being outside the EU but joined in a customs union with it, he  said that if the UK found itself unable to set its own rules in key sectors of the economy, this would "remove the bulk of incentives" for other countries to enter into comprehensive free trade agreements.
"The inevitable price of trying to negotiate with one arm tied behind our back is that we would become less attractive to potential trade partners and forfeit many of the opportunities that would otherwise be available."
Flexibility, he said, must be the basis of the UK's trade policy if it is to support the fledgling industries that will provide much of the employment and income of the future.
"There is a growing awareness that a full-blown gold-plated free trade agreement may not be the only solution in a fast-changing global economy," he said.
There is a "global trade toolbox" of different options, including "multi-country alliances of the like-minded", he said.
"All of these options are available. But only to countries with independent trade policies."
Labour said it made more sense for the UK to be negotiating new trade deals alongside the EU, adding: "Liam Fox is divorced from reality and isolated from British businesses and workers."
But Conservative MP Nigel Evans told BBC 2's Daily Politics: "When you're doing trade deals between one country and another country, it's a lot easier than when you're doing it with somebody representing 28 countries."
Meanwhile former World Trade Organisation chief Pascal Lamy argued that whatever Brexit option was chosen "will necessitate a border" between Northern Ireland and the Republic.
"There will have to be a border", he told the Commons Brexit committee, because checks will have to be carried out on goods and people. He suggested a "Macau option" for Northern Ireland.
"You should think about giving to Northern Ireland the same autonomous trade capacity that China has given to Macau, which doesn't mean that Macau doesn't belong to China," he said.
The European Commission will publish the first draft of its proposed withdrawal treaty on Wednesday, which it wants both sides to agree to by the autumn to allow for an orderly departure.

The UK has yet to finalise agreements to replace existing free trade deals the EU has with 40 big economies if there is a no-deal Brexit.
International Trade Secretary Liam Fox said he "hoped" they would but it depended on whether other countries were "willing to put the work in".
He said more deals were coming, after signing one with Australia.
Concerns have been raised that the UK will leave the EU without a deal that would protect current arrangements.
The UK is due to leave the EU on 29 March, under the Article 50 process and the UK's EU Withdrawal Act, with or without a deal - unless the UK chooses to revoke Article 50 and continues as a member of the EU.
MPs defeated the withdrawal deal negotiated with the EU by a huge margin earlier this week, which provided for a "transition period" of 21 months, under which much of the UK's relationship with the EU would remain the same.
In 2017, Mr Fox said that the UK could "replicate the 40 free trade agreements before we leave the EU", so that there would be no disruption to trade.
But with just over two months to go until Brexit, not one has been signed, said the BBC's business correspondent Jonty Bloom.
The Department for International Trade says some agreements are at an advanced stage but none of the 40 free trade deals that the EU has with other countries have so far been rolled over so that they will cover the UK after Brexit.
The closest the UK has come to rolling over a free trade deal is an initial agreement with Switzerland to replicate the existing EU-Switzerland arrangements "as far as possible".  But that deal has not been formally signed yet.
Asked about a report in the Financial Times that Britain would not be close to finalising most of the 40 free trade deals the EU currently has with other countries, Mr Fox told the BBC: "I hope they will be but there are not just dependent on the UK. Our side is ready.
"It's largely dependent on other whether countries believe that there will be no deal and are willing to put the work in to the preparations."
On Friday, he signed a "mutual recognition agreement" with the Australian high commissioner in London - to maintain all current relevant aspects of the agreement it has with the EU. The EU does not have a free trade agreement with Australia.
He said there would be a "pipeline of them to be signed as we go through" and the agreement made it easier for UK goods to comply with Australian standards.
Mr Fox also said that staying in a permanent customs arrangement with the EU would "not be delivering Brexit" as he did not believe it would allow the UK to pursue an independent trade policy.
Some opposition parties have been making the case for a customs union. Theresa May held talks with the leaders of parties including the SNP and the Lib Dems, about a way forward after she won a confidence vote by a narrow margin in the Commons on Wednesday.
She also spoke to German Chancellor Angela Merkel and Dutch Prime Minister Mark Rutte on the telephone on Thursday night, and will be speaking to more EU leaders over the weekend.
But Labour Leader Jeremy Corbyn, who wants the UK to be in a permanent customs union with "strong" ties to the single market, has refused to take part in talks with the prime minister until she rules out the prospect of leaving the EU without a deal.
In a letter to Mrs May, Mr Corbyn said her talks were "not genuine". He also accused her of "sticking rigidly" to her withdrawal agreement.
As many as 20 Tory ministers have also said they would quit the government unless the prime minister allows them to try to stop a no deal Brexit, according to the Telegraph.
Mrs May says ruling out no deal is impossible as it is not within the government's power.
Writing in the Financial Times, Shadow Chancellor John McDonnell said the Conservative Party was "riven with division" so Labour would "return to Parliament to promote the compromise we believe is not only in the best interests of our economy but is also capable of securing sufficient support both here and in Brussels".
If Parliament was at an impasse, and Labour could not get a general election "we should also retain the option of seeking a public vote," he added.
Mr Corbyn has come under pressure from dozens of his MPs to back calls for another EU referendum. On Friday a pro-referendum campaign group paid for a wrap-around advertisement in his local newspaper, the Islington Tribune , urging him to back a "public vote on Brexit".
In a speech at JCB Headquarters in Rocester, Staffordshire, former foreign secretary Boris Johnson said changing the date of leaving from 29 March would be "shameful", and the public would view it as "an elite conspiracy to thwart Brexit".
He instead urged the government to use Brexit to "unite the country".

Liam Fox's department is busier than it looks. The Department for International Trade has a huge amount to do to keep trade going smoothly, even if we stay in a customs union with the EU during our transition out.
But the trade secretary's department is also doing some emergency planning. What if the talks end acrimoniously? What if we need a radical Plan B?  This planning has been dubbed "Project After" -  a menu of options for life in that world. These are not firm proposals, but blue-sky "what-ifs" for a cliff-edge break with Europe.
These are radical - they include ideas like joining an Asia-focussed trade pact and dropping all our tariffs.
Planning for no-deal is not DIT's most pressing engagement, however - its key priority for now is making our transition out of the EU as seamless as possible.
At the moment, as the prime minister set out today in the Commons, the government intends that there should be a transitional deal which allows us to stay in the EU single market and join a customs union with the EU. This is likely to last for two years or so - and an important part of making that work will fall to DIT.
The point of staying attached to the EU during transition is that it would reduce the hassle involved in UK-EU trade so business would not face a sudden shock on the day after we officially leave the union. It would also mean that countries with EU trade agreements could keep selling us goods on the same terms as before.
So a South Korean-made car could be sold here much as though we were still in the EU. However, the reverse will not automatically be true. Even if we stay within the customs union, we will not be able to export to Korea under the terms of the EU-Korea deal. We would need a separate, bespoke deal with Korea for that during the transition period.
This is why Mr Fox has spoken about having around 40 free trade agreements ready to go on the day after Brexit. These are agreements the EU has with third parties, which cover 60 or so countries. He would like to replicate them - basically, cut-and-paste the terms into a temporary bilateral deal - to avoid transition bumps on day one after Brexit in March 2019.
Those 60-odd countries estimate they receive about $55bn of goods from the UK at the moment. The largest national markets covered by these deals, accounting for around $35bn of goods exports, are Switzerland, Norway, Canada and Korea.
If the agreements are not transferred to the UK, this is likely to cause a dent in that trade - and some of our services trade. Without new deals, some tariffs will rise and, in addition, exports may face regulatory or commercial barriers to getting their products to market.
It may also mean losing potential for future growth: the Canadian deal has only just come into force so has not yet shaped British industry. The Korea deal contains provisions to allow improved access to our financial services sector.
The government told Newsnight today that it remains committed to trying to replicate all 40, but officials with knowledge of progress have told Newsnight that they do not expect to be able to do so. The department is advising ministers to focus their fire on a small number of deals - perhaps as few as four.
There are lots of reasons for scepticism.
We, ideally, would have these deals ready to deploy by the time transition starts. But our negotiating partners may also see little purpose in rushing. After all, if we stay inside the customs union, they will still be able to access our market on close to current terms until transition ends. In some cases, including Korea, rushing might make no sense: the EU deals are not considered a great success for them.
Some treaties may also be politically contentious: a treaty with Israel will be a rallying point for the so-called "BDS" movement, which was quite visible at the Labour conference, and which seeks to boycott the Jewish state. The negotiations with Zimbabwe may also throw up some political problems.
There's another wrinkle, too. Even if we manage these issues, we are almost certain not to resolve problems with what is known as "rules of origin".
To sell a car to Korea under the terms of the EU-Korea deal requires 55% of the content to be EU-made. When we leave the EU, our contribution will not count to that EU-made total, even if we strike a parallel deal with Korea. That will give an incentive for EU-based automakers to switch production to the continent, to make sure that their goods still qualify for the EU-Korea deal.
A big task - but that is not all that DIT has to do.
What about those emergency plans? In common with the rest of government, DIT is considering life without an EU deal. This line of work has been dubbed "Project After".
One of the ideas under consideration is joining the Trans-Pacific Partnership - a putative trade area of Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam (the US withdrew earlier this year). Thought has, separately, been given to joining the North American Free Trade Area - the trade area consisting the US, Canada and Mexico.
There are significant problems with both ideas - TPP is still on the operating table after the US's withdrawal. NAFTA is hardly stable either. And the political choices required to make them work would be brave - but that's an intrinsic factor in trade policy that Westminster has yet to grapple with. There are trade-offs everywhere.
For example, one obvious issue with both is that they contain provisions to allow foreign investors to sue governments for damages in the event that a capricious policy change costs them money. In another context - the EU-US negotiation of the trade deal known as "TTIP" - this type of provision was opposed widely on the British left.
Within "Project After", however, there are other ideas. These include unilateral free trade: dropping our own tariffs. This is an idea that has some defenders in British politics because it would reduce import prices for Britons. Mr Fox recently cracked a joke in a meeting about "the c-word" in trade - "consumers".
Unilateralism, however, is not unproblematic. The promise of a targeted reduction in our tariffs is a chip we can use in negotiations to get other people to open themselves to us. Given that we are a service-heavy economy with strengths in heavily regulated sectors, using the offer of lowering our tariffs on goods to get past non-tariff barriers is an obvious negotiating strategy for us. Removing our tariffs up-front will weaken our position.
And the politics of unilateralism are rough - if we drop steel or agriculture tariffs, for example, it will create a lot of losers.
"Project After" also suggests what is, in effect, a halfway house on that idea: we could set up "Free Ports". That is to say, we could move our customs border back from our waterfronts. So you would only pay duty once goods left a harbour, not when they were landed. You could then create duty-free and tax-free hubs. It is a way to have a bit of unilateral free trade, but not overall.
A CPS paper by Rishi Sunak MP has even suggested we could subsidise companies to set up in free ports, and suggested they could be major manufacturing hubs. But there are problems with this - it's not clear how far our trading partners would allow this to go. Subsidies for exporters - however you dress that up - are not something the world of trade is relaxed about.
The Department for International Trade told Newsnight: "We are confident that we will find a deal that works for Britain and Europe too. But it is our responsibility as a government to prepare for every eventuality, and that is what we are doing."

MEPs have voted to urge the EU not to open the next phase of Brexit talks unless there is a "major breakthrough".
A motion in the European Parliament to back a delay in any decision over trade discussions was backed by 557 MEPs, with 92 against and 29 abstentions.
Several MEPs claimed UK divisions were hampering the process with one urging Theresa May urged to "put Britain first" and avoid internal "quarrels".
But UKIP's Nigel Farage accused the EU of "treating the UK like a hostage".
Tuesday's vote in Strasbourg was not binding, but does represent a chance to "take the political temperature", BBC Brussels reporter Adam Fleming said.
The UK government insists there is a new dynamic in the negotiations since Mrs May's Florence speech last month and "real momentum" behind the process.
The European Parliament, home to 751 MEPs from across the EU, has no formal role in the Brexit negotiations - but will get to approve any final deal agreed between the UK and Brussels.
As the debate opened, a number of MEPs drew attention to what they claimed were divisions in the Conservative government and Mrs May's cabinet over the terms of exit.
Manfred Weber, a German member of the European People's Party grouping, said: "Who do I call in London - Theresa May, Boris Johnson or David Davis? Please don't put your party first.
"We need a clear answer who is responsible for the British position," he added.
Guy Verhofstadt, who leads the Liberal ALDE group and is also the Parliament's chief Brexit spokesman, said he "deplores" the lack of progress so far, blaming open splits among leading British ministers.
"There are differences between Hammond and Fox... and Johnson and May."
He also criticised the UK's proposals for creating a new "settled status" for EU citizens after Brexit - which he said would cause a "huge administrative burden" for those affected.
Addressing the meeting, EU negotiator Michel Barnier suggested there has not been "sufficient progress" in Brexit talks yet to open trade discussions despite Mrs May's speech which "gave us some openings which are starting to be reflected in the negotiations".
MEPs will vote later on a motion saying the UK's approach to financial issues has "seriously impeded" progress, a motion the UK said was drafted before the most recent round of negotiations.
Mr Farage, a key figure in the campaign to leave the EU which won last year's referendum, accused the EU of "treating us (the UK) like a hostage".
"Unless we pay a ransom and meet your demands you won't have an intelligent conversation with us about trade... and no guarantee when we meet your demands you will come to us and have a sensible trade agreement," he said.
The UK is keen to start talking about what kind of trading relationship it will have with the EU after Brexit but it looks increasingly unlikely EU leaders will agree to this when they meet next month.
The EU says this can only happen when the European Council decides there has been "sufficient progress" on three issues: the so-called divorce bill when the UK leaves, the rights for EU citizens in the UK and UK citizens in the EU and the Northern Ireland border.
On citizens' rights, the two sides cannot agree on whether UK or EU courts will guarantee European nationals' rights in the UK after Brexit.
The motion - which has been proposed by the main political groupings so is likely to be passed - calls for "reciprocity, equity, symmetry and non-discrimination".
And on another sticking point, the amount of money the UK will pay as it leaves the EU, it says "substantial progress in that area is required before entering into discussions on other issues".
Speaking earlier, Mrs May said her Florence speech had "changed the dial" in the negotiations and European leaders were clear where the UK stood and who was in charge.

MPs have backed Prime Minister Boris Johnson's plan for the UK to leave the EU on 31 January.
They voted 358 to 234 - a majority of 124 - in favour of the EU (Withdrawal Agreement) Bill, which now goes on to further scrutiny in Parliament.
The bill would also ban an extension of the transition period - during which the UK is out of the EU but follows many of its rules - past 2020.
The PM said the country was now "one step closer to getting Brexit done".
Labour leader Jeremy Corbyn told his MPs to vote against the bill, saying there was "a better and fairer way" to leave the EU - but six of them backed the government.
Mr Johnson insists a trade deal with the EU can be in place by the end of the transition period, but critics say this timescale is unrealistic.
The bill had been expected to pass easily after the Conservatives won an 80-seat majority at last week's general election.
MPs also backed the timetable for further debate on the bill over three days when they return after the Christmas recess - on 7, 8 and 9 January.
The government says it will get the bill into law in time for the 31 January Brexit deadline.
The legislation, which would implement the Brexit agreement the prime minister reached with the EU in October, was introduced in Thursday's Queen's Speech, setting out the government's priorities for the next year.
By John Pienaar, deputy political editor
"Getting Brexit done" turned out to be a useful slogan, and no doubt it helped Boris Johnson win the election.
But almost nothing in politics is truly simple - least of all Brexit.
Today he passed an historic milestone - but the destination is still some way off.
Ruling out any extension to the Brexit transition period might mean Britain leaves with no deal - equally some in government believe it's possible we could see a kind of phased trade deal with the EU, thrashed out over the months and maybe years ahead.
Read the article in full
There are changes to the previous bill, which was backed by the Commons in October, but withdrawn by the government after MPs rejected a three-day deadline for getting it through Parliament.
The changes include:
The bill also loses a previous clause on strengthening workers' rights.
The government now says it will deal with this issue in a separate piece of legislation, but the TUC has warned that the change will help "drive down" working conditions.
Beginning the debate in the Commons, the prime minister said his bill "learns the emphatic lesson of the last Parliament" and "rejects any further delay".
"It ensures we depart on 31 January. At that point Brexit will be done. It will be over," he told MPs.
Labour leader Mr Corbyn said the government's "mishandling of Brexit" had "paralysed the political system," divided communities and was a "national embarrassment".
He said MPs "have to respect the decision" of the EU referendum in 2016 "and move on".
"However, that doesn't mean that we as a party should abandon our basic principles," he said.
"Labour will not support this bill, as we remain certain there is a better and fairer way for this country to leave the EU."
The SNP's Westminster leader, Ian Blackford, said: "Scotland still totally and utterly rejects Brexit, yet the prime minister is blindly hurtling towards the cliff edge with these Brexit plans that will leave us poorer, leave us worse off."
On the change in the bill that would legally prohibit the government from extending the transition period beyond 31 December 2020, Mr Blackford said: "By placing that deadline, that risk of a no-deal Brexit, that we all fear is very much, is on the table again."
And the Democratic Unionist Party's Sir Jeffrey Donaldson said there was a "major contradiction" in the prime minister's deal "that causes us great concern".
He said, while it mentioned "unfettered access" for Northern Ireland when it comes to trade in the UK, it also had customs arrangements "that inhibit our ability to have that unfettered access".
In the 2016 referendum, the UK voted by 52% to 48% to leave the EU. But the subsequent difficulties in getting Brexit through Parliament have caused gridlock at Westminster.
An earlier withdrawal agreement - reached between previous PM Mrs May and the EU - was rejected three times by MPs.

MPs have backed seeking "alternative arrangements" to replace the Irish backstop in Theresa May's Brexit plan.
The proposal - put forward by Tory MP Sir Graham Brady - had the support of the government and won by 16 votes.
Theresa May had urged MPs to vote in favour of it, to give her a mandate to return to Brussels and re-open negotiations in order to secure a "legally binding change".
But the EU has said it will not change the legal text agreed with the UK PM.
MPs voted on a string of amendments to Mrs May's plan to change the direction of Brexit.
Mrs May said that, after taking the votes into account and talking to the EU, her revised deal would be brought back to the Commons "as soon as possible" for a second "meaningful vote".
Another amendment, rejecting a no-deal Brexit, also won the support of Parliament on Tuesday, but the vote was not binding - meaning the date for exit remains 29 March.
Labour leader Jeremy Corbyn said as a result of the message from MPs rejecting no deal, he would now meet the prime minister to discuss the next steps.
He had previously refused to meet her unless she ruled out a no-deal Brexit herself.
Mr Corbyn said: "After months of refusing to take the chaos of no deal off the table, the prime minister must now face the reality that no deal is not an option."
Five other amendments, including Labour MP Yvette Cooper's bid to delay Brexit if Mrs May does not get her deal through Parliament, were defeated.
Tory MP Nick Boles, who worked with her on the amendment, tweeted out a joint statement, saying they "remain deeply concerned that there is no safeguard in place" to stop a no deal and said Mrs May's revised plan would have to "reflect the Commons opposition to no deal".
Mrs May hopes the support for Sir Graham's amendment - which won by 317 votes to 301 - to look at alternatives to the backstop gives her a stronger negotiating position with the EU.
The controversial element of Mrs May's original plan is the insurance policy to prevent checks on goods and people returning to the Northern Ireland border.
It would effectively keep the UK inside the EU's customs union, but with Northern Ireland also conforming to some rules of the single market.
It was one of the main reasons her Brexit deal was voted down in Parliament by an historic margin earlier in January as critics say a different status for Northern Ireland could threaten the existence of the United Kingdom and fear that the backstop could become permanent.
She told the Commons there was now a "substantial and sustainable" majority of MPs supporting leaving the EU with a deal, but admitted renegotiation "will not be easy".
The leader of the Democratic Unionist Party in Westminster, Nigel Dodds, said it was a "significant night" and his MPs would work with the prime minister "to deliver the right deal for the United Kingdom".
But the leader of the SNP in Westminster, Ian Blackford, said that passing the amendment had seen the government "rip up the Good Friday Agreement" - integral to the peace process in Northern Ireland.
Liberal Democrat leader Sir Vince Cable said the Commons had given the prime minister "contradictory instructions to have no deal but pursue a course of action that will lead to a no deal".
Theresa May was heading for another defeat, but she ended up with an unconventional win - a win nonetheless.
The Tory Party that was visibly split in two a fortnight ago is giving the impression of being largely united, even if that is temporary.
Yet the prime minister only won because she gave into Brexiteer and DUP demands, by making a promise that she can't be sure she can keep - one the EU says at the moment is impossible.
This process has for a long time been about No 10 stumbling, often seriously, then getting up again to try to take another step.
There is a valid question - to what end?
Speaking after the result, President of the European Council Donald Tusk said the withdrawal deal was "not open for re-negotiation" and "remains the best and only way to ensure an orderly withdrawal of the United Kingdom from the European Union".
But he said the EU would be willing to look at the political declaration again - the part of the deal that makes a pledge on the future relationship between the UK and the EU - and that the EU would "stand ready" to consider any "reasoned request" for an extension to the leave date of 29 March.
The Brexit Coordinator for the European Parliament, Guy Verhofstadt, welcomed Parliament's rejection of a no deal, but also said there was no majority in the EU to re-open or dilute the withdrawal agreement .
A statement from the Irish government said the withdrawal agreement "is not open for renegotiation... The best way to ensure an orderly withdrawal is to ratify this agreement," the statement said.
And Austrian Chancellor Sebastian Kurz also ruled out further negotiations on the withdrawal agreement.
The prime minister has invited Tory MP Caroline Spelman, Labour MP Jack Dromey and others who tabled amendments to prevent a no deal to discuss how to move forward and secure a deal for Brexit.
She also invited Mr Corbyn for talks and promised the government would "redouble its efforts to get a deal this House can support".
The so-called Brady amendment could pave the way for a plan known as the "Malthouse compromise" as an alternative to the backstop.
Engineered by both Leavers and Remainers - and led by Tory minister Kit Malthouse - the proposal includes extending the transition period for a year and protecting EU citizens' rights, instead of using the backstop.
The deputy chairman of the pro-Leave European Research Group, Tory MP Steve Baker, said he hoped by the group giving its support to the amendment, MPs could "now make rapid progress towards the Malthouse compromise".
But fellow ERG member Mark Francois warned there was no guarantee the group would back the PM, and said he would wait to see what she comes back with from Brussels.
Mrs May's spokesman said she would "engage" with colleagues proposing the compromise, but would also look at other options - including putting a time limit on the backstop and seeking a way to exit it.
The PM's revised deal will return to the Commons to be voted on.
But, if it is again rejected, the government will table an amendable motion - meaning MPs can put forward more amendments as they did earlier - for debate the following day.
And if no new deal is agreed by Parliament by 13 February, she will make a statement and, again, table an amendable motion for debate the next day.

MPs have backed a bid to stop a new prime minister suspending Parliament to force through a no-deal Brexit.
A majority of 41 approved an amendment that blocks suspension between 9 October and 18 December unless a Northern Ireland executive is formed.
Four cabinet ministers, including Philip Hammond, abstained and 17 Tory MPs rebelled, including minister Margot James, who has resigned.
Leadership contender Boris Johnson has not ruled out suspending Parliament.
His rival Jeremy Hunt has ruled out this move.
Ms James told the BBC attempting to suspend Parliament was "too extreme" adding: "I thought the time was right today to join people who are trying to do something about it."
The four cabinet ministers who abstained are International Development Secretary Rory Stewart, Business Secretary Greg Clark and Justice Secretary David Gauke, as well as Chancellor Mr Hammond.
Mr Clark defended his decision to abstain arguing: "I couldn't support the idea that we would allow the doors of Parliament to be locked against MPs at this crucially important time - that would be a constitutional outrage."
Mr Hammond tweeted: "It should not be controversial to believe that Parliament be allowed to sit, and have a say, during a key period in our country's history."
A Downing Street spokesman said the prime minister was "obviously disappointed that a number of ministers failed to vote in this afternoon's division".
"No doubt her successor will take this into account when forming their government," the spokesman said.
Labour leader Jeremy Corbyn said the vote was "an important victory to prevent the Tories from suspending Parliament to force through a disastrous no deal".
BBC political editor Laura Kuenssberg said the Commons had now made it harder for a new prime minister to suspend Parliament.
If the 31 October deadline is reached without Parliament backing an agreement between the UK government and the EU, the UK is scheduled to leave the EU without a deal.
MPs have consistently voted against a no-deal Brexit, but the prime minister could try to get around that by suspending Parliament - proroguing - in the run-up to the deadline, denying them an opportunity to block it.
The amendment to the Northern Ireland (Executive Formation) Bill was put forward by MPs including former minister Alistair Burt and Brexit committee chairman and Labour MP Hilary Benn.
It would mean that if Parliament is prorogued when the government publishes reports on the situation in Northern Ireland, MPs must be recalled to debate them.
Mr Burt told the BBC that Parliament had said "very clearly please don't bypass us... Parliament must be sitting in the run up to 31 October".
Mr Benn said: "This is a very significant amendment because it sends a very significant message to the prime minister - if you think you can lock the doors on that chamber and tell us to go away until the 31st October, Parliament will not allow that to happen."
Conservative MP Anne-Marie Trevelyan attacked those of her colleagues who voted against the government, describing the amendments as "cynical and corrosive".
However, she added: "They don't change the underlying legal realities one jot: we are leaving on 31 October with or without a deal."
DUP Westminster leader Nigel Dodds said it was "very disconcerting" to see a bill about Northern Ireland "hijacked for other purposes and particularly to see the debates taking place not even on the issues that directly affect Northern Ireland", like marriage and abortion.
In a taste of what and whom the still hypothetical Boris Johnson premiership is likely to face, the new rebel alliance in Parliament has shown its strength - winning a vote that would make it harder for the next PM to shut down Parliament to get round its likely opposition to leaving the EU without a deal.
And in political terms, it's an all-star cast list, populated with former Remainer ministers - the new "Gaukeward" squad, so-called after the until-recently achingly loyal Justice Secretary, David Gauke.
They are a currently powerful significant slice of the Conservative Party that, with years of ministerial experience between them, is willing to join forces with opposition MPs to make life harder for their next leader.
Those ministers are highly likely to be shoved out of government next week in any case - or, as I understand it, are already planning to congratulate Mr Johnson in one breath next Tuesday, then make it clear with the next that they'd never serve under him, denying the Brexiteers the pleasure of actually witnessing them being sacked.
But today's vote suggests they have no plans to go quietly. They might be losing their comfy ministerial cars and giving up the red boxes, but they will still have votes.
Read Laura's blog here
Leadership contender Mr Hunt admitted that, due to a misunderstanding, he missed the votes. However he said he was opposed to the way MPs had voted arguing Parliament "should not restrict the hands of an incoming government in this way".
When asked about suspending Parliament during his leadership campaign, Mr Johnson said he would "not take anything off the table".
He said he wanted to leave the EU on 31 October "come what may".
MPs also rejected a government attempt to disagree with an amendment put forward by a group of peers, which also bids to stop Parliament being suspended to force through a no-deal Brexit, by 315 votes to 273, a majority of 42.
The bill will now return to the Lords for further consideration.
Former Tory prime minister John Major has said he will seek a judicial review if the next prime minister tries to suspend Parliament.
Campaigner Gina Miller has threatened the same action.

MPs will meet the EU's chief negotiator later to call for UK citizens' rights to be protected in a no-deal Brexit.
The cross-party delegation will meet Michel Barnier in Brussels, and be led by Tory MP Alberto Costa.
He said government could protect the 3.6 million EU nationals in the UK, but did not have the power to do the same for 1.3 million UK citizens in the EU.
Mr Costa said, as it stands, a no-deal Brexit would "terminate the rights of British citizens overnight".
The meeting comes after MPs voted on Thursday to prevent the next prime minister from suspending Parliament in order to push through a no-deal Brexit.
Four cabinet ministers, including Chancellor Philip Hammond, abstained, while 17 Tory MPs rebelled against the government.
Foreign Secretary Jeremy Hunt has discounted the possibility of suspending Parliament - known as prorogation - if he becomes prime minister, but his rival in the Conservative Party leadership race, Boris Johnson, has refused to do the same.
Health minister Stephen Hammond - who abstained in Thursday's vote - said he would not rule out voting to bring down his own government if its policy became pursuing a no-deal Brexit, telling BBC Radio 4's Today programme: "A lot of people were taught that you must put the interest of the country before yourself."
But leading Brexiteer and Tory MP Jacob Rees-Mogg told the same programme those trying to prevent it were "not saying what they believe", and their intention was to "snub the British voters" and stop Brexit altogether.
Mr Costa resigned from the government in March to put forward an amendment to Prime Minister Theresa May's Brexit bill, calling for her to write to the EU to demand protections for UK and EU expats' rights if there was a no-deal Brexit.
It ended up gaining government support, and was passed by MPs.
As a result, Brexit Secretary Stephen Barclay wrote to Mr Barnier, saying there was growing support for a ring-fenced citizens' rights agreement in the European Parliament, and in June, he visited Brussels to make the case for a separate agreement in case of a no-deal scenario.
But the EU has refused to "negotiate mini deals", insisting the best way to safeguard citizens' rights was to implement the withdrawal agreement negotiated between the bloc and Mrs May - which has been voted down by MPs three times.
Mr Costa told Today the government would be "abrogating its responsibilities" to UK citizens if it did not make bilateral agreements with the different EU countries.
"In the event of no deal, the United Kingdom Parliament can take measures to protect EU nationals in the UK, but we do not have powers to pass legislation extraterritorial, in other words within the EU, to protect our own citizens," he said.
"If Britain chooses to exit without an agreement in place, it would be terminating the rights of British citizens overnight."
He added: "I want to understand from Michel Barnier what his position is in carving out citizens' rights, why he has said, thus far, no to that."
The current deadline for the UK to leave the EU is 31 October, but if it fails to agree a deal to do so, the legal default is to leave with no deal on that date.
Both contenders to be the next prime minister said they want to keep to the date and renegotiate with the EU.
Mr Hunt and Mr Johnson have also said they would keep leaving without a deal on the table to strengthen negotiations, despite Parliament voting to rule the option out.
The EU has consistently said the withdrawal agreement is closed and cannot be changed.
The incoming president of the European Commission, Ursula von der Leyen, has said she hopes the UK remains in the EU, but it was up to British authorities to "sort its side of things on Brexit".
Asked about Mrs von der Leyen's position, German Chancellor Angela Merkel said on Monday she understood that "if the UK wishes for more time [e.g. another delay to Brexit], then they would have more time", but it was "up to the UK".
She praised her "cooperative relationship" with Theresa May, adding: "She has not had an easy time dealing with this difficult question. I always found her to be a reliable and collegial partner, and I thank her for that."
But she added: "We now have the position that there will be a new PM, and then we have to watch what that person decides."

MPs will have their say on the next steps for Brexit later after European leaders indicated they would consider delaying the UK's departure if a deal is not agreed by 29 March.
Germany's Angela Merkel said if the UK needed more time to get Parliament's approval, she would "not oppose" it.
Theresa May has said MPs will get a vote on delaying Brexit if her deal and a no-deal outcome are both rejected.
MPs will vote on amendments to a government motion in the Commons later.
Wednesday's votes are not on Mrs May's Brexit deal itself - she says that will happen before 12 March.
Instead, MPs are seeking assurances and to hold the PM to her commitment, made on Tuesday, to allow MPs a vote on extending 29 March's Brexit deadline to avoid Britain leaving without a deal.
The prime minister's critics have accused her of "kicking the can down the road" with her pledge to hold more votes before 12 March - just 17 days before Brexit.
But she insisted her efforts to persuade the EU to make concessions had "already begun to bear fruit".
The government has accepted an amendment by Conservative MP Alberto Costa, which seeks to protect the rights of UK citizens in the EU, and vice versa, regardless of the outcome of UK-EU negotiations.
The amendment - which calls on the UK to secure agreement on this at "the earliest opportunity" - had gained significant cross-party backing from 141 MPs - including Labour and the Democratic Unionists.
Despite this, Mr Costa has resigned his job as aide to Scottish Secretary David Mundell, because, he told MPs, of a convention that members of the government should not amend government motions.
He said he "welcomed" the government's support for his amendment but it did not go far enough.
He said he wanted ministers to spell out "exactly what measures" Theresa May will now take to guarantee citizens rights and urged her to write to European Council President Donald Tusk.
He said the rights of the estimated million UK citizens living in the EU, and the three million EU citizens in the UK, "should never have been used as a bargaining chip" in the government's Brexit negotiations.
Green MP Caroline Lucas praised Mr Costa's stand and called for him to be reinstated in the government.
Analysis by Nick Eardley, BBC Political Correspondent
It looks a bit strange, doesn't it?
The government accepts an amendment from a member of the government - but then essentially sacks that member of the government for tabling it in the first place.
I'm told by several people that Alberto Costa was left with no decision but to resign. He met with the prime minister this morning made it clear he wasn't backing down which sealed his fate.
That's left some Tories furious. They point out he has a personal interest in the EU citizens' rights issue given his Italian parentage and say he was simply trying to get assurances he had been offered by Theresa May backed by the Commons. One member of the government said the treatment of Mr Costa had been appalling.
But a senior ally of the PM says Mrs May was left with no choice. It is, they point out, against the rules for members of the government to table amendments to government motions. This is a clear black and white example of breaking, they conclude, unlike some recent comments from cabinet ministers which could be open to interpretation (again their argument, not mine).
Another junior member of the government says that if Mr Costa had moved his amendment as a member of the government tonight - and it had been passed - it would have set a terrible precedent and led to many more similar situations.
Five amendments - out of 12 originally tabled - were selected for debate by Speaker John Bercow.
The Labour leadership's amendment calls on MPs to support its alternative Brexit plan, which would include a "comprehensive customs union" and close alignment with the EU in the future.
If that proposal is voted down, Jeremy Corbyn has said the party would move to formally back another EU referendum "in order to prevent a damaging Tory Brexit" or no-deal outcome.
Mrs May has accused Labour of "playing political games" and argued the best way for the country to move forward is for MPs to approve the revised deal she hopes to bring back.
The SNP amendment insists the UK should not leave the EU in any circumstances without a deal "regardless of any exit date".
On Tuesday, Theresa May promised MPs a vote on delaying Brexit for a short period if MPs reject her deal and leaving without a deal.
This was designed to head off a potential defeat on a cross-party amendment tabled by Labour MP Yvette Cooper, which calls for the same thing.
Ms Cooper has not withdrawn her amendment, because she wants to hold the prime minister to her commitment.
She said: "We will keep up the pressure working cross-party to ensure the commitments are implemented... to avoid any backsliding and to make sure we do not end up with a chaotic no deal."
An amendment by Conservative MP Dame Caroline Spelman and Labour's Jack Dromey amendment - calling for Parliamentary time to make the PM's no-deal vote commitment legally binding - will not be put to the vote, following government assurances.
"The government has just confirmed acceptance of all the proposals in our amendments. There will not now be a no-deal Brexit In 30 days' time because there is not a majority in the House for crashing out without a deal," the MPs said in a joint statement.
The process starts with the government putting down a motion. It is a plain piece of text, asking the House to note the prime minister's most recent Brexit statement - made on Tuesday - and that discussions between the UK and the EU are ongoing.
This then allows MPs to table amendments - alternative options - to that motion, setting out their proposals on what they think should happen next.
Mrs May said any delay to the UK's departure should not go beyond the end of June and "would almost certainly have to be a one-off".
Extending Article 50 would require the unanimous backing of the other 27 EU member states - something they have indicated they would be happy to do.
Speaking on Wednesday, German Chancellor Angela Merkel said she would "not oppose" a request from the UK for more time although French President Emmanuel Macron struck a more sceptical note, saying there had to be a "clear objective" behind any extension.
"As our negotiator Michel Barnier has said, we don't need more time but decisions," he said during a meeting in Paris. "The time has come therefore for the British to make choices."

MPs are awaiting the results of votes on eight different proposals for the future of Brexit.
Options they are considering include leaving without a deal, a customs union and a confirmatory referendum.
Speaker John Bercow will announce what support there is for each later after MPs took over the Commons timetable.
Theresa May has promised to stand down as prime minister if her own deal is approved, prompting several Tory Brexiteers to say they will back it.
Meanwhile, MPs have approved the legislation required to change the date of Brexit from 29 March - after the EU agreed to give the UK an extension last week.
Friday had long been the day written into law for the UK to leave the EU but the Commons approved a statutory instrument - by 441 votes to 105 - changing the deadline to 22 May if a withdrawal agreement is passed this week; or 12 April if it is not.
The prime minister is still trying to drum up support for her withdrawal agreement despite it being voted down by a large margin twice and the DUP saying they still cannot vote for it.
The government is seeking the support of MPs for the Commons to convene on Friday, if necessary, amid reports a third vote on the PM's deal could be held then.
But Mr Bercow reiterated his earlier warnings that the PM's deal could not come back for a vote if it had not significantly changed.
He said the government "should not seek to circumvent my ruling" by introducing procedures that could reverse his judgement.
But a Downing Street spokesman said there had been a "significant development" at the summit in Brussels last week, after Mrs May agreed "extra reassurances" over the Irish backstop with the EU, and the date of exit had changed.
MPs are currently voting on a statutory instrument to confirm a delay, after the UK was given until 12 April to propose a different way forward if the current agreement cannot get through Parliament and until 22 May to finalise Brexit if the deal is passed.
Earlier on Wednesday, MPs took control of parliamentary business from the government for several hours as they attempt to find a majority for the next steps in the Brexit process.
Conservative backbencher Sir Oliver Letwin, whose cross-party proposal ushered in today's debate, said the only way leaving the EU with no-deal can be prevented is by crystallising an alternative majority and trying to carry it forward.
He said that if MPs supported the prime minister's deal in another meaningful vote this would be "the easy route".
But he added that he "profoundly hopes" that if on Monday there is a majority view in favour of a particular position, that the government will say that it will carry that forward.
By Ben Wright, BBC political correspondent
Never afraid of stoking controversy, the Speaker has again infuriated many Tory MPs with his latest surprise pronouncement to the Commons.
Just as it seemed the government was poised to try and get its Brexit deal through again, John Bercow took it upon himself to tick ministers off before they had even tried.
Why? Because last week he ruled the deal could not be brought back to the Commons for a third time without "substantial" changes.
No 10 will only bring the deal back for a third vote if it thinks it could pass. That probably requires DUP backing and a guarantee some Labour MPs will vote for it too.
As it stands, there isn't yet a majority for the deal, but the mood is shifting fast.
Groups have put forward different options for the UK's future relationship with the EU, with several based on the assumption Mrs May's withdrawal agreement with the EU will be approved - albeit with changes to the controversial Northern Ireland backstop.
The Speaker of the House, John Bercow, chose eight to be voted on by MPs.
They are:
After a four-hour debate on each proposal, MPs were given a piece of paper listing the options, and had to mark each one with a "yes" or "no".
MPs used both lobbies for completing the ballots in a process that took about half an hour.
Several MPs, including Tory Michael Fabricant and Lib Dem Jo Swinson, posted images of their forms on social media.
The process is likely to continue on Monday as MPs seek to whittle down options which could command majority support in Parliament.
Now: Debate on statutory instrument (SI) bringing Brexit delay into law
21:00: Vote on SI
21:30: The Speaker announces the results of the indicative votes - though he could announce them earlier during SI debate
All times approx
Conservative MPs were given a free vote, meaning they were able to support or reject any proposal without pressure from party whips. Cabinet ministers will be abstaining.
The decision followed warnings that more than a dozen ministers might quit if they were told they had to follow party orders.
Labour MPs are being whipped to support the party's own proposal, as well as motions on a customs union, Common Market 2.0 and a confirmatory public ballot.
Mr Starmer told the Commons any deal "needs further democratic approval" before being enacted.
But the move has angered Labour MPs in Brexit-vote constituencies, with Great Grimsby MP Melanie Onn reportedly resigning as a shadow housing minister.

MPs have given their final backing to the bill that will implement the UK government's Brexit deal.
The Commons voted 330 to 231 in favour of the Withdrawal Agreement Bill and it will now pass to the House of Lords for further scrutiny next week.
If peers choose to amend it will it come back before MPs.
The bill covers "divorce" payments to the EU, citizens' rights, customs arrangements for Northern Ireland and the planned 11-month transition period.
The UK is due to leave the EU on 31 January.
The bill comfortably cleared its third reading in the House of Commons, as expected, with a majority of 99. All 330 votes in favour were Conservative.
It took just three days for the bill to pass the remaining stages in the Commons, after MPs gave their initial approval to the legislation before the Christmas recess.
Theresa May - Boris Johnson's predecessor in Downing Street - repeatedly failed to get her Brexit agreement passed by MPs, which led to her resignation as prime minister.
The latest vote gives approval to the 11-month transition period after 31 January, in which the UK will cease to be an EU member but will continue to follow its rules and contribute to its budget.
The purpose of the transition period is to give time for the UK and EU to negotiate their future relationship, including a trade deal.
Liberal Democrat Brexit spokesperson, Alistair Carmichael said his party would continue to oppose the "dangerous" bill.
"They have voted for a bill that will slash the rights of future generations to live and work across 27 other countries," he said.
"They have voted for a bill that strips away our guaranteed environmental protections, despite the fact that we are facing a climate emergency."
And SNP Westminster leader Ian Blackford said Scotland would "remain an independent European country".
"This is a constitutional crisis, because we will not and we cannot accept what is being done to us," he told MPs.
But Brexit Secretary Steve Barclay has said the bill will deliver on the "overwhelming mandate" his party was given at the general election to take the UK out of the EU on 31 January.
He has also said he is "confident" the UK will be able to negotiate a trade deal with the EU by the end of the year, despite critics saying that the deadline is too tight.
Mr Johnson has also insisted a deal is possible by December 2020 and has said the transition period will not be extended.
He has said the UK is ready to start negotiations "as soon as possible" after 31 January.
On Wednesday, new European Commission president Ursula von der Leyen warned it would be "impossible" to reach a comprehensive trade deal by the end of 2020.

Labour says the offer of a "take it or leave it" Commons vote on the final Brexit deal is "unacceptable" and MPs, not ministers, must agree the outcome.
Shadow Brexit secretary Sir Keir Starmer said it was "unthinkable" that if MPs rejected the agreement the UK just "crashed out" of the EU anyway.
In such an event, ministers should be able to resume negotiations, he said.
Theresa May has promised a "meaningful" vote on the deal but indicated the UK would still leave whatever the outcome.
The prime minister, who has said she is confident she will negotiate a deal that is in the interests of both sides, is currently updating MPs on the latest progress in the Brexit negotiations.
On Friday, the EU agreed to a 21-month transition period after the UK's exit, on 29 March 2019, and approved guidelines for the next phase of talks on its future economic and security relations with the UK.
Mrs May said while "not everyone" would be happy with the "continuation of existing trading arrangements" for 21 months, the period would provide stability for business and help them prepare for the future.
The focus, she said, should now be on securing a future partnership that "will endure for years to come" and while there were some key questions yet to be resolved, she believed the basis for a deal was there.
The EU wants to reach an agreement on the terms of the UK's withdrawal by October, allowing enough time for the UK and EU Parliament to vote on the deal prior to the UK's exit.
Should MPs reject the deal, it is not clear if there would be enough time for ministers to renegotiate a new one ahead of the deadline for leaving - unless the UK and all 27 other EU members agreed to extend the process.
Speaking in Birmingham, Sir Keir said the government's offer of a "take it or leave it" vote was "unacceptable", given the damage leaving without an agreement would do to the British economy and workers.
Labour, he said, would work with other parties to ensure Parliament "brought back control" of the process if the prime minister's deal was not satisfactory, by "strengthening" the terms of the promised vote in the EU Withdrawal Bill.
"If Parliament rejects the prime minister's deal that cannot give licence to her - or the extreme Brexiteers in her party - to allow the UK to crash out without an agreement," he said.
"That would be the worst of all possible worlds."
In such a scenario, Labour would not dictate what Parliament should do although its preference was for ministers to "go back to the negotiating table and work towards securing a deal that works for Britain", Sir Keir said.
"This would provide a safety valve in the Brexit process to safeguard jobs and the economy," he said.
"It would remove the possibility of a 'No' vote leading to a no deal. It would bring back control to Parliament."
Labour's Brexit policy has come under fresh scrutiny since Jeremy Corbyn sacked Owen Smith from the front bench on Friday after he broke ranks by calling for a referendum on the terms of final deal.
Labour has sought to differentiate itself from the government by calling for the UK to agree a new customs union with the EU after its exit, but some MPs want it go further and pledge to give the public the final say.
Responding to the PM's Commons update, Labour leader Jeremy Corbyn attacked what he said was the government's "posturing and dithering" over Brexit.
Its approach, he claimed, had been characterised by "wild claims and red lines which quickly become climbdowns and broken promises".
He asked what flexibility there was for extending the transition period if necessary and for the UK to remain in the Euratom nuclear association.
For the SNP, its Westminster leader Ian Blackford said the Scottish fishing industry had been "bargained away" in negotiations and left "hamstrung" during the transition period, where existing rules will continue to apply.
The PM said the UK would be leaving the Common Fisheries Policy and taking back control of UK waters and suggested the criticism was "a bit rich" coming from a party that opposes Brexit and wants to remain in the CFP "in perpetuity".

A cross-party group of MPs has put forward a bill to prevent a no-deal Brexit in 10 days' time.
If passed into law, the bill would require the PM to ask for an extension of Article 50 - which mandates the UK's exit from the EU - beyond the current 12 April deadline.
Labour MP Yvette Cooper presented the bill - which supporters hope they can pass through the Commons in one day.
The prime minister is expected to make a statement shortly.
It comes after the cabinet, which remains split over Brexit, met for eight hours in No 10.
The BBC's John Pienaar said Theresa May's ministers considered plans to "ramp up" no-deal Brexit preparations and a snap general election was also discussed.
Ms Cooper's bill would make it UK law for the PM to ask for an extension to prevent a no-deal, but it would be up to the EU to grant it - or not.
In March, MPs voted against leaving the EU without a deal, but it was not legally binding.
Meanwhile, the EU's chief negotiator has said a no-deal Brexit is now more likely but can still be avoided.
Michel Barnier said a long extension to the UK's 12 April exit date had "significant risks for the EU" and a "strong justification would be needed".
France's President Emmanuel Macron and Irish Taoiseach Leo Varadkar are meeting in Paris to discuss the impact of Brexit.
President Macron told reporters that the EU "cannot be hostage to the political crisis in the UK", and the government must come forward with "credible" reasons for an extension.
He said these could include an election, second referendum, or alternative proposals for the future relationship, such as a customs union.
Mr Varadkar said the UK was "consumed by Brexit", but the EU should not be.
He said the EU "needs to be open" about any proposals the UK brings, including a longer extension, and they will do what they can to "assist".
But he added: "We gave the UK some time, some space and some opportunity to come up with a way forward... [but] as things stand, they will leave on 12 April without a deal."
Tory MP Sir Oliver Letwin, who supports Ms Cooper's bill, said: "This is a last-ditch attempt to prevent our country being exposed to the risks inherent in a no-deal exit.
"We realise this is difficult. But it is definitely worth trying."
Ms Cooper said the UK was "in a very dangerous situation" and MPs "have a responsibility to make sure we don't end up with a catastrophic no deal".
Speaking to BBC Radio 4's World At One, she added: "We have been attempting to squeeze into just a couple of days a process that really should have been happening for the last two years - a process of trying to build a consensus around the best way forward.
"It is what the prime minister should be doing. It is the prime minister's responsibility to ensure we don't leave the country less safe."
Normally the government chooses which bills to present to Parliament in order for them to become law.
But - much to the government's disapproval - MPs voted to allow backbenchers to take charge of business in the Commons on Wednesday.
This gives backbenchers the opportunity to table their own bills, such as this one from Yvette Cooper.
A copy of the bill shows that they want to push it through the commons in one day.
As the backbenchers will be in charge, they will also be able to vote to set aside more time on another day, if they need to complete the process or hold further indicative votes.
However, the bill would also have to be agreed by the House of Lords and receive Royal Assent before it became law - which if the Commons agrees it on Wednesday, could happen as soon as Thursday.
Brexiteer Tory Sir Bill Cash said trying to go through these stages in one day made it a "reprehensible procedure".
But Speaker John Bercow said that, while it was "an unusual state of affairs", it was "not as unprecedented as he supposes" - citing recent bills on Northern Ireland that have been passed at the same speed.
In the latest round of indicative votes on Monday, MPs voted on four alternatives to the PM's withdrawal deal, but none gained a majority.
MPs rejected a customs union with the EU by three votes. A motion for another referendum got the most votes in favour, but still lost.
The votes were not legally binding, but they had been billed as the moment when Parliament might finally compromise.
The Independent MP Chris Leslie tweeted that MPs would be seeking more time for indicative votes to take place on Monday.
Liberal Democrat MP Norman Lamb said he is considering resigning the whip after his party refused to back proposals for a customs union and Common Market 2.0 on Monday.
He told BBC News: "If you are seen to be unreasonable, not engaging to find solutions, I don't think it is very attractive to the people."
Earlier, Mr Barnier said: "No deal was never our desire or intended scenario but the EU 27 is now prepared. It becomes day after day more likely."
Mrs May's plan for the UK's departure has been rejected by MPs three times.
Last week, Parliament took control of the process away from the government in order to hold a series of votes designed to find an alternative way forward.
Eight options were put to MPs, but none was able to command a majority, and on Monday night, a whittled-down four were rejected too.

MPs are putting forward plans to change the outcome of Brexit ahead of a vote next week on the PM's amended deal.
Theresa May said on Monday she was focused on altering the backstop - the "insurance policy" designed to avoid a hard border on the island of Ireland.
But Labour leader Jeremy Corbyn said the prime minister was in denial about the level of opposition to her deal.
Among the MPs' eight amendments are plans to stop a no-deal Brexit and to extend the deadline for leaving the EU.
But more amendments to change her next steps could be added in the coming days.
MPs are due to vote on Mrs May's proposals for Brexit on 29 January.
On Monday, the PM vowed to seek changes from the EU to the Irish "backstop" -  the measures intended to ensure that whatever else happens, there will be no return to a visible border between Northern Ireland and the Irish Republic after the UK leaves the EU.
Both the UK and the EU believe that bringing back border checks could put the peace process at risk.
Mrs May also scrapped the £65 fee EU citizens were due to pay to secure the right to continue living in the UK after Brexit.
However, she gave few details about how her deal would be changed before next Tuesday's vote.
The European Commission's chief spokesman, Margaritis Schinas, welcomed the dropping of the fee for EU citizens, but said it "does not provide the sort of clarification of intention that we are expecting as soon as possible on the broader picture".
He also said that if a no deal Brexit was to happen, it would be "pretty obvious" that there would be a hard border between Ireland and Northern Ireland - meaning checks on people and goods travelling between the two.
But the Taoiseach (Irish prime minister), Leo Varadkar, has said "we will have a real dilemma" if the UK leaves the EU without a deal.
He said there would have to be negotiations on customs and regulations that meant "full alignment", so there would be no hard border, saying: "We already have that agreement. That is the backstop."
He said nobody else has come up with an alternative and said: "We can't give that up for a promise that it will be all right on the night or will be sorted out over the next two years."
Meanwhile, civil service chief executive John Manzoni has warned that a no-deal Brexit might be a "bit bumpy" and was unlikely to go "swimmingly well".
An internal letter sent to staff at the National Crime Agency has warned of major disruption at ports, and possible transport blockages, fuel and food shortages and public disorder.
Speaking to BBC Radio 4's Today programme, Conservative MP Iain Duncan Smith, who voted against Mrs May's deal, said the backstop was "unworkable", adding that he also had objections to the £39bn so-called divorce bill the UK was preparing to pay the EU.
Conservative MP Damian Green, a close friend of Mrs May, voted for her deal, but told BBC Radio 4's World At One programme that he accepted the government would have to put forward "something different".
Roland Rudd, chairman of the People's Vote campaign for a fresh referendum said it was time for politicians to "put country before party".
"People had been hoping beyond hope that Theresa May would do that, and unfortunately she came up to speak yesterday and her 'Plan B' was just her 'Plan A' all over again, and it just looked like she was putting her party before country," he told the Today programme.
An official Labour Party amendment says that MPs should be able to vote on options such as the party's preferred outcome of a closer relationship with Europe, with a permanent customs union.
It also asks MPs to decide whether they should hold a further referendum on whatever Brexit plan is approved by the House of Commons.
Mr Corbyn said the amendment allowed MPs "to end this Brexit deadlock" and prevent the "chaos" of leaving the EU without a deal.
But Mrs May warned that another EU referendum could threaten the UK's "social cohesion".
Shadow business secretary Rebecca Long-Bailey said the issue of another referendum was "divisive" for both Labour and the Conservatives.
She would not be drawn on whether her party would back a further public vote, but said the option should be on the table for Parliament to discuss.
Ms Long-Bailey added: "Our job is to bring as many people together as we possibly can and that really is one option of many.
"Our priority always has been to secure a deal that really provides a consensus within Parliament and I think that deal can be found if we are actually given the opportunity to debate various options."
Among the other plans being put forward by MPs are:
Mr Duncan Smith said that plans to allow backbenchers to create legislation would create "mayhem" in the Commons and that anybody who believed the House could act as a government negotiating a trade deal was "living in cloud cuckoo land".
Some ministers are reportedly backing the proposals to block a no-deal Brexit, with the i newspaper and the Times saying that dozens could quit unless they are allowed a free vote on the issue.
The papers said that Work and Pensions Secretary Amber Rudd has warned Mrs May that up to 40 ministers could resign.
Speaking to reporters on her way into No 10 for Tuesday's cabinet meeting, Energy Minister Claire Perry said she didn't think there needed to be resignations and that MPs were "coming together" to support Mrs May's deal.
"Anyone in that House that wants to avoid no deal as passionately as I do, wants to deliver Brexit as much as I do and wants to avoid a people's referendum - which I think would be another extension of all of these really tough conversations - needs to come together and support the deal."
About 10,000 customers of Brittany Ferries have had their bookings amended to accommodate extra sailings in case of a no-deal Brexit.
The ferry company said timetables from Portsmouth, Poole and Plymouth were being modified to ensure "critical goods" could still be transported.
Another ferry company, P&O, has said it will re-register its six UK ships under the Cyprus flag ahead of Brexit so the firm can continue to benefit from the tax arrangements of EU states.
"The Cyprus flag is on the 'white list' of both the Paris and Tokyo Memoranda of Understanding, resulting in fewer inspections and delays, and will result in significantly more favourable tonnage tax arrangements as the ships will be flagged in an EU member state," a spokesman said.
And Dyson - whose founder Sir James Dyson has been in favour of Brexit - has announced that it is moving its headquarters to Singapore, from Malmesbury in Wiltshire.
However, chief executive Jim Rowan has said it is not to do with Brexit or tax, saying: "It's to make us future-proof for where we see the biggest opportunities."
Mr Rowan confirmed that Britain's departure from the EU would have little impact on the firm and that they had not made any contingency plans.
Last week MPs rejected the deal negotiated between the UK and EU on the terms of the UK's departure from the bloc by 432 votes to 202 - a majority of 230.
Outlining her proposed way forward on Monday, Mrs May refused to rule out a no-deal Brexit and insisted there was no majority in the House of Commons for another referendum.
But she promised Parliament a "proper say" in the next stage of negotiations on the future relationship between the UK and EU.
She also said she would conduct further talks on the Irish backstop plan, which is designed to prevent the need for a visible border and customs checks between Northern Ireland and the Irish Republic.
It means Northern Ireland staying aligned to some rules of the EU single market and effectively keeps the UK in the customs union until the UK and EU reach a lasting trade agreement.
The backstop is opposed by many Conservative MPs and the Democratic Unionist Party because they fear it could become permanent and because it means different rules for different parts of the UK.

MPs have rejected a Labour-led effort to take control of Parliament's timetable, blocking the latest attempt to stop a no-deal Brexit.
The Commons opposed the move by 309 votes to 298.
If passed, it would have given opponents of a no-deal Brexit the chance to table legislation to thwart the UK leaving without any agreement on the 31 October deadline.
The result of the vote was greeted with cheers from the Tory benches.
But Labour leader Jeremy Corbyn responded by shouting "you won't be cheering in September".
Ten Tory MPs, mostly pro-Europeans, rebelled against the government by backing Labour's motion. Conversely, eight Labour MPs - mostly Eurosceptics or MPs in constituencies which voted Leave at the referendum - defied party instructions and voted against it.
A key factor for the government was the support of Northern Ireland's Democratic Unionists, who have voted against Theresa May during previous Brexit votes.
No deal would mean the UK leaving the EU without any agreement about the "divorce" process.
Overnight, the country would be out of the single market, customs union and institutions such as the European Court of Justice and Europol.
There are fears about widespread disruption in such an event - to trade, travel and the functioning of the Irish border, in particular.
The opposition said the Commons defeat was disappointing, but it still believed there was a majority in the Commons against a no deal and it remained "determined to win this fight".
"There will be other procedural mechanisms we can use," shadow Brexit Secretary Sir Keir Starmer said. "We are already looking at what those other opportunities will be."
No 10 said giving MPs a "blank cheque" to dictate Brexit policy would have set a troubling precedent.
The UK was originally supposed to leave the EU on 29 March.
But the EU decided on a seven-month extension after MPs rejected the terms of withdrawal on three occasions.
Opponents of a no-deal exit are concerned that Theresa May's successor as prime minister could seek to take the UK out of the EU without parliamentary approval for such an outcome.
Tory leadership frontrunner Boris Johnson and several of his rivals have said the UK must leave the EU by the revised date, whether a deal is passed or not.
Wednesday's motion - supported by the Lib Dems, the SNP and Plaid Cymru, as well as some Conservatives, would not, by itself, have ruled out a no deal.
However, its supporters hoped to start a process on 25 June which could culminate with Parliament blocking the UK leaving without an agreement - in effect, tying the next prime minister's hands.
Backing the motion, Conservative ex-minister Sir Oliver Letwin said the case for ensuring Parliament had a "decisive vote" on the next PM's Brexit plan ahead of the 31 October deadline transcended party politics.
Given that leaving without a deal remains the default legal position, he said it was "perfectly possible" for the next PM to usher in a no-deal exit by "simply doing nothing" at all.
Tory Remain supporter and former Attorney General Dominic Grieve said the motion was the "last sensible opportunity" to stop no deal.
He added that in the future, if necessary, he would support efforts to bring down a Conservative government in a vote of no confidence if it was the only way to block such an outcome.
But veteran Eurosceptic Conservative Sir Bill Cash said it was a "phantom motion" which paved the way for "government by Parliament".
"It just simply opens the door for any bill of any kind to take precedence over government business," he told by MPs. "It is inconceivable as a matter of constitutional convention."
After the defeat, the deputy leader of the Liberal Democrats, Jo Swinson, accused the Conservatives of "putting party loyalty ahead of national interest".
This is not the first time that MPs have attempted to seize control of the Commons order paper in order to shift government policy on Brexit.
MPs voted in March to oblige Mrs May to seek a Brexit delay from the EU.
But efforts by Sir Oliver and others to come up with an alternative Brexit plan failed in April after MPs rejected all the options in a series of indicative votes.

MPs have rejected Theresa May’s EU withdrawal agreement on the day the UK was due to leave the EU.
The government lost by 344 votes to 286, a margin of 58, and means the UK has missed an EU deadline to delay Brexit to 22 May and leave with a deal.
The prime minister said the UK would have to find "an alternative way forward", which was "almost certain" to involve holding European elections.
Labour's Jeremy Corbyn said "this deal now has to change" or the PM must quit.
Meanwhile, thousands of Leave supporters gathered outside Parliament to protest against the delay to Brexit, bringing traffic to a standstill.
Mrs May now has until 12 April to seek a longer extension to the negotiation process to avoid a no-deal Brexit on that date.
With a clear majority in the Commons against a no-deal Brexit, and with MPs holding more votes on alternative plans on Monday, Mrs May said that the UK would have to find "an alternative way forward".
The prime minister said that the outcome was "a matter of profound regret", adding that "I fear we are reaching the limits of this process in this House".
Downing Street said it was still not an "inevitability" that the UK would have to take part in elections to the European Parliament in May.
It is highly likely that at least for another couple of weeks, Theresa May will look through every nook and cranny in Parliament to see if there is a way for her deal to pass through - somehow.
But that's a decision taken in the bunker, and the walls are closing in.
There is little reason tonight to think that, in the end, the burning core of Euroscepticism in the Tory Party will ever accept her deal.
There are few signs that any more than a handful of Labour MPs are really going to take the plunge and ultimately walk through the same lobbies as Theresa May, and Boris Johnson and Iain Duncan Smith.
The prime minister concluded today that our political process is reaching its limits.
But maybe soon it will be her leadership, her deal, that has passed its limits.
A No 10 source indicated that the prime minister would continue to seek support in the Commons for her deal.
"Clearly it was not the result we wanted. But, that said, we have had a number of senior Conservative colleagues who have felt able to vote with the government today. They have done so in higher numbers than previously," the source said.
"Clearly there is more work to do. We are at least going in the right direction."
Downing Street said Mrs May would continue to talk to the Democratic Unionist Party about more reassurances over the Irish backstop, which it says risks splitting Northern Ireland from the rest of the United Kingdom.
But the DUP's leader at Westminster leader, Nigel Dodds, told the BBC's Newsnight political editor Nick Watt: "I would stay in the European Union and remain, rather than risk Northern Ireland's position. That's how strongly I feel about the Union."
Responding to the vote, European Council President Donald Tusk tweeted: "In view of the rejection of the Withdrawal Agreement by the House of Commons, I have decided to call a European Council on 10 April."
In a statement, the European Commission said the UK would have to "indicate a way forward" by 12 April "for consideration by the European Council".
"A 'no-deal' scenario on 12 April is now a likely scenario. The EU has been preparing for this since December 2017 and is now fully prepared for a 'no-deal' scenario at midnight on 12 April. The EU will remain united," the statement said.
"The benefits of the withdrawal agreement, including a transition period, will in no circumstances be replicated in a 'no-deal' scenario. Sectoral mini-deals are not an option."
Despite all the drama, the money and time spent by EU leaders on Brexit (summits, dedicated governmental departments, no-deal planning) and all the hard, hard graft put in by the EU and UK negotiating teams, Europe's leaders are asking themselves what there is to show for it all.
Ongoing Brexit divisions in Parliament, in government and in Theresa May's cabinet were on screaming technicolour display again last week.
EU leaders used to use the threat of a no-deal Brexit as a negotiating tactic (as did the UK). They now believe it to be a very real prospect.
That has led to a number of countries - notably France - questioning the logic of delaying Brexit for much longer.
They wonder if the UK will ever unite around a Brexit Way Forward - be it a softer Brexit, no deal or no Brexit.
Would a Brexit extension, allowing for a general election or a second referendum, really settle the issue, they ask?
Read Katya's blog in full
Labour leader Jeremy Corbyn said: "The House has been clear, this deal now has to change.
"There has to be an alternative found. And if the prime minister can't accept that then she must go, not at an indeterminate date in the future but now.
"So that we can decide the future of this country through a general election."
Steve Baker, deputy chairman of the European Research Group of Brexiteer Conservatives, said it was time for Mrs May to quit.
"This must be the final defeat for Theresa May's deal. It's finished. And we must move on.
"It has not passed. It will not pass. I regret to say it is time for Theresa May to follow through on her words and make way so that a new leader can deliver a withdrawal agreement which will be passed by Parliament."
Mr Baker was one of 34 Conservative rebels to vote against the agreement, along with the Democratic Unionist Party and the Labour Party. Five Labour MPs voted for the agreement.
A number of high profile Tory Brexiteers, including Dominic Raab and Iain Duncan Smith, did vote for the agreement, but it was not enough to prevent another damaging defeat for Mrs May, who had offered to stand down to persuade her critics to back the deal.
This was not a third "meaningful vote" on the PM's EU deal, which also includes a political declaration on future relations between the UK and the EU, and which has previously been rejected by larger margins.
By holding a vote on the withdrawal agreement only, the government had hoped to secure a short delay to Brexit and avoid the UK taking part in May's European elections.
MPs are set to have another go at reaching a Brexit compromise in another series of votes on Monday and Wednesday next week.
If one of the options receives a majority, the government could use it as a basis for negotiating changes to the political declaration.

Theresa May's EU withdrawal deal has been rejected by MPs by an overwhelming majority for a second time, with just 17 days to go to Brexit.
MPs voted down the prime minister's deal by 149 - a smaller margin than when they rejected it in January.
Mrs May said MPs will now get a vote on whether the UK should leave the EU without a deal and, if that fails, on whether Brexit should be delayed.
She said Tory MPs will get a free vote on a no-deal Brexit.
That means they can vote with their conscience rather than following the orders of party managers - an unusual move for a vote on a major policy, with Labour saying it showed she had "given up any pretence of leading the country".
The PM had made a last minute plea to MPs to back her deal after she had secured legal assurances on the Irish backstop from the EU.
But although she managed to convince about 40 Tory MPs to change their mind, it was not nearly enough to overturn the historic 230 vote defeat she suffered in January, throwing her Brexit strategy into fresh disarray.
In a statement after the defeat, Mrs May said: "I continue to believe that by far the best outcome is the UK leaves the European Union in an orderly fashion with a deal.
"And that the deal we have negotiated is the best and indeed only deal available."
Setting out the next steps, she said MPs will vote on Wednesday on whether the UK should leave the EU without a deal or not.
If they vote against a no-deal Brexit, they will vote the following day on whether Article 50 - the legal mechanism taking the UK out of the EU on 29 March - should be extended.
Mrs May said MPs would have to decide whether they want to delay Brexit, hold another referendum, or whether they "want to leave with a deal but not this deal".
She said that the choices facing the UK were "unenviable", but because of the rejection of her deal, "they are choices that must be faced".
Mrs May also told MPs the government would announce details of how the UK will manage its border with Ireland in the event of a no-deal Brexit on Wednesday.
Mrs May said leaving without a deal remained the UK's default position but Downing Street said she will tell MPs whether she will vote for no-deal when she opens Wednesday's Commons debate on it.
The prime minister did not discuss resigning after her latest defeat because a government led by her had recently won a confidence vote in the Commons, added the PM's spokesman.
She has no plans to return to Brussels to ask for more concessions because, as she told MPs, she still thinks her deal is the best and only one on offer, he added.
What isn't clear is how the prime minister actually intends to dig herself out of this dreadful political hole.
Some of her colleagues around the Cabinet table think it shows she has to tack to a closer deal with the EU.
Some of them believe it's time now to go hell-for-leather to leave without an overarching deal but move to make as much preparation as possible, and fast.
Other ministers believe genuinely, still with around two weeks to go, and an EU summit next week, there is still time to try to manoeuvre her deal through - somehow.
Labour leader Jeremy Corbyn said the prime minister should now call a general election.
"The government has been defeated again by an enormous majority and it must accept its deal is clearly dead and does not have the support of this House," he told MPs.
He said a no-deal Brexit had to be "taken off the table" - and Labour would continue to push its alternative Brexit proposals. He did not mention the party's commitment to back another referendum.
Jacob Rees-Mogg, chairman of the European Research Group of Brexiteer MPs, said "the problem with the deal was that it didn't deliver on the commitment to leave the EU cleanly and that the backstop would have kept us in the customs union and de facto in the single market".
The Tory MP, who voted against Mrs May's deal, told BBC News: "The moral authority of 17.4 million people who voted to leave means that very few people are actually standing up and saying they want to reverse Brexit. They're calling for a second referendum, they're calling for delay.
"But actually very few politicians are brave enough to go out and say they want to overturn the referendum result."
Leading Conservative Remainer Dominic Grieve, who backs another referendum, said Mrs May's deal was now "finished".
The Tory MP, who voted against the prime minister's plan, said he was confident the majority of MPs would now vote against a no-deal Brexit - and he hoped they would then vote to ask for an extension to Article 50.
The EU's chief Brexit negotiator Michel Barnier said in a tweet: "The EU has done everything it can to help get the Withdrawal Agreement over the line. The impasse can only be solved in the UK. Our 'no-deal' preparations are now more important than ever before."
A spokesman for European Council president Donald Tusk echoed that message, saying it was "difficult to see what more we can do".
"With only 17 days left to 29 March, today's vote has significantly increased the likelihood of a no-deal Brexit," added the spokesman.
The EU would consider an extension to Brexit if the UK asked for one, he added, but the 27 other EU member states would expect "a credible justification" for it.
The PM's deal was defeated by 391 to 242.
Some 75 Conservative MPs voted against it, compared with 118 who voted against it in January.
The Democratic Unionist Party's 10 MPs also voted against the deal, as did the Labour Party, SNP and other opposition parties.
Three Labour MPs - Kevin Barron, Caroline Flint and John Mann - voted for the prime minister's deal.

Attempts to keep the UK in the European Economic Area after Brexit have been defeated in the House of Commons despite dozens of Labour MPs defying the leader's instructions on the issue.
MPs voted by 327 to 126 against a House of Lords proposal for a close relationship with the EU like Norway's.
Jeremy Corbyn urged his MPs to abstain but 75 voted for and 15 against, while six quit their Labour roles.
MPs overturned six further amendments peers had put forward.
MPs were deciding whether the UK should stay part of the European Economic Area after it leaves the EU - a similar arrangement to non-EU countries Norway, Iceland and Liechtenstein.
Like EU members, these countries are part of the EU single market - in return they are obliged to make a financial contribution and accept many EU laws. The free movement of people also applies in the zone as it does in the EU.
Supporters of the EEA argue it would give the UK the closest possible relationship with the EU without actually being a member, as it would offer full access to the single market.
But critics say it would require the UK to adhere to EU rules without having a say in them - and would not be in keeping with the spirit of the 2016 referendum result.
After the House of Lords altered the government's EU Withdrawal Bill in favour of EEA membership, the House of Commons agreed to change it back on Wednesday evening.
The government won the vote comfortably after Labour abstained, although three Tory MPs, Ken Clarke, Anna Soubry and Dominic Grieve, rebelled themselves and backed the motion.
Jeremy Corbyn said EEA membership was "not the right option" for Britain but that he understood the difficulties the issue posed for MPs representing strongly Leave or Remain constituencies.
Speaking on BBC Radio 4's Today programme, Labour MP Laura Smith defended her decision to quit as shadow defence minister because she did not want to follow the leader's instruction to abstain.
The MP for Crewe and Nantwich said she wanted to oppose the Lords amendment, saying remaining part of the EEA was not in the interests of her constituents who had voted to leave the EU in 2016.
Ms Smith, who backed Remain in the referendum, said there were "legitimate reasons" why people had backed Brexit, adding: "The country is divided on this issue and we need to start bringing people together."
On the other side of the debate were her Labour colleagues Ged Killen, Tonia Antoniazzi, Anna McMorrin, Ellie Reeves and Rosie Duffield who stepped down as parliamentary private secretaries to support EEA membership.
In her resignation letter to Mr Corbyn, Ms Reeves said her Lewisham West and Penge constituency had voted by two to one to stay in the EU and hundreds had contacted her in support of staying part of the EEA.
Earlier, Labour failed in an attempt to amend the bill with their own alternative motion to guarantee "full access" to European markets after Brexit from outside the EEA. This was defeated by 322 votes to 240..
By political editor Laura Kuenssberg
A wiser head than me - there's dispute over whether it was Mark Twain or Bismarck! - once remarked that laws are like sausages, if you respect them it's best not to watch them being made.
Well the last 48 hours in Westminster may give weight to that. Farce? Fiasco? Or maybe today in Parliament has been in the best tradition of British pantomime.
Or perhaps, this is in fact the completely predictable agony of split political parties, with leaders who struggle to command their troops, just trying to make it through after a huge vote that by its very nature, split the country in two.
The government is trying to pass a new law, called the EU Withdrawal Bill, which it says is needed to ensure a "smooth and orderly Brexit".
Its main purposes are to end the supremacy of EU law in the UK, and transfer existing EU law into UK law so the same rules and regulations apply on the day after Brexit.
But as it passes through Parliament, MPs and peers have been trying to change it, in some cases adding bits on that would change the government's Brexit strategy.
MPs also overturned other changes made to the bill by the Lords, including a requirement for ministers to set out steps to negotiate a customs union with the EU.
The government agreed a compromise with potential Tory rebels earlier this week to work towards a "customs arrangement" with the EU. This won the support of the Commons by 325 votes to 298.
Other changes insisted upon by the Lords relating to the Charter of Fundamental Rights, principles of EU law to be retained after Brexit and EU environmental principles were also removed.
In response to the votes, Lib Dem leader Sir Vince Cable accused Labour of conspiring with the Conservatives to "wave through a hard Brexit".
But ministers did make one significant policy concession - on refugee policy after Brexit.
They accepted a proposal by Labour MP Yvette Cooper to widen the terms under which unaccompanied child refugees can be reunited with family members living in the UK.
The government had already agreed to allow unaccompanied children to claim asylum in the UK if it was deemed to be in their "best interests".
But, following Ms Cooper's intervention, ministers have agreed to drop a clause stating this could only happen if their family members already in the UK were over 18 years of age.
Solicitor General Robert Buckland said ministers had listened "very carefully" to the views of MPs from different parties and would amend the bill when it returns to the Lords next week.

Theresa May must honour "assurances" she's given that Parliament will get a bigger say on any final Brexit deal, pro-EU Tory MPs say.
The government averted a rebellion on the issue after a meeting between the PM and more than a dozen MPs.
One of the potential rebels, Dominic Grieve, warned there would be consequences for the government if not.
BBC political editor Laura Kuenssberg said a government source had told her no actual concessions had been agreed.
And a senior minister, Solicitor General Robert Buckland, said the government had only agreed to "further discussions" about the way in which they could make "a further step forward".
A group of MPs said on Tuesday they were offered, in a last-minute concession, real "input" if no deal with the EU was done by December.
Details of precisely what this will involve could emerge in the coming days when the EU Withdrawal Bill is due to return to the House of Lords.
The UK is due to leave the European Union on 29 March next year, after the referendum in 2016 when people voted by 51.9% to 48.1% to leave.
The government is trying to pass a new law, called the EU Withdrawal Bill, which it says is needed to ensure a "smooth and orderly Brexit".
Its main purposes are to end the supremacy of EU law in the UK, and transfer existing EU law into UK law so the same rules and regulations apply on the day after Brexit.
But as it passes through Parliament, MPs and peers have been trying to change it, in some cases adding bits on that would change the government's Brexit strategy.
Given that politicians, like the rest of the country, are divided on what Brexit should look like, this is posing problems for the government as it tries to get the bill through both the House of Commons and the House of Lords.
The government is currently trying to persuade MPs to undo most of the changes made by the House of Lords, and on Tuesday this involved a tussle over how much of a say Parliament will get if it does not like the deal struck between the UK and the EU.
The government does not want to give MPs and peers the power to say what sort of Brexit deal the UK should strike with the EU, saying this should be left to ministers.
When it came to the key vote, a group of Conservatives who had threatened to rebel agreed at the last minute not to defeat the government after public haggling between ministers and would-be rebels and a meeting between Mrs May and more than a dozen Tory MPs.
But it is not yet clear exactly what the MPs were offered and whether they are happy with what has since been said by ministers.
"I expect the government to honour its commitments and I expect the PM to honour her commitments and I have no reason to distrust the approach she took with us," one of the would-be rebels, Dominic Grieve, told the BBC's Newsnight.
Ahead of the vote Mr Grieve tried to broker a compromise between MPs and ministers which would apply if Parliament rejects the final UK-EU Brexit deal.
Under his proposals, the government would then have to seek MPs' approval for its plan of action through a motion in the House of Commons. It would also have to do this if no deal has been agreed by the end of November 2018.
Ministers have agreed to consider these suggestions - but not a third strand of his proposals which would require the government to "follow any direction" from MPs if there is no deal by 15 February 2019.
Remain-supporting Conservatives Anna Soubry and Nicky Morgan were two of the MPs to meet with Mrs May.
Ms Soubry said she trusted Mrs May to "honour the undertaking she gave".
Ms Morgan told BBC Radio 4's Today programme: "What was agreed was the prime minister understood that Parliament wants to have a real say, in all circumstances, in relation to what's going to happen in the Brexit deal."
Politics is often about the big picture, but sometimes it is a festival for pedants.
Believe me, in Westminster, there is a very very big difference between the promise of more serious chat about something with the possibility of a change - and a promise actually to do something different, especially if it is made by the occupant of Number 10.
So just hours after the concession, (or non-concession) very, very dark mutterings began from those who had been persuaded by what they thought was a promise.
Read Laura's full blog
Eurosceptic MPs have criticised moves to give Parliament more power as Brexit approaches, saying this would be used to "wreck" the UK's EU departure.
Tory MP Andrew Bridgen, a leading Brexit backer, said the concessions could "come back to haunt" the government if they amounted to a veto over the terms of the UK's departure.
He told the BBC that rebels were seeking a "wrecking motion", stating: "It not only has the risk of stopping Brexit, it is certainly going to make the negotiating position of the government considerably diminished.
"It is hugely irresponsible, and I can't believe that those that are perpetrating this don't know exactly what they are doing. And, for me, it's a betrayal of the British people."
The EU Withdrawal Bill is now back in the House of Commons, with MPs debating the rest of the Lords amendments.
These include a requirement to seek membership of the European Economic Area - an arrangement like Norway's that would keep the UK part of the EU single market. This is opposed by both the Conservative and Labour leaderships, despite the backing of some pro-EU MPs in both parties.
There is also an amendment requiring the government to report to Parliament on steps taken to negotiate a customs union with the EU.
The government has rejected this one too, and has proposed an alternative amendment referring to a new "customs arrangement" which was thought to have averted the possibility of a rebellion on that subject.
Tempers flared in the Commons as MPs discussed immigration, with Speaker John Bercow appealing to members to "respect" each other's arguments.
Ms Soubry said she was "appalled" at a speech from Labour's Caroline Flint and accused her of not appreciating the value of immigrants.
Ms Flint had argued for new immigration controls, saying people wanted to be able to "turn the tap on and off when we choose".
She said she was not against all immigration but that her constituents wanted a "fair and managed system".
Earlier some MPs claimed an amendment passed on Tuesday night could have implications for the government's preferred trade options after Brexit.
Labour's Shadow Brexit Secretary Sir Keir Starmer highlighted the amendment, which committed the government to avoiding any "physical infrastructure, including border posts, or checks and controls" in Northern Ireland after Brexit.
He said this meant one of the government's proposals for replacing the customs union - a technology-based solution to minimise border delays - could be "unlawful" if it involves any border infrastructure checks.
Dominic Grieve agreed, saying: "Not only will we have to stay in a form of customs arrangement amounting to a union, but we're also going to have to have a high level of regulatory alignment because otherwise the life that takes place along the border will be impossible because of different regulations on either side."
Labour's whips' office said it expected eight votes to take place from 19:30BST.

MPs have set out details of their plan to consider other Brexit options, as Theresa May was warned more ministers could quit unless she changes course.
The Commons will begin voting on alternatives on Wednesday, in a process likely to continue into next week.
MPs will fill out a series of ballots testing support for different ideas.
Ex-minister Alistair Burt said the PM must recognise a "different answer" was now needed but ex-Brexit secretary David Davis warned of impending chaos.
As MPs seek to take the initiative from the government, there are signs that some Tory opponents of Mrs May's deal could be steeling themselves to back it if it returns to the Commons for a third time later this week.
Prominent Brexiteer Jacob Rees-Mogg indicated that he could be persuaded, given it now appeared to be a choice between her deal and no Brexit at all.
Ex-Foreign Secretary Boris Johnson told the BBC there was "no point" supporting Mrs May's deal "without any sign the UK is going to change its approach in phase two" of the negotiations - otherwise he feared the country would be indefinitely tied to the EU's rules.
But BBC political editor Laura Kuenssberg said the not very subtle subtext of Mr Johnson's remarks was "if the PM promises to go soon, then she might get my vote."
MPs took the unprecedented step of voting to seize control of the parliamentary timetable on Monday, in an attempt to end the deadlock over the terms of the UK's exit.
Groups are now putting forward a variety of different options for the UK's future relationship with the EU.
Several of these are based on the assumption that the existing withdrawal agreement with the EU will be approved, albeit with changes to the controversial Northern Ireland backstop.
Others call for a basic free trade agreement with the EU and another referendum on whether Brexit goes ahead. It will be up to Commons Speaker John Bercow to decide what is voted on.
According to a copy of a business motion released by Labour's Hilary Benn, there will be about five hours of debate on different options.
Voting by paper ballot will take place at about 19:00 GMT, with the results announced by Mr Bercow later that evening.
The process is likely to continue on Monday as MPs seek to whittle down options which could command majority support in Parliament.
The government has until 12 April to propose a different way forward to the EU if it cannot get the current agreement through Parliament.
There is a very strange mood around the place in Westminster, ahead of what could be a very messy and tricky day tomorrow.
MPs will spend much of Wednesday voting on different versions of Brexit. But the government is even at odds with itself over whether they should be given free rein to do so.
One source told me 19 ministers are ready to quit if they aren't allowed to have their say, which could, hypothetically at least, collapse the government itself.
Mr Burt, one of three ministers who quit on Monday to back the so-called "indicative votes" plan, said he still backed the prime minister's deal but she had a duty to look at other options.
"My advice to the prime minister would be to recognise that her duty now is perhaps to find a different answer than the one she has tried to find," he told Laura Kuenssberg.
But David Davis said the PM's deal was better than the alternatives and had a "decent chance" of getting through Parliament if put to the vote again.
"It's not a good deal but the alternative is a complete cascade of chaos," he said. "You are seeing proposals being put up which are all worse than hers."
The PM has signalled she will try to bring her deal, which has been heavily rejected twice, back to the Commons for a third time later this week but only if she believes she can win.
The Democratic Unionists, whose 10 MPs prop up Mrs May's government, urged Tory MPs to "stand firm" in their opposition unless there were "significant changes".
Tuesday: Theresa May met her cabinet. Tuesday had been considered as a possible day for the so-called third meaningful vote on Mrs May's withdrawal deal. But, on Monday, the PM said the deal did not have enough support to get through the Commons "as things stand".
Wednesday: This is when indicative votes will be held - we don't know yet whether MPs will be free to vote how they want or be directed along party lines. The prime minister is also due to address the 1922 Committee of Conservative backbenchers. MPs will also vote on changing the Brexit date in UK law from 29 March.
Thursday: A possible opportunity for meaningful vote three. The prime minister may hope that Brexiteers will finally decide to throw their weight behind her deal.
Friday: This is written into law as the day the UK leaves the EU, although the PM has said she will pass legislation this week to remove it. The earliest Brexit is likely to happen is now 12 April.

Theresa May is giving MPs another chance to vote on Brexit in early June - whether or not the government and Labour have reached a deal by then.
A vote on the bill that would pave the way for Brexit was "imperative" if the UK was to leave the EU before MPs' summer recess, Downing Street said.
Labour sources say they will not back the bill without a cross-party deal.
If Mrs May's plan is defeated, Number 10 said the UK is set for no deal or for Article 50 to be revoked.
That is because the EU will not grant a further extension beyond 31 October, says BBC assistant political editor Norman Smith.
Brexit Secretary Stephen Barclay also said the deal the PM negotiated with the EU would be "dead" if the bill did not pass.
Attempts to find a cross-party compromise began after Mrs May's Brexit deal was rejected three times by MPs.
But government sources have told the BBC that there would not be a further attempt if the plan is rejected.
The vote - which will take place when MPs return from half-term recess - would bring the withdrawal agreement into UK law via the Withdrawal Agreement Bill.
The prime minister has negotiated a withdrawal agreement with the EU, which MPs have effectively rejected three times in Commons votes.
No 10 described Tuesday evening's discussions between Mrs May and Mr Corbyn on Brexit as "both useful and constructive".
Mrs May had made clear the government's "determination to bring the talks to a conclusion and deliver on the referendum result to leave the EU", a spokesman said.
A Labour party spokesman said Mr Corbyn had "raised doubts over the credibility of government commitments, following statements by Conservative MPs and cabinet ministers seeking to replace the prime minister".
He said the Labour leader had called for "further movement" from the government and the prime minister's team would bring back "further proposals tomorrow".
Bringing the EU Withdrawal Agreement Bill forward would allow the prime minister to push ahead with her ambition of delivering Brexit before the summer - despite the lack of agreement so far in the cross-party talks, said BBC political correspondent Iain Watson.
Brexit Secretary Steve Barclay said: "It is now time for Parliament to make a decision, reflecting the manifestos of both the Conservative and Labour parties at the last general election and to deliver Brexit in the way that the public were promised."
In the 2017 general election, the two main parties promised in their manifestos to respect the result of the Brexit referendum.
International Trade Secretary Liam Fox said that if MPs do not vote for the government's Brexit plan next month, then it will "take us to either the potential of revocation of Article 50 or leaving without a deal".
He said MPs will have to decide "if they want to vote for Brexit or not".
Brexiteer and Conservative MP Steve Baker said bringing the bill forward "over the heads" of DUP MPs - on whom the government relies for a majority - would "eradicate the government's majority".
"What is the government thinking?" he asked.
DUP Westminster leader Nigel Dodds said: "If the prime minister brings the withdrawal bill to the Commons for a vote, the question will be, 'What has changed?'.
"Unless she can demonstrate something new that addresses the problem of the backstop, then it is highly likely her deal will go down to defeat once again."
The backstop is the controversial part of the withdrawal deal that aims to ensure an open border on the island of Ireland if the UK leaves the EU without securing an all-encompassing deal.
It's not exactly the same thumbs up or thumbs down that another meaningful vote would be. That is a straightforward yes or no to the divorce deal that the prime minister negotiated with the EU.
This time, it will be the Withdrawal Bill which is a whole tome of new laws that will be needed to take us out of the European Union.
The draft of that bill is still being kept under wraps. Very, very few people have seen it. It's much more detailed than just a vote on the agreement would be.
Of course, that gives people more things to object to.
Although Theresa May might have pleaded in cabinet that people on all sides have to move away from absolutism, and move to a mood of compromise, there's not much sign of it.
As and when that bill actually emerges, that may well - in the words of one cabinet minister - make things worse before they can get better.
The UK needs to pass a law to implement the withdrawal agreement - the part of the PM's Brexit deal which will take the country out of the EU - in UK law.
This is a requirement under the terms of previous Brexit legislation passed last year.
The legislation would make the citizens' rights part of the agreement directly enforceable in UK courts, and set their relationship with the EU's Court of Justice.
It will also allow ministers to make "divorce payments" to the EU foreseen under the current deal, and give effect to the so-called backstop plan for the Irish border.
MPs will be able to vote on amendments to the bill, and this could allow ministers to make good on any compromise they reach with Labour in the cross-party talks.
If the bill is introduced in the first week of June it will come seven days after the European Parliament elections -  which Education Secretary Damian Hinds has acknowledged could be "difficult" for the Conservatives.
A state visit by US President Donald Trump and a by-election in Peterborough will also take place that same week.

MPs who do not want the UK to leave the EU without a deal are trying to limit the government's financial powers in the event of a no-deal Brexit.
The House of Commons will vote shortly on a cross-party amendment to the Finance Bill, which enacts the Budget.
Several senior figures back the move, but International Trade Secretary Liam Fox called it "irresponsible".
No 10 said it would not stop tax being collected, describing the MPs' move as "more inconvenient than significant".
Downing Street said the amendment, which could be voted on about 19.00 BST, was "not desirable" and Mrs May was striving to get her deal through Parliament.
Meanwhile, minister Richard Harrington said he is prepared to resign to stop the possibility of a no-deal Brexit.
Mr Harrington suggested to BBC Newsnight that others might follow suit, saying his position was "not an uncommon one".
MPs will seek to turn the screw on ministers with Tuesday's amendment, which is intended to demonstrate to the government the strength of opposition to a no-deal Brexit in the Commons.
If passed, it would mean the government would not be able to raise certain taxes and take other financial steps arising from a no deal - unless Parliament had explicitly authorised the UK leaving the EU without a deal.
The UK is scheduled to leave the EU on 29 March whether there is a deal or not.
The deal which Prime Minister Theresa May has negotiated with the EU - which covers the terms of the UK's divorce and the framework of future relations with the EU - has not been formally approved.
Labour MP Yvette Cooper who, along with Conservative Nicky Morgan, is behind the amendment, said Parliament must act now to rule out a no-deal Brexit in the event of Mrs May's agreement being voted down next week and MPs being unable to agree any other course of action before the UK's exit in March.
She told the BBC: "There is a risk that we end up with no deal by accident, as a result of brinkmanship, delays and drift.
"That's why Parliament has to be sensible and say 'we have to rule out the worst option, the kind of damaging deal that would hit manufacturing industry and would also put our police and security at risk as well".
Labour have said they will back the amendment, prompting speculation that ministers will be forced to accept it in order to avoid a damaging defeat.
But Mr Fox, who backs Mrs May's deal, said it would be "irresponsible to tie the government's hands" at this stage by ruling out any options.
Speaking at a technology fair in California, Mr Fox said it would not take the possibility of a no-deal exit off the table.
"The government has to ensure that all eventualities are covered," he said. "It maybe that we cannot get agreement with the EU and that we have to leave without an agreement in which case the UK has to be prepared."
In other Brexit developments:
MPs will vote on 15 January on whether to accept the legally-binding terms of withdrawal negotiated by Mrs May, as well as a framework of future relations with the EU. Five days of debate in the Commons will begin on Wednesday.
The prime minister has said the UK will be in "uncharted territory" if the deal is not accepted although she has not ruled out asking the Commons to vote on it on several times prior to the 29 March deadline.
Mr Harrington, a minister in the business department, told Newsnight he was confident that Britain would leave the EU with a deal as the stark reality facing the UK became clear.
"We will not be leaving with no deal," he said. "I think people are beginning to realise that it's the prime minister's deal or there may not be a Brexit."
Asked whether he was prepared to resign to stop a no-deal Brexit, he replied: "Definitely, I would... The prime minister knows everybody's views and I think my view is not an uncommon one."
Another minister, Margot James, suggested on Monday that Brexit may have to be delayed and negotiations extended under the Article 50 process if Parliament could not agree on the terms of withdrawal.
The vote on the cross-party amendment is expected at about 19:00 GMT.
Government sources warned over the weekend of "paralysis" and an effective "shutdown" if the Treasury was stripped of the power to pass regulations relating to "no-deal financial provisions" without parliamentary approval.
One leading tax expert said ministers would still be able to make tax changes by introducing new clauses into future Finance Bills or introducing emergency legislation but would find it much "more cumbersome".
"Even if the clause were passed and there was a no-deal Brexit, the system could still function," Andrew Hubbard, a consultant at audit, tax and consulting firm RSM said.
"But there is no doubt that if the clause were passed, it would represent a huge challenge to the authority of the government and increase further pressure to find a negotiated way out of the current deadlock."

MPs have voted by 413 to 202 - a majority of 211 - for Prime Minister Theresa May to ask the EU for a delay to Brexit.
It means the UK may not now leave on 29 March as previously planned.
Mrs May says Brexit could be delayed by three months, to 30 June, if MPs back her  deal in a vote next week.
If they reject her deal again then she says she will seek a longer extension - but any delay has to be agreed by the 27 other EU member states.
Most Conservative MPs voted against delaying Brexit - including seven cabinet members - meaning Mrs May had to rely on Labour and other opposition votes to get it through.
But some Labour frontbenchers resigned to defy party orders to abstain on a vote on holding another referendum.
Shadow housing minister Yvonne Fovargue, shadow education minister Emma Lewell-Buck, shadow business minister Justin Madders, Ruth Smeeth, a shadow ministerial aide, and Labour whip Stephanie Peacock, all quit their roles to oppose one.
Theresa May, who has long insisted that the UK will leave the EU on 29 March with or without a withdrawal deal, voted to delay Brexit.
She had been forced to offer MPs a vote on delaying Brexit after they rejected her withdrawal agreement by a large margin, for a second time, and then voted to reject a no-deal Brexit.
She has warned that extending the departure date beyond three months could harm trust in democracy - and mean that the UK would have to take part in May's European Parliament elections.
Downing Street said the government was still preparing for a no-deal Brexit.
Theresa May is planning to hold another "meaningful vote" on her withdrawal deal by Wednesday - after it was overwhelmingly rejected on two previous occasions.
If she wins that vote, she will ask for a one-off extension to Brexit get the necessary legislation through Parliament at an EU summit on Thursday - if not she could ask for a longer extension.
A spokesman for the European Commission said extending Article 50, the mechanism taking the UK out of the EU on 29 March, would need the "unanimous agreement" of all EU member states.
And it would be for the leaders of those states "to consider such a request, giving priority to the need to ensure the functioning of the EU institutions and taking into account the reasons for and duration of a possible extension".
It is still technically possible that we could leave the EU at the end of this month - the law has not changed.
But politically it is now almost entirely out of reach.
The prime minister is accepting she will miss one of the biggest targets she has ever set herself.
Tonight's vote is awkward for another reason, as it again displays the Conservatives' fundamental divisions.
This is more than a quarrel among friends, but a party that is split down the middle on one of the most vital questions this administration has posed, with cabinet ministers, as well as backbench Brexiteers, lining up to disagree with Theresa May.
Downing Street said this was a "natural consequence" of Mrs May's decision to offer a free vote on an issue where there are "strong views on all sides of the debate".
Chief Secretary to the Treasury Liz Truss tweeted: "I voted against a delay to Brexit. As a delay was passed by Parliament, I want to see deal agreed ASAP so we can minimise to short, technical, extension."
Seven cabinet ministers - Ms Truss, Brexit Secretary Stephen Barclay, International Trade Secretary Liam Fox, International Development Secretary Penny Mordaunt, Commons leader Andrea Leadsom, Transport Secretary Chris Grayling and Defence Secretary Gavin Williamson - voted against the government motion.
Health Secretary Matthew Hancock said it would be "extremely difficult" but "still possible to deliver Brexit on 29 March with a deal".
He said there were now two options: "To vote for the deal and leave in orderly way or a long delay and I think that would be a disaster."
MPs earlier rejected an attempt to secure another Brexit referendum by 334 votes to 85.
And they also rejected a cross-party plan to allow MPs to take control of the Brexit process to hold a series of votes on the next steps, by the narrow margin of two votes.
Following the votes, Labour leader Jeremy Corbyn reiterated his support for a further referendum after earlier ordering his MPs not to vote for one.
He said: "Today I reiterate my conviction that a deal can be agreed based on our alternative plan that can command support across the House.
"I also reiterate our support for a People's Vote - not as a political point-scoring exercise but as a realistic option to break the deadlock."
Labour abstained when MPs voted on the referendum proposal, tabled by Independent Group MP Sarah Wollaston, arguing that now was not the right time to push for a public vote.
But 17 Labour MPs defied party orders and voted to oppose another referendum - while 24 Labour MPs rebelled to vote in favour of one.
Among frontbenchers to quit over the issue, Ms Peacock said: "It is with deep regret I tonight resigned from Labour's front bench, because I believe we should respect the result of the 2016 vote to leave the European Union."
Labour's plan to delay Brexit to allow Parliamentary time for MPs to "find a majority for a different approach" was defeated by 318 to 302 votes.

MPs have voted on the possible next steps for Brexit as they try to break the deadlock in Parliament.
Four options were chosen by the Speaker to be voted on, and results will be announced later.
Labour MPs were urged to back a plan to keep the UK in a Norway-style relationship with the EU.
Under the Common Market 2.0 proposal, the UK would leave the EU, but retain freedom of movement and make contributions to the EU budget.
In a letter to MPs, Labour leader Jeremy Corbyn asked them to support the motion, as well as one for a customs union, to "break the deadlock and find the consensus necessary to force a change to the red lines of the prime minister's rejected deal".
The party have also been asked to support a motion calling for a confirmatory referendum on any deal agreed by Parliament - although some rebels may vote against it.
Conservative MPs were given a free vote on the motions - meaning they were not be told by party bosses which way to go - but the cabinet was told to abstain.
During the debate, 11 climate change activists staged a protest in the public gallery, taking their clothes off to reveal slogans painted on their bodies.
Police were called to remove them from the viewing platform.
The Common Market 2.0 motion - put forward by Tory MP Nick Boles - may also be backed by the SNP.
But the PM's spokesman said ending free movement was a "very important factor" for the public when voting for Brexit, so they would oppose it.
Shadow foreign secretary Emily Thornberry, speaking to the BBC's World at One programme, refused to say whether Labour's position on free movement had changed.
When asked if she was compromising on freedom of movement, she said "we are trying to pull the House of Commons together".
None of today's votes on the proposals are legally binding, meaning it will be up to the government if they act on the results.
Theresa May tried to get MPs to back the withdrawal agreement element of her deal on Friday, but lost by 58 votes - having already failed twice to get support for her overall deal in Parliament.
She now has until 12 April to either seek a longer extension to the deadline or decide to leave the EU without a deal.
The cabinet is now split over whether to move to a softer deal that could mean including a customs union in her plan.
International Trade Secretary Liam Fox told the BBC joining a customs union would be a "betrayal of Brexit".
The Speaker John Bercow picked four of the eight amendments put forward for debate:
He did not choose motions calling for a unilateral exit to the backstop, to leave on 12 April without a deal, to hold a referendum in the case of no-deal or to rejoin the European Free Trade Association.
You can MPs have voted on the proposals and were given a piece of paper listing all the options and tick "yes" or "no" on as many as they want.
The House is now suspended as MPs await the result of the vote. It took two hours for the votes to be counted before.
When MPs voted on proposals last week, all eight failed to win a majority in the Commons.
However, the plan for a customs union - allowing UK businesses to move goods around the EU without tariffs, but stopping the UK striking independent trade deals - and a confirmatory referendum came the closest.
A number of cabinet ministers have spoken out against the customs union proposal.
Mr Fox said that if the UK pursued it, the country would have to follow rules set by the EU, adding: "It's time we went back to a proper Brexit."
Environment Secretary Michael Gove said a customs union would "compromise" pledges the party made in their 2017 manifesto, while Defence Secretary Gavin Williamson said ministers were "determined" to avoid that happening.
Meanwhile, Tory MP Huw Merriman has written to around 200 of his colleagues who have voted in favour of Mrs May's deal, appealing for them to back the confirmatory referendum motion to prevent the customs union option succeeding.
He said: "It is the only option which keeps the [PM's] deal alive and is not contingent on more EU negotiations."
Digital Minister Margot James also told BBC Two's Politics Live that she is thinking about changing her mind to back a confirmatory referendum.
Labour's Dame Margaret Beckett, who proposed the previous motion for a confirmatory public vote, said she was happy to vote for motions like a customs union, so it could attract scrutiny.
"But they're unlikely to command a stable majority in Parliament unless they are attached to much longer extension that allows enough time for them to be properly scrutinised and negotiated - while not precluding a new public vote," she said.

MPs have voted to take control of the parliamentary timetable in an unprecedented move to try to find a majority for any Brexit option.
The prime minister was dealt a fresh blow as the government was defeated by 329 votes to 302, setting up votes on Wednesday to find out what kind of Brexit has most support among MPs.
Theresa May has said there is no guarantee she will abide by their wish.
Thirty Tory MPs voted against the government, including three ministers.
Richard Harrington, Alistair Burt and Steve Brine resigned to join the rebels, with Mr Harrington accusing the government of "playing roulette with the lives and livelihoods" of Britons.
Former industry minister Mr Harrington said: "It's absurd that now we are in a position of political impasse and... Parliament hasn't actually talked about it on the floor of the House of Commons. That's what I call a democratic deficit."
Mrs May had tried to head off a defeat by offering MPs a series of votes on Brexit alternatives, organised by the government.
She said allowing MPs to take over the Commons agenda would set an "unwelcome precedent".
But supporters of Conservative backbencher Sir Oliver Letwin's cross-party amendment said they did not trust the government to give MPs a say on the full range of Brexit options.
Labour leader Jeremy Corbyn was among them. He said the government "must take the process seriously".
He added: "The government has failed and this House must, and I believe will, succeed."
He said MPs would want to find a consensus on the way forward, including a possible "confirmatory vote" on the PM's deal by the public - something Mrs May told MPs earlier she did not want because Remain would be on the ballot paper.
MPs involved in the bid on Monday night say if there is a majority for a plan that's not the prime minister's deal then there would be "uproar" if Theresa May tried to ignore it.
It is possible, of course, that Brexiteers who have been resisting the prime minister's deal so far take fright at Parliament having more control of the process, and are more likely to come in line.
That's because, generally, the make-up of MPs are more likely to back a softer deal than the one on offer.
So faced with the choice of Theresa May's compromise this week, or a much longer wrangle to a closer relationship with the EU than the prime minister has negotiated, it is not impossible that the numbers will move in her favour.
Read Laura's blog
Shadow Brexit secretary Sir Keir Starmer tweeted: "Another humiliating defeat for a prime minister who has lost complete control of her party, her cabinet and of the Brexit process.
"Parliament has fought back - and now has the chance to decide what happens next."
Hilary Benn said MPs have to take responsibility for the Brexit process because the government is not doing its job.
Mr Benn, chairman of the Commons exiting the European Union committee, told BBC Radio 4's Today programme: "If the government isn't going to do its job then Parliament is going to have to take responsibility, and that is what we are doing on Wednesday."
The SNP's Joanna Cherry said: "It isn't just Wednesday. Now that Parliament has control of the order paper... on Wednesday Parliament could award itself another day and so on and so forth.
"The consensus we are now trying to build is something Theresa May should have reached out to try to build two years ago."
Conservative former Brexit Minister Suella Braverman told the BBC's Newsnight it was "a Parliamentary massacre".
"MPs [in the House of Commons] where we know there is a majority against Brexit, who don't want to respect the referendum, who don't want to honour referendum pledges, are seeking to overturn that and it's unacceptable," she said.
Mr Harrington said in his resignation letter that as industry minister, he had been told the government approach was "resulting in cancelled investment decisions, business being placed abroad and a sense of ridicule for British businesses".
The MP said he thought it unlikely the Commons would back revoking Article 50, but another referendum to see "where the public are at" would be "very legitimate".
In a series of so-called indicative votes, MPs will be able to vote on a number of options - likely to include a "softer Brexit", a customs union with the EU and another referendum - designed to test the will of Parliament to see what, if anything, commands a majority.
But the precise format of the votes and how they will work was not set out in the amendment.
And the prime minister said she was "sceptical" about the process - as it was not guaranteed to produce a majority for any one course of action - and she would not commit the government to abiding by the result.
"The votes could lead to an outcome that is un-negotiable with the EU," she told MPs.
Parliament is expected to pass a law this week postponing the Brexit date from 29 March to at least 12 April.
A Department for Exiting the EU spokesman said that when considering Brexit options, MPs should take account of how long negotiating them would take and whether this would require a longer delay and the UK having to take part in European Parliamentary elections.
Those elections are taking place between 23 and 26 May. Both the British government and European Commission believe that if the UK has not exited the EU by the end of May it will be legally required to hold elections.
Mrs May remains committed to winning over MPs to the withdrawal agreement she negotiated with the EU.
She said on Monday it did not have enough support to get through the Commons "as things stand", but she still hoped to persuade enough MPs to back it so she could hold another vote on it this week.
The deal has already been rejected twice by a large margin - and the PM was forced to ask the EU for Brexit to be delayed.
On Monday the government was defeated on its main motion, as amended by Sir Oliver Letwin, by 327 votes to 300, a majority of 27.
The government narrowly defeated a bid by Labour's Dame Margaret Beckett to give MPs a vote on asking for another Brexit extension if a deal has not been approved by 5 April. Dame Margaret's amendment was voted down by 314 to 311, a majority of three.

MPs, including Tories expelled from the party, are preparing legal action in case the PM refuses to seek a delay to Brexit.
A bill requiring Boris Johnson to ask for an extension to the UK's departure date to avoid a no-deal Brexit on 31 October is set to gain royal assent.
But the PM has said he would "rather be dead in a ditch" than ask for a delay.
Legal experts have warned the prime minister could go to prison if he refuses to comply with the new law.
MPs have lined up a legal team and are willing to go to court to enforce the law to avoid no deal, if necessary.
Meanwhile, pro and anti-Brexit protesters held demonstrations in Westminster on Saturday, with some people arrested by police.
The cross-party bill - which requires the prime minister to extend the exit deadline until January unless Parliament agrees a deal with the EU by 19 October - was passed on Friday.
Although the government has said it will abide by the law, Mr Johnson described it as obliging him "in theory" to write to Brussels asking for a "pointless delay".
Downing Street said the British public had been clear that they wanted Brexit done.
Labour leader Jeremy Corbyn told BBC News the party was not taking legal action over the legislation, but said it was "aware of the actions that are being discussed and prepared for".
He added that Labour would allow a general election "when we are clear that there will be an end to the danger of no-deal on 31 October".
"We need a clear statement from the prime minister that he is going to abide by that act of Parliament," Mr Corbyn said.
Meanwhile, clashes erupted between pro-Brexit protesters and police in Parliament Square in London.
Several hundred people joined pro and anti-Brexit demonstrations in Westminster.
Pro-leave protesters were seen throwing a metal barricade at officers, while others tried to break the police cordon.
Anti-Brexit MP Anna Soubry, who leads the Independent Group for Change, said she had been due to speak at the March for Change rally in London but told organisers she was too frightened to do so, after consulting with police.
A spokesman for the Metropolitan Police said officers made 16 arrests in connection with the protests.
That included 13 arrests for violent disorder, one for possession of an offensive weapon, one for affray and one for a racially aggravated public order offence.
Some 35 other events were held across the UK and Europe, including a pro-democracy protest in Berlin.
The Daily Telegraph reported that the prime minister said seeking another extension is "something I will never do", fuelling speculation that ministers could try to find a loophole.
But David Lidington, who resigned as Cabinet Office minister in July, in opposition to Mr Johnson's no-deal Brexit strategy, told the BBC's Today programme: "The government is bound by the words of any statute that has been duly enacted by the Queen in Parliament, which is a fundamental principle of our constitution and our ministerial code.
"Defying any law sets a really dangerous precedent."
He added that at a time when other countries were "holding up alternatives to the rule of law and democratic government" it was imperative that British governments always demonstrate they comply with the law.
Mr Lidington, who supported the government in voting for an early general election, urged Mr Johnson to "re-double [his] efforts" in talking to a "wide range" of European leaders to get a Brexit deal he can put before Parliament in October.
Mr Johnson's options are "narrowing" after this week's Brexit defeats, says Dr Hannah White, deputy director of the Institute for Government.
Some possibilities being discussed are:
Former attorney general Dominic Grieve has warned the prime minister "could be sent to prison" if he refuses to obey the law and delay Brexit.
Mr Grieve told BBC News Mr Johnson would be "under an obligation" to abide by the law after it has received royal assent.
"If he doesn't, he can be taken to court which will if necessary issue an injunction ordering him to do it," he said.
"If he doesn't obey the injunction, he could be sent to prison."
Earlier the former director of public prosecutions Lord MacDonald told Sky News a refusal to delay Brexit in the face of court action "would amount to contempt of court which could find that person in prison".
One Tory MP said the idea of Mr Johnson ignoring the legislation was "nonsense".
Kevin Hollinrake, MP for Thirsk and Malton, tweeted: "Even if it was under consideration, which I'm sure it's not, you would see a very significant number of Conservative MPs resigning the whip, including me."
A number of cabinet sources have told the BBC in recent days that they have significant concerns about Number 10's strategy.
It comes in the wake of a series of Parliamentary defeats for the government, beginning after Mr Johnson announced his decision to suspend Parliament for five weeks in September and October.
First, the prime minister lost control of the House of Commons agenda.
That allowed opposition MPs and rebel Tories to put forward the bill to prevent a no-deal Brexit, which Mr Johnson said "scuppered" his negotiations with the EU.
In response, the prime minister expelled 21 of his own MPs for rebelling against the government over the vote and then called for a general election.
But on Friday, Labour, the Liberal Democrats, SNP and Plaid Cymru jointly agreed to reject Mr Johnson's demand for a snap poll before the EU summit in mid-October.
The day before, the prime minister's younger brother, Jo Johnson, resigned as an MP and minister, saying he was "torn between family loyalty and the national interest".
According to the Daily Telegraph, Mr Johnson wrote to Conservative Party members on Friday night, saying Labour MPs had "left us no choice" but to call for an election.
He said: "They just passed a law that would force me to beg Brussels for an extension to the Brexit deadline. This is something I will never do."
No 10 said an election would allow the public to choose between the government's approach - Mr Johnson's commitment to leave on 31 October, either with a re-negotiated deal or no deal - and "more delay, more dither" from Labour.
But opposition MPs say they will only agree to an election when the extension to the Brexit deadline has been secured, to ensure the UK does not "crash out" without a deal.
The bill, presented by Labour MP Hilary Benn, says the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK's departure date to 31 January 2020.
Unusually, the bill stipulates the wording of the letter Mr Johnson would have to write to the president of the European Council.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal.
During that time, MPs - not the government - will have the opportunity to reject that date.
The bill also requires ministers to report to the House of Commons over the next few months. potentially providing more opportunities to take control of the timetable.

The Commons Speaker has refused a government request to hold a "yes" or "no" vote on its Brexit deal.
John Bercow said a motion on the deal had been brought before MPs on Saturday, and it would be "repetitive and disorderly" to debate it again.
Saturday's sitting saw MPs vote to withhold approval of Boris Johnson's deal until it has been passed into law.
The government said it was disappointed, but would go ahead with introducing the necessary legislation.
The prime minister's official spokesman added: "The Speaker has yet again denied us a chance to deliver on the will of British people."
The UK is due to leave the EU in 10 days, and while Mr Johnson and fellow EU leaders have agreed a new deal to allow that to happen, it cannot come into force until it is approved by both the UK and European parliaments.
The government has presented the law which would implement the Brexit deal to the Commons, and it will begin its parliamentary journey on Tuesday.
KEY POINTS: What's new in the deal?
PEOPLE'S VIEW: Do voters support the deal?
EXPLAINED: What is the Withdrawal Agreement Bill?
IN GRAPHICS:  What happens now?
The government wanted to hold a "yes" or "no" vote - a so-called "meaningful vote" - on its deal on Saturday, but MPs instead chose to back an amendment tabled by former Tory Sir Oliver Letwin, which said that could not happen until all necessary Brexit legislation was passed.
That legislation, called the Withdrawal Agreement Bill (WAB), has been introduced and will then have to go through full parliamentary scrutiny in both the Commons and the Lords - something which usually takes weeks rather than days.
But Leader of the Commons Jacob Rees-Mogg announced plans to complete the Commons stages by the end of Thursday. He said the House would not sit on Friday.
The BBC's political editor said the government hoped to push the WAB through by getting MPs to sit until midnight on Tuesday and Wednesday - an aggressive timetable they may well reject.
MPs will vote on a so-called programme motion - which effectively approves or rejects that timetable - on Tuesday.
Labour's shadow Commons leader Valerie Vaz told MPs: "At every stage the government has been running scared of this House and democracy, and it's now attempting to force through a flawed Brexit deal which sells out people's jobs, rights and our communities."
The SNP's Westminster leader, Ian Blackford, called on the government "not to bulldoze" the bill through Parliament and give time for "full scrutiny".
BBC Brussels correspondent Adam Fleming said the European Parliament would only vote on the Brexit deal when it had reached a stage where it could not be modified any further at Westminster.
Officials believe that means it is virtually impossible for MEPs to approve it this week, but they are open to an extraordinary session of parliament next week, he added.
I know reporters like me love prattling on about "crunch points". And I know there have been one or two instances of it being "crunch point postponed".
But this really now is it for a government trying to deliver Boris Johnson's proposed Brexit deal by 31 October.
The time frame is mega tight - passing a new law, through the Commons and Lords, by a week on Thursday.
Some want to crack on with it, some want to tweak it and some want to wreck it.
What happens in the next few days will determine whether the UK leaves the European Union a week on Thursday and in what way.
And it is likely to shape when the next general election is.
And, perhaps, who wins it.
No 10 was pushing for a second shot at a meaningful vote on Monday, but Mr Bercow told the Commons he would not allow it, and had come to that decision on the basis of a parliamentary convention dating back to 1604.
He cited Parliament's rulebook, Erskine May, which says a motion that is the same "in substance" as a previous one cannot be brought back during the course of a single parliamentary session.
The Speaker also said the circumstances around the motion had not changed, so his ruling was "necessary... to ensure the sensible use of the House's time and proper respect for the decisions that it takes".
But Tory MP and Brexiteer Sir Bernard Jenkin appeared to accused Mr Bercow of bias, saying it was "remarkable" how often the Speaker "pleased one lot and not the other".
"It is most unusual for a Speaker so often to prevent the government having a debate on the matters which the government wish put before the House," he added.
Fellow Tory David TC Davies said: "The only consistency one can find in your rulings is that they always seem to favour one side of the argument and never the government."
But Mr Bercow disagreed, adding: "The consistent thread is I try to do what I think is right by the House of Commons."
The Letwin amendment also meant Mr Johnson was required to ask for an extension to the Brexit deadline, according to the terms of the Benn Act.
The PM sent the necessary letter to the EU but did not sign it, and sent a second letter saying he thought a delay was a mistake.
The deal ditches the backstop - the controversial "insurance policy" designed to prevent a return to physical checks on the Irish border.
Instead it will, in effect, draw a new customs border in the Irish Sea, because goods which could then travel onwards to Ireland will have to pay a duty tax.
Brexit Secretary Steve Barclay told a Lords committee Northern Irish businesses would also have to complete export declarations to send any goods to the UK.
The whole of the UK will leave the EU customs union, meaning it could strike trade deals with other countries in the future.
But many MPs, including the prime minister's erstwhile allies the DUP, say treating Northern Ireland differently from the rest of the UK is unacceptable.
The Treasury Committee has asked the government for an updated analysis of how the new deal may affect the UK economy.
Responding on Monday, Chancellor Sajid Javid said the Treasury would "provide analysis at appropriate points", but it would depend on the next set of negotiations with the EU about the future relationship.
He added: "[But] trust in democracy, and bringing an end to the division that has characterised this debate over the past three years, is something that cannot be measured solely through spreadsheets or impact assessments, important though they are."
The committee's interim chairman, Labour's Catherine McKinnell, said "the dearth of relevant economic analysis" was "deeply concerning" and MPs were being expected to "vote blindly".
The WAB will give legal effect to the withdrawal deal, as well as any agreed transition period, and fulfils requirements on the rights of EU citizens in the UK after Brexit.
It will also allow ministers to make "divorce payments" to the EU foreseen under the current deal.
But MPs will be able to vote on amendments - changes or add-ons - to the bill.
Labour's shadow Brexit Secretary Keir Starmer has said his party will push for a UK-wide customs union with the EU and single market alignment, and back moves to try to put the deal to a referendum.
But the PM's spokesman has reiterated the government's opposition to both proposals.
If the government cannot get the bill through Parliament, the default legal position is for the UK to leave without a deal on 31 October, but that will change if the EU grants an extension.
Monday - first reading - the bill will be introduced and its title read out, usually just a formality.
Tuesday - second reading - MPs' first chance to debate the bill and vote for its continued passage. If passed at second reading, committee stage begins the same day.
Wednesday and Thursday - committee stage - where detailed examination of the bill takes place and specific amendments - on a fresh referendum, for example - can be tabled and voted on. The bill then moves on to report stage, which offers further opportunities for amendments before it moves to third reading. This is MPs' final chance to debate the bill before voting on whether to approve it.
If approved, it then moves to the Lords to begin a similar scrutiny process.

European leaders have expressed sadness at the UK leaving the EU, with France's Emmanuel Macron emphasising Britain's "unrivalled ties" with the French.
Mr Macron said he was "deeply sad" while the EU's Guy Verhofstadt pledged to try and "ensure the EU is a project you'll want to be a part of again".
Celebrations and anti-Brexit protests were held on Friday night to mark the UK's departure.
Ex-Brexit Secretary David Davis said everyone would be a winner in the end.
The UK officially left the European Union on Friday at 23:00 GMT after 47 years of membership, and more than three years after it voted to do so in a referendum.
Brexit parties were held in some pubs and social clubs as well as in London's Parliament Square, as the country counted down to its official departure.
In Scotland, which voted to stay in the EU, candlelit vigils and anti-Brexit rallies were held.
In a message released on social media an hour before the UK left, Prime Minister Boris Johnson vowed to bring the country together and "take us forward".
"For many people this is an astonishing moment of hope, a moment they thought would never come," he said. "And there are many of course who feel a sense of anxiety and loss."
In an open letter to the British public, French President Mr Macron said he was thinking of the millions of Britons "who still feel deeply attached to the European Union".
"You are leaving the European Union but you are not leaving Europe," he said. "Nor are you becoming detached from France or the friendship of its people.
"The Channel has never managed to separate our destinies; Brexit will not do so, either."
Mr Macron also said the EU must learn lessons from the "shock" of Brexit, adding: "I am convinced therefore that Europe needs new momentum."
And he defended the way France acted in the Brexit negotiations, saying neither the French nor anyone else in the EU was "driven by a desire for revenge or punishment".
Meanwhile, the EU Parliament's Brexit co-ordinator Mr Verhofstadt responded to a message which had been projected onto the White Cliffs of Dover by a pro-EU group.
"We will look after your star and work to ensure the EU is a project you'll want to be a part of again soon," he said.
Speaking on BBC Radio 4's Today programme, Mr Davis - who quit as Brexit secretary in protest at former prime minister Theresa May's Brexit plan - said it would be a "fair race" to reach a trade deal with the EU by the end of 2020 but "it can be done".
The UK is aiming to sign a permanent free trade agreement with the EU, along the lines of the one the EU has with Canada, by the end of the transition period in December.
Mr Davis said reaching a deal was "not a charitable exercise, this is an exercise of both sides recognising their own best interests".
European leaders have warned that the UK faces a tough battle to get a deal by that deadline.
Mairead McGuinness, the vice president of the European Parliament, said progress to agree a trade deal "might be left to the very last minute".
"Normally in trade negotiations we're trying to come together," she told BBC Breakfast. "For the first time we're going try and negotiate a trade agreement where somebody wants to pull away from us. I can't get my head around that and I think it's going to be quite complicated."
We are separate after more than 40 years, but remember much of the status quo will hold for now - the UK and the EU, the awkward couple, finally divorced - but still sharing a house and the bills.
But what the prime minister hails as a new era, a bright new dawn, starts months of hard bargaining with our neighbours across the Channel.
Labour leadership hopeful Emily Thornberry said the exit talks were unlikely to go smoothly and said she expected the country would be "back in no-deal territory by the summer".
The shadow foreign secretary, speaking at an event in Bristol featuring the four Labour leadership candidates, said her party would need a Remain-backing leader who had been "on the right side of the argument all along".
However, the other three candidates - Keir Starmer, Rebecca Long-Bailey and Lisa Nandy - said the party needed to move on from debates over Brexit.
Shadow business secretary Ms Long-Bailey said that Labour needed to make sure Boris Johnson negotiated the "best possible trade deal" that could help "rebuild our communities".
Whilst never the most enthusiastic member, the UK was part of the European project for almost half a century.
On a personal level, EU leaders tell me they'll miss having the British sense of humour and no-nonsense attitude at their table.
If they were to be brutally honest they'd have admitted they'll mourn the loss of our not-insignificant contribution to the EU budget too.
But now we've left the "European family" (as Brussels insiders sometimes like to call the EU) and as trade talks begin, how long will it take for warm words to turn into gritted teeth?
UK citizens will notice few immediate changes now that the country is no longer in the European Union.
Most EU laws will continue to be in force - including the free movement of people - until 31 December, when the transition period comes to an end.
Thousands gathered in Parliament Square to celebrate Brexit on Friday night, singing patriotic songs and cheering speeches from leading Brexiteers, including Nigel Farage.
The Brexit Party leader said: "This is the greatest moment in the modern history of our great nation."
Pro-EU demonstrators earlier staged a march in Whitehall to bid a "fond farewell" to the union.
Police in Whitehall arrested four men and also charged one man with criminal damage and being drunk and disorderly, while in Glasgow one man was arrested.
Meanwhile, other symbolic moments on a day of mixed emotions included:

Former Labour minister Lord Mandelson has urged peers not to "throw in the towel" when they debate legislation paving the way for Brexit.
He said the Lords should amend a bill to protect the rights of EU citizens to ensure a "meaningful" vote on the final deal before Britain leaves the EU.
He urged fellow Labour peers to show "strength and clarity" over the issue.
Conservative Justice Secretary Liz Truss said Brexit opponents were "fighting yesterday's battles".
The House of Lords - in which the government does not have an in-built majority - will start considering proposed legislation to leave the EU on Monday.
But the former Labour cabinet minister, EU Trade commissioner and Remain campaigner said the "verbal guarantees" the government were offering EU citizens in the UK were insufficient.
Lord Mandelson told the Andrew Marr programme that the Lords should "reinstate" the protections into the bill in the coming weeks.
"The government used its majority to bulldoze the legislation through the House of Commons," he said. "I hope it won't be so successful in the House of Lords," he said.
"At the end of the day the House of Commons, because it is the elected chamber, will prevail but I hope the House of Lords will not throw in the towel early."
But Ms Truss said leaving the EU was the "settled will" of the British people and the House of Lords needed to "get on" with the process.
She told Andrew Marr that once the UK formally notified the EU of its intention to leave by triggering Article 50, she believed the process was "irrevocable".
Earlier this month, MPs overwhelmingly backed a bill to empower Theresa May to begin the Brexit process. The PM wants to do this by the end of March but needs the approval of both Houses of Parliament first.
MPs rejected calls for the status of EU citizens living in the UK and a parliamentary vote on the final terms of exit to be explicitly guaranteed in the bill - although ministers have conceded the Commons will have its say and it fully expects citizens of other EU countries to be able to stay in the UK after Brexit pending negotiations.
Lord Mandelson also said some Leave voters who were having second thoughts at the government's "Brexit at all costs strategy" needed to have their voice heard.
But Ms Truss said Lord Mandelson was speaking as if the referendum "never happened".
She told Andrew Marr that the House of Commons had "conclusively" voted to trigger Article 50, with the majority of Labour MPs backing the government.
"The fact is it is a simple bill on whether we trigger Article 50," she said.
"The British people have voted for that and was clear in the referendum.
"The House of Lords now needs to get on with it. I fully expect the House of Lords will recognise the will of the people and the House of Commons."
Although she voted to remain in the EU last year, Ms Truss said there was now a "new reality" and if a similar vote was held in the future, she would vote to leave.
Tory backbencher Dominic Raab warned the Lords would face a backlash if it tried to hold up the Brexit process.
"Voters will not look kindly on unelected politicians seeking to obstruct both the result of the referendum, and the vote of their elected representatives in the House of Commons earlier this month," he said.

UK manufacturers prepared for Brexit by stockpiling raw materials at a record pace last month, a closely-watched survey has suggested.
The research, by IHS Markit/CIPS, found companies were stockpiling goods in January at the fastest pace in the survey's 27-year history.
Employment in the sector fell, and the survey warned that export orders were "near-stagnant".
It added that there was a risk of the sector slipping into recession.
Overall, the survey's Purchasing Managers' Index fell to 52.8 last month from 54.2 in December, which was a three-month low and the second weakest reading since July 2016.
While the figure above 50 still implies activity in the sector is expanding, IHS Markit/CIPS said manufacturing had made a "lacklustre" start to the year.
With two months to go until the UK is due to leave the EU, the lack of clarity over the terms of the UK's departure means firms are having to make contingency plans.
"The start of 2019 saw UK manufacturers continue their preparations for Brexit," said Rob Dobson, director at IHS Markit.
"Stocks of inputs increased at the sharpest pace in the 27-year history, as buying activity was stepped up to mitigate against potential supply-chain disruptions in coming months.
"There were also signs that inventories of finished goods were being bolstered to ensure warehouses are well stocked to meet ongoing contractual obligations."
An equivalent survey of eurozone manufacturers also found the sector struggling in the 19-nation bloc. The PMI reading of 50.5 for January indicated minimal growth and was the lowest reading since November 2014.
The eurozone survey also found new orders were falling at the fastest rate in nearly six years,
By Dharshini David, BBC economics correspondent
With clarity as yet elusive, manufacturers are intensifying efforts to prepare for a possible a no-deal Brexit. Both raw materials and finished goods are being stockpiled at an unprecedented rate, to avoid disruption to supply chains and gaps on warehouse and shop shelves.
So on the face of it, the overall PMI activity balance for this survey suggests greater manufacturing momentum last month in the UK than in  France or Germany.
But away from the buzz of stockbuilding, orders, particularly for export, are struggling.  Overseas customers may be more reluctant to order goods, in case they face delays or tariffs on delivery in the event of a no-deal.
This survey tends to be more volatile than official manufacturing figures. But there is increasing evidence of dwindling export demand in many sectors. Orders for British malting barley, for example, from the rest of the EU has dried up, as that crop could attract particularly steep charges.
The report referred to some UK supply chains as being "closer to breaking point"
It noted there had been "a marked slowdown" in the growth of new orders, and those companies that did report an increase in output "mainly linked this to stock-building activity".
"January also saw manufacturing jobs being cut for only the second time since mid-2016 as confidence about the outlook slipped to a 30-month low, often reflecting ongoing concerns about Brexit and signs of a European economic slowdown," said Mr Dobson.
"With neither of these headwinds likely to abate in the near-term, there is a clear risk of manufacturing sliding into recession."

Senior Cabinet ministers have insisted the UK is prepared to walk away from Brexit talks without a deal, on the second anniversary of the referendum.
Liam Fox said Theresa May was "not bluffing" over her threat to quit negotiations, while Boris Johnson called for a "full British Brexit".
It comes as anti-Brexit campaigners, who want the public to have the final say on the UK's departure, prepare to march in London later.
They say Brexit is "not a done deal".
People's Vote - which wants a referendum on any exit deal - said people must make their "voices heard" about the "damage" of leaving next year without agreement.
Speakers at the demo will include actor Sir Tony Robinson and campaigner Gina Miller, who fought a successful legal battle last year to ensure the UK could not trigger talks on leaving without the approval of Parliament.
The UK voted to leave the EU by a margin of 51.9% to 48.1% in a referendum held on 23 June 2016.
The UK is due to leave on 29 March 2019, 46 years after it first joined the European Economic Community, the forerunner to the EU.
But the People's Vote campaign says this should happen only if the withdrawal deal negotiated by Mrs May and the other 27 EU members is approved in another public vote.
International Trade Secretary Liam Fox told the BBC it was in the interests of both sides to have a deal - but it was "essential" the EU understood that the UK could walk away if the terms offered were not good enough.
"The prime minister has always said no deal is better than a bad deal," Mr Fox said in an interview with the BBC's political editor Laura Kuenssberg, which was recorded on Wednesday - before Friday's warning from Airbus that it might cease manufacturing in the UK in such a scenario.
"It is essential as we enter the next phase of the negotiations that the EU understands that and believes it... I think our negotiating partners would not be wise if they thought our PM was bluffing."
Meanwhile, Brexit Secretary David Davis told the Daily Express the prime minister was going to get a "good deal" from Brussels and Brexit was going to be "fantastic".
"The best option is leaving with a good deal but you've got to be able to walk away from the table," he said.
And writing in the Sun, Foreign Secretary Boris Johnson warned the prime minister not to allow "bog roll Brexit" that is "soft, yielding and seemingly infinitely long" - calling for a "full British Brexit" instead.
Mr Johnson said people "just want us to get on with it".
By BBC political correspondent Nick Eardley
Two years on from the referendum, there are two very different messages today.
One is that Brexit is not a "done deal".
That's the argument from the Liberal Democrat leader Sir Vince Cable who will take part in a march in central London today.
On the other side, there is optimism and defiance from key Brexiteers like Boris Johnson.
Mr Johnson says the UK is confident and open.
The government firmly opposes a vote on the final deal - Mr Johnson believes people want the government to just get on with it.
Nine months before the UK is due to officially leave the EU, there are still very different visions.
Labour said Mr Fox's comments about a no-deal Brexit were the "height of irresponsibility".
"The next time Liam Fox parrots the slogan no deal is better than a bad deal he should give some thought to the 14,000 people who work for Airbus, and the thousands of other people who have jobs dependent on trade with Europe," said shadow Brexit minister Jenny Chapman.
Both the prime minister and Labour leader have rejected calls for another public vote, saying the will of the people expressed in the 2016 ballot was clear, although many Labour MPs now want another referendum.
Organisers of Saturday's demo say people "from all walks of life" will be present, demonstrating the "growing popular demand" for another vote.
Beginning in Pall Mall and ending outside the Houses of Parliament, the protest is part of a "summer of action" by campaign groups designed to increase pressure on Theresa May and Jeremy Corbyn.
By taking the UK out of the EU's single market and customs union, they say the Conservative government "remains intent" on a so-called hard Brexit that will - they say - destroy jobs and damage public services.
The leader of the Liberal Democrats, Sir Vince Cable, who will be at the march, told BBC Breakfast: "I think the public in general... do see there is a mess."
He added: "We've only got a year to go. And I think for the big companies that employ hundreds of thousands of workers in the UK... they want some clarity about what the trading relationships will be and there is absolutely none whatever."
But Conservative MP Peter Bone - who supports Brexit - said if there were a second vote, the leave campaign would win again.
"The vast, vast majority of people, whether they are Leavers or Remainers, just want us to get on and come out this dreadful European Union super-state," he said.
"There were 17.4 million people that voted for leave and if there are a few thousand in London complaining about it - that doesn't seem to really make much difference."
The government is giving Parliament a vote on the final deal, if one is reached, in the autumn - but it remains unclear what will happen if they reject it.

Tens of thousands of people have marched in central London to demand a final vote on any UK exit deal, on the second anniversary of the Brexit vote.
Organisers of the People's Vote march say Brexit is "not a done deal" and people must "make their voices heard".
Meanwhile, hundreds attended a pro-Brexit counter-protest.
It came as senior Cabinet ministers, including Liam Fox and David Davis, insisted the UK is prepared to walk away from talks without an agreement.
The protest is part of a "summer of action" by campaign groups designed to increase pressure on Theresa May and Jeremy Corbyn.
The organisers have said that at least 100,000 people attended the march.
World War Two veteran Stephen Goodall, 96, led the pro-EU protesters as they headed from Pall Mall to Parliament Square.
There were boos from the crowd as the march approached Downing Street. After showing anger towards the PM, some began to chant "where's Jeremy Corbyn?"
Among those addressing the demonstrators was Gina Miller, who successfully campaigned to ensure the UK could not trigger talks on leaving without the approval of Parliament.
She said: "Together we must stand up, demand our voices are heard, demand a people's vote so that future generations can hear us say we did our bit we stood up and shouted for a country that's together, kinder, tolerant.
"This is not a time to be silent."
Liberal Democrat leader Sir Vince Cable said Brexit was "not a done deal" and could be reversed, while Green Party co-leader Caroline Lucas told the crowd that Brexit "will be a disaster for this country".
One of the rally organisers, James McGrory from pressure group Open Britain, said there should be "a choice between leaving with the deal that the government negotiates, or staying in the European Union".
Britain is due to leave on 29 March 2019, 46 years after it first joined the European Economic Community, the forerunner to the EU.
The government is giving Parliament a vote on the final deal, if one is reached, in the autumn - but it remains unclear what will happen if they reject it.
Jennifer Scott, BBC News
EU flags slowly filled Pall Mall all morning, and with chants of "people's vote" echoing alongside drum beats and whistles, the protesters made their way towards Parliament.
This protest was a family affair - young children alongside veterans in wheelchairs, and all ages in between.
One 69-year-old woman, Dodo Pearce, said she travelled from Derbyshire to protest for the first time in her life.
And I received an eloquent lecture from an 11-year-old on the problems she thought Brexit would bring.
Despite the cheery demeanour of the marchers, the conversations were less hopeful.
One person said: "If a million people couldn't march to stop Tony Blair going into Iraq, what chance have we got in getting a vote on the deal?"
Protester Colin Hopkins, 62, from Ipswich, said: "It's really important to say we don't dispute the decision, but the process and the destination.
"There isn't any agreement on where we want to go with it, even in the government, and we have a right to a second opinion on that."
Lesley Haas, a teacher from Bury St Edmunds, said: "What is their future? A lot of companies are leaving, so there is going to be an effect on jobs.
"I'm a German teacher and I'm worried the attitude of Brexit will make it harder to learn languages here. If it goes through, we may leave."
Janet Watts, 61, from Suffolk, said she joined the march for her mother - who is from Denmark and arrived in Britain in 1953.
"She had her passport stamped when she got off the boat at Harwich, telling her she could stay," she said. "That has been the same until this referendum happened.
"I think it is disgusting putting families at risk and putting her through this at the age of 83."
But Shazia Hobbs, who attended the pro-Brexit UK Unity and Freedom march, said: "That march is silly. We voted to leave so we should leave.
"What do they want, best of three? We voted for Brexit."
Demonstrators also chanted "we want our country back" and: "What do we want? Brexit. When do we want it? Now."
Conservative MP Peter Bone - who supports Brexit - said if there were a second vote, the leave campaign would win again.
"The vast, vast majority of people, whether they are Leavers or Remainers, just want us to get on and come out this dreadful European Union super-state," he said.
"There were 17.4 million people that voted for leave and if there are a few thousand in London complaining about it - that doesn't seem to really make much difference."

The UK's proposed "backstop" plan for trade with the EU after Brexit has been published after an "expected" end date - of 2021 - was included in it.
It followed crunch meetings between Prime Minister Theresa May and Brexit Secretary David Davis, who insisted a cut-off date be included.
The proposal would see the UK match EU trade tariffs temporarily in order to avoid a hard Irish border post-Brexit.
Brexiteers want to ensure the backstop could not continue indefinitely.
Responding on Twitter, EU chief negotiator Michel Barnier set out the criteria on which he would judge the UK's proposal, including the need for a "workable solution" to avoid a hard border in Northern Ireland.
The European Parliament's Brexit co-ordinator Guy Verhofstadt went further, saying it was "difficult to see" how this could be achieved.
"A backstop that is temporary is not a backstop, unless the definitive arrangement is the same as the backstop," he added.
The UK is due to leave the EU in March 2019, and the government is trying to make progress before a crucial meeting of EU leaders later this month.
BBC political editor Laura Kuenssberg said Mr Davis had "pushed back very hard" against the proposals on Wednesday and had two meetings with the prime minister on Thursday before a deal was agreed.
After the publication, Mr Davis's chief of staff said there had been a "helpful dialogue" and that the document had now been "clarified and amended".
According to the document - which has yet to be agreed with the EU - the "temporary customs arrangement", if it is needed, would be "time-limited".
A long-term "future customs arrangement" will be in place "by the end of December 2021 at the latest", it says.
Another cabinet Brexiteer Liam Fox, who also met the prime minister on Thursday, told the BBC: "As everybody knows from the referendum, opinions and feelings run high on this issue but we've shown we can reach an agreement civilly and collectively."
The Brexit secretary claimed a victory, but in Westminster what starts out as a "win" can, by morning, seem like a hollow victory, writes BBC political editor Laura Kuenssberg.
Senior figures in government are questioning whether David Davis really achieved very much.
He may have saved face after making a huge fuss but look carefully at the concession he won, they say, and it doesn't really mean very much.
A few words here, a loosening up of the planned language there, perhaps the victory really was Theresa May's?
Read the rest of Laura's blog
The UK has said it will leave the EU's customs union, which allows trade within the EU without any tariffs or many border checks.
The UK and the EU are yet to agree how trade in goods will operate after Brexit - but they have said that a "backstop" option is needed in case no deal is done, or the technology is not ready in time, to avoid the return of a hard border between Northern Ireland and the Republic of Ireland.
The UK has said that the EU's initial "backstop" proposal - effectively keeping Northern Ireland in the customs union - would create what amounted to a border between Northern Ireland and the rest of the UK and was not acceptable.
Instead, the UK is proposing a backup plan which would see the whole of the UK temporarily aligned with the EU's customs union after December 2020 - when the 21-month post-Brexit transition period ends.
The plan, which Theresa May has said would only apply in a "limited set of circumstances", would see the UK match EU tariffs in order to avoid border checks.
With the EU sceptical about the two options the UK has suggested to replace its membership of the customs union - and government ministers yet to agree which one to pursue - the backstop is "rapidly becoming the only option on the table", former Brexit minister David Jones told the BBC, "so it must be got right".
He said not having a firm time limit would be "damaging to the country": "It would tie us effectively into the the EU's customs arrangement for an indefinite period".
It would prevent the UK from having its own independent trade policy, he said - customs union members are not allowed to strike their own international trade deals.
It would also mean the UK was still under the jurisdiction of the European Court of Justice, which would be unacceptable to most Conservative MPs, he added.
BBC Europe editor Katya Adler
"Wow," gushed a European journalist to me the other day, "normally we look to Italy for political drama and uncertainty but the UK is making a pretty good show of it."
So dizzying and confused is the news coming out of the UK about how the EU-UK relationship could and should work after Brexit, that EU negotiators say they are forced to stand on the sidelines while the British government talks and argues with itself.
"It just can't work," an EU diplomat told me in exasperation this week. "Theresa May has so many nooses dangling around her neck that one of those nooses is sure to hang her."
Read Katya's blog
BBC Brussels reporter Adam Fleming says the EU will apply a series of tests to any proposal about customs from the UK, including how it would interact with the EU's own customs policy, whether it would require the EU to change its rules, and what would happen when new ones were introduced?
The UK government said its latest proposals would deliver on a commitment, made in December, to avoid creating a hard border between Northern Ireland and the Republic of Ireland, which is an EU member.
In response, Irish Foreign Minister Simon Coveney said it was "vital" that a legally-binding backstop was found to prevent a hard border.
"Clearly, a great deal of work remains to be done and this needs to be the highest priority for all sides in the weeks ahead."
Northern Ireland's Democratic Unionist Party, whose support Theresa May relies on for a Commons majority, welcomed the proposal, saying the EU's version of a backstop had been "totally unacceptable".
"We must also remember that the backstop will only be used as a last resort," said the DUP's Nigel Dodds.
"The focus must now be on getting a new trade deal."
Labour MP Hilary Benn, who chairs the Commons Brexit committee, said the government's plans would effectively keep the UK in a customs union with the EU beyond the end of 2020.

Isolated and apparently friendless, Theresa May is retreating to her natural comfort zone.
The prime minister is embarking on yet another push to see if she can win over Brexiteer Tories and the DUP to support an amended version of her Brexit deal.
A senior Tory tells me that May is acting on the advice of her chief whip, Julian Smith.
"The chief whip told the prime minister that if she relies on Labour votes to get her deal through she will split the party," the former frontbencher tells me.
"So she has to do it with Conservative and DUP votes. God knows how she does that."
Labour MPs have accused the prime minister of an irresponsible approach of putting party in front of country after she outlined her strategy in a cabinet conference call on Sunday.
The mood in Downing St appears to be pretty gloomy at the moment. But there are some signs of movement among Brexiteer Tories.
The senior Tory tells me: "The Brexiteers have over-reached themselves and are realising that their zealotry is endangering Brexit. So they need some ladders to climb down."
Ladders are not quite popping up around Westminster, but in the last 48 hours Jacob Rees-Mogg and Boris Johnson have both indicated they could be more flexible than they appeared in the immediate aftermath of last week's vote.
In a Mail on Sunday article, Rees-Mogg identified the Northern Ireland backstop and the UK's £39bn payment to the EU as the "biggest obstacles". But then he indicated that he could live with the prime minister's deal if the alternative was no Brexit.
In his weekly Daily Telegraph column on Monday, Boris Johnson did not repeat his call of last week for the UK to cut back on the £39bn payment. He instead focused entirely on the Northern Ireland backstop. This is the mechanism to avoid a hard border by binding Northern Ireland closely to the EU if the UK and Brussels fail to agree a future relationship in time.
The former foreign secretary wrote: "Take that backstop out, or at the very least give us a legally binding change - within the text of the agreement - that allows for the UK to come out of its own accord, and then we will be able to say that the agreement is imperfect but at least tolerable."
So the prime minister could probably win over the two most prominent Tory Brexiteers on her backbenches if she managed to secure from the EU what she failed to achieve last year: a unilateral exit mechanism from the backstop.
Downing St is not holding its breath, even though Poland has indicated to the BBC that it supports a time limit to the backstop.
If a popular amendment on the backstop emerged from "clear blue sky" shortly before next Tuesday's Brexit vote, then the prime minister would be able to show the EU there is a deal that could pass, one Whitehall source says. But talks at Westminster will be held in the open well before next Tuesday, allowing the EU to "trash" such a proposal, according to my source - who says there is no sign that Brussels is backing away from its demand for an all weather backstop.
So there is little optimism in Downing St at the moment that the prime minister will eventually prevail. There appears to be a feeling that the prime minister is being buffeted by two forces: an EU which senses that Parliament might eventually take over, and a Parliament which looks increasingly likely to snatch decisive powers from the government.
"With the Speaker on the march there is probably little the government can do," one source laments.
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She was for budging. Today, the prime minister made her priority leaving the EU with a deal, rather than the happy contentment of the Brexiteers in the Tory party.
For so long, Theresa May has been derided by her rivals, inside and outside, for cleaving to the idea that she can get the country and her party through this process intact.
But after her deal was defeated at the hands of Eurosceptics, in the words of one cabinet minister in the room during that marathon session today, she tried delivering Brexit with Tory votes - Tory Brexiteers said "No". Now she's going to try to deliver Brexit with Labour votes. In a way, it is as simple as that.
That could mean, three cabinet sources suggest, accepting many of Labour's demands for the deal - those six tests, which it has often, frankly, been assumed were designed to be impossible to meet. Irony would ring out if in the end they were all delivered because of the desperation of the Tory prime minister.
One cabinet minister told me the offer to Labour is, "You want soft Brexit - here it is. You help shape it." Potentially, there are political smarts here - challenging Jeremy Corbyn to decide, finally, whether he leads a party that really is up for pushing through our departure from the EU, or a group that wants to fight it until its last breath. Either choice for him is complex given that his party is divided too.
And ministers tonight don't hold out huge hope of a genuinely productive cross-party process. Frankly, they don't know if they can trust Mr Corbyn enough to come to a genuine agreement that Labour would stick to.
Of course, for any opposition party the temptation might be always to play for political advantage. We know by now that is not necessarily exactly the same as the best interests of you and me.
And whether it's Theresa May or Jeremy Corbyn who sinks this still hypothetical process, it will be Parliament that takes the reins. That could, in turn, challenge reluctant Brexiteers to confront the reality that the prime minister's deal could be the best version of Brexit they are ever going to get - maybe, just maybe, swinging support for Theresa May's withdrawal agreement in the end. Stranger things have happened.
But the prime minister has taken a huge risk with her party, and an implosion may stop any of this process in its tracks. There's what's described as "genuine fury" among Brexiteer ranks and ministers that the PM has made this choice. One senior Tory said she is "making an art form of bad misjudgements - this is not just a Rubens or a Van Gogh, it's the whole Tate Modern".
As ever, there is a very big gamble that has just become a real risk. The prime minister can reach out for support from the other parties - and compromise to get it - and ultimately maybe get her deal through. But if and when she is able to do that, her party may be so split and so fractious that she may not be able to govern or do anything, ever again.
If she were actually to strike some form of weird pact with the Labour Party over Brexit how long could it reasonably last? And how could it function and deliver a sustainable agreement when she has already said that she is leaving and another leader will soon be along to take charge of the second phase of Brexit?
Perhaps right now we can only answer one question that for so long Theresa May has avoided answering. When it came to it, would she choose party unity or leaving the EU WITH a deal? To the irritation of many, but the relief of others, she's chosen trying to get it done with a deal.

Why is Theresa May rushing to Brussels on Wednesday when she has a fair few political headaches to contend with back home, and when she's due back here in just a few days for the seal-the-deal Brexit summit of EU leaders?
The answer: the prime minister wants to show she is fighting until the very last moment to get the best Brexit deal possible out of the EU.
Her Wednesday afternoon visit to see Jean-Claude Juncker, the head of the European Commission, provides her with a floodlit platform to do so.
Now, the plan had been for the two leaders to discuss a draft text of the political declaration on post-Brexit EU-UK relations.
Mrs May wanted to push for even closer trade ties than the EU has been willing to concede so far without the UK staying in the single market.
Essentially she is very, very keen for her Chequers proposal for Brexit (viewed in EU circles as cherry-picking non plus ultra) to be reflected in the document.
However, the Brexit process has now got a lot more complicated - meaning that the draft text on EU-UK future relations hasn't been finished in time for the prime minister to pick over.
You see, it's no longer just a matter of Mrs May wanting more from the EU.
A number of EU countries are suddenly pushing for a lot more from the British prime minister. For France, it's about fishing rights; for Spain, it's about the status of Gibraltar.
Others, meanwhile, such as the Netherlands and Denmark, think she should be getting a whole lot less when it comes to the UK-wide customs union, envisaged as part of the backstop for the Irish border. They want the UK to be tied tighter to EU environment regulations, for example, to avoid UK business having a competitive advantage over Europeans.
As for the PM's Chequers plan for trade and security (much maligned back in the UK, too, of course), Germany has said loud and clear it won't allow the political declaration on future EU-UK relations to be a means of what Berlin describes as "Chequers by the back door".
It is highly unlikely that all this can be sorted out in just one meeting between Mrs May and the European Commission chief.
So the big question is: will the draft text on EU-UK future relations be ready by the end of the week to give EU leaders at least one day to digest it? Or are the stars aligning for a dramatic showdown between those leaders and the UK prime minister at their Sunday summit?
One EU diplomat predicted possible similarities with a nail-biting, marathon summit at the height of the Greek debt crisis.
During the all-night meeting, Greece's Prime Minister Alexis Tsipras was invited to make his case to eurozone leaders on a number of occasions, before being sent out of the room to allow those leaders to decide the economic fate of his country amongst themselves.
EU rules do not allow Mrs May to negotiate Brexit with EU leaders directly. If a number of issues remain open on Sunday, their Brexit summit could turn out to be a lot, lot longer than the two-hour signing session and photo op originally envisaged.
The last question I'm going to ask in this post now is: could this all be more about optics than nitty-gritty politics?
Grumbling aside, no-one in European circles seriously thinks any EU country will refuse to sign up to the Brexit deal by end of play this weekend.
They're all keen to avoid a no-deal scenario and they want to help Mrs May get the Brexit texts through a vote in the House of Commons.
Engaging in last-minute political fisticuffs with the EU is arguably advantageous for her.
A high-drama, climactic Brexit summit ending in a late night/early morning bleary-eyed but triumphant resolution with EU leaders would allow Mrs May to claim that the final text of the deal was hard fought and hard won… in the fervent hope that will soften the stance of some of her many critics at home.

Theresa May has met EU officials as the two sides scramble to finalise a Brexit deal in time for Sunday's summit of European leaders.
The EU is in a race against time to complete the text of its declaration on future relations with the UK, amid concerns from several member states.
Contentious issues include fishing rights in British waters and Gibraltar.
The European Commission said "very good progress" had been made at Wednesday's meeting but work was continuing.
The PM, who is under pressure from her own MPs not to give any further ground, held talks lasting about an hour with European Commission president Jean-Claude Juncker.
Mr Juncker has cancelled a two-day trip to the Canary Islands, on Thursday and Friday, to deal with "the many important events taking place at the moment".
European Commission Vice-President Valdis Dombrovskis said "sherpas" - officials tasked with doing the detailed work ahead of summits - were due to meet on Friday to work on the final texts of the withdrawal agreement and the future relationship.
German Chancellor Angela Merkel said: "Both documents need to be ready by Sunday so that we can sign the exit agreement and accept the declaration on the future relationship."
Asked if the summit could be cancelled, Downing Street said the agenda had been published and it "looked forward to attending".
In other developments:
Before heading for Brussels, Mrs May came under fire from every Brexit faction in the House of Commons at a noisy Prime Minister's Questions - from those who want another referendum, to those who want Britain to leave the EU without a deal.
Labour leader Jeremy Corbyn zeroed in on comments by new work and pensions secretary Amber Rudd, who said MPs would prevent a no-deal Brexit, apparently putting her at odds with the PM's "no deal is better than a bad deal" stance.
He asked: "Does the prime minister agree there are no circumstances under which Britain would leave with no-deal?"
Mrs May replied "no" and said the alternative to her deal would "either be more uncertainty, more division or", in what looks like the emerging new emphasis from her government, "it could risk no Brexit at all".
Mr Corbyn said that "if the government can't negotiate an alternative then it should make way for those who can and will".
Mrs May replied: "He is opposing a deal he hasn't read, he's promising a deal he can't negotiate, he's telling Leave voters one thing and Remain voters another - whatever (Mr Corbyn) will do, I will act in the national interest."
Mrs May also rejected a call from the SNP's Ian Blackford to renegotiate her Brexit deal to keep the UK in the single market and customs union, saying it would "frustrate the vote of the British people".
And she branded Green MP Caroline Lucas's call for another referendum, on the grounds that public opinion had shifted since the 2016 referendum, "absolutely ridiculous," saying the public had given this Parliament "an instruction" to leave the EU.
Mrs May appears to have faced down the threat of a challenge to her position from Brexiteer critics of the deal, for the time being at least.
However, Tory MPs unhappy with Mrs May's handling of Brexit negotiations want much more clarity on the terms of the UK's future co-operation with the EU if they are to back the final deal.
All sides in the Commons have warned of a "blind Brexit" in which the UK signs up to a series of legally-binding commitments in the draft withdrawal agreement, without similar guarantees over future trading arrangements.
The withdrawal deal was agreed in principle by both Mrs May and the EU last week.
It includes a £39bn "divorce bill" and the controversial customs "backstop" which keeps the UK temporarily in the EU customs union as a way of preventing the return of manned customs posts at the Irish border.
However, the joint political declaration on future relations - still being drafted - would only set out the shape of the UK's trading relationship with the remaining 27-nation bloc, without any legal commitments.
Any binding trade deal would still have to be thrashed out in the 21-month transition period after Britain leaves the EU on 29 March 2019.

Theresa May has lost more ministers to Brexit, and more importantly perhaps, has lost even more control of the process at a time when her government is only just about holding on.
Sir Oliver Letwin's plan passed through the Commons tonight by a clearer margin than expected, a big win for the cross-party group of senior MPs who have been pushing plans of different flavours for a while that would allow Parliament to have more say over what's next.
Officially, what the proposal that won tonight does is give MPs control of the debates in the Commons for a day on Wednesday. They will use that to have a series of votes on different options.
This is exactly what some government ministers wanted and have been arguing for for ages.
But those ministers were opposed by their colleagues sitting round the same top table, who fought the idea from the start.
That's because they fear, as the prime minister does, that allowing the process to go forward cedes what little control they have left and potentially moves Parliament towards choosing a softer Brexit.
Now MPs have won the right to carry out this unusual process, there will be a series of votes in the Commons on Wednesday, where MPs will be able to have their say on a whole range of options - a customs union, a closer relationship with the EU than the PM has argued for, another referendum, and others which could emerge.
But it's important to note those votes won't at this stage force the government to do anything, they won't be binding, and the prime minister has indicated she could not, and would not ever support a plan that wasn't in the Conservative manifesto.
On the other side, MPs involved in the bid tonight say if there is a majority for a plan that's not the prime minister's deal then there would be "uproar" if Theresa May tried to ignore it.
It is possible, of course, that Brexiteers who have been resisting the prime minister's deal so far, take fright at Parliament having more control of the process, and are more likely to come in line. That's because generally, the make-up of MPs are more likely to back a softer deal than the one on offer.
So faced with the choice of Theresa May's compromise this week, or a much longer wrangle to a closer relationship with the EU than the prime minister has negotiated, it is not impossible that the numbers will move in her favour.
But with more former Remainers willing to make their voices heard now in Parliament, the prime minister's battle with her party could get even more intense.
Tonight could be the official start of a journey to a softer Brexit led by a majority in Parliament, Brexiteers beginning to back down in earnest, or the start of the next stage of a standoff between the government and Parliament that could only end with a 'democratic event' - code in Whitehall for what you and I would normally call an election.

Theresa May has refused to rule out another Commons vote on her Brexit deal if MPs reject it the first time.
The PM said she thought she could win the vote on 11 December despite dozens of Tory MPs being against the deal.
In an interview with the BBC's Laura Kuenssberg, she urged MPs to "deliver on the vote of the referendum".
EU Council President Donald Tusk warned if MPs rejected the deal, the UK would face a choice between leaving without a deal or not leaving at all.
Under Commons rules, the prime minister is not meant to ask MPs the same question twice - she would have to change the contents of her deal.
Alternatively, if enough MPs indicate they have changed their minds after voting the deal down, it could be held again, but it would be up to the Speaker to decide whether to allow that.
Pressed by Laura Kuenssberg on whether she would attempt to hold another vote, Mrs May - who is in Buenos Aires, Argentina, for a G20 summit of world leaders - said: "I'm focused on the vote that is taking place on 11 December and I want everybody who's going to participate, all members of Parliament, to focus on what this vote does."
Shadow chancellor John McDonnell said he did not now expect any Labour MPs to vote for Mrs May's deal, telling Talk Radio he thinks the party will "hold together".
The Labour leadership has said it is ready to support a cross-party amendment to the vote that would explicitly rule out a no-deal. The amendment would not be binding but it would be hard for the PM to ignore it, if it is passed by Parliament.
European Council President Donald Tusk, meanwhile, has stressed that the deal the EU struck with Theresa May was the "only possible one".
He said: "If this deal is rejected in the Commons, we are left with, as was stressed a few weeks ago from Prime Minister May, an alternative - no deal or no Brexit at all."
But a senior UK official said: "Right from the very outset, Donald Tusk has not hidden the fact that he finds (Brexit) a moment of sadness for himself and for the EU.
"But the prime minister has always been very clear to President Tusk that we are leaving on 29 March next year."
The BBC's Europe Editor Katya Adler
What is the EU up to while a fevered UK Parliament burns with questions and throbs with Brexit conspiracy theories?
Well, the EU is watching and waiting. Arms folded.
"It's groundhog day in this negotiation process," an EU diplomat told me.
"We (the EU) are again on the outside, watching the UK debate with itself, unsure of what direction to head in. They voted to leave. We've even got an exit deal on the table now but still the UK is undecided."
It is widely expected that MPs will reject the EU withdrawal agreement and blueprint for a future trade deal agreed with the EU.
In anticipation of this happening, some MPs are trying to mobilise support for the so-called "Norway Plus" option, which they claim could win support across the House of Commons.
Under their plan, the current withdrawal agreement would be honoured but the UK would seek to rejoin the European Free Trade Association (Efta), which it belonged to before entering the European Economic Community in 1973 - on an indefinite basis.
If Efta's existing members - Switzerland, Norway, Liechtenstein and Iceland - agreed, it would allow the UK to retain membership of the customs union and full access to the single market.
Advocates of the plan say the UK would still be outside the Common Agricultural Policy and the Common Fisheries Policy - but it would also mean continued free movement of people.
Mrs May said this kind of deal would not fulfil the referendum pledge to take back control of the UK's borders, laws and money.
Meanwhile three former Labour foreign secretaries have warned of the damage to British influence around the world if the UK leaves the EU. David Miliband, Jack Straw and Margaret Beckett told the Financial Times they all backed the People's Vote campaign for another referendum.
Although Labour is still committed to keeping all options open, Mr McDonnell said if it came to another referendum, it would be "difficult to see" an option to remain not being included on the ballot paper.
In a speech in Bristol, International Trade Secretary Liam Fox argued that while the deal will not please everyone, critics "are yet to face up to" the "tough choices" she had to make.
He told the BBC the PM was "changing the public mood" and while different approaches would give the UK a freer hand to strike other trade deals, they would come with a "price" in terms of reduced access to EU markets.
The Financial Times says Mrs May is enlisting the support of senior Brexiteers such as Michael Gove and Geoffrey Cox to try to sell her controversial Irish "backstop" plan to sceptical Tory MPs.
Mr Fox said he was not "enthusiastic" about the backstop, which could see the UK enter a customs partnership with the EU until its future relationship is sorted out and without the unilateral right to pull out.
But he insisted the chance of the backstop, described as an "insurance policy" by Mrs May, actually coming into force was slight as it was just as "unpalatable" to other EU members, including the Republic of Ireland.
And Treasury Minister Liz Truss, who is backing Mrs May to get the agreement through Parliament, suggested parts of it could be renegotiated after the UK left the EU.

Theresa May has said the UK should not hope for a "better deal" from the EU if MPs reject her Brexit agreement.
She told a BBC phone-in that there would be just "more division and uncertainty" if Parliament voted against the agreement next month.
But she declined to say whether the UK would be better off outside the EU, saying only it would be "different".
A summit of EU leaders to sign off the deal will go ahead on Sunday despite "unresolved" issues over Gibraltar.
Spain is seeking written assurances from the UK that it will be directly consulted over its future trade negotiations with the EU which relate to Gibraltar, a British Overseas Territory.
Its prime minister Pedro Sanchez has said he won't decide whether to attend Sunday's summit until these are provided.
He has said his backing for the overall deal cannot be taken for granted although no one country can block the withdrawal agreement on its own at this stage.
Meanwhile, the leader of the DUP, Arlene Foster, has said she will "look again" at her party's deal with the Conservatives if Mrs May's Brexit bill passes through parliament.
"But we are not there yet," Mrs Foster added.
Mrs May told the Emma Barnett Show that her job was to persuade MPs to back her but also to "explain" the merits of the deal to the public.
Asked what her plan B was, if MPs rejected the deal, she suggested there would be little point going back to the EU to ask for further changes.
"I believe if we were to go back to the European Union and say: Well people didn't like that deal, can we have another one? ... I don't think they're going to come to us and say: We'll give you a better deal."
Mrs May, who has previously warned about the dangers of the UK leaving without a deal or not leaving at all, would not be drawn on whether she would quit if MPs refused to back her deal.
Asked what was a more likely outcome in such an event - a no-deal exit or the UK remaining in the EU - she said "from my point of view, personally, there is no question of 'no Brexit' because the government needs to deliver on what people voted on in the referendum in 2016".
Asked by a caller called Michael if the UK would be better off outside the EU under her deal than staying in, she said that as someone who voted to Remain, she had never said the "sky would fall in" if Brexit happens.
"I think we will be better off in a situation which we'll have outside the European Union, where we have control of all those things, and are able to trade around the rest of the world," she said.
She added: "You say: Are we better off?... actually it's a different sort of environment, and a different approach that we'll be taking to things."
Pressed by Emma Barnett to answer the question, she said "it is going to be different," before adding: "We can build a better future outside the European Union."
The UK and EU have agreed in principle the framework for their future relations outlining how UK-EU trade, security and other issues would work.
The document, known as the "political declaration", is not legally-binding but will be the starting point for negotiations on co-operation after the UK leaves. It has been heavily criticised by many MPs for lacking detail.
This is a separate document to the legally-binding withdrawal agreement - setting out the terms of the UK's exit from the EU, including the £39bn "divorce bill", citizens' rights and the Northern Ireland "backstop" to keep the border with the Republic of Ireland open, if trade talks stall.
Former Brexit secretary Dominic Raab said what was on offer in the political declaration was inferior to EU membership, as it would leave the UK bound by the same rules but without control over them.
Meanwhile, EU officials are meeting to try to put the finishing touches to both the withdrawal agreement and the political declaration.
The future of Gibraltar and its 30,000 residents, 96% whom voted to remain in the EU in the 2016 referendum, remains a sticking point.
Spain has long contested Britain's 300 year-rule of the peninsula and there are concerns about how the territory's political status and economic ties with the Spanish mainland will be affected by Brexit.
Catherine Barnard, a professor of EU law and employment law at Trinity College, Cambridge, told the BBC that Spain's room for manoeuvre was limited as the "divorce" document only had to be agreed at EU level by qualified majority voting, meaning 20 of the 27 member states.
Fabian Picardo, the chief minister of Gibraltar, said the territory was perfectly happy to have "direct engagement" with Madrid over future trade relations but would not be "dragged" into doing so

Theresa May has dismissed as "Brussels gossip" an account of a dinner with EC President Jean-Claude Juncker, published in a German newspaper.
The pair reportedly clashed over Mrs May's desire to make Brexit "a success" and whether the issue of protecting the rights of expat UK and EU nationals could be agreed as early as June.
The Frankfurter Allgemeine claims Mr Juncker said: "I leave... 10 times more sceptical than I was before."
But Mrs May said it was "constructive".
And she told the BBC's Ben Wright: "I have to say from what I've seen of this account I think it's Brussels gossip."
Speaking during an election campaign event in Lancashire, she added: "Just look at what the European Commission themselves said immediately after the dinner took place, which was that the talks had been constructive."
The article said that, after last week's dinner, Mr Juncker was shocked at Mrs May's suggestion that a deal on citizens' rights could be achieved so quickly.
The German newspaper report also suggested Mr Juncker said there would be no trade deal between the UK and the rest of the EU if the UK failed to pay the "divorce" bill which it is expected to be asked for.
After bringing out paper copies of Croatia's deal to join the EU and the free trade deal recently signed with Canada to make his point, he said Brexit would be "very complex".
After the PM said she wanted to "make Brexit a success", the newspaper reported that Mr Juncker's response was: "Brexit cannot be a success. The more I hear, the more sceptical I become."
And when she said the UK owes no money to the EU, the president informed her that she was not leaving a "golf club".
The newspaper's Thomas Gutschker, who wrote the article, told BBC Radio 4's PM programme that EU officials "have an interest in conveying their sense of desperation after this dinner".
He added: "I don't think they have an interest in these talks collapsing. But they want to save the talks and they basically want to send a wake-up call to Downing Street."
Jeremy Cliffe, the Berlin bureau chief for the Economist, raised the article on Twitter, posting 30 tweets outlining the dinner's highlights.
Speaking to BBC Radio 4's World at One, he said people should take the article "with a pinch of salt" as it had reportedly been leaked by only one side of the talks.
But he added that the Europeans and the British are "in totally different universes" when it comes to their expectations of Brexit negotiations.
"EU nationals... was the first example of several in which the expectations of the two sides seem to be utterly at odds," he said.
The day after the meeting, Mr Juncker reportedly told German chancellor Angela Merkel that Mrs May was "deluding herself" and "living in another galaxy" when it came to the issue of Brexit talks.
Mrs May was asked about that quote during her interview on Sunday's Andrew Marr Show, and responded: "I'm not in a different galaxy. I think what this shows and what some of the other comments we've seen coming from other European leaders show is that there are going to be times when these negotiations are going to be tough.
"That's why you need strong and stable leadership in order to conduct those negotiations and get the best deal for Britain."
The accounts of the dinner - which appear to have come from sources within the European Commission - have been seized upon by opposition parties in the UK.
Liberal Democrat leader Tim Farron said: "These reports have blown a massive hole in the Conservative Party's arguments. It's clear this government has no clue and is taking the country towards a disastrous hard Brexit.
"This election offers us a chance to change the direction of our country, keep Britain in the single market and give the people the final say over what happens next."
Labour leader Jeremy Corbyn said of Mrs May: "She seems to be sending rather mixed messages.
"To start negotiations by threatening to walk away with no deal and set up a low tax economy on the shores of Europe is not a very sensible way of approaching people with whom half of our trade is done at the present time."
The EU set out tough terms for the Brexit negotiations at the weekend - and has followed up with a steady drumbeat of briefing suggesting that the UK is unprepared for the talks to come and harbouring delusions about the possible outcomes.
Officials in Brussels naturally have a vested interest in stressing that leaving the EU is difficult and dangerous - but there's enough detail in the descriptions of a difficult dinner in Downing Street last week to suggest that there are real problems alongside the tactical manoeuvrings.
The President of the European Commission, Jean-Claude Juncker, who was a guest of Theresa May, apparently told his host that the more he heard about the British position the more sceptical he was about the prospects of a deal.
British perceptions of the meal have not been leaked in the same level of detail but there's no doubt the European briefings will be seen in the UK as provocative - and designed to stir up fears among British voters about what Brexit is going to mean.
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Theresa May has told EU leaders she can get the Brexit deal through Parliament if they give her legally-binding changes to it.
The UK prime minister - who also vowed to deliver Brexit "on time" - was speaking after a series of meetings with top EU officials in Brussels.
European Commission President Jean-Claude Juncker again ruled out the kind of changes Mrs May wants to see.
But the two sides agreed to further talks to break the deadlock.
Mrs May said she had also spoken to European Council President Donald Tusk about his comments on Wednesday about there being a "special place in hell" for those who campaigned for Brexit without a plan to deliver it safely.
She said Mr Tusk's language "was not helpful" and had "caused widespread dismay in the United Kingdom".
Mrs May said she had told him he should be "focusing" on working with the UK to get a Brexit deal.
Mr Tusk tweeted that there was "no breakthrough in sight" following his talks with the UK prime minister.
Mrs May said she had "set out very clearly the position from Parliament that we must have legally binding changes to the withdrawal agreement in order to deal with Parliament's concerns over the backstop".
That, "together with the other work that we're doing on workers' rights and other issues, will deliver a stable majority in Parliament," she said.
Mr Juncker "underlined that the EU27 will not reopen the withdrawal agreement" in their talks, according to a joint statement released by the two sides.
But he "expressed his openness" to adding words to the non-binding future relationship document - that also has to be backed by MPs - to be "more ambitious in terms of content and speed".
Did anything change? Not that much.
But for Downing Street, this has not been a pointless stop-off in the almost never-ending Brexit adventure.
Because, while there hasn't been a breakthrough, the EU has agreed to more talks, which at least opens up the possibility of discussing the changes to the troubled backstop that has caused such political difficulty.
It might not sound like much, but "we can talk", is at least a different message to "this is over" .
Meanwhile, Brexit Secretary Steve Barclay and EU negotiator Michel Barnier will hold talks in Strasbourg on Monday, as the EU and UK Brexit negotiating teams discuss proposed changes to the deal.
Downing Street said these talks would cover "alternative arrangements" for the Irish border, as called for by MPs in a vote last week.
A spokeswoman said other UK ministers, such as Attorney General Geoffrey Cox could be involved.
Mr Cox is "working on working on possible ways in which legal texts could be drafted, that gave effect to the objective we want," Cabinet Office Minister David Lidington told the BBC.
Mrs May and Mr Juncker will meet again before the end of February, to review progress.
The prime minister is expected to put the deal to a vote in the Commons towards the end of February.
Jeremy Corbyn has written to the prime minister setting out his party's price for supporting a Brexit deal and to offer talks to secure "a sensible agreement that can win the support of Parliament and bring the country together".
The Labour leader's five demands include a "permanent and comprehensive UK-wide customs union" aligned with the EU's customs rules but with an agreement "that includes a UK say on future EU trade deals".
Mr Corbyn also wants close alignment with the EU single market and "dynamic alignment on rights and protections" for workers so that UK standards do not fall behind those of the EU.
He also proposes participation in EU agencies and funding programmes, and agreements on security and keeping access to the European Arrest Warrant.
The letter does not mention previous demands that any deal must deliver the "exact same benefits" that membership of the single market and customs union currently does - effectively scrapping the party's "six tests" that had been its Brexit policy.
The BBC's Political Editor Laura Kuenssberg said Labour's shadow Brexit secretary Sir Keir Starmer would be meeting Cabinet Office Minister David Lidington to discuss the proposals.
But the move was met with dismay by Labour members of the People's Vote campaign for another EU referendum, who accused Mr Corbyn of going back on his commitment, made at the party's conference, to back a public vote if he can't force a general election.
Labour MP Owen Smith, who made a failed leadership bid in 2016, has told the BBC he and others were thinking of quitting the party over Mr Corbyn's Brexit stance.
But Labour's Stephen Kinnock, who backs the "Norway Plus" model of a close economic partnership with the EU, welcomed Mr Corbyn's letter, tweeting: "This can break the deadlock."
Mr Lidington said he and Brexit Secretary Steve Barclay would be willing to discuss Labour's proposals with Sir Keir and other frontbenchers.
But he said Labour's call to have a say in trade deals while being in a customs union with the EU was "wishful thinking", because Brussels had ruled it out.
The European Parliament's Brexit co-ordinator Guy Verhofstadt welcomed Mr Corbyn's proposals, saying "the broadest possible majority" was needed for a Brexit deal in the UK and "cross-party co-operation is the way forward".
It was also backed by Conservative MP Sir Oliver Letwin, who wants to see the UK in a Norway-style relationship with the EU after Brexit.
The UK is due to leave the EU at 23:00 GMT on Friday 29 March, when the two-year time limit on withdrawal negotiations enforced by the Article 50 process expires.
In January, MPs overwhelmingly rejected the withdrawal deal that the government had negotiated with the EU, backing an amendment for the government to seek "alternative arrangements" to the backstop.
The backstop is an "insurance policy" designed to avoid "under all circumstances" the return of customs checkpoints between Northern Ireland and the Irish Republic after Brexit.
Many fear creating physical infrastructure along the border could threaten the peace process.
But the Democratic Unionist Party and Brexiteers believe the proposed temporary single customs arrangement could threaten the integrity of the UK, leaving it bound by EU rules if no trade deal is agreed.

Theresa May has insisted she will not be forced into watering down her Brexit plan during negotiations with the EU.
Writing in the Sunday Telegraph, the prime minister says she will "not be pushed" into compromises on her Chequers agreement that are not in the "national interest".
But Mrs May also warns she will not "give in" to those calling for a second referendum on the withdrawal agreement.
She says it would be a "gross betrayal of our democracy and... trust".
The Chequers agreement would see the UK agreeing a "common rulebook" with the EU for trading in goods, in an attempt to maintain friction-less trade at the border.
But critics say it will leave the UK tied to EU rules and prevent Britain from striking its own trade deals in years to come.
The People's Vote, a cross-party group including some MPs, is calling for a public vote on the final Brexit deal.
The UK is on course to leave the EU on 29 March but has yet to agree how its final relationship with the bloc will work. The EU has suggested that November is the latest a deal could be finalised.
The government had previously ruled out another referendum.
The prime minister writes that the coming months are "critical in shaping the future of our country", but that she is "clear" about her mission in fulfilling "the democratic decision of the British people".
She adds that following the Chequers agreement in July - which led to the resignation of two cabinet ministers - "real progress" has been made in Brexit negotiations.
While there is more negotiating to be done, Mrs May writes: "We want to leave with a good deal and we are confident we can reach one."
The government has been preparing for a no-deal scenario, even though this would create "real challenges for both the UK and the EU" in some sectors, she says.
But the PM adds: "We would get through it and go on to thrive."
She goes on to insist in her article that her government will not back another vote.
"In the summer of 2016, millions came out to have their say," she writes.
"In many cases for the first time in decades, they trusted that their vote would count; that after years of feeling ignored by politics, their voices would be heard.
"To ask the question all over again would be a gross betrayal of our democracy - and a betrayal of that trust."
David Davis, the former Brexit secretary who quit over the Chequers agreement, said he was also against a second referendum.
Speaking on the BBC's Andrew Marr Show, he said he would vote against the Chequers plan in any Commons vote, adding that it would be "almost worse" than staying in the EU.
He said the problems around the Northern Ireland border with the Irish Republic had been "heavily overemphasised" in the past.
"It's a border already - it works perfectly well with careful co-operation between sides," he said, and with "political will" from the UK and the Republic, it could continue to do so.
By Chris Mason, BBC political correspondent
Welcome to the new term in politics - it is getting loud already.
No sooner has the prime minister said she is committed to her Brexit blueprint than one of her previously loyal MPs has suggested signing up to it would be a "humiliation".
And no sooner has she insisted that another Brexit referendum would be a "gross betrayal of our democracy" than one of her own party donors says that is "balderdash".
It seems, to put it mildly, that we are in for quite a political term.
Both the big political parties at Westminster have their fair share of turmoil and the stakes could not be higher.
But if the last few months, or the last few years, have taught us anything, it is that we can be very confident there will be a few bumps in the road - whether a Brexit deal is done or not.
Writing in the same paper, Conservative MP Nick Boles - a former minister who backed Remain - said the Chequers policy had "failed" and he could no longer support it.
He wrote that the EU was treating the plan as "an opening bid", and the UK was facing "the humiliation of a deal dictated by Brussels".
Instead, Mr Boles, who is a member of the Brexit Delivery Group, believes the two-year transition period - which the government describes as an implementation period - should be scrapped and replaced with the UK becoming part of the European Economic Area for three years - giving more time for a trade deal to be negotiated.
"The plan I am setting out represents our only hope of a better Brexit," he added.
The People's Vote launched earlier this year to campaign for a vote on any final Brexit deal, and has a number of high-profile backers, including Sir Patrick Stewart and BBC football anchor Gary Lineker.
It has also secured funding from donors including Julian Dunkerton, co-founder of fashion label Superdry - who has given the largest donation of £1m to the group.
One of its supporters, the Labour MP Chuka Umunna, said the impetus had shifted toward a public vote over the summer and it would be a "betrayal of democracy" for Theresa May "to force a bad deal - or no deal - on Britain without giving the public the chance to have a final say".
The Conservative donor and former Rolls-Royce chairman Sir Simon Robertson has also joined calls for a second referendum, saying he is "deeply depressed" at the tone of the Brexit debate.
"I think it is complete balderdash to say the people have spoken, therefore you can't go back. The people can speak again - why can't we have another vote on it?" he asked, in an interview with the the Observer.
Earlier this week, it was revealed in a leaked memo that the People's Vote wants Labour MPs and activists to submit a motion at the party's conference this month, committing Labour to backing a new referendum on the final deal.
The party's current policy position is to respect the result of the 2016 Brexit referendum.

"Rich and deep conversations" are needed with devolved governments on the UK's future relationship with the EU, a senior cabinet minister has said.
Michael Gove met ministers from Wales, Scotland and Northern Ireland ahead of Brexit on Friday.
But Mr Gove did not commit to giving them a formal role in the negotiating process, after the meeting in Cardiff.
Wales' First Minister Mark Drakeford said there had been an "engaged discussion" on how to proceed.
With the UK leaving the European Union at 23:00 GMT on Friday, the Welsh and Scottish Governments and Northern Ireland Executive are seeking to influence the nature of the relationship with the bloc.
Britain will follow EU rules and have the same trading relationship as now until the end of the year, during a transition phase.
Prime Minister Boris Johnson has insisted a new relationship will be agreed with EU leaders over the next 11 months, but the European Commission has warned that timetable will be extremely challenging.
Speaking to BBC Wales after Tuesday's meeting, held at the Welsh Government headquarters in Cardiff, Mr Gove said he wanted to ensure "we have rich and deep conversations, not just with the Welsh Government but also with our colleagues in Northern Ireland and Scotland".
"Ultimately, it's the UK government that's in the negotiating room, and there was a very clear mandate at the general election," he said.
"People wanted Boris Johnson to deliver Brexit and to unleash Britain's potential.
"Alongside that, it's also important that we make sure that the contributions from politicians across the United Kingdom are there at the heart of our negotiating strategy."
In an upbeat assessment of the meeting, Mr Drakeford said: "I think today we did get a recognition from the UK government that it's good for the UK to go into the negotiations with other parties saying they represent the whole of the UK.
"Therefore we need a structure to allow that to happen, we discussed how that structure could be brought about. There are further discussion we need around it but I thought it was an engaged discussion."

The UK will regain full control over the country's fishing waters for the first time in 40 years after December 2020, Michael Gove has insisted.
The environment secretary said he shared the "disappointment" of fishing communities who hoped this would happen on Brexit day, 29 March 2019.
But Mr Gove urged them to keep their "eyes on the prize" of getting control.
Lib Dem Alistair Carmichael, who raised the issue, said "the mood in fishing communities is one of palpable anger".
The fishing industry had wanted the UK to regain full control over the country's fishing waters on Brexit day, 29 March, 2019.
Instead the deal will see the UK "consulted" on quotas with the situation remaining largely unchanged until 2021.
Mr Gove said the government had pressed for the UK to be an equal partner in fishing negotiations during the 21-month "implementation period" - but the EU had blocked this.
"We were disappointed the EU would not move on this," he told MPs, saying that the UK only had to wait a further year for complete control of its waters.
"In December 2020, we will be negotiating fishing opportunities as a third country, an independent coastal state deciding who can access our waters and on what terms for the first time in over 40 years," he said.
"It's important that all of us, in every area, accept that the implementation period is a necessary step towards securing that prize.
"For our coastal communities it's an opportunity to revive economically, for our marine environment it is an opportunity to be managed sustainably and it's critical that all of us - in the interests of the whole nation - keep our eyes on that prize."
But Mr Carmichael replied: "I have to tell you, if you don't already know it, the mood in fishing communities is one of palpable anger - this is not what they were promised."
He added that if the government can "let us down like this over a deal for the transitional period, how do we know they will not do it again when it comes to the final deal?"
The SNP's Stephen Gethins asked the minister to say "at what point our fishermen became a bargaining chip", adding: "Or has that been the case all along?"
Mr Gove replied: "For a party that has raised grievance to an art form, you have a damn cheek making that case."
Former Tory minister John Redwood pressed him to go back to the EU and say "this deal is unacceptable".
Mr Gove said: "We didn't get everything we wanted, but... it's the view of this government that we need to make sure this implementation succeeds to get the greater prize at the end of it."
Prominent Eurosceptic Tory Jacob Rees-Mogg said he was "slightly concerned" by Mr Gove's tone in relationship to negotiations that the European Commission "would not allow us something in a negotiation".
Mr Gove said the implementation period would allow the government to prepare "for all the benefits Brexit will bring".
The Commons exchanges came as Scottish Conservative MPs who held talks with the prime minister on fishing said she "reassured" them the UK would take control of its waters after the transition period.
Alister Jack, the MP for Dumfries and Galloway, said he felt assured by Mrs May's comments but John Lamont, the MP for Berwickshire. Roxburgh and Selkirk, warned: "The government should be clear that they are on notice - no deal for fishermen, and they will have to think again on the terms of our departure."
The Daily Telegraph reported that Tory critics of the deal are planning to protest on a boat on the Thames by Parliament on Wednesday.
Scotland's First Minister and SNP leader, Nicola Sturgeon, claimed the concession made to the EU in the transitional period was "shaping up to be a massive sell-out of the Scottish fishing industry by the Tories".
Labour's shadow fisheries minister Holly Lynch said it was "understandable" fishing communities felt "angry and let down".
Bertie Armstrong, head of the Scottish Fishermen's Association, accused the EU of asking "for the bargain of a lifetime" by seeking to keep the UK under Common Fisheries Policy rules for "as long as physically possible".
Compared with Iceland, which is allowed to keep 90% of fish caught in its waters, the UK keeps 40% under the Common Fisheries Policy, he told BBC Radio 4's Today programme.
But Niel Wichmann, head of the Danish Fishermen's Association, said the transition period "is a sensible agreement which gives us time - a couple of years - to work out how we keep our fishing stocks sustainable, how we keep our fisheries sustainable after Brexit".
On Monday, the EU's chief negotiator Michel Barnier said the legal text of the agreement for the 21 months after Brexit marked a "decisive step" but added that it was "not the end of the road".
The key aspects of the agreement announced in Brussels are:
Other aspects of the post-Brexit relationship yet to be agreed include what happens to the Northern Ireland border in the longer term.

Michael Gove has urged Tory MPs to back a compromise Brexit plan as the best chance of a "proper" exit from the EU.
He told the BBC it was not all he hoped for, but said he was a "realist" and dismissed claims it would leave the UK as a "vassal state".
But he warned the EU had to be more generous or the UK would have no option than to walk away without a deal.
Labour also urged the EU to be more flexible but said Theresa May's customs plan was a "fudge" and would "unravel".
In the Commons on Monday, Theresa May will tell MPs her plan will mean "a complete end to freedom of movement", restore the "supremacy of the British courts" and ensure no more "vast sums of money" would be sent to Brussels.
She is expected to say that since the 2016 referendum decision to leave the EU, "I have listened to every possible idea and every possible version of Brexit. This is the right Brexit".
Several Tory MPs have expressed unease since Friday, when the cabinet approved a document setting out the UK's vision for its future relationship with the EU after it leaves in March 2019.
Under the proposals, yet to be presented to the EU, there would be a free trade area for industrial and agricultural goods, based on a "common rule book" and a "combined customs territory".
Boris Johnson is understood to have strongly criticised the plan during the cabinet meeting at Chequers before signing up to it. He is said to have warned colleagues it could be a "serious inhibitor to free trade" and striking deals with other countries.
The foreign secretary then backed the proposals - despite claiming that defending the plans was like "polishing a turd".
But environment secretary Mr Gove, who campaigned for Brexit alongside Mr Johnson in the 2016 referendum, told the BBC's Andrew Marr show he was satisfied the solution would "honour" the result of the vote.
The free movement of people was ending, he said, and the UK Parliament would have the final say over rules governing a "huge swathe" of the British economy.
"In all the important areas where an independent country chooses to exercise sovereignty, the UK will be able to do so and, in so doing, respect the referendum result and the mandate we were given," he said.
Asked if Mrs May's offer was all he had hoped for, he replied: "No, but then I'm a realist and one of the things about politics is you mustn't, you shouldn't, make the perfect the enemy of the good."
While urging his colleagues to get behind the prime minister as she tries to secure a deal by October, he said the UK must be prepared for this not happening.
"We are being generous to the EU, we are showing flexibility," he said. "If the EU is not generous and flexible, we may have to contemplate walking away without a deal.
"No-one wants to walk away now because we are in the middle of a negotiation - what we need to be able to do is to walk away in March 2019."
After ministers signed up to the deal on Friday night, Mrs May said the time for them to air their concerns in public was over and collective cabinet responsibility had been re-instated - a stance endorsed by Mr Gove.
The prime minister has urged the EU to take her offer seriously. She refused to rule out offering EU citizens some form of special status as part of a proposed new "mobility framework".
But Tory Brexiteers not in the government have spoken out against the plan, warning the UK will have to follow EU laws and European Court of Justice rulings and not have an "effective international trade policy".
Conservative MP Andrew Bridgen said the proposed deal was "indefensible" as it was "probably worse than staying in the EU". He suggested his support for the prime minister was not unconditional.
"At the moment, she's not only let the party down, she's let herself down," he told the BBC. "If she sticks with this deal, I have no confidence in it. If she sticks with this, I will have no confidence in her."
And pro-Remain Tory MP Phillip Lee has suggested the offer was the "worst of all worlds" and restated his call for a second referendum - with the option of staying in the EU to be on the ballot paper.
Shadow Brexit secretary Sir Keir Starmer said proposals to avoid customs checks by differentiating between UK and EU-bound goods, in terms of what tariffs should be paid, were "a bureaucratic nightmare".
"This has got fudge written all over it," he told Andrew Marr. "She (Theresa May) has not met our demands. It is going to unravel and she will have to think again."
He urged Mrs May to put her customs proposals to a vote in Parliament in a week's time, suggesting Labour's alternative plan for a comprehensive customs union had the backing of the majority of MPs.
Scottish First Minister Nicola Sturgeon said it was "game on" for the SNP and others who wanted the UK to remain in the existing customs union and single market.
On the other side of the debate, UKIP leader Gerard Batten said Mrs May was "surrendering" to the EU and "dashing the hopes and dreams of 17.4 million British voters" who backed Brexit in 2016.
The main details from the Chequers statement, to be incorporated in a white paper next week, are:

EU chief Brexit negotiator Michel Barnier has criticised Theresa May's proposals for a customs arrangement.
He stressed that he was not rejecting the UK prime minister's ideas - but said any "backstop" to prevent a hard Irish border could not be time-limited.
The UK proposal would see the whole UK matching EU trade tariffs for a period, if a trade deal is not reached by 2021.
Mr Barnier said the UK paper "raises more questions than it answers" but would be examined "objectively".
He also said some Brexit supporters wanted to blame Brussels for the UK not keeping some of the benefits of EU membership after Brexit adding: "We are not going to be intimidated by this form of blame game."
The UK proposal was was drawn up after a row in cabinet in which Brexit Secretary David Davis reportedly threatened to resign.
By BBC Political Correspondent Alex Forsyth
This temporary "backstop" is meant to prevent a hard border on the island of Ireland by kicking in if alternative customs arrangements can't be negotiated and implemented in time for the end of the transition period in December 2020.
The EU's version would see Northern Ireland stay in the EU customs union, meaning a customs border in the Irish Sea.
That is wholly unacceptable to Theresa May  - and the DUP who back her in parliament.
So the prime minister proposed an alternative which would see the whole of the UK match EU tariffs.
Today Mr Barnier suggested that would be problematic.
And he raised concerns about the fact it would be time-limited; something key Brexiteers are demanding because they don't want the UK to stay closely tied to the EU indefinitely.
So while the EU's chief negotiator didn't rule out the UK's proposal altogether, he certainly poured cold water on it.
So far it seems agreement - even on the fallback option - is proving pretty tricky.
He said the UK's proposals would be measured against three questions - whether it was a "workable solution" to avoiding a hard border, whether it respected the integrity of the single market and customs union and whether it was what he called an "all weather backstop".
The EU's proposal, he told a press conference in Brussels, met these tests and that it was not necessarily "feasible" to extend the EU's offer of continued participation in key elements of the customs union in Northern Ireland to cover the whole of the UK.
"Let me be clear: our backstop cannot be extended to the whole UK. Why? Because it has been designed for the specific situation of Northern Ireland."
He also stressed his preference for the EU's border in the Irish sea plan, saying: "Checks carried out on ferries are less disruptive than along a 500km-long land border."
In addition, these checks can build on arrangements and facilities which already exist between the rest of the UK and Northern Ireland."
He said the "time-limited" nature of the UK proposal - with an "expected" end date of December 2021 - was also problematic.
With a nod to Mrs May's famous "Brexit means Brexit" phrase, Mr Barnier said:  "Backstop means backstop.
"The temporary backstop is not in line with what we want or what Ireland and Northern Ireland want and need."
But later he tweeted that he was not rejecting the UK customs paper:
In a statement issued following Mr Barnier's press conference, Downing Street said: "The prime minister has been clear that we will never accept a customs border between Northern Ireland and the rest of the United Kingdom.
"We are also committed to maintaining the integrity of our own internal market. That position will not change. The commission's proposals did not achieve this, which is why we have put forward our own backstop solutions for customs."
It added that all sides had agreed to "protect the Belfast Agreement [Good Friday Agreement] in all its parts".
"Michel Barnier has confirmed today that discussions will now continue on our proposal."
Northern Ireland's Democratic Unionist Party, whose MPs back Mrs May's minority government, responded angrily to Mr Barnier's comments, which they said they showed the EU negotiator had "no respect for the principle of consent or the constitutional integrity of the United Kingdom".
Deputy Leader Nigel Dodds said: "This is nothing more than an outrageous attempt to revert to the annexation of Northern Ireland.  We will not accept such a proposal."
At the end of a turbulent week for Mrs May - in which she saw off the threat of a cabinet resignation over the UK's customs paper on Thursday - another cabinet Brexiteer, Boris Johnson, was recorded talking about Brexit in very candid terms at a private dinner.
The foreign secretary said concerns about the Irish border had been overhyped and that Donald Trump might do a better job negotiating Brexit.
In a recording obtained by Buzzfeed, he was said to have described the Irish border issue as "pure millennium bug stuff" and added: "Imagine Trump doing Brexit.
"He'd go in bloody hard... There'd be all sorts of breakdowns, all sorts of chaos. Everyone would think he'd gone mad. But actually you might get somewhere. It's a very, very good thought."
He also took a swipe at Chancellor Philip Hammond, calling the Treasury "the heart of Remain".
Brexit-supporting Tory MPs applauded the foreign secretary but Mr Hammond said his "advice to colleagues" was to engage with the EU and to understand their concerns.

The EU's lead Brexit negotiator has rejected Boris Johnson's demands for the Irish backstop to be scrapped.
Michel Barnier said the backstop - intended to avoid a hard border on the island of Ireland - was the "maximum flexibility" the EU could offer.
Mr Johnson has previously told the EU the arrangement must be ditched if a no-deal Brexit was to be avoided.
Meanwhile, the PM has told rebel Tories they face a "fundamental choice" of siding with him or Jeremy Corbyn.
His comments come as some MPs who oppose a no-deal Brexit - including Conservatives - are planning to take action in Parliament next week.
The UK is due to leave the EU on 31 October, with or without a deal.
Former justice secretary David Gauke, who voted three times for the Withdrawal Agreement in the House of Commons, will meet the prime minister on Monday to ask about the practicalities of securing a deal.
"I want to hear from him as to what is his plan to deliver a deal, when are we putting forward proposals to deal with this backstop issue - which is the one issue he has identified as the problem within the Withdrawal Agreement," he said during an interview on Sky News' Sophy Ridge show.
"I want to hear how he's going to address that, and I want to hear how he plans to deliver the legislation if we get a deal by 31 October - because at the moment, frankly, I can't see how he's got time to do that."
The backstop is part of the withdrawal agreement negotiated between Brussels and former prime minister Theresa May, which has been rejected by Parliament three times.
If implemented, it would see Northern Ireland staying aligned to some rules of the EU single market, should the UK and the EU not agree a trade deal after Brexit.
Mr Johnson has said there has been some movement from the EU, as he attempts to broker a new deal and remove the arrangement, which he has described as "undemocratic".
However, writing in the Sunday Telegraph, Mr Barnier said: "On the EU side, we had intense discussions with EU member states on the need to guarantee the integrity of the EU's single market, while keeping that border fully open.
"In this sense, the backstop is the maximum amount of flexibility that the EU can offer to a non-member state."
Mr Barnier also said he was "not optimistic" about avoiding a no-deal Brexit, but "we should all continue to work with determination".
He added: "The EU is ready to explore all avenues that the UK government may present and that are compatible with the withdrawal agreement."
The EU could not stop the UK from leaving without a deal, he said, but he "would fail to understand the logic of that choice" because "we would still need to solve the same problems after 31 October".
Mr Johnson says he wants to leave the EU on 31 October with a deal, but it is "do or die" and he is willing to leave without one rather than miss the deadline.
That position has prompted a number of opposition MPs to come together to try to block a possible no deal.
MPs opposed to a no-deal Brexit are expected to try and seize control of the Parliamentary agenda this week to push through legislation that would force the PM to seek a Brexit extension beyond 31 October.
But Mr Johnson has warned Tory MPs who are considering lining up with opposition groups that they risk plunging the country into chaos.
In an interview with the Sunday Times, he said: "I just say to everybody in the country, including everyone in Parliament, the fundamental choice is this: Are you going to side with Jeremy Corbyn and those who want to cancel the referendum?
"Are you going to side with those who want to scrub the democratic verdict of the people - and plunge this country into chaos.
"Or are you going to side with those of us who want to get on, deliver the mandate of the people and focus with absolute, laser-like precision on the domestic agenda?"
His comments come after the Sun reported that No 10 would stop any Tory MP who votes to block a no-deal Brexit from standing for the party in a general election.
The report prompted former chancellor Philip Hammond to say it would be "staggeringly hypocritical" for the government to sack Conservative MPs who rebel over its Brexit plans, as eight current cabinet members had themselves defied the party whip this year by voting against Theresa May's Brexit deal.
Speaking on Sky News' Sophy Ridge show, International Development Secretary Alok Sharma said that Mr Johnson must be given time to secure a new deal.
"We want any future agreement not to have the backstop… The reality is that the previous Withdrawal Agreement, which contained the backstop, did not pass on three occasions. It didn't pass then, it won't pass again," he said.
"In fact, having the backstop also potentially makes us rule-takers from the EU forever. That is not what we want. We want that out, we want a deal, but we will be leaving on 31 October - no ifs, no buts."
Shadow chancellor John McDonnell told the same programme that a cross-party group that includes MPs and legal experts is looking at introducing a legislative measure next week to stop a no-deal Brexit without parliamentary approval.
"The technique of that will be published on Tuesday, and I'm hoping that we'll have a debate in which we can bring the House together," he said.
"The ultimate goal, very straightforwardly, this week, is to ensure that Parliament can have a final say... we cannot have a prime minister overriding Parliament - not just on this issue, on any issue."
On Saturday, demonstrations were held across the UK in response to Mr Johnson's plans to suspend Parliament in the run-up to Brexit.
The prime minister, who announced the move on Wednesday, said it would enable the government to bring forwards new legislation.
But the decision prompted an angry backlash from some politicians and opponents of a no-deal Brexit.
Labour leader Jeremy Corbyn accused Mr Johnson of a "smash and grab on our democracy" in order to force through no deal by leaving MPs too little time to pass laws in Parliament aimed at preventing such an outcome.
But Chancellor Sajid Javid defended the decision, adding: "It's right because we are focusing on the people's priorities."
If the prorogation happens as expected, Parliament will be closed for 23 working days.
MPs have to approve recess dates, but they cannot block prorogation.

A Tory MP who has put forward a plan to block a no-deal Brexit says ministers have told him they will quit, if they are ordered to vote against it.
His cross-party bill would force Theresa May to request an extension of Article 50 if she can't get a deal approved by MPs by the end of February.
Mr Boles told the BBC his bill had a "broad base" of support from different sides of the Brexit debate.
And he said he believed a number of ministers backed his plan.
But he believes his constituency party in Grantham and Stamford is looking to oust him as a candidate at the next election.
Asked if he thought local members would de-select him, the Tory backbencher told Nick Robinson's Political Thinking podcast: "I think if they were asked to now they probably would."
Theresa May has been meeting senior members of other parties to see if there is any room for a compromise after her EU withdrawal deal was overwhelmingly rejected by MPs this week. Labour Leader Jeremy Corbyn has refused to attend talks until the prospect of a no-deal Brexit has been ruled out.
The prime minister will publish a new plan on Monday with a full debate and key vote scheduled for Tuesday, 29 January.
Mr Boles's EU Withdrawal (Number 2) Bill aims to put Parliament in control of the Brexit process, demanding an extension to the Article 50 process to allow negotiations to continue beyond the scheduled date of Brexit on March 29.
But Mr Boles withdrew proposals for the cross-party Commons Liaison Committee of senior backbenchers to draw up an alternative Brexit plan, after its chair Sarah Wollaston indicated that it would not accept the role.
However, Mr Boles the bill would still go ahead and had sponsors from three different parties - the Conservatives, Labour and the Lib Dems.
"This bill is about creating the space for a compromise by ruling out a no-deal Brexit," he told the BBC.
To pass his new bill, Mr Boles will need to suspend the rules in Parliament so that he does not need government support to free up parliamentary time for it.
He could do this by amending the government's business motion which sets out the schedule ahead of the Commons debate on 29 January.
He told the Political Thinking podcast: "We have had indications that many ministers, including cabinet ministers are very, very keen to see it pass and are telling the prime minister that they will not vote against it.
"There is a bandwagon rolling, it's got a lot of momentum behind it and I very much hope that any MP who shares my view that a no-deal Brexit would be a disaster, will jump on board.
"I have been told directly by ministers, not in the cabinet, that they have said that they would resign if they are whipped to vote against it."
While he did not know if any cabinet ministers would quit, he said the transcript reported in the Daily Telegraph of a conversation in which Philip Hammond "made quite plain that he thought this was fantastic".
Mr Boles said he would not change his view on Brexit to please a small number of Conservative members in Grantham and Stamford.
"One hundred people in my local party have written in saying they're outraged by what I'm saying and want to de-select me," he told the podcast.
"And the truth is that many of them used to belong to UKIP only about a year ago.
"They're entirely entitled to their view, they're entitled to be members of the Conservative Party and they're entitled to de-select me.
"But I am not going to change what I believe is in the interest of the 80,000 people that I represent in Parliament because of 100 people in my constituency party."

The government has made a fresh plea to MPs to get behind Theresa May's Brexit deal in Tuesday's crucial Commons vote.
No 10 says it is alarmed by reports MPs plan to take control of Brexit if Mrs May's deal is voted down, although a leading Tory rebel denies such a move.
And Labour leader Jeremy Corbyn has vowed to table a vote of no confidence in the government if she loses, which could trigger a general election.
The PM has warned of a "catastrophic" breach of trust if Brexit is thwarted.
Writing in the Sunday Express, Mrs May told MPs: "It is time to forget the games and do what is right for our country."
About 100 Conservative MPs, and the Democratic Unionist Party's 10 MPs, are currently expected to join Labour and the other opposition parties in voting against the deal.
What is likely to happen next:
Brexit Secretary Stephen Barclay told the BBC's Andrew Marr show there was greater "uncertainty" after Commons Speaker John Bercow's decision last week to allow MPs to change the parliamentary timetable.
He warned "those on the Brexiteer side seeking ideological purity" by voting down Mrs May's deal they risked "leaving the door ajar to ways that increase the risk to Brexit".
"There are lots of different plans being put forward by Members of Parliament that don't respect the result (of the referendum) or risk no deal," he added.
Pressed on what would happen if the deal is defeated, Mr Barclay said he suspected the Commons would support something "along the lines of this deal" but declined to speculate on whether the government had a Brexit "plan B".
Mr Corbyn said Labour would vote against Mrs May's deal and, if she lost, would start moves to trigger a general election.
He told Andrew Marr: "We will table a motion of no confidence in the government at a time of our choosing, but it's going to be soon, don't worry about it."
The Labour leader has said his party does not have the votes in Parliament to win a confidence vote on its own and has appealed to other parties to support it.
Northern Ireland's DUP party, which keeps Mrs May in power, is also planning to vote against her deal but has said it will support Mrs May in a confidence vote.
If a majority of MPs back a no confidence motion, the government - or any anyone else with sufficient support - will get 14 days to try to win another confidence vote. If no-one can do that, a general election will be held.
Mr Corbyn is facing growing calls from within his own party to back a second EU referendum.
He told Andrew Marr he hoped to get a general election first - and ensure that the UK did not leave without a deal.
"My own view is that I'd rather get a negotiated deal now, if we can, to stop the danger of a no-deal exit from the EU on 29 March - which would be catastrophic for industry."
Asked whether Labour would campaign to leave the EU if a general election was called, Mr Corbyn said his party would "decide our manifesto content as soon as we know there's an election coming".
He said he would have to ask the EU to extend Article 50, the legal process taking the UK out of the EU on 29 March, if he won an election, which he said would take place in February or March, to allow time for a new Labour government to negotiate a Brexit deal of its own.
Mr Corbyn wants the UK to be part of a customs union with the EU, with access to the single market.
The UK will leave the EU on 29 March unless there is a new act of Parliament preventing that.
Because the government controls the timetable for Commons business, it was assumed that this would not be possible.
But a group of MPs, including former Tory ministers, are reported by the Sunday Times to be working on a way to allow non-government members to take control of the timetable and bring forward legislation making it illegal to leave the EU without a deal, if Mrs May loses Tuesday's vote.
Downing Street has said it is "extremely concerned" about the reported plot, which it says could potentially overturn centuries of Parliamentary precedent.
A leading Conservative Remainer, who declined to be named, has told the BBC he is not aware of any plans to change Commons rules. He dismissed newspaper stories about backbench plots as "fantasy", designed to frighten Brexiteer Tories into backing Mrs May's deal.
But the SNP's leader at Westminster, Ian Blackford, said MPs must now take control of the Brexit process from the government to prevent a no-deal scenario.
He told the BBC's Sunday Politics programme: "The prime minister's got to stop threatening Parliament and indeed, threatening the whole of the United Kingdom, that it's a choice between her deal and no deal - that's not the case."
Lib Dem leader Sir Vince Cable, who like Mr Blackford backs another EU referendum, said: "I think Parliament will take control of this process, will insist that we pursue the option of no Brexit."
Sir Vince said this could happen by cancelling Article 50 - which he noted would be "resented by lots of people" - or via a second referendum.
But former Brexit Secretary David Davis said MPs should vote down Mrs May's deal - and the government should then go back to the EU with "our best and final offer" of a free trade deal with no tariffs, along the lines of the deal the EU has with Canada.
"If the EU insists on no deal, then fine," he says in an article for the Sunday Times.
The government has previously rejected Mr Davis's proposals, which are backed by other Brexiteer Tories, saying they would not solve the Northern Irish border problem.
If you feel like you ought to know more about Brexit...

Details of the government's post-Brexit trade policy have been published.
Ministers say the Trade Bill includes provisions for the UK to implement existing EU trade agreements and help ensure firms can still access foreign government contracts worth £1.3tn.
It will also create a new trade remedies body to defend UK businesses against injurious trade practices.
International Trade Secretary Liam Fox said firms needed "as much stability as possible" on the day the UK leaves.
But Labour questioned why the bill was being published on the day Parliament rises for a week-long recess, suggesting ministers wanted to "minimise scrutiny".
And unions said workers' rights must not be sacrificed on the altar of doing "dodgy deals" with countries with insufficient employment protections.
The UK cannot sign or negotiate trade deals before its scheduled departure from the EU in March 2019. However, ministers say they can "scope" out future deals with key trade partners, such as the US, Australia and New Zealand.
Despite its publication, the Trade Bill, one of nine pieces of new legislation in the pipeline to prepare the ground for Brexit, will not be debated by MPs until a later date.
Mr Fox said the point of the bill was to "provide as much stability as possible" for businesses on the day Britain leaves the EU and to prevent market instability.
But looking beyond that, the UK wanted to negotiate "more liberal" trade agreements to "provide even better market access than we have through our EU membership".
"One of our worries is that global trade is not opening up," he told BBC Radio 4's Today programme, and the UK wanted to "use its influence to get a more liberal global trading system" once it had left the EU.
But TUC general secretary Frances O'Grady said the "ramshackle bill" offered no protection for workers' rights and for public services like the NHS from foreign contractors.
"The Trade Bill must guarantee that the price of entry to a trade deal involving Britain is signing up to the strongest protections for workers and public services," she said.
On the eve of the bill's publication, one of Donald Trump's leading allies said he was optimistic that the UK and US will sign a free trade deal after Brexit.
US Commerce Secretary Wilbur Ross told the BBC there had already been a "joint scoping exercise" in Washington in July on a free trade agreement and another similar meeting will be held in London next week.
"We're huge trading partners with each other and our economies are in many ways more similar to each other than either of us is to most of Europe," he said.
"So there's all the logic in the world for the US and the UK to be not only good trading partners, but FTA partners," he said.
Mr Ross, who met Theresa May and other senior ministers during a two-day visit, identified continued "passporting" of financial services, compliance with EU food standards on GM crops and chlorine-washed chicken and future trade tariffs as areas that could pose problems in negotiations between the nations.

Work and Pensions Secretary, Amber Rudd, has said history will take "a dim view" of ministers if the UK leaves the EU without an agreement.
Ms Rudd told a cabinet meeting earlier that the UK would be less safe if there was a no-deal Brexit.
Business Secretary Greg Clark has also told MPs a no-deal exit in March "should not be contemplated".
MPs are set to vote soon on a measure which may restrict the government's tax powers in the event of a no-deal exit.
The government has refused to rule out leaving the EU without an agreement and is continuing to make contingency plans.
Transport Secretary Chris Grayling told the Commons that ministers would be accused of "irresponsibility" if they weren't planning for all eventualities.
In other Brexit developments:
Mrs May appears to be facing a growing backlash against a possible no-deal Brexit - if her agreement is voted down next week.
It is understood during Tuesday's Cabinet that Ms Rudd, a former home secretary who was a leading figure in the 2016 Remain campaign, told MPs history would take a dim view of the government if it accepted no deal and it would leave the UK a less safe country.
"We have to face the world as we find it, not as we wish it to be, and we have to deal with the facts as we find them," she is reported to have said.
While she wanted Brexit to go ahead, she said it was important that Parliament tried to reach as much of a consensus as possible.
"More than ever we need to find the centre, reach across the House and find a majority for what will be agreed. Anything will need legislation."
Home Secretary Sajid Javid said no deal would limit the government's ability to return illegal immigrants to other EU countries.
And Environment Secretary Michael Gove said that those considering rejecting Mrs May's agreement in the hope of securing a better deal "were like swingers in their mid-50s waiting for film star Scarlett Johansson to turn up on a date".
Ms Rudd added "or Pierce Brosnan", only for Justice Secretary David Gauke to quip that it was like "waiting for Scarlett Johansson on a unicorn".
Leading Brexiteer Steve Baker, the ex-minister who was a key figure in the failed attempt to remove Theresa May as Conservative leader last month, tweeted that the swingers' allusion was "not persuasive nor impressive".
On Monday, Business Minister Richard Harrington became the first minister to publicly say he would resign if the government pursued a no-deal exit and told the BBC others could follow suit.
His boss, Business Secretary Greg Clark, told MPs on Tuesday a no-deal exit "should not be contemplated" because of the likely impact on business..
Meanwhile, a cross-party group of MPs, headed by Labour's Yvette Cooper and Conservative Nicky Morgan, will later attempt to make it harder for the UK to leave the EU without a deal.
The MPs have tabled an amendment to the Finance Bill in the hope of stopping the government raising money to implement a no-deal Brexit, without the explicit consent of Parliament.
The technical changes to a crucial piece of government legislation are intended to demonstrate to the government the strength of opposition to a no-deal Brexit in the Commons.
Government sources warned over the weekend of "paralysis" and an effective "shutdown" if the Treasury was stripped of the power to pass regulations relating to "no-deal financial provisions" without parliamentary approval.
Labour have said they will back the amendment, prompting speculation that ministers will be forced to accept it in order to avoid a damaging defeat.
If the government does not back down, a vote on the amendment is expected at about 19:00 GMT.
The UK is scheduled to leave the EU on 29 March whether there is a deal or not.
The deal which Prime Minister Theresa May has negotiated with the EU - which covers the terms of the UK's divorce and the framework of future relations with the EU - has not been formally approved.
MPs are expected to vote on 15 January following five days of debate in the Commons.
Brexit Secretary Stephen Barclay has said the UK remains committed to leaving on 29 March after the Daily Telegraph said UK officials had been "putting out feelers" about extending Article 50, the mechanism taking the UK out of the EU.
Mr Barclay said he had not spoken to the EU about that and any delay would cause "some very practical issues".
His remarks came the day after Digital Minister Margot James suggesting Article 50 might have to be extended in order to stop a no-deal Brexit if Mrs May's deal is rejected by Parliament.
The BBC's Brussels reporter Adam Fleming said extending Article 50 was the "default" back-up plan for the EU if MPs did not agree to the Brexit deal, although he was not aware of any officials who had discussed it at this stage.
A no-deal Brexit would see the UK leave without a withdrawal agreement and start trading with the EU on the basis of World Trade Organization rules, an outcome favoured by some Brexiteers.
David Davis, one of Mr Barclay's predecessors as Brexit secretary, told the BBC the fact that EU officials were talking about re-opening negotiations "tells you that Mr Barclay's assertion that this is the only deal on the table is not, actually, entirely accurate".
"Because what actually is going on, is the Europeans are thinking about the next stage, and the next stage is another round of negotiation," he told Radio 4's Today.
He was speaking after Irish premier Leo Varadkar said the EU would offer the UK government fresh "written" assurances to help Mrs May get her deal through Parliament.

It would take a "miracle" for Brexit talks to progress quickly enough to persuade the EU to start discussing trade soon, a top official has said.
EU Commission President Jean-Claude Juncker agreed progress had been made between the two sides this week.
But asked if it was enough to persuade the EU to agree to open trade talks, as the UK wants, at a summit next month, he replied only if "miracles happen".
But British PM Theresa May said she was "pleased" with recent developments.
Speaking in Estonia, where she is attending an EU security summit, Mrs May said there had been movement on issues such as citizens' rights during the fourth round of Brexit talks which concluded on Thursday.
British negotiators, led by Brexit Secretary David Davis, suggested there had been "decisive" steps forward although his EU counterparts have been more cautious, suggesting there was a lot more work to be done.
At a meeting next month, the other 27 EU leaders could decide whether "sufficient progress" has been made in the talks to date, which have focused on separation issues such as the Irish border and money, to move on to to consider the UK's future relationship with the EU after it leaves in March 2019.
Asked for his view as he arrived at the summit in Tallinn, Mr Juncker replied: "By the end of October we will not have sufficient progress."
While he acknowledged "we are making progress", he said "at the end of this week I am saying there will be no sufficient progress from now until October, unless miracles would happen".
European Council President Donald Tusk - who represents the EU 27 - has already suggested meeting the deadline is unlikely, while the EU's chief negotiator Michel Barnier has said a decision on opening the second phase of talks could be "weeks or months" away, amid speculation it could slip to December.
Mrs May was more bullish as she arrived, suggesting that there had been progress in the seven days since she gave a number of guarantees - including on honouring contributions to the EU budget - in a speech in Italy.
"In Florence, I set out the progress that has been made in the negotiations and my vision for a deep and special partnership with the EU," she said.
"I am pleased with the progress in the negotiations, and look forward to developing that special partnership as it's in the interests of EU as well."
Meanwhile, Irish Prime Minister Leo Varadkar has suggested this week's Boeing-Bombardier trade dispute illustrated the difficulties the UK could face in doing trade deals with other countries after leaving the EU.
"I think it could well turn out to be a lesson for the UK," he said in Tallinn. "I think it should that we are stronger together as a trading bloc, and that is something for people to consider."
At Friday's summit, Mrs May will make it clear to EU leaders that the UK is ready to continue contributing troops, equipment and money to EU operations and align foreign policy with Brussels where appropriate.
Addressing British troops stationed in the the country earlier, Mrs May said the UK was not leaving Europe and was "unconditionally committed to maintaining Europe's security".
Some 800 troops have been in Tapa since April, alongside Estonian and French forces, as part of a Nato effort to reassure eastern European nations fearful of Russia's increasing assertiveness.

Theresa May has said it is still possible to get the assurances MPs need to back her Brexit deal, despite EU leaders ruling out any renegotiation.
At a summit in Brussels, the UK PM said there was "work to do" but talks on "further clarification" would continue.
She admitted a "robust" discussion with European Commission President Jean-Claude Juncker, after he complained about "nebulous and imprecise debate".
Labour said the withdrawal deal was now "dead in the water".
The UK prime minister travelled to Brussels to make a special plea to EU leaders after delaying Tuesday's Commons vote on the deal, in anticipation of a heavy defeat.
She then went on to win a confidence vote brought by her own MPs but vowed to listen to the concerns of the 37% of Tory MPs who voted against her.
Many of them are concerned that the controversial "backstop" plan in the withdrawal agreement Mrs May has negotiated, which is aimed at preventing a hard border in Northern Ireland, would keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
Elsewhere on Friday, former UKIP leader Nigel Farage told a Leave Means Leave rally in London it was time for Brexit supporters to prepare for the possibility of another referendum.
Mr Farage added the treatment of Mrs May in Brussels this week had been a "shaming moment" for both the UK and the EU and that the PM's Brexit deal was now "dead".
Labour MP Kate Hoey and Wetherspoons chairman Tim Martin were among the other speakers at the rally.
After Mrs May addressed EU leaders at the summit on Thursday evening, Mr Juncker urged further clarity from the UK.
He said: "Our UK friends need to say what they want, instead of asking us to say what we want... because this debate is sometimes nebulous and imprecise."
Video footage of the two on Friday morning captured a tense exchange, apparently about his remarks, although the exact words were not audible.
Asked about what she had said to him, Mrs May told reporters: "I had a robust discussion with Jean-Claude Juncker - I think that's the sort of discussion you're able to have when you have developed a working relationship and you work well together.
"And what came out of that was his clarity that actually he'd been talking - when he used that particular phrase - he'd been talking about a general level of debate."
At a later press conference, Mr Juncker described Mrs May as a "good friend" who he admired as a "woman of courage".
He said he hadn't realised nebulous was a word in English and he had been referring, not to her, but to the "overall state of the debate in Britain".
He said: "I can't see where the British parliament is heading. That's why I was saying that it was nebulous - foggy in English - I was not addressing her."
He also said: "We have to bring down the temperature" of the debate amid "attacks coming from Westminster against Europe and the European Commission".
Various EU leaders, including European Council President Donald Tusk, Mr Juncker and Irish PM Leo Varadkar, reiterated on Thursday that there could be no renegotiation of the withdrawal deal.
And a paragraph which had appeared in the draft conclusions at the start of the summit, saying that the EU "stands ready to examine whether any further assurance can be provided" did not appear in the final conclusions.
But Mrs May said that, despite reports that the EU was unwilling to consider further clarification, she had talked to Mr Tusk, Mr Juncker and others that morning which "have shown that further clarification and discussion following the council's conclusions is in fact possible".
She also welcomed commitments by other EU leaders to try to get a new trade deal in place "speedily" so that the backstop would not be needed and said that, as formal conclusions from the summit, they had "legal status".
But she added: "There is work to be done. It is clear we can look at this issue of further clarification. We will be working expeditiously over the coming days to seek those further assurances I believe MPs will need."
BBC Brussels reporter Adam Fleming said the fact that the EU said it would use its "best endeavours" to get a future trade deal that would get rid of the need for a backstop - even if the backstop came into force - was seen as important by British officials who said it meant the UK could go to an independent arbitration panel if they felt the EU was dragging its feet.
Labour leader Jeremy Corbyn said: "The last 24 hours have confirmed that Theresa May's Brexit deal is dead in the water. The prime minister has utterly failed in her attempts to deliver any meaningful changes to her botched deal.
"Rather than ploughing ahead and dangerously running down the clock, the prime minister needs to put her deal to a vote next week so Parliament can take back control."
And Conservative Brexiteer Mark Francois told the BBC: "It is as plain as a pikestaff that this will never get through the House of Commons... the prime minister, I'm afraid, is completely boxed in."
The Democratic Unionist Party, on whom Theresa May relies for her Commons majority, said she must deliver "legally binding changes" to the withdrawal agreement if she wants her deal to get through Parliament.
Its leader Arlene Foster said the prime minister "has made commitments" to the DUP and "knows what she has to deliver on".
Meanwhile, the UK and Switzerland have provisionally agreed to keep their current trading rules after Brexit, the first of 40 existing EU trade deals with other countries the UK hopes to adopt.
The agreement, which will replicate the EU's current arrangement with Switzerland as closely as possible, is due to come into place at the end of 2020 when the Brexit transition phase ends.
But it could come into force at the end of March if the UK leaves with no deal.
The BBC's Brussels reporter Adam Fleming
Theresa May's mission to Brussels has not been a failure.
She has a written statement from her 27 fellow leaders confirming - reconfirming, really - that the Irish backstop is an insurance policy which would only ever be temporary.
If the backstop is activated, then the EU would use its "best endeavours" to negotiate a trade deal, which would mean it could be deactivated. That wording is crucial, say British officials, because it means the UK could refer the EU to the independent arbitration panel established in the Brexit treaty if London felt Brussels was moving too slowly.
The EU dropped a commitment to look for further ways to help the UK, which means there won't be a formal process to find them.
But it doesn't mean the search couldn't happen informally, or in private, or at the last minute.
The problem is that these commitments are unlikely to impress Theresa May's harshest critics. And they certainly wouldn't fit on the side of the bus as reasons to sign up to Mrs May's Brexit deal.

MPs will get another chance to vote on Brexit this month - even if Theresa May has not been able to negotiate a deal by then.
Housing Secretary James Brokenshire admitted it might not be the final, decisive vote on the PM's deal that Labour and some Tories are demanding.
The prime minister needs to get a deal approved by Parliament by 29 March to avoid a no-deal Brexit.
Labour has accused her of "cynically" running down the clock.
Instead of a "meaningful" vote on the prime minister's deal with the EU, MPs could be given another series of non-binding votes on possible Brexit alternatives by 27 February, with the final vote on whether to approve or reject the deal delayed until the following month.
On Wednesday, Mrs May will ask MPs for more time to get legally-binding changes to the controversial Northern Irish backstop, which she believes will be enough to secure a majority in Parliament for her deal.
But the following day, Labour will attempt to force the government to hold the final, "meaningful vote" on Mrs May's Brexit deal by 26 February.
Mr Brokenshire refused to commit to this date in an interview with the BBC's Andrew Marr Show, saying there could be more votes on amendments to the proposed deal instead.
"If the meaningful vote has not happened, so in other words things have not concluded, then Parliament would have that further opportunity by no later than 27 February," said Mr Brokenshire.
"I think that gives that sense of timetable, clarity and purpose on what we are doing with the EU - taking that work forward and our determination to get a deal - but equally knowing that role that Parliament very firmly has."
He also ruled out removing the Irish backstop from the government's deal with the EU, as some Conservative MPs are demanding.
He said ministers were exploring a possible time-limit to the backstop, or a legal mechanism allowing the UK to exit the backstop without the agreement of the EU, but he insisted some kind of "insurance policy" was needed to keep the Irish border free-flowing.
But Labour's shadow Brexit secretary, Sir Keir Starmer, says he believes the prime minister is "pretending to make progress" on the Irish backstop issue.
He says what she actually intends to do is return to Parliament after the 21/22 March European Council summit the week before Brexit and offer MPs a "binary choice" - her deal or no deal.
"We can't allow that to happen," Sir Keir told The Sunday Times.
"There needs to be a day when Parliament says that's it, enough is enough."
Lib Dem leader Sir Vince Cable said delaying the final vote on the Brexit deal was "worse than irresponsible" and he "would not be surprised if [Theresa May] faces a massive rebellion by Conservative MPs".
Conservative MP Sarah Wollaston, who like Sir Vince has campaigned for another EU referendum, called for ministers who were "serious" about preventing a no-deal Brexit to resign and vote against the government.
Fellow Conservative MP Heidi Allen also called for ministerial resignations, saying it was "completely irresponsible" for the government to keep delaying the final Brexit vote.
Labour is proposing its own Brexit plan, which would involve the UK staying in a customs union with the EU, which they say could get the backing of a majority of MPs.
The government has not ruled out supporting this - and has promised a formal response to it and further talks with Labour - but they say it would prevent the UK from making its own trade deals after Brexit.
There are fewer than 50 days until Brexit. The law is already in place which means the UK will leave the EU on 29 March 2019.
Mrs May's Brexit deal - which she spent months negotiating and had agreed with the EU - covers the terms of the UK's divorce and the framework of future relations.
But it was rejected by the UK Parliament and if it is not approved by Brexit day, the default position would be a no-deal Brexit.
Last month, Parliament voted in favour of an amendment that supported most of the PM's deal but called for backstop - which is a last-resort option to prevent a hard border in Ireland - to be replaced with "alternative arrangements". The prime minister is now in talks with Brussels to seek these changes to the backstop.
A number of government ministers will also be meeting their counterparts across the continent this week, in order to underline Mrs May's determination to achieve a deal.
Critics of the backstop in Mrs May's current deal say they could tie the UK to EU rules indefinitely or mean Northern Ireland ends up under a different system to the rest of the UK.
But the Irish government and the EU have repeatedly rejected calls for changes.
Other options likely to be debated by MPs on Thursday include extending Article 50, the legal mechanism taking the UK out of the EU on 29 March, to allow more time to reach an agreement with Brussels.

Former education secretary Nicky Morgan has warned pro-Brexit Tories against "sabre-rattling" over the UK's future customs arrangements with the EU.
She said speculation that Theresa May could face a challenge if MPs ended up backing some form of post-Brexit customs union was "deeply unhelpful".
MPs are to debate a backbench motion on Thursday calling for the UK to retain this type of arrangement after Brexit.
Labour says a union of sorts is the way forward but ministers reject this.
Downing Street's position is that staying within the EU customs union or joining some new form of union would restrict the UK's ability to strike trade deals with other countries and therefore be unacceptable.
The government is instead looking at two options after the UK leaves on 29 March 2019 - a new customs partnership with the EU - under which there would continue to be no customs border between the EU and UK - or a "highly streamlined customs arrangement" using technology to facilitate the movement of goods.
Labour, the Lib Dems and the SNP, plus some Conservatives, believe that only a fully-fledged union will protect existing trade. They say it is also the only viable way to avoid a hard border on the island of Ireland.
Thursday's backbench debate was tabled by senior cross-party MPs, including Ms Morgan, after ministers lost a vote on the issue in the Lords last week.
Although the vote will not be binding, it has raised temperatures in the Conservative Party and led to unconfirmed reports that top ministers might quit if the government has to concede defeat on the issue at some point in the future.
Speaking on the BBC's Sunday Politics, Mrs Morgan, the Treasury committee chair who is one of the most pro-EU voices in the party, said the PM's stated objective was to have frictionless trade and MPs should be able to "tease out" the best way to achieve this in a "calm and rational" way.
"If every time Parliament debates this issue or passes an amendment all we end up with is a sort of hysteria and leadership speculation, that is really not in Britain's interests," she said.
"All this sabre-rattling this weekend is not coming from the section of the party that I represent. It is coming from the pro-Brexit section of the party. And it is deeply unhelpful."
Although some MPs have questioned the point of Thursday's debate, Mrs Morgan said the views of businesses and constituents worried about the impact of Brexit on their livelihoods ought to be discussed in Parliament.
But Chief Secretary to the Treasury Liz Truss told Radio 5 Live's Pienaar's Politics it was very important that Parliament didn't seek to "bind the prime minister's hands" when it came to negotiations on a future customs framework.
"It's already a negotiation that has a lot of complex aspects to it," she said.
And Justice Secretary David Gauke said the government had to make and win the case that leaving the EU customs union would not result in "unnecessary barriers".
For Labour, shadow foreign secretary Emily Thornberry told the BBC's Andrew Marr show the opposition was committed to leaving the EU but doing so in a "pragmatic" way which did not puts jobs at risk.
"I think anybody who has looked into this issue has seen that it is quite clear that there is no other place that we can go than to remain in a customs union with the European Union - nothing else makes sense."
No 10 sources told the Press Association policy had not changed and the UK was leaving the customs union.

The group representing hospitals and ambulance services in England has warned of a lack of "contingency planning" to deal with the impact of a no-deal Brexit on the health service.
In a leaked email to NHS England boss Simon Stevens, NHS Providers says leaving the EU without agreement would immediately be a real risk to services.
The group warns it would make it harder to stop the spread of diseases.
NHS England said preparing for every possible Brexit outcome was a priority.
The Department of Health said it was confident of reaching a Brexit deal that benefits the NHS but was preparing for "the unlikely event of no-deal", to prevent disruption to patients.
It comes as Brexit Secretary Dominic Raab holds the latest round of negotiations with his EU counterpart Michel Barnier.
The UK is set to leave the EU on 29 March 2019 and the two sides are currently negotiating the terms of its exit and its future relations in a whole range of issues.
NHS Providers - which represents acute, ambulance, community and mental health services within the health service - has expressed concern about what it says is a lack of engagement with ministers in the email, seen by the BBC.
It has called for NHS England and NHS Improvement - which oversees NHS trusts and providers - to convene a group of trust leaders as a matter of urgency.
In an email sent to NHS chief executive Simon Stevens, also copied in to Mr Raab and Health Secretary Matt Hancock, it calls for a co-ordinated response to confront the challenges that would be presented by a no deal.
Chief executive of NHS Providers Chris Hopson writes that there has been "no formal communication" to trusts from either NHS England or NHS Improvement on this issue.
Without national planning and coordination "there could be both stockpiles and shortages of medicines and medical devices", Mr Hopson says.
He adds that "disease control coordination could also suffer".
Mark Dayan, policy analyst at the Nuffield Trust, said "a large degree of chaos" was "implicit" in a no-deal Brexit and, without a transitional agreement with the EU, it was difficult to predict the impact on supply of medicines.
"There's obviously been talk of stockpiling. There's been talk in some cases of chartered flights to bring over supplies that maybe don't have such a long shelf-life. And although that's drastic action, it's probably quite justified," he told BBC Radio 4's Today programme.
An NHS England spokeswoman said the health service was working with government, planning for different post-Brexit scenarios.
"We will be working with our colleagues and partners across the NHS to ensure plans are well progressed, and will provide the NHS with the support it needs," she said.
Labour MP Ben Bradshaw, who supports the People's Vote campaign for a referendum on the final Brexit deal, said the NHS letter was a "stark and urgent warning of the impact of a hard Brexit or no deal and of non-existent planning".
Another supporter of the campaign, Tory MP Sarah Wollaston, said another referendum would be like seeking "informed consent" from a patient before a major operation.
A series of technical notices - including advice for businesses, citizens and public bodies about a no-deal scenario - will be made public over the next month or so.
Downing Street has described the advice due on Thursday as "sensible, proportionate, and part of a common sense approach to ensure stability, whatever the outcome of talks".
On the same day, Mr Raab will make a speech in Westminster to outline the government's plans for the possibility of leaving the EU without a deal.
The UK is seeking "associate membership" of the European Medicines Agency, which evaluates and supervises medicines and helps national authorities authorise the sale of drugs across the EU's single market.

The Northern Ireland Assembly has passed a motion withholding consent for the UK's withdrawal from the European Union.
The motion put forward by the Executive Office asked MLAs to consider parts of the Brexit bill that affected Northern Ireland.
It passed without a formal division on Monday.
All 18 Westminster MPs from Northern Ireland opposed the prime minister's Brexit deal last month.
The bill includes a role for the assembly in deciding whether Northern Ireland should still follow some EU customs rules.
The motion was to "affirm that the assembly does not agree to give its consent" to that.
A request by the TUV leader Jim Allister for the assembly debate to be delayed until next week was rejected by MLAs.
Mr Allister argued the Executive Office had only submitted the motion on Friday and that there had not been enough time for MLAs to propose amendments.
The Speaker Alex Maskey said it was "regrettable" the motion had not been tabled earlier.
First Minister Arlene Foster apologised for the short notice, but said she felt it was important the assembly had its say on the matter before the EU Withdrawal Bill receives its third reading in the House of Lords on Tuesday.
A former secretary of state has said the government's Brexit plans will do "untold damage" to Northern Ireland businesses.
Labour's Lord Hain said the government was asking small and medium businesses in Northern Ireland to "buy a pig in a poke".
He said NI businesses have been told they would just have to adjust to new regulations, but it was still not clear what those would be.
Lord Hain also accused the government of "trying to have it both ways".
"On the one hand they're saying to businesses in Northern Ireland and to politicians it's important that you reform and make the Northern Ireland economy more competitive - fair enough," he said.
"But then they are imposing enormous shackles on the ability of enterprises to succeed with these uncertain, potentially costly, administerially difficult burdens that they will have to bear for trading across into Great Britain."
He added: "I don't think the government is being fair with Northern Ireland - either its businesses or its politicians - by telling them they have to reform and on the other hand making it more difficult for them to do so by weakening the economy."
After the UK leaves the EU on 31 January, it will enter an 11-month transition period, where it will largely follow EU rules but will not have any representation in the bloc's institutions.
At the end of the transition period, Northern Ireland will continue to follow EU rules on agricultural and manufactured goods, while the rest of the UK will not.
Additionally, the whole of the UK will leave the EU's customs union but Northern Ireland will continue to enforce the EU's customs code at its ports.
This will mean some new checks and processes for goods moving between Northern Ireland and other parts of the UK.
The details of those processes have to be negotiated between the EU and UK and new systems for businesses will have to implemented.

Northern Ireland must stay in a "full UK customs union" after Brexit, the Democratic Unionist Party's (DUP) deputy leader Nigel Dodds has said.
His comment came as UK and EU officials held what were described as "intense" talks in a bid to secure a new deal.
Neither side has given details about the common ground that has reportedly been found on the Irish border issue.
Mr Dodds said: "There is a lot of stuff coming from Brussels, pushed by the Europeans in the last hours.
"One thing is sure - Northern Ireland must remain fully part of the UK customs union and Boris Johnson knows it very well," he told the Italian newspaper La Repubblica.
Negotiations between the UK and the EU are taking part at the EU Commission in Brussels and are expected to continue on Sunday.
A summit of European leaders is due to take place next Thursday and Friday is seen as the last chance to agree a deal before 31 October - the date the UK is due to leave the EU.
Plans by Prime Minister Boris Johnson to avoid concerns about hard border on the island of Ireland after Brexit were criticised by EU leaders at the last week.
But he held talks with Taoiseach (Irish Prime Minister) Leo Varadkar on Thursday, with both leaders saying they could "see a pathway to a possible deal".
Since then, European Council President Donald Tusk has suggested there was only the slightest chance of an agreement.

Northern Ireland should remain in the single market and customs union after Brexit, four political parties have said.
They said there should be no hard border on the island of Ireland or between Ireland and the UK.
"This is critical to protecting investment, jobs, trade and the hard-won peace," the statement said.
It was signed by the leaders of the four parties: Michelle O'Neill, Steven Agnew, Naomi Long and Colum Eastwood.
The leaders said this week was "another crucial stage in the Brexit negotiations".
"All of the outstanding issues relating to the withdrawal agreement will be considered in relation to Northern Ireland/Ireland and the future relationship," they said.
"Theresa May has agreed that a backstop solution for the border will form part of the legal text of the withdrawal agreement, and that this backstop would apply, unless and until, another solution is found."
The leaders said time was "of the essence" in the run-up to June's meeting of the European Council.
The statement added that the protection of the Good Friday Agreement, including north/south and east/west co-operation, was "critical to maintaining relationships within, and between these islands".
It said that the backstop agreed by both the British Government and the EU27 was "the bottom line in order to safeguard our political and economic stability now and for the future".
Mrs O'Neill told BBC Good Morning Ulster: "In the contexts of Brexit, we need to see the interests of the people here being protected and that's why it's significant that the parties have come together to say very clearly that they have a very strong mandate, that they represent the majority view of the assembly, that people want to stay in the customs union and the single market.
"It's important that, as we reach this crunch time in negotiations, that negotiators hear the voice of the mandate which we've been given."
But DUP deputy leader Nigel Dodds said the statement "is silent about the catastrophic damage that would be done to Northern Ireland" if separated economically from the UK.
The MP added: "It is devoid of reality since even the Labour party has made clear that the UK is leaving the single market and cannot stay in the customs union.  And it is politically ironic since its main author, Sinn Fein, calls for it to be heard while it simultaneously prevents the formation of the Executive, the recall of the assembly, and actually boycotts Westminster where the main decisions are being discussed and decided."
Mr Dodds also said that any "so-called backstop arrangement must be a UK-wide solution" as the DUP's position remains "that there can be no border in the Irish Sea".
The DUP's 10 MPs are helping to keep Prime Minister Theresa May in power as part of a confidence and supply deal.
However, the party has made it clear that if the Irish Sea became a de facto trade border, it would withdraw its support for the Conservative government.
The UK is scheduled to leave the European Union at 23:00 UK time on Friday 29 March 2019.

Ireland's deputy prime minister has ruled out any renegotiation of the Brexit withdrawal deal if Theresa May is replaced as UK prime minister.
Speaking on RTÉ, Tánaiste Simon Coveney said "the personality might change but the facts don't".
He described Mrs May as a "decent person" and strongly criticised Conservative MPs at Westminster.
Mrs May has promised to set a timetable for the election of her successor after the next Brexit vote.
Mr Coveney described political events at Westminster as "extraordinary", as he questioned the logic of politicians who believed a change of leader would deliver changes to the agreement struck by Mrs May.
He said Conservative MPs were "impossible" on the issue of Brexit.
"The EU has said very clearly that the Withdrawal Agreement has been negotiated over two-and-a-half years, it was agreed with the British government and the British cabinet and it's not up for renegotiation, even if there is a new British prime minister," he said.
He told RTÉ's This Week programme that many British politicians "don't, quite frankly, understand the complexity of politics in Northern Ireland".
"They have tried to dumb this debate down into a simplistic argument whereby it's Britain versus the EU, as opposed to two friends tying to navigate through the complexity of a very, very difficult agreement," he added.
Mr Coveney also said the Irish government would continue to focus significant efforts and financial resources towards planning for a no-deal Brexit scenario, following Friday's collapse of Brexit talks in the UK.
He said time was of the essence for the UK to get a deal through Parliament, adding that he was concerned Britain would not "get its act together over summer" and leave without a deal.
On Wednesday, Mrs May announced that MPs would vote on the bill that would pave the way for Brexit in the week beginning 3 June.
If the bill is not passed, the default position is that the UK will leave the EU on 31 October without a deal.
Brexit had been due to take place on 29 March.
But the UK was given an extension until 31 October after MPs three times voted down the withdrawal agreement Mrs May had negotiated with the EU - by margins of 230, 149 and 58 votes.

The government has delivered its new Brexit proposals to the EU, including plans to replace the Irish backstop.
The plan, outlined in a seven-page document, would see Northern Ireland stay in the European single market for goods, but leave the customs union - resulting in new customs checks.
The Northern Ireland Assembly would get to approve the arrangements first and vote every four years on keeping them.
The European Commission said there had been progress but "problems" remained.
Irish Prime Minister Leo Varadkar said the new blueprint did not "fully meet the agreed objectives of the backstop", in terms of upholding the EU's single market, protecting peace in Northern Ireland and supporting economic co-operation with the Republic of Ireland.
But he said he wanted an agreement and talks would continue.
The UK is set to leave the EU on 31 October and the government has insisted it will not negotiate a further delay beyond the Halloween deadline.
Speaking at the Conservative Party conference earlier on Wednesday, Boris Johnson said the only alternative to his Brexit plan was no-deal.
In a letter to European Commission's president, Jean-Claude Juncker, the prime minister said the new proposals "respect the decision taken by the people of the UK to leave the EU, while dealing pragmatically with that decision's consequences in Northern Ireland and in Ireland".
Government sources hoped the UK might be able to enter an intense 10-day period of negotiations with the EU almost immediately, with the aim of coming to a final agreement at an EU summit on 17 October.
Mr Juncker welcomed what he said were "positive advances" in some areas but he said the UK's proposed system of "governance" of the new arrangements was "problematic" - and customs rules remained a concern.
Don't expect the EU to rush to reject the prime minister's proposals even though there are elements that clearly contravene EU red lines, such as the implementation of any kind of customs procedures between Northern Ireland and the Republic of Ireland.
Jean-Claude Juncker spoke today of "concerns" arising from the text but EU leaders won't want to be seen to be the ones closing the door to a deal.
Throughout the Brexit process they've repeatedly kicked the ball back into the UK government's court.
On cue, leaders are "welcoming the delivery of the proposals from the government" and inviting the prime minister to continue negotiations.
The fundamental questions for the EU remain: How much does does the prime minister really want a deal? Is he willing to move from his apparent "take it or leave it" position?
If he is, there will be something to talk about. If not, the EU will try its best to avoid being the ones to say "forget it".
But Mr Johnson should think again if he imagines his proposals, which do include concessions from his side, will prompt EU countries with a lot to lose in a no deal Brexit (like Germany) to try to force Ireland to accept his offer.
Angela Merkel today insisted EU leaders would stick together. With such an important EU member leaving, Mrs Merkel believes unity amongst those left behind is paramount.
Arlene Foster, leader of Northern Ireland's Democratic Unionist Party, supported the plan, saying it would allow Northern Ireland to leave the customs union and single market at the same time as the rest of the UK.
Several Conservative MPs who opposed Theresa May's agreement also signalled their likely support, with leading Brexiteer Steve Baker saying he was "cautiously optimistic".
But Sinn Fein said the plans were a "non-starter" and accused the DUP, their former power-sharing partners of "working against the interests of the people" of Northern Ireland.
And Labour leader Jeremy Corbyn said the deal was "not acceptable" and "worse" than Theresa May's agreement, as it "undermined" the Good Friday Agreement that secured peace in Northern Ireland.
The prime minister has set out details of his plan to replace the Irish border "backstop" in the current Brexit agreement.
The backstop is the controversial "insurance policy" that is meant to keep a free-flowing border on the island of Ireland but which critics - including the PM - fear could trap the UK in EU trading rules indefinitely.
Under Mr Johnson's proposals, which he calls a "broad landing zone" for a new deal with the EU:
The government is also promising a "New Deal for Northern Ireland", with financial commitments to help manage the changes.
German Chancellor Angela Merkel, who has spoken to Mr Johnson, said the EU would study the proposals carefully.
She said she "trusted" the bloc's Brexit negotiator Michel Barnier to maintain European unity.
But opponents of Brexit in Parliament indicated they would not support the proposals, unless they were accompanied by the promise of another referendum.
The Liberal Democrats, who want to stop Brexit, said the proposals would deal a "hammer blow" to the Northern Irish economy.
The Scottish National Party dismissed the proposals as "window dressing".

A new referendum on the UK's relationship with the EU is "an option for the future" but "not an option for today", Jeremy Corbyn has said.
The Labour leader confirmed on Sky News that his party would vote against the draft withdrawal agreement.
Mr Corbyn said Labour "couldn't stop" Brexit because it does not have enough seats in Parliament.
Prime Minister Theresa May has said that ousting her would not make it easier to deliver Brexit.
Asked about calls for a further referendum as demanded by some of his MPs, Mr Corbyn said: "If there was a referendum tomorrow what's it going to be on, what's the question going to be?"
If such a referendum were called, Mr Corbyn, who voted Remain in 2016, said: "I don't know how I am going to vote - what the options would be at that time."
Speaking on the Sophy Ridge on Sunday programme, the Labour leader said Mrs May's draft deal with the EU was a "one-way agreement" where the EU "calls all the shots".
It also failed to guarantee environmental protections or workers' rights, he said.
"We'll vote against this deal because it doesn't meet our tests. We don't believe it serves the interest of this country, therefore the government have to go back to the EU and renegotiate rapidly."
Mr Corbyn said Labour would focus on negotiating a permanent customs arrangement with the EU, otherwise the UK would "lose on jobs, lose on investment and we lose on future economic development".
But he admitted he had not read all 585 pages of the draft withdrawal agreement, saying: "I've read a lot of it."
On the same programme, Mrs May said further negotiations with the EU were taking place but that MPs should ensure "we deliver what people in this country voted on".
She warned rivals thinking of replacing her as Conservative leader: "It is not going to make the negotiations any easier and it won't change the parliamentary arithmetic."

Labour frontbencher Emily Thornberry has told the BBC "all options remain on the table", including a new referendum, if MPs vote down a Brexit deal.
She was asked about party leader Jeremy Corbyn's comment to a German newspaper that Brexit cannot be stopped.
Labour would prefer a general election, she said, but could campaign for "a People's Vote" if it were not possible.
Tory cabinet minister Damian Hinds said MPs must "consider the alternatives" if they vote down the deal.
The government has not yet agreed a withdrawal deal with the European Union, ahead of the UK's exit from the bloc next March.
While the UK government says it is 95% agreed - they have been unable to agree on the mechanism for ensuring that there will be no return to border checks between Northern Ireland and the Irish Republic, if a future trade deal is not ready in time.
On Friday, transport minister Jo Johnson, who voted to remain in the EU, quit the government saying he could not support the deal and called for another referendum.
Meanwhile Tory Brexiteer Steve Baker and Sammy Wilson, Brexit spokesman for the DUP - whose party's support Theresa May relies on for key Commons votes - have written a joint article in the Sunday Telegraph warning they are prepared to vote down any deal over proposals to manage the Irish border issue.
On Saturday, Jeremy Corbyn was quoted in Der Spiegel, having been asked if he would stop Brexit, as saying: "We can't stop it, the referendum took place."
Asked if Brexit could be stopped on BBC One's Andrew Marr Show, Ms Thornberry said the results of the referendum should be "abided by" but there had to be an "injection of democracy" in between that result and going any further. That should be a "meaningful vote" in Parliament, she said.
But she said Theresa May was only offering a choice between the UK "falling off a cliff" - with no deal agreed - or "get on this bridge to nowhere", by backing her deal. She said Labour would refuse to "play that sort of game" and, if the vote was lost, the party wanted a general election.
She added: "If we don't have a general election, which we think we should have, then yes of course all the options remain on the table and we would campaign for there to be a People's Vote but, you know, there are several stages before we get there."
The People's Vote campaign group organised the march in London in October which it said attracted about 700,000 people. The group wants a referendum on the final withdrawal deal.
Ms Thornberry said Mr Corbyn's comments had to be seen in context and he was explaining that: "We had a referendum, that we are democrats over and above everything else."
At the Labour Party conference in September, party members approved a motion that would keep all options - including a fresh referendum - on the table if MPs are deadlocked over Brexit. Mr Corbyn has said he would respect the result of the vote.
Labour's shadow Brexit secretary Sir Keir Starmer wrote in the Sunday Times: "There is no duty on MPs to surrender to a bad deal."
Instead, he said that MPs would be able to table motions, press amendments and trigger a no-confidence vote in order to prevent the UK leaving without a deal at all.
Sir Keir said: "I remain as convinced as ever that the consequences of no deal would be so severe that it cannot be allowed to happen."
But Education Secretary Damian Hinds told the BBC that people would have to consider a deal as a whole, stating: "They need to think about what the alternatives are as well.
"It is no good just not liking individual aspects. If you're going to take that view, you have got to have in mind a realistic, viable, deliverable alternative.
"I think people are going to be getting behind this deal and saying 'yeah, let's get on with it'."
He added: "It is not necessarily going to be something everybody is going to think is absolutely perfectly what they want.
"But that's the nature of these things, there are some trade-offs."

The government says it will try to get Theresa May's Brexit deal through the Commons, despite Speaker John Bercow throwing the process into doubt.
Brexit Secretary Stephen Barclay suggested a vote could take place next week - after Mrs May has sought a delay to Brexit from the EU.
Mr Bercow has ruled that the PM can not bring her deal back for a third vote without "substantial" changes.
The UK is due to leave the EU in 10 days with or without a deal.
The prime minister had hoped to have another try at getting MPs to back the withdrawal deal she has agreed with the EU this week - but Speaker Bercow effectively torpedoed that with his surprise intervention on Monday.
Stephen Barclay told BBC Radio 4's Today programme the Commons Speaker had made a "serious ruling" and ministers were giving it "serious consideration".
He said it was important to "respect the referee" and abide by his decisions - but, he added, Mr Bercow himself had said, in the past, that if Parliament was guided only by precedent then "nothing ever would change".
Mr Bercow cited a ruling from 1604 to justify his decision to block a third vote, after the PM's deal was rejected for a second time last week, by 149 votes.
Mr Barclay suggested that MPs would "find a way" to get another vote, if the government manages to persuade enough of them, including the 10 Democratic Unionists, to change their mind and back the deal.
He suggested it would also depend on Theresa May getting "clarity" from the EU on the "terms of an extension" to Brexit.
He accepted that there would now have to be a "short extension" to the Article 50 withdrawal process if the deal gets through Parliament, to get the necessary legislation through.
Mrs May is writing to European Council President Donald Tusk to ask for an extension.
The PM has warned Brexiteer Tories that a long extension may be needed if they do not back her deal but Downing Street said it would not reveal what the PM has asked for at this stage.
There would, however, need to be a vote in both Houses of Parliament to change the 29 March departure date, which is written into law, the PM's spokesman said.
Mr Bercow refused to discuss his decision when quizzed by the BBC, as he made his way to Parliament earlier.
Government ministers and MPs have been floating different ideas on how to get a vote on the prime minister's deal, in light of the Speaker's ruling.
Children and Families' minister Nadhim Zahawi told BBC Newsnight that one of the options was for MPs to vote on whether to ignore the 400-year-old convention that Mr Bercow had cited in making his ruling.
Mr Zahawi, who is a Brexiteer, was asked whether the government was going to bypass Mr Bercow's ruling. He said: "Let's see, we have to look at all our options."
Solicitor General Robert Buckland said a vote to overrule the Speaker was the most likely way forward.
He told BBC Radio Wiltshire that if enough MPs show they want another vote on the Brexit deal, it can return to Parliament despite the current block.
He said this would be a more practical solution than asking the Queen to formally close and reopen Parliament, which some have suggested would get round the rule that MPs cannot be repeatedly asked to vote on the same question in a Parliamentary session.
Nikki da Costa, former director of legal affairs at Downing Street, told the Today programme: "I think the PM and the government can still have a third meaningful vote... but it will be extraordinarily difficult to have a fourth meaningful vote so I think MPs really have to think very carefully if that vote does come back."
There is also a question mark over whether any agreement reached by Theresa May in Brussels on extending Brexit would overrule a vote by MPs, as it would have force under international law.
German Chancellor Angela Merkel said she would struggle until the last possible moment to achieve an orderly Brexit, saying the interests of Germany, Britain and the EU were at stake.
"I will fight to the last hour of the deadline on 29 March for an orderly exit," she told a press conference in Berlin. "We don't have a lot of time for it but still have a few days."
EU ministers are, meanwhile, meeting in Brussels to prepare for this week's summit.
Germany's Europe minister, Michael Roth, said: "Our patience is really being put to the test at the moment and I can only ask our partners in London to finally make a concrete proposal why they are seeking an extension."
France's Europe minister, Nathalie Loiseau, said:  "'Grant an extension, what for?' is always the question. Time is not a solution... we need a decision from London."
European Commission chief Jean Claude Juncker and European Council President Donald Tusk, who is holding talks with Irish premier Leo Varadkar in Dublin. are due to hold press conferences later.
Labour leader Jeremy Corbyn is due to meet the leaders of the SNP, Liberal Democrats, Plaid Cymru and Green Party for talks on Brexit.
The SNP's Westminster leader Ian Blackford, Lib Dem leader Vince Cable, Plaid Cymru's Westminster leader Liz Saville Roberts and Green Party MP Caroline Lucas have all released a joint statement calling for another referendum.
"The best and most democratic way forward is to put the decision back to the people in a new vote - with the option to Remain on the ballot paper," they said.
Mr Corbyn will also meet members of the group of MPs calling for a so-called Norway Plus style of future relationship with the EU.

A cross-party trio of pro-EU politicians jokingly branded themselves "the rebels" before holding talks with the European Commission's chief negotiator Michel Barnier.
Former Lib Dem leader Nick Clegg, Tory ex-chancellor Ken Clarke and Labour's Lord Adonis met Mr Barnier in Brussels.
Asked if he was there to stop Brexit, Mr Clegg said: "If only it were that easy."
A European Commission spokesman said Mr Barnier's door was "always open".
But he played down claims of a "shadow negotiation" with the Remain-backers, saying: "There are two negotiators - on the one side the Secretary of State for Exiting the EU, David Davis, and on the European side it's the chief negotiator of the EU, Michel Barnier. Nobody else."
As they arrived, Mr Clarke joked that "we are here to talk about cricket" and did not respond to questions about whether he had permission from the government to attend the meeting.
Mr Clegg said they were there to get a "better understanding" about what was going on in the talks, which have yet to reach a breakthrough on issues including citizens' rights and the UK's financial bill.
But on Twitter, Theresa May's former advisor Nick Timothy said their visit "undermines Britain's negotiating position" and UKIP MEP Gerard Batten told the Daily Express the three politicians had "no right to pretend to represent the British public".
In other Brexit news, the government has published a list of the 58 sectors of the economy on which it has assessed the impact of leaving the EU.
Ministers have refused requests to publish the actual reports, saying this could undermine its negotiating position. The list was published in a response by Brexit Secretary David Davis to a House of Lords committee.

Boris Johnson was "too eager by far to get a deal at any cost," the Democratic Unionist Party deputy leader Nigel Dodds has said.
A Brexit deal, between the UK and EU, was struck on Thursday before a meeting of EU leaders in Brussels.
The DUP said it is "unable" to back the proposals in the Commons as they are not in the best interests of NI.
The party's support is seen as crucial if the deal is to pass in Parliament before the 31 October deadline.
Speaking alongside DUP leader Arlene Foster, Mr Dodds said the Benn Act, which requires the prime minister to ask for an extension if there is no deal by Saturday, had forced Mr Johnson into "desperation measures".
"If he'd held his nerve - held out - he would have got better concessions which kept the integrity, both economic and constitutional, of the UK," said Mr Dodds.
He said the DUP believed that since it had been proved that the Withdrawal Agreement could be changed, it "should be changed much more for the better".
He added that the issue of consent in the deal is a "major rewriting of the Belfast Agreement" adding it was "something anyone who has any concern for any kind of political process in Northern Ireland should be very, very concerned about".
Mr Dodds also said he expected a "massive vote" against Mr Johnson's deal on Saturday, and said the DUP would not be isolated on that.
The UK and the EU have been working on the legal text of a deal but it will still need the approval of both the UK and European parliaments.
Speaking in Brussels, the EU's chief Brexit negotiator Michel Barnier described the consent proposal in the agreement as "a cornerstone of our newly agreed approach".
"Four years after entry into force of the protocol, the elected representatives of Northern Ireland will be able to decide by simple majority whether to continue applying relevant union rules in Northern Ireland or not," he said.
Speaking in Londonderry, the Northern Ireland Secretary Julian Smith said "we've abandoned nobody" when asked if the government had decided not to rely on the DUP's votes.
Taoiseach (Irish Prime Minister) Leo Varadkar, who is in Brussels for the EU summit, said: "It's up to the members of the House of Commons now to decide whether they want a deal."
"The deal agreed today is complex and wide-ranging and all aspects need to be considered in their entirety," she added.
Ulster Unionist Party (UUP) leader Robin Swann said the deal would "place Northern Ireland on the window ledge of the union".
He said unionist MPs should "think long and hard" before voting on the deal, adding: "What's more important? The pursuit of a puritanical Brexit or the security and integrity of the union?"
SDLP leader Colum Eastwood appealed to the DUP not to "shoot this down" because the alternative was a no-deal Brexit that would be a "threat to our peace process".
"[The DUP has] a responsibility to the farmers, to the business community, to the ordinary community out there to get this resolved," he added.
Alliance Party leader and MEP Naomi Long said she wanted the prime minister to put the deal to the public in a referendum.
"If the DUP are not willing to provide the arithmetic to get a deal through Parliament then I think Boris Johnson would be right to go to the public."
Conservative MP and Brexit supporter Iain Duncan Smith said he would "reserve judgement" on the deal until he had read the detail of it.
He said: "There are issues - if the DUP aren't backing it, what are their reasons for not backing it?"
The Brexit deal struck in Brussels would involve Stormont giving ongoing consent to any special arrangements for Northern Ireland.
It would not be the unionists' veto demanded by the DUP - instead the arrangements could be approved by a straight majority.
Pro-EU parties have a narrow majority at Stormont.
It would continue to follow EU rules on food safety and product standards.
The DUP has already accepted that Northern Ireland would have to align with some EU rules to avoid a hard border.
Northern Ireland would also leave the EU customs union.
But EU customs procedures would still apply on goods coming into Northern Ireland from Great Britain in order to avoid checks at the border.
Stormont would have to approve those arrangements on an ongoing basis.
Approval would involve a straight-forward majority, which would keep the special arrangements in place for four years.
Alternatively, if the arrangements are approved by a majority of nationalists and a majority of unionists, they would remain in place for eight years - that would incentivise a cross-community consensus.
If the Northern Ireland Assembly voted to end the arrangements there would be a two-year notice period, during which the UK and the EU would have to agree ways to protect the peace process and avoid a hard border.
There is no fallback position in case the two sides cannot find a solution.
If a vote was not held - by choice or because the assembly was not sitting - then the government has committed to finding an "alternative process".
The EU believes that replaces the backstop - which would have lasted "unless and until" an alternative was found - with arrangements that are sustainable over time and are democratically supported, as requested by the UK.

Boris Johnson will not make an election pact with Brexit Party leader Nigel Farage, Downing Street has said.
Mr Farage said his party and the Conservatives should make a deal and "together we would be unstoppable".
But a senior Conservative source said Mr Farage was "not a fit and proper person" and "should never be allowed anywhere near government".
Mr Farage said he was "disappointed" with the response as he was offering a "genuine hand of friendship".
He told the BBC's Andrew Neil show that he did not want a job in the Conservative government and accused the Tories of "petty, tribal, party politics".
"Can't we see that actually if we get a Labour government we're not going to get a meaningful Brexit of any kind at all? This is big chance to unite the Leave vote," he said.
"We've got a solution here."
Mr Johnson argues that an election is now the only way to break the deadlock over Brexit, but MPs have twice rejected his call to hold one.
Labour leader Jeremy Corbyn has said he is "eager for an election" but wants to see legislation designed to stop a no-deal Brexit on 31 October implemented first.
Parliament is now prorogued for five weeks and is not scheduled to return until 14 October, when there will be a Queen's Speech outlining Mr Johnson's legislative plans.
Meanwhile, Scotland's highest civil court has ruled that the prime minister's suspension of the UK Parliament was unlawful.
Mr Farage has offered a "non-aggression pact" between his party and the Conservatives, on the condition that Mr Johnson sign up for "a clean-break Brexit" - in other words, no deal.
The aim is try to see off the threat from a "Remain alliance" of opposition parties who oppose Brexit and could depose the Tories.
Mr Farage says he will not field candidates in any of the Conservatives' existing seats and targets if, in return, the Tories stand aside in more than 80 Leave-voting constituencies where they are unlikely to win.
He made the offer in a full-page advert in the Sun and a wraparound advert in the Daily Express on Wednesday.
At the weekend, the Brexit Party leader said the offer was "100% sincere" and would help return Mr Johnson to Downing Street.
He wrote in the Sunday Telegraph: "Johnson should cast his mind back to the European elections in May, in which his party came fifth, and ask himself: does he want the Tories to find themselves in a similarly disastrous position when the results of the next general election come in, or does he want to sign a non-aggression pact with me and return to Downing Street?"
When asked about a potential alliance on the Andrew Marr Show, Chancellor Sajid Javid said: "We don't need an electoral alliance with anyone. We can stand on our own two feet, put our message across."

Nigel Farage has said he is going "back on the road" to campaign against the prime minister's Brexit plan.
In the Daily Telegraph, the UKIP MEP said Theresa May's Chequers agreement was a "sell-out" as it included regulatory alignment with the EU.
He wrote he would join pro-Brexit group Leave Means Leave at UK public events.
Meanwhile, ex-civil service head Lord Kerslake has said consequences of a no-deal Brexit would be so serious, MPs would have to reconsider it.
The announcement by former UKIP leader Mr Farage comes after a string of resignations last month over the prime minister's Brexit strategy - including those of David Davis and Boris Johnson.
Mr Davis quit as Brexit secretary saying he did not agree with Mrs May's proposals, while former foreign secretary Mr Johnson accused the prime minister of pursuing a "semi-Brexit".
Mr Farage said "scores of people" had stopped him in the street to ask when he was "coming back".
He added: "Well now you have your answer: I'm back."
The 54-year-old said a "battlebus" had already been hired.
He later told the BBC that Mrs May's proposal was "a complete betrayal of what people voted for".
His comments also come amid calls for a second referendum on the final Brexit deal.
Campaign group People's Vote has also criticised the government's handling of negotiations with the European Union.
People's Vote argues the public should be allowed a say on the final deal agreed with the EU.
Lord Kerslake told BBC Radio 4's Today programme that, if the government was unable to strike a deal with Brussels, there would have to be a "pause" in the Article 50 process. under which the UK will leave the EU on 29 March 2019.
The crossbench peer said in those circumstances, the European Commission would likely insist on some "re-examination" of the 2016 referendum decision to leave.
"The consequences of a no deal would be so serious as I think Parliament would have to seriously consider whether it could contemplate this," he said.
"The question people need ask themselves is: is this a risk that they think we should be taking?
"If the government can negotiate a good deal, then so be it.
"But if they can't and we end up in this position, then we have to reopen the question of whether we go forward with Brexit at all. It is not too late to do that."
The government is due to publish a series of technical notes on preparations for a no-deal Brexit on areas including farming and financial services. But Lord Kerslake said this was "too little, too late".
On Friday, Foreign Secretary Jeremy Hunt insisted Britain would "survive and prosper" if it left the EU without a trade deal - but added it would be a "big mistake for Europe".

Downing Street has denied the government is split over how to move forward with the Brexit process.
The prime minister has said he will seek a snap general election if the EU decides to delay Brexit until January.
But some ministers are understood to be urging him to make another attempt to get his deal through Parliament first.
BBC Europe editor Katya Adler says the EU will decide on Friday whether to grant an extension and, if so, for how long.
"France is digging its heels in, while Germany and most other EU countries support idea of granting the three-month extension," adds our correspondent.
French President Emmanuel Macon is thought to be concerned that a long extension could lead to more UK indecisiveness or an inconclusive general election.
If France remains opposed to a three-month extension, there could be an emergency summit in Brussels on Monday so leaders reach agreement face-to-face, says Katya Adler.
On Tuesday, MPs backed the prime minister's Brexit deal at its first parliamentary hurdle but rejected his plans to fast-track the legislation.
That defeat effectively ended any realistic prospect of the UK leaving the bloc with a deal by the government's 31 October deadline.
On Saturday, the prime minister was forced by law to send a letter to Brussels requesting a three-month extension.
Neither a motion for an early election nor another attempt to get the Brexit deal through has so far been scheduled for next week's business in Parliament.
Outlining the agenda, Commons leader Jacob Rees-Mogg said the government "does not want an extension" and is "making every preparation to leave on 31 October".
BBC political editor Laura Kuenssberg said it was unlikely the government would decide on either option before the EU responded to the extension request.
After Tuesday's Commons defeat on the timetable, Mr Johnson said he would pause the progress of his Withdrawal Agreement Bill while he waited to hear from the EU.
But he insists the UK will still leave in a week's time, with or without a deal - and he says he has told EU leaders that.
If the EU approves the UK's request for a three-month extension, Mr Johnson would have to accept it under legislation passed by MPs last month.
He would also have to accept any alternative duration suggested by EU leaders, unless MPs decide not to agree with it within two days.
Dominic Cummings, Mr Johnson's chief adviser, is reported by the Sun to be urging ministers to abandon attempts to get the prime minister's deal through Parliament and go for a December election instead.
But the newspaper says a series of ministers think getting the Brexit deal through Parliament should be the priority.
On Wednesday, Northern Ireland Secretary Julian Smith suggested the government's top priority, after Tuesday's Commons votes, may not be securing an early general election.
He told the Northern Ireland select committee: "What I want to do is listen to Northern Irish MPs, get a programme motion that is to the satisfaction of a majority of people in this House and resolve this situation.
"That is where I feel our responsibility lies, and we can work together to address many of these issues and ensure this bill is completed.
"I think the prime minister had a big success [on Tuesday], and I hope we can build on that in the coming days and weeks."
On Wednesday, Mr Johnson met Jeremy Corbyn to discuss how to break the Brexit impasse.
The Labour leader was keen to discuss a different timetable for the Brexit bill, while the prime minister wanted to know what Mr Corbyn would do if the EU refused to grant an extension.
But nothing was agreed between the pair and no further talks have been planned.
Shadow business secretary Rebecca Long-Bailey told Radio 4's Today programme that Labour would vote for an early election if Mr Johnson pushes for one as soon as an extension is granted by the EU.
"That's our position. But we also want the prime minister to look at the compromise that's been offered that a lot of MPs support, and that's the ability to be able to properly scrutinise the bill," she added.
James Cleverly, Conservative Party chairman, told the Today programme the government was still preparing for a no-deal Brexit on 31 October.
"The EU has not agreed an extension and therefore it is absolutely essential that we prepare to leave," he said.
However, Labour MP Lisa Nandy said keeping to next week's deadline was "very unlikely".
The Wigan MP told the Today programme the "general consensus" in her party was that if the government wanted to propose a new schedule for the Commons to debate the bill, "five or six days" would be "sufficient".
Even if Mr Johnson does decide to press for an early election there is no guarantee he will succeed.
Under the Fixed-term Parliaments Act, the prime minister needs to have the backing of two-thirds of MPs to hold a snap poll. This has been rejected twice by MPs.
Another way would be for the Conservatives to vote for a no-confidence motion in their own government - which Mr Johnson could even call himself - which would only require a simple majority of one.
But Parliamentary rules state that if it passes, the Commons has 14 days to form an alternative administration, so he would run the risk of being forced out of Downing Street if opposition parties can unite around a different leader.
Another route to an election is a one-line bill, that requires only a simple majority, but any such bill is likely to incur a host of amendments, for example, giving 16 and 17-year-olds the right to vote.
Traditionally, UK elections are held on a Thursday. So, if an election were triggered in the week beginning 28 October, the earliest date the poll could take place is Thursday, 5 December.
That's because the law requires Parliament to dissolve 25 working days before the election.

The government has rejected claims it is unwilling to negotiate with the EU and wants talks to fail to allow a no-deal Brexit.
It comes after the EU said UK demands to remove the Irish backstop from Theresa May's deal were unacceptable.
EU negotiators told European diplomats there was currently no basis for "meaningful discussions" and talks were back where they were three years ago.
Downing Street said the EU needed to "change its stance".
The European Commission said on Tuesday morning it was willing to hold talks in the coming weeks by phone or in person, "should the UK wish to clarify its position in more detail".
A spokeswoman added the agreement negotiated by Mrs May - rejected three times by MPs - was the "best possible deal", and could not be re-opened.
Many opponents of Mrs May's deal cite concerns over the backstop - an insurance policy to prevent a hard border returning on the island of Ireland - which if implemented, would see Northern Ireland staying aligned to some rules of the EU single market.
It would also involve a temporary single customs territory, effectively keeping the whole of the UK in the EU customs union. These arrangements would apply unless and until both the EU and UK agreed they were no longer necessary.
A No 10 spokesperson said: "The prime minister wants to meet EU leaders and negotiate a new deal - one that abolishes the anti-democratic backstop.
"We will throw ourselves into the negotiations with the greatest energy and the spirit of friendship and we hope the EU will rethink its current refusal to make any changes to the withdrawal agreement."
New Prime Minister Boris Johnson has pledged to leave the EU by the deadline of 31 October, with or without a deal.
BBC Brussels reporter Adam Fleming said the meeting on Sunday between officials and diplomats was a debrief from discussions last week between the EU, UK Brexit Secretary Steve Barclay and Mr Johnson's European envoy, David Frost.
A senior EU diplomat told the meeting a no-deal Brexit appeared to be the UK government's "central scenario", according to the Daily Telegraph and the Guardian.
"It was clear UK does not have another plan. No intention to negotiate, which would require a plan," the diplomat is reported to have said.
Mr Frost reiterated the prime minister's stance that the backstop element of Mrs May's plan must be abolished, and stressed that Mr Johnson's new ministers were not bound by commitments made by the previous government.
He also raised concerns about the UK's "divorce bill" and the proposed role of the European Court of Justice, the EU's top court, after Brexit.
Further talks between the two sides have not been ruled out, and Adam Fleming said the G7 summit in France at the end of August could be the moment of truth - the point at which a no-deal Brexit becomes inevitable.
Meanwhile, Mr Johnson is meeting his first foreign leader since entering Downing Street - Estonian Prime Minister Juri Ratas.
The country's Foreign Minister, Urmas Reinsalu, said earlier that while the "reality" was the withdrawal agreement - including the backstop - had been jointly agreed by EU member states, there was still a need for continued dialogue in the coming weeks to avoid a no-deal Brexit.
He told BBC Radio 4's Today programme alternatives to the backstop could be discussed after the ratification of the withdrawal deal.
The EU is not optimistic about any agreement with the UK.
The message they are getting from Boris Johnson's team is that the UK is not going to sign another deal unless it involves getting rid of the backstop.
But the EU has been clear time and time again that it isn't going to do that - the backstop is an integral part of any withdrawal agreement and it has to stay.
So the conclusion of officials is there is no reason to get back round the table at the moment, for the simple reason that they don't think they can meet the conditions Boris Johnson has set.
There are a couple of months to try to eke something out from one of the sides - to see if somebody blinks and there is some room for negotiation either in Brussels or in London.
But at the moment, many people think the direction of travel is heading towards a no-deal Brexit.
The meeting follows an interview with Health Secretary Matt Hancock, who said he believed Parliament could no longer block the UK from leaving the EU without a deal.
In a no-deal scenario, the UK would immediately leave the EU with no agreement about the "divorce" process, and would exit overnight from the single market and customs union.
Opponents say a no-deal exit would damage the economy and lead to border posts between Northern Ireland and the Republic. Other politicians argue any disruption could be quickly overcome.
Prominent pro-EU Conservative Dominic Grieve has insisted there are still a number of options available to MPs to block a no deal - including bringing down the government with a vote of no confidence.
He told BBC Radio 5Live the idea that Mr Johnson might refuse to resign even if he lost such a vote and another PM secured the confidence of the Commons was "breathtaking, stupid, infantile, and it won't work".
"Quite frankly, I'm astonished to hear these suggestions coming out," he added.
Meanwhile, Foreign Secretary Dominic Raab will begin a tour of North America on Tuesday as part of a bid to "fire up" the UK's trade relationships with countries outside the EU.
Mr Raab said the foreign ministers he saw at a meeting of the Association of Southeast Asian Nations in Thailand last week expressed a "consistent warmth" for the UK and a "desire to work more closely with us".
However, the former US treasury secretary, Larry Summers, said the UK was "delusional" if it believed it could secure a post-Brexit trade deal with Washington.
He told BBC Radio 4's Today programme: "Britain has no leverage, Britain is desperate... it needs an agreement very soon. When you have a desperate partner, that's when you strike the hardest bargain."

The cabinet remains fully behind Theresa May's Brexit policy in the face of growing calls within her party to change direction, No 10 has insisted.
The prime minister is sticking by her Chequers plan for future co-operation despite European leaders attacking it.
She met senior ministers as pressure grows on her to ditch it in favour of a Canada-style trade accord.
Meanwhile, ministers have warned of the risk of disruption to flights in the event of the UK leaving without a deal.
The two sides are seeking to negotiate the terms of exit as well as an outline agreement on future co-operation, over the next month or so.
But the talks hit the rocks on Thursday when EU leaders dismissed the basis of the PM's plan - a free trade zone and common rule book for goods with greater divergence for services - as "unworkable".
At a cabinet meeting earlier, Mrs May defended her strategy following calls from leading Brexiteers in her party to keep the option of a Canada-style arrangement on the table as talks enter a crucial phase.
Afterwards, Downing Street said she had told ministers hers was the "only plan on the table" that secured the "frictionless trade" needed to avoid a hard border between Ireland and Northern Ireland.
Mrs May also defended her Brexit trade plans to the European Parliament's Brexit co-ordinator Guy Verhofstadt, who she hosted in Downing Street.
The prime minister also told him the UK would guarantee the rights of the three million EU citizens living in the UK even if it leaves without a deal.
Mr Verhofstadt described their meeting as an "open an honest exchange".
The government has now published 77 technical notices designed to prepare business and inform the public about what could happen in the "unlikely" event of the UK leaving without a deal.
The latest batch included warnings on aviation, pet transport and coach travel.
Canada's deal with the EU, signed in 2016, removes the vast majority of customs duties on EU exports to Canada and Canadian exports to the EU.
Former foreign secretary Boris Johnson said proposals put forward by the Institute for Economic Affairs on Monday showed there was an alternative to ending up as a vassal state with "colony status" through the Chequers route.
The IEA, a free market think-tank, said Mrs May should change tack and pursue an advanced free trade agreement with the EU, with full reciprocal market access, no tariffs in goods including agriculture and maximum recognition of regulatory standards.
It said new customs processes had to be put in place that could handle a potential five-fold increase in declarations after Brexit, using enhanced technology and information sharing to separate the movement of goods from the processing of forms for as many traders as possible.
What is the so-called Canada option?
Concerns over the Irish border could be "solved", the IEA argued, by bespoke technical solutions, including trusted trader schemes and streamlined procedures for small businesses.
Mr Johnson said the IEA blueprint would allow the UK to "do a big free trade agreement with the EU but also to do free trade deals around the world" while Jacob Rees-Mogg said it could win the backing of the EU, Parliament and also "public opinion".
But former education secretary Nicky Morgan, who favours closer links with the EU after Brexit, said a Canada-style deal would take years to negotiate and might not give the kind of access its supporters hoped for.
Mrs Morgan told Conservative Home that the fallback option was for the UK to rejoin the European Free Trade Association, the so-called Norway option which would give the UK preferential market access although it would be required to accept EU rules, including on freedom of movement.
Brexit Secretary Dominic Raab said the cabinet had had a "good, healthy discussion" and ministers would continue to press the EU on some of the criticisms it had made.
"Of course we respect different views across the board but we're not going to suddenly throw up our hands in despair because we've had a bump in the road in these negotiations," he said.

Boris Johnson has urged MPs to "come together" to back the Brexit deal he has secured with the EU, insisting there is "no better outcome".
The prime minister told the BBC's Laura Kuenssberg he wanted the country to "move on" from Brexit, which he described as "divisive".
And he said he was hopeful the deal would pass the Commons on Saturday.
The government's former allies in the DUP and every opposition party plans to vote against it.
The new deal, agreed by Mr Johnson and the EU on Thursday, is similar to the one agreed by Theresa May last year - but it removes the controversial backstop clause, which critics say could have kept the UK tied indefinitely to EU customs rules.
Northern Ireland would remain in the UK's customs union under the new agreement, but there would also be customs checks on some goods passing through en route to Ireland and the EU single market.
Mr Johnson and his team are trying to persuade enough Labour rebels, former Conservatives and Brexiteer Tory rebels to get it across the line in Parliament.
He told the BBC's political editor: "I just kind of invite everybody to imagine what it could be like tomorrow (Saturday) evening, if we have settled this, and we have respected the will of the people, because we will then have a chance to to move on.
"I hope that people will think well, you know, what's the balance, what do our constituents really want?
"Do they want us to keep going with this argument, do they want more division and delay? Look, you know, this has been a long exhausting and quite divisive business Brexit."
He repeated his commitment to leave the EU on 31 October, adding: "There's no better outcome than the one I'm advocating tomorrow."
Mr Johnson has repeatedly said Brexit will happen by the end of the month with or without a deal.
But MPs passed a law in September, known as the Benn Act, which requires the PM to send a letter to the EU asking for an extension until January 2020 if a deal is not agreed - or if MPs do not back a no-deal Brexit.
Former Tory Sir Oliver Letwin - who was kicked out of the party for backing the law - has put an amendment down to ensure the extension is asked for even if MPs back the deal in the Commons on Saturday.
He said the government could still leave without a deal on 31 October if the PM's proposals had not passed every stage in Parliament to become law - so the motion would withhold MPs' approval until that final hurdle is passed.
Meanwhile, responding to the deal, Bank of England Governor Mark Carney said taking no deal off the table was a "net economic positive".
It really is extremely tight. It would be foolish to make a guess on which way it will go.
What we do know might happen tomorrow is rather than there being a thumbs up or thumbs down vote to the deal, there could be an attempt by some MPs to bring in what they see as an insurance policy.
This could mean another delay in case this deal falls through in the next couple of weeks.
That is potentially being put forward as an amendment so MPs will have a chance to vote on it.
Without going in to all the potential machinations it could mean tomorrow turns, not just into MPs giving an opinion on Boris Johnson's deal, but also wrangling again about a potential delay.
This could make things more fuzzy, and certainly more frustrating for Downing Street.
It will be a showdown of sorts.
Downing Street always knew that Parliament would be a very tricky hurdle.
Mr Johnson was also quizzed about the deal he has struck with the EU to resolve the issues over the Irish border.
He denied breaking a promise to the DUP, saying: "No I don't accept that at all.
"I think that what you have is a fantastic deal for all of the UK, and particularly for Northern Ireland because you've got a single customs territory. Northern Ireland leaves the EU with the rest of the UK."
The DUP has accused Mr Johnson of "selling Northern Ireland short" by accepting checks on some goods passing through Northern Ireland to get a deal with the EU.
The party's Brexit spokesman, Sammy Wilson, has described the deal as "toxic" and is urging Conservative MPs not to back it.
The pro-Brexit European Research Group has previously given its full backing to the DUP.
On Friday evening vice-chairman Mark Francois told the BBC he would be voting for the deal, while another member, Andrew Bridgen, said the "vast majority" of the group "will come to the conclusion that this deal is tolerable".
Labour plans to vote against the government motion, and in a letter to his own MPs Jeremy Corbyn said it was a "worse deal" than the one Theresa May struck with Brussels.
He said the proposals "risk triggering a race to the bottom on rights and protections".
"This sell-out deal won't bring the country together and should be rejected," Mr Corbyn added.
The party also attacked the deal after one Conservative MP, John Baron, told the BBC's Victoria Derbyshire programme the UK would be able to leave the EU "on no-deal terms" if trade talks failed at the end of the so-called transition period in December 2020.
Labour chairman Ian Lavery said: "The cat has been let out of the bag... [and] no one should be in any doubt that Johnson's deal is just seen an interim arrangement."
However, the government appears to have moved to try and win the support of some Labour MPs by promising to boost workers' rights and environmental standards after Brexit.
Downing Street said the pledge followed discussions with Labour MPs and would also include a commitment to giving Parliament a say in the future relationship with the EU.
The SNP's Westminster leader Ian Blackford has also tabled an amendment, calling for a three-month extension to Brexit to allow for an early general election.
And Brexit Party leader Nigel Farage called the deal "the second worst deal in history" behind Theresa May's withdrawal agreement.
Commons business will start at 9:30 BST on Saturday - the first weekend sitting since the invasion of the Falklands in 1982.
Mr Johnson will make a statement to the House and face questions from MPs, before they move on to a debate about the deal.
The timing of any votes depends on which amendments are chose by the Speaker of the Commons, John Bercow.

The backstop element of the Brexit plan is "not going to change", Ireland's deputy prime minister has said.
The proposal - aimed at preventing a hard border between Ireland and Northern Ireland - played a major part in Theresa May's deal being voted down by a historic margin last week.
But Simon Coveney told the BBC's Andrew Marr Show that the EU would not ratify a deal without it.
Health Secretary Matt Hancock called the comments a "negotiating position".
Mr Hancock also denied reports that the government was "specifically" planning for martial law if the UK left without a deal  - but he did not rule it out.
He said that the government "looks at all the options in all circumstances," but when pressed by Andrew Marr, the health secretary added: "It remains on the statute book, but it isn't the focus of our attention."
Martial law involves the suspension of normal law, and temporary rule by the military. It can include measures such as curfews and travel restrictions.
The UK is set to leave the EU on 29 March, with or without a deal. If a hard border comes about, people and goods passing between Ireland and the UK will need to be checked.
Meanwhile, a leaked diplomatic note seen by the Guardian claims that the president of the European Commission, Jean Claude Juncker, has told Mrs May that to revisit the backstop issue she would need to agree a permanent customs union with the EU.
A customs union would mean that no tariffs would be put on goods travelling between the UK and the 27 member states of the EU, but that the UK could not negotiate its own trade agreements with other countries.
The comments come ahead of a crunch week in Parliament.
Mrs May will return to the Commons on Tuesday for a vote on her deal, which includes the withdrawal agreement - the so-called "divorce deal" on how the UK leaves the EU - and the political declaration - a statement on the future relationship.
It was voted down by 432 to 202 votes last week, with hard-line Brexiteers in her own party and members of Northern Ireland's Democratic Unionist Party - on whom Mrs May relies for votes in Parliament - citing the backstop as their main reason for voting against it.
A number of MPs have been tabling amendments in a bid to force the government to change direction.
One amendment, put forward by Labour's Yvette Cooper, seeks to introduce a bill that would allow the government to extend Article 50 - the mechanism by which the UK leaves the EU - by up to nine months in order to get a deal agreed in Westminster.
Also appearing on Andrew Marr, Ms Cooper said she was not seeking to "block Brexit" and said the bill would be amendable - meaning MPs could vote on how long any extension would be.
She appealed for the support of the prime minister and MPs, as well as for the backing of her own party leader Jeremy Corbyn, saying: "We can't keep waiting for other people to sort this out."
"We can't carry on with a kind of game of chicken," she said.
"In the end, someone has to take some responsibility and say, 'if the prime minister runs out of time, she may need some more time'.
"That is not about blocking Brexit, that is about being responsible and making sure you can get a Brexit deal."
The UK is allowed to scrap Article 50 altogether - and halt Brexit - but to extend it, it would need the approval of the EU.
Mr Coveney said Ireland "won't be an obstacle" if the UK wanted to go down the route of extending Article 50, adding: "Ireland wants to help in this process."
"Britain and Ireland are two islands next to each other," he said. "We have to work out these things together and stop talking about games of chicken."
But Mr Hancock said delaying Brexit would not help solve the arguments between MPs.
"You can't just vote for delay," he said. "You've got to vote positively for a deal".
Other amendments being put forward ahead of Tuesday's vote include a plan for putting a time limit on the backstop and another for scrapping it altogether.
These are in answer to critics who dislike the backstop because they believe it keeps the UK too closely aligned to the EU and fear that it could become permanent.
However, Mr Coveney said: "The European Parliament will not ratify a Withdrawal Agreement that doesn't have a backstop in it. It's as simple as that.
"The backstop is already a compromise. It is a series of compromises. It was designed around British red lines."
The former chief constable of the police in Northern Ireland (PSNI) echoed previous warnings that the return of a hard border between the two countries would become a target for dissident republicans.
Speaking to RTE, Sir Hugh Orde said there would be no way to avoid security patrols if the UK left without a deal, and security officers would be "at risk".
Across Sunday's newspapers and political TV programmes, politicians clashed over whether leaving the EU without a deal should remain an option for the government or not.
Leader of the House Andrea Leadsom wrote in the Sunday Times that trying to rule out a no deal was a "thinly veiled attempt to stop Brexit".
But despite his colleague's words, defence minister Tobias Ellwood wrote: "It is simply wrong for government and business to invest any more time and money in a no deal outcome that will make us poorer, weaker and smaller in the eyes of the world.
"It is now time to rule out the very possibility of no deal."
Mr Ellwood also said members of his own party seeking to "crash out" without a deal "risk inflaming a dangerous battle for the soul of the Conservative Party" - saying it could determine the outcome of the next election.
But Education Secretary Damian Hinds told Sky News no deal needed to remain on the table, although it would "not be a good outcome".
In other developments, the government is going to consult Parliament on whether to work extra hours and lose their February half-term break in order to get Brexit delivered by 29 March.
BBC political correspondent Iain Watson said the government's demand was a way of Mrs May sending a signal to MPs that she intends to stick to the planned March departure.

A no-deal Brexit is now "the only acceptable deal", says Nigel Farage.
The Brexit Party leader said his party would fight in every seat at a general election if the government tried to pass the existing withdrawal agreement.
But he said if Boris Johnson "summoned the courage" to pursue a no deal, The Brexit Party would work with him.
He added: "A Johnson government committed to doing the right thing and The Brexit Party working in tandem would be unstoppable."
The Brexit Party was launched in April this year ahead of the European Parliament elections, and after former Prime Minister Theresa May agreed to extend the Brexit deadline to 31 October.
Mr Johnson has promised the UK will leave on that date "do or die", including without a deal if necessary.
However, the PM has also said he is still pursuing a deal with the EU, urging European counterparts to reopen the withdrawal agreement agreed by Mrs May and make changes - especially to the backstop clause.
The backstop is the so-called insurance policy to preventing a hard border - things like cameras and security posts - returning to the island of Ireland.
If used, it would keep the UK in a very close relationship with the EU until a trade deal permanently avoiding the need for checks was agreed - but critics fear the UK would be trapped in it indefinitely.
Mr Farage was speaking at an event in London which saw hundreds of prospective parliamentary candidates for The Brexit Party gather.
He revealed it had vetted 635 people for any upcoming election - 15 short of ensuring the party can fight every seat - and he believed there was a "better than 50% chance" the country would go to the polls in the autumn.
He warned Mr Johnson not to try to revive the withdrawal agreement - already rejected by MPs in the Commons three times - in any form.
"I want to make this pledge from The Brexit Party," he said.
"The withdrawal agreement is not Brexit. It is a betrayal of what 17.4 million people voted for.
"If you insist on the withdrawal agreement, Mr Johnson, we will fight you in every seat up and down the length and breadth of the United Kingdom."
However, Mr Farage said he would be willing to work with the Tories if they backed a "clean break" from the EU and supported a no-deal Brexit.
"If Boris Johnson is prepared to do the right thing for the independence of this country, then we would put country before party and do the right thing.
"We would be prepared to work with him, perhaps in the form of a non-aggression pact at the general election.
"The Conservative Party has lost so much trust that the only way they could win a general election is with our support."
The Brexit Party event took place on Tuesday while members of opposition parties in Westminster were meeting to discuss how to prevent a no-deal Brexit.
Critics of no deal say it would damage the UK's economy and lead to a hard border returning between Ireland and Northern Ireland.
The SNP, Liberal Democrats, The Independent Group for Change, Plaid Cymru and the Green Party all accepted an invitation from Labour leader Jeremy Corbyn to talk about a strategy ahead of MPs returning from recess next week.
Mr Corbyn also invited five Conservative MPs opposed to a no-deal exit, but none attended.
Leader of The Independent Group for Change, Anna Soubry, said the meeting was "excellent" and party leaders had agreed to work together.

A no-deal Brexit is now more likely but can still be avoided, the EU's chief negotiator has said.
Michel Barnier said a long extension to the UK's 12 April exit date had "significant risks for the EU" and a "strong justification would be needed".
Meanwhile, the BBC's John Pienaar said Theresa May's cabinet has considered plans to "ramp up" preparations for a no-deal Brexit.
A snap general election was also discussed in the meeting, he said.
A second two-hour regular cabinet meeting will be held later, with the issues likely to be discussed again.
It comes after MPs voted on four alternatives to the PM's withdrawal deal, but none gained a majority.
In the Commons votes on Monday, MPs rejected a customs union with the EU by three votes. A motion for another referendum got the most votes in favour, but still lost.
The so-called indicative votes were not legally binding, but they had been billed as the moment when Parliament might finally compromise.
That did not happen, and one Tory MP - Nick Boles, who was behind one of the proposals - resigned the whip in frustration.
Brexit Secretary Stephen Barclay told MPs that if they wanted to secure a further delay from the EU, the government must put forward a "credible proposition".
One suggestion has been the possibility of a general election - but former foreign secretary Boris Johnson told BBC political editor Laura Kuenssberg that would be likely to "infuriate" voters.
Instead, Mr Johnson said he believed a new leader and "change in negotiation tactic" could "retrofit" the PM's "terrible" agreement with the EU.
Speaking on Tuesday morning, Mr Barnier said: "No deal was never our desire or intended scenario but the EU 27 is now prepared. It becomes day after day more likely."
Mr Barnier told the European Parliament's foreign affairs committee that "things are somewhat hanging on the decisions of the House of Commons", and that the deal was negotiated with the UK "not against the UK".
"If we are to avoid a no-deal Brexit, there is only one way forward - they have got to vote on a deal.
"There is only one treaty available - this one," he said, waving the withdrawal agreement.
Former Brexit Secretary David Davis told BBC Radio 4's Today programme the way forward was to address the controversial Irish backstop - a measure to avoid the return of a hard border on the island of Ireland.
He said the most "constructive outcome" would be the Malthouse Compromise - which includes extending the transition period for a year until the end of 2021 and protecting EU citizens' rights, instead of using the backstop.
But the Leader of the Commons Andrea Leadsom said the prime minister's deal was the best option.
"The compromise option, the one that delivers on the EU referendum but at the same time enables us to accommodate the wishes of those who wanted to remain in the EU - that is the best compromise," she said.
Labour MP and chairman of the Brexit select committee Hilary Benn told Today that a confirmatory referendum was the best solution.
"A good leader would be taking that decision and put it back to the people," he said.
"[The] fear is that the PM is not going to move an inch. That is why we are at a moment of crisis."
Mrs May's plan for the UK's departure has been rejected by MPs three times.
Last week, Parliament took control of the process away from the government in order to hold a series of votes designed to find an alternative way forward.
Eight options were put to MPs, but none was able to command a majority, and on Monday night, a whittled-down four were rejected too.
Those pushing for a customs union argued that their option was defeated by the narrowest margin - only three votes.
It would see the UK remain in the same system of tariffs - taxes - on goods as the rest of the EU, potentially simplifying the issue of the Northern Ireland border, but prevent the UK from striking independent trade deals with other countries.
Those in favour of another EU referendum pointed out that the motion calling for that option received the most votes in favour, totalling 280.
For months, Parliament has been saying "Let us have a say, let us find the way forward," but in the end they couldn't quite do it. Parliament doesn't know what it wants and we still have lots of different tribes and factions who aren't willing to make peace.
That means that by the day, two things are becoming more likely. One, leaving the EU without a deal. And two, a general election, because we're at an impasse.
One person who doesn't think that would be a good idea is former foreign secretary and Brexiteer Boris Johnson.
He told me going to the polls would "solve nothing" and would "just infuriate people". He also said that only somebody who "really believes in Brexit" should be in charge once Theresa May steps down. I wonder who that could be...
Hear more from Laura and the gang in Brexitcast

The threat of a no-deal Brexit is "focusing minds" and encouraging compromise, the chancellor has said.
Philip Hammond said the government was "determined to get a deal" before leaving the EU on 29 March but a "very bad" no deal outcome remained possible.
The government said talks on Thursday were "productive" and would "continue urgently at a technical level".
Jeremy Corbyn, who met EU negotiator Michel Barnier earlier, again accused the PM of "running down the clock".
Theresa May met the EU's Jean-Claude Juncker to discuss changes to the existing deal to win MPs' support on Wednesday.
The prime minister said progress had been made on Wednesday over legally binding guarantees about the Irish backstop - the insurance policy to stop a hard border returning to the island of Ireland - but "time is of the essence".
However, Mr Juncker said he was "not very optimistic" about securing a deal.
Brexit Secretary Stephen Barclay and Attorney General Geoffrey Cox were in Brussels on Thursday for talks with Mr Barnier.
They focused on "guarantees relating to the backstop that underline once again its temporary nature and give appropriate legal assurance to both sides, as well as alternative arrangements and the political declaration (the document setting out future UK-EU relations)", a government statement said.
Mr Barclay and Mr Cox will meet Mr Barnier again early next week, it added.
Labour leader Jeremy Corbyn, his Brexit spokesman Sir Keir Starmer and shadow attorney general Baroness Chakrabarti were also in Brussels to discuss their proposals, which include a permanent customs union and a close relationship with the single market.
Speaking after a meeting with Mr Barnier, Mr Corbyn urged Theresa May to "take the threat of no deal off the table", adding that the EU was "very worried about the consequences of it".
He did not rule out further meetings with Theresa May to discuss Labour's Brexit plans, which he says could get the backing of the House of Commons, but he added: "It is very clear that this prime minister, by refusing to change her red lines, is simply running down the clock".
The backstop has become the main sticking point of the prime minister's proposals - with critics fearing the policy would leave the UK tied to a customs union indefinitely - and it played a large part in her plan being voted down by a historic margin in January.
Earlier this month, Parliament voted for Mrs May to seek "alternative arrangements" to replace the backstop but the EU has consistently said it will not re-open the withdrawal agreement - the "divorce" deal where it features.
Speaking on BBC Radio 4's Today programme, Mr Hammond said government policy on Brexit was "very clear".
"We are determined to get a deal. We recognise that a no-deal Brexit would be a very bad outcome for the UK and we are doing everything we can to avoid that," he said.
"There is always a possibility of no deal as an outcome and that is why the government is carrying out appropriate contingency planning."
However, the chancellor said that the risk was helping push some people towards agreeing with the government's plan.
"I fully recognise that it is very uncomfortable that we are as close to the wire as we are but I am afraid that is just a feature of this kind of negotiation. We are making progress," he added.
Former Tory MP and new member of The Independent Group, Sarah Wollaston, predicted a third of the cabinet would resign if there was a no-deal Brexit.
Mr Hammond would not reveal if he was among that number but said: "My job is to avoid [a no-deal Brexit] and to make sure the government is focused entirely on avoiding that outcome."
Speaking from the European Commission on Thursday, Mr Juncker said he could not rule out a no-deal Brexit, which would have "terrible economic and social consequences both in Britain and the EU".
He added: "The worst can be avoided but I'm not very optimistic when it comes to this issue."
On Sunday, Mrs May will be attending a two-day EU-League of Arab States summit in the Egyptian Red Sea resort of Sharm el-Sheikh with about 20 EU leaders, including German Chancellor Angela Merkel and Irish Prime Minister Leo Varadkar.
She is expected to hold a series of one-to-one meetings as she continues to push for her deal.

None of MPs' eight proposed Brexit options have secured clear backing in a series of votes in the Commons.
The options - which included a customs union with the EU and a referendum on any deal - were supposed to help find a consensus over how to leave the EU.
Brexit Secretary Stephen Barclay said the results strengthened ministers' view their deal was "the best option".
The results capped a dramatic Wednesday in which Theresa May promised to stand down as PM if her deal was passed.
The prime minister told a meeting of Tory MPs she would leave office earlier than planned if it guaranteed Parliament's backing for her withdrawal agreement with the EU.
Her announcement prompted a number of Tory opponents of her deal to signal their backing but the Democratic Unionists suggested they would continue to oppose the agreement.
MPs hoped Wednesday's unprecedented series of "indicative votes" would help break the parliamentary deadlock over Brexit.
The failure to identify a clear way forward led to angry exchanges in the Commons with critics of the process saying it had been "an abject failure".
The proposal which came closest to commanding majority support was a cross-party plan - tabled by former Conservative chancellor Ken Clarke - for the whole of the UK to join a new customs union with the EU to ensure tariff-free trade after the UK's exit.
Its supporters included five Conservative ministers: Mark Field, Stephen Hammond, Margot James, Anne Milton and Rory Stewart.
All Conservative MPs - excluding cabinet ministers - were given a free vote, meaning they were not ordered to vote in a certain way.
Eight Conservatives voted for a referendum to endorse the deal, the proposal which secured the most affirmative votes. Labour controversially whipped its MPs to back the proposal but 10 shadow ministers abstained and Melanie Onn quit her job to vote against.
Labour's own alternative plan for Brexit - including "close alignment" with the single market and protections for workers' rights - was defeated by 307 votes to 237.
Five other propositions - including backing for a no-deal exit, the so-called Common Market 2.0 plan, a separate proposal to remain in the European Economic Area and one to stop the Brexit process by revoking Article 50 - all failed to secure the backing of a majority of MPs.
Brexiteer Mark Francois said "this attempt to seize the order paper" by MPs had failed and the public would be looking on "with amazement".
But Conservative MP Sir Oliver Letwin, who oversaw the unprecedented process of indicative votes, said the lack of a majority for any proposition was "disappointing".
While he said he believed MPs should be allowed to have another go at reaching a consensus on Monday, he said this would not be needed if the PM's deal was approved before then.
Independent Group MP Anna Soubry said more people had voted for the idea of another referendum than voted for Mrs May's deal on the two times it had been put to Parliament.
And Labour MP Dame Margaret Beckett, who put forward the motion for a confirmatory referendum, said the objective had not been to identify a single proposition at this stage but to get a sense of where a compromise may lie by, in her words, "letting a thousand flowers bloom".
The prime minister offered to pay the ultimate price, and leave office - the grandest of gestures any leader ever really has.
For a moment it seemed it might work and line up the support she so desperately needs.
But within a couple of hours her allies in Northern Ireland were refusing to unblock the progress of Theresa May's main mission.
That might not be terminal - one cabinet minister told me the PM may yet have another go at pushing her deal through Parliament against the odds on Friday.
But if Plan A fails, Parliament is not ready with a clear Plan B that could yet succeed.
For our politics, for businesses trying to make decisions, for all of us, divisions and tensions between and inside our government - and our Parliament - are too profound to bring this limbo to an end.
Commons Speaker John Bercow said the process agreed by the House allowed for a second stage of debate on Monday and there was no reason this should not continue.
While it was up to MPs, he said there was an understanding Wednesday's objective was to "shortlist" a number of options before moving on to consider the "most popular".
Mr Barclay appealed to MPs to back the PM's deal "in the national interest" when it returns to the House for a third time - which could happen as soon as Friday.
"The House has considered a wide variety of options as a way forward," he said.
"And it demonstrates there are no easy options here. There is no simple way forward. The deal the government has negotiated is a compromise...That is the nature of complex negotiations.
"The results of the process this House has gone through today strengthens our view that the deal the government has negotiated is the best option."

Theresa May's Brexit deal will not return to the Commons this week unless it has support from the DUP and Tory MPs, the chancellor says.
The PM's plan is expected to be voted on for a third time in the coming days.
But Philip Hammond told the BBC's Andrew Marr that it would only be put to MPs if "enough of our colleagues and the DUP are prepared to support it".
He did not rule out a financial settlement for Northern Ireland if the DUP backed the deal.
The party, which has 10 MPs in the Commons, negotiated £1bn in spending for Northern Ireland as part of a confidence and supply agreement with the Tories - giving the government a working majority.
Mr Hammond said they did not have the numbers "yet" to secure Mrs May's deal, adding: "It is a work in progress".
But he warned that, even with the DUP's support, a "short extension" would be needed to pass legislation in Parliament, adding that it was now "physically impossible" for the UK to leave the EU on 29 March.
The shadow chancellor, John McDonnell, said Mrs May risked "destroying all confidence in our political system" if her government was planning to give the DUP "another bung".
The prime minister has asked MPs to make an "honourable compromise" on her deal.
Writing in the Sunday Telegraph, she said failure to support it would mean "we will not leave the EU for many months, if ever".
Meanwhile, Labour leader Jeremy Corbyn has written to MPs across the Commons inviting them for talks to find a cross-party compromise.
He also told Sky's Sophie Ridge that Labour MPs could be told to vote in favour of an amendment calling for another referendum next week, and he could propose another vote of no confidence in the government if the PM's deal was voted down for a third time.
Earlier last week MPs rejected Theresa May's deal again - this time by 149 votes - and then backed plans to rule out leaving the EU without a deal.
They also voted in favour of an extension to the process - either until 30 June if Mrs May's deal is supported before 20 March, or a longer one that could include taking part in European elections if MPs reject her plan for a third time.
But legally the UK is still due to leave the EU on 29 March.
All 27 EU member states would have to agree to an extension, and the countries' leaders are expected to discuss it at a summit on Thursday.
Mr Hammond told Andrew Marr that it was now "physically impossible" for the UK to leave on 29 March.
"If the prime minister's deal is able to muster a majority this week and get through, then we will need a short extension," he said.
"But if we are unable to do that - if we are unable to bring a majority together to support what in my view is a very good deal for Britain - then we will have to look at a longer extension and we are in uncharted territory."
Asked if the deal would be voted on again this week, the chancellor said: "The answer to that is no - not definitely.
"We will only bring the deal back if we are confident that enough of our colleagues and the DUP are prepared to support it so we can get it through Parliament.
"We are not just going to keep presenting it if we haven't moved the dial."
A group of 15 Tory MPs from Leave-backing constituencies, including former Brexit Secretary David Davis, have written a letter urging colleagues to back the deal to ensure Brexit goes ahead.
And former Cabinet minister Esther McVey, who resigned over the Brexit agreement, told Sky's Sophy Ridge programme that she would "hold my nose" and vote for the deal after rejecting it twice herself, as it was now a choice between "this deal or no Brexit".
Asked on BBC Radio 5 Live's Pienaar's Politics whether it would be a good idea for Mrs May to confirm she would leave Number 10 by the summer, Ms McVey said only the PM knew what was best for her but she needed "a dignified departure".
Charlie Elphicke, Conservative MP for Dover, told the BBC there needed to be "a change of leadership" for him to support the deal, while Nigel Evans, Tory MP for Ribble Valley, said Mrs May should quit if there was a long delay to Brexit and the UK ended up contesting European elections.
Mr Corbyn has offered talks with opposition leaders and backbench MPs in an effort to find a Brexit compromise which could replace Mrs May's plan.
The Labour leader has invited Liberal Democrat leader Sir Vince Cable, DUP deputy leader Nigel Dodds, SNP Westminster leader Ian Blackford, Plaid's Liz Saville Roberts and Green MP Caroline Lucas.
In his letter, he called for urgent meetings to find a "solution that ends the needless uncertainty and worry" caused by Mrs May's "failed" Brexit negotiations.
Meanwhile, Tory MP Nick Boles has pledged to stay in the Conservative Party, despite quitting his local association over an ongoing row about Brexit.
He told the BBC's Andrew Marr that he would be meeting with the chief whip on Monday to find a way forward, but that he was "not going to be bossed around" by local members.

A no-deal Brexit could lead to the break-up of the UK, the ex-president of the European Council has warned.
Herman Van Rompuy told the Observer leaving the EU without a deal posed an "existential threat" to the UK.
He added a no-deal scenario would have a "big impact" on "regions such as Scotland".
First Minister Nicola Sturgeon has previously said she will decide whether to back a second referendum on independence by the end of 2018.
Mr Van Rompuy's comments come after the government published its first set of documents setting out no-deal advice for UK businesses and public bodies.
More documents are expected in the coming weeks - and Downing Street has scheduled a cabinet meeting to co-ordinate planning for the middle of September.
Currently, mid-October is seen as the likely deadline for an agreement setting out the terms of UK-EU divorce.
Speaking last week, UK Brexit Secretary Dominic Raab said reaching an agreement with the EU was still the most likely outcome - but preparing for other scenarios was the "responsible" thing to do.
Mr Van Rompuy said that discussion amounted to "nationalist rhetoric that belongs to another era".
The former Belgian prime minister added that he believed no-deal comments from government ministers were part of "operation fear", intended to scare the EU into compromising on a deal.
Former UK Brexit secretary, David Davis, has also accused the UK government of scaremongering over the implications of a no-deal Brexit in a tactic which he argues undermines the UK's negotiating position.
Writing in the Sun on Sunday newspaper, he said a warning from Chancellor Philip Hammond that such a scenario could hit GDP by up to 10% was "an attempt to frighten the population into imagining the most terrible consequences of leaving the EU without a deal".
A Downing Street spokeswoman said: "We have always said the United Kingdom would continue to thrive in the event of a no-deal Brexit.
"But we are confident of getting a good deal - one that delivers for every part of the United Kingdom and takes back control of our money, laws and our borders. That is what this government will deliver."
Scotland's Brexit secretary, Michael Russell, said Mr Van Rompuy's comments underlined the Scottish government's own warnings about the "catastrophic" implications for jobs, investment and living standards of a no-deal Brexit.
He said: "The UK government should instead commit to staying inside the customs union and single market - the biggest such market in the world, which is around eight times the size of the UK market alone.
 "It is extremely concerning - and irresponsible of the UK government - that the whole basis of our economic relationship with the European Union and critical issues such as customs arrangements have not been agreed, with the clock ticking towards an EU exit in March next year.
 "It is also deeply concerning that the potential chaos of a no-deal Brexit is now seen clearly by just about everyone concerned - including the former president of the EU Council - except the UK government."

If the new UK prime minister wants to "tear up" the existing withdrawal agreement with the EU "we're in trouble", Ireland's deputy PM has said.
Simon Coveney said the decision for a no-deal Brexit would be the UK's but added checks "of some sorts" would be needed in the Irish Republic.
Ireland would have to protect its place in the single market, he told the BBC.
Both men vying to become UK PM say they want to change the withdrawal deal and, in particular, the so-called backstop.
Mr Coveney warned: "That's a little bit like saying, 'Give me what I want or I'm going to burn the house down for everybody.'"
He told the BBC's Andrew Marr Show he hoped the UK and EU would negotiate a future relationship that would mean the backstop - designed as an insurance policy to prevent a hard border on the island of Ireland - could be avoided.
However, he warned it could not be removed from the withdrawal agreement.
"The EU has made it very clear that we want to engage with the new British prime minister, we want to avoid a no-deal Brexit but the solutions that have been put in place to do that haven't changed," Mr Coveney said.
"If the British government forces a no-deal Brexit on everybody else, the Republic of Ireland will have no choice but to protect its own place in the EU single market. That would fundamentally disrupt the all-Ireland economy."
He said the all-Ireland economy had helped maintain peace on the island of Ireland but that protecting it would "not be possible" in the event of a no-deal Brexit.
However, he added that contingency plans were being drawn up with the European Commission to try to minimise the disruption.
But former Tory leader and Brexiteer Iain Duncan Smith said both the EU's chief Brexit negotiator Michel Barnier and the Irish prime minister had told him there would be no hard border with Northern Ireland in the event of a no-deal Brexit.
"I asked, well, lay out what your proposals are - and we'd already proposed alternative arrangements - and basically what was described to me was alternative arrangements - the same thing we'd been talking to them about which would alleviate the idea of necessary checks on the island of Ireland based on what exists at the moment," Mr Duncan Smith said.
And DUP leader Arlene Foster said she was "disappointed, but not surprised" by what Mr Coveney had said, and accused him of trying to "look tough" in the eyes of the incoming prime minister.
The DUP, whose 10 MPs are crucial for the Conservative Party's majority, has said it does not want the UK to leave the EU without a deal, but believes ruling out no-deal would damage the UK's negotiating hand.
By Jayne McCormack, BBC Northern Ireland's political reporter
Much of what Simon Coveney had to say today mirrored his warnings in the past.
No time limit on the backstop, there is wiggle room on the political declaration and no deal would be a disaster for the economy.
But there was one key difference this time - his intended recipient of the message.
The Irish government is acutely aware that the incoming prime minister is likely to want to make good on his Brexit strategy.
No deal is still on the table.
The Republic of Ireland has managed to keep the EU on board and its backstop argument has not changed - but can it hold the line?
This was also the clearest interview from Mr Coveney yet - stressing if a no-deal Brexit does happen, the blame rests with Westminster, not Dublin.
DUP leader Arlene Foster hit back that the Irish deputy prime minister was trying to "look tough" to the new PM.
In the coming days, we will likely see much more "tough talk" emerging from both sides.
The withdrawal agreement has been rejected three times by MPs in the Commons, with the backstop a key sticking point among Brexiteers.
The two men vying to become the next prime minister, Boris Johnson and Jeremy Hunt, have said the backstop is "dead" - a position seen as increasing the likelihood of a no-deal Brexit.
If MPs fail to support a Brexit deal agreed between UK and EU by 31 October, the legal default is to leave with no deal on that date.
Both contenders to be the next prime minister have said they want to leave on that date and renegotiate with the EU, leaving with a deal.
But Mr Hunt and Mr Johnson have also said they would keep the possibility of no deal on the table to strengthen negotiations, despite Parliament voting to rule the option out.
Mr Johnson has also refused to rule out suspending Parliament to force a no-deal Brexit through.
This week, MPs backed a bid to make it harder for a new prime minister to do this.
A majority of 41 approved the amendment, with four cabinet ministers, including Chancellor Philip Hammond, abstaining.
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A leaked cross-government study warning of the impact of a no-deal Brexit outlines a "worst-case scenario", cabinet minister Michael Gove has said.
Details from the dossier warn of food and medicine shortages if the UK leaves the EU without a deal.
Mr Gove, who is responsible for no-deal preparation, said the document was old and Brexit planning had accelerated since Boris Johnson became PM.
But he acknowledged no deal would bring disruption, or "bumps in the road".
The leak comes as Mr Johnson is to meet European leaders later this week.
The prime minister will insist there must be a new Brexit deal when he holds talks with German Chancellor Angela Merkel and French President Emmanuel Macron.
According to Operation Yellowhammer, the dossier leaked to the Sunday Times, the UK could face months of disruption at its ports after a no-deal Brexit.
And plans to avoid a hard border between Northern Ireland and the Irish Republic are unlikely to prove sustainable, it adds.
The dossier says leaving the EU without a deal could lead to:
A No 10 source told the BBC the dossier had been leaked by a former minister in an attempt to influence discussions with EU leaders.
They added that the document "is from when ministers were blocking what needed to be done to get ready to leave and the funds were not available".
Responding to the leak, Mr Gove said some of the concerns about a no-deal Brexit had been "exaggerated".
He said: "It's certainly the case that there will be bumps in the road, some element of disruption in the event of no-deal.
"But the document that has appeared in the Sunday Times was an attempt, in the past, to work out what the very, very worst situation would be so that we could take steps to mitigate that.
"And we have taken steps."
Mr Gove also claimed some MPs were "frustrating" the government's chances of securing a new deal with the EU.
He said: "Sadly, there are some in the House of Commons who think they can try to prevent us leaving on October 31st. And as long as they continue to try to make that argument, then that actually gives some heart to some in the European Union that we won't leave on October 31st.
"The sooner that everyone recognises that we will leave on that day, the quicker we can move towards a good deal in everyone's interests."
Business minister Kwasi Kwarteng told Sky News' Sophy Ridge on Sunday:  "I think there's a lot of scaremongering around and a lot of people are playing into project fear."
But a former head of the civil service, Lord Kerslake - who described the document as "credible" - said the dossier "lays bare the scale of the risks we are facing with a no-deal Brexit in almost every area".
"These risks are completely insane for this country to be taking and we have to explore every avenue to avoid them," he told BBC Radio 4's Broadcasting House.
Irish Deputy Prime Minister Simon Coveney said, in a tweet, that Dublin had "always been clear" a hard border in Ireland "must be avoided".
The Irish backstop - the provision in former prime minister Theresa May's withdrawal agreement that could see Northern Ireland continue to follow some of the same trade rules as the Republic of Ireland and the rest of the EU, thus preventing a hard border - was an "insurance policy" designed to protect the peace process, he said.
Michelle O'Neill, Sinn Fein's deputy leader, accused Mr Johnson of treating the Northern Ireland peace process as a "commodity" in Brexit negotiations.
She said Ireland as a whole had been voicing concerns about a no-deal Brexit for months.
The SNP's Stephen Gethins said the documents lay bare the "sheer havoc Scotland and the UK are hurtling towards".
Liberal Democrat MP Tom Brake said they showed the effects of a no-deal Brexit should be taken more seriously.
"The government has simply, I think, pretended that this wasn't an issue," he said
Ministers were in "a real pickle" since "the US has said that if that border is jeopardised, we're not going to get a trade deal with them", he added.
Speaker of the US House of Representatives Nancy Pelosi said on Wednesday that a US-UK trade deal would not get through Congress if Brexit undermined the Good Friday Agreement.
The leak comes as the prime minister prepares to travel to Berlin to meet German Chancellor Angela Merkel on Wednesday, before going to Paris to see French President Emmanuel Macron on Thursday.
Mr Johnson is expected to say Parliament cannot and will not change the outcome of the 2016 EU referendum and will insist there must be a new deal to replace Mrs May's withdrawal agreement - defeated three times by MPs - if the UK is to leave the EU with a deal.
However, it is thought their discussions will chiefly focus on issues such as foreign policy, security, trade and the environment, ahead of the G7 summit next weekend.
Meanwhile, a cross-party group of more than 100 MPs has urged the prime minister to recall Parliament and let it sit permanently until the UK leaves the EU.
In a letter, MPs say the country is "on the brink of an economic crisis".
Labour leader Jeremy Corbyn also reiterated his call for MPs to work together to stop a no-deal Brexit.
Elsewhere, anti-Brexit campaigner Gina Miller said the government had "unequivocally" accepted it could not shut down Parliament to clear the way for a no-deal Brexit.
She told Sky's Sophy Ridge On Sunday: "What they have said is, unequivocally, they accept that to close down Parliament, to bypass them in terms of Brexit - stopping a no-deal Brexit, in particular - is illegal."
Ms Miller said she would continue to seek further reassurances that MPs would be able to pass legislation to stop a no-deal Brexit.

Trains will be permitted to use the Channel Tunnel for three months if the UK leaves the EU without a deal, under a proposed European Commission law.
The planned legislation, published on Tuesday, will give the UK and France time to renegotiate the terms under which the railway service operates.
The law must be agreed by the European Parliament and EU member states.
Britain leaving the EU with no deal is the default position on 29 March unless a withdrawal agreement can be approved.
Tuesday's proposal is aimed at mitigating the "significant impact" that a no-deal Brexit - the UK leaving the EU without any formal Withdrawal Agreement and no transition period - would have on rail transport and connectivity between the EU and the UK, the commission said.
The proposals "are intended to ensure the continuity limited to cross-border operations and services," it said, warning that "an interruption in these activities would cause significant social and economic problems."
The legislation states that, given the "exceptional" urgency of the situation, the proposal will not be subject to the normal eight-week consultation period.
The commission also emphasised that the period for renegotiation was "strictly limited" and that the UK must maintain safety standards "identical to EU requirements".
It will now work to ensure that the legislative measure is agreed and adopted by the European Parliament so that it is ready to come into force by 30 March 2019 if necessary.
In October, the UK said it was seeking bilateral arrangements with France, Belgium, the Netherlands and Ireland to "facilitate the continued smooth functioning of cross-border rail services".
In recent months the European Council has called for member states to "intensify" preparations for a no-deal outcome.
If this happens, there are a number of laws that need to be passed to ensure continuity in crucial areas.
UK Prime Minister Theresa May says she is currently working to get an improved deal from the EU.
She wants to secure changes to the legal text of the Withdrawal Agreement she had previously agreed with the 27 other member states, after it was rejected by the UK parliament.
The UK government has said that leaving the EU with a deal remains its "top priority".

"Nothing is off the table" when it comes to reassuring MPs over the Northern Ireland backstop, Downing Street sources say.
This could include reopening the EU withdrawal agreement, even though that comes with risk, the sources say.
Theresa May is understood to be pushing the EU for flexibility on the backstop.
This is the clause in the prime minister's EU withdrawal agreement that is meant to prevent the return of border checks in Northern Ireland.
It would see the UK aligned with EU customs rules until a future trade deal is agreed that does not include a physical border between the EU and the UK on the island of Ireland.
The backstop is meant to be a temporary measure but the UK can't leave it without the EU's say-so, under the terms of the withdrawal agreement.
Many MPs fear this will mean the UK will end up indefinitely tied to the EU with no say over its rules - and that is why they are planning to vote against the withdrawal agreement on Tuesday.
Those campaigning for another EU referendum have, meanwhile, been given a boost by the European Court of Justice (ECJ), which has ruled that the UK can cancel Brexit without the permission of the other 27 EU members.
Former foreign secretary Dame Margaret Beckett, who is campaigning for another referendum, said: "This is confirmation that it is still up to us to decide whether we want to keep the existing deal we've got in the EU rather than accept a bad deal negotiated by the government."
But Environment Secretary Michael Gove said the ruling does not alter the government's intention to leave the EU in March 2019.
He told BBC Radio 4's Today programme: "We voted very clearly - 17.4 million people sent a clear message that we wanted to leave the European Union and that means also leaving the jurisdiction of the European Court of Justice.
"So, this case is all very well but it doesn't alter either the referendum vote or the clear intention of the government to make sure that we leave on 29 March."
He rejected newspaper reports that Tuesday's Commons vote will be cancelled to prevent the prime minister suffering a defeat of historic proportions that could end her premiership.
Mrs May has previously insisted there can be no deal with the EU without the backstop - and it would be impossible to change the terms of the withdrawal agreement.
She has repeatedly warned her own MPs that a rejection of her deal could lead to a general election - or possibly "no Brexit" at all.
That has so far failed to convince dozens of Tory MPs who are planning to join Labour, the Liberal Democrats, the DUP and the SNP in voting against it.
So, in a change of tone, Downing Street is now saying the withdrawal agreement could be tweaked to reflect concerns about the backstop.
By BBC Political Editor Laura Kuenssberg
On the face of it, it's pretty extraordinary to imagine that the UK government could be genuinely asking to reopen an agreement that took 18 months to put together, has already been through the grinder on multiple occasions and was only concluded a fortnight ago.
But since the ink dried, it has become clear that the chance of getting the deal through Parliament is very small. One minister said: "It's only a deal if it's ratified." Perhaps for wavering MPs, even the sign of the PM continuing to push for more will make a difference.
Read Laura's blog
Mr Gove said the prime minister was "seeking to improve" the agreement but there were "risks" involved.
"If we do attempt a fundamental reopening or renegotiation of the withdrawal agreement, European Union countries, who recognise just how uncomfortable the backstop is for them, may change the withdrawal agreement in a way that may not necessarily be to our advantage," he said.
He said it was "extremely unlikely" that he would mount a Tory leadership challenge if Theresa May stood down or was forced out after losing Tuesday's vote.
On Sunday evening, Mrs May spoke on the phone to Irish Prime Minister Leo Varadkar, whose support could be vital if she were to negotiate further with the EU.
She also spoke to the European Council President Donald Tusk, who tweeted it would be "an important week for the fate of Brexit".
Boris Johnson said Mrs May could stay on if she lost Tuesday's vote - but must renegotiate the deal with Brussels.
Mr Johnson, who quit the cabinet over Mrs May's Brexit strategy, told the BBC he did not want a "no-deal" Brexit or another referendum, but it was not right to say there were no alternatives.
He said the Northern Ireland "backstop" put the UK in a "diabolical negotiating position".
MPs could give Mrs May "a powerful mandate to change that backstop" by voting it down on Tuesday, he said.
Former Cabinet minister and Leave campaigner Theresa Villiers has said that the UK could cope with a no-deal scenario if "preparation is stepped up" and the EU co-operated.
Meanwhile, Lib Dem leader Sir Vince Cable believes Brexit may not happen at all.
"Increasingly I doubt it," he said when asked about it becoming a reality, adding it was "more likely that it won't happen".
He added there could be a "hell of a backlash" if Mrs May's "economically damaging" Brexit were to be imposed without another referendum.

Parts of the UK that backed a Leave vote would face the heaviest hit as a result of Brexit, according to estimates by government officials.
The forecasts, seen by MPs, model the 15-year impact of the UK staying in the single market, doing a trade deal with the EU or leaving without a deal.
They suggest that in England, the North East and West Midlands would see the biggest slowdown in growth.
The government said the document did not represent its policy.
It added that the forecasts did not "consider the outcome we are seeking in the negotiations".
And one Eurosceptic Tory MP said the figures were "complete nonsense".
Following a leak of some of the information to Buzzfeed last week, and political pressure to release it, ministers agreed to allow MPs to see the reports on a confidential basis in the House of Commons library.
In each scenario in the forecasts, growth would be lower, by 2%, 5% and 8% respectively, than currently forecast over a 15-year period.
In north-east England growth would be 3% lower if the UK stayed in the single market, 11% under a trade deal and 16% with no trade deal compared with staying in the EU, the forecast says.
The research suggests London - which backed Remain - would fare the best, with reductions of 1%, 2% and 2.5% in each of the three scenarios.
Scotland's estimated hit would be 2.5%, 6% and 9%. Wales would see reductions of 1.5%, 5.5% and 9.5%.
Patrick Minford, of the Economists for Free Trade group, said: "The continued leaks from Whitehall sources about the results of civil servants' latest modelling attempts is, sadly, a continuation of Project Fear's effort to paint Brexit as a damage limitation exercise."
The group has produced its own forecasts, based on "proper, independent free trade policy," which predicts that UK economy would grow by 4% in the long term after Brexit.
Brexit-backing Conservative MP Jacob Rees-Mogg has accused Treasury officials of "fiddling the figures" to make all options but staying in the EU look bad.
Whitehall trade unions reacted angrily to this suggestion and government ministers have dismissed his allegation.
The government has said the analysis is preliminary and crucially does not measure the impact of the UK's preferred option of a bespoke and comprehensive trade agreement, covering goods and financial services.
A spokesman said: "As ministers clearly set out in the House, this is provisional internal analysis, part of a broad ongoing programme of analysis, and further work is in progress.
"We are seeking an unprecedented, comprehensive and ambitious economic partnership - one that works for all parts of the UK. We are not expecting a no-deal scenario."
The research suggests that the option of staying in the single market and customs union, which has been rejected by ministers, would be the least damaging but would still see growth across different parts of the country between 1% and 3% lower than current forecasts.
In the event of a limited free trade deal being negotiated, projected growth would be 8% lower in the West Midlands, north-west England and Northern Ireland, by 6% in Scotland and 5.5% in Wales.
Should the UK leave the EU in March 2019 without any kind of deal, it suggests four parts of the UK would see a double digit slowdown in GDP growth.
As well as north-east England, north-west England and Northern Ireland would see a 12% slowdown, while the West Midlands would see a 13% slowdown.
Other official estimates suggest the UK car industry's GDP would shrink by 1% if the UK remained in the EU single market but would lose 8% if there was a free trade agreement and 8.5% if the UK left without a deal and went to World Trade Organisation (WTO) rules.
The figures emerged as representatives of Nissan and other Japanese companies are set to meet Theresa May and Chancellor Philip Hammond on Thursday.
Former attorney general and Conservative MP Dominic Grieve said the figures illustrated the risks of leaving the EU without a deal, which he said would hurt the "poorest and vulnerable" in society.
Even if the UK achieved its stated objective of a deep and special partnership with the EU and trade deals with countries like the US, he said it was likely to yield, at best, a very small economic boost.
But Eurosceptic Conservative MP John Redwood said the risks of a no-deal scenario had been overestimated and the Treasury figures were "complete nonsense".

Theresa May has asked the EU for "one more push" to get her Brexit deal through Parliament and warned that, if it fails, "we may never leave at all".
The prime minister said the UK had tabled "serious" proposals to resolve the deadlock over the Irish backstop.
Warning of a "moment of crisis" if the deal was rejected again, the PM told EU leaders: "Let's get it done."
The EU said it would give "legal force" to assurances already made that the UK could not be stuck in a customs union.
Setting out the EU's position on Twitter, chief Brexit negotiator Michel Barnier said it was "not interested in the blame game" and talks would continue over the weekend.
The BBC's political editor Laura Kuenssberg said what the EU was offering amounted to a "legal beefing-up of existing promises".
Brexit Secretary Steve Barclay and the DUP, the party Mrs May's government relies on for a majority in Parliament, were both dismissive of Mr Barnier's proposal.
Mr Barclay tweeted: "With a very real deadline looming, now is not the time to rerun old arguments. The UK has put forward clear new proposals. We now need to agree a balanced solution that can work for both sides"
While Nigel Dodds, the deputy leader of the DUP, said Mr Barnier's proposal regarding the backstop "disrespects the constitutional and economic integrity" of the UK, and it was neither "realistic nor sensible".
He said the EU's proposal "demonstrates that they have a one-sided approach and a lack of understanding about the divisions in Northern Ireland".
The UK is due to leave on 29 March, although Parliament has yet to agree the terms of withdrawal.
MPs will vote for a second time on the withdrawal deal Mrs May has negotiated with the EU on Tuesday - after it was defeated by a historic margin in a Commons vote in January.
If they reject it again, they will get the option of either leaving without a deal or delaying the exit date.
In a speech to a green energy firm in Lincolnshire, Mrs May said she understood the "genuine concerns" about the backstop but appealed to MPs to recognise that the deal as a whole respected the 2016 referendum result and would ensure the UK's long-term prosperity.
"Back it and the UK will leave the EU," she said.
"Reject it and no-one knows what will happen. We may not leave the EU for many months. We may leave without the protections a deal provides, we may never leave at all."
It was in neither side's interest to prolong the uncertainty by "carry on arguing" about Brexit, she said, claiming any delay beyond 29 March only risked "creating new problems".
"It needs one more push to address the specific concerns of our Parliament," she said. "So let's not hold back and do what is necessary for MPs to back the deal.
"Because if MPs reject the deal, nothing is certain. It would be at a moment of crisis."
She suggested the British people, to whom Brexit "belonged", had "moved on" and "are ready for this to be settled", adding: "Everyone now wants to get it done."
But former Conservative minister Dominic Grieve, who backs a referendum to endorse the terms of Brexit, said it was "hard to see" how Parliament would agree to the current deal.
Speaking at the Scottish Labour conference, party leader Jeremy Corbyn said the prime minister sounded "desperate" in her speech.
"If she cannot get her botched Brexit deal through Parliament next week, it will represent an unprecedented failure in British political history.
"The utter mess the government has made of the Brexit negotiations, and their reckless abandon when it comes to people's jobs and livelihoods, is absolutely unforgiveable.
"Having already failed once to get her deal through, I want to make it clear to the PM that if she fails again, it will be the end of the road for her deal."
The SNP said the deal on offer was "fundamentally flawed" and would damage the Scottish economy.
"Theresa May must stop passing the buck and take personal responsibility for the Brexit crisis created as a result of her own intransigence," said its Westminster leader Ian Blackford.
The first Commons vote, in January, saw the deal rejected by 432 votes to 202, the largest defeat for a sitting government in history.
Mrs May is seeking legally enforceable changes to the backstop - a controversial insurance policy designed to prevent physical checks on the border between Northern Ireland and the Republic of Ireland - but there have been few visible signs of progress.
Leading Brexiteers are looking for reassurances that the backstop - which would see the UK aligned with EU customs rules until the two sides' future relationship is agreed or alternative arrangements worked out - will not endure indefinitely.
On Friday the EU said it was prepared to include a number of existing commitments relating to the application of the backstop in a legally-binding document.
Michel Barnier tweeted that the UK "will not be forced into [a] customs union against its will" as it could choose to exit the proposed "single customs territory" on its own. But Northern Ireland would remain part of the EU's customs territory, subject to many of its rules and regulations - something the government has previously said would threaten the constitutional integrity of the UK.
There will also be a reminder that the UK can suspend parts of the backstop if an independent arbitration panel rules that the EU is not behaving in good faith.
The BBC's Laura Kuenssberg said it was "not really a concession" as the suggestion that Great Britain could leave the backstop - and become free to diverge from EU rules - while leaving Northern Ireland behind, had already been rejected.
Any extension to the Article 50 process, under which the UK is due to leave the EU on 29 March, would need the unanimous approval of the EU.
Two former prime ministers, Sir John Major and Gordon Brown, have called for a delay of a year to allow for a "public consultation" on the way ahead and to ensure an orderly exit.
But Defence Secretary Gavin Williamson warned against any delay, telling Nick Robinson's Political Thinking podcast: "Wherever we are, and I very much hope we land it with a deal, but if we don't get a deal and we exit without a deal, Britain will succeed and thrive - I don't have a moment's doubt about that.
"But we need to deliver Brexit and ensure that's it's done. I personally believe 29th March is the best day for making sure that is delivered upon."

An exercise to test plans for border disruption in the event of a no-deal Brexit has been described as "too little too late" by hauliers.
A convoy of 89 lorries took part in two test runs from the disused Manston Airport, near Ramsgate in Kent, on a 20-mile route to the Port of Dover.
The Department for Transport said they went well and traffic ran smoothly.
But the Road Haulage Association said the process should have begun months earlier.
Its chief executive Richard Burnett said the trial "cannot possibly duplicate the reality of 4,000 trucks that would be held at Manston Airport in the event of a no-deal Brexit".
"It's too little too late, this process should have started nine months ago," he added.
"At this late stage it looks like window dressing."
Conservative MP for Dover, Charlie Elphicke, also questioned the usefulness of the test.
"We've got to remember 10,000 lorries visit the Channel ports every single day so a test with less than 100 is not even a drop in the ocean," he said.
"Sending lorries around Kent on a wild goose chase all the way to Manston in the extreme north-east corner and then sending them to the Port of Dover by a small A road is not the right answer."
But Toby Howe, from Kent County Council, said: "What we're learning from this is not based on 1,000 lorries or whatever.
"What we want to know is how quickly they can actually get out of the airport behind us and how quickly they will get to the various points on the stage.
"So whether it's 10 lorries, 20 lorries, 100 lorries, that will give us enough information and will give the Department for Transport enough information to then learn from that."
Up to 150 lorries had originally been expected to take part in the trial, known as Operation Brock, to test the airport site's suitability as a mass HGV holding bay.
The drivers congregated in a large group at the former airfield before being directed by officials from the Department for Transport (DfT), Kent County Council and police officers along the A256 towards Dover.
The first practice run began in rush-hour shortly after 08:00 GMT, with four convoys leaving at intervals between 08:13 and 08:39.
The first of the convoys arrived in Dover at 08:52 where they were directed to do a loop around the Eastern Docks roundabout, travel along Jubilee Way and drive straight back to the airport.
A second test run got under way at 11:00.
Lorry drivers who spoke to the BBC on arrival back at Manston after the first test said there had been "no problems whatsoever".
However, one driver said he thought it had been "a waste of time".
"Someone had to do it didn't they, really? But at the end of the day what will be, will be," he said.
Another driver, Ben Pearce, said the test "seems to be going quite well".
He added: "It will give them a fair idea how the traffic will behave if they do use the space as a holding bay."
Each driver taking part in the exercise was paid £550, the DfT said.
Operation Brock was intended to maintain traffic flow on the M20 and prevent the kind of disruption experienced in 2015 when parts of the motorway were closed to cars for several days.
The trial was organised alongside the Road Haulage Association (RHA) and the Freight Transport Association.
Some people on social media also question the usefulness of the trial.
The exercise coincided with the day many people returned to work and school for the first time since Christmas.
Tracey Ives, who owns haulier INT Logistics, said: "The roads were very quiet today.
"I would have thought we would have got a better, more realistic overview of it all if it hadn't been advertised beforehand."
Prime Minister Theresa May is attempting to persuade MPs to support her draft Brexit deal.
MPs will vote on her deal on 15 January, government sources have confirmed.
Information about BBC links to other news sites

A rise in public disorder, higher food prices and reduced medical supplies are real risks of leaving the EU with no deal, a UK government document says.
Ministers have published details of their Yellowhammer contingency plan, after MPs voted to force its release.
It outlines a series of "reasonable worst case assumptions" for the impact of a no-deal Brexit on 31 October.
Labour leader Jeremy Corbyn said the paper confirmed the PM "is prepared to punish those who can least afford it".
Michael Gove, one of Boris Johnson's senior cabinet colleagues who has been given responsibility for no-deal planning, said "revised assumptions" will be published "in due course alongside a document outlining the mitigations the government has put in place and intends to put in place".
However, ministers have blocked the release of communications between No 10 aides about Parliament's suspension.
Mr Gove said MPs' request to see e-mails, texts and WhatsApp messages from Dominic Cummings, Boris Johnson's chief aide, and eight other advisers in Downing Street were "unreasonable and disproportionate".
Publishing the information, he added, would "contravene the law" and "offend against basic principles of fairness".
The government sought to resist the publication of the Operation Yellowhammer document, but lost a vote on the issue in the Commons on Monday, prior to the suspension of Parliament, so it was compelled it to do so.
The six-page document, dated 2 August and leaked to the Sunday Times last month, warns of disruption at Dover and other channel crossings for at least three months, an increased risk of public disorder, and some shortages of fresh food.
On food, the document says certain types of fresh food supply "will decrease" and "critical dependencies for the food chain" such as key ingredients "may be in shorter supply".
It says these factors would not lead to overall food shortages "but will reduce the availability and choice of products and will increase price, which could impact vulnerable groups".
The document also says low-income groups "will be disproportionately affected by any price rises in food and fuel".
The flow of cross-Channel goods could face "significant disruption lasting up to six months".
"Unmitigated, this will have an impact on the supply of medicines and medical supplies," it says.
"The reliance of medicines and medical products' supply chains on the short straits crossing make them particularly vulnerable to severe extended delays."
Among its other key points are:
The document also warns of potential clashes if foreign fishing vessels enter British territorial waters on the day after the UK's departure and says economic difficulties could be "exacerbated" by flooding or a flu pandemic this winter.
The BBC's Chris Mason said some of the scenarios outlined were "stark", but ministers were insisting the paper was not a prediction about what will happen.
The document, which, until now, was categorised as "official, sensitive", is not an official cabinet paper. It dates from 10 days after Mr Johnson became prime minister.
Retailers said the document confirmed what they have been saying will happen in the event of a no-deal Brexit.
"Fresh food availability will decrease, consumer choice will decrease, and prices will rise," Helen Dickinson of the British Retail Consortium said.
And the British Medical Association described the Yellowhammer file as "alarming" and that it confirmed its warnings about no-deal, including the threat of medical supply shortages.
Labour's shadow Brexit secretary Keir Starmer said: "These documents confirm the severe risks of a no-deal Brexit, which Labour has worked so hard to block.
"It is completely irresponsible for the government to have tried to ignore these stark warnings and prevent the public from seeing the evidence."
MPs voted on Monday to order the release of all internal correspondence and communications, including e-mails, texts and WhatsApp messages, between nine No 10 advisers relating to Parliament's suspension.
But the government has said it will not comply with the MPs' request, citing potential legal breaches of data protection and employment rights.
This is not an "old" Yellowhammer assessment, as was claimed by the government in August.
It is from the latest internal no-deal planning, from August, from well within the time of Boris Johnson's administration.
The government hopes that its recent efforts will change some of the most concerning aspects of what is titled a "reasonable worst case assumptions" document, but they are yet to be able to make those changes.
Everything hinges on the core assumption made about disruption to freight traffic across the Channel - that over half would be stuck for up to two and a half days.
Those assumptions on trade flow have improved recently, but are still poor, and enough to have several highly concerning consequences, from fresh food supply, to stability in Northern Ireland, to social care providers and supplies of medicines for people and animals.
I have also been assured that a widely circulated version of this document, from the same day, had the phrase "base scenario".
It is somewhat confusing that there can be a base case of a worst case planning assumption.
In any event, these are the real, plausible short-term shocks from a no-deal Brexit.
The section on Northern Ireland is particularly concerning. In many respects it is incredible to have such a list of the plausible consequences of what is government policy.
It is not difficult to see why the government resisted its release. It is unlikely to improve the mood of an already sceptical Commons.
But it is really the first tangible, quotable, warts and all assessment of what Whitehall fears could be around the corner.
Mr Gove said the legal advice received by Mr Johnson before requesting the prorogation of Parliament was in the public domain after being disclosed as part of the ongoing court cases, but there was no justification for the "far broader" information being sought.
"To name individuals without any regard for their rights or the consequences of doing so goes far beyond any reasonable right of Parliament under this procedure.
"These individuals have no right of reply, and the procedure used fails to afford them any of the protections that would properly be in place.
"It offends against basic principles of fairness and the Civil Service duty of care towards its employees," he said.
He said it was ministers, not civil servants or special advisers, who were ultimately accountable to Parliament for decisions taken.
The request, therefore was "inappropriate in principle and in practice, would on its own terms purport to require the government to contravene the law, and is singularly unfair to the named individuals".
Correction 2nd October 2019: An earlier version of this story suggested the Yellowhammer document had referred to the potential risk of rioting; it has been amended to more closely reflect the paper's exact wording, which referred to protests and "a rise in public disorder and community tensions".

Jeremy Corbyn says opposition MPs will take the first steps towards trying to pass a law blocking a no-deal Brexit when Parliament returns next week.
The Labour leader was speaking after meeting other opposition leaders to discuss ways of averting a no deal.
The move could force the PM to ask the EU for a further Brexit delay, beyond the current 31 October deadline.
A No 10 source accused the MPs of "seeking to sabotage the UK's position" in talks with Brussels.
Those talks were "now making progress", the source added.
Prime Minister Boris Johnson has urged the EU to re-open the withdrawal deal reached with Theresa May, and to make key changes that would allow it to be passed by Parliament.
But he has insisted the UK will be leaving on 31 October even if no new agreement is reached.
At present, the default position in law is that the UK leaves the EU on 31 October with or without a deal.
MPs opposed to no deal want to pass a new law to change that.
They have already done that once - in April, faced with the possibility of a no-deal exit on the original Brexit date of 29 March, they passed a law forcing Theresa May to ask for an extension to the UK's EU membership.
Repeating that approach would require them to first take control of the parliamentary timetable.
This time round it will be harder because there are limited opportunities do that before 31 October, but one possible option would be as part of an emergency debate - a topical matter added to Commons business at short notice.
MPs plan to apply for an emergency debate as soon as next Tuesday or Wednesday, sources have told the BBC.
It is understood they hope to use the debate to set out a number of dates on which MPs would decide business - meaning Parliament could discuss legislation aimed at stopping no deal.
That could involve cancelling the conference recess in September, although that is not yet confirmed. The MPs are confident the Speaker John Bercow will allow the move.
Tory backbencher and former attorney general Dominic Grieve refused to reveal details of the plan he is backing, but believes enough colleagues on his own benches will join him and the opposition to stop a no-deal Brexit.
"There will be many who will be very, very worried about what the prime minister is doing, but they will also be loyal," he told BBC Radio 4's PM programme.
"But equally... we are facing a deep national crisis and many of my colleagues realise that very well.
"We have to make up our minds - what we are going to say to future generations about what we did during this national crisis?
"I think there are plenty of Conservatives who take the view that a no-deal Brexit would essentially be catastrophic for the country's future and will move to stop it."
Another way of potentially stopping no deal is to try to bring down the Johnson government via a no-confidence vote.
Mr Corbyn had said this was his preferred option, after which he would become interim PM, call a snap election and campaign for another referendum.
However, the Liberal Democrats and some Tory MPs said they would not support any plan that saw Mr Corbyn become prime minister - even on a temporary basis.
Lib Dem leader Jo Swinson said a no-confidence vote "remains a last resort, if you like, to be able to enforce the will of Parliament, but the main proposal is going down the legislative route".
Green MP Caroline Lucas said "the legislative way forward" was "the most secure way to... get rid of that 31 October deadline" and stop a PM "careering towards" no deal.
Mr Corbyn said opposition MPs had agreed to "first" try to avoid no deal using legislation, but using a vote of no confidence to bring down the government at "appropriate time" remained an option.
The meeting was also attended by the SNP and Plaid Cymru.
SNP Westminster leader Ian Blackford said it had been "positive and productive", adding: "Parliament must grasp this opportunity, unite to stop Boris Johnson shutting down democracy - and be ready to use all mechanisms to block a no-deal disaster, including deploying legislation as a priority."
Plaid Cymru leader Adam Price said his party was "committed to work co-operatively with every other opposition party and do everything in our power to avoid a catastrophic crash-out Brexit".
Mr Corbyn did also invite five Tory MPs opposed to a no-deal exit, but none attended.
The Labour leader has since written to 116 Conservative and independent MPs, who have previously voted against no deal, to ask them to join his efforts.
So how might opposition MPs' attempt to use legislation to prevent a no-deal Brexit work in practical terms?
The first challenge would be to get some Conservative rebels on board, because some in the Labour Party (namely Brexiteers) simply won't back it.
But with Boris Johnson still insisting he can get a deal, it could well be the case that some Tory rebels unhappy with the prospect of no deal would equally be unhappy to rush into anything that would undermine the PM at this stage.
So, it is not at all certain. And in any case, even if Mr Johnson was faced with being forced to do something against his will, he has the option of calling on MPs to vote for an election (under the Fixed Terms Parliament Act).
Yes, Lib Dem Leader Jo Swinson has urged MPs to block that move specifically if Mr Johnson wants to go to the polls only after Brexit.
But under most circumstances, when a PM throws down the gauntlet for an election, it would be an unusual leader of the opposition who doesn't take that challenge.
Brexit Party leader Nigel Farage, speaking earlier in the day, criticised those who took part, saying they were "very out of touch with public opinion" and leaving the EU without an agreement was now "the only acceptable deal".
A No 10 source said: "It's utterly perverse that Corbyn and his allies are actively seeking to sabotage the UK's position.
"This coalition of anti-democrats should be honest with the British public, they are against us leaving the EU no matter what."
Meanwhile, MPs from different parties have signed a declaration pledging to set up an alternative assembly if the PM prorogues - or suspends - Parliament.
Mr Johnson says he has no plans to do this, but has not ruled out such a move to make sure the UK leaves the EU by the end of October.

Opposition parties will not call for a vote of no confidence in the government to topple the PM this week.
Speaking after cross-party talks, Labour leader Jeremy Corbyn said he will back a motion "at a point we can win it and take no-deal off the table".
The SNP's Ian Blackford said his party was keen to push for an early no confidence vote but wanted to take the other parties with them.
Green Caroline Lucas said the parties were "united about stopping no-deal".
The cross-party group also requested an emergency debate on disclosure of no-deal Brexit planning papers, but this was rejected by the Speaker John Bercow.
Chancellor Sajid Javid has said a no-deal Brexit "may well happen" on 31 October, despite a law aimed at avoiding it.
The law, known as the Benn Act, forces the government to ask for an extension to the Brexit deadline if a deal is not agreed by 19 October, the day after a two-day EU summit.
Mr Corbyn, Mr Blackford, Ms Lucas, Lib Dem leader Jo Swinson, Plaid Cymru Westminster leader Liz Saville Roberts, and Independent Group for Change leader Anna Soubry met in the Labour leader's Westminster office.
The Labour leader said the parties were "absolutely clear we will do all we can within a Parliamentary scenario and within our own parties to prevent this country crashing out on the 31st October without a deal -  that is what is our agreed position".
When asked about options to ensure that including beefing up the Benn act, a motion of no confidence in the government or an emergency debate, Mr Corbyn said: "All those options are in play."
Mr Corbyn said there were "huge political differences" between the parties, "but we have come behind this point to stop a no-deal Brexit".
Opposition parties have been working together over the last few weeks to try and thwart Boris Johnson's Brexit strategy.
But with some worried the PM might be able to get around legislation to avoid no deal next month - there are real disagreements about what to do next.
The SNP spent the past few days trying to drum up support for a confidence vote to bring down the government and install a temporary PM to extend the Brexit deadline.
Other parties have ruled that out today because they can't agree on who should lead it.
There is a clear divide between Labour - who think it should be Jeremy Corbyn - and the Lib Dems, who don't.
So any hopes a big move from opposition parties this week has been sunk - because they just can't agree on what it should be.
Ms Swinson said a "precipitous" vote of no confidence motion could "increase the risk" of a no-deal Brexit and "play into Boris Johnson's hands".
Party whips would meet to consider different scenarios, including the possibility of an "insurance" option of a government of national unity, Ms Swinson added.
This would see a temporary "caretaker" prime minister heading a coalition of opposition parties - Tory veteran Ken Clarke or Labour grandee Margaret Beckett have both been mentioned - but it is likely to be resisted by Labour.
However, Ms Swinson rejected the possibility that her MPs could back Mr Corbyn as an interim prime minister, saying he would not command a majority in the Commons.
"He simply does not have the numbers," Ms Swinson said, referencing the 21 MPs expelled from the Conservative Party and the five within the Independent Group for Change.
"I have been crystal clear but I will do so again - Jeremy Corbyn is not going into Number 10 on the basis of Liberal Democrats' votes."
Ian Blackford, Westminster leader for the SNP - which wants a vote of no confidence as soon as possible - told Sky News: "We have to do everything we can and that includes a motion of no confidence and there's more work to be done on that over the coming days.
"We need to stop Boris Johnson crashing us out [in a no-deal Brexit], that is our priority, that is what unites all of us.
"I've made it clear that we want a motion of no confidence, but we need to do that on a basis that other parties come with us as well."
Earlier, Chancellor Sajid Javid told BBC Radio 4's Today programme that "every government should observe all laws at all times", adding: "We're taking a careful look at that law."
"We're also very clear that our policy has not changed. We will leave on October 31," he said.

The PM has said she is trying to get further assurances from the European Union so she can win the Commons vote on her Brexit deal next week.
Theresa May said that after delaying the vote last month, there was "some further movement from the EU" at December's European Council.
But Labour accused ministers of trying to "run down the clock" to "blackmail" the UK into backing a "botched deal".
Labour sources say they will back moves by MPs to frustrate a no-deal exit.
More than 200 MPs have signed a letter to Mrs May, urging her to rule out a no-deal Brexit - which is one where the UK leaves the EU but without any agreed arrangements covering things like how trade or travel will work in the future.
Labour sources told the Guardian that the party would back a cross-party amendment, to be debated on Tuesday, which would stop the government from taking economic measures arising from a no-deal, including raising taxes, unless Parliament had "explicitly" agreed to leave without a deal.
It comes as a major exercise involving more than 100 lorries has been carried out in Kent to test out how to manage traffic queues near the Channel ports in the event of a no-deal Brexit.
The prime minister has been hosting critics of her deal, including former foreign secretary Boris Johnson and former leader Iain Duncan Smith, at a reception in Downing Street - the first of a series of events for Tory MPs this week.
Her deal - which covers the terms of the UK's divorce and the framework of future relations with the EU - has already been agreed with EU leaders. But it needs to pass a vote by MPs before it is accepted.
Mrs May, who earlier on Monday was at Alder Hey hospital in Liverpool to launch a 10-year plan for the NHS, said that after delaying the vote on her Brexit deal last month, there had been "some further movement from the EU" and she continued to speak to European leaders.
"In the coming days what we'll set out is not just about the EU but also about what we can do domestically, so we will be setting out measures which will be specific to Northern Ireland; we will be setting out proposals for a greater role for Parliament as we move into the next stage of negotiations," she said.
"And we're continuing to work on further assurances, on further undertakings from the European Union in relation to the concern that's been expressed by Parliamentarians."
But the EU Commission said there would be no renegotiation. A spokesman said "everything on the table has been approved and... the priority now is to await events" in the UK.
Responding to an urgent question from Labour leader Jeremy Corbyn, who asked for an update on progress made in achieving legal changes to the withdrawal agreement, Brexit Secretary Stephen Barclay said the Commons debate would begin on Wednesday.
He said Mrs May had been in contact with "a number of her EU counterparts" over Christmas and said ministers "will be clear on Wednesday" what developments have been made.
"Securing the additional reassurance that Parliament needs remains our priority," he told MPs. "It's a good deal, it's the only deal, and I believe it is the right deal in offering certainty for this country."
But Mr Corbyn called Mrs May's deal a "Frankenstein monster of a deal".
"The government is trying to run down the clock in an attempt to blackmail this House and the country into supporting a botched deal," he said.
"We're now told, if we don't support it, the government is prepared to push our whole economy off a cliff edge."
Government sources have told the BBC the vote on the deal - which will come at the end of five days of debate - is set for Tuesday, 15 January, assuming MPs agree to sit this Friday.
The prime minister's deal is facing opposition from many of her own MPs, as well as Labour and other opposition parties including the Remain-supporting Liberal Democrats.
The DUP - which Mrs May's Conservative Party relies on for a majority in Parliament - has said it will not back the deal.
But Brexit minister Kwasi Kwarteng dismissed suggestions that the government had accepted it would lose next week's vote and was planning on returning to Brussels.
"The plan is to win the vote," Mr Kwarteng told BBC Radio 4's Today programme, adding that a week was "a very long time in politics" and he was "very hopeful" the deal would be voted through.
Fellow minister Margot James also urged MPs to back the deal but warned, if they could not reach agreement, Brexit might have to be delayed to allow for more negotiations.
"We have very little time left," she told the BBC's Politics Live. "We might have to extend Article 50. But I think it's very unlikely Parliament will actually stare down the barrel of that particular gun."
By the BBC's political editor Laura Kuenssberg
One source joked to me that I could just re-open my notebook from the last day before the Christmas break and carry on as if the past fortnight hadn't happened.
The prime minister is still pushing for extra promises from the EU about making the controversial Irish backstop temporary and a bigger role for Parliament and potentially for the Northern Ireland Assembly (which, remember, hasn't sat for a very long time now).
But there is precious little sign of anything that might be described as hefty enough to convince scores of MPs to change their minds and swing in behind her deal.
It is likely that something will emerge, a form of words, a stronger commitment to the hoped for start date for the long-term trade deal perhaps.
But the EU is in no mood for something big that could reopen the withdrawal agreement.

Theresa May must prepare to exit the EU with no deal to have "real leverage" in Brexit negotiations, a letter from 60 politicians and business figures says.
The prime minister should also reserve the right to "take with it the £39bn it has offered to pay as part of a divorce settlement", it says.
Signatories urge the government to accelerate plans to operate under World Trade Organisation (WTO) rules.
Downing Street said it was confident the UK would get a good deal.
Former cabinet ministers, economists and business figures including former chancellor Nigel Lawson, vocal Brexiteer John Redwood, and Wetherspoon chairman Tim Martin signed the letter.
It was organised by Economists for Free Trade (EFT) and asks Mrs May to warn the EU that despite its "intransigent and punitive stance" Brexit cannot be stopped.
"We believe you could also make clear that your preferred outcome is a free trade deal between Britain and the EU, an arrangement that is to the mutual benefit of both parties," the letter says.
It goes on to say that even though a free deal trade is "eminently possible", it believed it was "time" to move to a World Trade Deal under WTO rules "in light of the reluctance of the EU swiftly to secure a free trade deal".
Britain is due to leave on 29 March 2019, 46 years after it first joined the European Economic Community, the forerunner to the EU.
BBC political correspondent Ben Wright says the letter is "a sign of how frustrated hardline Brexiteers are becoming".
He adds: "The letter shows how intense the pressure is for Mrs May not to compromise, from some in her own party."
The UK wants to negotiate a "comprehensive, bold and ambitious" free trade agreement with the EU.
If it can't achieve that, there are a number of other possible arrangements of varying depth before the UK reaches the point where it has no preferential trade relationship with the EU other than common membership of the WTO.
If the UK had to trade under WTO rules, tariffs - a tax on traded goods - would be applied to all UK exports.
The average WTO tariff varies from product to product, from 0% on mineral fuels and pharmaceuticals, to around 20-35% on processed food and 45-50% on meat.
Reality Check: Does the UK trade with 'the rest of world' on WTO rules?
The warning from well-known Brexit supporters comes after tens of thousands of people marched in central London, demanding a final vote on any UK exit deal..
On Friday, plane-maker Airbus - which employs 14,000 people in Britain - said it could leave the UK if it exits the single market and customs union with no transition deal.
Car maker BMW also warned that clarity is needed on a trade deal by the end of the summer, potentially affecting the company's 8,000-strong staff in the UK.
In the letter, EFT says Britain can "flourish, even without a free trade deal, because of benefits of leaving the EU".
"This would give the chancellor ample scope to increase spending on priority public services such as the NHS, while reducing the too high UK tax burden."
Earlier this week, Theresa May said a so-called Brexit dividend could be used to fund part of an extra £20bn a year for the health service.
Although the Office for Budget Responsibility (OBR) calculates the UK will begin saving £3bn a year by 2020, this does not take into account Britain's expected £39bn divorce bill for exiting the EU.
When asked about the EFT's letter, a Downing Street source said: "We are confident of getting a good deal that delivers for every part of the UK and allows us to take back control of our money, rules and borders."

Theresa May has been accused of planning to "throw open" Britain's borders after Brexit, by a cross-party group of pro-European MPs.
It comes after Transport Secretary Chris Grayling said there won't be any border checks at Dover when Britain leaves the EU in March next year.
He said it would be "utterly unrealistic" to have checks and trade would be managed electronically.
The Open Britain group has written to the PM to demand clarification.
In their letter, the Labour, Lib Dem and Green MPs, who campaign against a "hard Brexit", say: "It is extraordinary that a government that says it aims to 'take back control' now admits it is not even going to try to control the transfer of goods across our borders, in the event we leave the customs union.
"This has major implications for our businesses, our infrastructure and our trade."
Such a plan would not avoid a hard border "because the EU would have to enforce checks on goods entering its common market", the MPs say.
And, in the event of no trade deal being reached with the EU, "it would be in breach of WTO rules to apply no tariffs on EU goods whilst continuing to apply tariffs on goods from outside the EU".
The MPs also call for the government to make its post-Brexit border plans public after Sky News reported that companies have been asked to sign non-disclosure agreements about briefings on the impact on freight traffic if there is no Brexit agreement as well as other possible scenarios.
The Department for Exiting the EU said while a trade deal was "by far and away the highest probability", it made sense to prepare for all possible outcomes.
The UK currently has a free-flowing border in Kent where lorries travelling within the EU do not complete customs declarations and passport checks are minimal.
Researchers estimate it takes an average of about two minutes for each vehicle at Dover to be processed.
There have been warnings that if additional customs checks are imposed after the UK leaves on 29 March 2019, it will add about 10 miles to the queues at peak times for every additional minute's worth of checks.
A study by Imperial College London earlier this week found that two extra minutes of checks on vehicles could more than triple the existing queues, potentially leading to motorway tailbacks up to 29 miles long.
But Mr Grayling told BBC One's Question Time it was "absolutely clear" that this "cannot happen".
"We will maintain a free flowing border at Dover - we will not impose checks in the port. We don't check lorries now - we're not going to be checking lorries in Dover in the future.
"The only reason we would have queues at the border is if we put in place restrictions that created those queues - we are not going to do that."
The government has said leaving the EU will allow the UK to take back control of its borders.
The UK is set to the leave the customs union, but ministers are hoping to negotiate a new customs partnership with the EU as part of a transition arrangement likely to last about two years after the UK's official exit from the union next March.
Mr Grayling said goods moved seamlessly across national borders elsewhere in the world and there was no reason this would not happen after Brexit.
"Go to our ports on the east coast that take goods from outside the European Union where goods... depart pretty much as soon as they arrive. That is what is going to happen.
"We will manage trade electronically. Trucks will move through the border without stopping. We will manage them electronically. In the way it happens between Canada and the US."
Labour said a new customs union with the EU was the only way to avoid "gridlock" at British ports.
"Chris Grayling let the cat out of the bag by exposing how unprepared the government are for leaving the EU," said shadow transport secretary Andy McDonald.
"The government said leaving the EU is about regaining control of our borders but the transport secretary's plan would achieve the exact opposite."
He warned of chaos unless the UK was able to negotiate a new arrangement replicating all the benefits of the existing customs union, which removes tariffs and other trade barriers between its members.
Under the terms of the Le Touquet agreement, in which juxtaposed border and immigration controls are in force on either side of the Channel, France has the power to carry out checks on outbound vehicles at Dover.
When France increased security checks in the summer of 2016, in the wake of a series of terror attacks in the country, it led to days of lengthy queues on the roads approaching the port as staff shortages meant checks on passenger coaches were taking 40 minutes.

Theresa May has set a date for what's probably her last attempt to pass a Brexit deal - and she's told Labour there's an urgent need to compromise.
The odds of her succeeding are faint - and her time's nearly up.
There's every risk Mrs May will fail, again, to deliver Brexit when she introduces her Brexit legislation in the first week of June.
This will come after what look like being tough European elections and, by the way, during the week of President Trump's official visit to the UK.
Tonight, she also told Jeremy Corbyn time was running out to reach any deal with Labour. But the reality is there has been no breakthrough in those talks, and no obvious reason to expect one.
A cross-party agreement which involved Labour's minimum demand of a customs arrangement with the EU would cause a mutiny among Tory MPs, as Tuesday's letter to the Times newspaper warns vividly.
It would also mean a revolt among Labour MPs if there's no guarantee of a new referendum, and Mr Corbyn has shown very little enthusiasm for that.
Meanwhile, Mrs May's under quite intense pressure. Her most senior MPs, the executive members of the 1922 committee, will press her this week for a timetable to step down.
Local Tory officials will gather in June and consider passing a humiliating vote of no confidence in her. And in the European elections, the polls are looking very promising for Nigel Farage's Brexit Party.
So promising that Mrs May's last, best, hope may be that the elections shocks both big parties into backing her.
And if that sounds like clutching at straws, well, Mrs May's in a corner, all but out of time, and reaching and clutching at any hope she can find in what are now the dying days of her premiership.

Theresa May and Jeremy Corbyn are meeting to discuss ongoing Brexit talks between their two parties.
A Labour source told the BBC it was about "keeping in touch" after meetings of both the PM's cabinet and the opposition leader's shadow cabinet.
Earlier, Labour's John McDonnell said there had been no "significant shift" in the government position.
Foreign Secretary Jeremy Hunt said a compromise was not impossible but talks could not continue "indefinitely".
The discussions have been going on for weeks with little sign of progress.
Following a cabinet meeting on Tuesday, BBC political correspondent Nick Eardley said ministers had agreed they would continue.
Speaking at a Wall Street Journal event in London, the shadow chancellor, Mr McDonnell, criticised a letter from senior Tories to Mrs May urging her not to agree a deal with Labour that includes a customs union.
The letter has been signed by 13 former Tory cabinet ministers and Sir Graham Brady, chairman of the backbench 1922 Committee.
Mr McDonnell said Labour had not seen enough movement from ministers to reach a deal - especially on the issue of a customs union with the EU - and insisted Labour had "compromised in some areas", but "we're not near what we want".
He said the letter gave Labour "no security" that any deal done would be honoured in the long-term - especially once Mrs May is replaced as Tory leader.
"We've gone into this in really good faith, we've tried to put party politics to one side," Mr McDonnell added.
"Our big problem now is if we're going to march our troops in Parliament to the top of the hill to vote for a deal and then that's overturned, literally, in weeks, I think that would be a cataclysmic act of bad faith."
But speaking at the same event, Mr Hunt said there was "potential" for a deal because it was in the interests of both main parties to resolve the Brexit impasse.
"Both of us would be crucified by our base if we went into a general election having promised that we would respect the referendum result and not having respected it," he added.
Attempts to find a cross-party compromise began after Theresa May's Brexit deal was rejected three times by MPs.
The inability to agree on a way forward led the UK to miss its 29 March deadline for leaving the EU - the current date for departure is 31 October.
So far both sides have resisted calls to set a deadline on the negotiations.
But the prime minister's official spokesman said the government believed it was "imperative" that the Withdrawal Agreement Bill - the legislation required to leave the EU - was brought to Parliament in time for it pass all its stages by the summer recess.
No date has so far been set for the summer recess, but Parliament usually rises towards the end of July.
The cabinet discussions came as the PM's Brexit negotiator Olly Robbins travelled to Brussels to explore the scope for changes to the political declaration between the UK and the EU.
The document sets out the parameters for the future relationship, and Labour negotiators have insisted that any deal they strike with ministers must be reflected in changes to it.
They want a permanent and comprehensive customs union with the EU after Brexit, meaning there would be no internal tariffs (taxes) on goods sold between the UK and the rest of the bloc.
But it would mean the UK cannot negotiate its own trade deals on goods with other countries around the world, something many Brexit-supporting Tory MPs support.
A Downing Street source told BBC political editor Laura Kuenssberg that a compromise was being sought with Labour on customs "as an interim position or a stepping stone".
"We will not sign up to a permanent customs union," the source said.
The big question at Westminster is how long can these talks go on for. The answer appears to be, a little while longer. But the odds are stacked against a Tory-Labour compromise.
Labour doesn't think the government has moved far enough. They remain worried that Theresa May's replacement will come in and decide they don't like what has been agreed and try to rip it up.
On the other side, prominent Tories are seething at the idea a customs union could be the price of getting a Brexit deal through.
No 10 sources said this morning the PM won't agree to a permanent customs union - but the idea of a temporary solution is exactly what frightens many on the Labour side.
In this process, taking a step to keep one group happy appears to mean you make another more annoyed.
Cabinet agreed today it was "imperative" that legislation to allow the UK's withdrawal is brought back to Parliament in time to pass before the summer recess. That sets up the prospect of another set of big Brexit votes in the coming weeks.
But for now, there's more talk than action.
Mr McDonnell also said Labour had told ministers they "may well have to concede that there is a public vote of some sort" to get a deal through Parliament.
At the weekend, shadow Brexit secretary Sir Keir Starmer said a "significant number, probably 120 if not 150" of Labour MPs would not back deal without a "confirmatory vote".
On the prospect of another referendum, Mr McDonnell said: "My view is that you'd put the deal to the people, but you'd have to also have the option of the status quo.
"Deep in my heart, I'm still a Remainer, but I've got to try and bring together effectively what is a British compromise."
Asked if Labour leader Jeremy Corbyn was also a Remainer in his heart, the shadow chancellor responded: "Yes."
But Jeremy Hunt said another referendum or a general election were the "least likely outcomes" of the current Brexit stalemate.
"When approximately half your constituents have voted to leave the EU, just imagine their anger if you went on to support a second referendum where you're basically saying 'we think you got it wrong first time'."

Theresa May will ask the EU for an extension to the Brexit deadline to "break the logjam" in Parliament.
The PM says she wants to meet Labour leader Jeremy Corbyn to agree a plan on the future relationship with the EU.
But she insisted her withdrawal agreement - which was voted down last week - would remain part of the deal.
Mr Corbyn said he was "very happy" to meet Mrs May, and would ensure plans for a customs union and protection of workers' rights were on the table.
The cross-party talks offer has angered Tory Brexiteers, with Boris Johnson accusing ministers of "entrusting the final handling of Brexit to Labour".
The former foreign secretary said Brexit was "becoming soft to the point of disintegration" and he could never agree with staying in a customs union.
BBC political editor Laura Kuenssberg said it probably means the prime minister is likely to adopt a closer relationship with the EU - a softer Brexit - than she had agreed so far.
The UK has until 12 April to propose a plan to the EU - which must be accepted by them - or it will leave without a deal.
Mrs May agreed a deal with the EU in November 2018, but it has been voted down twice in Parliament by huge margins, and a separate deal just on the withdrawal agreement section lost by 58 votes on Friday.
MPs have also twice held indicative votes to try to find a consensus, but none of the proposals won a majority.
The UK was supposed to leave the EU on 29 March, but Mrs May agreed a short extension after realising Parliament would not agree a deal by the deadline.
In a statement in Downing Street, Mrs May said she wanted any further extension to be "as short as possible" - before 22 May so the UK does not have to take part in European elections.
She said she wanted to agree a new plan with Mr Corbyn and put it to a vote in the Commons before 10 April - when the EU will hold an emergency summit on Brexit.
If she and Mr Corbyn do not agree a single way forward, she proposed putting a number of options to MPs "to determine which course to pursue".
But the EU would still have to agree to any extension.
The BBC's Europe editor Katya Adler warned their demands "haven't changed at all", and they are preparing "pretty strict conditions" for any further delay.
"Even though Theresa May says she doesn't want to, EU leaders will ask her to prepare the UK to take part in European Parliamentary elections by the end of May because they don't believe she will be able to get her Brexit house in order before then," she said.
Mr Corbyn said he saw the content of the prime minister's speech only when it went out on TV, but he recognised Mrs May had "made a move" and that he had a "responsibility" to engage in the talks.
Asked by the BBC if he was willing to compromise on his own red lines, he said: "I have been meeting MPs from all parties from the last couple of weeks. Yes, there is some common ground [and] there are some areas it is difficult to agree on.
"But there is far more that unites people on both sides about the kind of society we can be than divides them.
"We will discuss [this] with the prime minister. I don't want to set any limits one way or the other."
Earlier, Mrs May met her cabinet for more than seven hours.
Laura Kuenssberg said there were differing accounts of the level of support for any extension within the cabinet - from four ministers voicing opposition to it to as many as 14 being against it.
Pressed on this, Environment Secretary Michael Gove told the BBC none of the Brexiteers in cabinet were "happy at the situation we find ourselves in" and they would have preferred for Mrs May's withdrawal agreement to be passed by Parliament last week.
But he said there had not been a vote on the issue in the meeting, and there was a "critical consensus" about any extension being as short as possible.
The Leader of the House, Andrea Leadsom, said: "We are trying to find a way to deliver on the referendum to make sure that we leave the European Union with a good deal that enables all of those who voted to leave the EU to be satisfied, but also that protects jobs and our security.
"We continue to do that and that's what cabinet today was all about".
Leading Brexiteer Jacob Rees-Mogg said it was "not usually successful for governments to get their business passed on opposition votes when their own party is against it".
The chairman of the pro-Brexit European Research Group added he "doubts the wisdom" of the decision, saying: "To allow the Labour party to run Brexit, to decide you'd rather be supported by a Marxist than by your own party, is unwise."
Mrs May said she understood some people would prefer to leave without a deal, and she believed the UK "could make a success of no-deal in the long term".
But she added that leaving with a deal was "the best solution".
"This is a difficult time for everyone," she said.
"Passions are running high on all sides of the argument, but we can and must find the compromises that will deliver what the British people voted for.
"This is a decisive moment in the story of these islands and it requires national unity to deliver the national interest."
Scottish First Minister Nicola Sturgeon said it was another case of the PM "kicking the can", while Lib Dem leader Sir Vince Cable questioned the point of cross-party talks.
Hilary Benn, the Labour MP who chairs the Commons Brexit committee, said the PM's announcement was "good news" but she must show she was genuinely open to new ideas.
But Brexit-supporting Labour MP Kate Hoey said "whatever compromise" Theresa May and Jeremy Corbyn came up with, many MPs would simply not vote for the withdrawal agreement.
The Democratic Unionist Party - who give Mrs May a majority in Parliament but have repeatedly voted against her deal - said the move came as "little surprise" after the PM's "lamentable handling of the negotiations".
The DUP said: "It remains to be seen if sub-contracting out the future of Brexit to Jeremy Corbyn, someone whom the Conservatives have demonised for four years, will end happily."
After Mrs May's statement, the president of the European Council, Donald Tusk, called for patience.
Backbench MPs earlier tabled a bill to try to stop the UK leaving the EU without a deal on 12 April by forcing Mrs May to ask for an extension.
After the PM's statement, Labour's Yvette Cooper said it was "welcome", but added: "We are waiting to find out further details on how the government's proposed process will work, including how decisions will be taken about the length and purpose of an extension, and how indicative votes will work to make sure we don't just end up with no deal a bit later on."
June 2016: UK votes in referendum to leave EU
November 2018: UK agrees withdrawal agreement and framework of future relations with EU
December 2018: Theresa May postpones first meaningful vote on deal to seek further assurances from EU
15 January: House of Commons rejects overall Brexit deal by 230 votes
13 March: MPs vote down Brexit deal for second time by 149 votes
22 March: EU agrees to delay Brexit beyond 29 March - but only to 12 April if UK can't agree deal within a week
29 March: MPs reject withdrawal agreement on its own by 58 votes
2 April: PM says she will seek further "short extension" from the EU

The future of Boris Johnson's Brexit deal hangs in the balance as EU officials say the outcome of talks should be known by the end of the day.
The EU's Donald Tusk said he would have "bet" on a deal 24 hours ago, but "doubts" had appeared on the UK side.
The PM is trying to get Tory Brexiteers and Democratic Unionists on board for his revised plan for Northern Ireland.
Likening talks to climbing Everest, Mr Johnson said the summit was "not far" but still surrounded by "cloud".
He is in a race against time to get a deal before Thursday's crucial EU council meeting.
The BBC's political editor Laura Kuenssberg said she understood the issues between the UK, EU and Ireland were "pretty much sorted", but it was still not clear whether the Northern Irish DUP were ready to sign up or not.
Mr Johnson has been updating his cabinet on the state of the negotiations after further talks with the DUP, whose support could be vital if Parliament is to approve any agreement.
The PM also briefly addressed a meeting of Conservative MPs, comparing the current position to Edmund Hillary's ascent of Mount Everest in 1953.
The EU's chief negotiator, Michel Barnier, has just begun to brief EU ambassadors on the status of the talks - the meeting was originally due to take place at lunch time but was put back twice.
The issue of the Irish border - and how to handle the flow of goods and people across it once it becomes the border between the UK and the EU after Brexit - has long been a sticking point in the negotiations.
The border is also a matter of great political, security and diplomatic sensitivity in Ireland.
The backstop - the solution to border issues agreed by Theresa May - proved unpalatable to many MPs so Mr Johnson has come up with new proposals to dispense with it.
However, they would see Northern Ireland treated differently from the rest of the UK - something the DUP, among others, has great concerns about.
The BBC's Brussels reporter, Adam Fleming, said that during the course of Wednesday there had been a shift in emphasis in the talks away from issues around customs towards matters surrounding the so-called consent mechanism - the idea the prime minister came up with to give communities in Northern Ireland a regular say over whatever comes into effect.
The DUP is understood to be most concerned about this issue too. The party also fears the creation of a "customs border" in the Irish Sea, which would require checks on goods between the rest of the UK and Northern Ireland.
The DUP held their latest round of talks in Downing Street on Wednesday morning. After a 90-minute meeting on Tuesday, they said "it would be fair to indicate gaps remain and further work is required".
Party leader Arlene Foster dismissed suggestions that their concerns had since been allayed.
The UK is due to leave the EU at 23:00 GMT on 31 October and Mr Johnson has repeatedly insisted this will happen, regardless of whether there is a deal or not.
One senior EU diplomat has told journalists in Brussels it is now too late for EU leaders to formally approve a revised Brexit deal at the summit.
They said the most they could do was give a provisional thumbs-up - "a political yes" - to whatever emerges from the talks pending the release of the final legal text.
As I understand it, most of the issues between the UK, the EU and Ireland have pretty much been resolved, but it is still not clear whether the DUP are actually on board.
Like other factions in this drama, they have been in and out of Downing Street - recipients of a charm offensive by Boris Johnson's team.
But unless and until they decide it is worth their while to come on board, then it is just too soon to definitively say this is going to be a moment.
It may well be that later tonight this all snaps into place before European leaders gather in Brussels, and then, maybe, they'll give this a rubber stamp.
But the DUP are not a group of politicians who are a pushover.
And this is still something that is simply not yet in the bag.
The expectation on the EU side is that a new Brexit deal text is pretty much ready.
They are now just waiting to hear from the UK side whether it can be signed off.
Even if this text is ready, though, even if it can be signed off by EU leaders, the EU will not yet be breathing a sigh of relief because they have been here before.
Theresa May signed a Brexit deal with the EU and it went on to be rejected multiple times by House of Commons.
The fear is, if a new Brexit text meets the same fate, the government will come back to Brussels asking for more concessions.
Mr Tusk suggested earlier that an agreement was still possible by the end of the day.
"It is still undergoing changes and the basic foundations of this agreement are ready and theoretically we could accept a deal tomorrow." he told the TVN 24 News Channel.
French President Emmanuel Macron said he wanted to believe "the agreement is being finalised".
Irish Taoiseach Leo Varadkar also said there was still "a pathway to a possible deal" but "many issues" to resolve.
Thursday's EU summit is crucial because under legislation passed last month - the Benn Act - Mr Johnson is compelled to ask the EU for a delay to Brexit if he does not get a new deal approved by MPs by Saturday.
Brexit Secretary Stephen Barclay told MPs on Wednesday that Mr Johnson "will comply with the law" regarding the terms of any further extension.
If Mr Johnson gets an agreement with Brussels, he will ask MPs to back it and agree the next steps in an emergency sitting of Parliament on Saturday.
No 10 has confirmed the government will table a motion in the Commons on Thursday which, if approved by MPs, would pave the way for the first weekend session since 1982.
However, MPs may not be asked to sanction the extra sitting if there is not a successful conclusion to the Brexit talks.
Earlier, former Brexit Secretary David Davis said the support of Tory Eurosceptics could not be taken for granted and the view of the DUP would be important.
14:30 - The PM held a 40-minute cabinet meeting
16:30 - The PM spoke to the 1922 Committee of Tory backbenchers for about eight minutes
17:15 - Angela Merkel and Emmanuel Macron held joint press conference
18:00 - Michel Barnier is briefing EU ambassadors

Boris Johnson has sent a request to the EU for a delay to Brexit - but without his signature.
The request was accompanied by a second letter, signed by Mr Johnson, saying he believes a delay would be a mistake.
The PM was required by law to ask the EU for an extension to the 31 October deadline after losing a Commons vote.
EU Council President Donald Tusk tweeted that he had received the extension request and would consult EU leaders "on how to react".
Earlier, Mr Johnson rang European leaders, including Mr Tusk, to insist that the letter "is Parliament's letter, not my letter".
Opposition MPs have warned the PM that if he tries to circumvent Parliament's instructions to seek a delay, then he may find himself in the law courts.
Mr Johnson has vowed to press ahead with the legislation to implement his deal next week, but Labour says it will seek to amend it - to add additional measures on issues like workers' rights and environmental protections.
Shadow chancellor John McDonnell told Sky News Sophie Ridge the prime minister could "well be in contempt of Parliament or the courts" by sending a second letter to the EU that "contradicted" the first.
The PM has previously said he would "rather be dead in a ditch" than ask the EU to delay Brexit, and the UK would leave on 31 October "do or die".
But hours after losing a crunch vote in a historic Saturday session in the House of Commons, the prime minister ordered a senior diplomat to send an unsigned photocopy of the request for a delay, which was forced on him by MPs last month.
The second letter from Mr Johnson - signed off this time - makes clear he personally believes a delay would be damaging.
It says the government will press on with efforts to pass the revised Brexit deal agreed with EU leaders last week into law, and that he is confident of doing so by 31 October.
A cover note from Sir Tim Barrow, the UK's representative in Brussels, explained the first letter complied with the law as agreed by Parliament.
BBC political editor Laura Kuenssberg described the decision to send three documents as "controversial", predicting "there will be a fight about whether Boris Johnson is trying to circumvent the court".
"This is heading straight for the court, and it may very quickly end up in the Supreme Court," she added.
Asked on BBC Breakfast whether the PM's move was "childish, Conservative Brexiteer MP Nigel Evans said: "Well he was going to be criticised if he didn't send the letter, because it would have been against the law."
He added that "it's not all in our gift", and that EU leaders may look at both letters and deny the request for a delay.
Extracts from Mr Johnson's letter to Mr Tusk:
"The UK Permanent Representative will... submit the request mandated by the EU (Withdrawal) (No.2) Act 2019 later today. It is, of course, for the European Council to decide when to consider this request and whether to grant it.
"Although I would have preferred a different result today, the Government will press ahead with ratification and introduce the necessary legislation early next week. I remain confident that we will complete that process by 31 October.
"While it is open to the European Council to accede to the request mandated by Parliament or to offer an alternative extension period, I have made clear since becoming Prime Minister... that a further extension would damage the interests of the UK and our EU partners, and the relationship between us.
"We must bring this process to a conclusion so that we can move to the next phase and build our new relationship on the foundations of our long history as neighbours and friends in this continent."
Read the letters in full.
At the first Saturday sitting in the Commons for 37 years, MPs voted in favour of an amendment withholding approval of Mr Johnson's Brexit deal until all the necessary legislation had been passed.
Tabled by Tory MP Sir Oliver Letwin, the amendment was intended to ensure that Mr Johnson would comply with the terms of the so-called Benn Act.
Under that act, Mr Johnson had until 23:00 BST on Saturday to send a letter requesting a delay to the UK's departure.
In a letter to MPs and peers on Saturday evening, he said: "I will tell the EU what I have told the British public for my 88 days as prime minister: further delay is not a solution.
"It is quite possible that our friends in the European Union will reject Parliament's request for a further delay (or not take a decision quickly)."
The Commons defeat marked a major setback for the PM - although Mr Johnson said he was not "daunted or dismayed" and remained committed to taking Britain out by the end of the month with his "excellent deal".
John McDonnell said MPs should now have the chance to scrutinise the withdrawal agreement legislation. He said Mr Johnson had removed certain protections contained in Theresa May's deal with the EU and Labour wanted to see those reinstated.
"Do we want to go down the Boris Johnson proposals of diverging from our major trading partner and deregulating our economy, undermining workers' rights, consumer and environment rights? No we don't," he said.
"So what we'll try and do is, of course, try and amend that legislation and see if we can get agreement in Parliament."
Mr McDonnell said Mr Johnson was "behaving a bit like a spoilt brat" by sending an unsigned letter to Brussels.
Anna Soubry, from The Independent Group for Change, accused the prime minister of acting like a "truculent child", while Liberal Democrat Christine Jardine MP said Mr Johnson was going against the will of the Commons.
SNP leader at Westminster Ian Blackford said earlier that if Mr Johnson acted as if he was "above the law", he would find himself in court.
On the EU side, there has been no official response yet to the contents of the letter, except Mr Tusk confirming he received it.
But the French President, Emmanuel Macron, has already signalled that he believed a new Brexit extension was not good for anyone.
Boris Johnson literally spelling out his opposition to prolonging the Brexit process by writing a separate letter to Brussels to say so, makes it easier for his peers Emmanuel Macron, Angela Merkel and others to drag their feet a little.
They prefer first to look to the prime minister to make good on his promise to them that their newly-negotiated Brexit deal will *definitely* be passed by Parliament.
But, if push comes to shove, with the alternative being no deal at all... I cannot imagine the EU slamming the door in the face of the UK now.
They will want to know what [the extension] is for. Are there plans in the UK to hold a general election, a second referendum or a referendum on the new Brexit deal? Or is a bit more time needed to pass Brexit-related legislation?
Read Katya's full analysis
The EU Parliament's Brexit Steering Group will discuss the outcome of the latest UK vote on Monday, said Brexit co-ordinator Guy Verhofstadt.
He tweeted on Saturday: "Whatever happens next, the marches outside the Parliament show just how important a close EU - UK future relationship is."
Jacob Rees-Mogg, leader of the Commons, said the government planed to hold a meaningful vote on Monday - although it is not clear whether Commons Speaker John Bercow will allow it.

Boris Johnson will push for a general election if the EU agrees to delay Brexit until January, No 10 has said.
The PM "paused" his Brexit bill on Tuesday after MPs rejected his plan to fast-track it through Parliament.
Now EU leaders will consider whether to grant a delay to the 31 October Brexit deadline and what length it should be.
Mr Johnson was forced by law to send a letter the EU requesting a three-month extension but he insists the UK will still leave at the end of October.
Taoiseach (Irish prime minister) Leo Varadkar has confirmed he supports the proposal to grant the UK's request for a three month extension.
Mr Johnson may want a general election, but he cannot simply call one, as prime ministers did before the passage of the 2011 Fixed Term Parliament Act.
The move would need the backing of Parliament, and opposition MPs have previously ruled out holding one until the possibility of a no-deal Brexit on 31 October was ruled out altogether.
Justice Secretary Robert Buckland told BBC Breakfast that "regrettably it does seem that a general election is the only way to sort this impasse out".
His opposite number, Labour's Richard Burgon, told BBC Radio 4's Today programme his party would agree to a general election if the EU granted an extension because it meant a no-deal Brexit would certainly be "off the table".
There is also the option of a further referendum, although it would require a Brexit delay and, most likely, a change of government first.
However, Mr Burgon said holding a referendum before an election - a move favoured by some of his Labour colleagues - was "fantasy politics".
The SNP has indicated it wants an extension to allow for a general election, while the Liberal Democrats say the PM needs to get an extension to allow a further referendum. Both parties would rather the UK revoked Article 50 and stopped the Brexit process.
Some Conservative MPs say the government should take the Labour Party up on its offer to come up with a timetable for the Withdrawal Agreement Bill that satisfies all sides.
MPs voted to back the first stage of bill, which would enact Boris Johnson's deal, on Tuesday - the first time Parliament has expressed approval for a Brexit agreement.
They had been due to debate it on Wednesday and Thursday, but after voting against that timetable, they will instead discuss the contents of the Queen's Speech, which sets out the government's plans for the next session of Parliament.
There is a tension in the Tory party today - some would rather try again to get the bill through. Those MPs were cock-a-hoop at the fact they had managed to get 19 Labour MPs to cross the threshold to potentially back this kind of Brexit deal - even though that is a million miles away from it getting safe passage through Parliament.
But in the heart in Downing Street the instinct is: if a delay is agreed they throw everything into an election instead.
No 10's fear is, even if they say "maybe we could pass the bill in a fortnight," that delay might turn into a long one, tangling with Parliament and losing control of the timetable.
Just as Parliament doesn't trust the prime minister, the prime minister and his team don't trust Parliament.
Opposition parties have no interest really in helping Boris Johnson to complete the passage of this bill. They want to disrupt it for perfectly obvious and legitimate political reasons.
So as things stand, the prime minister would rather trigger an election... But it is not in his gift.
On Tuesday, MPs approved the Withdrawal Agreement Bill on its first hurdle through the Commons - called the second reading - by 329 votes to 299.
But minutes later Mr Johnson was defeated - by a majority of 14 - in a second vote on a fast-tracked timetable for the bill.
The prime minister insisted to MPs it was still his policy that the UK should leave the EU on Halloween, but acknowledged he would have wait to hear what other leaders said.
Following Tuesday's votes, Mr Corbyn said his party was prepared to work with the government to agree "a reasonable timetable" to enable the Commons to debate and scrutinise the Brexit legislation properly.
EU Council President Donald Tusk said he would recommend European leaders backed an extension to the Brexit deadline, though he did not say what length it should be. He said he would "propose a written procedure", thus negating the need for another summit meeting.
If the EU accepts the UK request for a straightforward extension to 31 January 2020 then that becomes the new date of Brexit. If the EU proposes a date other than this, even a short "technical extension" of a few days, the prime minister must approve it unless a motion is put before MPs and they decide not to pass it.
If the EU were to reject any extension, that would give MPs a stark choice between Mr Johnson's deal and no-deal.
Germany's Die Welt newspaper sums up EU thoughts on Brexit this morning with the headline: "The only thing that is clear is that Brexit is not happening on 31 October."
EU leaders must now agree on whether to grant the UK another Brexit extension and if so, how long for?
Don't forget every country has a veto on this. But after speaking extensively to EU diplomats and politicians, the consensus EU-side seems to be to say yes.
The EU's decision is expected by the end of the week, but you can expect a lot of EU grumbling beforehand. France's Europe minister was unsurprisingly (France has settled into role of "Brexit bad cop") one of first to speak on the record last night.
She noted that time alone wouldn't solve the UK's Brexit conundrum and the EU would want to hear UK's justification for another extension - i.e. what will be done with the time?
EU leaders are fully aware the PM's hand was forced by Parliament to request a three-month extension. Brussels does not want to get embroiled in heated UK debate, so it seems most likely it will say yes to that rather than "impose" their own "EU extension".
Whatever the time length of the extension granted, this will be another "flextension", meaning the delay can end earlier if and when Parliament ratifies the Brexit deal.
Under the Fixed-term Parliaments Act, the prime minister needs to have the backing of two thirds of MPs to hold a snap poll. This has been rejected twice by MPs.
Another route to an election is a one-line bill, that requires only a simple majority.
But former Tory MP Ken Clarke told the BBC that any such bill was likely to incur a host of amendments,  given Mr Johnson does not have a majority.
That included attempts to allow 16 and 17-year-olds to vote - something the government is likely to resist.
There is also the option of a vote of no confidence in the government, something which Jeremy Corbyn says he wants but only once the threat of a no-deal Brexit on 31 October has been removed.
Mr Johnson could even call one in his own government, but Parliamentary rules state that if it passes, the Commons has 14 days to form an alternative administration, so the PM would run the risk of being forced out of Downing Street if opposition parties can unite around a different leader.
If an election were to be triggered this week, the earliest it could take place would be Thursday 28 November, as the law requires 25 days between an election being called in Parliament and polling day.
Many observers think a 5 or 12 December election is more likely - but in general, parties tend to prefer polls in lighter, warmer months when the perceived wisdom is that campaigning is easier and voters are more likely to turn out.

Theresa May will make the case for her new Brexit plan in Parliament later, amid signs that Conservative opposition to her leadership is hardening.
The prime minister will outline changes to the Withdrawal Agreement Bill - including a promise to give MPs a vote on holding another referendum.
But shadow Brexit secretary Sir Keir Starmer said the offer was "too weak".
Some senior Tories will today ask party bosses for a rule change to allow a no-confidence vote in her leadership.
Environment Secretary Michael Gove defended the PM's plan, urging MPs to "take a little bit of time and step back" to "reflect" on the detail of the bill - due to be published later today.
Fellow cabinet minister and prominent Brexiteer Andrea Leadsom said she was "looking very carefully at the legislation" and "making sure that it delivers Brexit".
MPs have rejected the withdrawal agreement negotiated with the EU three times, and attempts to find a formal compromise with Labour have failed.
On Tuesday, the prime minister asked MPs to take "one last chance" to deliver a negotiated exit - or risk Brexit not happening at all.
But several Tory MPs have criticised her plan. Among them, Nigel Evans will today urge party bosses on the 1922 committee to change party rules to allow for an immediate vote of no-confidence in Mrs May.
Because the PM survived such a vote in December, the current rules say she cannot face another for 12 months.
The committee has said 'no' to such a change before.
But the Conservative Home website has urged people not to vote for the party in Thursday's European elections if Mrs May is still in post "by the end of today".
BBC political correspondent Iain Watson says a small number of Labour MPs have gone to a briefing with the government's Brexit negotiator, Olly Robbins, to discuss the deal.
But a number of the party's MPs have spoken out against the PM's plan, with Sir Keir saying all she had offered was votes on customs arrangements and a further referendum that MPs would be able to get anyway as amendments to the bill.
He told BBC Radio 4's Today programme: "This is not a compromise of policy, it is just saying you can have votes on these things.
"In reality, the prime minister ought to now admit defeat. I think she would do well to just pull the vote and pause, as this is just going to nowhere."
Leader of the Liberal Democrats, Sir Vince Cable, echoed the point, telling Today: "If [Mrs May] said 'we will put forward the Withdrawal Bill subject to a confirmatory referendum'… we would be obliged to support it on that basis, but she is barely saying Parliament can have a vote if it wants to have a referendum.
"[That] is not in her gift, Parliament will do that anyway. What appears to be a concession isn't."
The BBC's political editor Laura Kuenssberg said if the government tries to delay bringing the bill forward - expected in the week of 3 June - it is "extremely hard to see" how the prime minister stays in post after the Bank Holiday weekend.
Other senior Tories have suggested Mrs May drops her Withdrawal Agreement Bill to avoid defeat and humiliation.
Conservative MP Boris Johnson - who wants to succeed Mrs May as prime minister - said on Twitter: "We are being asked to vote for a customs union and a second referendum. The Bill is directly against our manifesto - and I will not vote for it.
"We can and must do better - and deliver what the people voted for."
Meanwhile Dominic Raab, another leadership hopeful, said Mrs May's deal would "break our clear manifesto promises".
Tory MP Priti Patel accused the "entire cabinet and especially the so-called Brexiteers in office" of being "responsible for the betrayal" of Leave voters.
It's become a painful ritual of a tortuous process: the prime minister unveils a vision for Brexit, and MPs queue up to demolish it in the House of Commons. On Wednesday it looks like it is going to happen again.
If Theresa May's speech yesterday sought to attract switchers - and turn sceptics into endorsers - it failed.
Worse than that for Downing Street, some Conservatives who backed the plan when it was last voted on, now say they'll reject it.
Among many Conservative MPs, there is a bleak, end of days mood. Some wonder if it's even worthwhile putting the bill to a vote.
Others ponder getting rid of the prime minister even sooner than she's promised. But those around Theresa May insist they are not willing to give up at least yet - they are determined her plan will be put to MPs in around a fortnight's time.
Mrs May is bringing the Withdrawal Agreement Bill - legislation required to bring her agreement into UK law - to Parliament in early June.
In an attempt to win over MPs across the House, she announced the following concessions:
In a letter to Labour leader Jeremy Corbyn, released on Wednesday, Mrs May said: "I have shown today that I am willing to compromise to deliver Brexit for the British people...
"I ask you to compromise too so that we can deliver what both our parties promised in our manifestos and restore faith in our politics."
But Labour has said it is not willing to back the bill at second reading, meaning it could fail at its first parliamentary hurdle.
And some Conservative MPs who backed Theresa May the last time she tried to get her withdrawal agreement through Parliament in March said they could no longer support her.
Tory MP Nadine Dorries said all scenarios led to Mrs May resigning, telling the BBC's Victoria Derbyshire: "I see no way out for the prime minister. I think we might be reaching the end game finally for [Mrs May]."
Meanwhile, Sammy Wilson, the Brexit spokesman for the DUP - whose support the government relies on to get its laws passed - said his party would "not accept this flawed agreement" that they believe would split Northern Ireland from the rest of the UK.
He told Today: "We have been through all of this before with the prime minister in the negotiations to date. It has been accepted by the government that [there] are flaws they cannot give an answer to.
"We will not vote for our own destruction."

Theresa May has been urged not to allow Eurosceptic MPs in her party to "impose their own conditions" on negotiations amid signs of fresh Tory infighting.
Nineteen Tory MPs who back a "soft Brexit" have written to her saying it is "highly irresponsible" for anyone to dictate terms which may scupper a deal.
It follows some Tories backing the DUP's decision to oppose a draft deal on the future of the Irish border.
The PM has spoken to the DUP's Arlene Foster to try to break the deadlock.
The DUP says there is "more work to be done" if it is to agree to plans for the future of the border between Northern Ireland and the Irish Republic after Brexit - a prerequisite for talks to move on to their next phase.
Irish PM Leo Varadkar, who also spoke to Mrs May on Wednesday, said he was willing to consider any new proposals, suggesting the UK might put something forward within the next 24 hours.
And the BBC understands the ambassadors of the 27 EU member states, who received an update from chief EU negotiator Michel Barnier on Wednesday, are "waiting for something from London" in the next 48 hours.
The BBC's Adam Fleming said Mr Barnier and the member states agreed there must be clarity within 48 hours for them to have enough time to consult with their capitals about draft guidelines for phase two of the talks.
At a summit next week, European leaders will decide whether enough progress has been made in the negotiations on Ireland, the UK's "divorce bill" and citizens' rights so far to open trade talks.
In their letter, the 19 MPs - who largely backed Remain in the 2016 referendum - say they support the PM's handling of the negotiations, in particular the "political and practical difficulties" relating to the Irish border.
But they hit out at what they say are attempts by some in their party to paint a no-deal scenario in which the UK failed to agree a trade agreement as "some status quo which the UK simply opts to adopt".
"We wish to make it clear that we are disappointed yet again that some MPs and others seek to impose their own conditions on these negotiations," the MPs, including former cabinet ministers Stephen Crabb, Dominic Grieve, Anna Soubry and Nicky Morgan - write.
"In particular, it is highly irresponsible to seek to dictate terms which could lead to the UK walking away from these negotiations."
It urges the PM to "take whatever time is necessary" to get the next stage of negotiations right.
On Tuesday, former Tory leader Iain Duncan Smith argued the time was fast approaching for the UK to consider walking away from the talks if the EU did not allow negotiators to proceed to the next phase - in which future trade and security relations will take centre stage.
The suggestion of "regulatory alignment" between Northern Ireland and the European Union and any continuing role for the European Court of Justice has also concerned some Eurosceptic Conservative MPs.
On Monday Northern Ireland's Democratic Unionist Party - whose support the PM needs to win key votes at Westminster - objected to draft plans drawn up by the UK and the EU.
The DUP said the proposals, which aimed to avoid a "hard border" by aligning regulations on both sides of the border between Northern Ireland and the Republic of Ireland, were not acceptable.
This has left the UK government racing to find an agreement suiting all sides in time for next week's summit.
The DUP's deputy leader Nigel Dodds said the Irish government, which has said it wants firm guarantees that a hard border can be avoided, was playing a "dangerous game" with its own economy.
At a press conference with his Dutch counterpart on Wednesday, Irish PM Leo Varadkar insisted he wanted the talks to move beyond consideration of divorce issues to the future.
"Having consulted with people in London, she (Theresa May) wants to come back to us with some text tonight or tomorrow," he said. "I expressed my willingness to consider that."
In a separate development, Chancellor Philip Hammond has suggested the UK could pay the so-called Brexit bill, regardless of whether or not there is a subsequent trade agreement with the EU.
He told MPs on the Treasury Committee he found it "inconceivable" that the UK would "walk away" from its financial obligations as "frankly it would not make us a credible partner for future international agreements".
On the issue of the divorce bill, a No 10 spokesman said the government's position remained that "nothing is agreed until everything is agreed and that applies to the financial settlement".
Reports have suggested the UK has raised its financial offer to a figure of up to 50bn euros (£44bn).

Theresa May has warned the UK faces "uncharted territory" if Parliament rejects her Brexit deal as she vowed to redouble her efforts to win MPs round.
Next week's vote would "definitely" go ahead, she told the BBC, as she promised new safeguards for Northern Ireland and to look at giving MPs more say in shaping future EU negotiations.
The UK's March exit was "in danger" if MPs did not back the deal, she said.
But one Tory Brexiteer said support for leaving without a deal was "hardening".
And one senior Labour figure said she believed a general election may be inevitable "within months" if there was deadlock in Parliament and Mrs May could not get her deal through.
The UK is due to leave the EU on 29 March 2019.
A deal on the terms of the UK's divorce and the framework of future relations has been agreed between the prime minister and the EU - but it needs to pass a vote by MPs in Parliament before it is accepted.
MPs are expected to be asked to vote on it on either the 14 or 15 of January.
The crunch vote was due to take place in December but was postponed at the last minute as Mrs May faced almost certain defeat amid opposition from many of her MPs, as well as Labour and other parties.
Asked by the BBC's Andrew Marr if the vote would "definitely" go ahead in the second week of January, she replied "yes, we are going to hold the vote".
She said she truly believed hers was a "good deal" for the country and that it was up to its opponents to spell out the alternatives to it.
Asked what had changed since last month, she said the EU had agreed to some "changes" and she was continuing to talk to European leaders as she tried to give MPs the "confidence" to support the deal.
She promised to give more detail in three areas in the coming days:
She said there were a "number of ways" of giving MPs more input in the next phase of the Brexit process, including allowing them a real say in shaping the "mandate for the negotiations for the future relationship".
Mrs May suggested that if her deal was rejected it would embolden both supporters of a no-deal exit and those who want to remain in the EU via another referendum.
"If the deal is not voted on, then we are going to be in uncharted territory," she said. "I don't think anyone can say what will happen in terms of the reaction we see in Parliament.
"What you have is a Labour leadership... which is opposing any deal to create the greatest chaos possible, people who are promoting a second referendum in order to stop Brexit and people who want to see their perfect Brexit... the danger there is we end up with no Brexit at all."
Asked whether she was prepared to stand down as PM and let someone else take over talks over the future relations if Tory MPs demanded it, Mrs May - who survived a vote of no confidence last month - said the party had made it clear they wanted her to "deliver on Brexit and that is what I am working on doing".
However, the DUP, which props up the government, said the fundamental problems with Mrs May's deal had not changed.
Deputy leader Nigel Dodds said: "The backstop remains the poison which makes any vote for the withdrawal agreement so toxic."
The backstop is a position of last resort, to maintain an open border on the island of Ireland in the event that the UK leaves the EU without securing an all-encompassing deal.
Many Conservative MPs continue to believe the deal does not represent the Brexit the country voted for in 2016.
Peter Bone told Sky News the best way to "get on" with Brexit was to leave without a deal,
"If there has been a change it is a hardening of attitudes among MPs to a no deal," he told Sophy Ridge, adding that there was increasing evidence that a no deal outcome was "absolutely OK".
And a succession of other Tory Brexiteers have taken to social media to say "nothing has changed" during the Christmas recess and they remain opposed to the deal.
But opponents of a no-deal exit have given notice they are determined to effectively rule the prospect out.
A cross-party group of Conservative, Labour and Lib Dem MPs are proposing amending the government's Finance Bill, to be debated on Tuesday, so that ministers would only be able to make tax changes in the event of a no-deal exit if Parliament had explicitly authorised them.
Labour MP Yvette Cooper said if the government "would not rule out no deal, Parliament must act".
As part of the government's preparations for a no-deal Brexit, the company Seaborne Freight had been given a contract to run a freight service between Ramsgate and Ostend in the event of the UK leaving the EU without a deal.
However the councillor for the harbour area has said the Port of Ramsgate "cannot be ready" for extra ferry services should a no-deal Brexit happen.
By political correspondent Nick Eardley
A new year is about to start at Westminster, but the political battleground feels very familiar.
The PM's message hasn't changed. She still thinks her deal is only one that delivers and rejecting it would lead to uncharted territory.
That's a warning to both sides; those who want another referendum could end up with no deal; those who want no deal could end up with no Brexit at all.
Her critics, though, don't appear to have had any New Year changes of heart either. The DUP and many Tories are still unhappy and as things stand won't back her.
Theresa May is promising to try and win more reassurances from Brussels. But for now it remains hard to see what she could secure that would win enough support for her to win the meaningful vote.
A poll of more than 25,000 Britons published on Sunday suggests Labour would be punished by voters if the party either ends up backing the government's deal or does not actively oppose it.
The YouGov poll, carried out for the People's Vote campaign which is demanding another referendum, suggests 75% of Labour supporters would prefer a final say on Brexit.
But the Labour leadership rejected claims that they were "enabling" Brexit by refusing, at this stage, to explicitly call for another referendum.
Shadow Foreign Secretary Emily Thornberry said the People's Vote campaign should focus on "changing people's minds" about whether to stay in the EU rather "smacking Labour around the head".
She told the BBC that Labour's focus was getting into power in a general election she now expected to take place "within months"
"If you are a government that does not have the support of Parliament and does not have the support of the people, you cannot drive us over a cliff and think you are going to get away with it," she told BBC Radio 4's The World This Weekend.
"Our democracy is about whether you have the permission of the public and... whether you can justify what you are doing to our country."
Liberal Democrat leader Sir Vince Cable said another referendum was the "least worst option", but he added that "it was going to be very messy whatever happens".

The prime minister would "never agree" to a permanent customs union with the EU, No 10 says, amid concern from ministers about Brexit compromises.
They are thought to fear that Theresa May will agree to such a move, if a trade deal cannot be done in time.
Downing Street insists any post-Brexit customs union would be "time limited".
EU leaders meet next week for what has been described by European Council president Donald Tusk as a "moment of truth for Brexit negotiations".
The EU leaders are not expected to reach agreement with the UK but they say they want to see if "decisive progress" has been made to convene a special summit in November, to finalise a deal.
Meanwhile, it has emerged that a motorway in Kent is being shut overnight as part of contingency preparations in case the Brexit negotiations ultimately fail and the UK leaves the EU in March 2019 without a deal.
And Northern Ireland's DUP, which supports Theresa May's government in key Commons votes, has warned it could vote against her Budget next month, if Brexit negotiations result in trade barriers between Great Britain and Northern Ireland.
The UK is due to leave both the customs union and the single market when it leaves the EU in March 2019.
Trying to resolve what should happen on the border between Northern Ireland and the Republic of Ireland - an EU member - has been a key sticking point in Brexit negotiations.
The UK and the EU both want to avoid a "hard border" - physical checks or infrastructure - should a long-term trade deal not be concluded before temporary post-Brexit arrangements designed to give businesses time to adjust come to an end in December 2020.
Brussels has suggested that, if that happens, Northern Ireland should stay in the EU customs union - something the UK says is unacceptable as it would effectively create a border between Northern Ireland and the rest of the UK, down the Irish Sea.
By BBC political correspondent Jonathan Blake
Delving into the detail can be fascinating, if frustrating, for those following Brexit closely.
But the big picture is always important and that has been playing out for all to see over the past 24 hours.
Theresa May, at a crucial stage in the negotiations, is having to work to keep her own side on side.
Days before a meeting of EU leaders in Brussels when both sides will want to show some sign of progress at least, ministers are worried about what the UK could be about to agree to.
Those unsure have a choice, stay and hope for the best or decide they can't support the prime minister's plan after all.
In June the UK government brought forward its proposal for a  "temporary customs arrangement" between the EU and the UK as a whole, which would eliminate the need for tariffs, quotas, rules of origin and customs processes on UK-EU trade.
That included the line that the "UK expects the future arrangement to be in place by the end of December 2021 at the latest", which followed a cabinet row.
BBC political editor Laura Kuenssberg said it was understood that the EU was now prepared to accept the idea of the whole of the UK remaining in the customs union if a trade deal cannot be done during the so-called "transition period". But it is understood they have not accepted that there should be a time limit on it.
Many Conservative Brexiteers argue an open-ended arrangement is unacceptable.
It is understood that cabinet ministers Liam Fox, Michael Gove, Dominic Raab and Jeremy Hunt expressed concerns about the possibility of such an outcome.
Speaking on Friday, Brexit Secretary Mr Raab said any such arrangement "would have to be finite, it would have to be short and it would have to be, I think, time-limited in order for it to be supported here."
He added: "What we cannot do is see the United Kingdom locked in via the backdoor to a customs union arrangement which would leave us in an indefinite limbo - that would not be leaving the EU."
A Downing Street spokeswoman said: "The prime minister would never agree to a deal which would trap the UK in a backstop permanently."
She added: "Our position is that this future economic relationship needs to be in place by the end of December 2021 at the latest."
Amid speculation she could resign, Commons Leader Andrea Leadsom told the BBC she was "really looking forward to us getting a good deal for the United Kingdom" and that was "all I am focused on".
Asked about the customs union concerns, she added: "We are at the final stages of a really complicated negotiation and I do think we have to give the prime minister the opportunity to be able to do a good deal for the United Kingdom, something that she is absolutely determined to do."
Conservative backbench Brexiteer Andrea Jenkyns tweeted that remaining in a customs union would be the "ultimate betrayal" of Leave voters.
Meanwhile, former Labour prime minister Gordon Brown said on Friday he thought there would be another Brexit referendum "sometime" adding:  "It will, in the end, be the only way to sort out the problem."

MPs have again rejected Boris Johnson's calls for a snap election, as the five-week suspension of Parliament begins.
In all, 293 MPs voted for the prime minister's motion for an early poll, far short of the number needed.
Earlier, opposition MPs confirmed they would not support an October poll, insisting a law blocking a no-deal Brexit must be implemented first.
Parliament was officially suspended - or prorogued - just before 02:00 BST on Tuesday and will reopen on 14 October.
A group of Labour backbenchers protested against the move, appearing to try to block Speaker John Bercow amid raucous scenes in the House of Commons.
Signs saying "silenced" were held up by the group in front of Mr Bercow - who earlier announced his resignation - just as he was due to lead MPs in a procession to the House of Lords to mark the suspension of Parliament.
In a hectic day of political developments:
At present, UK law states that the country will leave the EU on 31 October, regardless of whether a withdrawal deal has been agreed with Brussels or not.
But new legislation, which was granted royal assent on Monday, changes that, and will force the PM to seek a delay to 31 January 2020 unless a deal - or a no-deal exit - is approved by MPs by 19 October.
BBC political editor Laura Kuenssberg said although No 10 insisted it was not looking to break the new law, efforts were under way to examine ways of getting around it.
The prime minister said the government would use the time Parliament was suspended to press on with negotiating a deal with the EU, while "preparing to leave without one".
"No matter how many devices this Parliament invents to tie my hands, I will strive to get an agreement in the national interest," he said.
"This government will not delay Brexit any further."
But he was warned that ignoring the new law could prompt a legal challenge while ministers called it "lousy" and said they would "test to the limit" what it required of them.
Mr Johnson told MPs that Labour leader Jeremy Corbyn had previously said he would back an election if legislation to prevent the government from forcing through a no-deal Brexit on 31 October became law.
"By his own logic, he must now back an election."
But Mr Corbyn told MPs that Labour was "eager for an election - but as keen as we are, we are not prepared to risk inflicting the disaster of no-deal on our communities, our jobs, our services, or indeed our rights".
And he said the prime minister was suspending Parliament to avoid discussions of his plans.
Labour, the SNP, the Liberal Democrats, the Green Party, the Independent Group for Change and Plaid Cymru met on Monday morning and agreed not to back the motion for an election.
The prime minister's self-imposed Halloween Brexit deadline looks further out of reach than a few short days ago.
Is it impossible? Absolutely not.
There is the possibility, still, of a deal, with Number 10 today stressing it was still their primary aim.
Whispers again about a Northern Ireland only backstop, and a bigger role for the Stormont assembly, if it ever gets up and running, are doing the rounds.
Some MPs and some diplomats are more cheerful tonight about the possibilities of it working out.
If you squint, you can see the chance of an agreement being wrapped up at pace, although it seems the chances range somewhere between slim and negligible.
MPs backed calls, by 311 votes to 302, for the publication of government communications relating to the suspension of Parliament and no-deal Brexit plans, known as Operation Yellowhammer.
Former Conservative Dominic Grieve, the newly independent MP who tabled the motion, told MPs it was "entirely reasonable" to ask for the disclosure "so the House can understand the risks involved and this can be communicated more widely to the public".
But minister Michael Gove, who is in charge of no-deal preparations, said he had given evidence to the EU select committee on Yellowhammer and he hoped "those assurances were sufficient".
Attorney General Geoffrey Cox, meanwhile, questioned the legal right of the government to require employees - including the PM's top aide Dominic Cummings - to open up their private email accounts and personal mobiles to scrutiny.
After the vote, a government spokesman said it would "consider the implications and respond in due course".
Parliament's suspension means MPs will not get another chance to vote for an early election until they return, meaning a poll would not be possible until November at the earliest.
Earlier on Monday, Mr Johnson held talks with Leo Varadkar in Dublin on Monday morning - his first meeting with the Irish prime minister since he entered No 10.
The Irish border has proved a key sticking point in attempts to agree a Brexit deal between the UK and the EU.
Mr Johnson told Mr Varadkar that a no-deal Brexit would represent "a failure of statecraft" for both the British and Irish governments.

Philip Hammond has warned the UK will not be able to control key elements of a no-deal Brexit.
The chancellor told BBC Panorama that if the UK leaves without a deal, then the EU will control many of the levers - including what happens at the French port of Calais.
Ex Brexit Secretary David Davis told the programme that Whitehall never believed a no-deal Brexit would happen.
The EU has set the UK a deadline of 31 October to leave the bloc.
But despite spending £4.2bn on Brexit preparations, Mr Hammond warned that the government has limited influence on how a no-deal scenario might look.
Asked if the UK can control Brexit, he said: "We can't because many of the levers are held by others - the EU 27 or private business. We can seek to persuade them but we can't control it."
He added: "For example, we can make sure that goods flow inwards through the port of Dover without any friction but we can't control the outward flow into the port of Calais," he told Panorama.
"The French can dial that up or dial it down, just the same as the Spanish for years have dialled up or dialled down the length of the queues at the border going into Gibraltar."
French officials have previously rejected suggestions they could resort to a "go-slow" policy at Calais if there is no Brexit deal - insisting that closing the port would be "economic suicide".
Earlier this month, Mr Hammond told MPs a no-deal Brexit could cost the Treasury up to £90bn and said it would be up to them to ensure that "doesn't happen".
He has also said it was "highly unlikely" he would still be in his job after Theresa May stands down next month.
The Panorama programme - entitled Britain's Brexit Crisis - will outline the tensions in government during Theresa May's time at Number 10 when it is broadcast on Thursday.
Mr Davis, who quit as Brexit secretary last year, told the BBC that the Treasury wanted to avoid talking about the prospect of leaving without a deal.
He concluded that many in Whitehall did not believe it would ever happen - despite two years of planning.
"I've got to be able to say to you 'if this doesn't work we'll leave anyway' and you've got to believe it.
"And for you to believe it I've got to believe it. And I don't think Whitehall really ever believed that they would actually carry out the plans we laid so carefully over two years."
Tory leadership favourite Boris Johnson has pledged the UK will leave the EU on 31 October - with or without a deal.
His rival Jeremy Hunt has said he can negotiate a new deal for the UK "by the end of September" - and that he "expects" the UK will leave the EU before Christmas.
Voting among the party's 160,000 or so members is under way, with a winner expected to be announced on 23 July.
Britain's Brexit Crisis is on BBC1 this Thursday, July 18, at 9pm.
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Businesses have warned that food prices may rise and jobs may be affected after the chancellor vowed to end alignment with EU rules after Brexit.
Sajid Javid told the Financial Times the UK would not be a "ruletaker" after Brexit, urging businesses to "adjust".
The Food and Drink Federation said the proposals were likely to cause food prices to rise at the end of this year.
The Confederation of British Industry said for many firms, keeping existing EU rules would support jobs.
The automotive, food and drink and pharmaceutical industries all warned the government last year that moving away from key EU rules would be damaging.
In an interview with Financial Times, the chancellor said the Treasury would not support manufacturers that favour staying aligned with EU rules, as companies had known since 2016 that the UK was going to leave the EU.
"Admittedly they didn't know the exact terms," he said.
The UK's 11-month transition period begins after it leaves the EU on 31 January.
Mr Javid declined to specify which EU rules he wanted to drop, but said some businesses would benefit from Brexit, while others would not.
He added: "There will not be alignment, we will not be a ruletaker, we will not be in the single market and we will not be in the customs union - and we will do this by the end of the year."
Tim Rycroft, chief operating officer of the Food and Drink Federation, told BBC Radio 4's Today programme that it sounded like the "death knell" for frictionless trade with the EU.
Acknowledging that some industries might benefit from Brexit, he said: "We also have to make sure the government clearly understands what the consequences will be for industries like ours if they go ahead and change our trading terms."
The Confederation of British Industry (CBI) said it welcomed the chancellor's "ambitious" vision but said the government should not feel an "obligation" to depart from EU rules.
Carolyn Fairbairn, CBI director-general, said for many companies, "particularly in some of the most deprived regions of the UK", keeping the same rules would support jobs and maintain competitiveness.
The Society of Motor Manufacturers and Traders said the automotive industry in the UK and EU was "uniquely integrated" and its priority was to avoid "expensive tariffs and other 'behind the border' barriers".
It said it was vital to have "early sight" of the government's plans so companies could evaluate their impact.
And the Chemical Industries Association said: "The industry continues to support regulatory alignment with our European counterparts, which represents the largest single market for our products."
BBC business correspondent Katy Austin pointed out that the association's members were concentrated in the north of England, an area the government is particularly keen to be seen to support.
Shadow chancellor John McDonnell tweeted that Conservative promises about frictionless trade with the EU after Brexit were "now exposed as not worth paper they were written on".
By BBC political correspondent Susana Mendonca
This tough tone from the chancellor appears to have a two-pronged intention.
Firstly, there's the message to business, which is, effectively, that Brexit is going to happen so just get on with it.
Getting on the wrong side of businesses has never been familiar ground for the Conservatives, but a majority government gives you the freedom to do the uncomfortable stuff.
It means the Tories can now be emboldened to say some companies will suffer because of Brexit in a way they never would have before. And with the general election now behind them, they can also pay little heed to warnings from the shadow chancellor that no alignment could lead to food shortages and job cuts.
The second motivation for this tough talk is likely to be about positioning ahead of the trade deal yet to be done with the EU.
The rhetoric around not being a "rule-taker" suggests the Conservatives want to be seen as preparing to have a tough battle with the EU to secure a deal without regulations - if they can.
The government has not yet agreed a future trading relationship with the EU - it plans to do so during the 11-month transition period.
During this period the UK will continue to follow EU rules and contribute to its budget.
The chancellor also said he wanted to double the UK's annual economic growth to between 2.7 and 2.8%.
The outgoing governor of the Bank of England, Mark Carney, told the Financial Times last week he thought the UK's trend growth rate was much lower, at between 1 and 1.5%.
Mr Javid said the extra growth would come from spending on skills and infrastructure in the Midlands and the north of England - even if they did not offer as much "bang for the buck" as projects in other parts of the country.
He also pledged to rewrite Treasury investment rules, which have tended to favour government investment in places with high economic growth and high productivity.

Thousands of Leave supporters have protested at Westminster against the delay to Brexit, on the day the UK had been due to leave the EU.
Some demonstrators reacted with cheers, while others shouted "shame on you", as MPs rejected Prime Minister Theresa May's EU withdrawal agreement.
The March to Leave - which began in Sunderland two weeks ago - arrived in Parliament Square on Friday afternoon.
A separate Make Brexit Happen rally, organised by UKIP, was also held.
The rally was backed by English Defence League founder Tommy Robinson, who spoke to crowds, along with UKIP leader Gerard Batten.
Meanwhile, at the March to Leave protest, former UKIP leader Nigel Farage and Tory Brexiteer MP Mark Francois delivered speeches.
Campaign group Stand Up to Racism also held a counter-protest in Westminster, saying it was there "against the far right who are trying to capitalise on the Brexit crisis".
Some Brexit protesters continued to demonstrate into the evening, and lines of police were deployed to keep the crowds under control.
The Metropolitan Police said five arrests had been made at the demonstrations - although that included one man who was wanted in connection with an offence elsewhere.
Two other people were arrested on suspicion of assault, another on suspicion of assaulting a police officer and someone else on suspicion of being drunk and disorderly.
It comes as MPs on Friday rejected Prime Minister Theresa May's withdrawal deal, which she negotiated with the EU, by 58 votes.
The UK had been due to leave the EU on 29 March, but both sides agreed to postpone the date last week after Mrs May had twice been unable to get her Brexit deal through the Commons.
Friday's defeat of the withdrawal agreement led to mixed reactions.
Some in the crowd, who saw Mrs May's deal as too soft, welcomed its rejection, while others feared it could lead to another EU referendum.
Former UKIP leader and Brexiteer Nigel Farage spoke at the March to Leave rally - organised by campaign group Leave Means Leave - and was greeted by loud cheers as he took to the stage.
"It's brave of you to come," he told demonstrators. "Because I sense, being in Westminster, that we are in enemy territory.
"There are hundreds of people just over the street that have treated that referendum, and those who voted for it, with total and utter contempt for the past three years."
Mr Farage told Leave supporters "not to be disheartened", and also signalled that he would be willing to stand again as an MEP if the UK takes part in the European Parliament elections in May.
The UK has a new Brexit deadline of 12 April, by which point it needs to have told the EU what its next steps are.
If the UK wants to delay Brexit further, the EU is expected to insist that it takes part in the elections.
By BBC home affairs correspondent Dominic Casciani, in Parliament Square
The mood and atmosphere in Parliament Square is very strange for a demonstration.
There is a really significant police presence, yet a lot of quiet but angry, angry people who believe that Parliament has "betrayed" Brexit.
When the news came through that MPs had, yet again, refused to back the PM's draft deal, the reaction was rather muted.
George, from St Albans, told me he was satisfied, because he hoped the UK could now crash out without a deal, as the public demanded.
One man has a coffin as a prop, declaring the death of democracy. "Bring out your dead," goes the prop's recording.
UKIP leader Gerard Batten told the crowd at the Make Brexit Happen protest: "As of now we do not know when we are going to leave the European Union.
"Theresa May has had, for the third time, her not-really-leaving deal rejected by Parliament."
He added: "What we do know is that if we do not leave the EU it will mark the end of democracy in the UK."
Mr Robinson, whose real name is Stephen Yaxley-Lennon - also took to the stage, addressing the confusion over the latest defeat of the deal: "So Theresa May has lost her vote. Many people will be asking what does that even mean.
"It means we were betrayed. Today is supposed to be our Independence Day."
The BBC's Sarah Walton, who was also at the scene, said there were some pro-Remain campaign groups demonstrating in central London.
"But at the moment here, the majority are pro-Brexit supporters," she said, "some of whom have been telling me that they were always planning on coming to London today, 29 March, but for a celebration to celebrate the day the UK would leave the EU."
"People have been saying they have come here from all across the country. They are angry and frustrated. Some of the rally groups have said they plan to be here well into the evening."
Some of the protesters wore hi-vis yellow vests, like those worn by the "gilets jaunes" anti-government rioters in Paris.
Former black cab driver Colin Grostate, who was at the demonstration, said they were a "symbol from France", adding: "We support the populism.
"Our politicians are not listening. Too many people are trying to stop what people voted for."
The Metropolitan Police said it had "appropriate policing plans" in place.

Some EU countries are pushing for the European Union's no-deal legislation to be more generous to the UK.
The European Commission has proposed "bare bones" arrangements on aviation and road haulage if there is no deal.
The legislation would allow British truckers to carry goods into the EU and British airlines to fly in and out of the EU, from 29 March to 31 December.
But a group of countries want to give UK hauliers the right to operate within the EU as well, known as cabotage.
Some also want British airlines to be able to offer connecting flights within the EU.
Diplomats are also concerned that airlines will not be able to offer new routes or run more services because the number of flights would be capped at 2018 levels.
Speaking on BBC Radio 4's Today programme, France's Finance Minister Bruno Le Maire said: "You can't be out of the EU and be getting the benefits of the single market."
"That is the clear red line of France."
The issues were discussed at a meeting of member states' ambassadors in Brussels on Wednesday.
Officials will try to hammer out a compromise at a meeting on Friday and ambassadors will discuss it again next week.
"We've got to strike a balance between being prepared but not sending the message to the UK that no deal would be OK," a diplomat said.
The European Commission, which co-ordinates planning for no deal at a European level, is opposed to expanding the scope of the legislation, saying it would give the UK some of the benefits of membership of the single market.
The commission also urged member states not to engage in bilateral deals with the UK, which some countries have suggested, because much of the responsibility for these issues rests with national governments.
Details of the discussion are contained in a diplomatic note of a meeting of EU ambassadors on Wednesday.
At least one country asked whether the EU should consider additional contingency measures to guarantee co-operation on security issues, such as the Schengen Information System which is used to share information about stolen goods and people of interest.
The news will cheer supporters of a no-deal Brexit, who argue that the EU would be prepared to offer mini-deals with the UK if the withdrawal agreement it has negotiated with the UK is not approved.

Both sides in Brexit talks say progress is being made but without any breakthrough on the crucial issue of the Irish border.
Brexit Secretary Dominic Raab said he was "stubbornly optimistic" about getting a deal after talks in Brussels.
Unresolved issues include intellectual property, data protection and the role of the European Court of Justice.
EU negotiator Michel Barnier said he needed detail from the UK on its plan to avoid a hard border in Ireland.
He told journalists that remaining "bones of contention" between the two sides were being steadily eliminated with particular progress on issues of security, judicial and defence co-operation after "long" talks on Friday.
The UK is due to leave the EU on 29 March 2019.
Both sides are hoping to agree a divorce deal and a statement on future trading relations at a summit of EU leaders on 17 October, although Mr Raab said that deadline could be missed slightly.
He told reporters: "We're committed to resolving the deal by (the October council) and ultimately on my side I am stubbornly optimistic that a deal is within our reach."
Mr Barnier said there was a "measure of flexibility" and if the process slipped by a "few days or weeks" it would still be possible for the UK to leave the EU with a deal, if approved by the UK and EU Parliaments, on schedule.
The EU negotiator said the "building blocks" of an agreement were falling into place.
He repeated his offer of an "unprecedented" future partnership with the UK but insisted this depended on an "orderly" withdrawal and settling key outstanding issues.
He said the question of the Irish border had come down to "minutiae" and he needed to see the detail of how the UK proposed to manage cross-border trade between Northern Ireland and the Republic of Ireland in the event of there being no other solution - the so-called backstop - would work in practice.
"This backstop is critical," he said. "It is essential to concluding the negotiations. Without a backstop, there will be no agreement."
Mr Raab said he had used Friday's talks to explain in more detail the UK's proposal for its future relationship with the EU, the so-called Chequers plan agreed by Theresa May at her country residence in July.
The PM's blueprint, which would see the UK follow EU rules on trade in goods, is unpopular with many Tory MPs, with leading Brexiteers like Jacob Rees-Mogg and Boris Johnson calling for it to be ditched.
Mr Johnson, who quit the cabinet in July in protest over the PM's proposals, said he agreed with Mrs May's former aide Nick Timothy, who urged her to ditch the plan.
Mr Timothy wrote on Thursday that she would have to make further concessions to get EU backing for it and this would be unacceptable.
And Stuart Jackson, the former Tory MP who until recently was an aide to Dominic Raab's predecessor David Davis, said the Chequers plan "has not really got any friends" on either side.
"For the EU, it's outside their core principles and undermines the integrity of the single market," he told BBC Radio 4's Today. "In the UK, people believe it is Brexit in name only."
The two sides say they have agreed 80% of the withdrawal agreement. The remaining 20% includes:
Mr Raab vowed to increase the frequency of talks with Mr Barnier when he took over the job.
But Labour MP Ben Bradshaw, a supporter of the People's Vote campaign for a referendum on the outcome of the negotiations, said "nothing had changed" since then.
"Dominic Raab may say he is more confident about reaching agreement but he can offer nothing concrete," he said.
"He knows the EU27 are not buying the Chequers car crash - a proposal designed around the need to hold a fractured government together and not on the economic interest and well-being of either the UK or the EU."

The Irish prime minister says Brexit is fraying relations between Ireland and Britain.
Taoiseach Leo Varadkar said it had also "undermined" the Good Friday Agreement (GFA).
The Good Friday Agreement was signed in 1998 after intense negotiations between the UK government, the Irish government and Northern Ireland political parties.
The UK government says "nothing we agree with the EU will risk a return to a hard border".
The Irish border is one of the biggest sticking points in the Brexit negotiations.
"Anything that pulls the communities apart in Northern Ireland undermines the Good Friday Agreement, and anything that pulls Britain and Ireland apart undermines that relationship," said Mr Varadkar on RTE's Marian Finucane programme.
Earlier, the chair of the Republic of Ireland's Senate Brexit Committee said a return to a hard border threatened the peace process.
Senator Neale Richmond told pro-Brexit Conservative MP Owen Paterson on BBC Radio 4's Today programme that plans for solving the border dispute using "existing practical systems" was "completely unfeasible".
Brexit talks have reached an impasse over the EU's "backstop" plan, which would see Northern Ireland effectively remaining in the customs union and single market unless alternative arrangements were found to prevent a hard border.
The taoiseach's comments came two days after Nobel peace prize winner and Conservative Lord Trimble accused Mr Varadkar's government of "riding roughshod" over the GFA.
Lord Trimble, who helped draw up the landmark agreement, said the Brexit process could result in Northern Ireland ending up as part of an "effective EU protectorate".
Mr Paterson, a former Northern Ireland secretary, reiterated that claim, saying that any backstop which involved the whole UK staying in a customs union would be a "total betrayal" of millions of Leave voters and the 85% of voters at the last general election who backed Tory and Labour manifestos which committed to leaving.
The Irish prime minister said Ireland was entering into a potentially difficult period, even if an agreement was struck.
The UK government said any deal would not " threaten the arrangements under the Belfast Good Friday Agreement, and we continue to work very closely with the Irish Government on this".
"We are also working together to ensure the unique bilateral ties between our countries remain strong into the future," a spokesperson added.
Mr Varadkar also said he had a good relationship with Arlene Foster, leader of the Democratic Unionist Party (DUP).
If there was some clarity on Brexit in the next couple of weeks or months, there would be an opportunity to get the executive up and running again, Mr Varadkar added.
The UK and the EU both want to avoid a "hard border" between Northern Ireland and the Republic of Ireland, which may include physical checks or infrastructure, but cannot agree how.
A key part of the negotiation is the controversial border "backstop".
The backstop is a position of last resort, to protect an open border on the island of Ireland in the event that the UK leaves the EU without securing an all-encompassing deal.
In a backstop situation, there could in theory be two types of Irish Sea checks:
The government has been adamant it would never accept Irish Sea customs checks.
But it has also been careful not to completely close down the prospect of regulatory checks.

The Scottish and Welsh governments have threatened to block the key Brexit bill which will convert all existing EU laws into UK law.
The repeal bill, published earlier, is also facing opposition from Labour and other parties in the Commons.
Ministers are "optimistic" about getting it through and have promised an "ongoing intense dialogue" with the devolved administrations.
No 10 said it had to be passed or "there will be no laws" after Brexit.
Brexit Secretary David Davis called it "one of the most significant pieces of legislation that has ever passed through Parliament".
He rejected claims ministers were giving themselves "sweeping powers" to make changes to laws as they are repatriated.
It will be up to MPs if they want a say on the "technical changes" ministers plan to make to legislation, he told the BBC.
Labour says it will not support the bill in its current form and is demanding concessions in six areas, including the incorporation of the European Charter of Fundamental Rights into British law.
The party wants guarantees workers' rights will be protected and also want curbs on the power of government ministers to alter legislation without full parliamentary scrutiny.
Leader Jeremy Corbyn, who was in Brussels earlier for a meeting with the EU's chief negotiator Michel Barnier, said: "Far too much of it seems to be a process where the government... will be able to bypass Parliament.
"We will make sure there is full parliamentary scrutiny. We have a Parliament where the government doesn't have a majority, we have a country which voted in two ways on Leave or Remain.
 "The majority voted to leave and we respect that, but they didn't vote to lose jobs and they didn't vote to have Parliament ridden roughshod over."
The Conservatives are relying on Democratic Unionist Party support to win key votes after losing their Commons majority in the general election, but could face a revolt from Remain supporting backbenchers.
BBC political editor Laura Kuenssberg said there could be "parliamentary guerrilla warfare" on the bill, as opposition parties and "Remainer Tories" try to "put their version of Brexit, not Theresa May's, on to the statute book".
The repeal bill is not expected to be debated by MPs until the Autumn, but will need to have been passed by the time the UK leaves the EU - which is due to happen in March 2019.
But the Scottish and Welsh governments have to give "legislative consent" to the bill before it can become law - something they have said they are not willing to do.
In a joint statement, first ministers Nicola Sturgeon and Carwyn Jones, who also met Mr Barnier, described the bill as a "naked power-grab" by Westminster that undermined the principles of devolution.
They say the bill returns powers from Brussels solely to the UK government and Parliament and "imposes new restrictions" on the Scottish Parliament and the Welsh Assembly.
Ministers at Holyrood will not be able to amend EU rules in devolved areas such as agriculture and fisheries after Brexit until the UK Parliament and Scottish government have reached an agreement on them.
UK Scottish Secretary David Mundell claimed the repeal bill would result in a powers "bonanza" for Holyrood - a comment described as "ludicrous" by the SNP.
Theresa May's official spokeswoman said the repeal bill was a "hugely important piece of legislation" because "we need to have a functioning statute book on the day we leave the EU".
The spokesman said First Secretary of State Damian Green had contacted the devolved administrations in Scotland, Wales and Northern Ireland and the government was confident of gaining their consent.
Asked if there was a contingency plan if he didn't win their backing, the prime minister's official spokesman said "not that I'm aware of".
Lib Dem leader Tim Farron, whose party is seeking to join forces with Labour and Tory rebels, said he was "putting the government on warning", promising a tougher test than than it faced when passing legislation authorising the UK's departure from the EU.
"If you found the Article 50 Bill difficult, you should be under no illusion, this will be hell," he said.
Steve Baker, a minister in the Department for Exiting the European Union, said the government was "ready" for a fight over the bill but would also to "listen to Parliament".
Speaking to BBC political editor Laura Kuenssberg, Mr Davies predicted the bill "may get amendments here and there", saying he was open to suggestions from other parties for things that should be included.
"If we've missed something and got something wrong, then we'll debate that in the House of Commons," he said.
"That's how this works."
Mr Davis also insisted contingency plans were being made in case the UK and the EU cannot agree a Brexit deal.
"We are planning for all options," he said.
"The ideal outcome... right through to it not working at all and not getting a negotiated outcome at all."
Asked why Foreign Secretary Boris Johnson had said the government had "no plan" for such a scenario, he said: "That's possibly because it's my responsibility to plan for it."

Tory leadership candidate Rory Stewart says his competitors' claims they could negotiate a new Brexit deal before 31 October are "misleading".
Some candidates say they can agree a plan by the deadline set by the EU, but Mr Stewart said there was "not a hope".
Boris Johnson has warned the Tories face "potential extinction" if the UK doesn't leave by then.
Rival Jeremy Hunt said a revised deal could be done by then under a leader with "the right negotiating skills".
The former foreign secretary told a leadership hustings on Tuesday the party would "not be forgiven" if it failed, and said he was the candidate best placed to beat Labour and "put Nigel Farage back in his box".
The comments came as the Eurosceptic European Research Group (ERG) of Tory MPs called on leadership contenders to abandon Mrs May's Brexit deal and step up preparations for a no-deal exit in October.
International Development Secretary Mr Stewart told BBC Radio 5 Live's Emma Barnett that anyone promising to renegotiate by October was effectively committing to leaving without a deal because it was impossible.
Meanwhile, in other Tory leadership developments:
The EU has consistently said it is not willing to re-open the current withdrawal agreement negotiated between the bloc and Mrs May, despite it being voted down by MPs three times.
The winner of the contest to lead the Conservative Party will become the next prime minister.
Mr Stewart and Mr Johnson are two of 11 candidates running to become the next leader of the Conservative Party, and the next UK prime minister.
On Tuesday, two pulled out of the leadership race as the party tightened the rules for the contest amid concerns about the size of the field.
Candidates will now need the support of eight MPs to take part in the race, and to secure of 5% of the vote in the first round, and 10% of the vote in the second round, to progress.
Charles Walker, the acting joint-chair of the Tory backbench 1922 Committee, said it was "not unreasonable for someone seeking to be leader of the party and prime minister to be able to muster" that level of support.
He told BBC Radio 4's Today programme that he expected the Parliamentary side of the leadership contest - where MPs narrow the field down to two final candidates - to take no more than two weeks.
The winner will then be chosen by the wider membership of the Conservative Party.
Mr Johnson suggested the solution to the current deadlock would be to replace the Irish backstop - the controversial insurance policy designed to maintain an open border - with "alternative arrangements".
The EU, though, has said the backstop is a key part of the withdrawal agreement, which it is not willing to reconsider or subject to a time limit.
Mr Johnson, who has insisted the UK must leave by the end of October with or without a deal, said a no-deal exit would cause "some disruption".
But he warned that demands for a further referendum would grow if the country was forced to seek another extension from the EU.
Mr Stewart said "politicians need to stop pretending they are going to get a new deal from Brussels".
"Anyone who knows anything about Europe can assure you there is not the slightest hope of getting a new deal through Europe by 31 October. Not a hope.
"There is a lack of realism."
Earlier, Defence Secretary Penny Mordaunt would not be drawn on whether she planned to enter the leadership race, but she claimed that nobody wanted a no-deal Brexit, and the EU "understand they have to move on some things".
Speaking to BBC Radio 4's Today programme, the Brexiteer said: "I stayed in cabinet and fought to try and get a deal and to try and build a consensus, both in my party and but also in Parliament.
"What we have learnt though is if you are trying to get that objective, you can't take no deal off the table."
Fellow Leave-backer and Tory MP Steve Baker told BBC's Politics Live he had not decided whether to run, but said the party needed someone "very direct [and] with a clear plan" for Brexit.
He has published his own plan for leaving the EU, "A Clean Managed Brexit", calling for a future partnership "based not on the close mandatory alignment and single customs territory which the draft agreement was designed to facilitate, but one centred on a mutually-beneficial advanced free trade agreement".
Mr Baker added: "No one voted to ask permission to leave. We voted to leave with the hope of negotiating mutually-beneficial cooperation as an independent country. We continue to hope to do so."
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A public row has broken out at the top of the People's Vote campaign for another EU referendum.
Media chief Tom Baldwin has accused chairman Roland Rudd of putting "a wrecking ball" through the campaign.
Mr Baldwin said he had been fired by Mr Rudd - but would be going in to work as normal.
Mr Rudd denied firing Mr Baldwin, saying "he has an opportunity for a different type of role".
He also denied reports of strategic differences within the organisation over his desire to openly campaign for Remain.
On Sunday, the Observer reported others within the group want to concentrate on winning support for another vote among Leave voters and wavering Labour and Tory MPs.
But Mr Rudd told BBC Radio 4's Today programme: "There's no row about the Remain side and PV [People's Vote]. Everyone knows where we stand on this".
"This is an absurd argument. Everybody knows perfectly well that we're made up of people who want to vote to Remain. There isn't a problem".
The campaign is supported by five groups - the European Movement UK, the Joint Media Unit, Our Future Our Choice, For our Future's Sake and Wales for Europe and Open Britain - of which Mr Rudd is chair.
Over the weekend, the Financial Times reported that two senior figures of the campaign  - Mr Baldwin, the former top adviser to Ed Miliband when he was Labour leader, and James McGrory, ex-deputy PM Nick Clegg's former top adviser - had been asked to leave by Mr Rudd.
Mr Baldwin told the Today programme that although Mr Rudd "technically controls my contract, he didn't appoint me, he doesn't pay me" and added he was still planning to go into work.
He added it was "extraordinary that Roland Rudd is acting like this is his campaign".
"He is making the mistake a lot of businessmen do when they dabble in politics, which is to think, because they have a certain title and board they own the campaign," he said.
He also accused the Liberal Democrats of "playing some strange games" with the campaign, referring to their bid to have an election on 9 December.
Mr Rudd, who made his fortune as the founder of a financial PR firm, said "there is a problem when someone comes on this show and says the Lib Dems are no longer part of the People's Vote".
"The key thing now is that we have to keep our eyes set on the prize.
"We have every chance of getting that prize which is to get it back to the people - the more people see this deal the more they see its flaws."
Asked if he had fired Mr Baldwin, Mr Rudd responded that "he has an opportunity for a different type of role".
The BBC has been told that both Mr Baldwin and Mr McGrory were at the People's Vote offices on Monday morning, as their 40 staff gathered for a meeting.
Tweeting in support of Mr Baldwin, People's Vote campaigner and ex-adviser to Tony Blair Alastair Campbell said "after his [Mr Rudd's] rare visit to the building today it is to be hoped those actually working for a second referendum rather than talking about it to their business pals (none of whom have made donations for months) can get on with their jobs and put this silly episode behind us".

The government has axed its no-deal Brexit contract with a ferry company which had no ships, after the Irish company backing the deal pulled out.
Transport Secretary Chris Grayling had faced criticism for the £13.8m deal with Seaborne Freight, which the BBC found had never run a ferry service.
The government said it is in "advanced talks" to find another ferry firm.
But local MP Craig Mackinlay said this could be the "last throw of the dice" for commercial shipping from Ramsgate.
Meanwhile, Labour has called on Mr Grayling to resign or be sacked, describing him as "the worst secretary of state ever".
Seaborne Freight was awarded the £13.8m contract in December to run a freight service between Ramsgate and Ostend, Belgium, in the event that Britain leaves the EU without a deal.
The government was criticised for choosing Seaborne Freight, a company with no ships or trading history, and for leaving too little time to establish the new ferry service before the Brexit deadline of 29 March.
And local politicians in both Ramsgate and Ostend warned that the ports at both ends of the route will not be ready the deadline.
At the time, the government said it awarded the contract "in the full knowledge" that Seaborne, which was formed in April 2017, was "a new shipping provider" but said the company had been "carefully vetted".
On Saturday, the Daily Telegraph reported that Arklow Shipping, a major Irish shipping firm, withdrew its support from Seaborne "without warning".
The Department for Transport (DfT) said that it had become clear that Seaborne "would not reach its contractual requirements", after Arklow Shipping backed out of the deal.
A spokesman said: "The government is already in advanced talks with a number of companies to secure additional freight capacity - including through the Port of Ramsgate - in the event of a no-deal Brexit."
Thanet District Council - which covers Ramsgate - said it was "disappointing" that Arklow Shipping had pulled out of the deal. It said it was in talks with the DfT about the port's role "in terms of supporting Brexit resilience".
The council has been pumping money into the port to get it ready for ferry services. Earlier this week, it was considering cutting its budget for the port but, at the request of Mr Grayling, delayed its decision.
Ramsgate has not had a regular ferry service since 2013 and needs to be dredged before services can start.
Following the news that Seaborne Freight had lost the contract, the Conservative MP for South Thanet, Mr Mackinlay, said ferry companies had "come and gone over the last few years" but "none of them have come to anything".
"For me, this Seaborne operation was potentially the last throw of the dice for a chance for commercial shipping out of Ramsgate," he said.
"Perhaps it is time that we turned the page on Ramsgate port being for commercial activity and we can start doing something rather more exciting on those acres of land, potentially a marina village, hotels, restaurants, some housing, something really exciting that I think would be more welcomed by many people in Ramsgate."
Andrew Gwynne, the shadow secretary of state for communities and local government, told BBC Radio 4's Today programme: "This is yet again another indication of a government that had no plan for Britain should we leave the European Union without a deal.
"It's another example of a major disaster in the hands of Chris Grayling who must be classed as the worst secretary of state ever."
The government said that no taxpayer money has been transferred to Seaborne.
It added that its confidence in the viability of the deal with Seaborne was based on Arklow Shipping's backing of the company and the assurances it received from them.

Rebel Conservative MPs have joined forces with Labour to inflict a fresh blow on Theresa May's government in a Commons Brexit vote.
It means the government will have to come up with revised plans within three days if Mrs May's EU withdrawal deal is rejected by MPs next week.
It could also open the door to alternatives, such as a referendum.
No 10 said Mrs May's deal was in the national interest but if MPs disagreed, the government would "respond quickly".
The setback for the PM came as MPs started five days of debate on the withdrawal agreement with the EU, and the framework for future relations, ahead of the meaningful vote next Tuesday.
The government was expecting to have 21 days to come up with a "plan B" for Brexit if, as widely expected, Mrs May's deal is voted down.
But MPs backed calls for it to respond within three working Parliamentary days, a deadline likely to fall on Monday 21 January.
Theresa May lost by 11 votes, with 297 MPs siding with the government and 308 against.
Among those voting against were 17 Conservatives, including former ministers Justine Greening, Sam Gyimah and Jo Johnson who want to see another referendum to decide whether the UK should leave or not.
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Former attorney general Dominic Grieve, the Conservative MP who led the rebellion, said he hoped for a "serious dialogue" between government and Parliament on alternatives to Mrs May's deal to avert a possible crisis.
He told ITV's Peston that it would be up to Mrs May to decide what she wanted to do if her deal was rejected, but MPs would be able to vote on any motion she put forward within seven days.
While the PM would have the right to say she wanted the Commons to re-consider her deal, he said MPs could amend the motion, telling her in effect "we want you to do something else".
Fellow rebel Sarah Wollaston said she and other MPs opposed to a no-deal exit were engaged in a "guerrilla campaign" to show that it would never get the consent of Parliament.
By BBC Parliamentary Correspondent Mark D'Arcy
The new Grieve amendment, now passed by MPs, means that in the event the PM loses next week, the Commons will then have a chance to vote on alternative policies - everything from a "managed no-deal" to a further referendum, via a "Norway option" or a reheated version of the current deal, could be on the table.
If a majority could be found for anything, it would not have the force of law - but it would at least indicate a policy which had the support of MPs.
This is, in short, a massive ruling by the Speaker, made, apparently, against the advice of the Commons Clerk, Sir David Natzler.
I don't want to delve too deeply into the arcana of Business of the House motions only amendable by ministers of the Crown, but this drove a coach and horses through accepted normal practice, and will have huge implications for the course of Brexit.
Read Mark's full blog
But Conservative Brexiteer Jacob Rees-Mogg, who favours leaving without a withdrawal agreement, said it would not stop the UK exiting on 29 March.
"It merely requires a motion to be tabled not even debated," he said.
And prisons minister Rory Stewart, who backs the PM's deal, said requiring Mrs May to restart complex negotiations with the EU and come back with changes in three days, was "unreasonable".
He said Mr Grieve was "trying to provide more support for what he wants, which is a second referendum".
Downing Street said it would consider the repercussions of Wednesday's defeat but its intention had always been to "provide certainty" as soon as possible.
Labour has said it will table a motion of no confidence in the government if Mrs May's deal is voted down.
Shadow Brexit secretary Sir Keir Starmer said Parliament had to "take control of what happens next" and suggested delaying the date of the UK's exit beyond 29 March might be "inevitable".
He warned the UK's options were narrowing given the need to avoid, at all costs, a no-deal exit which he claimed was "simply not viable for practical reasons".
Commons Speaker John Bercow faced an angry backlash from some Conservative MPs over his decision to allow MPs to vote on the issue.
The MPs claim Mr Bercow broke Commons rules and ignored the advice of his own clerks.
Commons leader Andrea Leadsom was among MPs to challenge his ruling in a series of points of order after Prime Minister's Questions.
They argued that the business motion, tabled by the government, was not amendable and said the Speaker was breaking with precedent.
Mr Bercow said he had made an "honest judgement" after consulting his clerks but rejected calls from Ms Leadsom to publish the advice he had received.
He insisted he was "not setting himself up against the government but championing the rights of the House of Commons", adding that if people wanted to vote against the amendment they could.
But a number of Tory MPs said the decision cast doubt on Mr Bercow's impartiality, with Crispin Blunt questioning whether he remained a "neutral referee of our affairs".
The Commons defeat was the second in the space of 24 hours for the government on Brexit.
On Tuesday, MPs, headed by former Tory ministers Mr Grieve and Oliver Letwin, defied the government on an amendment aimed at making it more difficult to leave the EU without a deal.
The clashes in the Commons came as the PM, who cancelled a vote on her deal last month at the last minute to avoid a humiliating defeat, launched a fresh push to convince MPs.
She is hoping new proposals on Northern Ireland will change enough MPs' minds to save the deal.
Under the plans, the Northern Ireland Assembly would have a say on new EU rules if the backstop plan to prevent physical checks on the Irish border comes into force after Brexit.
But the Democratic Unionist Party, on whom Theresa May relies for her Commons majority, have already rejected the so-called "Stormont lock" plans as "cosmetic" and "meaningless".
Ministers have also accepted calls for MPs to be able to vote next year on alternatives to activating the backstop, such as extending the proposed 21-month transition period.
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A no-deal Brexit would hit UK-EU security ties and have a "real impact" on protecting the public, security minister Ben Wallace has warned.
In a speech to law enforcement leaders, he said close co-operation  was the "heart of effective security".
Mr Wallace said the PM's deal, which MPs vote on next month, would set the foundations for the most comprehensive security relationship in EU history.
But Labour's Diane Abbott said the plan "failed on guarantees for security".
The shadow home secretary's party is to table an amendment to reject the deal  but also "prevent the chaos of the UK crashing out of the EU".
The UK is due to leave the EU on 29 March 2019 but, under Theresa May's deal, there would then be a transition period, during which the UK and EU would continue to work together as they do now.
The deal for how the UK will leave the EU is accompanied by a non-binding declaration on the future relationship between the EU and UK after transition has ended, which includes the promise to co-operate on security.
MPs are due to vote on the deal on 11 December. If they reject it - and no other solution is found - the UK could leave without a deal. The current arrangements on security co-operation would then end on 29 March with nothing to replace them.
In the run-up to the vote, the public can expect a steady drumbeat of official warnings about the dangers of a no-deal Brexit, says BBC political reporter Brian Wheeler, as Mrs May and her team try to sell her plan.
A leaked copy of Downing Street's own timetable for media announcements has "security" listed as a Thursday priority with "international trade" scheduled the following day.
Mr Wallace was speaking at the International Security Expo in London, where he said that such a no-deal departure would be a step backwards for security co-operation.
He added that the UK, through the experience of the last few decades, had learnt the value of working with its European partners.
He said: "We and Europe know, from bitter experience, that often when there is a mistake or when something has been missed that we find, time and time again, that it has been due to a failure of co-operation.
"A no-deal situation would have a real impact on our ability to work with our European partners to protect the public."
By Dominic Casciani, BBC home affairs correspondent
The UK wants to maintain all the existing security arrangements - and it knows that the EU wants to maintain this high level of co-operation out of mutual self-interest. But there are problems.
Critics of the government's hopes for post-Brexit security are concerned that the proposed final relationship with the EU - that would kick in in 2021 - is long on aspirations but short on solutions.
It's not remotely clear if the UK will be able to access EU-organised databases, such as those that exchange criminal records, wanted alerts and DNA and fingerprint records, after the transition.
Once transition ends, so does access to the data - unless a security treaty can be agreed.
But even if that treaty is signed, it may come up short. Some nations, like Germany, have constitutional bars on how they can co-operate on security with non EU states.
In his address, Mr Wallace said that Mrs May's agreement would set the foundations for the broadest security relationship the EU has had with another country.
The partnership would include the ability to exchange information on criminals and tackle terrorism, to quickly share data on people travelling to and from the UK to spot potential threats, to exchange DNA and fingerprints, and to fast-track extraditions.
Ms Abbott described the government plans as "dangerously flimsy".
She said: "There is no new security treaty on offer, which is vital for cross-border policing arrangements, especially extradition."
She added that there were "only aspirations for a vague security partnership, no plans for proper security arrangements, including with Europol" and that it was "simply unacceptable".
As the vote on the PM's deal draws closer, details of what will happen in Parliament during the build up were released.
The Commons will debate the agreement for eight hours a day on 4, 5, 6, 10 and 11 December under business proposals set out by the government.
But MPs will be allowed to table six amendments to the Brexit motion, to be chosen by the Speaker of the House of Commons and heard before the vote on 11 December.
Labour has put forward an amendment "rejecting Theresa May's botched Brexit deal" and to stop a no-deal, calling for all options to be left on the table if it gets voted down.
The party's leader, Jeremy Corbyn, said the deal "is a miserable failure of negotiation by a government that has wasted the last two years fighting with itself, rather than securing a better deal with the EU".
Conservative Party chairman Brandon Lewis called the amendment "shameful and irresponsible behaviour", adding: "All they are interested in is trying to force a general election."

A powerful cross-party group of MPs is to force a vote on a customs union next week in the House of Commons.
The Liaison Committee, made up of Labour, Conservative and SNP committee chairmen, has tabled a debate calling for "an effective customs union".
Theresa May has pledged to leave the current customs union after Brexit.
Downing Street believes that trying to replicate it when the UK leaves the EU would stop the country from being able to sign its own trade deals.
The news about the Commons vote comes the day after the House of Lords inflicted a defeat on the government over the customs union issue.
The government had hoped to avoid a vote on the issue in the Commons until next month.
But the MPs, including Yvette Cooper, Nicky Morgan, Sarah Wollaston, and Hilary Benn, have secured a debate that will force the issue.
BBC political editor Laura Kuenssberg said that although a vote would not be binding on the government, it will ratchet up the pressure on No 10 to shift its position if the Commons agrees.
Conservative backbencher Anna Soubry said that it would "not be a meaningful vote at all" but the debate would be important.
She said the "crunch question" was whether the government would have sufficient MPs prepared to overturn the Lords amendments to the EU Withdrawal Bill, when it returned to the Commons.
She told BBC Radio 4's World at One programme the Lords vote had asked the government only to "explore" a customs union.
"There is an increasing number of Conservative MPs... who are worried and now understand the benefits of us having a customs arrangement, not just for the benefit of manufacturers in particular in our country... but also for peace in Northern Ireland.
"I do hope the government will look at the numbers - but look at the strength of the argument - do the right thing and that is not to seek to whip Conservative members of Parliament to take out this eminently sensible and hugely reasonable amendment that the Lords passed last night."
Shadow Brexit secretary Sir Keir Starmer said the Lords defeat on Wednesday should prompt the prime minister to change her approach.
He said: "There's a growing view, I think probably a majority view in Parliament now, that it's in our national interests and economic interests to stay in a customs union with the EU.
"We've got a huge manufacturing sector in the UK that needs to be protected, with many goods going over borders many, many times, and we need to protect that."
Environment Secretary Michael Gove told BBC Radio 4's Today programme that the government might face a battle in the Commons to overturn the Lords vote.
He said: "It is the case that there are lots of potential future votes - given the arithmetic in the House of Commons, given the fact that we don't have a majority - which are always going to rely on the persuasive powers of ministers to get colleagues to support the Government."
The Liaison Committee members calling for the motion also include the SNP's Angus McNeil, Lib Dem Norman Lamb, Labour MP Meg Hillier, Conservative Bob Neil, Labour's Rachel Reeves and the SNP's Pete Wishart.

Former UKIP leader Nigel Farage suggested earlier he was coming round to the idea of a second EU referendum - what is going on?
To paraphrase the old joke, there are probably two chances of a second EU referendum right now - slim chance and fat chance. Ladbrokes is currently offering odds of 5/1 on it. At 11/8 the bookmakers think it is more likely that no deal will have been agreed before Britain officially leaves the EU on 29 March 2019. Theresa May and Jeremy Corbyn have ruled out a second vote, both essentially arguing that it would be seen as a catastrophic breach of trust with a public already weary of broken promises.
The idea that the political establishment will just keep holding referendums until they get the result they want - or simply ignore the result if they don't like it - was a constant refrain during the Brexit campaign. It has happened before, say Brexiteers.
France and the Netherlands both rejected an EU constitution in 2005 referendums, which led to the document being repackaged and adopted by both countries as the Lisbon Treaty.
Ireland then rejected the Lisbon Treaty in a 2008 referendum - it was the only EU country to hold such a vote - but then accepted it in a second referendum the following year, following pressure from the rest of the EU.
But sometimes the establishment gets the result it wants and still has to face another vote.
The term "neverendum" was coined in the French Canadian province of Quebec, which has twice voted against independence from Canada - the first time in 1980 by a majority of 59%. the second time, in 1995, by a shade over 50%. The prime ministers at the time of the two votes were pro-Canada. The independence campaign has never stopped pushing for a third vote.
The former UKIP leader has angrily denounced "Remoaners" like Tony Blair and Sir John Major for suggesting the public should be given another vote.
"I think there are 17.4m people out there who voted Brexit despite being told it was the wrong thing to do and I really think it would be a big mistake if these people get pushed too far," he said on his LBC radio show in November 2016.
Yet before the referendum, he freely admitted he would have kept pushing for another vote if his side lost by a narrow margin.
"In a 52-48 referendum this would be unfinished business by a long way. If the remain campaign win two-thirds to one-third that ends it," he told the Daily Mirror.
There is a kind of consistency here - the former UKIP chief will not be satisfied until Brexit has been resoundingly backed by the people, to "finish the whole thing off".
"It may well be that Nigel would get what he wants which is a completely hard Brexit," veteran Tory Eurosceptic Bill Cash told the BBC.
But he added: "I do find his position quite unconvincing and for him to be, as it were, bedfellows with the Liberal Democrats I think is one of the funniest things I've ever seen in British politics."
Perhaps Mr Farage - and one-time UKIP donor Arron Banks who also now backs a second referendum - are missing the spotlight and fancy getting the Brexit band back together for one more tour.
He later clarified his remarks, saying a second referendum was the "last thing" he wanted to see but the Leave side had to be ready for one, as Remainers claimed support for another vote was growing.
For all the sometimes wild claims from both sides, if a second referendum was held now there is no guarantee the outcome would be any different. Polling suggests Britons are becoming increasingly sceptical about the government's handling of Brexit talks "but Leave voters for the most part have not changed their minds about their decision", pollster Sir John Curtice said this week.
But - say Remainers like Tony Blair - why should the 2016 referendum be the final word? That's not how democracy works, they argue.
Mr Blair said in a BBC interview that people should be given a chance to "think again" once they have seen the final exit deal.
He was a bit vague on how this might happen, suggesting it could be via another referendum or a general election, although this, he claimed, was a "second order" issue. Only the Liberal Democrats, with 12 MPs, are openly pushing for a second referendum.
Britain leaves the EU in March 2019. The next scheduled general election is on 5 May 2022.  It would take a change of Labour and/or Tory leadership, not to mention a major policy shift, and, in all likelihood, an early general election. So if there was to be another vote it would probably have to be held this year or, at the very latest, early next year.
The June 2016 question was simple: "Should the United Kingdom remain a member of the European Union or leave the European Union?"
The next one, if it is ever posed, might be a bit more convoluted...

On the face of it, there is nothing remotely surprising about Theresa May telling her Cabinet colleagues last night that she wants to have another go at trying to sort out the backstop.
The political implication of that is that she still thinks it is better at this stage for her to pursue a strategy that might just about conceivably see, in the end after a lot more wrangling, a version of her deal squeak through the House of Commons with support from her own MPs and having kissed and made up with the DUP.
Right now that seems a long way off of course, and it might prove impossible.
But the view at the top of government is that, on balance, this is the better choice. There are plenty of MPs and some in government on the other side of this argument who think it is not much short of insane to keep going with a strategy that has been so roundly kicked out by the Commons. You hear a lot of quoting of Einstein, who claimed the definition of insanity was doing the same thing over and over and expecting different results. (Although as so often there is a row over whether he actually said that at all)
And while it's scoffed at, some people in government believe in the end the EU might budge and that Ireland might be persuaded to look at a separate agreement to sort out the backstop. (Don't all scream at once, I know how far off that looks at the moment).
Remember, Theresa May just isn't the kind of politician who was ever going to tear up her Plan A overnight, however irritating it might be to some of her own ministers like the one who told me last week she would have to budge at "five past seven".
This doesn't of course mean in theory that the cross-party process is over. There are more talks between various MPs and senior ministers today.
But one senior MP involved in the process believes the problem is that by suggesting compromise in the Commons in the wake of defeat last week, then telling ministers Plan B is basically Plan A last night, the PM has "burned up the goodwill".
If she wasn't going to budge, what was the point of implying that she might?
In theory the point was, of course, that it's highly likely she will in the end need to compromise, and that every vote will count.
But one source joked that she won't do it until "she's in a half-Nelson" - the reality is by then, those MPs who were willing to help last week may have concluded, as some already have, that if she won't budge, Parliament will simply grab hold of the process when it comes to the vote next week.

"Are they serious?"
Labour and the Conservatives are separately pondering that same question tonight - wondering whether their political rivals really are genuine about finding common cause.
Guess what, just for a change, the leaderships of both of the main Westminster parties are dealing with boiling tensions on their front and back benches.
And they both have reasons to tiptoe towards each other in these cross-party talks, but both sides too have reasons to tread carefully.
In truth, both sides are serious that they could possibly get serious about a deal, but the obstacles are significant.
The Tories have still not, and may never feel able to offer a clear promise of pursuing a customs union.
What sources familiar with the talks say the focus is right now, is trying to point out to Labour that the existing deal contains the possibility of shaping that kind of arrangement in the future.
Irony upon irony, the backstop which the government has been protesting about for so long provides the ingredients for exactly that kind of relationship with the EU in the long term.
That is precisely why Brexiteers hated it so much - because they feared (correctly perhaps) it might be used as the basis on which to build the kind of tight trading deal with the EU they seek to avoid.
For the prime minister to overtly pursue such a deal is already provoking fury in parts of her party - although it's also striking now how frustrated some middle of the road Tory MPs are - fed up of what they see as both "extremes", hogging the oxygen and holding everything up.
But unless and until Theresa May is ready to give a firmer commitment on customs, it is hard to see how Labour would be ready to sign on the dotted line.
Although the two sides will meet again in the next 24 hours, Jeremy Corbyn again has expressed his view that the government hasn't shifted any of those red lines.
And even if that were to happen, there are (at least!) two other big blocks to success.
There is deep anxiety in the Labour Party about being able to trust anything that is agreed.
The government's already promised that they could change the law to give guarantees in the Brexit implementation bill.
But both sides admit privately even if they came up with some kind of "lock", it's just not feasible to rule out any future prime minister ever unpicking the deal.
In a different era this might not be such a problem.
But the prime minister has already said that she will quit, and quit once the deal is done.
So of course, Labour MPs are very nervous about how the promises made in these talks could last.
That's whether the next leader were to be Boris Johnson, Dominic Raab , Jeremy Hunt or frankly, the Queen of Sheba - it's about the permanence of any promise.
And, as I understand it, the two groups, even with serious intention, have not as things stand been able to come up with a formula that guards against this.
Second of all, officials and politicians in the discussions have talked about the possibility of another referendum on the EU - whether you call it a "confirmatory vote", a "ratificatory referendum", or a "people's vote" - another chance for all of us to have a say.
This has not though yet been a big focus of the talks - it seems like an issue that has been danced around the edges.
Here's the thing: a hefty chunk of the Labour Party is adamant that they will only back a deal if it comes with a promise of another referendum.
And that opinion among Labour backbenchers has been hardening, not softening in recent weeks.
So even if the talks can find away around the customs conundrum, and then find a "lock" to make Labour comfortable with any promises that are made, there is a third profound dilemma.
Number 10 has always made it abundantly clear that the prime minister believes that's a nightmare not worth contemplating.
The problem for these talks is that for a big chunk of the parliamentary Labour Party that's the dream they are pursuing.
There are others who disagree, and disagree profoundly.
But in terms of making this process work, the Labour Party's votes can't be delivered in one big chunk.
With huge political imagination, invention, (whose mother after all they say is a necessity, and there's certainly a necessity right now), it is of course possible that this process could get there.
In this long tangled process a lot of things that have seemed impossible can in the end come to pass.
But just as both sides in these talks are serious, the problems are serious too.

Senior Conservative backbencher Sir Graham Brady has told the BBC that he could accept a delay to Brexit - as long as a deal was already agreed.
He said a short delay to the 29 March exit date would be acceptable if needed to get legislation through Parliament.
The government says its position has not changed on the date but Foreign Secretary Jeremy Hunt has suggested "extra time" may be needed.
MPs rejected a bid to postpone Brexit if no deal was reached by 26 February.
That amendment, from the Labour MP Yvette Cooper, would have delayed the 29 March departure date by several months, but it was voted down by 321 to 298 on Tuesday.
But Sir Graham, chairman of the influential 1922 Committee of Conservative backbenchers, told Nick Robinson's Political Thinking podcast, the Cooper amendment "would have been deeply counter-productive because it moves off the decision point".
Putting off the decision would only lead to more uncertainty, he said.
"I would only countenance a delay if we already had a deal agreed, it's just a matter of doing the necessary work to implement it," said Sir Graham.
"Once we've reached an agreement and we know the terms on which we're leaving, if we decide that we need another two weeks in order to finish the necessary legislation through Parliament, I don't think anybody's going to be too worked up about that, because we will have made a decision."
The UK is due to leave the European Union at 23:00 on 29 March, however MPs have overwhelmingly rejected the withdrawal deal that the government had negotiated with the EU.
On Tuesday they voted for the prime minister to seek "alternative arrangements" to the controversial Irish "backstop" proposal, which is opposed by many Conservative MPs and the Democratic Unionist Party.
The backstop is an "insurance" policy to stop the return of checks on goods and people along the Northern Ireland border, if no deal is reached in time. It would effectively keep the UK inside the EU's customs union, but with Northern Ireland also conforming to some rules of the single market.
Its critics say a different status for Northern Ireland could threaten the existence of the UK and fear that the backstop could become permanent.
But the EU's chief Brexit negotiator Michel Barnier said on Wednesday the backstop was "part and parcel" of the withdrawal deal and would not be renegotiated.
Earlier on Thursday, Mr Hunt said "extra time" may be needed to finalise legislation for Brexit and a possible delay in the UK's departure from the EU depended on the progress made in the coming weeks.
And BBC political editor Laura Kuenssberg said there had been "growing chatter" about a potential delay and a potential extension to Article 50 - the mechanism by which the UK leaves the EU.
But the prime minister's official spokesman said the government remained committed to leaving the EU on 29 March.
Parliament had been due to rise for recess on Thursday, 14 February and return on Monday, 25 February but that has now been cancelled.
"The fact that recess won't be taking place shows you that we are taking all available steps to make sure that 29 March is our exit date," the spokesman said.
"The prime minister's position of this is unchanged - we will be leaving on the 29th."
Downing Street was also discussing the possibility of Parliament sitting for extra hours in the run up to Brexit, the spokesman said.
Labour leader Jeremy Corbyn accused the government of running down the clock on Brexit.
He said: "It is possible that there will have to be an extension in order to get an agreement because we cannot leave the EU on March 29 without an agreement.
"Crashing out would mean problems of transport, problems of medicine supply, problems of supply to the food processing industry that does just in time deliveries - and that simply is not acceptable.
"This government has had two-and-a-half years to negotiate and has failed to do so."
Meanwhile, Labour MP John Mann has said a group of 10 MPs from his party met the prime minister two weeks ago to ask for "a significant amount of money" for poorer areas, "so that we can actually move forward as we leave the EU".
When asked about a Times article that said Mrs May was preparing to entice Labour MPs to vote for her deal with money for constituencies, Mr Mann told the BBC he had voted for the deal already, "so I can't be bribed".
"There's no expectation, this isn't transactional politics. We're asking for money for areas that have not had their fair share in the past," he said.
Several Conservative MPs have been spotted going to meetings in Downing Street, including former Brexit minister Steve Baker, Iain Duncan Smith, Mrs May's close ally Damian Green and Nicky Morgan.
Ms Morgan, a former education secretary, said she was there to discuss a plan known as the "Malthouse Compromise".
Engineered by both Leavers and Remainers, the proposal includes extending the transition period for a year and protecting EU citizens' rights, instead of using the backstop.
Union officials have also been meeting with government officials in the Cabinet Office to discuss Mrs May's Brexit plan.
But a Trades Union Congress spokesman said the prime minister's deal came "nowhere close" to offering the safeguards desired for working people.

It cannot be said Britain will begin its exit from the EU with no destination in mind.
After today we have the clearest idea of the deal Theresa May wants: UK access to the European Single Market but no membership of it; a tariff-free customs union with the EU but freedom to sign trade deal with other countries; some sort of bridging arrangement between membership of the EU and life outside it to avoid "a disruptive cliff edge", to use Theresa May's phrase; a close security relationship with the EU.
Most strikingly, while the Prime Minister's speech tried to soothe friction between the UK and the EU by stressing the need for friendly mutual co-operation she had a blunt warning for the EU too. Britain will not sign a deal at any price.
"A punitive deal would be a calamitous act of self-harm", she told the audience of EU ambassadors gathered in the splendour of Lancaster House. But it is for the decision to take Britain out of the single market that historians will remember this speech.
The clues had been there for months. While claiming not to want a running commentary Theresa May has said many times Britain's break from the EU must result in control over EU migration and freedom from the jurisdiction of EU law. It was there in her speech to the Conservative Party conference in October.
Those political choices could only mean one outcome: Leaving the European Single Market. It is the most important economic decision Britain has taken for years.
It was at the same venue 28 years ago that Margaret Thatcher made a speech praising the embryonic single market.
"A single market without barriers - visible or invisible - giving you direct and unhindered access to the purchasing power of over 300 million of the world's wealthiest and most prosperous people", the former prime minster said.
Thatcher pioneered its creation (though later criticised the social dimension of the internal market) and the main political parties have been committed to it ever since.
The 2015 Conservative manifesto contained the following: "We benefit from the Single Market.... We want to preserve the integrity of the Single Market....We want to expand the Single Market". Of course, it also contained the promise of an EU referendum. And the Brexit vote has trumped continued membership of the single market.
The government could have made a different choice. Norway is an example of a country outside the EU that is a member of the single market. However, it has to pay a contribution to the EU budget, accept the freedom of EU citizens to live and work in Norway, is subject to European Court of Justice oversight and has no formal say in EU decision making. For Number 10 that was a non-starter.
For a start, this speech was not a full blueprint for Brexit for the obvious reason that Number 10 does not want to spell out its negotiation strategy before talks with the EU begin.
Crucially, the final shape of Britain's post-Brexit relationship with the EU can only be known after it has been agreed by the remaining 27 member states and European Parliament. They too will approach the talks with demands, red lines and guiding principles.
Today Chancellor Angela Merkel told German businesses that conditions for access to the single market could not be "loosened" otherwise every EU country would try and "cherry pick" a new deal. The big question is how flexible Theresa May's starting principles become when negotiations begin.
And huge unknowns remain. What budget payments will the EU demand for single market access? Will EU workers have some freedom to work in the UK? Will the EU allow partial membership of the customs union?
Today the Prime Minister painted a picture of an orderly Brexit conducted in the spirit of mutual self-interest.
But divorce is rarely so smooth.

There is still time to block a no-deal Brexit, despite claims to the contrary, senior Tory rebel Dominic Grieve says.
According to the Sunday Telegraph, top No 10 advisor Dominic Cummings has told MPs even losing a no-confidence vote could not stop Boris Johnson taking the UK out of the EU on 31 October.
He reportedly said the PM could call an election for after the deadline, with Brexit taking place in the meantime.
But Mr Grieve told the BBC Mr Cummings was a "master of misinformation".
He said that if Mr Johnson lost a no-confidence vote, MPs would have 14 days to form an alternative government.
"[Mr Cummings] has a point, but he may also be missing the point," Mr Grieve - a former attorney general who has repeatedly called for a further referendum - told Radio 4's Broadcasting House programme.
"There are a number of things which the House of Commons can do, including bringing down the government [via a vote of no confidence] and setting up a new government in its place."
This arrangement - known as a government of national unity - would involve a cabinet made up of MPs from multiple parties.
However, Catherine Haddon, from the Institute for Government think tank, said that while Mr Grieve's suggestion was possible, it would rely on Mr Johnson resigning as PM after losing a no-confidence vote - something he is not legally bound to do.
"The problem there is it requires the sitting prime minister to resign, and because it is untested territory we don't know how that might work," she said.
"If you go back over history, certainly when governments have lost confidence that's been the presumption - but the other presumption has been that if they wanted to go to the people they could.
"He could say: 'No, I'm staying as prime minister and we're having a general election.'"
James Cleverly MP, chairman of the Conservative Party, told Sky's Sophy Ridge on Sunday programme that the government was "not going to initiate a general election" before 31 October.
And Ms Haddon said that, even if Mr Johnson lost a vote of no confidence and did call a general election, he was "perfectly able, constitutionally" to schedule it for after the Brexit deadline.
There could be other ways for MPs to prevent no deal, Ms Haddon added, but she described them as "untested".
"We still don't know if there is something they could try involving an emergency debate," she said, "because the Speaker has previously implied that he thinks there's more scope there in terms of what Parliament can do, but again this is completely untested and falls on the Speaker reinterpreting previous parliamentary practice in a new way."
Like Mr Grieve, Labour's shadow health secretary, Jonathan Ashworth, said he still believed the government's no-deal Brexit plans could be stopped, though he did not specify how.
"There will be opportunities for us when Parliament returns [from summer recess] in September to stop no-deal," he told Sky.
He added Labour would work "across the parties, because we know there are plenty of Tory MPs who want to block no deal".
Meanwhile, preparations for leaving the EU without a withdrawal deal are being ramped up, with Mr Johnson saying the UK must leave by the 31 October deadline.
The PM has said his preference is to renegotiate the withdrawal agreement, remove the backstop and leave with a deal - but EU leaders have repeatedly stated the agreement is not open for renegotiation.

Ministers are trying to rally support for the PM's Brexit deal across the UK but a bid to find a compromise has been dismissed by the DUP and Brexiteers.
With Theresa May widely expected to lose Tuesday's Commons vote, No 10 has dismissed calls for it to be delayed.
Health Secretary Matt Hancock said with two days of debate remaining, there was still time to win over MPs.
But a Tory backbench amendment aimed at easing concerns about the controversial "backstop" has met with criticism.
Downing Street has said the vote is still due to take place on Tuesday, despite dozens of Tories threatening to reject the deal, along with the DUP, whose support keeps Mrs May's government in power.
But a senior minister has told the BBC "the only political common sense is to delay" it.
The minister, who preferred not to be named, said: "We need to find a solution and we can't find one by Tuesday."
Matt Hancock, Chancellor Philip Hammond, Cabinet Office Minister David Lidington and Scottish Secretary David Mundell are among those trying to sell it to the public in visits across the UK.
Amid calls from some Tory and Labour MPs for the UK to pursue an even closer Norway-style relationship with the EU, Mr Lidington said it was wrong to assume there was a "magic alternative" waiting in the wings which retained the existing benefits of membership without the obligations.
"If it is not this deal which the rest of the EU says they are not willing to renegotiate, then either you crash out of the EU without any deal, without any transitional period or you revisit the referendum result of 2016 and you stay in the European Union," he said.
The withdrawal deal negotiated between the UK and EU has been endorsed by EU leaders but must also be backed by Parliament if it is to come into force.
Many MPs have expressed concerns about the backstop, aimed at preventing a "hard border" between Northern Ireland and the Republic of Ireland, which will remain in the EU, if no trade deal is ready before the end of the post-Brexit transition period.
It would mean Northern Ireland staying aligned to some EU rules, which many MPs say is unacceptable. The UK would also not be able to leave the backstop without EU agreement.
Jeremy Corbyn told Euronews that in a Labour Brexit deal "there certainly wouldn't be a backstop from which you can't escape".
"We will have to come to an agreement on a customs union, a specific customs union with the European Union that does give us the opportunity to have a say in it all, but also guarantees that level of trade," the Labour leader said.
Downing Street has dismissed reports the vote could be delayed. And Mr Hancock told the BBC that "the best thing for the country" was for MPs to back Mrs May's deal.
"My view is we should continue the debate," he said. "We've had three days, there's two days more. I think we should make the argument, make the case and persuade people - that's what you have Parliamentary debate for."
Speaking to BBC Radio 5 live, Education Secretary Damian Hinds acknowledged the government had "a big job on" to win Tuesday's vote, but appealed to MPs to back the deal "in the national interest". And Chief Secretary to the Treasury Liz Truss said while the deal on offer was "not perfect" - it delivered on what people voted for.
The prime minister has suggested that MPs could be "given a role" in deciding whether to activate the backstop, and on Thursday night, a Tory backbench amendment was laid down intended to do that.
The amendment - which is understood to have government support - would also give the devolved administrations, particularly the Northern Ireland Assembly, although it is currently suspended, more say in the process.
It would also press the UK and EU to agree a future trade deal within a year of the implementation period ending.
Former Northern Ireland minister Hugo Swire tabled the amendment along with Bob Neill and Richard Graham.
Mr Swire told the BBC that many Tory MPs would like to see the backstop "disappear altogether or be time limited" but the European Commission had said it would not reopen negotiations on the withdrawal agreement, so the amendment was "about the nearest we feel we can probe".
He said it was aimed at "people like me, who would like to be able to support this deal but find they are unable to".
But Conservative Brexiteer Steve Baker dismissed the amendment: "Giving Parliament the choice between the devil and the deep blue sea is desperate and will persuade very few."
And fellow backbencher Peter Bone told the BBC the amendment was "absolutely meaningless".
DUP leader Arlene Foster tweeted: "Domestic legislative tinkering won't cut it. The legally binding international withdrawal treaty would remain fundamentally flawed, as evidenced by the attorney general's legal advice."
Meanwhile, former cabinet minister Justine Greening has told the BBC's Political Thinking podcast that a Conservative Party "that seems consumed by Brexit" would lose the support of "Middle England".
"One of the problems for the Conservative Party is it's now 31 years since we last won a landslide and we need to realise as a party if things don't change, that'll be our last landslide," she said.

There's been something completely surreal about watching Theresa May this week - hobnobbing with world leaders, discussing future trade arrangements and climate change, confronting the Saudi Crown Prince over the murder of the journalist Jamal Khashoggi.
But her efforts on all of those important discussions may prove entirely irrelevant if, in the next nine days, she can't persuade enough of her colleagues at home to come on board.
Because support for the prime minister's Brexit compromise seems to be shrinking, rather than growing.
If Theresa May acknowledges it in private, she certainly won't touch that notion in public.
The prime minister did not even mention the latest minister to quit by name, preferring, perhaps rather nervously, again to defend the agreement that she has reached with the European Union.
She admitted the next fraught week is vital and vowed to keep making the case.
Mrs May will arrive back in the UK at lunchtime on Sunday, facing perhaps the most important week of her career.
And even if she won't countenance conversations about a plan B, her colleagues certainly are.
Cabinet ministers are talking amongst themselves about how to survive if the vote falls.
One senior cabinet minister told me, when the moment comes the prime minister will have to be pragmatic. But for now, she gets "strength from absorbing humiliation".
Number 10's grip is shaky, very shaky - with one senior Tory telling me it almost seems as if "there is no government at all".
But asked if this might be her last overseas trip, the prime minister insisted "there's a lot more for me to do".
A senior member of the government told me not only would she not have discussions about losing the vote - only about how to win it -  but that those who believed that Theresa May would quit if her deal fell were misreading her.
They said that she would "not go until she was forced to go" and, contrary to some of the speculation in Westminster, even a heavy defeat for her plan would not automatically see her depart.
Of course, many of her critics - and the opposition parties - would beg to differ.
Traditionally it's impossible to see how a prime minister of a minority government would be able to survive a defeat of their main policy. But one Number 10 insider commented: "Stranger things have happened - most of them, in the last year."
But while there are conversations, there seems to be no fixed plan.
There is no "active conspiring" about what to do if the vote falls.
But I'm told, if the vote is lost by less than 50, there have been informal discussions about seeking some kind of additional clarifications from the EU then holding another vote relatively soon.
If the defeat were to be more significant than that, which seems feasible, then cabinet might take more time to regroup and work out their next moves.
As has been widely reported, there are big differences in cabinet over what to do next.
And of course, officially, no one in government would reveal any of their planning.
But don't be in any doubt about how important the next week is - for Theresa May, for Westminster, and of course, most importantly of all, for the public.

Parliament must vote on whether the government can start the Brexit process, the Supreme Court has ruled.
The judgement means Theresa May cannot begin talks with the EU until MPs and peers give their backing - although this is expected to happen in time for the government's 31 March deadline.
But the court ruled the Scottish Parliament and Welsh and Northern Ireland assemblies did not need a say.
Brexit Secretary David Davis promised a parliamentary bill "within days".
Sources have told the BBC the bill - to trigger Article 50 of the Lisbon Treaty and get formal exit negotiations with the EU under way - will be introduced this Thursday, with an expectation that it could pass through the House of Commons in a fortnight.
During the Supreme Court hearing, campaigners argued that denying the UK Parliament a vote was undemocratic and a breach of long-standing constitutional principles.
They said triggering Article 50 would mean overturning existing UK law, so MPs and peers should decide.
But the government argued that, under the Royal Prerogative (powers handed to ministers by the Crown), it could make this move without the need to consult Parliament.
And it said that MPs had voted overwhelmingly to put the issue in the hands of the British people when they backed the calling of last June's referendum in which UK voters backed Brexit by 51.9% to 48.1%.
Reading out the judgement, Supreme Court President Lord Neuberger said: "By a majority of eight to three, the Supreme Court today rules that the government cannot trigger Article 50 without an act of Parliament authorising it to do so."
He added: "Withdrawal effects a fundamental change by cutting off the source of EU law, as well as changing legal rights.
"The UK's constitutional arrangements require such changes to be clearly authorised by Parliament."
The court also rejected, unanimously, arguments that the Scottish Parliament, Welsh Assembly and Northern Ireland Assembly should get to vote on Article 50 before it is triggered.
Lord Neuberger said: "Relations with the EU are a matter for the UK government."
Outlining plans to bring in a "straightforward" parliamentary bill on Article 50, Mr Davis told MPs he was "determined" Brexit would go ahead as voted for in last June's EU membership referendum.
He added: "It's not about whether the UK should leave the European Union. That decision has already been made by people in the United Kingdom."
"There can be no turning back," he said. "The point of no return was passed on 23 June last year."
Outside the Supreme Court, Attorney General Jeremy Wright said the government was "disappointed" but would "comply" and do "all that is necessary" to implement the court's judgement.
A Downing Street spokesman said: "The British people voted to leave the EU, and the government will deliver on their verdict - triggering Article 50, as planned, by the end of March. Today's ruling does nothing to change that."
Foreign Secretary Boris Johnson, a leading Leave campaigner, tweeted:  "Supreme Court has spoken. Now Parliament must deliver will of the people - we will trigger A50 by end of March. Forward we go!"
Investment manager Gina Miller, one of the campaigners who brought the case against the government, said Brexit was "the most divisive issue of a generation", but added that her victory was "not about politics, but process".
"I sincerely hope that going forward that people who stand in positions of power and profile are much quicker in condemning those who cross the lines of common decency and mutual respect," she also said.
Her co-campaigner, hairdresser Deir Tozetti Dos Santos, said: "The court has decided that the rights attaching to our membership of the European Union were given by Parliament and can only be taken away by Parliament.
"This is a victory for democracy and the rule of law. We should all welcome it."
"The sighs of relief are real in Whitehall this morning for two reasons.
"The justices held back from insisting that the devolved administrations would have a vote or a say on the process. That was, as described by a member of Team May, the 'nightmare scenario'.
"And second, the Supreme Court also held back from telling the government explicitly what it has to do next. The judgement is clear that it was not for the courts but for politicians to decide how to proceed next.
"That means, possibly as early as tomorrow, ministers will put forward what is expected to be an extremely short piece of legislation in the hope of getting MPs to approve it, perhaps within a fortnight."  Read Laura's blog in full.
Labour leader Jeremy Corbyn said: "Labour respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50."
But he added that his party would "seek to amend the Article 50 Bill to prevent the Conservatives using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe".
However, UKIP leader Paul Nuttall warned MPs and peers not to hamper the passage of the legislation.
"The will of the people will be heard, and woe betide those politicians or parties that attempt to block, delay, or in any other way subvert that will," he said.
The Scottish National Party said it would put forward 50 "serious and substantive" amendments to the government's parliamentary bill for triggering Article 50.
Among them, it wants Mrs May to set out her negotiating aims in an official document known as a white paper and to consult the Scottish government and other devolved administrations through the UK-wide joint ministerial committee.
Several Conservative MPs, including former ministers Alistair Burt, Nicky Morgan and Anna Soubry, also want a white paper, but former party leader Iain Duncan Smith predicted any bill would be "very tight", offering little scope for amendments.
Liberal Democrat leader Tim Farron said his MPs and peers would vote against Article 50 unless there was guarantee of the public having a vote on the final deal reached between the UK and EU.
"This momentous judgement is about one thing alone: the rule of law and how the UK, as a champion of that steady, calm form of government, gets on with the business of leaving the EU.
"But what it also makes clear is that membership of the EU is messy in constitutional terms - so only Parliament has the right to pull us out. It can't be done by the stroke of a minister's pen.
"On the devolution side, the government did however win hands down. The court unanimously ruled that the devolved bodies have no real say in leaving the EU: constitutional power - the means to change the fabric of the United Kingdom, rests with the UK Parliament alone."
The Supreme Court's judgement backs that made by the High Court last year, against which the government appealed.
Those who rejected the government's argument were: Lord Neuberger, Lady Hale, Lord Mance, Lord Kerr, Lord Clarke, Lord Wilson, Lord Sumption and Lord Hodge
Those who decided in favour of it were: Lord Carnwath, Lord Hughes and Lord Reed.
During the four-day Supreme Court hearing in December, the justices heard arguments that Northern Ireland had a unique place in the UK constitution because of the nature of the 1998 Belfast Agreement and the devolved bodies that flowed from it.
Counsel argued that Northern Ireland's constitution could not be changed without a vote by its people.
But in its judgement, the Supreme Court unanimously ruled that not only did the devolved bodies have no role in deciding the future of the UK as a whole in the EU, Northern Ireland had no special status beyond this either.
They ruled that, while Northern Ireland's people did indeed have a fundamental constitutional say on being part of the UK, that did not extend to being part of the EU.

Reports of deadlock over Brexit negotiations may have been exaggerated, European Council President Donald Tusk has said after a Brussels summit.
Progress was "not sufficient" to begin trade talks with the UK now but that "doesn't mean there is no progress at all", he said.
EU leaders will discuss the issue internally, paving the way for talks with the UK, possibly in December.
Theresa May said there was "some way to go" but she was "optimistic".
Speaking at the end of a two-day summit, Mr Tusk told reporters: "My impression is that the reports of the deadlock between the EU and the UK have been exaggerated."
The EU's chief Brexit negotiator, Michel Barnier, described the talks as deadlocked earlier this month.
Mr Tusk said he was not at odds with Mr Barnier, but his own role was to be a "positive motivator for the next five or six weeks".
He said he felt there was "goodwill" on both sides "and this is why I, maybe, in my rhetoric, I'm, maybe, a little bit more optimistic than Michel Barnier, but we are also in a different role".
The so-called divorce bill remains a major sticking point in talks with the EU.
French President Emmanuel Macron said there was still much work to be done on the financial commitment before trade talks can begin, adding: "We are not halfway there."
Theresa May declined to say in a press conference after the summit what the UK would be prepared to pay, saying the "final settlement" would come as part of a "final agreement" with the EU.
The UK prime minister did not name any figures but refused to deny that she had told other EU leaders the UK could pay many more billions of pounds than the £20bn she had indicated in her Florence speech last month.
"I have said that ... we will honour the commitments that we have made during our membership," she said. But those commitments were being analysed "line by line" she said, adding: "British taxpayer wouldn't expect its government to do anything else."
By Laura Kuenssberg, BBC political editor
There are whispers that Theresa May has privately reassured the other leaders that she is willing to put a lot more than the implicit 20 billion euros (£17.8bn) on the table as we leave.
Number 10 doesn't deny this, Mrs May didn't deny it when we asked her in the press conference today, nor did she reject the idea that the bill could be as high as 60 billion euros.
If she has actually given those private reassurances though, there's not much evidence the other EU leaders believe her or think it's enough.
But if she is to make that case more forcefully she has big political problems at home.
Read Laura's blog
She said the two sides were within "touching distance" of a deal on other issues - particularly on citizens' rights.
"I am ambitious and positive for Britain's future and for these negotiations but I know we still have some way to go," she said.
The UK is due to leave the EU in March 2019, following last year's referendum result.
It had hoped to move onto phase two of negotiations - covering future trade arrangements - after this week's summit.
But EU leaders took just 90 seconds to officially conclude that not enough progress has been made on the issues of citizens' rights, the UK's financial obligation and the border in Northern Ireland, but "internal preparations" would begin for phase two.
The prime minister made a personal appeal to her 27 EU counterparts at a working dinner on Thursday night, telling them that "we must work together to get to an outcome that we can stand behind and defend to our people".
BBC Europe editor Katya Adler said all EU leaders knew Mrs May was in a politically difficult situation and did not want her to go home empty-handed, so had promised they would start talking about trade and transition deals among themselves, as early as Monday.
German Chancellor Angela Merkel said there were "encouraging" signs of progress in Brexit negotiations and the process was progressing "step by step".
And European Commission President Jean-Claude Juncker said he hoped it would be possible to reach a "fair deal" with Britain.
"Our working assumption is not the 'no-deal' scenario. I hate the 'no-deal' scenario. I don't know what that means," he said.
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What is Theresa May really willing to do if her deal falls in Parliament?
Increasing numbers of EU leaders and her own government ministers believe that she should acknowledge that she might have to delay the UK's departure from the EU if her agreement is rejected by MPs again next month.
The president of the EU Council, Donald Tusk, says it's "rational" to consider.
Extending the process was discussed by Theresa May and Angela Merkel over breakfast this morning - but not with any conclusion.
But the prime minister, herself, will do almost anything to avoid answering the question.
She told me: "I am clear what I am working for is to ensure that we get a deal negotiated with the European Union that addresses the concerns of Parliament, such that Parliament votes for that deal and we are able to leave with a deal."
Before too long, though, Parliament may make her respond.
Even if Theresa May offers worried former Remainers a concession this week, risking the wrath of Brexiteers, a delay would not necessarily be easily accepted by the European Union.
Mark Rutte, the Dutch prime minister, told me the UK would have to ask for an extension and explain what it's for - the EU could not, he warned, just spend another couple of months going round in circles.
Downing Street privately believes they are making genuine progress towards an extra assurance on the controversial Irish backstop, that would make the deal more palatable to Tory backbenchers - hoping that could mean they never have to make the choice of delay, or no deal.
But with time so short now - even if the deal is approved by MPs next month - another few weeks may still be needed to pass all the new laws that are required.

Downing Street is playing down reports of an imminent Brexit deal with the EU, saying talks are still ongoing.
Prime Minister Boris Johnson is under pressure to get a fresh agreement by Thursday's EU summit, but his spokesman said there was "more work still to do".
EU chief negotiator Michel Barnier had said the two sides must agree the details by the end of Tuesday.
But the BBC's Laura Kuenssberg said it was not clear whether a text could be signed off by then.
She said Mr Barnier was due to brief EU ambassadors at 1300 BST on Wednesday, after a possible European Commissioners meeting, meaning a new deal could get the "green light" from Brussels in the afternoon.
The Guardian is reporting that a draft treaty could be published on Wednesday morning, claiming the UK has made further concessions over the issue of customs and the Irish border.
The prime minister's official spokesman said: "Talks remain constructive but there is more work still to do."
Meanwhile, Irish Taoiseach Leo Varadkar said talks were "moving in the right direction" but gaps between the sides remained, and it was still unclear whether a deal would be ready in time for the Brussels summit.
His deputy, Tánaiste Simon Coveney, said earlier that "big steps" were needed on Tuesday "to build on progress that has been slow" because there would be no haggling over the details of the text once the summit began.
The two-day EU summit is crucial because, under legislation passed last month - the Benn Act - the PM must get a new deal approved by MPs by Saturday if he is to avoid asking for a delay.
The UK is due to leave the EU at 23:00 GMT on 31 October and Boris Johnson says that deadline must be honoured.
He is trying to hold together a coalition of Conservative Brexiteers and Democratic Unionists in support of his proposed alternative to the Irish backstop - the arrangement designed to keep an open border in Ireland.
The DUP leader, Arlene Foster, had more than an hour of talks in Downing Street on Monday night and met the PM again on Tuesday evening for a further 90 minutes.
Following that meeting, the DUP released a statement saying it would not give "a detailed commentary" but added "it would be fair to indicate gaps remain and further work is required".
Earlier, Mrs Foster had told the BBC her party would "stick with our principles" that Northern Ireland "must remain" within the UK's customs union.
She dismissed as "speculation" claims the new Brexit deal included a possible customs border in the Irish Sea - meaning Northern Ireland would be treated differently from the rest of the UK - saying the DUP could never accept that.
Giving the Northern Ireland Assembly a regular vote on post-Brexit customs arrangements - which is reported to have been ditched in response to Ireland's objections - was also important to the DUP, Mrs Foster said.
She said it was "right to give space and time" to negotiators to try to get a deal, but "everyone knows our position".
Earlier on Tuesday, members of the pro-Brexit European Research Group attended a meeting at No 10, with chairman Steve Baker saying afterwards he was "optimistic" that "a tolerable deal" could be reached.
BBC Brussels reporter Adam Fleming said the widely-held view there was that the UK was unlikely to be leaving on 31 October, and the question was whether an extension could be short in order to iron out some small issues, or had to be much longer to deal with bigger problems.
After updating EU ministers on Tuesday morning, Mr Barnier signalled that he expected the UK to share the legal text of any proposed changes to the withdrawal agreement within hours.
He said there was a "narrow path" to be trod between the EU's objective of protecting the single market and Mr Johnson's goal of keeping Northern Ireland in the UK's customs territory.
While there had been progress, Mr Barnier said there was still a big disagreement about the inclusion of so-called "level playing field" provisions in the political declaration sketching out the two sides' future trade relationship.
These provisions would limit the UK's ability to diverge from the EU across a whole range of areas, including competition policy, employment rights, environmental standards and state aid.
The UK says loosening these conditions is vital if it is to have an independent trade policy, but the EU says the UK cannot have privileged access to the single market market without following its rules as this would give it an unfair advantage.
Asked whether it recognised talk of an EU deadline later on Tuesday, No 10 said Mr Johnson was "aware of the time restraints" and the UK was working hard to secure a deal "as soon as possible".
Regardless of what happens in Brussels, a showdown is anticipated in an emergency sitting of Parliament on Saturday - the first in 37 years, if it goes ahead.
MPs will be able to back or reject any deal presented to them and there will be discussions on what to do next.
Labour has threatened court action to force the PM to obey the Benn Act, amid speculation the PM could seek to sidestep it somehow.
Speaking in Parliament, Leader of the House Jacob Rees-Mogg did not confirm whether the Saturday sitting would definitely go ahead, adding that it would depend on events in Brussels.
Thursday, 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday, 19 October - Special sitting of Parliament expected - and the date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by MPs and they have not agreed to the UK leaving with no-deal.
Thursday, 31 October - Date by which the UK is currently due to leave the EU.

Tory MPs have met the government to discuss alternative arrangements to the proposed Irish border "backstop", as three days of talks begin.
The Alternative Arrangements Working Group, with Leave and Remain MPs, met for the first time after the Commons voted to find another way of avoiding the return of Irish border checks.
A government spokesman said the talks had been "detailed and constructive".
But EU leaders have continued to rule out making changes to the backstop.
The Irish PM Leo Varadkar told RTE radio the UK was reviewing ideas that had "already been rejected", and it was "very frustrating" that the UK government was "going back to the idea of technology".
But German Chancellor Angela Merkel said the EU would listen to proposals to solve the Irish border "riddle", although they needed to hear how the UK wanted to do it.
The backstop is an insurance policy designed to avoid a hard border "under all circumstances" between Northern Ireland and the Irish Republic after Brexit.
Number 10 said the working group of Conservative MPs was set up following "significant support" for the so-called "Malthouse Compromise" - named after housing minister Kit Malthouse who encouraged talks between different groups of MPs.
Engineered by both Leavers and Remainers, the proposal includes extending the transition period for a year until the end of 2021 and protecting EU citizens' rights, instead of using the backstop.
Members of the working group include Conservative MPs Steve Baker, Marcus Fysh, Owen Paterson, Damian Green and Nicky Morgan.
The group will hold regular meetings with Brexit Secretary Stephen Barclay, as well as senior government officials from HMRC, Cabinet Office Europe Unit and Number 10.
Mr Fysh said the group had spoken to the EU and it was "very open" to the proposals, adding that they were not based on new technology.
A Department for Exiting the European Union spokesman said the group had explored the proposal "in detail" on the first day of talks.
The BBC's political correspondent Chris Mason said the government's willingness to provide civil service support to this group of Conservative MPs was an indication of how seriously Downing Street was treating their idea.
The backstop insurance policy would kick in if, after almost two years after Brexit, the two sides had not reached a trade agreement with one another that avoided the need for physical border checks.
It would keep the UK in a "single customs territory" with the EU and leave Northern Ireland effectively in the EU's single market for goods.
Critics fear the UK could be "trapped" in this arrangement for years, leaving it unable to strike its own trade deals on goods with the rest of the world.
Unionists also fear it would drive a wedge between Northern Ireland and the rest of the UK. But by changing the backstop, the PM could win support.
Ex-Northern Ireland first minister Lord Trimble has said he is planning to take the government to court over the Brexit deal, claiming the Northern Ireland protocol - which includes the backstop - breaches the terms of the Good Friday Agreement.
Mrs May will visit Northern Ireland on Tuesday to deliver a speech on Brexit and meet business leaders.
Alternatives to the backstop that the prime minister has said she wants to discuss with EU leaders include:
Mr Javid told the BBC's Andrew Marr Show that an alternative arrangement to the Irish backstop "can be done" using "existing technology".
He said the attorney general was "leading on another strand of work" - looking at whether a "hard time limit or proper exit mechanism" was possible.
The UK is due to leave the EU at 23:00 GMT on Friday 29 March, when the two-year time limit on withdrawal negotiations enforced by the Article 50 process expires.
Theresa May has said she is "determined" to deliver Brexit on time, but a number of cabinet ministers have indicated they would be willing to agree to a short extension to finalise legislation for Brexit.
However, a plan to delay Brexit for up to nine months to prevent a no deal - put forward by Labour MP Yvette Cooper - was voted down by Parliament.
Labour's shadow Brexit secretary Kier Starmer said he could not see Mrs May negotiating an alternative to the backstop at this late stage, saying the prime minister had effectively "run down the clock".
Meanwhile, Scotland's First Minister Nicola Sturgeon said contingency plans for Britain's departure from the EU with no deal were "genuinely astonishing", in a speech in the US.
She warned of food shortages and stockpiling of medicine amid a "real and growing risk" of a no deal scenario.
Numerous politicians have shut down the idea of looking at the backstop again, saying there was no desire to re-open negotiations on the withdrawal agreement in Brussels.
The BBC's Brussels reporter Adam Fleming said the EU was not looking for a substitute solution, because they say they've already investigated every other option that exists and none has the same effect as the backstop.
The EU's chief negotiator, Michel Barnier, said there was "full agreement" that the withdrawal agreement "cannot be reopened".
Irish Deputy Prime Minister Simon Coveney said the withdrawal agreement rejected by MPs already allowed the EU and UK to work on alternative arrangements for the backstop.
He added: "What Ireland is being asked to do by some in Westminster is to essentially do away with an agreed solution between the UK government and EU negotiators and to replace it with wishful thinking and I think that's a very unreasonable request to ask the Irish government to be flexible on."
Speaking during a trip to Japan, German Chancellor Mrs Merkel said: "To solve this riddle, you have to be creative and you have to listen to one another.
"We can have those conversations... But we must hear from Great Britain how they want to do it."
Labour's Hilary Benn met the Secretary General of the European Commission, Martin Selmayr, in Brussels.
Speaking after Monday's meeting, Mr Benn - who chairs the Brexit select committee - said the EU would be prepared to consider an additional legal protocol to the withdrawal agreement if they were convinced it would help a deal get through Parliament.
But Mr Selmayr later tweeted that when asked if such an assurance would help, the response from MPs was "inconclusive".
He added: "The meeting confirmed that the EU did well to start its no deal preparations in December 2017."
Leave supporter and Tory MP Andrea Jenkyns - who was also at the meeting - tweeted afterwards that Mr Selmayr revealed the EU had not been asked to remove the backstop or re-open negotiations by the British government.
By Katya Adler, BBC Europe editor
So. how open does the EU seem almost a week on from parliament narrowly voting in favour of an amendment to find alternatives to the backstop guarantee to keep the Irish border open after Brexit?
After all, with every passing day as we've heard, again and again and again, the clock is ticking towards an increased chance of a no-deal Brexit with all the costs and chaos that could involve.
Well, if I were to speak in weather forecast terms, I might describe current EU attitudes as frosty with a chance of ice.
If Theresa May comes to Brussels later this week, she will be received politely and listened to attentively.
But if her EU ask remains centred around getting a time limit to, or allowing the UK a unilateral get-out mechanism from, the Irish border backstop or if she pushes again for pure technology as a means of avoiding a hard border on the island of Ireland, then the likelihood of her being sent home empty-handed - or as good as - is very high indeed.

As the clock strikes 23:00 GMT on Friday, 31 January, the 73 MEPs who represent Great Britain and Northern Ireland in the European Parliament will bid farewell to their roles.
For some of them, there is only delight and relief as the UK approaches Brexit. For others, there have been tears and goodbye hugs.
"How I am feeling is how somebody feels when you have a redundancy and a bereavement at the same time," says Green MEP Molly Scott Cato, who has represented south-west England since 2014.
It's been a tearful goodbye and a "grim, grim week", she says, during a break from packing up her Strasbourg office.
But, in contrast, Brexit could not have come soon enough for Jake Pugh.
"We are delighted," says the Brexit Party MEP for Yorkshire and the Humber. "We were hired to be fired."
He is one of 29 Brexit Party MEPs who were elected in last May's European elections - a vote many considered as confirmation of the UK's desire to leave the EU.
The poll had also brought hope, however, for pro-EU Liberal Democrat MEPs who also enjoyed a successful campaign, winning 16 seats. They entered the parliament wearing yellow "stop Brexit" t-shirts.
Nine months on there remains a clear divide over Brexit among the MEPs, but the politicians appear united about a feeling of pride at what they have achieved.
"There has been so much warmth and comradeship," says Labour's Seb Dance of his final week in Strasbourg. "Most people are pretty sad about the whole thing."
The Labour MEP for London had previously campaigned for another vote on the UK's membership of the EU.
Speaking to the BBC as he dashes between trains in Paris, he says he is proud of the things that "never got the headlines" during his six years in the role.
He highlights his involvement in the European Parliament's special inquiry committee into the Volkswagen emissions scandal.
Ms Scott Cato says she is proud of her work on the issue of sustainable finance and new EU restrictions on the use of antibiotics in farms.
The European Parliament is a "real parliament", she says, expressing her frustration with the UK's first-past-the-post system - which means that parties like hers struggle to get people elected in Westminster.
"We don't get the parliamentary representation we should have."
Green Party colleague Magid Magid says there is a sense of sadness, but he feels "truly grateful and humble for this amazing opportunity".
Mr Pugh says he "fully recognises there are MEPs with different political outlooks who are sad to be leaving" but, he says, the EU "has some real issues".
"However cynical I was about the EU before I got here, it is way worse than I thought," he says.
The Eurozone is a "disaster", he says, and MEPs in Brussels and Strasbourg "are very remote from their electorate".
Brexit is "really good news for the younger generation", he says, adding that he has pursued Brexit for them, so young people can enjoy the same freedom he had growing up.
It's clear that view is shared among his colleagues, a number of whom shared their delight on Twitter at leaving the parliament building in Strasbourg for the final time.
Belinda de Lucy says leaving no more taxpayers' money will be wasted "on this ridiculous vanity project", while Ben Habib says he will not give the parliament "a second thought" after leaving.
"I'm actually just relieved that a democratic mandate's been realised," Brexit Party MEP Claire Fox says.
"I won't miss being in this institution... but of course I have been privileged and enjoyed being here for this historic moment."
And John Longworth, the former Brexit Party MEP turned Conservative, says that his time in the European Parliament has "reinforced" his view that the "whole set-up is bizarre, bureaucratic and wasteful".
They say that they are proud at having achieved what they set out to do - Brexit.
But even arch-Brexiteer Nigel Farage - who has been an MEP for south-east England since 1999 - called his time in European Parliament "an amazing journey".
He told his LBC radio show he will miss the "drama" and being "shouted at by (European Parliament Brexit co-ordinator) Guy Verhofstadt" and "mocked by hundreds many times over".
The UK's newly vacated parliament seats will be spread out among the EU's 27 remaining countries - Spain and France will gain five more seats in a process that takes into account the population of a country.
From Friday, the UK MEPs will no longer have to regularly do the four and a half hour journey from London to Strasbourg, via Paris, or the two-hour trip to Brussels.
But many of the pro-EU MEPs are hoping that they can keep the close ties formed with the bloc.
"We have built up relationships with colleagues, lots of them were in tears - not just Brits," Labour's Richard Corbett says.
It has been a sad and emotional time, he adds. But this is also tinged with "a lot of anger and frustration".
Wednesday will be the final time that the UK's MEPs sit in Brussels - when the Parliament is expected to rubber-stamp Boris Johnson's withdrawal deal taking the UK out of the EU.
As a party is held in London's Parliament Square to celebrate Brexit on Friday, a vigil is expected to be held in Brussels.
Some MEPs will then move on to other jobs - the Brexit Party's Jake Pugh says he will return to his business. Others are not sure yet what they will do, but are keen to maintain European relationships.
Labour's Seb Dance says he has a "few ideas" but "nothing 100%", adding "I'm just really proud to have been an MEP".

The post-Brexit customs system favoured by Boris Johnson and other leading Brexiteers could cost businesses up to £20bn a year, officials have suggested.
The chief executive of HM Revenue and Customs told MPs firms would have to pay £32.50 for each customs declaration under the so-called "max fac" solution.
Jon Thompson said any system may take between three and five years to bed in.
No 10 said the £20bn figure was "speculation" but "issues" remained with both options being considered.
The figure is higher than the £13bn UK contribution to the EU in 2016.
Leading Tory Brexiteer John Redwood said he did not accept what he described as the HMRC's "general figures" but told the BBC that "if it is going to cost this much it is the wrong system".
The UK is leaving the EU in March 2019, which is currently expected to be followed by a 21 month transition phase before the longer term post-Brexit system kicks in.
Ministers are currently considering two options to replace the existing customs union with the EU, which involves minimal checks, and which the government is committed to leaving.
Brexiteers are sceptical about what is believed to be Theresa May's preferred option of a "customs partnership", under which the UK would collect tariffs set by the EU customs union on goods coming into the country.
Their proposed alternative "maximum facilitation" proposal would rely on technology and advance verification to minimise, rather than remove, customs checks.
The EU has expressed doubts about whether either option would work.
During questioning by the Treasury Select Committee, Mr Thompson said that if ministers opted for the "max fac" solution this could cost UK and European businesses between £17bn and £20bn each year, reflecting the cost of customs declarations and complying with rules of origin requirements.
At the moment, UK firms exporting to other EU countries or importing goods from the continent are not routinely required to complete goods declaration forms.
Those doing business outside the EU must provide information about the type and value of goods, their destination and their tariff classification so that the right amount of VAT, duty or excise is paid.
Mr Thompson said there were about 200 million exports to the EU each year that could require customs declarations  - and a similar number of imports.
Citing research by the University of Nottingham business school and by KPMG, he said the likely cost of individual declarations was between £20 and £55 - and while an average could not be authoritatively calculated, ministers had been advised a figure of £32.50 was plausible.
Payments on either side of the border could cost £13bn a year in total while it was "reasonable" to assume any rules of origin requirements demanded by the EU could add "several billion pounds".
"You need to think about the highly streamlined customs arrangement costing businesses somewhere in the late teens of billions of pounds, somewhere between £17bn and £20bn," he said.
"And the primary driver here is the fact that there are customs declarations."
In contrast, he said the customs partnership option - which has been described as "crazy" by Boris Johnson and "flawed" by Michael Gove - would cost business a maximum of £3.4bn a year - depending on how much firms chose to claim back in differential tariffs.
It would, he said, take between three to five years to fully implement any new system after Brexit.
While a "functioning border" was possible by the end of the transition period it would not be, in his opinion, be "fully optimal". But he said no new customs infrastructure would be needed in Northern Ireland.
Mr Thompson declined to answer when it was suggested it would be easier if the UK just remained in the customs union - a solution favoured by business but rejected by ministers.
Former Conservative cabinet minister John Redwood said the starting point for any new customs system should be existing arrangements for importing goods from outside the EU.
"We have a perfectly good functioning trade system with the rest of the world at the moment," he said. "It does not cost anything like these figures."
The UK, he said, already had a VAT, excise and currency border with the EU based on pre-registration and electronic declarations which, if necessary, could be extended.
"None of these happen physically at the border any more with a man or a woman in a kiosk having to work it out with the lorry waiting.
"It is all done electronically away from the border with electronic manifests and computer registration... If we have to do customs dues as well it is not a greater increase in the complexity."

There is "no way" the Democratic Unionist Party will back Theresa May's Brexit deal, a leading figure has said.
Sammy Wilson told the BBC he was "more alarmed" than ever about what the deal would mean for Northern Ireland.
The DUP, which props up Theresa May's government, has held talks with the PM in recent days as she tries to persuade MPs to back the deal later this month.
The PM is seeking further legal assurances from the EU but it has said negotiations will not be re-opened.
The UK is due to leave the EU on 29 March 2019.
MPs will decide whether to accept or reject the withdrawal terms negotiated by Mrs May, as well as the framework of future relations, in a vote expected on 15 January.
The vote was due to be held in December but Mrs May postponed it after it became clear she would be heavily defeated.
In the three weeks since then, she has been appealing to EU leaders to do more to allay MPs' concerns over parts of the agreement, particularly the proposed Irish backstop.
This arrangement would see the UK remain closely aligned to EU rules if the two sides' future relationship is not settled by the end of 2020, when the proposed transition period will end, or if another way is not found of preventing physical checks on the border between Northern Ireland and the Republic of Ireland.
Mrs May, who had a "friendly phone call" with European Commission President Jean-Claude Juncker on Friday, insists it is a contingency plan that all sides agree should not be needed.
But the DUP are adamantly opposed, saying it will create new barriers between Northern Ireland and the rest of the UK and could end up as the default template for future relations.
Mr Wilson, the DUP's Brexit spokesman, told BBC Radio 4's Today programme that little had changed since mid-December and his party believed the backstop was a "con trick" that was being imposed on the UK.
Asked if there was any way the party could support the PM's deal, he replied "no there is not".
"It is not just because of the regulations which Northern Ireland would be subject to with the backstop, but also the fact we would have to treat the rest of the UK as a third country and we would not participate in any trade deals which the UK may enter into the future".
On Thursday, Irish Prime Minister Leo Varadkar said the border issue was the only "red line" his country has had in the Brexit negotiations and that would not change.
While he and other EU leaders were prepared to offer assurances and clarifications to help Mrs May get the agreement through Parliament, he said it has "to be a proposal that we can accept".
"It can't be a proposal that contradicts what is already in the withdrawal agreement," he said. "It can't be something that renders the backstop inoperable, for example."
The DUP have said talk of the return of a hard border on the island of Ireland is "nonsense propaganda", since neither London nor Dublin wants it or is willing to construct the infrastructure.
The BBC understands that up to 40 Conservative MPs are likely to vote against the Brexit agreement even if Mrs May secures further concessions on the backstop.
This would mean almost certain defeat for Mrs May, since Labour, the Lib Dems and the SNP have all vowed to vote against the deal.
Many Tory members of the European Research Group remain opposed to the UK handing over £39bn, as part of the proposed financial settlement, in return for what they say are vague promises over future trading terms and would prefer the UK to leave without a deal.
Meanwhile, preparations for a possible no-deal exit are being stepped up in a number of areas.
A plan to keep traffic moving around Kent and to minimise disruption and delays at Channel ports is to be tested in the coming days.
More than 100 HGVs will be parked at the disused Manston airport near Ramsgate and then driven the 20 miles down the A256 to the Port of Dover.
The Department for Transport said the manoeuvres, part of Operation Brock, were being carried out so that if they "need to be implemented, the system is fully functional".
And a new government website advising the public and business on how to prepare will be launched on Tuesday.
The Department for Exiting the European Union said the site, which will be available through the gov.uk portal, will contain "some new information".
There will be sections devoted to European nationals living in the UK and British expats living on the Continent.
A spokesman said there would be "advice" on what people need to do in the event of the UK leaving without a deal. The website will also cover other scenarios, including if the UK leaves on the basis of Mrs May's agreement.
The BBC's political correspondent Iain Watson
When Theresa May pulled the "meaningful vote" on Brexit last month, the day before MPs were about to pass their verdict on her deal, Downing Street hoped two things would happen.
First, that the EU would offer some form of legal guarantee that the Northern Irish backstop - the arrangements for avoiding a hard border on the island of Ireland - would be temporary.
This, in turn, would bring the DUP on board - and unlock further support from previously hostile Conservative backbenchers.
Second, that some sceptical MPs, once away from the febrile atmosphere at Westminster, would quietly reflect over Christmas that the deal wasn't as bad as all that, as it at least guarantees that the UK will leave the EU at the end of March.
So perhaps any rebellion would diminish, if not evaporate.
But neither hope has - yet - been realised, with the vote now less than two weeks away.

As the UK marks one year until Brexit, Brussels negotiators are indulging in a bit of muttering under their breath .
They consider the 12-months-to-go focus misleading for two main reasons:
As for a new EU-UK trade deal and other aspects of the future relationship, estimates as to how long that will all take to finalise vary from months to years.
Why can't it be all done and dusted by Brexit day on 29 March 2019?
Well, under EU law, Brussels can't finalise a new relationship with the UK until it is legally an "outsider" having formally left the club.
So, if all goes according to the EU-UK plan, by March next year they will have a completed withdrawal agreement under their belt, covering the transition period and the so-called divorce issues (the financial settlement to be paid by the UK; rights for EU citizens living in the UK and UK citizens in the EU after Brexit; and a concrete plan to avoid the re-introduction of a hard border between Northern Ireland and the Irish Republic).
This agreement will be a legal text, most of which has already been signed off by both sides.
The key sticking points that remain (and they're not small ones) are the Irish border and governance of the agreement - i.e. the role of the European Court of Justice.
The EU and the UK say they are committed to resolving outstanding problems.
Both sides really want a deal. Political, as well as economic and security, stakes are high.
In addition to the withdrawal agreement, the EU and UK are also working on what's being called a "political declaration" to outline the direction of their future relationship. As a declaration, rather than legal text, EU law does allow this to be negotiated ahead of Brexit day.
Just how much detail goes into the declaration is being debated at the moment between EU member countries.
For Theresa May, performing a delicate balancing act to try and keep her Brexit-divided cabinet and country together, the less detail the better.
It is at this stage of negotiations (as I've mentioned in this blog before) that EU unity will begin to fray as the national interests of different member states come to the fore.
Expect disagreements, though not deep rifts - and watch the EU do its best to keep any infighting behind closed doors as Denmark prioritises fishing rights, Luxembourg focuses on financial services, Spain, Slovakia and Czech Republic push for the freedom of their citizens to come and work in the UK while Poland advocates a close EU-UK security relationship post-Brexit to help bolster the country against its volatile neighbour, Russia.
Speaking to the Polish prime minister recently about Brexit, I was struck by how often he used the word "compromise" - not often heard in Brussels when it comes to negotiations.
A stark contrast to a conversation I had with France's economy minister when I sat down with him.
He said he wanted a fair Brexit but also insisted the EU had no intention of bending its rules to accommodate the UK.
"We have to protect ourselves," he told me.
Big EU powers France and Germany are convinced that they gain more by protecting the EU and its single market for members than they risk losing in establishing weaker trade relations with the UK after Brexit.
Heading into this one-year-to go countdown until Brexit, EU countries are feeling confident.
The mood music with UK negotiators has very much improved and besides, the EU believes it holds the best cards.

Did you watch Theresa May try to make the best of her Swedish photo opportunities yesterday? Or listen to David Davis as he urged the EU side to blink first, rather than the UK side?
They both know that time is short to guarantee the UK gets what it wants and pushes the EU to move to the next stage of vital Brexit talks at the next leaders' jamboree in December.
What's been missing until now is a sense of when the UK will be able to resolve its own short-term position.
Is the cabinet willing to sanction a political move to offer the promise (not the figure) of more money on the table to settle our EU accounts?
And if ministers are willing to do so, what do they expect in return - and when?
It's been all too obvious that the EU side has, for a long time, been clear that they'll only budge when the UK is ready to promise - even vaguely or implicitly - a lot more cash.
The hold-up has in part been that the UK has been pushing to make sure that taxpayers at home don't shell out when they don't have to.
And also because UK and EU officials have taken a very different approach to settling the bill.
But it's also the case that cabinet ministers have not been ready to agree how they want to proceed, and without that political agreement, it's been hard for the negotiations about the money to progress.
However, the crunch is coming fast.
I'm told on Monday there will be a significant meeting of the small cabinet committee that decides the Brexit negotiating strategy.
Several government sources say the meeting of the Brexit strategy group could change the course of our departure.
The question to be answered on Monday could be profound.
One source told me: "People have to decide if they really want to make progress and support this prime minister, or not."
For some in government that tight group of cabinet ministers must on Monday take a decision as vital as that - do they want to do a deal with the EU, or not?
Of course there is bravado on both sides.
As ever, whether thinking of talks on the continent, or in government, take every utterance with a pinch of salt.
Brexiteer ministers believe that they need to be clearer about what the UK would get in return for paying a bigger bill - a view that would no question have sympathy among swathes of taxpayers.
They are not, thus far, ready to sign up to what they see as Number 10's version of the next move - a promise to pay a lot more cash, potentially as much as 50bn-60bn euros.
They do not rule it out completely, but not before it is clear what we get in return.
But the lack of clarity in government about our eventual destination - whether we are closely, or loosely tied to the EU after departure - makes that hard to conclude.
One insider said: "We still have to settle the broader question - what do we actually want? That's the point to consider."
The discussion on Monday could therefore spill into conversations about the future relationship after Brexit, as well as cold hard cash.
For some in government, Monday feels vital. For others, it's OK in theory to let another decision point go past without conclusions.
But if they don't reach any conclusions, some in government believe that sets us on a course to crash out with no deal.
Time is running short for the discussion in government that Theresa May has put off for so long.
But one insider said there is no "limping" on until March: "We have to just decide."
Donald Tusk's deadline is hypothetical, but the pressure to move on is now not just coming from Brussels or Berlin, but from some elements in government.
Theresa May is yet to give her own public view.
But hard conversations don't get easier the longer you wait.

The EU has tried very, very hard throughout this Brexit process to present a cool, calm, united front while political volatility reigns in the UK.
"They want to come across as the adults in the room," one Spanish journalist put it to me.
But sometimes the EU's distant, business-like veneer noticeably cracks.
There are a few memorable examples: President Macron describing Brexiteers who promised the UK a better life outside the EU as liars; Luxembourg's prime minister recently pouring out in public the frustrations with the Brexit process felt privately by many in the EU; and now, on Tuesday, the president of the European Council, Donald Tusk, responding angrily to Downing Street finger-pointing about the state of Brexit renegotiations by addressing this tweet directly to the prime minister.
Mr Tusk's flash of emotion did not go down well in European government circles at this sensitive juncture, as the EU leaders summit and the 31 October Brexit deadline fast approach.
The EU wants a deal and, if negotiations fail, it wants voters across the EU to believe that Brussels did its best - staying focussed on the facts at the negotiating table, rather than getting involved in cross-Channel mud-slinging.
And bang on cue, not long after Mr Tusk's blame game outburst, the EU's chief Brexit negotiator tweeted that "efforts continue to find an agreement with the UK".
But no-one I speak to in the EU is holding his or her breath.
"We have no idea where the UK government wants to go in the next 20 days," (ie before the 31 October Brexit deadline) a diplomat from northern Europe told me.
He said the EU was still unclear how high getting a Brexit deal featured right now on the prime minister's list of priorities - compared, for example, with winning a general election.
So is the search for a deal now over in EU eyes?
Not really. The EU says it's still open for talks. It hasn't entirely ruled out the possibility of a deal by the end of this month.
Realistically though the prime minister's proposals on how to replace the Irish backstop in a Brexit deal are hugely problematic for Brussels.
While diplomats praise some aspects of Boris Johnson's offer, his insistence that Northern Ireland remains in the UK's customs territory after Brexit leaves the EU with unpalatable choices:
Either a) having customs infrastructure on the island of Ireland, which Dublin says is a no no.
or b) the EU not controlling its customs border which Brussels says would both lead to smuggling and contravene WTO regulations.
One high-level EU diplomat joked: "If that customs border between the Republic of Ireland and Northern Ireland were left open, as the UK pretty much asks, then I would quit my job and start a smuggling enterprise. Far more lucrative."
But the EU isn't laughing. Or playing politics, insists Brussels. It says its objections to Boris Johnson's customs proposals are practical, not political.
EU technocrats maintain that leaving a post-Brexit customs border open on the island of Ireland would compromise food safety and the safety of children's toys, for example.
They warn that any accident or contamination would affect the whole single market plus the EU's reputation amongst other trading partners.
"We won't do that," said a diplomat from a country traditionally close to the UK. "We can't risk that."
And if the EU did take that risk, then diplomats warn that Dublin would pay the price. Goods entering the single market via Ireland would be regarded with suspicion, they say, and the free movement of goods in the single market would be seriously compromised.
EU sources insist that whatever the Johnson government threatens or however it cajoles,  the EU "can't be bullied" into accepting the prime minister's proposals as they stand.
"It would be easier if this discussion were about money," a European civil servant told me. "Then both sides could haggle and reach agreement but there's no compromising over food safety."
EU diplomats say they accept the principle of two customs systems (EU and UK) on the island of Ireland but that it has to work.
EU leaders still look to the UK to be more flexible in its demands. Though they hear Boris Johnson when he says Northern Ireland must remain in the UK's customs union to preserve UK unity.
As always when it comes to the backstop, Ireland has a big role to play here too.
Since the EU won't compromise the single market, EU diplomats say Brussels will take its cue from Dublin as to how many checks/controls it could stomach on the island of Ireland.
The EU attitude here is: "What's ok for Dublin, works for the rest of us".
But the Johnson government has expressed frustration with the Irish government. Their belief is that Dublin is "holding out" on making compromises since they believe a new Brexit extension is around the corner.
And that is exactly what the EU thinks.
Though no-one I speak to is starry-eyed about the possibility of having more time to talk.
Whether next week or next month, a deal still needs to be found that's acceptable to both sides - and not just to negotiators but to the European and the UK parliaments.
And no-one is sure what that would look like. Which is why the feeling in Brussels is that the chances of no deal have gone up again. Extension or no extension.

She blinked.
Whatever else happens in the next two hours, Theresa May did what she previously said was impossible, and committed herself to try to reopen the divorce deal, the legal text negotiated over two years with 27 other countries.
After a fortnight of swearing it was not going to happen, her dire predicament and continued protest from Eurosceptics moved the prime minister to this point.
This path was probably, in the end, the one that she would always have to choose, having made clear in recent days that she would aim to preserve Tory party unity, to try to stay in power, rather than switch to pursue a closer relationship with the EU.
With the bulk of Brexiteers and the unionist DUP now on side, it was a straightforward political choice - even if, as a policy, it's been dismissed as chasing a fantasy.
Having promised to change part of it, the prime minister is likely to have more support for her deal, by the end of tonight.
But there are still strong demands for her to rule out leaving without a formal deal across Parliament.
There is still no sign that the EU is ready straight away to grant any of the revisions she may demand.
The move, as ever, is designed to get the prime minister more smoothly through the day. But the reversal solves only one of Theresa May's problems, and only solves it for now.

Theresa May has said she is "determined" to deliver Brexit on time, ahead of talks on the Irish backstop.
Writing in the Sunday Telegraph, the prime minister said she would return to Brussels with a "fresh mandate, new ideas and a renewed determination".
MPs have voted to seek an "alternative arrangement" to guarantee the Northern Ireland border stays open after Brexit.
But the Irish deputy prime minister has said "there are no credible alternative arrangements" to the proposal.
The backstop forms part of the withdrawal agreement negotiated by the UK and EU and is aimed at keeping the border between Northern Ireland and the Irish Republic open after Brexit.
BBC political correspondent Chris Mason said that while Mrs May pledged to "go back to Brussels to secure a plan that Parliament can stand behind", the EU remains publicly opposed to changing the backstop.
The UK is due to leave the EU at 23:00 GMT on Friday 29 March, when the two-year time limit on withdrawal negotiations enforced by the Article 50 process expires.
Some MPs have suggested Britain will need more time to negotiate its exit to avoid crashing out of the EU without a deal.
Mrs May has insisted the departure date will not change, writing in the Telegraph that she would "deliver Brexit on time".
And she said she rejected the suggestion "that seeking alternative arrangements for the backstop constituted 'ripping up the Good Friday Agreement'".
The prime minister added that MPs wanted the government to go back to Brussels to renegotiate the deal after the Commons voted in favour of Tory backbencher Sir Graham Brady's amendment on Tuesday that called for "alternative arrangements" to be found.
Mrs May wrote: "While replacing the backstop with alternative arrangements was one option, [Sir Graham] would also be happy with the current backstop if there was a time limit or unilateral exit mechanism."
Home Secretary Sajid Javid told the BBC's Andrew Marr Show that an alternative arrangement to the Irish backstop "can be done" using "existing technology".
Mr Javid said: "I asked Border Force months ago to advise me to look at what alternative arrangements are possible and they've shown me quite clearly you can have no hard border on the island of Ireland and you can use existing technology - that is perfectly possible.
"The only thing that's missing is a bit of good will on the EU side."
And International Trade Secretary Liam Fox said it was "irresponsible" for the EU and the Irish Republic to say they will not discuss changing the backstop in the withdrawal agreement.
He told Sky's Sophy Ridge on Sunday: "For the Irish it's even more important than for most to talk to us for alternative ways of achieving a no hard border."
He said a no-deal Brexit would have an impact on the EU's economy, saying: "Are they really saying they'd rather be in a no deal position? It's not a responsible position to take."
Mr Fox said Article 50 - the mechanism by which the UK is leaving the EU - should only be extended in the event there was a Brexit deal that needed "a little time to get the legislation through".
To "simply extend" it, without a deal in place, would not "provide the impetus for a deal", he said.
Chief Secretary to the Treasury Liz Truss told John Pienaar on Pienaar's Politics that she was confident a time-limited backstop could be negotiated.
"On the time limit to the backstop there are various people across the EU who have hinted that that could be acceptable," she said.
"The fact is the EU have always claimed that the backstop is a temporary measure."
She added: "I think we are seeing signs of the EU's position softening."
By Tom Edgington, BBC Reality Check
The backstop is an "insurance policy" - designed to avoid a hard border "under all circumstances" between Northern Ireland and the Irish Republic.
Under the current Brexit deal, the 310-mile Irish border would become the only land border between the EU and the UK.
This would probably mean checks on goods crossing it, unless both sides could reach a comprehensive trade deal.
If such an agreement could not be reached, then to avoid those checks and border posts or other infrastructure, the backstop would come into force.
It would keep the UK in a "single customs territory" with the EU and leave Northern Ireland effectively in the EU's single market for goods.
A number of MPs fear the UK could be "trapped" in this arrangement for years, leaving it unable to strike its own trade deals on goods with the rest of the world.
Writing in the Sunday Times, deputy Irish prime minister Simon Coveney said: "The EU will not renegotiate the withdrawal agreement and there will be no withdrawal agreement without the backstop."
Mr Coveney said the backstop was required to "ensure the protection of the Good Friday Agreement" which ended 30 years of armed struggle in Northern Ireland.
He said no alternatives have been put forward "that achieve the shared goal of the UK and EU to avoid a hard border", and the backstop was a "necessary guarantee".
Arlene Foster - leader of the DUP, the party that props up Mrs May's government - said dealing with the "toxicity" of the backstop would allow the EU and UK to move forward towards a Brexit deal.
She said she was hopeful of finding alternatives but it depended on the "willingness" of the Irish government.
Speaking on BBC Radio Ulster's Sunday News programme, Mrs Foster said that if the EU wants a deal, it has to be acceptable to both sides.
"I think we really need to focus on trying to get a deal. That's what the DUP want, that's what the government wants and I believe it's what the European Union wants."
She told the BBC's Sunday Politics "nothing good" would come from Brexit.
Meanwhile, some Conservative backbench MPs, including senior Tory Brexiteer Steve Baker, have said they still have other issues with the Brexit deal.
Mr Baker, deputy chairman of the Eurosceptic group the European Research Group (ERG), warned there was "trouble ahead" for the prime minister.
In response to Mrs May's article, he tweeted: "Leave-backing MPs voted to support alternative arrangements in NI but with grave misgivings about the whole agreement.
"Now the PM co-opts us into accepting everything but the backstop and, on the backstop, accepting a codicil."
He said a "further substantial defeat" for the agreement should be expected "if all we see is a codicil - a 'joint interpretive instrument'".
Tory MP Andrea Jenkyns tweeted that the UK "deserves a better deal".
"No PM, we said we would support the amendment to send a message to EU re the backstop, we all said there are other issues with WA (withdrawal agreement)," she said.
In January, MPs rejected Mrs May's withdrawal agreement by 432 votes to 202, with nearly 120 Conservative MPs voting against their leader.
After the Commons voted on the Brady amendment, the EU's chief negotiator Michel Barnier said the backstop is "part and parcel" of the UK's Brexit deal and will not be renegotiated.
Speaking at the European Parliament last week, Mr Barnier said the backstop was a "realistic solution" to preventing a hard border.

Talks between Theresa May and Jeremy Corbyn to break the Brexit deadlock have been called "constructive".
The two leaders met on Wednesday afternoon and agreed a "programme of work" to try to find a way forward to put to MPs for a vote.
It is understood that each party has appointed a negotiating team, which are meeting tonight before a full day of discussions on Thursday.
A spokesman for No 10 said both sides were "showing flexibility".
And he added that the two parties gave "a commitment to bring the current Brexit uncertainty to a close".
Speaking after the meeting, Mr Corbyn said there had not been "as much change as [he] had expected" in the PM's position.
He said the meeting was "useful, but inconclusive", and talks would continue.
Meanwhile, Chancellor Philip Hammond has said a confirmatory referendum on a Brexit deal was a "perfectly credible" idea.
He told ITV's Peston programme he was not sure if the majority of MPs would back it, but "it deserves to be tested in Parliament".
This evening, MPs have debated legislation which would require Mrs May to seek an extension to Article 50 and give the Commons the power to approve or amend whatever was agreed.
The bill passed its first parliamentary hurdle by 315 to 310 votes, and MPs are now voting on a raft of amendments.
Supporters of the bill, tabled by Labour's Yvette Cooper, are trying to fast-track the bill through the Commons in the space of five hours, in a move which has angered Tory Brexiteers.
Mr Corbyn said he raised a number of issues with Mrs May, including future customs arrangements, trade agreements and the option of giving the public the final say over the deal in another referendum.
The Labour leader is coming under pressure from senior colleagues to make a referendum a condition of signing up to any agreement.
Demanding the shadow cabinet hold a vote on the issue, Shadow Foreign Secretary Emily Thornberry said not backing a confirmatory vote would be a "breach" of the policy agreed by party members at its last conference.
The UK has until 12 April to propose a plan to the EU - which must be accepted by the bloc - or it will leave without a deal on that date.
The PM proposed the talks in a statement on Tuesday night. She wants to agree a policy with the Labour leader for MPs to vote on before 10 April - when the EU will hold an emergency summit on Brexit.
If there is no agreement between the two leaders, Mrs May said a number of options would be put to MPs "to determine which course to pursue".
In either event, Mrs May said she would ask the EU for a further short extension to hopefully get an agreement passed by Parliament before 22 May, so the UK does not have to take part in European elections.
The two leaders also met Scotland's First Minister Nicola Sturgeon.
The SNP leader said she had "good" and "open" conversations with both, and while she believed Mr Corbyn would "drive a hard bargain", she was "still not entirely clear" where the prime minister was willing to compromise.
The SNP leader, who backs a further referendum and wants to remain in the EU, told reporters: "My concern is that in the rush to reach some compromise with the clock ticking, what will happen over the next few days... is a bad compromise will be reached."
The SNP, Liberal Democrats, Green Party, Plaid Cymru and the Independent Group have also held a joint press conference, calling for any decision made by the leaders to be put to a public vote.
But some Tory Brexiteers have condemned the talks, with two ministers resigning over the issue.
Chris Heaton-Harris quit on Wednesday afternoon, claiming his job at the Department for Exiting the European Union had become "irrelevant" if the government is not prepared to leave without a deal.
Wales Minister Nigel Adams also resigned earlier, saying the government was at risk of failing to deliver "the Brexit people voted for".

The prime minister is continuing to consider her next move to break the Brexit deadlock following the latest defeat of her withdrawal plan.
Senior government sources say the "ambition" is still to get Theresa May's deal through the Commons.
But MPs will again vote on alternatives on Monday, a customs union with the EU thought to be MPs' most likely preferred option.
Some senior Brexiteers have warned Mrs May against pursuing such a move.
Following the UK's vote to leave the EU in 2016, Theresa May negotiated a withdrawal deal with the EU.
Although European leaders agreed to the plan, Mrs May has yet to get the deal approved in Parliament.
The prime minister has until 12 April to seek a longer extension to the Article 50 process to avoid the UK leaving without a deal.
Mrs May said the UK would need an "alternative way forward" after her plan was defeated by a majority of 58 on Friday, following earlier defeats by 230 and 149 votes.
The government has so far failed to win over 34 Conservative rebels. Remainers argue for another referendum and Brexiteers say Mrs May's deal leaves the UK too closely aligned to Europe.
Northern Ireland's DUP - which the government relies on for support in votes in the House of Commons - also continues to oppose the deal.
But a No 10 source indicated the prime minister would continue to seek support for her Brexit deal in the Commons and insisted efforts were "going in the right direction".
BBC political correspondent Alex Forsyth described the cabinet as "deeply divided" over what to do next.
Speaking on Sky News, shadow foreign secretary Emily Thornberry said under a Labour government it was "likely" that the UK would leave the European Union.
She also accused the prime minister of being "out of control", saying: "Theresa May is stamping her feet and saying I want this, no one else is allowed to do anything else."
It "looks like the time may come" for another attempted no confidence vote in the government, she added.
If passed, this would pave the way for a general election.
The deputy chairman of the Conservative Party James Cleverly told Sky News that his party is doing "sensible pragmatic planning" in case there is a snap general election, but not seeking preparing to call one.
And speaking to the Andrew Marr show, Justice Secretary David Gauke said he did not see how a general election would solve the current deadlock.
He added that if MPs are voting in favour of a softer Brexit it would not be "sustainable" for the government to ignore Parliament.
Tory Brexiteer Steve Baker, who resigned as a Brexit minister over the PM's handling of negotiations, wrote in the Sunday Telegraph that Mrs May's deal "cannot be allowed to go through at any cost".
He said the Conservative Party could split if the prime minister pursued a customs union with the EU as "it would amount to a reversal of the referendum result".
However, he also wrote that on Thursday evening he had decided to support the withdrawal agreement before being talked out of it.
A customs union is one of the options which could be considered by MPs from all parties during a second round of "indicative votes" on Monday.
MPs are to vote on a series of options designed to test the will of Parliament to see what, if anything, commands a majority.
None of MPs' eight proposed options secured a majority in the first set of indicative votes on 27 March, but those which received the most votes were a customs union with the EU and a referendum on any deal.
A customs union would allow businesses to move goods around the EU without tariffs, ie taxes - but membership would bar the UK from striking independent trade deals after Brexit.
Labour leader Jeremy Corbyn supports a customs union, to protect the issue of avoiding a hard border in Northern Ireland.
Leading Tory Brexiteer Jacob Rees-Mogg told the Sunday Telegraph that the party needs to be led by "someone who has always supported Brexit".
He wrote: "Now is the opportunity for the Tories to move from the current government's position of ameliorating a bad idea that, at its highest level, it never believed in, to one that embraces it."
Meanwhile, a number of senior MPs tipped as future Tory leaders have articles and interviews in the Sunday papers setting out their policies.
Dominic Raab, who quit the cabinet in protest at Mrs May's handling of Brexit, explained how he would tackle knife crime in the Sunday Telegraph.
Chief Secretary to the Treasury, Liz Truss, called for the Tories to "modernise" in a wide-ranging interview in the Sunday Times.
She highlighted cutting stamp duty for young homebuyers and business tax as key policies.
Former cabinet minister Justine Greening said she "might" run for the Tory leadership.
In an interview with The Sunday Times, the Remain campaigner said the party needed a leader for the "2020s, not the 1920s".
If Mrs May wants to hold another vote on her Brexit deal in Parliament, it must comply with Commons Speaker John Bercow's ruling that it can only be brought back with "substantial" changes.
That is why the government separated the withdrawal agreement from the political declaration - on the future relationship with the EU - for Friday's vote.
The withdrawal agreement is the part of the Brexit deal Mrs May struck with Brussels which sets out how much money the UK must pay to the EU as a settlement, details of the transition period and the so-called Irish backstop arrangements.
Following Friday's vote, Mrs May said there would be "grave" implications of rejecting the deal and warned they were "reaching the limits of this process in this House".
Her comments led to speculation the PM could try to call a general election.
But Foreign Office minister Sir Alan Duncan told The Observer: "If we have a general election before Brexit is resolved, it will only make things worse."
Under the terms of the Fixed Term Parliaments Act, the prime minister needs a two-thirds majority in order to call an election.

Theresa May has told MPs it remains her "priority" to deliver Brexit, defending the decision to delay the UK's exit from the EU.
The new deadline of 31 October means the UK is likely to have to hold European Parliament elections in May.
The prime minister said that if the deal agreed with the EU was passed, the UK could leave the EU "as soon as possible".
Labour leader Jeremy Corbyn called the latest delay a "diplomatic failure".
The prime minister promised to pursue an "orderly" Brexit, adding that the "whole country" was "frustrated".
Brexit was originally set to happen on 29 March. But after MPs repeatedly rejected Mrs May's withdrawal agreement with the EU, the deadline was put back to 12 April.
The new 31 October deadline averts the prospect of the UK having to leave the EU without a deal this Friday.
The government said on Thursday it would "continue to make all necessary preparations" for a no-deal Brexit, after it was reported that departments had stood down their planning.
A government source said "plans will evolve and adapt" but would not stop, while the chance of leaving the EU without an agreement remained.
The source added that a leaked message referring to the "winding down" of no deal preparation related only to Operation Yellowhammer, the contingency planning operation based on worst-case scenarios - and not no-deal planning in general.
Under EU rules, the UK will have to hold European Parliament elections in May, or face leaving on 1 June without a deal.
In a statement to the House of Commons, Mrs May said she "profoundly" regretted her deal not being agreed to by MPs.
She said: "The whole country is intensely frustrated that this process of leaving the European Union has not been completed."
On the latest delay, she said: "The choices we face are stark and the timetable is clear. I believe we must now press on at pace with our efforts to reach a consensus on a deal that is in the national interest."
And she told MPs that the UK would hold full EU membership rights during the extension, saying the country "would continue to be bound by all our ongoing obligations as a member state, including the duty of sincere co-operation".
The government is continuing to hold talks with Labour aimed at achieving a consensus on how to break the deadlock in Parliament.
Mrs May and Mr Corbyn had a "short meeting" on Thursday, Labour said.
In Parliament, Mrs May said: "Reaching an agreement will not be easy, because to be successful it will require both sides to make compromises.
"But however challenging it may be politically, I profoundly believe that in this unique situation where the House is deadlocked, it is incumbent on both front benches to seek to work together to deliver what the British people voted for."
In response, Mr Corbyn said: "The second extension in the space of a fortnight represents not only a diplomatic failure but is another milestone in the government's mishandling of the entire Brexit process."
He added: "The prime minister has stuck rigidly to a flawed plan and now the clock has run down, leaving Britain in limbo and adding to the deep uncertainty of business, workers and people all across this country."
Mr Corbyn said cross-party talks were "serious, detailed and ongoing", but warned that the government would "have to compromise".
If no agreement was possible, he said: "We believe all options should remain on the table, including the option of a public vote."
Shortly - Talks continue between the Conservatives and Labour on how to end the Brexit impasse
23 April - MPs return from Parliament's Easter recess
2 May - Local elections take place in England and Northern Ireland
23 May - European Parliament elections are scheduled to happen in the UK, if MPs do not back Theresa May's agreement with the EU in time to avert them
31 October - The UK leaves the EU, unless MPs back the withdrawal agreement in advance of this deadline
Ian Blackford, the SNP's Westminster leader, urged Mrs May to use the extra time to hold a second EU referendum.
"It's now a very real possibility that we can remain in the European Union," he said.
"As of today, there are 204 days until the new Brexit deadline on the 31 October, so will the prime minister now remove the ridiculous excuse that there isn't enough time to hold a second referendum with remain on the ballot paper?"
And Brexiteer Conservative MP Sir Bill Cash accused the prime minister of "abject surrender" to the EU in allowing the delay and said she should resign.
Before the Brussels summit, Mrs May had told leaders she wanted to move the UK's exit date from this Friday to 30 June, with the option of leaving earlier if Parliament ratified her agreement.
European Council President Donald Tusk said future developments were "entirely in the UK's hands", adding: "They can still ratify the withdrawal agreement, in which case the extension can be terminated."
Mr Tusk said the UK could also rethink its strategy or choose to "cancel Brexit altogether", but urged: "Please do not waste this time."
The EU had been split over the length of delay to offer the UK, and by law its other 27 member states had to reach a unanimous decision.

Theresa May has denied claims from DUP leader Arlene Foster that she had "given up" on negotiations before agreeing the Brexit deal.
Mrs Foster said the PM's trip to promote the deal to businesses in Wales and Northern Ireland was a "waste of time" as Parliament would not back it.
Meanwhile, former defence secretary Sir Michael Fallon told the BBC the deal was "doomed" and must be renegotiated.
Mrs May insists it protects the "vital interests" of the whole of the UK.
After enduring criticism of the Brexit withdrawal agreement in the Commons on Monday, the prime minister began the next day rejecting US President Donald Trump's suggestions that the deal could threaten future US-UK trade deals.
And as she travelled to Wales and Northern Ireland, promising that her Brexit plans would strengthen "every corner" of the UK, she came under fire from Mrs Foster, whose party has a parliamentary pact to support the Conservative government in key votes.
"The disappointing thing for me is that the prime minister has given up and she is saying... we just have to accept it," Mrs Foster told the BBC's political editor, Laura Kuenssberg.
"She may have given up on further negotiations and trying to find a better deal but I have not."
Sir Michael Fallon's decision to come out against the deal is another blow to the prime minister, who is struggling to muster support in Parliament ahead of a Commons vote on 11 December.
Labour, the Lib Dems, SNP and Democratic Unionists have all said they will reject the terms of the UK's withdrawal, and future relations negotiated by Mrs May.
Many Tories have also said publicly they are opposed to Mrs May's Brexit deal with the EU. Brexiteers fear it will keep the UK too closely tied to EU rules, making it harder to strike future trade deals with other countries.
If MPs voted against the deal, the government would have up to 21 days to tell the Commons "how it proposes to proceed" and a further seven to move a motion allowing MPs to express their views.
New laws would have to be passed if the UK wanted to avoid the default position of leaving without a deal on 29 March next year.
Sir Michael, who was previously regarded as a loyalist, now argues that Mrs May's deal "would see the UK give up its power to influence EU rules and regulations in return for vague assurances over future trade".
He told BBC Radio 4's Today programme it was the "worst of all worlds" and that Mr Trump's criticism of its repercussions for transatlantic relations "could not simply be brushed off".
However, the prime minister is continuing to make the case for the agreement, which she says delivers on the 2016 referendum vote in key areas and is in the national interest.
During a visit to an agricultural show in Builth Wells in Powys, Mrs May said: "We have already been talking to [the US] about the sort of agreement that we could have in the future... that is working very well."
When it was put to her that Mrs Foster had implied she "rolled over", Mrs May replied: "No, we have been resisting many of the things that the European Union wanted to put in this deal. When you negotiate neither side gets 100% of what they want."
Speaking later, in Northern Ireland, Mrs May said she had been given a "clear message" by businesses that the deal was in the national interest as it provided certainty.
"The overwhelming message I get is this is a deal that does deliver for constituents," she added.
Under the proposed agreement, the UK would not be able to bring into force any trade deal with a country outside the EU until the end of the proposed transition period - currently scheduled to last until 31 December 2020.
In reality, any bilateral agreement between the UK and the US is likely to take years to negotiate given its complexity, differing standards in areas such as agriculture, and the fact it would require ratification by the US Congress.
In other developments:
Sir Michael said the 29 March 2019 date for Brexit, which is enshrined in UK law, may have to be pushed back to give negotiators the time to make major improvements to the agreement.
All 28 EU states would need to agree to extend the Article 50 process of negotiations to allow this to happen, something Theresa May has repeatedly ruled out.
Cabinet Office David Lidington said he did not think doing this "would get us anywhere" as the EU had made clear this was the only deal on the table.
He told Today there was no "Plan B" and the agreement was a "decent compromise" which would provide a springboard to the next stage of negotiations on the two sides' future relationship.

Theresa May has said the UK is facing "one of the most significant moments" in its recent history as she prepares to begin the process of leaving the EU.
The prime minister, who will officially tell the EU of the UK's desire to leave on Wednesday, said her goal was a "deep and special partnership" after Brexit.
A "global Britain" could build new alliances outside the EU, she added.
But a group of pro-Remain MPs said she would struggle to meet her goals and must be held accountable if she fails.
Ahead of formally triggering Brexit using Article 50 of the Lisbon Treaty, Mrs May spoke on the phone to EU Council president Donald Tusk, European Commission president Jean-Claude Juncker and German Chancellor Angela Merkel.
On Wednesday, the prime minister will officially tell the EU's other 27 members that the UK wants to pull out, just over nine months after the British public backed withdrawal by a margin of 51.9% to 48.1% in a referendum.
By triggering Article 50, Mrs May will set in motion a two-year process in which the terms of exit will be negotiated. Unless both sides agree to extend the deadline for talks, the UK will leave on 29 March 2019.
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The two sides will also try to agree the basis of the UK's future relationship with the EU although some experts, including the former top civil servant at the Foreign Office, have said this could take many more years.
Speaking at a Qatari investment forum in Birmingham - where the Gulf State announced £5bn of further investment in the UK - Mrs May said this was "one of the most significant moments the UK has faced for many years".
"Tomorrow we begin the negotiations to secure a new deep and special partnership with the European Union. As we do so I am determined we should also seize this historic opportunity to get out in to the world and to shape an even bigger role for a global Britain.
"This means not just building new alliances but going even further in working with old friends who have stood alongside us for centuries."
A group of MPs who all backed the Remain campaign in last year's poll and are now part of the Open Britain group said the "phoney war" was coming to an end and voters must be able to hold Mrs May to account over whether the UK emerged stronger and more prosperous outside the EU.
Although the group, including former Lib Dem leader Nick Clegg, ex Conservative education secretary Nicky Morgan and Labour's ex-shadow chancellor Chris Leslie, said they wanted the best outcome for the country, they feared this was unlikely as the PM's approach was fraught with contradictions.
The PM has said the UK will leave the single market but wants the greatest possible access to it and while leaving the customs union as it stands, she wants a similar arrangement that provides "frictionless" trade across borders.
Mrs May, they said, should be judged not only on the promises her government had made in recent months but on the "expectations" they said people had when they voted Leave last year, including that Brexit would lead to a fall in migration and free up extra funding for the NHS and other domestic services.
"A clear direction of travel has been set by the government and it is largely based on that set by the Vote Leave campaign," they said.
"Vote Leave and the government have made specific promises: leaving is a cost-free option, trade will be enhanced not hampered, there will be major savings from the EU budget, core arrangements with the EU, for example over national security, will remain unchanged and the integrity of the UK will be protected".
They added: "There is no mandate for the form Brexit takes. Responsibility for the outcome now rests with those conducting negotiations and those advocating a hard Brexit."
But Mr Duncan Smith, the former work and pensions secretary and leading Brexit supporter, said that the EU had "decided to leave the UK" in the late 1980s when it embarked on what he said was a one-way process of economic and political union.
Writing for the ConservativeHome website, Mr Duncan Smith suggested that, from that moment on, the UK's exit had been largely inevitable and he was confident about what lay ahead.
"We do so with political leaders in the EU beginning to use common sense terms as they now speak of needing good arrangements with the UK to protect their markets and their access to financial services.
"After all, it must be in everyone's interest, as European Commission President Juncker said the other day, for the UK and EU to part as friends, co-operating and trading."
On a visit to Brussels, London Mayor Sadiq Khan said the EU should enter the talks with confidence and would be making a mistake if it sought to punish the UK for deciding to leave.
"I say this with friendship and all due respect," the Labour politician said. "But a bad Brexit deal that hurts London would hurt the EU too...There is no need - as some have suggested - for the EU to send a message or to instil fear by punishing the UK.
"Because a proud, optimistic and confident institution does not secure its future by fear."

MPs are voting on a motion that could oust Theresa May's government from power and start moves towards a general election.
Labour leader Jeremy Corbyn, who tabled the no confidence motion, said the PM's "zombie" administration had lost the right to govern, and they "should do the right thing and resign".
But Mrs May said a general election was simply not "in the national interest".
It comes 24 hours after MPs voted down the PM's Brexit plans by a huge margin.
Closing the debate, Labour's deputy leader Tom Watson said: "She is a prime minister without a majority for her flagship policy, with no authority and no plan B."
But Environment Secretary, Michael Gove, said Mrs May had provided "inspirational leadership".
He launched a scathing attack on Mr Corbyn over a number of his positions on national security issues, saying to loud cheers from Conservative MPs that the country could not have confidence in him as a leader.
Mr Corbyn's motion is backed by MPs from the SNP, Lib Dems, Plaid Cymru and Green Party.
But senior Labour figures accept it is not likely to succeed, as she has the backing of Tory rebels and the DUP's 10 MPs, who less than 24 hours ago helped inflict a humiliating defeat on her.
Labour says further no-confidence votes could follow if this one fails.
Mr Corbyn told MPs: "The prime minister has consistently claimed that her deal, which has been decisively rejected, was good for Britain workers and business… she should have nothing to fear by going to the people."
He added that 2011's Fixed-term Parliaments Act "was never intended to prop up a zombie government", saying that the prime minister had "lost control" and suffered an "historic and humiliating defeat".
Mr Watson added: "I don't doubt that [Mrs May] has sincerely attempted to fulfil the task given to us buy the voters in the referendum. I have no doubt too that she has tried her best and given it her all.
"But she has failed and I am afraid the failure is hers and hers alone.
"We know she has worked hard, but the truth is she is too set in her ways, too aloof to lead.
"She lacks the imagination and agility to bring people with her, she lacks the authority on the world stage to negotiate this deal. Ultimately she has failed."
Mrs May told MPs it was Parliament that decided to put the question of European Union membership to the people, "and now Parliament must finish the job".
She said extending Article 50, the legal mechanism taking the UK out of the EU on 29 March, to allow time for an election would mean "delaying Brexit for who knows how long".
She repeated her offer of cross-party talks to find a way forward on Brexit, but has not so far invited the Labour leader to take part in them.
A general election would "deepen divisions when we need unity, it would bring chaos when we need certainty," Mrs May said.
Tory MP for Croydon South, Chris Philip, accused Mr Corbyn of "shameless political opportunism", which put "party interests ahead of national interests".
James Morris, Tory MP for Halesowen and Rowley Regis, said the motion was "merely a tactical device by the opposition to cause chaos".
And Conservative ex-minister Anna Soubry, who wants Mr Corbyn to back another EU referendum, questioned why her party were six points ahead of Labour in a weekend opinion poll, adding: "Could it be because he's the most hopeless Leader of the Opposition that we've ever had?"
But other MPs backed Mr Corbyn, with Labour's Stephen Doughty saying his leader was "absolutely right" to call for a general election "because it is not just the government's record on Brexit which is at stake tonight".
Labour frontbencher Liam Byrne, MP for Birmingham, Hodge Hill, accused Mrs May of building "a cage of red lines" over Brexit.
SNP Westminster leader Ian Blackford accused the government of "seeking to run down the clock" over Brexit and warned that the UK could "crash out" of the EU with no deal.
"The risk of a no deal is something that is unthinkable," he said. "If the government and the prime minister want to drive the bus over the cliff, we will not be in the passenger seat."
Lib Dem leader Sir Vince Cable said 48% of the population who voted to remain in the EU had been "totally disregarded" by the government and Mrs May had an "unwillingness to listen".
He said a general election provided "another route and a welcome one" that could resolve the issue, and he also called for a "People's Vote".
The leader of Plaid Cymru in Westminster, Liz Saville Roberts, who will vote against the government later, added her support for a "People's Vote", and called for the House to come together to make progress, condemning the "pantomime point scoring" taking place.
The DUP's leader Arlene Foster and its Westminster leader Nigel Dodds have both said they will support the government in the confidence vote.
But, speaking after what she described as a "useful discussion" with the prime minister, Ms Foster said "lessons will need to be learned" from the defeat on the Brexit deal.
"The issue of the backstop needs to be dealt and we will continue to work to that end," she added.
A shift to promising some kind of closer relationship with the EU, whether an actual customs union or something by a similar name, seems to be becoming more likely.
That's not because everyone in the government, let alone in No 10 or in the Cabinet, thinks it's the right thing to do - Liam Fox, whose job it is to pursue an independent trade policy, is not the only one with significant doubts.
But you can see a realistic route of getting that kind of arrangement through the House of Commons.
One former minister involved in trying to persuade the PM to soften up said: "We have three days to push and push her to move, or there won't be anything that can get through."
Read Laura's full blog
David Cameron, who resigned the day after the UK voted in 2016 to leave the EU, said he hoped, and thought, Mrs May would win Wednesday's vote.
Speaking to the BBC he also insisted he did not regret calling the referendum.
BBC political correspondent Iain Watson says that if the prime minister sees off the challenge, she will begin a series of meetings with "senior Parliamentarians" on Thursday.
He said Mrs May intended to retain her "red lines" - ruling out Labour's demand for a customs union with the EU - with sources suggesting compromising on this would risk cabinet resignations.
However, speaking to BBC Radio 5 Live, Justice Minister David Gauke suggested that the customs union option could not be ruled out, saying: "We have got to engage and we have got to be constructive."
Earlier Leader of the Commons Andrea Leadsom told the BBC the government was clear that it will not delay or revoke Article 50, although Chancellor Philip Hammond reportedly suggested delaying Brexit in a conference call on Tuesday evening.
By the BBC's head of political research Peter Barnes
Under the Fixed Term Parliaments Act 2011, UK general elections are only supposed to happen every five years. The next one is due in 2022.
But a vote of no confidence lets MPs decide on whether they want the government to continue. The motion must be worded: "That this House has no confidence in Her Majesty's Government."
If a majority of MPs vote for the motion then it starts a 14-day countdown.
If during that time the current government, or any other alternative government cannot win a new vote of confidence, then an early general election would be called.
That election cannot happen for at least 25 working days.
European leaders reacted to Tuesday's vote with dismay but gave no indication they were willing to make concessions.
Several have warned of increased chances of a no-deal Brexit, which many MPs fear will cause chaos at ports and damage industry.
Michel Barnier, the EU's chief Brexit negotiator, said Brussels "profoundly regrets" how the UK's MPs voted and said it was "up to the British authorities" to indicate how it would move forward.
European Commission President Jean-Claude Juncker urged the UK to clarify its intentions, saying: "Time is almost up."
And European Council President Donald Tusk has appeared to suggest that the UK should stay in the EU.
"If a deal is impossible, and no one wants no deal, then who will finally have the courage to say what the only positive solution is?", he tweeted.
The Commons defeat - the largest in history, by 432 votes to 202 - came as a huge blow for Mrs May.
She had spent two years negotiating the plan aimed at bringing about an orderly Brexit on 29 March, 2019, and setting up a 21-month transition period to negotiate a free-trade deal with Brussels.
But it faced opposition across Parliament, which has never had a majority in favour of Brexit. The UK public voted by 52% to 48% to leave the EU in the 2016 referendum.
Some Remain MPs oppose the deal because they want a further referendum with the option to scrap Brexit, while others accept Brexit will happen but want the UK to have a closer relationship with the EU than currently proposed.
On the other side are MPs who think Mrs May's deal leaves the UK tied too closely to EU rules, while some want to see a no-deal Brexit, which is where the UK leaves the EU without any special arrangements in place.
A key sticking point on the plan remains the Northern Irish backstop - the fallback plan to avoid any return to physical border checks between the country and Ireland. Many MPs argue it could keep the UK tied to EU customs rules indefinitely.
Click here if you cannot see the look-up. Data from Commons Votes Services.
In the run up to the vote, the prime minister tried to reassure MPs from all sides of the House over the controversial backstop - having received new written assurances from the EU that it would be temporary and, if triggered, would last for "the shortest possible period".
But some 118 Conservative MPs - from both the Leave and Remain wings of Mrs May's party - voted with the opposition parties against her deal, while three Labour MPs supported the deal.

Theresa May and 11 senior ministers have been thrashing out the UK's approach to Brexit in an eight-hour discussion at the PM's country retreat.
BBC political editor Laura Kuenssberg said everyone is said to have left Chequers happy implying "baby steps forwards not a huge breakthrough".
The PM will set out the position in a speech next week, after a discussion by the full cabinet.
There have been clear differences between ministers over the way forward.
But Laura Kuenssberg said she had been told the prime minister had "played a blinder" and persuaded Brexiteers to shift their position.
However, a cabinet Brexiteer source had said "divergence has won the day" with mutual recognition between the UK and EU on goods in future, rather than the UK being forced to stick to EU rules.
Conservative Party chairman Brandon Lewis said on BBC Question Time the cabinet would agree on the Brexit position, following the Chequers talks.
"What I can say to you is the outcome of those discussions will come to cabinet in the next few days, and late next week the prime minister will make a statement, a speech and outline what that position is."
Pressed on whether everyone in the cabinet would agree with it, he replied: "Absolutely, yes."
The Brexit sub-committee includes key figures such as Foreign Secretary Boris Johnson and Chancellor Philip Hammond, who were on opposite sides of the EU referendum argument in 2016.
A Downing Street spokesman said: "The prime minister and cabinet ministers met at Chequers for eight hours.
"They held discussions including about the automotive sector led by Greg Clark, agrifood led by Michael Gove, digital trade by Liam Fox and a discussion on the overall future economic partnership that was led by the prime minister."
Chief Whip Julian Smith and senior UK diplomats Tim Barrow and Ed Llewellyn were among those present, alongside the cabinet's Brexit sub-committee.
Cream of sweetcorn soup with a ham hock croquette
Guinness short rib of Dexter Beef with onions and parsnip mash
Lemon tart with raspberry sorbet and fresh raspberries
Mrs May still has to get any agreement through the whole cabinet on Tuesday, through her party - and then through 27 other EU member states.
Documents suggest European Commission negotiators will not approve of a UK proposal that seeks to select which EU rules to stick to post-Brexit and which to diverge from.
Slides published online by the commission say such an approach would be "not compatible with the principles" set out in the EU's own guidelines and posed a risk to the "proper functioning" of its single market.
But an EU diplomat told the BBC "we are hoping for a relationship that is as close as possible to the existing relationship", adding that EU chief negotiator Michel Barnier should be given a mandate "to explore all possibilities".
Before the final arrangements with the EU kick in, a temporary transition period is planned - although the details have yet to be negotiated.
On Wednesday, the UK set out its plans for how this "status quo" transition phase should work.
The document suggests the UK will abide by new EU laws and be involved in talks on future fishing quotas, but will not be able to sign trade deals without the EU's permission.
It also says the period should last as long as it takes to "prepare and implement the new processes and new systems".
No 10 denied this meant it would be longer than the planned two years.
But Sir Bill Cash, chairman of the Commons European Scrutiny Committee, warned that the UK could face an extra £4bn-£5bn Brexit "divorce bill" if the post-withdraw transition period extends beyond the EU's preferred end date of 31 December 2020.
He said that the current £35-39bn agreement was intended to cover to the end of the current EU budget period at the end of 2020.
For Labour, shadow chancellor John McDonnell said he would like to see "a customs union" option on the table, which would "solve some of the issues around Northern Ireland" and enable the UK to influence future trade negotiations.
Taking questions after a speech in London, he also said Labour would rather have a general election than a second referendum on Britain's EU membership because "there needs to be a wider debate" about the UK's future relationship with Europe.
Shadow foreign secretary Emily Thornberry also told LBC that while Brexit meant the UK could not be in the customs union, a new agreement was needed: "That we think is likely to be a customs union that will look pretty much like the current customs union."
It could mean the PM faces the prospect of a Commons rebellion as Conservative MP Anna Soubry said she had cross-party support for an amendment to the trade bill, calling for the government to form "a" customs union with the EU after Brexit.

Theresa May is holding last-minute Brexit talks with the French President Emmanuel Macron, with the UK due to leave the EU in three days' time.
The UK PM will urge Mr Macron to back her request to delay Brexit again until 30 June, having earlier met German Chancellor Angela Merkel in Berlin.
After the talks, Ms Merkel said a delay that runs to the end of the year or the start of 2020 was a possibility.
There is a summit on Wednesday when all EU states will vote on an extension.
Cross-party talks in Westminster aimed at breaking the impasse in Parliament finished, with both sides expressing hope there would be progress.
A draft EU document circulated to diplomats ahead of the emergency meeting of EU leaders proposes an extension but leaves the date blank.
The BBC's Brussels correspondent Adam Fleming said the document refers to an extension lasting "only as long as is necessary and, in any event, no longer than XX.XX.XXXX and ending earlier if the Withdrawal Agreement is ratified".
European Council president Donald Tusk said there was "little reason to believe" that the ratification process of the withdrawal agreement could be completed by the end of June.
In a letter to EU leaders, he said at Wednesday's summit members should discuss "an alternative, longer extension" that will be flexible and "would last only as long as necessary and no longer than one year".
The UK is currently due to leave the EU at 23:00 BST on Friday.
Downing Street said Mrs May and Ms Merkel discussed the UK's request for an extension of Article 50 - the process by which the UK leaves the EU - to 30 June, with the option to bring this forward if a deal is ratified earlier.
The prime minister and Chancellor Merkel agreed "on the importance of ensuring Britain's orderly withdrawal", a statement said.
Ms Merkel said EU leaders would discuss a "flextension" - a one-year flexible extension - at Wednesday's summit.
Following a meeting of the EU's General Affairs Council in Luxembourg, diplomats said "slightly more than a handful" of member states spoke in favour of a delay to 30 June and a majority were in favour of a longer extension.
Adam Fleming said no maximum end extension date was agreed, although December 2019 and March 2020 were mentioned.
Conditions of a delay were discussed including UK participation in May's European Parliament elections, no re-opening of the withdrawal agreement and how to guarantee the UK's pledge of "sincere co-operation" in ongoing EU business.
So far, MPs have rejected the withdrawal agreement Mrs May reached with other European leaders last year.
One of most contentious parts of the plan is the Irish backstop - an insurance policy that aims to prevent a hard border returning to the island of Ireland.
The EU has continually said it will not re-open the withdrawal agreement for negotiations, but Leader of the Commons Andrea Leadsom renewed her plea for them to look again.
Meanwhile, Environment Secretary Michael Gove said cross-party talks aimed at breaking the impasse in Parliament had been "open and constructive", but the two sides differed on a "number of areas".
Labour's shadow business secretary Rebecca Long Bailey said they were "hopeful progress will be made" and discussions with the government will continue in the "coming days".
Further talks are due to be held on Thursday.
In a leaked letter seen by the Telegraph, International Trade Secretary Liam Fox has warned that agreeing with Labour over its demand for a customs union is the "worst of both worlds" and will leave Britain unable to set its own trade policy.
On Tuesday afternoon, MPs approved a government motion asking MPs to approve the PM's request to the EU to delay Brexit, required after a bill from Labour's Yvette Cooper became law.
The final decision on an extension lies with the EU - and the leaders of all the 27 other EU countries have to decide whether to grant or reject an extension.
If the UK is still a member of the EU on 23 May, it will have to take part in European Parliamentary elections.
Luxembourg's Foreign Minister Jean Asselborn said the UK would "certainly not" leave without a deal on Friday.
But Ireland's Deputy Prime Minister Simon Coveney said a no-deal Brexit was still possible - even though it would represent "an extraordinary failure of politics".
EU chief negotiator Michel Barnier said the EU has "hope and expectation" from the cross-party talks happening in Westminster and he would be willing to "improve" the political declaration "within hours".
EU leaders are curious to hear the prime minister's Plan B. They hope there is one, although they're not convinced.
They want to know, if they say yes to another Brexit extension, what it will be used for.
And they suspect Theresa May wants them to do her dirty work for her.
EU diplomatic sources I have spoken to suggest the prime minister may have officially asked the EU for a short new extension (until 30 June) as that was politically easier for her back home, whereas she believed and hoped (the theory goes) that EU leaders will insist instead on a flexible long extension that she actually needs.
The bottom line is: EU leaders are extremely unlikely to refuse to further extend the Brexit process.
If no cross-party compromise can be reached, Mrs May has committed to putting a series of Brexit options to the Commons and being bound by the result.
This could include the option of holding a public vote on any deal agreed by Parliament.
Tory MP and government aide to the chancellor, Huw Merriman, said he backed a "People's Vote" to secure the public's support for the prime minister's deal.
Speaking at a rally for the campaign, he said it was "seriously wrong" that he had been threatened with the sack, and said he wanted another vote in order to "get this country through the mess we are currently in".

Theresa May has responded to criticism from her own MPs over talks with Jeremy Corbyn by saying all MPs have a responsibility to deliver Brexit.
The PM said the public "expect us to reach across this House to find a way through this".
Mr Corbyn said he welcomed the PM's "willingness to compromise to resolve the Brexit deadlock".
The PM's move to hold talks has angered some Brexiteers, with two ministers resigning over it.
Chris Heaton-Harris became the latest to quit on Wednesday afternoon, claiming his job at the Department for Exiting the European Union had become "irrelevant" if the government is not prepared to leave without a deal.
Wales Minister Nigel Adams also resigned his role on Wednesday morning, saying the government was at risk of failing to deliver "the Brexit people voted for".
The PM met Mr Corbyn before holding talks with Scotland's First Minister Nicola Sturgeon and Welsh First Minister Mark Drakeford.
Ms Sturgeon - who also met Mr Corbyn earlier - said she had "good" and "open" conversations with both leaders, and while she believed Mr Corbyn would "drive a hard bargain", she was "still not entirely clear" where the prime minister was willing to compromise.
The SNP leader, who backs a further referendum and wants to remain in the EU, told reporters: "My concern is that in the rush to reach some compromise with the clock ticking, what will happen over the next few days... is a bad compromise will be reached."
The SNP, Liberal Democrats, Green Party, Plaid Cymru and the Independent Group have also held a joint press conference, calling for any decision made by the leaders to be put to a public vote.
Plaid Cymru's Westminster leader, Liz Saville-Roberts, said: "People have the opportunity to have another shot at it, [in the Commons], to change their mind.
"Surely if that is how democracy works here, then democracy should go back to the people and people should have their say on whatever model comes forward."
The UK has until 12 April to propose a plan to the EU - which must be accepted by the bloc - or it will leave without a deal on that date.
In a statement on Tuesday night, the PM announced she wanted to meet Mr Corbyn to agree a way forward and put the plan to a vote in the Commons before 10 April - when the EU will hold an emergency summit on Brexit.
She insisted her withdrawal agreement - which was voted down last week - would remain part of the deal.
If there is no agreement between the two leaders, Mrs May said a number of options would be put to MPs "to determine which course to pursue".
In either event, Mrs May said she would ask the EU for a further short extension to hopefully get an agreement passed by Parliament before 22 May, so the UK does not have to take part in European elections.
Brexiteers were quick to express their anger at the prime minister's move.
But at Prime Minister's Questions, Mrs May said she wanted to deliver Brexit "in an orderly way" and, to do that, "we have to get an agreement through the House".
And Brexit Secretary Stephen Barclay blamed hard Brexiteers in the pro-Leave European Research Group for making the PM move to these talks.
Mrs May told MPs there were a "number of areas" where she agreed with Mr Corbyn in relation to Brexit, including ending free movement.
The Irish Taoiseach Leo Varadkar said the talks were "timely", and he hoped Mr Corbyn would "rise to the occasion" and "come up with a compromise plan" with the prime minister.
The PM's negotiated plan includes two sections - the withdrawal agreement and the political declaration.
The withdrawal agreement sets out how the UK would leave the EU, including the money the UK must pay to the EU as a settlement, details of the transition period, and citizens' rights - as well as the controversial Irish backstop that aims to avoid a hard border on the island of Ireland.
The political declaration focuses on the future relationship with the bloc and, unlike the withdrawal agreement, is not legally binding.
Mrs May said on Tuesday that any plan she agreed with Mr Corbyn "would have to agree the current withdrawal agreement", but she was ready to discuss the future relationship, i.e. the political declaration.
Brexit Secretary Stephen Barclay also said that was the element Labour had expressed more concern about.
The BBC's Laura Kuenssberg said there was not much difference between the government's version of Brexit and Labour's version - but there did not seem to be "an enormous amount of confidence" a political consensus could be reached from either party.
The row comes after Mrs May had more than seven hours of talks with her cabinet on Tuesday.
Laura Kuenssberg said there was "rage and dispute" in the cabinet meeting, with "wildly varying accounts" of how many people were for and against different versions of Brexit extensions.
Labour has previously said it has five demand for supporting a Brexit deal, including protecting workers' rights and national security, and securing the same benefits of being in the single market the UK has currently.
Meanwhile, a cross-party group of MPs will attempt to push through legislation to stop a no-deal Brexit.
If agreed, the bill - presented by Labour MP Yvette Cooper - would require the PM by law to ask for an extension of Article 50.
MPs took part in a three-hour debate on a business motion to set out how proceedings would run throughout evening.
But a vote on an amendment to the motion, put forward by Labour's Hilary Benn, calling for time on Monday to hold more indicative votes, resulted in a draw - the first time such a result has happened in 39 years.
The Speaker John Bercow then used his casting vote to reject the amendment, meaning MPs will not have the indicative votes next week.
The overall business motion was passed, but by just one vote - with 312 MPs voting for it, and 311 against.
The SNP, Lib Dems, Plaid Cymru, Greens and the Independent Group are putting forward an amendment to the bill to again call for a public vote on any outcome to become law.
The approximate timings of the day are:
Other key dates coming up include:

The prime minister has met Leo Varadkar in Dublin for talks focused on Brexit and the political deadlock in Northern Ireland.
Theresa May has now returned to the UK after having dinner with the taoiseach (Irish prime minister).
The talks in Farmleigh House lasted about two hours.
The meeting took place after Mr Varadkar met Northern Ireland's main political parties in Belfast on Friday.
Mrs May was accompanied in Dublin by the UK's Brexit negotiator Olly Robbins and her chief of staff Gavin Barwell.
The Irish government said the two leaders discussed "the latest Brexit developments" as well as the "ongoing political impasse in Northern Ireland".
The meeting comes after the EU said it will hold more talks with the UK to help the prime minister get a Brexit deal through the Commons.
Earlier, Attorney General Geoffrey Cox met his Irish counterpart after travelling to Dublin for talks.
Speaking in Belfast, Mr Varadkar said it was "not a day for negotiations" but it was an opportunity to "share perspectives".
He added that he was looking to restore confidence and trust with the prime minister during their meeting on Friday night.
By Jayne McCormack, BBC News NI political reporter
A Friday night in Dublin for Theresa May as she continues trying to find a way through for her Brexit deal.
The prime minister came face-to-face with her Irish counterpart over a fillet of beef with dauphinoise potatoes and green beans.
It's been a diplomatic whirlwind of a week as Mr Varadkar and Mrs May have bounced from Belfast to Brussels, both seeking backing for their respective positions.
It seems certain that the House of Commons will not pass any Brexit deal that includes the current backstop.
But the Irish government again today insisted it has to stay, with Mr Varadkar adding that he and the EU speak with one voice on this.
On Monday, UK-EU talks begin (again) in Brussels - but there's no sign of a compromise coming down the tracks.
Several cabinet ministers have told the BBC a no-deal Brexit could lead to a vote on Irish unification.
But Democratic Unionist Party (DUP) leader Arlene Foster poured cold water on the prospect, saying that the 1998 Good Friday Agreement sets out "criteria for a border poll, and it hasn't been met - therefore it will not be called".
On Thursday, Mrs May met EU leaders in Brussels in a bid to secure changes to the Irish border backstop in the Brexit agreement.
European Commission President Jean-Claude Juncker ruled out legally-binding changes to the backstop clause in the 585-page withdrawal document.
But he said the EU would be open to adding words to the non-binding future relations document that goes with the withdrawal agreement.
Other officials, including European Parliament Brexit co-ordinator Guy Verhofstadt, have said the backstop is "non-negotiable".
On Wednesday, Mr Varadkar held meetings with top EU officials about the backstop and Ireland's plans for a no-deal outcome.
He said that while he was "open to further discussions" with the UK government about post-Brexit relations, the legally-binding withdrawal agreement remained "the best deal possible".
Speaking in Belfast, Mr Varadkar said "time is running out" to agree a deal, but that work needed to continue in order to ensure agreement was reached.
"When it comes to Brexit this is a negotiation that has the UK on one side and EU on the other," he said.
"Any negotiation can only happen with Ireland and the EU working together."
It is the insurance policy to maintain an open border between Northern Ireland and the Republic of Ireland unless and until another solution is found.
The UK and EU made a commitment to avoid physical barriers or checks on the border, if no UK-EU trade deal is agreed before the Brexit transition period ends.
Many people are concerned that the return of such checks would put the peace process at risk.
But there has been opposition to the backstop from the DUP and Brexiteer MPs, who believe its terms could keep the UK tied to EU rules in the long term.
Last month, MPs backed an amendment in Parliament calling for "alternative arrangements" to replace the backstop.
A group of Conservative MPs has held talks aimed at finding other Brexit options that would avoid a hard border.
The taoiseach travelled to Belfast to discuss the "ongoing political impasse", the Irish government said.
Northern Ireland has been without a devolved government for more than two years.
Mr Varadkar, whose trip came days after Theresa May met the parties at Stormont to discuss her bid to make changes to the withdrawal agreement, said he travelled north to "hear the perspective of the main parties".
DUP leader Arlene Foster said her party had a "wide-ranging" discussion with the taoiseach.
Mrs Foster also said some people were engaging in "project fear" with the Brexit negotiations.
The party's deputy leader, Nigel Dodds, said the backstop "is the problem", but would not specify which possible alternative his party is supporting.
She said he had given her an assurance he would remain firm with his stance.
The party also said they have been calling repeatedly for a border poll, and that they had urged Mr Varadkar to begin planning for one.
The Ulster Unionist Party's (UUP) Brexit spokesperson Steve Aiken said there needed to be "level-headed conversations" and that the UUP had told the taoiseach how concerned they are by the terms of the Irish border backstop.
The UUP said it is working on a number of alternative proposals it wants the UK and EU to consider.
Alliance Party leader Naomi Long said they had a very constructive and wide-ranging discussion with Mr Varadkar.
"It's fairly clear those this week suggesting there is some chance of the UK and Irish government doing a side deal without the EU are chasing after a no-way scenario," she said.
SDLP leader Colum Eastwood said that it had been a "good meeting" and added that he and the taoiseach are "on the same side of this argument".
"We have been watching with some dismay what has been going on in Westminster over the last couple of months," he said.
"I don't think anybody within the Irish government or the European Commission sees any opportunity for diluting the protection of citizens in Northern Ireland."
Brexit Secretary Steve Barclay and EU negotiator Michel Barnier will hold talks in Strasbourg on Monday, as the EU and UK Brexit negotiating teams discuss proposed changes to the deal.
British sources say the talks will include discussion of the legally-binding withdrawal agreement, the BBC's Brussels reporter Adam Fleming said.
An EU source said the further talks are an opportunity to listen to the UK's ideas.
Mrs May and Mr Juncker will meet again before the end of February, to review progress.
The prime minister is expected to put the deal to a vote in the Commons towards the end of February.
She said the plan must change if it is to win the support of MPs who urged her to seek "alternative arrangements" to the backstop when rejecting the deal last month.

Theresa May has met the chairman of an influential committee of backbench Tory MPs, Sir Graham Brady, amid calls for her to set a firm resignation date.
It followed a request from the 1922 Committee for "clarity" on the issue.
No 10 insisted the meeting was routine, but pressure is mounting on the PM, with local Tory associations confirming they will hold a vote of confidence in her leadership on 15 June.
Meanwhile, cross-party talks to break the Brexit deadlock resumed.
In March, Mrs May pledged to stand down if and when Parliament ratified her Brexit withdrawal agreement with the EU - but she has not made it clear how long she intends to stay if no deal is reached.
The UK had been due to leave the EU on 29 March, but the deadline was pushed back to 31 October after Parliament was unable to agree a way forward.
Opinion is split even within the 1922 Committee - an elected body of MPs which represents backbenchers and oversees leadership contests.
Treasurer Sir Geoffrey Clifton-Brown said Mrs May should announce a "road map" for her resignation after the European elections, set for 23 May.
But vice-chairman Charles Walker told BBC Radio 4's World at One there was a "blame displacement process" happening within the Conservative Party, laying it on Mrs May's shoulders.
"We all need to take personal responsibility for the fact that we are still in the EU," he said, adding that the idea a new prime minister would be able to sort Brexit out easily was "for the birds".
No confidence vote of Tory MPs: Theresa May won a leadership ballot by 200 to 117 votes on 12 December 2018. Under current party rules, there can't be another vote for a further year so the PM is technically safe until 12 December this year. Many MPs want to change the rules to allow an earlier contest but this would need to be agreed by the 1922 Committee.
No confidence vote in Parliament: The PM would have to resign if she lost a confidence vote in Parliament. Labour tried this manoeuvre in December but Tory MPs and their DUP allies backed the PM. Might some Tories now withhold their support if they think it will usher in a new leader rather than a general election?
Grassroots Tory revolt: Local Conservative associations seem to be turning against the PM, with one - Clwyd South - already passing a motion of no confidence in her. The National Conservative Convention's vote on 15 June is non-binding, though, so the PM could ignore it.
Cabinet revolt: Margaret Thatcher quit in 1990 after a number of ministers told her it was time to go. Could history repeat itself? There has been no sign of that so far and colleagues who want to succeed her - and there are many - may not want to be seen to be the ones wielding the knife or to risk sacrificing their own careers.
Quits of her own accord: The BBC's Norman Smith says there is no way the PM will "walk away" right now, but this could change in the aftermath of a "catastrophic" result in European elections.
Some Brexiteers are angry at Mrs May's efforts to find a compromise with Labour after her deal  with the EU was effectively rejected by MPs three times.
One leading Eurosceptic, Sir Bill Cash, told the Press Association "the time has come" for Mrs May to resign and she "needs to be given a date".
But Chancellor Philip Hammond defended the cross-party talks, suggesting the government had no other option.
He said the "most important thing" was to put in place arrangements to allow low-friction trade between the UK and the EU and "of course" the government should talk to Labour about it.
Pressure is building on Mrs May following last week's local election drubbing, in which the Conservatives lost 1,334 councillors in England.
In an unprecedented move, the National Conservative Convention - the most senior body within the voluntary party - is to hold a vote of confidence in her leadership next month.
It was triggered after 65 local Conservative associations said they had lost trust in the prime minister.
The prime minister has blamed the Brexit impasse for her party's terrible performance last week and urged Labour, which itself lost 82 seats, to compromise to agree a deal.
Will the cross-party talks get anywhere this week?
No 10 is trying to get Labour over the line by presenting the withdrawal agreement as a stepping stone - i.e. hold your nose for now and you can carve out your own deal if you win the next election.
Key to that is the promise of a "temporary customs union" - but Labour sources warn if that's all it is, that's what's already in the withdrawal agreement anyway (plus a few months) and doesn't add up to anything substantially new.
A senior government source says it IS possible, though, to see a way to a deal, but it is unlikely to be resolved this week - and their aim is not to create some kind of May-Corbyn Rose Garden moment (imagine!) but to set out a path to get the Withdrawal Bill to Commons with a fair wind.
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Theresa May has said a "new and improved" Brexit deal will be put to MPs when they vote on the EU Withdrawal Agreement Bill in early June.
Writing in the Sunday Times, Mrs May said the bill will be a "bold offer".
Cabinet minister Rory Stewart told the BBC he hoped extra guarantees on workers' rights would enable "sensible" Labour MPs to support the government.
But Jeremy Corbyn said Labour would oppose the bill and it was "very difficult" to see it making progress.
While he would consider new proposals "very carefully", he said what was being talked about did not appear "fundamentally different" from what was already on the table.
Scottish First Minister Nicola Sturgeon said support in Scotland for staying in the EU had strengthened since the 2016 referendum - when 62% of voters backed Remain - and voters should send a clear message about this in Thursday's European elections.
Mrs May announced this week that MPs would vote on the bill - which would bring the withdrawal agreement into UK law - in the week beginning 3 June. If the bill is not passed, the default position is that the UK will leave the EU on 31 October without a deal.
Labour has said it will vote against the bill after talks with the government on trying to agree a compromise acceptable to its MPs broke down.
The bill risks failing to clear its first parliamentary hurdle, with many Conservative Brexiteers, as well as the DUP, SNP and Liberal Democrats, also opposed.
But in her Sunday Times piece, Mrs May said she will "not be simply asking MPs to think again" on the same deal that they have repeatedly rejected - but on "an improved packaged of measures that I believe can win new support".
The PM said she wanted MPs to consider the new deal "with fresh pairs of eyes - and to give it their support".
By Jonathan Blake, political correspondent
With any sales pitch that sounds like it's too good to be true, it's important to check the small print.
And so with Theresa May's promise of a "new and improved" Brexit deal - MPs will be wondering what exactly has changed.
A promise of a further referendum would win plenty of support from Labour but Downing Street's ruled that out.
Changes to the Withdrawal Agreement, including the Northern Ireland backstop, would sway the DUP and many of her own MPs, but the EU won't agree to that.
Additions on workers' rights and environmental protections might be enough to sway a few Labour votes.
And there may be - after a series of votes in Parliament - some movement on the UK's future customs relationship with the EU, but that is as likely to turn off Tory MPs as it is to woo the opposition.
Not for the first time there appear to be no good options for Theresa May.
But a "bold offer" is quite a promise to make, and if her deal has a hope of passing, she will somehow have to live up to it.
Rory Stewart, who is the international development secretary, suggested the two main parties were "about half an inch apart" on the three main issues under discussion - protecting employment rights and environmental standards and having a strong trading relationship with the EU and the rest of the world.
"None of us want to remain in the European Union, none of us want a no-deal Brexit which means logically there has to be a deal," he said.
"We're in the territory of a deal and where we need to focus is Parliament and particularly getting Labour votes across - maybe not Jeremy Corbyn's vote but there are many other moderate, sensible Labour MPs that we should be able to bring across."
While Labour "reserved the right" to consider new proposals, Mr Corbyn said the official talks were at an end and he would not hand ministers a "blank cheque"
Any agreement, he said, must include the scope for future governments to exceed the EU's employment and environmental standards not just keep pace with them.
On the issue of another referendum, he said Labour had kept the option on the table but any vote would have to be on a "credible" deal - which he suggested did not exist right now.
Liberal Democrat leader Sir Vince Cable said he would be prepared to support the bill if the government agreed to give the public the final say on the terms of exit in a referendum.
He told the BBC's Andrew Marr his party had discussed the "practicalities" of holding another public vote and it was possible before the 31 October deadline.
"We need a proper referendum that will come to a resolution on the issue, with remain on the ballot paper."
But Change UK spokesman Chuka Umunna said there was "simply not enough time" to hold a referendum before 31 October.
Given it was "almost certain" the Withdrawal Agreement Bill would be defeated, he said the only option was for the the UK to stop Brexit by revoking Article 50.
"We are facing a national emergency," he told Andrew Marr.
"What would be undemocratic would be imposing a no-deal Brexit on the British people that there is not a mandate for."
A cabinet meeting on Tuesday is to consider plans for another series of "indicative votes" by MPs to establish which proposals could command a majority.
Asked if he would accept anything backed by Parliament, which has so far failed to unite behind an alternative, Mr Corbyn said it was "very unlikely" to resolve the impasse.
"The government has to come up with legislation, through negotiation with the EU," he said.
"The idea that they can produce a bill at the beginning of June and get it through all its stages by the end of July is very very unlikely."
Brexit had been due to take place on 29 March. But the UK was given an extension until 31 October after MPs three times voted down the withdrawal agreement Mrs May had negotiated with the EU - by margins of 230, 149 and 58 votes.

Theresa May has played down reports that she could force MPs to choose between backing her deal or accepting a delay to EU withdrawal.
ITV News said chief UK negotiator Olly Robbins was overheard in a Brussels bar saying the EU was likely to allow an extension to the Brexit process.
The PM suggested MPs should not rely on "what someone said to someone else as overheard by someone else, in a bar".
"It is very clear the government's position is the same," she said.
"We triggered Article 50 (the process by which the UK leaves the EU)... that had a two-year time limit, that ends on the 29 March.
"We want to leave with a deal, and that's what we are working for."
The prime minister has said she will lift the requirement for a 21-day period before any vote to approve an international treaty, which means she could delay the final Brexit vote until days before the UK is due to leave the EU.
No 10 insists Mrs May still plans to hold a vote on a deal as soon as possible but Labour has accused her of "running down the clock" in an effort to "blackmail" MPs into backing her deal.
And European Council President Donald Tusk tweeted that "no news is not always good news", saying the EU was "still waiting for concrete, realistic proposals from London".
At Prime Minister's Questions, the SNP's Westminster Leader Ian Blackford urged Mrs May to rule out holding a "meaningful vote" on the deal with less than two weeks to go until Brexit.
"The prime minister must stop playing fast and loose - businesses are begging for certainty," he said.
Mrs May said the way to give businesses certainty was to back the deal she had negotiated with the EU.
But Mr Blackford told her she had been "rumbled by your own loose-lipped senior Brexit adviser". It was a reference to the ITV report that Mr Robbins was overheard saying he expected MPs to be presented with a choice of backing either a reworked withdrawal deal, or a potentially significant delay to Brexit.
MPs rejected the deal negotiated with the EU by a historic margin in January and the prime minister says she is seeking legally-binding changes to the controversial "backstop" - the "insurance policy" aimed at avoiding a return to border checks between Northern Ireland and the Irish Republic.
The UK is currently due to leave the EU on 29 March, whether or not a deal has been approved by the Commons.
On Wednesday, Labour leader Jeremy Corbyn pointed to the decision to scrap a no-deal Brexit contract with a ferry company that had no ships as a "spectacular failure" which was "a symptom of the utter shambles of this government and its no-deal preparations". He described the prime minister's Brexit strategy as "costly, shambolic and deliberately evasive".
Mrs May accused Mr Corbyn of preferring "ambiguity and playing politics to acting in the national interest" saying MPs did not know if he backed another referendum, a deal or Brexit.
"People used to say he was a conviction politician - not any more," she said.
The PM has promised to return to the Commons on 26 February with a further statement - triggering another debate and votes the following day - if a deal has not been secured by that date.
If a deal is agreed, MPs will have a second "meaningful vote", more than a month after Mrs May's deal was rejected in the first one.
No 10 has indicated it is willing to make concessions on protection for workers but Labour's push for a closer future customs relationship than Mrs May proposes, remains a sticking point.
Shadow Brexit Secretary Sir Keir Starmer met Cabinet Office Minister David Lidington and Brexit Secretary Stephen Barclay on Wednesday for what he described as "frank and serious discussions". But he said he was given "no suggestion" that the prime minister was "diluting red lines".
He added that he had "set out the Labour Party position, which is the two options: On one hand a close economic relationship, on the other a public vote". He said the battle for now is "to stop the prime minister running down the clock".
Shadow Chancellor John McDonnell has acknowledged that the prime minister cannot back Labour's Brexit proposals, and said he thinks Parliament is going to end up taking over the Brexit process.
Asked at a Politico event on Wednesday how Labour was going to achieve its plans, including staying in a customs union, because, "you know she can't back it... she'll split her party", Mr Donnell replied: "Yeah... yeah".
"I genuinely think we're now into hard-nosed negotiations between pockets of support in all the different politics," he said.
He accepted that the general election Labour has been calling for was "unlikely".
Labour has tabled an amendment for Thursday that would force the government to come back to Parliament by the end of the month to hold a substantive vote in the Commons on its plan for Brexit.
"Our amendment says there should be a hard stop on February 26. The prime minister must either put up her deal or allow Parliament to take control," said Sir Keir.
Mrs May told MPs on Tuesday she was discussing a number of options with the EU to secure legally-binding changes to the backstop, including replacing it with "alternative arrangements", putting a time limit on how long it can stay in place, or a unilateral exit clause so the UK can leave it at a time of its choosing.
MPs are due to vote again on the Brexit process on Thursday in what was expected to be a routine procedure acknowledging the government's efforts.
However, BBC political editor Laura Kuenssberg tweeted that Mrs May could be faced with another defeat, with influential Brexiteers from the European Research Group of Tory backbenchers indicating that they will refuse to back the government.
They are angry at being asked to support the PM's motion, which combines the view backed by a majority of MPs last month that the government should seek an alternative to the backstop with a separate move to stop Brexit happening without a formal deal.
The group's deputy chairman, Mark Francois, told the BBC members had "pleaded" with Downing Street to change the wording, which he said goes back on what she has previously told MPs.
"We cannot vote for this as it is currently configured because it rules out no deal and removes our negotiating leverage in Brussels."
Most MPs want to avoid a no-deal scenario, fearing chaos at ports and disruption to business. However, some Brexiteers have played down that prospect arguing it is an example of "Project Fear".
Meanwhile, Labour have highlighted a government risk assessment that says "precisely four" of about 40 documents designed to replicate the existing 40 EU free trade agreements have been signed.
The party's trade spokesman Barry Gardiner said of the agreements, which were promised to be ready immediately after Brexit: "Nine are off-track, 19 significantly off-track, four are not possible to be completed by March 2019 and two are not even being negotiated."
International Trade Secretary Liam Fox responded: "A number of negotiations are at an advanced stage. As with all international negotiations, and indeed any negotiations, they will go down to the wire."

Theresa May and her cabinet are looking for ways to bring her EU withdrawal agreement back to the Commons for a fourth attempt at winning MPs' backing.
The PM said the UK would need "an alternative way forward" after her plan was defeated by 58 votes on Friday.
MPs from all parties will test support for other options during a second round of "indicative votes" on Monday.
However, Conservative Party chairman Brandon Lewis said the government did not support any of those options.
Labour leader Jeremy Corbyn refused to say whether his party would offer an option to remain in the EU during these votes, but said the obvious choice was "a good economic relationship with Europe".
The latest vote came on the day the UK was supposed to leave the European Union: 29 March. The date was postponed to allow Mrs May more time to find a Brexit solution.
Friday's defeat was the third time MPs have rejected her withdrawal agreement - the first vote was lost by 230 votes, the second by 149.
The government has so far failed to win over 34 Conservative rebels, including both Remainers as well as Tory Brexiteers, who say the deal still leaves the UK too closely aligned to Europe.
Northern Ireland's DUP - which has propped up Mrs May's minority government - also continues to oppose the deal.
But a No 10 source indicated the prime minister would continue to seek support in the Commons and insisted efforts were "going in the right direction".
MPs will hold another set of non-binding votes on various Brexit options in the Commons on Monday.
None of MPs' eight proposed Brexit options secured a majority in the last round of "indicative votes" on 27 March, but the options which received the most votes were a customs union with the EU or a referendum on any deal.
The customs union allows businesses to move goods around the EU without checks or charges. Continued membership would bar the UK from striking independent trade deals after Brexit.
Brandon Lewis told Radio 4's Today programme: "The government's position is very clear - we do not support these options. The government's position is we believe the best way to respect the referendum is to deliver the deal."
He said staying in a customs union with the EU would go against the result of the referendum and the Conservatives' election manifesto.
However, Mr Corbyn said Labour would propose a deal that did involve a customs union with the EU - to protect the issue of avoiding a hard border in Northern Ireland.
He said: "I'm convinced at that after spending a lot of time meeting with and talking to officials in Europe."
Nicky Morgan, a former cabinet minister and Tory MP, said one way to end the Brexit deadlock could be a government of national unity - which is a cabinet made up of different parties.
She told Today: "There have been periods in our history when we have had national unity governments or a coalition for a very specific issue."
There is every chance that the prime minister will again - with routes outside the normal boundaries - try to make a version of her Brexit deal the end result of all of this.
Despite a third defeat, despite the embarrassment of repeated losses, don't imagine that she is ready to say a permanent farewell to the compromise deal she brokered with the EU or, straightaway, to her time in office.
There is still a belief in the heart of government that there could be a way round, perhaps to include the prime minister's agreed treaty as one of the options that is subject to a series of votes that will be put in front of the Commons next week.
The aspiration, strange as it sounds, for some time now has been to prove to MPs that the deal is the least worst of all the options...
Earlier this month, EU leaders gave the PM until 12 April to come up with a Brexit solution; if her deal had made it through Parliament on Friday that date would have been pushed back to 22 May to allow time to pass the necessary legislation.
Since the deal was rejected, Mrs May now has until 12 April to seek a longer extension to avoid the UK leaving without a deal.
Commons leader Andrea Leadsom said she remained "confident" the government could deliver Brexit, adding that "we have to keep trying".
Tory Brexiteer Andrew Bridgen said leaving the EU without a deal was the best option on the table.
"No deal is the only way we're going to get out, fulfilling our manifesto pledges and the commitment we made to the British people after the referendum," he said.
Mrs May said it was "almost certain" there would have to be an extended delay to Brexit to allow the UK to take part in the European elections at the end of May if her deal does not go through.
But Downing Street later said this was not an "inevitability".
The withdrawal agreement is the part of the Brexit deal Mrs May struck with Brussels which sets out how much money the UK must pay to the EU as a settlement, details of the transition period, and the Irish backstop arrangements.
If Mrs May wants to hold another vote on the deal in Parliament, it has to comply with Commons Speaker John Bercow's ruling that it can only be brought back with "substantial" changes.
This is why the government separated the withdrawal agreement from the political declaration - on the future relationship with the EU - for Friday's vote.
Meanwhile, Leave voters registered their anger at the latest vote rejection with a protest at Westminster.
Thousands gathered outside Parliament to protest against the delay, bringing traffic to a standstill.
Meanwhile Conservative former Attorney General Dominic Grieve, who has campaigned for a further referendum on the deal, is facing deselection after losing a vote of no-confidence in his Beaconsfield constituency.
The prominent Remainer, who remains an MP for the time being, clashed with his local Conservative Party over Brexit.
Despite all the drama, the money and time spent by EU leaders on Brexit (summits, dedicated governmental departments, no-deal planning) and all the hard, hard graft put in by the EU and UK negotiating teams, Europe's leaders are asking themselves what there is to show for it all.
Ongoing Brexit divisions in Parliament, in government and in Theresa May's cabinet were on screaming technicolour display again last week.
EU leaders used to use the threat of a no-deal Brexit as a negotiating tactic (as did the UK). They now believe it to be a very real prospect.
That has led to a number of countries - notably France - questioning the logic of delaying Brexit for much longer.
They wonder if the UK will ever unite around a Brexit Way Forward - be it a softer Brexit, no deal or no Brexit.
Would a Brexit extension, allowing for a general election or a second referendum, really settle the issue, they ask?
Read Katya's blog in full

Theresa May has promised MPs a final, decisive vote on her Brexit deal with the EU - but not until she has secured changes to the Irish backstop clause.
The PM said she needed "some time" to get the changes she believes MPs want.
She promised to update MPs again on 26 February and, if she had not got a new deal by then, to give them a say on the next steps in non-binding votes.
Jeremy Corbyn accused her of "running down the clock" in an effort to "blackmail" MPs into backing her deal.
Britain is currently leaving the EU on 29 March, with or without a deal.
Labour claims Mrs May is planning to delay the final, binding vote on the withdrawal deal she has agreed with the EU until the last possible moment, so that MPs will be faced with a stark choice between her deal and no deal.
Labour and some Conservative MPs had been planning to have a fresh go at putting alternatives to Mrs May's deal to the vote on Thursday, in an effort to take control of the Brexit process.
But BBC Political Editor Laura Kuenssberg said Mrs May's announcement of returning to update MPs on 26 February and then more votes on 27 February - if she has still not got a final deal - meant Thursday's expected "high noon" for the prime minister had probably been postponed.
MPs are still expected to debate and vote on amendments to the Brexit deal on Thursday, however, although it will not be known until later what those amendments are likely to be.
Mrs May promised to give MPs a "stronger and clearer role" in the next steps on Brexit and said she would return to the Commons for a meaningful vote on her deal "when we achieve the progress we need".
The PM said she was discussing a number of options with the EU to secure legally-binding changes to the backstop: Replacing it with "alternative arrangements", putting a time limit on how long it can stay in place or a unilateral exit clause so the UK can leave it at a time of its choosing.
The backstop arrangement is the "insurance" policy in Mrs May's deal to avoid a return to border checks on the island of Ireland.
The EU has reiterated it will not renegotiate the withdrawal agreement.
Mrs May said talks were at a "crucial stage", but she still believed it was possible to get a deal MPs could support.
"We now all need to hold our nerve to get the changes this House requires and deliver Brexit on time," Mrs May told the Commons.
But Labour leader Jeremy Corbyn said MPs were being "blackmailed into supporting a deeply flawed deal", calling it "an irresponsible act".
By Daniel Kraemer, BBC Westminster
The prime minister's critics say she is just pretending to try to get changes to the deal she signed with the EU so she can push the final vote on it right down to the wire.
Labour's shadow Brexit secretary Sir Keir Starmer says what she actually intends to do is return to Parliament after the 21-22 March European Council summit, the week before Brexit, and offer MPs a "binary choice" - her deal or no deal.
Holding such a vote a few days before Britain leaves the EU might scare enough Labour MPs worried about a no-deal Brexit into backing the prime minister to get it through.
The government insists this is not its strategy and it will hold a "meaningful vote" as soon as it gets the changes to the deal it is seeking from Brussels.
Mr Corbyn said Mrs May was "merely engaged in the pretence of working across Parliament to find solutions", but she has "not indicated she will move one iota" on her red lines.
He told MPs: "We were promised a meaningful vote on a deal in December, it didn't happen. We were told to prepare for a further meaningful vote this week after the prime minister again promised to secure significant and legally binding changes to the backstop and that hasn't happened.
"Now the prime minister comes before the House with more excuses and more delays."
The SNP's leader at Westminster, Ian Blackford, was reprimanded by Commons Speaker John Bercow for shouting "liar" at the prime minister as she was making her statement.
Mr Blackford agreed to withdraw his remark "in deference" to the Speaker, but did not apologise to Mrs May. MPs are banned by Commons rules from calling other MPs liars in the chamber.
He said Mrs May was "lost in a Brexit fantasy", saying: "We're 45 days from Scotland being dragged out of the European Union against our will - 45 days from economic catastrophe."
Conservative MP Phillip Lee, who campaigns for another EU referendum, told the BBC he expected to see more ministerial resignations at the end of the month, when some of his colleagues "are going to have to make a stand and say: 'I'm sorry this is not acceptable'".
He said the promise of a further Commons vote on 27 February had taken the "fizz" out of Thursday's vote, which meant that the end of the month would "see some action from Conservatives in government".
Mrs May also set out plans to lift a requirement for a 21-day delay before any vote to approve an international treaty, in order to get a Brexit deal ratified in time for 29 March.
Former attorney general Dominic Grieve warned that time was running short for the ratification of a deal under the Constitutional Reform and Governance Act.
Mrs May said:  "In most circumstances, that period may be important in order for this House to have an opportunity to study that agreement."
Brexit Secretary Stephen Barclay has, meanwhile, told senior European Parliament members that the UK requires legally-binding changes to the Irish backstop, but kept open the idea that these could be achieved without rewriting the text of the withdrawal agreement.
On a visit to the European Parliament in Strasbourg, Mr Barclay said he would continue working with EU chief negotiator Michel Barnier and he will call him after Thursday's Commons votes.
Foreign Secretary Jeremy Hunt met French foreign minister Jean-Yves Le Drian and Europe Minister Nathalie Loiseau earlier, in Paris.
Following the meetings, a French Foreign ministry statement said France "supports the planned withdrawal agreement" and added that it was "up to the British authorities to clarify their intentions".

Theresa May has urged Jeremy Corbyn to discuss his Brexit plans with her, after he said he would not take part in talks until "no deal" was ruled out.
In a letter to the Labour leader, the PM wrote that ruling out no deal was an "impossible condition" as it was not within the government's power to do it.
She has been meeting other leaders to try to find a compromise on Brexit after her deal was rejected by MPs.
Earlier, Mr Corbyn dismissed the talks as a "stunt".
The PM will publish a new plan on Monday with a full debate and key vote scheduled for Tuesday, 29 January.
Senior politicians on all sides have also been meeting with cabinet ministers to try to find a way forward.
But Mr Corbyn, the leader of the opposition, declined to take part, telling Mrs May to "ditch the red lines" and "get serious about proposals for the future".
In a speech in Hastings Mr Corbyn said: "With no-deal on the table, the prime minister will enter into phony talks just to run down the clock and try to blackmail MPs to vote through her botched deal on a second attempt by threatening the country with the chaos that no-deal would bring."
Mr Corbyn said the "best outcome" was to call a general election to "break the deadlock".
The Labour leader has emailed Labour MPs urging them not to talk to Mrs May until she has ruled out a no-deal Brexit.
His stance has come under fire from Labour MP Mike Gapes, a longstanding critic of Mr Corbyn, who told BBC Radio 4's The World at One: "Jeremy Corbyn has been quite happy in the past to talk to Hamas, Hezobollah... I find it extraordinary he's not prepared to go and meet the prime minister."
In her reply, Mrs May said: "I note that you have said that 'ruling out' no deal is a precondition before we can meet, but that is an impossible condition because it is not within the Government's power to rule out no deal.
"Let me explain why. Under Article 50 of the Treaty on European Union and the Withdrawal Act 2018, we will leave the EU without a deal on 29 March unless Parliament either agrees a deal with the EU or the UK revokes article 50 and chooses to stay in the EU permanently.
"So there are two way to avoid no deal: either vote for a deal, in particular a Withdrawal Agreement, that has been agreed with the EU, or to revoke Article 50 and overturn the referendum result.
"I believe it would be wrong to overturn the referendum result."
She wrote that she would be "happy" to discuss Mr Corbyn's proposals.
On Wednesday night, speaking outside Downing Street after talks with the Lib Dems, SNP and Plaid Cymru, Mrs May called on MPs to "put self-interest aside".
"It will not be an easy task, but MPs know they have a duty to act in the national interest, reach a consensus and get this done," she said.
Separately, Downing Street said the government has produced a "very short paper setting out the factual detail on the number of months required" to hold another EU referendum, which suggests it would take "in excess of a year".
The point of the document was to "inform the expected discussion" Mrs May was likely to have with MPs who back another public vote, government sources say.
The prime minister is holding meetings with various party leaders as well as Tory Brexiteers and the DUP - both of whom rejected her withdrawal deal earlier this week - on Thursday.
Environment Secretary Michael Gove, Cabinet Office Minister David Lidington and Brexit Secretary Steve Barclay are also holding talks with senior opposition politicians, including Labour MPs Hilary Benn and Yvette Cooper.
The SNP's Westminster leader, Ian Blackford, said that the extension of Article 50 - the two year mechanism that means the UK leaves the EU on 29 March - the ruling out of a no-deal Brexit, and the option of a second EU referendum would have to form the basis of future discussions.
Party leader and Scotland's First Minister Nicola Sturgeon tweeted that the talks were just "time wasting" if the prime minister was not prepared to consider another referendum, rule out a no-deal Brexit or to extend Article 50.
Plaid Cymru's Westminster leader, Liz Saville Roberts, said they were "committed to finding a real solution" but "that means taking a no deal Brexit off the table and a People's Vote on our European future".
Liberal Democrat leader Sir Vince Cable, who wants a referendum, said he was encouraged by Mrs May's "willingness to talk about these issues in detail".
Following her meeting on Thursday, Green MP Caroline Lucas said the PM refused to rule out a no-deal Brexit.
"I repeatedly urged her again and again to take 'no deal' off the table because I think it completely skews the talks because you know that cliff edge is there," she said.
Mrs May was also resisting the option of extending Article 50, Ms Lucas said.
DUP leader Arlene Foster said the prime minister was in "listening mode" and there was optimism that a Brexit deal could still be reached.
She said she made a "clear ask" in relation to the Irish backstop, urging Mrs May to address it "in a satisfactory way".
When asked what the government was willing to compromise on, Conservative Party chairman Brandon Lewis refused to give specifics.
He told BBC Radio 4's Today programme that Mrs May would not consider a customs union and that he did not believe a new referendum was "the right way to go".
Meetings, on their own, are not a Plan B. Conversations, are not by themselves, compromises.
To get any deal done where there are such clashing views all around, it requires give and take. It feels like a political lifetime since there has been a fundamental dispute in the cabinet, in the Tory party and across Parliament. Theresa May has stubbornly, although understandably, tried to plot a middle course.
But that has failed so spectacularly at this stage. Ultimately she may well be left with the same dilemma of which way to tack.
Read full article.
EU's chief Brexit negotiator Michel Barnier has suggested that Brussels was ready to respond to any changes in Mrs May's "red lines", saying: "If they change, we'll change."
He said getting an agreement was "in everybody's interest" and that "something has to change" if it is to be secured.
The prime minister survived a vote of no confidence in her government by 325 to 306 votes - a margin of 19 - thanks to the backing of the 10 members of the DUP. Had they switched allegiance, the government would have lost by one vote.
Click here if you cannot see the look-up tool. Data from Commons Votes Services.
This came after MPs voted against Mrs May's plans for Brexit on Tuesday night by a historic margin when it was rejected by 230 votes -  the largest defeat for a sitting government in history.
Former prime minister Tony Blair told BBC Radio 4's Today that an extension to Article 50 was "inevitable" at this point and warned a no-deal Brexit would do "profound damage" to the UK's economy.
There remains deep division among Mrs May's own MPs - including within her cabinet - about possible compromises, such as the option of staying in a customs union.
The Times newspaper claimed Leader of the House Andrea Leadsom and other cabinet Brexiteers want Mrs May to present MPs with a "Plan B" on Monday that would include a promise to impose a time-limit on the Northern Irish backstop - the fallback plan to avoid any return to physical border checks between the country and Ireland - and to negotiate a Canada-style free trade deal.
And the Telegraph reported it had seen a leaked transcript of a conference call in which Chancellor Philip Hammond told business leaders that a no-deal Brexit could be "taken off the table".
Meanwhile, the SNP's Ian Blackford has also written to Mr Corbyn, along with other opposition leaders, to urge him to back another referendum as Labour's official position.
And, in a letter published in the Times newspaper, more than 170 leading business figures called for Theresa May and Jeremy Corbyn to back another referendum on withdrawal from the European Union "to stop us crashing out of the EU with no deal at all".
Addressing a Leave Means Leave gathering in Westminster on Thursday evening, former UKIP leader Nigel Farage said Brexiteers should "prepare" and "organise" for the possibility of a another referendum.
"If I have to fight again against this lot... it's no more Mr Nice Guy," he said.

The PM has rejected calls to quit over her handling of Brexit, saying it is "not an issue about me".
Theresa May was replying to Tory Brexiteer Andrea Jenkyns, who said she had "failed to deliver on her promises" and had lost public trust.
Calls have been growing for the prime minister to name an exit date.
The PM's spokesman said she had already promised to leave after delivering the first stage of Brexit and was sticking to that "generous and bold offer".
Mrs May has agreed to address a meeting of the 1922 Committee - an elected body of Tory MPs which represents backbenchers and oversees leadership contests - next week.
Its chairman, Sir Graham Brady, told the BBC he had had two "very good meetings" with the PM, organised to raise concerns about her leadership.
He said it was clear she "wishes and is determined to do her best to secure our departure [from the EU]", but the 1922's executive would have the opportunity after next week's meeting "to decide if the assurances they have had [from her] are sufficient or not".
Sir Graham also said he believed the PM would ask the Commons to vote again on the terms of the UK's exit before elections to the European Parliament take place on 23 May.
The withdrawal agreement has effectively been rejected by MPs three times already.
BBC political editor Laura Kuenssberg says the prime minister has bought herself a bit more time.
In March, Mrs May pledged to stand down if and when Parliament ratified her Brexit withdrawal agreement, but she has not made it clear how long she intends to stay if no deal is reached.
Pressure has grown on her since the Tories' local election drubbing last week, and there have been warnings they face a meltdown in elections to the European Parliament too.
At Prime Minister's Questions, Mrs May said she was "very sorry" that so many councillors - 1,300, in fact - lost their seats.
But she told Ms Jenkyns the resolution to the Brexit crisis was "not an issue about me or her" - and if it was up to the prime minister, the UK would have already left the EU.
Much of the anger in the parliamentary party is focusing on Mrs May's efforts to find a Brexit compromise with Labour.
Further pressure is also coming from the grassroots, with local Tory associations confirming they will hold a vote of confidence in her leadership on 15 June.
Analysis: By BBC political correspondent Jonathan Blake
Sometimes it can seem like Theresa May is surrounded by an invisible force field, deflecting blows from all directions.
Political flaming asteroids which might've seen off a prime minister in simpler times lie smouldering on the floor as she doggedly pushes on.
A failed snap election, no confidence votes, defeat after defeat in Parliament have all left her standing somehow.
But that survival is down in no small part to factors beyond her control; nobody wanting to inherit the mess, Tories terrified of losing power to Labour, and a party increasingly ill at ease with itself.
But if something shifts then her time and her luck may run out.
A candidate to replace her could decide it's now or never, her own MPs may run out of patience entirely or the European election results may simply be too bad to bear.
Holding her hands up and walking away would not be in Theresa May's nature, but just as events have shaped her survival, they may yet lead to her demise.
The 1922 has previously rejected calls to re-write its rules to bring forward another confidence vote in the PM's leadership, meaning that at the moment, the earliest it can happen is in mid-December.
Eurosceptic Conservative MP Peter Bone said "the majority" of Tory MPs "acknowledge she needs to go and needs to go soon".
Tory Brexiteer Sheryll Murray tweeted that she believed the PM "should resign immediately".
Former minister Robert Halfon said Mrs May had to set out a "proper timetable" for departure, but it had to be done in a "dignified way".
Some Conservatives, though, think she should be allowed to stay until the autumn, if necessary, to deliver the UK's exit from the EU.
Mel Stride, financial secretary to the Treasury, said: "At end of the day - if you change the pilot, you are not going to change the weather."
Discussions with Labour could still yield a way forward, he said - although as yet, the talks have not borne fruit.
Negotiations finished on Wednesday without an agreement between the two sides, but Downing Street said there will be more talks "over the coming days".
Conservative MPs have already begun to voice their intentions to stand in a Tory leadership contest once Mrs May leaves, including new International Development Secretary Rory Stewart.
Cabinet minister Andrea Leadsom is the latest to indicate an interest, saying she is "seriously considering" standing for a second time - she ran in 2016, but pulled out to give Mrs May a clear run at the job.
The UK had been due to leave the EU on 29 March, but the deadline was pushed back to 31 October after Parliament was unable to agree a way forward.
No confidence vote of Tory MPs: Theresa May won a leadership ballot by 200 to 117 votes on 12 December 2018. Under current party rules, there can't be another vote for a further year so the PM is technically safe until 12 December this year. Many MPs want to change the rules to allow an earlier contest but this would need to be agreed by the 1922 Committee.
No confidence vote in Parliament: The PM would have to resign if she lost a confidence vote in Parliament. Labour tried this manoeuvre in December but Tory MPs and their DUP allies backed the PM. Might some Tories now withhold their support if they think it will usher in a new leader rather than a general election?
Grassroots Tory revolt: Local Conservative associations seem to be turning against the PM, with one - Clwyd South - already passing a motion of no confidence in her. The National Conservative Convention's vote on 15 June is non-binding, though, so the PM could ignore it.
Cabinet revolt: Margaret Thatcher quit in 1990 after a number of ministers told her it was time to go. Could history repeat itself? There has been no sign of that so far and colleagues who want to succeed her - and there are many - may not want to be seen to be the ones wielding the knife or to risk sacrificing their own careers.
Quits of her own accord: The BBC's Norman Smith says there is no way the PM will "walk away" right now, but this could change in the aftermath of a "catastrophic" result in European elections.

Theresa May has asked officials to draw up "revised proposals" for post-Brexit customs arrangements after a key meeting with her most senior ministers.
The Brexit sub committee met to try to agree on a new model to replace the UK's membership of the customs union.
One of the government's preferred options - a "customs partnership" - has faced heavy criticism from Brexiteers.
A succession of senior ministers challenged her over this plan in Wednesday's meeting.
Two separate sources have told the BBC that a narrow majority of ministers expressed fears about the proposal - what some have described as "killing" it.
But Downing Street denied this, saying the meeting acknowledged there were "challenges" to the existing proposals but that both the options put forward so far by the UK are still on the table.
Mrs May has now asked for more work to be done on both options.
Brexit Secretary David Davis told MPs on Thursday that both options had merits and both had drawbacks "which is why we are taking more time over them".
All EU members are part of the customs union, within which there are no internal tariffs (taxes) on goods transported between them. There is also a common tariff agreed on goods entering from outside.
The UK government has said it is leaving the EU customs union so that it can strike its own trade deals around the world, something it cannot do as a member.
This means the UK and the EU will have to agree a new arrangement for what happens at their border post-Brexit.
The UK, which put forward two alternative proposals last year, has yet to confirm its favoured model.
It is under pressure to make progress on the issue before next month's EU summit.
The EU does not appear to be keen on either option.
Earlier Mrs May told MPs there were "a number of ways" to deliver Britain's objectives on customs arrangements after Brexit.
She says the final arrangement must avoid a hard border between Northern Ireland and the Republic - which is part of the EU - and that a customs border down the Irish Sea would be unacceptable.
On the eve of the Brexit cabinet meeting, Brexiteers urged Mrs May to abandon the partnership option, presenting a 30-page dossier claiming it would make meaningful trade deals "impossible" to forge and render the UK's International Trade Department "obsolete".
BBC political editor Laura Kuenssberg
Theresa May therefore asked for more work to be done, and for revised proposals to be produced. Essentially, she told colleagues and officials to go away and come back with better ideas.
You can make your own judgement on whether that is a good thing or not. But it does mean that as things stand, the UK government, nearly two years after the referendum, does not have an agreed position on how customs will work after Brexit that has the full backing of the cabinet - let alone Parliament - and let alone the country or the rest of the EU.
That means too that the government is saying to Brussels, where demands are building for more detail: "We're still not quite ready to talk."
Three separate sources have also told me that six ministers out of the 11 on the committee expressed fears about the viability of the customs partnership - yes, the "unicorn" proposal we've discussed here before.
Those ministers included Gavin Williamson and Sajid Javid, who were both Remainers during the referendum, but neither of whom as things stand were ready to back what's thought to be the PM's preferred option.
Read the rest of Laura's blog

Theresa May has said progress has been made in talks about changes to the Brexit deal that could win MPs' backing but admitted "time is of the essence".
The PM met the EU's Jean-Claude Juncker in Brussels to discuss legally-binding guarantees over the Irish border.
Earlier, Foreign Secretary Jeremy Hunt said "small but important" changes to the backstop would allay MPs' concerns it could be trapped in a customs union.
But Home Secretary Sajid Javid said the chances of a no-deal exit had risen.
Speaking on ITV's Peston show, Mr Javid said it was "fair to say that in the past few weeks the probability of a no-deal Brexit has gone up".
The prime minister is trying to renegotiate the backstop - the insurance policy to prevent the return of physical checks on the border between Northern Ireland and the Republic of Ireland.
It is the most contentious part of the withdrawal agreement Mrs May agreed with the EU in November, which was rejected by Parliament by a large margin last month.
Critics fear the backstop - which could be activated if the two sides do not settle their future partnership by the end of 2020 and choose not to extend the transition period - would leave the UK tied to a customs union indefinitely and see Northern Ireland treated differently.
The EU has consistently said it will not reopen discussions over the withdrawal agreement agreed in November.
Mrs May said the two sides had made progress and that she had made it clear MPs would only accept guarantees that had similar legal force to the agreement.
"We have agreed that work to find a solution will continue at pace, time is of the essence and it is in both our interests that when the UK leaves the EU it does so in an orderly way," she said.
The EU said the discussions, which are also focusing on the use of technology, were constructive but the timing was "tight".
On a visit to Germany earlier, Mr Hunt warned the greatest threat to Brexit was "defeatism" over getting a deal through Parliament.
Speaking after talks with his German counterpart in Berlin, Mr Hunt said it would be a "disaster" for both sides if the UK left the EU without a negotiated agreement on 29 March.
But he said the risk of "paralysis" in the process was equally damaging to business.
Amid speculation that Mrs May could put the deal to Parliament again as soon as next week, Mr Hunt said the role of Attorney General Geoffrey Cox would be vital in the unfolding process.
Mr Cox, who will also be in Brussels for talks later this week, told MPs in December that although the agreement stipulated the backstop would be temporary and only apply until the two sides settled their future relationship, there was no way for the UK to leave it without the approval of EU member states.
MPs gave their backing for Mrs May to renegotiate the policy in a vote earlier this month although many remain unconvinced that the EU can be forced to change its position.
But Mr Hunt said the government was confident, on the basis of discussions with Conservatives and some Labour MPs, that if the issue was resolved then the deal would pass.
"The critical thing is that Geoffrey Cox needs to be able to change his advice to Parliament," he said.
"The current text uses the word temporary to describe the backstop, so what we need to do is put some flesh on the bone of what temporary actually means," he said.
"I think... with political will and conviction we can find a way to solve that problem."

Theresa May says there is a "shared determination" among EU leaders to solve the Irish border problem preventing MPs from backing her deal.
She was speaking after meetings with German Chancellor Angela Merkel and Dutch Prime Minister Mark Rutte.
The prime minister says there can be no EU withdrawal deal without a backstop plan for the Irish border.
But she said she was seeking guarantees that it would be "only temporary" to address the concerns of her own MPs.
But Labour leader Jeremy Corbyn labelled Mrs May the "runaway prime minister" and said her trip was a "waste of time and public money".
The prime minister is now in Brussels for meetings with top EU officials Donald Tusk and Jean-Claude Juncker,
Mr Tusk, President of the European Council, tweeted: "Long and frank discussion with PM Theresa May ahead of Brexit summit. Clear that EU27 wants to help. The question is how."
Angela Merkel said the deal could not be re-negotiated but she was still optimistic a solution to the Irish border issue could be found.
Critics object to the backstop - a temporary customs arrangement designed to prevent the need for checkpoints at the Irish border if a long-term solution that avoids them cannot be agreed - because it imposes different regulations in Northern Ireland from the rest of the UK.
They also object to the fact that under the terms of the withdrawal agreement, the UK can not exit the backstop without the EU agreeing.
After aborting Tuesday's planned vote on the deal, Mrs May is believed to be considering how to give the UK Parliament a vote on whether to enter the backstop - and an annual vote on whether the country should remain in it.
Ministers have suggested this could be done in an "addendum" to the withdrawal agreement, without changing the main text of it.
Speaking in Brussels, Mrs May said a backstop was "a necessary guarantee for the people of Northern Ireland".
"Whatever relationship you want with Europe in the future, there's no deal available that doesn't have a backstop within it.
"But we don't want the backstop to be used and if it is, we want to be certain that it is only temporary. And it is those assurances that I will be seeking from fellow leaders over the coming days."
Irish Prime Minister Leo Varadkar, who will welcome Mrs May to Dublin on Wednesday, said he hoped to reassure the UK without changing the fundamental substance of the withdrawal deal, including the backstop.
"Our approach is that we have a deal on the table," he told the Irish Parliament. "Our objective is to get the deal ratified by the House of Commons.
MPs have to give the go-ahead for Mrs May's deal if it is to come into effect when the UK leaves the EU on 29 March.
Downing Street has said a Commons vote will be held on the deal before 21 January and Brexit minister Robin Walker told MPs he hoped it "would be sooner than that".
Mrs Leadsom earlier suggested talks with the EU could go right down to the wire, saying: "The EU is always in a position where it negotiates at the last possible moment."
It is not clear if any changes obtained would be enough to win over Conservative Brexiteers and the Democratic Unionist Party, whose votes Mrs May relies on to win key votes in the Commons, who have called for the entire backstop plan to be dropped.
The prime minister's U-turn sparked anger among MPs on all sides, who had spent three days debating the deal and had been promised the final say on it on Tuesday.
Buzzfeed claimed Mrs May had informed some EU leaders about her plan to abandon the vote on Sunday - well before she told the cabinet.
Speaking during an emergency debate in the Commons on the government's handling of the aborted Brexit vote, Mr Corbyn said such reports were "disturbing" and urged Mrs May to "admit her deal is dead".
"What is she doing in Europe? This runaway prime minister is not even seeking to negotiate. She confirmed she is only seeking reassurances. Our prime minister is traipsing round the continent in pursuit of warm words."
Labour late won a non-binding vote criticising the government's handling of the issue by 299 to zero after Conservative MPs chose not to take part.
Meanwhile, more backbench Tory MPs are considering submitting letters of no confidence in Theresa May in the hope of toppling her and forcing a Tory leadership contest. If she was no longer Conservative Party leader she would also be expected to step down as prime minister.
So far 26 MPs have publicly said they have written such letters - 48 of them are needed to trigger a vote.
The BBC's political editor Laura Kuenssberg said senior Tories were sounding "more confident" that the threshold had been reached.
Separately, Labour is coming under pressure from the SNP, Lib Dems, Plaid Cymru and the Green Party to call a vote of no confidence among all MPs to try and bring down Theresa May's government - something that can, effectively, only be done by the main opposition party.
The Labour leader told MPs he had no confidence in the government but his party needed "to do the appropriate thing at the appropriate time" if it was to succeed in bringing it down.
By BBC political correspondent Nick Eardley
Parliament feels like a confused and sometimes angry place today. As Theresa May fights for further assurances on the backstop, many are unconvinced. Even among Conservatives loyal to her, the mood is bleak.
One Tory MP who supported the PM's deal told me they didn't have a clue what was happening now. "We're rewriting the pantomime," they added.  Another pondered: "The Conservatives made this muddle - who is going to fix it?" One minister concluded things were at "breaking point".
Brexiteers speak openly of exasperation.
One source, who has been highly critical of the plan but not the PM, told me many were changing their minds now; Mrs May is now seen as the problem.  It's not the first time we've heard such claims - and in the past they haven't materialised.
But this person said a number of Brexit backers who have resisted pressure to send in letters calling for a vote of no confidence in the PM as Tory leader have now changed their minds.
"And it's not just the usual suspects," they added.

Theresa May has insisted the jurisdiction of the European Court of Justice in the UK will come to an end with Brexit.
As the government published new details of its position, the PM said the UK would "take back control of our laws".
But critics say it will be impossible to avoid European judges having a role in enforcing new agreements drawn up with the EU.
Ministers say the two sides will keep "half an eye" on each other's rulings.
The ECJ is in charge of ensuring member states abide by EU law.
Its rulings are binding on all member states, and it also settles disputes between countries and EU institutions.
In its new policy paper, the government:
The promise to end "direct jurisdiction" in recent policy papers - a phrase not used by Mrs May - has raised questions about what "indirect" jurisdiction the EU court could be left with.
In the latest publication, about how to enforce disputes after Brexit, the government has outlined several models used by other countries that it says show there is no need for the ECJ to be the final arbiter.
But some of these involve the ECJ having an influence on the outcome of disputes, for example by interpreting EU law in a way that binds a disputes panel, or for its past rulings to be taken into account.
Today's paper does not pin the government's colours to any particular mast.
It throws out a number of possible models for how a trade agreement with the EU would work in terms of resolving disputes.
All of the models make it clear that the ECJ will no longer have sole jurisdiction over disputes.
The key question is how much influence the ECJ would retain under a bilateral agreement with the UK.
The EU will not sign up to an agreement which allows to UK to depart from EU law to the UK's advantage and the EU's disadvantage on things like state aid to companies, or emissions standards.
It will want a level playing field in trade and that will mean a lot of EU law as part of the agreement.
The reality is that the more closely the Brexit trade agreement replicates EU law, the greater the influence of the ECJ will be.
Labour leader Jeremy Corbyn said the government was "clearly backtracking on its earlier red lines and saying there has to be some form of dispute resolution through some form of judicial process".
He added: "We have said that all along."
Asked if Labour would vote against the government's key piece of Brexit legislation, the repeal bill, when MPs returned from their summer break, Mr Corbyn said: "We will make that decision just before the vote."
The pro-EU Open Britain campaign group said the government's policy paper was a "climbdown camouflaged in jingoistic rhetoric".
The group called it "frustratingly vague", adding that in almost every example it provides, the ECJ would have "substantial direct or indirect power over the proposed new relationship between Britain and the EU".
The government said it was not committing to following any of the arrangements set out, ruling out an "off the shelf" model.
And sources played down the significance of the word "direct", saying it meant ECJ rulings would no longer automatically apply to the UK and that the court would no longer be able to strike down domestic UK laws.
Asked about her government's position, Mrs May said: "What we will be able to do is to make our own laws - Parliament will make our laws - it is British judges that will interpret those laws, and it will be the British Supreme Court that will be the ultimate arbiter of those laws."
Earlier Justice Minister Dominic Raab said there would be "divergence" between UK and EU case law after Brexit, adding: "It is precisely because there will be that divergence as we take back control that it makes sense for the UK to keep half an eye on the case law of the EU, and for the EU to keep half an eye on the case law of the UK."
In response, Guy Verhofstadt, the European Parliament's lead negotiator, tweeted that the ECJ had to "keep both eyes open" to protect citizens' rights.
The ECJ's remit extends into many of the areas where the UK is hoping to draw up new arrangements with the EU, including trade and citizens' rights.
Mr Raab said "some form of arbitration" would be needed, but that this would not be akin to a European court.
Arbitration is where disputes are settled by a neutral third party. The UK and the EU could each appoint arbitrators and agree on a third, Mr Raab suggested.
The SNP said the government had accepted the UK must continue to take account of judgements from the ECJ so it now needed to "ditch their previous so-called red lines to ensure a deal can be found".
SNP External Affairs Secretary Fiona Hyslop said the best option for Scotland and the rest of the UK was to stay in the EU single market.
Liberal Democrat leader Vince Cable said Mrs May's "red lines are becoming more blurred by the day", saying the ECJ had "served Britain's interests well" and should not be "trashed".
The European Commission, which is leading the negotiations for the EU, did not comment in response to the government's publication.

Theresa May has told the BBC that MPs will have a choice between her proposed deal with the EU - or no deal at all.
She was also critical of a plan by Brexiteers to resolve the Irish border issue, saying it would create a "hard border 20km inside Ireland".
The prime minister did admit that under "no-deal there would be some short-term disruption".
Shadow Brexit secretary Keir Starmer said no-deal would be "catastrophic" and people were "too casual about it".
He told Panorama: "It's not viable. It's rhetoric, not reality, and it can't be allowed to happen."
But Mrs May said it was the government's job to "make sure we make a success of no-deal, just as we make a success of getting a good deal."
Her comments were in response to questioning about the Bank of England's governor Mark Carney's warning that a no-deal Brexit could see house prices crash by more than a third.
Meanwhile, the International Monetary Fund has said the UK economy will shrink without a Brexit deal.
In its annual assessment of the UK economy, the IMF said that all likely Brexit scenarios would "entail costs", but a disorderly departure could lead to "a significantly worse outcome".
Chancellor Philip Hammond said the government had to listen to the IMF's "clear warnings".
The UK is set to leave the EU on 29 March 2019, and negotiations between the two sides are still taking place.
Mrs May set out her proposals for the key issue of cross-border trade after a Chequers summit in July, but it has been fiercely criticised by some Brexiteers who say plans for a "common rulebook" on goods would compromise the UK's sovereignty.
Speaking to Panorama, Mrs May said that if Parliament does not ratify the Chequers plan "I think that the alternative to that will be having no deal".
BBC political editor Laura Kuenssberg said Theresa May calculated that faced with a "binary choice" of the Chequers deal or no deal, Brexiteers would not have the "chutzpah to say 'no way'" and Remainers would decide that carrying on fighting the plan would be too risky.
But the risks are that the PM cannot say for certain what the final deal will look like - and some Brexiteers were already determined not to vote for it, she added.
Mr Johnson's column in Monday's Daily Telegraph renewed his attack on the Chequers proposals and the government's plans for avoiding new border checks on the Northern Irish border.
He criticised the UK's decision to agree with the EU on the need for a "backstop" to avoid a hard border irrespective of a trade deal, saying the issue was being used "to coerce the UK into becoming a vassal state of Brussels".
Downing Street responded by saying Mr Johnson had been part of the government that signed up to the backstop plan.
In her Panorama interview, Mrs May said there needed to be "friction-free movement of goods" with no customs or regulatory checks between the UK and EU on the island of Ireland, in order to avoid a hard border there.
Last week a group of Brexiteer Tory MPs said a hard border could be avoided by using "established" technology and "modifying" existing arrangements.
Mr Johnson refers to the suggestions by the European Research Group in his column, saying that "extra checks done away from the border" would prevent the need for physical checks when vehicles move between Northern Ireland and the Irish Republic.
But Mrs May insisted that any system of checks was "still a hard border".
"You don't solve the issue of no hard border by having a hard border 20km inside Ireland," she said.
Former Liberal Democrat leader Sir Nick Clegg told BBC Radio 4's Today programme it was an "insult to the intelligence of British voters" for the prime minister to say it was a "choice between either the Chequers fudge or a cataclysmic cliff edge".
Speaking later at a fringe event at the Lib Dem conference in Brighton, Sir Nick claimed European leaders were "seeking to find some way of giving Britain more time" to avoid a no-deal Brexit.
Brexiteer Jacob Rees-Mogg told LBC the prime minister should "try a bit harder" to get a better deal.
Mrs May has found herself embattled with some in her party, after about 50 European Research Group Tory MPs openly discussed how and when they could force her to stand down as prime minister.
On Sunday Brexit-supporting Environment Secretary Michael Gove said the Chequers plan was the right one "for now".
He told the BBC a future prime minister could alter the relationship between the UK and the EU.
Mrs May will attempt to persuade EU leaders of the merits of her plans at a summit in Salzburg on Thursday.
With nearly six months to go until exit from the EU on 29 March 2019, a poll commissioned by BBC Radio 5 Live suggests that the UK remains split over whether Brexit will be positive for the UK.
According to a Comres survey, 50% of British adults feel the overall impact will be negative, whereas 41% think it will be positive.
When asked about the handling of Brexit negotiations, almost 79% of people polled thought that the government had handled them badly, and 63% thought the EU had handled them badly.
The People's Vote campaign, meanwhile, claimed a "fresh wave" of 18-year-olds becoming eligible to vote was "transforming the dynamics of the Brexit debate" because they mostly back staying in the EU.
BBC Panorama, Inside No 10: Deal or No Deal? is on Monday 17 September at 20:30 BST on BBC One as part of a week of in-depth coverage across the BBC to mark Brexit: Six Months to Go.

Theresa May says she will be a "bloody difficult woman" towards European Commission president Jean-Claude Juncker during Brexit talks.
The PM revived a line used during her Tory leadership campaign to respond to claims the two clashed over dinner.
She also declined to commit to settling the issue of expats' rights by June.
EU sources claim UK misunderstanding of the talks process, and ignorance about how Brussels works, could lead to no deal being agreed on the UK's exit.
According to German newspaper Frankfurter Allgemeine, the prime minister and Mr Juncker  clashed last Wednesday at Downing Street over Mrs May's desire to make Brexit "a success" and whether the issue of protecting the rights of expat UK and EU nationals could be agreed as early as June.
Speaking to BBC political editor Laura Kuenssberg, Mrs May said there were a lot of similarities and common ground in the two sides' positions.
She added: "But look, I think what we've seen recently is that at times these negotiations are going to be tough.
"During the Conservative Party leadership campaign I was described by one of my colleagues as a bloody difficult woman. And I said at the time the next person to find that out will be Jean-Claude Juncker."
The "bloody difficult" quote came from former Conservative chancellor Ken Clarke, who was recorded discussing her after a TV interview last year.
Asked about the German newspaper report, Mrs May said: "I don't recall the account that has been given of the meeting that took place, I think that a lot of this is Brussels gossip."
But she said that the talks would be tough and would involve either her or Jeremy Corbyn lining up for the UK against the other 27 EU leaders.
Theresa May's comment is revealing about her strength, and also her weakness. No political leader wants to be seen to be pushed around. When the UK talked tough as a member of the EU the others had no choice but to listen.
But now the UK is on the way out, the incentives for the others to pay attention - let alone do our bidding - is very different.
Refusing to be pushed around is one thing, refusing to show any sign of compromise or listen quite another.
Pressed on whether she did believe the issue of the rights of EU nationals in the UK - and Britons abroad - could be settled in June, she said: "I've always said that I want this to be an issue that we address at an early stage."
"I've always said that there are complexities to this issue and lots of details that will need to be agreed. What people want to know is to have some reassurance about their future. I believe we can give that at an early stage. I've got the will to do this," she added.
She also said she would have "no intention of doing anything other" than serving a full term until 2022 if she wins the 8 June general election.
Opposition parties have accused the Tories of pursuing a "hard Brexit" strategy, with the PM insisting no deal is better than a bad one and planning to withdraw the UK from the EU single market.
The first edition of the London Evening Standard published under the editorship of ex-chancellor George Osborne was headlined "Brussels twists knife on Brexit", with an editorial warning the PM against seeking a "blank cheque" from the EU.
Launching his party's Brexit strategy, ex-Lib Dem leader Nick Clegg said Mrs May had "chosen to pursue the most extreme and damaging form" of EU departure.
He said his party would offer another EU referendum in which it would campaign to Remain.
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Theresa May has sought to reassure world leaders that her Brexit deal is "good for the global economy".
The PM was speaking at the G20 summit in Argentina, where she has met leaders for talks on trade deals after Brexit.
She said they were "keen" to sign free trade agreements and wanted certainty, which she pledged her deal would bring.
Asked about her legacy as PM, she said there was "a lot more for me still to do, not least being the prime minister that does take the UK out of the EU".
The G20, which this year holds its summit in Buenos Aires, is made up of the 19 of the world's most industrialised nations, plus the European Union.
It accounts for 85% of the world's economic output and two-thirds of the world's population.
"For the first time in more than four decades, the UK will have an independent trade policy," she told reporters at a press conference.
"That this deal sets a path for the UK to a brighter future has been affirmed by the discussions I've had on trade over the past two days with friends and partners making clear that they are keen to sign and implement ambitious free trade agreements as soon as possible."
The summit came as another government minister, Sam Gyimah, resigned over Mrs May's Brexit deal, saying he would vote against it when the agreement goes before Parliament on 11 December.
Labour, the Lib Dems, the SNP, the DUP and many other Tory MPs have said they will also vote against it.
Asked about the situation back in the UK, Mrs May said: "The next nine days are a really important time for our country leading up to the vote on this deal.
"I will be talking with members of Parliament obviously and explaining to them why I believe this is a good deal for the UK.
"Why it is a deal that delivers on Brexit but it is also a deal that protects jobs and the economy and why passing this deal in the vote that takes place in the House of the Commons will take us to certainty for the future, and that failure to do that would only lead to uncertainty.
"What I've been hearing here at the G20 is the importance of that certainty for the future."
The Brexit deal has already been agreed between the EU and UK.
If MPs reject the deal, a number of things could happen - including leaving with no deal, an attempt to renegotiate or a general election.
By Laura Kuenssberg, BBC political editor
Asked if this might be her last overseas trip, the prime minister insisted "there's a lot more for me to do".
A senior member of the government told me not only would she not have discussions about losing the vote - only about how to win it -  but that those who believed that Theresa May would quit if her deal fell were misreading her.
They said that she would "not go until she was forced to go" and, contrary to some of the speculation in Westminster, even a heavy defeat for her plan would not automatically see her depart.
Of course, many of her critics - and the opposition parties - would beg to differ.
Mrs May held one-to-one talks with the leaders of Australia, Canada, Japan, Turkey and Chile.
The Japanese prime minister, Shinzo Abe, urged her to avoid a no-deal Brexit.
Major Japanese companies such as Nissan - which employs 7,000 people at Britain's biggest car factory in Sunderland - and Honda are concerned about the possible impact on their supply chains across Europe.
She said told him she was confident Japanese businesses in the UK would continue to trade well with the EU.
Mrs May also held talks with Australian Prime Minister Scott Morrison, who praised her "great determination on one of the most vexed issues I think there is".
The prime minister was also quizzed about her meeting with the Saudi Crown Prince Mohammed bin Salman - who she shook hands with - on Friday.
She did not say whether she had confronted him directly over the murder of journalist Jamal Khashoggi at Saudi Arabia's consulate in Istanbul in October.
"What I said to the Crown Prince yesterday was the importance of a full, credible and transparent investigation that identifies those who were involved and the importance of ensuring that those who were involved are held to account," she said.
"That is the message we have consistently given since the terrible murder of Jamal Khashoggi and it is a message we will continue to give."

Theresa May is seeking Conservative MPs' backing for the cabinet's proposal for UK-EU relations after Brexit.
The plan was agreed by the prime minister's senior ministers at a 12-hour cabinet awayday on Friday.
Mrs May said the plan "will be good for the UK and good for the EU".
But there has been unhappiness among Tory Brexiteers, with Jacob Rees-Mogg telling the BBC that when the detail emerged, it could yet be worse than leaving the EU without a deal.
Mr Rees-Mogg, leader of the European Research Group of Tory MPs, said that so far only the three page summary of the deal had been published, and he would have to wait and see the full 100-plus page document to see whether it was in line with the Conservative election manifesto, or amounted to a "punishment Brexit".
Labour leader Jeremy Corbyn said he was "not convinced" by the deal, and criticised "leaving out services from trade arrangements in the future... I've got a feeling the whole thing might start to unravel in the next few days".
All Conservative backbench MPs were invited to a briefing with the party's chief whip Julian Smith in Downing Street on Saturday, with about 40 thought to have attended.
The message from those leaving the briefing, such as Tory MP Nigel Evans, was that the proposal was for a "pragmatic" Brexit delivering on the big referendum issues of sovereignty, immigration and the national finances without harming the ability to trade quickly and freely with the EU.
Mr Evans said Mrs May would make a statement to Parliament about the plan on Monday and also address a meeting of all Conservative backbench MPs.
The plan that ministers signed up to on Friday aims to create a free trade area for industrial and agricultural goods with the bloc, based on a "common rule book".
It also supports what could amount to a "combined customs territory" for the UK and EU.
BBC political editor Laura Kuenssberg said the prime minister had "picked a side" by opting for a closer relationship with the EU than many colleagues desired - and she now had to sell it to her party and the other European leaders.
No 10, she added, hoped the new commitments would unlock the next phase of talks with the rest of the EU but it was not yet clear how many, or what kind, of objections had been raised within the cabinet.
Downing Street said the proposals marked a "substantial evolution" in the UK's position and would resolve outstanding concerns about the future of the border between Northern Ireland and the Irish Republic.
"This is a proposal that I believe will be good for the UK and good for the EU, and I look forward to it being received positively," Mrs May told the BBC.
One pro-Brexit cabinet minister told the BBC there was "no point" pushing for a vote as "we were well and truly outnumbered by 20 to seven".
The UK said it now wanted to accelerate the negotiations in an effort to secure an agreement by October, but also warned it will step up preparations for leaving on 29 March 2019 without a deal.
EU negotiator Michel Barnier, who earlier suggested the EU would be willing to shift its position if the UK relaxed some of its "red lines", tweeted to say the plans would be assessed to see if they were "workable and realistic".
The prime minister had gathered her 26 cabinet ministers together at her country residence to try to resolve differences over the shape of the UK's relations with the EU and break the current deadlock with the EU.
The main details of the Chequers statement are as follows:
Mrs May said this was an "important step" in the process of negotiating the UK's smooth exit from the EU.
"Of course we still have work to do with the EU in ensuring that we get to that end point in October. But this is good we have come today, following our detailed discussions, to a positive future for the UK," she said.
She said the proposals, to be formally published in a white paper next week, would give the UK the freedom to strike trade deals with other countries while maintaining regulatory, environmental and consumer standards.
In a letter sent to all Conservative MPs, she said she had allowed colleagues to express their views while policy was developed but "agreement on this proposal marks the point where this is no longer the case and collective responsibility is fully restored".
There is no mention in the document of either the single market or the customs union, which the UK has committed to leave after the end of a transition period in December 2020.
Under plans for a free trade zone, the UK would be committed legally to following EU law for a large part of the economy, including manufacturing and farming.
While Parliament would retain the right to diverge from EU regulations in these areas, the document makes clear that "choosing not to pass the relevant legislation would have consequences for market access, security co-operation or the frictionless border".
The document also commits the government to step up preparedness for a no-deal scenario, as one of a range of possible outcomes, "given the short period remaining before the necessary conclusion of negotiations".
The CBI employers group welcomed the proposals for a free trade area in goods which it said would provide a "confidence boost" to business.
The Federation of Small Businesses said it was "encouraging" to see an agreed negotiating position from government.
But FSB chairman Mike Cherry warned: "The reaction from the rest of the EU is crucial for there to be concrete progress when negotiations restart in just over a week's time. The clock is ticking."
Shadow international trade secretary Barry Gardiner said there was "a danger that this is a lowest common denominator plan" designed to hold the cabinet together, rather than "secure the strong negotiating position that we need with the EU".
He told BBC Radio 4's Today programme: "Once upon a time we were told 'Brexit means Brexit', now we are told it means maintaining a common rulebook for all goods, a joint institutional framework for interpreting the agreement and the UK and EU forming this combined customs territory.
"That looks very much like regulatory alignment, the ECJ (European Court of Justice) and half a customs union to me."
Scotland first minister Nicola Sturgeon said the agreement was "hopefully a step forward".
But the SNP's leader at Westminster, Ian Blackford, called the agreement "a fudge", adding: "There might be agreement, for now, in the cabinet. The EU will not buy this."
Nigel Dodds, for the Democratic Unionist Party, said:  "The government's commitment at Chequers to the political and constitutional integrity of the United Kingdom with no borders between Northern Ireland and the rest of the United Kingdom is a welcome reaffirmation of what is an absolute priority for us."
Sir Vince Cable, leader of the Liberal Democrats, said it could be the case that "Brexiteers have signed up to it knowing perfectly well that it is not going to pass the European Union and they'll then be able to blame Europe for the fact that it won't work".
Plaid Cymru MP Jonathan Edwards said: "This latest proposal continues to cherry pick certain aspects of EU membership in a way that the EU's negotiators have made perfectly clear is unacceptable. More fudge means yet more uncertainty and yet more damage to our economy."
Transport Secretary Chris Grayling, who backed Brexit in the referendum, said the deal would end free movement of people and would end the remit of the European Court of Justice in the UK - saying that UK judges always pay regards to other countries' courts, such as Canada or Hong Kong.
He added, on BBC Radio 4's Today programme, that the cabinet had agreed to step up preparations for the UK leaving the EU without a Brexit deal.
Fellow cabinet Brexiteer Andrea Leadsom also tweeted her backing for the deal.
Pro-Brexit campaign group Leave Means Leave said it would represent a "bad deal for the UK" which would "only slide further as the EU takes more and more".
Former UKIP leader Nigel Farage said the plan amounted to a "sell-out to global corporates" and would do nothing for the 90% of British firms which do not export to Europe.
Veteran Eurosceptic Tory MP Sir Bill Cash said he was "deeply disappointed to say the least" about the plans, which he suggested could contradict the terms of the EU Withdrawal Act passed by MPs last month.

Prime Minister Theresa May has suffered another Commons defeat after MPs voted down her approach to Brexit talks.
MPs voted by 303 to 258 - a majority of 45 - against a motion endorsing the government's negotiating strategy.
The defeat has no legal force and Downing Street said it would not change the PM's approach to talks with the EU.
But Labour leader Jeremy Corbyn urged Mrs May to "admit her Brexit strategy has failed" and to come forward with a plan Parliament would support.
The defeat came after the pro-Brexit European Research Group (ERG) of Conservative MPs announced it had taken a "collective decision" to abstain, because backing the motion would have amounted to an endorsement of efforts to rule out a no-deal Brexit.
Mrs May has consistently rejected calls to rule out a no-deal Brexit, but Tory Brexiteer rebels believed the wording of what was meant to be a neutral government motion opened the door to that.
The motion reiterated support for the approach to Brexit backed by MPs in votes last month, one of which ruled out a no-deal Brexit.
The voting figures showed it was not just hardline Brexiteers that failed to support the government - a number of Tory Remainers also declined to vote, as more than a fifth of the party in the Commons failed to back the government.
Five Conservative MPs - Brexiteers Peter Bone, Sir Christopher Chope, Philip Hollobone, and Anne Marie Morris, and the pro-Remain Sarah Wollaston - even voted with Labour against the motion.
Downing Street blamed Mr Corbyn for the defeat, saying he had "yet again put partisan considerations ahead of the national interest" by voting against the government's motion.
A No 10 spokesman said the PM would continue to seek legally-binding changes to the controversial Irish backstop, as MPs had instructed her to do in a Commons vote on 29 January.
"While we didn't secure the support of the Commons this evening, the prime minister continues to believe, and the debate itself indicated, that far from objecting to securing changes to the backstop that will allow us to leave with a deal, there was a concern from some Conservative colleagues about taking no deal off the table at this stage," he added.
Plasters lose their stick, revealing the hurt underneath. And the fragile patch that was covering the Tory truce has been well and truly torn.
Just when Theresa May wanted to show the European Union that she could hold her party together to win, she lost.
And at home the prime minister has been shown in no uncertain terms that she simply can't count on the factions in her party to come through for her.
Downing Street had earlier warned that defeat could damage the prime minister's negotiating position, as she seeks to make changes to the controversial backstop "insurance policy" in her deal to avoid customs checks between Northern Ireland and the Republic of Ireland.
ERG deputy chairman Steve Baker told BBC News the group still supported efforts to get "alternative arrangements" to replace the controversial Irish backstop plan, describing Mrs May's defeat as a "storm in a teacup".
But business minister Richard Harrington said ERG members should join former UKIP leader Nigel Farage's new Brexit party, telling them: "In my view you're not Conservatives."
In an interview with The House magazine, he urged ministers opposed to a hard Brexit not to "give in" to the ERG by resigning.
He also said he was "disappointed" that Mrs May had not made a statement to the Commons today, and given MPs an outline of a revised deal to vote on.
"We're now told it will be in another two weeks' time so, being very conscious of the damage that not ruling out a hard Brexit is having on business and industry, I'm concerned that it's going to drag on.
"What concerns me most is there is now talk that there won't be a final decision until the next EU Council on 21 March which, as far as business is concerned, is completely unacceptable."
By BBC Europe editor Katya Adler
EU leaders still believe this is not the time to budge.
They see the UK arguing, debating and negotiating with itself again - as it has done so often during the Brexit process - rather than engaging with Brussels.
As a result of all this, the new round of EU-UK negotiations are going nowhere fast.
"Window-dressing" is how one senior EU figure described the talks to me - with each side simply repeating their red lines to the other.
So, the current favourite prediction in Brussels is that things will only be resolved in March.
Read Katya's blog
Commenting on Mrs May's latest defeat, Jeremy Corbyn said: "Two weeks ago, the prime minister told Parliament that her new approach could 'secure a substantial and sustainable majority' in Parliament.
"However, tonight's vote has proved that there is no majority for the prime minister's course of action.
"This can't go on. The government can't keep ignoring Parliament or ploughing on towards 29 March without a coherent plan."
He added that the PM needed to admit her strategy had failed "and come back with a proposal that can truly command majority support in Parliament".
Pro-EU Conservative MP Anna Soubry said: "The prime minister has been dealt yet another body blow. This is really serious stuff.
"What is happening is a profound lack of leadership from the very top of government."
She said it was "chilling" that ministers were still keeping no-deal on the table when they had seen economic analysis showing that it would be "absolutely disastrous" for the country.
"What an absolute fiasco this is," she added, blaming a "lack of leadership in both of our broken parties".
Mrs May has promised MPs a final, decisive vote on her Brexit deal with the EU when she has secured the changes to it that she believes MPs want to see.
She believes she can secure a Commons majority for the deal if she can get legally binding changes to the backstop clause - something the EU has consistently ruled out.
A Labour amendment calling for the final, meaningful vote to be held before 27 February was earlier defeated by 16 votes.
An SNP amendment, backed by the Liberal Democrats and calling for Britain's departure from the EU on 29 March to be delayed by three months, was defeated by 93 votes to 315 after most Labour MPs abstained.
Anna Soubry withdrew an amendment calling on the government to publish the latest cabinet briefing on the economic impact of a no-deal Brexit after ministers agreed to meet her and publish relevant documents. Ms Soubry said she would table it again on 27 February if ministers did not keep to their promise.
Brexit Secretary Steve Barclay had pledged to call the EU's chief negotiator Michel Barnier after the vote to discuss the result. The two men are set to resume talks in Brussels early next week.

Theresa May has said the EU must "evolve" its stance on the Irish border as she seeks to persuade fellow leaders about the viability of her Brexit plan.
The PM is using a dinner in Salzburg to make the case for her controversial Chequers strategy for future relations.
Before the event, she said it was the only credible plan to allay concerns on the Irish border and trade disruption.
Austrian chancellor Sebastian Kurz, who is hosting the event, said both sides needed to make compromises.
The UK and EU both want to avoid a hard border - meaning any physical infrastructure like cameras or guard posts - between Northern Ireland and the Republic of Ireland but can't agree on how.
Mrs May has previously rejected the EU's "backstop" plan - which involves keeping Northern Ireland aligned with its trading rules - saying it would divide up the UK.
Ahead of the Salzburg summit, the EU's negotiator Michel Barnier said most checks could take place away from border areas, an apparent concession to the UK.
Addressing reporters as she arrived for dinner in the Austrian city, Mrs May welcomed what she said was the EU's recognition its initial proposal were "unacceptable".
"If we're going to achieve a successful conclusion then, just as the UK has evolved its position, the EU will need to evolve its position too," she said.
After Brexit, the 310 mile border between Northern Ireland and the Republic of Ireland will become the UK's border with the EU.
At the moment, thousands of people cross it every day for both work and pleasure - as do goods, like food and medicines, being delivered across the two countries.
As part of the EU single market and customs union, these products do not need to be checked for customs and standards, but when the UK leaves these two arrangements, this all changes.
Nobody wants a hard border for the checks - in fact the 1998 Good Friday agreement, which helped bring peace to Northern Ireland, got rid of security checks as part of the deal, and police in Northern Ireland have warned reinstating them could make crossings targets for violence.
But there is no agreement between the UK and EU, or between Leavers and Remainers, about the answer.
Privately, EU officials say those checks could be carried out by British or EU officials, or by health inspectors rather than customs officials, to "de-dramatise" the border issue.
Mrs May has insisted there needs to be "friction-free movement of goods", with no customs or regulatory checks, between Northern Ireland and the Republic, in order to avoid a hard border there.
There are just over six months to go before the UK is due to leave the EU on 29 March 2019.
Negotiations are at a critical stage, with both sides hoping for an agreement on the terms of the UK's withdrawal and future trade relations by the start of November at the latest.
Speaking on Tuesday, Mr Barnier said the talks were in the "home straight" but there were still significant areas of disagreement - such as on the role of the European Court of Justice in enforcing the withdrawal agreement and intellectual property issues, including geographical protections for food and drink.
"October is the key point in time - it is the moment of truth," he added.
The EU is still insisting on its own "legally operationally backstop" - what it describes as an insurance policy to prevent the return of physical infrastructure on the border in the event no other solution can be found.
Brussels put forward a proposal in February that would see Northern Ireland stay aligned with the EU in key areas, effectively staying in the customs union and single market and not needing those border checks.
But the UK insisted this was unacceptable as it would split Northern Ireland off from the rest of the UK.
On Tuesday Mr Barnier said the backstop should focus on a "set of technical checks and controls" to make sure standards are met and customs are paid, and not be about a sea or land border.
"We are ready to improve this proposal," he said.
"Work on the EU side is ongoing. We are clarifying which goods arriving in Northern Ireland from the rest of the UK would need to be checked and where, when and by whom these checks could be performed.
"We can also clarify that most checks can take place away from the border at a company premises or at the markets."
BBC Northern Ireland business editor John Campbell said that the fact the EU was prepared to "improve" the language of the backstop was not news as it had been talked about before - so "we need to wait and see what any improvements might amount to".
Speaking in Salzburg, Mr Tusk confirmed a special EU summit dedicated to Brexit would take place in mid-November.
He welcomed some elements of the Chequers proposals - on security and policing - but said that on the Irish border and economic cooperation they will need to be "reworked and further negotiated".
At the dinner in Salzburg, Mrs May is expected to appeal for "goodwill and determination" from the EU, while stressing that "no other country" could accept the EU's backstop plan if they were in the same situation.
The UK put forward rival backstop proposals in June, which would see the whole of the UK staying in a customs union with the EU after the end of the proposed Brexit transition period in December 2020.
It also says its Chequers blueprint for a future trading relationship - involving a "common rulebook" for goods and treating the UK and the EU as a "combined customs territory" - would solve the border question.
Brexit Secretary Dominic Raab said the EU had to move closer to the UK's position or it would be a "lose-lose" for both sides.
"Chequers may not be perfect, but it's the most credible plan," he told LBC Radio.
"I think there is an understanding that we're approaching the endpoint of these negotiations, and there will need to be some movement on the EU side."
In an interview with the Daily Express, Mrs May said that going back on the 2016 vote to leave the EU would "destroy trust in politicians".
MPs had decided to give people a vote on EU membership by a large margin, she said: "People weren't saying it's the choice of the public except if we disagree with the answer we'll ask them again."
The People's Vote campaign wants the final terms of Brexit to be put to a referendum with the option of staying in the EU if it is rejected.
"My answer to the People's Vote is that we've had the people's vote - it was the referendum - and now we should deliver on it," the prime minister said.
On Tuesday People's Vote set out ways they said a new referendum could be achieved through votes in Parliament.

Theresa May has indicated she will fight a proposal to give residency rights to EU citizens during the transition period after Brexit.
She said there had to be a difference between those arriving after the UK leaves and those who came before.
She also sought to reassure Tory MPs worried about the length of transition.
The European Parliament's Brexit lead, Guy Verhofstadt, responded by tweeting:  "Citizens' rights during the transition are not negotiable."
He said that "for the transition to work" there could not be "two sets of rights for EU citizens".
And Labour leader Jeremy Corbyn said he opposed the PM's move, which he said would make it "harder for all of us" if it made it harder for EU nationals to come and work in the NHS.
Asked whether he believed he thought Mrs May had bowed to pressure from Brexiteers, the UK opposition leader said: "I think Theresa May is probably looking behind herself all the time.
"What she needs to be concentrating on is protecting jobs and ensuring we have good, tariff-free relations with Europe in the future."
The transition period - also referred to as an implementation period - is seen as a way to minimise disruption when the UK leaves the EU for things like business, holidaymakers and security.
Earlier this week, the EU set out what it was prepared to offer the UK, saying it expected the transition to last from the day of the UK's departure on 29 March 2019 to 31 December 2020.
Some Brexit-supporting MPs are worried that this period could be extended, but speaking during her trade trip to China, Mrs May insisted such an "implementation period" would last about two years.
"We are not talking about something that is going to go on and on... we're leaving the European Union. There is an adjustment period for businesses - and indeed government - for changes that need to be made," she said.
BBC political correspondent Iain Watson
Theresa May has been under pressure from pro-Brexit backbenchers to address the question of citizens' rights. They argue that the EU has accepted full citizens' rights would only apply to people who are here before Brexit on 29 March, 2019.
But the EU says arrangements during the transition period have to be negotiated separately and wants full rights to extend until December 2020.
The PM is saying no - it's an important principle that people who arrive during transition are treated differently. In practice, though, the only difference during transition would be that EU citizens arriving then would have to register that they are here.
But government sources say that what rights they have after transition has to be a matter for negotiation. For example, if there's a new system that requires visas or work permits, they may have to apply for one.
In December, the two sides agreed a deal setting out the proposed rights of EU citizens in the UK and British expats on the continent after Brexit.
It says that all EU nationals who have been in the UK for more than five years will be expected to be granted settled status, giving them indefinite leave to remain with the same access to public services as now.
Those who have been resident for a shorter period but who arrive before the Brexit cut-off date, currently expected to be 29 March, 2019, will also be able to stay and get settled status once they have been in the UK for five years.
At the time, Downing Street said it envisaged anyone arriving after Brexit being able to continue to live, work and study in the UK during the transition period but that they would need to register, and the future immigration rules would have to be agreed as part of the wider transition negotiations.
But the EU has since said it expects existing rules on freedom of movement - including the path to permanent residency - to apply in full until the end of the transition phase, which is currently expected to be 31 December 2020.
Mrs May, who is on the second day of a three-day trade trip to China, said she would contest the issue of long-term residency rights when transition negotiations begin in earnest next month.
"When we agreed the citizens' rights deal in December we did so on the basis that people who had come to the UK when we were a member of the EU had set up certain expectations," she said.
"It was right that we have made an agreement that ensured they could continue their life in the way they had wanted to - now for those who come after March 2019 that will be different because they will be coming to a UK that they know will be outside the EU.
"I'm clear there is a difference between those people who came prior to us leaving and those who will come when they know the UK is no longer a member."
The BBC's political editor Laura Kuenssberg, who is travelling with the prime minister, said Mrs May was showing she was willing to push back against the EU amid discontent on the Conservative benches.
But Mrs May is also under pressure from pro-European Conservative MPs who want to maintain close ties with the EU.
Speaking to the Today programme, former chancellor George Osborne questioned whether the prime minister had a Commons majority to leave the EU customs union.
Mr Osborne, who has criticised the prime minister several times since leaving front-line politics, also said an increasing number of Tory MPs were now considering whether the UK should be in the European Free Trade Association, like Norway and Switzerland.
Ministers have already said the UK has to leave the customs union and single market as part of Brexit.
Meanwhile, government analysis has emerged suggesting the cost of cutting EU migration would be much greater than the benefits of a US trade deal.
BuzzFeed News has claimed government studies on the economic impact of Brexit say reducing migration from the bloc into the UK would nullify the benefits of any trade deal struck with Washington.
Ministers agreed on Wednesday to let MPs see another leak from the same impact analysis which suggests the economy would be worse off as a result of a number of possible Brexit scenarios.
Asked about the latest Buzzfeed report in the Commons, Brexit Minister Suella Fernandes said the document was not government policy, and "comes with significant caveats".

Prime Minister Theresa May is writing to the EU to formally ask for Brexit to be postponed.
One ministerial source told the BBC the longer delay could be up to two years, amid reports of a cabinet row, but No 10 said no decision had been made.
EU Brexit negotiator Michel Barnier said the EU would not grant a delay without a "concrete plan" from the UK about what they would do with it.
Under current law the UK will leave the EU with or without a deal in nine days.
MPs rejected the withdrawal deal Mrs May has negotiated with the EU for a second time last week by 149 votes. They also voted in favour of ruling out leaving the EU without a deal, and in favour of extending the Brexit process.
The prime minister had hoped to have another try at getting MPs to back the deal this week - but Speaker John Bercow effectively torpedoed that with his surprise intervention on Monday.
She still hopes to ultimately get it in front of MPs for a third go, but says even if that happens and they vote in favour of it, the UK will need a short extension to get the necessary legislation through Parliament.
A cabinet source told the BBC she therefore plans to ask the EU to agree to postpone the UK's departure until 30 June, but with an option of a longer delay as well.
Mrs May has warned Brexiteer Tories that a longer extension will be needed if her deal does not get through Parliament.
One ministerial source told the BBC's Laura Kuenssberg there was "no agreement" around the cabinet table when a delay was discussed.
Another cabinet source said they were frustrated that the PM had not been clear about which delay option she would be arguing for.
Commons leader Andrea Leadsom is said to have criticised colleagues, saying they now amounted to a "Remain cabinet", not a "Brexit cabinet".
Chancellor Philip Hammond said ministers all wanted the "shortest possible delay" but cabinet members "have different approaches to how we should do this".
Any delay will have to be agreed by all 27 EU member states and Mrs May is heading to Brussels on Thursday to discuss the options with fellow leaders.
Meanwhile, former Prime Minister Tony Blair, who campaigned to remain in the EU, told BBC Newsnight that the question of whether to have another referendum was "for a later time".
Although leaving without a deal was still the default position, Mr Blair said a no-deal Brexit "won't happen", adding that the challenge now was making any extension to Article 50 count.
Mr Blair called for a delay of between nine months and a year to "allow Parliament to reach a conclusive opinion on the central Brexit question - soft or hard?"
On Monday, the Speaker said he would not allow a third "meaningful vote" in the coming days on "substantially the same" motion as MPs rejected last week.
Mr Bercow declined to discuss the reasons for his decision when questioned by the BBC, as he made his way in to Parliament the following day.
Brexit Secretary Stephen Barclay suggested a third vote on the Brexit deal could take place next week - after Mrs May has sought a delay.
On Mr Bercow's ruling, he said it was important to "respect the referee" and abide by his decisions - but, he added, the Speaker himself had said in the past that if Parliament was guided only by precedent then "nothing ever would change".
Mr Barclay suggested that MPs would "find a way" to get another vote, if the government manages to persuade enough of them, including the 10 Democratic Unionists, to change their mind and back the deal.
At a news conference in Brussels, Mr Barnier said it was up to the 27 EU leaders to decide whether to grant a delay, based on what was in the "best interest" of the bloc.
But for a longer delay "there needs to be a new event" or a "new political process" - so that "we are not back in the same situation as today".
"Extending the uncertainty without a clear plan would add to the economic cost for our business but will also incur a political cost for the EU," said Mr Barnier.
"It is for the British government and Parliament to decide very quickly what the UK wants to do next."
Mr Barnier also warned that UK MPs voting against "no deal" would not prevent it from happening, saying that "everyone should now finalise all preparations for a no-deal scenario".
BBC Europe editor Katya Adler said the EU had "little trust" in the prime minister, with some leaders wanting to see proof from Parliament that MPs would support a longer delay before the EU signed up to it.
She said there was "irritation" that those at Westminster appeared to be "inward-looking" and were not taking into account the cost of a delay to the EU.
And she said the EU's final decision on a delay may not be given this week, with talk of an emergency summit on 28 March.
Earlier, German Chancellor Angela Merkel said she would struggle until the last possible moment to achieve "an orderly Brexit", saying the interests of Germany, Britain and the EU were at stake.
Taoiseach (Irish PM) Leo Varadkar and European Council president Donald Tusk released a joint statement after their meeting in Dublin.
"They agreed that we must now see what proposals emerge from London in advance of the European Council meeting in Brussels on Thursday," it said.
Labour leader Jeremy Corbyn said the Speaker's intervention showed Mr Bercow was "ensuring Parliament is taken seriously".
He said he had spoken to Conservative and Labour MPs about a so-called Norway-Plus style of future relationship with the EU - a closer one than Mrs May's deal would bring about - calling it an "interesting idea" which had not got his "complete support".
When asked about another referendum, he said: "The issue has to be put to the people after Parliament has made some kind of decision."
He said a public vote had to be on a range of options, saying: "It cannot just be on Theresa May's deal or Remain - there has to be some choice for the people."
Mr Corbyn also held "constructive" talks with the Westminster leaders of the SNP, Liberal Democrats, Plaid Cymru and Green Party about the potential to unite around a closer future relationship with the EU, a Labour spokesman said.
But Liz Saville Roberts, Plaid Cymru's Westminster leader, suggested the Labour leader had not really engaged during the meeting with the case for giving the public the final say on Brexit.
"We were there to talk about a People's Vote and the only thing I felt he was comfortable talking about was Labour's version of Brexit," she said.

Theresa May is now thought to be in favour of giving MPs a vote on alternatives to her plans when they debate her Brexit deal.
The prime minister was previously thought to be against this idea.
But sources have told the BBC she wants the "meaningful vote" planned for the third week of January to be a "moment of reckoning" for Brexit.
It comes as the cabinet announced it was stepping up preparations in case there is a no-deal Brexit on 29 March.
The votes would be on amendments to the motion on her Brexit deal - and would take place before the key vote on her plan.
The Brexit deal Theresa May has reached with the EU has to be passed by Parliament but most MPs - including many on her own side - are against it.
She had been planning to present Parliament with a choice between her deal and no-deal, hoping that enough MPs would swallow their objections and get behind her version of Brexit.
But MPs are showing few signs of changing their minds - with some hoping that the next step after her deal being rejected would be leaving without a deal, others hoping for a fresh referendum and some backing alternative deals like the ones Norway or Canada have with the EU.
So rather than wait for what seems like an inevitable defeat, she is thought to be planning a new approach.
The prime minister does not believe any of the factions criticising her plan have enough support to get their own version of Brexit through Parliament.
By allowing them to put forward their proposals and vote on them, she is hoping they will be defeated and her plan will emerge by a process of elimination as the best and only alternative to leaving without a deal.
By BBC Deputy Political Editor John Pienaar
On all sides at Westminster, MPs feel sure her plan is doomed to defeat.
Many - including some in her own Cabinet - want other ideas: a Norway-style Brexit which leaves the UK closely tied to the EU, say, or a referendum, or no deal, put to MPs after that happens.
The prime minister's formula might flush out those who are quietly waiting for her plan to fail before offering their own ideas as a solution.
She wants, in effect, a moment of reckoning for Brexit, with all the rival outcomes debated and voted upon when MPs discuss and decide on her plan next month.
If MPs reject every plan - and that is possible - she might just be able to continue the fight for her own.
Several cabinet ministers have publicly suggested alternative next steps if Mrs May's plan is rejected.
At a marathon cabinet meeting earlier:
Mrs May was originally planning to put her plan to a Commons vote last week but pulled it at the last minute over fears it would be defeated, sparking widespread outrage among MPs.
"Last time, for one reason or another, people only set out what they opposed. Next time could be an opportunity for people to set down what they support - and vote on it,"  a senior source close to Mrs May said.
Downing Street is also hoping to get more reassurances from Brussels that any outcome that keeps the UK tied to EU rules - as part of measures to ensure there is no return to a physical Northern Ireland border, will be temporary.

EU leaders will meet at 17:00 BST for an emergency summit in Brussels to decide whether to offer the UK another delay to Brexit.
Theresa May wants to postpone the UK's exit beyond this Friday, until 30 June.
But the EU is expected to offer a longer delay, after European Council President Donald Tusk urged the other 27 leaders to back a flexible extension of up to a year - with conditions.
Mr Tusk added that "neither side should be allowed to feel humiliated".
Leaders will begin arriving at the summit from 16:00.
Earlier, Mrs May appeared in the Commons for the weekly question session with opposition leader Jeremy Corbyn at Prime Minister's Questions.
That head-to-head followed five days of talks between the government and Labour officials aimed at breaking the Brexit impasse.
The 1922 Committee - made up of Tory backbench MPs - will also meet at 17:00, with some members seeking a firm date for Mrs May to step down as leader of the party.
The UK is currently due to leave the EU at 23:00 BST on Friday, 12 April.
If no extension is granted, the default position would be for the UK to leave on Friday without a deal.
So far, UK MPs have rejected the withdrawal agreement Mrs May reached with other European leaders last year.
But the Commons has also voted against leaving in a no-deal scenario.
To prevent this happening, a group of backbench MPs managed to get a bill through Parliament to force Mrs May to ask for an extension to Article 50 - the process that defines the UK exit date - by law.
Mrs May will ask EU leaders to extend the exit date until 30 June.
BBC political editor Laura Kuenssberg said the PM had to convince EU leaders about the credibility of talks with Labour and prove they were "a genuine political plan that has a chance of getting the UK out of this maze".
Every EU member state needs to agree on any delay before it can be granted.
So, at the summit - which begins at about 18:00 local time (17:00 BST) on Wednesday evening - Mrs May will formally present her case for a short delay, with the option for the UK to leave earlier if her Brexit deal is ratified.
The other EU leaders will then have dinner without her and discuss how to respond.
EU Council President Donald Tusk and European Commission President Jean-Claude Juncker are expected to make statements afterwards.
In a formal letter to the leaders on the eve of the summit, Mr Tusk proposed a longer, flexible extension - although "no longer than one year" - to avoid creating more cliff-edge extensions or emergency summits in the future.
Any delay should have conditions attached, he said - including that there would be no reopening of the withdrawal agreement talks. And the UK would have the option to leave earlier if a Brexit deal was ratified.
Referring to Mrs May's proposal for an extension until the end of June, Mr Tusk said there was "little reason to believe" that Mrs May's deal could be ratified by then.
And if the European Council did not agree on an extension at all, "there would be a risk of an accidental no-deal Brexit", he added.
Mr Tusk also warned that "neither side should be allowed to feel humiliated at any stage in this difficult process".
EU officials have also prepared a draft document for the leaders to discuss at the summit - but the end date of the delay has been left blank for the EU leaders to fill in once deliberations have ended.
BBC Europe editor Katya Adler said the blank space showed EU leaders were still divided on the issue.
BBC Europe correspondent Kevin Connolly said "much has been spelled out in advance", including the condition that if the UK remains a member of the EU at the end of May it will have to hold elections to the European Parliament or be forced to leave immediately.
He added that, during the delay, the UK would be expected to commit to not disrupting EU business, such as the preparation of the next budget, and its influence "would be sharply reduced and its voice muted".
Brexit Secretary Stephen Barclay said neither he nor the PM wanted to see a longer extension, but it was a possibility because MPs had not backed Mrs May's deal.
But others have called for the UK to leave the EU on Friday without an agreement.
Tory Brexiteer Anne Marie Morris told BBC News that exiting on World Trade Organisation rules - the default if the UK leaves without an agreement - was "actually a very good deal" for the country.
Other Leave-supporting backbenchers are seeking an exit day for Mrs May, after she vowed to step down ahead of the second phase of Brexit negotiations.
Former Conservative leader Iain Duncan Smith said although the PM had "hinged" her resignation on MPs supporting her deal, the "reality" is her "firm date of departure" should be in May or June.
"To have a leadership contest in the Conservative Party is going to take the better part of 10 to 11 weeks, and that will take you to the autumn, so this thing is going to have to happen," he told the BBC.
But some in Westminster back a longer extension, saying it would give time for another referendum to take place.
The People's Vote campaign held a rally on Tuesday to drum up support, with former Speaker of the House, Baroness Boothroyd, calling for a public ballot.
Talks between Labour and the Conservatives are scheduled to resume after Mrs May returns from the summit.
The Brexit Secretary, Stephen Barclay, said holding talks with the opposition was "contrary to the normal tradition", but they were taking place "in good faith".
A Labour spokesman said the discussions were being conducted "in a serious, detailed, and engaged way", but they had "yet to see clear evidence of real change and compromise that would be necessary to find agreement".
If the two sides do not come to an agreement, the PM has said she will put a number of options on a way forward to Parliament and make the votes binding.

The UK's trade union movement chief has told Theresa May to "stop playing to the bad boys at the back of the class" over Brexit and "start listening".
Frances O'Grady said she did not get the workers' rights guarantees she wanted in a meeting with the PM.
The UK's most senior union leaders met Mrs May to urge her to rule out a "no deal" Brexit and extend negotiations.
Mrs May is seeking support for her Brexit deal ahead of a crucial Commons vote on Tuesday.
Labour leader Jeremy Corbyn has refused to join the talks until Mrs May rules out the UK leaving the EU with no deal, which he says would bring "chaos" to the country.
The UK is due to leave the EU at 23:00 GMT on 29 March.
Mrs May met Ms O'Grady, Unite leader Len McCluskey, Tim Roache of the GMB and Dave Prentis of Unison at Downing Street on Thursday.
TUC General Secretary Ms O'Grady said workers were worried about their jobs and needed reassurances about their future.
"We have a prime minister on a temporary contract - she cannot bind the hands of a future prime minister," she said.
"People wanting her job are on record as saying Brexit is an opportunity to reduce workers' rights.
"The prime minister, frankly, has to stop playing to the bad boys at the back of the class and start listening to where I think Parliament is, which is wanting no deal off the table and more time for genuine talks to take place."
Unite union leader Mr McCluskey, a close ally of Jeremy Corbyn, said he was "not full of optimism" after his meeting with Mrs May.
But he said the talks had been a chance to "re-emphasise" that a no-deal Brexit would be "disastrous".
"Is this just a PR stunt for the media… or this a genuine attempt to see if we can talk about issues that matter to us?," he said.
"Warm words are one thing but action is needed."
He said a nine-month delay to Article 50 -  the process taking the UK out of the EU at the end of March - would be "too long", but he would like an extension of three months.
And he said Mr Corbyn was "correct" not to hold Brexit talks with Theresa May because leaders from other parties, such as the SNP and the Lib Dems, had been made to look "rather stupid" for doing so.
It was different for union leaders, he added.
Unison leader Dave Prentis said he believed it to be "in everyone's interest" that Article 50 was extended and urged Mrs May to stop "appeasing the right wing" of her party while Mr Roache also asked for an extension but added that "most important of all" was ruling out the prospect of a no-deal Brexit.
Mrs May is hoping to tweak her deal to address concerns about the "backstop" among her own backbenchers and Northern Ireland's Democratic Unionist Party, which she relies on to keep her in power, ahead of another vote on her proposed way forward next Tuesday.
The backstop is the "insurance policy" in the withdrawal deal, intended to ensure that whatever else happens, there will be no return to a visible border between Northern Ireland and the Irish Republic after the UK leaves the EU.
Both the UK and the EU believe that bringing back border checks could put the peace process at risk but critics say the backstop keeps Northern Ireland too closely aligned with the EU and separate from the rest of the UK - and that the UK could be permanently trapped in it.
However Irish PM Leo Varadkar said the UK would find it "very difficult" to do trade deals after Brexit, if it has not resolved the Irish border issue.
Mrs May has not ruled out the prospect of the UK leaving the EU without a deal and has said the only way to prevent it is to leave with her deal.
But Business Minister Richard Harrington spoke out against a no-deal Brexit, at a meeting of business people at the German embassy on Thursday.
He said: "Crashing out is a disaster for business… Airbus is correct to say it publicly and I'm delighted they have done so."
He said he was "happy" to continue in his role, but added: "I quite understand if the prime minister thinks I'm not the right person to be business minister."
A number of MPs are proposing amendments putting forward alternative plans to the PM's deal with the EU - including seeking an extension to the UK's exit date.
Labour MP Yvette Cooper has tabled one that would give time for a bill to suspend the Article 50 process for leaving the EU to the end of the year if a new deal has not been agreed with Brussels by the end of February.
It is is backed by several Remainer Conservatives and is the only amendment that would be legally binding on the government, if passed.
Her Labour colleague, Rachel Reeves, has also tabled an amendment to extend Article 50.
Other amendments would ask the government to consider a range of options over six full days in Parliament before the March deadline, to set up a "Citizens' Assembly" to give the public more say or to insist on "an expiry date to the backstop".
Plans by a group of Tory and Labour MPs to table an amendment on another EU referendum have been dropped, but the Lib Dems will be tabling an amendment calling for a "People's Vote".
It will be up to Speaker John Bercow to select amendments to put to the vote.
Shadow Chancellor John McDonnell told the BBC's Hardtalk he believes it is "highly likely" Labour's front bench will support Ms Cooper's amendment but that it first had to go through the party's  "normal process". Party leader Mr Corbyn said the decision had not yet been made.
The EU's chief Brexit negotiator Michel Barnier reiterated on Germany's Deutschlandfunk radio that there can be no time-limit on the proposed backstop.
"If nothing moves, if no positive suggestions are put on the table, then we will be heading for a more or less bumpy or accidental no-deal on 30 March," he said.
Mr Barnier also played down suggestions that the two-year Article 50 process ought to be extended, saying: "I personally believe that we do not need so much more time, but that we now need to make decisions, to be taken by the British government and the Parliament of Great Britain."

Prime Minister Theresa May will return to Brussels later to continue Brexit talks with the European Union.
She is trying to renegotiate the Irish backstop - the insurance policy to prevent the return of customs checks on the Irish border.
Mrs May is expected to request legally-binding assurances that the backstop will not extend indefinitely.
However, European Commission President Jean-Claude Juncker has said he does not expect a "breakthrough" in talks.
The backstop policy is part of the withdrawal agreement Mrs May agreed with the EU, and became one of the main reasons her Brexit deal was voted down in Parliament in January.
Critics fear it would leave the UK tied to a customs union with the EU indefinitely and see Northern Ireland treated differently.
MPs gave their backing for Mrs May to renegotiate the policy in a vote earlier this month and said she was "working hard to secure the legally binding changes" that Parliament wants.
But the EU has consistently refused to make changes.
Chancellor Philip Hammond said on Tuesday evening the government accepted the EU will not agree to replace the backstop arrangements for the Irish border with technological alternatives in time for the scheduled date of Brexit on 29 March.
The so-called "Malthouse Compromise" - proposed by Remainers and Leavers - included proposals to use technology and checks away from the border to ensure the backstop was never activated.
But Mr Hammond said he hoped the technological solution would form part of negotiations over the following 21 months on the UK's future relationship with the EU.
He added that legally-binding changes to ensure the backstop does not become permanent "would deliver the core of a majority for a deal in the House of Commons".
Leading Brexiteers Jacob Rees-Mogg and Steve Baker insisted they were happy with this arrangement, saying the Malthouse proposals were "alive and kicking".
Jeremy Corbyn also announced he would be going to Brussels to meet the EU's chief negotiator, Michel Barnier, on Thursday.
The Labour leader said they would discuss his party's Brexit proposals - including a permanent customs union and a strong relationship with the single market - and that it was a "necessity" to take no deal off the table.
Brexit Secretary Stephen Barclay updated the Cabinet on talks with Mr Barnier on Tuesday.
The meeting, on the issue of the Irish backstop, was described as "productive" but Mr Barnier "expressed concerns".
At the time, a European Commission spokesman said: "The EU27 will not reopen the withdrawal agreement.
"We cannot accept a time limit to the backstop or a unilateral exit clause - and further talks will be held this week to see whether a way through can be found that would gain the broadest possible support in the UK parliament and respect the guidelines agreed by the European Council."
The PM has promised that if she is unable to negotiate an amended deal by 26 February then she'll return to Parliament and allow a further day of debate, with further chances for MPs to vote, the following day.

Theresa May is trying to "run down the clock" and minimise Parliament's role in Brexit, a former minister has said.
Jo Johnson - who resigned as transport minister over the PM's handling of negotiations - said MPs should be given a vote on her Brexit deal next week.
His comments come as Foreign Secretary Jeremy Hunt said it is still possible to get "a version" of Mrs May's Brexit deal approved by Parliament.
Another cabinet minister, Amber Rudd, called for cross-party co-operation.
MPs were due to vote on Mrs May's Brexit deal on Tuesday, but it was postponed when the prime minister admitted it would have been "rejected by a significant margin".
Mr Johnson - who is Boris Johnson's brother but voted Remain in the referendum - said he was concerned by the way Downing Street was treating Parliament.
He told BBC Radio 4's Today programme: "No 10 could try to leave that vote until the very last minute.
"Effectively, giving the country, giving Parliament, no choice at all except between her deal... and no deal at all."
He added: "It's simply unacceptable to run out the clock and face the country with the prospect of being timed-out."
Labour and the SNP have both said the prime minister should stop wasting time and put the deal to a vote in Parliament.
After postponing the vote in Parliament, Mrs May travelled to Brussels to make a special plea to EU leaders, in a bid to make her deal more acceptable to MPs.
However, the EU said there could be clarification but not renegotiation.
Many of Mrs May's MPs are concerned that the "backstop" - which is aimed at preventing a hard border in Northern Ireland - would keep the UK tied to EU rules and limit its ability to strike trade deals.
On Saturday, Mr Hunt said the EU needed to listen to appeals from the British government to provide "legally enforceable language" that the backstop would be temporary.
He told Radio 4: "The thing that the House of Commons will not accept is any risk of us being permanently trapped through the Northern Irish backstop in the customs union."
He added that the "only way" the deal would get through Parliament was "to have a version of the deal that the government has negotiated".
However, BBC deputy political editor John Pienaar said the problem remained that only "an end date or a key to the exit door" would make it possible for the deal to be supported by MPs.
He added: "The EU has shown no indication, publicly or privately at any point, that it is willing to give that."
Ms Rudd said she supported Mrs May's deal but advocated assembling a "coalition" to avoid what she called "the rocks of no deal".
"We need to find a plan that a majority in Parliament can support," she said.
"We need to try something different. Something that people do in the real world all the time, but which seems so alien in our political culture - to engage with others and be willing to forge a consensus."
One idea, favoured by at least one cabinet minister, is a series of votes on other plans, such as a relationship similar to Norway's with the EU, or another referendum.
By BBC political correspondent Tom Barton
A cabinet split? Certainly, a disagreement between senior ministers over the viability of Theresa May's Brexit deal.
Jeremy Hunt, the foreign secretary, telling Radio 4's Today programme that it will be possible to get "a version" of the prime minister's Brexit deal approved by MPs.
Amber Rudd, the work and pensions secretary, openly musing in the Daily Mail that the government needs need "to try something different" because Parliament is currently headed towards "no compromise, no agreement and no deal".
For the foreign secretary, the risk of no deal works as leverage in the UK's attempt to get the EU to reconsider the detail of the Northern Ireland backstop, warning European leaders that "they can't be sure" Parliament would stop it.
For Amber Rudd, it's something which "for the sake of all our futures, mustn't be allowed to happen".
At a Leave Means Leave rally in London on Friday, former UKIP leader Nigel Farage told the BBC it was "outrageous" another referendum could happen, but added: "I can see where we're going."
Mr Farage added the treatment of Mrs May in Brussels this week had been a "shaming moment" for both the UK and the EU and that the prime minister's Brexit deal was now "dead".
Scotland's First Minister Nicola Sturgeon said it was time "to stop this pretence" and "bring the vote to Parliament".

Theresa May has urged the EU to get on with discussing her "ambitious but practical" vision for economic relations with the UK after Brexit.
The prime minister told the BBC's Andrew Marr the "right deal for us will be the right deal for them too".
She said she was confident of a deal while accepting the UK could not expect the same market access in some areas.
But the CBI said there were some "big holes" in the UK's plan and action was needed to stop firms moving.
Conservative MPs have largely welcomed the PM's speech on Friday, in which she set out what she said were "the hard facts" on Brexit and the reality that neither side could have exactly what it wanted from the negotiations.
While the UK was leaving the single market and customs union, she said she envisaged continued close co-operation in many areas after the UK leaves on 29 March 2019 - including remaining a member of medicines, aviation and chemicals agencies.
She told Andrew Marr it was important to be "straight" with people that life would be different outside the EU but she believed both sides wanted the same overall outcome.
"It was a vision that was ambitious but was also practically based and therefore a credible vision," she said.
"The EU themselves have said they want an ambitious and wide-ranging arrangement with us in the future...  If we look at our future prosperity and in the other 27 countries, the right deal for us will be the right deal for them too."
While the UK would have the right to diverge from EU rules in some areas, she said it would "make sense" for the UK to keep exactly the same standards in others or achieve the same outcomes by different means.
Financial services, she insisted, would be a key part of what she hopes will be the most comprehensive free trade deal ever struck.
But she said arrangements would have to change once the UK left the single market, such as the end of passporting which allows firms based in the City of London to operate across the EU without the need for licences in individual countries
"If we were to accept passporting, we would just be a rule-taker," she said. "We would have to abide by their rules which were being set elsewhere.
"Given the importance of financial stability, we can't just take the same rules without any say in them."
Asked what she would do if she lost a Commons vote on remaining in the customs union - with some Tory MPs set to side with Labour over the issue - she said she would be making her case to Parliament.
"What I have set out in terms of a future customs arrangement with the EU, I think, is actually what most people want to see," she said.
A customs deal that ensured tariff-free trade and the most "frictionless" passage of goods was in the interests of both sides, she said.
But Carolyn Fairbairn, who heads the CBI employers' group, said thousands of manufacturing businesses would lose out from being outside of the customs union.
"Some of our sectors, automotive, and others, need to stay aligned," she told Pienaar's Politics on BBC Radio 5Live. "We would actually argue that many sectors want to stay aligned.
"We do not have any that say they want to diverge greatly."
Banks needed an alternative to passporting, she said, and the UK's outline proposals "need to be followed through very quickly because financial services firms are moving now".
"The speech on Friday was a step forward," she added. "But there are some big holes still. There is no answer still on how we can get frictionless trade."
Former Conservative leader Iain Duncan Smith said Mrs May had set out "common sense and practical solutions" to many of the concerns that the EU had.
But former EU Commissioner Lord Mandelson said the EU would not "in a month of Sundays" accept a trade relationship based on mutual recognition of standards and the freedom to diverge where the UK wanted to.
"Theresa May is dancing on the head of a pin that simply does not exit and it will be painful for the country as a result," the former Labour cabinet minister told Andrew Marr.

Theresa May has written to all 317 Tory MPs, urging them to unite behind a Brexit deal while warning them "history will judge us all" over the process.
Efforts will resume on Monday to persuade the EU to agree changes to the "backstop" plan to prevent the return of customs checks on the Irish border.
And Culture Secretary Jeremy Wright has hinted MPs' concerns about it could be addressed without reopening the deal.
Labour says the Tories cannot be united and has called for cross-party talks.
The UK remains on course to leave the EU on 29 March. But Mrs May has been unable to convince a majority of MPs to back the withdrawal terms she struck with the EU last year.
The prime minister told MPs in the letter she will return to Brussels to meet European Commission President Jean-Claude Juncker this week, and speak to the leaders of every EU member state over the coming days.
Her main goal is to win concessions over the backstop, which is widely disliked by members of her party.
Many fear it will mean the UK staying closely aligned to EU rules for the long term, without Britain being able to end the agreement unilaterally.
But EU leaders have repeatedly said the withdrawal agreement is not open for renegotiation.
The Sunday Times reported comments it said were leaked from a WhatsApp group suggesting ex-Brexit minister Steve Baker told fellow Brexiteers that Mrs May's talks with Brussels were a "complete waste of time".
However, Culture Secretary Mr Wright has hinted that there might be "a number of different ways" around the problem.
"I don't think it's the mechanism that matters, it's the objective," he told the BBC's Andrew Marr Show, when asked whether a codicil - a supplementary document explaining or modifying a legal agreement - might work.
"Parliament needs to give the prime minister space to have that conversation with Brussels," he added.
Attorney General Geoffrey Cox, who has warned the backstop indefinitely commits the UK to EU customs rules if Brexit trade talks break down, will set out what changes would be needed to address concerns in a speech on Tuesday.
Brexit Secretary Stephen Barclay is also due to meet the EU's chief negotiator Michel Barnier to discuss the controversial policy on Monday.
If MPs do not approve a formal deal, many fear chaos at ports and for business.
And Tobias Ellwood has become the first minister to publicly declare a willingness to rebel against the government if the PM failed to rule out a no-deal scenario.
"There are many ministers, me being one of them, that need to see 'no deal' removed from the table," the defence minister told BBC Radio 5 Live's Pienaar's Politics.
Labour's shadow chancellor John McDonnell told Andrew Marr that "serious discussion" around building cross-party consensus must happen by the end of the month.
"We have put our proposals on the table; we're willing to negotiate around those," he said. "They're the basis of what we think could secure parliamentary approval, but she has to start negotiating as well."
The PM's negotiating stance has never been "based upon mutual interest or mutual respect" but was "about banging the table and walking away", he added.
Asked about the prospect of a further referendum, Mr McDonnell said the party's priority remained a Brexit deal that protected jobs and the economy.
But he added: "We really are at the end of the line now... If [a deal] doesn't fly within Parliament, yes the option of going back to the people has got to be there."
Campaigners for another referendum on Brexit have said there will be a major protest the weekend before Britain's scheduled departure date on 29 March.
In her letter, Mrs May described the latest Commons defeat over her Brexit strategy, in which dozens of Conservatives abstained on Thursday, as "disappointing".
"I do not underestimate how deeply or how sincerely colleagues hold the views which they do on this important issue - or that we are all motivated by a common desire to do what is best for our country, even if we disagree on the means of doing so," she writes.
"But I believe that a failure to make the compromises necessary to reach and take through Parliament a withdrawal agreement which delivers on the result of the referendum will let down the people who sent us to represent them and risk the bright future that they all deserve."
Analysis by Peter Saull, BBC political reporter
Since Thursday and the 10th defeat in the House of Commons for Theresa May over Brexit, the tensions in the Conservative Party have threatened to boil over.
The war of words has reached ministerial level, with business minister Richard Harrington suggesting some of his pro-Brexit colleagues should join former UKIP leader Nigel Farage's new party.
Therefore while there's nothing new in terms of the substance of this letter, it represents a clear attempt by the prime minister to calm things down.
Theresa May is also making it clear she won't change tactics.
The PM believes the only way to get a deal through the Commons and keep her party together is by securing changes to the backstop, even if the EU shows no sign of budging.

Theresa May has promised Tory MPs she will quit if they back her Brexit deal.
She told backbench Tories: "I am prepared to leave this job earlier than I intended in order to do what is right for our country and our party."
The PM said she knew that Tory MPs did not want her to lead the next phase of Brexit negotiations "and I won't stand in the way of that".
But the DUP said it had not changed its position and would still vote against the deal.
The BBC's Laura Kuenssberg said the DUP's refusal to back the deal at this stage was a "huge blow" for Number 10.
Many Conservative Brexiteers - including the chairman of the European Research Group Jacob Rees-Mogg - had been waiting to see if the DUP's 10 MPs would back the deal before deciding whether to get behind it - and their decision makes it even more difficult for the deal to pass.
In a statement released after the PM announced her offer to stand down, DUP leader Arlene Foster said the "necessary changes" she wanted to see to the backstop clause in the withdrawal agreement had still not been secured.
She told the BBC the backstop threatened the integrity of the United Kingdom and her party would never "sign up to something that would damage the Union".
Justice Secretary David Gauke said he hoped Parliament would "rally behind" the PM's deal, and he thinks "there is a mood in that direction".
But ERG deputy chairman Steve Baker said after Mrs May's statement that he was "consumed with a ferocious rage after that pantomime".
Speaking at an ERG meeting, Mr Baker attacked those in the party whose "addiction to power without responsibility" had led them to confront MPs with a choice between the PM's deal and no Brexit and that he "may yet resign the whip" than "be part of this", sources said.
Mrs May did not name a departure date at a packed meeting of the 1922 committee of backbench Conservative MPs.
But if the deal is passed, she would resign as party leader after 22 May - the new Brexit date - but stay on as PM until a new leader is elected.
Downing Street said it would be a "different ball game" if the deal was not passed by Parliament.
It came as MPs seized control of the Commons agenda to hold a series votes on alternatives to the deal. None of the eight options won outright support.
Sir Oliver Letwin, who secured the votes, said he wanted to hold more of them on Monday, but he said he hoped MPs would back Theresa May's deal before then.
If the deal doesn't go through then it's not quite clear that Mrs May's offer to go still applies, although it is almost impossible, whether it stands or falls, that she would be able to stay.
The prime minister hopes that by offering to leave Number 10, she'll take the country out of the EU with her, smoothly, without more political turmoil.
And that order, of a sort, will be restored and the uncertainty for all of us will end.
If that happens, we'll see a new leader in Downing Street by mid-July.
But that is still a gamble.
Read Laura's blog
Mrs May told the 300 or so Tory MPs at the meeting "we need to get the deal through and deliver Brexit".
"I ask everyone in this room to back the deal so we can complete our historic duty - to deliver on the decision of the British people and leave the European Union with a smooth and orderly exit."
Labour leader Jeremy Corbyn tweeted that Mrs May's announcement "shows once and for all that her chaotic Brexit negotiations have been about party management, not principles or the public interest".
He added: "A change of government can't be a Tory stitch-up, the people must decide."
George Freeman, the prime minister's former policy adviser, said she had done the "right thing" in announcing her decision to stand down, even though it had been a "sad moment".
The Tory MP told BBC News her speech had been followed by a series of interventions from "very hardline Brexiteers" all saying "prime minister, thank you, I will now vote for this deal".
The PM has said she wants to bring the deal back to the Commons this week, after it was previously rejected twice, by large margins.
Commons Speaker John Bercow ruled last week that the government could not return for a third attempt, unless there had been "substantial" changes to the proposals.
And he warned ministers earlier that they should "not seek to circumvent my ruling" by introducing procedures that could reverse his judgement.
But a Downing Street spokesman said there had been a "significant development" at the summit in Brussels last week, after Mrs May agreed "extra reassurances" over the Irish backstop with the EU, and the date of exit had changed.

Theresa May has told EU leaders that she wants an early deal in Brexit negotiations on the status of Britons in Europe and EU citizens in the UK .
The PM attended a summit of EU leaders in Brussels before leaving while they discussed their approach to Brexit.
The remaining 27 agreed that the European Commission will take the lead role in negotiations.
Meanwhile Chancellor Philip Hammond has played down suggestions it could take ten years to reach a trade deal.
He told the BBC:  "I don't expect that it will take as long as that," following reports that Britain's ambassador to the EU, Sir Ivan Rogers, suggested that others in Europe believed this could be the case.
The prime minister was in Brussels on Thursday for a European Council meeting. She left the summit without answering any questions on Brexit but Irish PM Enda Kenny told reporters that she had given an update on the Supreme Court case the UK government is involved with on whether it can act alone in triggering Article 50 - the formal start of Brexit.
He added: "She would like to have the question of UK citizens living in Europe and European citizens living in the UK dealt with in the early part of discussions that take place."
A Downing St spokesman confirmed on Friday that the prime minister had raised the issue and been clear she would like to see the issue resolved as soon as possible.
He said: "We have been very clear we want to extend those rights to EU citizens here, as long as there are reciprocal arrangements for British citizens across the EU."
The question of what will happen to the estimated 2.9 million citizens of other EU countries who have made their home in the UK in recent years is one of the most controversial arising from the UK's vote to leave the EU in June's referendum.
The government has said it expects an early resolution of the issue once official talks on the terms of the UK's separation from the EU begin, something it plans to happen by next spring.
But it has not given any guarantees on their future status - saying this is impossible without similar safeguards for the estimated 1.2 million Britons living in Spain, France, Italy and other EU countries.
Mr Kenny also told reporters that the Irish Republic would not sign a bilateral trade deal with the UK and the UK had to agree its future relationship with the EU first.
Pictures from the summit which circulated on social media appeared to show Mrs May looking as though she had no one to talk to. However the BBC's Europe editor Katya Adler said other clips showed her chatting to EU leaders while German MP Stephan Mayer said reports of the PM being frozen out were "misleading".
Mr Mayer, who is home affairs spokesperson for the German Chancellor Angela Merkel, also told BBC Radio 4's Today programme that it was "reasonable" for the 27 EU leaders to meet without Mrs May, following the formal summit, to discuss their approach to Brexit.
The 27 agreed that European Commission official Michel Barnier will lead talks for the EU - although MEPs are said to want a greater say.
European Council president Donald Tusk said the "short, informal meeting" had "reconfirmed our principles, meaning the indivisibility of the four freedoms, the balance of rights and obligations and the rule 'no negotiations without notification'".
European Parliament president Martin Schulz has warned that negotiations could be vetoed if MEPs are not fully involved.
Downing Street meanwhile has indicated that it would be possible to complete a "divorce deal" and a new trade agreement with the EU within the timetabled two years of the UK invoking Article 50 - the formal start of the process of leaving.
But Germany's Mr Mayer said that it would be "a bit naive" to think a trade deal could be done in two years.
"It's very ambitious to finish these negotiations within two years, it's a huge project."
Chancellor Philip Hammond told the BBC the UK would negotiate a Brexit deal and, once that has started, would "in parallel" begin to negotiate new trade arrangements with the EU.
Meanwhile, reports suggest that Britain could face a £50bn bill to leave the EU, including payments to cover pension liabilities for EU staff.
Downing Street said the UK would meet its obligations while in the EU, but any financial settlement after that would be a matter for negotiation.
At the summit, the leaders also discussed Syria, controlling mass migration into Europe, the EU's relationship with Ukraine, co-operation with Nato and economic matters.

The government's Brexit bill has passed through Parliament after Theresa May saw off a revolt by Tory MPs.
Peers accepted the amendment to the EU (Withdrawal) Bill sent to them from the House of Commons, meaning the bill now goes for Royal Assent, becoming law.
Earlier, the government won the vote 319 to 303, after assurances were accepted by would-be rebels that MPs would have a meaningful say.
The PM called it a "crucial step" in delivering a "smooth" Brexit.
Mrs May said: "Today's votes show people in the UK, and to the EU, that the elected representatives in this country are getting on with the job, and delivering on the will of the British people.
"Over the next few weeks we will publish more details of our proposed future relationship with the EU in a White Paper, and will bring the Trade and Customs Bills back to the House of Commons.
"But today has been an important step in delivering the Brexit people voted for, a Brexit that gives Britain a brighter future, a Britain in control of its money, laws, and borders."
Before the Commons vote, Dominic Grieve, leader of the would-be rebels - who wanted to ensure MPs had the power to stop the UK leaving without a deal - said the "sovereignty of Parliament" had been acknowledged.
Both sides have claimed victory with Stephen Hammond, a pro-EU MP who eventually sided with the government, suggesting ministers had agreed to give Parliament a "real say" on top of other concessions.
But international trade secretary Liam Fox said nothing had really changed and the option of a no-deal Brexit had been left firmly on the table.
"There is no change to the fundamental issue here which is the government cannot be forced by Parliament to negotiate something which it does not want to do," he told the BBC's political editor Laura Kuenssberg.
He said the government had "to be able to hold out in our negotiations the prospect of no deal" otherwise the EU would get the upper hand.
On Wednesday evening, following the Commons vote, Leader of the Lords Baroness Evans of Bowes Park said the EU (Withdrawal) Bill had been "debated at length" and was very different as a result of amendments tabled by the Lords.
"I believe our role now is to accept their view as expressed in a vote a few hours ago," she said.
Peers approved the government's proposal without a vote.
The UK is due to leave the European Union on 29 March 2019 and negotiations have been taking place over the terms of its departure.
By Laura Kuenssberg, BBC political editor
The government was worried enough about losing today to budge, even if they only gave an inch.
It might be a concession that only really parliamentary lawyers understand, but the PM had to move, again, despite not wanting to.
And despite the fact that she did compromise even in a meaningless way (yes I can't believe that I did just write that sentence, but it is relevant), the vote was still relatively close, certainly not comfortable enough for the government to relax any time soon.
What's also the case is that the Tory rebels, or potential rebels more like, weren't willing to take dramatic action in enough number to humiliate the PM.
The vote result suggests that they have the hypothetical numbers, but their critics, and their internal opponents in the Tory party would question if they really have the guts.
The government has been at odds with the House of Lords in the long-running row over what happens if the UK cannot reach a deal with the EU, or if MPs reject whatever deal the government agrees with the EU.
The Commons vote had been expected to be tight and the government eventually prevailed by a majority of 16.
Six Tory MPs - Ken Clarke, Anna Soubry, Sarah Wollaston, Heidi Allen, Antoinette Sandbach and Phillip Lee - rebelled while four Labour MPs backed the government and six other Labour MPs abstained, as did Kelvin Hopkins, who sits as an independent after having the whip withdrawn.
Ms Wollaston tweeted that she was disappointed with the outcome.
One Labour MP, Naz Shah, voted in a wheelchair after being released from hospital amid Labour claims that normal arrangements sparing unwell MPs from having to enter the chamber had been abandoned.
The debate centred on what happens in three Brexit scenarios:
Under these circumstances, the government has said, a minister will make a statement in Parliament, setting out the proposed next steps.
MPs will then vote on this statement. According to the government, this vote should be "on neutral terms", with MPs simply noting what has been said.
But an amendment backed by the House of Lords on Monday went further, saying MPs should have to "approve" the minister's statement.
The Department for Exiting the European Union has now conceded that it will be up to Commons Speaker John Bercow to decide the matter at the time.
Speaking in the Commons, Dominic Grieve said the issue of the meaningful vote was about giving "assurances to the House and many, many people in the country who are worried about this process and how it will end".
If Parliament wished to "speak with one voice" and exert its influence in the face of a non-deal scenario, it "has the power to do it".
Mr Grieve said he had insisted on a key paragraph in the government statement accepting "it is open to MPs to table motions and debate matters of concern and that, as is the convention, parliamentary time will be provided for this".
Another potential rebel Nicky Morgan said she did not wish to see Mrs May "destabilised or undermined" ahead of next week's summit of EU leaders.
But she warned of further battles to come over the UK's trade and customs arrangements with the EU and suggested relationships between MPs had been "strained almost beyond belief".
And Conservative MP Vicky Ford, another pro-European MP who stuck with the government, said the outcome was "not a mandate for a no-deal Brexit".
She said MPs had secured a "backstop" which meant if Parliament rejected the deal it could trigger "another set of negotiations" between the UK and EU aimed at getting an agreement before the UK left.

Prime Minister Theresa May has said she will not lead the Conservative Party into the next general election.
She said the party would prefer to "to go into that election with another leader", as she arrived in Brussels for an EU summit.
It confirms what she told MPs ahead of a confidence vote triggered by MPs angry at her Brexit policy.
Mrs May won the vote but has vowed to listen to the concerns of the 37% of Tory MPs who voted against her.
The next scheduled general election is in 2022.
Mrs May said: "I've said that in my heart I would love to be able to lead the Conservative Party into the next general election but I think it is right that the party feels that they would prefer to go into that election with another leader."
Asked whether she would quit after Brexit, she declined to discuss dates but added: "What I'm clear about is the next general election is in 2022 and I think it's right that another party leader take us into that general election."
The prime minister said she hoped to "assuage" the concerns of Tory MPs who voted against her by seeking legal "assurances" from EU leaders that the backstop plan to prevent the return of a hard border in Northern Ireland would be temporary.
Critics say Mrs May's backstop plan will keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
The EU says it will not renegotiate the backstop, but may agree to give greater assurances on its temporary nature.
It seems unlikely that would win over enough support for her Brexit plan to have a realistic chance of getting through the House of Commons, with tensions heightened in the Conservative Party in the wake of Wednesday evening's confidence vote.
Downing Street confirmed on Thursday that the MPs' "meaningful vote" on the deal will not now take place before Christmas - it was abandoned this week when Mrs May admitted it would have been "rejected by a significant margin".
The PM's spokeswoman said it would happen "as soon as possible in January".
The prime minister's admission that she'll leave office before the next election fended off yesterday's clamour from a chunk of her party to go.
But it hardly makes things easier from today onwards.
Just as she is desperate to get a time limit on the controversial "backstop", she now has a limit on her time in office.
Now it is public, in her own words, questions won't just be about her impossible Brexit agreement but also about how, and when, she will finally go.
Earlier this week, the prime minister travelled to meet EU leaders, including German Chancellor Angela Merkel and Dutch Prime Minister Mark Rutte, to raise the issues surrounding the withdrawal agreement at Westminster one-on-one.
But a trip to meet the Irish Taoiseach Leo Varadkar had to be cancelled because of the leadership vote.
At Thursday's summit, Mrs May has the opportunity to spell out face-to-face the problems she faces to leaders of all the other 27 member states.
The EU leaders will then consider what could be done - without Mrs May in the room.
Theresa May said she had listened to the concerns of the MPs who had voted against her, adding that she knew what was needed to get her deal "over the line".
"I've already met [Irish Premier] Leo Varadkar, I'm going to be addressing the European Council later and I'll be showing the legal and political assurances that I believe we need to assuage the concerns that MPs have on this issue."
She added: "I don't expect an immediate breakthrough but what I do hope is that we can start work as quickly as possible on the assurances that are necessary."
Austrian Chancellor Sebastian Kurz, whose country holds the rotating six-month presidency of the European Council, said: "I believe that Theresa May knows that there can be no reopening of the withdrawal agreement."
But he said that it might be possible to "provide a little better explanation or definition or go into detail" on the provisions of the agreement.
"Hopefully that will allow Theresa May to bring a vote in January and obtain a majority," he said.
"If the British prime minister thinks one or another additional explanation can be helpful before she brings it to a vote, then we should do that."
Asked what concessions might succeed in winning over Mrs May's domestic critics, Mr Kurz said: "It is difficult to judge, because many of the sceptics do not argue in a way that is really rational."
Tory MP Iain Duncan Smith, a former party leader and a Brexiteer who voted against Mrs May in Wednesday's vote, said he wanted to "send a strong message" to the PM.
He told BBC Radio 4's Today programme: "We cannot go on just with the idea that a fiddle here and a fiddle there is what the problem is."
Instead, he said Mrs May should say that the £39bn the UK has agreed to pay the EU as part of the divorce deal is "at risk".
"They have got to say to the EU... we are not committed to this £39bn unless we get some resolution."
Lib Dem leader Sir Vince Cable, who is against Brexit, told BBC Breakfast: "We are still back with the problem that the government has a proposal that we can't get through Parliament and we have got to try and break that gridlock."
He called on Labour leader Jeremy Corbyn to "come off the fence" and back another public vote on Brexit.
Labour has said that it will table a no-confidence motion in Theresa May's government that all MPs - not just Conservatives - will be able to vote in - but only when they felt they had a chance of winning it, and forcing a general election.
But the DUP - which props up Mrs May's government - said it would not support such a motion at this stage.
Shadow Chancellor John McDonnell urged Theresa May to work with Labour on getting a deal with the EU that "will protect jobs and the economy".
He said there was an "overwhelming majority" in the Commons against a no-deal Brexit but the prime minister should now hold a series of votes to establish what other options MPs were willing to accept.
The prime minister won the confidence vote with a majority of 83 - 63% of Conservative MPs backing her and 37% voting against her.
A split was still clear in the Tory party after the result. Jacob Rees-Mogg, who led calls for the confidence vote, said losing the support of a third of her MPs was a "terrible result for the prime minister" and he urged her to resign.
But Nicholas Soames urged Brexiteers to "throw their weight" behind the PM as she sought to address the "grave concerns" many MPs had about aspects of the EU deal.
DUP deputy leader Nigel Dodds said his party was also still concerned about the Irish backstop plan, telling BBC News: "I don't think this vote really changes anything very much in terms of the arithmetic."

Prime Minister Theresa May's Brexit deal has been rejected by 230 votes - the largest defeat for a sitting government in history.
MPs voted by 432 votes to 202 to reject the deal, which sets out the terms of Britain's exit from the EU on 29 March.
Labour leader Jeremy Corbyn has now tabled a vote of no confidence in the government, which could trigger a general election.
The confidence vote is expected to be held at about 1900 GMT on Wednesday.
The defeat is a huge blow for Mrs May, who has spent more than two years hammering out a deal with the EU.
The plan was aimed at bringing about an orderly departure from the EU on 29 March, and setting up a 21-month transition period to negotiate a free trade deal.
The vote was originally due to take place in December, but Mrs May delayed it to try and win the support of more MPs.
The UK is still on course to leave on 29 March but the defeat throws the manner of that departure - and the timing of it - into further doubt.
MPs who want either a further referendum, a softer version of the Brexit proposed by Mrs May, to stop Brexit altogether or to leave without a deal, will ramp up their efforts to get what they want, as a weakened PM offered to listen to their arguments.
History was made tonight with the scale of this defeat - a higher figure than the wildest of numbers that were gossiped about before the vote.
But the prime minister's dilemma is a more serious version of the same it's always been.
She has no majority of her own in Parliament to make her middle way through stick. And her many critics don't agree on the direction she should take - a more dramatic break with the EU, or a tighter, softer version.
Those two fundamental and clashing positions have always threatened to pull her and the government apart.
The Brexit debate has cut across traditional party lines.
Some 118 Conservative MPs - from both the Leave and Remain wings of her party - voted with the opposition parties against Mrs May's deal.
And three Labour MPs supported the prime minister's deal: Ian Austin (Dudley North), Kevin Barron (Rother Valley) and John Mann (Bassetlaw).
The most controversial sticking point was the issue of the Northern Irish backstop - the fallback plan to avoid any return to physical border checks between the country and Ireland.
Mrs May had hoped new assurances from EU leaders this week, saying the backstop would be temporary and, if triggered, would last for "the shortest possible period", would help her garner more support.
But in the debate leading up to the vote, members from all sides of the House said the move did not go far enough.
Click here if you cannot see the look-up. Data from Commons Votes Services.
In normal times, such a crushing defeat on a key piece of government legislation would be expected to be followed by a prime ministerial resignation.
But Mrs May signalled her intention to carry on in a statement immediately after the vote.
"The House has spoken and this government will listen," she told MPs.
She offered cross-party talks to determine a way forward on Brexit, if she succeeded in winning the confidence vote.
Former foreign secretary and leading Brexiteer Boris Johnson said it was a "bigger defeat than people have been expecting" - and it meant Mrs May's deal was now "dead".
But he said it gave the prime minister a "massive mandate to go back to Brussels" to negotiate a better deal, without the controversial Northern Ireland backstop.
And he said he would back Mrs May in Wednesday's confidence vote.
Labour MP Chuka Umunna said that if his leader did not secure a general election, Mr Corbyn should do what the "overwhelming majority" of Labour members want and get behind a further EU referendum.
Lib Dem leader Sir Vince Cable, who also wants a second referendum, said Mrs May's defeat was "the beginning of the end of Brexit" - but conceded that campaigners would not get one without Mr Corbyn's backing.
Scotland's First Minister Nicola Sturgeon said Mrs May had suffered "a defeat of historic proportions" and called again for the Article 50 "clock to be stopped" in order for another referendum to take place.
"We have reached the point now where it would be unconscionable to kick the can any further down the road," she said.
However, government minister Rory Stewart said there was no majority in the Commons for any Brexit plan, including another referendum.
By the BBC's head of political research Peter Barnes
Under the Fixed Term Parliaments Act 2011, UK general elections are only supposed to happen every five years. The next one is due in 2022.
But a vote of no confidence lets MPs decide on whether they want the government to continue. The motion must be worded: "That this House has no confidence in Her Majesty's Government."
If a majority of MPs vote for the motion then it starts a 14-day countdown.
If during that time the current government, or any other alternative government cannot win a new vote of confidence, then an early general election would be called.
That election cannot happen for at least 25 working days.
MPs are set to debate Labour's no confidence motion for about six hours following Prime Minister's Questions at 1200.
Mr Corbyn said it would allow the House of Commons to "give its verdict on the sheer incompetence of this government".
But DUP leader Arlene Foster said her party, which keeps Mrs May in power, would be supporting her in Wednesday's confidence vote.
She told the BBC MPs had "acted in the best interests of the entire United Kingdom" by voting down the deal.
But she added: "We will give the government the space to set out a plan to secure a better deal."
In her statement to MPs, Mrs May said she planned to return to the Commons next Monday with an alternative plan - if she survives the confidence vote.
She said she would explore any ideas from cross-party talks with the EU, but she remained committed to delivering on the result of the 2016 referendum.
But European Commission President Jean-Claude Juncker said the risk of a disorderly Brexit had increased as a result of the deal being voted down.
He said the agreement was "the only way to ensure an orderly withdrawal" and that he and President of the European Council, Donald Tusk, had "demonstrated goodwill" with additional clarifications this week to put MPs minds at rest.
"I urge the United Kingdom to clarify its intentions as soon as possible," he said. "Time is almost up."
Mr Tusk said he regretted the outcome of the vote and later tweeted to ask "who will finally have the courage to say what the only positive solution is?"
A statement from the Irish government also said it regretted the decision and that it "continues to believe that ratification of this agreement is the best way to ensure an orderly withdrawal of the UK".
It also said it will "continue to intensify preparations" for a no deal Brexit.

Theresa May's offer to give EU citizens in the UK "settled status" after Brexit has been described as being "far short of what citizens are entitled to".
MEPs, including European Parliament chief Brexit negotiator Guy Verhofstadt say the proposal is a "damp squib".
It offers Europeans in the UK fewer rights than Britons in the EU, they say in a joint letter to newspapers.
Cabinet Office minister Damian Green said the "basic rights" of EU citizens living in the UK would be "preserved".
He urged Mr Verhofstadt to "read our proposal", which the UK government insists would allow about three million EU citizens to stay on the same basis as now.
EU migrants who had lived in the UK for five years would be granted access to health, education and other benefits.
But the prime minister's proposals would be dependent on EU states guaranteeing Britons the same rights.
The leaders of the four political groups who have signed the joint letter account for two-thirds of the votes in the European Parliament.
Their letter points out that that they have the power to reject any Brexit deal before it can go ahead because the parliament must approve the withdrawal agreement.
The leaders said they would not endorse anything that removed rights already acquired by citizens.
They said the UK proposal "falls short" because it would take away rights citizens currently have, and create new red tape and uncertainty for millions of people.
The letter said this contradicted promises made by the Leave campaign that EU citizens would be treated no less favourably after Brexit.
By contrast, the letter said the EU's offer - already on the table - was simple, clear and fair because it promised that all citizens, including UK nationals living in Europe, would be treated equally and lose no current rights.
Speaking on BBC Radio 4's Today programme, Mr Verhofstadt said EU citizens in the UK - and Britons living on the continent - should keep their current rights, rather than the government "inventing a new status".
What the UK is offering EU citizens?
In full: Safeguarding the position of EU citizens
What is the EU offering UK citizens?
In full: EU's essential principles on citizens' rights
"It creates a type of second class citizenship for European Citizens in the UK," he added. "We don't see why their rights should be diminished and that would be the case in the proposal.
"In the end, it is the European Parliament that will say yes or no, and I can tell you it not will be a yes if the rights of European citizens - and also the rights of UK citizens living on the continent - will be diminished [and] cut off, like it is at the moment."
The letter stated: "The European Parliament will reserve its right to reject any agreement that treats EU citizens, regardless of their nationality, less favourably than they are at present.
"This is a question of the basic fundamental rights and values that are at the heart of the European project."
It added: "In early 2019, MEPs will have a final say on the Brexit deal. We will work closely with the EU negotiator and the 27 member states to help steer negotiations."
A spokesperson for the UK government said the letter contained a "number of inaccuracies" which could cause unnecessary and needless concern to UK and EU citizens.
Mr Green, who as first secretary of state is a close ally of Theresa May's, told BBC Radio 4's Today that it was clear that EU citizens would have to comply with "basic" immigration rules after the UK leaves the EU to establish their identity and nationality.
But he insisted: "That is not an insuperable barrier. We all fill in forms when we go on holiday and have to get visas and all that."
He suggested the UK was doing "precisely" what the EU was calling for.
"Somebody who is here now will keep the rights they already have and we hope that British citizens living in other EU countries will keep the rights they already have...the basic rights will be preserved so that should not be an obstacle to a final deal."
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Theresa May is sticking to her Brexit strategy, despite her party rowing in the wake of her latest Commons defeat.
MPs rejected a motion endorsing her approach by 303 to 258, with 66 Tory MPs abstaining, leading one minister to accuse Brexiteer rebels of "treachery".
Steve Baker, of the backbench European Research Group which led the rebellion, called it a "storm in a teacup".
The PM will return to Brussels "within days", after her Brexit secretary met EU ambassadors in London on Friday.
Steve Barclay will also travel for further talks with the EU's chief negotiator Michel Barnier on Monday, with Parliament yet to back a deal ahead of the UK's withdrawal from the bloc on 29 March.
Mrs May is trying to renegotiate the Irish "backstop" after MPs voted to replace it with "alternative arrangements" earlier this month.
Some MPs fear the backstop - the insurance policy to prevent the return of customs checks on the Irish border - will see the UK tied to EU customs rules in the long-term.
Thursday's government motion called for MPs to back its renegotiating strategy, but ERG members believed it also meant endorsing calls to rule out a no-deal Brexit.
They say the option of leaving the EU without a formal deal offers essential "negotiating leverage" in Brussels. But a majority of MPs believe it would cause chaos at ports and massive disruption to business.
The EU has consistently ruled out changes to the backstop.
The latest government defeat has no legal force and Commons Leader Andrea Leadsom told BBC political correspondent Iain Watson the PM would return to Brussels for talks in the coming days.
Ms Leadsom also told BBC Radio 4's Today programme the loss represented "more of a hiccup than the disaster that is being reported".
"[Mrs May] will continue to seek those legally binding changes to the backstop that will enable Parliament to support our deal," she added.
Analysis by BBC political correspondent Iain Watson
Theresa May had a choice.
Abandoned by the ERG, she could have tried to build cross-party consensus by pivoting towards a customs union.
This option is favoured by Labour's frontbench and quite a few Conservatives, and Brussels feels it has potential to deliver a stable parliamentary majority.
But many in her grassroots would have pointed out a broken manifesto promise, and even re-badging it as a "common customs territory" might have caused a split.
So, the PM returns to Brussels to eke out changes to the backstop, and hopes to detach enough Labour MPs to help get a deal over the line by promising new employment laws.
If there is no revised deal before March, however, some ministers might abandon ship and urge her to delay Brexit.
But doing just that might convince some in the ERG to return to the fold, persuaded to back what they see as a bad deal over a delayed, maybe even endangered, Brexit.
Mrs Leadsom blamed Labour for "playing politics" to defeat the government.
But the chair of the Exiting the EU committee, Labour's Hilary Benn, said Mrs May had rejected party leader Jeremy Corbyn's proposed alternatives and instead sought approval from Tory Brexiteers.
"As long as the prime minister continues to try and keep the ERG on-side... we are not going to make any progress," he told Today. "We have to compromise."
Defence Minister Tobias Ellwood told BBC Newsnight the ERG was a "party within a party... flexing its muscle" to take advantage of Mrs May's lack of a Commons majority.
He called the group's actions "irritating, provocative and... unnecessary".
Business Minister Richard Harrington told The House magazine ERG members should defect to Nigel Farage's new Brexit Party - a move the former UKIP leader called "a jolly good idea".
But Transport Secretary Chris Grayling told the BBC: "That's not a sensible approach. The Conservative Party is a team - there's far more that unites us than divides us."
Former Education Secretary Nicky Morgan called for the Conservatives to take a "collective deep breath" and resolve matters to avoid a no-deal scenario.
Mr Baker, the ERG's deputy chairman, told Today he was "standing up for what the majority of the people voted for", while still "making enormous compromises".
But he added: "[The EU] should also understand that there are those of us unwilling to vote to take a no-deal off the table."
Former Attorney General Dominic Grieve accused the Conservative Eurosceptics of being "completely cavalier about the risks" of leaving the EU without a formal withdrawal agreement.
And he suggested a dozen or more ministers - including six in the cabinet - might resign if Mrs May refused to extend Brexit talks beyond 29 March.
Asked whether she would resign if there was not a deal before the end of the month, Work and Pensions Secretary Amber Rudd said she planned to work with all colleagues to help the PM get her withdrawal agreement through Parliament.
As to whether the ERG were "traitors", she responded: "No, certainly not."
Meanwhile, Irish foreign minister Simon Coveney suggested the UK could expect a "generous response" to any request to extend the withdrawal process beyond 29 March.
Speaking at a Brexit event in Dublin, he said: "With the practicalities around European elections, the establishment of a new European Commission... there is a natural extension date until the end of June perhaps."
However, Irish PM Leo Varadkar said anyone expecting the EU's solidarity over the Irish border issue to crumble at the final hour was in for a "nasty surprise".
By BBC Europe editor Katya Adler
EU leaders still believe this is not the time to budge.
They see the UK arguing, debating and negotiating with itself again - as it has done so often during the Brexit process - rather than engaging with Brussels.
As a result of all this, the new round of EU-UK negotiations are going nowhere fast.
"Window-dressing" is how one senior EU figure described the talks to me, with each side simply repeating their red lines to the other.
So, the current favourite prediction in Brussels is that things will only be resolved in March.
Read Katya's blog

Theresa May is a reserved figure who rarely betrays any emotions and certainly never likes to show any signs of weakness.
But the defection of Anna Soubry, Sarah Wollaston and Heidi Allen - three Conservative MPs from the One Nation wing of the party - may have struck a chord.
The prime minister wrote to the trio on Thursday, expressing sadness at their decision - although she did challenge their attack on her leadership.
Mrs May also called in two of the trio's political soulmates, the former ministers Justine Greening and Phillip Lee, for lengthy discussions at Number 10.
Lee, who was once one of the PM's closest friends at Westminster, had not spoken to her since he resigned as a justice minister in July in protest at her handling of Brexit.
Over the last 24 hours, he received texts from the party chairman Brandon Lewis and the chief whip Julian Smith. And then there was the invitation for a 45-minute chat with the prime minister at Number 10 to discuss Brexit and much else beyond.
"Something has happened," one source close to Lee says. "They must be worried."
The odd sign of prime ministerial nerves is explained by the potentially painful challenge facing Mrs May next week.
MPs are guaranteed a fresh Brexit vote next Wednesday. If she is unable to satisfy the likes of Mr Lee and Ms Greening, who are determined to rule out a no-deal Brexit, Mrs May could find her hand is forced by Parliament.
Former Conservative cabinet minister Sir Oliver Letwin is understood to be confident that, in such circumstances, he would win a vote on a cross-party amendment that could extend Article 50.
The amendment, drawn up with the former Labour cabinet minister Yvette Cooper, would seek to force the PM to avoid a no-deal Brexit by setting aside time for a Parliamentary bill.
If she fails to reach a deal with the EU by the middle of March, the bill would oblige the prime minister to:
A number of ministers are saying in private they would be prepared to lose their jobs to be able to support the Cooper-Letwin amendment.
Other ministers believe that, in the end, an insufficient number of their colleagues would resign to allow the amendment to pass.
The prime minister is taking no chances and is working hard to secure a revised deal with the EU by next Tuesday, the eve of vote.
She met European Commission president Jean-Claude Juncker in Brussels on Wednesday and will talk to EU leaders in the margins of an EU-Arab League summit in Sharm el-Sheikh on Sunday and Monday.
Downing Street is looking for changes to Mrs May's Brexit deal on two levels:
The EU is keen to help but has two concerns. It will not offer any legal guarantees that undermine the withdrawal agreement, and it fears that it could make concessions that are then rejected by MPs.
One cabinet minister told me they are confident that the prime minister will secure a deal in time for her to upgrade next week's parliamentary vote to a legally binding "meaningful" vote.
Another minister tells me: "There will be a deal... by 29 March. The EU always goes to the line."
But then the minister added: "Never underestimate the ability of this prime minister to muck things up."
The pointed remarks show that as Brexit nears the endgame, this lonely prime minister struggles to command loyalty even among her ministers.
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Warnings that a no-deal Brexit would be a "huge mistake" for the UK and the EU are "project reality" not "project fear", the foreign secretary has said.
Jeremy Hunt said: "We have to be very honest with ourselves about the choices that we face and we need to have these frank discussions".
Mr Hunt repeated a warning that "as things stand at the moment, we are heading for no deal by accident".
He was speaking after he met his Austrian counterpart Karin Kneissl.
Ms Kneissl said that they were "prepared for the different possible scenarios".
The UK is due to leave the EU on 29 March 2019, but the two sides have yet to agree on how their future relationship will work.
Key differences between the UK and the EU remain, more than a year after negotiations started.
Mr Hunt said no deal would be a "huge geo-strategic mistake" and would "have a profound impact on the relations between Britain and the EU countries for a generation".
He added: "We don't think this is in anyone's interests."
Asked by the BBC if this was "project fear part two", Mr Hunt said: "This is not project fear, this is project reality."
"We have to make a decision on Britain's future relationship with the EU by the end of this year and we have to be very honest with ourselves about the choices that we face - and we need to have these frank discussions because time is very, very short," Mr Hunt said.
"We are clear that what we want is a friendship that means we can stand as friends with EU countries - just as the friendship between Australia and New Zealand, between Austria and Switzerland.
"Britain will prosper and succeed whatever the outcomes of these talks because we are that kind of country."
He said it was important to point out that there were "very, very serious consequences" for all sides of the argument "if we get this judgement wrong".
The EU and the UK want a deal in place by October.
Government ministers say they want to reach a deal with the EU covering issues like trade and border checks, but are also making contingency plans to prepare for leaving with no agreement in place.
Last week the EU's chief negotiator, Michel Barnier, rejected a key part of Mrs May's proposals, which would involve the UK collecting customs duties on its behalf.

EU citizens will have to answer three "simple" questions online if they want to continue living in the UK after Brexit, the home secretary has said.
Sajid Javid said the government's "default" position would be to grant, not refuse, settled status.
People will be asked to prove their ID, whether they have criminal convictions and whether they live in the UK.
Their answers will be checked against government databases and a decision given "very quickly", said Mr Javid.
The scheme will operate online and via a smartphone app, Mr Javid said, and would be "as simple as people can reasonably expect", with most decisions turned around within two weeks or sooner.
Speaking to a House of Lords committee, Mr Javid said there would have to be "a very good reason" why an application would be refused.
The Home Office said the criminal record checks would be about "serious and persistent criminality, not parking fines".
The £170m scheme will be compulsory for all EU citizens living in the UK - the government expects a total of 3.5 million applications.
EU citizens and family members who have been in the UK for five years by the end of 2020 will be able to apply for "settled status", meaning they are free to go on living and working in the UK indefinitely.
Those who have arrived by December 31, 2020, but do not have five years' residence, can seek to stay until they have, at which point they can seek settled status.
The scheme also includes citizens of Switzerland, Iceland, Liechtenstein and Norway.
Applications will cost £65 for adults and £32.50 for children and be free for EU nationals who already have residency or indefinite leave to remain.
Applicants will be asked to provide their biographical information, declare whether they have any criminal records, and upload a facial photograph.
The process requires verification of the applicant's identity and nationality using a passport, ID card or other valid document, which can be done using a smartphone app or through secure post.
The government hopes to start trials within a few weeks, with people allowed to start registering in the autumn.
Mr Javid told the Lords EU Justice sub-committee he wanted it to be fully operational by the "start of next year", adding that he wanted to avoid a "surge" of applicants when the UK leaves the EU in March.
The scheme would run for at least two years after Brexit day, probably to around June 2021, said the home secretary.
The hope is that most applicants will not have to provide supporting documents because their answers will be checked against HM Revenue and Customs and other government databases.
Applicants with Android phones will be able to download an app which can read the chip in their passport to verify their identity - and they will be able to take a "selfie" that can be checked against Home Office records, said Mr Javid.
But he said there was an "an issue at the moment" with Apple device users, who will not be able to make use of this app, and instead will have to send in their passport to prove their identity.
The home secretary said he had raised the issue with Apple on a recent visit to Silicon Valley and the company was "looking at it actively".
Analysis by BBC Home Affairs correspondent Danny Shaw
What the Home Office is embarking on is a hugely complex project within a tight timescale.
When challenged about the potential for it go wrong, officials point to the Passport Office as an example of a service successfully processing millions of cases every year.
But unlike the biometric passport system, the EU registration scheme is being built from scratch.
For hundreds of thousands of EU nationals, who have a straightforward and legitimate employment history in Britain and are comfortable using digital technology, their applications may well be resolved "within days", the time officials rather ambitiously claim cases will take.
But for claimants hoping to bring in relatives, people unfamiliar with computers and those with a more sketchy background in Britain, perhaps involving some cash-in-hand work, the process may be a hurdle they'll struggle with - or avoid altogether.
Labour MP Yvette Cooper, chair of the Commons home affairs committee, said "far more" answers were needed from the government "about what happens to those who aren't registered by June 2021 through no fault of their own, such as children".
"At the moment it appears that if children aren't registered within the next three years then they will lose their legal rights even though they may have been here all their lives."
SNP home affairs spokeswoman Jo Cherry, speaking in the Commons, said: "There are potentially significant numbers of people who could fall through the cracks here.
"If just 5% of the estimated three million EU citizens living in the UK don't register by the deadline there would be a population of nearly 200,000 left without status."
Former Labour minister Hilary Benn, who chairs the Commons Brexit Committee, asked ministers if the scheme would still stand in the event of a no-deal Brexit.
Immigration Minister Caroline Nokes said: "We have confidence that there will be a deal."
Sajid Javid promised there would be no repeat of the Windrush scandal - which saw people who had lived in the UK for decades threatened with deportation because they did not have the right paperwork - for EU migrants, adding "lessons had been learned".
The new "settled status" scheme would establish the right of EU migrants to remain in the UK, unlike in the case of Windrush families where there was only an assumption they had a right to stay, without any documentary proof, he told the committee.
The home secretary accused EU nations, such as France and Spain, of failing to match the UK's progress on plans for expats after Brexit.
There are about 900,000 UK citizens in the EU, according to ONS figures.
Both sides of the Brexit negotiations have resolved to secure the status of expats by the time the UK leaves the EU in March 2019.
But any deal they reach will have to be ratified by the European Parliament and agreed to by member states.
If the UK leaves the EU without a deal then the status of British citizens living in the EU member states is less certain.
The UK would expect member states to allow Britons living in the EU the same rights as it plans to grant EU citizens in the UK but it would be down to individual countries to decide what to do.

A group of major European companies has warned the Prime Minister they may cut investment without more clarity over the terms of Britain's EU exit.
Business leaders, including from BP, BMW, Nestle, and Vodafone, told Theresa May that "time is running out".
In a statement after the Downing Street meeting, they said that a trade deal with the EU must be "frictionless as with a customs union".
Downing Street said that the meeting had been "open and productive".
The industry leaders warned that "uncertainty causes less investment."
The group, known as the European Round Table of Industrialists (ERT), includes BP chairman Carl-Henric Svanberg and his Nestle counterpart Paul Bulcke.
Others at the meeting were the chief executives of Vodafone, Vittorio Colao, and Royal Mail, Moya Greene.
Senior figures from firms including BMW, Phillips, E.On and Ferrovial also attended the meeting with Mrs May and Brexit secretary David Davis.
The ERT represents Europe's 50 largest companies, with combined revenues of 2.25 trillion euros (£2tn) and millions of employees.
In its statement, the ERT said: "The uninterrupted flow of goods is essential to both the EU and UK economies. This must be frictionless as with a customs union.
"We need clarity and certainty, because time is running out. Uncertainty causes less investment."
A Downing Street spokeswoman said that the PM told the business leaders that work was under way on two customs models, "and underlined the importance of ensuring that our future trading arrangements with the EU are as frictionless as possible".
She restated a commitment to avoid a hard border between Northern Ireland and Ireland, and allowing the UK to pursue an independent trade policy.
"The PM recognised the necessity of providing certainty for businesses, pointing to the agreement of an implementation period at the European Council in March to provide time to allow businesses to prepare for the new arrangements," the spokeswoman said.

The UK will not be allowed to leave the EU without a deal at any point, Defence Minister Tobias Ellwood has suggested.
He told the Political Thinking podcast he and like-minded colleagues will stop a no-deal exit "whenever" - even if Brexit is delayed until the summer.
MPs will get the opportunity to vote on a no-deal exit if Parliament rejects Theresa May's deal again this month.
Mr Ellwood suggested the PM may have to pursue a "softer" Brexit to build a Commons majority for her deal.
Asked by presenter Nick Robinson whether this could mean the UK ultimately staying in some form of customs union with the EU, he replied "possibly".
Mrs May has said she will bring the withdrawal agreement she has negotiated with the EU back to the Commons for a second time by 12 March.
If it is voted down, MPs will have the option of either supporting leaving without a formal agreement or delaying the exit date by extending the Article 50 process.
Mrs May was forced to concede a vote on extending Article 50 after a number of ministers who want to retain a close relationship with the EU after Brexit threatened to resign unless she ruled out the prospect of the UK leaving later this month without a deal.
However, the PM has refused to rule out the UK exiting this summer without an agreement if, as expected, the EU agrees to extend the process by about three months.
Mr Ellwood, who backed the PM's deal in the first Commons vote in January, told the Radio 4 podcast that the UK would be in "uncharted territory" if it did not leave on 29 March.
But he said the days of Mrs May having to "bend over backwards" to placate the European Research Group of Brexiteer Tory MPs, many of whom believe a no-deal exit is better for the UK in the long term, were over.
"I hope it is very clear that if it was the European Research Group's intent to take us to no deal, we will stop that, whenever," he said.
"No deal is not good for Britain. It will damage Britain in so many ways. No deal is not something we can contemplate."
Mr Ellwood said he would not quit over the issue and urged Tory MPs who wanted to keep close links to the EU to stay and fight for their beliefs, suggesting the tide was moving in their direction.
"If we are then to seek some form of consensus in Parliament that honours the referendum result then you are probably looking at an even softer form of Brexit than we have currently got," he added.
The PM is seeking to re-work her deal to reassure MPs the UK will not be stuck indefinitely in the backstop, - the controversial agreement to prevent a hard border in Ireland - and have to follow EU customs rules.
Former Brexit Secretary Dominic Raab said the PM must "face down" the EU over the issue and show that the UK would not be "shoved around".
"By suggesting to the EU that we might delay Brexit or take no deal off the table, it weakens the negotiating leverage in delivering the very aims that the government has set out," he told BBC Radio 4's Today programme.
"And that's what I think is so frustrating at this point in time."

Labour's deputy leader has stepped up calls for his party to promise a referendum on any Brexit deal in its European elections manifesto.
Tom Watson urged party members to message Labour's ruling national executive committee to call for a "confirmatory ballot" pledge.
The NEC meets on Tuesday to decide on Labour's campaign manifesto.
But frontbencher Barry Gardiner said a referendum on any Brexit deal would be a change in Labour policy.
The shadow international trade secretary told BBC Radio 5 Live's Pienaar's Politics that the party's policy agreed at last year's conference was to go for a referendum "to stop a no-deal or a bad Tory Brexit."
He added: "If we are being pushed into a no-deal by this government, we will have a second referendum. But we want to try - and that's why we're in there with the government now - trying to deliver on what people voted for."
Hundreds of thousands of people marched in central London last month to call for another EU referendum.
Labour agreed a policy at its last conference that if Parliament voted down the government's deal or talks end in no-deal, there should be a general election.
But if it cannot force one, it added, the party "must support all options remaining on the table, including campaigning for a public vote".
However, following parliamentary deadlock and a refusal by MPs to approve the withdrawal deal negotiated between the EU and UK, Labour has entered into cross-party talks with the Conservatives to see if they can reach a consensus.
And many Labour members now want the party to make its agreement to any deal conditional on it being put to a public vote - what Labour calls a "confirmatory ballot".
Mr Watson has been among figures calling for that pledge to be included in Labour's European Parliamentary elections campaign, arguing it is needed to counter the electoral challenge posed by Nigel Farage's newly formed Brexit Party.
On Friday it emerged that more than 90 Labour MPs and MEPs had written to the NEC, urging a "clear commitment" to a public vote on any Brexit deal agreed.
Asked whether another referendum was a "red line" for Labour in the talks, shadow business secretary Rebecca Long-Bailey told Sky News: "We are not being hugely prescriptive on the minute detail of specific elements because we are willing to compromise and we are willing to be flexible".
She said she was "hopeful" that in coming weeks "we will see some movement" in the talks.
If all of the party's criteria was not met, she said "all options are on the table which includes campaigning for a public vote".
And shadow communities secretary Andrew Gwynne told the BBC's Andrew Marr Show he expected the NEC to "endorse Labour's policy that came out of the conference".
Mr Gwynne said: "I want to ensure that we avoid a bad Tory Brexit or a no-deal scenario. In those circumstances, yes, I think that wasn't on the ballot paper in 2016, we should then perhaps ask the people 'is this actually what you want, a confirmatory vote, do you support what the government's proposition is?'.
"But let's see what comes out of these talks because I hope that the government can move on some of these red lines so that we can get a more sensible approach towards Brexit going forwards."
But Lib Dem deputy leader Jo Swinson, whose party launched its European parliamentary elections campaign on Friday with a "stop Brexit" message, told the BBC: "Every Liberal Democrat vote is a vote to stop Brexit.
"A vote for Labour is a vote for Brexit. Nigel Farage and Boris Johnson will use those votes to say the British people want Brexit to happen."
There is some opposition to another referendum within Labour, amid concern about alienating party voters who backed Leave.
Earlier this month 25 Labour backbenchers wrote to Mr Corbyn, urging him to rule one out and arguing that it would "be exploited by the far right, damage the trust of many core Labour voters and reduce our chances of winning a general election".

Jeremy Hunt has urged Tory MPs to get behind Theresa May - amid a backlash against suggestions the Brexit transition period could be extended.
The foreign secretary said the "great strength" of other EU nations was that they had stayed united in the talks - and he urged Tories to do the same.
The PM had to "maximise her negotiating leverage in Brussels," he added.
Scottish Secretary David Mundell has raised concerns about a longer transition period with No 10.
He told the BBC: "What I want to be quite clear is that we are still leaving the Commons Fisheries Policy at the end of 2020. I think that's a very important thing for fishermen here in Scotland to know and understand."
But he added there was not a "specific proposal" about extending the transition period, it was just "something that has been floated" and said the "prime minister has my full backing in terms of getting a deal".
Former Conservative leader and prominent Brexiteer Iain Duncan Smith said it would see the UK paying the EU "tens of billions" more.
He told BBC's Newsnight he could not understand an extension when the UK "still hasn't got anything back in return",  and said the negotiations "look more like a capitulation".
But Mr Hunt said it was precisely because Mrs May had not "capitulated" to EU demands that no agreement had been reached at the European Council summit this week.
And he told BBC Radio 4's Today programme: "The great strength of the EU in these negotiations is that the 27 EU nations have remained united. And we now need to do the same behind Theresa May to maximise her negotiating leverage in Brussels."
Mrs May briefed around 120 business leaders on Brexit negotiations in a conference call on Friday - Downing Street said while businesses were regularly briefed after European Council meetings, this was the first time Mrs May had conducted one personally.
By BBC political editor Laura Kuenssberg
As we move towards what the legal deadlines imply are the closing moments of this whole process, some of its moments are becoming pretty strange.
The prime minister had a hint of warmth from some parts of the EU empire for the idea of drawing out the implementation period, to give more time to work out the long term fixes.
But even so, the politics put such a straitjacket on proceedings that she can't even quite manage to be completely clear about that.
So we heard about a proposal that's not a proposal but an "idea that's emerged". An extension to an extension that's not a request for a longer transition period but a desire perhaps to have the option.
It might sound like Kafka. But it's the words of a government struggling to keep a set of almost impossible promises.
The UK is due to leave the EU on 29 March 2019, and the transition period, which Mrs May prefers to call the implementation period, is designed to smooth the path to a future permanent relationship between the UK and EU.
During this period, which is due to finish on 31 December 2020, the UK's relationship with the EU will stay largely the same. But with the two sides failing to reach agreement yet, Mrs May said this arrangement could be extended "for a few months", if needed.
The UK has signed up to the principle of agreeing an Irish border "backstop" - an insurance policy designed to prevent the need for customs checks - in case there is a gap between the transition period ending and the future permanent relationship coming into force.
The problem is that the two sides have yet to agree what form the backstop will take, and how long it could last.
Mr Hunt said the backstop remained the "key" outstanding issue to negotiating a withdrawal agreement for the UK.
The UK would not agree to allow "customs barriers down the Irish Sea" - the EU has suggested keeping Northern Ireland within EU customs rules for a period - or for the whole of the UK to remain in the customs union "indefinitely".
"Because she has held firm on that that has meant we haven't been able to solve the problem this week. But those are two very important matters of principle for the United Kingdom," he said.
While the issue about the Irish border could be resolved through a free trade deal between the UK and EU, the EU was insisting the UK's withdrawal agreement should be negotiated first, with a "backstop", before the "future relationship" discussion began, he added.
"If we are going to resolve this, we need to make more progress on the future relationship."
Asked if the UK would have to pay more into the EU budget, if the transition period were to be extended, he said: "All those are issues that would have to be discussed" adding that the issues of money and of the Common Fisheries Policy were "very difficult".
Eurosceptic backbencher Jacob Rees-Mogg said any proposal that meant an extra £15bn a year being paid into the EU budget in return for "a waffly political declaration" would be "very hard to get through the House of Commons".
He told the BBC: "We are going to be tied to the EU for longer if we go along with what the prime minister is saying, without having any votes.
"So we will pay the EU for the privilege of it making our laws and interpreting them through the European Court of Justice for an extended period - that is not a good deal."
EU Brexit negotiator Michel Barnier told France Inter radio on Friday that "90% of the accord on the table has been agreed with Britain" but added: "I'm convinced a deal is necessary, I'm still not sure we'll get one."
Asked if the whole agreement could fail on the issue of avoiding a hard border in Ireland, he replied: "My answer is yes."
In a separate development, Tory MP Johnny Mercer has hit out at the current state of the government, describing it as a "shit show".
In an interview with The House magazine, the former Army officer said he would not have stood as an MP "if the situation was like it is now" and that he was no longer sure that his "set of values and ethos" were still "aligned with the Conservative Party".

In Brussels there is a strong sense that the Conservative Party have not woken up to the trade offs and compromises that will inevitably characterise the talks, writes Nicholas Watt.
The drinks were flowing and the mood was humming as the Tory great and good met to celebrate their election victory this week.
Michael Gove had a telling analogy as he praised Tory thinkers who had steered the party towards the ambition of breaching Labour's "Red Wall".
The likes of the former No 10 aide Will Tanner had provided a form of "in-flight refuelling" for the aircraft of the Tory party.
There was a danger, Gove noted, that after nearly a decade in office, the Conservative Party could run low on the fuel of ideas.
But Will Tanner's Onward think tank had been on hand with its in flight refuelling tanker.
Onward had identified Workington Man, a northern rugby league supporter, as a key target for the Tories. The party duly won Workington for the first time in over 40 years.
The in-flight refuelling had performed a starring role, Gove noted, in helping to deliver an unprecedented fourth successive general election first place with an increased Tory vote each time.
All so happy, all so relaxed as the Tories celebrated their success at the Westminster gathering. But hovering in the air before, and long after that successful political in flight refuelling, is Brexit.
With or without the bongs of Big Ben, Brexit will, in a technical sense, be delivered on 31 January as Britain leaves the EU.
But the Brexit story will be far from over then as attention turns immediately to talks on the UK's future relationship with the EU.
As the Tories have been basking in their election victory, the EU has in recent weeks issued warnings about how tough the talks will be.
In Brussels there is a strong sense that the Tories have not woken up to the trade offs and compromises that will inevitably characterise the talks. Officials believe the UK has only tuned into two aspirations agreed by all - the need for zero tariffs and zero quotas on goods.
These EU officials fear the UK has not focused on a third EU demand - no dumping. That means that if the UK wants zero tariffs and zero quotas it cannot embark on social dumping - gaining a competitive advantage over the EU by cutting labour and environmental standards and lowering taxes.
Senior UK officials say they understand exactly what the EU is saying.
One tells me: "We understand the EU is nervous about having a big economy on its doorstep that could undercut it by reducing standards. But we're not bothered. We want to do our own thing. Lots of our standards will be better."
Cabinet ministers close to the future trade talks believe the UK also has two advantages in the talks:
Failure to reach a deal in the trade talks would have less grave consequences for Britain than a no deal Brexit without a withdrawal agreement last year, according to ministers.
They point out that the three elements at the heart of last year's deal - Northern Ireland, citizens' rights and the UK's exit payment - will stand whatever happens.
The cabinet minister told me:
"Boris can say to the EU: you know I was prepared for the original no deal last year but was thwarted by parliament which blocked no-deal. I am now prepared for a WTO no-deal [trading on WTO terms in the event of no trade deal] which isn't so bad and I can do what I like in Parliament. So it is a credible threat."
These interpretations will be hotly contested by the EU and by pro-Europeans who want to fashion a close relationship with the EU. Brussels will say the EU has an abiding and common interest in preserving the integrity of the single market.
And pro-Europeans will challenge the idea that relying on WTO trading terms for the largest part of the UK's exports would be straightforward.
The opening skirmishes in the next round of Brexit talks have so far been a gentle affair. The Tories are still riding high after their election win but the atmosphere will soon heat up as the pace quickens.
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A Conservative MP says she sees no alternative other than backing another referendum on leaving the EU.
Heidi Allen becomes the latest Tory to support a new vote, saying the "right-wing" of her party had made Theresa May's Chequers Brexit plan - "dead".
"They have behaved unacceptably through this and have completely tied her hands," she told the BBC.
The prime minister has ruled out a referendum on the outcome of the Brexit negotiations.
Mrs May's Chequers plan - which would keep the UK closely aligned with the EU in trade in goods - has been heavily criticised by Tory Brexiteers, including Boris Johnson.
Ms Allen - who campaigned to Remain in the EU in 2016 - told Radio 4's Today programme that while she would still support in principle an "11th hour" deal from Mrs May and the EU, "too many" of her party - especially those on the right - would not.
The South Cambridgeshire MP said she had been left with "no alternative other than asking - should we come to that, no deal, that looks like that's what's going to happen - then we need to go back to the public to decide what they want us to do next."
On what a further referendum could look like, Ms Allen suggested that it should include the option of staying in the EU under existing terms.
By Jessica Parker, political correspondent
Heidi Allen joins a handful of Tory backbenchers who've openly said a so-called people's vote may now be needed.
And as someone who supported Remain, her comments may come as no surprise.
But, perhaps more significantly, she is the latest person to suggest that Theresa May's Chequers plan is dead. The blueprint, for our future relationship with the EU, has never been liked by the Leave supporting contingent.
But people like Heidi Allen had previously said that they would at least give Chequers a chance. No more.
It comes as Labour - not to mention the EU - has also declared that the proposals are unworkable in their current form.
And while Number 10 is sticking to its guns, there must be a big question as to how long this situation can be sustained.
The People's Vote campaign group wants to give the public the final say over whether the UK leaves the EU, arguing that voters should be given a choice  between leaving with or without a deal or staying on current terms.
Anna Soubry, Justine Greening and Sarah Wollaston are among the Conservative MPs who have supported a further referendum.
Ms Allen's comments come after ex-PM Sir John Major also made the case for another Brexit vote and highlighted the "completely unacceptable" attacks by certain Tory MPs on Mrs May.
Former foreign secretary Mr Johnson set out his "better Brexit plan" and refused to rule out a leadership challenge.
Last week Labour members voted to keep the option of another referendum on the table if parliament is deadlocked over the final outcome the government's Brexit negotiations.
The UK is due to leave the EU on 29 March 2019, and negotiations on the terms of exit and future co-operation are continuing.
The Conservative party is gathering in Birmingham for its annual conference.

Conservative MP Phillip Lee has defected to the Liberal Democrats ahead of a showdown between Boris Johnson and Tory rebels over Brexit.
Dr Lee, the MP for Bracknell, took his seat on the opposition benches as the PM addressed the Commons.
His defection means Boris Johnson no longer has a working majority.
MPs hoping to pass legislation to block no deal have cleared the first hurdle after Speaker John Bercow granted them an emergency debate.
That debate could last up to three hours, followed by a vote. If the MPs win the vote - defeating the government - they will be able to take control of Commons business on Wednesday.
That will give them the chance to introduce a cross-party bill which would force the prime minister to ask for Brexit to be delayed until 31 January, unless MPs approve a new deal, or vote in favour of a no-deal exit, by 19 October.
It seems right now - although there is still some arm twisting going on behind the scenes - that the government is set to lose the vote.
We are finding ourselves in the middle of a full-throttle confrontation between a Parliament that does not want to allow the country to leave the EU without a deal and a prime minister who secured his place in power promising he would always keep that as an option.
Both of them cannot be the victors here.
And they are both determined to win.
Speaking in the Commons earlier, Mr Johnson told MPs he wanted a negotiated exit from the EU and insisted there was "real momentum" behind the talks with Brussels.
He said he would travel to Dublin on Monday for discussions with Irish Prime Minister Leo Varadkar, focused on proposed alternative arrangements to the Irish border backstop - a key sticking point in the negotiations.
Asked to provide evidence of progress by several Tory MPs, he said he would not negotiate in public but reassured them he would give details of the UK's proposals well before the end of September to meet a deadline set by German Chancellor Angela Merkel.
But he said the moves by MPs, including Conservatives, to pass legislation effectively blocking a no-deal exit on 31 October would "destroy any chance of negotiating a new deal".
If the rebels succeeded in their aims, Mr Johnson said it would force him to go to Brussels to "beg for another pointless delay" to Brexit and he would "never" do that.
"It is Jeremy Corbyn's surrender bill. It means running up the white flag," he added.
No 10 has said the prime minister will push for an election on 14 October if the MPs succeed in blocking no deal.
But asked if he might simply ignore them and press ahead with a no-deal Brexit regardless, he said: "We will of course uphold the constitution and obey the law."
Last-ditch efforts to get the Tory rebels on side have been taking place, but BBC political editor Laura Kuenssberg said the first meeting on Tuesday morning between the prime minister and the group went "less than swimmingly" and was "less than cordial".
Further discussions reportedly began shortly after the PM's Commons statement.
There are thought to be about 15 confirmed rebels. The government had hoped the threat of an election - and of deselection and expulsion from the party - would be enough to bring them into line.
Before Dr Lee's defection, Mr Johnson only had a working majority of one in the Commons.
In a letter to the prime minister, Dr Lee said Brexit divisions had "sadly transformed this once great party into something more akin to a narrow faction in which one's Conservatism is measured by how recklessly one wants to leave the European Union".
"Perhaps more disappointingly, it has become infected by the twin diseases of English nationalism and populism."
He told BBC Radio 4's PM the "bullying" of MPs opposed to no deal showed the "tone and culture" of the Conservative Party had fundamentally changed, and he knew of other like-minded colleagues who were also considering their futures.
Welcoming her latest recruit, Lib Dem leader Jo Swinson said they would work together to prevent a "disastrous Brexit" which would do untold damage to the NHS and other public services.
Dr Lee's decision to cross the floor - following that of ex-Tory MP Sarah Wollaston last month - was greeted with cheers on the opposition benches.
Amid angry exchanges during the PM's statement on last month's G7 summit, Jeremy Corbyn urged the PM to "reflect on his choice of language" to describe the rebels' bill.
The Labour leader said the UK was "not at war with Europe" and it was a no-deal exit which would see the UK "surrender" jobs, employment standards and social protections.
"His is a government with no mandate, no morals and, as of today, no majority," he added.
The SNP's leader in Parliament, Ian Blackford, said Dr Lee's defection capped what he said was the "shortest-lived honeymoon period ever" for a new prime minister.
He said his party was ready for a general election at any time.
But veteran Tory Ken Clarke, one of those set to rebel later, said the PM's strategy was to "set conditions which make no deal inevitable, to make sure as much blame as possible is attached to the EU, and as quickly as he can fight a flag-waving election before the consequences of a no deal become too obvious to the public".

Leaving the EU by the end of October is a "hard red line" and will happen in "all circumstances", Andrea Leadsom has said in her pitch for leadership.
The ex-Commons leader said she had a plan for a "managed exit", adding that Parliament could "not stop us leaving".
But her rival Mark Harper said it was "not possible" to leave by 31 October, and Rory Stewart said talk of a better deal on the table was a "fairy story".
Ten Conservative candidates are in the race to be leader - and the next PM.
The deadline for Brexit was pushed back to October after MPs rejected Theresa May's withdrawal agreement with Brussels three times.
The European Union has repeatedly said the agreement will not be re-opened, and on Tuesday, president of the European Commission Jean-Claude Juncker stressed that once again.
"This is not a treaty between Theresa May and Juncker, this is a treaty between the United Kingdom and the European Union," he told a Politico event in Brussels.
"It has to be respected by whomsoever will be the next British prime minister."
Irish Prime Minister Leo Varadkar said it was a "terrible political miscalculation" for UK politicians to believe they can get a better deal.
"In all circumstances we are leaving the European Union on 31 October," Mrs Leadsom told her official campaign launch. "Our country and our party cannot afford any more indecisiveness."
The Brexiteer MP set out her plan for what she calls a "managed exit" from the EU, which includes striking a "temporary trade agreement" and a plan to negotiate contingency arrangements with Brussels over the summer recess.
She said these could be discussed at a summit with the new incoming EU commissioners and heads of government in September.
But at his official campaign launch, Mr Harper - an outsider in the race - said it was "not possible or credible" to leave on the terms of a new deal by the existing deadline of 31 October. Renegotiating and getting a deal past MPs would take longer, he said.
He said there could be a majority in the Commons to leave without a deal, but only if ministers demonstrated they had "strained every sinew" to get a new one.
Meanwhile, Health Secretary Mr Hancock - who is also competing for the top job - told BBC Radio 4's Today programme his plan was "eminently deliverable" by 31 October, as the EU was open to changing the political declaration part of the agreement.
"We need to solve Brexit and we cannot do it by threatening no deal," he said, adding: "Parliament will not allow a no-deal Brexit to happen."
Home Secretary Sajid Javid reiterated that although he wanted a revised deal, "if we got to end of October and the choice was between no deal or no Brexit, I'd pick no deal."
Later in the day, launching his campaign in a circus tent in London, Rory Stewart - another outsider - said he wanted to "take the politics out" of the situation and find a way to get Mrs May's deal through Parliament.
He said he would ramp up pressure on MPs to back it by promising that otherwise, he would convene a "grand jury" of citizens to make recommendations on how to proceed which politicians would have to stick to.
Vowing to hold the UK together and reconcile "extreme Remain and extreme Brexit" arguments, he added: "My project is about one thing - it is about moderation and compromise."
At her official launch, Mrs Leadsom introduced several policies away from Brexit, including using overseas development aid to help poorer countries to decarbonise and helping young people to save for a house deposit with a new scheme.
When questioned on taxes - prompted by Boris Johnson's pledge to cut income tax for those who earn more than £50,000 a year - she said she believed in low taxes.
But tax reform could not get through a hung Parliament, so that "needs to wait".
Taking a swipe at Mr Johnson's idea, Mr Harper said he would focus his tax cuts "at the lower end of the spectrum", adding: "I don't think we should be promising more money to higher rate taxpayers."
He also said the lack of a majority meant certain things would not be deliverable and as Brexit showed, it was "toxic" to make promises and not fulfil them.
The winner of the leadership contest will become next Conservative leader and prime minister. They're due to be in place by the week beginning 22 July.
Mr Javid, who launches his campaign on Wednesday, released a campaign video which BBC political editor Laura Kuenssberg described as the first big attempt by a candidate to communicate a personal story, introducing viewers to his family and background.
He also told the Evening Standard he was "very open minded" about having different immigration rules for regions such as London after Brexit, and could scrap Mrs May's policy that EU migrants should earn at least £30,000 to be considered for admission.
Mr Johnson - accused by Michael Gove and other candidates of "hiding in his bunker" because he is yet to a do a major event or TV interview - is also launching his campaign on Wednesday.
It's day two of the official campaign to be the next prime minister.
Andrea Leadsom cheerily launched her campaign, promising she would never utter the phrase "as a mother" that did for her chances last time.
As promised, the former chief whip Mark Harper was jacket off, sleeves rolled up, answering any question that journalists were willing to put.
That included - because the early stages of this campaign are this surreal - predicting in a fight between a lion and a bear that the lion, patriotically, would win. (yes, you read that right).
And TV presenter Lorraine Kelly was back - this time with a slapdown of the whole lot of the political class.
But the hard reality bites today too. Labour has just announced that they are leading another cross-party attempt to grab control of the Commons.
Just in case the candidates needed a reminder of what they'll inherit, the politician who wins this race might find that MPs have changed the law to kill off their solution to Brexit before they even call the removal vans to move their stuff to Number 10.
Ten Conservative candidates will contest Thursday's first round of voting after nominations closed in the contest to succeed Theresa May as Tory leader and prime minister.
Over the next two weeks, Tory MPs will take part in a series of secret ballots to whittle the candidates down to the final two.
The party's 160,000 or so members will then pick a winner in a postal ballot, with the result announced in the penultimate week of July.
On Tuesday 18 June BBC One will host a live election debate between the Conservative MPs still in the race.
If you would like to ask the candidates a question live on air, use the form below. It should be open to all of them, not a specific politician.
If you are reading this page on the BBC News app, you will need to visit the mobile version of the BBC website to submit your question on this topic.

You can't resolve 40 years of differences with an extra 40 minutes.
The cabinet meeting on Friday to get the grumpy group on board with Theresa May's plan for Brexit ran a little longer than her team had hoped, by 40 minutes.
But now they are cock-a-hoop over what they achieved. Tensions in the Tory Party over Europe are still profound.
But the Brexiteers were subdued with some neat Whitehall manoeuvring, and strong political arguments in preparation.
Ministers this week received one paper explaining why a Canada-style trade deal couldn't work because it wouldn't prevent an Irish hard border.
Another then about why the Norway model, the European Economic Area, couldn't work.
A third paper too explaining how leaving with no deal might cause such an economic upset, that the Tories would be punished for a generation.
Then finally late on Thursday before the meeting - ta dah! - a paper proposing the magic solution, well at least the prime minister's compromise.
That layering of arguments was repeated in real life by the sessions on Friday at Chequers.
Experts (they're back apparently) from government explained the problems with the models, and answered questions from the floor.
The idea was to illustrate to those present that, while they might have their own desires, in the end, they were not compatible with the government's priorities.
One cabinet minister described it as "confronting reality rather than the referendum slogans".
Then, voila, they were presented again with the prime minister's "evolved Mansion House" model, the only answer on offer on Friday aside from stalking out.
One of those present said there was an "overwhelming sense" in the room that "we just had to decide".
The middle ground in the cabinet - those who aren't on either ardent wing - were, it's said, tangibly determined to push for a decision with the prime minister more or less giving the impression to ministers that the only way to avoid taking part in that decision was to quit.
With the day designed as it was, only one seemingly workable plan was presented, so despite deep political division it was inevitably agreed.
One cabinet minister joked: "Put people in a room until they are so hot they will agree to anything."
But Friday's scorching temperatures were coincidental. The way the plan was made by Number 10 and their officials absolutely was not.
Every member of the cabinet had their say. Not surprisingly, Brexteers Boris Johnson, Andrea Leadsom, David Davis and Esther McVey are said to have "moaned a bit", by one of their colleagues.
Home Secretary Sajid Javid asked for assurances from the prime minister that there'd be no sliding on the promise to end unlimited EU immigration.
But sources say Foreign Secretary Boris Johnson did not indulge in a fit of political pique, but actually "engaged on the substance", in what another described as a bit of a "symbolic pushback".
Despite all the turbulence of recent months there was no huge face off. All that Brexiteer bravado failed to emerge.
One crucial reason, those present say, is because early in the afternoon Michael Gove, one of their number, said overtly that he'd back the PM's plan.
One minister said: 'He pulled the rug from under Boris and DD's feet." Another said: "He was the decisive voice."
If one of the main voices from the Vote Leave campaign said the deal was a runner, immediately it became harder for the others to resist.
Had the Brexiteers been willing, or able, to put up common resistance, the day could have ended very differently.
But as one Brexit source described it, the way the Chequers summit moved: "The anger had no home."
Michael Gove, who of course is resented by many for knifing Boris Johnson, just gave Eurosceptics another reason to suspect him.
There are difficult questions now for the Brexiteers.
Be in no doubt, Theresa May's plan is a far closer relationship with the EU than they desired. They are not happy but they are also not united.
As a group they are still powerful, they still have the numbers to make life nigh impossible for the prime minister.
Even though their representatives at the cabinet table on Friday didn't bite, they have not disappeared.
There is discussion among them about what to do next.
Some will start the rattling, leadership chatter is likely to surface around the margins. Some may plot to vote against the government soon simply to make a point. Others will argue to let the prime minister have her way, for now.
On Friday the cabinet made a big decision. Theresa May's foes may not have Chequers as a base to hatch their plan, but in the coming days, they are likely to decide.

EU Brexit negotiator Michel Barnier has warned that a transition period immediately after Brexit in 2019 is "not a given".
He said "substantial" disagreements remained and he had "some problems understanding the UK's position".
And he said the UK decision to quit the customs union and single market meant Irish border checks were "unavoidable".
David Davis said he was "surprised" to hear Mr Barnier was unclear on the UK's stance on the transition period.
"We are seeking a time-limited period that maintains access to each other's markets on existing terms," said the UK's chief Brexit negotiator.
He suggested there was a "fundamental contradiction" in the approach the European Commission was taking to Brexit talks.
"Today they acknowledged that a way to resolve disputes and infringements is needed.
"Yet at the same time they dismissed the UK's push for reasonable safeguards to ensure our interests are protected. It is not possible to have it both ways."
Mr Davis says businesses need "about two years" with much the same trading rules as they have now to allow them to adjust after the UK leaves the EU on 29 March next year.
And he had hoped to get a deal with the EU on it by this March, so talks could then move on to the bigger issue of the UK's future relationship with the remaining 27 EU nations.
But Mr Barnier, speaking after a week of technical discussions between civil servants on both sides, said that three "substantial" disagreements remained over the transition period.
The pound fell sharply against the dollar and the euro during Mr Barnier's speech before recovering slightly to stand about 0.7% down on the day.
"To be frank, I am surprised by these disagreements. The positions of the EU are very logical, I think," said Mr Barnier.
He said the UK must "accept the ineluctable consequences of its decision to leave the EU, to leave its institutions and its policies".
"If these disagreements persist the transition is not a given."
By BBC Political Correspondent Leila Nathoo
This was a politely delivered but pointed message to Britain: you can't keep up your cake-and-eat-it approach of vowing to leave the single market and customs union while still wanting no checks at the Irish border.
And don't bank on a transition period (which was supposed to be the easy bit to agree) as there's still plenty we don't see eye-to-eye on.
Theresa May has been keeping the government's position deliberately vague as her ministers struggle to agree among themselves on exactly how they see Britain's future ties with the EU.
But the bottom line from Brussels today? Time to talk straight and put flesh on the bones.
Labour's Shadow Brexit Secretary Sir Keir Starmer said the prime minister should take immediate action to avoid a "cliff-edge" for business.
"Theresa May must end the infighting within her cabinet, drop her reckless redlines and accept Labour's proposals for a transitional deal.
"That means seeking to remain in a customs union with the EU and within the single market during that period."
Lib Dem leader Sir Vince Cable, who wants a referendum on any final deal with the EU, said the government "has no plan, no strategy, and no idea".
But Northern Ireland's Democratic Unionist Party, which supports Theresa May's minority government, accused Mr Barnier of "brandishing the threat of customs controls" when "everyone has committed to avoiding a hard border".
They argued that the best solution was to resolve the issue through a free trade agreement and "fresh customs partnership with Brussels".
Mr Barnier hit back at comments by David Davis, who described a leaked EU document suggesting any dispute with the UK during the transition period could mean UK benefits, such as access to the single market, being suspended as "frankly discourteous".
The EU negotiator said he had "not been in the least discourteous or vindictive" adding: "Quite simply we have to construct a withdrawal agreement which is legally sound and does not give rise to any uncertainty in anyone's mind."
On the thorny issue of the border between the Irish Republic and Northern Ireland, Mr Barnier said there was agreement that a hard border must be avoided, but added: "It is important to tell the truth.
"A UK decision to leave the single market and to leave the customs union would make border checks unavoidable."
Prime Minister Theresa May has said the UK will leave the single market and the customs union, although she has yet to spell out in detail what she wants instead.
She secured an agreement on withdrawal - including avoiding the return of a hard Irish border - in December.
But that has now got to be translated into a legal text before it can be ratified by the EU - and Mr Barnier said he wanted to get rid of any ambiguity on the Irish border question.
The withdrawal agreement includes a fall back position if the UK leaves without a deal, which proposes "full regulatory alignment" with the EU.
To some this sounds like staying in the single market and customs union - but other options, preferred by the UK, to avoid border checks are still on the table.
Mr Barnier said the UK has accepted the need to discus how to make "full regulatory alignment" work in practice, while the other options are discussed in parallel.
But he added: "Time is short - very short - and we haven't a minute to lose if we want to succeed. And we do want to succeed in this orderly withdrawal."

Trick or treat? You couldn't quite make it up.
It is approaching 03:00 GMT - it's weird enough at this time of day to be about to see Theresa May speak.
And the new Brexit deadline is, you guessed it, Halloween.
So to get all the terrible metaphors about horror shows, ghosts and ghouls out of the way right now, let's consider straight away some of the reasons why this decision is a treat in one sense, but could be a trick too.
A treat? First and most importantly, the EU has agreed to put the brakes on. We will not leave tomorrow without a deal.
The prime minister's acceptance that leaving the EU without a formal arrangement in place could be a disaster won out.
She has at least avoided the possible turmoil of leaving with no arrangement, which for so long Theresa May claimed to countenance.
The UK now has nearly six more months to work out exactly how it wants to leave the EU.
Of course it gives those trying to block the departure more time to try to make that happen too.
But in its simplest sense, the prime minister asked for a delay so that she didn't open Pandora's Box.
The EU eventually said yes, even on a different timetable. Theresa May is of course likely to still try to move as quickly as possible.
And there are quite a few potential tricks.
This new October deadline might not solve very much at all.
It's longer than those who wanted a short delay hoped. So there won't be immediate pressure on the prime minister's current plan (which might be a vain hope) of getting out of this - finding common ground with the Labour party.
Certainly, everyone in politics involved in Brexit could do with a breather, but a pause of such duration might just enable more delay, as the chance to quicken the tempo fades away.
And with only limited expectations for that process anyway, it's likely sooner or perhaps later that the prime minister will be back in Parliament again asking MPs to coalesce around an option that could command a majority that could last a while.
Again, without time pressure, it's not clear why Parliament would suddenly be in a rush to agree. That's why it's not entirely surprising to hear the EU Council president warn minutes after the agreement that the UK must not waste the extra time it's been given.
This could, although I hate to say it, just make way for months of extra gridlock before the UK and the EU find themselves back here in a similar situation in the autumn.
That's why, potentially, an election might become the way out that few want is still possible.
And don't be in any doubt that those in Parliament and outside pushing for another referendum, or to stop Brexit altogether, will use this opportunity to make their case more and more loudly.
Even Brexiteers in Cabinet, who are completely committed to the cause, acknowledge that the further away from the referendum in 2016, the weaker the mandate for departure becomes.
There is though, still time for a leadership contest in the Tory Party that would leave a new prime minister in charge, to find a new way out.
Even before the official confirmation of the decision came, one minister got in touch to say that now the prime minister can stay on "in name only" with a leadership contest getting going as early as just after Easter and a new leader in place by early summer.
Perhaps, by the time this new deadline approaches, someone else will be trying to untangle the mess.
If that happens, the EU, which deeply fears a more Eurosceptic leader, might just have played a trick on themselves.

Donald Trump has suggested Theresa May's Brexit agreement could threaten a US-UK trade deal.
The US president told reporters the withdrawal agreement "sounds like a great deal for the EU" and meant the UK might not be able to trade with the US.
No 10 insisted it is "very clear" the UK would be able to sign trade deals with countries around the world.
Downing Street added that Mrs May is ready to defend her deal in a TV debate with Labour leader Jeremy Corbyn.
It has been reported the debate could take place on 9 December - two days before the Parliamentary vote on Mrs May's deal.
Speaking to reporters outside the White House, Mr Trump said: "Right now if you look at the deal, [the UK] may not be able to trade with us. And that wouldn't be a good thing. I don't think they meant that."
It would appear Mr Trump was suggesting the agreement could leave Britain unable to negotiate a free-trade agreement with the United States.
Cabinet Office minister David Lidington said Mr Trump's comments "were not unexpected" and negotiations on a trade deal with the US were always going to be "challenging".
"The United States is a tough negotiator," he told BBC Radio 4's Today. "President Trump's always said very plainly 'I put America first'. Well, I'd expect the British prime minister to put British interests first."
The comments came after Mrs May fought off criticism of her Brexit deal from MPs on all sides of the Commons on Monday - insisting the agreement would allow the UK to regain control of laws, money and borders.
In other developments:
By BBC North America editor Jon Sopel
Theresa May took a kicking in the House of Commons and then her closest ally, in the shape of Donald Trump, puts on his size 12 hobnail boots and joins in.
When Donald Trump fired a broadside at Theresa May's Brexit deal there was nothing accidental or off the cuff about it.
Senior members of his administration maintain close contacts with prominent eurosceptics in the Conservative party.
But when the president says the agreement could jeopardise trade with the UK, it's hard to see what he means. During the transition period, business with the US would presumably carry on in exactly the same way as it does now.
Yet all the time that Britain is in some way yoked to EU rules then there are limits to what can be negotiated in terms of a free trade deal - all points that have been made by those who campaigned for a more decisive Brexit.
This intervention, coming post deal and pre-Commons vote, can only be interpreted in one way - the president is siding with the prime minister's critics.
Labour, the Lib Dems, the SNP, the DUP and many Tory MPs have said they will vote against the Brexit deal.
Sir Michel Fallon has launched a scathing attack on Mrs May's Brexit deal, labelling it "doomed".
The senior Conservative and long-standing party loyalist echoed Mr Corbyn's words when he described the deal as "the worst of all worlds".
Asked if the prime minister was now also doomed, he told BBC Radio 4's Today programme: "That's up to my colleagues."
As part of her two-week bid to convince MPs and the British public to back her deal, Mrs May will tell politicians and employers in Wales on Tuesday that they will have more power after Brexit, with more than 150 areas of policy passing to devolved parliaments and assemblies.
She will also highlight the potential benefits to farmers of leaving the EU's Common Agricultural Policy.
Then in Northern Ireland, she will tell representatives of the five main political parties her deal will allow employers to "trade freely across the border with Ireland and have unfettered access to the rest of the United Kingdom's market".
Northern Ireland has featured heavily in discussions about Brexit because both the UK and the EU want to avoid a physical border - with guard posts and checks - between it and the Republic of Ireland. The agreement includes a "backstop" - a fall-back position - that would mean Northern Ireland would still follow some EU rules on things such as food products if a long-term trade deal is not agreed.
The Democratic Unionist Party, which props up Mrs May's government, has accused the PM of breaking her promise that Northern Ireland would never be treated any differently from the rest of the UK - but the PM has said the backstop was an "insurance policy no-one wants to use".
The UK is due to leave the EU on 29 March 2019, under the terms of legislation already passed by Parliament.
Labour, the Lib Dems, the SNP, the DUP and many Tory MPs have said they will vote against the Brexit deal.
Lord Kerslake, the former head of the civil service, said government officials were probably working on a "plan B" in case the deal was rejected but there would be "no whisper of it" publicly until the outcome of the Commons vote.
He told the BBC that while the option of seeking changes to the withdrawal agreement remained on the table, if the defeat was extremely heavy then more radical alternatives, such as extending the talks, would have to be considered.
"If Parliament rejects the deal by a significant majority and no deal is not now unacceptable there is a responsibility on the government to look seriously at options they have previously ruled out," he told Radio 4's Today.

The UK may be forced to change its "economic model" if it is locked out of the single market after Brexit, Chancellor Philip Hammond has said.
Mr Hammond said the government would not "lie down" and would "do whatever we have to do" to remain competitive.
He had been asked by a German newspaper if the UK could become a "tax haven" by further lowering corporation tax.
Labour's Jeremy Corbyn said his comments sounded like "a recipe for some kind of trade war with Europe".
Having so far refused to offer a "running commentary" on her plans, Prime Minister Theresa May is expected to spell out the most detail so far of her Brexit strategy in a speech on Tuesday.
Reports have suggested she will signal pulling out of the EU single market and customs union, although Downing Street described this as "speculation".
In an interview with the German newspaper Welt am Sonntag newspaper, Mr Hammond said he was "optimistic" a reciprocal deal on market access could be struck, and that he hoped the UK would "remain in the mainstream of European economic and social thinking".
"But if we are forced to be something different, then we will have to become something different," he said.
"If we have no access to the European market, if we are closed off, if Britain were to leave the European Union without an agreement on market access, then we could suffer from economic damage at least in the short-term.
"In this case, we could be forced to change our economic model and we will have to change our model to regain competitiveness. And you can be sure we will do whatever we have to do.
"The British people are not going to lie down and say, too bad, we've been wounded. We will change our model, and we will come back, and we will be competitively engaged."
Asked about Mr Hammond's comments during an interview on The Andrew Marr Show Mr Corbyn said "He appears to be making a sort of threat to EU community saying 'well, if you don't give us exactly what we want, we are going to become this sort of strange entity on shore of Europe where there'll be very low levels of corporate taxation, and designed to undermine the effectiveness or otherwise of industry across Europe.'
"It seems to me a recipe for some kind of trade war with Europe in the future. That really isn't a very sensible way forward."
Mr Corbyn also said Mrs May "appears to be heading us in the direction of a sort of bargain basement economy", adding: "It seems to me an extremely risky strategy."
by BBC business correspondent Joe Lynam
According to Philip Hammond, Britain might be "forced" to change its economic model. To what?
For some, the true advantage of leaving the EU would be to tear up the 'rules' and make Britain more like Singapore.
Singapore abides by World Trade Organisation and ASEAN (the Association of Southeast Asian Nations) trade rules, but it's famed for its light touch regulation - especially when it comes to financial services - which some Brexiteers feel is the opposite of EU "meddling".
But turning a large G7 economy with a robust social model into a city state might be difficult. It might involve the government handpicking which industries it thinks will be successes and rapidly neglecting existing sectors.
Millions of people would need to get brand new qualifications while those with undesirable skills would become surplus to requirements. Massive infrastructure projects might be rushed through with minimal consultation.
For a country with Britain's past and present, is that a possible future?
Scottish First Minister Nicola Sturgeon said it appeared Brexit would mean a "low-tax, deregulated race to the bottom", with workers' rights and environmental protections threatened.
She wrote on Twitter: "If that is the case, it raises a more fundamental question - not just are we in/out EU, but what kind of country do we want to be?"
In her speech on Tuesday, the prime minister is expected to call on the country to "put an end to the division" created by the EU referendum result.
She will urge the UK to leave behind words such as "Leaver and Remainer and all the accompanying insults and unite to make a success of Brexit and build a truly global Britain".
Several of Sunday's newspapers claim Mrs May will outline a "hard Brexit" approach, a term used to imply prioritising migration controls over single market access.
Northern Ireland Secretary James Brokenshire said he did not think it was a "binary choice" between trade and migration, but added that the "very stark message" from the EU referendum was that "free movement as it exists today cannot continue in to the future".
Speaking on the BBC's Sunday Politics, Liberal Democrat leader Tim Farron said a "hard Brexit" had not been on the ballot paper in June's referendum and accused the PM of adopting "the Nigel Farage vision" of Brexit.
Mr Farage, the former UKIP leader, told Sky News he had "yet to be convinced" by the PM's approach.

The EU says it is ready to extend the proposed length of the post-Brexit transition period if the UK wants.
The current plan is for a transition period of 21 months to smooth the path from Brexit to the UK and EU's future permanent relationship.
But with the two sides failing to reach a deal yet, UK Prime Minister Theresa May said this arrangement could be extended "for a few months", if needed.
Some Brexit campaigners have reacted angrily to the suggestion.
Mrs May said she was not proposing extending the transition, but that having the option to do so could help solve the current impasse over the Irish border.
An EU source told the BBC there would have to be "financial implications" if the UK did extend the transition period.
EU Council president Donald Tusk spoke to journalists at the end of a Brussels summit where there was no major breakthrough on the key issue of how to avoid new visible border checks between Northern Ireland and the Republic of Ireland after Brexit.
He said that if "the UK decided an extension of the transition period would be helpful to reach a deal, I am sure the leaders would be ready to consider this positively".
Mr Tusk declared himself in a "much better mood" than after the last summit, in Salzburg.
Jean-Claude Juncker, the president of the European Commission, said extension of the transition period "will probably happen" saying it was a good idea because it would allow more time to draw up a long-term relationship between the UK and the EU.
In her post-summit press conference, Mrs May said the idea of having the option to extend the transition period could be "a further solution" to the search for a "backstop" to ensure no hard border.
"What we are not doing, we are not standing here proposing an extension to the implementation period," she said.
"What we are doing is working to ensure that we have a solution to the backstop issue in Northern Ireland."
Both sides are committed to resolving the outstanding issues as soon as possible, she said, adding there was a "very real sense that people want that deal to be done".
Irish prime minister Leo Varadkar said: "A lot of things have been agreed but there are still big gaps both in terms of the shape of the future relationship and also the protocol on Northern Ireland and Ireland and the backstop."
The UK is due to leave the EU on 29 March 2019, and the transition period, which Mrs May prefers to call the implementation period, is designed to smooth the path to a future permanent relationship.
During this transition period, which is due to finish on 31 December 2020, the UK's relationship with the EU will stay largely the same.
The UK has signed up to the principle of agreeing an Irish border "backstop" - an insurance policy designed to prevent the need for customs checks - in case there is a gap between the transition period and the future permanent relationship coming into force.
The problem is that the two sides have yet to agree what form the backstop will take, and how long it could last.
Nigel Dodds, of Northern Ireland's Democratic Unionist Party - whose support the government needs in key votes - said extending the transition phase would cost the UK billions of pounds and not change the "fundamental problem" with the EU's backstop plan.
This is because it involves Northern Ireland staying aligned to EU rules, which the DUP - and the UK government - says is unacceptable because it creates a new border in the Irish sea.
Brexiteers are not impressed, with Conservative backbench MP Jacob Rees-Mogg telling Sky News it was "a rather poor attempt at kicking the can down the road".
The Leave Means Leave campaign said a longer transition would give the EU "zero incentive to negotiate anything and gives Brussels the power to force whatever they want on to the UK".
Downing Street, meanwhile, insisted there was no difference of opinion with International Development Secretary Penny Mordaunt, who said earlier that the prime minister "has been very clear about when the implementation period will come to an end" and "this is about the rules within that implementation period".
Speaking on BBC Radio 4's Today programme, former Conservative minister Nick Boles described extending this period as as "desperate last move" and warned that Mrs May was losing the support of the Tory party.
Another former minister, Remain-voting Nicky Morgan, said an extension would be "unhelpful" and would leave the UK in a "Brexit holding pattern".
Asked earlier whether he would support a longer transition period, Labour leader Jeremy Corbyn said: "The prime minister has got herself into this mess by failing to reach any meaningful agreements with the EU".
Cabinet Office Minister David Lidington said the cost of extending the transition period would have to be "teased out" during the negotiations.

The UK government is planning to put out "concrete proposals" next week for reaching a Brexit deal with the EU, the BBC understands.
Brussels correspondent Adam Fleming said it was expected they would be revealed after the Tory conference but in time for scrutiny ahead of the EU summit on 17 October.
Brexit Secretary Stephen Barclay said the "moment of truth" was approaching.
The UK is currently due to leave the EU on 31 October.
Prime Minister Boris Johnson says this will happen whether or not there is a new deal with Brussels - but adds that he would prefer leaving with a deal.
However, MPs have passed a law requiring Mr Johnson to seek an extension to the deadline from the bloc if he is unable to pass a deal in Parliament, or get MPs to approve a no-deal Brexit, by 19 October.
Meanwhile, Scotland's first minister has warned that Mr Johnson could force through a no-deal Brexit unless the opposition acts.
Nicola Sturgeon said she was "open-minded" about who might emerge to lead a temporary government if Mr Johnson is removed from office in a vote of no confidence.
BBC political correspondent Nick Eardley said he had been told by a senior SNP source that the party's MPs were prepared to put Mr Corbyn in 10 Downing Street "as soon as next week" to extend the Brexit deadline and call an election.
Mr Barclay held talks with the EU's chief negotiator, Michel Barnier, on Friday, telling the BBC afterwards: "I think there is still a long way to go. I think we are coming to the moment of truth in these negotiations.
"We are committed to securing a deal. The prime minister has made clear he wants a deal, but there has to be political will on both sides and that's what we are exploring."
The biggest obstacle to a deal is the backstop - the plan to prevent a hard border between Northern Ireland and the Irish Republic.
The policy - agreed to by former PM Theresa May in her withdrawal deal with the EU, which was rejected three times by Parliament - is unacceptable to many Conservative MPs.
But the European Commission said Mr Barnier had stressed to Mr Barclay during the meeting that it was "essential" there was a "fully operational solution in the withdrawal agreement to avoid a hard border on the island of Ireland, protect the all-island economy and the integrity of the single market".
"The EU remains open and willing to examine any workable and legally operative proposals that meet all these objectives," a statement issued after the meeting said.
If the UK's new proposals prove acceptable to the EU it would trigger a frantic period of treaty-making.
The experts at the European Commission would have to assess whether they are legally watertight and politically acceptable.
The 27 other member states would have to be consulted and the deal tweaked if they had concerns.
Ideally this would all be done a week before the summit of EU leaders of 17 October.
That's an incredibly - and I mean incredibly - tight timeline by the standards of the Brexit process… by any EU process.
And Brussels diplomats are very gloomy because they say the ideas tabled so far by the UK do not go in the right direction.
Some think that means there's virtually no chance of agreement being reached next month.
Although if the prime minister is only going to unveil his plans when Tory party conference has finished, does that mean he has an ace up his sleeve that he knows will satisfy the EU and antagonise his own party?

Brexit supporters in the cabinet have agreed the UK should offer to pay more money to the EU as it leaves.
But no formal offer will be made until the EU agrees to begin talking about a new trade deal with the UK.
No new figure has been given - but it is thought it could be up to £40bn, which would be double what the UK's offers so far add up to.
The UK and the EU have yet to agree on the so-called "divorce bill" with the UK due to leave the EU in March 2019.
Some Conservative MPs have reacted angrily to the possibility of the UK agreeing to pay more - yesterday one, Nigel Evans, said it would be like a "ransom payment" to the EU while another, Robert Halfon, said it would make voters "go bananas".
But despite this, BBC assistant political editor Norman Smith said leading Brexiteers in Theresa May's cabinet, like Boris Johnson and Michael Gove, had agreed to support her in paying a "much larger sum" - as long as the EU agrees to begin trade talks, which it has refused to do so far.
And no final figure will be agreed until a trade deal is agreed, he added.
The UK voted to leave the EU in June 2016, and served the EU with formal notice of Brexit in March 2017. This began a two-year countdown to the UK's departure day which will be in March 2019.
Before that the two sides have to agree all sorts of things - including what happens to EU citizens living in the UK and British people living in the EU, and how the Northern Ireland border will work.
So the two teams of negotiators have been meeting in Brussels every month.
But there has not been much of a breakthrough so far, with the "divorce bill" proving to be one of the key sticking points.
Part of the problem for Theresa May is that while the EU wants the UK to offer more money, some of her MPs say this would be unacceptable and that the UK should just walk away and leave.
EU leaders are due to decide at a summit on 14 and 15 December whether to allow talks on a future trade relationship to begin.
It was billed as a key meeting where Theresa May would try to get her ministers on side to support her in negotiating cash with the EU.
Downing Street has been tight-lipped about what was actually discussed at the Cabinet Exit and Trade (Strategy and Negotiations) sub-committee, chaired by Prime Minister Theresa May.
But the BBC understands ministers concluded there is the possibility that talks with the EU will move on to the next phase in December but "we are not going to move on our own".
There were also tensions over the future role of the European Court of Justice.
Some believe the court will need to supervise the trading rules between the UK and EU during a period of transition after Britain leaves.
Chancellor Philip Hammond has floated the idea of a tribunal, similar to the arrangements in place in European Economic Area countries such as Norway, to settle any disputes.
But the EU may insist on a continued role for the European Court of Justice.
The EU says the UK needs to settle its accounts before it leaves. It says the UK has made financial commitments that have to be settled as part of an overall withdrawal agreement.
The UK accepts that it has some obligations. And it has promised not to leave any other country out of pocket in the current EU budget period from 2014-20.
But the devil is in the detail.
There are also issues like pensions for EU staff, and how the UK's contribution to these is calculated for years to come, and the question of what happens to building projects - for instance in Spain - that had funding agreed by all EU members including the UK but which will only begin construction after the UK has left.
Large amounts of the EU's budget are spent in two areas - agriculture and fisheries, and development of poorer areas.
Projects include business start-ups, roads and railways, education and health programmes and many others.
While Theresa May is battling to get her party onside, over in Germany there's more upheaval, where coalition talks have broken down, plunging Chancellor Angela Merkel into a political crisis.
This has raised the prospect of more elections in Germany, the EU's largest economy.
How might this affect Brexit? Tory backbencher Andrew Bridgen told the BBC there could be "no meaningful negotiations" with the EU until it was resolved, adding: "Why would we want to make concessions now when we don't have to?"
Tory MPs Jacob Rees-Mogg and Iain Duncan Smith agree - Mr Duncan Smith told The Times the UK should "sit tight".
But on the BBC's Today programme, German minister Christian Schmidt warned Tory Brexiteers not to try to take advantage of the political turmoil in his country to drive a harder bargain.
"I would suggest to all not to count on such a scenario," he said, adding that if the UK leaves the EU without a deal it will be a "disaster" for its economy.
The Sports Minister Tracey Crouch thinks people have had enough of the "daily commentary" on the UK's EU departure.
She tells HuffPost UK people urge her in the street to "ask the BBC to stop reporting on Brexit".
"They want us to do it, they want us to get on with it. I'm not sure they necessarily want the daily commentary on it," she says.
With this in mind, she recently wrote her weekly newspaper column on The Great British Bake Off instead.
"The only Brexit they care about is getting the bread out of the oven in time," it said.

The UK "would regret it forever" if it lost its status as a world leader in car manufacturing after Brexit, Business Secretary Greg Clark has said.
He added it was "concerning" that Toyota UK had told the BBC that if Britain left the EU without a deal it would temporarily halt production at its factory in Burnaston, near Derby.
"We need a deal," Mr Clark said.
The Japanese carmaker said the impact of border delays in the event of a no-deal Brexit could cost jobs.
The Burnaston plant - which makes Toyota's Auris and Avensis - produced nearly 150,000 cars last year of which 90% were exported to the rest of the European Union.
"My view is that if Britain crashes out of the EU at the end of March we will see production stops in our factory," said Marvin Cooke, Toyota's managing director at Burnaston.
Other UK car manufacturers have raised fears about leaving the EU without agreement on how cross-border trade will function, including Honda, BMW and Jaguar Land Rover.
BMW, for example, says it will close its Mini plant in Oxford for a month following Brexit.
The main concerns relate to what carmakers say are supply chain risks in the event of a no-deal Brexit.
Toyota's production line is run on a "just-in-time" basis, with parts arriving every 37 minutes from suppliers in both the UK and the EU for cars made to order.
If the UK leaves the EU without a deal on 29 March, there could be disruption at the border which the industry says could lead to delays and shortages of parts.
It would be impossible for Toyota to hold more than a day's worth of inventory at its Derbyshire plant, the company said, and so production would be stopped.
Mr Clark said Theresa May's Chequers plan for future relations with the EU is "precisely calibrated to avoid those checks at the border".
"We need to have a deal... we want to have the best deal that will allow as I say not just the success at present to be enjoyed but for us to grasp this opportunity," he told BBC Radio 4's Today programme.
"The evidence from not just Toyota but other manufacturers is that we need to absolutely be able to continue what has been a highly successful set of supply chains."
Toyota was unable to say how long production would be stopped, but in the longer term, warned that added costs would reduce the plant's competitiveness and eventually cost jobs.
Peter Tsouvallaris, who has worked at Burnaston for 24 years and is the Unite union convenor at the plant, said his members are increasingly concerned: "In my experience once these jobs go they never come back.
"And that's why we have to do everything possible to keep these jobs in the area."
A government spokesperson said: "We have put forward a precise and credible plan for our future relationship with the EU.
"As part of this we have proposed a UK-EU free trade area underpinned by a common rulebook on manufactured goods, such as automotives."
Started production December 1992
Employs 2,564 (inc 322 agency)
Produces Auris and Avensis - including pressing body panels, welding and assembly
Site is 580 acres - 2.35 million square metres
Total vehicles produced: 144,077, of which Avensis: 25,057, Auris: 34,899 and Auris Hybrid: 84,121

UK and EU officials have agreed the draft text of a Brexit agreement after months of negotiations.
A cabinet source told the BBC that the document has been agreed at a technical level by officials from both sides after intensive discussions this week.
A special cabinet meeting will be held at 14:00 GMT on Wednesday as Theresa May seeks ministers' backing.
The PM has been meeting ministers in Downing Street for one-to-one talks on the draft agreement.
BBC political editor Laura Kuenssberg said the agreement contained a UK-wide customs "backstop" aimed at preventing new border checks in Northern Ireland.
There is no additional Northern Ireland-only backstop - but sources wouldn't be drawn on any specific arrangements for Northern Ireland on rules and regulation within the UK-wide one, she added.
This "backstop" has proved to the most contentious part of the withdrawal negotiations, with concerns raised by Brexiteer Tories and the DUP over how it will work.
The pound surged against the dollar and the euro following the negotiations breakthrough - but analysts warned it could be short-lived, with the cabinet and Parliament yet to agree to the plans.
The EU said it would "take stock" on Wednesday, while the Irish government said negotiations were "ongoing and have not concluded".
Leading Brexiteers, such as Boris Johnson and Jacob Rees-Mogg, immediately criticised what has been reported to be in the draft agreement, saying it would keep the UK under EU control.
Northern Ireland's Democratic Unionist Party, which gives Theresa May vital support in key votes, said it would be a "very, very hard sell".
But Conservative Chief Whip Julian Smith said he was "confident" it would pass when put to a crucial Commons vote, and Transport Secretary Chris Grayling called for "a little bit of calm" before the cabinet gives its verdict on Wednesday.
Both the UK and EU hope to be able to schedule a special summit of European leaders at the end of November to sign off the deal.
The details of the draft agreement have not been published, so we don't know the small print yet.
But it is made up of a withdrawal agreement - said to run to 500 pages - alongside a statement about what the UK and EU's future relationship will look like.
The withdrawal agreement includes how to guarantee there will not be physical border checks reintroduced in Northern Ireland - the major sticking point in recent weeks.
Some Brexiteers fear the likely arrangement will keep the UK locked into EU trade rules for years to come in order to maintain a frictionless border.
The agreement also includes commitments over citizens' rights after Brexit, a proposed 21-month transition period after the UK's departure on 29 March 2019 and details of the so-called £39bn "divorce bill".
The future relationship statement is expected to be far shorter, with the UK and the EU's long-term trade arrangements yet to be settled.
No 10 said ministers were now being called to a special meeting to "consider the draft agreement the negotiating teams have reached in Brussels, and to decide on next steps".
Before they do so, they will be able to read relevant "documentation".
By BBC political editor Laura Kuenssberg
It doesn't seem to me that many of the cabinet are likely to walk on Wednesday over what's in the document.
It's suggested that those with bigger doubts are more likely to cause problems for the prime minister because it won't get through Parliament.
One source told me senior ministers are thinking not just about the wisdom of backing a deal they don't like because it's a sour compromise, but whether it is folly to back a deal they believe can't get through Parliament.
Slamming on the brakes now would force a crisis, but it could be less serious than the political disaster of pursuing this plan to an eventual calamitous defeat that could take them all down.
Former foreign secretary Mr Johnson said the plan would see the UK remain in the customs union and "large parts" of the single market.
He told the BBC it was "utterly unacceptable to anyone who believes in democracy" and he would vote against it.
Mr Rees-Mogg warned of the UK becoming a "vassal state" with Northern Ireland "being ruled from Dublin".
Labour leader Jeremy Corbyn said "given the shambolic nature of the negotiations, this is unlikely to be the good deal for the country."
Pro-EU Conservative MP Justine Greening said the agreement would leave the UK with less influence and undermine its credibility.
Speaking at a rally calling for another EU referendum to be held, she said: "Even if some people in my party can't see this is a bad deal, everyone else around this entire planet can."
Former Transport Minister Jo Johnson told the audience at a packed Westminster Hall that cabinet ministers were "looking deep into their consciences" about whether to support the deal.
Mr Johnson, who quit his ministerial role last week over Brexit policy, added: "The whips are going to tighten the thumbscrews on all our colleagues across Parliament in all parties probably, so it is very hard to predict."
BBC Europe editor Katya Adler
Brussels is keeping schtum this evening. This doesn't mean that nothing's going on. Those in the know simply prefer to keep quiet at this sensitive stage.
It seems what is being described to me as a "mutual understanding" has indeed been reached on a technical level between EU and UK Brexit negotiators.
This is not yet a deal. All eyes are now on the UK cabinet. If ministers reject the draft, then it's back to the drawing board.
If they approve it, then the 27 EU ambassadors scheduled to meet tomorrow may be told by the European Commission that decisive progress has been made in negotiations, meaning a Brexit summit could be convened with Theresa May, possibly in less than two weeks' time.
First though, all 27 EU countries and the European Parliament will want to pore over the text. And that won't be with an uncritical eye.
Meanwhile, following pressure from all sides of the Commons, ministers have agreed to provide MPs with a legal assessment of the implications for the UK of the Irish backstop and other controversial aspects of any deal.
Cabinet Office minister David Lidington said Attorney General Geoffrey Cox would make a statement to MPs and take questions ahead of the final vote on any Brexit deal.
MPs, he said, would get to see "a full reasoned position statement laying out the government's both political and also legal position on the proposed withdrawal agreement".

European Union leaders have granted the UK a six-month extension to Brexit, after late-night talks in Brussels.
The new deadline - 31 October - averts the prospect of the UK having to leave the EU without a deal on Friday, as MPs are still deadlocked over a deal.
European Council President Donald Tusk said his "message to British friends" was "please do not waste this time".
Theresa May, who had wanted a shorter delay, said the UK would still aim to leave the EU as soon as possible.
The UK must now hold European elections in May, or leave on 1 June without a deal.
The prime minister will later make a statement on the Brussels summit to the House of Commons, while talks with the Labour Party, aimed at reaching consensus on how to handle Brexit, are set to continue.
Mrs May tweeted: "The choices we now face are stark and the timetable is clear. So we must now press on at pace with our efforts to reach a consensus on a deal that is in the national interest."
So far, MPs have rejected the withdrawal agreement Mrs May reached with other European leaders last year and they have voted against leaving the EU without a deal.
The EU has ruled out any renegotiation of the withdrawal agreement.
Before the summit, Mrs May had told leaders she wanted to move the UK's exit date from this Friday to 30 June, with the option of leaving earlier if Parliament ratified her agreement.
For Labour, shadow Brexit secretary Sir Keir Starmer called the delay to 31 October "a good thing", saying businesses would be "relieved".
He added: "Negotiations are in good faith. We all feel a deep sense of duty to break the impasse.
"But there's also this question of how on Earth do we ensure that anything this prime minister promises is actually delivered in the future because of course she's already said she's going to step down, probably within months."
One government minister told BBC political editor Laura Kuenssberg the latest delay to Brexit could mean a Conservative Party leadership contest after Easter, with a new prime minister potentially in place by June.
Former Brexit Secretary David Davis said: "There's been no progress whatsoever, really."
He added that it was still "difficult to see how" Mrs May could get her deal with the EU through Parliament and said: "The pressure on her to go will increase dramatically now, I suspect."
Scotland's First Minister Nicola Sturgeon tweeted her "relief" that the UK wouldn't be "crashing out" on Friday, adding that "allowing people to decide if they still want to leave is now imperative".
Donald Tusk emerged from the talks - and a subsequent meeting with Mrs May - to address reporters at a news conference at 02:15 local time (01:15 BST).
"The course of action will be entirely in the UK's hands," he said. "They can still ratify the withdrawal agreement, in which case the extension can be terminated."
Mr Tusk said the UK could also rethink its strategy or choose to "cancel Brexit altogether".
He added: "Let me finish with a message to our British friends: This extension is as flexible as I expected, and a little bit shorter than I expected, but it's still enough to find the best possible solution. Please do not waste this time."
European Commission President Jean-Claude Juncker said: "There will probably be a European election in the UK - that might seem a bit odd, but rules are rules and we must respect European law and then we will see what happens."
Mrs May spoke at 02:45 local time (01:45 BST). She said that, although the delay extends until 31 October, the UK can leave before then if MPs pass her withdrawal deal.
"I know that there is huge frustration from many people that I had to request this extension," she said. "The UK should have left the EU by now and I sincerely regret the fact that I have not yet been able to persuade Parliament to approve a deal."
She added: "I do not pretend the next few weeks will be easy, or there is a simple way to break the deadlock in Parliament. But we have a duty as politicians to find a way to fulfil the democratic decision of the referendum, deliver Brexit and move our country forward. Nothing is more pressing or more vital."
The PM said the UK would "continue to hold full membership rights and obligations [of the EU]" during the delay.
You couldn't quite make it up. The new Brexit deadline is, you guessed it, Halloween.
So to get all the terrible metaphors about horror shows, ghosts and ghouls out of the way right now, let's consider straight away some of the reasons why this decision is a treat in one sense, but could be a trick too.
A treat? First and most importantly, the EU has agreed to put the brakes on. We will not leave tomorrow without a deal.
The prime minister's acceptance that leaving the EU without a formal arrangement in place could be a disaster won out.
And there are quite a few potential tricks. This new October deadline might not solve very much at all.
This could, although I hate to say it, just make way for months of extra gridlock before the UK and the EU find themselves back here in a similar situation in the autumn.
Read Laura's blog here
The EU had been split over the length of delay to offer the UK, and by law its other 27 member states had to reach a unanimous decision.
Although other countries backed a longer delay, French President Emmanuel Macron pushed for a shorter extension. He called the 31 October deadline "a good solution".
Taoiseach Leo Varadkar, the Irish prime minister, said the extension gave the UK time "to come to a cross-party agreement".
Fudge and can-kicking are the EU-familiar words that spring to mind at the end of this Brexit summit.
After all the drama and speculation leading up to the meeting, effectively all that happened here is that the threat of a no-deal Brexit has been postponed for another six months.
Time enough for the EU to hold European parliamentary elections, choose a new president of the European Commission and pass a new budget - without EU leaders having to keep one eye at least on the day-to-day dramas in the House of Commons.
Despite EU leaders' rhetoric beforehand, they granted this extension without hearing a convincing plan of Brexit action from Theresa May.
In the summit conclusions there is no evidence of the punitive safeguards mooted to ensure the UK "behaves itself" - refraining from blocking EU decisions - as long as it remains a club member.
Yes, EU leaders worry about who might replace Theresa May as prime minister. Yes, they're concerned these six months could fly past with the UK as divided as ever but their message to the UK tonight was: "We've done our bit. Now you do yours. It's up to you. Please use the time well."

The UK and EU are still at odds over citizens' rights and the amount the UK will pay to leave the bloc, at the end of the second week of Brexit talks.
EU negotiator Michel Barnier said the UK had not been clear enough about where it stands on these issues and that was hampering progress.
UK Brexit Secretary David Davis said the negotiations on the so-called divorce bill had been "robust".
He said progress had been made but both sides needed to show "flexibility".
Mr Barnier said: "We require this clarification on the financial settlement, on citizens' rights, on Ireland - with the two key points of the common travel area and the Good Friday Agreement - and the other separation issues where this week's experience has quite simply shown we make better progress where our respective positions are clear."
Mr Davis said: "We have had robust but constructive talks this week. Clearly there's a lot left to talk about and further work before we can resolve this. Ultimately, getting to a solution will require flexibility from both sides."
Michel Barnier said there had been some areas of agreement about how Britons living abroad and EU nationals living in the UK should be treated after Brexit. A jointly agreed "technical note" outlining the UK and EU's positions on citizens' rights has been published.
But there was disagreement over "the rights of future family members" - meaning children born in the future to EU citizens in the UK - and "the exports of certain social benefits".
The EU wants rights currently enjoyed by EU citizens in the UK - access to healthcare, welfare, education - to apply to children and family members, whether they currently live in the UK or not, and to continue in perpetuity, after the death or divorce of the rights-holder.
But it says children born to UK citizens in EU states after the withdrawal date would be considered "family members", not rights holders themselves - the UK says it would allow children born to EU citizens to acquire the same "settled status" or, in some cases, British citizenship.
The UK wants to give all EU nationals living in the UK the same rights as British citizens once they have been resident in the country for five years, as long as they arrived before a specified "cut-off" date, probably 29 March 2017, when Article 50 was triggered. After this date, they could continue to build up their five years' entitlement if necessary.
The EU's position also requires that citizens live in a host country for five years before acquiring permanent residency rights.
In addition, EU nationals who get married after March 2019 would lose the right to bring family members to the UK, unless they pass an income test, like non-EU migrants.
They could also risk losing their right to return to Britain if they leave for more than two years - as would be the case for British citizens in EU countries. The UK says it is prepared to offer some flexibility on this for some citizens on overseas postings or studying abroad and wants the EU to offer the same.
David Davis said the UK had published its approach to citizens' rights since the first round of negotiations, which he described as "both a fair and serious offer" and had now published a joint paper setting out areas of agreement, and issues for further talks.
He said sticking points in the talks included the rights of employees of EU-based companies to work for extended periods in other countries, such as the UK. British officials highlighted that British expats would lose the rights to vote and stand in local elections under the EU plan - while the UK position is to protect the rights of citizens to vote and stand in elections in their host country.
EU negotiators have said that British people living in an EU country would lose their guaranteed rights if they moved to another EU country.
A senior EU source said there was a willingness to be flexible on this point during the negotiations, depending on the UK's position in the next set of talks.
Senior British sources called the proposal "unprecedented" as it would leave British expats with worse rights than those coming from outside the EU and it would be "interesting" to see what the public reaction would be to it.
David Davis and Michel Barnier stood at matching podiums in Brussels, side by side but not entirely in step.
Mr Davis talked breezily about work done constructively and "at pace" and even injected a slightly bantering note into proceedings, quoting back to Mr Barnier his own earlier warning line that "the clock is ticking".
Mr Barnier's take appeared to be slightly less positive and was much more focused on the need for further clarification from the UK side on a whole range of issues - we counted him using the word clarification or variations on it at least eight times in a relatively short news conference.
There are plenty of briefings around on points of detail - would the UK for example have the right to conduct blanket criminal record checks on EU citizens applying for residence in post-Brexit UK.
But the big stumbling blocks are obvious and have been obvious for a while.
One is the "divorce bill" - when will a figure emerge into the public domain and what might the UK be prepared to pay.
The other is the future role of the European Court of Justice in overseeing the rights of EU citizens who remain in the UK - the EU sees that as a basic right but from the British perspective it's being seen as "a very big ask".
Britain has agreed in principle to meet its financial obligations as it leaves the EU, to cover things like the cost of relocating London-based EU agencies and the pensions of EU officials.
But a senior EU source said the UK negotiating team had not said what they might be prepared to pay - and there had been no "serious discussions" about what the bill might include.
David Davis said: "We both recognise the importance of sorting out the obligations we have to one another, both legally and in a spirit of mutual cooperation."
But Michel Barnier has called for "clarification" on where the UK stands.
UK Foreign Secretary Boris Johnson has said the EU can "go whistle" if it demands an "extortionate" payment but other ministers have struck a more conciliatory tone. Sources have suggested to the BBC the bill could be between 30 and 50 billion euros.
Downing Street said the UK was "looking at the legal commitments" it faces, adding: "There are points of difference and that's one of them."
But there were no plans to produce a position paper on the divorce bill, the No 10 spokesman said.
David Davis rejected the suggestion that there was a lack of clarity from his team on Northern Ireland, saying the two sides had discussed ways of "achieving a flexible and imaginative solution to address the unique circumstances around the border" and preserve the common travel area.
A senior EU source said they were still waiting for concrete proposals from the UK side on the kind of border that is achievable.
This is the biggest current sticking point, according to British officials.
The ECJ settles disputes between member states about the free movement of workers and other cross-border issues.
UK Prime Minister Theresa May has said the UK will be leaving its jurisdiction.
The UK has floated the idea of a new international body, made up of British and EU judges, or, according to UK officials, "some kind of ombudsman", to settle disputes, but the EU is rejecting this out of hand.
There can't be any agreement on citizens' rights until this one is settled, EU sources say.
The UK wants to carry out criminal record checks on all EU citizens who want to live in the UK. The EU says they should only be carried out where there is a suspicion of wrongdoing.
This will be looked at in more detail during the August talks.
On a trade deal, David Davis said the UK could not accept a "punishment" deal, but added: "Nobody expects a punishment deal. Michel and I are going for a good deal."
Gibraltar did not come up as an issue in the current round of talks, sources say.
Labour's shadow Brexit secretary Sir Keir Starmer said the "lack of progress" on issues such as the rights of EU citizens in the UK and UK citizens in Europe was "deeply concerning" and would cause "anxiety for millions of families".
He questioned whether phase two of the talks could get under way in October as planned, something that would "trigger deep concern for businesses and communities across the UK".
"The reality is that we have a government that is unprepared, divided and incapable of securing a good deal for Britain. We urgently need a fresh approach," he added.
The EU has said talks won't move on to the subject of future trading arrangements until it judges there's been adequate progress on the separation issues.
The two sides are meeting for four days each month, with this week's talks aimed at scoping out points of difference and common ground in those areas that have been identified as requiring urgent attention.
Mr Barnier has said the EU side are hoping to agree the basic terms of a deal on EU citizens and the exit bill in October - which he says would open the way for talks on the UK's future trade relations with the EU to begin in December.
Meanwhile, the UK government has announced that MPs are set to debate the repeal bill - a key piece of Brexit legislation that will transform EU laws into British laws - for two days from 7 September.

The UK won't pay a 100bn-euro (£84bn) "divorce bill" to leave the EU, Brexit Secretary David Davis has said, as the two sides clashed over the issue.
He told ITV's Good Morning Britain the UK would pay what was legally due, in line with its rights and obligations, but "not just what the EU wants".
EU chief negotiator Michel Barnier said there was no desire to punish the UK but "its accounts must be settled".
While he wanted a "cordial" Brexit, he warned the "clock was ticking" now.
Publishing his Brexit mandate, Mr Barnier said the EU would "put all its efforts" into reaching a deal but said negotiations must start as soon as possible after "ten months of uncertainty" and suggested the outcome of June's general election would not change anything.
While approaching the process in a "cool-headed and solution-oriented" manner, he said it was an illusion to think it would be concluded "quickly and painlessly" or that there would be "no material impact" on lives.
An EU source has told the BBC that officials in Brussels will not enter into a discussion about potential figures for a final bill, likely to be one of the hardest-fought and most sensitive areas of the Brexit process.
On Wednesday, the Financial Times claimed the likely bill had risen sharply from 60bn to 100bn euros, basing its calculations on new data from across Europe.
Mr Barnier said there was no agreed figure but the UK and EU had entered into "mutual commitments" which must be honoured. "There is no Brexit bill. The final settlement is all about settling the accounts."
Mr Davis said the negotiations had not started in earnest but he indicated the UK would set down a marker when it came to talks over the divorce settlement.
"We are not supplicants," he said. "This is a negotiation. They lay down what they want and we lay down what we want."
Various figures ranging from 50bn to 100bn euros had been knocking around, he said, but he had "not seen" any official numbers. Asked directly whether a figure of 100bn euros - was acceptable, he replied: "We will not be paying €100bn."
He added: "We will do it properly. We will take our responsibilities seriously. What we've got to do is discuss in detail what the rights and obligations are.
"We have said we will meet our international obligations, but there will be our international obligations including assets and liabilities and there will be the ones that are correct in law, not just the ones the Commission want."
He subsequently told the BBC that the 100bn euro figure should be viewed "with a pinch of salt" and the negotiations would not "end up there", adding that it was up to the two sides to agree and he did not want the European Court of Justice to become involved.
Many Conservative MPs argue the UK does not owe the EU anything given the size of the contributions it has made over the past 40 years. A recent report by a House of Lords committee argued the UK was not legally obliged to pay a penny although to do this would threaten any chance of a post-Brexit trade deal.
Former Chancellor Lord Lawson, a strong supporter of Brexit, said the UK's withdrawal would have a big impact on the bloc's finances and that was why the EU was "so exercised" about the issue.
He told BBC Radio 4's World at One that the current political climate - with elections in the UK, France and Germany - was not conducive to a "rational" negotiation but once these were all over, the UK should make a "very good" offer to the EU on a range of issues.
If this was rejected, he suggested the UK should effectively suspend talks and "wait patiently" until the time came to leave.
Some sort of financial resolution is seen by the EU as a precondition for opening talks on a trade deal.
There are reports in Brussels that countries like France and Poland could ask the UK to contribute to farm subsidies while the EU may also be planning to refuse to allow the UK a share of the EU's assets including buildings and bank deposits.
Zsolt Darvas, a senior fellow at the Bruegel think tank, said a range of factors would have to be taken into account - including the UK's rebate on budget payments and its share of EU borrowing - but he believed a credible figure would be somewhere between 25bn and 65bn euros.
There have been growing tensions between the UK and EU since a dinner in Downing Street last week, in which European Commission President Jean-Claude Juncker is reported to have told Theresa May that Brexit could not be a success.
Mr Davis, who was one of ten people present at the dinner, said accounts of the meeting were "gossip and spin" and while there were some differences in key areas, the atmosphere had been "constructive" rather than hostile.
While the process was currently in a "rough and tumble" phase of manoeuvring, he believed a "generous settlement" could be reached over the status of EU nationals living in the UK and Britons living on the continent which guaranteed "pretty much exactly" the same rights they enjoy at the moment.
Labour leader Jeremy Corbyn said the 100bn euro figure was the "opening gambit of negotiations" but that commitments that have been made by the UK government must be honoured.
For the Lib Dems, Tim Farron said no divorce bill had ever been mentioned during last year's referendum and it strengthened his party's call for a further vote on the terms of exit.
But UKIP leader Paul Nuttall said talk of a 100bn euro figure was "ridiculous" and the UK "should not be paying anything at all".

Theresa May has written to the European Union to request a further delay to Brexit until 30 June.
The UK is currently due to leave the EU on 12 April and, as yet, no withdrawal deal has been approved by MPs.
The government has been in talks with the Labour Party to try and find a compromise to put to the Commons.
But shadow Brexit secretary Sir Keir Starmer said the Tory negotiating team had offered no changes to Mrs May's original deal.
The PM said from the outset she wanted to keep her withdrawal agreement as part of any plan, but was willing to discuss the UK's future relationship with the EU - addressed in the deal's political declaration.
Sir Keir said the government was "not countenancing any change to the actual wording of the political declaration", adding: "Compromise requires change."
The prime minister has proposed that if UK MPs approve a deal in time, the UK should be able to leave before European Parliamentary elections on 23 May.
But she said the UK would prepare to field candidates in those elections in case no agreement is reached.
It is up to the EU whether to grant an extension to Article 50, the legal process through which the UK is leaving the EU, after MPs repeatedly rejected the withdrawal agreement reached between the UK and the bloc.
The BBC's Europe editor Katya Adler has been told by a senior EU source that European Council President Donald Tusk will propose a 12-month "flexible" extension to Brexit, with the option of cutting it short, if the UK Parliament ratifies a deal.
But French President Emmanuel Macron's office said on Friday that it was "premature" to consider another delay while French diplomatic sources described Mr Tusk's suggestion as a "clumsy test balloon".
The prime minister wrote to Mr Tusk to request the extension ahead of an EU summit on 10 April, where EU leaders would have to unanimously agree on any plan to delay the UK's departure.
Mrs May has already requested an extension to the end of June but this was rejected at a summit last month.
Instead, she was offered a short delay to 12 April - the date by which the UK must say whether it intends to take part in the European Parliamentary elections - or until 22 May, if UK MPs had approved the withdrawal deal negotiated with the EU. They voted it down for a third time last week.
A Downing Street spokesman said there were "different circumstances now" and the prime minister "has been clear she is seeking a short extension".
The 30 June date is significant.
It's the day before the new European Parliament will hold its first session. So the logic is, that it would allow the UK a bit longer to seal a deal - but without the need for British MEPs to take their seats in a parliament that the UK electorate had voted to leave as long ago as 2016.
But, this being Theresa May, it's a plan she has previously proposed - and which has already been rejected.
It's likely the EU will reject it again and offer a longer extension, with the ability to leave earlier if Parliament agrees a deal.
But by asking for a relatively short extension - even if she is unsuccessful - the prime minister will be hoping to escape the ire of some of her Brexit-supporting backbenchers who are champing at the bit to leave.
And she will try to signal to Leave-supporting voters that her choice is to get out of the EU as soon as is practicable - and that a longer extension will be something that is forced upon her, rather than something which she embraces.
In her letter, the prime minister says she would continue to seek the "rapid approval" of the withdrawal agreement and a "shared vision" for the future relationship between the UK and EU.
She said if cross-party talks with the Labour Party could not establish "a single unified approach" in the UK Parliament - MPs would be asked to vote on a series of Brexit options instead which the government "stands ready to abide by", if Labour commits to doing the same.
The UK proposes an extension to the process until 30 June, she wrote, and "accepts the European Council's view that if the United Kingdom were still a member state of the European Union on 23 May 2019, it would be under a legal obligation to hold the elections".
To this end, she says the UK is "undertaking the lawful and responsible preparations for this contingency".
But she suggests the UK should be able to leave earlier, if the UK Parliament approves a withdrawal deal before then, and cancel preparations for the European Parliamentary elections.
The EU's chief Brexit negotiator Michel Barnier, at a meeting of EU ambassadors in Brussels, said any extension granted should be the last and final offer, to maintain the EU's credibility.
You could almost hear the sound of collective eye-rolling across 27 European capitals after Theresa May requested a Brexit extension-time that Brussels has already repeatedly rejected.
Most EU leaders are leaning towards a longer Brexit delay, to avoid being constantly approached by the PM for a rolling series of short extensions, with the threat of a no-deal Brexit always just round the corner.
Donald Tusk believes he has hit on a compromise solution: his "flextension" which would last a year, with the UK able to walk away from it, as soon as Parliament ratifies the Brexit deal.
But EU leaders are not yet singing from the same hymn sheet on this.
Expect closed-door political fireworks - though it's unclear whether it'll be a modest display or an all-out extravaganza - at their emergency Brexit summit next week. Under EU law, they have to hammer out a unanimous position.
Read Katya's blog
Talks between Labour and the Conservatives are continuing on Friday.
Speaking to Labour activists in Newport on Friday, Mr Corbyn said the government "haven't appeared to have changed their opinions very much as yet". He said Labour would push to maintain the UK's "market relationship with Europe", including defending rights and regulations.
Foreign Secretary Jeremy Hunt said the UK still hoped to leave "in the next couple of months" but it may have "little choice" but to accept a longer delay if Parliament could not agree a solution.
But Conservative Brexiteer Jacob Rees-Mogg said the EU "should be careful what it wishes for".
"If we have EU elections, it is likely UKIP, Tommy Robinson and Nigel Farage will do well," he told BBC Radio 4's World at One.
Another Tory Eurosceptic, Sir Bernard Jenkin, said he would prefer to stay in the EU for another year than for Britain to accept a "humiliating defeat" of a withdrawal agreement.
The Scottish National Party's Stephen Gethins said that the prime minister's proposal "demonstrates beyond doubt she is putting the interests of her fractured Tory Party above all else".
"It is clear that with the UK Parliament unable to reach a consensus - coupled with everything we now know on the damaging impact Brexit will have on the UK economy, jobs and living standards - it must now be the priority that the issue is brought back to the people in a fresh second EU referendum, with the option to remain on the ballot paper."

The UK has offered a larger potential "divorce bill" to the EU - which could be worth up to 50bn euros (£44bn), the BBC understands.
It was "broadly welcomed", political editor Laura Kuenssberg said, although No 10 has played down reports the final sum could be up to 55bn euros (£49bn).
Asked on a trip to Iraq if a figure had been agreed, Theresa May said talks were continuing.
And the EU's negotiator Michel Barnier said "we are not there" yet.
In September Theresa May suggested the UK was willing to pay about 20bn euros to meet obligations arising from its membership but the EU has been calling for its offer to be increased.
The UK is hoping to move on to talking about trade but the EU will only do this when it deems "sufficient progress" has been made on three areas - the so-called divorce bill, the rights of EU citizens in the UK after Brexit and the Irish border.
The EU says the UK needs to settle its accounts before it leaves. It says the UK has made financial commitments that have to be settled as part of an overall withdrawal agreement.
The UK accepts that it has some obligations. And it has promised not to leave any other country out of pocket in the current EU budget period from 2014-20.
But the devil is in the detail.
There are also longer term issues like pensions for EU staff, and how the UK's contribution to these is calculated for years to come, and the question of what happens to building projects that had funding agreed by all EU members including the UK but which will only begin construction after the UK has left.
Large amounts of the EU's budget are spent in two areas - agriculture and fisheries, and development of poorer areas.
Pressure is mounting to make progress on the Brexit talks before a crunch summit in mid-December, when EU leaders will decide if enough progress has been made on the first set of subjects to open negotiations on a future trade deal between the EU and the UK.
According to the Daily Telegraph and the Financial Times, agreement has now been reached between the two sets of negotiators on how the bill could be calculated.
Speaking in the Commons, Treasury minister Liz Truss declined to comment on what she described as media speculation and insisted any financial settlement was "contingent" on the UK getting the right overall outcome.
But Foreign Secretary Boris Johnson said the UK would make a "fair offer" to help break the current deadlock.
"Now is the moment to get the whole ship off the rocks and move it forwards," he said during a trip to Ivory Coast, where he is attending a meeting of European and African leaders.
The BBC understands detailed conversations are still taking place on which specific components will be included in the final bill and how they are calculated. The final bill is likely to be paid over many years rather than in a single upfront sum.
At the moment no.
But there appears to have been an agreement on the way that the amount the UK pays will be calculated and the BBC understands that the range of possible settlements is between approximately 40bn and 55bn euros.
Transport Secretary Chris Grayling told BBC Radio 4's Today: "There are no numbers for us to discuss this morning. We haven't committed to numbers."
Labour said it was not asking for a precise figure to be published as this was clearly "sensitive".
But it said there needed to be a "transparent process" with the final figure subjected to scrutiny by Parliament and independent bodies.
It is trying to force a vote on this next week.
Former Tory leader Iain Duncan Smith said the UK - which according the the House of Commons Library paid an estimated £12.2bn to the EU in 2016-17 - would save a "staggering amount of money" after Brexit.
"Leaving the EU is always a bargain because we get our money back," he told BBC Radio 5 Live.
But former UKIP leader Nigel Farage said the figures being reported would mean "Christmas has come early" for the EU.
The long-time Brexit campaigner told ITV's Good Morning Britain that the UK was "selling out" and that even if such a sum secured tariff-free access to EU markets, this would not be worth it.
But former chancellor Ken Clarke said the UK had to pay its "fair share" and "repudiating" the UK's financial obligations would result in a hard Brexit - damaging jobs and investment.
Remember there also has to be sufficient progress on the issues of citizens' rights and the Irish border for EU leaders to agree to move the talks on in ten days' time.
The first issue should not be a stumbling block - there has been talk of agreement being within "touching distance" but the second issue is now the "main sticking point", the BBC's Europe editor Katya Adler says.
The Irish government has said it wants firm guarantees on what kind of border controls there will be after Brexit and it is prepared to wait until next year, if necessary, for them.
The BBC's political editor Laura Kuenssberg said there was some talk in Whitehall of trying to agree a position which would stress agreement in the first two areas and "park" the Irish question until early next year.
But she said EU officials were "pouring a freezing cold bucket of water" over the idea of a staged approach.
In the meantime, she said both sides were discussing whether a joint paper could be produced before next Monday formalising what has been agreed so far so it could not potentially be unpicked at a later date.
MEPs on the European Parliament have warned "considerable problems" remain and that more progress is needed before talks can move to the next phase.
In a letter to chief EU negotiator Michel Barnier, the Parliament's Brexit steering group cited differences between the two sides on citizens' rights and said progress had "stalled" on the role of the European Court of Justice.
The European Parliament is not leading the negotiations (that is the job of the European Commission) but it will get to vote on the final deal.

Large parts of the British economy are not ready for a no-deal Brexit, Bank of England governor Mark Carney has said.
Fewer than half of businesses have initiated contingency plans, Mr Carney told BBC Radio 4's Today programme.
He said the UK would need a transition period to adapt to whatever form of exit from the EU that Parliament chose.
He denied that the Bank's warning that no-deal could lead to a UK recession was intended to scare people into backing his favoured form of Brexit.
Mr Carney told the BBC that "we know from our contacts with business, others know from their contacts, that less than half the businesses in the country have initiated their contingency plans for a no-deal Brexit".
"All the industries, all the infrastructure of the country, are they all ready at this point in time? And, as best as we can tell, the answer is no," Mr Carney said.
It is in the interests of the country that there should be a transition to whatever new relationship the UK has with the EU, he said.
He added: "We know issues around the borders, we go to the ports and we know the issues that are there today. So we need some time to get ready for it."
On Wednesday, MPs warned that there was a "real prospect" of "major disruption" at UK ports in the case of a no-deal Brexit, with government plans "worryingly under-developed".
However, the Department for Transport said the Public Accounts Committee's conclusions "were not accurate".
Conservative MP and Brexiter Jacob Rees-Mogg accused Mark Carney of talking down the pound on Wednesday, saying the Bank of England's warnings tonight "lack all credibility".
Mr Rees-Mogg said "project fear" had become "project hysteria".
"The overwhelming majority - 87% - of British companies do not trade with the European Union," he said.
"It will not have an effect on them. Leaving the European Union is a real economic opportunity and it's an opportunity that neither the Bank of England nor the Treasury in its forecasts wishes to recognise," Mr Rees-Mogg added.
Mr Carney's comments come after government forecasts warned that the UK would be economically poorer under any form of Brexit, compared with staying in the EU.
Under Theresa May's Chequers Brexit plan, the UK economy could be up to 3.9% smaller after 15 years compared with staying in the EU, government analysis suggested.
With a no-deal Brexit, the hit to the economy would be 9.3%.
"Our deal is the best deal available for jobs and our economy, that allows us to honour the referendum and realise the opportunities of Brexit," Mrs May said at Prime Minister's Questions.
The Bank of England, meanwhile, said on Wednesday that the UK economy could shrink by 8% in the immediate aftermath of Brexit if there was no transition period, house prices could fall by almost a third, and that the pound could fall by a quarter.
The UK's financial regulator, the Financial Conduct Authority, has said the risks of the draft Brexit agreement were "preferable to the risks of a no-deal scenario".
"Leaving the EU creates a number of risks for us regardless of the form of exit," the FCA said in a report.
"The implementation period helps address these at the cost of a lower ability to influence regulation during that period. An exit without agreement would carry much higher risk and carry significant uncertainty for us and for firms.
"Against that background, and viewed through the lens of our statutory objectives, the draft Withdrawal Agreement and the outline political declaration are preferable steps."
The FCA was asked by the Treasury Select Committee to consider the impact of Brexit in three areas: a no-deal scenario; the draft withdrawal agreement; and the outline political declaration on the future relationship between the EU and UK.
In a letter to the committee's chairman, Nicky Morgan, FCA chief executive Andrew Bailey said a no-deal scenario "would create significant challenges and risks in terms of firms' readiness, potential market disruption and insufficient public-policy solutions put in place on the side of the EU".

Boris Johnson has said the UK has "crossed the Brexit finish line" after Parliament passed legislation implementing the withdrawal deal.
The EU Bill, which paves the way for the country to leave the bloc on 31 January, is now awaiting royal assent.
The PM said the UK could now "move forwards as one" and put "years of rancour and division behind it".
The EU's top officials are expected to sign the agreement in the coming days, while MEPs will vote on it next week.
The European Parliament will meet on 29 January to debate the agreement, which sets out the terms of the UK's "divorce" settlement with the EU, the rights of EU nationals resident in the UK and British expats on the continent and arrangements for Northern Ireland.
Its ratification is expected to prove a formality.
The UK will officially leave the bloc at 23:00 GMT on 31 January - more than three and a half years after the country voted for Brexit in a referendum in June 2016.
From 1 February, the UK will enter into an 11-month transition period in which it will continue to follow EU rules but without representation in the bloc's institutions.
This arrangement will come to an end on 1 January 2021, by which point the two sides hope to have completed negotiations on their future economic and security partnership, at the heart of which the government believes will be an ambitious free trade deal.
The government's Brexit Bill, which enshrines the agreement reached by Mr Johnson in October, is one step away from becoming law after completing its passage through Parliament without any changes.
MPs overwhelmingly rejected all the changes made to the bill in the House of Lords earlier this week - on citizens' rights, the power of UK courts to diverge from EU law, the independence of the judiciary after Brexit and the consent of the UK's devolved administrations.
MPs also removed an amendment which would have obliged the government to negotiate an agreement with the EU to allow unaccompanied children who have claimed asylum elsewhere but have a relative in the UK to be re-united with their family.
The bill, as agreed by Parliament, would only compel the government to make a statement on the issue within two months.
Ministers insisted they backed the principle of the Dubs amendment, tabled by the Labour peer Lord Dubs, but argued that there was no point legislating before the UK reached an agreement with the EU on future numbers.
Lord Dubs, who has been campaigning on the issue for years, said the outcome was "bitterly disappointing" while Green Party MP Caroline Lucas said the government had shown a "compassion by-pass".
The ratification process will be completed over the next week in time for the 31 January deadline.
Belgian politician Charles Michel, who represents the 27 remaining states as president of the European Council, is expected to sign the document in the coming days as will European Commission President Ursula von der Leyen.
Mr Johnson will also sign officially the agreement on behalf of the UK government.
The prime minister, who became Tory leader in July on the back of a promise to "get Brexit done" and won an overwhelming victory at last month's general election, said Parliamentary approval was a major milestone.
"Parliament has passed the Withdrawal Agreement Bill, meaning we will leave the EU on 31 January and move forwards as one United Kingdom.
"At times it felt like we would never cross the Brexit finish line, but we've done it. Now we can put the rancour and division of the past three years behind us and focus on delivering a bright, exciting future."
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Talks between the UK and the European Union need to "speed up" if a deal on a future relationship can be made in time for Brexit, the EU's negotiator says.
Speaking in Lisbon, Michel Barnier said the UK needed to stop playing "hide and seek" and instead clarify its demands.
It comes as the EU Withdrawal Bill is due to return to the House of Commons, having suffered defeats in the Lords.
The PM faces a rebellion over her move to rule out any future membership of the customs union and single market.
The government fears MPs may follow suit and attempt to amend the bill.
Earlier this week, UK officials warned the EU that its approach to Brexit negotiations risked damaging its security and economic relationship.
Addressing a gathering of jurists in Portugal on Saturday, Mr Barnier called for more clarity on the UK's position, saying an effective negotiation was dependent on knowing what the other side wanted.
He said the EU would be ready to accept movement on Theresa May's "red lines" that insist Brexit must see the UK leave both the European single market and customs union.
"The UK can change its mind," he said, but stressed that "time is tight".
"If the UK wishes to modify its red lines, it will have to tell us so - the sooner the better," he added.
Referencing a row over the UK's potential exclusion from the EU's Galileo project - a multibillion euro plan to build a European GPS system - Mr Barnier said the EU would not be influenced by a "blame game" which seeks to hold the organisation responsible for Brexit's "negative consequences".
The UK said on Friday that it wanted the EU to repay £1bn if it was excluded from the Galileo satellite system,.
"It is the UK which is leaving the EU. It cannot, in the act of leaving, ask us to change what we are and how we function," Mr Barnier said.

The UK must have the power to end any post-Brexit "backstop" customs accord with the EU on its own, International Trade Secretary Liam Fox has said.
The Brexiteer said the UK had voted to leave the EU and "that decision can't be subcontracted to somebody else".
The UK and EU want to avoid a hard Irish border after Brexit but cannot agree on how to do so.
The EU has said it cannot agree to any arrangements which could be left unilaterally by the UK.
Prime Minister Theresa May is keen to reach a withdrawal agreement with the EU this month.
But her cabinet has been unable to agree on the mechanism for ensuring that there will be no return to border checks if a future trade deal is not ready in time.
Q&A: The Irish border Brexit backstop
One option could be for the whole of the UK to remain temporarily aligned to the EU's customs union, avoiding the need for customs checks at the border until a free trade deal is ready.
But Leave campaigners want a clear exit strategy from any such arrangement.
Mr Fox told reporters: "We have an instruction from our voters to leave the European Union. That decision can't be subcontracted to somebody else. That needs to be an issue for a sovereign British government to be able to determine."
Earlier this week Simon Coveney, Ireland's foreign minister, tweeted that "a backstop that could be ended by UK unilaterally would never be agreed to" by Ireland or the EU.
In Paris earlier, Foreign Secretary Jeremy Hunt said negotiations with the EU were "in the final stage" and he was confident an agreement could be reached.
But asked if a deal could be reached in the next week, he said: "I think seven days is probably pushing it but I am optimistic. I am optimistic that there will be a Brexit deal but I wouldn't want to be drawn on a specific timetable."
Mr Coveney told the Irish Canada Business Association conference in Dublin: "I would urge caution that an imminent breakthrough is not necessarily to be taken for granted, not by a long shot.
"Repeatedly people seem to make the same mistake over and over again, assuming that if the British cabinet agrees something, well, then that's it then, everything is agreed.
"This is a negotiation and needs to be an agreement of course between the British government but also with the European Union and the 27 countries that are represented by Michel Barnier and his negotiating team."
Brexit is due to happen on 29 March 2019, as a result of the referendum in June 2016 in which people voted by 51.9% to 48.1% for the UK to leave the European Union.
Although 95% of a Brexit deal is said to be agreed, the backstop remains a sticking point.
It is effectively an insurance policy that would only be triggered if a future trade deal is not in place by the end of 2020 - or if this final deal does not ensure a "frictionless" border.
This is because there have been warnings that a return of visible border checks could undermine the peace process in Northern Ireland, as well as damaging businesses operating on both sides.
If a Brexit deal is agreed between the UK and the EU, it then has to be approved by the House of Commons and the remaining EU member states.
Earlier, former Brexit Secretary David Davis, who quit the cabinet over Mrs May's Brexit plan in July, told the BBC that defeat in the Commons for the current plan was "looking like a probability", especially if MPs were not shown the full legal advice on the Irish border backstop plan.

Any Brexit deal negotiated with the EU must not "trap" the UK in a customs arrangement it cannot choose to leave, Andrea Leadsom has told the BBC.
The Brexiteer minister urged Tories to back the PM and said she was "sticking in government" to work for a good deal.
But the UK must not be "held against its will" in any "backstop" aimed at avoiding a hard Irish border, she said.
On Friday, pro-Remain minister Jo Johnson quit the government and called for a new referendum on the final deal.
Asked if other ministers might resign, Commons leader Mrs Leadsom told BBC 5 live's Pienaar's Politics she was not expecting any, adding: "I do urge colleagues to support the prime minister.
"We are at a very difficult stage. What we have to do is hold our nerve and keep negotiating, make sure that we are pointing out to our EU friends and neighbours that it's in all of our interests to get a good deal."
The government has not yet agreed a withdrawal deal with the European Union, ahead of the UK's scheduled exit from the bloc next March.
While it says a deal is 95% agreed, they have been unable to agree on a legally binding mechanism for ensuring that there will be no return to border checks between Northern Ireland and the Irish Republic, if a future trade deal is not ready in time.
Earlier shadow foreign secretary Emily Thornberry told the BBC "all options remain on the table", including another referendum, if a Brexit deal was voted down in the Commons.
Mrs Leadsom, who Theresa May beat to the Conservative leadership in 2016, said there would not be another referendum if MPs rejected the final withdrawal deal.
But she said she believed "most members of Parliament would vote for a deal rather than no deal".
If sufficient progress is made on the "backstop" it is thought a special cabinet meeting could be held next week for ministers to approve the draft agreement on the terms of the UK's exit.
One option is for the whole of the UK to remain temporarily aligned to the EU's customs union, avoiding the need for customs checks at the border until a free trade deal is ready.
But Leave campaigners want a clear exit strategy from any such arrangement - while the EU says any "backstop" must apply "unless and until" it is no longer needed.
By BBC political correspondent Jessica Parker
MPs on all sides are readily setting out their conditions and caveats when it comes to a potential Brexit deal.
And while Andrea Leadsom made it clear that she still supports Prime Minister Theresa May, there was a hint too that she has her own red lines, saying that the UK must not end up trapped in an EU customs arrangement.
This plays into wider fears in some Conservative quarters that Mrs May could end up accepting a compromise too far on the "backstop" issue, in order to get a withdrawal agreement with the EU over the line.
Mrs Leadsom said while the backstop was not a "likely scenario" - because she believed a trade deal could be reached before it would be necessary - it must be "time limited" and "include the entire UK", rather than just Northern Ireland. And the UK must be able to decide to leave it - without the EU overturning that decision.
She added: "The UK cannot be forced to remain in a customs arrangement. Now how that specifically works is exactly what is being discussed and negotiated on now. The UK cannot be held against its will in a customs arrangement."
Earlier Education Secretary Damian Hinds said: "If you have too hard a line about saying, 'Well we must just have a totally unilateral exit, or there's an absolutely fixed, hard end date,' that is... very, very unlikely that is going to be negotiable with the other side.
"On the other hand, people here rightly want comfort and they should be able to have comfort and confidence that it isn't an open-ended thing."
Meanwhile, General Sir Nick Carter, chief of the defence staff, was asked on the BBC's Andrew Marr Show what the military might be called on to do, in the event the UK leaves the EU with no withdrawal deal in place, saying "we stand ready to help in any way we can".
Defence minister Tobias Ellwood told Sky News the government had to plan for every scenario adding: "There are contingency plans being made, there are discussions being held behind the scenes as to what support our armed forces will do."
Brexit is due to happen on 29 March 2019, as a result of the referendum in June 2016 in which people voted by 51.9% to 48.1% for the UK to leave the European Union.
If a Brexit deal is agreed between the UK and the EU, it then has to be approved by the House of Commons and the remaining EU member states.

There is "still the potential to improve" the draft Brexit deal, Commons leader Andrea Leadsom has said.
While she backed Prime Minister Theresa May's efforts to get the "best possible deal", she warned the UK could not be "trapped" in an EU customs union.
The BBC understands that Brexiteer Mrs Leadsom is part of a group of five ministers hoping to amend the deal.
Despite widespread criticism of the draft withdrawal agreement, Mrs May has vowed to "see it through".
The 585-page document sets out the terms of the UK's departure, including details such as how much money will be paid to the EU, details of the transition period and citizens' rights. It is due to be finalised at an EU summit next Sunday, 25 November.
The publication of the draft text prompted the start of a tumultuous few days for Mrs May, with two senior ministers and several other junior ministers and aides resigning.
Some Conservative Brexiteers who are unhappy with the agreement have also been submitting letters of no-confidence in Mrs May. If 48 letters are sent, then a vote will be triggered and she could face a challenge to her leadership.
Mark Francois, one of the 21 Conservative MPs who have publicly said they have sent a letter, said Mrs May's plan would leave the UK "half in and half out" of the EU and everyone knew she would never get it through Parliament.
But Conservative MP Sir Alan Duncan urged his other fellow MPs to "stop and reflect", saying a leadership challenge was not going to get the country a better deal than Mrs May's.
"All it's likely to do is create chaos, break the government, break the party and leave the country in great disarray."
If there were to be a confidence vote in Mrs May's leadership, party veteran Ken Clarke said she would "easily" win it but Nadine Dorries was doubtful, saying "when pen comes to paper" most MPs would vote against her in a secret ballot.
By Susana Mendonça, BBC political correspondent
When they didn't jump ship over Theresa May's Brexit deal you might have thought that meant these key Brexiteers in her cabinet were ready to toe the line in a show of what's supposed to be known as "collective responsibility".
But the fact that they're still manoeuvring to change the details of the prime minister's deal (while declaring their support for her), is yet another sign of the extraordinary political times we are in.
This apparent gang of five inside the cabinet differ in their priorities. Andrea Leadsom - who's understood to be leading them - doesn't want Britain to be trapped in an endless backstop, and wants technological solutions to get around it.
Environment Secretary Michael Gove is worried about treating Northern Ireland differently from the rest of the UK. The group is at an "embryonic" stage but will they get their tweaks?
Andrea Leadsom thinks there's "still more to be done" and that they "do still have more time" before the EU Council at the end of the month. But that leaves only just over a week - and the EU doesn't look to be in the market for renegotiation at the moment.
On Friday evening, it emerged that Mrs Leadsom hopes to work with the four other cabinet ministers to change the draft withdrawal deal into something "winnable and supportable".
The four ministers believed to working with Mrs Leadsom are Michael Gove and Liam Fox - who on Friday publicly threw their support behind the PM - plus Penny Mordaunt and Chris Grayling.
Speaking to the BBC in her constituency, Mrs Leadsom said: "What I'm doing is working very hard to support the prime minister in getting the Brexit deal that 17.4 million people voted for.
"I think there's still the potential to improve on the clarification and on some of the measures within it and that's what I'm hoping to be able to help with."
Among her concerns was that "the UK cannot be trapped in a permanent customs arrangement" with the EU, she said.
She added: "I wouldn't describe myself as a plotter. I'm really just trying to make sure that we get the best possible Brexit deal."
The cabinet "gang of five" specifically want to change the part regarding the Irish backstop - which has been one of the main sticking points in talks with Brussels.
Both the UK and the EU want to avoid a hard Northern Ireland border so they agreed to put in place a "backstop" - or back-up plan - in case they cannot reach a long-term trade agreement which does this.
The backstop would mean that Northern Ireland would stay more closely aligned to some EU rules on things like food products and goods standards than the rest of the UK, which critics say is unacceptable.
The UK would not be able to leave the backstop without the EU's consent.
According to the BBC's political editor Laura Kuenssberg, the group of ministers want a change in the draft text to include the possibility of new technology or a free trade deal as alternative solutions to the Irish border issue.
The group's plans were described as a "work in progress", and a "last-ditch attempt to find something to put to the Commons".
The deal is expected to be approved at a special EU summit on 25 November, before being voted on by MPs in Parliament.
Ahead of the vote, the EU is saying it intends to stick to the existing text, according to BBC Europe editor Katya Adler. If it is voted down, the EU would be open to "tweaks" but a source close to French President Emmanuel Macron has said "nothing fundamental" could change.
Our correspondent adds that if it came to a general election or another referendum, the EU would likely be open to putting the leaving process on ice to avoid a no-deal Brexit and in the hope the UK might change its mind and stay in the EU.
The EU's chief Brexit negotiator, Michel Barnier, said the EU should not enter "some kind of bargaining process" over parts of the text, and German Chancellor Angela Merkel insisted the EU and the UK had agreed the text so negotiations should not continue.
Shadow chancellor John McDonnell has suggested that Labour could renegotiate the deal before the UK is due to leave the EU in March next year.
"I think we can do it with good will, we can change the atmosphere of negotiations into one of mutual interest and mutual benefit," he told Sky News.
Meanwhile, the prime minister told the Daily Mail the withdrawal agreement was "not everybody's ideal deal" but said her job was to make "tough decisions" and "find a way through".
She also warned her opponents their alternative Brexit plans would not resolve the Irish backstop issue.
Commenting on the backlash to the deal, Mrs May acknowledged it had been "a pretty heavy couple of days".
She revealed her husband Philip, who she described as her "rock", had helped her through it - at one point pouring her a whisky and making beans on toast.
On Friday night, Mrs May called dozens of constituency chairmen to appeal to them to back her deal and her leadership - and this weekend she is expected to embark on a "social media blitz" to try to sell her plans to people not usually engaged in politics.
Mrs May's comments come after Stephen Barclay was picked as the new Brexit secretary - replacing Dominic Raab who quit on Thursday.
A No 10 spokesman indicated that Mr Barclay, who becomes the third Brexit secretary since the role was created, would focus on domestic preparations for Brexit, rather than the negotiations.
In other developments:
The draft withdrawal agreement for Brexit that Mrs May agreed with her cabinet on Wednesday has been signed off by negotiators from both the UK and EU.

The UK must provide more clarity about its negotiating position on Brexit, the French president has said.
Emmanuel Macron said the issues of EU citizens' rights, the exit bill and the Irish border question must be settled before talks could be held on trade.
On Friday, Theresa May made suggestions including a two-year transition period after Brexit, and that the UK pay the EU for "commitments" previously made.
She hoped this offer, made in a speech in Italy, would unblock Brexit talks.
In the first response by a European leader to the speech, Mr Macron welcomed her initiative, but said the British position still needed to be fleshed out.
"Before we move forward, we wish to clarify the issue of the regulation of European citizens, the financial terms of the exit and the question of Ireland," he said.
"If those three points are not clarified, then we cannot move forward on the rest."
Mrs May said there should be a transition period of "about" two years after March 2019 - when the UK leaves the EU - during which trade should continue on current terms
EU migrants would still be able to live and work in the UK but they would have to register with the authorities, under her proposals.
And she said the UK would pay into the EU budget for decisions made while it was a member, so other member states were not left out of pocket.
She did not specify how much the UK would be prepared to pay during the transition period, but it has been estimated as being at least 20bn euros (about £18bn).
In Germany, the ruling CDU's European spokesman Michael Stuebgen said Mrs May's speech would not provide the "new dynamism" needed as details had not been fleshed out.
And the head of the country's small and medium business association said her speech was a "wasted opportunity".
At home, Mrs May's speech was welcomed by senior Conservative figures including Foreign Secretary Boris Johnson and Chancellor Philip Hammond.
But former Brexit minister Lord Bridges, who resigned from the department in June, said Britain needed to be ready for the scenario where the country crashed out of the EU without a deal.
"What will happen at customs, data, aviation, energy, law? The list goes on and on. I would urge the government to not be too coy about this," he told BBC Radio 4's Today programme.
If the EU senses the UK is not ready to leave without a deal, it would be "captured" at the negotiating table, he said.
Backbench MP Jacob Rees-Mogg criticised the PM's stance on freedom of movement until March 2019, offering the union money, and the role of the European Courts of Justice on Britain.
In her speech, the prime minister suggested there should be a new security agreement and a new model for trade
She said the UK and EU would continue to work together on long-term economic projects and the UK would want to contribute to costs.
When the two-year transition period was up, the UK and EU could move towards a new "deep and special partnership," she said.
By March 2019, neither the UK or EU would be ready to "smoothly" implement new arrangements, Mrs May said, so she suggested current trade terms should remain in place.
That would last until new systems were set up.
It's been pretty well established in Whitehall for many months - the most eager Brexiteers who wanted short, sharp exit lost that battle some time ago.
Her acknowledgment of that pulls against her repeated insistence in the election that the public just want politicians to "get on with it".
And there were new nuggets of information that will influence the talks.
Read Laura's full blog
Mrs May said she hoped to build a "comprehensive and ambitious" new economic partnership with the EU in the long-term.
She reassured EU citizens in the UK that "we want you to stay, we value you" and said she wanted UK courts to take account of rulings by the European Court of Justice.
The EU's chief Brexit negotiator Michel Barnier described the speech as "constructive" and said the prime minister had shown "a willingness to move forward".
But he said statements must now be translated into a precise negotiating position of the UK government.
And he said he would look at the implications of the UK's pledge that no member state would have to pay more as a result of Brexit.
European Parliament Brexit negotiator Guy Verhofstadt said the UK's position was becoming "more realistic" but ruled out the UK registering EU citizens who wanted to stay.
Labour Leader Jeremy Corbyn acknowledged a transition was needed to provide stability for businesses and workers.
Mr Barnier meets Brexit Secretary David Davis for a fourth round of talks on Monday.

UK officials have warned the EU that its approach to Brexit negotiations risks damaging its security and economic relationship.
It comes as a senior EU official said the UK was living in a "let's just keep everything we have now... fantasy".
A UK official described those remarks as "laughable" and warned against "trying to insult us".
Meanwhile the UK says the EU should repay £1bn if it is excluded from the Galileo satellite navigation system.
In a briefing on Thursday, following three days of Brexit talks, a senior EU official told journalists the UK was in a fantasy that everything could stay as it is, which would mean that the EU would have to change so that Britain could remain the same.
"I'm a bit concerned because the precondition for fruitful discussions has to be the UK accepts the consequences of its own choices," the official said.
"The sooner we move beyond 'let's just keep everything we have now'… the sooner we move away from this fantasy, then the quicker we can make progress."
On the issue of the Irish border, the official said "we are running out of time" and that there had been no agreement, in three days of talks this week, on the "crunch items" of customs and regulatory alignment between Northern Ireland and the Irish Republic.
The UK government has proposed a fallback option if the UK and EU cannot agree new customs arrangements in time, to avoid a "hard border" in Ireland. It would see the UK remaining aligned with the EU customs union for "a limited time" after 2020 - something Theresa May has said would only be needed in "a very limited set of circumstances".
But the EU official said any solution must be "Northern Ireland-specific" and they must "do away with fantasy that it can be a whole-of-UK solution" because that would provide a back door for the UK into the EU's single market.
The official also suggested the row over the UK's access to the Galileo system was about the UK wanting to turn it from an EU programme into a joint UK/EU programme which was "a big ask" and would give the UK more influence than some EU member states.
But a UK official said the remarks were simply the EU's "public negotiating position".
He said: 'We presented seven papers this week, in the interests of resolving difficult issues in the interests of both sides, so the claim we aren't providing enough detail is laughable.
"The risk is that, if they follow down this track, putting conditions on our unconditional offers and trying to insult us, the EU will end up with a relationship with its third biggest economy and largest security partner that lets down millions of citizens in the EU and UK."
Brexit Secretary David Davis also tweeted that "a relationship based solely on existing third country precedents, as some seem to be suggesting, would lead to a substantial and avoidable reduction in our shared security capability".
He added: "Our citizens depend on this, let's not let them down."
BBC Brussels reporter Adam Fleming said it was meant to be a good week for the British, who had published a series of documents proposing future co-operation on issues ranging from data protection, research and foreign policy to fighting crime.
He added it could be typical posturing before a summit of EU leaders next month, or it could herald another low in the Brexit process.

The Bank of England is to unveil plans allowing European banks to operate in the UK as normal post-Brexit.
The BBC has learned that banks offering wholesale finance - money and services provided to businesses and each other - would operate under existing rules.
It means EU banks operating through branches can continue without creating subsidiaries - an expensive process.
Branches offer an easy way for banks to move money around their international operations.
But they present the risk that, in the event of a financial crisis, funds are quickly repatriated to the foreign bank's headquarters - leaving customers of the UK branch out of pocket.
Subsidiaries are forced to hold their own shock-absorbing capital which can't cut and run - they essentially become UK companies.
Changing from a branch to a subsidiary could cost billions for a bank like Deutsche Bank, for example, which employs 9,000 people in the UK.
Currently, banks based anywhere in the EU can sell services to anywhere else in the EU thanks to an instrument known as a financial services passport.
On Monday, EU chief negotiator Michel Barnier was talking tough on UK-based financial services access to the European single market after Brexit.
"There is no place (for financial services). There is not a single trade agreement that is open to financial services. It doesn't exist. In leaving the single market, they lose the financial services passport," he said.
Which begs the question - if they are playing hard ball - why are we being so nice in rolling out the red carpet?
Miles Celic, head of the lobbying group TheCityUK, said offering continuity to EU banks was an act of goodwill, but it was also one of enlightened self interest.
"Encouraging EU banks to continue to operate in the UK will help preserve financial stability for the UK and the EU and will help defend London's position as an open global financial centre," he said.
Forcing EU bank branches in the UK to become separately capitalised subsidiaries may well have encouraged European banks to pull out of London - gradually eroding its pre-eminence as a financial centre.
But on the other hand, London acts as the wholesale bank to the EU and access to its expertise and capital is highly prized. Some may see this decision as surrendering a trump card that should have been held back for the tough negotiations ahead.
So, why are we allowing the EU access to this valuable resource while the EU threatens to create barriers the other way?
Government sources said there are three reasons.
First, there are the jobs. Tens of thousands of highly paid people work in the London branches of big EU banks. That also creates knock on jobs in other professions like accountancy and law.
Second, those people pay a lot of tax to the exchequer.
And third, there is another important economic point. Services sold by the UK branch of a French or German bank to a third country like the US, for example, count as UK exports - something the government is keen to maximise.
In a speech back in October, Sam Woods, the head of the Prudential Regulation Authority (the bit of the Bank of England that supervises banks) said the reason the European financial markets work so well is not just due to the "passport" that Michel Barnier insists will be revoked.
He said he hoped "for a strong, co-operative relationship in which wholesale banks can continue to operate across the UK and EU27 in branches... We have embedded a sophisticated framework of supervisory co-operation... There is every reason to think these will continue into the future"
This sentiment echoes what a senior banker told me six months ago - "if the regulators were in charge, and not the politicians, this would all be sorted out in a fortnight."
They are not in charge. But I understand the bank has the blessing of the government in offering this "no new post-Brexit strings attached" access to the world's largest financial centre.

The UK government has set out proposals to ensure trade in goods and services can continue on the day the UK leaves the EU in March 2019.
A position paper calls for goods already on the market to be allowed to remain on sale in the UK and EU without additional restrictions.
It also calls for consumer protections to remain in place.
The Brexit department aims to keep pressure on the EU ahead of the third round of talks in Brussels next week.
A second paper calling for a reciprocal agreement to ensure continued confidentiality for official documents shared by Britain with its EU partners while it was a member state has also been published on Monday.
Further papers are due in the coming days, including one on the crucial issue of the European Court of Justice - a sticking point in talks.
Brussels is refusing to discuss future arrangements, such as trade, until citizens' rights, the UK's "divorce bill" and the Northern Ireland border have been settled.
EU leaders reiterated their stance last week as the UK published proposals about new customs arrangements.
Mr Davis said the latest batch of publications would "drive the talks forward" and "show beyond doubt" that enough progress had been made to move to the next stage of talks.
David Davis said: "These papers will help give businesses and consumers certainty and confidence in the UK's status as an economic powerhouse after we have left the EU.
"They also show that as we enter the third round of negotiations, it is clear that our separation from the EU and future relationship are inextricably linked.
"We have already begun to set out what we would like to see from a future relationship on issues such as customs and are ready to begin a formal dialogue on this and other issues."
But European Commission spokesman Alexander Winterstein said the UK's position papers would not alter the framework for talks drawn up by chief negotiator Michel Barnier and approved by the other 27 EU member states.
"There is a very clear structure in place, set by the EU27, about how these talks should be sequenced and that is exactly what we think should be happening now," Mr Winterstein told a Brussels press conference.
"So the fact that these papers are coming out is, as such, welcome because we see this as a positive step towards now really starting the process of negotiations.
"But as Michel Barnier has said time and again, we have to have sufficient progress first on the three areas of citizens' rights, financial settlement and Ireland, and only then can we move forwards to discussing the future relationship."
He added: "Hopefully we can make fast progress on the three areas I have mentioned because once we have reached sufficient progress there, we can move on to the second stage."
A Downing Street spokesman said: "Both sides need to adopt a flexible approach. We are working at pace. We are confident we will make sufficient progress.
"David Davis has said we want to move to the next stage in October."
Monday's publications urge the EU to widen its "narrow" definition of the availability of goods on the market to also include services, arguing this is the only way to protect consumers and businesses trading before Brexit.
The goods and services paper calls for:
Business group the CBI described Mr Davis's position on trade as a "significant improvement" on EU proposals which would create a "severe cliff-edge" for goods currently on the market.
But CBI campaigns director John Foster said: "The only way to provide companies with the reassurance they need is through the urgent agreement of interim arrangements.
"This would ensure that goods and services can still flow freely, giving companies the certainty they need to invest.
"The simplest way to achieve that is for the UK to stay in the single market and a customs union until a comprehensive new deal is in force."
The most contentious of the week's publications is expected to be about "enforcement and dispute resolution", as it tackles the question of the UK's future relationship with the European Court of Justice.
Theresa May has promised the UK will leave the jurisdiction of the EU court, with the government saying Parliament will "take back control" of its laws.
But the EU has insisted the ECJ must have a role in enforcing citizens' rights, and how to enforce any future trade deal has yet to be agreed.
Other papers expected this week will look at how to maintain the exchange of data with other European countries and future "co-operation" between the different legal systems.

The government has revealed details of its proposed new security treaty between the UK and the EU after Brexit.
Ministers hope the treaty will provide a legal basis for co-operating on law enforcement, security and criminal justice, but did not outline any costs.
Whitehall officials are understood to be optimistic the plans will be agreed.
Both Labour and the Lib Dems criticised a specific proposal to end the direct jurisdiction of the European Court of Justice (ECJ) after the UK's departure.
The government document outlining the plans said the new security treaty would need to be underpinned by a new legal agreement since the UK would leave the ECJ.
But it said it should be possible for the UK to secure an agreement with Europol - the EU intelligence agency - that provides the same benefits as now.
Theresa May has previously said membership of the ECJ, the EU's highest legal authority, was "not going to happen" after Brexit.
But Labour's Yvette Cooper, who chairs the home affairs select committee, said the paper failed to "answer the crucial question" of what could replace the court.
"Where are the proposals for an alternative model of dispute resolution?" she said, adding: "As the paper makes clear, it would be really dangerous to end up with operational gaps in law enforcement and justice."
Lib Dem shadow home secretary, Ed Davey, said the paper was based on "delusion", insisting that leaving the ECJ would be a "major stumbling block" to thrashing out a security agreement.
"Instead of accepting a role for the ECJ, the paper repeats Theresa May's ridiculous red line," he said.
However, the government described the plans as a new, "ambitious" model of co-operation - rejecting the idea of negotiating a number of separate agreements covering each area of law enforcement.
The National Crime Agency (NCA) said the paper was an "important milestone" in tackling pan-European threats such as organised crime, child sex abuse, cyber-attacks and terrorism.
In a statement, the agency said there was "broad consensus on the need to retain our ability to share intelligence, biometrics and other data at speed".
Officials say the new treaty would aim to replicate the provisions of the European Arrest Warrant system, under which suspects can be speedily extradited between member states, but it would not necessarily mean Britain belonging to the EAW.
Brexit Secretary David Davis said: "Together with the EU we have developed some of the world's most sophisticated systems in the fight against crime, because cross-border co-operation is absolutely crucial if we're to keep our citizens safe and bring criminals to justice.
"That is why we want to build a new partnership with the EU that goes beyond any existing relationship it has with non-member states, so we can continue countering these cross-border threats together."
Other areas listed in the document that the government wishes to continue to contribute to and benefit from are:
The UK has the largest defence budget in the EU and, along with France, is one of only two countries in the bloc with permanent membership of the United Nations Security Council.
German Chancellor Angela Merkel has previously said Europe can no longer "completely depend" on the US and UK following the election of President Trump and the Brexit vote, while European Commission President Jean-Claude Juncker recently called on EU member states to step up their military co-operation.
In her letter formally triggering Brexit in March, Prime Minister Theresa May warned that failure to reach a deal with Brussels would mean "co-operation in the fight against crime and terrorism would be weakened".

The UK will seek "new arrangements" with the EU in order to allow for the continued free flow of personal data, according to a government paper.
It argues the UK starts from "unprecedented" alignment with EU law, but acknowledges collaboration will be needed to protect British interests.
Many UK businesses and law enforcement agencies rely on EU data.
One legal expert said the paper was a "step forward" but overlooked some key points.
The paper puts forward the UK government's position that a UK-EU model for exchanging and protecting data will be essential to maintain a "deep and special partnership" - a phrase used four times in the document.
Regarding how to achieve this, the government suggests that the Information Commissioner be "fully involved" in future EU regulatory discussions.
It also raises the possibility of the UK and EU mutually recognising each other's data protection rules as the basis for allowing the free flow of data to continue.
And there should be an agreed timeline for implementing more long-term arrangements to reassure businesses, the government adds.
"It will help businesses who need to be able to plan their future - they need a sense of what the law will be," said Dr Karen Mc Cullagh, a legal expert at the University of East Anglia.
However, the UK's approach to surveillance might give EU negotiators cause for concern when considering business-as-usual, she added.
"[The paper overlooks] some important facts - the most important one being the Investigatory Powers Act which is likely to present a hurdle."
On the idea that the Information Commissioner should still have access to EU regulatory dialogue, Dr Mc Cullagh said: "There will be a concern that [UK lawmakers] will lose the ability to influence if they're not at the table, if they can't shape future laws."
Earlier this month, the government said that it would implement the EU's overarching General Data Protection Regulation (GDPR) within British law.
These regulations allow for bigger fines on firms that flout the rules - and it will also be easier for consumers to control information about them online and in databases controlled by companies.
"We want the secure flow of data to be unhindered in the future as we leave the EU," said Matt Hancock, Minister for Digital, on the publication of the paper.
"So a strong future data relationship between the UK and EU, based on aligned data protection rules, is in our mutual interest."
Many UK businesses, law enforcement agencies and research institutions rely on quick and easy access to EU data in order to do their work.
In fact, the UK has the largest internet economy as a percentage of GDP out of all the G20 countries, according to the Boston Consulting Group - and much of that relies on data flowing freely.
A House of Lords report recently found that if data transfers were hindered, "the UK could be put at a competitive disadvantage and the police could lose access to information and intelligence mechanisms".
The GDPR means that - once implemented next year - data transfers across the EU will be updated and aligned between member states.
At the moment, the UK's access to EU data is largely safeguarded, but upon leaving the union and - potentially - the European Economic Area, it will need to show that it still protects data properly.
An assessment that the UK meets data "adequacy" requirements will have to come from the European Commission and it is currently unclear whether such a decision will be made quickly when the UK leaves.
Another important factor is the EU-US Privacy Shield, which was set up to tighten controls after Edward Snowden's revelations about US intelligence agency snooping.
The UK's position has its complexities - not least thanks to the Investigatory Powers Act, which Sir Tim Berners-Lee has called a "security nightmare".
"Unless the Investigatory Powers Act 2016 is amended, it is highly likely that the UK will not be granted an adequacy decision and data flows will be blocked," says Dr Mc Cullagh.
Plus, once out of the EU, the UK will also depart the EU-US Privacy Shield - meaning that the EU could raise concerns about data it passes to the UK.
Might such data, for example, be transferred to the US without EU-worthy oversights?
These are potential stumbling blocks for Britain as it moves out of the EU - but seeks to retain the same access to data that it enjoyed as a member state.

The government says it will propose an "innovative and untested approach" to customs checks as part of its Brexit negotiations.
The model, one of two being put forward in a newly-published paper, would mean no customs checks at UK-EU borders.
The UK's alternative proposal - a more efficient system of border checks - would involve "an increase in administration", it admits.
A key EU figure said the idea of "invisible borders" was a "fantasy".
On Twitter, Guy Verhofstadt, the European Parliament's negotiator, added that other issues had to be agreed before negotiations on trade could begin - views echoed by the EU's overall chief negotiator, Michel Barnier.
The UK has already said it will leave the customs union - the EU's tariff-free trading area - after Brexit, and businesses have been calling for clarity on what the replacement system will involve.
The UK's proposals, detailed in what it calls a "future partnership paper", also include the possibility of a "temporary customs union" after the UK leaves the EU in March 2019 to avoid a "cliff-edge" for business as they adapt to the new arrangements.
Countries in the customs union don't impose tariffs - taxes on imports - on each other's goods.
Every country inside the union levies the same tariffs on imports from abroad.
So, for example, a 10% tariff is imposed on some cars imported from outside the customs union, while 7.5% is imposed on roasted coffee.
Other goods - such as soap or slate - have no tariffs.
The UK has said it is leaving the EU's customs union because as a member it is unable to strike trade deals with other countries.
According to the new paper, the UK could ask Brussels to establish a "temporary customs union" after it leaves the EU in March 2019.
But during this period, it would also expect to be able to negotiate its own international trade deals - something it cannot do as an EU customs union member.
Ministers said the use of interim arrangements would mean businesses would only have to adjust once to the new arrangements.
Once this period expires, the UK will look to agree either a "highly streamlined" border with the EU, or a new "partnership" with no customs border at all.
The "partnership" arrangement would be an "innovative and untested approach" which would remove the need for any customs checks between the UK and the EU. This would be because the UK's regime would "align precisely" with the EU's, for goods that will be consumed in the EU.
However, the UK would continue to operate its own checks on goods coming from outside the EU - and the government said safeguards would be needed to prevent goods entering the EU that had not complied with its rules.
These could include a repayment mechanism, which would see importers to the UK pay whichever is the higher tariff, Britain's or the EU's, and then face having to claim money back if their goods were sold to a customer in the region with a lower tariff.
An alternative scenario the government is proposing would involve the UK extending customs checks to EU arrivals - but under a "highly streamlined arrangement" to minimise disruption at ports and airports.
It said it would seek to make the existing system of customs checks "even more efficient", for example using number plate recognition technology at ports, which could be linked to customs declarations for what the vehicles are carrying, meaning the vehicles do not have to be manually stopped and checked.
The UK would also allow some traders to do self assessment, calculating their own customs duties.
However, the government acknowledged this option would still involve "an increase in administration" compared with being in the existing customs union.
All of this will have to be negotiated with the EU - and the two sides have not yet even started discussing trade matters.
Other obstacles - including the size of the UK's "divorce bill" - need to be agreed first.
The government will also set up its own "standalone" system in the event of no deal being reached, which would involve charging customs duty and VAT on imports from the EU, although it says it is keen to avoid this scenario.
Previous estimates by HMRC have predicted a sudden increase in the number of customs declarations after Brexit - subject to any new arrangements agreed with the EU - from a maximum of 55 million to 255 million per year.
David Davis, Secretary of State for Exiting the European Union, said he envisioned the interim customs system being "as close as we can to the current arrangements", but with the UK able to negotiate and sign its own international trade deals.
Speaking on BBC Radio 4's Today programme, he did not rule out the UK paying to be part of the arrangement, saying he was not going to conduct negotiations on air.
And he said he did not believe the European Court of Justice would be the arbiter of the temporary arrangement, adding that the government would publish proposals on "international arbitration" next week.
Mr Davis said the transition period should be "something like two years, maybe a bit shorter" but that it had "to be done by the election", meaning 2022 at the latest.
Analysis by the BBC's Eleanor Garnier
These proposals are designed to demonstrate unity - after reported cabinet splits - and show the government has a plan in place.
Chancellor Philip Hammond has got his way in seeking an interim customs arrangement as much like the status quo as possible.
And Liam Fox could potentially win the right to negotiate international trade deals during the transition period.
But this is about much more than domestic political battles - it's about whether the UK can succeed in getting Brussels negotiators to talk about trade at the same time as the so-called divorce arrangements, something they have steadfastly refused to do so far.
The EU is also working on a position paper on the customs union.
Its chief negotiator, Michel Barnier, tweeted that customs could not be discussed until the Irish border, citizens' rights and the UK's separation payment had been settled.
A European Commission spokesman added: "As Michel Barnier has said on several occasions, 'frictionless trade' is not possible outside the single market and customs union."
Sir Keir Starmer, Labour's shadow Brexit secretary, said the proposals were "incoherent and inadequate" and were designed to "gloss over deep and continuing divisions within the cabinet".
But his party also faced questions on its position.
Speaking to Emma Barnett on BBC Radio 5 live, shadow international trade minister Bill Esterson would not say whether Labour would remain in the customs union after March 2019.
Asked repeatedly, he said Labour would seek "the same relationship that we have now".
"The detail of whether it's defined as being membership or not isn't the point," he added.
Scotland's first minister Nicola Sturgeon accused the UK of a "daft have cake and eat it" approach.
Pro-EU Conservative MP Anna Soubry said ministers were "moving in the right direction" with their proposals for an interim arrangement.
But she said they should admit that "no new agreement with the EU can fully replace the benefits of customs union membership".
Liberal Democrat leader Sir Vince Cable accused ministers of "kicking the can down the road" and argued for staying in the customs union.
But the CBI, which represents British businesses, said the proposal was "encouraging".
Its deputy director general, Josh Hardie, added: "The clock is ticking and what matters now is giving companies the confidence to continue investing as quickly as possible."
Adam Marshall, director general of the British Chambers of Commerce, said most businesses were more concerned about future customs arrangements with the EU than future trade deals.
"In the long term, we should aim to avoid imports and exports being subjected to two sets of customs checks, and to ensuring the smoothest possible future trade relationship between the UK and EU."
MEP and former UKIP leader Nigel Farage attacked the government's proposals.
"We might find ourselves 10 years down the road from Brexit having not got what we wanted," he said.
"There's no doubt that during this transitional period, the free movement of people will continue, the European Court of Justice will go on having judgements over British business and, of course, we'll go on paying a membership fee.
"None of those three things are acceptable to Brexit voters in any way at all."
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The EU's Brexit negotiator has said he sees the process as an opportunity to "teach" the British people and others what leaving the single market means.
Michel Barnier said: "There are extremely serious consequences of leaving the single market and it hasn't been explained to the British people."
The UK has hit back, saying the EU does "not want to talk about the future".
Brexit Secretary David Davis said it was "frightened" and the UK would not be bounced into a divorce bill deal.
The latest salvos come after a week of talks in Brussels about the UK's withdrawal from the EU - scheduled to take place in March 2019 - which increased tensions between the two sides.
The EU suggested little substantive progress had been made on three key "separation" issues, the size of the UK's financial liabilities to the EU, the future of the Irish border and citizens' rights after Brexit.
Mr Barnier accused the UK of "nostalgia" and cast doubt on whether enough progress had been made to broaden the discussions, in the autumn, to consider the UK's post-Brexit trading relationship with the EU.
This led to a frosty response from British ministers, one of whom, International Trade Secretary Liam Fox, said the UK would not be blackmailed into doing a deal on money in order to open discussions on trade.
Speaking at a conference in Italy on Saturday, Mr Barnier said he did not want to punish the UK for leaving but said: "I have a state of mind - not aggressive... but I'm not naïve."
"We intend to teach people… what leaving the single market means," he told the Ambrosetti forum.
On the issue of finance, he said the UK must accept some key principles, such as honouring the commitment it made in 2014 to pay 14% of the EU budget until 2020
He said that a future free trade deal would be different to all others in the past and there had to be assurances there would be no unfair competition in the form of social, environmental or fiscal dumping, or state aid.
But speaking to BBC One's Andrew Marr Show, Mr Davis insisted the UK would not be pressured into agreeing an EU divorce bill until it is sure the sums being demanded are fair.
He dismissed newspaper reports the UK had secretly agreed to pay a figure of up to £50bn as "nonsense".
The UK was assessing the EU's financial demands on an item-by-item basis in a "very British and pragmatic fashion" - which he said the EU found difficult.
While Mr Davis said he personally liked his counterpart, he said the European Commission risked making itself appear "silly" when it claimed no progress had been made in areas such as access to welfare and healthcare rights across Europe for British expats.
"What he's concerned about of course is he's not getting the answer on money… they've set this up to try and create pressure on us on money… they're trying to play time against money".
He added: "We're going through [the bill] line by line, and they're finding it difficult because we've got good lawyers… He wants to put pressure on us, which is why the stance this week in the press conference. Bluntly, I think it looked a bit silly, because plainly there were things that we've achieved.
"We put people before process, what they're in danger of doing is putting process before people".
Foreign Secretary Boris Johnson said some of the figures touted for the size of the divorce bill were "extravagant" and the UK would only respect a number that was "serious and validated in law".
"We will certainly honour our legal obligations as we understand them," he said, while stressing the UK would "certainly not pay for access to the European markets".
The continuing tit-for-tat between the two sides comes as Downing Street called for unity among its MPs as they prepare to debate the government's flagship Brexit bill.
The EU Withdrawal Bill will repeal the law that paved the way for the UK to join the European Economic Community in the 1970s and convert 40 years worth of EU statutes into domestic law.
Labour has said it will seek to amend the bill to stop the government from automatically accruing new powers after Brexit.
The opposition is courting europhile Conservative MPs, claiming its position on remaining in the single market and customs union during any Brexit transition is more "clear and coherent" than the Tories.
"To suggest, as some do, that you can have, as it were, bespoke, special arrangements negotiated between now and March 2019 is nonsense, and so this is grown-up politics from the Labour party in the public interest," shadow Brexit secretary Sir Keir Starmer told Andrew Marr.
But Mr Davis said Labour was onto its "perhaps seventh, eighth, ninth" policy on Brexit and the opposition knew the legislation was essential to ensuring legal certainty and practical continuity as the UK takes responsibility for policy in a wide range of areas.
4 September 2017: This story was updated to amend the wording of some direct quotes from Michel Barnier.

Theresa May has said the UK "cannot possibly" remain within the European single market, as staying in it would mean "not leaving the EU at all".
The PM promised to push for the "freest possible trade" with European countries and warned the EU that to try to "punish" the UK would be "an act of calamitous self-harm".
She also said Parliament would vote on the final deal that is agreed.
Labour warned of "enormous dangers" in the prime minister's plans.
And the European Parliament's lead negotiator said there could be no "cherry-picking" by the UK in the talks.
Mrs May used her much-anticipated speech to announce her priorities for Brexit negotiations, including maintaining the common travel area between the UK and Irish Republic and "control" of migration between the UK and the EU.
Negotiations are set to begin after notice under Article 50 of the Lisbon Treaty is served by the end of March.
It was not her intention to "undermine" the EU or the single market, Mrs May said, but she warned against a "punitive" reaction to Brexit, as it would bring "calamitous self-harm for the countries of Europe and it would not be the act of a friend".
She added: "I am equally clear that no deal for Britain is better than a bad deal for Britain."
By Laura Kuenssberg, BBC political editor
Since the referendum she and her ministers have simply refused to be so explicit.
For months, some ministers have privately whispered about complex solutions that might keep elements of membership - the choices not being binary, mechanisms that might give a sort of membership with a different name.
Well, no more. The simple and clear message from Theresa May's speech this morning is that we are out.
Read Laura's blog here
The prime minister had some strong words of advice for the EU and its treatment of member states, arguing it could "hold things together by force, tightening a vice-like grip that ends up crushing into tiny pieces the very things you want to protect" or "respect difference, cherish it even".
But the most keenly awaited part of the speech dealt with the UK's post-Brexit trading relationship with the rest of Europe.
Any agreement with the EU must "allow for the freest possible trade in goods and services", Mrs May said.
"But I want to be clear: what I am proposing cannot mean membership of the single market.
"It would, to all intents and purposes, mean not leaving the EU at all.
"That is why both sides in the referendum campaign made it clear that a vote to leave the EU would be a vote to leave the single market."
EU leaders have warned that the UK cannot access the single market, which allows the free movement of goods, services and workers between its members, while at the same time restricting the free movement of people - and the PM has pledged to control EU migration.
Mrs May also indicated the UK's relationship with the customs union - under which EU countries do not impose tariffs on each other's goods, while all imposing the same tariff on goods imported from outside the EU - would change.
She said she did not want the country to be "bound" by the shared external tariffs. Instead, the UK would be "striking our own comprehensive trade agreements with other countries".
To the 27 other EU member states, she said: "We will continue to be reliable partners, willing allies and close friends.
"We want to buy your goods, sell you ours, trade with you as freely as possible, and work with one another to make sure we are all safer, more secure and more prosperous through continued friendship."
Mrs May, who backed Remain in the referendum, called for a "new and equal partnership" with the EU, "not partial membership of the European Union, associate membership of the European Union, or anything that leaves us half-in, half-out".
"We do not seek to adopt a model already enjoyed by other countries. We do not seek to hold on to bits of membership as we leave."
When asked about the prime minister's promise of a Parliamentary vote following Brexit negotiations, her spokeswoman said: "You can regard it as binding."
Pressed on what would happen if MPs or peers rejected any deal, she replied: "Either way, we will very clearly be leaving the EU."
Until now, Mrs May had revealed little of her strategy for the talks, which could last up to two years - or go on longer if all 28 EU members think this is necessary.
Responding on Twitter, Guy Verhofstadt, the European Parliament's chief negotiator, welcomed Mrs May's "clarity", adding: "But the days of UK cherry-picking and Europe a la carte are over."
In a reference to Mrs May's warning that the UK could "change the basis of Britain's economic model" if denied single market access - taken to mean lowering corporation tax to attract businesses - he added: "Threatening to turn the UK into a deregulated tax heaven will not only hurt British people - it is a counter-productive negotiating tactic."
Mr Verhofstadt added that the views of people who voted Remain must be taken on board.
Labour leader Jeremy Corbyn argued that the prime minister still needed to "be clearer" about her long-term objectives, and that she wanted to "have her cake and eat it" over the single market.
He added: "I think we have to have a deal that ensures we have access to the market - we have British jobs dependent on that market - that's what we'll be pushing for."
Mr Corbyn also said: "There are enormous dangers in all of this and when she talks about future trade arrangements, all she said was that Donald Trump said we'd be first in the queue - first in the queue for an investor protection-type treaty? I don't know exactly what she has in mind on that."
After Mrs May's speech, Liberal Democrat leader Tim Farron said: "Ripping us out of the single market was not something proposed to the British people. This is a theft of democracy."
UKIP leader Paul Nuttall said he feared a "slow-motion Brexit", adding: "We want this done quickly."
Scottish First Minister Nicola Sturgeon claimed leaving the single market would be "economically catastrophic".
She hinted at a second independence referendum, saying Scotland - which voted against Brexit - should have "the ability to choose between that and a different future".
In a statement, the Irish government said the UK's "approach is now firmly that of a country which will have left the EU but which seeks to negotiate a new, close relationship with it".
It added it was "acutely aware of the potential risks and challenges for the Irish economy" but also of "the potential economic opportunities that may arise".
Michel Barnier, the European Commission's chief Brexit negotiator, tweeted: "Ready as soon as UK is. Only notification (that is, invoking Article 50) can kick off negotiations."

Taxpayers' money will not be spent on preparing for a "no-deal" Brexit until the "very last moment", Chancellor Philip Hammond has suggested.
He said he was preparing for "no deal" and all other outcomes and would make money available when needed.
But he said he wouldn't take money from other areas, like health or education, now just to "send a message" to the EU.
At PM's questions Theresa May rejected claims she was ramping up "no deal" talk, insisting she wanted agreement.
"We are actively working... with the EU to ensure a good deal, the right deal for Britain for a brighter future for this country," Mrs May told MPs at Prime Minister's Questions.
One ex-minister, David Jones, has said billions should be set aside in November's Budget for a "no deal" scenario, arguing that if this did not happen it would be seen as a "a sign of weakness" by EU leaders who would think the UK was not serious about leaving the EU without a deal.
The chancellor, who has been accused of being too pessimistic about Brexit, told the Treasury committee of MPs a "cloud of uncertainty" over the outcome of negotiations was "acting as a dampener" on the economy.
He said this could only be removed by progress in the talks, which he said was dependent on the EU agreeing to discuss its future relationship with the UK as soon as possible.
He told MPs one worst case scenario for a "no deal", would see no air travel taking place between the UK and the EU on Brexit day - 29 March 2019 - but added that he did not see that as likely to happen, even if the UK/EU talks failed to reach agreement.
Writing in the Times ahead of next month's Budget, Mr Hammond said he had a responsibility to be "realistic" about the challenges of leaving the EU and would spend money only when it was "responsible" to do so.
An extra £412m has already been allocated to government departments to prepare for Brexit over the next four years and Treasury sources suggested more would be made available if negotiations faltered.
Asked about the article as he appeared before the Commons Treasury committee, Mr Hammond said he was "committed" to funding departments for Brexit preparation and he was "rather surprised" that the article might be interpreted as saying that he was reluctant to do so.
"We are prepared to spend when we need to spend against the contingency of a 'no deal' outcome," he said.
"I am clear we have to be prepared for a 'no deal' scenario unless and until we have clear evidence that this is not where we will end up."
"What I am not prepared to do is allocate funds to departments in advance of the need to spend," he added.
"We should look in each area at the last point that spending can begin to ensure we are ready for a day-one 'no deal' scenario.
"Every pound we spend on contingency preparations on a hard customs border is a pound we can't spend on the NHS, social care or education. I don't believe we should be in the business of making potentially nugatory expenditure until the very last moment when we need to do so."
Theresa May was pressed on the issue at Prime Minister's Questions, in which former Tory leader Iain Duncan Smith sought assurances "all necessary monies" would be spent preparing for a no deal outcome.
"Where money needs to be spent it will be spent," the prime minister replied, adding that government departments would be given an extra £250m this year to prepare for a range of Brexit outcomes.
Labour's Heidi Alexander accused Mrs May of "running scared" of Tory backbenchers - prompting the PM to reply "the honourable lady could not be more wrong... we are not ramping up a no deal scenario".
On Tuesday, Mrs May - who backed Remain in last year's vote - repeatedly refused to say if she would now vote for Brexit, telling LBC radio: "I don't answer hypothetical questions."
At PMQs, the SNP's Ian Blackford claimed the PM "could not answer a simple question" and urged her to "come off the fence" and recognise the risk to jobs in Scotland from leaving the single market and customs union.
In response, the prime minister said she was clear the UK would be leaving the EU in March 2019 and that there would be no second referendum.
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The UK has been urged to submit fresh proposals within the next 48 hours to break the Brexit impasse.
EU officials said they would work non-stop over the weekend if "acceptable" ideas were received by Friday to break the deadlock over the Irish backstop.
The UK has said "reasonable" proposals to satisfy MPs' concerns about being tied to EU rules had already been made.
Chancellor Philip Hammond has warned Brexiteers to vote for the PM's deal or face a delay to Brexit.
The PM is seeking legally-enforceable changes to the backstop - an insurance policy designed to prevent physical checks on the border between Northern Ireland and the Republic of Ireland, but there have been few visible signs of progress.
MPs are due to vote for a second time on the Brexit deal next week. If they reject the deal again, they will get to choose between leaving without a deal or deferring the UK's exit from the EU beyond the scheduled date of 29 March.
Speaking to BBC Radio 4's Today programme, Mr Hammond refused to be drawn on how he would vote if Mrs May's deal is defeated.
"If the prime minister's deal does not get approved on Tuesday then it is likely that the House of Commons will vote to extend the Article 50 procedure, to not leave the European Union without a deal, and where we go thereafter is highly uncertain," he told BBC Radio 4's Today programme.
"For those people who are passionate about ensuring that we leave the European Union on time it surely must be something that they need to think very, very carefully about now because they run risk of us moving away from their preferred course of action if we don't get this deal through."
By Laura Kuenssberg, BBC political editor
What we heard from the chancellor this morning was that he was clear about the uncertainties ahead - and rather unclear (cagey, in fact) about how he might vote when it came to decision-time about a no-deal.
There was an explicit warning to Brexiteers: vote for the prime minister's deal because otherwise, it's delay and a soft Brexit.
As one minister expressed to me yesterday, they believe the vote does have a chance of getting through because Brexiteers will realise - just in time - that it's either the PM's deal next week, or what this minister described as "soft, softer, then meltdown".
But across government, the mood is not optimistic about what's going to happen next week and most ministers are expecting a defeat.
French Europe minister Nathalie Loiseau reiterated the EU's position that the withdrawal agreement cannot be reopened and said the deal was the "best possible solution" with the controversial Irish backstop a "last resort solution".
She said: "We don't like the backstop, we don't want to have to implement it, and if we have to, we don't want to stay in the backstop.
"We all agree that it should be temporary."
Mrs May is pinning her hopes on getting changes to the backstop that will prevent the UK from being tied to EU customs rules if no permanent trade deal is agreed after Brexit.
Critics say that - if the backstop were used - it would keep the UK tied to the EU indefinitely.
Negotiations between British ministers and the EU officials over the past 24 hours have been described as "difficult", with the EU insisting there has been no breakthrough.
Diplomats from the 28 member states were told on Wednesday that Mrs May could meet European Commission President Jean-Claude Juncker on Monday if progress was made.
But the BBC's Europe reporter Adam Fleming said talk of a 48-hour deadline for new proposals and a weekend of negotiations was "a notional timetable" and that more flexibility could be possible.
Attorney General Geoffrey Cox, who is leading the UK team, has conceded that negotiations are at a sensitive point and the exchanges have been "robust".
Mr Cox, who will take questions from MPs on Thursday, has played down reports he has abandoned hopes of getting the EU to agree to a firm end date to the backstop or some kind of exit mechanism - key demands for many Tory Brexiteers.
By BBC's Brussels reporter Adam Fleming
The latest talks aimed at securing legal guarantees about the Irish backstop foundered over a British proposal for the role of the independent arbitration panel which will be set up under the Brexit deal.
It will be made up of judges and lawyers, and will handle disputes between the UK and the EU about the withdrawal agreement.
The British suggested it have a role in deciding whether the backstop should come to an end - if it's ever needed.
But the EU felt that went beyond the panel's remit, which is to ensure each side sticks to the rules - not to make big decisions like the future of the Irish border.
Hence the request for the UK to think again. And quickly.
Jeremy Corbyn has met Conservative MPs to discuss possible alternatives to the PM's deal.
The Labour leader held talks with ex-Tory minister Nick Boles and Sir Oliver Letwin, who favour a closer, Norway-style relationship with the EU.
He said he had discussed the so-called "Common Market 2.0 option" - which would see the UK remain in the EU's single market by staying part of the European Economic Area - but would not commit to backing it at this stage.
The government has suffered the first of what are expected to be a number of defeats in the Lords on a key piece of post-Brexit legislation.
Peers voted to amend the Trade Bill to call on the government to join a new customs union with the EU after Brexit.
The result means MPs now will get a vote on whether to stay in the existing customs union when the legislation returns to the Commons.
Ministers also lost a vote obliging them to get Parliament's approval for its negotiating strategy ahead of the next phase of talks on future relations with the EU.
Meanwhile, Mr Corbyn said he had agreed to meet Conservative MPs because he was adamantly opposed to a no-deal exit and he wanted to hear "what their ideas and options are".
While Labour wanted an agreement encompassing a customs union, unhindered access to EU markets and legal protection of workers rights, he said that "what exact form that takes is subject to negotiation".
Mr Boles said the goal was to reach a cross-party compromise to ensure the UK left the EU but in a manner which protected its economic interests.

The UK wants the EU to repay £1bn if it is excluded from the Galileo satellite navigation system after Brexit.
David Davis's Brexit department is also warning the scheme could cost the EU an extra €1bn (£876m) without the UK's continued involvement.
The row could harm wider post-Brexit security co-operation, the department says in a new paper.
UK ministers are angry about the EU's decision to limit access to Galileo, an alternative to the US GPS system.
The UK played a major role in developing satellites for Galileo, which is expected to be fully operational in 2026.
But Brussels has cited legal issues about sharing sensitive information with a non-member state for its decision to shut British firms out of the project. Brussels has also said it will restrict access to encrypted signals from Galileo.
In its position paper, the UK government repeats its threat to build its own satellite navigation system - which has been estimated would cost up to £5bn - as a rival to Galileo.
The paper registers the UK's "strong objection to its ongoing exclusion from security-related discussions" about Galileo, which it says "risks being interpreted as a lack of trust in the United Kingdom".
Downing Street said the UK has held "constructive discussions" with the European Commission on staying in the Galileo satellite navigation project.
But the BBC's Brussels reporter Adam Fleming said the EU had not accepted UK proposals for continued participation in the technology behind Galileo, nor co-operation on security and data protection.
Asked if the EU would repay the £1bn already invested in Galileo if the UK was excluded from work on the project, European Commission spokesman Margaritis Schinas said: "This issue is being discussed with our British partners, negotiations are ongoing, these are precisely the sort of issues we need to address."
The UK government has also threatened to block Galileo satellites from using ground tracking stations in British overseas territories, such as the Falklands.
The European Commission says the UK will have to apply to use the Public Regulated Service (PRS), a key element of the Galileo system, like any other non-EU country after its March 2019 departure.
A navigation and timing signal intended for use by government agencies, armed forces and "blue light" services, PRS is designed to be available and robust even in times of crisis.
Brussels says the UK cannot immediately have access to it when it leaves the European bloc because it will become a foreign entity and PRS is for EU member states only.
In the Department for Exiting the EU position paper, UK officials warn that excluding the UK from Galileo contravenes the withdrawal deal agreed by Theresa May and the EU in December.
It says: "Excluding industrial participation by UK industry in security-related areas risks delays of up to three years and additional costs of up to €1 billion.
"It will not be straightforward to effectively fulfil all Galileo security work elsewhere."
Sir Ivan Rogers, who quit as the UK's ambassador to the EU last year in protest at the "muddled" Brexit negotiations, suggested the EU was partly motivated by a desire to transfer work on Galileo to firms based in the EU.
In a speech on Wednesday, Sir Ivan said: "The UK genuinely wants to remain a major player in the project, with privileged ongoing access from outside the EU, and views its capabilities and contribution to date as giving it the right to that ticket.
"For the EU, the decision to leave inevitably entails relegation to a different role and status in the project, and, let's be candid, offers scope for EU-located firms to take contractual business away from UK ones."
Sir Ivan also suggested in his speech that some in Brussels might also recall that the British government, under pro-EU Tony Blair, tried to prevent Galileo getting off the ground 18 years ago.
He said it was ironic that "a much more Eurosceptic set of politicians" were now "complaining bitterly" that "post Brexit, the field might be somehow tilted more against the depth of participation we now are enthusiasts for".
Separately, the UK has outlined the extent of existing law enforcement capabilities which would be lost if a bespoke security deal is not agreed after Brexit.
According to details of a presentation seen by the BBC, the UK says there will be "significant gaps" in a wide range of areas including prisoner transfers, asset recovery, sharing of financial intelligence, victim compensation and access to criminal records for child protection vetting.

The UK will not cut tax and regulations after Brexit in a bid to undercut EU rivals, Philip Hammond has suggested.
The chancellor told French newspaper Le Monde that tax raised as a percentage of the British economy "puts us right in the middle" of European countries.
"We don't want that to change, even after we've left the EU," he added.
It has been viewed as a softer tone from Mr Hammond, who in January said the UK would do "whatever we have to do" post-Brexit to stay competitive.
But Labour said Mr Hammond was "in open dispute" with himself.
BBC political correspondent Chris Mason says that having lost their majority at this year's general election, the Conservatives would struggle to persuade the Commons to support slashing taxes and regulation.
In his latest interview, Mr Hammond told Le Monde: "I often hear it said that the UK is considering participating in unfair competition in regulation and tax.
"That is neither our plan nor our vision for the future.
"I would expect us to remain a country with a social, economic and cultural model that is recognisably European."
Our correspondent said those words "appeared to be at odds with some of his own comments earlier this year".
During an interview in January, Mr Hammond was asked by Welt am Sonntag whether the UK could become a tax haven after leaving the EU.
He said he was "optimistic" about securing a good trade deal with the EU but if this did not happen "you can be sure we will do whatever we have to do".
"If we have no access to the European market, if we are closed off, if Britain were to leave the European Union without an agreement on market access, then we could suffer from economic damage at least in the short-term," he said at the time.
"In this case, we could be forced to change our economic model and we will have to change our model to regain competitiveness."
Labour said Mr Hammond was now contradicting what he had said at the start of the year.
"The truth is that the British people will not believe the fake U-turn of a Tory chancellor in a French newspaper, while he is still going ahead with billions of pounds in corporation tax giveaways in this parliament, and refuses to rule out further cuts," said shadow minister Peter Dowd.
In his latest interview, Mr Hammond also said the UK wanted EU workers be part of the British economy and carry on with their family life in the country, and the same for British expats working in Europe.
He said the bill for Brexit was not a question about money, but how the UK leaves the EU without causing problems for businesses and people.
Breaking up the City of London would benefit New York not Frankfurt or Paris, he added.
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The UK will have to hold European elections, despite hopes from the government a Brexit deal would be done by then, says the PM's de facto deputy.
The vote is due on 23 May, but Theresa May said the UK would not have to take part if MPs agreed a Brexit plan first.
Now, David Lidington says "regrettably" it is "not going to be possible to finish that process" before the date the UK legally has to take part.
He said the government would try to make the delay "as short as possible".
The UK was due to leave the EU on 29 March, but as no deal was agreed by Parliament, the EU extended the deadline to 31 October.
It can leave the bloc earlier, but if the UK has not left by 23 May, it is legally obliged to take part in the EU-wide poll and to send MEPs to Brussels.
Mrs May's spokesman said she "deeply regrets" that the UK did not leave as planned in March and recognised many people felt "great frustration" that the European elections were going ahead.
But she hoped Parliament would agree a Brexit plan before MEPs start their session in July.
The deadline to register for the EU elections was Tuesday 7 May.
The government has resumed talks with Labour to try to break the deadlock in Parliament over the terms of withdrawing from the EU. It has promised that if no compromise is reached it will offer indicative votes on possible next steps to Parliament.
Labour's shadow business secretary Rebecca Long Bailey said Tuesday's talks were "very robust", but nothing had been agreed, and the government still needed to move on its "red lines" in order to reach a compromise.
A Labour source told BBC political editor Laura Kuenssberg that talks had been "tense" with some frustration on the Labour side and said there were still "fundamental" problems and divisions between the two sides.
The government was being "disingenuous" to suggest that ministers were offering a significant new compromise beyond what was already available in the existing agreements with the EU, the source said.
Downing Street said the talks had been "constructive and detailed" and they would continue on Wednesday afternoon.
"Constructive and detailed" - that sounds quite positive - Number 10's description of the talks today.
"Robust" - not quite so chirpy - Labour's use of political speak for what most of us might call a bit tricky.
"Disingenuous" - oh dear - a different Labour source's description of ministers' claim that what they were putting on the table in the cross-party talks today was something genuinely new on the vexed question of customs arrangements after we leave the EU.
As we reported this morning there didn't really seem to be much from the government that was concrete beyond what's already possible under the agreement that's been hammered out with Brussels.
The divorce deal and indeed yes, you guessed it, the backstop, both have forms of temporary customs unions in them to make trade between the UK and the EU easier.
Of course the precise language and mechanisms matter enormously.
But was there some big shiny new offer today? The short answer is: no.
A number of other parties have already announced their candidates and launched their European election campaigns, but the Conservatives have yet to do the same.
Cabinet Office Minister Mr Lidington said: "We very much hoped that we would be able to get our exit sorted… so that those elections did not have to take place, but legally they do have to take place unless our withdrawal has been given legal effect."
Mr Lidington said the government would be "redoubling efforts" in its talks with other parties to find a way forward to "make sure that the delay after [the elections] is as short as possible".
He added: "We would like to be in a situation… certainly to get this done and dusted by the summer recess."
Government sources say if the Brexit process is completed before 30 June, UK MEPs will not take up their seats at all. If it is done and dusted after that date but before Parliament begins its summer recess in July, MEPs will only need to sit for a month, until 1 August.
Sources estimate that the cost of holding the European elections will be roughly £150m.
Analysis: By Chris Morris, BBC Reality Check
Even if an unexpected deal were to emerge in the next few days between the Conservatives and Labour, it would only be a very tentative first step towards Brexit, with no guarantee that it would enjoy a parliamentary majority.
And a first step isn't enough.
The conclusions of last month's EU summit, agreed by all EU leaders including Theresa May, said that if the Brexit withdrawal agreement has not been ratified in parliament by 22 May, the European elections will have to take place in the UK.
The ratification process means Parliament would have to pass a meaningful vote on the withdrawal agreement (the deal negotiated between the government and the EU), and then turn it into UK law in the form of a Withdrawal Agreement Bill.
And, as Mr Lidington has now conceded formally, time to do all of that has run out.
Some Brexiteers are angry at Mrs May's efforts to find a compromise with Labour after her deal with the EU was effectively rejected by MPs three times.
One leading Eurosceptic, Sir Bill Cash, told the Press Association "the time has come" for the PM to resign and she "needs to be given a date".
But Chancellor Philip Hammond defended the cross-party talks, suggesting the government had no other option.
The BBC's political editor Laura Kuenssberg says No 10 is trying to get Labour over the line by presenting the withdrawal agreement as a stepping stone - i.e. hold your nose for now and you can carve out your own deal if you win the next election.
Key to that, she says, is the promise of a "temporary customs union", but Labour sources are warning that would not be enough.
Labour has previously said it wants a permanent customs union - an arrangement not to carry out checks or put tariffs (extra payments) on goods that move around between the UK and the EU after Brexit.
The election in May will see 751 MEPs sent to the European Parliament to make laws and approve budgets for the EU.
Each country is allocated a set number of seats, depending on the size of its population.
The smallest member, Malta (population: around half a million) has six MEPs, while the largest, Germany (population: 82 million) has 96.
The UK is divided into 12 regions, each represented by between three and 10 MEPs depending on population size, ending with a total of 73.
Seats in England, Scotland and Wales are awarded to parties according to their share of the vote, then to the candidates on the lists drawn up by the parties.
Northern Ireland elects MEPs using a single transferable vote system, with voters able to rank candidates in order of preference.
The European Parliament has agreed that 46 of the UK's 73 seats will be abolished after Brexit, and the remaining 27 will be redistributed among countries that have complained of under-representation.
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Free movement of people between the EU and UK will end in March 2019, UK government ministers have said.
From that date EU workers moving to the UK will have to register, at least until a permanent post-Brexit immigration policy is put in place.
But Home Secretary Amber Rudd has sought to reassure business there will not be a "cliff edge" in terms of employing foreign workers after Brexit.
She said policy would be evidence-based and take into account economic impact.
The CBI said businesses "urgently" needed to know what EU migration would look like, both in any "transitional" period after March 2019 and beyond.
Immigration was one of the central topics of last year's EU referendum campaign, and ministers have promised to "take back control" of the UK's borders as they negotiate Brexit.
The UK is currently due to leave the EU at the end of March 2019, but there has been increasing talk of a "transitional" (or "implementation") stage of around two years to smooth the Brexit process.
Speaking on BBC Radio 4's Today programme, Home Office minister Brandon Lewis said details of how the government would manage immigration after Brexit would be revealed in a white paper later this year, and that the immigration bill would go through Parliament in 2018.
Mr Lewis said it was a "simple matter of fact" that EU free movement rules would not apply after 2019.
More detail of what would happen was later provided by the home secretary, with Ms Rudd, speaking during a visit to Troon, South Ayrshire, saying the "implementation phase" would involve new EU workers registering their details when they come to the UK.
She also said the government had promised an "extensive" consultation to listen to the views of businesses, unions and universities.
The Home Office has asked the Migration Advisory Committee to study the "economic and social costs and benefits of EU migration to the UK economy", its impact on competitiveness, and whether there would be benefits to focusing migration on high-skilled jobs. It is due to report back by September 2018 - six months before Brexit.
The home secretary said: "We will ensure we continue to attract those who benefit us economically, socially and culturally.
"But, at the same time, our new immigration system will give us control of the volume of people coming here - giving the public confidence we are applying our own rules on who we want to come to the UK and helping us to bring down net migration to sustainable levels."
Speaking in Sydney, Foreign Secretary Boris Johnson said he was unaware of the report that has been commissioned, adding that immigration had been "fantastic for the energy and dynamism of the economy" but "that doesn't mean that you can't control it".
For Labour, shadow home secretary Diane Abbott said there was "far too much heat and not enough light about immigration, so any truly objective and well-informed analysis must be welcome".
But she raised concerns about the timescale for the Migration Advisory Committee report: "Six months before Brexit will not be enough time to structure a new immigration system."
Lib Dem home affairs spokesman Sir Ed Davey said the move would "do nothing to reassure the hospitals that are already seeing record numbers of EU nurses leaving, or the companies struggling to recruit the staff they need".
"The NHS, businesses and universities that depend on European citizens need answers now, not in another 14 months' time," he added.
The CBI said commissioning the report was a "sensible first step", adding: "Workers from across Europe strengthen our businesses and help our public services run more smoothly - any new migration system should protect these benefits while restoring public confidence."
But the Labour MP Yvette Cooper, who chairs the Commons home affairs committee, said it was "staggering" that it had taken the government a year since the EU referendum to commission it.
And property developer Richard Tice, co-chairman of Leave Means Leave, told BBC Radio 4's World at One: "This commission should be reporting by this Christmas, not by next September. It's completely unacceptable for this to drag on ... the government needs to rapidly accelerate this."
Manufacturers' organisation EEF said the migration committee was "best placed" to advise on what EU migration should look like after Brexit.
Both EEF and the CBI called for an immediate resolution of the question of the status of EU nationals already living in the UK.

Donald Trump's offer of a "quick, massive, bilateral trade deal" will not be possible if Theresa May's EU withdrawal agreement is approved, the US ambassador to the UK has warned.
President Trump had previously said her Brexit proposal sounded like a "great deal for the EU".
Woody Johnson told the BBC the UK was "in need of leadership" over Brexit.
A Downing Street spokeswoman said Mr Johnson recently said the UK was "the perfect trading partner for the US".
Mr Johnson told Radio 4's Today programme there was still hope for a UK-US trade deal.
"What I'm focusing on here is something the president has also said - that is looking forward to, and hoping, that the environment will lead to the ability for the US to do a quick, very massive bilateral trade deal," he said.
He added it could be "the precursor of future trade deals with other countries around the world for Great Britain that will really take you way, way into an exciting future".
"We're still going through the stages of deciding exactly where the country is going," said Mr Johnson. "If it goes in a way that allows these kinds of agreements to occur then I think that will be very positive in the president's eyes."
Asked if that would go ahead under the current proposed Brexit deal, which MPs are due to vote on in January, he replied: "It doesn't look like it would be possible."
He said ministers - and the prime minister - had to "measure the impact of all the other trade offs" and how different trade agreements would benefit the UK.
Mr Trump has said Mrs May's deal could leave Britain unable to negotiate a free-trade agreement with the US.
Mr Johnson did not give more details about what such a deal would entail.
However, while the UK is either in a transition period after Brexit - or in a temporary customs union - it will not be able to implement its own free trade deals, with the US or any other third country.
Reacting to Mr Johnson's comments on Brexit, the Downing Street spokeswoman said both the UK and the US had been clear that "we want an ambitious trade agreement and we stand ready to conclude such an agreement as a priority after we leave the European Union".
Mr Johnson also said that he had been surprised by the "defeatism" felt in the UK over Brexit.
"All of the reporting looks back and it looks at a very static future, rather than an active British future - about solving problems, entrepreneurialism and taking advantage of opportunities and being very innovative," said Mr Johnson.
"If you look back and try to project the past into the present and future, it's going to be bleak.
"But you're leaving out the great thing that Britain has to offer and that is all of the people and all of their efforts and their ability to solve problems. If you factor that in, I think the future is extremely positive, extremely bright."
He added that it would be "great" if President Trump's postponed state visit could take place in May, around the time of World War Two commemorations - if his schedule, and that of the Queen, allowed.

Boris Johnson and his Irish counterpart Leo Varadkar have had their first exchange of views on Brexit in their first phone call since the former Mayor of London became Prime Minister.
Mr Varadkar reiterated that the backstop - the mechanism to avoid an Irish hard border - was needed because of decisions made by the UK.
The taoiseach also invited Mr Johnson to Dublin to discuss Brexit.
The PM again said the backstop must be removed from any deal with the EU.
He insisted the UK will be leaving the EU by the 31 October deadline "no matter what".
But Mr Varadkar maintained there could be no reopening of the withdrawal agreement.
A UK government spokesperson said that during the call both leaders had reiterated their commitment to work together in the spirit of the "warm and deep relationship" the two countries share.
A spokesperson for Mr Varadkar said he had explained to the new prime minister that the EU was "united in its view" on the withdrawal agreement.
Mr Johnson repeated his commitment that the British government would "never put physical checks or infrastructure on the border".
He said any further Brexit negotiations would be approached by his government in a spirit of friendship - but that any deal must be one that "abolishes the backstop".
The backstop is a key piece of the Brexit deal dictating what will happen to the border between Northern Ireland and the Republic of Ireland.
It is a last resort that guarantees a frictionless border if no better solution is devised in time - by maintaining close ties between the UK and the EU until such a solution is found.
The two men also discussed attempts to restore the Northern Ireland Assembly, which collapsed in January 2017.
Mr Johnson said the current talks have his "unequivocal support" and that he looked forward to visiting Northern Ireland shortly to talk to the leaders of the five main parties about restoring devolution.
The taoiseach restated the need for both governments to be "fully committed" to the Good Friday Agreement and restoring the institutions.
He invited Boris Johnson to Dublin to "share their respective analyses" on Brexit, and to continue discussions about Northern Ireland, the Good Friday Agreement and the Common Travel Area.

The Irish and German leaders have discussed how to help Theresa May get her Brexit deal through Parliament.
Taoiseach (Irish PM) Leo Varadkar said he held a 40-minute phone call with German Chancellor Angela Merkel on Thursday morning at her request.
He said they agreed to offer reassurances and guarantees to the UK, but would not change the existing deal.
Meanwhile, DUP deputy leader Nigel Dodds reiterated objections to the deal during a meeting with Mrs May.
His party, which is propping up Mrs May's government, is strongly opposed to the Irish border backstop element of the draft EU withdrawal agreement and described concerns over a hard border as "nonsense propaganda".
The draft deal requires the support of Parliament, and the prime minister is facing significant opposition from a cross-section of Westminster MPs, including the DUP.
Addressing reporters in Dublin on Thursday afternoon, Mr Varadkar said Brexit "was a problem created in the UK" and it was up to Westminster to offer a solution.
"It was an opportunity to brain storm a bit as to what we could do to assist Prime Minister May in securing ratification of the withdrawal agreement," Mr Varadkar said of his conversation with Mrs Merkel.
Planning for a no-deal Brexit was also discussed during their phone call.
"What we both really agreed was that, once again, this is a problem that's created in London," Mr Varadkar said.
"The inability to ratify the withdrawal agreement is a problem in Westminster, and we're really looking to them for a solution," he said.
"But it has to be a proposal that we can accept. So it can't be a proposal that contradicts what is already in the withdrawal agreement.
"It can't be something that renders the backstop inoperable, for example. So we want to be in a position to give guarantees, give assurances, give clarifications."
The taoiseach added that the Irish border was the only "red line" his country has had in the Brexit negotiations and that would not change.
The DUP criticised the Irish government's strategy after several of its senior figures had lunch with Mrs May on Thursday.
"The Irish Republic's 'no deal' preparations published just before Christmas have laid bare the nonsense propaganda about a hard border," Mr Dodds said.
"No one wants a hard border between Northern Ireland and the Republic. Indeed, its becoming clearer by the day that no one is ever going to construct such a border.
"With this clarity emerging in London, Dublin and Brussels, there is evidently no need for the aspects of the Withdrawal Agreement which have been so vigorously opposed by a broad cross section of the House of Commons."
Mr Dodds repeated his party's claim that the backstop would place a "barrier" between Northern Ireland and its "main trading partner", Great Britain.
"Brussels must now demonstrate that if it truly cares about Northern Ireland, then erecting a new east-west barrier should be no more palatable than having any new north-south barriers," he said.

Theresa May has told MPs there might not be a third vote on her Brexit deal next week if there is insufficient support for it to pass.
If it does not pass, the EU has set a deadline of 12 April for the UK to propose a new plan.
Supporters of another EU referendum are due to march through central London later.
Labour's Tom Watson will speak at the event, pledging to back May's deal if she agrees to hold a referendum on it.
Meanwhile, an online petition calling for the UK to remain in the EU has attracted a record number of signatures.
By 11:32 GMT, the total number of signatures calling for Article 50 to be revoked stood at 4,151,815 - beating the previous record reached by another Brexit-related petition in 2016.
If Mrs May's deal is approved by MPs next week, the EU has agreed to extend the Brexit deadline until 22 May. If it is not - and no alternative plan is put forward - the UK is set to leave the EU on 12 April.
In a letter to all MPs on Friday evening, Mrs May offered to talk to MPs over the coming days "as Parliament prepares to take momentous decisions".
She said there were now four "clear choices". These were:
Children's minister Nadhim Zahawi told the Today programme failing to support Mrs May's deal would lead to a "meltdown in our politics, not just for the Conservative party but for all parties".
He said all the other alternatives would require MPs asking for a much longer extension, which Mrs May has said she is not prepared for.
Indicating he would stand down if Mrs May's deal is not voted for, Mr Zahawi said he "cannot justify" going to his constituents and saying: "We failed to deliver this and that now we are having to stay in the EU and go into European elections."
Mrs May also confirmed in her letter that the government would change the law to officially change the UK's departure date from the EU next week.
Her letter came after the DUP - whose support will be crucial if the government is to win - indicated they still would not back her deal.
Mrs May also referred to her televised address on Wednesday, in which she blamed the delay to Brexit on MPs.
She acknowledged that "a number of colleagues had raised concerns" about her words and said it had not been her intention to make their "difficult job... any more difficult".
Former Tory chief whip Andrew Mitchell told BBC Radio 4's Today programme "there was a very strong feeling she'd made an error of judgement" on this.
But dismissing reports of growing pressure on Mrs May to quit, he said: "To change prime minister would be a colossal error - it won't change the numbers [in the vote for Mrs May's deal]".
By Jonathan Blake, political correspondent
Theresa May's admission that there may not be a third vote on her deal after all will focus minds on what an alternative plan might be.
To avoid asking the EU for a longer extension and holding European parliament elections, the prime minister will need a new course of action.
A series of indicative votes in Parliament looks the most likely way to decide that - but there is no agreement on whether the government should lead that process or relinquish control to Parliament.
And when and if a consensus in Parliament emerges, there is no guarantee it will automatically become government policy.
It has taken two years for the government to formulate, negotiate and attempt to get a Brexit deal through Parliament.
Finding an alternative which ministers, MPs and the EU are happy to embrace within the next two weeks will be a very tough task indeed.
Meanwhile, campaigners say they expect hundreds of thousands of people to march through central London as part of the 'Put It To The People' demonstration.
Speakers at a rally afterwards will include Labour's deputy leader, Tom Watson, Scotland's First Minister, Nicola Sturgeon, London Mayor Sadiq Khan and others.
Mr Watson will say: "I've come to the reluctant view that the only way to resolve this and have legitimacy in the eyes of the public is for the people themselves to sign it off."
James McGrory, the Director of the People's Vote campaign, told BBC Radio 4's Today programme: "Politicians are unable to agree on a way forward so it seems to the People's Vote campaign that the only way forward it to put any Brexit deal - whether it's the government's deal or any alternative form of Brexit - put it to the people."
Ms Sturgeon said now was "the moment of maximum opportunity" to avoid a no-deal Brexit.
A petition on Parliament's website calling for Brexit to be cancelled by revoking Article 50 has attracted more than four million signatures.
Lib Dem MP Layla Moran said the petition could "give oxygen" to the campaign for another Brexit referendum.
Speaking in Brussels on Friday after the European Council agreed to delay the Brexit date, Mr Tusk said that until 12 April, "anything is possible" including a much longer delay or cancelling Brexit altogether.
"The fate of Brexit is in the hands of our British friends. As the EU, we are prepared for the worst, but hope for the best. As you know, hope dies last."
According to the final summit conclusions, the UK is expected to "indicate a way forward" before 12 April, if MPs do not approve the withdrawal deal negotiated with the EU, which would then be considered by the European Council.
The UK must decide by then whether it will take part in European Parliamentary elections from 23-26 May - if it does not, then a long delay would become "impossible", Mr Tusk said.
Mrs May will need to table secondary legislation to remove the date March 29 from Brexit laws.
29 March: Current Brexit date in UK law
12 April: If MPs do not approve the withdrawal deal next week - "all options will remain open" until this date. The UK must propose a way forward before this date for consideration by EU leaders
22 May: If MPs do approve the deal next week, Brexit will be delayed until this date
23-26 May: European Parliamentary elections are held across member states

The government will not sign up to a Brexit agreement that breaks up the UK, Commons Leader Andrea Leadsom has said.
EU chief negotiator Michel Barnier said on Friday that the UK would be free to leave a proposed single customs territory with the EU - provided Northern Ireland remained within it.
The DUP - the party Theresa May relies on for a majority in Parliament - has rejected the proposal.
The plan is designed to avoid physical checks on the Irish border.
The UK is due to leave on 29 March, although Parliament has yet to agree the terms of withdrawal.
The UK and the EU remain at loggerheads over the contentious issue of the Irish backstop - which is designed to maintain an open border on the island of Ireland by keeping the UK aligned with EU customs rules until the two sides' future relationship is agreed or alternative arrangements are worked out.
The Commons Northern Ireland Affairs Committee has suggested there may be a possible technical solution to the border problem "but only if there is trust and goodwill".
On Friday the EU said it was prepared to include a number of existing commitments relating to the application of the backstop in a legally-binding document.
In a series of tweets Mr Barnier said the UK would not be forced into a customs union against its will through the Northern Ireland backstop.
He said it would be able to exit the single customs territory unilaterally if it chose to do so.
But, he added, Northern Ireland would remain part of the EU's customs territory, subject to many of its rules and regulations.
Mrs Leadsom said she was "deeply disappointed" by the proposal.
She told the BBC: "We will not break up the United Kingdom and have a border down the Irish Sea - so, I have to ask myself: what game are [the EU] playing?"
Brexit Secretary Stephen Barclay has also been dismissive of Mr Barnier's proposal.
Mr Barclay tweeted on Friday: "With a very real deadline looming, now is not the time to rerun old arguments.
"The UK has put forward clear new proposals. We now need to agree a balanced solution that can work for both sides."
The DUP said the proposal disrespected the constitutional and economic integrity of the UK, and was neither "realistic nor sensible".
The UK government has previously said it will not agree to anything which threatens the constitutional integrity of the UK.
But Sinn Fein leader Mary Lou McDonald backed Mr Barnier's position and said the Irish government needed to "hold firm" regardless of "pressure that might be applied from London".
Meanwhile, a report published on Saturday by the Northern Ireland Affairs Committee has suggested a "world first" mobile phone identification system could be the way to achieve invisible border controls.
The system would use either the mobile phone network or radio frequency identification to check goods or driver's IDs without them leaving the vehicle, in combination with a trusted trader scheme.
Border surveillance would utilise automated number plate recognition and CCTV.
Lars Karlsson, a former director at the World Customs Organisation, said all the separate elements which made up the proposal  had been tested "somewhere in the world, just not in one single border".
The border in Northern Ireland would be "the first and a leading example in the world of this kind," he added.
However, the committee urged the UK and EU negotiators to agree on a definition of a hard border by 12 March.
"Mistrust over the backstop protocol has been heightened by lack of clarity on what exactly constitutes a 'hard border'," said chairman Andrew Murrison.
"My committee is calling for clarification of the term in a legally explicit way to ensure both parties share the same understanding of how the backstop can be avoided."
"Time is running out to reach common ground," the Conservative MP warned.
MPs are due to vote again on Theresa May's Brexit deal on Tuesday, but so far the UK has not secured any changes to the withdrawal agreement in its negotiations with Brussels.
UK and EU negotiating teams will meet again over the weekend but correspondents say there is little sign of a breakthrough.
The first Commons vote on the deal was rejected by 432 votes to 202 in January, the largest defeat for a sitting government in history.
Leading Brexiteers are unlikely to change their position on the deal unless Mrs May can secure promises that the backstop will not endure indefinitely.
Remainer Dominic Grieve, who supports a referendum to endorse the terms of Brexit, said it was "hard to see" how Parliament would agree to the current deal.
The Labour leadership is also unlikely to back Mrs May's deal.

MPs have taken part in a second round of votes on alternative proposals to Theresa May's Brexit deal.
None of the four options chosen by the Speaker, John Bercow, were backed outright by MPs.
The first series of "indicative votes" on various options was first held last week, on 27 March.
None of MPs' eight proposals secured a majority then either.
The House of Commons is attempting to find a strategy that can gain majority support after the prime minister's plans were rejected on three occasions - so far.
Proposer: Ken Clarke, Conservative
Result: 273 votes for and 276 against
This option commits the government to negotiating "a permanent and comprehensive UK-wide customs union with the EU" as part of any Brexit deal.
This arrangement would give the UK a closer trading relationship with the EU and reduce the need for some (but not all) checks at the Irish border.
But it would prevent the UK striking independent trade deals with other countries, and has previously been ruled out by Mrs May.
A version of this proposal received the most support in the first round, falling just six votes short of a majority.
Proposer: Nick Boles, Conservative
Result: 261 votes for and 282 votes against
This proposal would mean joining the European Free Trade Association and European Economic Area, with countries such as Norway.
It means the UK would remain part of the EU single market and would retain freedom of movement, so British citizens would keep the right to live and work in the EU and vice-versa.
In the last round, 188 MPs voted for this plan and 283 voted against.
Proposers: Peter Kyle and Phil Wilson, Labour
Result: 280 votes for and 292 votes against
This gives the public a vote to approve any Brexit deal passed by Parliament, before it can be implemented.
Tabled last time by Labour former minister Dame Margaret Beckett, this option won the highest number of votes, with 268 MPs for and 295 against.
Proposer: Joanna Cherry, Scottish National Party
Result: 191 votes for and 292 votes against
This option offers a series of steps to prevent the UK leaving the EU without a deal. First, it requires the government to seek an extension if a deal has not been agreed two days before the deadline for leaving.
If the EU does not agree to an extension, on the day before the UK was due to leave, MPs would be asked to choose between a no-deal Brexit or revoking Article 50 to stop Brexit altogether.
In the event of revoking Article 50, an inquiry would be held to find out what type of future relationship with the EU could command majority support in the UK and be acceptable to Brussels.
MPs previously voted against a proposal to cancel Brexit by Joanna Cherry, but have not considered this plan before.
The following four motions were rejected by Mr Bercow.
Proposer: John Baron, Conservative
This proposal aimed to commit the UK to leave the EU on 22 May with an amendment to Prime Minister Theresa May's withdrawal agreement. That would allow the UK to exit the so-called Irish backstop whenever it wants, without the EU's permission.
The backstop is an insurance policy designed to keep an open border between Northern Ireland and the Irish Republic "under all circumstances", if the UK and EU do not manage to agree a permanent trade relationship in time.
Many MPs fear that it could mean the UK is tied to EU rules for years, while the Democratic Unionist Party has voted against it because it would mean Northern Ireland was treated differently from the rest of the UK.
This was a new motion, which was not considered by MPs on 27 March. But the EU has said that the backstop is not up for renegotiation.
Proposer: John Baron, Conservative
This motion asked MPs to support the UK leaving the EU without a deal on 12 April, if they have not agreed to support the prime minister's withdrawal agreement by then.
If the UK did leave the EU with no deal, it would mean initially trading on World Trade Organisation (WTO) terms, which could mean tariffs on certain goods and extra checks on UK goods entering the EU.
On 27 March, a similar motion was backed by 160 MPs, but opposed by 400.
Proposers: Graham Jones, Labour, and Dominic Grieve, Conservative
This was another proposal for the public to vote on the future of Brexit, but in this case it would only happen if the UK was otherwise going to leave the EU without a deal.
MPs have not voted on this motion before.
Proposer: George Eustice, Conservative
This motion proposes that the UK rejoins the European Free Trade Association as soon as possible, meaning the UK stays in the single market.
It also requires negotiations with the EU over "additional protocols" to resolve the issue of the Irish border and agri-food trade.

A public row has broken out between leading figures in the People's Vote campaign for another EU referendum.
The director and head of communications for the campaign both appear to have been sacked, and many of the staff are reported to have walked out in protest.
The People's Vote campaign is an organisation campaigning for a new referendum on the UK's membership of the EU.
The campaign, which was launched in 2018, officially supports a new referendum on any Brexit deal, with the option of remaining in the EU being on the ballot paper.
It is a coalition of five different coalition groups - the European Movement UK, the Joint Media Unit, Our Future Our Choice, For our Future's Sake and Wales for Europe and Open Britain.
The director of the campaign is James McGrory, ex-deputy PM Nick Clegg's former top adviser, and the head of communications is Tom Baldwin, the former top adviser to Ed Miliband when he was Labour leader.
However, on Sunday evening, Roland Rudd, the chairman of Open Britain, the company which runs the People's Vote campaign. sent an email to staff announcing that Mr McGrory and Mr Baldwin were leaving the organisation and being replaced with Patrick Heneghan, a former head of campaigns for the Labour party.
Staff angry at the changes walked out of the People's Vote office, in Millbank tower, on Monday morning.
Prominent supporters such as Alistair Campbell, the former No 10 director of communications under Tony Blair, have questioned whether Mr Rudd even has the power to dismiss Mr McGrory and Mr Baldwin.
The campaign is split on whether it should commit to supporting remaining in the EU in any future referendum.
The Observer has reported that Mr Rudd wants the campaign to pursue a more explicitly pro-Remain position.
Mr McGory and Mr Baldwin feared this would stop the campaign from winning over "soft Leave" voters - and Labour and Conservative MPs who may support a second referendum.
Mr Baldwin defended this position in an interview with BBC Radio 4's Today programme,
"It's not the best way to win the argument with Conservative MPs who back a deal, or Labour MPs that back a deal, or indeed the public, many of who voted leave and still want to leave, to say that this is just a ruse to overturn the result of the last referendum," he said.
Speaking on the same programme, Mr Rudd said: "There's no row about the Remain side and PV [People's Vote]. Everyone knows where we stand on this.
"This is an absurd argument. Everybody knows perfectly well that we're made up of people who want to vote to Remain. There isn't a problem."
This is not the first time internal debates over whether the campaign should explicitly back Remain have become public.
In July, Buzzfeed News published a series of leaked emails and exchanges between senior members and supporters of the campaign revealing tensions over staff and strategy, specifically around whether or not the campaign should take part in an pro-EU march that month.
Six prominent supporters of the campaign emailed Mr Rudd to complain that the infighting meant the organisation was "not fit for purpose".
Divisions over the campaign's strategy are not just limited to whether or not they back Remain.
It was also reported in January that there were internal arguments over when to table an amendment for a second referendum, with some in the campaign wanting MPs to wait until all other options had been rejected.
There have also been clashes over personalities before today, when Mr Baldwin accused Mr Rudd of putting "a wrecking ball" through the campaign.
Mr Rudd, who is standing down as chair of Open Britain, has been criticised for trying to use a new pro-EU group, registered under a new company, Baybridge, as a way to take more control over the Remain campaign in any future referendum.
However, according to The Observer, this new group has been defended by allies as being necessary to bring direction to the campaign.
Mr Rudd's opponents have also previously faced accusations of trying to gain more power within the campaign.
The Mail on Sunday has reported that Mr Campbell had attempted to work with Labour peer Lord Mandelson, both allies of Mr Baldwin, against Mr Rudd.
They were accused of trying to organise a "coup" against Mr Rudd with Mr Campbell writing in one email: "I do not see how this gets done without a public battle and it should happen soon and be fast and brutal".
Mr Rudd is., according to the Politics Home, due to address People's Vote staff tomorrow.

 Prime Minister Theresa May has used a speech in Florence to set out the UK's position on how to move Brexit talks forward. With further negotiations planned next week, what did her speech tell us about the sort of Brexit deal we might end up with? Reality Check correspondent Chris Morris has been scanning the speech.
What's the significance? It's worth noting that a lot of Brexit supporters in the UK jumped on Jean-Claude Juncker's State of the European Union speech last week - in which he set out an ambitious agenda of greater integration - as an example of why they wanted to leave in the first place.
The PM picked up on this - we're getting out of your way while you move in a different direction that we've never felt entirely comfortable with.
That's good for both of us she implied. It slightly ignores the fact that many EU leaders wouldn't agree with Mr Juncker's proposals - but it's a point that will go down well on the Tory backbenches.
What's the significance? The tone matters here. Urging EU leaders to be creative, ambitious and to share a "profound sense of responsibility to make this change work" is a bit of a departure from the language in her last major speech on Brexit at Lancaster House in London in January.
It contained warnings of "an act of calamitous self-harm" for the countries of Europe if they sought to punish the UK, and the famous assertion that "no deal is better than a bad deal" for Britain.
The rest of the EU will take note of this more collaborative appeal but will also be watching to see whether the tone changes again in the prime minister's speech to the Conservative party conference next month.
What's the significance? The prime minister is saying she wants to incorporate an agreement on EU citizens' rights into UK law, and she thinks UK courts should be able to "take into account" the judgements of the European Court of Justice.
It's a real guarantee, she says: "We want you to stay." The trouble is that it's not what the EU is demanding.
The chief EU negotiator Michel Barnier insisted in a speech yesterday that the Court of Justice should remain the ultimate guarantor of any agreement.
The big difficulty here is that jurisdiction is a pretty black-and-white issue - there are few grey areas. As things stand, the UK view is that British courts should have the final say, and the EU sees that as unacceptable.
What's the significance? So the Prime Minister has ruled out a European Economic Area-style solution to a future relationship (this would be like Norway - part of the single market but not part of the EU). Mrs May says it would still be too restrictive for the UK.
And she ruled out an ambitious free trade deal like the one the EU has with Canada - it would take too long and would ignore the fact that we start from a position where all our rules and regulations are the same.
So she wants a unique solution - a new deep and special partnership. But in this speech she hasn't really given more details of exactly what that solution would be.
What's the significance? This is important. It means that during a transition period - the prime minister suggested two years as a possibility - all the rules will remain the same.
That means payments into the EU budget, free movement of people and the jurisdiction of the European Court of Justice would stay in place.
That's always been the position of the rest of the EU - it now appears that the UK has accepted that there is no way round this.
Mrs May confirmed that there will be no restrictions on EU citizens coming to the UK during the transition, but that after Brexit they will be registered as they arrive. That is something that the UK could already do under current EU rules, but it never has done so.
What's the significance? The prime minister is trying to reassure other member states that no net contributor will have to pay more, and no net recipient will receive less, during the current seven-year budget period, which runs until the end of 2020.
That suggests that the UK will provide the sum of roughly 20bn euros (£18bn) in the two-year transition period that it has now proposed.
What's not yet clear is whether the UK thinks these payments will also cover some of its outstanding debts - debts that the EU insists have to be settled as part of a withdrawal agreement.
The rest of the EU will view the £18bn as payment for the UK being allowed to maintain its current role in the single market.
A lot depends on what exactly Mrs May meant by this key sentence: "The UK will honour commitments made during the period of our membership."
Note she didn't say "all" our commitments.
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The European Union has issued a 16-page document outlining the preparations that need to be made for Brexit. It includes advice on how countries, companies and individuals should prepare for the prospect of the UK leaving with "no deal" in place.
BBC Reality Check correspondent Chris Morris has read the document so you don't have to. Here are some key excerpts, and explanations of what they mean:
From the outset, the EU makes one thing clear - even if negotiations go better than expected, it thinks there will be significant disruption, and everyone needs to be ready for it. (The EU talks about 30 March as exit day, by the way, because the precise time of withdrawal is due to be midnight on 30 March in Central European Time, but 23:00 on 29 March in GMT).
The document emphasises that negotiations on a withdrawal agreement are continuing and that a negotiated settlement is the EU's preferred outcome.
But it also notes that important issues remain unresolved - including on the protection of personal data sent to the UK while it was a member state and on the role of the European Court of Justice (ECJ) in policing a withdrawal agreement.
In particular, it states that there has been "no progress" in agreeing a "backstop" solution to avoid the imposition of a hard border between Northern Ireland and the Republic of Ireland.
The EU notes, as it has done many times before, that time to both reach and ratify an agreement is running short.
This is why preparations for "no deal" are so important.
If there is a deal, there will also be a transition period running until 31 December 2020 during which EU rules and regulations will continue to apply in the UK.
That will give businesses and governments more time to prepare for a new relationship.
Without a deal, the transition (or "implementation period" as the UK government calls it) falls away and the relationship will change abruptly at the end of March next year.
If both sides come to the conclusion several months before the end of March that there will be "no deal", they can at least make some contingency plans to deal with that.
But if there is a last-minute hitch, time will have run out.
So, from the EU's perspective, thinking about "no deal" means "preparing for the worst and hoping for the best".
Much of the UK government would probably look at it in the same way - but there are many Brexiteers who think that "no deal" would be perfectly acceptable as long as sufficient preparations have been made.
This kind of language is scattered throughout the document. "Don't say we didn't warn you," would be another way of putting it.
The document stresses that some things will have to be done whatever the outcome.
One thing it mentions is the need for companies to take steps to ensure that they have the right authorisations and certificates to access the EU market after Brexit.
But contingency planning for "no deal" is the main emphasis - the EU says this is a prudent step because the outcome of negotiations "cannot be predicted".
Among other issues, it notes that there would be no arrangement in place for EU citizens in the UK or UK citizens in the EU.
It says controls at borders "could cause significant delays, eg in road transport, and difficulties for ports", where there could be "long lines of vehicles waiting for customs procedures to be fulfilled".
It also says that the UK would become a third country for trade and regulatory issues, which would "represent a significant drawback compared to the current level of market integration".
It also emphasises that while many measures would have to be taken at EU level, national, regional and local governments also need to step up their levels of preparation to "mitigate the worst impacts of a potential cliff-edge scenario" - cheerful stuff.
And of course a lot of the attention is focused on making sure that individual EU businesses, big and small, are going to be ready for whatever emerges at the end of a highly unpredictable process of negotiation.
The document notes that several EU governments, such as the Irish and the Dutch, have set up online platforms to help their companies prepare for different potential Brexit scenarios.
The document also claims - in a sentence that won't please the UK government - that "many companies are relocating to the EU27" or expanding their operations there.
EU officials insist that they are not trying to add fuel to the fire and that they are simply engaged in prudent planning.
But it's a reminder that there are people in Europe, as well as in the UK, who see Brexit as an opportunity rather than a threat.
The commission has now published 68 notices (anyone with a few hours to spare can read them here) on preparations in specific sectors of the economy, including health and food safety, financial services, customs, transport, and company law.
They set out the legal and technical issues that governments and companies need to take into account and are another glimpse into the complexities of Brexit that stretch into every area of economic life.
In the UK, the government has not yet published any comparable information of its own.
However, on Wednesday, Theresa May told MPs at the Liaison Committee that a similar number of technical notifications about what to do in the event of a "no deal" Brexit will be released during August and September - aimed at businesses and citizens.
In response to the EU document, the Department for Exiting the European Union said "It is the duty of any responsible government to prepare for every eventuality, including the unlikely scenario that we reach March 2019 without agreeing a deal. We have already done a lot of work behind the scenes to prepare for this - it is only natural that our European partners would seek to make similar preparations. We are keen to work closely with the EU on preparedness issues."
There are all sorts of EU databases, including many dealing with policing and internal security issues, to which the UK wants to retain access after Brexit.
But the EU has argued that the UK can't simply pick and choose the bits of membership it likes - and this part of the document emphasises that work is well under way to remove the UK from numerous databases and IT systems once it becomes a "third country".
The commission is also making preparations for changing international agreements that currently involve the UK as a member state. It says it will notify its international partners formally once it has sufficient certainty about the outcome of the current negotiations - not for a while, then.
Finally, the EU document says work is under way to relocate or reassign tasks that are currently performed in the UK - such as the Galileo Security Monitoring Centre (part of the EU's project for satellites in space) or the UK-based EU Reference Laboratories - because it will not be possible "to entrust a third country" with such EU tasks after the withdrawal date.
Two London-based agencies, the European Medicines Agency and the European Banking Authority, are already moving to Amsterdam and Paris respectively.


If the prime minister's team and the government machine of a small country can't agree happily on arrangements for a press conference, then it doesn't exactly feel like anyone is in the mood to edge a little bit closer to a Brexit deal.
"Podiumgate", as it has inevitably been labelled, immediately gave a pantomime distraction - complete with a booing crowd - to Monday's developments in the bigger Brexit story.
It's no secret that the Luxembourg Prime Minister Xavier Bettel held the views that he was so happy to express.
He has gladly - and candidly - expressed on many occasions his sadness that the UK voted to leave, and his frustration with how UK governments have handled it so far.
But if what happened was an expression of the state of diplomacy between the UK and EU member states, then don't hold your breath for a breakthrough in understanding between the two sides that could lead us all to a new version of a Brexit deal.
As ever with the UK's departure from the EU, there are two dramatically different interpretations of what happened.
If you think that it's a bad idea and Boris Johnson is blundering his way to a crash-out, then the Luxembourg leader's protestation will have given yet more evidence to that cause - the suggestion that the UK has made a terrible mistake, the EU has tried its best, and yet the prime minister is insisting on carrying on and, to boot, failing to offer any real and new options that could provide a civilised exit.
If, on the other hand, you reckon that the EU's leaders have looked for every opportunity to thwart the UK's reasonable efforts to deliver the referendum result, you may well think that it was another episode in the pantomime that demonstrates the continent's unwillingness to acknowledge the UK's decision to leave.
Forget those two sides for a second. What do the last 24 hours tell us about the chances of a deal actually being done?
Podiumgate tells us that both sides find it hard to present a joint front, and perhaps the relations of Brexit are so fractured that political leaders are not willing to observe the normal rules of diplomatic engagement.
And if, in the months to come, either side is looking to apportion blame, Monday's events could play equally strongly into both sides' hands.
More pertinently maybe, when we asked the prime minister how he actually intended to get a deal, he suggested that there was space to revise the arrangements around the controversial backstop but simply wouldn't elaborate on what those details might be.
And when we asked, repeatedly, exactly how he intends to get round Parliament's decision to try to outlaw leaving without a deal he just would not say.
Right now it seems the volume is rising, but the clock is still ticking down.

The draft withdrawal agreement is all about how the UK leaves the European Union. It's not about any permanent future relationship.
It's a long read - 585 pages long - and we've just had a first look at the text. There will be plenty more to say in the days ahead.
But what's in this draft document, that some people thought might never materialise?
Well we've known about a lot of the content for some time.
There are details of the financial settlement (often dubbed the divorce bill) that the two sides agreed some months ago: over time, it means the UK will pay at least £39bn to the EU to cover all its financial obligations.
There's also a long section on citizens' rights after Brexit for EU citizens in the UK and Brits elsewhere in Europe. It maintains their existing residency rights, but big questions remain about a host of issues, including the rights of UK citizens to work across borders elsewhere in the EU.
The legal basis for a transition (or implementation) period, beginning after Brexit. It would be 21 months during which the UK would continue to follow all European Union rules (in order to give governments and businesses more time to prepare for long term change).
That means that during transition, the UK would remain under the jurisdiction of the European Court of Justice (in fact, the ECJ is mentioned more than 60 times in this document). The document says that decisions adopted by European Union institutions during this period "shall be binding on and in the United Kingdom".
The transition period is also designed to allow time for the UK and the EU to reach a trade deal. The draft agreement says both sides will use their "best endeavours" to ensure that a long term trade deal is in place by the end of 2020. Significantly, if more time is needed, the option of extending the transition appears in the document (although, it makes it clear that the UK would have to pay for it).
The document doesn't say how long the transition could be extended for (in fact they've left the date blank), only that the Joint Committee may take a decision "extending the transition period up to [31 December 20XX]." UK officials hope that the date will be clarified by the time of the proposed EU summit on 25 November.
If there was no long term trade agreement and no extension of the transition, that's when the so-called "backstop" would kick in. It's the issue that has dominated negotiations for the last few weeks and months: how to ensure that no hard border (with checks or physical infrastructure) emerges after Brexit between Northern Ireland and the Republic of Ireland.
Both sides agreed back in December 2017 that there should be a guarantee to avoid a hard border under all circumstances. That guarantee came to be known as the backstop, but agreeing a legal text proved very difficult.
So what exactly does this draft agreement say about the border, the backstop and the legal guarantees that underpin it?
If a backstop is needed, it will - as expected - take the form of a temporary customs union encompassing not just Northern Ireland but the whole of the UK.
The draft agreement describes this as a "single customs territory".
Northern Ireland, though, will be in a deeper customs relationship with the EU than Great Britain, and even more closely tied to the rules of the EU single market.
One policy area is excluded from these potential customs arrangements: fishing.
That's because the trade-off between access for UK fish produce to EU markets, and access for EU boats to UK waters, is too controversial. The draft agreement simply states that "the Union and the United Kingdom shall use their best endeavours to conclude and ratify" an agreement "on access to waters and fishing opportunities".
There are also details of one of the last issues to be negotiated - the terms on which the UK may be able to leave this temporary customs arrangement in the future.
If either party notifies the other that it wants the backstop to come to an end, a joint ministerial committee will meet within six months to consider the details.
But the backstop (which is part of the Protocol on Ireland/Northern Ireland) would only cease to apply if "the Union and the United Kingdom decide jointly" that it is no longer necessary. In other words, the UK will not have a unilateral right to bring those arrangements to an end.
For some Brexiteers, that is simply unacceptable.
But, don't forget, other countries will also have their concerns.
They too will focus on the language surrounding a temporary customs union, to ensure that nothing is hidden there which could, in their view, give the UK rights without responsibilities; and - potentially - a competitive advantage.
The EU insists the draft agreement "includes the corresponding level playing field commitments and appropriate enforcement mechanisms to ensure fair competition between the EU27 and the UK."
So, it's not just in London that this document will be closely scrutinised.
Finally one big question: to what extent could these temporary customs arrangements form the basis for a permanent future relationship, which can only be negotiated formally after Brexit has actually happened?

Parliament might have to decide what to do next if Theresa May's Brexit deal is rejected by MPs, cabinet minister Liam Fox has said.
The senior Brexiteer said the PM's deal was unlikely to pass through Parliament unless the backstop issue was resolved.
He said one option could be a "free vote" for MPs.
An alternative being widely suggested is another referendum - but Mr Fox told the BBC's Andrew Marr Show this was unlikely and would not "heal division".
Other options backed by different groups of MPs include leaving without a deal, another referendum, or Norway or Canada-style alternative deals. Norway has a very close relationship with the EU but is not a member, while Canada has an extensive trade deal with the bloc.
Education Secretary Damian Hinds has also suggested "flushing out" the levels of Parliamentary support for different Brexit options although he told BBC Radio5Live's Pienaar's Politics there was not a majority for any of them.
And Lib Dem MP Tom Brake, who is part of the anti-Brexit "Best for Britain" campaign, said: "When even Dr Fox does not rule out free votes and encourages the idea of indicative votes in Parliament, the Brexit project is clearly in jeopardy."
By BBC political correspondent Chris Mason
What we are witnessing is a bursting out in public of conversations that have been happening for a while, at a senior level, in private.
They can be summarised like this: 'What on earth do we do next?'
One idea, now floated by three cabinet ministers in public, and others privately, is a series of so called "indicative votes".
These would flush out Parliament's view on a range of options which could include different models of Brexit: something akin to Norway's relationship with the EU for instance, or Canada's looser one. Another referendum and no deal are other possibilities.
Some ponder doing this before the vote on the prime minister's deal, in the hope it highlights that her plan is the only workable Brexit deal achievable now.
"Things are not as hopeless as they look," one cabinet minister told me.
But when I wished them a merry Christmas and a happy new year, that word 'happy' was met with a wry smile. None of this is remotely straight forward.
On the possibility of another referendum, International Trade Secretary Mr Fox said one could result in a narrow Remain win on a lower turnout, in which case, "People like me will be immediately demanding that it's best of three - where does that end up?"
It comes after Theresa May accused former Labour PM Tony Blair of undermining Brexit negotiations by calling for another referendum amid continuing calls for one to be held to solve the impasse over the UK's exit from the European Union.
Two of Mrs May's key allies - chief of staff, Gavin Barwell, and her effective second-in-command David Lidington - distanced themselves from reports they were involved in planning for a new referendum.
On Thursday about 10 Labour MPs met Mr Lidington to argue for another public vote.
Mr Lidington tweeted that he had told the Commons last week that another referendum would be "divisive" and would not guarantee a "decisive" ending to the debate.
Mr Barwell also used Twitter to say he did not want another referendum and was not planning one.
Mrs May met EU leaders on Thursday - after postponing a Commons vote on the withdrawal deal she has negotiated, fearing its heavy defeat. The government says the Commons vote will go ahead in January, as talks continue with the EU on the issue of the Irish border "backstop".
The backstop is an insurance policy in the withdrawal deal to prevent the return of a hard border with Northern Ireland if no trade deal is reached - but many of Mrs May's MPs say they cannot support it, arguing it would keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
EU leaders have said the deal is "not open for renegotiation" - but that there could be some further clarification.
Mr Fox said talks would continue over Christmas and the new year. He said it was "clear" that the EU understood the problem, and it was now a question of finding a "mechanism" that would remove MPs' concerns, without which, he suggested it would not be worth putting it to a Commons vote "knowing it would be rejected".
If the deal could not get through the Commons, he said: "Parliament would have to decide on the alternatives."
Meanwhile, Labour frontbencher Andrew Gwynne told the BBC his party would be trying to bring the MPs' "meaningful vote" on the deal forward to this week.
The Labour leadership is under pressure from other opposition parties to call for a vote of no confidence in the government.
But Mr Gwynne said: "We can't move to the next stage until Parliament has decided whether or not to back the prime minister's deal."
Asked whether his party would campaign for Brexit under a Labour deal if there were to be another referendum, he said: "Let's wait and see. These things are moving very quickly.
"We are a democratic party and we will put our decision to the party members in a democratic way before we decide what the next steps are."
Labour's official position is to argue for a general election if Mrs May's deal cannot get through the Commons but to keep all options open if that doesn't happen - including another referendum.
Anti-Brexit Labour backbencher Chuka Umunna told the BBC it was time to "clear the decks" and hold the MPs' vote on the deal before moving on to "consider the other options".
He said there was no majority for another referendum in the Commons at the moment but said: "I think the position of members of Parliament will change, according to what happens."

Claim: Labour is proposing a new permanent customs union with the European Union (EU) after Brexit which would allow the UK "a say" in future trade deals.
Reality Check Verdict:  EU law currently does not allow non-EU members to have a formal say or veto in its trade talks. Labour says the EU has shown flexibility in the past and its proposal cannot be ruled out until the party has had a chance to negotiate formally.
 There's renewed focus on Labour's Brexit policy as Theresa May holds discussions with opposition MPs, in the wake of the historic defeat of her Brexit deal.
One area under the spotlight is Labour's plan for the UK to have a new permanent customs union with the EU after Brexit and the power to have a say in future EU trade talks.
The idea that the UK would be allowed such a say has been dismissed by Michael Gove, the Environment Secretary.
He's declared Labour's position "an unprecedented legal and political novelty of the kind that is rightly called a unicorn".
So how realistic is Labour's plan?
The purpose of a customs union is to make trade easier.
Countries in a customs union agree not to impose charges - known as tariffs - or custom checks on each other's goods.
The rules also mean that any goods coming in from the rest of the world pay the same tariff - irrespective of where in the customs union those goods first enter.
This is known as a common tariff.
For example, a car from the US entering the EU customs union currently attracts a tariff of 10% of the car's value. It doesn't matter if the car arrives in France, Spain or anywhere else - the same one-off 10% charge is applied.
That car can then move between all the customs union countries without incurring extra costs or custom checks.
The EU customs union includes the 28 EU member states as well as Monaco.
The EU also has customs union arrangements with non-EU members: Turkey, Andorra and San Marino.
But under (the EU's) customs union rules, members cannot negotiate their own independent trade deals with countries from the rest of the world.
Instead, free trade deals (ie agreements that reduce or eliminate tariffs between countries) can only be negotiated by the EU as a whole.
As a result, Theresa May's government has ruled out remaining in the customs union after Brexit, arguing it would prevent the UK from setting its own trade policy.
At the moment, the EU is negotiating trade agreements with 21 countries.
So what are the chances of Labour's proposal of leaving "the" EU customs union and replacing it with "a" customs union arrangement where the UK could have a say in those talks?
It somewhat depends on what Labour means by a "say".
Barry Gardiner, the shadow international trade secretary, told the Commons that he favoured: "A new customs union in which the UK would be able to reject any agreement it believed was concluded to its disadvantage."
He told MPs that this position should have been adopted at the start of the Brexit talks.
But allowing the UK a formal role in EU trade talks after Brexit, would not be allowed under current EU rules:
"Trade outside the EU is an exclusive responsibility of the EU.... this means the EU institutions make laws on trade matters, negotiate and conclude international trade agreements," says the European Commission.
Holger Hestermeyer, an expert in international dispute resolution at the British Academy, agrees it would be very difficult:
"To give the UK a say in the EU's talks, the procedure, as set out in EU treaties, would need to be changed.
"A treaty change in that respect will not happen and to give the UK a say without such a change is legally doubtful and politically impossible," he says.
Labour points out that the EU is already in favour of the UK remaining in a customs union after Brexit. Therefore it believes the EU may well be receptive to the idea of the UK also having a say in future trade deals.
Jeremy Corbyn told the BBC that "the EU is well-known for its ability to be flexible".
If a "say" means something less formal, it may be more achievable.
But even then it would still be unique - the EU currently has no relationship with any country like the one Labour is asking for.
A Labour source told Reality Check that determining exactly how the arrangement could work would be subject to any future negotiation with the EU.
Turkey has often been held up as example of a non-EU country entering into a customs union arrangement with the EU.
It's had a customs union deal with the EU since 1995, although it's not as comprehensive as the one Labour is seeking.
That's because Turkey's customs arrangement only applies to industrial products.
This means Turkey has some limited freedom to strike its own trade deals, but only in the areas not covered by its customs union arrangement - such as agriculture.
Turkey can also strike deals around the world on services - as this is not a customs union issue.
It has a number of trade deals with nearby countries, such as Georgia and Lebanon as well countries as far afield as Chile.
However, Turkey is also obliged to apply common external tariffs on industrial products arriving from outside the EU customs union.
This is a very strict rule, according to Catherine Barnard an EU law professor at Cambridge University.
"Under no circumstances may Turkey be authorised to apply a customs tariff which is lower than the common external tariff for any product," she says.
"The arrangement has boosted trade between the two sides," says Alex Stojanovic from the Institute for Government.
However, Mr Stojanovic adds that neither the EU nor Turkey is entirely happy with the current arrangement:
"The EU Parliament has released reports criticising the governance of resolving disputes. From Turkey's point of view, it argues it has little input or say in EU trade policy."
Labour says it has ruled-out a Turkey-style arrangement on the grounds it is "asymmetrical" and only covers certain goods.
However, it remains to be seen whether the EU would accept the type of customs union arrangement the Labour is pursuing instead.
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A revised Brexit deal has been agreed by the UK and EU. What is in it?
Most of the changes - to the deal agreed by Theresa May with EU in November 2018 - are to do with the status of the Irish border after Brexit. This issue has dominated talks for months.
All sides want to avoid the return of a "hard border" between Northern Ireland and the Republic of Ireland after Brexit - with checks and infrastructure that could be targeted by paramilitary groups.
Coming up with solutions to this - acceptable to all sides - has been very challenging.
The new protocol replaces the controversial Irish backstop plan in Theresa May's deal. Much of the rest of that deal will remain.
Here are some of the key new parts:
The whole of the UK will leave the EU customs union. The customs union is an agreement between EU countries not to charge taxes called tariffs on things coming from other EU countries, and to charge the same tariffs as each other on things coming from outside the EU.
Leaving the customs union means the UK will be able to strike trade deals with other countries in the future.
Legally there will be a customs border between Northern Ireland (which stays in the UK) and the Republic of Ireland (which stays in the EU), but in practice things won't be checked on that border.
The actual checks will be on what is effectively a customs border between Great Britain and the island of Ireland, with goods being checked at "points of entry" into Northern Ireland.
Taxes will only have to be paid on goods being moved from Great Britain to Northern Ireland if those products are considered "at risk" of then being transported into the Republic of Ireland.
A joint committee made up of UK and EU representatives will decide at a later date what goods are considered "at risk".
If taxes are paid on "at risk" goods that do not end up being sent on from Northern Ireland into the EU, the UK would be responsible for whether to refund the money.
Individual travellers won't have their baggage checked and taxes will not have to be paid by individuals sending goods to other people.
Separately, there will be limits agreed by the joint committee on the amount of help the government can give to Northern Irish farmers. The figure will be based on the amount they currently receive from the EU's Common Agricultural Policy.
When it comes to the regulation of goods (that's the rules they have to follow on things like labelling and manufacturing processes) Northern Ireland would keep to EU rules rather than UK rules.
That removes the need for checks on goods including food and agricultural produce at the border between Ireland and Northern Ireland, because both will be part of an "all-island regulatory zone".
But it adds to the checks between the rest of the UK - which will not necessarily be sticking to EU single market rules - and Northern Ireland.
This will be done by UK officials at "points of entry" into Northern Ireland, but the EU will have the right to have its own officials present.
It seems those EU officials may be able to overrule UK officials. The agreement states that EU representatives will be able to ask UK authorities to take certain steps in individual cases and they will have to do so.
Because Northern Ireland will be set apart from the rest of the UK when it comes to customs and other EU rules, the deal gives its Assembly a vote on these new arrangements.
But this vote would not happen until four years after the end of the transition period (the time after Brexit when everything stays the same to allow everyone to prepare for the changes while the UK's future relationship with the EU is discussed). The transition period is due to run until at least the end of 2020. So the four-year period would run until the end of 2024.
If the Northern Ireland Assembly votes against the new arrangements, they would stop applying two years later, during which time the "joint committee" would make recommendations to the UK and EU on what to do about this.
If there were to be no agreement during this two year period, some form of hard border could re-emerge in Ireland, but it's unlikely that would be allowed to happen.
If the Assembly accepts the continuing provisions by a simple majority, they will then apply for another four years. If the deal has "cross-community support" then they will apply for eight years.
The deal defines cross-community support as more than 50% of unionist and nationalist Assembly members voting in favour, or at least 40% of members from each designation if in total at least 60% of members have voted in favour.
The UK government has said that if the Northern Ireland Assembly is still not sitting at that point, it will make alternative arrangements to make sure a vote can take place.
The new agreement says that EU law on value added tax (VAT - a tax added when you make purchases) will apply in Northern Ireland, but only on goods, not services.
But it also allows Northern Ireland to have different VAT rates to the rest of the UK, which would not normally be allowed under EU law.
For example, if the UK decided to reduce the VAT on household fuel to zero, Northern Ireland would still have to keep it at 5%, which is the EU minimum.
It also means that Northern Ireland may get the same VAT rates on certain goods as the Republic of Ireland, to stop there being an unfair advantage on either side of the border.
Much of Mrs May's original Brexit deal will remain as part of the overall agreement. Some of the key areas are:
The transition - a period of time during which all of the current rules stay the same allowing the UK and the EU to negotiate their future relationship - is due to last until the end of December 2020.
The UK will need to abide by EU rules and pay into the EU budget, but will lose membership of its institutions.
The transition can be extended, but only for a period of one or two years.
Both the UK and EU must agree to any extension.
UK citizens in the EU, and EU citizens in the UK, will retain their residency and social security rights after Brexit.
Freedom of movement rules will continue to apply during transition. This means that UK nationals will be able to live and work in EU countries (and EU nationals will be able to live and work in UK) during this period.
Anyone who remains in the same EU country for five years will be allowed to apply for permanent residence.
(UPDATE: 13 December 2019 - This piece has been updated and reflects the delay of the Brexit date to the end of January 2020.)
The UK will have to settle its financial obligations to the EU.
There is no precise figure but the biggest part of this "divorce bill" will be the UK contributions to the EU budget until the end of the transition period at the end of 2020.
When Brexit was delayed it meant that some of that money was paid as the UK's normal membership contributions, so less of it was part of the divorce bill.
When the Brexit date was 31 October 2019, the Office for Budget Responsibility (OBR) estimated that the bill was about £32.8bn (down from £39bn).
To reach an estimate of what the bill would be for departure on 31 January 2020, you could subtract the £1.62bn that the OBR said was left to pay in membership fees in 2019 and 14% of the £10.69bn for the whole of 2020 (it's more than one twelfth because the EU usually requests a higher proportion of the contributions earlier in the year). That gives a total of just under £30bn.
The OBR expects that most of the money - about three-quarters of the total - would be paid by 2022, with some relatively small payments still being made in the 2060s.
This is addressed in the political declaration. This text, which is not legally binding, has also been revised by UK/EU negotiators.
It says that both sides will work towards a Free Trade Agreement (FTA) and a high-level meeting will happen in June 2020 to see how that work is going.
The text also contains a new paragraph on the so-called "level playing field" - the degree to which the UK will agree to stick closely to EU regulations in the future.
The references to a "level playing field" were removed from the legally-binding withdrawal agreement and put in the political declaration, which is not binding.
It says that both sides will keep the same high standards on state aid, competition, social and employment standards, the environment, climate change, and "relevant tax matters".
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The UK left the European Union at 23:00 GMT on 31 January, but that is not the end of the Brexit story.
That's because the UK is now in an 11-month period, known as the transition, that keeps the UK bound to the EU's rules.
So what is the transition and why is it necessary?
The transition (sometimes called the implementation period) will end on 31 December 2020. It cannot be extended beyond that date.
While in transition, the UK remains in both the EU customs union and single market.
That means - until the transition ends - most things will stay the same. This includes:
Despite many things staying the same the UK has already left the EU's political institutions, including the European Parliament and European Commission.
So while the UK will no longer have any voting rights, it will continue to follow EU rules during the transition. For example, the European Court of Justice will have the final say over any legal disputes.
The transition also means the UK will continue to contribute to the EU's budget.
The idea behind the transition period is to give some breathing space while new UK-EU negotiations take place.
These talks will determine what the future relationship will eventually look like.
Negotiations started in March and both sides have agreed to intensify talks over the summer.
Top of the to-do list will be a UK-EU free trade deal. This will be essential if the UK wants to be able to continue to trade with the EU with no tariffs, quotas or other barriers after the transition.
Tariffs are a type of tax, usually paid on imported goods. If goods are subject to quotas, it means there are limits on how many can be traded over a given period.
Both sides will also need to decide how far the UK is allowed to move away from existing EU regulations (known as level playing field rules).
However, a free trade deal will not eliminate all checks between the UK and EU - so businesses will need to prepare.
In 2018, total UK trade (goods and services) was valued at £1.3 trillion, of which the EU made up 49%.
As well as negotiating a UK-EU trade deal, the transition will also allow the UK to hold formal trade talks with other countries - such as the US and Australia. If completed and ready in time, these deals could also take effect at the end of the transition.
The pro-Brexit camp has long argued that allowing the UK freedom to set its own trade policy will benefit the economy - although critics say it's more important to remain close to the EU.
Aside from trade, many other aspects of the future UK-EU relationship will need to be decided. For example:
The UK will also need to design and implement many new systems, such as how it will handle immigration once freedom of movement comes to an end.
At the end of the transition phase, there will be two possible outcomes:
A UK-EU trade deal comes into force
If a UK-EU trade deal is ready by the end of the year, the UK could begin the new trading relationship as soon as the transition ends.
If the trade deal is reached but questions remain in other areas - like the future of security co-operation - than the trade deal might go ahead, with contingency plans used for other parts of the relationship.
However, the EU wants one comprehensive deal covering all aspects of the future relationship while the UK argues there should be a series of separate agreements, including a basic free trade deal.
The UK exits transition with no EU trade deal
Under this scenario, UK and EU negotiators fail to agree and implement a trade deal by 1 January 2021 and no transition extension is agreed.
That would leave the UK trading on WTO (World Trade Organization) terms with the EU. This means that most UK goods would be subject to tariffs until a free trade deal was ready to be brought in.
If other aspects of the future relationship aren't ready, they too would have to proceed on no-deal terms.
The deadline for extending the transition has now passed.

MPs will soon decide the fate of Theresa May's Brexit deal.
There are many views about why they should back or reject the deal, which was struck late last year with the European Union.
But what do voters want MPs to do? And what do they think should happen if the deal is rejected?
Polls suggest the deal has not proved popular with the public.
YouGov has asked people whether they support or oppose it on no fewer than 11 occasions since it was first unveiled in mid-November.
Never have more than 27% said that they support the deal, while at least 42% have always said they are against it.
Other polls show a similar pattern.
Opinium found only one in 10 thinks the deal is good for the UK, while as many as half believe it is bad.
Ipsos MORI has reported only a quarter think it would be a good thing for the UK to leave the EU on the terms of the deal. More than six in 10 believe it would be a bad thing.
It is perhaps unsurprising then that many more voters say MPs should reject the deal than believe they should back it.
More like this
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Not only do Remain supporters seem inclined to reject the deal, but Leave voters do as well.
In its recent polls, YouGov has found an average of 30% of Leave voters back the deal, while 47% are opposed to it.
This arguably makes it harder for the PM to say that her deal fulfils the expectations of those who voted Leave in the referendum.
That said, many voters have not made up their mind about the deal on offer.
YouGov is still finding that about three in 10 still do not know whether they support it or not, well after the deal was revealed.
This suggests some voters could yet be won round to Mrs May's proposal.
While Remain and Leave voters appear to oppose the Brexit deal, they are split over what should be done instead.
Opinium has repeatedly asked voters which of five possible options should be pursued if Parliament were to reject the current deal.
None of the options comes close to being backed by a majority.
The most popular every time - backed on average by just over a quarter - has been to leave without a deal at all.
Meanwhile, the second most popular option each time - supported by just over a fifth - has been to hold a "public vote" on whether to accept the deal or to stay in the EU.
While these options enjoy similar levels of support, they come from very different voter groups.
Leaving without a deal is easily the single most popular option among those who voted Leave, chosen by an average of 46%.
Holding a "public vote" on the deal, with an option to stay in the EU, is favoured among backers of Remain, 38% of whom pick this option.
However, other courses of action also gain support.
Fifteen per cent of all voters prefer attempting to negotiate a better deal, while 12% back Labour's preferred option of holding a general election.
A further 9% support a different "public vote" in which the choice would be either Mrs May's deal or leaving the EU without one.
The idea of a second Brexit vote has attracted particular interest in recent weeks, thanks not least to a high-profile campaign.
However, public support for the idea depends on how the poll question is worded.
Polls asking whether there should be a "public" or "people's vote" - without specifying what the options would be - typically find that the idea is relatively popular.
For example, Survation found that 48% support holding a "people's vote" to gauge the public's reaction to the deal, while 34% are opposed.
Similarly, Populus reported that 44% believe the public should have the "final say" on the deal via a "people's vote", while just 30% are against this.
However, when voters are asked about holding another referendum that might have the effect of reversing Brexit, the proposal attracts less support.
ComRes has reported as many as 50% oppose "holding a second referendum on whether to Remain or Leave", with only 40% in favour.
Similarly, according to polling commissioned by Lord Ashcroft, a former deputy chairman of the Conservative party, 47% are against holding a "second referendum", while 38% are in favour.
In that scenario, voters would choose between leaving the EU under the terms of Mrs May's deal and remaining in the EU.
The wording of the poll question seems to make a significant difference, particularly to Leave voters.
Putting "the people" in charge of Brexit appeals to some Leavers, but a ballot which could potentially reverse the decision does not.
Broadly, the idea of another referendum appears as controversial to voters as Brexit itself continues to be.
When it comes to how people say they would vote if there were another referendum, the country still appears quite evenly divided.
Remain, with an average score of 53% is enjoying just a narrow lead over Leave, which scored 47% in the most recent polls.
Sir John Curtice is professor of politics at Strathclyde University, senior fellow at NatCen Social Research and The UK in a Changing Europe. He is also chief commentator at WhatUKthinks.org.
Edited by Eleanor Lawrie

So, finally, Theresa May has found a way. Not to get Brexit over the finishing line, obviously. But at least out of the starting block. Or so she hopes.
Not to unite the Cabinet. No-one could do that. But at least to herd most of them into line behind her. Or so she hopes.
And if one or two can't or won't get with the programme - there's the door.
The door, of course, being the door of Chequers, her country retreat, where she'll gather her Cabinet again on Friday and try - very hard, apparently - to get agreement on her plan for a negotiating position which might, just might, fly in Brussels.
How, though? Theresa May's "red-lines" always look and sound very red and very clear. They did again yesterday in the Commons when she pledged Britain to leave the EU, the customs union and the single market.
That, I'm now told by well placed sources, is still the plan. Sort of.
Only the so-called "third option" for Britain's future customs relationship with the EU looks much like an amalgam of the two which ran into a Cabinet road block - and on close examination more like the close "customs partnership", which Mrs May came to prefer, than any other.
Not that it's being sold to Brexiteers like that. And there is a lot in the new plan that might appeal, as it must, to the Brexiteer gallery.
So what's the big idea?
A single market trade deal on goods is the vital component. Business will probably like that, as far as it goes. Though, it won't be called a single market because that sounds too aligned to Brussels. Agri-food trade would be part of that deal too.
It has to be to avoid a hard border on the island of Ireland - which is vital if Brexit talks in Brussels are to get anywhere at all.
What then of services? And financial services? The Cabinet is split. Business Secretary Greg Clark's not alone in wanting a single market deal - or whatever it's called - to include services. But that's not, I gather, the plan. City firms saw this coming, and are saying again today they want in.
But Theresa May's way is to make them wait during the Brexit transition while negotiations go on.
The City is undoubtedly concerned about the impact of Brexit, particularly the risk of a "hard Brexit" and negotiations ending in no deal at all. Mark Carney, the Governor of the Bank of England, expressed the same concerns last week.
But the fact is you don't need a single services market to avoid a hard Irish border. There is still time to negotiate the nature and degree of alignment between the UK and the EU.
Theresa May will stick to her red lines. Only they'll soon start to look a little blurred. No customs union, at least as it's defined now. No customs checks, or tariffs on goods either, but Britain would apply EU level tariffs, except where the UK can seek and sign trade deals beyond Europe (leave aside, for a moment, the view of much derided "experts" that outside trade deals will be low value or, in the case of America, say, tough on the UK and dependent on deregulation - and not just of chlorinated chicken).
Where UK tariffs are lower than the EU's there'd be refunds.
The European Court of Justice has been a huge sticking point. May's solution, I'm told, envisages some middle way; some some form of trade arbitration that ultimately, in some way, recognises, the court's authority.
And as for the big deep red line of freedom of movement of people. There's room for some concession here too, in the name of "labour mobility".
It's been thought that Home Secretary Sajid Javid is against preferential access for EU citizens. But I'm hearing he may be open to the idea if it's part of a decent trade deal.
So, will the Cabinet Brexiteers and sceptics buy it? That's the prime minister's big gamble. Some in government suspect she may duck a decisive confrontation even now.
But assuming she's up for it: Boris must decide whether to work with her, and fight his corner on the inside, or walk and pursue his private interests, somehow becoming Britain's next prime minister conceivably somewhere on the list.
Brexit Secretary David Davis? Hard to know. But he sees his job as a contribution to history and won't, surely, want to give it up if he can avoid it.
His hopes of becoming PM may, like Boris Johnson's, have taken a knock. But then the list of Tories who want to be prime minister is now almost as long as the list of those who don't.
The Tory MPs' shop steward, the Chairman of the Tory 1922 Committee of MPs, Sir Graham Brady has been appealing for order and loyalty in the weekend papers, and recently in a BBC interview.
That's the sort of thing chairmen - and chairwomen if there ever is one - of the "22" are meant to say. But remember Graham Brady is also a passionate Brexiteer. He was being helpful to Mrs May.
There's a plan then. There are still lots of blanks to wrangle over at Chequers before it can be slotted into the gaps in the coming policy Brexit White Paper, and that won't be settled quickly or easily. It's a test of the prime minister's nerve, and the willingness of her Cabinet colleagues to cause trouble.
Brussels won't like much or any of it very much. They will likely fear leaving a Britain-shaped hole in the borders of the EU single market. They won't like the "cherry picking" of the rules which govern single market or customs union membership - however you may choose to describe those arrangements.
Plans, even definitive plans, can change and often do. But at least there is a plan. And that's something. What could go wrong now? Apart from everything.

It feels like Westminster is tumbling towards a political crisis without modern precedent.
On Tuesday 11 December, the House of Commons will conclude five days of debate with a vote on a government motion to approve the EU withdrawal agreement and accompanying political declaration. The terms of the UK's departure from the EU.
But at the moment, it looks as if Theresa May faces an incredibly hard job getting it passed.
She leads a government with a working majority of just 13. Only seven Tory rebels are needed to defeat it.
But according to the latest number-crunching by BBC researchers, 81 Tory MPs have said they object to the deal Mrs May hopes to sign off with EU leaders on Sunday.
With Labour, the Liberal Democrats, the SNP and even perhaps the DUP set to vote against the motion too, the withdrawal agreement looks set to be torpedoed in the Commons.
Between now and then Theresa May will exhaustively insist the deal is in the national interest and the only way of ensuring Brexit happens.
But if the withdrawal agreement is defeated, what happens then?
The default position in that scenario would be for the UK to leave without a deal.
Under both EU law and the UK's Withdrawal Act, Brexit day is chiselled into the diary for 11pm on 29 March, 2019.
That's when the EU Treaties will stop applying to the UK.
If Parliament rejects the deal, the same Withdrawal Act sets out what the government must do next.
Ministers would have up to 21 days to make a statement to the Commons on "how it proposes to proceed".
The government would then have a further seven days to move a motion in the Commons, allowing MPs to express their view on the government's course of action.
Crucially though, this would not be opportunity for MPs to throw a road-block in the way of a no-deal Brexit if that's what the government wanted to happen.
Whatever motion the government brings back to Parliament will now have to be amendable, after MPs backed a change to it tabled by Conservative MP Dominic Grieve.
MPs are hoping this will allow them to vote to rule-out a no-deal Brexit.
The government would find it hard to ignore such a vote - but it would not carry the legal force to stop the UK leaving without a deal next March.
Instead, the government would have to put new legislation before Parliament and secure the approval of MPs if it did not want the UK to leave without a deal.
As the clerk of the House of Commons, Sir David Natzler, told a committee of MPs last month, "there is no House procedure that can overcome statute. Statute is overturned by statute."
But in addition to the rigid legal position there would be the frenzied political reality.
The maximum three-week window between the government's deal being defeated and the requirement on ministers to propose a way forward would see several alternative scenarios come into play.
The prime minister could make a second attempt at getting the withdrawal deal through the Commons.
 Sir David Natzler said, in procedural terms, that would be possible.
"The words might be the same but the underlying reality would be self-evidently be different", Sir David said.
Brussels might be persuaded to tweak the political declaration on the future relationship to meet the concerns of MPs.
Theresa May could try to return to Brussels to renegotiate the Northern Irish "backstop" - the main sticking point for many MPs. The government has long insisted this is not an option, because the EU has said the existing deal is final and there is no alternative.
Might Brussels give Mrs May some leeway if she loses the vote by a narrowish margin?
Some MPs hope she could get behind another version of Brexit at this point. There is support on the Tory benches for a membership of the European Free Trade Area, which would see the UK staying closely linked to the EU, like Norway.
This would not be a straightforward move - and would require extensive renegotiation, even if the EU was prepared to contemplate it, and the extension of Article 50, delaying Brexit day.
Then there is Labour's proposal for a permanent customs union - Mrs May has always ruled that out, but if enough MPs get behind it, it might be an option, although, again, it would need Article 50 to be extended to allow for more talks.
Unlikely, given her track record of doggedly ploughing on against the odds - but if she is defeated by a heavy margin on 11 December she may feel she has no other option. There would then be a Tory leadership contest, which would turn into a fight to the death between the Leave and Remain wings of the party, with profound effects on the future of Brexit and, indeed, the country.
Jacob Rees-Mogg's band of Brexiteers famously failed to reach the magic 48 letters of no confidence in the PM to trigger a leadership contest last month.
But if she tries to cling on after a significant defeat on 11 December, more MPs could add their names to the list, forcing a no-confidence vote that she might struggle to win.
MPs might suddenly shift in large numbers towards the idea of another referendum to break the Parliamentary impasse and open the possibility of stopping Brexit.
At the moment, about eight Tory and 44 Labour MPs have publicly committed to another referendum.
Theresa May is dead set against another referendum and it's hard to see an alternative Tory leader picking up that baton.
But the Labour leadership has said all options should remain on the table (including another referendum) and the SNP and Lib Dems say there should be one too.
However, a second referendum can only happen if the government brings forward legislation to hold one and a majority in the Commons supports it. There would have to be legislation. The rules for referendums are set out by the Political Parties, Elections & Referendums Act 2000.
The Electoral Commission's recommendation is that there should be six months between the legislation being passed and referendum day.
This could be shortened but, realistically, not by all that much. The UCL Constitution Unit, a research centre on constitutional change, suggests that could be 22 weeks.
So for the referendum to happen there would have to be a delay to Brexit - and that would require all 27 EU member states and the UK to agree.
This is Labour's preferred outcome to the deal being rejected.
But as Dr Jack Simson Caird from the Bingham Centre for the Rule of Law says, "with the ticking clock of Article 50 it's very difficult to see that this represents a solution to the problem" of a deadlocked parliament.
That will be the other critical factor at play.
Unless the government asks for an extension to the negotiating period - ie Brexit being delayed - the time for parliament and the government to agree a way forward is incredibly tight.  The clock won't wait.
There are two routes to a general election through the Fixed Term Parliament Act.
Two-thirds of MPs could vote for one. This is the quickest route - a poll could be held as soon as 25 working days later.
Alternatively MPs could go for a no confidence motion in the government - Labour has said they will table such a motion if Mrs May loses on 11 December.
This is a straight majority rather than requiring two thirds of MPs to vote for it.
This gives two weeks for someone to demonstrate they can command a majority in the Commons. If that does not happen, the 25 working days countdown to a general election kicks in.
Any election now would be on the existing constituency boundaries. The new ones have to be approved by the Commons and the Lords. And that has been put on hold until after Brexit.
Another idea that has been floated is a "negotiated no deal" in the which the UK would ask the EU for a (paid) one year extension of membership before leaving on World Trade Organisation terms.
Some Brexiteers might like the idea but it's hard to see Parliament supporting such a move - with or without an explicit vote.
Because Parliament will have to come to a view.
As Maddy Thimont Jack, from the Institute for Government think tank says: "We do have Parliamentary sovereignty and there are clear ways for Parliament to express a very strong political view.
"I cannot see how a government can get through a legislative programme, for no deal, for example, if you don't have the support of Parliament."
Theresa May might have neutralised the chance of defeat in the Commons if she had found a Parliamentary consensus for the Brexit she planned to negotiate right at the start of the process.
Instead, she faces a fraught few days and a vote that will define the country's future for many years.
Right now, it looks like the government's deal cannot get through the Commons.
But the mood in Westminster could shift quickly in the current pandemonium.

Donald Tusk rejected Theresa May's Brexit proposals at an EU summit this week and posted an Instagram story shortly afterwards.
 "A piece of cake, perhaps?," said the head of the European Council, alongside a picture of him and May at the summit in Austria. "Sorry, no cherries."
This provocative post was Tusk's idea and is part of a wider strategy to appeal to young people via the app, an EU source has told the BBC.
Here are five things to know about how Donald Tusk and other EU leaders use Instagram.
"He's the one coming up with these posts - he has a good sense of what works and what doesn't," says an EU source working with Tusk on social media.
"He's not the biggest social media geek but he likes it.
"He jokes and laughs and wants to show humour. This post was clearly something he was into - we produced the image [of cherries] and he said let's do it!"
The post combines the EU's favourite Brexit cliches. First, the idea that the UK wants to "have its cake and eat it".
Second, that the UK is guilty of "cherry-picking" - keeping the bits of EU membership it likes and ditching the bits it doesn't.
"The cherry-picking one is something we have talked about a lot and finally we had a good pic from a good angle," says an EU source
Many Brexit supporters reacted angrily to Tusk's post on social media.
Conservative MP Charlie Elphicke described the post as "extraordinarily disrespectful".
Pro-Europeans had mixed views, with one describing it as "brilliant trolling" by Mr Tusk, while another said it was "grim and not on, frankly".
A source close to Tusk said the message should not be taken too seriously. "It was an innocent gesture. He is always expressing how sad he is about the U.K. leaving.
"We were taking the difficulty of the situation and giving it a soft touch."
Tusk's team did an in-house analysis of various social media platforms and ultimately decided to focus on Instagram, the BBC understands.
 They found that while Twitter is useful for communicating with journalists, not so many other people people use it regularly.
However, Tusk did post this bombastic video on his Twitter account, showing his Autumn priorities in the style of an action film trailer.
Instagram, on the other hand, is very popular with a range of groups, especially younger people.
"We have political messages but we also want to move away from the cold politician image," an EU source told the BBC.
"For example we launched on his birthday with a picture with his grandchildren, and this kind of personal touch has proven really successful."
 As well as transmitting the EU's core messages, Instagram can also be a place where politicians can joke and show a sense of humour.
"It's more positive, everyone is cheering each other," said an EU source. "We are reaching different audiences and the discussion isn't so violent."
Tusk's Instagram account combines serious messages with light-hearted pictures -  sometimes in the same post, including one notable example from the Salzburg summit.
 "We aren't focusing just on the political angle and we showed that with the ice cream - it's fun but also has a message," said an EU source.
"Eating an ice cream is sweet but the expression is sour, talks are tough but it's important to be managed."
The press teams in the European Parliament and Commission have noticed the effort put into Tusk's Instagram and are paying attention, according to an EU source.
 "All around the EU everyone is on Instagram. It is new and we need to use it."
German Chancellor Angela Merkel was an inspiration for Donald Tusk - she has long been active on Instagram but not Twitter.
"We are still communicating the position of the EU, it still has to reflect this but with more emotion."
 Although Donald Tusk's Instagram account has received a lot of attention from political journalists lately, he has a long way to become the biggest name in his own family.
His daughter Katarzyna, an Instagram influencer in her native Poland, has more than four times as many followers as her dad.
Her account combines "photography, style and daily moments".

Boris Johnson is the UK's new prime minister and will now begin the task of trying to deliver Brexit.
The former foreign secretary has pledged the UK will leave the EU on 31 October, "do or die", accepting that a no-deal Brexit will happen if an agreement cannot be reached by then.
He has called the withdrawal agreement "dead" but says he will "take the bits that are serviceable and get them done" - such as guaranteeing the rights of 3.2 million EU citizens in the UK.
The withdrawal agreement (WA) is the deal negotiated by the UK government and the European Union (EU) to settle the basis on which the UK will leave. As part of it, the UK agreed to pay the EU a "divorce bill" (estimated to be £39bn), guarantee EU citizens' rights and sign up to the Irish backstop - an insurance policy designed to avoid a hard border in Ireland.
The deal allowed for a transition period after Brexit, during which things like UK-EU trade would stay the same, while both sides worked out their future relationship. But the withdrawal agreement was rejected three times by MPs - leading to Theresa May's downfall.
After Brexit, Northern Ireland and the Republic of Ireland could be in different customs and regulatory regimes, which might mean products being checked at the border. To avoid border posts (which some believe could threaten the peace process), Mrs May and the EU agreed on the backstop. In the event that no free trade deal was agreed that avoided a hard border, this insurance policy would effectively keep the UK and EU in a customs union. This proved controversial because it would stop the UK doing some of its own trade deals.
Mr Johnson is saying the Irish border can be dealt with after the UK leaves the EU, instead of as part of the withdrawal agreement.
Obstacle: The EU has said the Irish backstop cannot be removed from the withdrawal agreement - the deal to delay the UK's exit until the end of October specifically prohibited its renegotiation. If the UK leaves with no deal and seeks a free trade agreement, the EU has said it will not begin negotiations until the issue of the Irish border is settled.
Boris Johnson wants to ditch the Irish backstop - he's called it "a prison". He has said there are "abundant, abundant technical fixes" to avoid checks at the border. He concedes there is "no single magic bullet" but points to a "wealth of solutions" instead.
Obstacle: The UK and the EU have previously looked for technological solutions to the Irish border without success. EU deputy chief negotiator Sabine Weyand said in January: "We looked at every border on this Earth, every border the EU has with a third country - there's simply no way you can do away with checks and controls." There are "alternative arrangements" which could help: trusted trader schemes (where businesses are certified to make sure they meet certain standards) and ways of making customs declarations away from the border, but they wouldn't eliminate the need for checks altogether. After Brexit, the EU would still require inspections of things like animal and plant products entering its single market, and the new entry point to that market would be at the Irish border.
Boris Johnson has said he is prepared to withhold the money the UK has agreed to pay the EU and use it as a negotiating tool to get a better deal. Settling the UK's financial obligations (which include previously agreed contributions to the EU budget and funding things like EU staff pensions) was agreed by Theresa May as part of the withdrawal agreement. The figure for those obligations has been calculated at £39bn.
Obstacle: The EU has said it will not start future trade talks until the issue of money (along with citizens' rights and the Irish border) is settled. Refusing to pay would almost certainly sour relations between the two, and could lead to a legal challenge from the EU.
While accepting that a "disruptive... badly handled" no-deal Brexit would be costly, Mr Johnson said it was "vanishingly inexpensive if you prepare" and added that "much of this work has been done".
Obstacle: Mr Johnson's view of the cost of a no-deal Brexit is at odds with the vast majority of economists, a significant number of his own backbenchers, and organisations such as the Office for Budget Responsibility (OBR), which calculates the government's forecasts for the economy. The OBR said no deal would push the UK economy into recession.
Mr Johnson has said he would mitigate the effects of no deal on the UK economy (which he admits would cause "disruption") by relying on a piece of trade law known as Article 24. He originally said this would allow the UK and the EU to have zero tariffs (taxes on imports) on trade while the two sides negotiated a trade deal. This would, in theory, help keep trade flowing and would stop the EU imposing tariffs on goods being imported from the UK (cars, for example, are subject to a 10% import tax from non-EU countries, and on agricultural produce it's even higher).
Obstacle: Boris Johnson was wrong to say Article 24 would automatically allow for a standstill in trade relations, and indeed - when challenged in interviews - he later accepted that it would require the agreement of both sides. Also, Article 24 only covers the trade in goods (not services) and it does not cover non-tariff barriers such as regulations. The EU has ruled out signing any Article 24 agreement immediately after a no-deal Brexit.
Mr Johnson has just over three months until Brexit day. He will become prime minister on 24 July and Parliament begins its summer recess the following day.
A week later there will be a by-election and the rest of August will be pretty quiet, both in Westminster and Brussels. Parliament returns at the start of September but will take another recess later in the month for party conferences.
On 17 October there will be a summit of EU leaders. Brexit is scheduled for 31 October, the day before the new European Commission takes office.
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By the time you read this, Labour delegates might have decided what to do.
Or perhaps not.
Their meetings have form. They've been discussing how to find a decent compromise on a Brexit vote at conference since 18:30 BST. These are issues that have been running hot for months and months, and I am writing this five hours later.
What are they arguing about?
A significant chunk - polling suggests a hefty majority of members - of the party would like to see another vote on the European Union, with the party's leanings overwhelmingly towards Remain.
Jeremy Corbyn vowed he would be a different kind of leader and listen to his party's membership. So what's the problem? Surely he should just say "sure", and acquiesce?
Guess what, it's not nearly so simple. First, repeat again and again, any party's members are not the same as their voters, and potential voters.
That's always so. But it is clear as day now. Because while Labour MPs and members are overwhelmingly among those who voted Remain, millions of people who had voted Labour put their cross in the Leave box.
To campaign immediately for another EU referendum risks infuriating huge swathes of voters, and opens Labour up to accusations from their opponents that they are insulting voters and ignoring democracy.
The second reason why another referendum is only being reluctantly considered is that it's not clear how you actually get there.
Referendums need legislation. They then need a Parliamentary process to decide questions. If there were to be a vote, should it be on the terms of a deal or no deal, or reopen the whole question of staying or leaving?
Should it be straight away? Is it possible to do in the time given that we are due to be leaving the EU in about six months.
Why does Labour think it would be able to get a better deal than the Tories in any case?
Those campaigning for the vote of course say they have answers to those questions. But many senior figures aren't convinced.
One member of the shadow cabinet, frustrated, said it's not realistic to see how it could happen, and the People's Vote campaign is just like "praying for a fairy godmother".
Another told me "it's just a distraction", and could even give Theresa May a way out if she ends up completely stuck.
They believe the party has to be "resolute", and keep pushing, pushing and pushing for a general election instead.
Neither of those are in the party's gift. But even theoretical choices matter in a time of such political turmoil.
And it's an interesting test for a leader who transformed his party based on the promise of giving members more say.
By the early hours, the leadership may have given party members some, but not all of what they want - a compromise motion that will give the party a chance to commit to some kind of vote.
It won't be as explicit as some want.
But remember last year the debate was not even fully permitted on the conference floor. Jeremy Corbyn's supporters were reluctant to allow any divisions to be displayed.
So, however vague the compromise, however late tonight's discussions go, those who've been pushing the party to commit to another referendum for months are encouraged just to have got this far.

Prime Minister Theresa May has been holding talks with MPs in the aftermath of the heavy defeat of her Brexit deal in the Commons - and following a slim victory in a no-confidence vote.
Environment Secretary Michael Gove, Cabinet Office Minister David Lidington and Brexit Secretary Steve Barclay are also holding talks with senior opposition politicians.
Meetings are being held in No 10 Downing Street and 70 Whitehall, the Cabinet Office.
First up was SNP Westminster leader Ian Blackford, Plaid Cymru's Westminster leader, Liz Saville Roberts, and Lib Dem leader Sir Vince Cable, who all had talks with the prime minister on Wednesday night.
Mr Blackford said that the extension of Article 50 - the two-year mechanism that means the UK leaves the EU on 29 March - the ruling out of a no-deal Brexit, and the option of another EU referendum would have to form the basis of future discussions.
Ms Saville Roberts said they were "committed to finding a real solution" but "that means taking a no-deal Brexit off the table and a people's vote on our European future".
Sir Vince said he was encouraged by Mrs May's "willingness to talk about these issues in detail". The preferred choice of his party is another referendum.
Labour leader and leader of the opposition Jeremy Corbyn said he was "quite happy" to talk with Mrs May but she had to rule out a no-deal Brexit first.
Tory colleagues and Brexiteers Owen Paterson, Iain Duncan Smith, David Davis, Mark Francois and Steve Baker were among the first politicians spotted in Whitehall on Thursday morning, as well as Conservative MP and former Northern Irish Secretary Theresa Villiers. They are all members of the Tories' influential European Research Group (ERG).
Brexiteer John Whittingdale tweeted afterwards that their group's meeting with the prime minister had been "constructive".
Former Conservative cabinet minister Mr Paterson described the meeting as "thoroughly worthwhile", "very constructive" and a "good exchange".
On the subject of taking a no-deal Brexit off the table, he said:  "You will lose all the pressure on the EU if we give up no-deal, WTO (World Trade Organization) terms, and you give up the date. And we just drift on month after month and this whole saga continues."
Sir Graham Brady, who chairs the 1922 Committee of Tory backbenchers, and Cheryl Gillan, MP for Chesham and Amersham and a vice-chair of the 1922 Committee, were also seen arriving at the Cabinet Office.
They were later photographed leaving Downing Street with other members of the committee, after a meeting with the prime minister.
09:00 GMT - After her meeting with the prime minister, Caroline Lucas, the Green Party's only MP, said Mrs May had refused to rule out a no-deal Brexit and resisted the option of extending Article 50.
"I repeatedly urged her again and again to take no-deal off the table because I think it completely skews the talks - because you know that cliff edge is there," she said.
10:40 - DUP leader Arlene Foster and DUP Westminster leader Nigel Dodds arrived for their meeting. The prime minister relies on their party's support to prop up her government.
Speaking in Downing Street following their meeting with Mrs May, Ms Foster said the prime minister had been in "listening mode" and there had been optimism that a Brexit deal could still be reached.
She said she had made a "clear ask" in relation to the Irish backstop, urging Mrs May to address it "in a satisfactory way".
Tom Brake, the Lib Dem's Brexit spokesman, Alistair Carmichael, the Lib Dem's chief whip, and deputy Lib Dem leader Jo Swinson were all spotted arriving to the Cabinet Office.
After his meeting with Mr Lidington, Mr Brake said a no-deal Brexit needed to be off the table.
10:49 - Conservative MP Shailesh Vara arrived at the Cabinet Office.
11:27 - Plaid Cymru leader Adam Price met with Mr Lidington and Mr Gove, who he said had been in "listening mode".
"If the government were to come out on Monday with that position [of another referendum] then the gridlock, the impasse, the logjam would be broken, and we could move forward," Mr Price said.
"We talked in detail about the practicalities of how we could make it [another referendum] happen."
11:30 - Conservative MP Nicky Morgan, who chairs the Treasury Select Committee, arrived at the Cabinet Office.
After 12:00 - Tory MPs Damian Green and Andrew Mitchell spoke to journalists outside the Cabinet Office after their meeting.
"No two members of Parliament think precisely the same way but now we've got to make progress," Mr Mitchell said.
"It's in the national interest and it's the right thing for the prime minister to do, to corral people together and make Parliament focus on what the answer to all of this is and what we agree about, not what we disagree about."
Mr Green, a close ally of Mrs May, criticised Mr Corbyn's decision not to take part in the talks, saying the move was "completely absurd".
John Mann, a Leave-supporting Labour MP and long-term critic of Mr Corbyn, was spotted coming out of the Cabinet Office.
13:05 - Tory MPs George Freeman and James Cartlidge arrived at the Cabinet Office.
13:57 - Labour MPs Yvette Cooper, who chairs the Home Affairs Select Committee, and Hilary Benn, who chairs the Brexit Select Committee, arrived at the Cabinet Office.
After meeting Mr Lidington, Mr Benn said the government had to rule out a no-deal Brexit as a first step and secondly the prime minister had to change her "red lines".
Ms Cooper said: "The most important thing now is that the government actually listens and it doesn't just think that a defeat that was that huge can simply be dismissed."
They said they had attended the meeting in their capacity as chairs of cross-parliamentary committees, after Mr Corbyn barred Labour MPs from taking part in the talks while a no-deal Brexit remains an option.
14:07 - Tory MPs Peter Bone and Tom Pursglove arrived at the Cabinet Office.
On his way to meet the prime minister, Eurosceptic Mr Bone said he was "hopeful we can get a deal".
15:31 - Tory MPs Tom Pursglove and Julian Lewis were seen leaving the Cabinet Office.
15:50 - Labour MP Stephen Kinnock went into the Cabinet Office.
16:08 - Tory MPs Steve Brine, Richard Harrington, Robert Buckland and Margot James were spotted outside the Cabinet Office.

So the focus of the Brexit talks has shifted slightly as a result of the EU leaders' summit in Brussels.
There is still plenty of tough bargaining ahead in the next few weeks, especially on the question of money.
But there is also going to be more and more talk about preparing for a transition period - for what happens immediately after the UK leaves the EU in March 2019.
Plenty of people see transition as a way to buy a little more time to sort things out - to finalise negotiations on a future trade deal. But the UK government prefers to calls the transition phase a "period of implementation".
It is not entirely clear what would be implemented.
But the Brexit Secretary David Davis warned this week that without a final deal on a future partnership with the EU - at least in principle - the government would not want to trigger any kind of transition at all.
Does it mean the two sides view the prospects for transition very differently?
The EU27 - the other member states without the UK - have now agreed to start working on new guidelines for their negotiators.
And both the EU and Theresa May (in her Florence speech) have said that any transition/implementation period would take place under "the existing structure of EU rules and regulations".
There will be plenty of technical challenges: what happens, for example, to the UK's role in EU trade agreements with third countries? Those third countries might have their own opinions about that.
But there is also the question of what happens during a transition period itself?
It could mean roughly two more years to continue negotiations on the details of a future partnership with the EU on trade, security and a host of other issues.
The Confederation of British Industry, for example, argues that in order to avoid a "cliff-edge" Brexit, negotiations on a trading agreement should continue during a transition.
But UK government policy is rather different. It still argues that a deal on our "final relationship" with the rest of the EU can be completed before the UK leaves the EU at the end of March 2019.
Most observers are convinced that, for practical reasons, that will not be possible - there is simply too much to do.
But Mr Davis insisted in the House of Commons this week that if the broad outlines of a permanent deal are not in place when the UK leaves, a transition period will not be triggered.
Asked by Conservative MP Rishi Sunak for reassurance that "what is meant to be a transitory state of affairs does not become a permanent bridge to nowhere", Mr Davis said: "We will try to get the nature of the implementation phase agreed as soon as possible, so that businesses can take that into account."
He added: "But he's right that such a transition phase would only be triggered once we've completed the deal itself, we cannot carry on negotiating through that - our negotiating position during the transition phase would not be very strong."
In other words, Mr Davis is saying - in stronger language than the government appears to have used before - that if there is no final deal by March 2019, at least in principle, then the UK would not want to trigger a transition period.
The words "at least in principle" contain a fair amount of wiggle room. And the EU itself would be delighted if the outlines of a future agreement could be agreed so quickly.
It says only that a withdrawal agreement (as opposed to a future trade agreement) has to be finalised in order for there to be a transition. And Article 50 simply says the withdrawal agreement must "take account of the framework for a future relationship".
But Mr Davis appears to be upping the ante. "No final deal" equals "no transition" equals "hard Brexit".
As a negotiating tactic, it may be designed to keep the pressure on. But it may not be what many business leaders want to hear.
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After a public shout-out of "no way!" to renegotiating the Brexit backstop plan or draft withdrawal agreement, the EU now waits for the British prime minister to come to Brussels.
Parliament appeared to lob the ball back in the EU's court last night, with the majority of MPs uniting around a request for alternatives to the backstop.
But the EU is preparing to swing it back to the UK pronto, with a direct question to Theresa May:
"What concrete alternative do you have worked out?"
Remember that EU and UK negotiators spent 18 difficult months trying to come up with a bilaterally acceptable fallback mechanism to keep the Irish border open, in case their (still to be negotiated) post-Brexit trade deal wasn't up and running in time, or didn't fully resolve the issue.
The UK-wide customs aspect of the backstop plan - where the whole of the UK would stay in a customs agreement with the EU to avoid Northern Ireland being "isolated" from Great Britain by remaining under EU regulations to avoid border checks - came at the prime minister's insistence, not the EU's.
No other workable alternative was found and the document was signed off by the cabinet and 27 EU leaders in late November.
Touching the backstop text risks the EU seeming disloyal to member state Ireland, while caving in to departing member UK. That's a message of "weakness" Brussels does not want to send to international trade partners, or to the not-exactly-EU-enthusiastic governments of Poland and Italy, for example.
It also risks contravening the Good Friday Agreement and the integrity of the single market.
But... when push comes to shove, EU leaders want to avoid a no-deal Brexit.
If it comes about, they will be answerable to their voters whose lives and businesses could well be affected.
So, while taking a hard line in public, those leaders are also doing some hard thinking behind closed doors.
This does not mean Brussels will do anything to get a deal.
When it comes to the backstop, EU leaders will resist compromising on core principles. Theresa May has spoken again of seeking a time limit to the backstop or a unilateral exit mechanism for the UK.
EU diplomats tell me she has to be more realistic.
Brussels intends to stonewall her until "the message is driven home", they say. Expect the EU to stand very firm for now and for some tense days ahead.
Brussels' deadline is 29 March, whereas the prime minister, who has promised to hold another vote on the Brexit deal, has a self-imposed deadline of mid-February.
The EU will not rush to help her with that one.
Brussels takes heart from the fact that the Brady amendment on the backstop, passed last night by a majority of MPs, is actually pretty ambiguous.
"If Theresa May seeks changes to the backstop," according to one diplomat I spoke to, "then that might be fine if she widens her thinking as to what constitutes a 'change'."
The amendment talks about finding "alternatives" to the backstop.
And this is something the Withdrawal Agreement already says both the EU and UK would be open to if alternatives became viable.
One thought doing the EU rounds is to attach a list of possible alternatives to the backstop text.
This could include technological solutions the more hard-line conservative MPs are so keen on.
The EU has said time and again that technology alone is not adequate to totally do away with physical checks on the border but the option could be placed on a list of potential alternatives to be judged - as to whether they are actually workable or not - at a later stage were the backstop ever to be needed.
Another idea is to take the UK-wide customs aspect out of the backstop, seeing that it provoked so much opposition in the UK, adding it instead to the above-mentioned list of "alternatives".
There is at the moment a huge amount of resentment in EU circles that so much about Brexit seems to them to be "all about appeasing the Conservative Party": the referendum itself, Theresa May's "red lines" on leaving the customs union and single market, and now the push for more on the divorce deal which UK civil servants negotiated and which the Prime Minister herself signed off on.
EU leaders are in no hurry to convene another Brussels summit - which they would need to do if the withdrawal agreement text were to be changed. The last thing they want is to be holding one every two weeks for Theresa May until Brexit day, should she be pushed by MPs to keep coming back for more.
They hope EU unity - so palpable until now - will hold while the pressure mounts.
At some point in the near future, Europe's leaders will decide the right time has come to engage. To their mind, that's clearly not now.
For the prime minister it will be an uncomfortable wait.

In contrast to the sound and fury coming out of Westminster on Thursday night, the silence on EU leaders' Twitter accounts was deafening.
In part it is surely a stunned silence. Europe's politicians gaze open mouthed at the maelstrom of division and chaos currently whirling through the House of Commons.
Three years after the UK voted to leave the EU - two weeks before the official Brexit day - Parliament appears to be in meltdown with no unifying solution in sight.
EU politicians breathe deep, shuddering sighs at the thought of prolonging the cross-Channel agony of the Brexit process.
So will they or won't they agree to an extension? What conditions could they demand and how long would Brexit be delayed by?
Like so many things to do with Brexit - the answer is: we're not 100% certain.
Earlier this week, a number of EU leaders including France's Emmanuel Macron, Mark Rutte of the Netherlands and Spain's Pedro Sanchez sounded pretty hard-line.
They wouldn't agree to delay Brexit, they said, unless the prime minister came up with a very good reason.
EU leaders are frustrated, irritated and fatigued by the Brexit process but it's also worth bearing in mind that they have two specific audiences in mind these days when they take to the cameras:
- UK MPs whom the EU wishes to pressure into voting for Theresa May's negotiated deal or something else Brussels believes to be realistic
-  EU citizens about to cast their ballots in the upcoming elections for the European parliament. The EU's intended message to them: We're tough on those who mess with our club, so don't vote for Eurosceptic nationalists like Marine Le Pen!
EU leaders' silence after Thursday's vote by the House of Commons to delay Brexit may also have been because they realise - whatever their individual opinions on an extension - that they are obliged by law to come to a unanimous decision. And they won't reach that decision until they are all stuck in a room together, which they will be at an EU summit in a week's time.
In the meantime, former UK Independence Party (UKIP) leader Nigel Farage says he is lobbying countries to make sure at least one of them vetoes a Brexit delay.
But that rather overplays Mr Farage's power of influence on European governments. His claim is little more than a publicity stunt.
The EU's final decision on an extension will be dictated by political and economic self-interest.
Delaying Brexit will prolong the uncertainty for European businesses and citizens - and ensure that the issue continues to hang over EU affairs.
But EU leaders don't want to be blamed by their voters for a costly no-deal Brexit either. An extension might avoid that.
So, tough talk aside, realpolitik is likely to win the day.
It could be a longer-term extension, favoured by European Council President Donald Tusk in order to give the UK time for a "rethink", he says.
Or a shorter extension, if Mrs May can show next week that she's close to parliament approving her deal.
EU leaders will probably say yes to a Brexit extension, even if it's through gritted teeth, though they may decide not take a final decision next week.

How much of a threat is the Spain/Gibraltar question to the Brexit summit on Sunday?
Well, it could turn out to be either huge or simply a puff of smoke. Madrid and Downing Street say they are working on it.
There's not much time left for the question to assume either form.
UK Prime Minister Theresa May meets EU leaders in Brussels to sign off on the Brexit texts in just over 36 hours.
Grandstanding for his domestic audience aside, Spanish Prime Minister Pedro Sánchez feels hoodwinked and angry.
Gibraltar is of great national interest, and hurt pride, for many Spaniards. It became official government policy during the Franco dictatorship to get back what Spaniards nickname "El Peñón"  (The Rock).
After the UK's Brexit vote, Spain at the very least saw an opportunity to re-gain considerable influence over Gibraltar.
Eyebrows shot up in the UK at the very start of the Article 50 process when article 24 of the EU's negotiating guidelines stated: "After the United Kingdom leaves the Union, no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without the agreement between the Kingdom of Spain and the United Kingdom."
In fact, though, the bilateral UK-Spain talks that then took place in parallel to EU-UK Brexit negotiations went extremely smoothly... until just recently.
Spanish resentment started building after the EU's chief negotiator, Michel Barnier, and his team proposed going into a "tunnel" with UK negotiators - blocking out political and media noise - in an attempt to break the lengthy impasse over the wording of the Irish "backstop" - that guarantee to avoid a border between Northern Ireland and Ireland.
It is during that tunnel moment that Spain feels it was "betrayed".
By the time EU and UK negotiators emerged, the Irish backstop had become a UK-wide customs area, meaning it was potentially straying into post Brexit trade deal territory.
Yet neither in that text, nor in the draft of the political declaration on EU-UK future relations published on Thursday, is there mention of Gibraltar and the need for Spanish approval.
Prime Minister Sánchez believes the positive attitude Spain had shown in bilateral Brexit talks over Gibraltar is now being abused; that Spanish national interest was sacrificed in the tunnel in order to offer an extra "sweetener" to the UK in wider Brexit negotiations.
European Commission negotiators flatly deny this.
But Spain is not alone in believing that priorities of individual EU countries were ignored during tunnel negotiations.
France, Denmark and the Netherlands felt let down by their EU negotiators over pinning down ongoing fishing rights in UK waters in the political declaration on post Brexit EU-UK relations.
We have now heard that the fishing issue has been "resolved" (for now). The details have yet to emerge.
This means Gibraltar is the only outstanding issue ahead of Sunday's Brexit summit, according to the EU.
Now, Spain's Prime Minister is hugely pro-European. He sees himself as a bit of a Macron number two.
It is not in his nature to scupper EU plans or an EU summit.
Remember when Italy's Deputy Prime Minister Matteo Salvini refused to take in migrant boats earlier this year, Mr Sánchez was the first to step in and help in order to avert an EU crisis - and also to win brownie points in Brussels.
Pedro Sánchez is under a lot of domestic pressure. He heads a minority government and has been repeatedly accused by the main conservative opposition of being "soft" over Gibraltar in Brexit negotiations.
He also faces elections in the politically significant Andalucia region on 2 December. A part of Spain that neighbours - you guessed it - The Rock.
It is possible that Spain's prime minister has learned a lesson from Italy's deputy prime minister: that if you dig in your heels in the EU, you can get results.
He knows, of course, that holding the Brexit summit now, in November, was at Theresa's May's insistence; that the EU thought it possible to seal the deal next month instead.
This knowledge is in Mr Sánchez's back pocket.
It's important to bear in mind that while Spain doesn't have an actual veto over the Brexit divorce deal, EU leaders need to reach decisions by consensus at their summits. They don't actually put up their hands to vote.
There is no way they can rubber stamp a text designed for a leaving member (the UK) when an existing member (Spain) is so strongly opposed.
It is true, there is less EU solidarity with Spain over Gibraltar than there was with Ireland over the border issue. But the EU has been so proud about the very unusual unity amongst its members over Brexit, they won't want to give that up at this late stage.
So, in effect, Spain could exercise a moral or political "veto" on Sunday.
Which means that although Spain does not have a formal veto, it could exercise moral and political objections that would effectively stop other countries from voting against it.
EU insiders don't think it will come down to that. They believe this can be solved without reopening the Brexit texts by noting Spain's insistence on continuing UK.-Madrid bilateral talks in a declaration added to the texts or other possible EU formulas.
But even if Spanish opposition melts away before Sunday, the bitterness over Gibraltar, over fishing rights, over ensuring that the UK has no competitive advantages over European businesses in a post-Brexit trade deal, these are examples of the substantial obstacles the UK will face from EU countries in negotiating a trade deal with EU after Brexit.
And that's a deal the parliaments of every single EU country - including Spain's - will need to ratify unanimously.

As we talked about late on Monday, there has been a sense building in Westminster that the prime minister is, maybe by accident, maybe increasingly by design, looking to almost the last possible minute for the definitive Brexit vote.
While ministers speak publicly of "talks" that must be given time to be completed with the EU, and officials continue to chew over the possibility of the "Malthouse compromise" (remember that? It already seems like months ago that it emerged, blinking, into the Brexit saga) more and more MPs believe it is displacement activity - ministers keeping outwardly busy while they run down the clock.
Early on Tuesday morning, Commons leader Andrea Leadsom did not exactly quash that notion in an interview with the Today programme.
She appeared to open up the possibility that MPs might in the end be asked to vote at a moment of peak jeopardy, and that ministers might be willing to let the matter run that long.
Then, on Tuesday afternoon, the prime minister herself hinted that the government was prepared to do that.
She was answering a technical question about the CRAG (the constitutional reform and governance bill before you ask, Brexit is nothing if not replete with acronyms).
For ages, the existence of that bill has built a theoretical pause between a vote on the deal, and our actual departure from the EU.
But today the prime minister said that process could be put on fast forward.
So, in practice, if she wants to push this vote later, and later, then only to the very last minute (and remember the EU doesn't want to budge until then), that bit of legislation might not be a block, because if MPs approve it, she can get round it.
That's always a big if, of course, but it certainly suggests that the government can at least foresee a situation where they have to take dramatic last-minute action, whatever the existing law says.
What's also emerging though is how former Remainers want to stop that happening.
They won't be using up their energy this week on votes that might not get anywhere.
But their concerns have pushed the PM now to promise a vote will take place on 27 February.
And there will be another go from the prominent Labour frontbencher Yvette Cooper, working with backing from Tories like Sir Oliver Letwin and Nick Boles.
They will again try to force through legislation that would delay Brexit if the government can't get a deal done in time, removing the possibility of that last-minute kamikaze choice.
But that will only work if enough Tory Remainers are ready to vote with them.
And the way the numbers stack up, that probably has to mean ministers being ready to quit.
One member of the government told me on Tuesday: "They have to realise that is it - and if no senior member of the cabinet is willing to do it, then we're heading for that terrible choice."
Another minister, one of those who is thinking about departure, said: "I have to look the PM in the eye and ask what she is really willing to do. But for a number of us it's party versus country, and the Tories don't do well if we put ourselves before the public."
Some of those organising the push to take the March "deal or no deal" choice off the table believe there are at least 10 government ministers who would be ready to quit.
Maybe so.
On past evidence, ministers who see themselves as moderate and pragmatic hang back in the end.
But the end of February really does seem to be the last moment where they could do more to stop no deal than just pass a resolution the government could then ignore.
If they are not willing to give up their ministerial red boxes on 27 February, their chance really will have gone.

What now?
Theresa May has been granted a little breathing space. The EU has allowed a few more days to try to get her deal through the House of Commons.
But it's not the timetable that she chose.
And as things stand, the expectation that the compromise deal will get through is low.
And, more to the point, the government does not believe that it can hold off another attempt by a powerful cross-party group of MPs who are resolved to put Parliament forcibly in charge of the process to find alternatives.
Ministers are therefore today not just wondering about how to manage one last heave for the prime minister's deal, but what they should do next, when - odds on - the whole issue is in the hands of the Commons, not Number 10.
Within days, MPs will push for a series of votes on different versions of Brexit - the "Norway" model, another referendum, Labour's version of Brexit with a customs union, the list goes on.
But here's the dilemma.
Does Theresa May just wait for Parliament to do what one minister describes as "grab control of the order paper"?
Or should they instead try to lead the process, forcing what another member of the cabinet described as a "fresh start", even though it seems "ludicrous" to be resetting the whole process in this way at this stage?
Some in the government believe the best choice is to take charge of this next stage - to lead the process as Parliament and the opposition parties try to find a new compromise.
Sounds like a no brainer.
But there is a real hesitation over whether the Labour frontbench are really interested in trying to find a compromise or will, ultimately, be too tempted by the political opportunity of pulling the rug from under the government at the very last minute.
And given that the majority of MPs are, theoretically, in favour of a softer Brexit than the one the prime minister has negotiated, could Theresa May really preside over a process that would end up there?
But if the government sits back and just lets Parliament get on with it, then Number 10 accepts becoming a passenger - entirely in the hands of the MPs whose behaviour the prime minister so reviled in that controversial address in Number 10 on Wednesday night.
Don't forget - for many Brexiteers in the Conservative Party, the idea of a softer Brexit than the one the prime minister has negotiated is nothing short of an abomination.
(That could, in a hypothetical world, mean that more of them are willing to back Theresa May's deal than currently expected - if it is the "hardest" brexit that is on offer).
So for Theresa May's survival as leader of the Conservative Party, there is a case, strange as it sounds, for her to hang back from leading the next phase.
If Parliament chooses a softer Brexit in the end, it could suit Mrs May not to have her fingerprints on it.
But is it really a tenable leadership strategy, choosing not to lead?
Brexit has done some very strange things to our political process. The reality is though, if Theresa May next week accepts the will of Parliament and it is "soft Brexit", the reaction from the Conservative Party could be explosive.
Frankly, the choices for Theresa May are running out.
Many Tories on all sides of the debate are deeply alarmed by how things have unravelled in the last few days.
One senior, influential, MP who has been studiously loyal to the prime minister is incandescent, saying that she has "angered all the people whose support she needed", and that "she is the most stubborn and ill-suited person for this job".
Another former minister suggests Theresa May's deal still could pass, but only if she tempts Labour rebels across with a promise of a referendum to give the public the chance to rubber stamp it, or "we'll have a new PM with a new plan", and maybe soon.
One current member of the government says "only Number Ten can't see that she is on her way out".
Another minister says the situation is "super dangerous".
All of the fundamental factors that have preserved her so far remain - there is no obvious alternative plan that is certain to get a majority of MPs on side.
There is no obvious leader in waiting that the whole Conservative Party would gladly choose. The Labour Party have their own battles with their own divisions over Brexit.
The traditional claim of TINA - There Is No Alternative - has helped Theresa May hang on.
But now an alternative to her deal is likely to be forced upon her, one that could make her leadership impossible to maintain.
Theresa May arrives back in Number 10 today having won a little bit of extra time, but she has less and less space to breathe.

It is almost the end of another very long and fractious week in Westminster (although their lordships look like they'll be going for quite some time yet).
But the main item of business in the last frantic 24 hours has been the cross-party talks between the Conservatives and the Labour Party.
From both sides, it sounds like they are serious and genuine, and negotiators got into the guts of both their positions and technical details on Thursday.
Remember, behind the scenes there isn't as much difference between the two sides' versions of Brexit as the hue and cry of Parliament implies.
But the political, not the policy, distance between the two is plainly enormous. I'm told there might be more contact tonight between the two sides, although not more face to face talks until Friday.
And there is scepticism in Labour circles over whether the government is doing more so far than trying to explain merits of its deal, rather than suggest areas where they might be willing to budge.
Sources involved in the process suggest that there is yet to be the promise of a big move from Theresa May, a promise about the price she is willing to pay for Labour support.
But the talks are not just a stunt and there are suggestions it might be clear by Friday afternoon, if the process will actually be able to deliver an outcome.
Talks, as we know, often turn to more talks, and more talks, and more talks.
You don't need me to remind you, when Theresa May has the option of playing something long, which choice she makes.
There is, though, the obvious deadline of the prime minister's trip to Brussels next week, where she has to present something to her EU counterparts, in order to justify asking for another delay.
But presenting something is not the same as having to deliver a fully worked-out deal with every "i" dotted, every "t" crossed.
It would be an enormous political turnaround if a fully worked out cross-party compromise emerges by then, that can last.
But after months of Brussels pondering openly why the UK has not been able to work in a cross-party way, if Theresa May can show evidence that that process is under way, perhaps that will be enough.
One cabinet minister suggested to me today that, if they can show there isn't a "permanent standoff" in Parliament between the two main parties, then the EU will give the UK more time.
Don't forget though, behind the scenes, some Brexiteers are still trying to organise to push for departure from the EU next week.
Labour has a problem too - a big split over whether they could accept compromise to deliver Brexit, without the promise of another referendum.
Theresa May and Jeremy Corbyn may have a lot of gaps to bridge between them, but they have gaps among their own sides too.

Clearly Europe was fully expecting the defeat of the Brexit deal in parliament on Tuesday night.
Seconds after the results were announced, pre-prepared tweets expressing disappointment came flooding in from EU leaders.
Here in Brussels, frustration hung in the air. With 73 days to go until Brexit day, Jean-Claude Juncker and European Council President Donald Tusk appealed (once again) for clarity from the UK.
"MPs keep saying what they don't want," fumed one of their colleagues. "They reject this deal. They reject no deal. They need to decide now what it is they will agree to."
Those in the UK who expect the EU to 'rush to the rescue' with proposed changes to the Brexit agreement are in for a let-down.
Europe's leaders have no agreed Plan B up their sleeve and see no advantage in scrambling to find one.
They believe the debate in the UK still needs to play out.
"It's important not to rush now," urged Annegret Kramp-Karrenbauer, widely tipped to become Angela Merkel's successor.
With the prospect of a softer Brexit looming, as well as the possibility, however small, of no Brexit at all, the EU thinks this is not a time to meddle.
It's far more effective to keep up the pressure.
One EU diplomat told me Theresa May should save on the plane fuel and not bother flying out to Brussels any time soon.
"We're not going to hold a special summit or anything," he said.
"There's nothing we Europeans can do today or tomorrow that will solve this. London has to come up with solutions, then we have to decide if we can accept them."
For now the EU insists it hasn't the slightest intention of re-negotiating the divorce deal, known as the Withdrawal Agreement.
Leaders are fully aware many MPs hate the backstop, the Irish border guarantee written in to the agreement, but there's no indication the EU would give it up.
It has insisted over and again that it intends to protect the Northern Ireland peace process, to stand up for the concerns of member state Ireland and - very important indeed to Brussels - to protect the single market (don't forget the land border between the EU and a post-Brexit UK will run down the island of Ireland).
Brussels also interprets the sheer scale of the vote against the Brexit deal on Tuesday as a sign that MPs were rejecting far more than the backstop.
So what now?
EU leaders think it increasingly likely that the Prime Minister will ask them for an extension to the Article 50 leaving process to allow her more time.
And while European hearts sink at the thought of months' more uncertainty, indecision and going around in Brexit-related circles, they will most probably grant the extension.
Preferably no longer than July to avoid having to select new UK MEPs - the European Parliament holds elections this year - but my contacts tell me the EU could extend Article 50 even longer if necessary.
Bottom line: it's worth it to the EU, if it means avoiding a costly, chaotic no deal Brexit which would also hit European citizens and businesses hard.
Back to Tuesday night's vote, EU diplomats tell me the bloc's position should become clearer next week.
It's no mean feat coaxing 27 different leaders towards a common position. And EU countries' unity over Brexit is something Brussels is anxious to maintain.

The government should add a public vote to the Brexit legislation which MPs will vote on next month, the shadow Brexit secretary has told the BBC.
Sir Keir Starmer said including another referendum in the Withdrawal Agreement Bill would "break the impasse".
Talks between Labour and the government to find a compromise Brexit deal broke down on Friday without agreement.
Theresa May has said she would consider putting different Brexit options to MPs to see which ones "command a majority".
Labour's preferred plan is for changes to the government's Brexit deal or an election, but if neither of those are possible, it will support the option of a public vote.
There have been calls for giving the public another say on Brexit. One widely discussed option is for a "confirmatory vote" with the choice between accepting whatever deal the government agrees, or remaining in the EU.
Others argue any new referendum should include the option of leaving the EU without a deal.
Speaking to BBC Radio 4's Today programme, Sir Keir suggested the government should seek "further changes to the political declaration", which sets out the UK's future relationship with the EU after Brexit.
He added: "Or of course they could seek to break the impasse by putting a confirmatory vote on the face of a bill.
"But whatever happens they have to find a way of breaking the impasse. We've got five and a half months which seems like quite a long time but in reality, once we get to the summer recess, we've only got only two weeks in September and two weeks in October."
Brexit had been due to take place on 29 March - but after MPs voted down the deal Mrs May had negotiated with the bloc three times, the EU gave the UK an extension until 31 October.
Mrs May announced this week that MPs will vote on her EU Withdrawal Agreement Bill in the week beginning 3 June.
This will be the second reading vote on the bill, which is the key piece of legislation to implement the withdrawal agreement - the legally binding part of the Brexit deal that covers exit terms - and take the UK out of the EU.
The second reading is the first opportunity for MPs to debate the bill. If it is not passed by Parliament, the default position is that the UK will leave the EU on 31 October without a deal.
Sir Keir said Labour would vote against the Withdrawal Agreement Bill, accusing the government of attempting "an experiment" and bringing the UK to "a cliff edge".
"If that bill goes through second reading and then collapses at third reading we are then up against the cliff edge in October, which is why we've said we'll vote against that at second reading if there isn't an agreed deal before we start," he said.
He denied that would make a no-deal Brexit more likely. "I don't accept that. What we can't do is keep on buying another week at a time which is what the prime minister has been doing for months."
Discussions between the Conservatives and Labour - to see if they could come to an agreement on Brexit despite differences over issues including membership of a customs union and a further referendum - lasted six weeks before ending on Friday.
Sir Keir blamed the collapse of talks with the government on the inability to "future proof" a deal against an "incoming Tory leader" and said although the two sides had conducted the talks "in good faith", they were "a long way apart" on substance.
He said: "During the talks, almost literally as we were sitting in the room talking, cabinet members and wannabe Tory leaders were torpedoing the talks with remarks about not being willing to accept the customs union.
"In terms of the team that we were negotiating with, I'm not blaming them.
"Circling around those that were in the room trying to negotiate were others who didn't want the negotiation to succeed because they had their eye on what was coming next."
Mrs May has previously blamed the collapse on the lack of a "common position" within Labour.
It comes as a poll of Conservative members for The Times suggest former Foreign Secretary Boris Johnson is the favourite to succeed Mrs May.
A YouGov poll commissioned by the Times suggests Mr Johnson is the first choice for 39% of those Tory party activists who responded.
The former London mayor, who announced his intention to run earlier this week, was three times as popular as the next closest choice, ex-Brexit secretary Dominic Raab (13%).
Of the others, Home Secretary Sajid Javid and Environment Secretary Michael Gove were both on 9%, with Foreign Secretary Jeremy Hunt on 8% and Health Secretary Matt Hancock on 1%.
Meanwhile, Mr Hancock told the Daily Telegraph that Mrs May's successor as prime minister should not call a general election until Brexit is completed.
He said an early election risked losing to Labour and "killing Brexit altogether".
He added: "We need to take responsibility for delivering on the referendum result."

The government is aiming to secure a "zero tariff, zero quota" free trade deal with the EU, Brexit Secretary Stephen Barclay has said.
He told the BBC's Andrew Marr the UK would not diverge from current EU trade regulations "for the sake of it".
Mr Barclay added the government's objectives for the trade talks would be published after Brexit on 31 January.
Prime Minister Boris Johnson will make a speech next month setting out more details, he said.
Mr Barclay's comments come after the US treasury secretary said his country wants to agree to a post-Brexit trade deal with the UK this year.
After Brexit happens at 23:00 GMT on Friday, the UK will be free to negotiate and sign new trade deals with countries with no existing EU deals - like the US.
The UK then enters into an agreed transition period with the EU, which lasts until 31 December 2020. During this time the UK will aim to negotiate a free trade deal with the EU to ensure that UK goods are not subject to tariffs and other trade barriers.
Speaking to the BBC's Andrew Marr, Mr Barclay said: "We are going to publish our objectives for the negotiation and we will set that out in due course after the 31st.
"The key issue is that we will have control of our rules, we will not be a rule-taker, we will not diverge for the sake of diverging.
"We start from a position of alignment but the key opportunity is that we will be able to set our standards, high standards, on worker's rights, on the environment, on state aid as part of that trade policy."
He said "both sides are committed" to securing a trade deal by the end of December, adding: "It's in both side's interests to keep the flow of goods going."
Irish minister for European affairs, Helen McEntee, told Sophy Ridge on Sky News that "Brexit is really only at half-time, we have a huge amount of work still to do".
"However, the idea that we can negotiate a trade deal with one that is comprehensive, one that provides very little change for our citizens, not just in the UK and Ireland, but the EU as well, within about a 12-month space, it's very difficult."
The new European Commission president Ursula von der Leyen  has previously shared concerns about the timeframe, saying it would be "impossible" to reach a comprehensive trade deal by the end of 2020.
Meanwhile, the home secretary told Sophy Ridge UK businesses have been "too reliant on low-skilled cheap labour from the EU".
Priti Patel said the government will be able to control levels of low-skilled migration after Brexit.
She also confirmed that the Migration Advisory Committee will report this week on the UK's future immigration system.
The government was "absolutely determined to change the immigration system, end the complexity of the immigration system, have simpler rules, have a points-based system where we can absolutely have people that bring the right kind of skills for our labour market", she said.
On the UK's post-Brexit relationship with EU rules, Ms Patel appeared to adopt a harder approach than Mr Barclay, saying: "In terms of divergence, we are not having alignment. We will be diverging. We want to take control of our laws, money and our borders."
Last week, Chancellor Sajid Javid said the UK would use the power to diverge from EU rules on trade only when it was in the interests of business.

Two leading Brexiteers have said any delay to Brexit would do "incalculable" harm to public trust in politics.
Writing in the Sunday Telegraph, Tory MP Steve Baker and the DUP's Nigel Dodds said the "extended uncertainty" would be a "political calamity".
On Tuesday, Theresa May will again ask MPs to back her Brexit deal, but if they reject it they may get a chance to vote to delay Brexit.
The UK is due to leave the EU on 29 March.
Mr Baker, who is deputy chairman of the pro-Brexit Tory European Research Group (ERG), and Mr Dodds wrote that, for some, any delay would mean "democracy would be effectively dead".
They said that such an outcome would be "a costly delay for businesses which have prepared to exit on 29 March".
Both were confident that without changes to the deal, Mrs May would be "defeated firmly" again on Tuesday.
MPs rejected the prime minister's deal by 230 votes in January - the largest defeat for a sitting government in history.
If they do the same this week, MPs have been promised a vote on whether the UK should leave without a deal.
If they then reject a no-deal Brexit they could get a vote on Thursday on whether to request a delay to Brexit from the EU.
Speaking on Sky News, Shadow Brexit Secretary Sir Keir Starmer said: "A delay or extension of about three months is probably doable. Beyond that it becomes much more difficult."
He added that Labour's front bench would not put down an amendment to secure another referendum, ahead of the vote on Mrs May's deal on Tuesday. He said any such amendment should come from a backbencher in order to get more widespread support from MPs.
Health Secretary Matt Hancock told the same programme it was not inevitable that the withdrawal deal negotiated with the EU would be rejected on Tuesday.
He added: "It's in the gift of MPs to get on and deliver on Brexit and I very much hope that that is what people will vote for."
Since January, the prime minister has been trying to seek assurances from the EU about the so-called Irish backstop - an aspect of her plan which is a sticking point for many MPs.
If Parliament approves Mrs May's withdrawal agreement, and the UK leaves the EU on 29 March, it will begin a transition period, when the two sides will attempt to agree a comprehensive trade deal.
If a trade deal is not agreed by the end of the transition period, the backstop is designed to maintain an open border on the island of Ireland.
It would keep the UK in a "single customs territory" with the EU, and leave Northern Ireland in the EU's single market for goods.
But some MPs fear that - in its current form - the backstop may leave the UK tied to the EU indefinitely.
They want Mrs May to change this aspect of the deal.
Discussions between the UK government and EU officials on how to resolve the problem continued over the weekend.
On Friday, Mrs May said the UK had put forward "serious" proposals to resolve the deadlock.
The EU said it was prepared to include a number of existing commitments relating to the application of the backstop in a legally-binding document.
Its Brexit negotiator Michel Barnier tweeted that the UK "will not be forced into [a] customs union against its will" as it could choose to exit the proposed "single customs territory" on its own. But Northern Ireland would remain part of the EU's customs territory, subject to many of its rules and regulations - something the government has previously said would threaten the constitutional integrity of the UK.
Brexit Secretary Steve Barclay and the DUP, the party Mrs May's government relies on for a majority in Parliament, were both dismissive of the EU's latest proposal.
Meanwhile the US Ambassador to the UK, Woody Johnson, has urged the British public not to let the "distraction" of the debate over food standards and chlorine-washed chicken block the "huge opportunity" of a trade deal between the countries.
He said the US was the world's largest food importer, but currently bought less than one per cent of its food from the UK.
Writing in the Mail on Sunday, he said: "It's time to move on from chlorinated chicken. It's just a bogeyman used to scare you out of doing a great trade deal with America that will give your businesses a huge competitive advantage."

Brexiteers who have questioned the sustainability of the Good Friday Agreement have been branded "reckless" by the Irish deputy prime minister.
Simon Coveney warned they could undermine the foundations of Northern Ireland's "fragile" peace process.
It followed suggestions by number of high-profile Brexiteers that the 1998 deal may no longer be fit for purpose.
Critics include ex-Northern Ireland Secretary Owen Paterson, Tory MEP Daniel Hannan, and Labour MP Kate Hoey.
The 1998 Good Friday Agreement, also known as the Belfast Agreement, demands mandatory coalition government involving both unionists and nationalists.
Responding to Mr Coveney's comments, UK Brexit Secretary David Davis said that he was "not conscious of anybody talking down the Good Friday Agreement, adding that "certainly nobody in government has".
Speaking in Vienna, Mr Davis said that "everything we are doing is aiming towards ensuring we meet every aspect of it (the 1998 Agreement), so I don't foresee that being a problem".
The three Brexiteers have expressed support for a rethink of the political arrangements brought about by the Good Friday Agreement after the failure of the latest attempt to restore devolution.
On Friday, Mr Paterson retweeted an article by Telegraph columnist Ruth Dudley Edwards entitled: "The collapse of power sharing in Northern Ireland shows the Good Friday Agreement has outlived its use."
On Sunday, Mr Hannan wrote a column in the same newspaper saying the 1998 power-sharing accord represented "a bribe to two sets of hardliners".
Mr Hannan said his objections to the Good Friday Agreement (GFA) "were not on orange or green grounds but on democratic grounds".
Ms Hoey argued that her scepticism of the 1998 accord had "nothing at all to do with Brexit".
She tweeted: "Hiding head in sand over viability of sustainability of mandatory coalition is reckless and wrong."
Ms Hoey was responding to criticism from her Labour Party colleague, Owen Smith, the shadow secretary of state for Northern Ireland.
Mr Smith said it was "reckless and utterly wrong to question the value and sustainability of the Good Friday Agreement".
"Their concerted, transparent effort to undermine the GFA is driven by their blind, misplaced faith in Brexit.
"They should know better."
Tanaiste (Irish Deputy Prime Minister) Simon Coveney echoed Mr Smith's comments in a tweet sent to Ms Hoey, Mr Hannon and Mr Paterson on Tuesday.
"Talking down Good Friday Agreement because it raises serious and genuine questions of those pursuing Brexit is not only irresponsible but reckless and potentially undermines the foundations of a fragile peace process in Northern Ireland that should never be taken for granted," Mr Coveney wrote.
He added that the current British and Irish governments remain "absolutely committed to GFA".
Mr Coveney's party colleague, Fine Gael Senator Neale Richmond, was even more forthright in his criticism of Brexiteers.
He tweeted: "Not content with stirring up horrible xenophobia in the campaign, they now want to destroy peace in Ireland for their petty brand of British nationalism!"
Mr Richmond added: "The same people who bleat on about respecting democracy willing to run roughshod over an agreement backed by 71% in the North & 94% here [the Republic of Ireland]."
However, Mr Paterson robustly defended his position, saying: "Brexit is emphatically not a threat to peace in Northern Ireland."
He added that it was "disgraceful that hysterical Remainers and Brussels are weaponising the Irish border issue".
Mr Paterson also pointed to a recent interview with former Ulster Unionist Party leader, Lord Trimble, one of the architects of the 1998 peace deal.
Lord Trimble told BrexitCentral that it was "rubbish that Brexit will undermine the Good Friday Agreement".
Mr Paterson, who served as Northern Ireland secretary from May 2010 to September 2012, now supports calls for interim direct rule from Westminster in the absence of a Northern Ireland Executive.
He said this would also provide time "to discuss practical improvements to Belfast Agreement".
The Conservative MP told those who were angered by Ruth Dudley Edwards' article they "should recognise that NI citizens deserve good government" as their health services were "falling behind the rest of the UK".
In December the UK and the EU reached a deal on Brexit which specifically referenced the Good Friday Agreement.
The deal contained a "fallback" clause regarding Northern Ireland in which the UK undertook, in the absence of other agreed solutions, to "maintain full alignment with those rules of the internal market and the customs union which, now or in the future, support north-south co-operation, the all-island economy and the protection of the 1998 Agreement".
The latest political exchanges come as British and EU officials are working on how to put the Brussels deal into a more legally enforceable form.

Labour has urged the government to nationalise British Steel in order to protect jobs and the steel industry.
Labour leader Jeremy Corbyn said the collapse of British Steel would have a "devastating impact" on Scunthorpe.
British Steel is on the verge of administration as it continues to lobby for government backing, sources say.
The UK's second-biggest steel maker had been trying to secure £75m in financial support to help it to address "Brexit-related issues".
If the firm does not get the cash it would put 5,000 jobs at risk and endanger 20,000 in the supply chain.
"If an agreement cannot be struck with British Steel, the government must act to take a public stake in the company to secure the long term future of the steelworks and protect peoples' livelihoods and communities," said Mr Corbyn.
The government said it would leave "no stone unturned" in its support for the steel industry.
British Steel's main plant is at Scunthorpe, but it also has a site in Teesside.
Speaking in the House of Commons, Business Minister Andrew Stephenson said: "I can reassure the House that, subject to strict legal bounds, the government will leave no stone unturned in its support for the steel industry."
UK Steel's director general, Gareth Stace, said: "The statement from the business minister today provided a glimmer of hope for the Scunthorpe site.
"This does provide some breathing space for the company, its employees, and the wider steel sector, providing a potential route towards a stable and sustainable future."
The request for emergency financial support from the government is understood to have been reduced from £75m to about £30m.
In April, British Steel borrowed £100m from the government to enable it to pay an EU carbon bill, so it could avoid a steep fine.
Reports have said that British Steel shareholder Greybull Capital and lenders have agreed to pump new money into the firm.
However, unless a deal is reached by Tuesday afternoon, the firm could go into administration within 48 hours. EY would be expected to be appointed as administrators on Wednesday.
If a company goes into administration, then the insolvency practitioners appointed to run the business will try to rescue it by selling it, or parts of it, as a going concern.
But if that is not possible it will be liquidated, meaning that it will be closed down and its saleable assets will be sold.
For staff in Scunthorpe, it's a waiting game.
The BBC's consumer affairs correspondent Colletta Smith spoke to a British Steel staff member who was too worried to be named. He said that two of his colleagues have just got mortgages and are petrified they won't be able to make payments.
News that the company is in trouble isn't a surprise though, as there are piles of finished steel on the factory floor, with no customers to send it to, he said.
"We're doing a bit at work, but it's mostly sitting around doing nothing as the orders just aren't there".
He said staff feel let down by the owners.
"They've just stripped this company and now they're putting nothing back. Our only hope is a government bailout, but this time it feels different. I don't think they'll save us."
Sources close to Greybull Capital say its lenders have told them that unless they can secure a £30m lifeline they will pull the plug on British Steel tomorrow.
The timing of this could hardly be worse for the government coming as it does right before the European elections.
Cynics might suggest that Greybull is not unhappy with the timescale of the plea.
Business Secretary Greg Clark has a very tough decision, as I've already written.
The question may be whether the government can put this down to Brexit mitigation and tap the same source of contingency funds Chris Grayling disastrously used to procure emergency ferry capacity.
At least there would be an immediate dividend - to stave off the collapse of a firm that employs 4,500 people directly and has 20,000 more at risk in the supply chain.
However, having already lent £100m to cover a genuinely Brexit-related carbon emissions bill - further assistance to a private company struggling in a deeply challenged industry may be a precedent they would rather not set.
Last Thursday, British Steel said it had the backing of shareholders and lenders and that operations were continuing as usual while it sought a "permanent solution" from the government to its financial troubles.
It is understood that along with administration, nationalisation or a management buyout are being discussed as fall-back options for the company.
British Steel's troubles have been linked to a slump in orders from European customers ‎due to uncertainty over the Brexit process.
The firm has also been struggling with the weakness of the pound since the EU referendum in June 2016 and the escalating trade US-China trade war.
One of its biggest customers is Network Rail, 95% of whose rails are supplied by British Steel's Scunthorpe plant.
In 2007, India's Tata conglomerate entered the UK steel market after it bought the Anglo Dutch group, Corus. In 2010, the business was renamed Tata Steel Europe.
After a difficult few years, Tata sold the Scunthorpe long products division to private equity firm Greybull Capital for a nominal £1.
Greybull's rescue came during the depths of the steel crisis in 2016 and saved more than 4,000 jobs.
It then rebranded the company as British Steel and recently returned it to profit.
On Monday, the government, trade unions and employers signed a UK Steel Charter in Parliament.  The charter calls on the government and large companies to buy British to boost UK industry.

Britain's farmers should no longer get "privileged" access to low-skilled, low-paid workers from the EU after Brexit, says a top government adviser.
Alan Manning, who chairs the Migration Advisory Committee, said fruit and vegetable growers would probably "go backwards".
But it would not be the "end of the earth" for the UK economy as a whole.
The National Farmers Union has warned that without seasonal workers crops like strawberries will go unpicked.
The government has said high-skilled workers would be prioritised after Brexit, with no preferential treatment for people from the EU compared with those from the rest of the world.
The policy is based on recommendations drawn up by Mr Manning's committee, which have also been backed by the Labour Party.
Mr Manning said the rules on skilled workers - which say they must earn more than £30,000 a year to get a visa - might be relaxed for a "tiny" number of highly-skilled, low-paid individuals, such as musicians or dancers.
But he said many firms who had benefited from the influx of low-skilled East and Central European workers over the last 14 years would "find life a bit harder" under the proposed new regime.
"Most of them are not musicians, these are people working in warehouses and food manufacturing, in hospitality and so on," he told the Lords EU home affairs sub-committee.
"Our view would be they have had a tailwind since 2004, which those sectors would understandably want to continue, but it's not necessarily clear that that is in the interests of the wider economy and society."
He said seasonal agricultural workers were a special case, because they all came from EU countries (99% according to the Office for National Statistics).
Mr Manning told the Lords committee there was "no realistic prospect" of that work being done by British people.
The government has launched a pilot scheme to allow farmers to recruit 2,500 non-EU migrants to help the industry adjust - a move welcomed by the National Farmers Union, which has been warning of crops being left to rot in the ground.
Mr Manning said the fruit and veg growing sector had "expanded a lot" since the so-called A8 countries, including Poland, joined the EU, with an "extraordinary" increase in the amount of land given over to crops like asparagus, strawberries and other seasonal produce.
"If you cut off the access to that labour those sectors would find it much harder," he said.
"To some extent, it's quite likely that they would contract."
He said agriculture as a whole was a low productivity sector, about 40% of the national average.
"So if you are wanting to make the UK a high wage, high productivity economy, which we generally are, it's not clear that making life very easy for agriculture - giving them privileged access to labour - is a way to achieve that.
"That really wouldn't be the end of the earth for the country as a whole. Obviously the NFU are not going to be very enthusiastic about it."
The Migration Advisory Committee has suggested forcing farmers to pay a higher minimum wage in order to encourage increases in productivity - or charging them for every additional foreign worker they employ.

British citizens should be allowed to keep the benefits of EU membership, according to the chief Brexit negotiator at the European Parliament.
Guy Verhofstadt said allowing individuals to keep rights, such as freedom to travel and vote in European elections should be a priority.
He also warned the European Parliament had veto powers over any deal struck.
Meanwhile EU chief Jean-Claude Juncker has said he hopes the British will one day be persuaded to re-join the EU.
Prime Minister Theresa May wants to trigger Article 50 of the Lisbon Treaty by the end of March, which would pave the way for Brexit negotiations, in which the rights of EU nationals living in the UK and Brits living on the continent will be a key issue.
Mr Verhofstadt, who leads the liberal group of MEPs in the European Parliament, told the BBC that the matter had to be prioritised and "cannot be part of the political games" that have taken place over the last few months.
He told BBC Radio 4's Today programme he had received more than 1,000 letters from UK citizens who did not want to lose their relationship with "European civilisation".
Mostly these were driven by emotion and a feeling that they did not want to lose their European identity post-Brexit, he said, adding that he did not understand why the negative fall-out from the decision had not been discussed during the referendum, which had instead focused on the economics of Britain leaving the EU.
Many of the letters began with the appeal that "'I'm a UK citizen - I don't want to lose my relationship with Europe and European civilisation,'" he said.
"So emotion is now coming up and all those voters will want to remain in the European Union and have the feeling that they are lost, that nobody is defending them anymore, that they are losing a part of that identity - and it's for that reason that I'm trying to convince the European Union, not only the European Parliament, to take on board that feeling of UK citizens.
"I think we need to examine what type of special arrangement we can make for those individual citizens who want to continue their relationship with the EU, and the opposite - it's for both sides."
Mr Verhofstadt said the situation "is a crisis for the EU". "The fact that a large country like Britain is leaving the EU...? It's shown a crisis in the European Union - it's a disaster. That Britain goes out of the EU is a tragedy, a disaster, a catastrophe - you name it."
He said the responsibility now is to look for "a new partnership" between the EU and the UK, but he stressed: "Unfortunately, because of the decision taken by the UK government, it can't be the single market - because they don't accept the full freedom.
"It cannot be the customs union, because they want to make their own trade deals. It cannot be the European Court of Justice - it cannot be the European economic area."
Pressed on whether a good deal could still be reached that can work for both sides, he said: "That's exactly what we're going to try to do."
But European Commission President Jean-Claude Juncker told reporters he hoped that the British could one day be persuaded to re-join the EU.
"I don't like Brexit because I would like to be in the same boat as the British," he said. "The day will come when the British will re-enter the boat, I hope.
"But Brexit is not the end of Europe. By contrary, Brexit is encouraging the others to continue, unfortunately without the British.... Brexit, it's not the end - I regret it but we will continue."
During the BBC interview, Mr Verhofstadt insisted that there could be "no hard border" between the Republic of Ireland, that will remain in the EU, and Northern Ireland, which is leaving.
"What can't happen is that we destroy all the efforts that have been undertaken over the last 20 to 30 years to have peace there, so no hard border," he said.
He also warned the European Parliament will have the power of veto any deal brokered between the UK and the European Commission on Brexit.
"We vote no - that is possible," he told Today. "It has happened in a number of other cases that a big international multilateral agreement was voted down by the European Parliament after it was concluded.
"The fact that in the treaty it is stated we have to say yes or no doesn't mean that automatically we vote yes."
Prime Minister Theresa May has indicated that the UK Parliament will vote on the terms of exit before the European Parliament but that the UK will leave the EU anyway, irrespective of whether MPs approve or reject them.
Asked whether the UK would welcome the opportunity for British nationals to retain some of the benefits of EU citizenship after Brexit, No 10 said it was "not something that we have ever proposed or said that we are looking at".
"We will go into negotiations and discuss the ideas put forward by the EU and its various institutions," said a Downing Street spokesman.

David Davis's resignation was met with a collective shrug of the shoulders in Brussels on Monday. "How can we miss a man who was never here?", one EU source commented to me. The Brexit secretary made one visit to Brussels in the last four months.
The president of the European Council, Donald Tusk, said Europe was deeply troubled not by British cabinet resignations, but by Brexit itself.
"Politicians come and go," he said. "But the problems they have created for the people remain. The mess caused by Brexit is the biggest problem in the history of EU-UK relations. And it is still very far from being solved."
A sense of unease hangs heavy.
"Theresa May is respected in Europe," one contact told me. "But so many times since this Brexit process began, we've had to ask ourselves: will she stay or will she go? And now here we are again."
Political uncertainty in Britain makes the possibility of a no-deal Brexit seem far more likely in the eyes of Brussels bureaucrats.
Not because either side want it, but because time for EU-UK negotiations - as the European Commission never tires of repeating - is simply running out.
And if the prime minister does indeed survive, what then? Most EU sources I spoke to believe she will. One compared the prime minister to Germany's Angela Merkel and said both women were consistently under-estimated.
Listen to Theresa May's impassioned address to Parliament today - promising a return to UK sovereignty after Brexit, yet simultaneously keeping close ties to Europe (no country with an EU association agreement has so far avoided signing up to binding relations), with frictionless trade and a close customs relationship that is not a customs union (honest), while remaining free to strike the UK's own trade deals.
The EU is holding fire for now on her plan.
Leaders are mindful of not wanting to further weaken Theresa May at home by rushing forward with their manifold objections - but it's just a matter of time.
The next Brexit negotiating round is pencilled in for a week today.
Now, Downing Street believes that the hot water the prime minister is in today will shock EU leaders into realising they need to start compromising themselves - not just perpetually demanding capitulations on the UK's red lines.
Privately, key EU figures admit there will be some give from Brussels - eventually. But how much?
Certainly not what would be needed to make Theresa May's proposed third way for Brexit work as she currently presents it.
"On the one hand, it's true what Downing Street says," one EU source told me. "The UK is bigger than Norway and strategically, politically and economically more important to us than Switzerland, yes. But EU countries benefit more from keeping their club - the single market and customs union - intact, than they would do by compromising everything just for the sake of better bilateral relations with the UK after Brexit. You can forget it."
The EU definitely expects more concessions from Theresa May in negotiations if she wants what she describes as a deep and special partnership post Brexit.
But the bottom line in Brussels is: hard or soft, Brexit must be done in time.
Whether Theresa May or another is at the helm in the UK, EU diplomats say they need a leader who has to power to make a deal in Brussels and see it through back home.
Otherwise, they believe a disorderly no-deal Brexit beckons - with all the consequences they think that will have in the UK and across the EU.

Business groups have said they are "devastated" after Parliament's latest rejection of the prime minister's EU withdrawal plan.
They urged MPs and the government to find a solution and stave off the "nightmare" of a no-deal Brexit.
"The UK's reputation, people's jobs and livelihoods are at stake," said CBI deputy director-general Josh Hardie.
And the Institute of Directors' Edwin Morgan said businesses were "sick" of being stuck in "spirit-sapping limbo".
Mr Morgan, the IoD's interim director-general, said: "The Brexit merry-go-round continues to spin, but the fun stopped a long time ago."
MPs are set to have another go at reaching a Brexit compromise in another series of votes on Monday and Wednesday next week.
Stephen Phipson, chief executive of manufacturers' group Make UK, said: "Business is devastated that after two years of negotiations, months of increasing uncertainty and weeks of building frustration, after three attempts the withdrawal deal has not been agreed by the House of Commons.
"This now makes the nightmare of a no-deal scenario more likely than ever."
Helen Dickinson, chief executive of the British Retail Consortium, said businesses were "paying the price of the political uncertainty".
"There are still options open to MPs and they must get behind one of them," she added.
The Food and Drink Federation's chief executive, Ian Wright, said Parliament had to lead the country out of "our current shambles" by seeking a long extension to the UK's EU exit.
"Business - particularly food and drink - requires a stable operating environment and a clear path forward. On Monday, Parliament must create both," he said.
The ADS Group, which represents the aerospace and defence sectors, said that if there was not sufficient support for Theresa May's deal, the UK should "pause and reset the process".
ADS chief executive Paul Everitt said: "It is for government and Parliament to decide the way forward, but the voice of UK businesses, their employees, customers and suppliers must be given greater priority."
Small business representatives also reacted with dismay to the political deadlock over Brexit.
The national chairman of the Federation of Small Businesses, Mike Cherry, said: "Our small firms are sick and tired of politicians debating and dithering over Brexit. They are trying to get on with their jobs and it's time that politicians get on and do the same."

Time is running out on Brexit, and the UK should remain in a customs union with the EU, the CBI has warned.
Carolyn Fairbairn, head of the UK business group, said there was a "lack of clarity" surrounding ongoing talks about the future of UK-EU trade.
Speaking on ITV's Peston on Sunday, she also said a customs union would be best for UK economic growth and prosperity.
The UK's Department for Exiting the EU said Brussels had an "ambitious free trade approach" to exit discussions.
"We are confident of negotiating a deep and special economic partnership that includes a good deal for financial services - that will be in the EU's best interests, as well as ours," a spokesman said.
But they added "as the prime minister has already made clear, we will be leaving the single market and the customs union after EU exit day", referring to 29 March 2019.
Being a member of a customs union means that once goods have cleared customs in one country, they can be shipped to others in the union without further tariffs being imposed.
Businesses have been calling for clarity on what a replacement system will involve.
In a speech at Warwick University on Monday CBI director general Ms Fairbairn will elaborate on her concerns, and say progress is needed on a transitional EU trade deal by April.
She will also say the framework for a future business trading relationship with Europe must be set out by October.
Theresa May has already rejected full membership of the customs union as it could prevent the UK striking its own post-Brexit trade deals.
But Ms Fairbairn will say: "There may come a day when the opportunity to fully set independent trade policies outweighs the value of a customs union with the EU.
"A day when investing time in fast-growing economies elsewhere eclipses the value of frictionless trade in Europe. But that day hasn't yet arrived."
Remaining a member of a customs union "for as long as it serves us to do so is consistent with the result of the referendum and would be good for EU firms too" she will add.
Ms Fairbairn will set a 70-day deadline for a written agreement on a transitional trade deal between the UK and EU.
"Decisions must be taken fast, or firms will have no choice but to trigger their plan Bs," she will warn.
"More jobs and investment will leave our shores and future generations will pay the price."
But Richard Tice, Co-Chair of campaign group Leave Means Leave said:  "Only by leaving the customs union can the UK forge new independent trade deals with the rest of the world. Remaining in a customs union with the EU will eliminate major economic benefits of Brexit.
"Remaining in a customs union will handcuff all of British businesses to bureaucratic EU red tape even though approximately 90% do not trade with the EU. This is one of the major benefits of leaving."

Sections of UK industry face extinction unless the UK stays in the EU customs union, the CBI president has said.
He said car firm bosses had come to him saying the industry would suffer unless we get "real frictionless trade".
Paul Drechsler also said there was "zero evidence" that trade deals outside the EU would provide any economic benefit to Britain.
The government said it was "focused on delivering a Brexit that works for the whole of the UK".
But Mr Drechsler blamed a "tidal wave of ideology" for the government's Brexit approach.
"If we do not have a customs union, there are sectors of manufacturing society in the UK which risk becoming extinct," Mr Drechsler said.
"Be in no doubt, that is the reality."
Mr Drechsler, who is due to step down from his role next week, said car industry bosses were concerned that greater costs caused by the imposition of trade tariffs and delays at the border would affect not only individual companies, but also the entire supply chain.
He added that the UK would be much better using the scale of the EU to negotiate trade agreements than going it alone.
"There's zero evidence that independent trade deals will provide any economic benefit to the UK that's material. It's a myth," he said.
Delays to business investment were also affecting the UK economy, he said.
"We already know tens of millions, in fact hundreds of millions have been invested by UK pharmaceutical and finance companies to create continuity post a worse-case Brexit scenario. Tens of millions. What could we have done with that money?" Mr Drechsler said.
The government has not given business the necessary clarity to make investment decisions, he said.
"We have a negotiation within the UK government that's gone on for nearly three years. We still haven't got clarity about the future direction, about where we're heading, what will the future relationship with Europe be, at a level of detail that matters for investment."
Brexit campaigner Patrick Minford, of the Economists for Free Trade group, said the CBI was "the voice of the large industrial vested interests that oppose the competition and productivity growth that free trade under Brexit will bring, as well as the fall in consumer prices that goes with it".
A  Department for Exiting the EU spokesperson said the government would soon publish a White Paper with "detailed explanations of our ambition for a future relationship with the EU".
Correction: This article has been amended to reflect that Mr Drechsler was referring to 'sectors of manufacturing' which 'risk becoming extinct' rather than the car industry specifically.

A vote in Parliament to seek a delay to Brexit could only be "a stay of execution", according to business group the CBI.
Industry bodies saw a glimmer of hope in the vote, but said the UK could still crash out of the EU with no deal.
The British Chambers of Commerce said the vote "leaves firms with no real clarity on the future."
The pound fell a third of a cent against the dollar immediately following the vote.
The fall follows a climb to nine-month highs against the US dollar and a nearly two-year high against the euro after a vote on Wednesday.
The House of Commons voted by a majority of 210 for Theresa May to request an extension to the two-year Brexit negotiation process, pushing the EU exit back from its current 29 March deadline, as long as the 27 other European Union states agree.
The latest vote came after MPs rejected Theresa May's withdrawal agreement for the second time and then ruled out a no-deal Brexit.
Mrs May will now renew efforts to get her Brexit deal approved by Parliament.
She is putting pressure on MPs to back her by threatening a longer delay if they vote against her.
However, business groups remained sceptical about the Brexit process.
Josh Hardie, CBI deputy director-general, said: "After an exasperating few days, Parliament's rejection of no deal and desire for an extension shows there is still some common sense in Westminster. But without a radically new approach, business fears this is simply a stay of execution."
Helen Dickinson, chief executive of the British Retail Consortium, said: "Britain stands on a knife edge. Parliament must put an end to this uncertainty."
"Without definitive action by MPs in the next six days, we will see the UK crashing out of the EU on 29 March without a deal."
Brexit uncertainty has had mixed effects on the UK economy.
Retail spending slowed sharply towards the end of last year, while surveys suggest an increase in manufacturing has largely been driven by companies speeding up production due to the risk of no-deal disruption.
Business investment has been one casualty of the uncertainty, with a slow down in December recorded by the Office for National Statistics.
It said that investment had fallen quarter on quarter all through the year for the first time since the economic downturn of 2008 to 2009.
The Bank of England ascribed the falls to "rising uncertainty, mostly related to concerns around Brexit".
Business groups have been increasingly exasperated by a lack of progress in Parliament on Brexit.
Dr Adam Marshall, director general of the British Chambers of Commerce (BCC), said: "Once again, businesses are left waiting for Parliament to reach a consensus on the way forward and are losing faith that they will achieve this.
"In the meantime, firms are continuing to enact their contingency plans, anxiety amongst many businesses is rising, and customers are being lost.
"Businesses, jobs, investment and our communities are still firmly in the danger zone."
Catherine McGuinness, policy chair of The City of London Corporation said: "The clock is ticking. Further delays will mean households and businesses remain hostage to the crippling economic uncertainty that has already plagued them since the referendum."
Tech industry body TechUK said "We remain days away from a chaotic exit from the EU."

A customs proposal aimed at preventing a hard border in Ireland after Brexit has been agreed by cabinet.
Ministers signed off on the "backstop" that would see the UK match EU tariffs after 2020, if there is no deal on their preferred customs arrangements.
Brexiteers fear the proposal amounts to staying in the customs union longer.
No 10 says the UK would still be able to sign and implement trade deals, and the measure would only last for a matter of months.
The UK is due to leave the European Union in March 2019, after which a 21-month transition period is due to begin, which aims to smooth the way to a post-Brexit relationship between the UK and EU.
Government sources have told the BBC's political editor, Laura Kuenssberg, that the newly-agreed proposal was very unlikely to be needed - as they are confident a customs deal that avoids bringing back a hard border can be agreed with the EU.
Earlier, Irish PM Leo Varadkar said ensuring there was no hard border between the Irish Republic and Northern Ireland was "an absolute red line" for the Irish government.
"We need that [backstop] to be part of the withdrawal agreement, and if it's not, then there will be no withdrawal agreement and no transition period."
After meeting Mrs May at an EU summit in Bulgaria on Thursday, he said he expected the UK to table new proposals within weeks but warned: "Resolving the issue of avoiding a hard border requires more than customs."
Mrs May said they had held a "very constructive" meeting, adding: "The commission published a fallback option which was not acceptable to us and we will be bringing forward our own proposal for that fallback option in due course."
She also met European Commission President Jean-Claude Juncker, and European Council President Donald Tusk.
The government's new proposal is expected to be discussed formally in Brussels next week.
Ministers are yet to settle on what permanent model they want to see replace the customs union when the UK leaves the EU.
They are under pressure to decide on their policy before a key EU summit in June.
Labour Shadow Brexit Secretary Sir Keir Starmer called the situation "farcical", saying: "The government is fighting over two options, neither of which are going to work, neither of which are acceptable to the EU, and neither of which would have the support of the majority in parliament."
He added: "We need certainty and the right approach is to stay in a customs union with the EU as the long-term objective."
The UK is due to officially leave the EU on 29 March 2019, with a transition period until the end of 2020 intended to smooth the way to the permanent new relationship.
But the two sides have just five months to get an agreement on post-Brexit trade, so it can be ratified before Britain leaves in March next year.
Key to this is how the UK and EU's customs systems will work together in years to come.
Currently, the UK is in the EU's customs union, which means member states all charge the same import duties to countries outside the EU.
It allows member states to trade freely with each other, without burdensome customs checks at borders, but it limits their freedom to strike their own trade deals.
The UK government has said it wants to leave the EU customs union in order to strike its own trade deals with other countries, promising trade will still be as "frictionless" as possible.
But ministers do not agree on how to replace it.
Brexiteers are against Mrs May's preferred option of a "customs partnership", under which the UK would collect tariffs set by the EU customs union on goods coming into the UK on behalf of the EU.
The alternative proposal would rely on technology and advance checks to minimise, rather than remove, customs checks. The EU has expressed doubts about whether either option would work.
On Wednesday, senior ministers acknowledged there has been "serious criticism" of both proposed models.

Apart from Michael Gove only narrowly avoiding a bus on Whitehall as it broke up, on the face of it the meeting tonight was rather uneventful.
No decisions were taken. There were, as yet, no resignations. No-one, I'm told, even had a big strop. Honestly!
But after two years of huffing and puffing and haggling, one thing is becoming clear.
The prime minister has always said that the UK could not accept staying in the customs union.
But there are signs that the UK is considering whether to stay in an almost-identical arrangement for good, if a wider trade deal can't be done.
You guessed it, it's all about Northern Ireland again. And regular readers here will know that avoiding a return to the borders of the past has for months been the biggest headache.
In theory if, as Number 10 hopes, a super-duper trade deal can be done, then you don't have to worry about it.
But there are such doubts about that happening in time, that the backstop argument is politically vital.
Here's what might be good news for the UK.
The negotiators seem to have persuaded the EU that if the trade deal isn't done by the end of 2020, then the whole country, not just Northern Ireland, should stay in what's essentially the customs union (even though it would probably be known by another name).
This hope was set out months ago under the so-called Temporary Customs Arrangement.
There was a row in cabinet then about whether it needed to include a time limit. In the end, it did have one written into it, after threats of resignations.
Back then, the EU just would not accept that kind of arrangement for the whole country. Brussels' alternative backstop proposal would basically carve off Northern Ireland.
They have now, it seems, accepted the notion of a customs union for the whole country as part of the deal.
But they are not budging on giving that to the UK with a time limit too.
For several cabinet ministers, that's simply not acceptable. The Brexit Secretary himself is on the record saying as much.
Brexiteers have long argued that if the UK stays in the customs union, it's hardly like leaving the EU at all.
And at the meeting today, several ministers, including Dominic Raab, Liam Fox, Jeremy Hunt and Michael Gove made that concern plain, not just because there are questions about whether it's the right thing to do, but also about whether it could clear the House of Commons.
Brexit: All you need to know
And at least one cabinet minister, Andrea Leadsom, is thinking carefully about whether she could put up with such a compromise. Essentially that's code for deciding whether to resign.
At the meeting this afternoon, I'm told the prime minister did not explicitly tell her colleagues she was planning to do this, rather she was sounding them out.
But in other briefings today, officials are understood to have been rather more clear, saying that Number 10 stands ready to accept a backstop with no explicit time limit.
None of this is at this stage being officially confirmed.
But it's clear tonight that Number 10 is considering whether what was once seen as an unpalatable step to take, is the reasonable price for a deal.
One senior government figure suggested to me months ago this was the only eventual outcome. But the prime minister's critics will come roaring out if and when she makes that clear.
PS: Number 10 won't comment officially
PPS: Those of you who have really been paying attention will know this is separate to the other big problem in the potential compromise, increasing the number of checks on goods moving between Britain and Northern Ireland.
That's a different headache for Theresa May and no less problematic.

It is pretty clear how it all went wrong yesterday.
But as we left Brussels in the pitch black this morning we're still in the dark about what happens next, and how Theresa May can get this whole process back on track, and smartish.
While it's not the end of the potential overall deal if the two sides can't move on to the next phase of talks at the summit next week, it is what both sides desperately want.
The longer it takes, the more risk there is of course of other parts of yesterday's draft being unpicked. The idea was, remember, to lock in the agreement so far, then get on with the rest. It isn't clear what happens next though.
There are some big political and practical questions to ask. (If you are not very interested in the minutiae of all of this, look away now.... but guess what, it's not just about a fight with her allies in Northern Ireland, but her friends and rivals around the cabinet table too).
1. How can Theresa May get the DUP back on board quickly?
There is a dispute over whether or not they had seen the full text of the draft agreement yesterday.
Some sources say they hadn't seen the whole thing, therefore they hadn't seen the full context of what was being said, and flew off the handle over the initial leaks from Brussels over what had been agreed, the UK government "conceding" on the border as MEPs outside the Commission building told us before May even arrived.
While it's clear the DUP was in close contact with the government it is possible to believe they hadn't seen the whole text complete with the caveats, because even senior officials involved in the talks weren't allowed to have electronic copies of the document, only hard copies.
And as there had been lots and lots of changes to the text over the weekend, it's not impossible to imagine that the final, final, final version that then emerged had not been shown in full to the DUP.
Others in government suggest the DUP had seen it all, and as we reported last night, the Tory chief whip told the PM it was all signed off. If that's the case, it is a much bigger political problem of trust for the PM, if the DUP had been kept in the loop and given their approval, but then threw their toys out of the pram.
It's not clear whether the PM and Arlene Foster will meet in the next couple of days in person, but from late last night talks between the two sides were under way.
But with such strong objections on the record now, it is very difficult to see how the DUP can just say, ok then prime minister, when we said we couldn't back it, we really meant that we could, unless there is a change in the language in the text that has already taken weeks of painful negotiation to agree. It's said there are three different policy options that could provide a fix, but this feels more like a battle of wills.
And don't forget, there are a number of Tory MPs who agree with them. The idea of close "alignment", is anathema to some Conservative Brexiteers too.
There is however a very big difference between allowing Northern Ireland to choose to keep cooperating in some sectors and write that into the deal, and imposing a much bigger change where it essentially stands alone from the rest of the UK, and is pushed much closer to the EU.
2. This morning it feels pretty much impossible for the other side, Dublin, to back down in any way.
Irish leader Leo Varadkar, who is in the middle of a political whirlwind of his own, went public yesterday to make it clear that there was indeed an agreed text, and that there was no way that it could be unpicked.
Beyond the reassurances on policy that the Irish so desired, to change tack politically and suddenly give back the concessions that appear to have been so hard won seems extremely unlikely to happen.
3. It's worth pondering too whether the EU pushed the Republic of Ireland, or the Republic of Ireland pushed the EU, too hard?
The last week or so have been the moment of maximum leverage for the Republic of Ireland and they have squeezed every drop out of it. But if, with the EU's backing, they have pushed May into an impossible trap, no one will win. Several weeks ago a senior government official suggested to me that we should be worried about France and Germany underestimating the PM's political difficulties.
If the calculus became impossible for her to stay at the table, there was, they feared, no guaranteed way of her being being able to "get back in the harness". Because we are leaving the EU, the old expectations that the UK will always be able to keep talking, to keep going, don't apply any more.
4. Is the only way out then for the prime minister to face down her allies?
Perhaps, indeed, but why didn't she do that yesterday? There was not due to be a vote in Parliament on the suggested deal at the end of phase one. There was no moment on this specific issue when she required the DUP's backing. Northern Ireland is yet to receive the bulk of the billion that was promised to them after the DUP did a deal with the government.
One insider wondered aloud yesterday why she just hadn't dared them to take her on. The DUP will try to max out its influence at every stage and won't give up easily. The government knows how hard they can negotiate, after they spun out their confidence and supply agreement with No 10 over many days in the summer.
But when the stakes are high, the one thing the Northern Ireland contingent truly don't want is a Jeremy Corbyn government. And if Brexit is completely derailed, arguably that risk for the DUP and the Tories moves into view. And above all, if all the PM has really promised is voluntary alignment in some sectors that shouldn't be hypothetically impossible to agree, if she really demands it.
5. The amount of trouble the prime minister is in also depends what the cabinet demands to know this morning, and what the promises over "alignment" really amounted to.
While the crucial paragraphs over the Irish border did emerge into the public, the text of the whole document is still a secret.
The suspicion in some circles is that Theresa May and Olly Robbins, her top EU official, might have been suggesting that "regulatory alignment", where the rules in the UK mirror very closely those in the EU, was an option, not just for Northern Ireland, but for the rest of the country, or at least some sectors of the economy.
That had not been scoped out by the Brexit department, it's suggested, let alone signed off by the cabinet.
Round that table, be in no doubt, there are very different views over how close the UK's "alignment" should be. If Brexiteers Michael Gove, Boris Johnson and others feel this morning that the prime minister somehow tried to bounce them into agreeing to a future outside the EU where the UK was permanently bound tightly to Brussels, expect fireworks at home.
That could end up being much more troublesome for Theresa May than the behaviour of the Northern Ireland party whose votes she needs.
No 10 sources say the suggestions that the PM wants alignment for the whole of the UK are wide of the mark. But Brexiteers are likely to demand reassurance.

Can a Conservative and DUP pact possibly govern for the life of this Parliament? They face a long, precarious high wire act if they attempt to do so, and they - and any alternative alliance - will be beset by troubles and entanglements at every turn.
Armed with a combined majority of three MPs, their pact would also be bolstered by the absence of the seven Sinn Fein MPs who continue to refuse to take their seats, and probably by the support of the independent unionist, Lady Sylvia Hermon.
But those numbers assume all MPs toe the party line in every vote. And that looks unlikely.
Imagine you are Tory MPs Zac Goldsmith - with a majority of 45 votes - or Theresa Villiers - who has a majority of 353 - or one of the legion of other Conservatives who have just scraped in - often having seen apparently comfortable majorities dissolve.
Suppose you are asked to support a measure which could have constituency consequences, like a squeeze on school funding, or a hospital downgrade. It's easy for the opposition parties, they can oppose.
However, you face a choice between braving the wrath of the government whips, or providing your local opponents with a new stick with which to beat you.
Nobody knows what those particular individuals would do, when confronted by such a choice, but it is a fair bet that some Conservative MPs might be prepared to defy the whip - and it would only take a handful, fewer even than in the last Parliament.
The same problem applies to infrastructure mega-projects - can a government with such a small majority deliver the next phases of HS2 or Heathrow expansion?
Then we come to Brexit. This election was supposed to be about strengthening the prime minister against inimical anti-Brexit forces in Parliament. Yet she emerges far weaker.
I question whether the new government can cobble together a majority for any version of Brexit - hard, soft, poached, scrambled, or devilled with Tabasco sauce - without losing the support of some Conservative MPs, and potentially losing a Commons vote.
The DUP factor matters here.
Remember the DUP are a Northern Ireland party, with deep concerns about maintaining a "frictionless" border with the Republic of Ireland, which could complicate the ultimate deal, possibly dragging the government into a deal which could arouse the ire of Conservative Brexiteers, if it did not ditch the European Court of Justice, or if it involved unacceptable payments to the EU in return for market access.
The other aggravating factor about the DUP is its coldly transactional approach.
Of course they have a policy agenda - but they also want what the Americans call "pork". Extra funding for all things Northern Ireland, more powers for the NI Executive - if it can be reconstituted - localised tax concessions, you name it. And some of these things would have to come at the expense of English constituencies.
It is worth remembering that the last time a UK government was sustained by Northern Irish votes, it didn't end well.
James Callaghan's minority Labour government of the mid 1970s survived, hand to mouth, for years until Callaghan could no longer stomach the endless deal-making. He might have survived the famous 1979 Commons no confidence debate, if he'd been prepared to fund a gas pipeline to Northern Ireland, but he'd had enough.
Half way through the election campaign I was hearing that the government's chief whip, Gavin Williamson, had embarked on a tour to meet and mark the cards of the candidates who were expected to win in the predicted Tory landslide.
Most will not be arriving, and if he stays in post, his job will be the kind of extreme whipping last seen when Callaghan's legendary parliamentary ringmaster, Walter Harrison (the hero of James Graham's great play This House) ducked, dived, manoeuvred, cajoled and arm-twisted to keep the minority Labour government in power.
On one level it was one of the most brilliant whipping performances in Parliamentary history; on another the spectacle of endless wheeler-dealing may have worsened Labour's ultimate electoral crash, when the government finally fell.
Now, Mr Williamson, or his successor, will have to hold the Tory factions together, possibly through a divisive leadership battle.
He will have to soothe ideological and Brexit divisions, and smooth the ruffled feathers of ministers who were said to be facing removal from the cabinet - as well as ex-ministers dropped when the prime minister took over.
An early test will be the appointments to her new government. Will unifying figures like the 1922 Committee Chairman Graham Brady be brought into the fold? Will dangerous luminaries of the David Cameron years - such as former chief whip Mark Harper - return to government. There are, at least, vacancies to fill.
If the government can dance with sufficient agility, it might be able to survive for a fair while. But there is a difference between survival and governing.
The Brexit clock is ticking, the economy needs attention, and the world is a dangerous place. Decisions are unavoidable, but getting them through the Commons may prove impossible.
And at some point another election may become unavoidable, too.

Cross-party talks are continuing in Whitehall, amid parliamentary deadlock over Theresa May's Brexit deal. So what are the sticking points and can Labour and the Conservatives reach an agreement?
Public statements on the talks have tended to be bland, ranging from "constructive" and "serious" to the slightly more negative: "We have some way to travel."
Behind the scenes, the prospect of a deal, while difficult, is not impossible.
There is a big incentive for both sides to reach agreement: the avoidance of next month's European elections.
Prime Minister Theresa May doesn't want to give a platform to parties such as Nigel Farage's new project which could appeal to Brexit-voting Conservatives.
And, frankly, some of her own activists would be conflicted over how, or whether, to vote.
For Labour leader Jeremy Corbyn, awkward questions about a second referendum could be ducked if there is no election campaign.
So the talks are serious and not just political window dressing, and the fact that Mr Corbyn and Mrs May met on Thursday is significant.
The Labour leader's policy guru Andrew Fisher joined shadow chancellor John McDonnell for the cross-party talks on Friday.
But, as I understand it, significant hurdles remain. Some of the detail of possible changes to the Political Declaration - the blueprint for the UK's post-Brexit relationship with the EU - is being discussed.
But sequencing is a problem.
Labour wants to discuss legally binding changes to the document, future-proofing it, where possible, against a change of Conservative leader.
Broadly speaking, the government would rather do "the easy bit" first - discussing legislation to protect  workers' rights.
Resolving this tension is key to a deal.
Labour is also keen to secure agreement on a customs union. It is flexible on what it would be called - an "arrangement", for example - and Mrs May hinted on Thursday that the two sides were close on this.
But they are not yet close enough.
The definition of what a customs union/arrangement does is vital to the Labour side.
But the main constraints to a deal may come from Mrs May and Mr Corbyn's parties, rather than their negotiators.
If there is too much compromise on a customs union, Mrs May risks losing more cabinet ministers.
For Mr Corbyn, the pressure from many Labour members is for him to exact a referendum, in return for passing the deal.
So far, the prime minister isn't budging on this.
One way round this obstacle would be to hold a separate vote in Parliament on a referendum, possibly as an amendment to the forthcoming Withdrawal Agreement Bill.
Both Mrs May and Mr Corbyn - who is not an enthusiast for a public vote - believe this would fall.
But some of the Labour leader's shadow ministers - including some who are firmly on the Left - are pushing for a referendum, or confirmatory ballot, to be tied explicitly to any Brexit deal.
So, getting a deal passed would be totally dependent on approving a public vote at the same time.
I am told shadow Brexit secretary Sir Keir Starmer is pressing for a ballot to be part of any final package.
If, in the end, these difficulties can't be overcome then the hope is that both sides will at least agree a parliamentary process for discussing and voting on options which might finally break the deadlock.

A storm is brewing as clouds gather over Bristol Port, with the rain set to fall on tens of thousands of vehicles parked in the port's car compounds, ready for export by ship, or destined for UK dealerships.
It is an apt backdrop for the UK automotive sector's current predicament.
"Brexit has derailed the industry," says Sarwant Singh, senior partner and global head of automotive and transportation at consultants Frost & Sullivan.
"The uncertainty causes people not to buy cars."
The number of cars sold in the UK dropped 5.7% in 2017, according to industry body the Society of Motor Manufacturers & Traders, and ratings agency Moody's predicts a further 5.5% fall this year.
There has been little respite from foreign markets, with exports slipping 1% last year.
Each year, about 80% of the vehicles built in the UK are exported, so smooth international trade relations are vital for the automotive sector's continued prosperity.
But these days, the relations are as choppy as the sea in the Bristol Channel.
Industry executives' main fear is that Brexit will result in heightened barriers to trade, not only with the European Union, but with the rest of the world too, once the transition period ends on 31 December 2020.
The prospect of an escalating trade dispute between the US and its main trading partners, the EU and China, also looms large, after US President Donald Trump's recent threat to tax cars imported into the world's largest market.
"All of Europe is exposed," says Justin Cox, director of global production at consultants LMC Automotive, "but some plants are more exposed than others, and it so happens that several of those are in the UK."
Then there's China, the world's second-largest car market. Trading relations with China are already complicated, and may well be subject to even greater complexity in future.
"A UK-China free trade agreement will be neither easy nor clearly advantageous for the UK," says Bruegel, a European think tank that specialises in economics.
Part of the issue, it says, is that the UK would like to land better trade deals with China when it leaves the bloc than the ones the EU already has in place. But being smaller, the UK will be in a weaker position during trade talks, so there are no guarantees China will be prepared to offer better terms.
On top of this, UK automotive trade with China - and other fast-growing markets such as India, Brazil and Russia - could suffer, depending on the terms of a post-Brexit trade deal with the EU, Mr Singh says.
That's because the UK might not be able to piggyback on the EU's existing bilateral trade agreements with third countries, including those entered into since the Brexit vote with Canada and Japan. Instead, it would face years of protracted trade talks with dozens of countries.
Getting a good Brexit deal is also important because of the interdependence of European automotive companies.
"The motor industry has taken advantage of the EU's single market as much as, perhaps more than, any other industry," says Mike Hawes, chief executive of SMMT.
As a result, EU customers buy about €15bn ($18.5bn; £13bn) worth of British-made cars per year, accounting for some 53% of the UK's vehicle exports, according to the European Automobile Manufacturers Association (ACEA).
Conversely, EU manufacturers deliver 81% of the cars imported by the UK, to the tune of about €45bn, a trade imbalance that Brexit supporters hope will give the UK leverage during trade talks.
At the same time, about 80% of the parts and components used to build cars in the UK are also imported from the EU, while 70% of the parts and components made in the UK are exported to EU countries.
"Any changes to the deep economic and regulatory integration between the EU and the UK will have an adverse impact on automobile manufacturers with operations in the EU and/or the UK, as well as on the European economy in general," the ACEA says.
Hence, both the UK and the European car industries are keen to see a final UK-EU deal that retains frictionless trade in the long-term.
"Anything short of single market membership could be a problem for the UK," says Simon Dorris, managing partner at Lansdowne Consulting.
Free trade is indeed key to future prosperity, not just within Europe but beyond, according to Prof Patrick Minford of Cardiff University, who chairs Economists for Free Trade, a group of pro-Brexit economists.
Its much debated paper, From Project Fear to Project Prosperity, suggests fears of rising trade barriers for carmakers after Brexit are misplaced.
Prime Minister Theresa May has said that Brexit presents an "opportunity to strike free trade deals around the world".
"Auto manufacturers will improve profitability post-Brexit," Prof Minford predicts.
Source: ACEA
Despite the uncertainty about a future trade deal, a number of big carmakers have committed to building more cars in the UK since the Brexit vote, including Nissan, BMW, Toyota, and last week Vauxhall, which is owned by French group PSA.
But Parliament's cross-party Business, Energy and Industrial Strategy Committee is pessimistic, recently warning that "there are no advantages to be gained from Brexit for the automotive industry for the foreseeable future".
The UK prime minister's desire for free trade is shared by the global motor industry more generally.
Executives are nevertheless pragmatic, and accept that although international trade is governed by rules policed by the World Trade Organization, free trade is rarely a reality.
Trade-distorting subsidies and a variety of measures, such as regulatory barriers, internal tax measures, and intellectual property rights, still impede the free flow of goods, even when trade agreements are in place, according to the European Commission.
The EU, for instance, will not import cars unless they meet EU safety and emissions requirements.
Moreover, trade agreements are generally conditional. For instance, cars exported from the EU must be predominantly made within the EU to be allowed free entry into other markets.
Such "Rules of Origin" could complicate exports for UK carmakers after Brexit, as an estimated 55%-75% of the parts and components that make up a car built in Britain are imported, according to Mr Hawes of SMMT.
More from the BBC's series taking an international perspective on trade:
Whatever level of access UK-made cars get to markets around the world after Brexit, the manufacturers ultimately have to try ensure that their vehicles will be popular with overseas buyers.
Mr Hawes says that this is not always easy, citing the fact that the UK's best-selling car is the compact Ford Fiesta, whereas the most popular vehicle in the US is the large Ford F150 pick-up truck.
Consequently, there are reasons to question whether the US market is the most natural one to focus on for UK manufacturers, which tend to produce cars that suit British and European consumers, he observes.
"So it's also about producing the right car for the market," he says, pointing to how Honda is producing the Civic in Swindon for global markets. "They have shown it can be done".

So, he's said it.
Mark Carney made the direct link between "weaker real income growth" and the process of leaving the European Union.
Brexit is likely to make people poorer, the governor of the Bank of England said.
Since the referendum the markets have sold off sterling, making the currency weaker and increasing inflation in the UK.
That means that price rises are now running ahead of wage growth and real incomes are falling again.
Mr Carney's speech at the Mansion House called for an "innovative, co-operative and responsible" approach to Brexit.
"Fragmentation is in no-one's interest," he argued when it came to the key relationship of financial services in particular.
Some might describe that as a plea for a "soft" Brexit - no cliff edge at the end of exit negotiations, rather a "slope" - as the chancellor has described it.
Speaking alongside the governor, Philip Hammond said that no-one voted for Brexit to become poorer.
He also made it clear that he wants to put the economy at the heart of the Brexit negotiations.
Rather than sovereignty or controlling immigration, which are the issues likely to motivate other colleagues in the Cabinet and certainly in the Conservative Party.
The tensions are clear.
The chancellor - strengthened since the general election - gave the greatest detail yet about what his approach might mean for our future relationship with the EU.
Yes, as he said at the weekend, the UK will be leaving the customs union.
But he made the case for a new form of customs agreement with "current border arrangements" - which presumably means agreeing to some form of EU oversight for some years following Britain's exit from the union.
It is nailing down this "transition" or "implementation" period which is important for many businesses.
Some will be relieved that both Mr Carney and Mr Hammond are calling for Britain to play a longer game when it comes to the Brexit process.
Others may fear that tying the UK formally to the EU after Britain leaves the union in March 2019 could mean, for a few years of transition at least, Brexit does not, quite, mean Brexit.

The possibility of a no-deal Brexit is "uncomfortably high" and "highly undesirable", Bank of England governor Mark Carney has told the BBC.
Mr Carney said the prospect of the UK leaving the EU without a deal was "a relatively unlikely possibility, but it is a possibility".
He said it was "absolutely in the interest" of the EU and UK to have a transition period.
Critics poured scorn on the comments, calling them part of "Project Fear".
Mr Carney's warning came ahead of Theresa May's meeting with French President Emmanuel Macron at his summer retreat on a small island off the French Mediterranean coast.
The prime minister is cutting short a holiday in Italy as she continues to seek support among European leaders for her Brexit plans.
The Bank governor told the BBC that the financial system was robust and could withstand any post-Brexit shocks.
"We have made sure that banks have the capital, the liquidity that they need and we have the contingency plans in place," he told the BBC's Today programme.
"There is a very broad range of potential outcomes to these Brexit negotiations and we are entering a crucial phase."
The pound declined on the currency markets in the wake of Mr Carney's comments, falling below the $1.30 mark, but had recovered by early afternoon.
Mr Carney said that if a no-deal Brexit were to happen, it would mean disruption to trade and economic activity, as well as higher prices for a period of time.
"Our job in the Bank of England is to make sure that those things don't happen. It's relatively unlikely but it is a possibility. We don't want to have people worrying that they can't get their money out," he said.
Mr Carney added: "We've put the banks through the wringer to make sure that they have the capital. Whatever the shock could happen from, it could come from a no-deal Brexit, we've gone through all the risks of a no-deal Brexit."
However, he said that even with liquidity and capital, the banks could not solve all Brexit-related financial problems.
"There are a few things the EU government has to solve, " he said.
"The UK has taken all the steps, all the secondary legislation it needs to. The European authorities still have some steps they need to take. We're having conversations and we expect those to be addressed."
Simon Jack, BBC business editor
The governor of the Bank of England doesn't say anything by mistake. Like all central bank chiefs, he knows that his every utterance is subjected to minute scrutiny.
So this warning appears to be a deliberate intervention at a crucial moment in Brexit negotiations from a governor who considers it part of his job to highlight risks to the financial system and the wider economy.
Others consider him too political by half - his previous statements were labelled "beneath the dignity of the bank" by leading Eurosceptic MP Jacob Rees-Mogg.
Mark Carney has been clear that the banking system is resilient enough to handle a no-deal Brexit, but today he made it just as clear that it's a test we should be very keen to avoid.
As he has pointed out in the past, the UK is the financial hub for the whole of the EU so leaving without a negotiated settlement would have serious consequences for both sides.
As government ministers tour the scorching capitals of Europe, Mark Carney has cranked up the temperature at home.
Critics rounded on the governor, with Jacob Rees-Mogg, who leads the Tory pro-Brexit European Research Group, saying: "Mark Carney has long been the high priest of Project Fear, whose reputation for inaccurate and politically motivated forecasting has damaged the reputation of the Bank of England."
The former work and pensions secretary, Iain Duncan Smith, said: "There is no such thing as a no-deal, as the [World Trade Organization] is where the EU and the UK are already and as a rule-based organisation, both sides would have to abide by those rules.
He said the Treasury and the Bank of England had "struggled to understand how this would work".
And economist Ruth Lea, adviser to the Arbuthnot Banking Group, tweeted that Mr Carney was crying wolf and few people would listen.
However, Catherine Barnard, professor of EU law at Cambridge University, said Mr Duncan Smith's idea of falling back on WTO rules would not work, because in that case, the UK would not be allowed to let EU goods in tariff-free without extending that to the rest of the world.
She told the BBC's The World At One programme: "That would make it very difficult for us to negotiate trade deals in future, because we'd got nothing to negotiate over. We'd already given up the right to impose tariffs."
Meanwhile, Gen Sir Nick Carter, the new head of the armed forces, was asked on the Today programme about reports that the army was being put on standby for a no-deal Brexit - which could see troops help deliver food, medicines and fuel.
He said: "There hasn't been any request yet as far as I'm aware."
Pressed if there had been any discussions about a no-deal Brexit, the chief of the defence staff added: "The Armed Forces are always doing contingency planning but we've not been asked that specific question."

Chancellor Philip Hammond has backed a transitional deal for Brexit saying it would be "helpful" to allow longer than two years for the UK's EU exit.
Mr Hammond told the Treasury select committee that there was an "emerging view" that having longer would tend towards a "smoother transition" .
There would be "less risks of disruption" including "crucially risks to financial stability", he added.
However, both business and government would have to make changes, he said.
His comments are being seen as the strongest signal yet from the government that the Brexit process could take a lot longer than the two years needed for the official Article 50 exit process to be completed.
On Monday the Treasury Select Committee called for written submissions on transitional arrangements as part of its inquiry into the UK's future economic relationship with the EU.
It defines "transitional arrangements" as being "any arrangement that takes effect between the point at which the UK formally leaves the EU... and the point at which the UK's final, settled relationship with the EU becomes effective."
"I would not want anybody to think this is just about financial services," Mr Hammond told MPs.
"For example, depending on what future customs arrangements are between the UK and European Union, there could be significant physical infrastructure changes that need to be made at ports of entry and exit, not only in the UK but on continental Europe as well," he added.
He said there could also be a need to train large numbers of people in anticipation of a "much more intensive process at borders.
"So it's not just the business sector, it's also the government sector that has to think about how long it takes to make changes, hire people, train people, introduce IT changes.
"And I think the further we go into this discussion, the more likely it is that we will mutually conclude that we need a longer period to deliver," he  added.
The government position is becoming clearer.
By the end of the Article 50 timetable - which Number 10 believes will be March 2019 - the UK will have legally agreed to leave the EU.
But it will not be like jumping off a cliff edge.
Rather, Britain and the EU will still have a close relationship, with many EU rules remaining in place.
They will slowly be unravelled over subsequent years as Brexit is made a reality.
Committee chairman Andrew Tyrie said it sounded like two years was the "bare minimum, we're probably going to need more."
Mr Tyrie also said he had received briefings from firms about the need for transitional arrangements, including one from a major financial institution which said insufficient time to adjust could result in severe disruption to client services, causing financial instability and significant cost to the wider economy in Europe and globally.
Mr Hammond said he was also hearing about concerns in this area, particularly from the financial services sector.
Later he added that there were "compromises between the political will to get things done and to move on and the bureaucratic and/or business desire to have the largest period possible to make any change".

The UK may not have voted for Brexit if it had not been for "cheating" by the Leave campaign, a former employee of Cambridge Analytica has claimed.
Christopher Wylie said Vote Leave and other pro-Brexit groups had a "common plan" to get round spending controls.
He told MPs they all used Aggregate IQ, a "franchise" of the data analytics firm, to target swing voters, using information drawn from CA's databases.
Cambridge Analytica said it had played "no role" in the Brexit referendum.
The firm accused Mr Wylie, who it said had no "direct knowledge" of its work after he left the firm in July 2014, of peddling "false information, speculation, and completely unfounded conspiracy theories".
And Vote Leave have denied accusations that they broke the spending rules during the UK's 2016 referendum on whether or not to stay in the European Union.
Cambridge Analytica, which is facing claims it amassed the data of millions of Facebook users without their consent and used it in political campaigns, is under investigation by the Information Commissioner.
MPs have said Facebook founder Mark Zuckerberg's decision to decline an invitation to appear before them is "astonishing" amid reports he will testify before a US Congressional committee inquiry into data privacy.
Former Vote Leave volunteer Shahmir Sanni has claimed the official Leave campaign may have used a different pro-Brexit group, BeLeave, to get round spending controls by giving it £625,000 but requiring it to spend the money on Aggregate IQ - a Canadian data firm Vote Leave used for its digital advertising.
Vote Leave, which would have gone over its campaign spending limit of £7m if it had spent the money itself, has denied the claims, which are being investigated by the Electoral Commission.
Vote Leave says that it only donated the money to BeLeave after the Electoral Commission gave it the go-ahead.
Environment Secretary Michael Gove, a key Vote Leave figure, dismissed the allegations, adding that the referendum was a "free and fair vote".
He said: "I think that some of the allegations have already been investigated by the Electoral Commission, twice in fact, and it's clear from those investigations that actually there wasn't anything that went on that was wrong."
Appearing before the Commons Media Committee, Mr Wylie said he was "absolutely convinced" that Vote Leave, BeLeave and other groups were working together and had a "common plan".
"All of these companies somehow, for some reason, all decided to use AIQ," he said.
"When you look at the accumulation of evidence, I think it would be completely unreasonable to come to any other conclusion other than this must be co-ordination."
Mr Wylie told MPs he had met Dominic Cummings, Vote Leave's campaign director, in November 2015, and that shortly afterwards the campaign group had hired Aggregate IQ.
He rejected Cambridge Analytica's assertion that it was not linked to Aggregate IQ, saying that although they were separate corporate entities, Aggregate IQ was essentially a "franchise" of Cambridge Analytica and its parent firm SCL Group.
At the time of their meeting, he said, Cambridge Analytica was working for rival Brexit group Leave.EU and Vote Leave had got the "next best thing" by hiring a firm "that can do everything that Cambridge Analytica can do but with a different billing name".
He said he was sure Aggregate IQ had drawn on Cambridge Analytica databases during the referendum, saying it "baffled" him how a firm in the UK for only a couple of months had "created a massive targeting operation" without access to data.
"You can't have targeting software that does not access the database," he said.
The data, he suggested, was used to aim material to between five and seven million people Aggregate IQ believed could be persuaded to vote for Brexit.
"They were targeting a very specific cohort," he said.
"They posited that if x per cent of these people turn out, they can win. I think it is incredibly reasonable to say AIQ played a very significant role in Leave winning."
On the basis of Aggregate IQ's use of data and political activities in other countries, he said questions had to be asked as to whether it was "compliant" with the law during the referendum.
"I think it is completely reasonable to say there could have been a different outcome of the referendum had there not been, in my view, cheating."
Lawyers for Aggregate IQ have said the firm had "never entered into a contract with Cambridge Analytica" while Mr Cummings said the claims were "factually wrong" and the Electoral Commission had approved donations in the run-up to the referendum.
In a statement, Cambridge Analytica said it had sub-contracted some work to Aggregate IQ in 2014 and 2015 but that claims it worked with them on the EU referendum were "entirely false".
"Beyond an early-stage sales pitch to Vote Leave, Cambridge Analytica had no interaction with that group or any of their vendors," it said.
During a debate later in the Commons, Conservative Sir Edward Leigh suggested the claims of undue influence had been "grossly exaggerated" and the British electorate had had "the good sense to make up their mind" when it came to backing Brexit by a 52% to 48% margin.
But Labour MP Frank Field said that although he supported Brexit, he believed that if offences had been committed "the full weight of the law" should be thrown at anyone found culpable.
Cabinet Office minister Chloe Smith said ministers should not pre-empt the findings of the independent Electoral Commission's investigations into whether any campaigners breached political finance rules.

A former Conservative leader has warned Eurosceptics could "endanger everything they're trying to achieve" if they vote down Theresa May's Brexit plans.
Lord Hague said the proposals agreed at Chequers were "the most that can be achieved within the inevitable and inescapable constraints".
Being a "romantic on this issue" was "an indulgence not a policy", he told colleagues.
The foreign and Brexit secretaries have both quit over the plans.
The resignations of David Davis and Boris Johnson - who said they could not support Mrs May's proposed trading relationship with the EU - have piled pressure on the PM and prompted speculation about a leadership challenge.
But one Brexiteer Tory MP played down the speculation.
Bernard Jenkin said the European Research Group - led by influential Eurosceptic Jacob Rees-Mogg - did not expect more resignations and backed Mrs May's leadership.
The UK is due to leave the European Union on 29 March 2019, but the two sides have yet to agree how trade will work between the UK and the EU after that.
The delay has been partly blamed on deep disagreements within the Conservative Party over what shape Brexit should take.
This has focused on whether the UK should prioritise business interests and keep a close relationship with the EU in order to maintain trade links - which critics say will mean the UK still abiding by EU rules and leaving "in name only".
In a sign of the dissatisfaction in Tory ranks, MP Henry Smith announced on Twitter he had refused an invitation to watch England's World Cup semi-final clash with Croatia at 10 Downing Street because the prime minister "isn't bringing Brexit home".
And the former adviser to Mr Davis, Stewart Jackson, claimed there was a "plan" to curtail the role of the Brexit department and that Downing Street had blocked his reappointment under new Brexit Secretary Dominic Raab.
In the House of Commons, Labour's Emily Thornberry - standing in for Jeremy Corbyn at Prime Minister's Questions - said the Chequers agreement was a "dog's Brexit" that would "satisfy no-one".
Mrs May's deputy David Lidington urged Labour to "work in the common interest instead of carping from the sidelines".
The strategy announced after Friday's meeting at the PM's Chequers country retreat came after months of cabinet divisions.
More details will be set out on Thursday of the proposed model, which has yet to be negotiated with the EU, but it would see the UK agreeing a "common rulebook" with the EU for trading in goods, in an attempt to minimise friction for trade at borders.
Critics say it will leave the UK tied closely to EU rules and prevent it from striking its own trade deals in years to come.
But Lord Hague said it was the best available option.
Speaking on BBC Radio 4's Today programme, he said the balance of the House of Commons was a "limiting factor" to what the UK could propose, as was the need of business for frictionless trade across borders.
And the need to avoid a hard border between Northern Ireland and the Republic of Ireland - which is part of the EU - are not an "inconvenient detail, it's a fundamental part of ending centuries of conflict in the British Isles", he said.
Following Mr Johnson and Mr Davis's resignations, two deputy chairmen of the Conservatives - Ben Bradley and Maria Caulfield - quit their posts on Tuesday, claiming the PM's proposals would not harness the benefits of Brexit.
Lord Hague, who despite being a Eurosceptic backed a Remain vote in the 2016 referendum, said that if MPs voted down the UK's final deal with the EU, "that's the point at which they're going to endanger everything they're trying to achieve".
This could mean Brexit being delayed, a change of government or a second referendum, he said.
"It would be hard to say at this moment what the consequences would be, but the consequences would be very serious for delivering Brexit," he said.
Another leader would face "exactly those same constraints", Lord Hague said.
In a Daily Telegraph article, he added: "Being a romantic on this issue is all very well but is of no practical use to the country. It is an indulgence not a policy."
Theresa May defended her plans as she arrived at a Nato summit in Brussels, saying it had been agreed by the government and "delivers on the vote that people gave on Brexit".
"We deliver that Brexit and we do it in a way that protects jobs and livelihoods and meets our commitment to Northern Ireland," she added.

The cost of cherry tomatoes could increase by more than 10% if there is a no deal Brexit, say growers in southern Spain.
Earlier this week, I visited a vast site near Alicante, where 60 million kilograms of cherry tomatoes are grown, picked and shipped every year and a third of them are bound for the UK.
But growers are worried that a no deal Brexit is going to push up the price we pay for them in the shops.
Jorge Brotons is the commercial director for Bonnysa and deals with all the big UK supermarkets. The business has been growing tomatoes for the UK since 1956.
"We're trying to understand what the different scenarios can be. If there is no deal, we'll have to trade in a different way as tariffs will be applied, new inspections and this means we add new processes to current situations," he says.
Ultimately it means more work, more time, more people to make checks and all that means more costs.
"The cost in agriculture and margins are very very tight, and the history of prices shows tomatoes haven't increased in 15 years," he says.
"With all costs increasing our margins are so tight - we can't absorb any more cost and any more costs in that chain means losses and having to decide to do something else."
We start the day at Bonnysa's vast greenhouse complex which spans a huge valley in northern Alicante. The sun shines brightly and the temperature is around 15 degrees, a reminder of why salad growing here is much easier than in the UK in January.
In the greenhouse we visit, we meet two pickers undertaking the fortnightly harvest. Within 15 minutes they've gathered trays of their bright red bounty and it is on to the factory for processing.
The pickers have no idea how many cherry tomatoes pass across the factory floor per year - they laugh when I ask. And it's not hard to understand why. They're everywhere.
One sorting line spreads them, then photographs them and another separates them. We see all of the big UK supermarkets' labels on the boxes bound for the UK, but I can't tell you who they are as the firms requested confidentiality. For them, it is too sensitive to be heard talking about Brexit - even when it's just tomatoes.
Angel Jiminez is director of exports at Trota, a logistics firms that sends 200 lorries of tomatoes to the UK every week.
So how would a no deal Brexit affect their business? "Right now there is no paperwork involved to cross the border and we can cross easily, but more paperwork means delays. Time is money, more days is more time - and it is the final buyer who pays for everything."
He also says the haulier industry is no where near prepared enough: "Brexit is not going to be easy at the beginning."
Uri is one of the many Trota drivers that transport Bonnysa's cherry tomatoes to the UK. It's Monday and he's just about to begin the 2,000km journey from the Alicante plant, across Spain and France, and on to Britain through the Channel Tunnel.
Eurotunnel is the preferred crossing for most perishable food items, and by volume the tunnel carries more food than car parts because of its speed and access to market. For Bonnysa it is vital that it continues to function smoothly after Brexit, whatever deal is achieved.
At least according to the company that operates the tunnel, firms need not worry.
"Here at Eurotunnel we're ready, soft Brexit, hard Brexit we've been preparing for two and a half years. We've taken the worst case scenario as our goal all the way through," says John Keefe, director of public affairs at Eurotunnel.
"We will be able to deliver our transport system from day one from both sides."
I join Uri in the truck from Calais and we head through the tunnel and into Folkestone for the final leg of his journey - on to the supermarket distribution centre. All in all, it takes just over two and a half days to transport a tomato from Bonyssa's vines to sub-zero temperatures in Dartford.
They'll be on the supermarkets on Friday in time for your weekend salad.
There is zero friction on our journey (apart from some snow), but the concern from Spain is that the introduction of new checks and customs at any point in the trip will add new costs if there's a no deal Brexit - and that means higher prices for UK shoppers, a thought shared by Justin King, former boss of Sainsbury's.
"The nature of our very efficient food supply chain is there is little surplus cost or margin along the way," he says. "The more inefficient it becomes, the ability of suppliers and retailers to absorb that is very limited. They will be passed on to consumers and really quite quickly."

John Bercow says he will stand down as Commons Speaker and MP at the next election or on 31 October, whichever comes first.
Speaking in Parliament, Mr Bercow said his 10-year "tenure" was nearing its end and it had been the "greatest honour and privilege" to serve.
If there was no early election, he said 31 October would be the "least disruptive and most democratic" date.
The ex-Tory MP succeeded the late Michael Martin as Speaker in 2009.
He has faced fierce criticism from Brexiteers, who have questioned his impartiality on the issue of Europe and claim he has facilitated efforts by MPs opposed to a no-deal exit to take control of Commons business.
He has also been criticised for not doing more to tackle allegations of bullying and harassment in the House of Commons.
Mr Bercow himself has been accused of mistreating several members of his own staff, which he denies.
In a break from normal convention, Mr Bercow was facing a challenge from the Conservatives in his Buckingham constituency at the next election - whenever it is called.
His wife, Sally, was in the public gallery as he made his announcement - which comes just hours before Parliament is due to be suspended or prorogued for five weeks.
Mr Bercow said he had decided at the time of the 2017 election that this would be his last Parliament as Speaker.
If MPs reject calls for an early election later on Monday, as seems likely, the Speaker said it was important an "experienced figure" chaired debates in the final week of October leading up to the UK's possible exit from the EU.
The period between 14 October - when the Queen will open the new session of Parliament and the government announces its new legislative programme - and 31 October is likely to be among the most eventful and unpredictable in living memory.
Prime Minister Boris Johnson has said he will not ask for a further Brexit delay and the UK must leave the EU on Halloween.
But, unless he negotiates a new deal acceptable to Parliament, he will be legally obliged to seek a delay under the terms of legislation passed by MPs and which gained Royal Assent on Monday.
There has been speculation that, to avoid this, Mr Johnson could resign or force a vote of confidence which, if he lost, would trigger 14 days of negotiations over forming a new government.
Mr Bercow warned that if the appointment of his own successor was left until after the next election, newly-elected MPs might find themselves being "unduly influenced" by party whips in their choice of figure.
"It will mean a ballot is held when all members have some knowledge of the candidates. This is far preferable to a contest at the start of a Parliament where new MPs will not be similarly informed," he told the Commons of his plans.
"We would not want anyone to be whipped senseless, would we?"
In an emotional speech, he said he had been proud to stand up for the interests of MPs and to act as the "backbenchers' backstop".
"Throughout my time as Speaker, I have sought to increase the relative authority of this legislature for which I will make absolutely no apology to anyone, anywhere, at any time."
Mr Bercow received a standing ovation from the Labour benches after announcing his imminent departure, but most Tory MPs stayed in their seats.
Labour leader Jeremy Corbyn led tributes, saying the Speaker had stood up for and promoted democracy, adding that the "choice and timing" of his exit date was "incomparable".
For the government, Michael Gove said his determination to give MPs increased opportunities to hold the government to account were "in the best tradition of Speakers".
When he was first elected, Mr Bercow said he intended to serve no more than nine years in the job.
The Speaker is chosen by all MPs in the House by secret ballot.
For many years, the role alternated between the two largest parties although this unwritten convention was broken in 2000 when Labour's Michael Martin succeeded his colleague Betty Boothroyd.
Potential Labour successors to Mr Bercow include Commons deputy Speaker Lindsay Hoyle, who announced his candidacy on Twitter.
Labour's Chris Bryant and Conservatives Sir Edward Leigh and Eleanor Laing, also a deputy speaker, have also announced they will stand.
Other possible contenders include Harriet Harman, the former Labour deputy leader and the longest-serving female MP in the House.

The House of Lords voting to reject the government's existing plan for how customs will work after we leave the EU was as surprising as the sun rising in the morning and setting at night.
Why it mattered was the political encouragement and cover it gives to Conservative rebels who are considering defying Theresa May on the issue in the Commons next month.
The extent of the Lords defeat last night gave succour to MPs from different parties who are working closely together to try to change the government's current position of avoiding any form of customs union once we are completely out of the EU.
Ministers had hoped to avoid the nightmare of holding a vote on the issue in the Commons until next month, giving more time to get likely rebels on board, more time to persuade and cajole.
The fact is, as the government knows full well, if there was a one-off vote on the issue with no other strings attached, most MPs would probably choose to stay in some form of customs union.
Despite strong feelings in Number 10 and among Brexiteers that such a policy is unacceptable, the Parliamentary arithmetic on the green benches is against them.
But no more will ministers be able to run from the issue.
It's just emerged that a powerful cross-party group of MPs is to force a vote on a customs union next week.
The Liaison Committee, made up of Labour, Conservative, Lib Dem and SNP select committee chairs, has tabled a debate for next week calling for "an effective Customs Union".
The MPs, including Yvette Cooper, Nicky Morgan, Sarah Wollaston, and Hilary Benn, are voices who carry credibility with them.
The vote would not be binding on ministers, but will ratchet up the pressure on Number 10 to shift its position if, as seems likely, the numbers go against the government.
And, remember, there are ministers in government, even though they are probably a minority, who also believe that in the end, staying in some form of customs union is the way to go.

To govern is to choose. The prime minister has now chosen to exercise her power over the constitution, reserved to Westminster under the Scotland Act 1998.
This is about competing power, competing mandates, competing interpretations of the verdicts delivered during the European referendum last year.
Theresa May accords primacy to the Brexit negotiations. She says she does not want even to contemplate the prospect of indyref2 during that period. That means she will not countenance a transfer of powers under Section 30 of the Scotland Act, again at this stage.
Nicola Sturgeon accords primacy to the impact upon Scotland of the Brexit process. She says it is undemocratic for the PM to refuse to give Scotland a meaningful choice - that word again - within a suitable timescale, proximate to the Brexit plans. It is sinking the ship and puncturing Scotland's lifeboat.
But this is also about political confidence. Political calculation. Ruth Davidson, the Scottish Conservative leader, plainly calculates that she will have Scottish public opinion on her side. Or, more precisely, a sufficient quotient of public opinion.
The Tories in Scotland have been through a period where they were the party which dared not speak its name, the toxic party. They now reckon those days are behind them. And why? The Union, post-2014.
Their calculation - and it is an arithmetical sum - is that they can corral behind them the supporters of Union in Scotland. That, just as in the past, in the 1950s for example, they can draw backing from a relatively wide range of Scottish society, predicated upon concrete support for the Union - and fixed opposition to the SNP.
It worked, to a substantial degree, in the last Holyrood elections when they became the largest opposition party. Their calculation is that it will work again, this time.
Will there be anger in some quarters at the Prime Minister's decision? There will indeed. Stand by for demonstrations to that effect at the SNP conference in Aberdeen.
But the calculation by the Tories - and this is less quantifiable, but a calculation nevertheless - is that sufficient numbers of the populace in Scotland will be relieved that they do not have to decide on independence in the next 18 months to two years.
The Tory leadership insists that they are not blocking a referendum entirely. That was Ruth Davidson's answer when she was reminded that she had told my estimable colleague Gordon Brewer in July last year that there should not be a constitutional block placed upon indyref2.
The argument was that they are merely setting terms: evident fairness and discernible popular/political support for a further plebiscite.
However, these are not absolute, they are open to interpretation. It would seem to be that the verdict on these factors would also lie with the Prime Minister. Such is the nature of reserved power.
But, again, the Tory triumvirate - PM, secretary of state, Scottish leader - stress that a referendum might be feasible once Brexit is signed, sealed and settled. David Mundell seemed particularly keen to stress that point.
However, if they won't contemplate Section 30 meantime, then the time needed for legislation, consultation and official preparation would suggest that - by that calendar - any referendum would be deferred until 2020 or possibly later. Possibly after the next Holyrood elections.
Options for the FM? She could sanction an unofficial referendum, without statutory backing. Don't see that happening. It would be a gesture - and Nicola Sturgeon, as the head of a government, is generally averse to gestures. Unless they advance her cause.
She could protest and seek discussions. Some senior Nationalists believe this to be a negotiation ploy by the PM, the prelude to talks.
Will the first minister proceed with the vote next week at Holyrood, demanding a Section 30 transfer in which the Greens are expected to join with the SNP to create a majority? I firmly expect her to do so, to add to the challenge to the PM.
Beyond that, expect the First Minister to cajole, to urge - but also to campaign. To deploy this deferral of an independence referendum as an argument for…an independence referendum. She will seek public support, arguing that Scotland's interests have been ignored. Just as Ruth Davidson will seek public support, arguing that she is protecting those interests.
Final thought. One senior Nationalist suggested to me that delay might, ultimately, be in the SNP's interests: that people were already disquieted by Brexit and would prefer a pause. Perhaps, perhaps, perhaps, to quote the old song.

Tory MP Nick Boles, who quit his local party on Saturday over his stance on Brexit, says his priority lies with his constituents and he will not be "bossed around by a small number of people".
He told the Andrew Marr Show he thought about standing as an independent MP.
But he said he had decided to remain as he was not "ready to give up on the Conservative Party yet".
Mr Boles, MP for Grantham and Stamford, has been an outspoken critic of leaving the EU with no deal.
The MP - who is in favour of a closer Norway-style relationship with Europe - said he was "proud" of his role in the cross-party campaign to force the prime minister to request an extension to Article 50 beyond 29 March, and to block a no-deal Brexit.
But Councillor Martin Hill, vice president of the Grantham and Stamford Conservative Association, told members they had been "betrayed by their parliamentary representative", calling on him to take the "honourable course" and quit as an MP.
Mr Boles said a "certain amount of pressure was applied" by the local party after he was asked to tell them if he intended to stand as their representative at the next general election.
But he told the BBC's Andrew Marr: "I represent 100,000 people in Parliament. I have roughly 500 members in my local association and roughly 60 people on my executive.
"I'm afraid I'm going to claim the right to interpret what is in the best interest of the 100,000 people I represent and I'm not going to be bossed around by a very small number of people with very ideological views."
Despite leaving the local association, whose members he wrote to this weekend, Mr Boles said he remains loyal to the party.
He said: "I have voted for Theresa May's deal every time it has been offered and I will vote for it again on Tuesday.
"The only thing and, in truth , the real area where I fell out with some members of my association, was in my efforts to stop a no-deal Brexit - and obviously I was very much involved in this plan that reached its fruition last week to stop a no-deal Brexit."
He said he had been told he could continue as a Conservative MP, with his membership being transferred from his local party to the national party. He is to meet the chief whip on Monday.
His announcement came after a busy week in Westminster, when MPs voted to seek a delay to the UK's departure from the EU.
The third "meaningful vote" on Prime Minister Theresa May's deal is expected to take place next week. If it is agreed, she has promised to seek a shorter extension to the departure date.
But if it does not gain support, she has warned a longer extension may be needed - and the UK might have to take part in European elections.

Conservative Eurosceptics have launched a new attempt to change the government's Brexit strategy by targeting a key piece of legislation.
Amendments tabled to the customs bill threaten to undermine Theresa May's plan for future UK-EU relations.
Some Brexiteers are unhappy at the plan, agreed by the cabinet at Chequers last week, saying it will keep the UK tied to EU rules.
The PM says it honours the Leave vote and protects jobs.
With numbers tight in the Commons, the prime minister - who relies on Northern Ireland's DUP to win key votes - would be vulnerable to any rebellion among Eurosceptic MPs as she tries to pass key laws needed for Brexit preparation.
The UK is due to leave the European Union on 29 March 2019, but the two sides have yet to agree how trade will work between the UK and the EU after that.
The delay has been partly blamed on deep disagreements within the Conservative Party over what shape Brexit should take.
This has focused on whether the UK should prioritise business interests and keep a close relationship with the EU in order to minimise friction for cross-border trade - which critics say will mean the UK still abiding by EU rules and leaving "in name only".
The Chequers proposals, which have yet to be negotiated with the EU, prompted the resignations of Boris Johnson, the foreign secretary, and David Davis, the Brexit secretary, who both said they could not support them.
Analysis by BBC Political Editor Laura Kuenssberg
Brexiteers are trying to force the government to drop its Chequers compromise, and dangling the threat of voting down legislation if Theresa May doesn't budge.
Brexiteer ministers are this afternoon, I'm told, still trying to get "edits" to the final White Paper, the souped-up version of the Chequers plan.
Their fellow Leavers on the backbenches are clearly going to kick up a stink if Number 10 won't move, and if they choose to, they have the numbers to defeat the government time and again.
Read Laura's full blog
More details will be set out on Thursday. So far Downing Street has said it would see the UK agreeing a "common rulebook" with the EU for trading in goods, in an attempt to minimise friction for trade at borders.
This has angered some Conservative backbenchers, who say it will prevent the UK from having its own independent trade policy, and they want to see the Chequers blueprint rewritten.
The customs bill - formally known as the Taxation (Cross-Border Trade) Bill, will give the government the power to adopt a new customs policy after it leaves the EU.
The legislation returns to the Commons on Monday.
One of the Eurosceptic rebel amendments demands that the UK should not be allowed to collect customs duties on behalf of the EU, unless the EU does the same for the UK.
But in the Chequers agreement, there are plans for a "combined customs territory" where the UK would charge EU tariffs for goods which will end up heading into the EU.
Other amendments would make it impossible for Northern Ireland to be in a separate customs arrangement to the rest of the UK - an arrangement previously suggested by the EU - and would require the UK to have a separate VAT regime from the EU.
Jacob Rees-Mogg, who leads the European Research Group of Tory MPs, said the amendment would "put into law the government's often stated position that Northern Ireland should be treated the same way as the rest of the country", and "ensure reciprocity of customs collection, and treating the UK and EU as equals".
"They will put into law the government's stated position that we will not be part of the EU VAT regime," he added.

An agreement has been reached which will see the Democratic Unionist Party back Theresa May's minority government.
The deal, which comes two weeks after the election resulted in a hung Parliament, will see the 10 DUP MPs back the Tories in key Commons votes.
There will be £1bn extra for Northern Ireland over the next two years.
DUP leader Arlene Foster said the "wide-ranging" pact was "good for Northern Ireland and the UK" but one critic said it was a "straight bung".
Labour leader Jeremy Corbyn said the deal was "clearly not in the national interest", and Sinn Fein's Gerry Adams said it enabled a "Tory Brexit which threatens the Good Friday Agreement".
It has prompted calls for matching public investment in Wales and Scotland.
A three page document outlining the terms of the agreement has been published in full. The DUP said it would apply for the lifetime of the Parliament, scheduled to last five years, but would also be reviewed at the end of the current session in two years' time.
There will be £1.5bn in funding - consisting of £1bn of new money and £500m of previously announced funds - to be spent over the next two years on infrastructure, health and education in Northern Ireland, money Mrs Foster said was needed to address the challenges from Northern Ireland's "unique history".
As part of the deal, the military covenant will be implemented in full in Northern Ireland, meaning more focus on the treatment of military veterans, while the triple lock guarantee of at least a 2.5% rise in the state pension each year, and winter fuel payments, will be maintained throughout the UK.
Other key points of the agreement include:
Mrs May shook hands with DUP leader Arlene Foster as she and other senior party figures arrived at Downing Street on Monday to finalise the pact. The two leaders then watched as Conservative chief whip Gavin Williamson and his DUP counterpart Jeffrey Donaldson signed the documents in No 10.
Speaking outside Downing Street, Mrs Foster said the agreement would bring stability to the UK government as it embarked on the Brexit process,
"This agreement will operate to deliver a stable government in the United Kingdom's national interest at this vital time," she said.
Analysis by BBC political editor Laura Kuenssberg
The Tories now face a bumpy day of criticism, about how the DUP have been bought off - £100m for each of their ten votes in Parliament. The other devolved nations will cry foul.
Some Tories too are deeply uncomfortable about the association with the DUP brand of unionism. And if the cuts are to be eased in Northern Ireland, what about other parts of the country?
But the money that's been found down the back of the Number 10 sofa for Northern Ireland may be worth it for Theresa May as the price of holding power, for now.
She now has her majority, whatever the cost, and a dividend could be the conclusion of a deal to get power sharing at Stormont up and running too.
Read Laura's blog in full
Welcoming the additional funding for Northern Ireland, she said it would benefit all communities. "Following our discussions the Conservative Party has recognised the case for higher funding in Northern Ireland, given our unique history and indeed circumstances over recent decades."
The UK prime minister said the pact was a "very good one" for the UK as a whole.
"We share many values in terms of wanting to see prosperity across the UK, the value of the union, the important bond between the different parts of the UK," Mrs May said. "We very much want to see that protected and enhanced
First Secretary of State Damian Green, a close ally of Mrs May's, said he hoped the extra money would help revive devolved government in Northern Ireland.
"The money that is attached to this agreement is actually less than the money attached to the original Stormont agreement in 2014," he told the BBC. "We know Northern Ireland has particular needs, because of its history and difficulties.
"There are parts of the Northern Ireland infrastructure that needs particular help and that has been recognised on a continuing basis."
The BBC's political editor Laura Kuenssberg said most of the money being allocated to Northern Ireland would go to specific projects rather than general spending, meaning it would not necessarily impact on the Barnett formula which determines overall expenditure across the nations of the UK.
She said DUP sources pointed to the creation of a "coordination committee", suggesting this would give them a direct line in to government discussions and that this may prove particularly influential over the Brexit negotiations.
Northern Ireland has been without a devolved government since March and parties have until Thursday to find agreement.
The cash will go to the Northern Ireland executive if the devolved institutions are restored by the deadline of 29 June.
Under the so-called "confidence and supply" arrangement, the DUP will line up behind the government in key votes, such as on the Queen's Speech and Budgets, as well as Brexit and security matters, which are likely to dominate most of the current Parliament.
On other legislation, the DUP's support is not necessarily guaranteed - although the Northern Ireland party is expected to back the majority of the government's programme for the next two years after many of its more controversial policies were dropped.
The support of the DUP will give Mrs May an effective working majority of 13, given that Sinn Fein do not take up their seven seats and Speaker John Bercow and his three deputies - two of whom are Labour MPs - do not take part in votes.
Several senior Tories had advised her to govern without any formal agreement with the DUP, arguing the unionist party would not be prepared to bring Mrs May down and run the risk of triggering a fresh election given their longstanding hostility to Jeremy Corbyn and other senior Labour figures.
Former PM Sir John Major warned that a formal association with the DUP could undermine attempts to restore power-sharing government in Northern Ireland while some MPs said the DUP's socially conservative stance on issues such as gay marriage and abortion could damage the party in the longer term.
Welsh First Minister Carwyn Jones suggested Mrs May was "throwing money at Northern Ireland while ignoring the rest of the UK", in what he called "cash for votes".
"Today's deal represents a straight bung to keep a weak prime minister and a faltering government in office," the Labour politician said.
Mr Corbyn said public service cuts should be stopped "right across the UK, not just in Northern Ireland".
He demanded to know where the extra money for Northern Ireland was coming from, and whether other parts of the UK would get a similar cash injection.
"This Tory-DUP deal is clearly not in the national interest but in May's party's interest to help her cling to power," he added.
Mr Adams, the president of Sinn Fein, said: "The Tory government has slashed more than £1bn from the block grant over the last seven years.
"The allocation of additional funds could help to ease the enormous pressure on our public services.
"The devil is in the detail."
On the plan to implement the military covenant in Northern Ireland, Mr Adams added: "Sinn Fein will resolutely oppose any attempt to give preferential treatment to British forces, either in terms of legacy or the provision of public services."
In the Commons, MPs from other parties lined up to criticise the new arrangements, with the SNP's Pete Wishart saying it was a "pathetic grubby little deal" and accusing the Tories and DUP of "pork barrel politics".
But Nigel Dodds, the DUP's Westminster leader, said his party could publish details of its correspondence with Labour and the SNP at the time of previous elections.
"Some of the faux outrage we have heard is hypocrisy of the highest order," he said.
Mr Dodds said the extra investment would be "for every section of the community in Northern Ireland".

The Conservative Party is being "manipulated" by Brexit "zealots" and the "mainstream majority" of MPs must reassert itself to stop a damaging EU exit, Sir John Major is to argue.
In a lecture in Glasgow, the former prime minister will urge Parliament to "dig deep into its soul" and act before the scheduled departure, on 29 March.
Brexit will cost billions and risk the break-up of the UK, he will say.
Theresa May is continuing talks with the EU to try to salvage her deal.
Parliament rejected the terms of withdrawal negotiated with the EU by a huge margin last month, raising the prospect of the UK leaving without a formal agreement.
Mrs May intends to put the deal to the vote again - although it is unclear when this will happen.
Speaking at the University of Glasgow, Sir John will say he hopes Parliament has the "wisdom and the will to exert its democratic right" to stop a no-deal Brexit in its tracks and give the people another say on whether to leave.
Sir John, who led the country between 1990 and 1997, will urge MPs to act in the UK's economic interest given what he says is the calamitous threat to jobs, investment and the public services from leaving.
"The decision Parliament takes next week can undermine or revive the reputation of representative politics and from that flows so much of our whole way of life," he will say.
"Every so often, in our long history, there has come a moment when Parliament has had to dig deep into its soul. Now is such a moment."
"I believe we have a right to expect members of Parliament to vote for an outcome that best protects the future welfare and prosperity of our nation - without fear or favour and without deference to party allegiance."
Sir John will suggest "fringe opinion" is driving Conservative and Labour policies towards Brexit, attacking "rogues and chancers" in both parties for whom the "truth is nothing more than a plaything".
The "intransigence" of the European Research Group of Conservative MPs is determining policy, with little regard to the "pragmatic and tolerant" brand of Conservatism that attracted him to the party in the 1960s, he will say.
"Some, who can fairly be called zealots, seem incapable of looking beyond the one issue of Europe," he will say. "It is not just that it dominates their thinking, it seems to obsess them."
While expressing admiration for the seven ex-Labour MPs who quit the party on Monday, he will say a "moderate" Labour party is essential if the centre of British politics is not to be overwhelmed by populism.
"When I refer to the centre, I don't mean some amorphous party of moderates and centrists," he will say.
"When I speak of the centre, I mean that our three main national parties - Conservative, Labour and Liberal Democrat - must each retain a mainstream majority of their own.
"Currently, both the Conservative and Labour parties are being manipulated by fringe opinion.
"Complacent voices dismiss the chances of fringe opinion gaining control of the political agenda.
"Britain is too pragmatic, they say, too stable and our political system too mature. I hope they are right".
The ERG has dismissed Sir John's earlier warnings as sour grapes, accusing him of wanting to overturn the 2016 Brexit referendum vote and ignoring MPs' decision to trigger the two-year process of leaving, in 2017.

Jeremy Corbyn has warned shadow cabinet ministers not to expect to stay in their jobs if they vote against starting the process of leaving the EU.
The Labour leader told ITV it was "impossible" for members of his top team to remain in place if they rebelled against a three-line whip.
Shadow Welsh Secretary Jo Stevens quit last week over the issue - other senior MPs say they will rebel.
Mr Corbyn has ordered all Labour MPs to support the bill triggering Article 50.
Labour backed the campaign to keep the UK in the EU in the referendum in June and many Labour MPs represent constituencies which voted for Remain.
But many seats which voted to leave the EU are also represented by Labour MPs.
Mr Corbyn says he understands the pressures on MPs in pro-Remain constituencies but has called on them to unite around the important issues.
His shadow home secretary Diane Abbott has said that, since a UK-wide referendum with a 72% turnout returned a vote in favour of withdrawing from the EU, it would "be very undermining of democracy" for MPs to vote against beginning the formal process of leaving.
Ms Stevens quit on Friday saying Brexit was a "terrible mistake". Shadow minister Tulip Siddiq also quit last week saying she would vote against the EU (Notification of Withdrawal) Bill.
Two Labour whips, Jeff Smith and Thangam Debbonaire, who are in charge of party discipline, have also said they will rebel - though they have not resigned.
Another shadow minister Daniel Zeichner has said he will vote against the bill, as will other MPs including former Culture Secretary Ben Bradshaw.
Mr Corbyn told ITV's Peston on Sunday: "There was no need for anyone to resign at this stage. It's obviously impossible to carry on being in the shadow cabinet if you vote against a decision made after a very frank and very long discussion of the shadow cabinet earlier this week."
Labour's deputy leader Tom Watson has said divisions in the party will be handled sensitively and suggested some rebels could be back in senior roles "within months".
The European Union (Notification of Withdrawal) Bill was introduced after the Supreme Court ruled that parliament - not just the government alone - must vote to trigger Article 50 of the Lisbon Treaty, which starts the formal process of the UK leaving the EU.
Prime Minister Theresa May has promised to begin the formal process of leaving by the end of March.
The bill is due to be debated by MPs on Tuesday - in a sitting that may last until midnight - and clear the Commons on 8 February, after which it will move to the House of Lords.
Labour has demanded changes including giving the Commons a vote on the final Brexit deal before European leaders or MEPs consider it.
The Liberal Democrats have vowed to oppose the triggering of Article 50 unless there is a guarantee of another referendum on the final Brexit deal that is agreed with Brussels, while the SNP has vowed to table 50 amendments to the legislation.

The architect of the Vote Leave campaign says it is possible last year's Brexit vote could turn out to have been an "error".
Ex-campaign director Dominic Cummings said "lots" of things could happen to make him wish his side had lost.
But he also stressed there were more possible outcomes in which leaving would be good for the EU and the UK.
Mr Cummings made the comments in a Twitter exchange with legal commentator David Allen Green.
He tweeted (his Twitter name is @odysseanproject) that there were "more possible branches of future" in which leaving was "a good thing", saying it increased Europe's  "overall ability to adapt more effectively to an uncertain world".
Mr Cummings also warned Brexit negotiations were heading for a "debacle" without "management changes" in Downing Street, although he said warned the importance of the talks was "greatly overstated" compared with domestic reforms that could be carried out.
"Decisions re our own institutions will decide success/failure," he tweeted.
Critics, including pro-Remain Lib Dem leader Tim Farron, seized on his comments.
The UK is due to leave the EU in March 2019, and formal negotiations between the two sides have started.
Earlier former Tory chancellor Nigel Lawson, who campaigned to leave the EU, predicted a £10bn "Brexit dividend" for the UK once it leaves, describing this as a "great chink of light" for current Chancellor Philip Hammond.
"Once we leave there will be this £10bn a year bonus - unless we are foolish enough to negotiate it away," he told BBC Radio 4's Today programme.
Leave campaigners have previously cited a £32bn "dividend" in the three years after Brexit, calculated by adding together the UK's net contribution for each year.
The issue of any "divorce bill" the UK might face is expected to be tackled at an early stage of the talks.
Before the negotiations started, the government set out its negotiation aims, including a new "comprehensive" free trade deal with the EU.
Another former chancellor, Labour's Alistair Darling - who campaigned to stay in the EU - said the UK looks "pretty clueless" as it attempts to negotiate its way out.
Lord Darling, whose stark economic warnings before the Brexit vote have not yet materialised, said: "Until we know what the Brexit settlement is, and frankly at the moment we haven't a clue what it is - and every day the government is giving an impression that it hasn't a clue either what it's going to look like - you won't know what the economy is going to do."
He added: "Here we are, shaping the future... and the UK looks pretty clueless at the moment - I don't ever recall a situation where our country has been in that position before."

Judges at the Supreme Court have rejected the Scottish government's argument that Holyrood should get a say on the triggering of Article 50.
The court decided that MPs must have a say on starting the formal process of Brexit via an act of parliament.
However, they also rejected arguments from the Lord Advocate that devolved administrations should also have a say.
First Minister Nicola Sturgeon has pledged to hold a Holyrood vote on the matter regardless of the ruling.
She said there remained a "clear political obligation" on the UK government to consult devolved administrations, adding that "it is becoming clearer by the day that Scotland's voice is simply not being heard or listened to within the UK".
Ministers wanted to invoke Article 50 of the Lisbon Treaty, the formal process for leaving the European Union, without consulting the Westminster parliament.
Campaigners disputed this, saying the referendum result alone does not give ministers the power to change the British constitution and supersede legislation.
The Supreme Court justices backed the challenge by eight votes to three, with President Lord Neuberger summarising their ruling as: "The Government cannot trigger Article 50 without an Act of Parliament authorising it to do so."
With Jeremy Corbyn pledging the support of Labour MPs to backing the government on Article 50, the defeat in court is not expected to derail the Brexit process, although it could pose complications.
The SNP have vowed to vote against invoking Article 50 if it does go to a vote at Westminster, while the Lib Dems have said they will oppose it unless there is a referendum on the final Brexit deal.
Today's Supreme Court ruling delineates precisely where formal, statutory power lies on the issue of reshaping Britain's relationship with the EU.
Europe, as an issue, is reserved to Westminster along with foreign affairs more generally.
It falls to the UK Parliament to implement the expressed popular will of the UK as a whole.
Quite right, say supporters of the Union, advising Nicola Sturgeon to fall into step. Which brings us back to the fundamental issue in Scottish politics.
Ms Sturgeon does not accept a UK mandate but rather seeks the power to implement an independent Scottish mandate.
Two competing options, then. It seems now very likely - perhaps indeed "all but inevitable" - that the people of Scotland will be asked, once more, which constitutional arrangement they favour.
Meanwhile, the Scottish government was also represented in the Supreme Court case, with Lord Advocate James Wolffe arguing Holyrood's consent should also be sought due to the "significant changes" Brexit would have on devolved powers.
Lawyers for the UK government rejected this, saying the argument was "fatally undermined" by the fact that powers over foreign affairs are reserved to Westminster.
The judges unanimously rejected Mr Wolffe's arguments, saying that the principle of legislative consent "does not give rise to a legally enforceable obligation".
They said the Sewel Convention, which provides that Holyrood should be consulted where Westminster legislation cuts across devolved areas, plays "an important role in the operation of the UK constitution", but is not a matter for the courts.
They added: "The devolved legislatures do not have a veto on the UK's decision to withdraw from the EU."
The SNP welcomed the ruling in relation to the Westminster vote, with the party's international affairs spokesman Alex Salmond pledging to introduce 50 amendments to the Article 50 legislation as it passes through parliament.
Later in the day, Ms Sturgeon will convene a meeting of her Standing Council on Europe, a team of legal, economic and diplomatic advisors.
Also in attendance will be External Affairs Secretary Fiona Hyslop, Brexit minister Mike Russell and Europe minister Alasdair Allan.
The first minister, who has said a second Scottish independence referendum is "undoubtedly" closer due to Theresa May's Brexit plans, declared her intention to hold a Holyrood vote on Article 50 regardless of the ruling of the court.
She said: "We are obviously disappointed with the Supreme Court's ruling in respect of the devolved administrations and the legal enforceability of the Sewel Convention.
"It is now crystal clear that the promises made to Scotland by the UK government about the Sewel Convention and the importance of embedding it in statute were not worth the paper they were written on.
"Although the court has concluded that the UK government is not legally obliged to consult the devolved administrations, there remains a clear political obligation to do so.
"The Scottish government will bring forward a Legislative Consent Motion and ensure that the Scottish Parliament has the opportunity to vote on whether or not it consents to the triggering of Article 50."
Ms Sturgeon also said the ruling raises "fundamental issues above and beyond that of EU membership", saying it was "becoming ever clearer" that Scots face a fresh choice over independence.
The Scottish Conservatives called on the SNP to stop trying to "hold the UK to ransom" over Brexit.
Leader Ruth Davidson said: "Whatever side people were on last year, Scotland wants to get on with the negotiations so we can start to leave the uncertainty of the last few years behind us.
"We have all had enough of the nationalists using every diversionary tactic they can to try to use Brexit to manufacture a case for separation.
"The SNP needs to decide: does it want Britain's renegotiation to succeed or fail? If it is the former, it needs to end the attempts to sow division and add to the uncertainty we face, and instead get behind the UK attempt to get the right deal for the whole UK."
Scottish Labour leader Kezia Dugdale said her party would "continue to work with the Scottish government to get the best deal for Scotland within the UK".
She added: "Both the SNP and the Conservatives are casting about for an expedient political position rather than working in the national interest. Unity cannot be achieved by a politics that sees one half of the country constantly facing off against the other.
"We are divided enough already. That's why there will be no support from Scottish Labour for any SNP plan for a second independence referendum."
Scottish Green co-convener Patrick Harvie said the ruling showed Scotland is "not an equal partner in the UK", saying it was "hard to see any other option" than a second independence referendum.
And Scottish Lib Dem leader Willie Rennie said the case presented "a huge opportunity" for a referendum on the final Brexit deal.

"Constructive and detailed" - that sounds quite positive - Number 10's description of the talks today.
"Robust" - not quite so chirpy - Labour's use of political speak for what most of us might call a bit tricky.
"Disingenuous" - oh dear - a different Labour source's description of ministers' claim that what they were putting on the table in the cross-party talks today was something genuinely new on the vexed question of customs arrangements after we leave the EU.
As we reported this morning there didn't really seem to be much from the government that was concrete beyond what's already possible under the agreement that's been hammered out with Brussels.
The divorce deal and indeed yes, you guessed it, the backstop, both have forms of temporary customs unions in them to make trade between the UK and the EU easier.
Of course the precise language and mechanisms matter enormously.
But was there some big shiny new offer today? The short answer is: no.
And after hours of talks this afternoon, Labour sources suggest ministers in the end more or less admitted that in pointed discussions.
As we've talked about here before, the cross-party talks process is real.
Plenty of people in the Tory party hate it. Plenty of people in the Labour Party hate it.
But inside both leaders' camps, there is a genuine desire, more intense since they both had a bad night at the polls on Thursday, to see if they can sketch out a joint escape route from the mess of Brexit.
But the historically awful result for the prime minister does not seem to have shocked her into ditching her red lines - at least not yet.
It's important to understand this process is always unlikely to end up with some kind of joint defining pact - sources involved joke about the preposterous idea of some kind of May-Corbyn Rose Garden love-in - fond or awful memories of that summer's day when the Cameron-Clegg bromance was born in public (take your pick which).
The fact the talks have gone on for so long hint that there is serious merit in finding some kind of agreement on some kind of process.
At the very least senior figures in the government hope that the talks might mean Labour would allow the Brexit legislation to move on to its next phase.
In nerd terms, this is to allow the Withdrawal Bill to get through its so-called "second reading", knowing that at the next stage in Parliament where a committee of MPs would pore over every line, multiple layers of objections would be made, suggestions and changes put forward and then voted on, before finally, the bill would have its third reading, when MPs are able to give their final yes or no.
It is hard right now though to make a call on whether that is viable.
One former minister, experienced and not prone to make wild prediction, told me Number 10 was in "la la land" if they believed that could happen.
About half an hour later, another former and experienced minister told me they believe, in fact, it will fly and perhaps by the end of this month.
Whoever you ask, it is clear it is not straightforward.
So when the two teams sit down again on Wednesday afternoon, whether it is "constructive" or "robust", there's still an awful lot to do.

If Brexit is going to end up feeling like a long toe-to-toe boxing match then at last we can say that the first round is over.
Theresa May has come out jabbing - offering crisp points about the UK's plans to leave the single market and its readiness to walk away from a bad deal if that's all that's on offer.
The European side for the moment is still acting as if what we've seen so far this week is just the posturing and chest-beating you see at the pre-fight weigh-in rather than the fight itself.
Their big-hitters - politicians like the President of the European Commission Jean-Claude Juncker and his equivalent at the European Council Donald Tusk - have confined themselves to a little nifty defensive work pointing to the likely difficulty of the talks, hoping for a fair outcome and reiterating that until Britain formally triggers the departure process everything is mere shadow boxing.
None of that of course will stop individual MEPs and commentators from offering their assessment of where the balance lies between the EU and the UK after Theresa May's Brexit declaration.
Brexit at-a-glance: What we learned from Theresa May
Why Brexit is still undefined
One German colleague said to me jokingly: "I didn't realise that the EU had decided to leave the UK until I heard your prime minister's speech."
And elsewhere in the corridors of the European Parliament you heard plenty of surprise at the confidence of the tone coming from London, the crispness of the decision to leave the single market and the sudden shafts of clarity after weeks in which the UK had appeared to not know what it wanted.
That's not to say of course that everyone has been impressed, even though Mrs May was praised in some quarters both for realism and for clarity.
It's worth remembering that most mainstream politicians in Europe view Brexit as an act of madness to be spoken of with hostility and incomprehension. Britain in this analysis has taken the decision to walk away from an institution that's been an engine of peace and prosperity.
Hence these remarks from the German MP Norbert Roettgen, who represents Angela Merkel's Christian Democrats.
He said: "The UK's two main economic weaknesses are its considerable trade deficit and a big budget deficit. As such [UK Chancellor Philip] Hammond's threats with duties and tax cuts would primarily damage the UK and should be regarded as an expression of British cluelessness."
That dismissal of an option Britain is keeping in reserve - the option of operating as a low-tax base for business if Europe refuses to cut an attractive deal - would be seen in Strasbourg as one weakness in the Theresa May strategy.
From elsewhere on the German political spectrum came an alternative strand of criticism - not that the UK was trying to set up a kind of low-tax magnet for foreign investment into Europe but simply that it was cutting ties in too brutal a fashion.
Ska Keller represents the German Greens in the European parliament.
She told us: "My overall impression is that May wants to go for a super-hard Brexit. She wants to cut all ties and I don't think that's going to fly well on the rest of the continent. Theresa May didn't really make friends in the last couple of days here in the overall European Union."
To the right of that broad European mainstream of course, things are seen rather differently.
France's far-right National Front looks at the success of the Leave campaign in the UK with a degree of envy. It doesn't like the EU either and would like to see its core treaties renegotiated.
Its senior MEP Bruno Gollnisch said: " I do think that in the end Britain could settle down to a situation rather like what it had before Brexit - after all in those days we managed things like exchanges of school pupils. And the UK will have commercial ties that reflect its specific Anglo-Saxon nature. There is no real reason why not."
So there has been a sense in Strasbourg this week that a phase in a kind of phoney war has finally ended and after months of speculating about what Britain might or might not want, a degree of clarity has emerged about British ambitions towards the single market and to a lesser extent the custom unions.
So far in this cautious round it was the UK which came out swinging rather than the European side.
But there is a very long way to go in this negotiation and by the end of it both sides will have endured defeats and disappointments alongside their occasional moments of triumph.
The UK might feel for now that its ahead on points, but everyone knows there's a long way - a very long way - to go.

 What's in a word? Number 10 will have cheered some of their Brexit backing troops this morning by ruling out, (again), staying in the customs union.
This time they have, for good measure and just to be clear, ruled out not just staying in 'the' customs union, but also remaining in 'a' customs union.
This might sound bonkers to you, but the inclusion of 'a' as a mere possibility had given hope to some MPs that the government was open to the idea of essentially replicating the current arrangements and calling it something else.
An explicit reminder in those terms therefore will be a frustration to that group which have been pushing for a softer approach. In political terms therefore, it is an important signal at the beginning of an important week.
What Sunday's late night statement is not, however, is anything like a new explanation of what the government actually wants to do. It does not mean that there will definitely be a border on the island of Ireland.
It does not mean definitely that there will suddenly be vast lorry parks across the whole of Kent or around the ports at Hull or Holyhead.
The government's overall aims remain the same - no hard border, and trade that is as frictionless as possible after Brexit. But there are emerging signs of the 'c' - the compromise that Theresa May will try to broker with her party, and her cabinet colleagues in the coming weeks to establish the government's actual position.
That is, before of course, Brussels and 27 other countries either say "oui", "non", or "peut-etre".
Back in the summer the UK set out two broad possibilities. The fault line that Theresa May needs to walk carefully over this week is between those in her cabinet who want to crack on as fast as possible with agreeing trade deals with other countries, and those who put the preservation of the existing arrangements above that.
As we saw last week on her trade trip to China, the prime minister does not want to accept publicly that one of these choices trumps the other. But as her colleagues who toured the broadcast studios yesterday displayed, there are divisions in the Tory party over who wants what, so there does have to be compromise.
There are whispers around, as The Times reports, that putting a time limit on to some of the existing arrangements could provide a way through. Interestingly, that's the approach that eventually found favour between Westminster and Brussels over another of the points of contention.
The UK accepted that the European courts would continue to have a role in enforcing the rights of EU nationals who live in the UK, but for a time-limited period of 8 years.
That gave the PM enough wriggle room to contain the wishes of the rest of the EU and her party. Senior figures in Number 10 suggested then the idea of putting time limits could be a useful precedent for other parts of the deal.
This could, perhaps, therefore provide one of the routes out of this tangled part of the Brexit talks. But there are still weeks and months of talking ahead to do.

Boris Johnson should again seek to re-negotiate the Brexit deal if he wants DUP support, Arlene Foster has said.
The DUP leader told the party's conference that the DUP had sent the PM to the "naughty step in Parliament" twice in the last week.
The DUP has twice voted against the government on crucial Brexit votes recently, because of its opposition to Mr Johnson's Brexit strategy.
The party said it would not support the NI arrangements negotiated by the PM.
This is because it "creates a border in the Irish Sea".
The DUP leader told Saturday's annual conference she would encourage the PM to seek further changes to the deal.
"We will not give support to the government when we believe they are fundamentally wrong," she said.
Boris Johnson does not have a Conservative majority in Parliament and the DUP's votes hold the balance of power on key decisions in the Commons.
Mrs Foster accused Number 10 of acting in a way that was "detrimental" to Northern Ireland and was taking the country in the wrong direction.
She also said if the government did not change its strategy that the DUP's 10 MPs would "oppose them and we will use our votes to defeat them".
On Monday, the government will ask MPs to vote in favour of its call for a general election.
Mrs Foster did not say whether the party would vote with the government, but said the DUP was "ready for any general election that may come".
The DUP leader also addressed the Stormont deadlock.
Northern Ireland has been without a government since 2017, when the two main power-sharing parties split in a bitter row.
One of the key sticking points has been the demand from Sinn Fein to legislate for an Irish language act, with the DUP refusing to agree to it.
Mrs Foster said her party remained committed to "legislate in a balanced way for language and culture".
"If we can find a way to craft language and culture laws that facilitates those who speak the language, but does not inappropriately infringe on or threaten others, the DUP will not be found wanting," she added.
"But overall agreement needs to be a two-way street."
Speaking earlier, Nigel Dodds told the conference that the union of the United Kingdom was "non-negotiable" in any Brexit deal.
The party has said it will not support the Brexit arrangements for Northern Ireland negotiated by Boris Johnson as it "creates a border in the Irish Sea".
The DUP deputy leader urged the prime minister to stick to commitments he made last year, when he said no Conservative government would support such a plan.
The party argued the deal would damage the local economy and undermine the union.
"I say it again clearly for those who have failed to listen… the union of this United Kingdom is non-negotiable," said Mr Dodds.
At last year's conference, Boris Johnson was the keynote speaker.
He told DUP members that no Conservative government should support a plan that would lead to differences between Northern Ireland and the rest of the UK.
Mr Dodds accused Mr Johnson and other government ministers of not knowing "what on earth" they had negotiated as part of the revised withdrawal agreement with the EU.
He said the plan, which would see NI businesses having to fill in exit declaration forms on goods going to GB, new checks on goods crossing the Irish Sea and extra administration, as "the worst of all worlds".
The North Belfast MP also said the DUP would not back down from opposing the deal.
"The coming days will not be easy, the pressures will be great," he added.
There was a more muted feel at this year's DUP conference, with no star turn from Boris Johnson.
Instead the party's leadership took turns to chastise him for reneging on Brexit commitments he made when he stood on that very stage last November.
Both Arlene Foster and Nigel Dodds seemed angry and emotional during their speeches - as many DUP politicians have sounded in recent days.
Just like last year when it opposed Theresa May's Brexit deal, the DUP is again in a political corner.
But this time, it does not have the ear of many Conservative Brexiteer MPs, who have sided with Boris Johnson and will likely dismiss the DUP's demands.
The DUP has said it will wait until Monday before giving its response to Mr Johnson's call for a general election.
The prime minister wants Westminster parties to agree to an election on 12 December.
The DUP entered a confidence and supply arrangement with the Conservative Party almost two and half years ago and helped prop up the minority government under Mr Johnson's predecessor, Theresa May.
The DUP has met Mr Johnson many times since he became prime minister.
At the start of this month, DUP members chanted his name when he addressed their fringe event at the Conservative Party's annual conference in Manchester.
But the relationship soured on 17 October, when Mr Johnson struck a Brexit deal with EU leaders that the DUP said it could not endorse.
All Northern Ireland MPs who take their seats in the Commons - the 10 DUP representatives and independent North Down MP Lady Hermon - opposed the government in votes over the EU withdrawal deal and an accelerated timetable to fast-track the bill through Parliament.

The Irish Government are using Brexit negotiations to put forward their vision for the future of the island of Ireland, Arlene Foster has said.
The DUP leader accused Dublin of not allowing EU negotiations "to move forward until they have certain things they demand".
Meanwhile, Irish Foreign Minister Simon Coveney said the UK desire for no hard-border in Ireland was "aspirational".
He said there could be no movement to phase two "on the basis of aspiration".
Arlene Foster was speaking to the BBC's Today programme ahead of the DUP's annual conference on Saturday.
She accused the Irish government of having taken an "absolutist position" on the border between Northern Ireland and the Republic of Ireland, making it difficult to achieve agreement on its future status without moving on to the next stage of Brexit negotiations on trade.
"You can't have it both ways," she said.
Mrs Foster also said that she could not accept any position after Brexit that would give the perception that Northern Ireland is in any way different from the rest of the United Kingdom.
"We've heard from the foreign minister of the Republic of Ireland, just yesterday, talking about his aspiration for a united Ireland.
"He's of course entitled to have that aspiration but  he should not be using European Union negotiations to talk about those issues - what he should be talking about are trading relations.
"I think what we don't want to see is any perception that Northern Ireland is in anyway different from the rest of the United Kingdom because that would cause us great difficulties in relation to trade because of course the single market that really matters to us is the market of the United Kingdom," she added.
Mrs Foster's comments follow the leaking of an Irish government report branding the UK's approach to Brexit as "chaotic".
Speaking on arrival at an EU summit in Brussels on Friday morning, the Irish Foreign Minister Simon Coveney said that leak was "unfortunate" and "not helpful".
But in relation to phase two of Brexit talks he said; "We have to move on the basis of a credible roadmap or the parameters around which we can design a credible roadmap."

Democratic Unionist Party sources have urged the Conservatives to give a "greater focus" to their negotiations.
A senior DUP source said the party could not be "taken for granted" - adding that if the PM  could not reach a deal, "what does that mean for bigger negotiations she is involved in?"
No deal has been reached after 10 days of talks between the parties.
But sources told the BBC's Laura Kuenssberg they believed a deal would still be done.
The Conservatives are hoping the DUP will sustain their minority government.
The warning from a senior DUP source to BBC Northern Ireland political editor Mark Devenport comes the day before the government's Queen's Speech is presented to Parliament.
Although they have not reached a final deal, DUP leader Arlene Foster has said it is "right and proper" that her MPs support the Conservative government's first Queen's Speech.
A Conservative source said it was important the party "gets on with its business" as talks continue by putting forward Wednesday's Queen's Speech.
Earlier cabinet minister Chris Grayling predicted a "sensible" deal would be reached.
The transport secretary said the talks were "going well", adding that the DUP, which has 10 MPs, did not want another election or Jeremy Corbyn in Downing Street.
Theresa May is seeking to negotiate a so-called "confidence and supply" arrangement whereby the DUP will throw their weight behind the government in key Commons votes, such as on the Queen's Speech and Budgets.
It is a week since DUP leader Arlene Foster visited Downing Street for talks with Theresa May, with reports that a final agreement is being held up by discussions over extra funding for Northern Ireland.
Should Mrs May lose any votes on the Queen's Speech, which are expected to take place next week, it would amount to a vote of no confidence in the government and put its future in doubt.
But Mr Grayling told BBC Radio 4's Today programme that he did not expect this to happen.
"The talks are going on but one thing I am absolutely certain of is that the DUP do not want to see another election and Jeremy Corbyn in Downing Street," he said. "We are having good, constructive discussions and I am confident we will reach a sensible agreement."
Former Prime Minister Sir John Major has urged Theresa May to reconsider her approach, saying a deal with the DUP could threaten the Northern Ireland peace process and "carry baggage" for his party. He has said the Conservatives should be able to govern anyway with the DUP's tacit support.
Asked about the repercussions if there was no agreement, Mr Grayling replied: "I am not pessimistic about this. I think we will have a sensible arrangement.
"We have got some days until we have a vote on the Queen's Speech. It is not on Queen's Speech day. The vote happens many days later as we have an extended debate first and I am sure we will have a sensible arrangement between the parties when that time comes."
The DUP had made it clear, he added, that they did not want "an unstable government undermining our union" and wanted to see us "go ahead with the Brexit negotiations with a sensible government in place".

Theresa May's former right-hand man has criticised colleagues "who won't accept evidence" on Brexit, and suggested more of Whitehall's economic forecasts should be published.
Damian Green rejected "conspiracy theories" that there was a plot to thwart the Leave vote.
And he acknowledged differences of opinion between ministers on Brexit.
Meanwhile ex-Brexit Minister David Jones said the Treasury was trying to "drag out" and "soften" the UK's exit.
Mr Green, the former first secretary of state, was sacked in December after being found to have made "inaccurate and misleading" statements over what he knew about claims pornography was found on his office computer in 2008.
In his first interview since leaving government, he spoke to BBC Radio 4 documentary The Ministry of Leave about the challenges facing the civil service as the UK prepares to leave the EU.
Last month's leak of government forecasts predicting a hit to the economy as a result of Brexit provoked a political row, with some Tory Brexiteers aiming criticism at the civil service.
In the aftermath, Brexit Minister Steve Baker said Whitehall forecasts were never accurate, while prominent backbencher Jacob Rees-Mogg accused the Treasury of "fiddling the figures" on Brexit to maintain a close economic relationship with the EU.
Speaking to the BBC's Ben Wright, Mr Green hit back, saying: "I do reject all the conspiracy theories that suggest there's some sort of plot inside the official machine to thwart the will of the people.
"There's a great problem of politicians who won't accept evidence. We can all argue about economic forecasts and none of them are 100% accurate but you have to rely on them and if you reject evidence you don't like then you are likely to end up producing faith based policies."
Asked whether some of his former cabinet colleagues were resistant to the facts and evidence, he replied, "not so much former cabinet colleagues.
"I think there are politicians who would prefer not to have the evidence there."
Earlier this month MPs were allowed to see a set of regional forecasts that predicted hits to economic growth across the UK, based on three possible new trade arrangements.
The government has faced calls to publish all of its analysis of the impact of Brexit in full, but says that to do so at this stage would damage its hand in negotiations.
It also argues that its preferred option of a bespoke trade deal has not been modelled in the leaked forecasts.
Mr Green added: "If analysis is being produced then publish it. And frankly there will be a big political debate it. Let's have this argument in public, that's what democracies do."
He described Brexit as probably the hardest task faced by Whitehall since the Second World War.
Ministers are still discussing "the very big picture. which end state we want" he said, adding: "it's not a surprise to anyone there are differences of view inside the government on that".
Speaking on the same programme, former Brexit minister Mr Jones praised the civil service's response to the challenge of preparing for Brexit, but added: "Probably the last of the Remain tendency are deep within the bowels of the Treasury.
"There is a constitutional aversion in the Treasury to Brexit as a concept and I think in the Treasury there is an effort being made at the moment to try and drag the process out and soften it."
Mr Jones also said that Brexit Secretary David Davis had wanted the Department for Exiting the EU - set up after the Leave vote - to be called "Department X".
He added: "David Davis said subsequently that he preferred Department X because it had suitably sinister overtones which I think appealed to him as a former Special Forces officer."

David Davis, who has quit as Brexit secretary, had one of the toughest jobs in politics - negotiating Britain's exit from the EU - and he also has one of the most colourful CVs.
A former SAS reservist, who grew up on a south London council estate, David Davis is a self-styled political maverick who had carved out a career as a champion of civil liberties before his unexpected return to front-line politics in July 2016 as secretary of state for exiting the EU.
He took to the role of negotiating Brexit with characteristic swagger, brushing off accusations from critics that he was too lazy, or lacked the intellectual depth, for such an apparently complex and nuanced task.
"What's the requirement of my job? I don't have to be very clever. I don't have to know that much. I do just have to be calm," he told LBC radio.
The Brexit secretary job might have been unexpected, but as a long-time opponent of Britain's EU membership it was an opportunity he grabbed with both hands.
He proved more publicly loyal to Theresa May than fellow Brexiteer Boris Johnson, earning the trust of the prime minister as her representative in Brussels, in what have turned out to be fraught talks with his opposite number, Michel Barnier.
His former reputation as someone who likes to be the centre of the media's attention - he once dramatically walked out of David Cameron's shadow cabinet and called a by-election - lingers on.
His appearances before Hilary Benn's Brexit select committee have become box-office moments at Westminster.
On one occasion, Mr Benn tried to pin him down about comments he had made in July 2016 - two days before Mrs May drafted him into the cabinet - when he said the UK would be able negotiate a free-trade area "massively larger than the EU" within two years of Brexit.
A laughing Mr Davis said the comments had been made before he had become a minister, later adding: "That was then, this is now."
Some of his former allies on the libertarian left struggled to come to terms with the new, ministerial Mr Davis.
Journalist Henry Porter, who often shared a platform with him at debates and campaign events, wrote in the Observer:  "I came to like him a lot and to admire his bounce and pugnacity.
"Among all the politicians I knew - with the possible exception of [Remain-supporting Tory MP] Dominic Grieve - David possessed the deepest instinct for liberty."
But Brexit clearly mattered far more to Mr Davis than protecting ancient Parliamentary liberties, said Porter, as he lamented the changes he had seen in his friend since taking on ministerial office.
"While I would be happy to be in the jungle or stuck in a lift with him, I would draw the line at being stranded in a planning room with him," he said.
Date of birth: 21 December, 1948 (69)
Most recent post: Secretary of state for exiting the EU, MP for Haltemprice and Howden since 1987
Education: Tooting Bec grammar school, Warwick University (Bsc molecular science and computer science), London Business School, Harvard University management school
Family: Married Doreen in 1973. Three children
Before politics: Senior executive at sugar giant Tate and Lyle
Initially seen as an ultra-Thatcherite, David Davis was elected to Parliament in 1987, at the age of 38, after a career in management with sugar giant Tate and Lyle. But Mr Davis did not fit the traditional mould of a Tory MP.
Despite being a passionate opponent of socialism in all its forms, his political hero is the late Tony Benn, father of Hilary and hero of the radical, Corbynista left.
He had a troubled background. "I was a wild kid," he told an audience at the Royal Festival Hall in 2002, where he shared the stage with Mr Benn, something, he said, that would have made his Labour-voting parents very proud. The two bonded over their shared Euroscepticism - but little else - at that event.
He got into Warwick University on an army scholarship and trained with the SAS as a reservist to help pay his way.
His military background, and fearless attitude, endeared him to Tory grandees such as the late Alan Clark, another of his heroes, as he began his rise through the party ranks in the early 1990s.
Over dinner hosted by Clark at his medieval Saltwood Castle, in Kent, Mr Davis agreed to walk along the crumbling ramparts overlooking the ruins of a chapel.
"[He] did the 'black' route without turning a hair, then retraced his footsteps, hands in pockets - first time that's ever been done!" Clark wrote in his diary.
"He is an extraordinarily optimistic and self-confident person," Tory MP Andrew Mitchell - a long time friend and ally - told the BBC's Newsnight programme's Nick Watt last year.
"I remember one of the Cameroons saying to me in exasperation that he was the only person he knows who did not go to Eton but has the same level of self-confidence you get from an Eton education."
Despite his Eurosceptic views, Mr Davis served as a government whip under pro-EU Prime Minister John Major in the early 1990s, attempting to get rebel Tory MPs to support the Maastricht Treaty, which paved the way for closer European integration.
He later served as Mr Major's Europe minister, helping to negotiate some of the agreements with Brussels he has since been charged with unpicking.
His "hard man" image, working-class background and staunch right-wing credentials made him the frontrunner to replace Michael Howard as Conservative leader in 2005 (he had made an unexpected, and unsuccessful tilt at the job in 2001).
He lost out to David Cameron, who made him shadow home secretary, where he carved out a distinctive niche for himself as a defender of traditional British freedoms, even though the two men had little time for each other.
In 2008, he dramatically resigned his Haltemprice and Howden seat, and his frontbench role, to fight a by-election in protest at Labour's plans for identity cards and 42-day detention without charge.
He won easily but rejected a job in the coalition government in 2010 to continue his civil liberties crusade from the backbenches, often in conflict with then Home Secretary Theresa May.
He was involved in legal action against the government over Mrs May's data-retention plans - dubbed the "snoopers' charter" by critics - when he got the call to join her cabinet.
Mr Davis will celebrate his 70th birthday in December, just over three months before Britain officially leaves the EU at the end of March 2019.

David Davis has said there is "no difference" between him, the chancellor and prime minister following a Tory row over the terms of a Brexit transition.
The Brexit Secretary said all three wanted the UK's exit from the EU in March 2019 to "serve the British economy... and the British people".
There was a "diversity of views" in all parties and EU member states, he said.
Backbench Tories had criticised Philip Hammond for saying that changes to UK-EU relations could be "very modest".
No 10 distanced itself from Mr Hammond's remarks and one Tory MP said he should "stick to the script" the PM had laid out.
Following a speech outlining some of his ambitions for an "implementation period" immediately after the UK leaves the EU in March 2019, Mr Davis was asked about the row.
He said: "I'm in politics, people debate and  they have different views and there is a diversity of views on this subject in all parties. That doesn't mean we can't have a coherent and forceful view in the interests of the United Kingdom."
He added: "There is no difference between the chancellor, and myself - and indeed the prime minister - in terms that we both want a Brexit which serves the British economy and which serves the British people. There will be arguments about the tactics but they will change - the options available to us will change throughout the negotiations.
"We want a good Brexit for British business and a good Brexit for the British people and we will deliver that on a frictionless access to the single market and political and economic freedom for us in the future."
In his speech, Mr Davis said that the UK would be able to sign new trade deals in the "implementation" period - thought likely to last up to two years.
The UK would still effectively follow the rules of the EU customs union for the period immediately after Brexit and no trade deals could come into force until it ended.
But he said: "As an independent country - no longer a member of the European Union - the United Kingdom will once again have its own trading policy.
"For the first time in more than 40 years, we will be able to step out and sign new trade deals with old friends, and new allies, around the globe."
He said existing international agreements - which include trade deals with other countries and agreements on aviation and nuclear power - should continue to apply during the period.
The "immediate goal" in negotiations, he added, would be to secure political agreement on an implementation phase by March's European Council summit.
Analysis by BBC Reality Check correspondent Chris Morris
This speech comes three days before the other EU member states are due to publish their formal guidelines (their terms and conditions in other words) for negotiations on the nature of a transition period after Brexit.
Those negotiations are due to begin shortly, and Mr Davis is getting his response in first, as well as trying to address some of the political heat he's now feeling from Brexiteers.
That's why he used the term 'implementation' rather than 'transition' period throughout his speech - it suggests that the UK will be implementing the consequences of Brexit.
EU documents though always refer to a transition because other countries are convinced that negotiations on the future EU-UK relationship will not have been completed by the time the UK leaves.
As well as smoothing the path for business, they argue that a transition is necessary to allow negotiations on future relations to continue.
Failing to reach agreement would mean uncertainty for businesses, resulting in delayed investment and a "stifling of hard-won economic growth".
Mr Davis also stressed the need for an "appropriate process" to allow the UK to resolve any concerns about new EU laws introduced during the implementation phase which were against its interests.
The speech comes amid a row in his party over the government's approach to Brexit negotiations, following Mr Hammond's comments at the World Economic Forum in Davos on Thursday.
Downing Street distanced itself from his remarks although the prime minister's spokesman said on Friday she had full confidence in the chancellor.
Asked whether his comments had been destabilising for the prime minister, Mr Hammond told the BBC: "I think the context is important. I was speaking about our trade relationship with the EU, and it is the government's policy that we want to maintain the maximum possible access to markets and the minimum friction at our borders because that's good for the British economy."
But Eurosceptic Tory backbencher Bernard Jenkin told the BBC it would be easier for the PM if Mr Hammond and other cabinet ministers "stuck to her script" while Jacob Rees-Mogg said Mr Hammond "must have been affected by high mountain air" in the Swiss resort.
In response to Mr Davis's speech, Hilary Benn, Labour chairman of the Commons Brexit committee, said "what we really needed to hear is what the government's proposals are for the most important trade negotiation of all - with the European Union... On that, we are none the wiser"
And Shadow Brexit Secretary Sir Keir Starmer said nothing Mr Davis had said "can mask or hide the bitter infighting that is going on in the government about what form Brexit should take".

Brexit Secretary David Davis has described his meeting with the European Parliament's chief negotiator Guy Verhofstadt as a "good start".
Although they could not negotiate yet, he said their discussions had been able to cover structures and how both sides propose to approach the Brexit talks.
He said a deal was possible that was in the interests of the EU and the UK.
Mr Verhofstadt said he wanted an exit deal completed before the next European Parliament elections in 2019.
Ahead of their talks the two men laughed off an apparent misunderstanding over Mr Davis's comment - "get thee behind me Satan" - in September when answering a Commons committee question about Mr Verhofstadt.
Mr Verhofstadt was referring to that when he said he was looking forward to a "hell of a conversation".
But ahead of the meeting Mr Davis said his Satan reference was to the person trying to tempt him to comment on Mr Verhofstadt, rather than directed at the former Belgian prime minister.
The European Parliament has to vote on, and could therefore veto, both the terms of the UK's exit and the even bigger subsequent deal to establish Britain's future relationship with the EU.
After the meeting Mr Davis called Mr Verhofstadt "a very nice man" and said that although they could not go into the details of negotiations they could lay the ground work for how the process might work.
BBC Europe correspondent Damian Grammaticas said that how the two men get on could play an important role in the success of the Brexit negotiations - which are due to begin after Theresa May triggers the official two-year process in March.
The heart of the negotiations is likely to be the balance between UK firms being able to trade freely within the European single market, and the UK's desire to end the right of all EU citizens to live and work in the UK.
Manfred Weber, leader of the EPP, the largest grouping in the European Parliament, also had talks with Mr Davis and said that the free movement of people was non-negotiable.
He said: "We need to take into account the interests of 450 million European citizens... What we really expect are clear proposals.
"Today, in my talk with David Davis, unfortunately I haven't really heard anything new. I haven't really heard how the British government want to tackle Brexit or what Brexit really means."
But Mr Davis said: "Our view is that we can get an outcome which will be in the interests of the European Union and in the interests of Britain and which will meet the requirements of the referendum. All of those are possible. That's what the negotiations are about."
Mr Verhofstadt said: "In the meeting I repeated what are, for us, essential key points. That is, that... these negotiations, in the interest of everybody, need to be concluded before the European elections.
"We cannot imagine, or at least it would be very strange, if the UK have to organise elections for the UK parliament after the outcome of the Brexit vote. And it gives us the possibility  of a fresh and new start with new people."

David Davis has urged MPs to back the Brexit bill and insisted the UK would be prepared, if it has to leave the EU with no deal in place.
The Brexit secretary urged MPs not to "tie the prime minister's hands" over MPs getting a final vote on the deal and on EU citizens' rights in the UK.
He said while they were preparing for a "no deal" Brexit he thought it was unlikely negotiations would break down.
The bill returns to MPs on Monday after two defeats in the Lords.
Peers want to guarantee the rights of EU citizens in the UK and to ensure Parliament has a vote on any deal in two years' time.
Labour's Sir Keir Starmer said they would fight to keep the amendments in the Bill, urging the government: "Don't just have this obsession with getting Article 50 triggered this week".
If MPs do pass it, Theresa May could trigger the formal process of Brexit as early as Tuesday.
The prime minister has said she will take the UK out of the EU even if Parliament votes against the deal she is offered.
Mr Davis, who will lead negotiations for the UK, addressed the issues of citizens' rights and a Parliamentary vote in an interview on BBC One's Andrew Marr Show.
"It's inconceivable to me that there wouldn't be a vote on the outcome," he said.
He urged MPs: "Please don't tie the prime minister's hands in the process of doing that, for things which we expect to attain anyway."
Pressed on whether a rejection by Parliament of any deal would send the UK back to the negotiating table, he said: "It's a two-year time [limit] on Article 50 so there'll be a limit to which we can do that.
"What we can't have is either House of Parliament reversing the decision of the British people - they haven't got a veto."
He said citizens' rights in the UK and Europe would be "the first thing" discussed in Brexit talks and said he believed there was a "moral responsibility" to EU citizens but the issue had to be "resolved together" with other EU countries.
He also said the government was working on "a contingency plan" in case a deal could not be reached with the EU - after a report by the Foreign Affairs Committee said it had found no evidence of serious contingency planning by the government.
Mr Davis said he believed it was "not remotely likely" that there would be a complete breakdown in negotiations.
But he said: "The simple truth is, we have been planning for the contingency, all the various outcomes, all the possible outcomes. It's not just my team, it's the whole of Whitehall, it's every single department. But, understand, it's the contingency plan. The aim is to get a good outcome."
International Trade Secretary Liam Fox, told BBC Radio 5 live's Pienaar's Politics: "Certainly it wouldn't be the end of the world if we had no deal, but it would be preferential to have a deal".
Foreign Secretary Boris Johnson told ITV's Peston on Sunday: "It would be perfectly OK if we weren't able to get an agreement but I'm sure that we will."
He added: "I don't think the consequences of 'no deal' are by any means as apocalyptic as some people like to pretend."
His comments were dismissed by the Conservative former deputy PM Lord Heseltine as "rubbish".
The Tory grandee, who was sacked last week as a government adviser having voted against the Brexit bill in the Lords, told ITV: "The fact is that a huge number of Conservatives are appalled, they feel they have been betrayed by what is going on now."
Shadow Brexit Secretary Sir Keir urged the PM to consider keeping the "really important" Lords amendments - adding that EU citizens in the UK had been "left in limbo".
He told Sky News that the prospect of the UK "crashing out without a deal" would be "a disaster".
"You absolutely have to have a vote in Parliament before that could possibly happen. So we'll be fighting for those tomorrow," he said.
The bill could complete its final stages on Monday if the Lords accepts the decisions made by MPs.
Among potential Conservative rebels is the MP Anna Soubry who told BBC One's Sunday Politics she had not heard any assurances that Parliament would get a vote in the event of no deal being reached.
Without them, she said: "I will either vote against my government which I do not do lightly… or I will abstain, which... has pretty much the same effect."

Theresa May will probably lose a Commons vote on her Brexit deal, former Brexit Secretary David Davis has said.
But Mr Davis - who quit his cabinet role over the Brexit plan in July - said he believed defeat  would prompt the UK and EU to agree a "better deal".
He also said the UK had hundreds of plans ready in case the country leaves the EU without any agreed Brexit deal.
Mr Davis said there might be "some hiccups" but the UK was "a big country" and "we can look after ourselves".
Brexit is due to happen on 29 March 2019, as a result of the referendum in June 2016 in which people voted by 51.9% to 48.1% for the UK to leave the European Union.
Although 95% of a Brexit deal is said to be agreed, the UK and the EU have yet to agree on how to guarantee that there will be no return to a visible border between Northern Ireland and the Republic of Ireland in future.
Both sides agreed to put in place a "backstop", also referred to as an insurance policy, that would only be triggered if a future trade deal is not in place by the end of 2020 - or if this final deal does not ensure a "frictionless" border.
This is because there have been warnings that a return of visible border checks could undermine the peace process in Northern Ireland, as well as damaging businesses operating on both sides.
One option for the backstop is for the whole of the UK to remain temporarily aligned to the EU's customs union, avoiding the need for customs checks at the border.
But how long this would last, and how the arrangement could be terminated, has not yet been settled. The government is under pressure from some Tories, as well as Labour, to publish the precise legal advice about how the arrangement would work.
If a Brexit deal is agreed between the UK and the EU, it then has to be approved by the House of Commons and the 27 remaining EU member states.
Mr Davis told BBC Radio 4's Today programme that defeat in the Commons for the current plan was "looking like a probability", especially if MPs were not shown the full legal advice on the Irish border backstop plan.
He said MPs needed to see the "complete legal advice, not a summary" before voting on such a crucial issue.
Mr Davis added: "Are we going to have to wait until the Irish government says it's OK to leave? If so, that's not acceptable.
"Are we going to have to wait until it's convenient for the (European) Commission to say when we leave? If so, it's not acceptable.
"I suspect that they have not pinned down any of these issues and they need to be pinned down before Parliament votes."
International Trade Secretary Liam Fox said that the UK government must have the right to decide when to leave any backstop which involves a customs arrangement.
It is understood that the Cabinet has discussed using a mutual (UK and EU) review mechanism to leave any backstop.
When asked if a system requiring a mutually agreed withdrawal from a backstop arrangement would be of concern, Mr Fox said that the government "had an instruction from our voters to leave the European Union and that decision can't be subcontracted to somebody else. That needs to be an issue for a sovereign British government to be able to determine".
UK Foreign Secretary Jeremy Hunt delivered a speech in Paris, in French, in which he said the UK and France would remain tied by "bonds of friendship" after Brexit.
On the issue of publishing the full legal advice, he said: "We have an excellent attorney general and he is giving very good legal advice on everything that we are considering signing up to, so we are going into this with our eyes open".
Mr Hunt also said that it was "entirely possible to reach an agreement" within the next three weeks, although to reach agreement within the next week might be "pushing it a bit".
In Dublin, the Irish foreign minister Simon Coveney told the Irish Canada Business Association conference: "I would urge caution that an imminent breakthrough is not necessarily to be taken for granted, not by a long shot.
"Repeatedly people seem to make the same mistake over and over again, assuming that if the British Cabinet agrees something, well, then that's it then, everything is agreed.
"This is a negotiation and needs to be an agreement of course between the British Government but also with the European Union and the 27 countries that are represented by Michel Barnier and his negotiating team.
"So while of course we want progress to be made and we want it to be made as quickly as possible because time is moving on, I would urge caution that people don't get carried away on the back of rumour in the coming days."

Justice Secretary David Gauke says he will resign if the next prime minister chooses to pursue a no-deal Brexit.
Tory leadership favourite Boris Johnson has pledged the UK will leave the EU on 31 October - with or without a deal.
However, Mr Gauke told the BBC's Andrew Marr Show that a "sizeable" number of Conservative MPs believed the UK should leave with a deal.
His comments come as Tory MP Sam Gyimah said more than 30 Tory MPs could vote against a no-deal Brexit.
The EU has set the UK a deadline of 31 October to leave the bloc.
Mr Gauke said he believed Parliament "will find a mechanism" between now and 31 October to prevent the UK leaving without a deal.
When asked whether he thought he would be sacked from the cabinet if Mr Johnson became prime minister, he said: "I  suspect that I will possibly have gone before then."
He added: "Assuming that he wins, if Boris's position is that he is going to require every member of the cabinet to sign up to being prepared to leave without a deal on 31 October, to be fair to him I can't support that policy - so I would resign in advance."
Former Tory leadership hopeful Mr Gyimah - who resigned as a minister over Theresa May's Brexit plan - said there were more than 30 Tory MPs looking at legislative options to block a no-deal Brexit.
He told Sky News: "I wouldn't want to announce them before they have been tested as being viable."
"But there is a real concern. The real concern here is not about Leavers or Remainers. The real concern here, is that this is not in the interest of our country."
He added: "What all this is about is staving off economic mayhem."
Pro-Remain Tory MP Dominic Grieve has suggested MPs could use a Commons vote on Northern Ireland on Monday to launch a fresh bid to block a no-deal Brexit.
The government has tabled a Bill to delay any new election to the Northern Ireland Assembly while talks to restore power-sharing are ongoing.
Northern Ireland has been without a functioning government since 2017, when the power-sharing parties split in a bitter row.
Mr Grieve told Radio 5 Live's Pienaar's Politics: "The chances are, if Brexit goes through - a no-deal Brexit - it is going to be the end of Northern Ireland's union with the United Kingdom, with serious political consequences flowing from it.
"That's a Bill that is a perfectly legitimate place to start looking at how one might make sure no-deal Brexits are fully debated before they take place."
Asked about the possible number of MPs who might back such a bid, Mr Grieve said he did not know.
He added: "Like all these things, colleagues are pulled in different directions, perfectly understandably, by various considerations."
Leader of the pro-Brexit European Research Group, Jacob Rees-Mogg, told 5 Live he thought the only way to stop no-deal was to pass a new law.
He added that he would be "very surprised" if that happened.
Mr Johnson has insisted he is not bluffing over his promise to stick to the 31 October deadline for leaving the EU - even if that means walking away without a deal.
Asked in an interview with the Sunday Telegraph if his commitment to 31 October was a bluff, Mr Johnson said: "No ... honestly. Come on. We've got to show a bit more gumption about this."
He added: "It's vital that our partners see that. They have to look deep into our eyes and think 'my god, these Brits actually are going to leave. And they're going to leave on those terms'."
His leadership rival Jeremy Hunt has also said he was willing to leave without a deal, although he told the Sunday Telegraph it was "not the most secure way of guaranteeing Brexit" because MPs would try to block it.
Mr Johnson and Mr Hunt have been travelling around the country as they seek to win backing from Conservative party members, ahead of the vote closing on 22 July.
Home Secretary Sajid Javid has come out in support of Mr Johnson, saying the former foreign secretary was "better placed" than Mr Hunt to "deliver what we need to do at this critical time".
Tory MP Mr Rees-Mogg has suggested Mr Javid - along with Chief Secretary to the Treasury Liz Truss - are the main candidates to become the next chancellor.
Mr Rees-Mogg, who is supporting Mr Johnson in the leadership contest, said both had "very strong" credentials.

There were "frank discussions" about the Irish border in the latest round of Brexit talks, David Davis has said.
The Brexit Secretary was speaking in Brussels after a meeting with chief EU negotiator Michel Barnier.
Mr Davis said any solution for the border could not be at the expense of the constitutional integrity of the UK.
The EU tabled a paper which suggested Northern Ireland will have to continue to follow many EU rules after Brexit if a hard border is to be avoided.
The paper hinted that Northern Ireland may need to stay in the EU customs union if there are to be no checks at the border.
That is something which the Conservatives and DUP have said they cannot accept as it would effectively create a border between Northern Ireland and the rest of the UK.
Meanwhile, Mr Barnier said the UK has two weeks to clarify what it will pay the EU if progress is to be made in Brexit talks.
Britain and the EU say they are committed to ensuring Brexit does not undermine the Good Friday agreement.
Neither want Brexit to lead to the emergence of a hard border with the Republic of Ireland.
"Let me be clear, we cannot have anything resulting in a new border being set up with in the UK," said Mr Davis after the sixth round of UK-EU talks on citizens' rights, the Irish border, and the UK's "divorce bill".
"We remain firmly committed to avoiding any physical infrastructure.
"We respect the EU desires, but they cannot come at the constitutional integrity of the United Kingdom."
Mr Davis said the EU and UK teams had drafted joint positions on the common travel area, as well as joint principles and commitments for the second phase of talks.
The EU leaked paper stops short of saying a hard border can only be avoided by the UK or Northern Ireland staying in the single market or customs union.
However, it brings the commission closer to the European Parliament position which "presumes" that the UK or Northern Ireland will have to stay in the internal market and customs union.
It is also the clearest indication that the commission has accepted the Irish position on Brexit and the border issue.
Irish Prime Minister Leo Varadkar has said the only way of avoiding a hard border in Ireland after Brexit is for the whole of the UK, or Northern Ireland, to follow the rules of the customs union and single market.
Speaking at a meeting of the British-Irish Council in Jersey, Mr Varadkar said his proposal would not mean the UK or Northern Ireland had to be members of the customs union and single market, but "it would mean continuing to apply the rules".
DUP Parliamentary leader and North Belfast MP Nigel Dodds rejected the suggestion that a hard border can only be avoided if the UK or Northern Ireland continue to abide by the rules of the single market and customs union after Brexit.
He said the paper shows the EU is unwilling to engage in negotiations on the border issue in a "meaningful fashion".
"Northern Ireland will not be separated from the rest of the UK as a result of Brexit," he said.
"Brussels must realise this and accept that progress will not be achieved through bully-boy tactics."
Meanwhile, Irish Foreign Affairs Minister Simon Coveney said talk of individual countries vetoing a move to the next stage of Brexit negotiations is "unhelpful", but progress still had to be made on the border issue.
"There is a way to go between the two negotiating teams to be able to provide credible answers and sufficient progress in the context of the Irish border before we can move on to Phase Two," he told Irish state broadcaster, RTE.
Former Irish Taoiseach and Good Friday Agreement signatory Bertie Ahern told BBC Newsnight that a hard border would be a "huge setback" for the peace process and that a physical border across the island of Ireland would give a "huge incentive" to those that want to cause mischief.

The EU's chief negotiator Michel Barnier says there has not been enough progress to move to the next stage of Brexit talks as the UK wants.
He said there was "new momentum" in the process but there was still "deadlock" over how much the UK pays when it leaves, which he called "disturbing".
Brexit Secretary David Davis said he still hoped for the go-ahead for trade talks when EU leaders meet next week.
The pair were speaking after the fifth round of Brexit talks in Brussels.
Mr Barnier said: "I am not able in the current circumstances to propose next week to the European Council that we should start discussions on the future relationship."
The UK's Brexit Secretary David Davis urged EU leaders at the summit, on 19 and 20 October, to give Mr Barnier a mandate to start trade talks and to "build on the spirit of co-operation we now have".
He said there had been progress on the area of citizens' rights that had moved the two sides "even closer to a deal".
The EU chief negotiator told reporters at the joint press conference he hoped for "decisive progress" by the time of the December summit of the European Council.
He said Theresa May's announcement that Britain would honour financial commitments entered into as an EU member was "important".
But he said there had been no negotiations on the issue this week because the UK was not ready to spell out what it would pay.
"On this question we have reached a state of deadlock which is very disturbing for thousands of project promoters in Europe and it's disturbing also for taxpayers."
Not even Brexit's biggest cheerleader could claim the discussions in Brussels have been going well. And there are visible frustrations on both sides.
But before claiming this morning's drama means the whole thing is doomed there are a few things worth remembering.
At the very start of this whole process, the hope was that in October, the EU would agree to move on to the next phase of the talks, to talk about our future relationship. But for months it has been clear that the chances of that were essentially zero.
It is not, therefore, a surprise to hear Mr Barnier saying right now, he doesn't feel able to press the button on phase 2, however much he enjoyed the drama of saying so today.
Second, behind the scenes, although it has been slow, there has been some progress in the talks but officials in some areas have reached the end of the line until their political masters give them permission to move on.
Read Laura's full blog
The so-called divorce bill covers things like the pensions of former EU staff in the UK, the cost of relocating EU agencies based in the UK and outstanding commitments to EU programmes. The UK has said it will meet its legal requirements and there has been speculation the bill could be anywhere between £50bn and £100bn, spread over a number of years.
BBC Europe Correspondent Kevin Connolly said the UK sees its total financial commitment "as its best negotiating card to be played somewhere near the end of the talks - the EU wants that card to be shown now at a point which is still relatively early in a two-year game".
The UK has also offered to keep paying into the EU budget during a proposed two-year transition period.
The EU had two other issues on which it would not make any "concessions", said Mr Barnier - citizens' rights and the Northern Ireland border.
On the status of the border, Mr Barnier said negotiations had "advanced" during this week's discussions.
But he said there was "more work to do in order to build a full picture of the challenges to North-South co-operation resulting from the UK - and therefore Northern Ireland - leaving the EU legal framework".
Asked about speculation that the UK could exit the EU in March 2019 without a trade deal, Mr Barnier said the EU was ready for "any eventualities" but added: "No deal will be a very bad deal."
Mr Davis said: "It's not what we seek, we want to see a good deal, but we are planning for everything."
Both men said progress had been made on citizens' rights, with Mr Davis saying there would be an agreement "soon" to ensure EU nationals in the UK would be able to enforce their rights through the UK courts.
He said EU citizens would still have to register with the UK authorities but the process would be streamlined to make it as simple and cheap as possible.
According to Mr Davis, the remaining sticking points include:
Labour leader Jeremy Corbyn said: "I think it's quite shocking. We're now 15 months on since the referendum and the government seems to have reached deadlock at every stage."
He said "falling out" of the EU without a trade deal would threaten "a lot of jobs all across Britain".
Labour is calling for "emergency" talks between Mr Davis and the EU early next week, to try to break the deadlock ahead of the EU summit.
Earlier this week, European Council President Donald Tusk suggested that the green light to begin talks about a post-Brexit trade deal would not come until December at the earliest.
Meanwhile, draft conclusions for next week's summit of EU leaders - which could yet change - call for internal work to begin on possible transitional arrangements and trade talks with the UK.
That would mean they could move ahead with negotiations on a future relationship, if "sufficient progress has been achieved" in talks.
But the draft conclusions seen by the BBC, if adopted, suggest EU leaders are not yet ready to begin talks with the UK about a post-Brexit transition deal.
Last month Prime Minister Theresa May used a speech in Florence to set out proposals for a two-year transition period after the UK leaves the EU in March 2019, in a bid to ease the deadlock.

Conservative rebel Dominic Grieve has urged the prime minister to delay Brexit if her EU withdrawal deal is rejected by MPs next week.
Mr Grieve, who backs calls for another referendum, said she could remove the 29 March date from UK legislation and ask the EU for more time.
Cabinet ministers who oppose leaving the EU without a deal had a "duty to resign" if she refused to do so.
Ministers warn the UK faces Brexit "paralysis" if the deal is rejected.
And the prime minister's spokesman said on Friday that the government wouldn't extend Article 50, the legal mechanism taking Britain out of the EU on 29 March.
Mr Grieve, who tabled the amendment that led to a government defeat on Wednesday, has been at the forefront of cross-party efforts to ensure MPs have a say in what happens if Mrs May's deal is voted down.
In those circumstances, another of Mr Grieve's amendments means that the Commons will then have a chance to vote on alternative policies - everything from a "managed no-deal" to a further referendum could be on the table.
MPs are widely expected to reject the withdrawal deal negotiated between the EU and UK in a key Commons vote on Tuesday, with more than 100 Conservative MPs among those opposing it.
Foreign Secretary Jeremy Hunt warned that the possibility of Brexit not happening at all had increased, with Parliament showing this week it would not accept leaving without a deal.
This he said would be an "incredibly damaging breach of trust and it would also be very bad for Britain's reputation abroad".
But former attorney general Mr Grieve, who earlier addressed a rally of people calling for another referendum, said he hoped that cabinet ministers known to be opposed to a no-deal Brexit would be "frank" with the PM, if - as expected - she loses next week's vote.
"I think the options are very limited and the reality in my view is that the only way out of this difficulty is go back to the public and ask for their opinion," he said.
He said, if MPs reject the deal, the government should act immediately to strike the 29 March Brexit date from UK legislation before going to the EU to ask for an extension of the Article 50 process.
"I believe the EU will extend Article 50 for us but I think they would only do it in a very limited number of circumstances ... and we need to explore what those circumstances may be."
If the prime minister would not agree to do so, he added: "If a cabinet minister feels the government is doing something they can't accept, it is probably their duty to resign".
"My feeling is that this will have its own dynamic and whilst I want to keep the government stable ... I hope the prime minister will listen carefully to what members of Parliament and members of her own government are saying to her."
Earlier he said it was the duty of MPs to "stop people committing national suicide" by going ahead with a no-deal Brexit.
The pound rose on Friday after a report in London's Evening Standard suggested Brexit looked increasingly likely to be delayed.
However, during the third day of Commons debate on Mrs May's withdrawal deal, another senior pro-EU Tory backbencher, Sir Nicholas Soames, warned against moves to extend the Article 50 process.
"I believe it would be quite wrong to postpone the Article 50 deadline and the House must be prepared to earn the undying contempt of the country if it simply does not have the collective will, discipline and sense of duty to come to an agreement", he added.
Meanwhile, as many as 4,000 civil servants are being asked to move from their usual work to prepare for and handle a possible "no deal" Brexit.
The departments which will see staff redeployed include Defence,  International Development, Work and Pensions and the Education department.
The plans involve moving some staff within their department, and transferring others to departments and agencies with the greatest extra no-deal-related workload, such as HMRC and Defra. according to a memo leaked to The Times.
A government spokesman said: "As we get closer to the time where we will leave the EU, it is sensible and right for the Civil Service to accelerate preparations."

Take a breath. That was more or less the prime minister's message to MPs in the Commons today.
We've all just lived through a historic political period when the levels of anger and anxiety and frustration and fury have gone up and up and up and up in Westminster, and maybe beyond.
Up until this moment, the prime minister has simply been unable to deliver the support for her compromise deal with the EU.
Parliament has not managed to agree a consensus around anything else.
And both sides - for it has felt like the Executive versus the Commons - have become more and more irritated as time has ticked down towards this week's deadline.
The Brexit delay that the EU has agreed gives Westminster's village a pause, a moment to take a breath, and maybe to take stock.
The EU has placed a little faith in the idea that there could be a cross-party compromise.
Whispers suggest that ministers will meet Labour counterparts on Friday and are telling business leaders tonight that there could be a bespoke deal for the UK, if those cross-party talks can deliver.
So, the screaming alarm, warning against leaving with no deal in a few hours' time, has been silenced, at least for now.
And while there is, inevitably, rising chatter about ushering Theresa May out of office, it seems clear that none of the candidates who would love to replace her, want to be the person to take over right now.
Whether it is Dominic Raab, Boris Johnson, Jeremy Hunt, Liz Truss, or someone else on the long list of potential candidates, none appear on the point of jumping forward to say: 'This is a slow-motion disaster, I have a better idea.'
Ironically, none of the people at the top levels of the Tory Party who believe they could lead, want to do it at this moment - where arguably, leadership has never been so in demand.
The prime minister won a delay, and got through yet another bumpy session in Parliament on Thursday without too much harm.
But the policy clashes, the battle of ideas, and yes, the grudge matches, have not been played out to their conclusion.
For Brexit therefore, and for all of us, there is no sign of conclusion.
MPs might come back in ten days, clear-headed and ready for compromise on all sides.
But our political system's track record on Brexit suggests that a moment of harmony is still out of reach.

Well. However she did it, Theresa May managed to roll Donald Trump back from the outright and overt criticism of her, and her most important policy, before their press conference today.
Rather in the manner of a boss telling staff who'd been caught bunking off that they would work extra hours, almost the first words out of the prime minister's mouth were that he did actually agree that the UK and the US would sign a trade deal after Brexit, and enthusiastically so.
The president was not quite so effusive in his statements and betrayed frankly what many members of the public feel about the government's Brexit plans - "I don't know what they're going to do but whatever you do is ok with me".
But he did, it seemed obediently, crank out the prepared line from his notes that the US was committed to doing a deal. Between now and next March you can bet you'll hear those remarks used as evidence by the prime minister of the UK's exciting future outside the EU again, and again, and again, oh and again.
I'm sure you can picture the scene - whether an MP or a journalist asks, 'Prime Minister, this deal means it will be hard to do other trade deals', 'Donald Trump said the contrary, that the US was committed to work to seize the opportunities with a comprehensive deal'.
That doesn't mean that's what will happen. Off script the president's doubts were pretty clear that for a trade deal to work the UK can't sign up to many restrictions. And while she denied it today, the prime minister and her colleagues well know that agreeing the 'common rule book' as we've discussed so much in the last week or so, does make the UK a less attractive trade partner for other countries.
Indeed in officialese the government's own documents acknowledge as much. It is a decision that she has taken, that Donald Trump might not like much, but she has taken it for a reason.
For the choreography of today though to be just awkward, not downright cringeworthy, it was important for Number 10 to pull Donald Trump back from his previous statements.
He, true to form, tried to pretend that he hadn't really said what he said, even though his remarks were made on the record. 'Fake news', it was not. That is important to understand, because it means that the difficulties between our two countries over a tighter trading relationship have not disappeared.
And for Theresa May, the bigger problem is that many in her party agree with him, not his world view, but the fact that her Brexit compromise could cut off some of what Leavers saw as the greatest possibilities of leaving the EU.
This was a difficult day for the PM for sure, but not a disaster. But at a time when she desperately needs friends and allies, the American president is not necessarily one upon whom she can totally rely.

Jacob Rees-Mogg has warned fellow Tory MPs that if they don't ditch Theresa May now she will lead them into the next election, scheduled for 2022.
Few Tories thought this was a "good idea", the Brexiteer MP suggested.
Mr Rees-Mogg wants to oust the PM over her EU withdrawal agreement but has so far failed to get enough colleagues to back his call for a no confidence vote.
Meanwhile, ministers have had to accept Labour amendments to the Finance Bill after the DUP withdrew its backing.
Labour said the government was "falling apart in front of us" after ministers accepted a series of technical changes to the bill to pass the Budget.
They were made after it became clear the Democratic Unionists, on whom Theresa May relies for her Commons majority, again said they would not support the Tories.
Mr Rees-Mogg said he had not given up hope of getting the 48 letters of no confidence in the PM needed to trigger a vote.
"What we are seeing from this government is a deliberate decision not to deliver a proper Brexit," he told reporters at a Westminster news conference.
"We have a government led by Remainers who want to keep us tied into the EU as tightly as possible."
He said the 48 letter threshold might be reached next month when MPs get a "meaningful vote" on the withdrawal agreement.
But he added: "I think (the time) is now, or the prime minister will lead the Conservatives into the next election.
Mrs May's allies insist she would win a no confidence vote and under Conservative rules she would then be immune from a challenge for 12 months.
The PM says her Brexit deal is the best the UK can get from Brussels and it will allow the country to take back control of its "money, laws and borders".
In other developments:
Downing Street said that, during talks with Scotland's First Minister Nicola Sturgeon, the PM had emphasised that the draft Brexit terms would give Scottish businesses the "clarity and certainty they need to protect jobs and living standards and see us take back control of our waters".
The SNP leader also met Labour leader Jeremy Corbyn earlier to discuss tactics ahead of the Commons vote.
Ms Sturgeon held a separate meeting with Lib Dem leader Sir Vince Cable, Green MP Caroline Lucas and Plaid Cymru's Westminster leader Liz Roberts, who all back another EU referendum.
She told the BBC's Laura Kuenssberg she wanted to form a "coalition of opposition" to Mrs May's Brexit plans, and that momentum for another referendum was growing.
She described her talks with Mr Corbyn as "exploratory" and said she did not know whether he would back a referendum.
But she said they both agreed that the PM's Brexit deal is a bad one and that no-deal should not be the only alternative presented to MPs.
A Labour spokesman said: "They discussed their common opposition to Theresa May's botched Brexit deal and determination to work across Parliament to prevent a disastrous no-deal outcome."
As it stands, there appears to be a majority in Parliament against the deal.
And Mrs May is coming under growing pressure from the DUP, whose 10 MPs keep her government in power.
The DUP abstained in Monday night's Budget votes as a warning shot over what they say are her broken promises on Brexit.
After the DUP indicated they would abstain again on further votes on Tuesday, ministers accepted Labour and SNP amendments in order to avoid likely defeat.
These will require the government to conduct a review into the public health impact of gaming, a report into the impact of Brexit on international tax enforcement and a review into the impact of tax avoidance measures on income inequality and child poverty.
Under the terms of their House of Commons deal, agreed after Mrs May lost her Commons majority in last year's general election, the DUP is supposed to back the government on Budget matters and on confidence votes.
Shadow chancellor John McDonnell said their refusal to do so now was "absolutely staggering", adding that the Conservatives were "in office but not in power".

On 29 March Theresa May sent a six-page letter notifying the EU of the UK's intention to leave. The Article 50 letter contained a clause little discussed at the time - notifying the EU of the UK's withdrawal from the European Atomic Energy Community, also known as Euratom.
But this previously obscure section has now been put under the political spotlight, with some MPs, including a number of Conservatives, gearing up for a fight on the subject. One prominent Leave campaigner has even said the UK should stay in Euratom after Brexit.
On Thursday, the government will clarify its stance on the issue in a position paper. But what is Euratom and why does it matter?
Euratom regulates the nuclear industry across Europe, safeguarding the transport of nuclear materials, disposing of waste, and carrying out research. It was set up in 1957 alongside the European Economic Community (EEC), which eventually morphed into the EU. The 1957 treaty established a "nuclear common market" to enable the free movement of nuclear workers and materials between member states.
The UK joined Euratom when it joined the EEC in 1973. It is a separate legal entity from the EU, but is tied up with its laws and institutions, and subject to the jurisdiction of the European Court of Justice (ECJ). No country is a full member of Euratom without being a member of the EU.
When EU countries transport nuclear materials or trade them with other countries, Euratom sets the rules. The body also co-ordinates research projects across borders. For example the Culham Centre for Fusion Energy, a laboratory near Oxford, is largely funded by the EU and many of its scientists are EU nationals.
Euratom also reports to the International Atomic Energy Agency (IAEA). If the UK were to leave Euratom it would need to come to a new arrangement with the IAEA.
There are two main arguments why Brexit should involve quitting Euratom.
Firstly, staying in would raise lots of tricky legal questions. For example, the Euratom treaty states that it applies only on the territory of EU member states. Legal opinion is divided on whether a country could leave the EU and retain Euratom membership, according to research by the House of Commons library. But the UK government has made up its mind.
"The triggering of Article 50 on Euratom is not because we have a fundamental critique of the way that it works. It was because it was a concomitant decision that was required in triggering Article 50," said Brexit Secretary David Davis.
The second reason for quitting Euratom is the government's interpretation of the Brexit result. Vote Leave campaigned to restore British sovereignty and "take back control" by ending the supremacy of EU law over domestic law.
In her speech to the Conservative Party conference in October, Theresa May made this rather more specific, pledging to ensure "the authority of EU law in this country ended forever". This stance has been called the "ECJ red line" - in other words stopping the European Court of Justice in Luxembourg having any authority in the UK.
The nuclear agreement is underpinned by the ECJ. That means if states signed up to the Euratom treaty breach its terms, they can be hauled before European judges. This could happen to Britain after Brexit, if it remains signed up to Euratom. Full membership would apparently be incompatible with a strict interpretation of the ECJ red line.
Also, the Euratom treaty requires members to allow the free movement of nuclear scientists, which could fall foul of the government's wish to cut net migration drastically from its current level.
Dominic Cummings, who was campaign director of Vote Leave, this week criticised what he called "government morons" who want to withdraw from Euratom. "Tory Party keeps making huge misjudgements re what the REF was about. EURATOM was different treaties, ECJ role no signif problem," he said on Twitter.
Although the agreement is overseen by the ECJ, the court does not intervene very often, according to those who want to stay in.
Conservative MP Ed Vaizey and Labour MP Rachel Reeves published an article in the Sunday Telegraph this week defending Euratom membership. "There appears never to have been an ECJ case involving the UK and Euratom," they said. "Whatever people were voting for last June, it certainly wasn't to junk 60 years of co-operation in this area with our friends and allies."
James Chapman, a former special adviser to David Davis, has also criticised the application of the "ECJ red line" to Euratom: "I would have thought the UK would like to continue welcoming nuclear scientists who are all probably being paid six figures and are paying lots of tax," he told the BBC last month. "But we're withdrawing from it because of this absolutist position on the European court. I think she [the prime minister] could show some flexibility in that area."
Mr Vaizey and Ms Reeves also raised the issue of cancer medication. Euratom supports the "secure and safe supply and use of medical radioisotopes". Radioactive isotopes are essential for various types of cancer treatment but cannot be stockpiled because they decay quickly.
In the UK they are imported, often from Belgium and the Netherlands. Some experts worry that leaving the treaty will delay the delivery of drugs to patients who need them. Global demand for isotopes is rising rapidly, and many of the reactors that produce them are getting old.
The government's answer to this is that medical isotopes are not fissile nuclear material - that is, capable of reacting - so they are not subject to international nuclear safeguards. According to Science Minister Jo Johnson, their availability "should not be impacted by the UK's exit from Euratom".
In February, Parliament passed a bill giving the government permission to trigger Article 50. Labour MPs tried to add an amendment keeping the UK in Euratom, but it was comfortably voted down.
Last month Theresa May's Conservatives lost their majority in the general election, which has emboldened opponents to the government's Brexit stance.
Though the government's position has been firmed up by signing a confidence-and-supply deal with the DUP, it can still lose key votes if just seven Conservatives vote the other way.
Several of Ed Vaizey's colleagues have backed his position on Euratom. Given the Labour manifesto pledge to "retain access" to the nuclear agency, this means the government could well lose a vote on the issue.
Given that Euratom was explicitly mentioned in the Article 50 letter, any reversal of withdrawal would be difficult, and an act of Parliament would probably not be enough.
Changing or reversing the UK's withdrawal from Euratom would probably need to be done formally by the government. If that were to happen, it would raise another contentious legal question - whether the notification of withdrawal from the EU can be amended or revoked. The government really does not want to open that can of worms.
What's more, staying in the nuclear agreement would not be a matter purely for the UK to decide. The EU, which has published a position paper on Britain's departure from Euratom, would also have to agree. That could make things complicated.
Various options have been mooted for an alternative to full Euratom membership. Switzerland, not an EU member, has a special status as an equal partner as an "associated country". This could be an option explored by the UK. But sticking to the ECJ red line might make that path difficult.
Euratom also has looser co-operation agreements with other countries such as the US and Australia. These third-party countries help fund projects such as the International Thermonuclear Experimental Reactor in France, which is run by Euratom. But moving to a looser agreement could cause disruption when the UK is so integrated into the EU's nuclear energy market. Given the long timescale needed for nuclear projects, scientists worry about the uncertainty.
The final arrangements between the UK and Euratom after Brexit will have big repercussions for a country which is committed to atomic energy for the long term - unlike Germany, which ditched nuclear power in the wake of the 2011 Fukushima disaster.
Last September the government approved a new £18bn power station, financed by the French and Chinese governments, at Hinkley Point in Somerset.
Sellafield, where plutonium is reprocessed and stored, is Europe's largest nuclear facility. The Cumbria site has the largest stockpile of civil plutonium in the world. Euratom runs the on-site laboratory there, and also spends a big chunk of its EU-wide resources running safeguard checks there. There's also the centre at Culham, where Euratom plays a big role.
In May the Commons Energy Committee, which has been investigating the impact of Brexit on energy policy, urged the UK to delay leaving Europe's nuclear regulator. Power supplies could be threatened if a new regulator was not ready, it said.
Whatever decision is finally made on Euratom, it will matter for decades to come.

"They need us more than we need them," has been a recurrent theme in the Brexit debate.
After the referendum, the idea has been used to suggest the government could have taken a tougher line in the negotiations over the terms of the UK's departure from the European Union.
Before the vote, it was used to suggest that the UK would have no difficulty retaining full access to the EU market, because it was in the EU's interests to allow it.
German carmakers were often invoked as likely allies in achieving that goal.
In early 2016, David Davis, then a Conservative backbench MP who was later the Cabinet Minister for Brexit, said: "Within minutes of a vote for Brexit the chief executives of Mercedes, BMW, VW and Audi will be knocking down Chancellor Merkel's door demanding that there be no barriers to German access to the British market."
One central element (though not the only one) in the argument is the fact that the UK has a deficit in its trade with 27 EU member countries.
That is: they export more to the UK than the other way round.
So if there were new barriers to trade, the 27 have more sales of goods and services at risk than the UK does.
New barriers could arise as a result of a no-deal Brexit in the near term, or in a negotiated future relationship that gives less market access than currently prevails.
Even the much vaunted "Canada deal" with additions would involve some new hurdles for exporters to jump.
Depending on exactly what deal, if any, is achieved those barriers would include some combination of tariffs (taxes that are applied only to goods traded across borders), customs procedures and regulatory barriers, such as product standards and authorisation to provide services.
The basic facts of the trade balance are that yes, the UK certainly does buy more from the 27 than the other way round.
The UK had a bilateral trade deficit to the tune of £67bn in 2017. That breaks down to a larger deficit of £95bn for goods, but a surplus of £28bn for services.
So in total, the amount of exports potentially at risk from new trade barriers is greater for the 27 than for the UK.
But that is a rather crude measure of how much each side has to lose.
Let's take another example to illustrate the point.
The EU - with a population of more than half a billion and an annual economic activity or GDP of around £15 trillion - has a trade surplus with Andorra, which has a population of about 80,000 and GDP of less than £3bn.
Does that mean that the EU needs Andorra more than Andorra needs the EU? It would, of course, be an absurd suggestion.
Why? Because the EU's economy is so much larger.
For sure, disruptions to that trade would be a serious problem for some Spanish and French businesses and jobs near the border. But for the EU economy as a whole the impact would be tiny.
Now to state the obvious, the UK is not Andorra. It matters far more to the EU as an export market than Andorra does.
That said, a more revealing measure of what is at stake is to look at the amount of trade exposed to some risk of new barriers as a percentage of either a country's total exports or GDP.
Take goods first, as goods and services data is generally collected differently and is often published separately.
The EU 27 accounts for 48% of UK exports of goods, and 8% of GDP (in 2017, from the European Commission database).
When we look at the share of the EU's exports going to the UK there is a choice to make about whether to include trade among the remaining 27 EU countries in total goods exports. If we do include it, the UK share is 6.2%; if we don't it's 18% of the total.  UK exports account for 2.3% of the EU 27 GDP.
You sometimes hear the suggestion that these figures miss an important point because the two biggest players in the EU, Germany and France, are the true political driving forces in the EU. So are they any more reliant on the UK market than the EU average?
For Germany, the figures are 6.6% of goods exports going to the UK, accounting for 2.6% of GDP. The latter figure is slightly above the EU average.
For France, the equivalent figures are 6.7% of exports and 1.4% of GDP, the latter comfortably below the average for the EU as a whole.
The countries that do have a relatively large exposure to the UK are Ireland, Belgium and the Netherlands.
And what about Germany's carmakers? They didn't show up for battle in the way David Davis hoped.  The head of Germany's car industry association Matthias Wissman said last year: "however important the United Kingdom is to us as a market, the cohesion of the EU 27 and their single market are even more important to our industry".
That said, the UK would be a leading export market for the EU 27. For goods in 2017 it was very slightly behind the US, but well ahead of the next largest China. But it is important to remember: internal trade within the EU is really big for the 27.
There is a significant complication underneath these figures, sometimes known as the Rotterdam effect.
Exports are generally recorded as going to their first destination. So if a container goes initially to Rotterdam in the Netherlands (or Antwerp in Belgium or some other ports) and is then transferred for onward transport to somewhere else, it is nonetheless recorded as an export to (or an import from) the Netherlands (or another EU country).
It has proved impossible to quantify this effect with any real precision. It affects figures for trade going into the UK and out.
But even if we make some fairly extreme guesses about its magnitude, the UK still exports more as a share of its own GDP to the EU 27 than the other way round.
For the services trade, the case is even clearer.
The UK economy is both smaller than the EU's and has a services trade surplus.
In 2016, services exports to the EU were 7.2% of UK GDP; for the EU 27 services exports to the UK were 1.1% of their GDP.
All these figures point in the same direction. The UK looks more exposed in the event of disruption to trade relations.
That is not to say the impact on the EU would be trivial, far from it.
The EU 27 would undoubtedly face significant economic harm from major disturbances to their trade with the UK.  But on the basis of the trade data, the "they need us more" claim looks very shaky.
One point to add about the data. You may see figures elsewhere that are somewhat different.
There are inconsistencies in the way trade data are put together in different countries.
Some of the figures involve converting currencies and exchange rates vary. And there variations from year to year.

The anger directed against MPs over Brexit is "not surprising", the PM's adviser, Dominic Cummings, has said.
The former Vote Leave campaign director said the only way the issue of abuse would be solved is if MPs "respect" the result of the EU referendum.
Mr Cummings's remarks came after Boris Johnson defended language he used in Parliament amid criticism from MPs.
The parliamentary tensions have led 120 archbishops and bishops to warn against "further entrenching our divisions".
The intervention followed an ill-tempered debate on Wednesday, as MPs returned to Parliament after the Supreme Court ruled the suspension of Parliament was unlawful.
The prime minister was criticised by a number of MPs for - among other remarks - describing one Labour MP's safety concerns as "humbug" and repeatedly referring to legislation aimed at blocking no-deal as "the surrender bill".
On Thursday, the Commons heard of threats faced by politicians, with independent MP Caroline Nokes describing how someone had called her a "traitor who deserved to be shot" on a walkabout in her constituency.
Speaking at a book launch that evening, Mr Cummings said MPs had spent three years "swerving all over the shop" following the referendum and it was "not surprising some people are angry about it".
He said both Leave and Remain campaigners had received "serious threats" of violence, which he said should be taken seriously.
But he added: "If you are a bunch of politicians and say that we swear we are going to respect the result of a democratic vote, and then after you lose you say, 'We don't want to respect that vote', what do you expect to happen?"
"In the end, the situation can only be resolved by Parliament honouring its promise to respect the result," he said, echoing sentiments expressed by the prime minister in the Commons on Wednesday.
But former Justice Secretary David Gauke told BBC Radio 4's Today programme: "Some of the language from the prime minister this week has clearly made it harder to win support from Labour MPs for any kind of a deal."
Mr Cummings denied that Downing Street was under pressure following the Supreme Court ruling, a series of parliamentary defeats and the backlash against Mr Johnson's comments.
"This is a walk in the park compared to the referendum. We are enjoying this. We are going to leave and we are going to win," he said.
But, when questioned as he left his home in London on Friday morning, Mr Cummings said: "Who said it would be a walk in the park?"
Told that he had made the remark, he replied: "No."
MPs have expressed concern that Downing Street could seek to bypass legislation - passed earlier this month - to block a no-deal Brexit.
The Benn Act - which Mr Johnson has been referring to as the "surrender act" - says the prime minister will have to ask the EU for an extension to the 31 October Brexit deadline if he is unable to pass a deal in Parliament, or get MPs to approve a no-deal Brexit, by 19 October.
When Mr Johnson talks about the "surrender bill", he is referring to the European Union (Withdrawal) (No. 2) Act, also known as the Benn Act after Labour MP Hilary Benn, who introduced the legislation to the Commons.
The act - which became law earlier this month - stipulates the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK's departure date to 31 January 2020 from the EU.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal. But during this two-day period, MPs - not the government - will have the opportunity to reject the EU's date.
Former Prime Minister Sir John Major - who on Thursday accused Mr Johnson of "wilfully" destroying the prospects of a cross-party agreement on Brexit - expressed concern that the government might sidestep the law by suspending the Benn Act until after 31 October.
Sir John said he thought ministers might be planning to do this by passing an Order of Council, which can be approved by Privy Councillors - government ministers - and has the force of law.
Asked if he was looking at using this method to get around the Benn Act, the prime minister said "no".
And senior cabinet minister told the BBC that such a plan would be "too clever by half".
Downing Street has consistently said the government will obey the law, but Mr Johnson has also insisted he will not seek a delay to Brexit, which the act mandates.
Questioned on the government's position, International Development Secretary Alok Sharma told Today: "I'm not going to set out discussions that have occurred in the privacy of cabinet."
He added that the government would "absolutely" comply with the law.
In interviews with the BBC, Mr Johnson acknowledged that "tempers need to come down" in Parliament.
But he added: "I do think in the House of Commons it is important I should be able to talk about the surrender bill, the surrender act, in the way that I did."
Meanwhile, the College of Bishops has called on politicians to "speak to others with respect", adding that the result of the EU referendum "should be honoured".

Dominic Raab has been appointed Brexit secretary by Theresa May after David Davis resigned from the government.
Mr Raab, who is currently housing minister, was a prominent Leave campaigner during the 2016 referendum.
Mr Davis quit late on Sunday night, saying Theresa May had "given away too much too easily".
The 44-year old Mr Raab, a lawyer before becoming an MP in 2010, will now take over day-to-day negotiations with the EU's Michel Barnier.
The UK is due to leave the European Union on 29 March 2019, but the two sides have yet to agree how trade will work between the UK and the EU afterwards.
There have been differences within the Conservative Party over how far the UK should prioritise the economy by compromising on issues such as leaving the remit of the European Court of Justice and ending free movement of people.
The simple question for Davis, by Laura Kuenssberg
What sticks out the most from my interview with David Davis this morning is a very simple question we asked.
Is the prime minister's plan really leaving the EU? "I don't think so," he said.
That is the sentiment that's widely shared among the Tory party, and perhaps among many voters too. And guess what? It doesn't always matter which side of the referendum they were on either.
Some former Remainers say "look, this is a dodgy compromise, what's the point? If we are going to do this, then for goodness sake let's do it properly or just stay in".
From some Leavers, like Mr Davis, you also get "look, this is a dodgy compromise, what's the point? If we are going to do it, then for goodness sake let's do it properly".
Mrs May's Conservative Party only has a majority in Parliament with the support in key votes of the 10 MPs from Northern Ireland's Democratic Unionist Party, so any split raises questions about whether her plan could survive a Commons vote - and has also led to renewed questions about whether she will face a challenge to her position.
Mr Raab has served in government since after the 2015 election, initially working in the Ministry of Justice before moving to the communities department in January.
The European Commission has declined to comment on the change of personnel, saying it would continue to negotiate with "goodwill" to try and secure an agreement on the terms of the UK's exit and future relations.
Asked how much of a problem Mr Davis's resignation was for the future of the negotiations, a spokesman replied: "It is not for us, we are here to work."
Mr Davis said he could not remain in his post because he no longer believed in the plan for the UK's future relations with the EU which was backed by the cabinet on Friday.
He said he hoped his resignation would make it easier for the UK to resist EU attempts to extract further concessions - but he insisted he was not seeking to undermine or challenge the prime minister.
In an interview with the BBC's political editor Laura Kuenssberg, Mr Davis said Mr Raab would be "very effective" in the post.
Reflecting on his resignation, he said he had lived with compromises in Brexit policy for two years but there came a point where these went "too far".
"I worry about the fine detail and that it will not work out as we hope," he said.
Asked what he would say to colleagues who thought it was time to remove Theresa May, he replied it was "not a good idea" - insisting that she was a "good prime minister".
Junior Brexit minister Steve Baker, who also resigned overnight, launched an attack on government policy.
He told the BBC's Daily Politics that he had been "blindsided" by the Brexit proposal agreed at Chequers.
Mr Baker also said that he and his team had been preparing a white paper "which did not accord with what has been put to the cabinet at Chequers".
The mood at Westminster, by Iain Watson
The atmosphere is volatile. The long-standing Leave supporters of the European Research Group of Tory MPs will have two meetings today - either side of the PM's address to her own MPs - to discuss next steps.
Views differ on whether the government's position is simply impractical - "the worst of both worlds" - or whether it actually breaches a manifesto commitment by offering a customs union in all but name.
But there is agreement amongst many Brexiteers that the policy should change, and quickly. It is less clear how they will bring that about. If there is not a direct triggering of a leadership contest, what are the options?
One is that Brexiteers go "on strike" and refuse to back government policy in parliament, weakening her premiership unless she changes course.
Another is that backbench Brexiteers put more pressure on like-minded cabinet colleagues to follow David Davis out the door.
Speaking to the BBC last week, Mr Raab said the process of negotiating Brexit was "rocky" but what mattered was getting there in the end, which would require "flexibility and pragmatism".
He told the Political Thinking podcast that he was "relaxed" about the UK leaving without a deal and it was "not something I would fear".
Conservative MPs welcomed the appointment of Mr Raab, who has a black belt in karate, one describing him as a "highly capable" figure with a clear attention to detail.
But Labour said a new man fronting the negotiations "changed nothing".
"The deep division at the heart of the Conservative Party has broken out in public and plunged this government into crisis," said shadow Brexit secretary Sir Keir Starmer.
"It is now clearer than ever that Theresa May does not have the authority to negotiate for Britain or deliver a Brexit deal that protects jobs and the economy."
Asked whether Mr Raab would be in charge of the talks, No 10 said Mrs May had "always been, from the outset, the lead negotiator".
But a spokesman said there was a "huge body of work to be done, in terms of preparations for the UK leaving the EU and that obviously includes no-deal preparations as well".
Mrs May will address Parliament later on the plan agreed at Chequers on Friday as well as address Tory MPs as she seeks to keep her Brexit strategy on track.
Ahead of Monday's statement, opposition MPs and peers - as well as Tory MPs - are being offered briefings by Downing Street on the detail of the Chequers statement.
A spokesman for the European Research Group of eurosceptic Tory MPs told the BBC that involving opposition MPs had caused considerable anger and was the government's "stupidest mistake".
And Jacob Rees-Mogg, who chairs the group, likened a PM relying on opposition MPs to the children's story in which the gingerbread man accepts the offer of a ride across a river from a fox, only to get eaten by it.

A deal with the EU can be reached by October but the UK is preparing for the possibility of no deal, Brexit Secretary Dominic Raab has said.
He said he would return to Brussels for talks on Thursday and strain "every sinew" to get "the best deal".
But the government had plans in place in case talks did not end well, he told the BBC.
Labour leader Jeremy Corbyn said there must be a "serious stepping up of negotiations" to avoid no deal.
The UK is due to leave the European Union on 29 March 2019, but the two sides have yet to agree how trade will work between the UK and the EU afterwards.
Theresa May hopes the government's plan, detailed recently in the Brexit White Paper, will allow the two sides to reach a deal on relations by the autumn.
Downing Street said on Sunday that cabinet ministers would be promoting the plan across Europe over the summer.
Theresa May would "take the lead" by meeting the Austrian chancellor, Czech prime minister and Estonian prime minister next week.
Mrs May said: "We must step up the pace of negotiations and get on to deliver a good deal that will bring greater prosperity and security to both British and European citizens.
"We both know the clock is ticking - let's get on with it."
Mr Raab told the BBC's Andrew Marr Show if the "energy, ambition and pragmatism" the UK brought to negotiations was reciprocated, a deal would be done in October.
He noted that 80% of the withdrawal agreement was already settled.
And he said it was "useful" that EU chief Brexit negotiator Michel Barnier had raised questions about the prime minister's blueprint for the UK's future trading relationship with the EU.
"The fact Michel Barnier is not blowing it out of the water but asking questions is a good, positive sign - that's what we negotiate on."
But he said preparations such as hiring extra border staff were being made because "any responsible government" would make sure plans were in place in case negotiations failed.
Technical notices would be released for businesses and citizens affected during the summer to be "very clear about what they should do and what we are doing on their behalf" he added.
Asked about European Commission comments that there were no arrangements in place for UK and EU expats in the event of no deal, Mr Raab said: "Well, I think that's a rather irresponsible thing to be coming from the other side.
"We ought to be trying to reassure citizens on the continent and also here.
"There is obviously an attempt to try and ramp up the pressure."
Analysis by Jonathan Blake, BBC political correspondent
We've heard it often enough: "No deal is better than a bad deal".
But for EU negotiators to believe the UK would walk away without agreement, the government has to be seen to be taking that option seriously.
And so we are told about "planning" and "technical notices" to prepare for a "clean break" Brexit.
Reports of food stockpiles and a motorway becoming a lorry park are dismissed as "unhelpful snippets" but contingency plans will be made nonetheless.
Both sides agree a deal needs to be reached by October, and negotiations are likely to go down to the wire.
So even if a deal appears to be in sight, expect the talk of the UK leaving the EU without one to continue.
He added that the prospect of people being removed from the UK was "far-fetched and fanciful" and said it would be "frankly irrational" for the EU to go for the "worst case scenario" of no deal.
But the UK had to be prepared with things like allocating money, preparing treaty relations, and hiring extra border staff "so that Britain can thrive, whatever happens," he said.
Labour leader Mr Corbyn, on a visit to the annual Tolpuddle Martyrs Festival in Dorset, said it seemed the priority was preparation for no deal.
He added that would be "very bad", as "we then go onto World Trade Organization tariff rates that would hit the manufacturing industry and hit the food processing industry, and hit an awful lot of things in Britain very rapidly".
"There has to be a serious stepping-up of negotiations to reach an agreement on customs and on trade."
Earlier, Mr Raab suggested to the Sunday Telegraph that he was still persuading other cabinet ministers that the government's "pragmatic" strategy for leaving the EU was the "best plan" and that the UK could refuse to pay its so-called divorce bill, a payment from the UK to the EU estimated to be about £39bn, if it does not get a trade deal.
Theresa May's proposal for a future trade relationship with the EU sparked two cabinet resignations, including Mr Raab's predecessor David Davis.
The White Paper proposes close ties in some areas, such as the trade in goods, but will end free movement and the jurisdiction of the European Court, and allow the UK to strike trade deals with other nations.
Critics at Westminster say it is an unworkable compromise which would leave the UK being governed by the EU in many areas, but with no say in its rules.
And EU chief negotiator Michel Barnier questioned on Friday whether UK plans for a common rulebook for goods and agri-foods were practical and said the EU would not run the risk of weakening its single market.
Meanwhile, Mr Davis, whose resignation from Mrs May's top team was followed by that of former Foreign Secretary Boris Johnson, told the Sunday Express the government should "start again" on withdrawal plans.

Theresa May and Donald Trump are holding talks at her country retreat Chequers, following his controversial comments on the PM's Brexit plan.
In an interview with the Sun, Mr Trump said the PM's plan would "probably kill" any trade deal with the US.
But on Friday, he said he and Mrs May had "probably never developed a better relationship" than during this trip - his first to the UK as president.
Meanwhile, a giant blimp of Mr Trump as a baby is floating in central London.
It is part of a demonstration in Parliament Square, one of many due to take place across the UK on Friday.
In his interview with the Sun, Mr Trump also said that former Foreign Secretary Boris Johnson - who disagrees with the PM on Brexit and resigned this week - would make a "great prime minister", adding "I think he's got what it takes".
He also renewed his criticism of London Mayor Sadiq Khan over last year's terror attacks in London, saying he had done "a terrible job".
Downing Street has not yet reacted to Mr Trump's remarks, but Chancellor Philip Hammond said the talks will be "very positive".
Theresa May has been making the case for a US free trade deal, and says Brexit is an "unprecedented opportunity" to create jobs in the UK and US.
The US president and his wife, Melania, were given a red carpet reception at Blenheim Palace, Oxfordshire on Thursday evening.
They were at a black-tie dinner with Mrs May as news broke of his interview with the newspaper, which said it was conducted while he was in Brussels.
After it was published, White House spokeswoman Sarah Sanders said the president "likes and respects Prime Minister May very much", adding that he had "never said anything bad about her".
Mr Trump - who has been a long-time supporter of Brexit - told The Sun that the UK's blueprint for its post-Brexit relations with the EU was "a much different deal than the people voted on".
He said the Brexit proposals Mrs May and her cabinet thrashed out at the PM's country house Chequers last week "would probably end a major trade relationship with the United States."
"We have enough difficulty with the European Union," he said, saying the EU has "not treated the United States fairly on trading".
He also said Mrs May had not listened to his advice on how to do a Brexit deal, saying: "I would have done it much differently.
"I actually told Theresa May how to do it but she didn't agree, she didn't listen to me. She wanted to go a different route," he said.
Tom Newton Dunn, the Sun journalist who interviewed Mr Trump, said the US president seemed "sensitive" and knew about the "Trump baby" inflatable.
"He's really quite stung by the criticism he's been getting," said Mr Newton Dunn. "He knew all about the baby blimp. I think it hurt him."
The BBC's political editor, Laura Kuenssberg, said Mr Trump's interview had "driven a bulldozer" through Mrs May's claim that the UK would be able to get decent trade deals with the wider world, while sticking to the EU rules.
But Foreign Office minister Sir Alan Duncan said things had "moved on" since Mr Trump's interview - which was carried out before he arrived in the UK - and the mood at Thursday night's dinner was "fantastically positive and did focus a lot on trade".
The government does not see Mr Trump's behaviour as "rude", said Sir Alan, adding: "Donald Trump is a controversialist. That's his style."
Mayor of London Sadiq Khan defended his decision to allow the giant Trump baby inflatable to fly over London, saying: "The idea that we limit the right to protest because it might cause offence to a foreign leader is a slippery slope."
And, responding to Mr Trump's criticism of his response to terrorism, Mr Khan said it was "interesting" that he "is not criticising the mayors of other cities" which have also experienced terror attacks.
Meanwhile, Shadow Foreign Secretary Emily Thornberry said the PM "should be standing up to [Mr Trump]" after he "slagged her off", instead of holding his hand.
Mr Trump's comments came on the same day the UK government published its proposal for its long-term relationship with the EU.
The plan is aimed at ensuring trade co-operation, with no hard border for Northern Ireland, and global trade deals for the UK. Mrs May said the plan "absolutely delivers on the Brexit we voted for".
But after ministers reached an agreement on the plan at Chequers a week ago, leading Brexiteers Boris Johnson and David Davis resigned from the cabinet.
Mrs May and Mr Trump are watching a joint counter-terrorism exercise by British and US special forces at a military base.
The pair will then travel to Chequers - the PM's country residence in Buckinghamshire - for talks also being attended by Foreign Secretary Jeremy Hunt.
Extra security is in place to police protests planned for the second day of Mr Trump's visit.
The president and first lady will travel to Windsor on Friday afternoon to meet the Queen, before flying to Scotland to spend the weekend at Mr Trump's Turnberry golf resort. This part of the visit is being considered private.

The UK is "doing great" following its vote to leave the EU, US President-elect Donald Trump has said.
In his first UK interview - with former Justice Secretary Michael Gove for the Times - Mr Trump said he thought the UK was "so smart in getting out".
Mr Trump promised a quick trade deal between the US and the UK after he takes office on Friday.
But the European Commission reacted to the comments by saying no formal talks were allowed before the UK left the EU.
Mr Trump, who also criticised "obsolete" Nato and German Chancellor Angela Merkel's immigration policies, spoke to the Times and German newspaper Bild ahead of his inauguration on Friday.
Outgoing US President Barack Obama said in April last year that the UK would be "at the back of the queue" if it quit the EU.
Mr Gove - a prominent Leave campaigner during last year's referendum - asked Mr Trump whether the UK was now "at the front of the queue" for a trade deal with the US following the Brexit vote.
"I think you're doing great," Mr Trump said. "I think it's going great."
The president-elect said: "Trump said Brexit is going to happen, and it happened. Everybody thought I was crazy.
"Obama said, 'They'll go to the back of the line,' and then he had to retract his statement."
Mr Trump added: "Countries want their own identity and the UK wanted its own identity, but I do think if they hadn't been forced to take in all of the refugees then you wouldn't have a Brexit."
On a potential US-UK trade deal, he said: "We're gonna work very hard to get it done quickly and done properly. Good for both sides."
Mr Gove told BBC Radio 4's Today programme the president-elect wanted a trade deal "signature-ready at the earliest possible opportunity" - former UKIP leader Nigel Farage later said he expected a trade deal within three months of Mr Trump becoming president.
However a European Commission spokeswoman said that "categorically won't be possible" because formal talks "cannot take place in any official capacity until Britain has finished its negotiations with the EU".
Mr Gove, a columnist for the paper, added: "He (Mr Trump) stressed that he believed the European Union would potentially break up in the future and that other countries would leave.
"So in a sense he is both emotionally and financially invested in it."
Arriving at a summit in Brussels, Foreign Secretary Boris Johnson said: "I think it's very good news that the United States of America wants to deal a good free trade deal with us and wants to do it very fast, and it's great to hear that from President-elect Donald Trump.
"Clearly it will have to be a deal that is very much in the interests of both sides, but I have no doubt that it will be."
In his interview, Mr Trump talked about the recent dip in the value of the pound.
"The fact that your pound sterling has gone down?" he said. "Great, because business is unbelievable in a lot of parts in the UK, as you know. I think Brexit is going to end up being a great thing."
The president-elect's views came as Chancellor Philip Hammond said the UK may be forced to change its "economic model" if "closed off" from the European single market.
During the Times/Bild interview, held in Trump Tower, New York, the president-elect said he thought Mrs Merkel was the "by far the most important European leader".
"If you look at the European Union, it's Germany - it's basically a vehicle for Germany," he said.
Mr Trump said Mrs Merkel had made a "big mistake" by admitting more than one million migrants to the country.
"I think she made one very catastrophic mistake and that was taking all of these illegals, you know, taking all of the people from wherever they come from. And nobody even knows where they come from," he added.
Mr Trump also stressed that he would "start off trusting both Russian President Vladimir Putin and Mrs Merkel" on taking office, but would "see how long that lasts".
Talking about international security, Mr Trump argued that he had said "a long time ago that Nato had problems".
"One, that it was obsolete because it was designed many many years ago, and number two, that the countries weren't paying what they're supposed to pay."
Last November, Downing Street said Prime Minister Theresa May and Mr Trump had discussed the need for more countries to commit to spending 2% of national income on defence, when speaking on the telephone after the US election.
Mr Trump's comments on the UK and the EU came ahead of the launch of a cross-party campaign called Brexit Together.
It aims to bring together political voices from both sides of the referendum debate to develop a "shared vision" on immigration, the economy and market access, security and sovereignty.
One of the campaign's founders, Labour MP Caroline Flint, said "a lot was said in both campaigns... that left the public feeling quite baffled at some of the rhetoric".
It was "absolutely right we should have a good trading relationship with the EU and, of course, getting a deal with the US would be a fantastic opportunity as well", she added.
A separate report, co-written by Boris Johnson's former economic adviser, Gerard Lyons, says membership of the single market has been a "major drawback" for the UK's service industries. It recommends a "clean Brexit", leaving this and the customs union.
Meanwhile, the man tipped to become Mr Trump's ambassador to the EU has said the president-elect is committed to securing a trade deal with the UK, and preliminary talks could begin ahead of its formal departure from the 28-nation bloc.
Theodore Malloch, a professor at Henley Business School in Reading, told BBC Radio 4's Today programme: "If you want to facilitate something it can be done in an expeditious manner, so I would hope on the day Britain triggers Article 50 Mrs May would be able to announce we have just started discussions with the United States."
In his Times/Bild interview, Mr Trump also discussed his Scottish-born mother, saying: "She was so proud of the Queen. She loved the ceremony and the beauty, because nobody does that like the English, and she had great respect for the Queen and liked her.
"Any time the Queen was on television, for an event, my mother would be watching."
Liberal Democrat leader Tim Farron dismissed Mr Gove's interview with Mr Trump as "a puff piece from a clearly admiring fan".
He added: "I don't know the shape of the Europe that Trump dreams of, but I know it frightens me."

US President Donald Trump has said Boris Johnson would do "a great job" as UK prime minister and they would have "a very good relationship".
"He's a different kind of a guy but they say I'm a different kind of a guy too," Mr Trump told reporters.
Outgoing prime minister Theresa May "has done a very bad job with Brexit", he added.
Mr Johnson is the frontrunner in the contest to become the next Tory leader and UK prime minister.
He and Foreign Secretary Jeremy Hunt are the final two candidates, with the winner announced on 23 July and taking office the next day.
President Trump said he had spoken to Mr Johnson on Thursday, adding: "We get along well."
"I like Boris Johnson, I always have," he told reporters in the Oval Office in Washington DC.
Commenting on the UK's Brexit negotiations, he said: "It's a disaster and it shouldn't be that way."
"I think Boris will straighten it out," he added.
The US president has previously said Mr Johnson would be an "excellent" choice as Conservative leader.
He has also been critical of Mrs May's Brexit policy in the past, saying he was surprised by how "badly" the negotiations had gone.
Some 160,000 Conservative Party members are voting in a postal ballot to elect the next leader. Ballots must be returned by 17:00 BST on Monday.

President Trump has promised a "very big trade deal" with the UK, saying its departure from the EU will be like losing "an anchor round the ankle".
Mr Trump was speaking after a breakfast meeting with Mr Johnson at the G7 summit in Biarritz in France.
But Mr Johnson said the US must open up its markets if a post-Brexit trade deal is to be agreed.
"I don't think we sell a single joint of British lamb in the United States, we don't sell any beef," the PM said.
Mr Johnson's breakfast meeting came before a day of discussions with other world leaders at the summit.
The PM also met European Council President Donald Tusk, a day after the two men clashed over who would be held responsible for a no-deal Brexit.
Speaking to reporters after the working breakfast, Mr Trump said a deal with the UK would happen "quickly".
"We're going to do a very big trade deal, bigger than we've ever had with the UK," he said.
"And now at some point they won't have the obstacle, they won't have the anchor around their ankle, because that's what they have."
Mr Johnson told Mr Trump: "Talking of the anchor, Donald, what we want is for our ships to take freight, say, from New York to Boston, which for the moment they're not able to do."
In a later interview with the BBC, Mr Johnson said agreeing any trade deals with the US within a year "would be tight".
"My own experience of the way Americans work, the size and complexity of the deal we want to do probably means we won't be able to do within a year.
When asked if it could take five years, he replied: "No, we'll do it faster than that.
"We need to do it fast, but to get the whole thing done from soup to nuts within a year is going to be a big ask."
Before his talks with the US President, Mr Johnson spoke about "massive opportunities for the UK to prise open the American market".
As a member of the European Union, the UK cannot make its own trade deals with other countries - and the EU does not have a free trade deal with the US.
The UK has already agreed 13 "continuity" deals with 38 countries that will apply post-Brexit.
Offering an example of an American trade restriction, Mr Johnson said: "Melton Mowbray pork pies, which are sold in Thailand and in Iceland, are currently unable to enter the US market because of, I don't know, some sort of food and drug administration restriction."
He continued: "UK bell peppers cannot get into the US market at all.
"Wine shipments are heavily restricted. If you want to export wine made in England to the US you have to go through a US distributor.
"There is a tax on British micro-breweries in the US that doesn't apply to US micro-breweries in the UK."
The government added that tariffs on some UK goods in the US can reach up to 28% for fashion, 15% for machinery and 35% for food and drink.
David Henig, the UK director of the European Centre For International Political Economy, said the US "would be loathe" to get rid of the barriers intended to protect US producers.
He added: "The US is quite protectionist - the US have never done a trade deal the likes of which Mr Johnson is describing.
"The question is whether the US is prepared to give the UK something and what we would have to give them in return.
"It is less clear what Trump wants in terms of trade altogether."
In June, Mr Trump made comments that the NHS "was on the table" in US-UK trade deal - but later rowed back on his remarks.
At the G7 summit Mr Johnson was asked if he had made it clear the NHS was not on the table.
He replied: "Not only have I made clear of that, the president has made that very, very clear. There is complete unanimity on that point."
Trade deals involve two or more countries agreeing a set of terms by which they buy and sell goods and services from each other.
Deals are designed to increase trade by eliminating or reducing trade barriers. These barriers might include import or export taxes (tariffs), quotas, or differing regulations on things such as safety or labelling.
Last month, President Trump said talks about a "very substantial" trade deal with the UK were already under way.
He said a bilateral post-Brexit deal could lead to a "three to four, five times" increase in current trade - but provided no details about how that would be achieved.
However, the Speaker of the US House of Representatives, Nancy Pelosi, said a UK-US trade deal would not get through Congress if Brexit undermined the Good Friday Agreement.
Ms Pelosi said the UK's exit from the EU could not be allowed to endanger the 1998 Irish peace deal, which the US helped facilitate.

The UK and the EU face a "furious race against time" to finalise Brexit talks before March 2019, the head of the European Council says.
Donald Tusk urged EU leaders to show unity as they try to negotiate what the future relationship will look like and to set up transitional arrangements.
The EU is set to agree this week that enough progress has been made so far to move on from the first phase of talks.
The UK has been told not to "backtrack" on last week's divorce deal.
The comment from EU chief negotiator Michel Barnier came after UK Brexit Secretary David Davis suggested the divorce agreement unveiled by Theresa May amounted to a "statement of intent" rather than a binding agreement.
Mr Davis - the UK's Brexit secretary - said he was quoted out of context.
But European Parliament negotiator Guy Verhofstadt said the "unacceptable remarks" would harm "good faith" in the process.
The UK is set to leave the EU in March 2019, two years after Mrs May served formal notice of Brexit.
Both sides hope to finalise a deal by October 2018 on the future relationship, including trade, so the UK and European Parliaments have time to vote on it before the UK leaves.
In his formal letter on Tuesday inviting leaders to this week's EU summit, Mr Tusk told the 27 member states: "This will be a furious race against time, where again our unity will be key."
On Sunday, Mr Davis said guarantees on the Northern Ireland border - included in a joint EU-UK report published on Friday - were not legally binding unless the two sides reached a final deal.
But he told LBC Radio on Monday they would be honoured whatever happened.
A European Commission spokesman said the first-phase deal on the Northern Ireland border, the divorce bill and citizens' rights did not strictly have the force of law.
"But we see the joint report of Michel Barnier and David Davis as a deal between gentlemen and it is the clear understanding that it is fully backed and endorsed by the UK government."
The Brexit secretary's comments at the weekend about the legality of what's been agreed so far between the UK and the EU have been widely noted in Brussels, and a handful of member states have brought them up with me.
"To say we are annoyed is putting it too strongly, though," said one diplomat. "This is the sort of stuff we expected," said another. "It's never good when someone questions an agreement 24 hours after it was done," a third official suggested.
This forms the backdrop to the discussion taking place among EU ministers about the European Council's draft guidelines for Phase 2 of the Brexit talks.
But it is not clear if it will lead to any changes to the draft text that will be discussed by leaders on Friday morning. The document already states in its first paragraph that progress in phase 2 of the talks is contingent on commitments from phase 1 being kept.
Mr Verhofstadt has tabled two amendments for MEPs to debate on Wednesday, one of which says Mr Davis's comments risk undermining "the good faith that has been built during the negotiations".
Another amendment calls on Britain to "fully respect" last week's Brexit deal and ensure it is "fully translated" into a draft Withdrawal Agreement.
On Monday morning, he tweeted:
And at a press conference in Brussels, he said the UK must "stick to its commitments" and put them into a draft Withdrawal Agreement "as soon as possible" if there is to be progress in the second phase of talks.
Mr Davis replied with two tweets of his own, promising to work with Mr Verhofstadt to allay his concerns:
The European Parliament gets a formal vote on the final Brexit deal but it has also been holding debates and issuing resolutions throughout the process to make its voice heard.
Mr Verhofstadt has introduced the amendments alongside the leaders of four other European Parliament political groups.

The EU will be "defeated" in Brexit negotiations unless it maintains absolute unity, European Council president Donald Tusk has said.
The ex-Polish prime minister told the European Parliament the UK's departure was the EU's "toughest stress test" and it must not be divided at any costs.
"If we fail it then the negotiations will end in our defeat," he told MEPs.
But one German MEP said the EU's stance was "illogical, dangerous and unfair" and UKIP accused the EU of "extortion".
The UK is due to leave the European Union at the end of March 2019 and until Mr Tusk's comments both sides have sought to avoid talking about victory, defeat and winners and losers in the negotiations.
In an update following last week's Brussels summit where the Brexit process was discussed, Mr Tusk said he was "obsessed" with preserving the unity of the other 27 members.
BBC's Brussels correspondent Adam Fleming
Article 50 of the EU's Lisbon Treaty allows the UK and the EU to negotiate an orderly withdrawal, a transition period and the shape of the future relationship within a two-year window.
Mr Barnier plans to complete the withdrawal agreement by the autumn of 2018 so it can be ratified by the European Council and the European Parliament.
So we could know the outlines of the future relationship by then.
But under EU law, a trade deal would have to be signed when the UK became a so-called "third country" and it is this that would likely have to be ratified by Parliaments in the member states.
"We must keep our unity regardless of the direction of the talks," Mr Tusk said. "The EU will be able to rise to every scenario as long as we are not divided."
"If we fail it then the negotiations will end in our defeat," he told MEPs.
He added: "It is in fact up to London how this will end: with a good deal, no deal or no Brexit. But in each of these scenarios we will protect our common interest only by being together."
Responding to suggestions that the UK might choose to stop its withdrawal, a Downing Street spokesman said: "Brexit is not going to be reversed."
So far, the Brexit negotiations have focused on the three "separation" issues of how much the UK has to pay to "settle its accounts" when it leaves, what happens to EU citizens in the UK and Britons elsewhere in the EU after Brexit, plus what happens with the Northern Ireland border.
The EU says it will only move on to discuss the UK's future relations with the EU after "sufficient progress" has been made on these three issues.
At last week's summit EU leaders decided more work was needed on these items before trade talks could begin with the UK - although the remaining 27 EU members have agreed to talk about the future options among themselves. The UK wants the second phase to start as soon as possible.
On Monday, Theresa May told MPs she had a "degree of confidence" of making enough progress by December to begin trade talks.
Meanwhile, the EU's chief negotiator Michel Barnier has suggested negotiations on a UK-EU trade deal could take three years if they begin in December.
He told the Belgian newspaper L'Echo that the process would not be "without risks" because national parliaments in all the 27 remaining states would "have to give their approval" to any deal.
A spokesman for Mr Barnier confirmed the remarks but stressed anything was possible and it was not a definitive statement that a deal would be done by December 2020.
Speaking in Tuesday's debate, Conservative MEP Syed Kamall, who heads the European Conservatives and Reformists Group, called for more pragmatism and less idealism from the EU in their approach to the talks.
"There needs to be an understanding from the EU 27 where the British people are coming from," he said.
And Hans-Olaf Henkel, a German MEP from the Conservatives and Reformists Group in the European Parliament, urged Mr Tusk and European Commission President Jean-Claude Juncker to demonstrate more of the "British values of fairness" asking "whether you would agree a price on something you don't know or what you buy for".
For UKIP, MEP Ray Finch warned that the UK would "remain subservient to the EU legally and financially" if talks continued on their current trajectory.
Referring to demands for the UK to pay a so-called divorce settlement, he said: "This extortion will poison UK and EU relations for years to come," adding that the two sides should "shake hands and walk away" now.

European Council President Donald Tusk has spoken of a "special place in hell" for "those who promoted Brexit without even a sketch of a plan of how to carry it out safely".
He was speaking after talks with Irish leader Leo Varadkar in Brussels.
Brexit-backing MPs reacted with anger to the comments, accusing Mr Tusk of "arrogance".
Downing Street said it was a question for Mr Tusk "whether he considers the use of that kind of language helpful".
The prime minister's official spokesman said: "We had a robust and lively referendum campaign in this country. In what was the largest democratic exercise in our history, people voted to leave the EU."
He added that everyone should now focus on delivering that.
Mr Tusk's Twitter account tweeted his comments immediately after he made them in a news conference.
And at the end of their news conference, Mr Varadkar was picked up by the microphones telling Mr Tusk: "They'll give you terrible trouble in the British press for that."
Mr Tusk nodded at the comment and both laughed.
Brussels officials were quick to clarify Mr Tusk's remarks, stressing to BBC correspondent Adam Fleming that the Brexiteers' special place in hell would be for when they are dead and "not right now".
Jean-Claude Juncker tried to laugh off the comments at a later press conference with Mr Varadkar, saying the only hell he knew was doing his job as the president of the European Commission.
And Guy Verhofstadt, the European Parliament's chief Brexit negotiator, referencing Mr Tusk's comments, later tweeted: "Well, I doubt Lucifer would welcome them, as after what they did to Britain, they would even manage to divide hell."
But leading Brexiteers in the UK took to social media to express their anger at Mr Tusk's remarks.
Former UKIP leader Nigel Farage, who is now an independent MEP, tweeted: "After Brexit we will be free of unelected, arrogant bullies like you and run our own country. Sounds more like heaven to me."
Commons leader Andrea Leadsom, who also campaigned for Britain's exit from the EU, said Mr Tusk should apologise for his "disgraceful" and "spiteful" comments.
"I'm sure that when he reflects on it he may well wish he hadn't done it," she told BBC Radio 4's World at One.
Former Brexit Secretary David Davis, when asked on ITV Peston's programme how he felt "when President Tusk practically reserved your place in hell?", said: "Perhaps he'll join us there.
"When people throw insults around it says more about them than the people they're insulting."
The Democratic Unionist Party's Brexit spokesman Sammy Wilson said: "This devilish Euro maniac is doing his best to keep the United Kingdom bound by the chains of EU bureaucracy and control.
"It is Tusk and his arrogant EU negotiators who have fanned the flames of fear in an attempt to try and overturn the result of the referendum."
But Sinn Fein President Mary Lou McDonald backed Mr Tusk, arguing that it was the position of "hardline" Brexit-supporting MPs like Boris Johnson and Jacob Rees-Mogg that was "intemperate" and "untenable".
And Labour MP Ben Bradshaw, who supports having another EU referendum, said Mr Tusk was "absolutely right" and it was "painful" for leading figures in the Leave campaign, such as Boris Johnson and David Davis, "to have the truth pointed out to them".
Theresa May - who supported the UK staying in the EU during the 2016 EU referendum but has always insisted that Brexit must be delivered because that was what people voted for - is due to arrive in Brussels on Thursday to seek legal changes to the withdrawal deal she signed with the EU. She hopes these changes will help her get it through the UK Parliament.
BBC political correspondent Iain Watson said the government was likely to publish a new employment bill before the next vote on Mrs May's deal, with the aim to maximise support for it from Labour MPs.
Meanwhile, Labour leader Jeremy Corbyn has set out five demands for his party to support a Brexit deal - calling for them to be enshrined as objectives in domestic law.
In a letter to the prime minister, he said Labour wanted a UK-wide customs union, close alignment with the single market, "dynamic alignment" on rights and protections, "clear commitments" on participation in EU agencies and funding programmes and "unambiguous agreements" on the detail of future security arrangements.
He said Labour did not believe that "simply seeking modifications" to the backstop was a sufficient response.
Mr Corbyn added that EU leaders had been clear that changes to the political declaration were possible if a request was made by the UK government "and if the current red lines change".
By BBC Brussels reporter Adam Fleming
The EU has been absolutely scathing about some of the British political class today.
The dam broke on Donald Tusk's pent-up feelings about the leaders of the Leave campaign.
The Irish prime minister suggested that MPs either didn't know what they were doing or were misled when they voted to look for alternatives to the Irish backstop.
But - and it's a big but - they have all been open to the prime minister coming to Brussels with a solution to break the deadlock.
And while Jean-Claude Juncker ruled out the idea of the UK having the right to pull out of the backstop if it were ever needed, he didn't say anything about the other idea doing the rounds - a time limit.
Donald Tusk said that the other 27 EU members had decided in December that the withdrawal agreement was "not open for renegotiation" - a message echoed by Mr Juncker.
Mr Tusk also had a message for Remain supporters in the UK, with 50 days to go until Brexit happens, with a deal or without one, saying: "I have always been with you, with all my heart".
But he added: "The facts are unmistakable. At the moment, the pro-Brexit stance of the UK prime minister, and the Leader of the Opposition, rules out this question.
"Today, there is no political force and no effective leadership for Remain. I say this without satisfaction, but you can't argue with the facts."
Mr Tusk said the Irish border issue and the need to preserve the peace process remained the EU's "top priority".
He hoped Mrs May would "give us a deliverable guarantee for peace in Northern Ireland and the UK will leave the EU as a trusted friend" that can command a Commons majority.
Mr Varadkar said that while he was "open to further discussions" with the UK government about post-Brexit relations, the legally-binding withdrawal agreement remained "the best deal possible".
And the backstop was needed "as a legal guarantee to ensure that there is no return to a hard border on the island of Ireland".
He later said he will meet Theresa May for talks in Dublin on Friday.
Jean-Claude Juncker said alternative arrangements - the form of words backed by MPs in a vote last week - "can never replace the backstop".
Clarification 27 February 2019: While the summary of this story and opening paragraph made clear that Mr Tusk was referring to a specific group of people - those who promoted Brexit without a plan - the original headlines were misleading and so were amended shortly after publication on 6 February.

Theresa May's proposed new economic partnership with the EU "will not work", the head of the European Council has said.
Donald Tusk said the plans risked undermining the EU's single market.
He was speaking at the end of an EU summit in Salzburg where leaders of the 27 remaining member states discussed Brexit.
Mrs May said her proposals were the "only serious credible" way to avoid a hard border in Northern Ireland.
She said she had held "frank" talks with Mr Tusk, adding: "Yes, concerns have been raised and I want to know what those concerns are."
There was "a lot of hard work to be done", she said, but added that the UK was also making preparations in case no deal could be reached.
Mrs May reiterated that she would not accept the EU's "backstop" plan to avoid a hard border in Northern Ireland, and said the UK would shortly be bringing forward its own proposals.
The UK is due to leave the EU on 29 March 2019, and both sides are trying to reach a deal in time.
There is still no agreement on some issues, including how to avoid new checks on the Northern Ireland-Republic of Ireland border.
At a press conference, Mr Tusk said there were some "positive elements" in the UK's blueprint for future relations with the EU, which was agreed by ministers at Chequers in July.
But, he added: "The suggested framework for economic cooperation will not work."
Mr Tusk added that October would be the "moment of truth" for reaching a deal, and that "if the conditions are there" an additional summit would be held in November to "formalise" it.
Can the prime minister really cling on to her Chequers plan now?
The EU clearly won't accept it as it stands. Significant chunks of her party won't wear the deal either. The opposition parties won't back her.
Of course there are tactics at play here. One government minister has already suggested that the EU always knows how to overplay their hand.
Sometimes in negotiations, there needs to be a crisis to focus minds.
And in her press conference, Theresa May seemed frustrated that her proposals perhaps have not been properly digested or considered yet.
Of course this is only one day, one set of fraught meetings, in a tangled and lengthy process.
But as things stand, it seems Theresa May is going to have to budge, or walk away.
Read the rest of Laura's blog
The EU leaders had been discussing the UK's plans, which were presented to them by Mrs May on Wednesday evening.
German Chancellor Angela Merkel said "substantial progress" was needed on the UK's withdrawal agreement by the next European Council meeting in October, with "still a large piece of work" on the separate issue of future trade relations with the UK.
The 27 remaining EU members were "united that, in the matter of the single market, there can be no compromises," she said.
French President Emmanuel Macron said Brexit had been "pushed by certain people who predicted easy solutions".
He added: "Brexit has shown us one thing - and I fully respect British sovereignty in saying this - it has demonstrated that those who said you can easily do without Europe, that it will all go very well, that it is easy and there will be lots of money, are liars.
"This is all the more true because they left the next day, so they didn't have to manage it."
As well the criticism from the EU, Mrs May's proposal for the UK to sign up to a common rule book for trade in goods and a combined customs territory with the EU is unpopular with many in her own party, who believe it will erode British sovereignty and is not what people voted for when they backed Brexit in the 2016 referendum.
Former Brexit secretary David Davis said although EU leaders "were trying to give some warm words" it was now going to be "very, very difficult" to meet their requirements: "So it's time for a reset, time for a rethink".
And another prominent Brexiteer, Tory MP Jacob Rees-Mogg, said Mr Tusk's remarks signalled the end for the Chequers proposals.
"I think Chequers now has no supporters at all," he told the BBC.
"I think the time has come for Mrs May to say 'This is not going to work'."
For Labour, shadow Brexit secretary Sir Keir Starmer said Mrs May had to "urgently drop her reckless red lines and put forward a credible plan for Brexit".
But DUP deputy leader Nigel Dodds blamed the EU for its "unreasonable and inflexible approach" adding: "The UK government must demonstrate a resolute determination not to be bullied."
He said preserving the "political, constitutional and economic integrity of the United Kingdom" was the "absolute priority for us".
Earlier Scotland's First Minister Nicola Sturgeon said Mrs May must delay Brexit beyond next March if there is not a detailed agreement on future trading arrangements.

The UK's approach to the next stage of Brexit negotiations seems to be based on "pure illusion", Donald Tusk says.
The European Council president told a news conference in Brussels that the UK was still trying to "cherry pick" its future relationship with the EU.
Mr Tusk said he could only go on media reports of Brexit talks at the PM's country retreat Chequers on Thursday.
Theresa May is set to deliver a key speech setting out British ambitions on Friday of next week.
Mr Tusk, who is due to meet the PM the day before, said media reports suggested that the "cake philosophy is still alive" in the UK.
He added: "If the media reports are correct I am afraid that the UK position today is based on pure illusion."
He went on to reject - as he has done before - any notion of the UK "cherry picking" aspects of its future relationship with the EU or being able to join a "single market a la carte".
The BBC understands that the 11 senior ministers at Chequers made a breakthrough on so-called "managed divergence", where the UK could select EU rules to stick to post-Brexit.
Mr Tusk said the EU would continue to be "extremely realistic" during the forthcoming negotiations.
The second phase of Brexit negotiations will cover transitional arrangements after the UK leaves and economic and security co-operation in the future.
Mr Tusk, who spoke at an informal meeting of 27 European heads of states and governments, said he would present draft guidelines on the future EU-UK relationship at a summit in March.
"Our intention is to adopt these guidelines, whether the UK is ready with its vision of our future relations, or not," he said.
"Naturally it would be much better if it were. But we cannot stand by and wait."
He said he hoped to have more clarity when he meets the PM in London next week.
The leaders also spoke about the EU's post-2020 budget, the composition of the European Parliament, Turkey and Syria.
The government is set to pursue a policy which puts the UK outside a customs union with the EU - but matching EU rules in some industries in an attempt to achieve "frictionless trade".
Health Secretary Jeremy Hunt, who did not attend the meeting of senior ministers, said despite "divergent views" there was a "central common understanding".
He said some sectors could align regulations with European regulations, adding: "But it will be on a voluntary basis, we will as a sovereign power have the right to choose to diverge."

Downing Street has "wholeheartedly" rejected comments in a memorandum leaked to the press describing cabinet "divisions" over Brexit.
The document, compiled by consultancy firm Deloitte and obtained by the Times newspaper, says Whitehall is working on 500 Brexit-related projects and could need 30,000 extra staff.
But the prime minister's spokeswoman said the work had been "unsolicited".
And Deloitte said there had been no "access" to Number 10 for the report.
No "input from any other government departments" had been received, the company added.
Prime Minister Theresa May wants to invoke Article 50 of the Lisbon Treaty - beginning the formal two-year process for leaving the EU - by the end of March next year.
The government said the leaked memo - entitled "Brexit Update" of 7 November - had been written by a consultant and was not a Cabinet Office document, as reported in earlier versions of this story.
The prime minister's spokeswoman added that someone from the accountancy firm Deloitte  had produced it and "the individual is not working for the Cabinet Office on this". The person had never been inside 10 Downing Street and had not engaged with officials since Theresa May had become prime minister, the spokeswoman said.
The document identifies cabinet splits between Foreign Secretary Boris Johnson, Brexit Secretary David Davis and International Trade Secretary Liam Fox on one side, and Chancellor Philip Hammond and Business Secretary Greg Clark on the other.
It says Mrs May is "acquiring a reputation of drawing in decisions and details to settle matters herself" - an approach it describes as being "unlikely to be sustainable".
It says: "Every department has developed a 'bottom-up' plan of what the impact of Brexit could be - and its plan to cope with the 'worst case'.
"Although necessary, this falls considerably short of having a 'government plan for Brexit' because it has no prioritisation and no link to the overall negotiation strategy."
But the PM's spokeswoman said it was "so far removed from the government's assessment". She also "wholeheartedly" disputed the suggestion in the memo that there was no plan for Brexit.
Late on Tuesday afternoon Deloitte issued a statement about the memo saying: "This was a note intended primarily for internal audiences. It was not commissioned by the Cabinet Office, nor any other government department, and represents a view of the task facing Whitehall.
"This work was conducted without access to Number 10 or input from any other government departments."
Former Conservative Chancellor Ken Clarke, a prominent supporter of the UK staying in the European Union, told BBC Radio 4's The World at One said of the memo: "I think it's probably entirely accurate. It rings very true."
He added: "It's going to take a good six months to work out how to manage the damage [from Brexit]."
Meanwhile, shadow chancellor John McDonnell said the government's "shambolic" approach to Brexit was failing to equip the UK economy for leaving the EU.
In a speech, he described the chancellor as isolated from cabinet colleagues and "too weak" to make Brexit a success.
However, Mr McDonnell said Labour would not attempt to block or delay the triggering of Article 50 in Parliament.
"To do so would put Labour against the majority will of the British people and on the side of certain corporate elites, who have always had the British people at the back of the queue," he said.
Liberal Democrat EU spokesman Nick Clegg said: "The problem is we don't have any decisions from the government. We don't know what it means when it says, 'Brexit means Brexit.'"
The government is appealing against a High Court ruling that Parliament should have a say before the UK invokes Article 50. The hearing is due to begin at the Supreme Court on 5 December.

Downing Street has insisted Britain will leave the EU customs union after Brexit amid claims of Tory disunity over the UK-EU future relationship.
Theresa May has faced calls to spell out what she wants from the talks ahead of the UK's departure in March 2019.
In a customs union the UK would have tariff-free trade within the EU, but would lose the ability to strike its own deals with other countries.
It comes ahead of a meeting with the EU chief negotiator Michel Barnier.
The prime minister and Brexit Secretary David Davis will meet Mr Barnier ahead of the next round of negotiations getting under way.
Later, talks between officials will focus for the first time on the transitional period planned for after Brexit.
Potential sticking points include citizens' rights, with the UK insisting EU nationals arriving during this time should not have the same rights as those who arrived before Brexit day.
As he set off for London, Mr Barnier said there was "not a moment to lose" in order to secure a deal before the end of the year.
Asked about the UK's position on the customs union, he said Downing Street's "red lines" would be respected but the UK must respect the "rules of the union".
How close the UK will remain to the EU's single market and customs union has been a topic of debate among leading Brexiteers and some of those closest to the prime minister.
Conservative MP Kwasi Kwarteng, who is an aide to Chancellor Philip Hammond, suggested the latest statement on the customs union was "perfectly consistent" with what No 10 had been saying all along, given that Mrs May had been "pretty clear" in her January 2017 Lancaster House speech the UK would be leaving.
Pressed on how he squared this reality with Mr Hammond's stated desire for the UK and EU to move "very modestly" apart in terms of trade, he told BBC Radio 4's Today that "being modestly apart does not mean you have to be in a customs union".
He said the government had to make it clearer its core aim was a free trade deal with the EU.
On Sunday Eurosceptic Tory Bernard Jenkin accused the government of being "vague" and "divided", saying Chancellor Philip Hammond was not sticking to the approach put forward by the prime minister.
Home Secretary Amber Rudd - who was a leading figure in the Remain campaign - played down the divisions in the cabinet, telling the BBC's Andrew Marr Show on Sunday: "I have a surprise for the Brexiteers, which is the committee that meets in order to help make these decisions is more united than they think."
Future options?
In a position paper published in August, the UK set out two potential options for future long-term customs operations.
A "partnership" arrangement would see the UK "align precisely" with the EU in terms of imports and exports, removing the need for any customs checks between the two.
The UK would continue to operate its own checks on goods coming from outside the EU - and safeguards would be needed to prevent goods entering the EU that had not complied with its rules.
An alternative scenario would involve the UK extending customs checks to EU arrivals but under a "highly streamlined arrangement" to minimise disruption at ports and airports.
This would seek to make the existing system of customs checks "even more efficient", for example using number plate recognition technology at ports, which could be linked to customs declarations for what the vehicles are carrying, meaning the vehicles do not have to be manually stopped and checked.
Ms Rudd said they agreed on the need for "frictionless trade", the ability to strike international trade deals and to avoid a hard border in Ireland, hitting back at those who question whether such a deal can be secured.
"We want to have a bespoke agreement," she said. "Now we're not going to surrender before we have that battle."
She said Mrs May - who will chair a meeting of the 10-strong Brexit cabinet sub-committee on Wednesday and Thursday - had an "open mind" on how customs will be managed after Brexit.
Quizzed on what the model might look like, she said she was "not intimidated at all" by critics' warnings about customs unions membership.
Labour said it was "foolhardy" to rule out any kind of customs union with the UK's largest trading partner.
"The government must put jobs and the economy first, not their own internal party wrangling," a party spokesman said.

Brexiteer cabinet minister Liam Fox has accused pro-Remain MPs of trying to "steal Brexit", amid backbench moves to take control of the process.
He told the BBC: "You've got a Leave population and a Remain Parliament. Parliament has not got the right to hijack the Brexit process."
There are various backbench moves to prevent the UK leaving the European Union without a deal on 29 March.
Labour's Sir Keir Starmer said the PM should rule out a no-deal Brexit.
He said he believed it was "inevitable" that Article 50 would be delayed and that events in Parliament last week - when MPs heavily rejected the withdrawal deal Theresa May has negotiated with the EU - mean that another referendum was now more likely.
He told the BBC the prime minister must also change her "red lines" adding: "If she won't, it's difficult to see where we go from here."
On Monday, Theresa May will make a statement to MPs setting out how she intends to proceed with Brexit, amid apparent deadlock in Parliament over a way forward.
She will also table a motion to be debated and voted on, on 29 January. It is expected that various MPs will try to amend that motion over the course of the next week to put forward proposals to test the will of the Commons.
International Trade Secretary Mr Fox told BBC One's Andrew Marr Show: "Parliament has not got the right to hijack the Brexit process because Parliament has said to the people of this country: 'We make a contract with you, you will make the decision and we will honour it.'
"What we are now getting are some of those who were always absolutely opposed to the result of the referendum, trying to hijack Brexit and, in fact, steal the result from the people."
He warned that, if the referendum result was not honoured: "The consequences politically would be astronomical"
Mr Fox also said that he believed the way to break the deadlock was to win over more Conservative MPs to the PM's deal by finding a "different mechanism" to the controversial "backstop" proposal, to prevent a return to a hard border between Northern Ireland and the Republic of Ireland.
Various MPs are likely to try to amend the PM's "neutral" motion - simply saying that the Commons has considered the PM's statement - which Theresa May will put forward on Monday.
One group, including Labour's Yvette Cooper, the Conservative former Education Secretary Nicky Morgan, and Liberal Democrat MP Norman Lamb, among others, want the UK to extend its negotiations with the EU beyond 29 March - if MPs do not approve a withdrawal agreement by 26 February.
MPs voted in favour of invoking Article 50 of the Lisbon Treaty - which allows the UK and EU two years to negotiate the terms of Brexit - in 2017 and the 29 March date is in UK legislation - the EU Withdrawal Act.
Ms Morgan told Sky News the law would have to be changed if the UK was to be prevented from leaving the EU without a deal in place - and that is where the "very short" bill she is backing came in.
Meanwhile Conservative Remainer Dominic Grieve wants backbench MPs to be able to choose to debate and vote on Brexit issues, one day a week - breaking with the usual practice where the government controls the parliamentary timetable. Mr Grieve said those debates could then give an indication to the government about what the Commons wanted.
"My intention is not to stop Brexit," he told BBC Radio 4's Broadcasting House.
"My intention has always been to try to ensure that the government is forced to listen to what the majority view of the House of Commons is on this."
But Conservative Brexiteer Peter Bone said Mr Grieve had "lost the plot" and his plan would not get through Parliament.
By Nick Eardley, BBC political correspondent
The government is continuing to look at ideas to end the deadlock in Parliament over Brexit.
The key one Liam Fox was alluding to this morning is finding an alternative to the "backstop".
But some MPs are now so angry with the government, they want to take control.
Dominic Grieve's plan would allow Parliament to put its own ideas forward and be voted on.
The working plan is 300 MPs would have to back a proposal for it to be discussed.
A majority would have to then back it for it to be approved.
The battle for control of Plan B is well under way.
Article 50 of the Lisbon Treaty is the formal route for any country leaving the EU and it allows for a two-year process of negotiation. At the end of that period "the treaties shall cease to apply to the state in question" unless Article 50 is extended or revoked.
It was backed by MPs and invoked on 29 March 2017, meaning the UK is due to leave the EU on 29 March this year. But the withdrawal agreement reached by the EU and UK was rejected by MPs by 432 votes to 202 on Tuesday. If MPs do not approve a deal, the UK is due to leave the EU without one, which would mean trade reverting to World Trade Organization rules.
To extend Article 50, the UK would first have to make a request to the EU - which could be granted if all EU countries agree at a vote of the EU Council. Then it would have to table a statutory instrument to change the definition of "exit day" in the UK's EU Withdrawal Act. MPs would get a chance to vote on this change.
According to an European Court of Justice ruling in December, the UK could choose to cancel Brexit altogether without seeking the permission of the rest of the EU - something the government says it has no intention of doing.

Two of the world's biggest drugs firms are stockpiling medicines in case of supply disruptions after Brexit.
France's Sanofi is increasing its stocks by four weeks to give it a 14 week supply of medicines.
Switzerland's Novartis said it was also preparing for the possibility of a no-deal Brexit.
Sanofi, which makes insulin, is worried about any transport delays following Brexit, as most of its supplies have to cross the Channel.
"The uncertainty in the Brexit negotiations means that Sanofi has been planning for a 'no deal' scenario," said Hugo Fry, managing director, Sanofi UK, adding this was in line with recommendations by the European Federation of Pharmaceutical Industries and Associations.
"Patient safety is our main priority and we have made arrangements for additional warehouse capacity in order to stockpile our products, where global supply allows, in the UK and increase UK-based resource to prepare for any changes to customs or regulatory processes," said Mr Fry.
Sanofi's Brexit preparations were first reported by the Wall Street Journal.
The extra four weeks of supply is being built up as most of Sanofi's supplies arrive in the UK through the Channel Tunnel. Disruption to this route in 2005, when there were strikes in France, led to around four weeks of disruption.
Another area of concern is the need to send batches of medicine back to the continent for quality control, which could become difficult if there is a hard Brexit. This means that some quality controls tasks performed by its Haverhill manufacturing facility in Suffolk will be conducted in the remaining 27 EU countries.
"This will lead to 12 planned job losses across several functions by summer 2020 although we are doing all we can to mitigate redundancies where possible," Mr Fry said.
"Sanofi is confident that its contingency plans will ensure that people in the UK can access the treatments they need after the UK leaves the European Union," said Mr Fry.
Novartis did not disclose the extent of its plans but said that there were no plans to change its 1,500 workers in the UK .
"Alongside most other pharmaceutical companies, Novartis is preparing for the possibility of a no-deal Brexit. We are planning to hold increased inventories across our portfolio of medicines from both Novartis and Sandoz," the company said in a statement.
"Novartis has been in close consultation with the UK government about Brexit-related issues since before the 2016 referendum, both directly and via industry associations. We have apprised officials of our preparedness plans and status, including plans to increase our UK inventory holding," it added.
Sanofi said it had written to the Health Secretary Matt Hancock.
Last week, Mr Hancock said the NHS in England was preparing to stockpile medicines and blood in case the UK left the EU without a deal.  He told the Health Select Committee that he had asked the department to work up options for stockpiling by industry".
Other pharmaceutical companies have also begun to increase their stock piles.  Last month, AstraZeneca said it was increasing drug stockpiles by about 20% in preparation for a no-deal Brexit.
It is not just pharmaceutical companies that are talking about stockpiling.
Plane manufacturer Airbus has said it may have to build supplies as its operates as "just in time" supply chain that replies on frictionless trade across the EU. UK engine maker Rolls-Royce has also warned about the need to stockpile parts.

"It's like musicians in their bow-ties playing on board the Titanic," remarked a friend of mine as I was talking to them about the EU's 60th anniversary celebrations in Rome.
A mild exaggeration, shall we say - but the image sticks in my mind.
Because as the leaders of the EU's 27 countries clink champagne glasses in plush, security-tight surroundings on Saturday - all is not well in the Europe outside their gates: youth unemployment persists (especially in the south), terror attacks, illegal migration, inequalities in the Eurozone, Brexit and a tide of anti-establishment populist nationalism across much of the bloc.
To name a few of the challenges. Not to mention "strongmen" Presidents Trump, Putin and Erdogan who all eye the EU with suspicion and some animosity.
"Yes," conceded European Commission President Jean Claude Juncker to me in an exclusive interview. "We are not in the best form and shape we could be in."
But, he insisted, the EU was still young, adding that what the bloc had achieved in six decades was remarkable - Europe is now a continent of stability and peace.
But that was the vision, the goal after World War Two, I countered.
Surely there's a need for a new vision? Something to capture the public imagination. To re-enchant the disenchanted?
Mr Juncker recently published a White Paper on the future of the EU. where he explored five different scenarios - from increased union to paring pooled powers back to the common market only.
In between, he breathes life into the old idea of a "two-speed Europe" - where some countries share more sovereignty for example over defence or migration, while others opt out.
That proposal appears to be the most popular amongst politicians and civil servants, but to me it sounds like an open admission that there is, in fact, no common EU vision - with everyone doing different things at different times.
All this at a very sensitive moment - when one of the EU's biggest and most influential members, the UK, is about to walk out of the door.
And unity amongst the remaining 27 countries is key for Brussels - to prove to the outside world that the EU still stands strong.
Theresa May's absence at the 60th birthday bash on Saturday will be screamingly noticeable.
"Of course we will miss her," President Juncker told me.
"I am everything but in a hostile mood with Britain. Britain is part of Europe, and I hope to have a friendly relationship with the UK over the next decades."
Well, that of course will depend on what kind of future relationship the UK and EU can hammer out during Brexit negotiations.
I wondered how the EU would balance the competing desires to keep the UK close yet not give it too good a deal so as to avoid the risk of other EU countries walking away?
Mr Juncker admitted he did not want any more "exits": Nexit, Oexit, Dexit, Frexit or otherwise.
That would be the end, he said, if three, four or five more countries left. The EU would collapse.
But he doesn't believe that will happen.
The EU and the Commission, he said, would negotiate with the UK in a friendly way - fair but never naive.
Interesting choice of adverbs there. Echoed precisely in a speech delivered on Thursday by the EU's chief Brexit negotiator - Commission man Michel Barnier.
"Not naive"…
Now, does that refer to talk of the UK aiming to cosy up to individual EU countries (like the Baltic nations with promises of security co-operation) to cajole them into pressing for a good trade deal for Britain?
Or does it perhaps allude to the government rejecting the idea of an "exit bill" as part of the EU divorce?
It's an invoice that Mr Juncker insists must be paid.
"You cannot pretend you were never a member of the union," he practically spluttered.
"The British government and parliament took on certain commitments as EU members and they must be honoured. This isn't a punishment or sanctions against the UK."
Despite mutterings about the Commission drawing up a £50bn ($63bn) bill, Mr Juncker said the precise amount remained to be "scientifically calculated."
But one thing he insisted that could not be haggled over was the fate of the 4.5 million EU citizens living in the UK and British citizens currently living across the EU.
President Juncker said no-one had a right to eject them from their homes and jobs.
"This is not about bargaining," he insisted. "This is about respecting human dignity."
As they  mark the EU's anniversary on Saturday, the bloc's remaining leaders will look with furrowed brows towards the future.
But they may well take heart in a new trend emerging.
While populist nationalist, anti-establishment candidates enjoy strong followings, at the same time unashamed Europhiles like the youthful leader of the Netherlands Green party, the French presidential hopeful Emmanuel Macron and the German candidate for Chancellor Martin Schulz resonate with the large sections of the public too.
But Mr Juncker and others I've spoken to in the lead-up to the EU's anniversary, like his Vice-President Frans Timmermans and Antonio Tajani, the new President of the European Parliamant, all believe this is no time for complacency.
In just a few days' time Britain will deliver a letter to Brussels, officially triggering the countdown to Brexit.
How will Mr Juncker feel that day, I asked.
"Sad," he replied. "It's a tragedy.
"A failure and a tragedy."

The government's flagship Brexit legislation has officially become law, Speaker John Bercow has announced.
Mr Bercow told MPs the EU Withdrawal Bill had received royal assent - meaning the Queen has agreed to make it into an Act of Parliament.
The legislation enables EU law to be transferred into UK law in an attempt to ensure a smooth Brexit.
It was subject to fierce debate as it passed through Parliament, with many attempts to change its wording.
This culminated in a series of defeats for the government in the House of Lords - but ministers secured the necessary agreement for the legislation to clear the Commons last week.
In the House of Commons, the government was defeated once, in December, over giving Parliament a "meaningful vote" on the final Brexit deal.
The EU Withdrawal Act, as it is now known, will also repeal the 1972 European Communities Act, which took Britain into the EU and meant that European law took precedence over laws passed in the UK Parliament.
The government said that in the coming weeks it would begin using the powers in the new law.
Brexit Secretary David Davis said it was a "landmark moment" in the Brexit process.
"We will now begin the work of preparing our statute book, using the provisions in this Act, to ensure we are ready for any scenario, giving people and businesses the certainty they need," he added.

The European Union has set out its demands for the temporary transition period after the UK leaves in March 2019.
The EU wants the UK to continue to follow its rules but not be involved in making decisions.
Brexit Secretary David Davis said the UK wanted a "right to object" to new laws passed by the EU during this time.
Downing Street said there would "naturally" be differences between the sides ahead of negotiations.
The UK hopes the two sides can reach agreement by March.
The transition period - also referred to as an implementation period - is seen as a way to minimise disruption when the UK leaves the EU for things like business, holidaymakers and security.
It will also allow more time to finalise the terms of the UK's post-Brexit relations with the EU.
In their guidelines, the EU say:
Speaking at a press conference after EU ministers agreed the negotiating guidelines, chief negotiator Michel Barnier said the UK would be allowed to attend decision-making meetings on a "limited, exceptional, case  by case basis."
It would be able to negotiate trade deals with other countries but the deals could not come into force until the transition period was over, he added.
This is in line with the UK's negotiating stance, as set out by Mr Davis in a speech on Friday.
Mr Davis also said existing international agreements - which include trade deals with other countries and agreements on aviation and nuclear power - should continue to apply during the period.
Giving evidence to a House of Lords committee on Monday, Mr Davis said the UK wanted a "right to object" to new laws passed by the EU during the transition phase over which it had no say and disagreed with.
"It's not particularly democratic practice to just have the country accept without any say-so, anything - particularly if... the European Union takes it on itself to do something which is actively disadvantageous to a major British industry or something like that," he said.
"So that's why we've raised the matter, and let's see how it goes."
Asked what legal status this would have, he said he wanted such a safeguard included in the withdrawal agreement.
It's the sort of amazing coincidence that the Brexit process throws up all the time.
Minutes after the Brexit Secretary David Davis laid out his concerns about the EU's transition proposals to a House of Lords Committee, Michel Barnier held a press conference where he knocked them down.
For example, David Davis wants a mechanism where the UK has a say on new European laws that might affect Britain while it's not in the club but still subject to the rules. The best Mr Barnier was prepared to offer was consultation "on an exceptional, case-by-case basis agreed by the 27 remaining member states".
And don't dare call it anything as grand as "observer status", he warned.
He dismissed the Brexit secretary's demands that Britain be allowed to negotiate trade deals with other countries during the transition period.
Of course they can, Mr Barnier said. In fact, Britain had better get a move on if it wants to replicate the 750 international agreements that come with EU membership.
True, this is the start of a negotiation but it is not clear that the EU sees anything to negotiate. Mr Barnier feels that he has already made the UK a generous offer that's in Britain's economic interest.
Plus, there was a reminder that the deal on the transition period is linked to a deal on everything else: no agreement on a final Brexit treaty means no transition.
Some in the UK are unhappy at the idea that the UK will have to follow the rules of the single market and the customs union, including freedom of movement for EU citizens, but will lose its voting rights.
Mrs May's Brexit ''inner circle'' of senior ministers met in sub-committee on Monday morning to discuss how the transitional phase could work, including the UK's demand that it be free to negotiate trade deals with other countries during the period.
Earlier a Downing Street spokesman said: ''There is obviously going to be a negotiation on what the implementation period looks like.
''The formal directives will be released this afternoon. This will be a negotiation and there will naturally be some distance in the detail of our starting positions."

EU citizens living in the UK say they are being denied a guarantee of permanent residency because they do not have health insurance.
Under a little-known rule, EU citizens not in work or those looking for work must buy comprehensive insurance.
One man told the Today programme his application had been  rejected, despite living in the UK since the age of 13.
Peers are now trying to change the law. The Home Office said securing the status of EU migrants was a priority.
Since the referendum in June, many EU citizens have applied for documents guaranteeing the right to live permanently in the UK.
But the documents can only be obtained by migrants who have consistently either worked, sought work, or bought the insurance for five years.
The Home Office does not remove people for failing to buy insurance, but will not issue them with the guarantee of permanent residence.
As EU migrants can use the NHS, many did not realise they needed health insurance.
Students and full-time parents are among those affected. They are worried they could be vulnerable after Britain leaves the EU.
Tim Strahlendorf moved to the UK from Germany when he was 13.
He said he had been refused a residency document because he had spent time studying in the UK without paying for health insurance.
He said: "It never would have occurred to me that anything like this could have happened."
Nina Hofmann, a married language tutor who moved from Germany to the UK in 2006, said her solicitor told her not to apply for residency because she would be refused.
She took time out of work to care for her children - Benjamin, 6, and Sophia, 8 - and had not bought health insurance.
She told Today: "It is this fear I could be asked to leave in the end sooner or later.
"Maybe not with a knock on the door but with a letter because I've fallen through the cracks."
Migrants worried
Another failed applicant for a permanent residence document was told by the Home Office she should make arrangements to leave.
The government has since re-worded the letter, and failed applicants are not removed from the country, but many are worried they could be vulnerable after Britain leaves the EU.
Liberal Democrat, Labour and crossbench peers want to amend the bill to include a fast track procedure to give EU migrants a reassurance they can live in the UK.
The rule change would give people from the European Union, European Economic Area (EEA) and Switzerland the right to live permanently in the UK, without having to prove they bought insurance.
The amendment has been tabled by Liberal Democrat Lord Oates, Labour's Lady Kennedy and crossbench peer Lord Cromwell.
It is one of many amendments tabled, but its backers will hope for a concession from ministers as the Lords consider the Article 50 bill.
A Home Office spokesman said EU citizens made a vital contribution and securing their status - and those of British nationals elsewhere in the EU - was a priority.
He said: "The rights of EU nationals living in the UK remain unchanged while we are a member of the European Union.
"For self-sufficient people or students and their relevant family members, it's always been the case that exercising Treaty rights includes a requirement to have comprehensive sickness insurance and sufficient resources to not become a burden on the social assistance system of the United Kingdom."
According to the Migration Observatory at Oxford University, a quarter of applications for permanent residence documents were refused in 2015.
Almost 15,000 EEA nationals received permanent residence documentation in the third quarter of 2016, after the referendum.

"The ball is not in our court. The balls are all stuck in the UK's net."
The EU diplomat I was speaking to was frustrated. Hugely frustrated that the EU's newly negotiated Brexit deal was now stuck in limbo after Tuesday's votes in the House of Commons. He was irritated too that the prime minister said the next move would be decided in Brussels.
"We've done our part," said the diplomat, who represents a key EU country.
"The 'what next' cannot be seen as our responsibility. We negotiated two Brexit deals with two different UK prime ministers over more than three years. Now we're asked to grant yet another Brexit extension. We have to dance like Pinocchio in this game that isn't ours. It's very upsetting."
But like it or not, Brussels is now the focus of attention.
Will the EU grant a new Brexit extension? If so, for how long?
The answer to these questions will most likely influence the next political events in the UK.
For example, if the EU refuses a new extension, MPs might well rush to approve the new Brexit deal, rather than face the possibility of no deal. The EU is hardly likely to run that risk though.
But if the bloc goes for a longer Brexit delay, then Boris Johnson will want to hold a general election (if parliament grants him one).
In Brussels, as European Council president, Donald Tusk, tweeted, some kind of new extension is seen as all but inevitable.
The EU doesn't need to wait for the prime minister to ask for one.  Forced to do so under UK law (even though he made his personal opposition obvious) the prime minister submitted a letter of request at the weekend.
EU leaders are painfully aware that the length of any extension they now grant will be viewed through a political prism in Brexit-divided UK.
A short delay could be seen by those who want to Remain and who hope for a second referendum - as Brussels throwing the UK out on the streets. While a long extension could be perceived by Brexiteers as an EU attempt at holding on to the UK for dear life.
Anxious to come across as being as neutral as possible and to avoid becoming entangled in the bitter UK debate, many EU leaders seem to prefer adopting the UK request outlined in the prime minister's letter: a three month Brexit extension lasting until 31 January, to avoid a no deal scenario.
For the EU, any Brexit delay is a so-called 'flextension' - meaning the extension can fall way ahead of time.
In this case, as soon as parliament ratifies the new Brexit deal. But don't expect the EU to deliver its decision in a hurry. EU leaders are openly fed-up with having to interrupt busy schedules to rush to Brussels for more emergency Brexit summits.
They intend to try to agree the length of this new extension in writing, rather than in person. And this will only work if there are no major disagreements between EU members over the length of the new delay.
In the meantime, you can expect at least some posturing/grandstanding from certain countries like France, which want to keep the pressure up on MPs and the government.
Immediately after Tuesday night's vote for example, the French Europe minister growled that "an extension is requested but with what justifications? Time alone will not bring a solution (to Brexit)."
EU leaders have welcomed the fact that on Tuesday - for the first time ever - a Brexit deal did get the nod from the UK parliament but diplomats point out that the reason they are all especially fatigued and frustrated by the one step forward, at least two steps back Brexit political dance in the UK, is because they fully appreciate this is not even nearly the end of the road.
What the EU and UK are grappling with now is merely the UK's leaving process. Real negotiations on the future trade and security relationship - including painful political trade-offs involving fishing rights, work visas and the UK's ability to do trade with other countries - only begin in earnest after Brexit.
The words of one exasperated EU diplomat from a country traditionally close to the UK were "I feel like this will never end."

Former Foreign Secretary Jeremy Hunt has issued a plea to EU foreign ministers to avoid a "catastrophic failure in statecraft" over Brexit.
He has urged them in an open letter to reach a compromise with Prime Minister Boris Johnson while they still can.
Delaying Brexit would only increase the chances of a no-deal exit, he warned.
"If they think this is bad - just wait until what happens after Boris wins an election," he told the BBC's Laura Kuenssberg in an exclusive interview.
Mr Hunt - who lost out to Mr Johnson in July's Conservative leadership contest - has written to the 27 EU foreign ministers, urging them to show greater flexibility in talks with the UK.
In his interview with Laura Kuenssberg, he said: "I think we could be about to see a catastrophic failure in statecraft, not because of malevolence by the EU. I think they are sincere in wanting a deal.
"But just because they haven't really understood what's happening in British politics right now.
"And there is bureaucratic inertia. If you're trying to get 27 countries to agree a common position the easiest thing is always to do nothing. And that's the risk we face."
Mr Hunt, who backed Remain in the 2016 EU referendum but went on to be a strong supporter of Mrs May's withdrawal agreement, quit the cabinet in July after Mr Johnson attempted to remove him as foreign secretary.
He told the BBC Mr Johnson had made mistakes in his handling of Brexit, although he declined to say what they were, but stressed they both agreed on the need for a speedy resolution to Brexit.
He argued that the EU had been guilty of misreading the political situation in the UK in the past - over David Cameron's ill-fated renegotiation attempt in 2015 and Theresa May's withdrawal agreement - and could do so again.
"My worry is that they're about to make the same profound miscalculation that 'oh we can just hang tight, see if there's an election and if Boris Johnson wins it we can negotiate on the same deal but if he doesn't, so much the better because maybe we'll have a second referendum.'
"If Boris wins, which is what the polls are saying, at the moment, and he comes back with a majority, that British government will be much less willing to compromise," he said.
This, he argues in his open letter to his former EU colleagues, will make a no-deal Brexit more likely - an outcome they had always agreed it was "vital" to avoid.
"I fear a profound and mutual lack of understanding is leading the EU to make the same mistakes over and over again," he writes.
"I am hoping and praying that does not happen because the implications for our future relationship would be extremely grave."
Mr Johnson has said he remains "cautiously optimistic" about a deal, while continuing to insist the UK will leave on 31 October with or without an agreement.
He is set to meet his Irish counterpart, Leo Varadkar, on Thursday to try and break the deadlock.
Mr Varadkar has expressed concern about Mr Johnson's proposal to give the Northern Ireland Assembly a vote over entering into a "regulatory zone" with the EU, which would involve it leaving the customs union.
Mr Hunt said: "I'm sure they would love to keep Northern Ireland in the single market and customs union in perpetuity.
"But in the end, that is not going to work for the UK, I don't think this is just the strong supporters of Boris Johnson who feel this, this would be to divide up a sovereign country, and that wouldn't be acceptable I don't think any other country in Europe either."
He urged Ireland to take a "statesmanlike approach at this stage" adding that there was a "deal to be done which prevents a hard border on the island of Ireland, which allows regulatory alignment, the smooth flow of people and products across that border, which is so important for the Belfast Good Friday Agreement, it's going to need compromise on all sides".
He added: "It's Ireland's call now because I don't think that the EU are going to budge unless they get that signal from Varadkar."

European Council President Donald Tusk has said that the 27 European Union countries meeting in Brussels to discuss Brexit must remain united.
Mr Tusk, who will chair the special summit, said he had strong support from all the EU institutions as well as the 27 remaining states.
The UK is not taking part in the talks.
The EU leaders are meeting to finalise guidelines ahead of discussions with the UK on both the "divorce deal" and its future relationship with the EU.
The EU will insist that progress must be made in talks on separating the UK from the EU before any discussions can begin about future trade relations.
Official talks between London and the EU will not begin until after the UK general election on 8 June.
Arriving for the talks on Saturday morning, Mr Tusk told reporters: "We need to remain united as EU-27. It is only then that we will be able to conclude the negotiations, which means that our unity is also in the UK's interest."
In an earlier letter to leaders of the EU-27, he wrote that progress on "people, money and Ireland" must come before negotiations on the EU's future relationship with the UK.
The UK government has said it does not want to delay talks on future trade relations.
The summit brings together the heads of state or government of the EU-27 countries to discuss the draft guidelines for Brexit negotiations issued on 31 March.
Brexit: All you need to know
The people who will negotiate Brexit
Brexit - special report
French President Francois Hollande, arriving at the talks, said there would inevitably be "a price and a cost for the UK - it's the choice that was made".
"We must not be punitive, but at the same time it's clear that Europe knows how to defend its interests, and that Britain the UK will have a less good position tomorrow outside the EU than today in the EU."
Luxembourg's Prime Minister Xavier Bettel said that there needed to be a solution found with Britain that was a "level playing field" with "no cherry picking" - but "we must not punish" Britain.
Mr Tusk's letter - calling for a "phased" approach to Brexit - echoed German Chancellor Angela Merkel's priorities, which she set out on Thursday.
"Before discussing our future, we must first sort out our past," Mr Tusk said, listing three priorities:
"We will not discuss our future relations with the UK until we have achieved sufficient progress on the main issues relating to the UK's withdrawal from the EU," he said.
Meanwhile, German Finance Minister Wolfgang Schaeuble said the UK would not have advantages over 27 EU members once Brexit negotiations were concluded.
"There is no free lunch. Britons must know that," he told Germany's Funke Media Group.
EU officials estimate that the UK faces a bill of €60bn (£51bn; $65bn) because of EU budget rules. UK politicians have said the government will not pay a sum of that size.
Reports say Irish Prime Minister (Taoiseach) Enda Kenny will also ask his EU partners to back the idea of Northern Ireland automatically joining the EU if the province's people vote to unite with the Republic.
The UK Brexit Secretary, David Davis, has said that in the event of such a vote, Northern Ireland could become "part of an existing EU member state".

EU leaders have approved an agreement on the UK's withdrawal and future relations - insisting it is the "best and only deal possible".
After 20 months of negotiations, the 27 leaders gave the deal their blessing after less than an hour's discussion.
They said the deal - which needs to be approved by the UK Parliament - paved the way for an "orderly withdrawal".
Theresa May said the deal "delivered for the British people" and set the UK "on course for a prosperous future".
Speaking in Brussels, she urged both Leave and Remain voters to unite behind the agreement, insisting the British public "do not want to spend any more time arguing about Brexit".
The UK is scheduled to leave the EU on 29 March 2019.
The EU officially endorsed the terms of the UK's withdrawal during a short meeting, bringing to an end negotiations which began in March 2017.
European Commission President Jean-Claude Juncker said anyone in Britain who thought the bloc might offer improved terms if MPs rejected the deal would be "disappointed".
But European Council President Donald Tusk, who broke the news of the agreement on Twitter, said he would not speculate on what would happen in such a situation, saying: "I am not a fortune teller."
The UK Parliament is expected to vote on the deal on 12 December, but its approval is far from guaranteed.
Labour, the Lib Dems, the SNP, the DUP and many Conservatives MPs are set to vote against.
Mrs May has appealed to the public to get behind the agreement - saying that although it involved compromises, it was a "good deal that unlocks a bright future for the UK".
At a news conference in Brussels, she said the agreement would:
The agreement, she added, would not remove Gibraltar from the "UK family" - a reference to a last-minute wrangle with Spain over the territory.
The EU leaders have approved the two key Brexit documents:
There was no formal vote on Sunday, with the EU proceeding by consensus.
Mr Juncker said it was a "sad day" and no-one should be "raising champagne glasses" at the prospect of the UK leaving.
While it was not his place to tell MPs how to vote, he said they should bear in mind that "this is the best deal possible...this is the only deal possible".
His message was echoed by Irish Prime Minister Leo Varadkar who said "any other deal really only exists in people's imagination".
But Lithuanian President Dalia Grybauskaite suggested there were a number of possible outcomes if the UK Parliament rejected the deal, including an extension of the negotiations, or another referendum.
By Laura Kuenssberg, BBC political editor
It's a compromise. It was always going to be. It's not a happy compromise either. People on both sides of the Brexit argument are already screaming their protests.
And although the prime minister must be relieved, she didn't exactly say that she was pleased about the deal when I asked her at a news conference this lunchtime.
Instead, she said she was sure the country's best days are ahead.
But however she really feels about it - and with this prime minister it is hard to tell - her strategy for the next couple of weeks is crystal clear.
Her case? This is all there is.
No member states raised objections to the Brexit withdrawal deal and it was approved in a matter of seconds, according to a senior EU official.
Around seven leaders spoke in the session of the 27 member states, mostly to say this was a sad day and they wanted the future relationship with the UK to be as close as possible.
After Mrs May's address, roughly half of the leaders spoke. Several wished her good luck with the meaningful vote in Parliament.
No "what ifs" were discussed.
Mrs May will now need to persuade MPs in the UK Parliament to back it.
She is expected to spend the next fortnight travelling the country trying to sell the deal before a parliamentary vote in the second week of December.
If MPs reject the deal, a number of things could happen - including leaving with no deal, an attempt to renegotiate or a general election.
Foreign Secretary Jeremy Hunt said the parliamentary arithmetic was "looking challenging" and warned "nothing could be ruled out" if Mrs May lost the vote, including the government collapsing.
He told the BBC's Andrew Marr that the UK was getting "between 70% and 80%" of what it wanted, while the agreement "mitigated" most of the negative economic impacts.
Asked if the UK would be better off than if it stayed in, he said the country would not be "significantly worse or better off but it does mean we get our independence back".
The agreement will also have to go back to the European Council, where a majority of countries (20 out of 27 states) will need to vote for it.
It will also need to be ratified by the European Parliament, in a vote expected to take place in early 2019.
Labour leader Jeremy Corbyn responded to Sunday's summit by calling the deal "the worst of all worlds".
He said his party would oppose it, but would work with others "to block a no deal outcome" and ensure "a sensible deal" was on the table.
Former Conservative leader Iain Duncan Smith said he would find it "very, very difficult" to support the agreement as it stood.
"I don't believe that, so far, this deal delivers on what the British people really voted for," he told Sky's Sophy Ridge show. "I think it has ceded too much control."
SNP leader Nicola Sturgeon - who wanted to stay in the EU - said it was a "bad deal" and Parliament should consider "better alternatives", such as remaining in the single market and customs union permanently.
And Democratic Unionist leader Arlene Foster - who wants to leave the EU - said her party's parliamentary pact with the Conservatives would be reviewed if MPs approved the deal.
She told the BBC's Andrew Marr show the agreement as it stood would leave Northern Ireland and the rest of the UK "still within European structures with no say in its rules".
Former PM Tony Blair, who backs another referendum, said the deal was "a dodo".

Nicola Sturgeon has warned of broken promises over fishing as EU leaders agreed to Theresa May's Brexit deal.
A document published by the remaining 27 EU countries made clear they hoped to negotiate access to UK waters based on existing rights.
Ms Sturgeon said that could not be squared with promises made to the UK fishing industry.
Theresa May has said her deal would take the UK out of the controversial Common Fisheries Policy (CFP).
The prime minister and EU27 leaders approved the Brexit deal on Sunday after less than an hour's discussion at a meeting in Brussels.
But a document published online made clear the remaining EU members were still seeking to negotiate continued access to UK fishing grounds during the two-year transition period.
The document said a fishing deal was a priority and "should build on, inter alia, existing reciprocal access and quota shares".
Scottish Secretary David Mundell has previously said he could not support any extension of CFP rules beyond 2020.
Ms Sturgeon tweeted: "I'll be interested to hear David Mundell explain how this - 'existing reciprocal access and quota shares' - can be squared with the promises made to the Scottish fishing industry. (Hint - it can't)."
The Brexit deal has implications for the debate over Scottish independence and the future of fishing.
The withdrawal agreement does not let Scottish Conservatives off the hook over the fishing industry.
All 13 Scottish Tory MPs demanded exit from the common fisheries policy by 2020 and insisted "access and quota shares cannot be included" in the future economic partnership.
Both the UK and EU say they'll use "best endeavours" to conclude a new fisheries agreement by 2020 but the EU has certainly not given up on keeping its current share of the UK catch.
A statement agreed by the EU27 makes clear they will prioritise an agreement that builds on "existing reciprocal access and quota shares".
In short, the fight over fishing is deferred.
Read Glenn's analysis in full
Mr Mundell later responded, saying any future deal on fishing had still to be agreed, and that the prime minister had made clear she would defend the UK's fishing interests robustly.
He tweeted: "The Prime Minister made clear earlier today, the UK will be an independent coastal state once again, in full sovereign control of our waters, able to decide for ourselves who we allow to fish in them, with that access not tied to any other aspect of our economic partnership."
Nicola Sturgeon has also criticised Theresa May's appeal to the public to get behind the Brexit deal.
In a letter to the nation Mrs May has said leaving the EU next year would be "a moment of renewal and reconciliation for our whole country".
The 800-word message said the UK would "take back control" of laws and money which, it suggested, could be spent on the NHS."
But Ms Sturgeon said that "almost nothing in this desperate letter is true".
She said the UK Parliament should consider "better alternatives", such as remaining in the single market and customs union permanently - and she urged MPs to reject it.
In Brussels, French president Emmanuel Macron stressed the importance his country placed on fishing in future talks.
He said "all of our fishermen will be protected", with the French planning to "defend access as part of the indispensable balance".
The Aberdeen South MP Ross Thomson, the only Scottish Tory who has so far said he will vote against the Brexit deal in the House of Commons, said the EU27 document was "troubling".
He told the BBC's Sunday Politics Scotland: "The arrangement that we have on fisheries has been devastating to fishing communities across Scotland and across the whole of the UK.
"It's in the interest of the EU to keep it going and they want to build on those existing arrangements, so to my mind that can only mean the continuation of some form of common fisheries policy.
"It may not be called that but if it looks like the CFP and behaves like the CFP, it is the CFP."
Mrs May, in her letter to the nation, insisted that the UK would become an independent coastal state with "full control over our waters".
She wrote: "We will be out of EU programmes that do not work in our interests: out of the Common Agricultural Policy that has failed our farmers, and out of the Common Fisheries Policy that has failed our coastal communities."
Labour, however, has written to Scottish Secretary David Mundell asking him to clarify his position in light of the EU document.
Shadow Scottish Secretary  Lesley Laird wrote: "I do not need to tell you that this is a clear breach of your red line on fishing.
"I would therefore be grateful if you were able to clarify that you will not be voting for the deal on this basis.
"If that is the case, I really must ask why you have not resigned your position in the Cabinet?"

David Davis has described a leaked EU paper suggesting it could cut UK access to the single market if there was a post-Brexit row as "discourteous".
A draft document leaked on Wednesday suggested any dispute could mean UK benefits being suspended in the "transition period" after Brexit.
The UK Brexit secretary said it had not been "in good faith" to publish it.
He also said every economic forecast about Brexit had been "proven wrong so far".
Official forecasts out earlier suggested it would mean a slowdown in growth across the UK.
Mr Davis was speaking after the prime minister chaired meetings of the Brexit cabinet committee, aimed at sketching out what the UK wanted its future relationship with the EU to look like.
He said the atmosphere had been "very constructive" and there had been "lots of things resolved" but admitted there was "still progress to be made".
He described the draft section of the withdrawal agreement that leaked out on Wednesday as "hardly a legal document, it was a political document".
"What we're about, is building an implementation period which is to build a bridge to a future where we work well together," he said.
"I do not think it was in good faith to publish a document with frankly discourteous language and implying that they could arbitrarily terminate in effect the implementation period.
"That's not what the aim of this exercise is. It's not in good faith. We think it was unwise to publish that."
The transition - or implementation - period is expected to begin straight after the UK officially leaves the European Union, on 29 March 2019, and end on 31 December 2020.
The UK says this will allow businesses to adapt to its new relationship with the EU.
The EU says its rules should still apply during the transition period, as will rulings of the European Court of Justice.
According to a footnote in the EU papers leaked to journalists in Brussels, if referring a dispute to the EU court during that period took too long, the withdrawal agreement "should provide for a mechanism allowing the union to suspend certain benefits deriving for the United Kingdom from participation in the internal market".
Mr Davis was also asked about UK officials' economic forecasts that model the 15-year impact of the UK:
The government agreed to show them to MPs, following a leak of some of the information to Buzzfeed last week.
The estimates suggested north-east England and the West Midlands would be hardest hit although others would also see a slowdown in growth.
But Mr Davis said: "Every single financial or economic forecast related to Brexit has proven wrong so far, massively wrong - all on the same side, all underestimating the progress of the economy.
"[The] second point is that this is a work in progress. This is not a complete policy document.
"You wouldn't drive a car that is half finished. You shouldn't use a forecast that is half complete."
A Downing street source said the prime minister had told the Brexit cabinet committee that her starting point was to aim for "something that hadn't been done before in order to come to a new relationship that will last a generation or more".
Meanwhile Italian MEP Roberto Gualtieri, who sits on the European Parliament's Brexit steering committee, said it was unlikely, during the transition period, that Britain would have to follow any new EU rules drawn up when it was no longer a member state.
He said it was unlikely there would be time for new legislation to be brought forward within the period - expected to be around two years - because of European Parliament elections in 2019 and the fact a new European Commission would not be in place until autumn that year.
David Davis says the UK will seek an "appropriate process" to object to any new laws introduced during the period.
But Mr Gualtieri said the UK was likely to have had its say as a member state on any new EU rules that come into force during that period.

EU leaders refused to comment on the Brexit tensions inside Theresa May's Conservative Party, but some might say this was the elephant in the room at the Brussels summit.
For decades the UK's disputes with the EU have mainly centred on British payments to Brussels. And now Brexit is that writ large.
In 1979, then-PM Margaret Thatcher famously told EU leaders: "I want my money back". And many Conservatives still fondly remember her stand against Brussels, which won the UK an ongoing budget rebate of several billion pounds annually.
Given that turbulent history, it is no surprise that EU leaders sought to put a positive spin on the complicated Brexit negotiations.
They dismissed talk of a "no-deal" scenario - despite intense speculation in the UK about just such a scenario becoming reality in 2019.
Nicknamed the Brexit "cliff edge", that scenario would mean World Trade Organization (WTO) rules, with the EU imposing tariffs and barriers on the UK's vital services sector.
They assured Mrs May of their determination to make progress before a key December summit, and they will discuss among themselves what sort of trade partnership they could have with the UK post-Brexit.
But German Chancellor Angela Merkel stressed the difficulty of getting 27 EU nations to agree on new trade terms.
Mrs May's election losses in June left her heading a government reliant on support from right-wing Northern Ireland politicians. Her EU partners know that she is much weakened, but they also know how strong the Leave camp is in the UK, so they want a deal with her.
European Council President Donald Tusk said they had managed to "rebuild this atmosphere of trust and goodwill" with Mrs May, helped by her recent Florence speech.
Commission President Jean-Claude Juncker said "we are doing all we can to reach a correct, balanced, fair arrangement with the UK".
But he also had some sharp words for the British negotiators.
"I hate the no-deal scenario and nobody knows what that means," he told a news conference. "No member of the UK delegation explained what it meant."
The real haggling over UK commitments to EU finances is only just beginning.
Mrs Merkel said moving to "Phase Two" - trade and the future EU-UK relationship - "depends how much the UK makes progress possible - especially the financial settlement is the top issue".
The clock is ticking, as the UK has to leave at the end of March 2019, and international trade deals are notoriously difficult to negotiate.
 The EU-Canada Ceta deal took seven years to negotiate, and was nearly scuppered at the last moment by MPs in Belgium's Wallonia region.
Mrs May said the UK would "honour the commitments we made in our membership" - but still avoided specifying what her government sees as UK commitments to the EU. So far there is no advance on 20bn euros (£18bn; $23.6bn), a figure already attributed to her.
The so-called divorce bill requires detailed work, going through the figures "line by line", she said. "The British taxpayer wouldn't expect anything else."
But in contrast with the gloomy reports of Brexit "impasse" in the British media recently, Mrs Merkel was upbeat. She saw no reason why the EU's three priorities - citizens' rights, the Northern Ireland border and the financial settlement - could not be resolved, to allow trade talks to start within months.
Mrs May said negotiators were "in touching distance of an agreement" on the thorny issue of citizens' rights.
But the powers of the European Court of Justice (ECJ) in a post-Brexit UK remain unclear - along with so much else besides.

It's extremely hard to see how a new Brexit deal can still be agreed by this Thursday.
Negotiations continue - but time is tight, and, to use the words of even the most upbeat of those involved, "there's still much work to do".
EU internal talk is focussing now on a possible "holding pattern statement" at this week's EU leaders summit, along the lines of "we've made great progress in negotiations but still need more time".
There are also renewed mutterings about a new Brexit summit maybe towards the end of the month.
So how did we get here?
At the end of last week there was hope in the air. It seemed an understanding had been reached between Boris Johnson and the Irish Taoiseach (Prime Minister), Leo Varadkar.
Now there's lots of speculation, smoke and mirrors - but no sign of white smoke that a new Brexit deal is nigh.
"We felt last week that things would now move very quickly," one northern European diplomat told me. "Now we realise we're still pretty far apart."
Replacing the Irish backstop guarantee remains the main stumbling block in ongoing negotiations, particularly when it comes to customs.
The EU's dual priorities complicate things. Brussels wants:
The European Commission says both sides - the EU and UK - are negotiating in good faith, but the not so secret EU hope right now is that time pressure and political pressure will build on Mr Johnson to such an extent this week, that he might yet blur some more of his red lines.
The EU thinking is that the UK prime minister is running out of options. He  promised to do his best to deliver a new Brexit deal this week and he promised not to ask for another Brexit extension.
With so little time to go before the EU summit, Brussels believes the only option for a deal is for Mr Johnson to pivot towards an already set-to-go replacement for the current UK-wide Irish border backstop.
And this is the EU's preferred option: a backstop that would see only Northern Ireland, not the rest of the UK, following EU customs rules after Brexit, while not affecting its territorial identity as part of the UK.
Now for those who've followed the twists and turns of the Brexit process, you'll recognise the EU proposal as what was formally known as the Northern Ireland-only backstop.
Meanwhile, Mr Johnson's offer is reminiscent of his predecessor Theresa May's Chequers plan for two customs systems (one EU, one UK) on the island of Ireland.
Each proposal was roundly rejected by the other side.
The difference now is the political will to get a deal done. And not just in Downing Street.
Those in the UK who claim the EU wants another Brexit extension to keep the UK in the bloc as long as possible are mistaken.
EU leaders are fed up with the Brexit process. They want a deal.
Realistically there is no time this week to work out a painstaking middle ground between the EU and UK positions.
And EU leaders are adamant that they won't be negotiating directly with Boris Johnson at the summit.
Germany, France and others say they want a Brexit deal they can live with, rather than something cobbled together in a rush to "get it over with" that could leave problems for the Northern Ireland peace process and/or the single market for years to come.
While the technical details need to be ironed out (and that cannot be taken for granted), the EU political mood is determinedly more can-do now.
If the prime minister balks at doing a U-turn on a Northern Ireland-only backstop, despite being encouraged by still-to-be revealed EU sweeteners, then negotiations towards a hybrid solution will likely pick up again next week.
First, though, all EU eyes would be on Westminster and the extraordinary session of Parliament on Saturday to see if another Brexit extension will be requested, or not.

There has been a sharp drop in nurses registering to work in the UK since the EU referendum, figures suggest.
Last July, 1,304 nurses from the EU joined the Nursing and Midwifery Council register, compared to 46 in April this year, a fall of 96%.
The Health Foundation said the findings could not be more stark and said they should act as a "wake-up call".
But the NMC said the introduction of English language testing for EU nurses is also likely to have played a role.
It comes as the NHS is already struggling with nurse vacancies and, without this supply line, shortages could get worse.
In May, research by the Royal College of Nursing found one in nine posts in England was vacant.
The union said it meant the NHS was 40,000 nurses short of what was needed.
The figures - obtained by the Health Foundation under the Freedom of Information Act - cover the numbers applying to go on the register so they do not necessarily mean they are employed by the NHS.
But they give an indication of the supply line from the EU which provides a significant proportion of the workforce.
Anita Charlesworth, director of research and economics at the Health Foundation, said the drop since the Brexit vote could not be more "stark".
"Without EU nurses, it will be even harder for the NHS and other employers to find the staff they need to provide safe patient care.
"The findings should be a wake-up call to politicians and health service leaders."
The NMC has also drawn attention to the introduction of English language tests, which were brought in for EU nurses for the first time in January 2016 - they were already in use for non-EU nurses.
It normally takes a few months from being tested to making it on to the register so officials believe this could have also played a role in the drop in numbers.
A Department of Health spokeswoman said EU nurses played a "valued" role in the NHS and they would be a priority in Brexit negotiations.
But shadow health secretary Jonathan Ashworth said the government was making a mess of things.
"Theresa May's weak and unstable government has pushed NHS services to the brink, and it is patients who will pay the price.
"Our health service has always relied on the contribution of overseas workers, yet these staff are being forced out by this government's neglect and disregard.
"The Tories are overseeing an unforgivable drain of talent out of our country, because of their chaotic attitude to the Brexit negotiations."
And Lib Dem health spokesman Norman Lamb added: "These figures are profoundly worrying and the possible implications for the NHS and patients cannot be underestimated."
Overall there are 650,000 nurses on the register. Just over 36,000 of these have been trained in the EU, 5.5% of the total. Another 67,000 come from outside the EU with the rest from the UK.
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The decline in EU nurses and midwives wanting to work in the UK since the referendum is continuing, figures show.
The trend was first noticed earlier this year, and now a new batch of figures released by the Nursing and Midwifery Council have reinforced the idea that Brexit is having an impact.
In September the register showed just over 36,200 EU nurses and midwives - over 2,700 less than a year before.
But ministers said a rise in training places would compensate for the drop.
That will take some time to start having an impact though, and union leaders believe the government in England may struggle to fill these places as they have removed bursaries for nursing degrees and introduced fees.
The data released by the Nursing and Midwifery Council (NMC) cover the number of nurses and midwives registered to work in the UK, not the numbers actually working.
Rises in the numbers of nurses and midwives leaving the register was seen among all types of staff - those trained in the UK, in the EU and in the rest of the world.
If you can't see the NHS Tracker, click or tap here.
But what marked the EU trend out was the rate of change being seen.
There was a 67% rise in the number of EU nurses and midwives leaving the register in the 12 months up to September compared to the same period the year before.
By comparison the number of UK-trained staff leaving the register rose by less than 10%.
That rise in leavers was off-set by just over 1,000 new joiners from the EU, but that in itself was an 89% drop in the numbers who signed up the year before.
The NMC pointed out this change in new joiners was also likely to have been influenced by the introduction of English language testing around the same time as the Brexit vote in the summer of 2016.
Overall, the number of nurses and midwives on the register has started to drop for the first time in a decade.
There were just under 690,000 nurses and midwives registered to work in the UK in September - over 1,600 less than there were the year before.
This comes at a time when unions report there are significant shortages in the number of nurses employed by the NHS.
Research by the Royal College of Nursing (RCN) said there were over 40,000 unfilled vacancies - one in nine posts.
The NMC said the rising numbers leaving the profession across the board was "worrying" and needed to be responded to.
An ageing workforce, which is seeing growing numbers reach retirement age, and the pressures of working in the health service have been cited as factors for UK-trained nurses leaving the register.
RCN general secretary Janet Davies said it was "no surprise" EU nurses were also turning their backs on the UK given what was happening with Brexit.
"These alarming new figures represent a double whammy for the NHS and patients."
But the Department of Health played down the significance of the overall drop, pointing out it represented a "mere" 0.2% fall in the numbers registered to work.
A spokeswoman said the number of training places would increase by 25% in the coming years and that ministers had been "very clear" that EU nationals would remain a valued part of the workforce after Brexit.

The European Union plans to have a 29-strong team of diplomats in London to represent it after Brexit.
It will be called a "delegation" - not an embassy - and will be part of the EU's foreign policy arm, the European External Action Service (EEAS).
There will also be a mission with five staff in Belfast to oversee the implementation of the withdrawal agreement in Northern Ireland - if there is a Brexit deal.
The plans will be discussed next week.
They will be presented for approval by ambassadors from the 27 remaining EU countries on Wednesday.
The European Commission has offices in all member states. Currently it has a team of 27 staff based at Europe House, in Smith Square, Westminster.
Once the UK leaves the EU in March next year, that office will be replaced by a new London outpost for the EEAS.
It will be about a third of the size of its equivalent in Washington DC, which has 90 personnel - although only 30 of them are classed as European diplomats.
Whether the delegation will stay in the Smith Square building - the former headquarters of the Conservative Party - is not yet known.
However, the European Commission's offices in Scotland and Wales are likely to close.
The new European Union ambassador to the UK will be appointed at a later date by its foreign policy chief Federica Mogherini.
Being Brussels' man or woman in London could be a plum job, or the occupant could find themselves sidelined in future negotiations with London.
Earlier this year, the European Commission denied that Martin Selmayr - its secretary-general and a former aide to its president Jean-Claude Juncker - was a potential candidate.
The EU has 140 delegations to countries and organisations, including the United Nations and the World Trade Organization.
Its External Action Service was established by the Lisbon Treaty to develop and deliver the EU's common foreign and security policy.

Draft EU guidelines for Brexit rule out starting free trade talks with the UK before "sufficient progress" is made on other issues.
The paper presented by European Council President Donald Tusk will have to be approved by the 27 member states.
Other issues include the status of three million EU citizens in the UK and a million Britons in the EU.
Separately, another top EU official suggested the bloc could manage without the UK in defence and security matters.
The UK formally triggered the Brexit process on Wednesday after calling for simultaneous talks on exit terms and future trade ties.
At a news conference, Mr Tusk said: "Starting parallel talks on all issues at the same time as suggested by some in the UK will not happen.
"Only once we have achieved sufficient progress on the withdrawal can we discuss the framework for our future relationship."
It is clear the UK will face a tough divorce, the BBC's Gavin Hewitt says, but there were some hints at flexibility from Mr Tusk.
Talks would be "difficult, complex and sometimes even confrontational", Mr Tusk predicted, but the EU would not "pursue a punitive approach".
UK Prime Minister Theresa May formally triggered the Brexit process by sending the Article 50 notification letter to Mr Tusk on Wednesday.
The two are to meet in London ahead of an EU summit on Brexit, which will not include her, on 29 April.
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The draft says the EU's overall objective is "to preserve its interests, those of its member states, its citizens and its businesses".
Calling for a "phased approach giving priority to an orderly withdrawal", it suggests starting with discussions on the separation arrangement. They could then move on to talks about a future trade relationship between the EU and the UK.
The draft raises the issue of what the UK might have to pay to leave the EU, bills earlier estimated to be as much as €60bn (£51bn; $64bn).
In a sign of the bloc's determination to secure a "divorce bill", it says that a "single financial settlement should ensure that the Union and the United Kingdom both respect the obligations undertaken before the date of withdrawal".
The guidelines call for "flexible and imaginative solutions'' on the issue of the UK's land border with the Republic of Ireland, with the aim of "avoiding a hard border".
As for Gibraltar, Spain will have a special say on the future of the disputed British territory, according to the guidelines.
"After the United Kingdom leaves the union, no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without the agreement between the Kingdom of Spain and the United Kingdom," they state.
Gibraltar's chief minister, Fabian Picardo, accused Spain of manipulating the European Council for its own political interests, saying this was "unacceptable".
Conservative MPs in the UK warned that the sovereignty of the UK overseas territory was non-negotiable.
Mrs May's letter had been interpreted by some as threatening to withdraw co-operation with the EU on security matters.
Speaking at a Nato meeting in Brussels, EU foreign policy chief Federica Mogherini said: "The UK contributes today only for 3% of our civilian capabilities in our EU operations and missions, and 5% to the military ones.
"So for sure it's a valued contribution, but for sure a contribution without which the European Union defence and security work can continue perfectly well."
What next? Analysis by BBC Europe editor Katya Adler
This is the start of a two-year, cross-Channel political rollercoaster ride. The EU's draft guidelines for Brexit are uncompromising and firm.
They say they will update them "as necessary" during negotiations, meaning they are ready for anything, including, the text explicitly says, for talks with the UK to fail altogether.
Gone are the words of sadness and regret at Britain's departure. The message is: Roll up your sleeves, we're ready for you.

A "transition period" after the UK leaves the EU should not continue beyond 31 December 2020, Brussels says.
This would put a 21-month limit on the temporary arrangement - the UK says it should last for about two years.
And some business groups have called for a much longer transition period once the UK leaves in March 2019.
The terms of the transition period, which the UK calls an implementation phase, have yet to be negotiated between the two sides.
The EU says the UK will have to continue to follow its rules and cannot adopt an "a la carte" approach.
It has just published its guidelines for the next phase of Brexit negotiations.
These talks will initially focus on agreeing the precise terms of the transition phase, before moving on to the UK and EU's long-term future relationship.
It will be a temporary period after the UK leaves the EU and before the final arrangements kick in. Both sides have talked about having such an arrangement, although they use different names for it.
The UK says the "implementation phase" will avoid a "cliff edge" for businesses on Brexit day.
The European Commission's guidelines state that the UK should continue to follow EU law and stay in the European customs union and single market during the transition phase. Rulings of the European Court of Justice will continue to apply, it says.
"The transition period needs to be clearly defined and precisely limited in time," the EU says.
"The commission recommends that it should not last beyond 31 December 2020."
This date marks the end of the EU's seven-year budget cycle.
Giving evidence to a committee of MPs, Prime Minister Theresa May said a 31 December 2020 cut-off offered a "neatness" for the EU, but suggested the length of the transition phase would be a matter for the negotiations.
Long-term, the UK has already said it plans to leave the customs union and single market and end the supremacy of EU court rulings as part of Brexit.
Some Brexit-supporting Tory MPs have warned the UK could become a "colony" of the EU during the transition period if it continues to closely follow the same rules.
Looking beyond the transition phase, the UK is hoping to strike a "comprehensive" and "bespoke" trade deal with the European Union to replace its membership of the single market and customs union.
Talks on this have not started and the European Union says it will not have been fully agreed by the time the UK leaves in March 2019.
But Mrs May disagrees - asked earlier whether she still believes the entire agreement can be negotiated by Brexit day, she said: "That is what we are working to and that is what I believe we can do."
The prime minister said the UK would "start off at a different point" from other countries because of its current trade relationship with the EU.
The overseas territory of Gibraltar - whose sovereignty is disputed by Spain - has been raised as a potential sticking point in Brexit negotiations.
The EU has said that Spain must agree to any arrangement between the UK and the EU applying to Gibraltar, a stance reiterated in the latest negotiating guidelines.
Asked whether he expected Spain to agree to the transitional arrangement covering Gibraltar, Mr Barnier said decisions on the issue would be "made for the 27, unanimously, by consensus".
Later in Prime Minister's Questions, Theresa May was asked to promise not to enter into any agreement that excluded Gibraltar.
She said the UK would not exclude Gibraltar from either the temporary implementation period or the long-term future agreement with the EU.

The world and her mother, brother, sister and aunts are more than aware by now of the splits in the British government over the kind of relationship the UK should have with Brussels after Brexit. But how united is the EU?
We keep hearing in social and traditional UK media about supposed EU plots, plans and intentions for Brexit. But are all 27 EU countries, plus the European Commission and Parliament, really singing from one hymn sheet?
If they were, it would be an absolute first.
The EU is famous for its internal bickering: small countries resenting larger ones; larger ones trying to dictate; splits between northern and southern Europe, never mind east and west.
As a result, EU countries find it hard to reach consensus over most things - migration, ever closer union, foreign policy. So why should it be any different over Brexit?
In fact, the wisdom across the Channel is that if only Theresa May and her government had had their Brexit ducks in a row from the moment they triggered formal negotiations with Brussels, they would undoubtedly have had the upper hand. One tight, crack team against an overgrown, unwieldy, fractious bunch.
But quite the reverse happened in stage one of Brexit negotiations last year.
The UK side appeared to the Europeans as shambolic, divided and (initially) ill-prepared, while the EU put on a rare show of unity - largely helped by the fact that all EU players were shoulder-to-shoulder in pressurising the UK to honour financial pledges made while still a member.
But fissures in the EU armour are now showing as we approach Brexit negotiations on the future EU-UK relationship.
Working groups from the 27 EU countries meet regularly in Brussels to discuss different aspects of Brexit.
They say they're finding it tough to agree a common position on future relations with the UK, as long as the British government remains opaque over its stance.
Listening to grumbling European players, it would be tempting to paint them as divided too, between the camps of dogmatists and pragmatists: those who value trade, security and other relations with the UK over an EU rule or regulation; and others who believe the integrity of the EU rulebook governing, amongst other things, the European single market, is ultimately the higher prize.
An influential player from a smaller EU country told me: "We all hate that the UK is leaving, but this will always be an important relationship. One contract binding us to the UK will simply be replaced by another. We have to be practical. And positive."
EU big guns France and Germany are proving to be the most hardline. "Paris above all," one EU diplomat told me. "Is this payback for Waterloo? I don't know, but sometimes the rest of us can only roll our eyes."
Now, tempting as it may be to hear comments like that and think 'Aha! The EU really is out to punish the UK for leaving', my sense from meetings with key figures is that the overall mood is one of growing pragmatism and gradual detachment.
In the UK Brexit continues to hoover up the nation's headlines and political energy - despite government attempts to focus on other issues of public concern like health and education.
But in the rest of Europe, there is not so much focus on Brexit.
On Friday the leaders of the 27 EU countries meet to debate life after Brexit (primarily how to plug the hole in the EU budget that the UK will leave behind), rather than discussing what to do about the UK.
Of course the Danes worry about fishing, the Germans about cars, the French about the impact of Brexit on the port of Calais. But for most EU countries, trade with the UK is not the be-all and end-all.
You can expect the EU's chief Brexit negotiator Michel Barnier to maintain a hardline stance in Brexit talks for now.
The EU has long dismissed the UK aim of "cherry-picking" sector-by-sector privileged access to the single market.
EU diplomats like to refer to the UK government's "three basket" idea of varying alignment/divergence in regulations as "fit for the waste paper basket".
But remember we haven't yet actually started formal negotiations on EU-UK future relations.
They won't begin until around Easter at the earliest.
In the meantime there's a lot of shadow-boxing going on.
These will be no ordinary trade negotiations between two parties, after all.
Brexit is a political event for the UK and EU.
Both sides will want to demonstrate to their constituents that they hammered out the best possible deal in their interests.
But it's also important to bear in mind that what we are working our way towards here in the Brexit process - ie before the UK leaves in March 2019 - is in EU-speak "a political understanding on the future relationship between the EU and the UK".
Not a final trade deal.
EU law dictates that a member has to leave the bloc and become an outsider or, in EU-speak again, a "third country" before it can hammer out new trade and other relations with the EU again.
So although now feels like crunch time, with speculation of a showdown between in-fighting members of the UK cabinet, and intra-EU differences on Brexit also coming to the fore, arguably in good old Brussels tradition there is a huge opening to kick the can down the road.
That is why EU diplomats are quietly confident now that - from their side at least - a Brexit deal can be struck by March 2019.
Reaching only an "understanding" on the shape of future relations will allow both the UK and the EU more time during the planned (but not yet agreed) transition period after Brexit to hammer out the details on trade, services and more and - maybe - reach a compromise on both sides.
The potential is there, though predictions carry a strong health warning.

The European Union wants to be able to restrict the UK's access to the single market if there is a dispute after Brexit, a leaked document suggests.
The power to suspend "certain benefits" would apply during the post-Brexit transition phase before the final arrangements come into force.
It is revealed in a draft section of the UK and EU's withdrawal agreement, which has yet to be finalised.
The UK said the document simply reflected the EU's "stated directives".
But it provoked an angry reaction from former UKIP leader Nigel Farage who said the transition deal on offer would be tantamount to creating a "Vichy Britain".
Theresa May is to chair the first of two key Brexit meetings with her senior ministers later as the government faces more calls to clarify the UK's position.
The first Brexit cabinet committee will focus on Northern Ireland and immigration, while trade will be discussed on Thursday.
The transition period is expected to begin straight after the UK officially leaves the European Union on 29 March 2019, and end on 31 December 2020.
The UK says this will allow businesses to adapt to its new relationship with the EU.
The EU says its rules should still apply during the transition period, as will rulings of the European Court of Justice.
According to a footnote in the EU papers leaked to journalists in Brussels, if referring a dispute to the EU court would take too long, the withdrawal agreement "should provide for a mechanism allowing the Union to suspend certain benefits deriving for the United Kingdom from participation in the internal market".
It does not go into detail about what disputes could trigger the powers being used, or which parts of the single market could be suspended.
It also says the UK would be consulted about fishing quotas, and would have to pledge not to act against the EU in international organisations.
A Department for Exiting the European Union spokesman said: "This is a draft document produced by the EU that simply reflects their stated directives."
Together with the UK's position as set out last month, it provides a "solid foundation for the negotiations on the implementation period".
The UK plans to continue participating in the single market - which allows frictionless trade and the free movement of people between EU members - during the transition phase, before the final trading relationship - which has yet to be negotiated - comes into force.
Some Conservative MPs are unhappy at the idea of the UK following EU rules but having no say on them, and have warned that when Brexit happens in March 2019 it will be "in name only".
Bernard Jenkin, chair of the Commons Public Administration Committee, said it would be "utterly perverse" if the EU ended up imposing tariffs on British goods given the current levels of alignment between it and the UK.
"This is an indication of how fearful the EU is that they have to make these silly threats," he told BBC Radio 4's Today.
"Of course we are going to do rather well outside the EU and we are going to show the EU up as a rather less successful organisation than it is."
And former trade minister Lord Jones, a leading pro-Leave voice within the business community, said it was increasingly clear no deal was better than a bad one.
We've had position papers. We've had guidelines, directives and a joint report.
This is the first draft of legally-binding words that will end up in the withdrawal agreement - the Brexit treaty that will seal the UK's departure from the EU and a document of real historical significance.
EU sources say it proves that they are getting a move on - "Please! No more position papers" - which the UK wants too.
The EU's suggestion, in a footnote, that the UK's access to parts of the single market will be curtailed if the European Court of Justice cannot solve any disputes within the two-ish year timeframe of the transition, will sound threatening to some.
To others it will sound like an obvious back-up plan to deal with the famously long time it takes for the ECJ to make a decision.
The Brits caution that this is a first draft for the EU27 and does not reflect any negotiations over what they prefer to call the implementation phase.

European Commission chief Jean-Claude Juncker says he believes Brexit will go ahead and the EU should tackle its looming budget shortfall.
"Don't believe those who say that it's not going to happen and that people in the UK have realised their error... I don't think that's going to be the case," he told a Brussels conference.
The EU budget commissioner said the UK's departure would leave a hole of about €12-13bn (£11-12bn; $14-$16bn).
The UK's exit is set for March 2019.
Budget Commissioner Günther Oettinger said the budget gap would have to be closed with 50% spending cuts and 50% fresh money. He suggested a Europe-wide tax on plastic products as a source of extra revenue.
The Commission will publish a proposal in May this year and has urged EU leaders to agree a budget deal by May 2019.
Liberal Democrat leader Vince Cable and former Prime Minister Tony Blair are among the prominent voices arguing that Brexit can still be reversed, possibly by holding a new referendum on whatever deal is reached on the UK withdrawal.
The EU is bracing for hard bargaining between the bloc's net contributors and net recipients for the next budget period, 2020-2026. The UK is currently among the major net contributors.
By Adam Fleming, BBC News, Brussels
"There will have to be cuts in some major [EU] programmes - some significant cuts," Mr Oettinger warned.
UK Prime Minister Theresa May has said Britain will honour its current commitments to the EU budget, until 2020.
The UK is one of 10 member states who pay more into the EU budget than they get out. Only France and Germany contribute more.
According to UK Treasury figures, the UK's net contribution for 2014/15 was £8.8bn. The total contribution was more, but the UK received a £4.6bn rebate. That annual rebate was won by the late Margaret Thatcher.
In 2014/15, Poland was the largest beneficiary, followed by Hungary and Greece.
On Monday the veteran pro-Brexit campaigner Nigel Farage met EU chief negotiator Michel Barnier in Brussels. "Mr Barnier clearly did not understand why Brexit happened," he said after the meeting.

What on earth happens now? Summits have setbacks. It's written into the script.
It's not unusual even for choreographed emergencies to take place because then, lo and behold, just when all seems lost, the apparent grit and determination of political leaders can rescue victory from the jaws of defeat.
What happened in Salzburg feels different though. That's partly because one of the principal players, the UK, was taken aback by the turn of events.
The hoped-for polite reception turned into a firm, embarrassing rebuff. But it's more acute because the expected platitudes were meant to be an insurance policy for the prime minister to protect her from increasingly vitriolic attacks at home.
If the EU had created a sense of momentum for Theresa May in the last 24 hours, the din of criticism in Westminster might have felt misplaced, even petty.
If the country's leader was making progress internationally, well then, the riposte to her enemies could have been: She has bigger things to worry about than her back benches, there is progress. Look! Progress!
Against the odds, despite the difficulties, she was meant to have been able to claim steady, if slow and troubled steps to the eventual outcome.
And if she had a united party at her back, the prime minister's defiant tone could have even found her favour at home.
She wouldn't be the first leader to try to rally her domestic troops by standing up to the EU, for refusing to roll over, holding firm in the face of continental misgivings, and grumblings about Britain's familiar demands for special treatment from their friends across the Channel.
The EU's rejection of her controversial compromise is so toxic because it leaves her surrounded by foes, and less insulated from criticisms that will come of her approach, and what seems to be the UK's total misreading of the EU's willingness to soften their position.
That's stirring up trouble already with some Tories  pointing fingers of blame. One senior Tory demanded that questions be asked of her senior team, including Olly Robbins, her top European adviser, seen as the architect of the Chequers plan.
There are accusations swirling that the prime minister was "misled by bad advice", having been persuaded to pursue a compromise plan that cost her two cabinet ministers, and now rejected, "has left her humiliated".
Another senior Conservative told me the prime minister had been "in denial - as a strategy that will fail her and it will fail us", saying: "We are two years on and the basic political questions have not been answered."
Theresa May and her government have been trying to pursue a middle way, to find a stance between the basic options - a close "Norway style" deal, or a free trade deal roughly like Canada - a compromise that we've discussed many times here. It feels that the search for something else has been in vain.
But there are questions too about the extent of the EU's pushback.
Sources on the EU side express irritation at the UK's approach, at what they see as a strident tone the prime minister took in the last 48 hours.
The European Council is not the same as Prime Minister's Questions, it's suggested. But to kick out publicly, as they did in Salzburg, certainly runs the risk of pushing Theresa May too far - it gives succour to those arguing at home that the EU isn't capable of playing fair.
In the coming days there will, of course, be hype and clamour on both sides.
But it's true that, instead of throwing the prime minister a lifeline in the run-up to conference, they have chucked petrol on a fire that was already alight.
Some MPs are already suggesting that if the EU is going to react like this, perhaps the government's only choice might be to cut and run.
But take a breath - it is not the case that all is lost.
The overriding incentive on both sides is to try to find a deal.
The consensus is still that somehow, it can be done.
But perhaps what the Salzburg setback has laid bare is the biggest risk to the deal of all.
The two sides seem again and again to misunderstand the other's position. And talks where no-one is really listening maybe can't really be genuine conversations after all.

Liam Fox has called for an end to the "obsession with Europe" in economic matters, saying the focus should be on "growing markets" around the world.
The international trade secretary said because the proportion of the UK's exports that go to the EU was falling, "we've got to be focussing on the growing bits of the global economy".
He was speaking to the BBC during a visit to China alongside Theresa May.
Mr Fox also defended Mrs May from the recent criticism she has faced.
The prime minister has come under pressure from Eurosceptics worried about concessions in the Brexit talks, while other MPs have called for more direction on domestic policies.
Speaking to BBC political editor Laura Kuenssberg, Mr Fox praised the prime minister's "vision" and said he wished people saw her the way she was perceived around the world, rather than by "internal tea room discussions in the UK".
As International Trade Secretary, Mr Fox is responsible for striking international trade deals that will come into force when the UK leaves the EU.
He said the UK would be able to "roll over" 40 existing trade deals it is part of as an EU member, as well as reaching its own arrangements with the likes of the United States, India and China.
China, Mr Fox said, was a "real success story" for the UK, with exports rising by 25% in the past year.
"All of this adds up to a much improved trading performance," he said.
And while the UK wants an "open and liberal partnership" with the EU, he added: "We've got to get away from our obsession with Europe in terms of its relation to the global economy - according to the IMF - in fact according to the European Commission - 90% of global growth in the next 10 to 15 years will be outside the European continent, clearly that's where we have to focus our attention."

The government has begun inviting applications for the Turing scheme, which will enable UK students to study in other countries.
The scheme is named after the mathematician Alan Turing, and replaces Erasmus, a European Union (EU) programme which UK students can no longer take part in.
The UK turned down an offer to continue participating in Erasmus after Brexit.
Universities minister Michelle Donelan said the Turing scheme would "enable up to 35,000 students throughout the UK to work or study across the globe".
The new scheme will provide funding "towards placements and exchanges" of students.
Universities and other organisations in the UK can apply for grants to help cover travel expenses and living costs as well as the administrative costs of running the scheme.
Applications have to be made by bodies such as universities, further education colleges and schools. If they are successful, these bodies can invite their own students to apply for individual funding.
The Turing scheme will provide placements across the world.
Erasmus covers placements across the EU and some non-EU countries that pay to be part of the scheme.
Both schemes are open not only to university students but also those in vocational training, apprentices or those who are retraining through a college or school.
Erasmus offers placements for teaching and college staff and youth workers as well, but the Turing scheme will not.
The amount of money you get under Erasmus depends on where you are going and whether you are a student, apprentice, trainee or staff.
The Turing scheme will offer different amounts based on where you are going and for how long.
For example, a university student going to France for six months would get £335 (€390) per month under the Turing scheme, while the Erasmus scheme paid £317 (€370) per month in 2020-21.
UK students did not have to pay tuition fees when studying abroad under Erasmus because the scheme was reciprocal - it allowed EU students to come and study in the UK as well.
The Turing scheme will not pay tuition fees for UK students studying abroad or for students from other countries studying in the UK. Instead, it expects the fees to be waived by the universities that take part.
Universities Minister Michelle Donelan told the Today programme "The way it'll work is our universities will partner with another university and they will waive the fees because they will be exchanging students."
The government has allocated £110m for the first year of the scheme, which starts in 2021/22, but it is not currently funded after that.
Both schemes offer support.
Erasmus pays an additional £103 (€120) per month - a total of £420 (€490) per month for a poorer student going to France for six months in the current academic year.
The Turing scheme would pay £445 (€519) per month to the same student, but also contribute to travel costs (the amount will depend on how far the student is travelling).
It will also provide poorer applicants with additional expenses, such as the costs of visas, passports, and health insurance.
Again, both Erasmus and Turing offer support.
The Turing scheme website says that, unlike Erasmus, it will "cover preparatory visits to carry out risk assessments and ensure participants will be able to equally access and take part in all elements of a placement".
Students at universities in Northern Ireland will be able to participate in either scheme, as part of an arrangement with the Irish government.
Students at universities in Great Britain will only be eligible for Turing.
Some UK students are still participating in Erasmus programmes using funding awarded before the end of 2020, which may allow them to continue until the end of the 2021-22 academic year, but no new funding will be available.
Since Brexit, UK students have had to deal with immigration regulations in the EU.
UK nationals are only able to stay in an EU country for 90 out of every 180 days without a visa (except for Ireland, which will still have free movement with the UK).
The government has published guidance for UK nationals planning to study in the EU, and encourages students consider wider issues such as health and travel insurance.
You can find UK government advice on countries around the world here.
Although coronavirus is now affecting student mobility, figures from before the pandemic showed that about half of UK university students who studied abroad did so through Erasmus.
In 2017, 16,561 UK students participated in Erasmus, while 31,727 EU nationals came to the UK.
"The Erasmus+ programme has delivered and continues to deliver significant benefits to the UK and we need to ensure the positives of the programme are not lost as we move into the next stage," Jane Racz, the director of the programme in the UK, told BBC News last year.
"Since 2014, almost €1bn [£900m] of funding has been distributed to UK Erasmus+ projects, with over 930,000 participants involved."
The National Union of Students has said the government's decision to replace Erasmus will "damage" the potential for many students to study abroad.
"Despite the claims of this government, they have not backed up the new Turing scheme with the funding required to support disadvantaged students to study abroad," Hillary Gyebi-Ababio, NUS vice-president for higher education, said. "This will harm the futures of thousands of students for years to come."
Kate Green MP, Labour's shadow education secretary, said government "rhetoric on the Turing Scheme does not live up to the reality".
Correction: This piece has been updated to make it clear that students from other countries will be able to study in the UK but they will not receive funding under the Turing scheme.
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Esther McVey has declined to back Theresa May's Brexit plans, saying she did not want to add to "speculation".
The work and pensions secretary said she was "fully, 100% behind the prime minister" without endorsing her proposal for future trade with the EU.
Cabinet ministers expressed concern about potential compromises with the EU at a meeting at No 10 on Thursday.
The BBC understands concerns centred around plans to ensure no hard border between Ireland and Northern Ireland.
The UK and the EU both want to avoid a "hard border" - physical checks or infrastructure between Northern Ireland and Ireland - but cannot agree how.
The EU has proposed a backstop that would mean Northern Ireland staying in the EU customs union - something the UK says would create a border down the Irish Sea.
BBC political editor Laura Kuenssberg said it was understood that the EU was prepared to accept the idea of the whole of the UK remaining in the customs union if no trade deal can be done by the end of 2020, the so-called "transition period".
But the EU would not accept the UK's bid to put an end date on it -  many Brexiteers argue an open-ended arrangement is unacceptable. It is understood that cabinet ministers Liam Fox, Michael Gove, Dominic Raab and Jeremy Hunt expressed concerns.
Meanwhile Arlene Foster, leader of the DUP, which supports Mrs May's government on key votes, has said Theresa May cannot in good conscience recommend a Brexit deal that places a trade barrier on businesses moving goods from one part of the UK to another.
The DUP has threatened to withdraw its support for the government if it is not happy with the final Brexit deal.
But Tory MP Helen Grant, a Tory vice chairwoman, told the BBC's Politics Live: "I think they're bluffing."
The UK and the EU have yet to strike a deal on how Brexit will work, with less than six months to go before the UK leaves on 29 March.
Mrs May says she is working for a deal and has urged MPs to "put the national interest first" and support it.
Earlier, asked several times if she backed Mrs May's approach, set out in a White Paper in July, Ms McVey told the BBC: "I am completely supportive of the prime minister as she well knows, what I won't do even for you right now is speculate."
The prime minister says her plan (often called the Chequers plan because that is the name of the country residence where it was agreed) for the UK and EU to share a "common rulebook" for goods, but not services, is the only credible way to avoid a hard border between Northern Ireland and the Republic of Ireland.
But it is opposed by some within her own party who argue it would compromise the UK's sovereignty - former foreign secretary Boris Johnson has led criticism and Brexiteers have backed a "Canada plus plus" deal instead, modelled on Canada's free trade deal with the EU.
Sir Ivan Rogers, the UK's former ambassador to the European Union, dismissed both options in a speech in Cambridge, saying the chances of the EU agreeing to either was "precisely zero" and that there had been "culpable naivety" in the negotiations.
Meanwhile the EU says its negotiators are working "day and night" to try to reach an agreement ahead of Wednesday's summit.
The UK is expected to come up with new proposals as an alternative to the "backstop" put forward by the EU - which the government has rejected, saying it would threaten the integrity of the UK.
Mrs May relies on DUP support in key votes because the Conservatives do not have a majority in the House of Commons.
On Wednesday it was revealed that the DUP was prepared to vote against the Budget on 29 October - which could threaten the future of the government - if there are any new barriers between Northern Ireland and the rest of the UK as a result of Brexit.
And in a vote on the Agriculture Bill, it did not back the Conservatives in what DUP sources said was a "warning shot" for the government.
On Wednesday, EU chief negotiator Michel Barnier said there would have to be checks on goods travelling to Northern Ireland from the rest of the UK, because they would effectively be arriving in the EU's single market if there was no hard border with the Republic of Ireland.
"I understand why such procedures are politically sensitive," he said, but added "Brexit was not our choice, it is the choice of the UK."
The EU and UK have agreed that these checks "cannot be performed at the border" and the EU proposes to carry them out "in the least intrusive way possible", he said.
Former Prime Minister Sir John Major, meanwhile, has said he has "great sympathy" for Mrs May, telling the BBC's Political Thinking podcast that "the way she's being treated by some of her colleagues is absolutely outrageous".
He hit out the "not so subliminal bullying" by Tories opposing her strategy in the middle of negotiations and also criticised International Development Secretary Penny Mordaunt, who declined to give the PM's plan her explicit backing when asked earlier this week.
"If people are sitting in cabinet they either support the government's policy or they don't sit in cabinet," Sir John said.

Prime Minister Theresa May's Brexit speech is being seen in Europe as the "hard" option of full UK withdrawal - and there is some relief that the British position is clearer now.
"Finally we have a little more clarity re the British plans," German Foreign Minister Frank-Walter Steinmeier said.
Germany also wanted a "close and trusting relationship", he said.
The Czech Europe Minister, Tomas Prouza, tweeted: "UK's plan seems a bit ambitious".
"Trade as free as possible, full control on immigration... where is the give for all the take?" he asked.
The Italian daily La Repubblica commented: "Out of the EU, out of common market, out of everything. It appears that Theresa May's intention through negotiations with the EU at the end of March is 'a hard Brexit' - a very hard Brexit indeed."
BBC live coverage in full here.
May: UK must leave EU single market
One of the top EU officials, European Council president Donald Tusk, voiced regret but some relief too in a tweet: "Sad process, surrealistic times but at least more realistic announcement on #Brexit."
Belgian liberal Guy Verhofstadt, named as the European Parliament's lead negotiator on Brexit, warned that any deal for the UK would be worse than EU membership.
He said it was an "illusion" for Mrs May to suggest "that you can go out of the single market, that you can go out of the customs union and that you can cherry-pick, that you can have still a number of advantages - I think that will not happen".
Mrs May's mention of a possible alternative economic model for the UK was a "threat", he said, that could obstruct the negotiations.
Norway's Aftenposten daily said Mrs May's speech signalled "a clear rejection of a Norwegian-type involvement in the [EU] internal market".
Norway has very close ties to the EU - as a member of the European Economic Area (EEA) it has open, tariff-free access to the EU single market, though Norwegian fisheries and agriculture are excluded.
The price for that advantage is high Norwegian contributions to the EU budget and automatic acceptance of most EU laws.
"Even though she rejects the term, it is indeed a hard Brexit," commented France's Le Figaro daily.
Marine Le Pen's far-right National Front (FN) in France praised Mrs May's speech.
FN vice-president Florian Philippot tweeted: "Bravo to T. May who respects her people with a 'clear and clean' Brexit. Sovereignty cannot be a half-measure. French independence soon!"
Michael Fuchs, a close conservative ally of German Chancellor Angela Merkel, accused Mrs May of "cherry-picking" in her speech, Sky News reported in a tweet.
EU politicians have stressed that they will not let the UK "cherry-pick" parts of its EU membership terms.
They insist that the single market's four freedoms - covering goods, services, capital and labour - cannot be diluted.
The Dutch daily Algemeen Dagblad called Mrs May's speech "not just a bit of Brexit but the full whack".
"Bye bye EU... the unspoken, big threat from London is creating a tax paradise in front of the gates of Europe," it said.
Sweden's former Foreign Minister Carl Bildt tweeted: "I regret the approach the UK government has taken.
"I think most of the EU would have preferred a closer relationship with the UK."
Sweden has long been one of the UK's closest allies in the EU.

Anti-Brexit campaigners have been given permission to take their case to Europe's highest court as they seek a ruling on whether it can be halted.
The cross-party group of politicians argue that Article 50 can be revoked if MPs vote to do so.
The Court of Session in Edinburgh had previously rejected their bid to have the case referred to European judges.
But they have now won an appeal, and the European Court of Justice will be asked to give a definitive ruling.
The panel of appeal judges at the Court of Session said the "urgency of the issue" - with the UK due to leave the EU on 29 March - meant its request to the European Court was being done under expedited procedure.
The UK government said it was "disappointed" by the decision and was giving it "careful consideration".
But a spokesman stressed that the government remained committed to implementing the result of the EU referendum and "will not be revoking Article 50."
The legal case has been brought by politicians including Scottish Green MSPs Andy Wightman and Ross Greer, Labour MEPs David Martin and Catherine Stihler and SNP MEP Alyn Smith, who have claimed that Brexit is "not inevitable" and "there is still time to change course".
Welcoming the ruling, Mr Greer said: "If negotiations collapse, as appears to be happening, we have to know that a no deal disaster is not the only option on the table."
The politicians have been joined by lawyer Jolyon Maugham QC, the director of the Good Law Project, who said the latest ruling was a "bombshell" that could "decide the fate of the nation" and potentially allow the country to "wake up from the nightmare that is this government's Brexit".
Prime Minister Theresa May has admitted that negotiations with the EU have reached an "impasse" after her Brexit plans were rejected at a summit in Salzburg earlier this week.
But in a speech outside Downing Street she insisted that: "Nobody wants a good deal more than me - but I will not overturn the result of the referendum, nor will I break up my country."
The speech was described as "dreadful" by First Minister Nicola Sturgeon, who claimed Mrs May's so-called Chequers proposals for Brexit were now a "dead duck" and that Brexit "should not happen" if the PM was not going to keep the country in the single market and customs union.
The petitioners argue that the UK should now effectively be allowed to change its mind on Brexit, without needing the permission of the other 27 EU members.
If it is successful, their case could strengthen the hand of any attempt by MPs to keep the UK in the EU after the final details of its departure terms are known.
This is because it would give parliament the power to unilaterally halt Brexit if it feels any final deal - or no deal - is unacceptable, even if the government wants to leave regardless.
Court of Session judge Lord Boyd ruled in June that the case could not go to the European Court in Luxembourg as it was "hypothetical" and did not reflect political reality as it "seems highly unlikely that this government will revoke the notification".
The campaigners appealed against that decision, and on Friday the court ruled in their favour.
The ruling was delivered by Scotland's most senior judge, Lord Carloway, and his colleagues Lord Menzies and Lord Drummond Young.
The appeal judges said matters had "moved on" since Lord Boyd's original ruling, with the European Union (Withdrawal) Act now setting out how parliamentary approval is to be sought once the negotiations between the UK government and the EU conclude.
Lord Carloway said it was therefore "clear" that MPs at Westminster would be required to vote on any Brexit deal agreed by the EU and the UK government.
He stated: "It seems neither academic nor premature to ask whether it is legally competent to revoke the notification and thus to remain in the EU.
"The matter is uncertain in that it is the subject of a dispute; as this litigation perhaps demonstrates.
"The answer will have the effect of clarifying the options open to MPs in the lead up to what is now an inevitable vote."
The judge also said the European court would not be advising parliament on "what it must or ought to do".
Instead, he said it would be "merely declaring the law as part of its central function", adding that "how parliament chooses to react to that declarator is entirely a matter for that institution".
In their draft reference to the European Court, the judges ask: "Where a member state has notified the European Council of its intention to withdraw from the European Union, does EU law permit that notice to be revoked unilaterally by the notifying member state?
"And, if so, subject to what conditions and with what effect relative to the member state remaining within the EU?"

There were two largely separate battles taking place in the European elections in the UK.
The first was for the support of those who voted Leave in the 2016 referendum, many of whom are disappointed that the UK has not yet left the EU.
The second was for the backing of those who voted Remain, many of whom are hoping that the decision to leave the EU might yet be reversed, perhaps via a second referendum.
The outcome of the first battle was decisive and widely anticipated. The second was rather messier, but might have just as important an impact on the debate about Brexit between now and when the UK is due to leave the EU on 31 October.
Many Leave voters had previously supported UKIP under Nigel Farage's leadership, before backing the Conservatives in the 2017 UK general election.
They switched en masse towards Mr Farage's new organisation, the Brexit Party. With 32% of the vote, its level of support was as much as five points higher than that of UKIP in the last European elections, in 2014.
The Brexit Party performed much better in those areas that voted most heavily for Leave in the 2016 referendum than it did in those places that voted most heavily for Remain.
As a result, the party scored much less well in London (18%) and Scotland (15%) - where a majority voted for Remain - than in the rest of England (36%) and Wales (32%), which had provided the foundations of Leave's success in 2016.
Because of this surge, the Conservatives fell to just 9% of the vote.
Governments often perform badly in European elections, as voters take the opportunity to express their disappointment with its performance without the risk that their vote might put the opposition into government.
Yet the rebuff suffered by the Conservatives was far worse than the previous worst snubbing to have been suffered by a government in a European election. That was the 15% to which Labour sunk in 2009, during the darkest days of Gordon Brown's premiership.
It was also easily the Conservatives' worst ever performance in a nationwide election. Its performance was weak everywhere - the party did not manage to come first in a single council area.
In sharp contrast to the position in the 2017 general election, when it was much stronger in Leave-voting areas than in Remain-inclined ones, the party did equally badly in both.
It is an outcome that would seem to confirm the message of the opinion polls that the party has lost the confidence of many Leave voters.
However, dramatic though it was, the outcome of the battle between the Conservatives and the Brexit Party had been widely forecast by the polls.
Indeed, politicians had already begun to react to it in the period between Thursday's vote and last night's count.
It arguably contributed to the downfall of Prime Minister Theresa May on Friday, while many of the candidates to be her successor are arguing that 31 October should be a firm and final deadline for the UK's exit from the EU.
The European election result will simply ensure that that debate continues.
The second contest in these elections was for the support of those who want to remain in the EU.
The polls had suggested that during the campaign Labour, which has been somewhat equivocal in its support for a second referendum, had been losing the backing of Remain supporters to the Liberal Democrats and the Greens.
However, there was disagreement as to whether the Lib Dems would challenge Labour for second place.
In the event, the Lib Dems won this battle hands down.
The party won 20% of the vote, its best European election performance ever, while Labour secured just 14%.
Sir Vince Cable's party not only beat Labour but managed to come a clear first in those places that voted most heavily for Remain including, most remarkably, in London.
There is no doubt that the party was the single most popular party among Remain supporters, a position that had hitherto been enjoyed by Labour.
The Lib Dems, who are themselves about to embark on a leadership contest, will hope the outcome signals that the party is finally recovering from the dramatic decline it suffered following its involvement in the 2010-15 coalition.
However, it was not the only party in favour of a second referendum to do well.
So too did the Greens, whose 12% of the vote was its best European election performance since 1989. However, in its case support was only marginally higher in Remain-voting areas.
In Scotland, the SNP, led by Nicola Sturgeon, won no less than 38% of the vote, its best ever European election result. It is an outcome that confirms its dominance of the electoral scene north of the border.
In Wales, Plaid Cymru also enjoyed some success with 20% of the vote, its highest since 1999.
Though nothing like as devastating as the loss suffered by the Conservatives, Labour's poor performance could, in truth, also lead to a rethink just as important as that now going on inside the government.
The party's attempt to keep both its Remain and its Leave supporters on board seems to have resulted in a loss of support among both groups.
Although Labour's vote fell most heavily in the strongest Remain voting areas, its vote also fell, by as much as 11 points, in the most pro-Leave areas.
There have already been signals from Labour that it might now fall in more firmly behind the idea of a "confirmatory vote" in which whatever deal is eventually struck with the EU is put before voters in a second referendum.
It will hope that this stance will help reverse the loss of support to the Lib Dems and Greens, without losing it too much ground among its minority of Leave supporters.
Such a development would certainly ensure that the government and the opposition are further apart on Brexit than at any point since the EU referendum.
More like this
On the other hand, the newest of the pro-second referendum parties, Change UK, led by Heidi Allen, had a bruising night, winning just 3% of the vote.
Even in London, where its hopes were highest, the party managed to win no more than 5% of the vote.
It seems likely that the party will have to seek some form of collaboration with the Lib Dems rather than continue to attempt to compete for much the same body of voters.
Inevitably, the outcome of the two battles led those on the Eurosceptic side of the Brexit argument to say the result showed that the electorate were willing to leave the EU without a deal.
Those in favour of a second referendum claimed the result indicated that voters wanted just that.
In practice, it would seem safer to argue that the outcome confirmed that the electorate is evenly divided as well as polarised between those two options.
Overall, 35% of voters voted for parties comfortable with no deal (the Brexit Party and UKIP).
Equally, 35% backed one of the three UK-wide parties (Lib Dems, Greens and Change UK) that supported a second referendum. If Plaid Cymru (1%) and the SNP (3.5%) are included, the Remain share of the vote is just over 40%, although the SNP is known to secure considerable support from those who voted Leave.
Far from providing a clear verdict, the result simply underlined how difficult it is likely to be to find any outcome to the Brexit process that satisfies a clear majority of voters.
Meanwhile, the poor performance of both the Conservatives and Labour will inevitably raise questions about the future of the country's two-party system.  At 23% their joint tally was well below the previous all-time low of 43.5% in 2009.
European elections are, of course, not the same as a general election; voters have long shown a greater willingness to vote for smaller parties.
However, the issue that caused both parties such difficulties in this election - Brexit - is not going to go away any time soon.
In truth, both the Conservatives and Labour have been on notice that they need to handle the issue much better than they have done so far.
Otherwise, voters might yet turn elsewhere at the next general election too.
About this piece
This analysis piece was commissioned by the BBC from experts working for an outside organisation.
Sir John Curtice is professor of politics at the University of Strathclyde. He worked with Stephen Fisher, associate professor of political sociology, University of Oxford; Patrick English, associate lecturer in data analysis, University of Exeter and Eilidh Macfarlane, a doctoral student at the University of Oxford.

MP Antoinette Sandbach, who was expelled from the parliamentary Conservative Party last month, has joined the Liberal Democrats.
The Remain-voting Cheshire MP was among 21 rebels who lost the Tory whip after rebelling against Boris Johnson in a bid to prevent a no-deal Brexit.
She will stand as a Liberal Democrat candidate in her Eddisbury constituency in December's general election.
Explaining her decision, she said the Tory Party had "moved their values".
Her move makes her the eighth MP to have joined the Lib Dems this year.
Speaking to Radio 4's Today programme, she said she had considered not standing for re-election.
"Like many of the MPs that have stood down, I have been subjected to abuse."
"It has been incredibly difficult for my family and for me. But this is a critical time in our nation's history," she said.
Announcing her decision earlier, as campaigning got under way ahead of the 12 December election, Ms Sandbach said: "People have a very clear choice.
"The Conservative Party offers years of uncertainty, whilst the Liberal Democrats will stop Brexit.
"I will stand on my strong local record, helping to secure local investment, fighting for fair funding for our schools and to secure additional funding in local health services.
"Our country deserves so much better than Boris Johnson and Jeremy Corbyn."
Ms Sandbach was not among the 10 rebels readmitted to the party last month, shortly before the Commons backed the legislation to approve the 12 December election.
Earlier this month, she lost a confidence vote among her local party members - she described it as "symbolic" but added that "it most likely means that I am not going to be the Conservative candidate in the next election".
Contesting her Eddisbury seat as a Conservative candidate in 2017, Ms Sandbach won a near-12,000 majority over Labour, with the Lib Dem candidate third with 2,804 votes.
She was among 19 former Tories who backed the prime minister's Brexit deal legislation last week but voted against his proposed three-day timetable for it to be considered in the Commons ahead of the original Brexit deadline of 31 October.
Speaking after joining the Lib Dems, she said she was concerned Mr Johnson's deal was "a trap door to a no-deal Brexit".
She follows MPs Sarah Wollaston, Philip Lee and Sam Gyimah to become the fifth ex-Tory to join the Lib Dems in recent months.
Ex-Conservative Heidi Allen also joined the party earlier this month, after quitting the fledgling Change UK party she joined after leaving the Tories.
Liberal Democrat leader Jo Swinson said Ms Sandbach was a "passionate campaigner" and would be a "fantastic candidate" in the election.
"Her defection clearly shows that the Liberal Democrats are the strongest party of Remain and attracting support from right across the political spectrum," she added.

Facebook has removed threatening messages posted in reaction to a paid-for advert by a pro-Brexit group.
It said the advert itself, which attacked "Remoaner globalist scumbags" and accused pro-EU MPs of "treason", did not break its community guidelines.
But the social media giant took down posts threatening violence against anti-Brexit politicians, after being alerted to them by BBC News.
The ad, by the "Brexit Defence Force", was seen fewer than 5,000 times.
The site has vowed to do more to crack down on "hate speech" on its platforms but its team of moderators, and the artificial intelligence software it is developing, have sometimes struggled to identify inflammatory content.
The Brexit Defence Force ad was promoted to UK Facebook users on Sunday and Monday, mentioning several politicians by name and accusing them of "crossing the line of treason to our democracy".
"Make some noise on their pages, show them we are watching their treacherous devious antics and they will be held accountable," it says.
Less than £100 was spent promoting the advert but it attracted dozens of comments, some of which advocated violence.
After BBC News approached Facebook for comment, these threatening posts were deleted.
"Any content that violates our Community Standards on violence or harassment is absolutely not permitted on our platform," said a Facebook representative, adding: "This particular ad does not breach our policies."
Facebook recently unveiled new transparency measures for political adverts, following data scandals in the US and UK.
And anyone running ads in the UK now needs to verify their identity and location and carry a "paid for by" disclaimer if the ad references political figures, parties, elections, or laws.
The Brexit Defence Force Facebook page, which BBC News was able to contact through Facebook Messenger, includes this disclaimer, which references the "yellow vest" movement:
But the page gives no further information about identity or location and does not link to a website.
The Facebook representative added: "We have taken an industry-leading position on political ad transparency in the UK, introducing new tools including an archive of all political ads in a searchable ad library for seven years, going beyond what is currently required of us by law and further than anywhere else that allows political advertising."
And this "ad library" shows more than £1m has been spent on UK political ads since October - with two pro-EU groups leading the way.
Anti-Brexit groups People's Vote UK and Best for Britain, which campaign for another referendum, are responsible for about 40% of the total cash spent on UK political Facebook advertising in the past three months.
And a Telegraph investigation last week found Best For Britain adverts linking Brexit to palm oil deforestation and the death of orangutans had been viewed more than a million times.
"This is the same old scaremongering from the same people who didn't want us to leave the EU in the first place," Environment Secretary Michael Gove told the Telegraph.
"It didn't work last time and it won't work this time."
Pro-Brexit groups have spent less money on promoting their cause.
But a BBC News investigation recently revealed one of them had been buying up Google adverts in an attempt to reach the top of the rankings when people put "What is the Brexit deal?" into the search engine, putting it in an online bidding war with the government, which was trying the same tactic.
 In the run-up to a cancelled Brexit vote in December, the government spent over £100,000 of taxpayers' money promoting its deal on Facebook and spent money on Google and Twitter ads.

The "febrile" atmosphere around Brexit could be exploited by far-right extremists, the UK's most senior counter-terrorism officer has warned.
Assistant Commissioner Neil Basu said 18 terror plots were foiled in Britain since 2017, four of them far-right.
He said a "far-right drift into extreme right-wing terrorism" was a concern but officers were working to ensure groups did not gain a "foothold".
Mr Basu added leaving the EU with no deal would be "very bad" for policing.
The head of the Metropolitan Police's counter-terrorism operations was speaking at the launch of a new cinema advert aimed at encouraging people to report their suspicions about all forms of terrorism.
The 60-second film portrays a series of scenarios, including a man stockpiling hazardous material and another buying weapons.
Mr Basu revealed that a record 700 terror investigations are currently taking place, up from about 500 in March 2017.
Fourteen of the attacks foiled since 2017 involved Islamist suspects, Mr Basu said, adding that he was concerned about the possibility of radicalised fighters returning from abroad.
Another concern was the spread of propaganda online.
Mr Basu said while extreme right-wing activity was still a "relatively small threat", it was also "something we've got to pay very close attention to in this country - that we don't let that kind of far-right drift into extreme right-wing terrorism and we're working very hard to stop that".
Asked about the background of Brexit, Mr Basu told the BBC: "We saw a spike in hate crime after the referendum, that's never really receded.
"So there's always a possibility people are being radicalised by the kind of febrile atmosphere we've got at the moment.
"We want people to report anything that we think is going to lead to violent confrontation and people need to calm down and understand that we are paying very close attention to that and we will stop it wherever we see it."
Mr Basu said there was no intelligence pointing to an increased level of attacks after Brexit, but added: "What's most concerning me... is its potential to divide communities and set communities against each other."
His warning comes as Labour MP Melanie Onn revealed she had been threatened with being "gunned down".
The MP for Great Grimsby quoted the threatening email on Twitter, which was filled with swear words and called her a "traitor".
Ms Onn, who came out against another referendum on Brexit this week, said: "Everyone in Grimsby knows I've never backed down from a debate, even when I've had unpopular POV (including in referendum), but we must be allowed to have an opinion without this nonsense."
The threat against Ms Onn echoes the murder of Jo Cox, MP for Batley and Spen, who was shot and stabbed in 2016. Her killer, Thomas Mair, gave his name in court as "death to traitors, freedom for Britain".
It also follows concerns from a cross-party group of MPs that police were failing to prevent them being abused outside Parliament, with pro-EU Tory MP Anna Soubry being taunted with chants of "Nazi" during a live interview.
Mr Basu also told the BBC the possibility of a no-deal Brexit was "incredibly concerning" for police operations.
Echoing comments from Met Police Commissioner Cressida Dick in December, he said the UK and Europe would be in a "very bad place" if police could not exchange data or biometrics on suspected criminals and terrorists.
Mr Basu said the Met was working on contingency arrangements with police forces and agencies in Europe.
Home Secretary Sajid Javid said this week that he was confident that with or without a Brexit deal Britain would "continue to be a very safe country".

Nigel Farage has accused Theresa May of "wilfully deceiving" people over her negotiated EU deal.
The Brexit Party leader told the BBC's Andrew Marr the PM's proposed Brexit deal was a "new European treaty".
In a tense interview, Mr Farage said he would demand his party became part of the government negotiating team if it was successful in the forthcoming European elections.
Elections to the European Parliament take place on 23 May.
Asked why he did not advocate a no-deal Brexit at the time of the EU referendum in 2016, Mr Farage said: "Because it was obvious that we could do a free trade deal.
"The problem is the prime minister never asked for it, so we finished up in the mess that we're in," he said.
"She chose to go for this close and special partnership. Basically right from the start she was happy for us to be kept very close to the customs union.
"So where we are now, the only way the democratic will of the people can be delivered is to leave on a WTO (World Trade Organization) deal."
The interview on the BBC programme also saw Mr Farage asked about past comments on NHS privatisation, climate change, gun control, immigration and Russian President Vladimir Putin.
Responding angrily to the line of questioning, he said: "This is absolutely ludicrous, I've never in my life seen a more ridiculous interview than this.
"You're in denial, the BBC is in denial, the Tory and Labour parties are in denial.
"I think you're all in for a bigger surprise on Thursday week [the EU elections] than you can even imagine."
Mr Farage's fellow guests on the Marr programme included Education Secretary Damian Hinds, who said the European Parliament elections would be seen by some people as a protest vote.
"For some people this is the ultimate protest vote opportunity. Actually, ironically this is, in a sense, for some people, this is the second referendum," he said.
Mr Farage said he believed that if there was a second referendum, the campaign to leave the EU would win by a bigger margin.
He said he was "mentally preparing myself for one", adding: "I'm thinking we may well have it forced upon us."
Lib Dem deputy leader and People's Vote supporter Jo Swinson said Mr Farage had refused to "own up to well-documented and abhorrent views on NHS privatisation, his admiration for Vladimir Putin and his denial of the facts about climate change".
She said: "Despite his claims to the contrary, everyone remembers that he promised in 2016 that there would be an amazing cost-free Brexit deal available to Britain if we voted to leave the EU.
"To say today that he always advocated 'no deal' is a mark of just how shameless he is, and how little he cares for the jobs and livelihoods of the people of this country."

A UK port and Danish ferry operator DFDS have agreed to increase roll-on, roll-off, capacity by more than 40% to help freight shipping after Brexit.
Felixstowe Port's chief executive, Clemence Cheng, said the deal with DFDS comes as "shippers seek to minimise risks to their supply chains resulting from Brexit."
One freight transporter said the expansion could help ease bottlenecks.
New bridges, tractor units and trailer parking facilities will also be built.
The investment comes as suppliers on both sides of the Channel look for alternatives to Dover once the UK leaves the European Union in March.
"Demand on DFDS' service to Rotterdam has been growing steadily for a number of years and we are delighted to have agreed a new contract with them to secure the service at Felixstowe for another 15 years," added Mr Cheng.
"Dover is a port where the cargo tends to be accompanied by the driver so if there are delays, you get bottlenecks," Tim Wray of Multimodal Logistics said.
"Felixstowe is primarily an unaccompanied port where cargo arrives without a lorry, is taken from the boat to the port and on to a holding area. A vehicle then applies for the cargo and takes it away."
Hutchison Ports added it was seeing "increasing interest in both roll-on, roll-off and short sea container connections" at all three of its UK ports, which include Harwich and London Thamesport.
Niels Smedegaard, president of DFDS, said the contract was "striving to provide necessary capacity to continue... even in a possible post-Brexit world."
Information about BBC links to other news sites

Thousands of cross-channel ferry passengers have had their bookings amended to accommodate extra sailings in case of a no-deal Brexit.
Brittany Ferries said timetables from Portsmouth, Poole and Plymouth were being modified to ensure "critical goods" could still be transported.
Some passengers took to social media after the firm got in touch to tell them their trips had been cancelled.
Brittany Ferries said about 10,000 customers were affected.
In December, the government announced it was awarding £102.9m to three suppliers to provide extra capacity to ease congestion at Dover if the UK leaves the European Union without a deal on 29 March.
French company Brittany Ferries was awarded £46.6m, £42.5m was awarded to Danish shipping firm DFDS and £13.8m to British firm Seaborne Freight.
A statement on Brittany's website said: "The contract guarantees space on some of our ships and Channel routes for the delivery of critical goods post-Brexit, like medicines.
"It has been described as a kind of insurance, or safety net, to help ensure the smooth transit of these critical goods in the event of a no-deal Brexit after the 29th March."
A spokesman said about 5,000 bookings - 10,000 passengers - were affected.
He said: "In most cases it's no change or a small change. But In some cases it can involve moving from an overnight sailing to a morning or afternoon sailing or vice versa.
"We apologise in advance for any inconvenience that these changes may cause, but hope that the additional sailings will offer customers more choice."
The affected Brittany routes (and ships) are:
The company said it had modified its schedules and was contacting all affected customers.

Ferry and freight firms will be urged to plan alternative routes for drugs and other vital supplies if a no-deal Brexit blocks cross-Channel traffic.
The suppliers will be told to use Belgian and Dutch ports if blockages at Calais threaten to delay shipments.
The news emerged after a "passionate" cabinet meeting in which ministers were told about contingencies for no deal.
Meanwhile, a government watchdog is warning new UK border controls may not be ready in a no-deal situation.
Cabinet ministers are receiving weekly updates about preparations for Brexit until the UK leaves the EU next March.
After Tuesday's cabinet meeting a senior government source denied there were plans to buy or charter vessels to keep the NHS working or to guarantee food supplies.
Instead, private carriers would be expected to carry out their normal roles, the BBC has been told.
But there are worries among ministers and officials that the sudden introduction of border checks at Calais could cause sudden and serious backlogs.
The Sun reported that ministers had been warned that France could effectively shut down Calais, which it said would have a devastating effect on food exporters and manufacturers reliant on the port.
And BBC Newsnight's political editor Nick Watt said there was a discussion at the cabinet meeting that there could be a 75-80% drop-off on traffic across the Calais-Dover route, causing a huge impact on supplies including food.
The BBC's deputy political editor, John Pienaar, said one source described the meeting as "passionate".
Foreign Secretary Jeremy Hunt was said to have expressed concern that the UK must not be trapped indefinitely in the so-called "backstop" customs union arrangement with the EU, which could hamper the UK from striking wider trade deals.
Attorney General Geoffrey Cox compared that status to being trapped in Dante's "first circle of hell".
The BBC's deputy political editor says the mood among ministers at the meeting was more evidence of the prime minister's limited room for manoeuvre in the Brexit talks, as she prepares to address Tory backbenchers on Wednesday.
Theresa May's appearance before the 1922 Committee will see her face some MPs who have been critical of her Brexit plans and leadership.
It comes as a National Audit Office report says the the UK needs to replace IT systems, boost Border Force staffing levels and build new infrastructure to track goods.
The government said it was confident of striking a "good" deal with the EU for as "frictionless" trade as possible.
It said that plans were already 95% complete.
The government has already asked firms to start stockpiling a six-week supply of drugs and if necessary plan to fly in medicines which cannot be stockpiled because of their short shelf life.
The UK imports 37 million packs of medicine each month from the EU. Concern has been raised that prolonged disruption at the borders could disrupt the supply chain.
On Tuesday, Martin Sawer, of the Healthcare Distributors Association, told MPs that the pharmaceutical  industry was "very concerned" about a no-deal as it could have "catastrophic" consequences for the supply of drugs.
He warned it could lead to patients being put on drugs that they are not currently prescribed.
The Department for Transport said that while it was confident of the UK reaching an agreement with the EU on the terms of its exit, it was sensible to plan for all possible outcomes.
"We are continuing to work closely with partners on contingency plans to ensure that trade can continue to move as freely as possible between the UK and Europe," a spokesman said.
But Labour MP David Lammy, who supports a new referendum on the outcome of the negotiations with the option of remaining in the EU, said Brexit had become "like a declaration of war on ourselves".
France has also stepped up its planning for a no-deal Brexit, publishing a draft law last week which would give the government powers to deal with visas, transport and other services.
The UK is due to leave on 29 March 2019 but during the post-Brexit "transition period", set to run until 31 December 2020, the UK-EU relationship will stay largely the same.
Mrs May has insisted that if an extension is necessary it should only last a few months.
However, the Times newspaper says a leaked document given to ministers warns the transition period tying the UK to Brussels until the end of 2020 "could, in theory" turn into a long-running arrangement over "many years".
A Downing Street spokesman said this was "nothing more than a partial reflection of advice to ministers, and not of decisions taken".
He said Mrs May had made her position "absolutely clear" on Monday when she told the Commons she intended any such backstop arrangement to be temporary, and would end "well before" the next election.

New EU rules on fishing quotas could have a "grave" impact on the UK's fishing industry, a House of Lords committee has said - just a day before the new policy is introduced.
Under previous rules, crews often discarded, into the sea, fish that took them over their quota for that species.
But under the new policy, fishers must bring the full haul back to shore. This change is to stop fish being wasted.
The legislation has been called "badly designed" by UK industry bodies.
The House of Lords EU Energy and Environment sub-committee heard evidence that the legislation could mean fishermen hitting their annual quotas much earlier in the year and have to stop fishing.
The committee was told this would be particularly problematic in "mixed fisheries" where it would be hard for boats to avoid catching a fish species for which they have a very low quota.
Once they reached their quota for a particular species, fishers would be forced to choose between halting operations for the rest of the year or breaking the law by continuing to fish for other species and discarding anything over quota.
The committee also said it had worries about how the rules - which come into effect in full after a four-year phasing-in period - would be enforced.
It said patrol vessels would only be able to cover a small percentage of boats, creating a temptation for fishers to break the rules.
Committee member Lord Krebs said: "It is deeply concerning that so many people - fishers, environmental groups, even the enforcement agencies themselves - do not think these new rules can be implemented from January 1."
He added: "Most people we spoke to thought nothing would change - fishers will continue to discard, knowing the chances of being caught are slim to none and that to comply with the law could bankrupt them."
Barrie Deas, the chief executive of the National Federation of Fishermen's Organisations, said the rules were "badly designed" and would result in boats having to stop fishing for long stretches after reaching quotas on specific species.
The Department for Environment, Food and Rural Affairs said it was working with the industry to address the challenges posed by the new sustainable fishing policy.
The committee is due to publish its report on the implementation and enforcement of the EU "landing obligation" in February.

I've got five take-outs from the Article 50 bill so far.
There may be 101 pages of amendments down so far, but the government is in no mood to take any of them on board; on the contrary, their aim is to repel boarders, to the point where they would even resist the one amendment being mooted by the Brexiteer camp, which would aim to forbid ministers from accepting any extra time to extend the two year negotiating window specified by the EU's Lisbon Treaty. Ministers do believe that the EU's Michel Barnier's strategy is to enmesh the UK in a long-term negotiating limbo, perhaps including a post-Brexit transitional deal, but they don't want their hands tied.
Many of the amendments, thus far, look like the product of an amendment generating bot, standard stuff about laying reports and regular debates. But ministers are wary of some of the substantive ones setting conditions - and in particular of the emotive issue of EU nationals resident in Britain, a matter now featuring regularly in most MPs' constituency surgeries. There is strong pressure for some kind of unilateral move for the UK to guarantee their right to remain - but, the government retorts, if that was passed, its backers would be to blame if one or two European states didn't reciprocate and allow UK nationals to stay within their borders.
In the debate, Labour's frontbench Brexit spokesman, Sir Keir Starmer, looked and sounded like a lawyer delivering a plea in mitigation on behalf of a convicted prisoner. Early in his speech, he appealed to the Commons for a courteous hearing - something his opposite number, David Davis, would never have got away with. It just about worked, because the House genuinely wanted to hear what he had to say, but he does suffer from the lawyer-turned politician's tendency to address MPs as if they were the Court of Appeal. But leaving aside the style points, forging a line on Brexit which can stitch together the strongly pro-Brexit and strongly pro-Remain elements of Labour's heartland, let alone unify the deeply divided Parliamentary Labour Party, may prove an impossible challenge.
Whether it's in the leadership ratings in Conservative Home, where he has now edged ahead of the prime minister herself, or in the growls of approval from his colleagues in the regular statements in the chamber, the Brexit Secretary, David Davis, increasingly commands the status of second minister in this government. This is not a wholly comfortable place to be - flying perilously near to the Sun - but as someone reconciled, not that long ago, to seeing out their parliamentary career on the backbenches, I suspect Mr Davis can bear it.
The Lib Dems have sought to position themselves as the last champions of the Remain cause (although two of their MPs, Norman Lamb and Greg Mulholland have promised to abstain on the Article 50 Bill). But they can't claim to be the arch-opponents of Brexit and fail to maintain a presence for the big debates on it - and their leader, Tim Farron, had a chastening time at PMQs when this was pointed out. In truth, their much-reduced parliamentary party has been pretty bad at showing the flag, since the last election. It's rare to see all nine Lib Dem MPs on the green benches. This is one area where they are not very good at remaining.

Former Conservative MP Sam Gyimah has joined the Liberal Democrats.
Six MPs have defected to the party in recent weeks, including former Tory MP Philip Lee, and ex-Labour MPs Luciana Berger and Chuka Umunna.
Mr Gyimah was one of the 21 Tories who had the Conservative whip removed after rebelling against Boris Johnson in a bid to prevent a no-deal Brexit.
Last December, the East Surrey MP quit as science and universities minister in a row over Theresa May's Brexit deal.
The 43-year-old briefly stood in the race to become Conservative Party leader after Mrs May quit.
The Lib Dems currently have 18 MPs, having been boosted by a victory in the Brecon and Radnorshire by-election and the defections.
Mr Gyimah told BBC News that "the hard Brexiteers have won in the Conservative party - it is a hard Brexit party".
"There just aren't enough Conservatives like me," he said, explaining his decision to join the Liberal Democrats.
"If I want to fight for the values for which I came into politics.. the values of tolerance, the values of being sensible and pragmatic and acting in the interest of the country, then the Liberal Democrats is where I can do that from."
Not long ago at Westminster, if you were on the hunt for a smile, you wouldn't bother with the Lib Dems.
There weren't many of them, for a start, and those left were the last survivors of a near apocalypse for the party; shrivelled, ignored and drowned out.
Not any more.
They are bouncy, tiggerish and expanding.
They hope their clarity on Brexit - win an election and scrap it - will win favour with Remain inclined voters who may find Labour's pitch rather more ambiguous.
But their newbies face a big challenge: can they, realistically, win the seats they currently hold as Liberal Democrats?
Or will they go hunting for more fertile Lib Dem territory elsewhere - potentially dislodging long standing local party stalwarts?
Addressing the Liberal Democrats conference in Bournemouth, Mr Gyimah said: "There is now no orderly way for the UK to leave the EU on October 31.
"If the prime minister got a deal at the European Council on October 17 and 18, it would not be possible for us to leave on October 31 in an orderly way."
He added that the government has been left in a position where "no-deal" is the only outcome that can be delivered.
He said he had been "disheartened" by the way the whipping process "had been framed... for us MPs to choose our careers, in other words our own salaries, over putting the country first."
Mr Gyimah, who has been sitting as an Independent after losing the Conservative whip, has been a prominent advocate for a second referendum.
He previously signalled his intention to stand as an independent candidate in East Surrey in the event of a snap general election.
Mr Gyimah was born in Beaconsfield, in Buckinghamshire.
When he was six years old, his parents split up and he moved with his mother to her native Ghana, while his father remained in the UK.
He attended Achimota school, a state school in the capital of Accra, before returning to the UK to complete his GCSEs and A-levels at Freman College, a comprehensive in Hertfordshire.
Mr Gyimah went on to win a place at Somerville College, Oxford, to read philosophy, politics and economics (PPE), and served as president of the Oxford Union in 1997.
An Arsenal fan, he worked for Goldman Sachs for five years as an investment banker before moving into politics, standing unsuccessfully for Camden council elections in 2006.
In 2010 he became the MP for East Surrey and had been in Westminster for two years when he was made parliamentary private secretary to the then PM David Cameron.
He went on to become a government whip in 2013 and childcare and education minister a year later, before becoming prisons minister in 2016 and universities minister after that.
The married father-of-two quit as universities minister in December last year over Theresa May's Brexit deal.
He was introduced to delegates at the conference by the party's leader Jo Swinson as the "newest Liberal Democrat MP".
Speaking to the conference, Mr Gyimah said he did not take the decision to join the Lib Dems lightly and had started reconsidering his position in the Tories while Mrs May negotiated her deal with the EU.
But he said his concerns with the Conservative party now "go beyond Brexit".
"The values we have taken for granted for so long in our country... are under threat," Mr Gyimah said. "What Jo and I discussed are the Liberal Democrats have a unique opportunity to fight to defend those values and create a new force in British politics. That is why I find myself here today."
He said "the problem is not just on the Conservative side. When I look across the aisle, I also see on the Labour benches the same issue I have seen on the Conservative side, a doctrinaire, intolerant approach which means centrists are being squeezed out".
Mr Gyimah's move was welcomed by Lib Dem MPs.
Mr Umunna tweeted he was "absolutely delighted" and Layla Moran said: "Welcome... So delighted to have you on the team".
Chris White, a former government adviser, told the BBC it was "extremely disappointing" to see Mr Gyimah join the Lib Dems because he "stood on a manifesto pledge to deliver the referendum and here he is switching to a party which is manifestly not going to do that".
A bid by Mr Johnson for an autumn general election has so far been rejected by MPs who wanted to first make sure a bill designed to avoid a no-deal Brexit became law.
But since the bill, which seeks to force Mr Johnson to ask for a extension to the deadline, has been given Royal Assent, opposition MPs are preparing to start their general election campaigns.
As the Lib Dem conference opened, Ms Swinson said the party's anti-Brexit message should be "unequivocal" in a general election campaign.
She expressed her hopes that members would back her policy proposal of scrapping Brexit without another referendum.

President Emmanuel Macron of France has urged "swift clarification" on Brexit after the resignation of UK Prime Minister Theresa May.
He stressed the need to "maintain the smooth functioning of the EU", as the European Commission ruled out any change to Brexit policy.
Mrs May is stepping down after failing to get her Withdrawal Agreement through Parliament three times.
Mr Macron also joined EU leaders in paying tribute to Mrs May's "courage".
The Withdrawal Agreement was reached with the EU in November after arduous negotiations.
The European Commission made clear it would work with Theresa May's successor but that there would not be any changes to the Withdrawal Agreement.
"[EU Commission] President [Jean-Claude] Juncker followed Prime Minister May's announcement this morning without personal joy," said Commission spokesperson Mina Andreeva.
"The president very much liked and appreciated working with Prime Minister May and, as he has said before, Theresa May is a woman of courage for whom he has great respect.
"He will equally respect and establish working relations with any new prime minister, whoever they may be, without stopping his conversations with Prime Minister May. And our position on the Withdrawal Agreement and anything else has been set out. There is no change to that."
In an interview before Mrs May's resignation, Mr Juncker asked: "How could anybody else achieve what she couldn't?"
The UK's previous prime minister, David Cameron, clashed with Mr Juncker over the EU budget and other issues before arguing - unsuccessfully - to stay in the EU in the 2016 referendum.
Reflecting on that vote, Mr Juncker told the German public broadcaster ARD: "If you tell people for 40 or 45 years 'we're in it, but not really in it', we're part-time Europeans and we don't like these full-time Europeans, then you should not be surprised if people follow simple slogans once they're asked to vote in a referendum."
He also accepted that the EU had "failed" by not adopting "the position that was necessary". "Abstention is not a position," he said.
A statement from the French president's office said: "The principles of the EU will continue to apply, with the priority on the smooth functioning of the EU, and this requires a rapid clarification.
"At a time of an important choice, votes of rejection that do not offer an alternative project will lead to an impasse."
In other EU reaction:
By Adam Fleming, BBC News, Brussels
The EU establishment, like everyone, marvelled at Theresa May's amazing ability to stay standing.
"If you're a lion tamer you're going to get bitten," said one diplomat this morning. They were grateful that she respected the rules of the negotiations and didn't rock the boat on other EU business.
EU leaders would bolster her position when things got tough - a photo-op here, some complimentary words there. But they weren't prepared to compromise on the big one - the backstop to prevent a hard border between Ireland and Northern Ireland - because they think it's already a compromise.
They think it took her too long to realise - or admit - that the UK's economy required something that looked like a customs union. And they were amazed at her regular misreading of her own party and parliament.
EU Brexit negotiators have been war-gaming potential replacements for weeks and the scenario that seems to have been considered most seriously is a Prime Minister Boris Johnson asking for changes to the backstop that cannot be granted, and then blaming the EU.
But there's been no formal discussion about what comes next. That will probably happen at a summit of leaders next week, supposedly about appointments to the EU's top jobs and now inevitably about Brexit.
Mr Juncker will be replaced by a new Commission chief - not yet chosen - in November. New leaders will be chosen for all the EU institutions after the 23-26 May European elections.
He belongs to the centre-right European People's Party, the bloc which won the last European elections in 2014.
He voiced hope that the UK would leave the EU by 31 October - the new deadline set by EU leaders. The UK did not meet the planned 29 March deadline as exit terms had not been ratified.
Mr Juncker denied that the UK Brexit vote was a personal defeat for him.
"Nobody listens to me in Britain anyway. They should, but they don't. There was nobody in Britain who confronted the lie with the incontrovertible truth," he said.

Boris Johnson spoke to the BBC's political editor Laura Kuenssberg about Brexit, borders and his personal behaviour during the Conservatives conference in Manchester.
Here is the full transcript of the interview.
Laura Kuenssberg: Prime Minister, in the last few weeks, you've lost major votes in the Commons, you've chucked some MPs out of your own party, the highest court in the land has found you broke the law and gave the wrong advice to the Queen. How do you think this is going?
Prime Minister: Well, I think that it's going about as well as could be, especially, if not slightly better.
LK: Really?
PM: Yeah. Because look, this was always going to be a very difficult time. What we've got, basically, is a situation in which the people voted for leaving the EU in the greatest expression of popular will in favour of any party or proposition in history. And, yes, there are many people in all sorts of positions, who don't think that was the right way to go. And I am tasked with getting it over the line, getting Brexit done by October 31. And I think we always knew that as we came up to that deadline, things would get choppy, but...
LK: You are blaming all of your woes on people who are trying to stop Brexit?
PM: No, I think it's just the just the predicament, is just the it's just the situation, that we're in as a country. And I think that things are actually much much better than they, than the political situation, might lead you to believe. Unemployment is at record lows. Foreign direct investment is at record highs. We're seeing this country at the cutting edge of innovation in everything from battery technology to bio science, we are doing fantastically well in so many ways. And if only we could all come together, get Brexit over the line, I think that fevers would cool, tempers would come down. And it would be a great thing.
LK: But you're suggesting that people ought to come together, when transparently, you have been trying to create this idea of them and us, you who want to get Brexit done, which you said every possible opportunity. And the people on the other side, which you've just suggested, are only trying to hold you up and stop Brexit. And that's transparent, you're trying to create a situation of them and us are you not?
PM: I think that the truth is, there's no way of getting Brexit done without, as it were, displeasing people who don't want Brexit to get done - no way of delivering Brexit, sort of 52% Brexit and 48% Remain, that's just logically impossible. And so that I think is, is the problem. But I think once we get it done, and once we can begin building a new partnership with our new friends, once we can start thinking about how we can do things differently, how we can interact with the rest of the world, how we can recover on our impetus, our mojos, as a global outward looking... I think things will will go really well for us. And they already are going very well for us.
LK: But as things stand, are you prime minister sitting there and saying that the last couple of months is anything like a normal situation?
PM: No, because obviously what the UK is going through is a big constitutional change. The extrication, after 45 years of our legal system, from the orbit of European law, which is you know, has become very, very pervasive. It's a very complicated thing to do. And the most complex thing is clearly trying to unravel our relationship with the EU customs union and the EU single market, and the empire of the EU law as it were.
LK: Let's talk about that. So let's be completely clear, under the proposals that you were about to take to Brussels, there would be extra checks on the island of Ireland, how and where?
PM: Well, I mean, if I made the the proposals are not yet made, I probably ought to make them to the EU...
LK: But you know there are suggestions of what is out there, which you deny. So how would you describe what you will put forward?
PM: What I can say is that, and I think this is crucial for everybody to understand, because it's just the limit of what a sovereign country can can do. If the EU is going to insist on customs checks as we come out as it as it is, then we will have to accept that reality. And there will have to be a system, for customs checks away from the border. Now, we think those checks can be absolutely minimal and non-intrusive and won't involve new infrastructure. But that is absolutely, Laura, that is where the argument is going to be. And that's where the negotiation will be will be tough
LK: To be really clear about that. It wouldn't be the EU insisting on checks happening somewhere. If we are in two different economic systems, Of course, there would have to be checks. And that seems to be, the idea of that seems to be toxic to a lot of people. So isn't this just you putting forward similar proposals to what have been suggested that been turned down so many times?
PM: Well, let's see where we get to. And as you know, we made some very constructive and far-reaching proposals...
LK: ... that you haven't published them?
PM: Well, well, we actually the I think that they're quite widely known to minimise the checks for agri-foods for cattle for food. So that stuff moving around the island of Ireland doesn't need to have any checks at all. And that's a huge volume of the north-south trade. Just to set this in context for you this argument, it's important to understand that trade north-south of the border, is dwarfed by trade east-west, i.e. from Northern Ireland to GB. So it would be wrong to, as it were, to create a series of custom to keep Northern Ireland in a customs union with the EU and to create new checks down the Irish Sea for customs....
LK: So you are ruling out checks in the Irish Sea, because that is something that has done the rounds as an idea every now and again.
PM: Well, there already are some checks, as you know,
LK: But extra new checks?
PM: That is epidemiological purposes. Insofar as we've made, I mean, we're really getting into the weeds now. But insofar as we've made it, far as we've made a big move on sanitary, which we have, then that will logically imply some more checks down the Irish Sea. But we think that's liveable with provided it's done in the right way.
LK: If there isn't a deal whose fault will it be?
PM: Well, I'm, you know, I don't want to get into a blame game. But I think that the UK has really moved a long, long way. And what I think we can do, is we can sort out the issue of the UK leaving the EU whole and entire. We can protect the Good Friday process. We can protect the peace process in, in, in Northern Ireland. We can ensure that there aren't checks at the border, no physical, no interruption of trade or movement of people. Absolutely not. And we can also protect the benefits that Ireland has got over the years from the EU single market.
LK: But given the scepticism and concern on the other side about what they've heard so far from your government repeatedly saying it does not go nearly far enough. You really believe that what you're about to put on the table could win the EU round? You do?
PM: Yes, I absolutely do. Yes. And I urge you, Laura to keep hope alive and not, to not, listen...
LK: This is not about people feeling hopeful. This is about whether or not the government can come up with a deal with the European Union, to protect the economy to protect people's jobs and livelihoods. This is not about telling people to cheer up, this couldn't be more serious.
PM: I know. But it's also a question of getting Brexit done by October 31. And doing it in a way that protects the unity and integrity of the United Kingdom. And we are entitled to protect our customs union, and we are entitled to exit as a sovereign state. And, and we can do it in such a way as to preserve the, as I said, all those benefits that Ireland has. So with great, with great respect to, to all those who are currently anxious about it, and particularly in in Ireland, we do think that our proposals are good and creative. But but I accept also, Laura, that, you know, there may be hard yards ahead.
LK: And if we end up, contrary to what you desire, still in the European Union after October 31, you said that the UK would be truculent, suggesting that somehow we would not be a co-operative friend and partner to the EU. What would you do, play rough?
PM: Well... (sighs) I... it goes without saying that the UK would be held against the will of its government and indeed against the will of the of the people of the UK who'd voted to leave. And I think that would be a very unhappy and unfortunate situation. I don't think that is where our EU friends and partners want us to be. So I'm hopeful that we'll get a deal. I'm sorry to sound hopeful. But I think I feel, I'm sorry, if you think that hope is not called for these circumstances. But I do think there is a good chance, gonna put it no higher than that, but a good chance of getting a deal. And we're going to work very hard to do that.
LK: Now you have also this week had to deal with allegations about your own behaviour in the past. And yesterday, you denied that you touched a women inappropriately at lunch, she said you did, is she lying?
PM: I don't want to minimise the importance of this issue or people's concerns about this kind of thing. But in this case, it is simply not true.
LK: So she is lying?
PM: Look, I'm not going to go into whatever when people make these kinds of, of allegations and always be taken very, very seriously. But in this case, it is not true.
LK: Do you remember the event in question?
PM: There is not much more I can say.
LK: Do you remember the event in question?
PM: There is not much more I can say. It is not true.
LK: Well, if there is, because also some people would think in this kind of situation, there should be some kind of investigation, questions should be asked. Should people try to find out what happened because we have completely a "he says, she says" situation here?
PM: I can tell you it is not true. And what I want to do is get on with delivering on what I think is the, I must say, important issue of our domestic agenda, getting not just getting Brexit done, but...
LK: But shouldn't this be cleared up somehow? I mean, you hold the highest political office in the land, this allegation has not been retracted. You yourself wrote almost a year ago, "to all those who worry if we might be a teensy bit unfair on the male sex, I say forget it, put a sock in it. We need that feminist rage." You wrote that these kinds of allegations should be taken seriously.
PM: They should be. But I'm just telling you, I'm just telling Laura, that there's not much more I can say about this issue. Since I've said it several times. But what I can say is that we are focused on delivering on our domestic agenda, I'm very proud of what we're doing on the living wage, which is a massive expansion of the living wage. Taking huge numbers of people out of low pay, effectively abolishing low pay over time and will take the living wage down to people who will receive it at 21...
LK: But do you worry about what female voters think of you?
PM: Yes, of course, Of course. And I think that these are important issues. But I can't really can't give you any more on that subject than what I've already said. Perhaps I could I could remind you that when I, when you ask about, about female voters, we are doing. When I was running in London, we had an administration that was very, very largely women-led and I was very proud of that. We have large numbers of women in the cabinet today. I think we're as many as that are that has ever been. Home secretary, business secretary and so on. And we're very, very, very proud of that. And when I was foreign secretary, my signature policy, most important thing we did was to campaign for 12 years of quality education for every girl in the world. That's a fantastic thing to...
LK: Finally... is the job harder than you thought it might be?
PM: It's a wonderful job. And I...
LK: Wasn't my question. Is it harder than you thought it might be?
PM: Well, I don't want to sound... I don't want to, it's, it's a, it's a, it's a wonderful job. It's a yes, it's a hard job. But I think that every day we are making progress. And I think we can get Brexit done. And I think we can get the country to... I know we can get Brexit done. I think we can get the country to focus on what we're trying to do for people who care about the NHS, for people who care about their kids' education for people who want to see the opportunity extended across this country through infrastructure, education and technology. I think this is going to be a fantastic government and we want to get on and deliver for the people of this country.
LK: Thank you very much.

 A number of obscure pieces of trade law have taken on near mythical status in the Brexit debate.
One of them is Article 24 of the General Agreement on Tariffs and Trade (Gatt). - Article XXIV for the purists.
Supporters of a no-deal Brexit say it would allow the UK to continue to trade with the EU without tariffs (taxes on goods crossing borders) for up to 10 years, while the two sides negotiated a permanent future trade agreement.
Boris Johnson said in the BBC's leadership debate: "There will be no tariffs, there will be no quotas because what we want to do is to get a standstill in our current arrangements under Gatt 24, or whatever it happens to be, until such a time as we have negotiated the [free trade agreement]."
But Bank of England governor Mark Carney told BBC News: "The Gatt rules are clear... Gatt 24 applies if you have an agreement, not if you've decided not to have an agreement, or you have been unable to come to an agreement.
"We should be clear that not having an agreement with the European Union means that there are tariffs."
So what is this all about?
The key point is that you need a trade agreement in order to make use of Article 24, and the EU would be under no obligation to agree anything with the UK in the aftermath of a no-deal Brexit.
In other words, if the UK leaves the EU with no deal, and therefore no trade agreement, it will not be able to use Article 24. Instead it will fall back on the basic rules of the World Trade Organization (WTO) - the building blocks of international trade.
The WTO has 164 members and each of them has a list of tariffs and quotas (limits on the amount of goods traded) that they apply to other countries.
In the event of no deal, the UK could choose to continue applying zero tariffs to goods being imported from the EU in order to minimise disruption to trade and prices.
But under rules set out in Article 1 of Gatt (which are commonly known as Most Favoured Nation (MFN) rules), it would have to offer the same terms to the rest of the world.
So what is the problem with that? If no-one had to pay anything to get goods into the UK, it would certainly mean cheaper imports. But it would also put a lot of British companies, that were unable to compete with cheap imports, out of business.
It is also worth remembering that there would be no obligation on other countries to offer the UK the same tariff-free access in return.
There are of course ways to bypass MFN rules and do specific deals - and this is where Article 24 comes in.
It allows countries or trade blocs to agree lower (or zero) tariff rates with other countries or blocs, if they set up a customs union or a free trade area, or if they have an interim agreement - which acts as a stepping stone to a permanent agreement in the future.
That is how international trade works, and the WTO's own database shows that 311 free trade agreements have been notified under Article 24.
This is outlined in an explainer from the pro-Brexit group Lawyers for Britain. But they are clear that there does need to be an agreement - it is not automatic.
The UK leaving the EU with no deal suggests there would be… well, no deal.
Or to put it in the words of Peter Ungphakorn, a former WTO secretariat official: "No deal means there is no agreement with the EU and therefore Gatt Article 24 doesn't apply."
And, to state the obvious, to have a deal, you need both sides to agree - the UK cannot invoke Article 24 on its own.
Supporters of a no-deal Brexit are betting that the EU would be keen to do a quick, basic trade deal if the UK leaves without any withdrawal agreement. But that is not what the EU itself is saying.
The EU chief negotiator Michel Barnier has said no future trade talks can begin until agreement is reached on three key issues: citizens' rights, the Irish border and the UK's financial obligations.
And EU Trade Commissioner Cecilia Malmstrom has said that the idea Article 24 could be used to avoid tariffs without an agreement was "completely wrong".
"They will have to trade with us and other countries, until there are trade agreements - and we hope that will be a trade agreement - on the 'most favoured nation' basis. And that will mean new tariffs," she said.
The other broad point to consider is that Article 24 applies to the trade in goods only. It has no effect on the trade in services, or on other important issues such as regulations and standards.
It has been applied to "interim agreements" only on rare occasions since the WTO was established in 1995 and never to anything approaching the scale of the UK-EU trade relationship.
Anyone looking for more detail on Article 24 could do a lot worse than read this explanatory piece from the House of Commons Library.
It even quotes Theresa May saying: "The question of Gatt 24 is perhaps not quite as simple as some may have understood it to be."
But that may not stop it being cited as a solution on a regular basis.
This piece was first published on 13 March 2019. It has been updated to reflect comments about the use of Article 24.
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Brexit is a major issue at the UK general election - here's what we know about where the main parties across the UK stand.
In short: Prime Minister Theresa May was against Brexit before the EU referendum but now says there can be no turning back and that "Brexit means Brexit". The reason she gave for calling a general election was to strengthen her hand in negotiations with the EU.
How the party sees Brexit: The Conservatives' priorities were set out in a 12 point plan published in January and the letter formally invoking Brexit in March.
Key elements include:
What we don't know: The Conservatives have not said how they will control migration from the EU after Brexit. They have also not committed to the size of any separation payment they would accept, beyond saying the UK would meet its international obligations.
They have not specified which matters returning from Brussels will be handed to devolved administrations and which will be kept at Westminster.
Negotiating style: Mrs May has talked tough towards the EU in recent weeks, claiming some key figures were trying to interfere in the general election and promising to be a "bloody difficult woman" during negotiations.
Where the MPs stand: More Tory MPs backed Remain than Leave in last year's referendum - but they now strongly support the UK leaving - in February, only one voted against the government beginning Brexit by invoking Article 50 of the Lisbon Treaty.
Risks and rewards: Theresa May would use an election victory to say the country is uniting around her approach to Brexit, and has moved on from the divisions of the referendum campaign. But her uncompromising approach to leaving could upset some of the 48% who wanted to stay in, with the Lib Dems hoping to capitalise in areas - like London's Richmond Park in last year's by-election - that backed Remain.
In short: The Labour Party campaigned against Brexit in the referendum but now says the result must be honoured, and is aiming for a "close new relationship with the EU" with workers' rights protected.
How the party sees Brexit: Labour has set out several demands and tests it says Brexit must meet:
What we don't know: Like the Conservatives, Labour has yet to spell out how it will manage migration after Brexit, and has not been drawn on the size of "divorce bill" it would be willing to pay.
Negotiating style: Jeremy Corbyn says he is aiming for "sensible and serious negotiations" and will not be "threatening Europe".
Where the MPs stand: The vast majority of Labour MPs backed Remain ahead of the referendum - but most followed party orders to allow Article 50 to be invoked in February's vote.
Risks and rewards: Labour is hoping its acceptance of the result will fend off attacks from the Tories and UKIP in Leave-backing areas - including Stoke Central where it won February's by-election. But there are divisions among MPs on the best way forward, and Labour faces the challenge of having to appeal to both sides of a polarising debate.
In short: The Liberal Democrats are strongly pro-EU, and have promised to stop what they call a "disastrous hard Brexit".
How they see Brexit: Central to the Lib Dems' offer is another referendum - this time on the terms of the final Brexit deal - in which the party would campaign to stay in the EU.
The Lib Dems also say they will fight with "every fibre of their being" to protect existing aspects of EU membership, such as the single market, customs union and the free movement of people.
They would guarantee EU citizens' rights and remain in Europe-wide schemes like Erasmus.
Where the MPs stand: All of the Lib Dem MPs backed staying in the EU, and seven out of nine opposed triggering Article 50, with two abstaining.
Risks and rewards: The Lib Dems are hoping their pro-EU pitch will help them gather voters in pro-Remain areas, as when they captured Richmond Park in London in December's by-election. But according to estimates based on the referendum results, two of their sitting MPs represent areas that backed Leave last June - which might make the party's second referendum policy a tough sell on the doorstep.
In short: SNP leader Nicola Sturgeon wants Scotland to have a special status after Brexit and for a second independence referendum to take place before the UK leaves.
How they see Brexit: The SNP's manifesto says it will demand a place for the Scottish government at the Brexit negotiating table.
It says it will fight to keep Scotland in the EU single market. The SNP says it will also press the UK government to guarantee the status of NHS workers from mainland Europe, and oppose any attempt to treat the fishing industry as a "bargaining chip".
Once negotiations are complete, and before the UK has left, the SNP wants a referendum on Scottish independence to take place.
Where the MPs stand: The SNP's 54 MPs voted en masse against triggering Article 50 and are expected to maintain their vocal opposition to Brexit in the next Parliament.
Risks and rewards: The SNP will hope to harness Scotland's support for remaining in the EU (it voted Remain by 62% to 38%). But a significant minority of its supporters are thought to have backed Leave - while the Tories are said to be targeting the Moray seat of SNP Westminster leader Angus Robertson, where Remain only narrowly saw off the Leave campaign in the EU referendum.
In short: UKIP has long campaigned to leave the EU - and having finished on the winning side in the referendum, is now styling itself as the "guard dog of Brexit".
How they see Brexit: The party has set six "key tests" for Brexit: Supremacy of Parliament, full control of migration, a "maritime exclusive economic zone" around the UK's coastline, a seat on the World Trade Organisation, no "divorce" payment to the EU and for Brexit to be "done and dusted" by the end of 2019.
Green Party of England and Wales joint leader Caroline Lucas has called for a second EU referendum on the Brexit deal reached with Brussels, and the Greens have promised "full opposition" to what they call "extreme Brexit".
Plaid Cymru, which campaigned to stay in the EU, says it accepts that the people of Wales voted to leave, but says single market membership should be preserved to protect Welsh jobs.
The DUP campaigned in favour of leaving the EU - and, in its manifesto for this year's Assembly elections, said it wanted to see a "positive" relationship with the rest of Europe, involving "mutual access to our markets to pursue common interests".
Having campaigned to stay in the EU, the SDLP's MPs have opposed the invoking of Article 50, saying it is being done "against the will of people in Northern Ireland", where most people voted to Remain in the EU.
Before the referendum, the Ulster Unionist party said that on balance, it was better for Northern Ireland to stay in the EU - although not all its members agreed. It says it would honour the referendum result, and wants "unfettered" access to the single market and no hard border with the Republic of Ireland.
Sinn Fein has accused the Conservative government of "seeking to impose Brexit on Ireland". It wants Northern Ireland to have a "designated special status" inside the EU.

Boris Johnson has rejected the suggestion from Nigel Farage and Donald Trump that he should work with the Brexit Party during the election.
The Tory leader told the BBC he was "always grateful for advice" but he would not enter into election pacts.
His comments come after the US president said Mr Farage and Mr Johnson would be "an unstoppable force".
Downing Street sources say there are no circumstances in which the Tories would work with the Brexit Party.
In an interview with BBC political editor Laura Kuenssberg, the prime minister said the "difficulty" of doing deals with "any other party" was that it "simply risks putting Jeremy Corbyn into Number 10".
"The problem with that is that his [Mr Corbyn's] plan for Brexit is basically yet more dither and delay," Mr Johnson said.
Mr Johnson also said there was "no question of negotiating on the NHS" as part of any future trade deal with the US, but he did not rule out expanding the amount of private provision in the health service in the future.
But Labour's shadow health secretary, Jonathan Ashworth, said the public "can't trust the Tories on the NHS", saying they would "increase privatisation even further and do a deal with Donald Trump".
When pushed on whether he would rule out a deal with Mr Farage, Mr Johnson replied: "I want to be very, very clear that voting for any other party than this government, this Conservative government… is basically tantamount to putting Jeremy Corbyn in."
The UK is going to the polls on 12 December following a further delay to the UK's departure from the EU, to 31 January 2020.
The BBC will be talking to other party leaders during the course of the campaign.
US president Donald Trump told Nigel Farage's LBC show on Thursday that the Brexit Party leader should team up with Mr Johnson to do "something terrific" and he also criticised the prime minister's EU withdrawal agreement.
Meanwhile, Mr Farage has called on the prime minister to drop his Brexit deal, unite in a "Leave alliance" or face a Brexit Party candidate in every seat in the election.
Mr Johnson said there were "lots of reasons" why he thought a Labour government would be a "disaster".
He said he Labour government would lead to a renegotiation with Brussels on a Brexit deal, then another referendum.
"Why go through that nightmare again?" he said.
The prime minister also suggested that the US president was wrong to believe a trade deal would be impossible with the UK after Brexit.
Mr Johnson said his "proper Brexit" deal "enables us to do proper all-singing, all-dancing free-trade deals".
"It delivers exactly what we wanted, what I wanted, when I campaigned in 2016 to come out the European Union," Mr Johnson said.
When asked about the criticism from Mr Trump, Mr Johnson said: "I am always grateful for advice from wherever it comes and we have great relations as you know with the US and many many other countries.
"But on the technicalities of the deal anybody who looks at it can see that the UK has full control."
The prime minister is never short of a word or two, never short of a colourful phrase or a metaphor.
When we sat down this afternoon there was no suggestion of him being the Hulk, but Remain-tending MPs were accused of "rope-a-doping" the government, planning eventually to batter the prime minister and his Brexit deal into submission until he would have had to give up.
But in Downing Street there is a serious awareness that trademark Johnson verbal gymnastics are no guarantee of success at the ballot box in six weeks' time, no guarantee at all.
That's not just because there are even friends, like Donald Trump, and of course foes, like Jeremy Corbyn, whose words and actions will hamper his attempt to secure a majority to call his own.
But also because this is a snap election, not a routine poll, and the public is hardly in a forgiving mood of our politicians right now.
Mr Johnson said he hoped the government could get Brexit "over the line" by the middle of January if he won a majority, claiming the current Parliament would never have passed his deal.
He said he'd had "no choice" but to call a general election, saying: "Nobody wants an election but we've got to do it now.
"This is a Parliament that is basically full of MPs who voted Remain.
"They voted Remain and they will continue to block Brexit if they're given the chance - we need a new mandate, we need to refresh our Parliament."
Mr Johnson said his government was determined to increase taxpayer funding of the NHS but said: "Of course there are dentists and optometrists and so on who are providers to the NHS, of course, that's how it works," he said.
"But... I believe passionately in an NHS free at the point of use for everybody in this country."
Labour's Mr Ashworth said: "Forced NHS privatisation has doubled under the Conservatives and Boris Johnson has refused to rule out expanding this further.
"You can't trust the Tories on the NHS. They will increase privatisation even further and do a deal with Donald Trump that will see as much as £500m more a week sent to US corporations."

Donald Trump has criticised Boris Johnson's Brexit deal with the EU, saying it restricts the US's ability to do future trade with the UK.
Speaking to LBC, he said that, without the deal, the two countries could "do many times the numbers" than now.
The US president also took a swipe at Labour leader Jeremy Corbyn, saying he would be "so bad" as prime minister.
Mr Corbyn accused him of "trying to interfere" in the UK general election to boost "his friend Boris Johnson".
The UK is officially going to the polls on 12 December after the early election bill became law when it was given royal assent on Thursday.
It follows a further delay to the UK's departure from the EU, to 31 January 2020.
In August, Mr Trump promised a "very big trade deal" with the UK and predicted that leaving the EU would be like losing "an anchor round the ankle".
But speaking to friend and supporter Nigel Farage on LBC, Mr Trump was critical of the withdrawal agreement Mr Johnson recently reached with EU leaders.
Mr Trump told LBC: "We want to do trade with UK and they want to do trade with us.
"To be honest with you... this deal... under certain aspects of the (Brexit) deal... you can't do it, you can't do it, you can't trade.
"We can't make a trade deal with the UK because I think we can do many times the numbers that we're doing right now and certainly much bigger numbers than you are doing under the European Union."
by Jessica Parker, BBC political correspondent
Diplomatic norms dictate that leaders don't wade into the electoral events of other countries.
But of course this isn't the first time that an American president has decided to cross that particular transatlantic channel.
During the 2016 referendum, Barack Obama said that Brexit would put the UK at the "back of the queue" for trade deals.
In June, Donald Trump offered his views on the Conservative leadership contest.
Now, in this fairly wide-ranging discussion, he's talked about both Boris Johnson's Brexit deal and Jeremy Corbyn's suitability for the role of PM.
But the Labour leader doesn't appear too put out - even retweeting the relevant part of the interview.
The truth is that Mr Corbyn is more than OK with putting some distance between himself and Donald Trump; the US President isn't exactly a poster boy for socialism.
And while his comments on the implications of Boris Johnson's Brexit deal on US-UK trade may cause Downing Street some discomfort, some mystery surrounds exactly where Mr Trump believes difficulties may arise as he didn't elaborate.
The prime minister aims to get his deal through Parliament if he wins the general election.
However, Mr Trump also praised Mr Johnson as "the exact right guy for the times".
In response, a Downing Street spokesman said Mr Johnson's Brexit deal with the EU "ensures that we take back control of our laws, trade, borders and money".
"Under this new deal, the whole of the UK will leave the EU customs union, which means we can strike our own free trade deals around the world from which every part of the UK will benefit."
Mr Trump also said Mr Farage, who leads the Brexit Party and is planning to stand in the general election, and Mr Johnson should "get together" to create "an unstoppable force" in UK politics.
The president, who has previously expressed his backing for Brexit, added: "And Corbyn would be so bad for your country, so bad. He'd take you in such a bad way. He'd take you into such bad places.
"But your country has tremendous potential. It's a great country."
Mr Corbyn and Mr Johnson are battling it out for the keys to 10 Downing Street, with the Conservative leader promising to get the UK out of the EU as soon as possible, and the Labour leader promising another referendum.
Kicking off Labour's general election campaign, Mr Corbyn earlier warned a post-Brexit trade deal with Mr Trump's administration would give US companies greater access to the NHS, and allow them to profit from it at UK taxpayers' expense.
The prime minister's planned agreement, he said, would "mean yet more NHS money taken away from patients and handed to shareholders."
However, Mr Trump dismissed the Labour leader's claim, saying: "Not at all. We wouldn't even be involved in that, no.
"It's not for us to have anything to do with your health care system. No, we're just talking about trade."
The UK government has said that, under any future trade deal with the US, it wants protections for the NHS.
Elsewhere, Mr Johnson blamed Mr Corbyn for the delay to Brexit.
He said he was "incredibly frustrated" that the 31 October deadline had to be extended, but a Conservative election win would remove the "logjam".
Both leaders, and those of other parties, are beginning six weeks of campaigning.
It comes as John Bercow's 10-year reign as Speaker of the House of Commons came to an end.
He presided over business in the chamber for the final time before his successor is chosen on Monday.

Nigel Farage has called on Boris Johnson to drop his Brexit deal or face his party's candidates in every seat.
Speaking at the Brexit Party's election campaign launch, he called on the PM to "build a Leave alliance" and seek a free trade agreement with the EU.
If Mr Johnson refuses, Mr Farage said he already had 500 candidates he could field against the Tories in seats across England, Scotland and Wales.
The Conservatives have consistently ruled out a formal pact with the party.
A Tory source told the BBC: "A vote for Farage risks letting Jeremy Corbyn into Downing Street via the back door. It will not get Brexit done and it will create another gridlocked Parliament that doesn't work."
It comes after President Donald Trump said Mr Farage and Boris Johnson should team up as "an unstoppable force".
Recent opinion polls have shown the Conservatives with a double-digit lead over Labour.
Polling expert Sir John Curtice said Boris Johnson had received a boost after he negotiated a deal with the EU and brought the deal back to Parliament before 31 October deadline.
However, MPs turned down his plan to pass the deal in three days, leading to a three month extension to the deadline - something vocal Brexiteers, including Mr Farage, have criticised the PM for.
Having not got Brexit through by Halloween, some Tories fear that Mr Farage's candidates could split the pro-Brexit vote and prevent their party from winning a majority in 12 December poll.
Mr Farage used the launch to condemn the PM's deal, urging him to "drop [it] because it is not Brexit".
Instead, Mr Farage urged him to pursue a free trade agreement with the EU - similar to the deal the bloc has with Canada - and to impose a new deadline of 1 July 2020 to get it signed off.
If an agreement was not done by then, the UK should leave the EU without a deal and move to World Trade Organisation trading rules.
"I would view that as totally reasonable," he said. "That really would be Brexit."
But Mr Farage said if Mr Johnson did not pursue the route, the Brexit Party would contest every seat in the country - with 500 candidates ready to sign the forms to stand on Monday.
"The Brexit Party would be the only party standing at these elections that actually represents Brexit," he said.
But Tory Brexiteer Mark Francois said Mr Farage's pitch for an alliance had "screwed it up".
"If you genuinely want to work with another party, you don't go on live national television and call them liars," he told BBC Radio 4's World at One.
He said the PM's agreement with the EU was not a "perfect deal", adding: "We are not in Valhalla here. But the deal takes us out of the European Union.
"Nigel is a very talented politician but anyone who works with him will tell you he is his own worst enemy and his ego has got the better of him."
Nigel Farage has, in effect, given Boris Johnson an ultimatum - abandon your central Brexit policy or the Brexit Party will challenge your deal at every opportunity across the country.
With the prime minister highly likely to refuse, it seems Mr Farage will have to live up to his promise of fielding 500 or more candidates in this election by Monday - and his claim that he has the resources to do so.
That's a tall order for a party that only launched in April.
He's no doubt buoyed by the Brexit Party's success in the European elections earlier this year.
But in the past, when at the helm of UKIP, Mr Farage has struggled to turn popular support into Westminster seats.
He has been targeting Labour leave areas in Wales, the Midlands and the North of England - the very seats Mr Johnson has in his sights.
But the risk for both parties is by splitting the Leave vote they give Jeremy Corbyn an unintended boost.
Mr Farage also attacked Labour for a "complete and utter betrayal on Brexit" - and said his party would target Labour seats in the Midlands and North of England.
He said Labour's plan to renegotiate a deal then put it to a referendum was offering a choice of "remain or effectively remain".
Mr Farage said there were five million Labour voters who had supported Leave in the 2016 EU referendum - although that is likely to be an overestimate - meaning his party "posed a very major problem" for Jeremy Corbyn.
"So many Labour Leave seats are represented by Remain members of Parliament," he said. "We view those constituencies around the country among our top targets."
He ridiculed the reported Conservative plan to target "Workington man" - Leave-supporting traditional Labour voters in northern towns - saying Tories needed to get out of London more.
Nigel Farage claimed in his speech that when UKIP did well under his leadership, it was doing more damage to Labour than the Conservatives.
Yet, he seems to think the threat of standing everywhere is going to have an impact on the Tories' Brexit stance by making them afraid they are going to lose out.
At the end of the day, what Nigel Farage is promising is to fight this election across the piece and on a stance which the Brexit Party has been very clear about for a while.
The interesting question there is how successful he is going to be persuading the Leave voters of this argument.
Boris Johnson and the Conservative Party have a lead as they have been gradually squeezing the Brexit Party vote, with Leave voters coming to them.
Relatively few Leave voters seem to blame Mr Johnson for the fact that he failed to meet the 31 October deadline.
But on the other hand, it is also clear from the polling there is a substantial body of Leave voters who would prefer to exit without a deal rather than supporting the PM's plan.
So, you can see how Mr Farage may be able to push some people back in his direction.
On the other side of the Brexit debate, Remain-supporting parties have been negotiating electoral pacts in certain constituencies.
The potential agreements would see the Liberal Democrats, Greens and Plaid Cymru stand aside for each other to ensure the election of as many MPs who back a second Brexit referendum as possible.
Green Party co-leader Jonathan Bartley said it was "no secret" that the his party was "talking to the Lib Dems and Plaid" but "nothing has been finalised".
Elsewhere on the election trail:

At first glance, Labour's campaign launch appeared like a replay of its 2017 election launch.
Back then, Jeremy Corbyn attacked vested interests - and pledged that his party would be battling for the many not the few.
Businessman Mike Ashley has had the honour - if that's the word - of featuring in Labour's rogues' gallery of "bad bosses" in both the 2017 general election campaign launch and again today.
But the tone, if anything, is more strident now.
Channelling the left-wing folk singer Pete Seeger, the Labour leader repeatedly - and rhetorically - asked his audience whose side they were on.
He made it clear his party was against "dodgy landlords", big polluters, tax dodgers, rich media magnates.
It looks like this will be something of an insurrectionary campaign.
Partly, this is to inoculate the party against the Conservative charge that it is siding with the political class against the people on Brexit - causing "dither and delay".
So Jeremy Corbyn is trying to get his retaliation in first - by arguing it is Boris Johnson and Tories' financial backers who are really part of a privileged elite.
But Labour's tone is a form of attack as well as defence.
As in 2017, Labour is aiming to win over younger voters and those who rarely vote - and who need to be convinced that politics can make a difference.
Hence the clear blue - or red - water between Labour and their opponents.
And it's part of a wider strategy to try to appeal to potential Labour voters beyond the Brexit debate.
Jeremy Corbyn for some time has argued that while working class voters may be divided on the EU, they can be united in support of better working conditions, fairer taxes, and more investment in public services.
The strategy is to try almost to divorce Brexit from the other issues, arguing that can be settled further down the line in a referendum with a "credible" Leave option and Remain on the ballot.
In Leave areas - where Labour is seriously worried about suffering losses - the hope is that however much the party's voters or ex-voters want Brexit done, they will prioritise other issues directly affecting their lives.
So, Labour strategists believe it is essential on the wider non Brexit agenda to have as distinctive a message as possible.
Now, some Labour MPs argue that - with circumstances rather different now than in 2017 -  Labour could have played this election differently.
With an exodus of former Remainers from the Conservative ranks, technically the party could have blurred its more radical edge - don't forget, in 2017, the leadership claimed their manifesto's policies were in the tradition of mainstream European social democracy - and made a pitch for the centre ground,
But that is unlikely to have passed the authenticity test with Jeremy Corbyn at the helm.
And some in Labour's ranks have been saying privately that the uncompromising messaging and the forthcoming radical manifesto are designed to shore up, rather than greatly expand, the Labour contingent in Parliament.
After all, the campaign launch was in Battersea - a marginal they hope to hold, rather than a seat they aspire to win.
Policies that will motivate the party's foot soldiers will help in the defence of some seats won by very slim majorities last time round.
And there are sophisticated methods being deployed by the left-wing group Momentum to move activists around to where they are most needed.
There are, of course, different measures of what winning looks like.
For Boris Johnson an overall majority is essential.
If Labour, though, can become not outright winners but the largest party in a hung Parliament, it could very likely form a minority government with tacit support from the SNP and, possibly, the Liberal Democrats in order to deliver a new EU referendum.
But, of course, Jeremy Corbyn insists he is fighting to win and that most opinion polls are probably as misleading now as they were two and a half years ago.
And that even more now than then, middle as well as working-class voters do not feel, in their day-to-day lives, that austerity is over - whatever spending pledges are being made by the prime minister.
So the potential reservoir of support could be greater than the current state of the polls suggest.
But some challenges lie ahead for Labour - including how far the Brexit issue really can be contained within a "cordon sanitaire".
And there remains a question - whatever the rhetoric - about just how radical Labour will be.
Will a conference policy on abolishing private schools, and another on extending the free movement, really make it in to the manifesto?
This is an election many Labour MPs didn't appear to want, with widespread abstentions in Tuesday evening's vote.
But some of those closest to Jeremy Corbyn were champing at the bit for an election.
They believe if Labour are currently being seen as also-rans, opponents will become complacent and in the end - however radical the party's message - progressive centre-left voters will be forced to back them if they want to stop Boris Johnson.
In this election, though, there is no such thing as a sure thing.

Nigel Farage says there needs to be "some kind of alliance" between the Tories and the Brexit Party for the upcoming election.
Reports have suggested Mr Farage's party would stand down hundreds of election candidates for December's poll to stop a split in the pro-Brexit vote.
The Conservatives have consistently ruled out a formal pact with the party.
It comes after President Donald Trump said Mr Farage and Boris Johnson should team up as "an unstoppable force".
The Brexit Party's launch for its official election campaign has just begun and Mr Farage is expected to announce the party's strategy.
Chairman of the party, Richard Tice, said: "We have a major role to play in the outcome of this general election."
The Brexit Party's MEP for the North West of England, Claire Fox, said she was "really excited by this election because voters can take centre stage again".
In August, Mr Farage tweeted the party had "635 men and women from all walks of life who are prepared to fight a general election".
And in September, the party issued a list of 409 candidates standing in England, Scotland and Wales.
Mr Farage has been critical of Mr Johnson's failure to deliver on his promise that the UK would leave the EU on 31 October.
But earlier this week, the Telegraph reported the Brexit Party was considering removing candidates to help the Conservatives win a majority of seats in 12 December's election to ensure the UK leaves the EU.
Instead, it said, they would focus their energies on Labour-held seats which voted Leave in the 2016 EU referendum.
Mr Farage called the reports "idle speculation".
But speaking about his party's launch on Friday morning, he told LBC radio: "Most of what I will be saying will be about Boris' deal and the need, in my view, for some kind of alliance."
He refused to comment on whether the Brexit Party would be fielding "20 or 200 candidates".
On the other side of the Brexit debate, Remain-supporting parties have been negotiating electoral pacts in certain constituencies.
The potential agreements would see the Liberal Democrats, Greens and Plaid Cymru stand aside for each other to ensure the election of as many MPs who back a second Brexit referendum as possible.
Green Party co-leader Jonathan Bartley said it was "no secret" that the his party was "talking to the Lib Dems and Plaid" but "nothing has been finalised".

Nigel Farage has said he will not be standing as a candidate in the general election on 12 December.
The Brexit Party leader told the BBC's Andrew Marr he had thought "very hard" but had decided he could "serve the cause better" by supporting his party's 600 candidates "across the UK".
"I don't want to be in politics for the rest of my life," he said.
Jeremy Corbyn said Mr Farage's decision was "a bit weird" given the Brexit Party hopes to stand in most places.
The Labour leader said: "It's obviously his decision. It's a bit weird to lead a political party that is apparently contesting all or most of the seats up in the election and he himself is not offering himself for election."
Mr Farage, who has stood unsuccessfully for Parliament seven times and currently sits in the European Parliament, also also criticised the PM's Brexit deal..
The 55-year-old told BBC One's Andrew Marr Show the deal agreed earlier this month was "virtually worse that being in the EU".
"If Boris Johnson was going for a genuine Brexit, we wouldn't need to fight against him in this election," he said.
On Friday, the prime minister rejected an alliance with Mr Farage's Brexit Party, telling BBC political editor Laura Kuenssberg doing deals with "any other party... simply risks putting Jeremy Corbyn into Number 10".
Mr Farage had called on the prime minister to drop his Brexit deal, unite in a "Leave alliance" or face a Brexit Party candidate in every seat in the election.
He told the Marr show: "I always thought that to win an election, get a big majority so we can get a proper Brexit, a coming-together would be the objective.
"I still hope and pray it happens but it doesn't look like it will."
Mr Johnson maintains that the only way out of the EU is to "go with the deal we've got".
The prime minister told Sophy Ridge on Sky that he was "deeply, deeply disappointed" to miss the 31 October deadline to secure Brexit, calling it "a matter of deep regret".
The PM had previously said he would rather "die in a ditch" than ask the EU to delay Brexit beyond Halloween.
Mr Johnson told the programme that he was sorry, and took responsibility, for missing the date, but accused Parliament of failing to implement his deal.
He also said Donald Trump was "patently in error" when the US president warned the government's Brexit deal would hamper a UK-US trade deal.
Mr Farage said Mr Johnson's deal "kills off any chance of genuine independence".
"If Boris is determined to stick to this new EU treaty, then that is not Brexit," he said.
By political correspondent Jessica Parker
Political opponents of Nigel Farage will accuse him of running scared after he said he would not stand as a candidate in December's poll.
They will suggest he's not going to run because he thinks he's not going to win.
But the flip side is that rather than concentrating on one constituency where he personally might try to win, Mr Farage is making it clear he's going to try to make Boris Johnson's life pretty difficult.
That's if this so-called Leave alliance doesn't happen - and it doesn't look like it will.
The Brexit Party leader has made it clear he has no interest in getting on board with Mr Johnson's deal at all.
It's likely Mr Farage will spend a lot of the campaign really criticising it, whereas the Tory party leader will say he's got an oven-ready deal to present and get through Parliament within weeks.
Treasury minister Rishi Sunak hit back at the criticism of the deal, telling the Andrew Marr show: "I campaigned for Leave, I spent a lot of time talking to my constituents and others across the North East and in Yorkshire - what do they want from Brexit?
"They want to end free movement and replace it with a points system, they want to end the fact that money keeps going to the EU year after year, they want to make sure we're in control of our laws, and also they want us to have an independent trade policy. These are all things the prime minister's deal delivers.
"What I would say to Nigel Farage is, sometimes in politics, as in life, you've got to take yes for an answer."
Also appearing on the programme, shadow chancellor John McDonnell suggested that a Labour government would seek to end privatised contracts in the NHS.
He said that, as the contracts ran out, the work should be brought in-house, and that the public didn't want money "being poured into the pockets of profiteers".
Pushed on whether an incoming Labour government would see the eradication of all privatisation in the NHS, Mr McDonnell said "we'll see how those contracts run out."
The Conservatives have strongly denied that the NHS is "up for sale".
Asked if Labour would scrap the expansion of Heathrow airport, Mr McDonnell said the party would make the decision based on a set of criteria covering the environmental, economic and social impact of the project.
"On the current criteria, we've said very clearly, Heathrow expansion doesn't qualify."
And on taxes, he said Labour would increase income tax for the top 5% of earners and raise corporation tax in order to pay for "investments in schools and training".

The general election could be "a moment for seismic change", when "a new and different politics" emerges, Lib Dem leader Jo Swinson has said.
In a speech at the party's campaign launch, she said she could do "a better job" than either Boris Johnson or Jeremy Corbyn as prime minister.
In response, the Conservatives said a vote for the Lib Dems "risks putting" Mr Corbyn into Downing Street.
The UK will go to the polls on 12 December.
Elsewhere in the election campaign:
The political parties are ramping up their campaigning, ahead of the official start to the five-week election period at just after midnight on Wednesday.
On Tuesday, the Lib Dems said they would take legal action against ITV over its plans for a head-to-head election debate including only Boris Johnson and Jeremy Corbyn, saying the decision to exclude its leader was "outrageous".
The party's lawyers have written to the broadcaster to give it "the opportunity to correct this serious mistake".
ITV has said it intends to offer viewers balanced election coverage.
Speaking in London, Ms Swinson said: "Our country needs us to be more ambitious right now - and we are rising to that challenge.
"It is not about the red team or the blue team, because on this issue they merge into one - both Labour and the Conservatives want to negotiate and deliver Brexit.
"I never thought that I would stand here and say that I'm a candidate to be prime minister, but when I look at Boris Johnson and Jeremy Corbyn, I am absolutely certain I could do a better job than either of them."
Ms Swinson said Mr Johnson had "lied to the Queen, lied to Parliament and lied to the country" and "was not fit to to be prime minister".
And she accused the Labour leader of failing to "give a straight answer on the biggest issues facing this country".
The Lib Dems currently have 20 MPs - out of a possible 650 - and they are especially hopeful of gaining seats in London and south-west England, but they would need a dramatic shift in the electoral landscape if they were to win a majority.
However, responding to questions from journalists, Ms Swinson said "stranger things have happened" and pointed to the SNP's success in the 2015 general election.
By chief political correspondent Vicki Young
Jo Swinson says she wants to be prime minister - but how credible is that?
The Lib Dems are not at the moment even the third largest party in the UK.
Ms Swinson cites the example of the SNP surge in 2015, when the party won almost every seat in Scotland - and she personally lost her seat to the SNP candidate.
She argues that politics is volatile, it is in flux, and things have changed because of Brexit - people are voting for very different reasons. Therefore, there is no reason why the party can't be incredibly ambitious, she argues.
But the problem for the Liberal Democrats is that the way their votes are distributed around the country, it is much harder for them to win seats than for other parties.
In 2010, they won seven million votes but got fewer than 60 seats.
The Lib Dem leader was introduced by one of the party's newer MPs, Luciana Berger, who used to be in the Labour Party but quit over the issue of anti-Semitism - something Ms Swinson accused Mr Corbyn of failing to "root out".
Asked whether her party could support a Labour government in the event of a hung Parliament, Ms Swinson said: "I am absolutely, categorically ruling out Lib Dem votes putting Jeremy Corbyn in No 10."
The Lib Dem leader said her party was "the only party standing up to stop Brexit and build a brighter future for the UK".
She argued that stopping Brexit would deliver a £50bn "Remain bonus" for public services over the next five years
The Liberal Democrats have pledged to cancel Brexit altogether if they win power at the next general election.
If they do not win a majority at the election they would support another referendum.
Labour's shadow Brexit secretary, Sir Keir Starmer, told the BBC many Remain supporters were "uncomfortable" with the Lib Dems' plan to effectively "rub out" the 2016 referendum result and believed EU membership had to be "argued for and won" in another public vote.
The party said the £50bn figure - the amount that it has calculated will be saved over the next five years by staying in the EU - is based on the UK economy being 1.9% larger in 2024-25.
It reflects the extra tax income over the next five years and is based on a 0.4% average annual boost to GDP if the UK stays in the EU.
Deputy leader Sir Ed Davey told BBC Radio 4's Today programme that the Lib Dems "actually think these are quite cautious figures", adding that all the independent forecasters "were clear that there will be a big boost if we stay".
Paul Johnson, from the independent Institute for Fiscal Studies, said it was a reasonable calculation in line with their own forecasts, adding: "We could expect the economy to be bigger if we were to remain and this assumes a relatively modest effect if anything, although obviously subject to a huge amount of uncertainty".
BBC Reality Check correspondent Chris Morris said the vast majority of forecasts do expect the economy would be bigger if the UK were to stay in the EU.
But he said the size of that "bonus" cannot be predicted with any certainty, and £50bn was not a hugely significant amount in terms of overall government expenditure.

Ruth Davidson and Michael Gove have teamed up to call for the UK to leave the common fisheries policy (CFP) when Britain leaves the European Union.
The Scottish Conservative leader and UK environment secretary say it is "vital" that the country regains control over its own fisheries management.
It came as Scottish fishermen demanded the UK operated as a "fully-functioning coastal state" after leaving the EU.
The SNP warned the future of Scotland's fishing communities was "at risk".
Ministers in London could "trade away our valuable fishing rights" in Brexit negotiations to protect other sectors, Scotland's fisheries secretary Fergus Ewing added.
The UK government wants to agree reciprocal access to fishing waters with the EU.
In a joint statement, Ms Davidson and Mr Gove say: "We believe it is vital that we regain control over our own fisheries management.
"We want to use the opportunity of Brexit to secure a sustainable marine environment for the next generation.
"As proud Scots, we feel a particular debt to fishing communities who are looking to government to deliver a better deal for them. We agree we must deliver a fairer allocation for the British fleet in our own waters.
"As we leave the EU, we want the UK to become an independent coastal state, negotiating access annually with our neighbours. And during the implementation period we will ensure that British fishermen's interests are properly safeguarded."
The politicians were on opposing sides in the EU referendum campaign in 2016, but say they are united in their determination to ensure "Brexit delivers for Britain's fishing communities".
The statement continues: "The Prime Minister has been clear: Britain will leave the CFP as of March 2019. We both support her wholeheartedly.
"Whatever differences we had on Brexit, we both agree that our fishing industry stands to benefit from our departure from the common fisheries policy. We are both committed to doing all we can to make those benefits real."
The intervention follows the recent publication of draft guidelines for the EU side of Brexit trade talks, which seek "existing reciprocal access to fishing waters".
The politicians spoke out as the Scottish Fishermen's Federation (SFF) set out its "red lines" which the industry is warning the UK government not to cross in Brexit negotiations with the EU.
The SFF is demanding an immediate exit from the CFP in March 2019, "ensuring the EU does not have the right to grant access and set fishing opportunity and management rules within UK waters during the implementation period".
Chief executive Bertie Armstrong said: "In her Mansion House speech, the Prime Minister spoke of ensuring 'fairer shares' for our fishermen - that must mean an immediate end to the current situation in which EU vessels are entitled, gratis, to 60% of the fish in UK waters while our own vessels are allowed to catch just 40%."
The Scottish government called on UK ministers to "urgently explain" how their position on CFP would benefit Scottish fishermen.
Fergus Ewing said: "The UK government continues to put the future of Scotland's fishing communities at risk - no-one should be in any doubt that ministers in London are prepared to trade away our valuable fishing rights to protect sectors which are more important to them.
"The UK government's position will result in a situation where the UK could be forced to apply the rules of the Common Fisheries Policy after Brexit but would have no influence at all over fish quotas or access to Scottish waters.
"They must urgently explain how such a situation would be advantageous to Scottish fishermen in any way, shape or form."
A UK government spokesman said: "When we leave the European Union, we will leave the common fisheries policy and regain control of access to our waters.
"As part of a new economic partnership we want to continue to work with the EU to manage shared stocks in a sustainable way and to agree reciprocal access to waters and a fairer allocation of fishing opportunities for the UK fishing industry."

Michael Gove has hit out at the way social media "corrupts and distorts" political reporting and decision making following a row about animal welfare.
The environment secretary said attacks on MPs over a vote on EU laws on animal "sentience" were "absolutely wrong".
The Commons vote sparked protests and social media campaign backed by high-profile figures such as Ben Fogle.
The explorer has apologised for posting "misleading threads" but defended sharing details on "important stories".
Last week MPs voted not to incorporate part of an EU treaty recognising that animals could feel emotion and pain into the EU Withdrawal Bill.
Green Party co-leader Caroline Lucas had tabled the amendment to the EU bill, which would have transferred the EU protocol on animal sentience - the ability to experience feelings - into domestic law.
But ministers argued that the recognition of animals' sentience already existed in UK law and MPs rejected the amendment.
Mr Gove told BBC Radio 4's Today programme: "On social media there was a suggestion that somehow the MPs had voted against the principle that animals are sentient beings, that did not happen, that is absolutely wrong."
"There is an unhappy tendency now for people to believe that the raw and authentic voice of what's shared on social media is more reliable than what is said in Hansard or on the BBC.
UK law 'to recognise animal feelings'
"More than that there is a particular concern somehow, a belief somehow that outside the European Union our democratic institutions can't do better than we did in the EU. We've got to challenge both those points."
He said Parliament was "an effective and vigorous institution which can ensure protection for human rights and animal rights".
"We've also got to stand up against the way in which social media corrupts and distorts both reporting and decision making... It's important that all of us do that and that some of us who shared some of these messages on social media have been generous enough to acknowledge ... that they may have unwittingly passed these messages on."
Among others who shared material posted by campaign groups which criticised MPs were the comedian Sue Perkins and Countdown host Rachel Riley.
Mr Fogle said he accepted the government's arguments but insisted it was not only up to social media users to spread inaccurate reports, pointing out that a number of established newspapers published stories based on the same information.
Mr Gove said there would not be a "gap" in animal welfare provisions as a result of the vote, once the UK left the EU, because the UK would "ensure we have stronger protection written into law". He argued that the EU legislation was "poorly designed" and said there was "no way in which animal protection can be diminished in any way, in any shape, or in any form".
But Ms Lucas said the government had been "backpedalling" since the vote: "What I was told in the chamber was that they had no need to take any account of my amendment because this principle of animal sentience was already recognised in UK law in the Animal Welfare Act of 2006.
"Now that is patently untrue, wrong and I am very glad in the last 24 hours Michael Gove and others have been rapidly backpedalling and admitting that that's not true."
And David Cameron's ex-director of communications suggested Mr Gove reflect on the impact of social media during the EU referendum - in which he was a passionate Leave campaigner.
British Veterinary Association senior vice president Gudrun Ravetz told the BBC that there was a "significant difference" between the Article 13 EU protocol, which put a duty on the state to pay full regard to animal welfare when formulating and implementing policies, and the UK legislation, the 2006 Animal Welfare Act, which put the duty on the owner.
The first was "explicit" about "animal sentience", the latter was only "implicit about sentience of animals and vertebrates".
"That is a very important principle, we have the duty of animal welfare for the owner and keeper under the Animal Welfare Act, and that will continue but what we want to see is that duty to the state," she added.
Mr Gove was a relatively late convert to social media, only joining Twitter in June 2016 after he was sacked as a minister by Theresa May.
But he has continued to tweet since rejoining the cabinet this summer.
Hansard is the name given to the daily verbatim transcripts of parliamentary debates in Westminster, which have been officially printed since 1909 and are available online too.

The government is facing an unprecedented backlash from five key industries over Boris Johnson's plans for post-Brexit trading arrangements.
The aerospace, automotive, chemicals, food and drink and pharmaceutical sectors warn they could pose "serious risk to manufacturing competitiveness".
Collectively, the sectors employ 1.1 million people, contributing £98bn to the UK economy each year.
The group has sent a letter to the government highlighting its concerns.
The BBC has seen extracts of the letter, which was sent this week to Brexit Secretary Steve Barclay and the Cabinet Office minister, Michael Gove.
While such bodies have in the past made clear their concern at the prospect of a no-deal Brexit, this is the first time they have directly expressed to government their joint concern about a possible Brexit deal, after mostly supporting Theresa May's negotiated proposal.
The letter outlines their growing concern that Boris Johnson's Brexit negotiators have dropped existing commitments to maintain regulatory alignment in relevant sectors. The manufacturers' key concern is that they may no longer participate in specific EU regulatory institutions after any Brexit deal.
The group is asking for a "reassurance" that industry interests are still being prioritised by EU negotiators, and the letter warns of the "damage which would be done by the current approach on regulatory divergence".
It says: "Pan-European regulatory alignment has been a success in our industries, supporting continued creation and retention of highly skilled manufacturing jobs in the UK.
"It is important this regulatory alignment should continue after Brexit as a critical element of the UK's future relationship with the EU".
A government spokesperson said the UK was "seeking a best in class" free trade agreement drawing on existing EU deals.
"We have been clear that we are committed to maintaining high standards after we leave the EU," the spokesperson said.
However the public and private noises emerging from London and Brussels is that the government has markedly changed its plan for a future relationship. They say the new proposal has low alignment with EU regulations, and does not have level playing field conditions attached on the environmental, social and labour standards, as proposed in Theresa May's deal.
After failing to get reassurances in recent weeks, particularly on the membership of key EU agencies, various sectors joined forces to warn the government directly.
The letter says that the serious risk to manufacturing "will result in huge new costs and disruption to UK firms".
"It would be disruptive to our complex international supply chains and has the potential to risk consumer and food safety, and confidence, access to overseas markets for UK exporters and vital future investment in innovation in this country."
This letter sees the Society of Motor Manufacturers and Traders, the Chemical Industries Association, the Food and Drink Federation, and the Association of the British Pharmaceutical Industry join an existing call from the aerospace industry, reported by the BBC earlier on Friday.
The aerospace industry body the ADS wrote to the government asking for "reassurance" that there would be "continued membership of the European Aviation Safety Agency (EASA) and alignment with EU chemicals regulations" which "are vital for our sector".
Repeated attempts to get clarity on this issue have not reassured the aerospace and other industries on this topic.
Other industries have asked for similar reassurances, only to be told in recent weeks that the government is seeking a "best in class" free trade agreement, where the UK would set its own regulatory standards.
The government has acknowledged that it wants to take the "level playing field" arrangements out of the political declaration that promised alignment on environmental, social, labour and some tax measures.
These were also seen as crucial to ongoing industrial regulatory co-operation, and preventing the introduction of many types of checks on trade.
But the government fears such measures agreed by Theresa May will restrict the ability of a post-Brexit government to strike meaningful trade deals with other countries such as the US.
A source close to the talks acknowledged to the BBC that among changes being negotiated in the political declaration, these references to EU agencies could get scrapped.
Even as most of the negotiating attention remains on Northern Ireland, the change in approach from the Johnson government suggest a significantly different, more diverged end-point for Brexit for England, Scotland and Wales, than envisaged under Theresa May.
A number of Labour MPs who say they want to support a deal have already expressed a desire for a deal with less scope for regulatory divergence.

A number of EU diplomats believe the UK government is having second thoughts about its threat to leave the bloc without a trade deal should negotiations break down, the BBC understands.
They say, in private, that the government fears the economy could be left in "havoc" if Britain left without agreeing any preferential access to EU markets.
But a government spokesman said they "did not recognise" the claims being made by the EU diplomats.
Theresa May warned in January that no deal would be better than a bad deal, should the EU try to impose a punitive trade deal.
The threat was seen by EU diplomats as lacking credibility because of the huge costs that might be imposed on the British economy without an agreement.
UK firms would have to follow World Trade Organisation rules, which would mean paying more tariffs on some goods and facing non-tariff barriers such as increased red tape.
One EU diplomat said he had urged the government not to repeat the "no deal" threat in its letter triggering Article 50 this week.
"They have realised that 'no deal is better than a bad deal' won't fly," he said.
"They are worried about people in this country who have an ideological and political intention of creating chaos," the diplomat added.
"The civil service has told them it would create havoc."
As an example, he said the number of customs checks on goods would rise from 17 million per year to 350 million.
Diplomats also suggested the government was becoming more pragmatic - in private - about some of its other Brexit demands.
One said that officials "don't exclude that the UK, as part of a transitional arrangement, could stay in the customs union for a limited period of time."
The diplomat said officials accepted this would allow them more time to sort of any future border arrangement for Northern Ireland.
Diplomats added they were also sensing a change in the government's rhetoric about curbing immigration from the EU.
"The British do realise that [immigration curbs] are a bad idea for British society and economy," one said. "They will focus more on control and not quantitative limits."
They added that the UK would "talk themselves out of the 100,000 thing", in reference to a government pledge to reduce net migration to below 100,000 by 2020.
Diplomats also pointed out that economic growth was picking up on the continent, meaning there would be greater competition for labour.
Earlier this month, Foreign Secretary Boris Johnson said the UK would be "perfectly OK" if there was no agreement with the EU and the consequences were not "by any means as apocalyptic as some people like to protest."
But the Brexit Secretary, David Davis, later told MPs that the government had not made an overall assessment of what "no deal" would cost the British economy.
The EU's chief Brexit negotiator, Michel Barnier, warned in the FT this week that no deal would have "severe consequences for our people and our economies. It would undoubtedly leave the UK worse off".
He predicted burdensome customs checks, lorry queues at Dover, disruption to air traffic into the UK and extreme uncertainty for four million expat UK and EU citizens across the continent.
This week, the manufacturers' lobbying organisation, EEF, urged the PM to drop her threat to leave without a deal.
They said no deal would be a "risky and expensive blow" that could result in tariffs averaging more than five percent on their members' exports to the EU.
For its part, the government said it was confident of "delivering the right deal for the UK".
A spokesman said: "We are planning for and expecting a constructive negotiation and a deal on a positive new partnership that works for both the UK and the EU.
"We have also said we would not accept a bad deal which seeks to punish the UK, and that no deal is better than a bad deal."

The government's "shambolic" approach to Brexit is failing to equip the UK economy for leaving the EU, shadow chancellor John McDonnell has said.
Mr McDonnell accused Chancellor Philip Hammond of being isolated from cabinet colleagues and said he was too "weak" to make Brexit a success.
He also said Labour would not vote to block Brexit or push for a second referendum.
Treasury minister David Gauke said Labour had "zero" economic credibility.
In a speech in central London, Mr McDonnell accused ministers of plotting a "closed-minded Brexit" that "works only for bankers and the rich, instead of one that's based on fairness and works for the rest of us".
Setting out Labour's position ahead of the Autumn Statement - to be made next Wednesday - he said the government's approach will "continue to undermine the ambitions of working people", he said.
Mr McDonnell said: "We need a credible fiscal framework that supports Brexit; we need actual support for those in work on low and middle incomes; and we need secure and properly funded public services.
"We want to see an end to austerity, with the NHS and social care properly funded and ESA (employment and support allowance) and Universal Credit cuts reversed.
"We want to see an end to tax giveaways for the wealthy. And we need a serious commitment from government to invest across the whole of our country."
Labour, Mr McDonnell said, would "offer a positive, ambitious vision instead of leaving the field open to divisive Trump-style politics".
"This means we must not try to re-fight the referendum or push for a second vote and if Article 50 needs to be triggered in Parliament Labour will not seek to block or delay it."
Tom Bateman, BBC political correspondent
Since the EU referendum, the Treasury has steered away from the tougher deficit reduction rules imposed by former Chancellor George Osborne.
It has chosen instead to speak of a "pragmatic" approach to balancing the books, given what Philip Hammond described as the "turbulence" that Brexit may bring.
But his Labour opponent today condemned this approach as weak, arguing the government must go further and end austerity rather than postpone it.
Mr McDonnell also called for a focus on borrowing to create jobs and infrastructure - a policy he has previously said would go alongside a rule to balance day-to-day taxation and spending.
Labour knows its task is to present itself to voters as credible on the economy, as the battle lines are set out before the first major economic announcement of Theresa May's government next week.
Chief Secretary to the Treasury David Gauke said Labour had "zero credibility when it comes to the economy".
"They drove Britain to the brink of bankruptcy last time, opposed everything we did to clear up the mess - and now all they offer is a recipe for economic ruin.
"Ordinary working people would pay the price for Jeremy Corbyn's fantasy economics."
Green Party joint leader Caroline Lucas also attacked Mr McDonnell, accusing him of a "capitulation" over Article 50, which formally begins Brexit talks.
"The government should not be able to ride roughshod over Parliament - and MPs should be demanding more details from ministers before standing aside and letting them pursue Brexit entirely on Tory terms," she said.
It comes as the Institute of Directors  called on Mr Hammond to "act decisively" and use the Autumn Statement to introduce tax breaks to boost investment.
It released survey figures indicating business confidence had declined in recent weeks, with 50% of the 1,071 respondents asked between 12 and 27 October saying they were pessimistic about the economy over the next 12 months. Some 30% said they were optimistic.
The institute's director general Simon Walker said: "This is a moment for the government to act decisively to make it easier for firms to expand and find more opportunities.
"We know that there isn't a limitless source of funds, so we urge the chancellor to make tax changes that incentivise investment, alongside targeted infrastructure investment."

The government will pay £33m to Eurotunnel in an agreement to settle a lawsuit over extra ferry services in the event of a no-deal Brexit.
In December, the Department for Transport (DfT) contracted three suppliers to provide additional freight capacity on ferries for lorries.
But Eurotunnel said the contracts were handed out in a "secretive" way.
As part of the agreement, Eurotunnel has agreed to make some improvements to its terminal.
One of the firms awarded a ferry contract, Seaborne Freight, has already had its deal cancelled after the Irish company backing it pulled out.
Shortly after it was awarded the contract, the BBC found out that Seaborne had no ships and had never run a ferry service.
Transport Secretary Chris Grayling has been heavily criticised for the Seaborne deal, which would have been worth £13.8m.
In January, Eurotunnel wrote to Mr Grayling to complain that it had not been considered when the contracts were awarded.
It argued that unlike Seaborne, it has actually run a cross-Channel ferry service (MyFerryLink, which closed in 2015) and should have been approached.
In a statement accompanying the agreement, Mr Grayling said: "While it is disappointing that Eurotunnel chose to take legal action on contracts in place to ensure the smooth supply of vital medicines, I am pleased that this agreement will ensure the Channel Tunnel is ready for a post-Brexit world."
Under the agreement Eurotunnel will make improvements at its terminal in Folkestone, including installing new scanners and changing traffic routing to ease congestion.
Andy McDonald MP, Labour's shadow transport secretary said that Mr Grayling had shown "misjudgement" in awarding the ferry contracts.
Criticising his record, including problems on the railways, he said: "This trail of destruction has gone on long enough. It's time for Chris Grayling to go."
By Alex Forsyth, BBC political correspondent
The procurement of extra ferry services has proved highly problematic. First the fact a contract given to a firm with no ships was later cancelled, and now the decision to settle with Eurotunnel rather than face a lengthy legal fight.
Critics say it shows that, despite the government's insistence that it is preparing for a possible no-deal Brexit, plans have fallen short.
Others point the finger at the transport secretary himself.
Labour has repeatedly called for Chris Grayling to resign, citing what the party describes as a series of failures including the introduction of a new rail timetable that led to delays and cancellations and criticism of probation reforms introduced while he was justice secretary.
But while there is a chorus of criticism aimed at Mr Grayling, No 10 maintains the prime minister has confidence in him. Theresa May can ill afford further disruption in government, or to lose a loyal minister.
The idea behind the extra ferry services was to raise freight capacity at ports other than Dover, in the event of a no-deal Brexit.
Brittany Ferries, DFDS and Seaborne Freight were awarded contracts, worth more than £100m, to provide additional capacity for lorries.
There was particular concern over maintaining the supply of medicines to the NHS.
Speaking on Friday, Health Secretary Matt Hancock said: "While we never give guarantees, I'm confident that, if everyone - including suppliers, freight companies, international partners, and the health and care system - does what they need to do, the supply of medicines and medical products should be uninterrupted if we leave without a deal."
A Eurotunnel spokesman said that the deal would ensure that the Channel Tunnel would be the "preferred route" for goods to travel between the EU and the UK.
The company said the money would allow the "development of infrastructure, security and border measures that will guarantee the flow of vehicles carrying urgent and vital goods and that will keep supply chains essential to both industry and consumers moving".
By Joe Miller, BBC business reporter
It was the now notorious contract with Seaborne Freight that catapulted the government's no-deal Brexit contracts into the headlines, but it's the handling of the entire procurement process that has cost taxpayers some £33m.
Eurotunnel argues it would have been a strong contender for a contract, having run a ferry service as recently as 2015.
But the Department for Transport said the "urgency" of the situation forced it to hurry through the awarding of contingency planning contracts.
However, had it gone to court, Eurotunnel was going to argue that the DfT had ample time for a full, public tender process, and could have foreseen all Brexit eventualities from at least the date on which Article 50 was triggered in 2017.
Sources familiar with the case say the government was essentially "held over a barrel" by Eurotunnel, and was left with little choice but to settle.
And Andrew Dean, from law firm Clifford Chance, warns this may not be the end of the matter.
Mr Dean, who used to advise the government and is a procurement specialist, says:  "If Eurotunnel were required to develop or redevelop infrastructure that delivers or supports a public function as part of this settlement, there is a risk it could be construed as another piece of public procurement without open and transparent competition.
"In which case the government would be back to square one, with other potential providers able to challenge the process."

The government is being sued for its decision to charter firms to run extra ferries, including one with no ships, in the event of a no-deal Brexit.
Channel Tunnel operator Eurotunnel, said the contracts, revealed after Christmas, were decided in a "secretive and flawed procurement process".
The move comes days after Seaborne, one of the firms chosen, had its contract axed after its funding fell through.
The government said it had carried out a "competitive procurement process".
"The Department for Transport acted transparently and competitively throughout the process of securing extra freight.
"This was done by approaching ferry operators and encouraging bids that could be fairly assessed against each other," a spokeswoman said.
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At a High Court hearing in London, Eurotunnel claimed the government contracts, announced on 29 December, were awarded without any public notice.
Eurotunnel's barrister Daniel Beard QC said Eurotunnel only found out "when contract notices were published three days after Christmas".
He said it was "quite remarkable" his client had not been informed given its recent history in running cross-Channel services.
Ewan West, representing Transport Secretary Chris Grayling in court, said the government's procurement process was only for "maritime freight" services and that Eurotunnel "could never have provided that capacity" and "could not have complied" with the terms of the contracts.
Judge Peter Fraser ruled a four-day trial will begin on 1 March given the "obvious" urgency of the case and the "very important public interest matters" involved.
When the Department for Transport announced the contracts in December, in documents outlining the agreements it stated that an "unforeseeable" situation of "extreme urgency" meant there was no time for the contracts to be put out to tender - the standard practice for public procurements.
However, the BBC understands that a number of firms were considered and there was a private negotiation process.
Three suppliers were awarded a total of £102.9m in late December, aimed at easing "severe congestion" at Dover, in the case of a no-deal Brexit:
The decision to award a contract to Seaborne, a firm with no ships which the BBC found had never run a ferry service before, has been heavily criticised.
After Seaborne's contract collapsed Mr Grayling faced calls for his resignation, with Labour accusing him of "rewriting the textbook on incompetence.".
But Prime Minister Theresa May has said she continues to have full confidence in him.

The minority Conservative government has survived its first major test after its Queen's Speech cleared the Commons.
MPs backed the legislative programme - stripped back after the Tories lost their majority - by 323 to 309.
But the government had to make a late pledge on funding abortions in England for women from Northern Ireland, amid fears of a Conservative rebellion.
The Democratic Unionist Party's 10 MPs had agreed to support the government as part of a deal with the Tories.
Three Labour frontbenchers - shadow ministers Ruth Cadbury, Catherine West and Andy Slaughter - were sacked by the leadership while shadow transport minister Daniel Zeichner had resigned.
The sackings relate to the MPs' support for Labour MP Chuka Umunna's amendment during the Queen's Speech debate, which was defeated.
The amendment aimed to preserve the UK's EU single market membership. This is not Labour policy, and the party's MPs were told to abstain but 50 rebelled.
The government averted a possible rebellion by announcing women from Northern Ireland would get free access to abortions on the NHS in England.
Abortions are only allowed in Northern Ireland if a woman's life is at risk or there is a permanent or serious risk to her physical or mental health - while they can travel to England to have one privately, they have had to pay for the procedure.
Labour MP Stella Creasy had tabled an amendment which had attracted cross-party backing - but she agreed to withdraw it when the government announced its concession.
Labour's amendment, which was defeated by 323 to 297, called for Brexit to deliver the "exact same benefits" as the EU single market and customs union, as well as scrapping tuition fees, increasing public spending and ending the public sector pay cap.
Proposing it earlier, shadow chancellor John McDonnell described the Queen's Speech as a "threadbare scrap of a document" with many of the Tories' key pledges removed since the general election.
He also claimed the cabinet was divided over Brexit, with "weekly changes of direction".
Chancellor Philip Hammond challenged him to a "grown-up" debate about public spending, accusing Labour of asking voters "would they like someone else to pay higher taxes?"
During the debate, one Tory MP, Heidi Allen, criticised the arrangement between her party and the DUP, saying she could "barely put into words" her "anger" at the £1bn deal.
Ms Allen, who also criticised the Tories' general election campaign, said she wanted to put on record her "distaste for the use of public funds to garner political control" and warned that "never again" should a government prioritise spending in such a way.

A second referendum would be divisive but a price worth paying to prevent the "catastrophic damage" of a no-deal Brexit, Greater Manchester's mayor has said.
Andy Burnham said he would support a fresh vote only as a "last resort" to prevent the UK leaving the European Union with no agreement.
He said it could "widen" divisions and even "create social unrest".
The government said it was "confident of a mutually advantageous deal".
Speaking at Westminster, Mr Burnham argued if Parliament was heading towards a no-deal Brexit then the EU should be asked to postpone the March 2019 departure deadline to allow further negotiations.
If that fails and a deal acceptable to Parliament cannot be agreed between the UK and Brussels, a second referendum should be held, the former Labour cabinet minister said.
"I have to think seriously about what a second vote would mean on the streets of Greater Manchester," he said.
"If we thought the first was bad, the second would be a whole lot worse.
"It won't heal divisions but widen them, it would be angrier, create social unrest and open up a massive opportunity for the populist far right in a way we are seeing elsewhere in Europe and the USA."
Mr Burnham said the alt-right could be pushing the no-deal agenda "to exploit splits in British society".
However, he also said he was not supporting the People's Vote campaign for a referendum, and only advocated a second vote if the alternative was leaving with no deal.
He continued: "A second vote would further erode trust in Parliament and politicians, but that price is worth paying to stop the catastrophic damage to jobs that would come with a no-deal Brexit."
Mr Burnham, who is campaigning for extra powers to be given to the devolved regions and cities, said the 2016 Brexit referendum result was as much an "instruction for Westminster to review its relationship with the rest of England" as a message to Brussels.
"If the phrase 'take back control' is to mean anything, it must mean substantial devolution of power and resources out of Westminster to all of the English regions," he said.
A spokesman for the Department for Exiting the European Union said: "As a result of the significant progress made in negotiations, we remain confident we will agree a mutually advantageous deal with the EU."
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Caroline Lucas has asked 10 female politicians from all parties to join her in forming an "emergency cabinet" in a bid to stop a no-deal Brexit.
Writing in the Guardian, the Green Party MP said the all-women cabinet could "bring a different perspective".
Ms Lucas, whose party wants another Brexit referendum, said the aim would be to force a no-confidence vote in Prime Minister Boris Johnson.
She would then hope to form a "national unity government".
This arrangement - when a group of MPs of multiple parties choose to work together and form a government - has not been seen since the Second World War.
In her Guardian article, Ms Lucas - a former Green Party leader - said the national unity government would "press the pause button" and organise another referendum offering a choice between staying in the EU or the government's Brexit plan, whether that is an agreed deal or no deal.
"In my experience, women tend to be less tribal, they tend to find it easier to establish trust more quickly," she told BBC Radio 4's Today programme.
She also added that her proposed unity government would have to be led by a female Labour MP, as they would be representing the largest opposition party.
But her idea was criticised by International Trade Secretary Liz Truss, who tweeted: "Is there anything more sexist than claiming your gender determines your worldview/behaviour/attitude?"
Among the women Ms Lucas has invited to join her are Labour's shadow foreign secretary Emily Thornberry, Liberal Democrat leader Jo Swinson, Scotland's First Minister Nicola Sturgeon, Conservative MP Justine Greening, and Plaid Cymru Westminster leader Liz Saville Roberts.
The others are: Heidi Allen, Kirsty Blackman, Yvette Cooper, Sylvia Hermon, and Anna Soubry. She has asked to meet the 10 women in the coming days.
On Monday, Ms Lucas told the BBC she had received responses from five of the women she has written to, expressing differing levels of interest.
She added she wasn't completely against involving men - for instance accepting that a key anti-Brexit campaigner like Dominic Grieve could be given a cabinet seat.
Ms Thornberry tweeted a reply to say she would not be able to take part in the planned talks because she is currently on holiday.
She added that returning the issue of Brexit "to the people" was the "best route to go down at this point".
"My fear with the other suggested route - imposing some alternative coalition government without any reference to the public - would risk worsening the feelings of anger and resentment towards 'Westminster' that have led us into this Brexit mess," she added.
Ms Saville Roberts welcomed Ms Lucas's bid to break the deadlock over Brexit, but said she was "not entirely comfortable" that only women would be involved.
Ms Lucas's suggestion has also attracted widespread discussion on social media, with many people expressing criticism.
Labour's shadow home secretary Diane Abbott tweeted it "won't work... whatever the gender of the participants".
Labour MP Clive Lewis called it a "very interesting proposal", but asked: "Where are the BAME women politicians?"
Ms Lucas replied to him, saying she agreed that the list should be opened out further and she would love Ms Abbott to be involved.

Guy Verhofstadt has said he does not "know" if Brexit will go ahead.
Questioned on this during a visit to London, the leader of the liberal group in the European Parliament told reporters: "Ask Theresa May."
Meanwhile, European Council President Donald Tusk said there was a "20 to 30%" chance Brexit would not happen.
But Home Secretary Sajid Javid told the BBC it was "still possible" to get Theresa May's withdrawal agreement with the EU through Parliament.
The House of Commons has rejected it three times, with the deadline for Brexit being delayed from 29 March to 31 October.
Mr Verhofstadt, who is the European Parliament's Brexit co-ordinator as well as leader of the Alliance for Liberals and Democrats in Europe, campaigned in London on behalf of the Liberal Democrats ahead of European elections on 23 May.
Asked whether the UK would leave the EU, he replied: "I don't know. It's a question to ask Mrs May at Westminster."
He also said the Brexit process so far "had done more damage than has ever been predicted" and that "people can change their opinion".
Meanwhile, Mr Tusk told the Polish newspaper Gazeta Wyborcza: "Today the chance that Brexit will not happen is, in my opinion, 20 to 30%. That's a lot."
But Mr Javid told the BBC's Political Thinking with Nick Robinson podcast: "What would make me happy is that we get this deal through. What would make me happiest is that we do it with my colleagues.
"It is still possible to get this through with support from Conservative MPs and the DUP and support this deal as it is and without any further changes and any further compromises."
If this did not happen, he warned, MPs could seek to revoke the Article 50 process by which the UK is leaving the EU, in order to stop an exit without a trade deal with the EU.
"I can absolutely see MPs trying to come together to pass legislation to force the government's hand to try and revoke," he added. "That would be an absolute disaster."
Cross-party talks between the government and Labour have been taking place to try to solve the Brexit impasse.
However, Labour leader Jeremy Corbyn said on Thursday that discussions had been difficult and that "so far there have been no big offers".
Meanwhile, a city financier who has previously donated hundreds of thousands of pounds to the Conservative Party has been revealed as a key funder of Nigel Farage's Brexit Party.
Jeremy Hosking told the Daily Telegraph he has donated £200,000 to the Brexit Party in recent weeks, urging those who want a "proper conservative party" to offer support too.
He told the paper the Conservatives had taken people for "fools", adding: "I look at Nigel Farage and I see a political leader who is the only person in a leadership position who has been telling us the truth for 25 years."
Mr Hosking donated around £350,000 to Conservatives at the last general election, sources close to him said. He was also a key funder of pro-Brexit groups ahead of the 2016 referendum.
Mr Farage has previously been reluctant to name his major donors - saying it was "irrelevant".

The chancellor has called on Tory leadership candidates to "stop and think" about their spending promises.
Both Jeremy Hunt and Boris Johnson have announced a raft of policies during the contest, including cutting taxes and increasing spending on public services.
But Philip Hammond said they needed to "be honest" as the policies "greatly exceed" the Treasury's coffers.
He also said available money would be needed to support the UK economy in the case of a no-deal Brexit.
Asked by BBC political editor Laura Kuenssberg if the candidates were being honest with the electorate, he said: "I think they need to be very careful about setting out these ambitions and being clear about the consequences of them."
The warning comes after Mr Hunt said he would decide by the end of September whether there was a "realistic chance" of reaching a new deal with the EU were he to become PM.
The foreign secretary said he would deliver a provisional "no-deal Brexit budget" in early September, but abandon talks at the end of the month if there was no "immediate prospect" of progress - instead moving to a no-deal footing.
His rival Boris Johnson has vowed to leave "come what may" by 31 October.
Speaking to reporters on Monday, Mr Johnson said it was important to have a "hard deadline" for leaving, adding that previous no-deal preparations had "sagged back down" after exit dates were not met.
The Conservative Party's 160,000 members will begin voting next week and Theresa May's successor is expected to be announced on 23 July.
Mr Hammond said the Treasury had "built up fiscal headroom to protect against the cost of a no-deal Brexit" and that money could be released "if we have a smooth Brexit with a transition period in an orderly way".
But he said the current proposals on the table from Mr Hunt and Mr Johnson would already require increased borrowing beyond the government cap, or spending cuts or tax rises elsewhere - even without a no-deal Brexit-shaped "hole" in the public finances.
Jeremy Hunt and Boris Johnson have been busy spraying around hypothetical cash - whether on defence, on care for the elderly, on schools, for more police, the list goes on.
It is not politically surprising that they both want to signal they would turn on the spending taps a bit after a long, long period of cuts. But one of their erstwhile colleagues seems to have had enough.
After making some carefully crafted warnings in the last couple of weeks, Chancellor Philip Hammond has tried to call a halt, telling the BBC that both of the candidates have to resist the temptation of a bidding war, worrying that the party's reputation is at risk too.
Mr Hammond told me the candidates needed to "stop and think". And that by his calculation, both of the candidates' plans "greatly exceeds" the amount of wriggle room they will inherit from No 11 if they are lucky enough to be the one that moves in next door.
Mr Hammond also said the headroom wasn't "a pot of money sitting in the Treasury", but a way of borrowing more without breaching government limits.
"Whether it is a leadership competition or a general election, there is always a temptation to get into a bidding war about spending more and cutting taxes," he said.
"But you can't do both, and if we're not careful, all we end up doing is borrowing more, spending more on interest, instead of on our schools, hospitals and our police, and delivering a bigger burden of debt to our children and grandchildren."
He said the candidates' policies were "sensible and interesting ideas", but said the government had "built up a reputation for fiscal responsibility... and it is very important we don't throw that away".
"We have to live within our means and people have to be honest about the consequences of either spending more money or of cutting taxes that will have implications for borrowing or spending elsewhere," he added.
Cabinet Office Minister David Lidington has also warned the candidates about their spending promises, saying they had to "raise the money honestly from somewhere".
The de-facto deputy prime minister said: "While in a short term crisis you can ease up on the borrowing, money borrowed has to be repaid by the next generation with interest - so you shouldn't take on extra borrowing lightly, nor should we be wanting to impose more taxes on people already working very hard.
"Sound money and restraint in public spending remains a good Tory principle."
He said the "stewardship" of Mr Hammond meant "money is available" to "cushion the impact" of a no-deal Brexit.
But, he added: "I don't think any of us should pretend that no-deal would be easy even with the most meticulous and thorough planning."
Mr Hunt has said he wants to negotiate a new deal with the EU and would be building a team to create an "alternative exit deal" to be published by the end of August.
He would then engage with other EU leaders, but keep up preparations at home for a no-deal Brexit.
But BBC political editor Laura Kuenssberg said the timeline Mr Hunt was setting out was very tight - especially given the notice the government's fiscal watchdog, the OBR, usually needs to prepare for a Budget.
Earlier, one of Mr Johnson's leading backers, Health Secretary Matt Hancock, told the Times the days of public sector "pay freezes" under Theresa May and David Cameron would be over if Mr Johnson was elected.
But during a campaign visit in Kent on Monday, Mr Johnson declined to make a detailed pledge on public sector pay, saying only that remuneration should be "decent".
A no-deal exit on 31 October remains the default position in UK law after MPs rejected the deal Mrs May had agreed with Brussels three times.
If that does happen, the UK will automatically begin trading with the EU under the basic World Trade Organization (WTO) rules.
Under these rules, the tariffs - the taxes on imported and exported goods - will be different to what the UK currently trades under.

It is time to get Brexit "off the table" so that Britain can focus on other issues, the chancellor has said.
Philip Hammond told the BBC that getting a deal done soon would release the "bandwidth" needed to take key economic decisions facing the country.
He called the UK's involvement in May's European elections "pointless" and hoped a deal would be done before then.
Mr Hammond was speaking in Washington, where he is attending World Bank and IMF meetings.
The chancellor said talking to the Labour Party about finding a way forward to resolve the Parliamentary impasse was not his "preferred route".
But it offered a new way forward to achieve a Brexit deal, after which he could concentrate on issues such spending and "where our economy is going over the next few years".
"I would like us to spend more of our bandwidth focused on growing our economy," he told the BBC's economics correspondent Dharshini David. "Until a deal is done we cannot make decisions about the spending review."
If a deal on leaving the EU cannot be agreed by the end of May, the UK is committed to fighting the European elections.
"Clearly nobody wants to fight the European elections. It feels like a pointless exercise, and the only way we can avoid that is by getting a deal agreed and done quickly.
"If we can do that by 22 May, we can avoid fighting the European parliamentary elections.
"In any case, we want to ensure any British MEPs that are elected never have to take their seats in the European Parliament by ensuring this is all done well before the new European Parliament convenes," he said.
The chancellor is in Washington at the World Bank and IMF spring meetings.
He rejected suggestions that the handling of Brexit negotiations was being seen overseas as a national humiliation.
"Britain is known as a bastion of democracy, and how we manage a challenging and complex issue like this is of huge interest," he said.
"In a year's time, when this is behind us and people are focussed on other things, all this will be forgotten."

The Treasury is not "the enemy of Brexit", Chancellor of the Exchequer Philip Hammond has insisted.
In a speech in the City of London, Mr Hammond said the UK needed to protect patterns of trade with the EU that had been "built over decades".
The chancellor also used his Mansion House speech to confirm taxes will have to go up to boost spending on the NHS.
But he said the increase would be partly funded by lower contributions to Brussels post-Brexit.
In the past the chancellor has come under fire from supporters of Brexit.
Earlier this month Foreign Secretary Boris Johnson called the Treasury "the heart of Remain", in comments to a private dinner.
However, addressing a City audience on Thursday, Mr Hammond said the "immediate key" to the UK and London's economic success was "ensuring we get a good Brexit deal".
He said the goal was a partnership that "recognises that our European neighbours are our most important trading partners, and that Dover to Calais is the busiest trading corridor in Europe".
As the UK leaves the EU, he said the new relationship should "maintain low friction borders and open markets".
He went on: "That does not make the Treasury, on my watch, 'the enemy of Brexit'; rather, it makes it the champion of prosperity for the British people outside the EU, but working and trading closely with it."
Mr Hammond also said the £20bn five-year NHS funding package announced by the prime minister this week would be partly funded by lower contributions to Brussels.
However, he also said the government would stick to its fiscal rules and "continue to reduce debt".
As a result taxpayers will have to "contribute a bit more", he added.
Earlier this week, Prime Minister Theresa May announced a boost in NHS spending, which will see NHS England's budget increase by £20bn by 2023.
The plan also means more money will be given to the rest of the UK - about £4bn - although it will be up to the Welsh and Scottish governments to decide how that is spent.
Mr Hammond said the NHS was the government's "number one priority for the forthcoming spending review".
"So, as the Prime Minister said, taxpayers will have to contribute a bit more, in a fair and balanced way, to support the NHS that we all use."

Most of the MPs elected last week want to avoid a so-called "hard Brexit", pro-EU politicians claim.
Having called Thursday's election to seek an increased mandate for her Brexit strategy, Theresa May ended up losing seats and her Commons majority.
Conservative ex-minister Anna Soubry said: "The people have spoken - and they have rejected a hard Brexit."
Defence Secretary Sir Michael Fallon said the government's view of Brexit had not changed.
Negotiations with Brussels on the UK's departure from the EU are due to start on 19 June, and Mrs May is now seeking the backing of the Democratic Unionist Party to prop up her minority government.
The DUP supports Brexit - but also wants to avoid a hard border with the Republic of Ireland and to maintain as far as possible the current access to EU markets - both of which would be jeopardised if the UK leaves without a deal in place, an outcome known as a "hard Brexit".
Ex-chancellor George Osborne said the DUP's position made Ms May's "central claim" - that no deal is better than a bad deal - "undeliverable".
And Ms Soubry - a leading figure in the Remain campaign before last year's EU referendum - told the BBC's Sunday Politics programme that Mrs May would have to listen to businesses and "wise owls" in her government who are calling for the single market to be a priority over immigration curbs.
This is not the approach adopted by the PM, who plans to withdraw from the single market and customs union and bring net migration below 100,000.
On the BBC's Andrew Marr Show, the pro-EU former deputy prime minister Lord Heseltine described Brexit as "the cancer gnawing at the Conservative Party" and urged a "period of contemplation" on the subject before negotiations begin.
The "right leader of the Conservative Party", he claimed, could appeal to German and French presidents for a deal to keep us "within the European family" while addressing immigration concerns.
But Labour's shadow chancellor John McDonnell told ITV's Peston on Sunday that full single market membership was not "on the table" and would be seen by voters as not respecting the referendum result.
Speaking on Marr, Sir Michael said the government wanted maximum access to the EU single market and an "arrangement on immigration".
He said he believed there was a majority in the Commons for such an approach.
"I think everybody wants to see an agreement in the end that does respect what the British people voted for last year - makes sure that our cooperation with Europe continues, our trade with Europe continues, our security cooperation with Europe continues," he said.
Leave-backing Conservative MP Dominic Raab told the Sunday Politics the country was "quite clear that they want us to make a success of Brexit".

UK Prime Minister Boris Johnson hopes to persuade MPs to back a deal to take the UK out of the EU.
Doing so would implement the result of the referendum of June 2016, in which 52% of voters backed Leave and 48% Remain.
But where do voters stand on Brexit now, after more than three years of debate and negotiation?
First, no single course of action is preferred by a majority of voters.
For example, polling firm Kantar has asked voters on a number of occasions which of four possible outcomes they prefer.
The most popular choice has been to remain in the EU. However, this secured the support of only about one in three.
The next most popular, leaving without a deal, is preferred by slightly less than a quarter.
Much the same picture has been painted by another survey. BMG asked people which of five alternatives they would prefer if a deal is not agreed by the end of this month. None has come even close to being backed by more than half of voters.
Should no agreement be reached, the single most popular option is to leave the EU without a deal. Even so, it is still only backed by about one in three.
Both of the next most popular options - holding another referendum and reversing Brexit without a referendum, are only chosen by about one in five.
Three polls, by Opinium, Panelbase and ComRes have asked people what they thought of proposals for a deal put forward by Mr Johnson.
All three found that slightly more voters were in favour of them than against. However, they were still backed by well under half.
In Opinium's poll, just 27% thought the proposals would represent a good deal, while 22% reckoned they would represent a bad one.
Most people either said it would neither be good nor bad, or that they did not know.
Both Panelbase and ComRes found that 31%-32% support the proposals, while 27%-28% oppose them. But in both cases 41% said they did not know.
Against this backdrop, what voters will make of any compromise deal that Mr Johnson might strike with the EU is far from clear.
Second, those who voted Remain and those who backed Leave have very different preferences.
The single most popular option among Leave voters is to exit the EU without a deal. According to Kantar, at least half of them prefer that course of action.
Only about three in 10 pick either of the deals put before them by Kantar: the agreement Mrs May negotiated with the EU, or a "soft" Brexit under which the UK will still be part of the single market and customs union.
Meanwhile, in the event of no deal, on average nearly seven in 10 Leave voters tell BMG they back leaving without one.
In contrast, most of those who voted Remain believe that Brexit should be reversed. On average two in three of them tell Kantar they think Article 50 should be revoked.
BMG offered its respondents both the possibility of holding another referendum and of reversing Brexit without a ballot.
On average, nearly four in 10 Remain voters say Brexit should simply be reversed, while about three in 10 opt for another vote.
Third, very few voters on either side of the argument have changed their minds about whether the UK should leave the EU. The country appears to be just as divided as it was three years ago.
On average, during the last month, polls that ask people how they would vote in another referendum suggest that 88% of those who backed Remain would do so again. Among those who voted Leave, 86% have not changed their minds.
These figures have changed very little during the last two years.
True, most polls suggest - and have done so for some time - that the balance of opinion might be tilted narrowly in favour of remaining a member of the EU. On average, this is by 53% to 47%.
However, this lead for Remain rests primarily on the views expressed by those who did not vote three years ago - and perhaps might not do so again.
In truth, nobody can be sure what would happen if there were to be another referendum.
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Fourth, voters are divided about whether any agreement that might be reached with the EU should be put to a referendum.
The balance of opinion differs from poll to poll.
When people are asked about a "public vote" they are more likely to show support for another ballot than when asked about a "referendum" on the UK's membership of the EU.
But they all agree that those who voted Remain are much keener on another vote than those who backed Leave.
All five of the polls put support for another ballot among Remain voters at over two-thirds.
In contrast, four of them find that fewer than 20% of Leave supporters are in favour of the idea. The fifth, by Kantar, puts it only somewhat higher, at 37%.
So those who voted Remain are much more likely than those who voted Leave to welcome a ballot that might overturn the result of three years ago.
Whatever the outcome this week, the division between Remainers and Leavers does not look as though it is going to be easy to heal.
About this piece
This analysis piece was commissioned by the BBC from an expert working for an outside organisation.
Further details of the research on which it is based are available here.
Sir John Curtice is professor of politics, Strathclyde University, and senior research fellow at NatCen Social Research and The UK in a Changing Europe.
*Full wording of questions for the chart "attitudes towards a second referendum". Kantar: Should the final deal/agreement reached by the government be put to a public vote?; YouGov: Would you support or oppose a public vote on Brexit?; Deltapoll: Would you support or oppose a second referendum on British membership of the European Union?; Panelbase: Do you think there should be a new referendum on Brexit?; BMG: To what extent do you support or oppose [holding] a second in-out EU referendum?
Edited by Duncan Walker
Charts by David Brown and Dominic Bailey

A conservative think tank is calling for Tory grandee Lord Heseltine to have the whip withdrawn for his "sniping" about Brexit.
Members of the Bow Group have accused the former deputy prime minister of "outright sabotage" and want him expelled from the Tories' Lords group.
It comes after he suggested a Labour government would be preferable to the "long-term disaster" of Brexit.
Lord Heseltine is a high-profile critic of leaving the EU.
Comments made by Lord Heseltine more than a month ago have triggered a backlash from the Bow Group after they were reported in The Guardian and other newspapers this week.
The Bow Group includes big name Tory Brexiteers Lord Tebbit, its chairman, and Lord Lamont, a senior patron.
Speaking to the Limehouse Podcast about the prospect of a Jeremy Corbyn-led Labour government, Lord Heseltine said: "We've survived Labour governments before.
"Their damage tends to be short-term and capable of rectification.
"Brexit is not short-term and is not easily capable of rectification.
"There will be those who question whether the short-term pain justifies the avoidance of the long-term disaster."
Tory MP Daniel Kawczynski, a Bow Group board member, said: "His lack of respect and loyalty towards the Conservative Party is deeply regrettable."
And the group's chairman, Ben Harris-Quinney, added: "Heseltine has made clear it is his aim to prevent Brexit at all costs, including the sabotage of his own party and nation, the Conservative Party must therefore withdraw the whip and end the inevitable continuation of his sniping from inside the tent."
The Bow Group describes itself as "the United Kingdom's oldest conservative think tank" which "represents all strands of conservative opinion".
Ahead of the 2015 general election, Mr Harris-Quinney was rebuked by its patrons when he urged Tory supporters in some areas to "lend their votes to UKIP" to help prevent a Labour government.

Honda has confirmed it will close its Swindon car plant in 2021, with the loss of about 3,500 jobs.
The Japanese company builds 160,000 Honda Civics a year in Swindon, its only car factory in the EU.
Honda said the move was due to global changes in the car industry and the need to launch electric vehicles, and it had nothing to do with Brexit.
Business Secretary Greg Clark said the decision was "devastating" for Swindon and the UK.
A fall in demand for diesel cars and tougher emissions regulations have shaken up the car industry.
Ian Howells, senior vice-president for Honda in Europe, told the BBC: "We're seeing unprecedented change in the industry on a global scale. We have to move very swiftly to electrification of our vehicles because of demand of our customers and legislation.
"This is not a Brexit-related issue for us, it's being made on the global-related changes I've spoken about.
"We've always seen Brexit as something we'll get through, but these changes globally are something we will have to respond to. We deeply regret the impact it will have on the Swindon community."
Mr Howells said that, in the light of changes in the industry, the company had to "look very closely" at where it was putting its investment.
The company sells many more vehicles in North America, Japan and China than it does in Europe.
"It has to be in a marketplace of a size for Honda, where it makes investment worthwhile.
"The conclusion coming out of that is that that doesn't include Swindon - the relative size of the marketplace in Europe is significantly different."
Honda said it would begin consulting immediately about the proposed closure with potentially affected employees.
A union source told the BBC that Honda had sent the workforce at its Swindon factory home for the day.
Honda also announced it would stop making the Civic at its plant in Turkey in 2021. Its European HQ will continue to be located in the UK after the changes.
Earlier this month, Nissan switched plans to build its X-Trail SUV from the UK to Japan.
At that time the firm's Europe chairman, Gianluca de Ficchy, said that "the continued uncertainty around the UK's future relationship with the EU is not helping companies like ours to plan for the future".
Dominic O'Connell, Today business presenter
Honda says the Swindon closure is not Brexit-related. Is this the unvarnished truth, or is the company simply trying to avoid a political storm?
Honda has in the past been vocal about the difficulties a disorderly Brexit would bring, and the timing of the announcement, a little more than a month before the UK leaves the European Union, is curious.
But the Honda statement makes no mention of Brexit at all, instead pointing to the greater forces that are reshaping the car industry.
Honda is not, on the world stage, a big player, being dwarfed by the likes of Toyota, Volkswagen, General Motors and Ford.
It needs to find the resources to invest in electric power plants and autonomous vehicles - a strain that has already led to its larger rivals closing plants and cutting jobs.
Honda said it needed to invest in these new frontiers and concentrate its production resources where it could be sure there would be high volumes.
Swindon, which has had one of its two production lines shut for several years and which makes only 160,000 cars a year, does not fit that future. Nor does an even smaller plant in Turkey.
Brexit issues may be lurking in the background, but Honda's real reasons for closing Swindon are about the future of the global car industry, not Britain's future relationship with Europe.
The EU and Japan recently struck a trade deal which lowers tariffs on both parties' car exports to zero.
BBC business editor Simon Jack said the trade deal means there is a dwindling rationale to base manufacturing inside the EU.
He said production at Swindon had also been in decline for some time, with the plant currently running at about half its capacity.
Business Secretary Greg Clark said he would convene a taskforce with local MPs, civic and business leaders, as well as trade union representatives, to help Honda workers get new skilled jobs.
"The automotive industry is undergoing a rapid transition to new technology," he said.
"The UK is one of the leaders in the development of these technologies and so it is deeply disappointing that this decision has been taken now."
Unite union official Alan Tomala said employees at the Swindon factory felt "betrayed" by the closure announcement.
"They feel that the company owes them a little more than hearing the news in the media.
"I left work yesterday to 57 missed calls and around 130 emails, and not one from Honda.  It surprises me and I'm angered by it."
Outside the factory gates, employee Chris, whose son also works at the plant, told the BBC he was "extremely disappointed".
"I've been here 19 years and it's devastating for all involved," he said.
"You've only got to look across the road at the large warehouses here too, I don't know what the jobs will be replaced with."
Local employment agencies have begun setting up meetings to prepare employees.
Kath Curr, managing director of C&D Recruitment in Swindon, said the closure was "devastating for the town as a whole", but Honda workers' skills were "completely transferrable" .
In a joint statement, Adam Marshall, director general of the British Chambers of Commerce, Phil Smith, chief executive of Business West, and Paul Britton, chief executive of Thames Valley Chamber of Commerce, said the planned closure of the Swindon plant would have a major impact, not only on Honda staff but also on the company's supply chain.
"Given the size of the operation, there will be a wide and diverse network of regional suppliers that will now be hugely concerned about their future business prospects.
"Employers, government and local authorities must do all they can to deliver tangible assistance and guidance for the people and communities that will be affected by an announcement of this scale," they added.

With two months to go until the UK is due to leave the EU, how are firms and the UK economy faring?
The economy's "resilience through the turbulence of the Brexit process has been particularly noteworthy", according to Chancellor Philip Hammond.
But some businesses claim to have been put under unprecedented pressure.
What is going on?
It's impossible to put absolute numbers on how jobs, output and investment have been affected so far.
No one knows how these will have fared had the outcome to the referendum in 2016 been different.
Other factors have influenced the business environment - not least slower growth in the likes of China and Europe
But there is a range of evidence that can give us an idea of how UK companies are faring.
On the face of it: no.
The number of people employed is at an all-time high. But there's a lot going on under the surface.
Banks' contingency plans mean setting up alternative bases in the likes of Frankfurt, Paris or Dublin. Individual banks are coy about revealing too much.
But reports about banks such as Morgan Stanley, Barclays and Bank of America moving, or creating, hundreds rather than thousands of jobs at those sites suggest the total affected in the City is much smaller than the 65,000 or so predicted by some immediately after the referendum.
London's Lord Mayor has said that the total by 29 March is likely to be below 13,000.
What we don't know is if jobs created in European cities such as Paris and Frankfurt are at the expense of potential ones here - or the final implications of the future trading relationship with the EU, whenever that is agreed.
While some - including JLR and Ford - have cited Brexit when cutting jobs, it has been a contributing rather than a deciding factor.
Car companies are facing a seismic shock in the face of slowing global demand, oversupply and the shift away from diesel.
In advance of departure, it is rare for firms to blame Brexit alone for job cuts. Chef and restaurant owner Jamie Oliver faced derision for doing so within a few months of the referendum, with critics instead blaming his business model.
As the uncertainty continues, companies may be putting hiring plans on hold - not least as they ramp up spending on no-deal contingency plans. How that impacts overall employment won't be known for a while.
There has probably never been a better time to be a trade negotiator - or a business adviser.
Overall employment has continued to rise to record levels since the referendum in June 2016.
In total, £95m worth of contracts were awarded last year to consultancy firms to advise the public sector on Brexit.
And 20,000 more civil servants have been employed since the referendum, in a reversal to earlier trends.
They are concentrated in the departments  most affected by Brexit.
And that's just the public sector.
Some companies continue to hire apace for other reasons. Telecoms giant Openreach, for example, has said that it will hire a further 3,000 engineers to support its rollout of full fibre broadband.
Business investment is stagnant and more than 10% lower than official forecasts had predicted prior to the referendum.
A lifting of the uncertainty could persuade firms to start spending again - a "deal dividend".
But investment  has been relatively sluggish since the financial crisis.
Firms instead opted to hang on to workers, as they are relatively cheap. They may be continuing this strategy, which could help explain why job creation has remained so resilient.
And as businesses enact contingency plans, money earmarked for investment may have been diverted.
Drugmaker AstraZeneca has spent £40m building extra testing facilities as it increases its drugs stockpile.
Some are forging ahead with plans for a variety of reasons.
Sony is moving its electronics HQ to the Netherlands, to pre-empt any customs problems.
James Dyson claims he's moving his company's base to Singapore to be closer to its fastest growing markets.
But luxury brand Chanel cited the same reason for moving its global business functions to London.
Drugmakers aren't the only ones stockpiling.
Associated British Foods, the company behind Twinings tea and Ryvita, has bought up extra machinery and packaging to prevent disruption to supply chains.
Mondelez, the makers of Cadburys, is stocking up on ingredients and the finished article.
More from the BBC's series taking an international perspective on trade:
With Majestic Wine buying an extra £8m in drinks, and Nestle investing in more coffee, there is a reduced risk of us having to forego some of life's luxuries.
Of course, these extra stocks may not be needed - and so the effort and money that's gone into organising and storing them will have been wasted.
But at this point, many companies feel they have no choice.
The UK's exit from the EU may be two months away but for some Brexit has in effect already happened.
Orders are often put in months in advance.
Those for British malting barley from the EU have dried up.
Barley, which is the UK's second largest arable export, could attract tariffs of around 50% of the current market price.
And it's not just food. At September's London Fashion Week, buyers were voicing concerns about placing orders for the spring that might face disruption.
Many of the impacts of the run-up to Brexit, as far as business is concerned, are likely to be temporary, reflecting contingencies or uncertainty.
The overall impact on the economy will become a bit clearer when GDP figures are released in about a week.
And what follows next will depend on Westminster's actions.
The impact of those, in whatever direction, may dwarf what we've seen so far.

Just how long will it take?
The government is intent on persuading us Brexit can be done smoothly, and to time.
So the suggestion that the UK's most senior diplomat in Brussels has privately told the government that a final trade deal with the rest of the EU might not be done for 10 years, and might ultimately fail, may give rise to more nerves.
The BBC understands that Sir Ivan Rogers, the British ambassador to the EU, warned ministers that the European consensus was that a trade deal might not be concluded until the early to mid-2020s at the earliest - possibly a decade after the referendum.
And Sir Ivan, who conducted David Cameron's pre-referendum renegotiation, warned that approving an agreement in every country's domestic parliament - the process of ratification - might prove impossible.
That's despite the public hope from ministers that a trade agreement can be done before we leave the union.
Officially Number 10 says it doesn't recognise the advice. They are confident of negotiating a deal in the interests of the UK and the EU.
Sources say Sir Ivan was representing others' views, rather than reflecting the view of the British government.
But as Theresa May arrives at only her second EU summit as prime minister, where she won't be in the room when the other 27 leaders discuss Brexit over dinner, this is perhaps a reality check of just how hard these negotiations might prove.

The former US President Lyndon Baines Johnson said the first rule of politics is being able to count.
And looking at the numbers in the Commons Theresa May must wonder how on earth she can get a Brexit deal through Parliament, even if she breaks the impasse in Brussels.
As it stands, Tory Brexiteers say they have dozens of MPs ready to vote against the emerging deal.
The DUP's 10 MPs are incandescent about the current proposals for the Irish border and may be tempted to join them.
And crucially, Labour has six tests to judge any Brexit deal by which the government seems certain to fail.
The Labour leadership's strategy is to vote against the Brexit deal in the hope a general election will follow.
If it doesn't, Jeremy Corbyn says "all options are on the table" and several of his MPs believe at that point another referendum will come into play.
However, a split is emerging on the Labour backbenches which may prove vitally important in the final vote on the Brexit deal.
In an interview for the World at One on Radio 4, Labour MP Gareth Snell warned his party not to be the "midwife" of a no-deal Brexit.
Mr Snell represents part of Stoke-on-Trent that voted overwhelmingly to leave the EU and is adamant the party must honour its manifesto promise to leave the EU.
"I don't think that we should dismiss at this point supporting any deal just because it is coming from the government," said Mr Snell.
"I think the Labour Party has to be very careful that we are not unwittingly becoming the midwife to a no-deal Brexit baby, if by voting down the deal that comes forward the only alternative is crashing out next March with a no-deal."
Mr Snell's view follows comments on Sunday by Labour MP Caroline Flint, who asked "if a reasonable deal is on the table, the question for my Labour colleagues is why wouldn't you support a deal?".
I understand the issue was raised at a meeting of the Parliamentary Labour Party last Monday and conversations are certainly going on between Labour MPs.
The big question of course is how many Labour MPs might be tempted to vote for a Brexit deal or abstain - in defiance of the party?
And would they balance out the number of Tories who seem likely to vote against the government?
At the moment, that seems very unlikely.
Eight Labour MPs told the BBC, off the record, they would consider voting for the deal brought back to the Commons.
Since that deal is not nailed down, the numbers are fluid.
But if it contains a plan to keep the EU and UK economically close after Brexit (yet still falls short of Labour's six tests) the opposition might start to fracture - particularly if the vote occurs in December or January, with time almost up.
Add in the handful of Labour Brexiteers and these would potentially be very useful recruits for the government.
But other Labour MPs are appalled at the prospect some of their number might vote for the deal emerging in Brussels.
Ben Bradshaw said fellow Labour MPs should not fall what he called Theresa May's "false choice" between the deal on the table or nothing at all.
"There is no obligation on Labour MPs to vote for a deal they know will hurt their constituents, make them poorer, particularly some of those heartland leave - Labour constituencies that will be most badly affected by a hard Brexit or a no-deal Brexit," he said.
Mr Bradshaw's hope is that in the political chaos that would follow the Commons rejecting the deal, Parliament would swing behind calls for another referendum.
The looming vote on any Brexit deal will be momentous.
The outcome is impossible to predict, so too the ramifications of it being rejected.
MPs will wrestle with conscience, party instruction, their constituents' views and the referendum result.
There will be unlikely alliances in the division lobbies and the decision of just a few MPs could make a big difference.
So in the coming weeks, listen carefully to Labour MPs representing constituencies in the party's midland and northern heartlands that voted decisively to leave. The government's whips certainly will be.

Boris Johnson and Jeremy Hunt are pitching to Conservative Party members in Northern Ireland as they battle to become the next prime minister.
But what are their plans for Brexit, the backstop and the border?
Both men have been clear that the backstop should be removed from the withdrawal deal, or at least radically changed.
The backstop was the most controversial part of the deal Theresa May negotiated with the EU.
It is a position of last resort to prevent any new checks or controls on the Irish border after Brexit.
The UK and EU would prefer to maintain the border status quo through a comprehensive trade deal.
If such an agreement cannot be reached, or if a technological solution does not emerge, the backstop would come into force.
It would keep the UK in a single customs territory with the EU, and leave Northern Ireland in the EU's single market for goods.
That would mean goods crossing the border would not be subject to checks for customs or product standards.
Many Conservative MPs fear the UK could be "trapped" in that arrangement for years, leaving it unable to strike its own trade deals on goods with the rest of the world.
The Democratic Unionist Party (DUP), which props up the government, also do not want to see Northern Ireland treated differently from the rest of the UK.
Both men say they would seek a renegotiation, although EU leaders have consistently said the withdrawal deal will not be reopened and the backstop must remain in place.
Jeremy Hunt has suggested EU leaders have told him privately that they would be prepared to look again at "the whole package" if the UK has some new ideas.
He would add the DUP to his negotiating team and give three weeks for talks with the EU and then decide by 30 September whether a deal can be done.
Mr Johnson has suggested that the backstop be removed from the withdrawal deal and the Irish border issue be resolved in the second phase of Brexit talks which concern a trade deal.
He told the Sunday Times that is "logically" where the border should be discussed "and where it should have been all along".
That would have to involve some sort of standstill agreement to ensure no change at the border while the final deal is worked on.
Both men are agreed that a deal on so-called alternative arrangements is the key to replacing the backstop.
Alternative arrangements are ways of maintaining a soft border without regulatory alignment between the UK and the EU.
It is normally used to refer to a package of technical, technological and administrative solutions.
A lengthy alternative arrangements plan was recently published by the Prosperity UK think tank.
It was praised by both candidates.
Mr Hunt described it as a "useful and thorough contribution," while Mr Johnson said it demonstrated that there were "plenty of checks that you can do away from the border if you had to do them without any kind of hard infrastructure at the Northern Ireland frontier."
However, the Prosperity UK report makes a number of assumptions which are worth examining.
Firstly, there is an important definition, or redefinition. In 2017, the EU-UK joint report said the UK was committed to avoiding a hard border, including any physical infrastructure or related checks and controls.
The EU view was this meant the status quo must be maintained with no new procedures at all relating to the border. The UK appeared to go along with this.
However the Prosperity UK report essentially concludes this is too restrictive and it should only mean no new checks and controls at the border.
The inevitable checks and controls will happen elsewhere.
There is also the expectation that the Irish government, political nationalism and some businesses would have to take a bit of pain.
The Irish government would have to back down on no checks and controls, nationalism would have to accept a new distinction between the two states and some Northern Ireland traders would have to bear new costs and trade frictions.
The report also suggests that on the very tricky issue of food standards the best, perhaps only, solution is to have some system of shared rules.
It alights on a convoluted UK-Irish food standards zone, which they say will be 'difficult' to negotiate.
That is perhaps an understatement as it would seem to compromise Ireland's place in the EU single market.
So alternative arrangements are not straightforward.
Mr Johnson has acknowledged they do not provide a "single magic bullet" while Mr Hunt says they can only work with "goodwill and flexibility on all sides."
The EU has committed to exploring alternative arrangements, but only once a withdrawal agreement containing the backstop is passed.
At a recent EU summit, the Taoiseach (Irish prime minister) said that alternative arrangements would not be able to replace the backstop in time for the UK's planned exit date.
Leo Varadkar said: "We can't accept that alternative arrangements are an alternative to a backstop unless we see what they are, know how they would work and see them demonstrated."
"That hasn't been done yet and I don't see that being done this side of October 31, which is why we certainly can't accept the deletion of the backstop."

Commons votes are normally as mannered and sequenced as a minuet, but the "indicative votes" on alternative Brexit options will be different, and MPs will have to learn some new steps.
The debate will begin with a hard start time of 2pm - it might be a little earlier, but will not be any later.
This was laid down in the motion from Conservative MP Sir Oliver Letwin and others to ensure that time was not taken away from it by, for example, a sudden rash of ministerial statements or urgent questions.
Up to the first hour can be taken up by debate on a Business of the House motion, setting out the ground rules for the debate itself - which could see, for example, attempts to amend the voting system between the various options, or maybe separate out means from ends, so that different variants of Brexit were considered, but options like a second referendum were not mixed in.
That might be problematic, if, say, some MPs wanted to approve the prime minister's Brexit deal only subject to a referendum...
Again, there is a hard time limit, to stop MPs filibustering about procedure rather than getting onto the meat of the debate.
Once the Business of the House motion and any amendments to it are dealt with, Mr Speaker will announce which amendments he has selected for debate.
This will be an important moment, because the credibility of the entire exercise rests on MPs having a broad choice of options, and any selection seen to exclude part of the spectrum of possible choices would defeat the point of having indicative votes.
The selection of amendments would be based on (highly flexible) criteria, like the breadth of support, and the distinctiveness of each possible alternative; it is unlikely that the Speaker would choose two almost identical propositions for example.
But he would be keen to avoid swamping MPs with too many alternatives.
Much will depend on the precise terms of the final, possibly amended, Business of the House motion - the motion itself would probably emanate from the group behind Monday's Letwin amendment, but there is nothing to stop someone else, including the government, tabling their own rival version.
It would then be for the Speaker to select.
In the main debate the expectation is that there would be movers speaking for each proposition, and MPs could then debate them all together - and there would probably be speakers from the Opposition and the government winding up.
The voting is expected to take place over half an hour, from the end of the debate at 7pm. It will probably take place in the "No" lobby, immediately next to the Commons Chamber.
MPs will vote, not by filing through the lobbies, as usual, but by filling out a ballot paper.
They would be invited to vote Yes or No to each alternative on offer, and the totals for and against each of them would then be counted by the clerks.
And because the ballot papers would be signed by the MP completing them, the result will eventually be a full list of who is for and against each option.
The sitting of the Commons will be suspended for that half hour - but it will doubtless take rather longer for the results of the vote to emerge.
When MPs get back into the Chamber they will have 90 minutes to debate the statutory instrument which postpones Brexit Day - a debate which is pretty sure to result in a traditional Commons vote.
It is possible that the Speaker may be able to announce the results of the indicative votes in the middle of this debate.
The other little detail tucked away at the end of the Business of the House motion proposed for Wednesday is a proposal to provide another opportunity for MPs to take control of the Commons agenda on the following Monday 1 April - so be prepared for a repeat performance.

Few issues divide opinions between different age groups quite as sharply as Brexit. And it could be that the differences are becoming even more pronounced.
Voters remain evenly divided about the issue, just as they were at the time of the EU referendum two years ago.
If there were to be a second referendum now, 52% would vote Remain and 48% Leave, an average of polls over the past three months suggests.
So, it is a stable picture, albeit one that reverses the position in 2016.
But the opinions of voters vary dramatically across different groups - none more so than between young and old.
Just over 70% of 18 to 24-year-olds who voted in the referendum backed Remain, four major academic and commercial polls conducted shortly after the ballot agree, with just under 30% backing Leave.
In contrast, only 40% of those aged 65 and over supported Remain, while 60% placed their cross against Leave.
These younger and older voters may be even more polarised now.
A total of 82% of 18 to 24-year-olds with a voting preference say they would vote Remain in a second referendum, an average of polls conducted in the past three months suggests, while only 18% of this age group say they would vote Leave.
In contrast, two-thirds of those aged 65 and over would back Leave, while only one-third would favour Remain.
And it is not only the youngest and the oldest voters who have very different views about Brexit. Every age group is different.
The younger someone is, the more likely they are to favour Remain over Leave.
As a result, the UK is divided into the under-45s who, on balance, favour staying in the EU, and the over-45s, who want to leave.
More like this
This pattern reflects very different outlooks about some of the central issues in the Brexit debate.
On immigration, the most recent British Social Attitudes survey shows that 61% of those aged 18 to 34 think that immigration enriches Britain's cultural life.
In contrast, only 38% of those aged 55 and over feel that way.
When it comes to the economy, 54% of 18 to 34-year-olds disagreed with the statement "Britain will be economically better off post-Brexit" in polling by ORB International between May and July. Half that number, 27%, thought the country would be better off.
Among those aged 55 and over, the balance of opinion is almost exactly the opposite - 54% agree that Britain will be better off, while 30% disagree.
Consequently, younger people are also less concerned about an end to free movement - the right of EU citizens to come to Britain to live and work - and more concerned for Britain to remain part of the EU single market.
When asked if they would choose to stay in the single market even if it means allowing free movement, 50% of 18 to 34-year-olds said they would do so, compared with 35% of 55 to 64-year-olds.
This difference of outlook is reflected in attitudes towards holding a second referendum.
Younger people are much keener on the idea of revisiting the Brexit vote.
Asked whether there should be a referendum on whether to accept the terms of Britain's exit from the EU once they have been agreed, about half of 18 to 24 year-olds say they are in favour of another poll.
Only three in 10 of those aged 65 and over hold that view.
However, only half of 18 to 24-year-olds said that they would be certain to vote in a second EU referendum, according to recent polls by Survation. This compares with 84% of those aged 65 and over.
So if there were another ballot, it is far from certain that young people would necessarily take the opportunity to register their distinctive views.
About this piece
This analysis piece was commissioned by the BBC from an expert working for an outside organisation.
Sir John Curtice is professor of politics at Strathclyde University, senior research fellow at the NatCen Social Research, a senior fellow at The UK in a Changing Europe and chief commentator at WhatUKthinks.org.
Edited by Duncan Walker

Jeremy Hunt has clarified his comments about a no-deal Brexit, saying Britain "would survive and prosper" - but it would be a "big mistake for Europe".
On Thursday he told ITV News a "messy" no-deal Brexit "would be a mistake we would regret for generations".
But he later tweeted that his words "should not be misrepresented" and the UK would only "sign up to a deal that respects the referendum result".
Tory MP Nigel Evans said: "We don't need any lectures from Remainers."
The backbencher, who campaigned for Brexit, told the BBC: "He's got his own views. He voted remain. The prime minister needs to ensure, as she promised, that Brexiteers are in charge of our leaving the European Union."
And fellow Conservative Brexiteer Conor Burns told the Telegraph: "The thing that we want to avoid for 'generations to come' is being locked into a permanent orbit around the EU where we end up with a deal but don't have a seat around the table".
It comes as Brexit talks resumed in Brussels between UK and EU officials, amid growing speculation about the possibility of the UK leaving the European Union without a deal in March 2019.
On Friday, Danish finance minister Kristian Jensen told BBC Radio 4's Today programme that Theresa May's Brexit plan drawn up at Chequers was a "realistic proposal for good negotiations".
But asked about comments by Latvia's foreign minister, that the chance of a no-deal Brexit was "50-50", he said: "I also believe that 50-50 is a very good assessment because time is running out and we need to move really fast if we've got to strike a deal that is positive both for the UK and EU."
Mr Hunt told ITV on Thursday that he believed the government's Chequers plan was the "framework on which I believe the ultimate deal will be based".
But he said, although the UK must be "prepared for all outcomes", if the UK were to leave without a negotiated deal: "It would be a mistake we would regret for generations, if we were to see a fissure, if we had a messy, ugly divorce.
"Inevitably that would change British attitudes towards Europe."
On Friday, he tweeted: "Important not to misrepresent my words. Britain would survive and prosper without a deal... but it would be a big mistake for Europe because of inevitable impact on long-term partnership with UK. We will only sign up to deal that respects referendum result."
Business Secretary Greg Clarke, who has been meeting counterparts in Austria and Finland, said on Thursday he was "confident" a "mutually beneficial deal" could be reached.
But he said that if the European Commission did not "respond positively and constructively" to the UK's proposal, "the disruption and impact on our continent's businesses, economies, and millions of hard-working families across the UK and EU will be significant and lasting".
The government has been touting its plans for Brexit agreed in July at Chequers - the prime minister's country residence in Buckinghamshire - to the EU and its leaders over the summer.
But the EU's chief negotiator Michel Barnier has appeared to rule out a key UK proposal - allowing the UK to collect EU customs duties on its behalf - in July.
Meanwhile, Buzzfeed News is reporting that it has seen a list of 84 areas of British Life - from organic food production to travelling with pets - which would be affected, should the UK leave the EU without a negotiated withdrawal.
The government is expected to publish a number of technical documents on the consequences of leaving with no deal in the coming weeks.
Former Brexit minister David Jones told the BBC's World at One it was a "great shame" they had not been published earlier as "people do need assurance that leaving the European Union without a negotiated agreement is not necessarily going to be the end of the world - in fact, far from it."
He added: "I think that what we need to do is to see these technical notices presented in neutral terms so that both businesses and the wider country can understand what the consequences would be."
Brexit talks resumed in Brussels this week between UK and EU officials, with the focus on the Irish border - a key sticking point - and future relations.
A European Commission spokesman said: "As this week's round is at technical level, there won't be a meeting between Michel Barnier and Dominic Raab.
"We will confirm in due course whether a subsequent meeting has been arranged."

Ex-Prime Minister Sir John Major has been accused of "an absolute dismissal" of democracy after he suggested there should be a second Brexit vote.
Iain Duncan Smith, Leave campaigner and another ex-Conservative leader, said: "You can't claim democracy when you want it and reject it when you don't."
He spoke out after Sir John also warned against Brexit being dictated by the "tyranny of the majority".
Mr Duncan Smith said: "We had a vote, that vote now has to be acted on."
The dispute came after Sir John, Conservative prime minister between 1990 and 1997, called for the 48% of people who voted against Brexit in June's referendum to have their views considered.
"The tyranny of the majority has never applied in a democracy - and it should not apply in this particular democracy," he said.
He argued that Parliament would have to ratify whatever deal is finally reached by the Brexit negotiators and there could be a case for a second referendum, depending on the deal on offer.
Mr Duncan Smith told BBC Radio 5 live's Emma Barnett: "The idea we delay everything just simply because they disagree with the original result does seem to me an absolute dismissal of democracy.
"And that's what I thought John Major's comments were today. The tyranny of the majority? What's the tyranny?"
Bernard Jenkin, a Conservative MP and leading figure in the Vote Leave campaign, also dismissed Sir John's talk of a second referendum.
"The idea this particular genie can be put back in the bottle after the British people have voted in a year-long debate - that we are now going to vote to stay in the EU - is absolute rubbish," he said.
Mr Jenkin argued that the UK could have avoided Brexit if Sir John had held a referendum on the Maastricht Treaty, which was responsible for the creation of the European Union almost 25 years ago.
"If he had stopped the Maastricht Treaty, there would have been no monetary union, there would have been no eurozone crisis, no bailouts, no centralisation of power in the EU - we might even still be a member of the EU," he told the BBC.
"And it's because he gave in on the Maastricht Treaty that we've had to finish up leaving the EU."
Liberal Democrat MP Nick Clegg, the former deputy prime minister, weighed in to add that while the government had a mandate to leave the EU, it did not have a mandate on "how" to leave.
Speaking on BBC Radio 4's World at One, he criticised what he called the "almost hysterical fervour of the hard Brexiteers" to turn Britain into "a low regulation, low tax, enlarged offshore Singapore for which they have no mandate".
He insisted it was "quite right that people, particularly from the centre ground point of British politics, say: 'Hang on a minute, that's actually not what people necessarily voted for on 23 June'."
He added: "Brexit yes, but not this very hard ideological Brexit that they seem determined to pursue."

Three days after Theresa May called the general election, I interviewed the chancellor about what we could expect from any new Tory government.
On tax the signal was clear.
Philip Hammond was no fan of the triple tax lock David Cameron promised voters before the 2015 election - no increase in income tax, national insurance contributions or VAT.
He suggested the lock should be dropped, and it was.
Towards the end of the interview I turned to immigration and, given the events of last Thursday, it is worth going back to the exchange.
And understanding that Mr Hammond's backing for an immigration target of "tens of thousands" per year is at best luke-warm.
I asked the chancellor: "Immigration is a big issue for businesses - skilled and less-skilled immigration coming into the country. Do you agree that immigration in the UK should be brought down to the tens of thousands even though many businesses say that will damage economic growth?"
Mr Hammond replied: "What businesses want to do is bring skilled migrants in, move skilled migrants around their global businesses to do the jobs that are open in the UK.
"No businesses are unable to bring skilled workers into the UK to work in their companies because we have run out of space on a visa cap.
"At the moment we cannot control migration from the European Union into the UK. That situation will end.
"We will regain control of our borders and we will use that control to manage the migration system in the interests of our economy and our society. "
Me: "Do you think it should be brought down to the tens of thousands a year, immigration in the UK?"
Mr Hammond: "We've got to get migration back to sustainable levels; we've got to focus on skilled migration. The Prime Minister has made it very clear that she believes that needs to be tens of thousands a year."
Me: "Do you believe it?"
Mr Hammond: "The Prime Minister has been very clear that is the target that we are going for - tens of thousands."
Mr Hammond is a careful man.
And the fact that he refused to say directly that he supported the target is worthy of note.
Those close to the chancellor have revealed his concern.
Far from putting up barriers to immigration, many in the Treasury believe that Britain will be engaged in a "global battle for immigrants" to support the economy.
Now, that is not to say that Mr Hammond is in favour of free movement of people from the EU.
As he made clear to me, "that situation will end".
And nothing has changed sufficiently enough since last Thursday to alter that.
Which seems to me to rule out unfettered membership of the single market unless the European Union decides to reform one of the four principles of membership - open borders.
And the chance of that appears vanishingly small.
What has changed is that Mr Hammond is much strengthened in government - as Theresa May has been weakened.
Many in Number 10 were no fans of the Treasury and wanted to curtail its influence at the centre.
That power relationship has shifted.
And Mr Hammond's reluctance to back an immigration numbers target has become much more significant.
"Jobs and skills" to support the economy will be a new mantra in the Brexit discussions - pushed by the chancellor.
Carolyn Fairbairn, the director general of the CBI writing in this morning's Financial Times, talks about the need for "access to the skills and labour companies need to grow".
My colleague Simon Jack reports this morning that businesses feel their voice should now be heard more loudly.
Michael Gove's reappearance in the Cabinet provides another "pro-skills" voice.
Yes, Mr Gove is a firm Brexiter, but of the "open-but-controlled borders" variety.
"People who come here who have got skills that can contribute to our economy are welcome," he said during the referendum campaign.
There is much talk that a "soft" Brexit may now be more likely given the perceived weakness of the Prime Minister.
As far as "soft" means an economically closer relationship with the EU - and a more porous approach to immigration controls - that certainly appears to be the case as far as the chancellor is concerned.

Immigration should rise and fall depending on the UK's needs after it has left the EU, the Brexit secretary says.
David Davis said a "sustainable" system would take into account the needs of the NHS and different industries.
He also said the government had a "huge contingency plan" for the UK leaving the EU without a deal.
Mr Davis was speaking on a special edition of BBC Question Time ahead of Wednesday's formal Brexit notification.
The government has yet to specify how the UK's immigration system will work once it is no longer bound by EU free movement rules, but has promised to restore "control" to borders with new curbs in place.
Mr Davis said the new system would be "properly managed".
It would be for the home secretary to decide the system to be used, he said, but added: "I cannot imagine that the policy will be anything other than that which is in the national interest.
"Which means that from time to time we will need more, from time to time we will need less.
"That is how it will no doubt work and that will be in everybody's interests - the migrants and the citizens of the UK."
The Brexit secretary was urged by a German NHS worker in the audience to "do the decent thing" and guarantee EU nationals the right to stay in the UK.
He promised the issue would be a priority when talks begin.
On Wednesday Prime Minister Theresa May will invoke Article 50 of the Lisbon Treaty, which begins the negotiation process.
During the Britain after Brexit debate the panellists, who included former Scottish first minister Alex Salmond and Labour Brexit spokesman Sir Keir Starmer, were asked what would happen if no deal was reached.
Mr Davis said the government had spent the nine months since June's Brexit vote preparing a plan.
He said it was not a scenario the government wanted to see, but added: "We have got a huge contingency plan, exercised across all of these issues, every department of government."
Mr Salmond said the government's view that no deal is better than a bad deal was "nonsensical".
But UKIP's Suzanne Evans criticised "hyperbole" about "crashing out" of the EU.
Mr Davis also said the UK would abide by its obligations when it comes to settling outstanding liabilities with the EU, but played down claims these could amount to £50bn.
Former Lib Dem leader Nick Clegg said the EU was "simply going to ask us to settle the tab before we leave", and Mr Starmer said the UK had to honour its debts "otherwise no country is going to want to deal with us" in future trade negotiations.
But a man in the audience compared the EU's demands with "the bully in the playground taking our lunch money".
On Wednesday, the prime minister will send a letter to the president of the European Council telling him officially that the UK wants to leave.
Triggering Article 50, the letter will set in motion a two-year process in which the terms of the UK's departure from the EU will be hammered out, as will the outline of the UK's future relationship with the remaining 27 EU members.
As things stand, the UK is set to leave the EU on 29 March 2019 although this deadline could be extended if both sides agree.
More than 33.5 million people voted in a referendum last June on the UK's future in the EU. They voted to leave by a margin of 51.9% to 48.1%.

The BBC's Laura Kuenssberg sat down for an interview with Prime Minister Boris Johnson after his meeting with the European Commission president Jean-Claude Juncker.
Here is the full transcript of what they said.
Laura Kuenssberg: You've just been with [European Commission president] Jean-Claude Juncker.
Do you feel you've made any progress since seeing him. I mean he could be the deal maker?
Boris Johnson: Yes. I mean obviously I've talked to him several times since becoming prime minister, but he's... I've known Jean-Claude for many, many years and he is a very, highly, highly intelligent guy and I think that he would like to get a deal if we possibly can, but clearly it's going to take some work.
We think that there are, we can satisfy the European Commission and our friends on the key points. Can we protect the single market the integrity the single market? Can we ensure there's no checks at the border in Northern Ireland? Can we protect all the achievements of the Good Friday Agreement and peace in Northern Ireland? Yes I think we can, while simultaneously allowing the whole of the UK to withdraw.
It will now take an accelerated timetable of work to, to get that done. And it maybe - you know - just have to say that it may be that we have to come out without an agreement if necessary on 31 October.
LK: And we will come to that in a second.
But just in the last few minutes, the [European] Commission has put a statement out, saying after your lunch that they still are yet to see proposals that they think are viable and workable.
So it doesn't feel like this is going anywhere at the moment?
BJ: Well, it's certainly the case that the Commission is still officially sticking on their position that the backstop has got to be there.
But clearly if they think that we can come up with alternatives, then I think they're on the mark.
I think the big picture is that the Commission would like to do a deal.
[Pause to adjust the microphone]
LK: I mean the Commission has immediately after your lunch put out a statement saying they still haven't seen viable workable proposals.
Do you feel they're listening or is this that they're saying something else behind closed doors to what they say publicly?
BJ: No, I think the Commission, I think Jean-Claude himself certainly would like to do a deal and would like the UK to, and would like to settle this if he possibly can.
They have their own constraints. They've got the European Parliament they've got to deal with. I think there's a deal there to be done and of the kind that I've described.
But clearly if we can't get movement from them on that crucial issue of whether the EU can continue to control the UK and our trade policy and our regulation - which is how it would work under the current Withdrawal Agreement - we won't be able to get that through the House of Commons, no way.
And we'll have an exit with no-deal on 31 October. That's not what I want. It's not what they want. And we're going to work very hard to avoid it. But, but that's the reality.
LK: But what is the broad shape of a deal that you think is there? I mean we've heard many times from you and ministers that there is a landing zone.
As simply as you can, what is the nature of the deal you think you can get?
BJ: I mean, I think that the important thing here is not to be... I mean, there is a negotiation going on, has been for a long time now about how to do this.
So there's a limit to how much the details benefit from publicity before we've actually done the deal. But the shape of it is, the shape it is...
LK: Slice and dice the backstop as it exists?
BJ: The shape of it is all about who decides.
Fundamentally, the problem with the backstop, as you remember, is that it's a device by which the EU can continue after we've left to control our trade laws, control our tariffs, control huge chunks of our regulation, and we have to keep accepting laws from Brussels long after we've left with no say on those laws.
Now that just doesn't work. It doesn't work for the whole of the UK and it doesn't work for Northern Ireland. So we have to find a way to avoid that situation.
LK: But what is that way? Because what you're saying there is just articulating the problem that's been articulated forever, about the backstop and people's concern that Northern Ireland would still have to and the rest of the UK would have to go along with EU rules.
But can you foresee a solution, for example, when in some areas, Northern Ireland would follow EU rules and the rest of the UK would not?
BJ: What we want to see is a solution where the decision is taken by the UK and clearly that's the problem with the, with the backstop. It basically leaves the decision making up to Brussels and that's no good.
LK: What's the actual solution that you're proposing? Is it giving more power to Stormont, for example, that's being talked about a lot, that the Northern Irish assembly might be given a lock on opting out or opting in on EU regulation?
BJ: These are certainly some of the ideas that are being talked about and as are the ideas that you're familiar with to do with maximum facilitations, to do with checks away from the border, all sorts of ways in which you can avoid a hard border in Northern Ireland.
This is all doable. It's all doable with energy and goodwill.
But I mentioned the other day when I was in in Dublin, you know the famous dictum attributed I think probably incorrectly to Ian Paisley the elder, [in] Northern Ireland the people are British, but the cattle are Irish, you know there's a there's a germ of an idea there.
LK: But it's just the germ of an idea...
BJ: There's a lot of thinking going on about how to get an agreement that gets the UK out whole and entire, but also protects that Northern Irish border, protects that peace process and protects all the gains that Ireland has got from its membership of the EU single market.
So, I'm, you know, I mean, more or less where I was the other day. I'm cautiously optimistic, cautious.
But it is vital that we're ready to come out on 31 October.
And of course what the... parliamentarians threatening to extend and all that kind of thing. They hear that they listened to that over here, but I didn't think it substantially changes their calculations.
LK: MPs though haven't just threatened to extend, MPs have changed the law to try to stop you taking the UK out without a deal at the end of October.
How do you propose to get round that? Because you keep saying you've got no intention of delay...
BJ: I won't. Here's, here's what I want. I will uphold the constitution, I will obey the law, but we will come out on 31 October.
LK: But how if MPs have changed the law to stop you doing that?
BJ: We're going to come out on 31 October and it's vital that people understand that the UK will not extend.
We won't go on remaining in the EU beyond October. What on earth is the point? Do you know how much it costs?
LK: But how will you do that if MPs have changed the law to stop you?
Are you looking for a way round the law? Because that's what it sounds like...
BJ: We will obey the law but we will come out - and - we will come out I should say on 31 October.
LK: But that means you are looking for a way round the law.
I mean, to be really clear about this, Parliament has changed the law to make it almost impossible to take us out of the EU without a deal at the end of October. But you say that you will not do it.
That means that you must be looking for a way around the law?
BJ: Well, you know those are your words. What we're going to do is come out on 31 October deal or no-deal. And staying in beyond 31 October completely... crackers.
You're spending £1bn a month for the privilege remaining in the... what is the point?
The people of this country want us to get on and leave the EU and deliver on the mandate of the people.
And staying in costs £250m a week, which is which is roughly the same as what it would cost to build a new hospital every week.
That's what Jeremy Corbyn and the opposition parties seem to think is a good idea. I don't think it's a good idea.
LK: You used to say it cost £350m a week, now you're saying £250m a week?
BJ: I think the priorities of the British people are to come out and that's what we're going to do.
LK: But do you really think that you want to be the kind of prime minister that is looking of ways of sneaking around the law to keep to your political promise?
I mean, everybody knows how strongly you feel...
BJ: These are all your words.
LK: But how will you do it then?
Will you challenge it in court? Will you take Parliament to court?
BJ: Our first priority, if I may say so, just to try and look on the bright side for a second or two, is to come out with a deal and that's what we're working to achieve. And I think we have every prospect of doing that.
LK: But if you don't, I mean you are looking, you know the law has been changed to try to make this impossible.
If you want to look for a way round it, many people believe that means you must be preparing somehow to ignore the law or to challenge that because it's a new area of law.
Would you seek to challenge the law in court? Will the government take Parliament to court?
BJ: What we're going to do is work very hard to get a deal that will allow us to come out.
I see no point whatever in staying on in the EU beyond 31 October and we're going to come out. And actually that is what our friends and partners in the EU would like too. And I think that they've had a bellyful of all this stuff.
You know they want to develop a new relationship with the UK. They're fed up with these endless negotiations, endless delays. They've now delayed twice before to achieve what is completely unclear to me.
LK: And you're completely clear that politically the promise you gave to your party was to leave on 31 October. And that was clear as crystal.
But since you've been in office you've suspended Parliament. You say you might find a way around the way that Parliament might change the law...
BJ: Well, that's what you've just said.
LK: Well, you haven't denied it prime minister. I mean it does seem since you've been in office that, some of the things that you have done, you seem to believe the conventions and rules somehow don't apply to you really?
BJ: Obviously I humbly, respectfully, disagree. If you're talking about having a Queen's Speech, I think that was the right thing to do. This Parliament has gone on for longer than any time since the Civil War.
It's right to have a Queen's Speech, it's right to set out our ambitious agenda for the country. There's all sorts of things we want to do. Whether it's investing in health care and putting police on the streets.
We've got a fantastic agenda for investing in science. A huge, huge agenda for this country. On the environment, on housing we have big, big projects.
We need a Queen's Speech. And by the way, all this mumbo jumbo about how Parliament is being deprived of the opportunity to scrutinise Brexit. What a load of claptrap.
Actually, Parliament I think has lost about four or five days. I don't think Parliament has sat during the period from late September beginning of October for about 120 years.
With great respect, I don't think people are aware of that fact. I think people think that we've somehow stopped Parliament from scrutinising Brexit. What absolute nonsense.
Parliament will be able to scrutinise the deal that I hope we will be able to do both before and after the European Council on 17 October.
LK: But when it comes to sticking to the promise you made to leave on 31 October...
BJ: We're going to do that.
LK: Is there a line that you would not cross?
BJ: Well yes, obviously I didn't want to go beyond 31 October. I think that would be a mistake.
LK: In order to stick to that goal, is there anything that you would not do?
Would you rule out suspending parliament again?
BJ: As I say, we're going to uphold the constitution and we're going to obey the law. And it's very important to realise that actually, I think our friends and partners in the EU are keen to work with us to get a deal.
That's what I've been doing here with Jean-Claude Juncker and Michel Barnier. We've been working very hard. We've had a good productive exchange.
Has there been a total breakthrough? I wouldn't say so. But I would say that a huge amount of work is now going to be done to sort it out.
Am I more optimistic than I was when I, when we took office? This morning? I would say a little bit, but not much, just a little bit.
Because I think that there's a, perhaps an even greater willingness on the part of the Commission to engage than I had, than I had thought.
So, so yes. I'm cautiously optimistic, but I'm not counting my chickens. And it is absolutely vital, it's absolutely vital for people to understand that the UK is ready to come out with no-deal if we have to.
LK: Do you feel that the UK is stable right now? I mean, it looks like chaos, doesn't it?
BJ: No, I think it's extremely stable. We've got unemployment at record lows. We have record levels of investment from overseas - one point £3tn pounds. There's no other country in Europe that gets these levels of investment.
If people genuinely thought, if people genuinely thought that there was some political risk in the UK, would they be investing in this in this country in the way that they are?
LK: Does it look politically stable?
BJ: This is an immensely, but it is an immensely stable country. We are going through what is, after all, a quite difficult exercise in democracy.
Which is, what happened is that the people of this country decided after 45 years of EU membership that that highly intricate relationship was one that they no longer wished to pursue. And that has had a great deal of consequence.
The disentangling of that relationship is obviously complex, but it can be done and it is being done. And we will get on with it successfully.
And I think people should be very optimistic about the future of this country, because it's a fantastic country. It is the leader and the cutting edge of most of the 21st century technology in Europe.  And a place that attracts, not just huge quantities of inward investment, but the best and brightest from around the world.
And what we will, what we will ensure as we become, as we take advantage of Brexit, is that we remain not just open to our friends in the rest of the EU, but we reach out now to the rest of the world and take advantage of the opportunities the Brexit offers.
And I think actually what the people of our country want is a little less of this sort of gloom and kind of, you know, I think most people think that, honestly it's just nonsensical to think that democracy in the UK is any way endangered or the UK economy is in any way endangered.
We're going through a period of constitutional adjustment caused by the decision of the people to leave the EU. That was always going to be logistically and practically difficult to accomplish.
But we're going to do it and we're going it by 31 October, and we will be in very good shape whether we get a deal or not.
And if we don't get a deal, I'm still, as I say, cautiously optimistic that we will. If we don't get a deal, we will come out nonetheless
LK: One of the people who is extremely gloomy about what's happened is your old friend and rival and colleague David Cameron.
Now he says that the Leave campaign that you led lied.
He said that you behaved appallingly and he's a prime minister, a Tory prime minister, who left behind a total mess over Europe.
Are you worried you might face the same fate?
BJ: I have nothing but admiration. Look I don't want to say anything further about David Cameron and his memoirs than what I said the other day, which is I have the highest respect and affection, regard for him.
He and I worked together for many years and I think he has a legacy, in terms of turning around the economic chaos that Labour left, helping to introduce a jobs miracle in this country, turning the economy around, I think he can be very very proud of.
So that's my view on Dave and what he's got to say.
LK: He's been pretty brutal about you...
BJ: Well. Really? I mean you know. I think that he has a lot to be proud of and there you go.

Three Tory MPs have resigned from the party to join an independent group, set up by former Labour MPs.
Anna Soubry, Sarah Wollaston and Heidi Allen wrote a joint letter to Theresa May to confirm their departure.
The three held a press conference, criticising the government for letting the "hard-line anti-EU awkward squad" take over the party.
The PM said she was "saddened", but her party would "always offer... decent, moderate and patriotic politics".
The pro-Remain trio will join the new Independent Group - made up of eight Labour MPs who resigned from their party over its handling of Brexit and anti-Semitism - saying it represented "the centre ground of British politics".
At a press conference on Wednesday, Ms Soubry criticised Theresa May for being "in the grip" of the Democratic Unionist Party and the pro-Leave European Research Group, and allowing Brexit to "define and shape" the Conservative Party.
She said: "The battle is over, the other side has won.
"The right wing, the hard-line anti-EU awkward squad that have destroyed every leader for the last 40 years are now running the Conservative Party from top to toe. They are the Conservative Party."
Ms Wollaston said she felt "great sadness" at quitting the party, but said Mrs May "simply hasn't delivered on the pledge she made on the steps of Downing Street to tackle the burning injustices in our society".
And Ms Allen highlighted her concerns around poverty, as well as Brexit, saying: "I can no longer represent a government and a party who can't open its eyes to the suffering endured by the most vulnerable in society - suffering which we have deepened whilst having the power to fix."
The three MPs said they will support the government on areas such as the economy, security and improvements to public services, and Ms Soubry defended the record of the coalition government - including the "necessary" austerity measures taken by chancellor George Osborne.
But they felt "honour bound to put our constituents' and country's interests first" over Brexit.
Watched by the eight other members of The Independent Group on the front row at the press conference, Ms Allen said she was "excited" about the future, adding: "I want to be part of something better, a party that people vote for because they want to, not because they feel they have to."
The departure of the three MPs - who all support the People's Vote campaign for another EU referendum - has reduced the government's working majority to nine MPs, and Ms Allen claimed there were "absolutely" other colleagues "keen" to join the group.
And the Independent Group now has more MPs in Parliament than the Democratic Unionist Party and equals the number of Liberal Democrats.
Today's departures are evidence of how serious Conservative divisions have become.
Right now, as with Labour, it's a splinter, not a split. But don't underestimate how hard a decision it is for any MP to abandon their tribe.
These departures illustrate, therefore, a real problem for the governing party.
Like Labour, the Tories have big questions they can't answer at the moment - profound quandaries that it's not clear their leaderships are ready, or perhaps even capable right now of meeting.
Mrs May said the UK's membership of the EU had been "a source of disagreement both in our party and our country for a long time", so "ending that membership after four decades was never going to be easy".
But, she added: "By delivering on our manifesto commitment and implementing the decision of the British people we are doing the right thing for our country."
Former Prime Minister David Cameron said he respected the decision of the three MPs, but disagreed with them, calling for "strong voices at every level of the party calling for modern, compassionate Conservatism."
Mr Cameron added: "Our party has long been able to contain different views on Europe. Everyone must ensure that can continue to be the case."
A Labour spokesman criticised The Independent Group, saying they had formed "what is effectively an establishment coalition based on the failed and rejected policies of the past", such as austerity, corporate tax cuts and privatisation.
But Liberal Democrat leader Sir Vince Cable said his party would "hold out the hand of friendship" to the group and said they already had "a good working relationship" with the MPs.
The Conservative party's deputy chairman, Tory MP James Cleverly, told BBC Radio 5 Live that the resignations were "very sad and disappointing", which was echoed by Communities Secretary James Brokenshire. But he added that the focus "has to remain on delivering Brexit" and the Conservative party was "a broad church and will remain so".
Work and Pensions Secretary Amber Rudd said it was a "great shame to have lost the commitment and undeniable talent" of the three MPs.
Remain-backing Tory MP Nicky Morgan said the party "should regret losing three such talented women from the Conservative Party".
Former Cabinet office minister, Damian Green, tweeted that he hoped the three MPs rejoined the party one day.
Some Labour MPs have been criticising their former colleagues for joining forces with ex-Conservatives.
Shadow education secretary Angela Rayner said it was "a new low" to see the MP of her home town, Ann Coffey, welcoming an MP responsible for government cuts, adding: "I'm utterly disgusted."
Scottish Labour MP Danielle Rowley also questioned her former colleagues, tweeting: "How people who once called themselves Labour can cosy up next to the likes of Soubry, smiling and laughing, is absolutely beyond me.
"I guess we now know how their policies and values differ from Labour."
Others have been criticising the group for not holding by-elections to win back their seats as independent MPs.
Douglas Carswell, who resigned from the Conservatives to join UKIP in 2014, tweeted: "When I changed parties it didn't occur to me to not hold a by election.  If my own electorate weren't supportive, what was the point?"
However, Ms Allen rejected calls for them to step down to contest by-elections, saying: "This is what the big parties do. They want to crush the birth of democracy. They want to crush people like us trying to change things for this country.
"This is the game, of course, they will play but we are better than that, and we think our constituents and the country deserve better than that."

The UK government has been told by Ireland to "stand by its commitments" on avoiding a hard border between Northern Ireland and the Republic.
Irish prime minister Leo Varadkar said an arrangement with a time limit would not be "worth the paper it's written on".
The border issue is the main barrier to progress between the two sides.
With time running out, Theresa May, who briefs her cabinet on Tuesday, has to get both the EU and her MPs on side.
The European Union's Brexit negotiator Michel Barnier has said divorce negotiations with the UK are not driven by a sense of revenge and that a no-deal, or a "hard" Brexit, would be a leap into the unknown for Britons living in the EU and EU citizens in the UK.
Speaking at an event in Brussels, Mr Barnier also said any Brexit deal had to maintain an open Irish border to protect peace on the island that has seen decades of sectarian violence.
The UK is due to leave the EU in March, and although 95% of the deal is said to be complete, the tricky bit is proving to be how to honour the commitment by both sides to guarantee no new hard border in Ireland.
It is an issue because after Brexit it will become the UK's land border with the rest of the EU, which has a single market and customs union so products do not need to be checked when they pass between member states.
There have been warnings that a hard border would undermine the peace process in Northern Ireland.
But unless negotiators can make decisive progress on how to guarantee no new visible checks, a special summit to finalise the UK's withdrawal will not take place.
There is disagreement on whether the "backstop" they have agreed to put in place should apply to Northern Ireland, or the whole of the UK - and on whether it can be time-limited or revoked by the UK.
Tory Brexiteers are concerned the UK could end up locked in a customs union with the EU without a fixed end point.
Writing in The Sun, former foreign secretary Boris Johnson said this would be an "absolute stinker" of a deal and warned of a "surrender to Brussels" with the UK staying tied to EU rules in years to come.
Mrs May has insisted that any arrangement would be "strictly time limited".
This, however, is not the view of the EU.
On Twitter, Irish Foreign Minister Simon Coveney said a time-limited arrangement - or one that could be unilaterally ended by the UK - would never get EU backing.
"Still necessary to repeat this, it seems," added the EU's deputy chief negotiator, Sabine Weyand.
And Mr Varadkar said the UK had agreed to a legally-binding "backstop" to apply "unless and until" it is superseded by a new agreement.
"I think it's reasonable for us to expect a country like the United Kingdom and a government like the UK government to stand by its commitments," he said.
Mr Varadkar described the UK as a "divided kingdom" over Brexit, saying this made it "very difficult to come to an agreement".
While the EU has objected to a time-limited UK-wide arrangement, its suggestion of a backstop that is specific to Northern Ireland has been ruled out by Mrs May who says it would undermine the integrity of the UK by creating a new border down the Irish Sea.
The prime minister says she does not think a "backstop" arrangement will be necessary as she wants to solve the border problem through the UK's long-term trade relationship with the EU, which has yet to be agreed.
Mrs May spoke to Mr Varadkar by phone on Monday morning "to take stock of the progress being made", Downing Street said, adding that: "In order to ensure that the backstop, if ever needed, would be temporary, the prime minister said that there would need to be a mechanism through which the backstop could be brought to an end."
The Irish government said Mrs May had "raised the possibility of a review mechanism for the backstop", and that Mr Varadkar had "indicated an openness to consider proposals for a review, provided that it was clear that the outcome of any such review could not involve a unilateral decision to end the backstop".
Meanwhile, 1,400 lawyers have signed a letter calling for another EU referendum to be held.
Among the signatories of the letter are Labour peer Baroness Kennedy QC, former Court of Appeal judge Konrad Schiemann and David Edward, a former judge at the European Court of Justice.
They say questions over the validity of the 2016 vote mean it should not be the public's final word, any more than the 1975 referendum on membership of what was then the European Economic Community.
In the earlier referendum, voters faced a clear choice between alternatives once negotiations had been completed, the lawyers said.
By contrast, during the 2016 vote, "the nature of the negotiation process and its outcome were unknown", said the letter.
"Voters faced a choice between a known reality and an unknown alternative. In the campaign, un-testable claims took the place of facts and reality."
The UK government has said asking the public to vote again would be a betrayal of the public's trust after the result of the referendum in 2016.
A spokeswoman for the Department for Exiting the European Union said that the government was confident of a "mutually advantageous" deal with the EU.
"The people of the United Kingdom have already had their say in one of the biggest democratic exercises this country has ever seen and the Prime Minister has made it clear that there is not going to be a second referendum," she said.

Irish Foreign Minister Simon Coveney has warned that the UK "cannot afford" to leave the EU without a deal.
Speaking to the Today programme Mr Coveney described talk of the UK "crashing out of the EU" as "bravado".
The UK is due to leave the EU on 29 March 2019 but has yet to agree how its final relationship with the bloc will work.
The White Paper on the UK's future relationship with the EU was published earlier this month.
Mr Coveney said the negative implications of a no deal Brexit are "very significant for Ireland and for the UK".
"I don't believe Britain crashing out of the EU without any agreed process is likely to happen.
"There is an obligation on me, and others, to instil some positivity into this negotiation process rather than political standoffs which is what we've seen to date".
Ireland's deputy prime minister said his government would back moves to lengthen the negotiating period by extending Article 50 if the UK government requested it, adding the deadline would only be extended if it was "necessary to get a sensible agreement".
Chancellor Philip Hammond said the UK was "well positioned" to get a good deal, and that he did not believe that there was a legal basis to delay Britain leaving the European Union.
Welcoming the publication of the White Paper, Mr Coveney said it gives the negotiating teams a degree of clarity.
"For much of the last six months effectively Britain has been negotiating with itself on Brexit.
"Now at least we have a White Paper where there's a clear British government position and the negotiation between the EU and the UK really starts now in earnest," he added.
Mr Coveney dismissed as a "simplistic notion" the idea that the only infrastructure in the event of a hard border would be from the EU.
"If the commitments given in December are followed through on then there will be no need for that external border of the EU to result in physical infrastructure.
"We will ensure that the commitments that we have been given around guarantees of no border structure or related checks and controls on the island of Ireland on the Irish border is followed through on," he added.

The big sticking point in the Brexit negotiations has been described as a "red herring" by one of the 10 Democratic Unionist MPs propping up Theresa May's minority government.
Sammy Wilson told the BBC World Service there was no "real problem".
The EU says there must be an arrangement to prevent physical checks on the 310-mile border between Northern Ireland and the Republic of Ireland.
So far, London and Brussels have failed to settle the issue.
This raises the prospect of the UK leaving the EU with no deal in March 2019.
Mr Wilson, the Democratic Unionist Party's (DUP) MP for East Antrim and the party's Brexit spokesman, said: "This is a red herring that's been thrown in to either string out the negotiations until there's a change in government in the UK, or to make the price of leaving the EU the break-up of the UK, or to keep the UK in the customs union and the single market".
The MP pointed to comments from the Irish Taoiseach (prime minister), Leo Varadkar, who said he had been given assurances about the border by the European Commission president Jean-Claude Juncker.
In July Mr Varadkar said: "President Juncker and my EU colleagues have on many occasions said that they wouldn't require us to put in place a physical infrastructure and customs checks on the border between Northern Ireland and Ireland."
President Juncker's office refused to say whether he had made such an assurance, saying simply it would not comment on the ongoing negotiations.
Sammy Wilson added: "There's no real problem, as the EU have now confirmed. If they say in the event of no deal, we'll not be putting up any border, then what's the issue?"
A spokesperson for the Taoiseach said: "The British government, the Irish government and the European Union have all made clear, repeatedly, their determination to avoid a hard border on the island of Ireland following the UK's withdrawal from the EU."
So why all the discussion then?
The EU wants a so-called backstop arrangement, an insurance policy, to ensure the border on the island of Ireland continues to be open if the UK and EU can't agree a future trade deal or a technological solution.
That could include keeping Northern Ireland in the EU customs union and tied to some rules of the single market.
Theresa May has previously said any proposals for a common area across the Northern Ireland border would "undermine the UK common market and threaten the constitutional integrity of the United Kingdom".
And DUP MPs have warned they would vote against any Brexit deal that treats Northern Ireland differently to the rest of the UK.
"We don't want to change the government; we simply want to change its policy.
"If that means the current leader falls by the wayside, that's an issue for the Conservative Party, not for us," said Mr Wilson.
Ireland's deputy prime minister, Simon Coveney, told the BBC in October that the UK must stick to promises around the border backstop that it made last year, saying, "Britain has signed up to in writing... a backstop".
"We do need to insist on the commitments the prime minister has made to Ireland and to the EU around providing guarantees there could never be physical border infrastructure," he said.
"There needs to be a backstop unless and until something better can be negotiated," Mr Coveney said.
When discussing Theresa May's agreement to a backstop for Northern Ireland last year, Sammy Wilson said, "The mind boggles that anyone can be so stupid".
Theresa May recently said 95% of the Brexit deal has been agreed.
Sammy Wilson said that claim should be treated cautiously.
"Although the prime minister might think she's 95% of the way there, the captain of the Titanic thought he was 95% of the way to his destination.
"He didn't quite reach it because an iceberg hit them on the way there. There are huge icebergs sitting in the way of this deal at present," he said.
At the moment, people, goods and services move freely across the land border in Ireland.
The UK and Ireland are both part of the EU, so products do not need to be checked to make sure they comply with customs and standards rules.
If there is no Brexit deal, companies exporting goods to the EU "will be required to follow customs procedures in the same way that they currently do when exporting goods to a non-EU country," according to UK government advice for businesses.
A lot of this work would be done electronically, away from the border.
The guidance says exporters will need to apply for a UK Economic Operator Registration and Identification (EORI) number, consider engaging the services of a customs broker, submit export declarations to HMRC and apply for any relevant export licences.
The Irish Revenue has issued similar advice to companies about new customs processes.
"In the post-Brexit era the administrative and fiscal burden on the traders involved cannot be underestimated," an advice document states.
Under World Trade Organisation rules, countries cannot normally discriminate between their trading partners unless there is a formal trade deal.
So a no-deal Brexit would mean, for example, that Irish products would have to be treated the same way as goods from the US or China.
"Grant someone a special favour and you have to do the same for all other WTO members," says the organisation.
That reduces the ability of the UK and the Republic of Ireland to treat each other's products more favourably than those from other nations.
That is why talks about the Irish border are seen as so important.

The Irish government is to hold an all-island forum examining the implications of Brexit later on Monday.
The meeting will be hosted by the Taoiseach (Irish prime minister), Leo Varadkar, and his deputy, Simon Coveney.
It will be the fourth time the forum has met since it was set up following the EU referendum in June 2016.
The Democratic Unionist Party (DUP), who supported Brexit, has always said there is no need for the forum.
Monday's meeting will take place at the Dundalk Institute of Technology, with representatives from the other main political parties expected to attend.
The EU's Brexit negotiator, Michel Barnier, will also attend the event to give an update on the state of the overall negotiations.
Mr Barnier will also visit Northern Ireland on Monday and Tuesday, and he will meet politicians and cross-border business owners in Londonderry, Letterkenny and Dungannon to discuss what impact - if any - a future deal with the UK could have on border towns and cities.
The question of what will happen to the Irish border after Brexit has been a sticking point throughout the talks, with no solution so far.
The Irish government first proposed an all-island forum in the wake of the EU referendum result in June 2016.
It said its priorities for the forum are the Irish economy and trade with the UK, the peace process and Northern Ireland and the Common Travel Area (CTA) between Ireland and the UK.
Last week, tensions grew between the Irish government and the DUP, after the party's deputy leader Nigel Dodds accused the Irish government of being "aggressive" in its approach to Brexit.
Although the UK voted overall to leave the EU, a 56% majority in Northern Ireland wanted to remain.

The number of British applications for an Irish passport has boomed following the UK's vote to leave the European Union.
Some UK residents are entitled to an Irish passport if their parents or grandparents were born in Ireland.
In 2015, the year before the Brexit vote, more than 46,000 applications were lodged from Britain - excluding Northern Ireland.
By the end of 2017 that number had nearly doubled to 81,000.
In an earlier version of this story, the BBC wrongly reported there had also been a surge in the number of rejections of British applicants.
A discrepancy between the number of applications made and passports issued through the London embassy amounted to some 15,000 people. However, Ireland's Department of Foreign Affairs said that figure did not represent the number of passport applications refused.
Instead it reflects the fact that not all applications from residents are submitted via the London embassy, it said.
The actual number of rejected applications is not clear. Applications can be rejected for a range of reasons including incomplete applications or uncertain identity.
Citizens of the Republic of Ireland, an EU member state, will retain visa-free travel benefits after Brexit, no matter the outcome of the UK's negotiations with the EU.
In the first five months of this year, almost 45,000 British people had requested an Irish passport,  according to figures from Neale Richmond, Chair of the Irish Senate's Brexit committee.
London's Irish embassy has issued more than 176,000 since 2016 - more than 10 times that of any other office.
Mr Richmond said embassy staff were expecting 2018 to be the busiest year ever.
Each application for a standard 10-year passport costs €80 (£71).
You can claim an Irish passport (or Irish citizenship) if:
Several other exemptions apply for those resident in Ireland for extended periods, adoptions, children of refugees, and other special circumstances.
There has also been a surge in applications from Northern Ireland, where most UK citizens are automatically entitled to an Irish passport if they so wish.
Senator Richmond's figures show that applications from there grew from 53,715 in 2015 to 82,274 in 2017.
Excluding Northern Ireland, Mr Richmond said at least 10% of Britain's population were thought to qualify for an Irish passport.
"In light of Brexit many including a number of my own family members are staking their claim," he said - and "there is no sign of this rush for Irish passports abating."

The UK should not seek convergence with EU regulations after Brexit, the DUP's Ian Paisley has said.
A Times newspaper story says Britain is prepared to offer to avoid any divergence in trade rules between Northern Ireland and the Republic.
The paper says it would devolve a package of powers to Northern Ireland to enable customs convergence on areas like agriculture and energy.
Mr Paisley said matching "red tape" was not the way ahead.
According to the paper, the government's offer would enable customs convergence in areas such as agriculture and energy.
It adds that sources in Dublin said there had been "movement" on the issue, and there was confidence a deal could be reached at the EU summit in December.
"We are not about convergence here, we are about co-operation," said the North Antrim MP.
"(Northern Ireland) will continue to trade with out biggest partner, which is the rest of the UK and I imagine that given the UK is one of the Republic of Ireland's largest trading partners that (the Republic) will want to continue to trade with us.
"We're not about stopping that, but I'll tell you what, if you try to prevent part of the United Kingdom from leaving the EU, or trip us up, that will reflect very badly on the deals that we do after we leave."
Mr Paisley is one of 10 DUP pro-Brexit MPs who are propping up Theresa May's minority government on key votes.
The EU is concerned about how it can protect the integrity of the single market if goods which do not comply with its standards are imported across a future open border within Ireland.
However, unionists and government ministers have strongly resisted the idea that there should be any checks on trade between Northern Ireland and Great Britain - claiming this would disrupt the UK's own home market.
The suggestion of regulatory changes were welcomed by Joe O'Reilly, Fine Gael spokesman on foreign affairs and trade in the Irish Senate, who said they would represent "a massive move towards a frictionless border".
"To have a different tariff regime would very adversely affect agriculture and a lot of other local industries and have a huge effect in a border context," he added.
Some sources have urged caution about the Times report, which implies the devolution of extra powers to a Northern Ireland executive that currently does not exist.
The EU has said "sufficient progress" has to be made on the Irish border before negotiations on a future relationship can begin.
Downing Street has said the whole of the UK will leave both the customs union and the single market when it leaves the EU in 2019.
European Council President Donald Tusk is set to meet Irish prime minister (taoiseach) Leo Varadkar in Dublin on Friday, while British Prime Minister Theresa May is due to have talks with European Commission President Jean-Claude Juncker on Monday.
Irish minister for agriculture, Michael Creed, said on Thursday that the talks on Brexit were at a critical point and described it as "squeaky bum time".
He told Irish national broadcaster RTÉ that the border was the most complex issue and it was incumbent on the British government to deliver a roadmap on how a "frictionless border" can be achieved.
Addressing the issue, Northern Ireland Secretary James Brokenshire said Mrs May had "been very clear in saying that as we leave the European Union, we leave the single market and we leave the customs union".
"But we know that there need to be specific outcomes to meet the unique circumstances of Northern Ireland and the island of Ireland as a whole," he added.
"That's why we have focused on a number of different issues on the way in which the trade approaches work and we want a bold and ambitious free trade agreement and equally looking at the customs arrangements with either a highly streamlined customs approach or, indeed, a new customs partnership with the EU. "

When Theresa May pulled the "meaningful vote" on Brexit last month, the day before MPs were about to pass their verdict on her deal, Downing Street hoped two things would happen.
First, that the EU would offer some form of legal guarantee that the Northern Irish backstop - the arrangements for avoiding a hard border on the island of Ireland - would be temporary.
This, in turn, would bring the DUP on board - and unlock further support from previously hostile Conservative backbenchers.
Second, that some sceptical MPs, once away from the febrile atmosphere at Westminster, would quietly reflect over Christmas that the deal wasn't as bad as all that, as it at least guarantees that the UK will leave the EU at the end of March.
So perhaps any rebellion would diminish, if not evaporate.
But neither hope has - yet - been realised, with the vote now less than two weeks away.
So as things stand, the prime minister is once again facing defeat.
But her difficulties could run even deeper than assumed.
It was undoubtedly disappointing for Downing Street that the DUP's Westminster leader Nigel Dodds declared that the Withdrawal Agreement "flies in the face" of the government's commitments on Northern Ireland following his meetings with Theresa May and the Conservative chief whip Julian Smith this week.
The government quite simply couldn't tell him that that the EU, at this stage, was willing to go any further than offering "reassurances" and "clarifications" on the temporary nature of the backstop, rather than legal guarantees.
But even if the EU does move significantly in the next ten days, the prime minister could still be facing defeat.
What the DUP's Brexit spokesman Sammy Wilson said on BBC Radio 4's Today programme on Friday was significant.
He said he was "alarmed" that the Northern Irish backstop could become the "settled arrangement" on Brexit.
Let's unpick this for a moment - because it goes to the core of Theresa May's difficulties.
The DUP want to make sure the backstop is temporary and that the UK, including Northern Ireland, can exit from it without EU approval.
If the EU can guarantee this, it's possible the DUP's MPs may grit their teeth and back - or abstain on - the deal, as would some long-standing Leave campaigners on the Conservative benches.
But, as I understand it, up to 40 Conservative MPs still wouldn't back the deal because they, like Sammy Wilson, are worried about what the "settled arrangement" on Brexit might look like.
They believe that the way the government will avoid a hard border in Ireland - and avoid triggering the backstop - is by agreeing a permanent trade deal that actually looks a lot like the backstop in any case.
That is, the whole of the UK, not just Northern Ireland, would mirror some EU regulations on goods and stay close to the EU's customs arrangements.
This would, they fear, then constrain the UK's ability to do future trade deals with the rest of the world.
This suspicion is fuelled by the following words in the political declaration document - the blueprint for the post-Brexit relationship with the EU:
"The economic partnership should ensure….ambitious customs arrangements that.. build and improve on the single customs territory provided for in the Withdrawal Agreement."
Downing Street officials have pointed out - until they are almost blue in the face - that the political declaration also specifically mentions an "independent trade policy" for the UK.
But this doesn't appear to have neutralised some backbench concerns.
The prime minister will launch a "charm offensive" with Conservative MPs next week to try to allay any suspicions - though whether they will be charmed or offended is still an open question.
Such is the lack of trust amongst a small but potentially crucial contingent of her MPs, I am told that in order for them to vote for her deal, she would need to convince them that she wouldn't handle the future trade negotiations after Brexit.
And/or give them a firm date for her departure from office.
Downing Street - and more widely, the government's - tactic is to raise the possibility of No Brexit unless long-standing Leave campaigners hold their noses and vote for her deal.
This process has already begun. But expect it to be ramped up next week.
The PM's allies will argue that unless the deal is settled soon, then opponents of Brexit and supporters of a new referendum will try to amend forthcoming non-Brexit legislation to make it contingent on a public vote taking place.
And MPs who don't want a referendum but do want Theresa May's deal fundamentally renegotiated will be told that would mean extending Article 50 and therefore, in No 10's eyes, breaking faith with leave-supporting voters.
So far these arguments don't seem to have worked.
Some of her MPs will doubtlessly be poring over a YouGov survey published today. This was commissioned by London's Queen Mary University and Sussex University as part of a wider project into party members' attitudes and views.
It suggested more than half of Conservative members - 53% - believe Mrs May's deal doesn't respect the result of the referendum. And 59% of them oppose her deal, while 38% support it.
No 10 would argue that there is private polling which suggests her deal is more popular with the wider public.
The You Gov survey itself suggests that 46% of likely Conservative voters (as opposed to members) back the deal, with a smaller number - 38% -opposing.
There is another potential fly in the ointment for the prime minister - although here, adversity could be turned to advantage.
It is assumed that the Lords will insert an amendment in to legislation on trade which would require the prime minister to negotiate a customs union with the EU.
The government, in the normal run of things, would then vote this change down when the legislation returns to the Commons.
But with Labour formally backing a customs union - and some Conservative MPs who backed Remain in the referendum also very warm to the idea - government sources are concerned that the Commons might not overturn it.
So the argument that is likely to be made by government whips to the Brexiteer opponents of Theresa May's deal is this: Unless they grab the prime minister's deal before the trade legislation comes to the Commons, they might be landed with a customs union.
And this wouldn't just constrain, but prevent, future independent trade deals.
But the most likely option for at least reducing the size of any defeat on the deal is further movement from Brussels.
The prime minister is talking the EU Commission President Jean Claude Juncker later and I am told she will be talking to other EU 27 leaders over the next ten days.
There is a feeling in Whitehall that it may take more than one attempt to get the deal through parliament.
One government insider likened the prime minister's situation to a game of American football.
Things can look chaotic at any given moment but as long as you don't give the ball away to your opponents you can move incrementally towards your goal.
But she has already had to make one backward pass - delaying the vote on her deal - and may need some trick play to get her deal over the line.
As MPs return to parliament next week, the prospect of a prime ministerial victory appears some way off.

Is it really leaving at all?
"I don't think so."
Forget the politicking and the crazy, bitter briefings.
If the past few weeks has been like watching the Conservative Party have a nervous breakdown in front of our eyes, this morning they are truly losing the plot.
Set aside the psychodrama about minicab cards, late night phone calls, toasts over dinner at Chequers, a foreign secretary no one can find. More of that later no doubt.
What sticks out the most from my interview with David Davis this morning is a very simple question we asked. Is the prime minister's plan really leaving the EU?
"I don't think so", he said.
That is the sentiment that's widely shared among the Tory party, and perhaps among many voters too. And guess what? It doesn't always matter which side of the referendum they were on either.
Some former Remainers say "look, this is a dodgy compromise, what's the point? If we are going to do this, then for goodness sake let's do it properly or just stay in".
From some Leavers, like Mr Davis, you also get "look, this is a dodgy compromise, what's the point? If we are going to do it, then for goodness sake let's do it properly".
Yes, I did mean to write the same line twice just then. We are a million miles from Tory unity, but weirdly there is some agreement at the fringes of the party that the current compromise is, as compromises so often are, something that pleases hardly anyone.
And it would be better for No 10 just to go the "full Norway", a close relationship with the EU not a Viking experience, or the "Canada plus", a free trade agreement not a ten-day tour of the Rockies, or frankly, not leave at all.
David Davis' resignation on its own - so far - is not going to bring down the government. It could well unleash a host of events that leads us to that place, but we're still a long way from that.
But what it does do is take the lid off the boiling pot of frustration, angst, ambition and despair you find in pockets of the governing party and a sense on both sides that this kind of Brexit might not be worth it. That's not to say most Tory MPs are in the mood for a giant ruckus.
Most of them in fact probably back the Chequers compromise, grateful at last that the Cabinet - well most of them - found agreement.
And believing, quite possibly correctly, that the vast majority of the public aren't paying attention to much of the flouncing in any case, so can ministers please, please, please, please, get on with it and just shut up.
For Number 10, the Chequers plan is a clever enough compromise they believe can get the EU on to the next phase of negotiations.
Remember - all of this is happening in order that officials can get down to actually negotiating the nitty-gritty of the long term relationship.
It is perfectly possible that within 72 hours or so it is situation normal, well normal-ish.
But David Davis was an "active backbencher", who delighted in making waves on the issues he cares about for many years.
If he thinks Theresa May's Brexit does not mean Brexit, expect plenty of trouble ahead even if today's particular storm passes before the heat wave breaks.

In the last six days  you might have been enraged, you might have been shocked, you might have been excited, or you might have just shrugged your shoulders.
But we are watching a conflict over an issue that is based on what one cabinet minister described as "love and passion" - politically, at least.
The grinding three years of the previous period of Brexit conflict has been superseded in the last week by a hyper-speed helter-skelter, with a new administration, long aware their stance could end up in a battle in the courts.
As MPs reluctantly pack up for a break of five weeks after the prime minister sent them packing, can we conclude anything lasting from this bout?
Boris Johnson has undeniably had a rude awakening of how Parliament will respond to him.
It's been a shocker in terms of early defeats for the new prime minister, an unsurprising but dramatic series of clashes between a leader who wants to keep the option of leaving the EU without a deal on the table, and most MPs who don't want to allow him to open that Pandora's box.
Number 10 has also indulged in tactics that have alarmed many Conservatives, including some of Boris Johnson's team who sit around his cabinet table.
If you had followed the way that Vote Leave ran its campaign, the subsequent appointment of Dominic Cummings and some of its former staffers, again, that shouldn't surprise you.
But there are unquestionably plenty of Conservative MPs who have been horrified that it's this version of Boris Johnson, a politician with many guises, that's in charge at Number 10.
And some of those tactics have been, at least temporarily, destructive, with a voluntary surrender of his own majority. (Interestingly, there's a whisper that a way back could soon emerge for some of the 21 MPs who were booted out.)
That "long shopping list" of errors, according to one member of the cabinet, means the prime minister's self-imposed Halloween Brexit deadline looks further out of reach than a few short days ago.
Is it impossible? Absolutely not.
There is the possibility, still, of a deal, with Number 10 today stressing it was still their primary aim.
Whispers again about a Northern Ireland only backstop, and a bigger role for the Stormont assembly, if it ever gets up and running, are doing the rounds.
Some MPs, and some diplomats are more cheerful now about the possibilities of it working out.
If you squint you can see the chance of an agreement being wrapped up at pace, although it seems the chances range somewhere between slim and negligible.
It is still possible too, as Number 10 bombastically suggests, that they could just ignore the demand from Parliament that he seeks a delay if there is no-deal.
This is not as straightforward as ignoring a parking ticket, of course.
But if the prime minister asks formally, but politically makes it clear he doesn't want it and would do nothing with it, would the EU really force such a policy on an unwilling government with no political reason given? What if the EU was to offer only an extension of several years?
These are not predictions, but they are imponderables, talking about a political landscape that is some weeks off, and there are all sorts of political gymnastics to come before then that could again turn the situation on its head.
And for all that Parliament protests, some Brexiteers, including in Number 10, glory in 'evidence' they could use in an eventual election campaign that tries to pit MPs against the people.
No question, however, it's been a bruising period for the prime minister, which could be the beginning of a very rapid downfall.
But just as so many things in politics have changed in the last few years, some of the old truths remain.
A week is still a long time in politics - the seven weeks before Halloween another age.

The EU's "relative silence" about the kind of post-Brexit relations it wants with the UK must end, Philip Hammond is to tell German business leaders.
There is "little, if any signal" from the EU about its priorities for talks on future co-operation due to begin in March, the chancellor is claiming.
"They say it takes two to tango," he will say in in Berlin. "Both sides need to be clear about what they want."
The EU has warned the UK cannot cherry-pick the kind of arrangement it wants.
The second phase of Brexit negotiations, covering transitional arrangements after the UK leaves in March 2019 and future economic and security co-operation, are set to begin officially in March.
However, internal discussions within the EU about the framework of future relations have already begun following December's first-phase agreement on so-called divorce issues, like money and citizens' rights.
Mr Hammond and Brexit Secretary David Davis are aiming to lay down a marker for the talks ahead when they address the Die Welt Economic Summit.
In his speech, the chancellor will say the EU must "put behind" it any talk of punishing the UK for voting to leave the 28-member bloc and concentrate on maximising the mutual benefits of close co-operation in areas such as defence, education, science, technology and culture.
"I know the repeated complaint from Brussels has been that the UK "hasn't made up its mind what type of relationship it wants," he will say.
"But in London, many feel that we have little, if any, signal of what future relationship the EU27 would like to have with a post-Brexit Britain."
Earlier on Wednesday, in a joint-article for the Frankfurter Allgemeine newspaper, the two men argued that financial services were pivotal to the "bespoke" Brexit trade deal wanted by the UK.
They acknowledge that their stated objective of leaving the EU's internal market and customs union means the UK will not be able to enjoy all the benefits it currently does as a member of the EU after leaving.
Kamal Ahmed, BBC business editor
He is taking his message to the heart of Europe.
In a speech to business leaders in Berlin tonight, the chancellor will say it is time for the European Union to engage more positively in the Brexit negotiations. And stop talking about "punishing" the UK over Brexit.
After months of grumpy noises from Brussels over a perceived lack of clarity from the UK, Philip Hammond will say that Britain needs to hear about the ambition the EU has for a deep trading relationship with the UK.
My sources point out that with Australia, Canada and America all making positive overtures about free trade agreements with Britain, the lack of a similar offer from the EU could lead to unintended consequences.
Logically, "no deal" could be one of those. And certainly the present tone of the debate from the EU is damaging the chances of a positive outcome of the Brexit negotiations, my sources say.
Read Kamal's full blog
But they insist the EU's desire to protect the integrity of the single market for its other 27 members is "not inconsistent" with the UK's desire for the most comprehensive agreement possible.
"It makes no sense to either Germany or Britain to put in place unnecessary barriers to trade in goods and services that would only damage businesses and economic growth on both sides of the Channel," they write.
"So as Brexit talks now turn to trade, the UK will look to negotiate a new economic partnership with the EU - the most ambitious in the world - that recognises the extraordinary levels of interconnectedness and co-operation that already exist between us.
"We should use the imagination and ingenuity that our two countries and the EU have shown in the past, to craft a bespoke solution."
The UK's preferred model for a post-Brexit deal is what Mr Davis has described as Canada plus, plus, plus - a reference to Canada's low-tariff free trade deal with the EU but with services included as well as goods.
The two men make clear in the article that unrestricted trade in services - which makes up about 80% of the UK economy - will be pivotal to any successful deal, as will financial and regulatory co-operation within Europe.
The EU's chief negotiator, Michel Barnier, has warned the UK it cannot hope to get a special deal for the City of London and that its options have narrowed as a result of it turning its back on the single market.
UK-based banks and financial firms are worried they will lose the passporting rights that allow them to trade freely in the EU after Brexit - an outcome that is likely to see firms moving jobs to the continent.
Separately, International Trade Secretary Liam Fox has urged Conservative backbenchers to not view everything through the "prism of Brexit", says BBC political correspondent Iain Watson.
Dr Fox told the 1922 Committee of backbench Tory MPs on Wednesday to focus on the "bigger picture", pointing to an increase in UK manufacturing orders and expectations that the economy will grow in the next quarter.
He said there was a political danger in suggesting events were "because of" or "despite" Brexit because the government could lose credit for the economic recovery - that it would not "own" the recovery.
He is also believed to have told his Conservative colleagues that Labour remained in a state of confusion on Brexit and that some of their voting record on the withdrawal bill could be used as a weapon against them in key constituencies.

The minister responsible for Brexit has told the EU to "get real" and reach a deal with the UK.
Dominic Raab also said EU chiefs had disrespected Theresa May with "jibes" at a recent summit.
He said the UK would leave without a deal rather than be "bullied" into signing a "one-sided" arrangement.
Meanwhile EU figures hit back after Foreign Secretary Jeremy Hunt likened it to a Soviet-era prison, comments diplomats called "insulting".
In a speech to the Conservative conference on Sunday, Mr Hunt compared what he said were the EU's attempts to stop members leaving with the actions of the Soviet Union during the Cold War.
His words were criticised by a number of European politicians and diplomats while a European Commission spokesman suggested everyone "could benefit from opening a history book from time to time".
Speaking in Birmingham on Monday, Mr Raab said the government's proposed deal with the EU was not "perfect" but he urged Tory Eurosceptics who are campaigning for the plan to be ditched to get behind it.
And Chancellor Philip Hammond predicted that there would be an economic bounce if and when a Brexit deal was agreed by the UK and the EU.
He reminded people saying that a deal could not be struck that people had had the same scepticism about the electric light bulb ever working.
With less than six months to go before Brexit day, the UK and the EU have not yet reached a deal on how separation will be managed and what their new relationship will look like.
Mr Raab said that if the EU insisted on trying to "lock us in via the back door" of its customs union and single market, the UK could be left with "no choice" but to leave without a deal.
The "whole of the government machine is busy preparing for no deal" - not because they want it to happen or because it's likely, but "because it might happen", he said.
He dismissed "lurid predictions from the prophets of doom" about no-deal, including planes being grounded and ports blocked.
Even if the UK did not reach an agreement with the EU, he said: "I find it hard to believe that they would, for narrow political ends, seek to punish Britain in such a crass and counterproductive way."
Mr Raab criticised the EU over its reaction to Theresa May's proposals at last month's summit in Salzburg.
"Our Prime Minister has been constructive and respectful," he said.
"In return we heard jibes from senior leaders, and we saw a starkly one-sided approach to negotiation."
Brexiteers feel it keeps the UK far too close to Brussels and doesn't fulfil the Leave campaign's promise during the 2016 referendum campaign to "take back control".
EU leaders have rejected the plan because they believe it would undermine the single market by allowing the UK to "cherry pick" from EU law.
Theresa May says the ball is now in the EU's court and she wants a more detailed response from them on their objections.
The government has said it will not agree to anything that divides Northern Ireland from the rest of the UK nor makes the country a member of the European Economic Area like Norway.
One of the most vocal critics of the government's Brexit approach has been former foreign secretary Boris Johnson, who branded Theresa May's plan "deranged" in a newspaper interview at the weekend.
Despite not being in Birmingham, Mr Johnson made an eye-catching appearance as he was photographed running through fields near his Oxfordshire home.
Given that Mrs May famously said her naughtiest moment was running through fields of wheat as a child, some pundits are wondering whether this was an attempt to "troll" the PM by the former Leave campaign frontman, who resigned in protest at the Chequers plan in July.
Jeremy Hunt has seemingly provoked a diplomatic row after accusing the EU of seeking to punish the UK in order to "keep the club together".
In Sunday's speech, he recalled a visit to Latvia earlier this summer and the role that the UK and others played in helping it transition from Soviet rule to becoming a modern democracy and market economy.
"What happened to the confidence and ideals of the European dream?", he asked. "The EU was set up to protect freedom. It was the Soviet Union that stopped people leaving."
Guy Verhofstadt, the European Parliament's Brexit co-ordinator, tweeted that the remarks were "outrageous and offensive".
And EU Commissioner Vytenis Andriukaitis suggested Mr Hunt needed a history lesson.
Also on the conference stage on Monday, Mr Hammond warned that slow wage growth and job insecurity meant too many people feared they were being left behind.
He announced the government's intention to increase the number of people who can access science and technology courses and spend about £30m on encouraging big business to mentor small firms.
His plans also included a £125m package allowing large employers to transfer up to 25% of their apprenticeship levy funds to businesses in their supply chain from April next year.
The apprenticeship levy is a tax on large companies intended to pay for training at smaller companies, but uptake of the new policy has been slow.
Mr Hammond rejected suggestions that Brexit had caused an irreparable rift between his party and business, telling activists the Conservatives were and "always will be the party of business".

Prominent Brexiteer Jacob Rees-Mogg has accused Treasury officials of "fiddling the figures" on Brexit to keep the UK in the European Union customs union.
It comes amid claims, which the Treasury has denied, that it had deliberately created an economic model that made all other options look bad.
The FDA union, which represents civil servants, attacked the MP for peddling "unsubstantiated conspiracy theories".
The Treasury said it was working hard to deliver the best deal for Britain.
Conservative MP Mr Rees-Mogg told BBC Radio 4's Today programme: "If you look at the forecasts the Treasury made before the referendum, they were a humiliation.
"They were clearly politically influenced."
But FDA general secretary David Penman said the comments were "clear evidence" that the MP was "prepared to sacrifice anyone or anything on the altar of his own ideology".
He told the BBC Theresa May had to "get a grip on both her ministers - who are peddling these myths as well - and on Conservative politicians".
He said it should be the prime minister or Cabinet ministers defending the civil service - not him, and called for an end to "constant swiping at the messenger" which was undermining trust in the government and the civil service.
The Treasury said that both the prime minister and the chancellor have repeatedly stated the UK will be leaving the single market and the customs union and that "any suggestion to the contrary is simply false".
Mr Rees-Mogg said former chancellor George Osborne had set up the Office for Budget Responsibility, which provides independent analysis of the UK's public finances, because Treasury forecasts "had been politicised".
"And it was thought they were unreliable on political grounds," he added.
"With the referendum and with the EU, the Treasury has gone back to making forecasts.
"It was politically advantageous for them in the past. It is the same now.
"So yes, I do think they are fiddling the figures."
By BBC political correspondent Matthew Cole
This is more than a row about a backbench MP challenging Treasury figures he doesn't like.
Jacob Rees-Mogg leads a section of MPs on whom Theresa May's future might depend.
That bloc - the Tories' European Research Group - are vehemently opposed to the UK staying in ANY form of customs union with the EU after Brexit.
This week, key ministerial meetings will take place on that very subject, with Theresa May known to be against staying in THE customs union, but open-minded to setting up a less expansive arrangement.
So Jacob Rees-Mogg's intervention could be taken as upping the ante, exerting extra pressure on Mrs May ahead of this big week, which could provide crucial answers to our future relations with the EU, and to the prime minister's future.
His comments came after Theresa May, on the final day of her official visit to China, appeared to suggest some sort of customs agreement with the EU could be possible - even though ministers have said Britain will leave the existing customs union.
Mr Rees-Mogg stated any such deal would be unacceptable to Tory Brexiteers as it would prevent the UK from striking free trade deals with other countries.
"We need to be free to do deals with the rest of the world," he said.
"We must be out of the protectionist common external tariff which mainly protects inefficient EU industries at the cost to British consumers."
It is the second time this week that Mr Rees-Mogg has condemned civil servants' economic forecast concerning the impact of Brexit.
The row began on Tuesday with a report leaked to Buzzfeed which said growth would be lower in each of three different Brexit outcomes than if the UK had stayed in the EU.
The government said its preferred option however - a bespoke deal covering trade and financial services - was not among those analysed in the leaked paper.
But in the Commons on Thursday, Mr Rees-Mogg asked Brexit minister Steve Baker to confirm whether he had heard that officials were deliberately trying to influence policy in favour of staying in the EU customs union.
He attributed the remarks to Charles Grant, the head of the Centre for European Reform.
On Friday, Mr Baker apologised to MPs for saying Mr Rees-Mogg's account of the remarks was "essentially correct".
Mr Grant had denied making them and an audio recording emerged where he did not say what was attributed to him.
However, Mr Rees-Mogg said he stood by his original claim.
Mr Grant told the BBC he was surprised that Mr Rees-Mogg had not apologised to him.
Lib Dem leader Sir Vince Cable called Mr Rees-Mogg's claims about the Treasury "absolutely outrageous".
"The government should be thinking about all possibilities and how to minimise the damage from Brexit," he said.
"Serious Conservatives inside and outside government are saying that whatever happens with Brexit, we should remain in a customs union.
"The Treasury would be failing in its duty if it didn't examine that possibility seriously; we should be inside a customs union whatever happens."

A man who sent "threatening" emails to seven MPs, including two ex-cabinet members, has been jailed for 42 weeks.
Jarod Kirkman, 51, used a fake email address to target a cross-party selection, including Nicky Morgan, Yvette Cooper and Heidi Allen.
Kirkman, of Torquay Drive, Luton, had admitted sending malicious communications at Westminster Magistrates' Court on 8 April.
Ms Morgan said the messages were death threats "related to Brexit".
Prosecutors said malicious emails were sent to Labour MPs Ms Cooper and Jenny Chapman, Conservative Ms Morgan, former Tory Nick Boles, as well as Sarah Wollaston, and Heidi Allen interim leader of the Independent Group.
Kirkman also pleaded guilty to a charge of racially or religiously aggravated intentional harassment against Labour MP David Lammy.
The messages were sent between 4 December and 21 January, police said.
The court heard his first email was sent to Ms Allen, MP for South Cambridgeshire on the 4 December 2018.
Using the address mp@deadpoliticianwalking.com, Kirkman contacted Mrs Allen via her constituency "contact form".
In it he wrote, "your days are numbered" before musing about whether she would die from polonium or Novichok poisoning.
Following subsequent emails sent to six other MPs, he was arrested on 29 January of this year.
Kirkman told police he was "just being a stupid idiot over Brexit" and had "no intention of carrying out the threats".
The court heard he described himself  as a "passionate pro-leaver"
Following sentencing, Ms Allen said: "MPs are doing a job like everybody else and we deserve to feel safe in our work.
"I hope this judgement will act as a powerful message to anybody who thinks that they can threaten us anonymously or otherwise."
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The president of the European Commission has said claims he wants to create a European "superstate" are "total nonsense".
Jean-Claude Juncker said some Britons wrongly saw him as a "stupid, stubborn federalist".
He was responding to a speech about Brexit by UK Foreign Secretary Boris Johnson.
Mr Johnson said the EU wanted to create an "overarching European state" and that integration was deepening.
"British politicians, Labour and Tory, have always found that ambition very difficult," Mr Johnson said.
"It is hard to make it cohere with our particular traditions of independent parliamentary and legal systems that go back centuries."
Asked about the foreign secretary's remarks, Mr Juncker replied: "Some in the British political society are against the truth, pretending that I am a stupid, stubborn federalist, that I am in favour of a European superstate.
"I am strictly against a European superstate. We are not the United States of America, we are the European Union, which is a rich body because we have these 27, or 28, nations.
"The European Union cannot be built against the European nations, so this is total nonsense."
Analysis by BBC Brussels correspondent Adam Fleming
As Boris Johnson spoke, the European Commission president Jean-Claude Juncker was holding a press conference in Brussels, completely by coincidence.
He was in typically jolly mood, joking about the drinks EU leaders order at European summits. But the laughing stopped when a British journalist asked him about the foreign secretary's suggestion that there was a plan to build an EU superstate.
"Total nonsense," said President Juncker, who complained that the British political class always misrepresents him.
But he had just spoken about plans for a bigger EU budget and his dream of a directly-elected president of the EU, which some might say made Boris Johnson's point for him.
The foreign secretary's speech has been noted in Brussels - particularly his reference to organic carrots - but negotiators are waiting for the UK to adopt a formal position about its post-Brexit relationship with the European Union.

Jeremy Corbyn is "open to" using legislation to prevent a no-deal Brexit if his plan to overthrow the government in a vote of no confidence fails, the BBC has learned.
The Labour leader is understood to have had a discussion with the SNP on Friday over passing a law to extend Article 50, which would delay leaving the EU.
Several Labour figures believe the plan could gain a majority in the Commons.
PM Boris Johnson says the UK will leave the EU on 31 October "do or die".
He added that, even though he wants a deal with Brussels, Brexit will go ahead if one is not agreed.
Mr Johnson argues that it is vital to honour the 2016 referendum, in which 52% of voters supported leaving the EU.
But opponents say leaving without a deal will damage the economy and is not wanted by many of the voters who backed Brexit.
Labour's existing plan is to bring down Mr Johnson's government in a no-confidence vote in the Commons after MPs return in September and install Mr Corbyn as temporary prime minister.
However this has been met with opposition by several Remain-supporting Conservative MPs who want to stop no deal, but do not want to put the Labour leader in Downing Street.
Liberal Democrat leader Jo Swinson has also said she would not support making Mr Corbyn prime minister.
She has suggested the possibility of installing either former Conservative Chancellor Ken Clarke or ex-Labour deputy leader Harriet Harman in Downing Street instead.
BBC political correspondent Nick Eardley said it was being suggested within Labour that a no-confidence motion in Mr Johnson's government and moves to extend Article 50 could run in tandem, with the latter operating as back-up to the main plan.
Opposition figures are drawing up proposals to seize control of the parliamentary agenda when MPs return from recess.
They would then try to pass a law mandating the prime minister to seek a further extension to the Brexit process to avoid no deal.
Those involved in the plan have suggested the law would be co-signed by opposition leaders and prominent Tory rebels to maximise its appeal. A source said: "We need to coalesce around legislation".
Downing Street has said Mr Corbyn will "overrule the referendum and wreck the economy" if he became prime minister.
A No 10 spokesman said: "Jeremy Corbyn believes that the people are the servants and politicians can cancel public votes they don't like."
Mr Johnson has also said the EU has become less willing to compromise on a new deal with the UK because of the opposition to leaving in Parliament.
He said this increased the likelihood of the UK being "forced to leave with a no deal" in October.
If the government loses a no-confidence motion, it would trigger a critical 14-day period, after which a general election could be triggered.
If Mr Johnson failed to win such a vote, then a general election would be called.
There are no firm rules about who else, if anyone, should get the chance to form an alternative government during this time.
The leader of the opposition is clearly a likely candidate, but that is not an inevitable outcome.
The Cabinet Manual - a document which sets out the main rules covering the working of government - suggests that the principles applied should be similar to those after an election in which no one party wins a majority.
That means that the old prime minister should only resign if and when it's clear that somebody is more likely to have the support of MPs.
So it is possible that the existing prime minister would stay in place, or that more than one leader would get a chance.
Mr Johnson has a working majority of just one in the House of Commons, with the backing of Northern Ireland's Democratic Unionist Party.
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Labour leader Jeremy Corbyn has backed the UK being in a permanent customs union with the EU in a speech setting out his approach to Brexit.
He said this would avoid the need for a "hard border" in Northern Ireland and ensure free-flowing trade for business.
The policy shift could lead to Labour siding with Tory rebels to defeat Theresa May on her Brexit strategy.
But a customs union after Brexit would be a "complete sell out", International Trade Secretary Liam Fox will argue.
Mr Corbyn insisted in an interview with BBC Political Editor Laura Kuenssberg that his speech was a "firming up" of Labour's existing policy, which was to back customs union membership during the planned two-year transition period after the UK leaves the EU in March 2019.
In his speech, at Coventry University, Mr Corbyn said Labour would be "looking for a Brexit that puts the working people first".
In a shift from the party's policy at last year's general election, he said the UK should strike a new customs deal with the EU at the end of transition.
"Labour would seek a final deal that gives full access to European markets and maintains the benefits of the single market and the customs union," he said.
"We have long argued that a customs union is a viable option for the final deal.
"So Labour would seek to negotiate a new comprehensive UK-EU customs union to ensure that there are no tariffs with Europe and to help avoid any need for a hard border in Northern Ireland."
The prime minister has insisted the UK will leave both the single market and the customs union, allowing it to negotiate its own post-Brexit trade deals.
Mrs May will give details in a speech on Friday of how her plan for a "managed diversion" from the EU will work in practice, after first briefing the cabinet.
The Conservatives accused Mr Corbyn of "betraying millions of Labour voters" who had backed Brexit.
International Trade Secretary Liam Fox said Labour's "confused policy would be bad for jobs and wages".
And in a speech on Tuesday, he will say the UK would find itself in a "worse position" than it is now if it leaves the existing customs union but negotiates a similar arrangement.
A customs union allows free-flowing trade between member nations without making companies pay export taxes, or tariffs, at the border.
However, the members normally have joint trade agreements with countries not in their customs union.
A single market is a deeper form of co-operation, which effectively merges the economies of member states together, allowing the free movement of goods, services, money and people as if they were part of a single country.
Mr Corbyn rejected calls from pro-EU figures like Lord Mandelson and a number of his own backbenchers to commit to staying in the EU single market, saying instead that he wanted a "close relationship" with it.
Shadow Brexit Secretary Sir Keir Starmer has not ruled out continuing with free movement of people between the UK and the EU in some form after Brexit, under Labour's plans, but he told BBC News it would have to be negotiated - as would any financial contribution the UK would make.
He said the UK could work "jointly" with the EU after Brexit to strike trade deals with other nations - something the government insists is not possible.
Analysis By BBC political correspondent Ian Watson
So the dividing lines are clear politically - if less clear in practice. Clear politically, because the government is committed to coming out of the customs union. And in contrast Labour now says it wants to negotiate "a new comprehensive customs union" with the EU.
That puts clear blue water between opposition and government - and may signal to Remain voters that Labour wants a 'softer' Brexit, staying closer to the EU.
But in practice, there may be fewer differences than meets the eye.  Jeremy Corbyn wants a customs union that would still give the UK a say in EU-led trade deals - which the EU may resist.
And Theresa May has spoken of a new "customs arrangement," which would, er, allow independent trade deals.  But it's currently in the government and opposition's political interests to emphasise the differences,  not the similarities.
Jeremy Corbyn refused to be drawn on whether his policy shift was an attempt to remove Theresa May from office and force a general election.
Tory rebels have been tight-lipped about whether they would vote against Mrs May if it came down to a confidence vote in her premiership, saying that was unlikely to happen.
But Labour MP Frank Field, who backed Leave and said Mr Corbyn was once more Eurosceptic than him, told the BBC that being in a customs union or the single market would be a "deceit" and dismissed suggestions Tory rebels could join with Labour to defeat the government as "fairy tales" and they would win any vote by a large majority.
Mr Corbyn was an opponent of the EU when he was a backbench Labour MP, as he explained in his speech.
"I have long opposed the embedding of free market orthodoxy and the democratic deficit in the European Union, and that is why I campaigned to 'remain and reform' in the referendum campaign."
He said scepticism was "healthy" but "often the term 'Eurosceptic' in reality became synonymous with 'anti-European' and I am not anti-European at all, I want to see close and progressive cooperation with the whole of Europe after Brexit".
He said this "new relationship" he wanted to negotiate with the EU would ensure Labour could deliver on its plans to nationalise public utilities, invest in industry and curb the outsourcing of public services.
Mr Corbyn's speech was welcomed by Britain's largest trade unions while industry body, the CBI, said staying in a customs union would "grow trade without accepting freedom of movement or payments to the EU".
Pro-European Labour MPs said he had not gone far enough and urged him to commit to staying in the single market.
But former UKIP leader Nigel Farage said it was the "first step in a complete Labour sell-out" while the DUP, the party Mrs May relies on to win key votes in the Commons, said it was "cheap political opportunism".
Liberal Democrats leader Sir Vince Cable tweeted that Mr Corbyn's customs union stance was a "small step to sanity", but added: "In #SingleMarket he is still following @theresa-may cake and eat it policy. Just wants red cherries rather than blue raisins."

Jeremy Corbyn is coming under pressure amid divisions over Labour's Brexit strategy as leading figures call for the party to back staying in the EU.
Shadow foreign secretary Emily Thornberry said Labour must "say no" to leaving the EU at its party conference.
And deputy leader Tom Watson said it must settle its position as "a Remain party" once and for all this week.
But Unite leader Len McCluskey said anyone who could not support Jeremy Corbyn's position should stand aside.
He said talk of divisions were "fake news" given that Labour had a policy of giving the public the final say in another referendum which the shadow cabinet could unite around.
The party's NEC, or governing body, has agreed a motion which calls for the party to renegotiate the current terms of exit and then give voters the choice to back the new Brexit deal or to remain in the EU.
Mr Corbyn has persistently refused to be drawn on which way he would campaign in another vote, saying it would depend on the kind of agreement he struck.
Labour will also decide the terms of further motions on Brexit, which could call for the party to endorse a remain stance outright.
The exact wording of the motion to be debated will be decided later on Sunday and voted on Monday.
Mr Corbyn is under growing pressure to declare his hand from pro-EU figures in the party.
Addressing a rally organised by the Progress group in Brighton, Mr Watson - who saw off an attempt to oust him on Saturday - said the "simple truth is whatever anyone says - Labour is a remain party".
Calling on the leadership to "to settle once and for all our position", he said by backing remain "I'm sure we can deliver a Labour government".
And Ms Thornberry questioned "why on earth" Labour would be complicit in allowing the UK to leave the EU.
"Are we going to celebrate a Labour version of Brexit? No. We must have the Labour Party this week saying no to Brexit and we must lead the campaign to remain."
You might think policy is made on the conference floor but what goes behind closed doors - in smoke free rooms these days - is often more important.
Representatives from constituencies and from trade unions try to distil disparate motions on the same topic down in to just one, on which they can all agree - and this is then put to the conference for approval the following day in the full knowledge that it will pass.
But on Brexit, this usual template isn't working.
The gap between the leadership and many in the grassroots has proved difficult to bridge.
Labour's ruling national executive - which includes representatives of the big unions - has agreed a statement which would not commit the party to backing leave or remain until after any snap election.
On Sunday night, though, grassroots delegates are expected to agree a motion, which would commit the party to campaigning to remain in the EU during the election.
The pro-remain Mayor of London Sadiq Khan told me he would be urging delegates to stand firm on this and not to accept a fudge.
And I understand it, the call from Len McCluskey of Unite - for remainers to back down in the interests of party unity - is likely to go unheeded.
So as things stand, the differences between the leadership and much of the rank and file will be displayed in the full glare of publicity.
However, the unions account for 50% of the votes at Labour conference - and if they continue to stand firmly behind Jeremy Corbyn then the overtly pro-remain position will be defeated.
The political price could be high, though, and there will undoubtedly be further appeals for the remain motion to be withdrawn.
Speaking on the BBC's Andrew Marr show, Mr Corbyn acknowledged that most Labour supporters backed staying in the EU.
But he said the party needed to show more understanding of why the country voted leave and even if the UK were to remain in the EU, there needed to be serious reform.
Mr McCluskey, a key ally of Mr Corbyn, appealed for loyalty on the issue, saying the party must go into the looming general election "united".
"When we have a policy on Brexit and Jeremy Corbyn makes it clear that that is the policy, then that's what leading members of the shadow cabinet should argue for," he told Sky News.
"If they find they can't argue for it because they feel strongly, well, of course they have that right but they should step aside from the shadow cabinet…and they can argue whatever they want."

Jeremy Corbyn has refused to follow two senior colleagues who say they would back Remain in any further Brexit referendum.
His close allies Diane Abbott and John McDonnell both say they would campaign for Remain, regardless of the other options on the ballot paper.
But the Labour leader chose only to say he would campaign for Remain if the alternative was no deal.
Earlier, Ms Abbott said Mr Corbyn would "follow what the party says".
The Labour leader has been under pressure for months to give his full-throated support to continued EU membership.
More and more of his senior colleagues have come round to that position, some blaming lacklustre election results for the party earlier this year on its Brexit equivocation.
Speaking on Tuesday, Mr Corbyn was asked whether he too would campaign for Remain, even against an alternative Brexit deal negotiated by any future Labour government.
He replied: "What we've said is, if it's no deal or Remain, we'll campaign for Remain."
Pressed for further clarification, he repeated: "Between no deal and remain, I'll argue for remain."
Mr Corbyn has outlined a plan to stop a no-deal Brexit, which involves defeating the government in a no-confidence vote then becoming a caretaker PM.
If he succeeds, he hopes to head a temporary government which would delay the Brexit date and hold a general election.
In that general election, Labour would call for a "public vote" - a referendum - on the terms of leaving the European Union.
In the public vote he has said he wants "credible options for both sides", including the option to remain.
It is not yet clear whether any Labour government would try to reopen negotiations with the EU over a deal to leave, or proceed straight to a referendum.
The party has told the BBC it would decide this when it produced its manifesto, which it will need to publish if a general election is called.
Lib Dem leader Jo Swinson tweeted that Mr Corbyn would not "fight for Remain".
"He wants to deliver a Labour Brexit, because he is a Brexiteer," she said.
Earlier, shadow home secretary Diane Abbott confirmed she would "personally" campaign for Remain in the event another referendum is held.
She told BBC Radio 4's Today programme remaining would be the "best option for the country and my constituents".
"The party and the shadow cabinet will have to debate this and arrive at a position - whatever the position is Jeremy will follow what the party says."
On Monday, shadow chancellor John McDonnell made the same commitment, adding he couldn't envisage another option with the "same benefits as Remain".
Asked whether the party could even stay neutral in a referendum, he replied: "That's one of the issues we've got to debate in the party."
"I know people get frustrated with this […] but we're a democratic party," he added.
"If you sign up to democratic rules, you have to abide by them."
Mr Corbyn's "credible leave option" would presumably resemble Labour's previous policy of maintaining a close relationship with Brussels.
But Diane Abbott also suggested her leader would "follow what the party says" - so at this year's annual conference there will be a concerted push to get the party to commit to Remain
But some powerful voices - including the leadership of the giant Unite union - are still likely to resist.
Labour insiders expect an early election. Remainers - including Ms Abbott - fear an equivocal policy will gift votes to the Lib Dems.
Labour Leavers say an all-out Remain position will gift votes to the Brexit Party.
Not an easy choice.
But with more of Jeremy Corbyn's usual allies - including John McDonnell - now backing Remain, it feels that this option is gaining momentum.

Jeremy Corbyn risks jeopardising a vote of no confidence in the government by insisting he becomes caretaker PM, Lib Dem leader Jo Swinson has said.
If he wins a no-confidence vote, the Labour leader plans to form an emergency government and then delay Brexit to avoid a no-deal scenario.
But in a new letter, Ms Swinson said Mr Corbyn's insistence on being interim leader meant there was a danger not enough MPs would support the vote.
Labour did not respond to the letter.
Instead, the party referred to comments made by its shadow international trade secretary, Barry Gardiner, who on Sunday described Ms Swinson as "extremely petulant" for dismissing Mr Corbyn's initial proposal to lead a temporary government.
Prime Minister Boris Johnson has repeatedly insisted that the UK will leave the EU on 31 October, with or without a deal.
On Sunday, he told the BBC the chances of securing a new Brexit deal were "touch and go", having previously said the odds of no deal were "a million to one".
Ahead of cross-party talks on how to avoid no deal - due to take place on Tuesday - Ms Swinson said the discussions should examine how to seize control of Commons business, oust Mr Johnson and install an emergency "government of national unity".
In her letter to Mr Corbyn, Ms Swinson added: "Insisting you lead that emergency government will therefore jeopardise the chances of a no confidence vote gaining enough support to pass in the first place.
"As you have said that you would do anything to avoid no deal, I hope you are open to a discussion about how conceding this point may open the door to a no-confidence vote succeeding. Its success must be the priority."
Earlier this month, Mr Corbyn outlined his plans to avert a no-deal Brexit - which involve him becoming a caretaker prime minister - but was met with resistance from some key potential allies.
Ms Swinson and Conservatives opposed to no deal were among those who rejected the idea of Mr Corbyn being interim leader, but Scottish First Minister Nicola Sturgeon criticised the Lib Dem leader's stance, adding that "nothing should be ruled out".
Mr Corbyn said he would call a no-confidence vote at the "earliest opportunity when we can be confident of success". That cannot happen before 3 September, when MPs return from summer recess.
In order for such a vote to succeed, Labour would require support from across the House of Commons, including the Lib Dems, the SNP and Conservative rebels.
Ms Swinson has suggested Tory MP Ken Clarke and former deputy Labour leader Harriet Harman as possible caretaker leaders, and both have expressed willingness to do the role, she said.
In her letter, Ms Swinson also called on Mr Corbyn to "clarify" his position on whether he was opposed to Brexit altogether.
The SNP, Liberal Democrats, Change UK, Plaid Cymru and the Green Party have all accepted the invitation to meet Mr Corbyn to discuss proposals for an alternative government to be formed when Parliament returns in September.
Speaking ahead of the meeting, Labour's Barry Gardiner told Sophy Ridge on Sky News on Sunday Labour was offering a "failsafe procedure to stop no deal" by holding a vote of no confidence followed by a temporary government to set up a general election.
Former Prime Minister Gordon Brown told BBC Radio 4's Today programme: "I think it is more likely Parliament will force Boris Johnson to delay a no deal and the question is whether in these circumstances he will think it is the right thing to call an election.
"My view is that an election at this point will not solve the problem we have - and the problem we have is making sure that we do not inflict harm on ourselves, by leaving the EU with no deal."

Three Labour frontbenchers have been sacked for defying Jeremy Corbyn and backing a call for the UK to stay in the single market after Brexit.
Ruth Cadbury, Catherine West and Andy Slaughter had supported Chuka Umunna's amendment to the Queen's Speech.
Staying in the single market is not Labour policy and Mr Corbyn had ordered his MPs to abstain - but 50 rebelled.
His deputy Tom Watson said he was disappointed with Mr Umunna for trying to "divide" Labour MPs with the vote.
Mr Watson added: "I just felt that given we'd come out of the general election with such an unexpected result, and there's a real euphoria, to try and divide Labour MPs a week and a half in was a little disappointing.
"But, you know, we're still buzzing, we still want to hold the government to account, we'll get over it and move on."
Ms Cadbury said she was aware that, as she was breaking the Whip, she could not retain her frontbench role.
"I had no doubt that I had to support the amendment moved by Labour colleagues with cross-party support.
"The amendment ruled out withdrawing from the EU without a deal, sought a parliamentary vote on the final negotiations, and proposed remaining in the customs union and single market.
"Only then can we protect jobs, trade and certainty for business, as well as protecting the rights of EU citizens, with reciprocal rights for UK citizens."
Forty-nine Labour MPs voted for the amendment while a 50th - Heidi Alexander - acted as a teller, one of the MPs who count the votes.
Daniel Zeichner quit as shadow transport minister to take part in the vote.
He said in a statement he was resigning "with great regret" but added: "My position on Europe has always been clear. I am a passionate pro-European and a straight-forward politician."
Despite the support of the Lib Dems and SNP, Mr Umunna's amendment was defeated by 322 votes to 101, majority 221, during a series of final votes on the government's Queen's Speech.
Among the Labour MPs who backed it was Stella Creasy, who appeared on the BBC's Question Time on Thursday.
She said she had done so because she wanted single market membership to be "part of the [Brexit] negotiations... because the economic and social cost of these things is going to be horrific" - arguing 650,000 jobs in London alone depended on the single market.
"I want all of these options on the table," she said, arguing there were "101 different combinations" that could see the UK leave the EU while remaining in the single market.
Labour's Wes Streeting, who backed the amendment, said the vote had "clarified" Labour's official position but he was "surprised and disappointed" at the outcome.
"I don't believe that Labour can achieve our objectives of tariff-free, barrier-free access to the single market, and a jobs-first Brexit, outside of membership of the the single market," he told Radio 4's World at One.
But Stephen Kinnock, who like many Labour MPs did not take part in the vote, said the decision to fire the rebels was "regrettable" but "had to be done".
"I suppose I'm quite old-fashioned on this stuff," he told the BBC. "If you have a frontbench amendment and a backbench amendment and you are whipped in a certain way, if you are a frontbencher and you don't follow the whip there is only one conclusion that can be drawn from that."
Mr Corbyn has committed to leaving the single market after Brexit. A Labour amendment proposed by shadow chancellor John McDonnell was defeated by 323 to 297.
It called for Brexit to deliver the "exact same benefits" as the EU single market and customs union, as well as scrapping tuition fees, increasing public spending and ending the public sector pay cap.
Labour MP Hilary Benn told the BBC: "I think we recognise that membership of the single market creates a difficulty because... you can't control free movement if you are in the single market.
"The policy on which we fought the election was to say that we wish to retain the benefits of the single market and the customs union.
"I think if the reference to the single market had not been in Chuka's amendment then you would've seen a different outcome."
Unison's general secretary Dave Prentis was very critical of Mr Umunna's amendment, saying it was "totally inappropriate for Labour MPs to create a split over Europe" and "utterly self-defeating to become bogged down in the worst kind of gesture politics".
The government survived its first major Parliamentary test when MPs voted 323 to 309 in favour of the Queen's Speech - the government's package of legislation - which was stripped back after the Tories lost their Commons majority.
The Democratic Unionist Party's 10 MPs had agreed to support the measures as part of a deal with the Tories.

Theresa May is to call on rival parties to "contribute and not just criticise" as she signals a post-election change in her style of government.
In a speech on Tuesday the PM will say she still wants to change the country, but will say that losing her majority means a new approach is needed.
Labour says it shows the Conservatives have run out of ideas.
But First Secretary of State Damian Green said it was a "grown-up way of doing politics".
Ministers loyal to Mrs May have dismissed reports of plots to remove her as drink-fuelled "gossip", but Labour remains on an election footing, with leader Jeremy Corbyn saying he hopes for a fresh poll in September.
Mrs May will return to the message from her first day in Downing Street last July, when she succeeded David Cameron, and vow to lead what she called a "one nation" government that works for all and not just the "privileged few".
The speech is being seen by some as a "re-launch" or "fightback" after Mrs May lost her majority - and much of her authority - in the snap election last month.
Theresa May's speech is a pitch for cross-party consensus.
"Come forward with your own views and ideas about how we can tackle" the challenges the country faces, Mrs May will say, adding: "We may not agree on everything, but ideas can be clarified and improved and a better way forward found."
Bluntly, it is an explicit acknowledgement of her fragility; her authority and majority shrivelled.
Government sources say it is a mature approach that maintains a commitment to taking on big, difficult and complex challenges; not just Brexit but reform of social care, too, for instance.
Labour says Mrs May's speech proves the Conservatives have "completely run out of ideas" and were reduced to "begging" for policy proposals from them.
In her speech, the PM will say that although the result of June's election was not what she wanted, "those defining beliefs remain, my commitment to change in Britain is undimmed".
Her "belief in the potential of the British people and what we can achieve together as a nation remains steadfast, and the determination I have to get to grips with the challenges posed by a changing world never more sure", she will say.
She will unveil a review - of casual and low-paid work - by Matthew Taylor, a former top adviser to Tony Blair, which she commissioned when she became prime minister.
It is thought Mr Taylor, who has been examining the use of zero-hours contracts and the rise in app-based firms such as Uber and Deliveroo, will stop short of calling for a compulsory minimum wage for those employed in the so-called gig economy, who do not have guaranteed hours or pay rates.
But he is expected to propose a series of extra rights for those in insecure jobs and could also recommend shaking up the tax system to reduce the gap between employees and the self-employed.
He is also likely to call for measures to improve job satisfaction for people working in minimum wage jobs, according to The Guardian.
In her speech, Mrs May will say: "When I commissioned this report I led a majority government in the House of Commons. The reality I now face as prime minister is rather different.
"In this new context, it will be even more important to make the case for our policies and our values, and to win the battle of ideas both in Parliament as well as in the country.
"So I say to the other parties in the House of Commons... come forward with your own views and ideas about how we can tackle these challenges as a country.
"We may not agree on everything, but through debate and discussion - the hallmarks of our parliamentary democracy - ideas can be clarified and improved and a better way forward found."
She will acknowledge the fragile nature of her position in the Commons but insist it will not stop her taking "the bold action necessary to secure a better future".
Speaking at a press conference with Australian counterpart Malcolm Turnbull on Monday, Mrs May said she had sought input from other parties in the past on issues like counter-terrorism and modern slavery.
She also said she was happy to work with Labour's Yvette Cooper and others in a cross-party approach to tackling intimidation and online abuse of MPs and others involved in the political process.
Asked if her desire for co-operation extended to Brexit, including on the government's Repeal Bill when it is published later this week, the prime minister said she was seeking the "broadest possible consensus" surrounding the terms of the UK's exit.
But former shadow business secretary Chuka Umunna said people would take the calls for cross-party working with "a lorry load of salt" - and he questioned why Mrs May had not raised the issue a year ago when she entered Number 10.
"The reason she wasn't asking for it then was she didn't need to," he said.
Lib Dem Brexit spokesman Tom Brake said: "A call for Labour to contribute is superfluous. On the single biggest issue of our generation, Brexit, Corbyn isn't contributing, he is cheerleading."
Scottish Government Brexit minister Michael Russell said: "If the prime minister is genuinely interested in creating a consensus then Scotland should have a seat at the negotiations to leave the EU."
But Mr Green, who has known Mrs May since university and is effectively her deputy prime minister, said the public would welcome a move away from politics in which parties "just sit in the trenches and shell each other".
"Politicians of all parties are invited to contribute their ideas - that's a grown up way of doing politics," he told BBC Radio 4's Today programme.
He said Mrs May was motivated by "her duty" to carry on, adding: "She still has the same ambitions for this country as she had a year ago and she's determined to put them into practice for the good of this country - that's what drives her."
Asked if the PM could be tempted to step down after her summer holiday, he said: "No. She thinks not just that it's her duty, but she has a programme for Britain that encompasses not just a good Brexit deal, but also a domestic agenda that will spread prosperity around this country, make this a fairer society, tackle some of the injustices that we still have in our society - and that fire burns within her as strongly as ever."
The BBC's assistant political editor, Norman Smith, said that the Conservatives and Labour were "poles apart" on many significant policy areas.
He told BBC Radio 4's The World at One: "More brutally, Jeremy Corbyn is not minded to help Theresa May. He smells blood in the water.
"He wants to do everything he can to stampede Mrs May into another election, so the idea he might somehow seek to cooperate with her, I think, is bordering on the fanciful."
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Labour leader Jeremy Corbyn has welcomed the prime minister's election announcement, calling it a "chance to vote for a government that will put the interests of the majority first".
Mr Corbyn said the Tories had "failed to rebuild the economy" and that he would be campaigning on housing, education and the NHS.
Theresa May says she wants a general election to take place on 8 June.
MPs will vote on Wednesday to approve her plan.
Explaining her decision to hold the vote, Theresa May said Britain needed certainty, stability and strong leadership following the EU referendum.
Asked whether he was the next prime minister, Mr Corbyn added: "If we win the election, yes - and I want to lead a government that will transform this country, give real hope to everybody, and above all bring about a principle of justice for everybody and economic opportunities for everybody."
The Labour leader, who was elected to replace Ed Miliband after Labour lost the 2015 election, said this time the party would be challenging the "economic narrative" that requires "huge cuts" to pay for the banking crisis.
Mr Corbyn also said Labour had been setting out policies offering a "clear and credible choice for the country", adding: "We look forward to showing how Labour will stand up for the people of Britain."
Labour's shadow cabinet met in the aftermath of Mrs May's announcement.
Former home secretary Alan Johnson said he would not be seeking re-election in the Hull West and Hessle seat he has represented since 1997.
And Tom Blenkinsop, who has been MP for Middlesbrough South and East Cleveland since 2010, said he would not be standing for re-election, citing "irreconcilable differences" with the party's leadership.

A Labour government would seek to ensure "we build things here that for too long have been built abroad", party leader Jeremy Corbyn has said.
He told the EEF manufacturers organisation that new train carriages, defence, NHS and new passports were areas where money was spent abroad.
Mr Corbyn also said he would end the "racket" of public sector outsourcing.
He said that on Brexit the UK needed a new customs union with the EU to avoid ending "in hock to Donald Trump".
Mr Corbyn, launching his Build it in Britain campaign in Birmingham, said: "For the last 40 years... we've been told that it's good - advanced even - for our country to manufacture less and less and rely instead on cheap labour abroad to produce imports, while we focus on the City of London and the finance sector.
"A lack of support for manufacturing industry is sucking the dynamism out of our economy, pay from the pockets of our workers and any hope of secure, well-paid jobs from a generation of young people."
He added: "Labour is determined to see public contracts provide public benefit, using our money to nurture and grow our industries, our people and to expand our tax base."
Mr Corbyn said Labour would intervene to bring quality jobs to all regions, saying that his party would opt out of parts of world trade rules if necessary to ensure jobs went to local people, rather than sit back "and manage decline".
On Brexit, Mr Corbyn said the fall in the value of the pound as a result of Brexit had not provided the benefits to exporters it should have, because the Conservatives had "sold out" manufacturers.
He said the prime minister "and her warring Cabinet should think again, even at this late stage, and reconsider the option of negotiating a brand new customs union".
"This decision doesn't need to be a matter of ideology... it ought to be a matter of practical common sense."
Otherwise a "botched" Brexit "will sell our manufacturers short with the fantasy of a free trading buccaneering future, which in reality would be a nightmare of our public services sold to multinational companies and our country in hock to Donald Trump, while we are all told to eat chlorinated chicken."
For the Conservatives, Robert Jenrick, exchequer secretary to the Treasury, said: "This is laughable coming from the Labour Party who oversaw millions of jobs lost and a record decline in manufacturing.
"We know from last time Labour don't know how to handle the economy and now their plan would mean higher prices for families and lower wages for workers.
"Under the Conservatives, exports are up, there's more business investment, more manufacturing jobs and employment is at a record high - meaning more people have the security of a regular pay packet."
The Lib Dems Brexit spokesman Tom Brake accused Mr Corbyn of living in a world of "alternative facts" by talking about the benefits of Brexit, adding he was "laying the path for the Tories' chaotic Brexit".
Stephen Martin, director general of the Institute of Directors, called Mr Corbyn's plans "protectionism".
He said: "For all the criticism of America's current approach to trade in this speech, the proposals of subsidies and 'buying British' are just as protectionist as tariffs.
"Britain has many fantastic manufacturing firms, but the fetishisation of factories and production lines over all other parts of the economy is misguided. We should not be ashamed of our world-class creative, digital and professional services."

The resignation of shadow business secretary Clive Lewis to vote against the Brexit bill was "not a disaster", Labour leader Jeremy Corbyn has said.
The party backed the government in Wednesday's vote, but 52 MPs rebelled.
Mr Lewis quit, saying he could not "in all conscience" support triggering Article 50 of the Lisbon Treaty, getting talks with the EU under way.
But Mr Corbyn told the BBC that Labour had been right to "respect" the result of last year's EU referendum.
He dismissed as "fake news" and "absolute nonsense" suggestions that he was considering his own future as Labour leader.
And he added that Donald Trump "should not be coming to the UK", after it was announced recently that the US president had been invited to make a state visit later this year.
The European Union (Notification of Withdrawal) Bill was approved by 494 votes to 122 on Wednesday, and now moves to the House of Lords.
Mr Lewis, who earlier said he was undecided on whether to support the bill, announced his resignation as MPs began voting for the final time on Wednesday.
In a letter to Mr Corbyn, he wrote that he was leaving the shadow cabinet "with a very heavy heart", but Labour had not won "the protections the people of this country need" during the Commons debates on Brexit.
Mr Lewis added: "I know you understand the deep divide this issue has opened up in the country and it is to your credit that you have lead the debate in our party such an open and comradely way."
Asked on BBC Breakfast about Mr Lewis's departure, Mr Corbyn said: "It's not a disaster. The majority of Labour MPs voted to trigger Article 50. Fifty-odd voted against it, mainly on the basis of their strong message from their own constituents.
"My argument is it was a national vote, it was a national referendum, and Parliament has to respect that."
He added that the party would continue "demanding from the government social justice in Britain".
One of the stars of the 2015 parliamentary intake, Clive Lewis is seen by many on Labour's left as a potential successor to Jeremy Corbyn.
He was born in London and grew up on a council estate in Northampton, moving on to become a BBC TV reporter.
Mr Lewis has quickly established himself as one of the most high-profile Corbynite MPs, rising from backbencher to shadow defence secretary in a matter of months. He became shadow business secretary last October.
Mr Lewis's resignation from Labour's frontbench team occurs as the party continues to grapple with the UK's exit from the European Union.
In a interview with the Guardian in August, the MP for Norwich South said: "I've been thrust too quickly into the shadow cabinet. I want to be in my constituency. I want to be a constituency MP."
His exit from the shadow cabinet means he can do just that.
Asked about the US president's planned state visit, Mr Corbyn said: "My position is Donald Trump should not be coming to the UK.
"I think we have to have relations with the USA. I'm not sure he's going to want to have a meeting with us."
He added: "The point is Donald Trump has been promoting something that undermines international law. He's been promoting misogyny. He's been making some awful statements in the USA. He's threatened to build a wall against Mexico.
"Our government seems to think this is a man they should do deals with."
Mr Corbyn also said: "I think it would be right to meet the president of the USA, but I think it would be wrong for him to come here."

Jeremy Corbyn says Labour is "not supporting or calling for a second referendum" on the UK's EU membership.
The party leader reiterated his call for MPs to have a "meaningful vote" on the final Brexit deal.
Meanwhile, shadow foreign secretary Emily Thornberry said that if 90% of people were calling for another vote, it would present a challenge "for all of us who are democrats".
But as things stand the UK is leaving the EU, she said.
Mr Corbyn also hit back at critics within the party calling for the UK to remain in the EU single market and customs union after Brexit.
"The single market is dependent on membership of the European Union," he said.
But he said the existing arrangements needed improvement.
Both Labour and the Conservatives have said the 2016 vote to leave the EU should be honoured.
But some in the pro-EU campaign, like the Liberal Democrats and former Labour Prime Minister Tony Blair, want another referendum before the UK leaves the EU, which is due to happen in March 2019.
And last week former UKIP leader Nigel Farage said a second vote might be needed to end the "whinging and whining" of anti-Brexit campaigners.
Mr Corbyn was asked about this issue on ITV's Peston on Sunday.
"We are not supporting or calling for a second referendum," he said.
"What we have called for is a meaningful vote in Parliament."
When it was put to Mr Corbyn that he was not saying he would never support another referendum, the Labour leader said: "We are not calling for one either".
On the BBC's Andrew Marr show, Ms Thornbery was asked about demands for a second nationwide vote.
"If 90% of the population was now saying we must stay in the European Union and we must not leave then that would be a challenge that would be there for all of us who are democrats," she said.
"But, at the moment, and as things currently stand, we proceed in good faith, we do as we are instructed and we are leaving the European Union."
While the result of the referendum means the UK must leave, she added that "we have to look after the economy which, in my view, means that we don't go very far".
Conservative deputy chairman James Cleverly said the two Labour politicians had "failed to rule out a second referendum".
"Every step of the way Labour are trying to frustrate the Brexit process rather than make a success of it," he said.
Mr Corbyn is facing calls from within Labour - as well as other opposition parties - to commit to keeping Labour in the EU single market and customs union after Brexit.
This is the goal of an amendment to the EU (Withdrawal) Bill being backed by the SNP, Liberal Democrats, Plaid Cymru and Greens which returns to the Commons this week.
Labour has said it wants the "closest possible ties" with EU markets after Brexit.
Mr Corbyn said the UK would "obviously" have to be in "a customs union" with the EU after Brexit, but suggested the existing arrangements needed improvements.
But he expressed reservations about the EU single market, which allows for goods to be traded freely between EU members.
"There are aspects of the single market one wants to think about such as the restrictions on state aid to industry, which is something that I would wish to challenge," he said.
He also called for changes to the EU customs union, which sets common external tariffs for countries outside the EU, suggesting it was "in come cases protectionist against developing countries".
In his ITV interview, Mr Corbyn also criticised Donald Trump, accusing him of making "endless offensive remarks" about women, minorities and different faiths.
Labour has been strongly critical of the US president and the decision to invite him on a state visit to the UK.
Asked whether the UK's relationship with the US was the most important relationship it had with another country, the Labour leader replied: "No. I think there are many important relationships.
"The US one is obviously culturally and economically significant and important.
"Also the trading relationships we have around the world with obviously the EU, but also with India and China and the rest of the world are very important.
"Also our relationship with international institutions such as the United Nations is very important."
Last week Foreign Secretary Boris Johnson accused Mr Corbyn and London mayor Sadiq Khan of putting the UK-US relationship "at risk" with their criticism of Mr Trump.

Jeremy Corbyn says Labour is the "party of choice" when it comes to Brexit.
He told BBC deputy political editor John Pienaar he would "make a case" to Parliament in September to get another referendum after "an awful lot of listening to an awful lot of people".
He said Labour would back Remain against no deal or a Tory deal, but denied bowing to pressure from colleagues to take a pro-EU stance.
"We will give people the choice on this," he added.
"That is surely something that is very important."
Earlier, in a letter to members, Mr Corbyn called for the next prime minister - Boris Johnson or Jeremy Hunt - to hold a further referendum on Brexit, and promised his party would campaign for Remain to stop "no deal or a damaging Tory Brexit".
It follows a meeting with unions earlier this week, who agreed a position to hold another public vote and to fight for Remain.
But their leaders also said Labour should negotiate their own Brexit deal if they were to win the next general election and also put that to a vote - with Remain as an option on the ballot.
Mr Corbyn has not gone that far - refusing to say at this stage what he would do if he makes it to Downing Street.
The Labour leader said the party had pledged to respect the referendum in 2016 and had done so by voting to trigger Article 50 and fighting the last general election campaign on that promise.
But after Labour went into talks with the government, "it became very clear they simply could not deliver".
He said he now believed both Tory leadership candidates were "vying with each other in the extremities of no deal" which he saw as "very dangerous" for the UK.
So, Mr Corbyn said he would try to go to Parliament in July to call for a referendum - or again in September if there was not enough time before recess.
"What I have tried to do is to reflect a majority and consensus position and I believe I have achieved that," he said.
He added that he was very grateful to those who had "made a little bit of a jump to get to a decision we can all live with".
Asked if he had changed his position because of pressure from colleagues, Mr Corbyn said: "Not a bit of it. I've been listening and I've enjoyed it."
He added: "What I have done is what I think a leader should do and that is spend some time listening to people.
"Many of my colleagues have found this a very frustrating experience because they have said, 'why don't you just tell us what to think?'
"But I said no, I want to take the movement with me, I want to take the the membership with me, I want to take the unions with me, I want to take the public with us if we can, because this is a very important time for this country."
Pushed on whether he would support the union's position of negotiating a new deal were he to get into No 10 - and putting it to a public vote - Mr Corbyn said it was too early to say, and more listening needed to take place.
"The next election will come when it comes," he said. "It could be this October, it could be next year, it could be even 2022.
"We have a very large party, a very large membership and many parts to our party and our movement and we have a democratic process.
"We will decide very quickly at the start of that campaign, because we don't know by that stage whether we would have left the EU, still be in the EU or part of a Parliamentary struggle with Johnson or Hunt trying to take us over a cliff edge."

The UK government would have to return to the EU negotiating table if Parliament rejects its Brexit deal, Jeremy Corbyn has told the BBC.
Mr Corbyn said Labour would decide whether to back the deal based on its six tests - which the party says the government is currently nowhere near meeting.
He denied this made the possibility of no Brexit deal more likely.
He also refused to say how he would vote if there is another EU referendum.
"It's a hypothetical question," he said.
Mr Corbyn was speaking to BBC political editor Laura Kuenssberg ahead of his speech at the Labour conference in Liverpool on Wednesday.
Also at the party conference, Labour delegates approved a motion that would keep all options - including a fresh referendum - on the table if MPs are deadlocked over Brexit.
The UK is due to leave the EU on 29 March 2019, and negotiations are still taking place between the two sides.
Parliament is set to vote on the outcome of the talks, with Prime Minister Theresa May saying this will be a choice between her deal and leaving without one.
Earlier, shadow Brexit secretary Sir Keir Starmer it looked "increasingly likely" Labour's tests would not be met and it would vote against the deal in Parliament.
Speaking to the BBC, Mr Corbyn said he did not know what the deal would look like, but if it was rejected by MPs, the government "will have to go back to the EU and say 'our parliament can't agree to this'".
He predicted the government would "collapse itself" and cause a general election.
Mr Corbyn denied he was pushing the UK closer to leaving without a deal - a scenario Labour has repeatedly warned about - saying: "What we're making more likely is that we will force a deal that protects jobs and living standards on both sides of the Channel."
He added: "What are we supposed to do - keep quiet and say nothing and leave it to the incompetence of this government?"
Speaking on a visit to New York, Prime Minister Theresa May told the BBC Labour was "playing politics" over the final UK-EU deal.
"The Labour Party are saying they will vote against any deal that I bring back from Europe, regardless of how good it is for the United Kingdom, and they would support any deal that Europe gave to us, regardless of how bad it was for the United Kingdom," she said.
"That's not working for the national interest - that's playing politics."
Labour says it could call for another EU referendum if the Brexit deal is rejected and there is no general election - and it is not ruling out that one option could be to stay in the EU.
Theresa May has ruled out a public vote on the outcome of her Brexit negotiations - but it is not yet clear what will happen if Parliament votes it down.
Pro-EU campaigners say MPs will have "multiple opportunities" to legislate for a so-called "People's Vote", including by amending laws that have been promised to implement the UK's withdrawal.
Mr Corbyn denied leaving the door open to this scenario was letting down Leave voters, saying Labour was telling them "that we will deal with the situation as it comes up and we will understand, many of them, the reasons why they voted Leave".
The Labour leader cited de-industrialisation and anger at the loss of quality skilled jobs as factors behind the 2016 referendum result.
On the possibility of another referendum, he added: "We haven't said there's going to be anything yet.
"What we've said is all options must be considered if and when this government collapses or its negotiations collapse - the options are still there."

Labour's shadow chancellor says he does not trust Theresa May after details from cross-party talks on Brexit were leaked to the press.
The PM has called on Labour leader Jeremy Corbyn to "put their differences aside" and agree a Brexit deal.
But John McDonnell said she had "blown the confidentiality" of the talks and "jeopardised the negotiations".
The UK was due to leave the EU on 29 March, but it was delayed to 31 October after MPs failed to agree a deal.
Mrs May put the plan she had negotiated with the EU to Parliament three times, but it did not have the support of the Commons.
Writing in the Mail on Sunday, Mrs May said Mr Corbyn should "listen to what voters said" in Thursday's local elections - which saw the Conservatives lose 1,334 councillors and Labour fail to make expected gains, instead losing 82 seats.
The Liberal Democrats benefited from Tory losses, gaining 703 seats, with the Greens and independents also making gains.
The prime minister blamed the Brexit impasse for the losses - but said the elections gave "fresh urgency" to find a way to "break the deadlock".
Mrs May also said she hoped to find a "unified, cross-party position" with Labour - despite admitting that her colleagues "find this decision uncomfortable" and that "frankly, it is not what I wanted either".
Mr McDonnell agreed that the message from the polls was to "get on with it" and come to an agreement over Brexit quickly.
But while he said the talks between the two parties would continue on Tuesday, he said they had been undermined after an article in the Sunday Times detailed where Mrs May was willing to compromise - namely on customs, goods alignment and workers' rights.
The paper also said the PM could put forward plans for a comprehensive, but temporary, customs arrangement with the EU that would last until the next general election.
Mr McDonnell told the BBC's Andrew Marr show: "We have maintained confidentiality as that is what we were asked to do. We haven't briefed the media.
"So it is disappointing the prime minister has broken that, and I think it is an act of bad faith.
"I fully understand now why she couldn't negotiate a decent deal with our European partners if she behaves in this way."
Asked if he trusted the prime minister, the shadow chancellor said: "No. Sorry. Not after this weekend when she has blown the confidentiality we had, and I actually think she has jeopardised the negotiation for her own personal protection."
By Nick Eardley, BBC political correspondent
Clearly both sides think there is fresh impetus to get a deal after the local elections.
The government seems prepared to move towards Labour's position, but it's far from clear that it will be enough.
There's a real fear on the Labour side that if this isn't a permanent arrangement, a new Tory leader - perhaps Boris Johnson or Dominic Raab - could come along and try to change it.
So success isn't guaranteed when the two sides get back around the table on Tuesday, and both sides need to know they can take a big chunk of their parties with them.
If Theresa May faces losing dozens of Tories opposed to a customs union, or Jeremy Corbyn faces losing dozens of labour MPs who want another referendum, they might not have the numbers to get this through the Commons.
And in that case, a compromise is useless.
Sir Graham Brady, the chairman of the 1922 committee of Tory backbenchers, told the Daily Telegraph that staying in a customs union could lead to a "catastrophic split" in the Conservative Party.
And Brexit Party leader Nigel Farage told Sky News' Sophy Ridge on Sunday programme that millions of people would give up on Labour and the Conservatives if they agreed a deal, adding it would be the "final betrayal".
But the new International Development Secretary Rory Stewart told BBC Radio 5 live's Pienaar's Politics the Tories might have to "take some short-term pain" to finish the job.
The leader of the Scottish Conservatives, Ruth Davidson, also said her party needed to "start walking ourselves back" from the extremes of the argument to find a compromise, telling the BBC's Andrew Marr "there is a deal to be done" with Labour.
Meanwhile, Labour's deputy leader Tom Watson said it was "absolutely right" for the talks to continue, but told Pienaar's Politics: "I don't think we should be in any doubt that the Labour Party membership and vast numbers of my colleagues in Parliament don't want us to just sign off on a Tory Brexit.
"They don't want us to bail the prime minister out of the problem of her own making and a very large number of our members think the people should decide on what that deal looks like."
The comments come after the People's Vote campaign - which wants a referendum on a final Brexit deal - published a letter signed by more than 100 opposition MPs saying any new, agreed deal should be put to the public for a vote.
Labour MP Bridget Phillipson, who backs the campaign, told Sky's Sophy Ridge: "I think we have reached a stage now that whatever deal is agreed... it has to go back to the British people.
"Something stitched up, cobbled together in Westminster will not be sustainable in the long run. I want to check it is what people want now."

Boris Johnson has insisted he "deplores any threats to anybody, particularly female MPs", after he described one MP's safety concerns as "humbug".
The PM also said that "tempers need to come down" in Parliament.
It follows a stormy debate as MPs returned to Parliament after a Supreme Court decision that the suspension of Parliament was unlawful.
Mr Johnson defended his description of a law seeking to block a no-deal Brexit as "the surrender bill".
The law, known as the Benn bill, forces the government to ask for an extension to the Brexit deadline.
During a number of interviews with BBC political editors, the PM argued it would "take away the power of the government... to decide how long it would remain in the EU".
Speaking to the BBC political editor for the North West of England, Nina Warhurst, the prime minister said: "I totally deplore any threats to anybody, particularly female MPs, and a lot of work is being done to stop that and give people the security that they need.
"But I do think in the House of Commons it is important I should be able to talk about the surrender bill, the surrender act, in the way that I did."
He argued the law would "take away the power of this government, and the power of this country to decide how long it would remain in the EU and give that power to the EU and that's really quite an extraordinary thing".
When Mr Johnson talks about the "surrender bill", he is referring to the European Union (Withdrawal) (No. 2) Act, also known as the Benn bill.
The act - which became law earlier this month - stipulates the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK's departure date to 31 January 2020 from the EU.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal. But during this two-day period, MPs - not the government - will have the opportunity to reject the EU's date.
MPs on Thursday debated an urgent question over "the use of language" during Wednesday's ill-tempered debate.
Speaker John Bercow began the day's proceedings, by asking MPs from all sides of the house to temper their language and to "treat each other as opponents, not enemies".
In the heated debate that followed, several MPs said the prime minister should apologise for saying the best way to honour Jo Cox, the MP murdered during the EU referendum campaign, was to "get Brexit done".
Labour MP Jess Phillips said saying sorry would be the "bravest" thing for Mr Johnson to do.
Shadow cabinet office minister Cat Smith compared the language being used to that of drill artists, a type of rap which has been linked to gangs and violence.
"How are we as politicians in any position to accuse drill artists of glorifying violence when politicians themselves are not held responsible for the violent language they use and the impact it has on the culture and climate of debate?" she asked.
MPs also detailed some of the threats they had faced, with Tory MP Caroline Noakes describing how someone called her a "traitor who deserved to be shot" on a walkabout in her constituency.
Meanwhile, the longest-serving male and female MPs in the Commons - Ken Clarke and Harriet Harman - have asked for a Speaker's Conference, or meetings chaired by the Speaker, to discuss threats to MPs.
MPs returned to Parliament on Wednesday, following the Supreme Court ruling that the prorogation of Parliament was unlawful.
Labour MP Paula Sherriff said she had received death threats which often quoted the prime minister's words, including "surrender act", and called on him to moderate his language.
In response, Mr Johnson said: "I have to say, Mr Speaker, I've never heard such humbug in all my life."
The prime minister also later said: "Believe me: the best way to ensure that every parliamentarian is properly safe and to dial down the current anxiety in this country is to get Brexit done."
Speaking at a book launch on Thursday evening, the prime minister's adviser Dominic Cummings said it was "not surprising" that some voters were angry.
"The MPs said we will have a referendum, we will respect the result and then they spent three years swerving all over the shop," he said.
"In the end the situation can only be resolved by Parliament honouring its promise to respect the result."
Mr Cummings - who was the campaign director at Vote Leave - also attempted to paint a picture of calm at No 10, saying: "This is a walk in the park compared to the referendum."
Meanwhile, Rachel Johnson, the prime minister's sister, told BBC Radio 4's World at One that her brother was using the Commons as a "bully pulpit".
Ms Johnson, who stood for pro-European party Change UK - which has since altered its name to The Independent Group for Change - in June's European elections, added: "It's not the brother I see at home. It's a different person."
Elsewhere, former Conservative prime minister Sir John Major has criticised Mr Johnson and warned that a "general election would solve nothing" in the Brexit crisis.
Mr Johnson has been calling for an early general election, but under the Fixed-term Parliaments Act he needs the support of two-thirds of MPs. He has twice failed to achieve this.
Speaking to the Centre for European Reform, Sir John said an election "would merely fuel the current feeling of disillusionment and disunity".
He also said he feared the government would seek to bypass the Benn Act, by suspending it until after 31 October when the UK is set to leave the EU.
He said he thinks they will do this by trying to pass an Order of Council, which can be approved by Privy Councillors - government ministers - without involving the Queen.
"I should warn the prime minister that - if this route is taken - it will be in flagrant defiance of Parliament and utterly disrespectful to the Supreme Court," he said.

Boris Johnson has denied lying to the Queen over the advice he gave her over the five-week suspension of Parliament.
The prime minister was speaking after Scotland's highest civil court ruled on Wednesday the shutdown was unlawful.
Asked whether he had lied to the monarch about his reasons for the suspension, he replied: "Absolutely not."
He added: "The High Court in England plainly agrees with us, but the Supreme Court will have to decide."
The power to suspend - or prorogue - Parliament lies with the Queen, who conventionally acts on the advice of the prime minister.
The current five-week suspension began in the early hours of Tuesday, and MPs are not scheduled to return until 14 October.
Labour has said it is "more important than ever" that Parliament is recalled after the government published the Yellowhammer document, an assessment of a reasonable worst-case scenario in the event of a no-deal Brexit.
Meanwhile, the EU has said it is willing to revisit the proposal of a Northern Ireland-only backstop to break the Brexit deadlock, despite Mr Johnson ruling this out.
The President of the European Parliament, David Sassoli, said there would be no agreement without a backstop - which aims to avoid a hard Irish border after Brexit - in some form.
But the EU's chief negotiator Michel Barnier told MEPs that the "situation in the UK remains serious and uncertain", saying: "We do not have reasons to be optimistic".
He also warned the UK could still leave without a deal, despite Parliament introducing a law to avoid the scenario.
The Yellowhammer document - published on Wednesday after MPs forced its release - warned of food and fuel shortages in a no-deal scenario.
But Mr Johnson insisted the UK "will be ready" to leave the EU by the current 31 October deadline without an agreement "if we have to".
"What you're looking at here is just the sensible preparations - the worst-case scenario - that you'd expect any government to do," he said.
"In reality we will certainly be ready for a no-deal Brexit if we have to do it and I stress again that's not where we intend to end up."
But shadow chancellor John McDonnell said he was "angry" that MPs would not be able to debate the planning document during the suspension.
If you had a usual prime minister who'd been accused overnight of misleading MPs, of breaking the law, having been forced to publish a government report warning of riots and food shortages and telling porkies to the Queen; you would imagine they would emerge a broken, humbled, crushed individual.
Not so Boris Johnson. He emerged characteristically brimming with optimism and confidence.
No deal? He insisted he had got in place the necessary preparations to avoid the sort of dire scenarios forecast.
An agreement with the EU? Yes he was hopeful of getting an agreement.
And telling lies to the Queen? Absolutely not.
But the difficulty is optimism and confidence only get you so far. MPs want details. They want details about what he's actually doing to avoid the grim no-deal forecast and what he's doing to get an arrangement with the EU
And they want details - or the truth - about why he chose to prorogue Parliament.
Which means if the judges decide on Tuesday that Parliament should be recalled then I suspect Boris Johnson's going to need an awful lot more than bullish bravado.
In a unanimous ruling on Wednesday, the Court of Session in Edinburgh said Mr Johnson's decision to order the suspension was motivated by the "improper purpose of stymieing Parliament".
It came after a legal challenge launched by more than 70 largely pro-Remain MPs and peers, headed by SNP MP Joanna Cherry.
But a ruling last week from the High Court in London had dismissed a similar challenge brought by businesswoman and campaigner Gina Miller.
In their rejection of her claim, the judges argued the suspension of Parliament was a "purely political" move and was therefore "not a matter for the courts".
Mr Johnson has suggested it was "nonsense" to suggest the move was an attempt to undermine democracy, insisting it is normal practice for a new PM.
Prorogation normally takes place every year, but the length and timing of the current suspension - in the run-up to Brexit - has attracted controversy.
Opposition parties have accused the prime minister of ordering it to prevent criticism of its Brexit strategy and contingency plans for a no-deal exit.
They backed a move to order the release of communications between No 10 aides about the decision to order the suspension.
But the government has blocked their release, saying the request to see e-mails, texts and WhatsApp messages from Dominic Cummings, Boris Johnson's chief aide, and eight other advisers in Downing Street was "unreasonable and disproportionate".
The Yellowhammer file, which is redacted in parts and almost identical to a version leaked to the Sunday Times last month, says in a reasonable worst-case scenario a no-deal Brexit could lead to:
The document also says some businesses could cease trading, and the black market could grow in response to disruption along the UK's border with Ireland.
"This will be particularly severe in border communities, where both criminal and dissident groups already operate with greater threat and impunity," it added.
It also raised the prospect of "protests and direct action" in Northern Ireland as a result of disruption to key sectors.
Michael Gove, the cabinet minister with responsibility for no-deal planning, told the BBC the government had taken "considerable steps" to ensure the safest possible departure after a no-deal Brexit in the six weeks since 2 August, the date which appears on the document.
On Wednesday, he said "revised assumptions" will be published "in due course alongside a document outlining the mitigations the government has put in place and intends to put in place".

PM Johnson said he had come to Scotland to renew the ties that bind the United Kingdom. Yet his trickiest task may be to try and restore the ties between him and the leadership of his Scottish party.
On Monday, during his first trip to Scotland as prime minister, Mr Johnson met the first minister of Scotland.
Nicola Sturgeon was expected to tell him that Scotland did not vote for Brexit and they certainly didn't vote for a "catastrophic no deal Brexit."
But his toughest meeting might not have been with the FM, but with the Scottish Conservative leader Ruth Davidson.
Ms Davidson made no secret of the fact that she did not want Mr Johnson as PM.
And in the few days since he took charge relations have already gone further south.
He ignored his Scottish leader's advice not to sack the Scottish Secretary David Mundell and replace him with the pro-Brexit MP Alister Jack.
He then further snubbed the Scottish contingent of parliamentarians when he put an MP who sits for an English seat into the Scotland office as a minister.
Ms Davidson has said publicly that she would not support a no-deal exit from the EU and that as leader of the Scottish party she does not have to sign up to any loyalty pledge to support a no deal.
She believes the PM would have sacked her if he could. But he can't - and she will take full advantage of her ability to speak out in public.
Ms Davidson is highly regarded by Tories as she led the party from having one MP in Scotland to 13.
But not all of those MPs are lining up behind her - most of them will support the PM if push comes to shove. Contrast that with Scottish Conservative MSPs who are more loyal to Ms Davidson. However, they don't have any votes in the House of Commons.
Talk of the Scottish Conservatives forming a breakaway party is premature. Ms Davidson says she will not allow it to happen on her watch. And a Scottish separation is not exactly a good look for a party that is supposed to be wholeheartedly supporting the Union between Scotland and the rest of the UK.
It may not solve any issues for the Tories in Scotland anyway. As one former Tory strategist put it to me - when they rebranded Marathon bars as Snickers they still had peanuts inside and if you have a nut allergy they are still a problem

A no-deal Brexit would be a failure that both the British and Irish governments would be responsible for, Boris Johnson has said.
The prime minister was in Dublin for his first meeting with Irish PM Leo Varadkar since he entered Number 10.
The government has confirmed Parliament will be suspended later after a vote on holding an early general election.
Opposition parties will not back the vote, meaning there will be no election in October as the PM had hoped.
Mr Johnson said he believed a Brexit deal was still possible by the EU summit in October, but Taoiseach Varadkar said there was no such thing as a "clean break" between the UK and the EU.
Mr Johnson has ruled out asking the EU to delay the Brexit deadline of 31 October, although the Irish government has said it would support another extension.
But Mr Johnson told reporters in Dublin he was "absolutely undaunted" about what might happen in Parliament.
The prime minister also said he had looked at the consequences of a no-deal Brexit, and "wanted to find a deal".
The two leaders spoke privately for half an hour before joining their delegations for another half-hour meeting, said a joint statement.
"While they agreed that the discussions are at an early stage, common ground was established in some areas although significant gaps remain," it added.
"We must restore Stormont and we must come out [of the EU] on 31 October, or else permanent damage will be done in the UK to trust in our democratic system," he added.
During their press conference, Mr Varadkar used a classical reference about his British counterpart that gained attention.
"Negotiating FTAs [free trade agreements] with the EU and US and securing their ratification in less than three years is going to be a Herculean task for you," he said.
"We want to be your friend and ally, your Athena, in doing so."
In Greek mythology, the goddess Athena did assist Hercules as an ally - but it was by knocking him out and stopping him from killing his family when he went mad.
By Jayne McCormack, BBC News NI Political Reporter
Boris Johnson arrived in Dublin trying to strike a more conciliatory tone than in previous weeks.
Perhaps brought to bear by cabinet ministers concerned about no deal, Mr Johnson insisted he wants an agreement.
But trust is a crucial tenet of any political relationship.
A stony-faced Leo Varadkar said a deal was still possible, but warned that promises from the UK wouldn't cut it.
The Irish government is also watching Westminster closely, knowing the prime minister is currently boxed in by opposition parties, with few options left.
A breakthrough was never going to happen today, but what went on behind closed doors around this key meeting could pave the way for movement.
The taoiseach invited Mr Johnson to Dublin two months ago, shortly after he was installed in Downing Street, to discuss Brexit.
The Irish government maintains that the backstop - the mechanism to avoid an Irish hard border - is needed in any withdrawal agreement, because of decisions made by the UK.
But Mr Johnson has said he will not sign up to a deal unless the backstop is removed, because it is "anti-democratic".
There is also speculation that the government could propose returning to a backstop that would only apply to Northern Ireland, with the possibility of a role for the Stormont assembly before it could be triggered or new EU rules would take effect.
However, DUP leader Arlene Foster told the BBC she is convinced that Boris Johnson will not pursue the NI-only backstop.
She also said she was encouraged to hear both the British and Irish prime ministers "dialling down the rhetoric" and wanting to find a Brexit deal.
Parliament will be suspended when business in the Commons finishes later on Monday, after MPs have voted again on whether to hold an early general election.
Before Parliament is prorogued, MPs will debate progress reports updating them on efforts to restore the Stormont assembly.
Unless power-sharing talks succeed before Brexit happens, Mr Smith has said direct rule powers from Westminster will need to be implemented at pace.
Meanwhile, legislation designed to delay a no-deal Brexit and force the prime minister to request an extension to the EU deadline received royal assent on Monday afternoon and has become law.
However, Mr Johnson has said he will not ask the EU for another extension, so it is unclear what might happen next.
The government will move another motion asking MPs to vote for a general election on Monday too, but it is unlikely to pass because opposition parties have agreed to reject the demand, saying Mr Johnson is trying to force through a no-deal exit.
The backstop is a key piece of the Brexit deal dictating what will happen to the border between Northern Ireland and the Republic of Ireland.
It is a last resort that guarantees a frictionless border if no better solution is devised in time - by maintaining close ties between the UK and the EU until such a solution is found.

European Commission President Jean-Claude Juncker has said he hopes that the UK will rejoin the European Union at some point in future.
Mr Juncker, the most senior official in Brussels, said he did not like Brexit because he wanted "to be in the same boat as the British".
"The day will come when the British will re-enter the boat, I hope," he said following an EU summit.
Former UKIP leader Nigel Farage said: "The ship will have sunk by then."
The UK is expected to trigger the formal Brexit process this month, beginning a two-year negotiation process of withdrawal.
German Chancellor Angela Merkel said if the UK invoked Article 50 next week, an extraordinary meeting of the other 27 EU states would be held on 6 April.
"We are well prepared and we shall wait with interest," she said.
Prime Minister Theresa May attended the Brussels meeting on Thursday, but left early as the remaining 27 members stayed on to discuss the future of the European Union.
She told reporters before leaving:  "At this summit we've shown once again how Britain will continue to play a leading role in Europe long after we have left the EU" - citing the examples of security cooperation and hosting a summit for the Western Balkans.
European Council President Donald Tusk said the EU would be ready to respond within two days of Mrs May triggering Brexit: "We are well prepared for the whole procedure and I have no doubt that we will be ready in 48 hours."
Meanwhile the European Parliament's chief Brexit negotiator, Guy Verhofstadt has said he would like a "special arrangement" for UK citizens who want to continue their relationship with the EU, so they can continue to keep some rights, such as freedom to travel.
The UK voted by 52% to 48% to leave the EU in last year's referendum.

Downing Street has rejected Justine Greening's call for a fresh referendum on the UK's exit from the EU, saying it will not happen "in any circumstances".
The former education secretary argued the final Brexit decision should be given back to the people and out of the hands of "deadlocked politicians".
She called for three options to be on the ballot paper: the prime minister's Chequers deal, staying in the EU or a clean break from Europe with no deal.
The UK is due to leave in March 2019.
Amid continuing Tory divisions over Mrs May's strategy, the government has accepted changes to legislation for customs arrangements after the UK leaves to avoid a Commons rebellion by Brexit-backing MPs.
No 10 said the amendments to the Customs Bill, including one that would preclude the UK from collecting tariffs on goods bound for EU countries, were "consistent" with the blueprint agreed by the cabinet.
Asked during a Commons statement on last week's Nato summit whether she was "rolling over", Mrs May said she would continue to "listen to the concerns" of colleagues regarding Brexit-related legislation.
Ms Greening, who resigned after the cabinet reshuffle in January, said the referendum should offer a first and second preference vote so that a consensus can be reached.
Speaking on BBC Radio 4's Today programme, Ms Greening said the government's proposals were a "genuine clever attempt at a compromise that could work" but "suits no-one".
The MP for Putney said: "The reality is Parliament is now stalemated. Whatever the proposal on the table, there will be MPs who vote it down. But Britain needs to find a route forward."
Ms Greening, who supported Remain in the EU referendum, is the highest profile ex-Cabinet minister to call for a second referendum.
She said there were other senior Conservatives who agreed with her stance, adding that people who supported Leave in the referendum would also feel the government's approach is "not what they voted for".
In her article in the Times, she lambasted the PM's Brexit blueprint, saying: "We'll be dragging Remain voters out of the EU for a deal that means still complying with many EU rules, but now with no say on shaping them.
"It's not what they want, and on top of that when they hear that Leave voters are unhappy, they ask, 'What's the point?'
"For Leavers, this deal simply does not deliver the proper break from the European Union that they wanted."
By Chris Mason, BBC political correspondent
Combine a hung parliament with Brexit, and when you scan your eye around the House of Commons, you sometimes wonder if they can collectively agree on anything.
The one thing there is certainly not much public support for right now among MPs is another referendum.
Whatever the view of an individual MP on Brexit, most see making the case for another schlep to the polling station a hard argument to flog.
And so while those doing so are a pretty small tribe, and it is a million miles from a majority view, there is pride among them that they can add another name to their gang.
But it is worth remembering that Justine Greening is a pro-European in a marginal seat - Putney in London - that voted heavily to Remain.
Ms Greening, who grew up in Rotherham, where 68% people voted to leave the EU, said the parliamentary stalemate "risks a no-confidence vote and, worse, a Corbyn government, which would be disastrous for the economy".
She had previously suggested a future generation of MPs will seek to "improve or undo" Brexit if it does not work for young people.
Fellow Tory MP Sir Bernard Jenkin, who backed Leave in the referendum, said he agreed with Ms Greening that the PM's plan was "dead" but described her call for a second vote as "a little ill-thought-out".
"If we wanted to extend the uncertainty for another long period this is one way of doing it," he told Today.
Mrs May has ruled out a second vote, as has Labour leader Jeremy Corbyn, although a number of senior Labour figures are backing the cross-party People's Vote campaign for a final vote on any exit deal.
Pro-EU Conservative MP Dominic Grieve told BBC Radio 4's The World at One programme the possibility of holding a second referendum should not be excluded but Mrs May was "entitled to try to develop" her Chequers plan.
"My primary political duty at the moment is to try and help get this country through a Brexit process that is endangering its stability and its wellbeing," he said.
Former UKIP leader Nigel Farage said another referendum was "heading much closer" but could be avoided if the Tories changed leader, adding there was "uproar out there" about the prime minister's proposals.
Suella Braverman, who used to lead a Eurosceptic group of Tory MPs and is now a minister in the Brexit department, said there were "obviously strong views" within her party and described the Chequers plan as a "starting point" for negotiations with the EU.
But the disagreements in the party have also led to another resignation from the government.
Scott Mann has quit his job as a parliamentary private secretary at the Treasury, saying Mrs May's plan was "in direct conflict" with the views of his Leave-voting constituents in north Cornwall and he did not want to deliver a "watered-down Brexit" to them.

Britain and Spain can overcome their differences and maintain strong ties after Brexit, the king of Spain has said in a speech at Westminster.
King Felipe VI said he believed they could begin "the necessary dialogue" to form an arrangement over Gibraltar.
But the government of Gibraltar said the king's focus on a dialogue between London and Madrid was "undemocratic".
The start of a three-day state visit to the UK by the king and queen of Spain ended with a Buckingham Palace banquet.
King Felipe made his comments on Gibraltar in a speech in the Palace of Westminster.
While discussing Britain's decision to leave the EU, he said: "To overcome our differences will be greater in the case of Gibraltar. I am confident through the necessary dialogue and effort, our two governments will be able to work... towards arrangements that are acceptable to all involved."
The government of Gibraltar said it would have to be involved in any discussion between Spain and the UK.
It added that two referenda in 1967 and 2002 showed the people of Gibraltar voted to remain British.
Chief minister Fabian Picardo QC said: "We have no desire to part of Spain or to come under Spanish sovereignty in any shape or form.
"In the times in which we live, territories cannot be traded from one monarch to another like pawns in a chess game."
During the speech, King Felipe said Britain and Spain were "profoundly intertwined" and he respected the UK's decision to leave the EU.
Hundreds of thousands of Britons live in Spain, and a similar number of Spaniards live in the UK, King Felipe told MP and peers.
They "form a sound foundation for our relations," he added.
"These citizens have a legitimate expectation of stable living conditions for their families," he said.
The king highlighted the two countries' important trading arrangements, adding that Britain is "the second largest investor in our country".
At the banquet later hosted by the Queen and Prince Philip at Buckingham Palace, the British monarch acknowledged the two countries had not always seen "eye to eye".
In a speech, she also said: "A relationship like ours founded on such great strengths and common interests will ensure that both our nations prosper now and in the future whatever challenges arise."
The banquet menu began with poached fillet of salmon trout with fennel. It was followed by a medallion of Scottish beef with bone marrow and truffles, with a sauce made from Madeira, and a dark chocolate and raspberry tart for dessert.
The Duke and Duchess of Cambridge, Prince Harry, the Prince of Wales, the Duchess of Cornwall, the Princess Royal, the Duke of York and the Earl and Countess of Wessex also attended.
Earlier the Queen and the Duke of Edinburgh greeted King Felipe and Queen Letizia at Horse Guards Parade, in a traditional welcoming ceremony.
The trip is the first state visit by a Spanish king to the UK since Felipe's father, Juan Carlos, came 31 years ago.
The Queen gifted King Felipe copies of love letters from his great-grandmother to King Alfonso XIII.
Queen Victoria's grand-daughter Princess Victoria Eugenie met King Alfonso on a state visit to Britain in 1905.
The pair married and Princess Victoria Eugenie became Queen Ena of Spain, making King Felipe a descendant of Queen Victoria.
The wind died down and the sun broke through the clouds just as the Queen and Duke of Edinburgh stepped on to the dais at Horse Guards.
Every visiting head of state gets the same welcome - their national anthem and the chance to inspect the guard of honour with Prince Philip. With his retirement imminent, this could be the last time he performed that particular public duty.
Then King Felipe stepped into a carriage with the Queen for the traditional procession down the Mall accompanied by the Household Cavalry. The Duke of Edinburgh and Queen Letizia travelled in a separate carriage.
It was a chance for Britain to show off how well it can do "pomp".
On Thursday, Prince Harry will accompany the royal visitors to Westminster Abbey.
King Felipe will lay a wreath at the Grave of the Unknown Warrior and the prince will join them on a short tour of the abbey, including the Tomb of Eleanor "Leonor" of Castile - the 13th-Century Spanish princess who married Edward I.

Dozens of Labour MPs might be prepared to go against the party's leadership if there is a vote on starting the Brexit process, the BBC understands.
Jeremy Corbyn has said all his MPs will be told to approve the triggering of Article 50 because they should accept the result of last year's referendum.
Lib Dem Tim Farron says generations to come will not forgive that position.
The Supreme Court will announce next Tuesday whether the government needs to seek Parliament's approval.
Ministers say they already have enough powers under the Royal Prerogative to go ahead with Brexit.
But campaigners argue that starting Brexit in this way would be undemocratic and unconstitutional.
In June's referendum, 51.9% of voters backed leaving the EU, while 48.1% supported remaining in the 28-nation group.
Mr Corbyn said he did not think it was right to block Article 50 in the wake of the referendum result.
"It's up to us to use the opportunity that's provided to stop the Tories from doing this bargain basement, low tax haven on the shores of Europe," he told the BBC.
"What I'm saying to all of my MPs is we've supported the principle of holding the referendum, the referendum was held, it delivered a result - I don't think it's right to block Article 50 negotiations.
"It's absolutely right that we're involved in these negotiations and making the case for a fairer and socially just Britain."
Asked if that meant he would be imposing a three-line whip - the strongest available sanction - on Labour MPs, requiring them to back Article 50, he said: "It means that all Labour MPs will be asked to vote in that direction next week or whenever the vote comes up."
However, a senior Labour source has told the BBC between 60 and 80 of the party's MPs might be ready to defy the leadership if there is a vote in Parliament.
Shadow business secretary Clive Lewis said the government's current position is "unacceptable" and he wants further assurances.
Another Labour MP told the BBC there would be a "swathe" of resignations from the front bench if Mr Corbyn instructed his MPs to vote for Brexit.
The MP said that for colleagues in constituencies that voted strongly for Remain it would be "suicide" to back Article 50.
And Labour's Mike Gapes, who has been outspoken in his criticism of Mr Corbyn in the past, told the Ilford Recorder he would not be toeing the party line.
"I am going to vote against triggering Article 50 and let me be clear, I am going to be as loyal to Jeremy Corbyn as he was to previous Labour leaders," he said.
"I will show the same loyalty he did when he voted, 500 times, against the Labour whip under successive party leaders. The people of Britain did not vote to become poorer and I will not vote in favour of any deal that would see us leave the single market."
BBC political correspondent Ben Wright said nobody expected Parliament to stop Brexit being triggered, but Mr Corbyn could struggle to keep his party's position coherent, whether he insists on a three-line whip or not.
Lib Dem leader Mr Farron accused Labour of "lamely" giving up against the government's drive for a hard Brexit.
He said he believed Mr Corbyn had put the party on the wrong side of the biggest political issue in a generation.
"I think what Labour has done is to believe this is too difficult for them politically, let's just wait for it to go away, and the meeker we are, the quicker it will go away," he told the Guardian.
"I think that's the calculation they've made, and this and future generations are not going to forgive them for that.
"It's not divisive to hold the government to account, and not just to lamely give up as we go over a cliff, and that is what Labour are doing - they are being the most ineffective opposition in living memory."
Mr Farron added that his party, which has just nine MPs, would not consider an electoral deal with Labour because Mr Corbyn is "electorally toxic".
Green Party co-leader Caroline Lucas claimed Mr Corbyn was "trying to deny Labour MPs the chance to make their own principled choice on one of the most important decisions of the UK's recent history".

A butterfly flaps its wings with hardly a care in the world and innocently triggers a tornado, goes the theory.
The diehard Remain supporters advocating a further EU referendum are hardly retiring butterflies and their campaign is no political tornado.
But their call for voters to be given another say on the EU is now, at the very least, a gentle breeze whistling through British politics. It will be felt by all sides in the final phase of the Brexit negotiations.
A compromise motion, thrashed out during late night negotiations at the Labour conference in Liverpool, now specifically ties a reluctant Labour leadership to another referendum.
The party would back such a move if the leadership's preferred option of a general election failed.
John McDonnell, the shadow chancellor, dashed the hopes of pro-Europeans in the party by suggesting on the Today programme that the option to Remain in the EU should not be on the ballot paper.
The choice should instead be about the proposed Brexit deal.
But the loose wording of the Labour party does not rule out a Remain option on the ballot paper and McDonnell conceded that it would be up to Parliament to decide the wording.
The wrangling has led to much soul searching in the new Labour movement taking shape under Jeremy Corbyn's leadership. The Momentum group, established to shore up his leadership at the grassroots, has been torn between pro-European instincts and loyalty to Corbyn.
He is heir to the Bennite tradition which regards the founding principles of the EU as anathema to Socialism.
Momentum was thinking of taking a neutral position had the motion been difficult for Jeremy Corbyn. One Momentum source told me that, while the organisation is strongly pro-European, it would do nothing to jeopardise its main goal; the election of a truly Socialist government.
The People's Vote campaign are reasonably content. They know their greatest weakness in Liverpool is they are seen as a bunch of unreconstructed Blairites seeking to thwart the will of the people on the EU and undermine Corbyn in the bargain.
The campaign believe they have shown they have far wider support. They hope to have created a space in November for Labour to be able to endorse a referendum on the grounds that warring Conservative MPs agree on one thing - there must be no general election before 2022.
And they believe that the motion leaves open the possibility of an option to Remain in the EU on the ballot paper. One source in the People's Vote campaign told me: "The door is now wide open."
The numbers in parliament suggest that if Labour endorses a further referendum it would be difficult to pass the legislation without a sizeable contingent of Tory MPs defying Theresa May.
But the events in Liverpool now set the stage for the issue of a further referendum to become everyone's favourite weapon in the final phase of the Brexit negotiations.
To pro-Europeans it is an escape hatch if Theresa May fails to negotiate a deal with the EU or she negotiates a deal that is rejected by Parliament.
To Brexiteers the People's Vote campaign does their work for them. Leavers have consistently said that the pro-European side represents an out of touch elite afraid to accept the judgment of the people. And along comes a well funded campaign seeking to overturn the results of a referendum they won by more than a million votes.
Theresa May is using the threat of another referendum to warn Brexiteers opposed to her plan to be careful what they wish for.
Brexiteers invited to dinner in Downing Street recently were reportedly told if the prime minister's plans collapse then the commons speaker John Bercow will help create the conditions to vote through a further referendum.
The EU is, of course, watching events very closely. Some EU leaders said at last week's summit that they would be happy to extend the article 50 negotiations to allow a further referendum to take place.
Innocently or not that sort of talks infuriates Theresa May who says the mere talk of a vote allows the EU to hold back in the hope the UK changes its mind.
An innocent butterfly going about its business may never unleash a tornado over British politics. But it is certainly changing the weather.
You can watch Newsnight on BBC 2 weekdays 22:30 or on Iplayer. Subscribe to the programme on YouTube or follow them on Twitter.

Labour delegates have approved a motion that would keep all options - including a fresh referendum - on the table if MPs are deadlocked over Brexit.
It was passed by a show of hands at the party conference in Liverpool.
The vast majority were in favour of the motion, with only a small number against.
Leader Jeremy Corbyn - who has previously ruled out another EU referendum - has said he will respect the result of the vote.
Sir Keir Starmer said earlier that the option of staying in the EU would be on the ballot paper in any future referendum if Labour gets its way.
In his party conference speech, the shadow Brexit secretary said all options should be kept on the table, including a so-called People's Vote, to "stop a destructive Tory Brexit".
But a senior Unite official said another vote would "reopen the wounds of Brexit" not heal them.
Labour's policy had been to force an election if MPs are deadlocked over Brexit but members succeeded in getting a debate on getting a fresh referendum on to the agenda at the conference.
Sir Keir told Labour activists if a general election was not possible "then other options must be kept open".
"That includes campaigning for a public vote," he said.
"It is right for Parliament to have the first say but if we need to break the impasse, our options must include campaigning for a public vote and nobody is ruling out Remain as an option."
Monday saw confusion over whether the leadership thought any fresh referendum should include staying in the EU as an option.
Shadow chancellor John McDonnell said he thought any vote should be on the terms of a Brexit deal - rather than on remaining in the EU.
But he later said "all options" were on the table - a point reinforced by Sir Keir.
Labour - which wants the UK to remain in a customs union but not the single market - has not ruled out voting for any deal Mrs May brings back from Brussels, ahead of the UK's 29 March departure date.
But Sir Keir said the six tests his party has set - including guarantees on workers' rights and retaining the economic benefits of existing market arrangements - were unlikely to be met.
"Some have said Labour could vote for any deal the Tories reach. Some have said we may abstain. Some have said we may vote for a vague deal," he said.
"So, let me be very clear - right here, right now: if Theresa May brings back a deal that does not meet our tests - and that looks increasingly likely - Labour will vote against it. No ifs, no buts.
"And if the prime minister thinks we'll wave through a vague deal asking us to leap blindfolded into the unknown, she can think again."
But Unite assistant general secretary Steve Turner said any vote on the outcome of the Brexit negotiations could not be a re-run of the 2016 in-out referendum.
"Despite what Keir said earlier, it's a public vote on the terms of our departure," he said.
"We desperately need a better, fairer society - we need to heal the wounds of Brexit, not reopen them, and only our movement, united with a proud socialist government, is capable of doing that."
The Labour Leave campaign group, which backed Brexit in the 2016 referendum, said Sir Keir was "playing with fire" and talk of a referendum made Labour look like "the party of Remain".
"We're damaging the Labour brand and alienating our supporters," said its general secretary Brendan Chilton.
"We have already had a vote on the UK's membership of the EU; it's been done and dusted. The Labour Party and its members must accept this and move on."
The prime minister's Chequers plan, which would see the UK staying closely aligned to the EU in some areas, such as the trade in goods, has been criticised by EU leaders and many of her own MPs.
The Conservatives accused Labour of "playing political games".
"Labour seem determined to take us all back to square one by rejecting a deal out of hand then trying to delay Brexit and re-run the referendum," said Brexit minister Robin Walker.

Labour's Brexit spokesman has insisted the party could back another referendum that offered voters the chance to stay in the EU.
Sir Keir Starmer said the party was "certainly not ruling out" such a move.
He was speaking after shadow chancellor John McDonnell said he thought any vote should be on the terms of a Brexit deal rather than staying in the EU.
Mr McDonnell later said "all options" were on the table if it came to another referendum.
On Tuesday, Labour's conference in Liverpool will debate and vote on a motion to keep a new referendum "on the table" if Labour is unable to force a general election.
Key delegates - including Sir Keir and leading figures from some trade unions - decided the text at a meeting which lasted several hours on Sunday evening.
The final draft for the vote says: "If we cannot get a general election, Labour must support all options remaining on the table, including campaigning for a public vote."
Since the draft was finalised, key figures have faced questions on whether it will include the option to stay in the EU.
Speaking on BBC Radio 4's Today programme, Mr McDonnell said that Labour would continue to respect the 2016 referendum, in which people voted by 51.9% to 48.1% for the UK to leave the European Union, adding: "If we are going to respect the referendum it will be about the deal."
And he said a general election was needed so a Labour government could strike a Brexit deal with the EU which "brings the country together".
But later, Sir Keir told the BBC the party was deliberately not being "prescriptive" about the question that could be posed in another referendum, saying it was "certainly not ruling out" the option to stay in the EU.
Backbench MP David Lammy, a prominent campaigner for a second referendum, said it would be "farcical" to have a vote without the option of remaining in the EU.
After the late-night meeting on Sunday night, a Labour source told the BBC's political editor Laura Kuenssberg: "There was consensus in the room opposing the Tories' chaotic approach to the Brexit negotiations... and that a general election should be called as soon as any deal is voted down by parliament.
"It was then agreed that if we cannot get a general election Labour must support all options remaining on the table, including campaigning for a public vote."
The Labour Party has never formally rejected the option of a so-called people's vote on Brexit, but both Mr Corbyn and his deputy, Tom Watson, have indicated they would prefer it to be resolved by a general election.
On Twitter, Prime Minister Theresa May said Labour's approach sought to "Britain back to square one - betraying all those who voted in the 2016 EU referendum".
By Iain Watson, BBC political correspondent
After what I am told was six re-drafts and five and a half hours of discussion, wording that could bridge the gap between campaigners for a new referendum and a reluctant leadership was agreed.
But what was left out of the conference motion is as important as what went in.
The leadership had to agree that wording which restricted a future referendum to "the terms of Brexit" had to go.
This means that the party could, in theory, back a referendum that gave voters the option of remaining in the EU and not just a vote on the final deal.
Campaigners for a new vote see this as significant step forward.
But allies of Jeremy Corbyn say the wording doesn't commit him to backing a referendum as it is still only "an option on the table" if Theresa May refuses calls for a general election.
So still a fudge of sorts - but one with a slightly sweeter taste for supporters of a new vote who firmly believe that "all options" will become their option.
However, even the hint of a new referendum will allow the Conservatives to claim that Labour weren't serious enough about respecting the previous one.
Pressed on the issue on BBC One's Andrew Marr Show on Sunday, Mr Corbyn, who has said he is not calling for another referendum, said "our preference" is for a general election.
He said that would then allow a Labour government to negotiate the UK's future relationship with Europe.
"Let's see what comes out of conference. Obviously I'm bound by the democracy of our party," he added.
Brexit Secretary Dominic Raab ruled out a snap election this autumn, saying the idea was "for the birds".
The UK is due to leave in March 2019 and Theresa May has been negotiating with other EU leaders on the UK's future relationship with the bloc.
Talks hit a stumbling block at a summit in Salzburg on Thursday when EU leaders rejected Mrs May's plan for Brexit - known as the Chequers agreement, and she warned them she was ready to walk away rather than accept a "bad deal".
By Newsnight political editor Nick Watt
The wrangling has led to much soul searching in the new Labour movement taking shape under Jeremy Corbyn's leadership. The Momentum group, established to shore up his leadership at the grassroots, has been torn between pro-European instincts and loyalty to Corbyn.
He is heir to the Bennite tradition which regards the founding principles of the EU as anathema to Socialism.
Momentum was thinking of taking a neutral position had the motion been difficult for Jeremy Corbyn. One Momentum source told me that, while the organisation is strongly pro-European, it would do nothing to jeopardise its main goal; the election of a truly Socialist government.
The People's Vote campaign are reasonably content. They know their greatest weakness in Liverpool is they are seen as a bunch of unreconstructed Blairites seeking to thwart the will of the people on the EU and undermine Corbyn in the bargain.
The campaign believe they have shown they have far wider support. They hope to have created a space in November for Labour to be able to endorse a referendum on the grounds that warring Conservative MPs agree on one thing - there must be no general election before 2022.

Labour could form the next government without a general election if MPs don't back Theresa May's Brexit deal, John McDonnell has suggested.
The shadow chancellor said Labour should be offered the chance to form a minority administration if Mrs May keeps losing Commons votes.
The party would then seek to get majority for its version of Brexit.
Failing that, he said, there should be a general election and the final option would be another EU referendum.
Theresa May is heading to Brussels for talks with EU leaders and is hoping they will finalise the Brexit withdrawal agreement on Sunday. MPs will then get a vote on the deal.
As things stand, it appears there is no majority for Mrs May's deal in the Commons - but ministers hope enough MPs will swing behind it to get it through because the only alternative is no deal or "no Brexit".
Labour and the other opposition parties are trying to find a way to present MPs with other options.
Mr McDonnell said there could be a series of votes and it was "very difficult to predict" what the final outcome would be - but, echoing Conservative cabinet minister Amber Rudd, he said he did not think there was a majority for a no-deal Brexit.
He said: "My own view is we haven't explored sufficiently, neither has the media, these concepts, the constitution, our custom and practice,
"If it's a minority government and they can't obtain a majority in parliament, usually it's then the right, the duty of the Monarch to offer to the Opposition the opportunity to form a government and that would be a minority government, and see if they can secure a majority in parliament.
"I think we can secure a majority in parliament for some of the proposals we're putting forward."
He said opposition parties were normally asked to form a government when a minority government was losing votes in the House of Commons.
This was already happening as the Democratic Unionist Party withdrew its support for Mrs May in Budget votes in protest at her EU withdrawal agreement, he said.
"However, I think the test is whether the government is losing consistent votes on the issue of the deal itself," he argued.
In that case, he argued, Labour should be given a chance to try and get a majority for its plans.
"Failing that I think a general election is the route we need, and obviously, if we can't secure that then a further referendum."
At the moment Labour was working an amendments to the meaningful vote, that will give MPs an "opportunity to avoid no deal at all costs - and I think there is a vast majority of MPs that would support that".
He said he hoped "to demonstrate over the next couple of weeks that there is a consensus in Parliament for a new approach".
The shadow chancellor was sceptical about the chances of Brexit being stopped by another referendum, as some of his party's own MPs in the People's Vote campaign are hoping.
"My fear is that if we did have another referendum, we might get the same or similar result and the country will still be divided. Somehow we have got to try and bring the country back together again."
If there was another referendum, putting the option of staying in the EU on the ballot paper should be "part of the discussion", he told the event.
He said Labour would seek to negotiate a permanent customs union with the EU after Brexit, which he said would remove the need for a Northern Ireland "backstop" that has caused so much controversy.

Labour will back Conservative rebels over Brexit unless the prime minister accepts changes to its repeal bill, the party's shadow Brexit secretary says.
Sir Keir Starmer wants six changes to the bill, which aims to transfer EU legislation into British law.
If these are not accepted Labour will back Tory rebels in an attempt to force a vote on the final EU deal, he said.
The government said it would listen to MPs about possible improvements to the bill but would not let it be "wrecked".
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The loss of the government's Commons majority in the June general election means a relatively small revolt by Conservative MPs could derail the legislation.
Hundreds of amendments to the bill have already been tabled by Tory rebels, as well as opposition MPs.
Writing in the Sunday Times, Sir Keir said the government had withheld the legislation from the House of Commons for two weeks running because it fears defeat on at least 13 amendments at the hands of Tory rebels.
He said it was "clear" that ministers could not proceed with the bill as it stands and threatened to "work with all sides" to get his changes made - unless ministers adopted them and end the "paralysis".
Sir Keir demanded that:
The shadow Brexit secretary wrote: "I believe there is a consensus in Parliament for these changes.
"And there is certainly no majority for weakening rights, silencing Parliament and sidelining the devolved administrations.
"There is a way through this paralysis.
"Labour will work with all sides to make that happen."
Sir Keir's intervention comes days after EU leaders agreed to begin scoping work on trade talks.
But they also made clear Britain must make further concessions on its divorce bill to unlock talks on a future trading relationship.
Brexit Secretary David Davis will travel to Paris for Brexit talks on Monday after France appeared to emerge as the most hardline EU member state on the exit bill.
The prime minister is due to update the Commons on Monday on the progress made during the summit on Thursday and Friday.
Mrs May is expected to say that while negotiations on Brexit are "deeply technical" she has never forgotten that millions of people are at the heart of the process and they remain her "first priority".
She will also say that the millions of European citizens living in the UK make an "extraordinary contribution" to our society and that "we want them to stay".
A government spokesman said the repeal bill was "essential" to deliver on the result of the referendum while ensuring the maximum possible legal certainty for businesses and citizens.
The UK is due to leave the EU in March 2019, following last year's referendum result.

Jeremy Corbyn has sought to play down divisions within his top team after one of his closest aides said he would quit and criticised the party's leadership.
Andrew Fisher's exit comes after a failed bid to oust deputy leader Tom Watson, as Labour conference begins.
Mr Corbyn said he got on well with both men and Mr Fisher was "extremely distressed" when he wrote a memo saying the leader's office was "incompetent".
He said he would serve five years if elected PM, adding: "Why wouldn't I?"
On the second day of its conference, Labour is unveiling plans to scrap Ofsted and replace it with a new school inspection system.
Mr Corbyn said the regulator was too "assertive" and its system of oversight needed to be more "supportive" of schools and pupils.
Labour is also promising to axe prescription charges in England if the party wins power, taking it in line with Scotland, Wales and Northern Ireland, where they are already free.
In a wide-ranging interview with the BBC's Andrew Marr, its leader dismissed talk he could stand down as Labour leader in the next year or so as "wishful thinking".
He also defended the party's Brexit policy - to be debated later - amid calls for him to come out unambiguously to remain in the EU rather than sit on the fence.
While most Labour supporters wanted to remain in the EU, he said the party must respect the result of the Brexit referendum and do more to understand why people voted to leave.
If it wins power, Labour would negotiate a new Brexit deal in three months, which would then be put to the people in a referendum within six months, with the option to leave or remain.
Mr Corbyn would not be drawn on which side he would back, saying "let's see" what kind of new deal he was able to negotiate with the EU.
However, he suggested he would ultimately go along with whatever party members decided at a special conference which could be held to settle the issue.
At a fringe event at the party's conference, deputy leader Tom Watson said Labour was a "remain party" and should lead the campaign to remain in the EU in a second referendum.
"By backing a people's vote, by backing remain, I am sure we can deliver the Labour government the people of this country so badly need," he said.
BBC political correspondent Iain Watson says the NEC, Labour's governing body, agreed Brexit proposals on Sunday.
Labour conference will be voting on that motion and a Brexit motion on an issue put forward by members on Monday.
Ahead of next week's Supreme Court's ruling on whether the suspension of Parliament is lawful or not, Mr Corbyn said if the judges found against Boris Johnson, MPs must be recalled.
If that happened, he said he would "take immediate action" in Parliament along with other opposition parties to put pressure on the prime minister.
But Conservative chairman James Cleverly said Mr Corbyn could not say whether he would back Brexit even if the party negotiated its own deal.
"Jeremy Corbyn can't even make up his mind on the most important issue facing the country. He would delay Brexit until at least 2020 and even longer if the EU demand it."
Mr Corbyn was dealt a blow on Saturday when it emerged one of his aides, head of policy Andrew Fisher, revealed he will quit his post by the end of the year.
He said he wanted "to spend more time with his young family", but the Sunday Times claims he warned Mr Corbyn would not win the next general election and criticised the leader's office "lack of professionalism, competence and human decency".
Mr Corbyn acknowledged Mr Fisher, who helped write the 2017 manifesto, had expressed concerns about the party's direction and he had spoken to him "at length" about it.
He said Mr Fisher was "extremely distressed" when he made the comments, suggesting it was the sort of disagreement which happened in many workplaces.
"He is a great colleague, he is a great friend. We get along absolutely very well. He has promised whatever happens in the future, we will work together on policy issues."
Amid continuing fallout from the bid to oust Mr Watson, Mr Corbyn also said he was not told beforehand of Friday's move by left-wingers on Labour's ruling body to abolish the role.
The party will now consult on replacing the single role with two deputies - one of whom will be a woman.
Mr Corbyn, who has been at odds with his deputy over Brexit, said he got on "absolutely fine" with him and suggested his intervention had "put the issue to bed".

Holding another referendum on the UK's EU membership could lead to "civil disobedience", a shadow minister says.
Labour's Barry Gardiner said calls for another vote undermined "the whole principle of democracy in this country", warning voters could turn to "more socially disruptive ways of expressing their views".
Both Labour and the Conservatives have ruled out another referendum.
But some MPs want a vote on the final Brexit deal.
One of the supporters of the People's Vote campaign, Labour MP Ben Bradshaw, said Mr Gardiner was ignoring "the democratic right of the people to change their minds".
The UK voted to leave the EU in June 2016, and this is due to happen in March 2019. Negotiations are taking place on what their final relationship will look like.
The government has promised MPs a "meaningful vote" on any deal reached with Brussels - but the People's Vote campaign think this should be the subject of a new nationwide referendum.
Speaking on BBC Radio 4's Today programme, Mr Gardiner, the shadow international trade secretary, said that while he had campaigned for a Remain vote, there was "more to this than simple economics - there is also the social, the democratic principles at play here".
Remain and Leave campaigners had told people that voting in the 2016 referendum would determine the UK's future for the next 40 or 50 years, he said.
"We meant it," he added.
Warning against Remain campaigners telling people they were "stupid enough to do what you wanted rather than what we wanted", he said: "You never give as much succour to the extreme right as when you cut off the mechanism of democratic change.
"If people want to be able to achieve change through democratic means, if they feel that that is being denied to them, they then turn to other more socially disruptive ways of expressing their views, and that is the danger here."
Holding another referendum would be "playing with the foundations of our country in a way that is really, really damaging," he added.
"We have to respect people's vote in that referendum. We told them we would, we must do it."
Pressed on whether he believed another referendum could prompt violence on the streets, Mr Gardiner insisted he "didn't say that" but added: "In any situation, if people feel the route to change is no longer a democratic route, then you look to social disruption, perhaps civil disobedience in a different way".
Liberal Democrat Brexit spokesman Tom Brake said he was "appalled" at Mr Gardiner's comments:
Labour leader Jeremy Corbyn was pressed on Mr Gardiner's remarks during a visit to New Lanark as part of a four-day trip to Scotland.
"There are no plans for anyone to hold a second referendum," he said.
"What we have to do, I think, is concentrate on the relationship we have with the European Union in the future, but we're obviously part of the continent of Europe and we have to have a trading relationship with all countries in Europe."
Mr Corbyn also said the government should not be preparing for no Brexit deal being reached, saying that instead "we should be making sure that there is an agreement and there is a deal so there isn't a cliff edge".
The government has said it believes a deal to be the most likely outcome of the negotiations but that it is also putting in place contingency plans in case this doesn't happen.

Owen Smith says he "stood by his principles" in calling for another EU referendum - a move which resulted in his sacking from Labour's shadow cabinet.
The former shadow Northern Ireland secretary said Jeremy Corbyn had made a "mistake" in firing him.
He also said the party should "shift its position" on Brexit.
Mr Smith was asked to stand down on Friday after he wrote an article for the Guardian calling for a second vote.
Speaking about his sacking on BBC Radio 4's Today programme, he said: "I think it is a mistake, for Jeremy Corbyn in particular, who has always understood the value of people standing by their principles.
"It is the position that he has often adopted, and it is certainly a value in him that others have extolled."
"In truth I think that is all I have done. I have stood by my principles."
Mr Smith said leaving the EU was "the biggest economic crisis that our country will have faced for many, many generations" and he believed Labour should stand against it.
Referring to Mr Corbyn's views on Brexit as "a more Eurosceptic position", he added: "It's the first instance that I can think of in living memory of a government pursuing a policy that they know is going to make our economy smaller and reduce people's livelihoods and life chances and I cannot understand why we in Labour would support that."
Party figures have criticised Mr Corbyn's decision to sack Mr Smith, with Labour peer Peter Hain describing the dismissal as a "Stalinist purge".
The former Northern Ireland secretary said Mr Smith was widely respected for his work in the role.
Labour MP Chuka Umunna said it was "extraordinary" that the shadow minister had been sacked for advocating a Brexit policy which, he said, had wide support in the party.
Fellow MP Anna Turley said Mr Smith's departure was "disappointing" and he would be a loss to the front bench, while former cabinet minister Ben Bradshaw told Mr Smith he was "very sorry" to see him go.
By Jonathan Blake, BBC political correspondent
In a phone call from Jeremy Corbyn and what a source described as a "civil conversation", Owen Smith was told he was being sacked.
Mr Smith's comments on Brexit policy were seemingly a step too far for the party leadership, who'd welcomed him back into the fold after his leadership challenge in 2016.
The angry response from some MPs has again laid bare their opposition to Jeremy Corbyn as leader.
But Mr Corbyn's grip on power in the party has never been stronger.
The fact that he can make this move without fear of open rebellion, is a demonstration of that.
However shadow home secretary Diane Abbott said although Mr Smith was "a valued colleague", he could not sit on the opposition front bench while advancing "a position which was simply not Labour Party policy".
Ms Abbott, who in November told constituents she would push for a referendum on the final Brexit deal - before clarifying she wanted a Parliamentary vote - said Mr Smith would be able to "make a contribution to the debate" outside the shadow cabinet.
BBC Newsnight's political editor Nick Watt said supporters of Mr Corbyn thought Mr Smith "wasn't very collegiate" and had defied collective responsibility.
Mr Watt also reported that friends of Mr Smith complained that journalists knew about the sacking before Mr Corbyn phoned him - a claim disputed by the Labour leader's office.
Mr Smith has been replaced by Rochdale MP and shadow housing minister Tony Lloyd.
Mr Corbyn said that Mr Lloyd was "highly experienced" and "committed to ensuring that peace in Northern Ireland is maintained", as well as helping to steer the devolution deal "back on track".
In a tweet, Mr Smith said his concerns about Brexit, which he outlined in a Guardian article, were shared by other supporters and members of the Labour party.
In the article, Mr Smith called for Labour to back membership of the EU single market.
The Labour leader announced last month that the party wanted the UK to be a permanent member of a customs union with the EU after Brexit.
But Mr Smith, who unsuccessfully challenged Mr Corbyn for the party leadership in 2016, insisted Labour needed to do more than "just back a soft Brexit or guarantee a soft border in Ireland".
He wrote: "If we insist on leaving the EU then there is realistically only one way to honour our obligations under the Good Friday Agreement and that is to remain members of both the customs union and the single market."
Labour's shadow Brexit Secretary Sir Keir Starmer has said the party was "not calling for a referendum at this stage".

We have just witnessed a classic conference '360'.
It's a row in these heady days where one major player in the bubble promises something, then a rival says something rather different.
Then, whoops, fearing a story about splits and dissent within a matter of hours, there is what is officially called a "clarification" - in other words one of those involved in the clash eats their words.
As we reported last night, before midnight, Labour delegates agreed there would be a compromise to hold out the possibility of having another referendum.
It was difficult to decide because the party leadership is conscious of not hacking off millions of Labour voters who want to leave, but also have to try to keep the membership - who, if they had a choice, would probably stop Brexit dead in its tracks tomorrow - happy.
That's why there was so much discussion last night over the wording. But by midnight, allies of Keir Starmer and the Labour elements in the campaign for another vote were content.
Not only did they have the idea on the agenda, but they had been able to keep the promise vague enough that if the circumstances emerge, there could be another referendum with, crucially, the option of staying in the EU on the ballot.
But at 7:30am the shadow chancellor piled in telling the BBC that it was important to "respect the referendum", explaining that in his view another public vote should be on the terms of the deal.
Was he trying to kill off the idea of another vote on stay or leave? It seemed that way. Then Tom Watson, who had been part of the push to change the policy, didn't quite agree with him.
He told me a couple of hours later there was an "inevitable logic" to in or out being part of this hypothetical vote. Then Keir Starmer, who was in the room for all of those hours, came striding across the conference plaza to make absolutely clear that deliberately, and explicitly, the agreement in the room was to leave the option of holding another EU referendum on staying in or leaving on the table (in the end).
Then lo and behold, perhaps thinking of the headlines his own dramatic speech this afternoon might generate, John McDonnell popped up again, to say that after all, guess what, "all options", including a vote, perhaps, one day, to stay in the EU, are after all still on the table.
So, as you were.
The 360 is complete. Labour is still inching towards the possibility of a second public vote that might include staying in the European Union.
But the reluctance of Jeremy Corbyn's close allies seems clear. Conference will vote for the promise of that possibility, but that's a long way from vowing the party would make it happen.

Talks between Labour and the government aimed at breaking the Brexit impasse have ended without an agreement.
Jeremy Corbyn said the discussions had "gone as far as they can", blaming what he called the government's "increasing weakness and instability".
Theresa May said the lack of a "common position" within Labour over a further referendum had made talks "difficult".
The prime minister said she would now consider putting options to MPs on Brexit that may "command a majority".
But Irish Prime Minister Leo Varadkar called the end of the talks a "very negative development".
Mrs May has promised to set a timetable for leaving Downing Street following a House of Commons vote on her EU Withdrawal Agreement Bill in the week beginning 3 June.
Brexit had been due to take place on 29 March - but after MPs voted down the deal Mrs May had negotiated with the bloc three times, the EU gave the UK an extension until 31 October.
This prompted negotiations between the Conservatives and Labour to see if the parties could come to a Brexit agreement, despite differences over issues including membership of a customs union and a further referendum.
The forthcoming leadership contest may firm up opposition to Theresa May's bill on the Conservative benches
By putting the Withdrawal Agreement Bill out of its misery almost as soon as it appears, the prime minister's critics know she will vacate office sooner rather than later.
But some candidates will be keener for her to get Brexit over the line, even with a less than optimal deal, so they don't immediately get bogged down with difficult votes. It would also allow them to make their pitch based on the future relationship with the EU.
So could some of their supporters - irrespective of their public criticism of the deal - quietly vote to get it over the line?
Read the full article
But in a letter to the prime minister, Labour leader Mr Corbyn wrote: "I believe the talks between us about finding a compromise agreement on leaving the European Union have now gone as far as they can."
The move towards choosing her replacement meant "the position of the government has become ever more unstable".
He later said his party had negotiated "in good faith and very seriously, and put forward a lot of very detailed arguments", which he thought was "the responsible thing to do".
He added: "The issue [is] that the government has not fundamentally shifted its view and the divisions in the Conservative Party mean the government is negotiating with no authority and no ability that I can see to actually deliver anything."
Speaking after meeting Tory activists in Bristol, Mrs May said: "There have been areas where we have been able to find common ground, but other issues have proved to be more difficult.
"In particular, we haven't been able to overcome the fact that there isn't a common position in Labour about whether they want to deliver Brexit or hold a second referendum to reverse it."
She said the government would consider what had come out of the meetings with Labour and "consider whether we have some votes to see if the ideas that have come through command a majority in the House of Commons".
Labour's favoured plan includes a permanent customs union with the EU, meaning no internal tariffs (taxes) on goods sold between the UK and the rest of the bloc.
It also keeps the option of a further referendum on the table, giving the public a say on the deal agreed by Parliament.
Both scenarios have caused anger among Brexit-backing Conservatives, who claim a customs union would prevent the UK from negotiating its own trade deals around the world after leaving the EU, and who believe another public vote is undemocratic.
Some MPs have also criticised Mrs May for even entering into talks with Labour, but the prime minister said the government had "no choice but to reach out across the House of Commons".
Before the talks with Labour, the prime minister - whose Conservative Party does not have a majority in the Commons - failed to get her deal through three times, by margins of 230, 149 and 58 votes.
The DUP, which supports her government on certain issues, opposes Mrs May's agreement with the EU over its implications for Northern Ireland.
Following the collapse of the discussions with Labour, DUP leader Arlene Foster said: "This round of talks has wasted time rather than making progress and reducing uncertainty. It was always doomed to failure."
Shadow Brexit secretary Sir Keir Starmer said the PM was "trying to blame everyone but herself for the collapse of cross-party talks".
He tweeted: "She knows the reality is she couldn't carry her own side or offer a realistic compromise. Any deal agreed wouldn't last a day under a new Tory leader."
But Brexit Secretary Stephen Barclay said the government had moved in some areas - specifically on workers' rights and environmental standards - and had been "having discussions around where we were on customs arrangements".
He said senior Labour figures like Sir Keir had been insisting on a further referendum on any deal, adding: "It begs the question why have they taken six [or] seven weeks for talks?"
Liberal Democrat leader Vince Cable criticised both of the main parties, tweeting: "The weakness of the government and the vacillation of the Labour Party put their talks on very shaky ground from the beginning."
The director general of the CBI business group, Carolyn Fairbairn, called the end of the talks "another day of failed politics" and "another dispiriting day".
She called for Parliament's recess at the end of this month to be cancelled, adding: "This is no time for holidays. It's time to get on with it."
On Thursday, former Foreign Secretary Boris Johnson became the latest MP to put his name forward as a possible successor to Mrs May.
Asked by reporters on Friday if he would be running for the leadership, Environment Secretary Michael Gove said it was now time for colleagues to "focus" on delivering Brexit.

Jeremy Corbyn's policy on Brexit has triumphed at Labour conference, as members endorsed his stance to stay neutral while negotiating a new deal.
The party voted against a motion which would have seen Labour backing Remain in any future referendum.
But there was confusion as the votes were called, as the chair of the proceedings faced calls for a recount.
Labour's position on Brexit has dominated the conference agenda, with huge disagreements over the issue.
The party's draft plan for its Brexit policy, put forward by Mr Corbyn, suggests that, if Labour wins power in a general election, it would remain neutral while negotiating a new deal with the EU within three months.
It would then hold a referendum within six months, and the party would decide which side to back ahead of that at a special conference.
Grassroots activists at the conference have been pushing for an unambiguous stance, tabling a motion calling for Labour to campaign "energetically" to Remain.
But this motion was rejected in a show of hands while a motion setting out the leadership's official position and another endorsing its handling of Brexit were overwhelmingly passed.
After the results were announced by trade union official Wendy Nichols, there were charged scenes in the conference hall.
Several delegates called for the votes to be counted individually, suggesting the outcome of the Remain motion was much closer than officials had suggested.
One delegate said there had to be an official card vote as "this is one of the most important decisions Labour is going to take in the next decade".
The result is a major boost for Jeremy Corbyn, who was backed by the majority of Labour's 12 affiliated unions, including Unite and the GMB.
Unison had broken ranks with other unions to back the Remain motion.
Shadow Brexit secretary Sir Keir Starmer said he was disappointed by the result of the vote, and that he would campaign for Remain.
"Would I have liked us to have gone a bit further and won that vote? Of course I would - but I don't want to take away from the fact that is quite considerable movement," he said.
The leader of the Unite union, Len McCluskey, said the vote showed ordinary members coming behind the Labour leader's stance in a show of loyalty.
"What you've seen here is a massive show of support for Jeremy Corbyn," he said, adding that it was "time to unite".
The vote was decisive - the Labour leadership position on Brexit triumphed.
Those calling for a more robust Remain stance at the likely snap election were defeated.
But the manner of the triumph was immediately called in to question.
The vote wasn't a secret ballot, it was a show of hands.
Calls for a card vote - where the vote of each delegate is individually counted in secret - were dismissed by the chair.
That's not to say there wasn't clear show of support for the leadership.
But some remainers maintain that the vote would at least have been closer if it wasn't conducted in public.
That's because the debate  became - for some delegates - a demonstration of support for the leadership, close to an election, rather than a pure test of opinion on Brexit.
The conventional wisdom was that Jeremy Corbyn might have to rely on the big unions - with 50% of conference votes - to win.
But some unions chose to defy him, making a defeat possible.
In the end a section of the grassroots - the ordinary members - did not prioritise their own pro-Remain position and rallied round Jeremy Corbyn.
Remainers are now accentuating, for them, the positive - that the party is now unambiguously backing a new referendum, with Remain as an option.
Nonetheless, Labour will go in to the election unable to say whether it will officially back leave or remain in a subsequent referendum.
But after a difficult few days, most of those close to Jeremy Corbyn are relieved tonight, and some are jubilant.
Andrew Lewin, the founder of Remain Labour, said the vote represented the "grassroots against the party machine - and the machine won".
"If this fudge is the Labour policy at the next general election, we will drive Remain voters away."
Another campaigner, Michael Chessum, from Another Europe is Possible, said: "Labour members, 90% of whom want to stay in the EU, will be deeply disappointed with this decision."
But Labour MPs remain divided over the issue.
Speaking before the vote, shadow Treasury minister Annaliese Dodds said the economic consequences of Brexit were "so severe" that she believed Labour must back remain in another referendum.
"Is it going to be easy?" she told the BBC's Carolyn Quinn. "No it is not, because people are passionate in both directions."
But Stephen Kinnock, the MP for Aberavon, told a fringe meeting organised by the Social Market Foundation that Labour had had "more Brexit positions than the Karma Sutra".
Describing the first two days of conference as an "utter shambles", he said Labour should have stuck with its 2017 manifesto pledge to honour the referendum result and moving away from this this would not go down well in Leave constituencies.
"Our position on Brexit is being treated with ridicule on the doorsteps in my constituency," he said.
Away from Brexit, Labour has announced a pledge to introduce free personal care in England for over-65s, so they will not have to pay for help with dressing, washing and meals.
In his speech, Mr McDonnell also pledged to end in-work poverty within five years and to move to a four day, or 32-hour, working week within a decade without any cut to pay.
These are the latest of several new policies likely to feature in the party's next election manifesto, including pledges to:

If you follow politics and were lucky enough to have been enjoying a summer break (and I hope so, I was!), it's over.
In the next few hours, after formal calls and a Privy Council meeting at Balmoral, No 10's plan that puts them on a full collision course with Parliament will be in train.
The prime minister says 14 October will be the day when he sets out his plans for the NHS, for tackling crime, and for aggressive tax cuts.
This has been an extraordinarily long parliamentary session, and governments have the right to shut up shop and return to announce their proposals in a new one with all the golden carriages, fancy Westminster costumes, banging of doors and splendour that goes with it.
But that new timetable means Parliament will be suspended for longer than had been expected - likely now to be prorogued, to use the technical term, around 10 September, instead of going into recess on 14 September ahead of conference season.
It's only a matter of days. But those are days that might matter enormously, because the crucial and controversial political side effect is that MPs will have less time to try to change the law to stop Boris Johnson taking the UK out of the EU if he can't agree a new deal with Brussels by the end of October.
MPs, including many senior Tories, have already been trying to find a way to take that option off the table, fearing the turmoil.
Mr Johnson's move to reduce the time Parliament has to make its moves has been described by some of his opponents as a constitutional outrage.
And it might embolden those who were trying to stiffen the spines of former Remain MPs looking for ways to block it - maybe by trying to rush through emergency laws next week or maybe even by a rapid vote of no confidence that could bring down the government.
But Mr Johnson secured his place in No 10 by promising he'd do whatever it takes to leave the EU on Halloween.
This decisive and intensely risky plan will satisfy many of those who backed him.
But some others in his government are worried - moving now, even with the accompanying controversy, he sets the stage and the terms for an epic fight with MPs on all sides.

An application to join the Conservative Party by Leave.EU co-founder and former UKIP donor Arron Banks has been turned down, the Tories have said.
Mr Banks and the pro-Brexit group's communications director, Andy Wigmore, both announced on social media that they were joining the party.
The pair said they had received a confirmation email welcoming them.
But a Conservative Party spokesperson later said their "applications for membership... have not been approved".
The BBC understands from Tory sources the pair were were judged "likely to bring the party into disrepute".
Earlier this week Mr Banks called on supporters of his pro-Brexit Leave.EU group to join the Conservative Party so they can vote in the party's next leadership election.
He posted a series of tweets about joining the Tories - including one saying he had made the move "to ensure he has a vote on the inevitable leadership contest. Let's back a Brexiteer and make this country great again!"
Mr Wigmore tweeted a copy of a letter from Conservative Party chairman Brandon Lewis stating that their membership was "activated" and they would be able to take part in candidate selection and future leadership elections after three months.
The 52-year-old is a multi-millionaire who co-founded the Leave.EU campaign.
Having made his money in vehicle insurance, he was one of the largest donors to the UK Independence Party and gave £9m to Leave.EU which he has said came from his personal wealth.
In May Leave.EU was fined £70,000 for breaches of election law in the 2016 EU referendum by, according to the Electoral Commission, failing to report "at least" £77,380 it spent.
He has also been grilled by MPs about his influence on global politics with Mr Banks laughing off the idea he was an "evil genius with a white cat".
Anyone can apply to join the Conservative Party with standard membership costing £25 a year (it is £5 for under 22s and £15 for members of the armed forces).
Applicants fill in a form which is then reviewed by the party.
If accepted, members will receive confirmation in writing "as soon as possible", but the party "reserves the right to not accept a donation or application for membership".
The Conservatives will not accept applications from people who have been suspended from or expelled from the party.
There is no appeals process.

Boris Johnson's claim that world trade rules could be used after Brexit to avoid tariffs "isn't true", cabinet minister Liam Fox has said.
The international trade secretary, who is backing Jeremy Hunt for leader, said the EU will apply trade tariffs.
Mr Fox, a Brexiteer, said he would prefer to leave with a deal and Mr Hunt has a "good chance" of getting one.
Tory MP Liz Truss, who is backing Mr Johnson, said not leaving the EU on 31 October would be a "disaster".
It has been three years since the UK voted to leave the EU in a referendum.
Speaking to the BBC's Andrew Marr Show, Mr Fox rejected Mr Johnson's claim that the UK could secure a 10-year standstill in current arrangements using an article of the General Agreement on Tariffs and Trade known as "Gatt 24".
"It isn't true, that's the problem," he said.
Mr Fox said Mr Johnson's argument that a new free trade agreement could be negotiated during an implementation period "doesn't actually hold".
"If you don't get the withdrawal agreement through Parliament, there is no implementation period during which we can do anything at all," he said.
"Secondly, if we leave the European Union without a deal the EU will apply tariffs to the UK because you can only have exemptions, as described, if you already have a trade agreement to go to.
"Clearly if we leave without a deal it's self-evident we don't have that agreement, so Article 24 doesn't hold in that circumstance."
But he said a no-deal Brexit is the "legal default position" and the UK will have "no negotiating capital" if it is ruled out.
Justice Secretary David Gauke, who had been backing Rory Stewart for leader until the international development secretary's elimination, also criticised Mr Johnson's Brexit plan, saying it was not "credible".
And Scottish First Minister Nicola Sturgeon told Sky News's Sophy Ridge on Sunday that choosing Mr Johnson as prime minister would be "disastrous" for the Conservatives, particularly in Scotland - which voted to remain in the EU.
When asked what she thought of SNP Westminster leader Ian Blackford's comments during PMQs last week that Mr Johnson was a "racist", she said: "I agree with Ian Blackford's comments."
She said Mr Johnson has "made overtly racist comments" during his career.
But also speaking on Sky News, Conservative MP Rishi Sunak, who is backing Mr Johnson, defended the leadership hopeful.
He said Mr Johnson was not racist and has "apologised for any offence caused" by his comments over the years.
Elsewhere, Chief Secretary to the Treasury Liz Truss, told BBC 5 Live's Pienaar Politics that Brexit was a matter for the executive and not for Parliament - which rejected Theresa May's Brexit deal three times.
She also criticised Mr Hunt, accusing him of "kicking the can down the road" on Brexit, which "would be a disaster".
She said Mr Johnson would seek to re-negotiate with the EU and would be "much clearer that we are prepared to leave on 31 October".
Mr Hunt has said he would delay leaving on 31 October only if a potential deal with the EU was in the pipeline.
While Mr Johnson has been more outspoken on the subject, Mr Fox said he had not heard Mr Johnson say he would definitely leave on 31 October, even if a new deal was within reach.
The EU has repeatedly said the withdrawal agreement will not be renegotiated.

Liam Fox has downplayed talk that a future US-UK trade deal after Brexit could be threatened by disagreements over chlorinated chicken imports.
The international trade secretary said the issue of whether the current UK ban on chlorine-washed poultry would be lifted was "a detail of the very end stage of one sector" of future talks.
The EU bans imports on health grounds but free market groups want a rethink.
Downing Street said any trade deal must work for both consumers and farmers.
Mr Fox is in Washington DC for two days of talks with US officials about the existing transatlantic trade relationship and how this will change once the UK leaves the EU in March 2019.
Although the UK cannot seal a free trade deal of its own with the US until it leaves the EU, both sides have expressed a desire to make quick progress and to scope out some of the barriers to an expedited deal.
The EU currently bans imports of poultry meat which is rinsed in chlorine and it will be up to the UK to decide, after it leaves the EU, whether this ban stays in place.
Environmental campaigners have expressed concerns that the UK's desire for a quick deal could pave the way for the ban to be lifted as well as a loosening of other restrictions on imports of unlabelled genetically modified (GM) foods and beef from cattle implanted with growth hormones.
Concerns about differing EU and US standards were among issues that resulted in the two sides failing to agree a comprehensive trade and investment partnership last year.
In the US, it is legal to wash chicken carcasses in strongly chlorinated water.
Producers argue that it mitigates the spread of microbial contamination from the animal's digestive tract to the meat while regulators agree
The practice is banned in the EU on health grounds, arguing it could increase the risk of bacterial-based diseases such as salmonella on the grounds that dirty abattoirs with sloppy standards would rely on it as a decontaminant rather than making sure their basic hygiene protocols were up to scratch.
There are also concerns that such "washes" would be used by less scrupulous meat processing plants to increase the shelf-life of meat, making it appear fresher than it really is.
Asked whether he would be happy eating chlorinated chicken, Mr Fox suggested that the British media was "obsessed" by the issue and asked whether reporters would be shunning US chicken during their visit.
In what he described as the "complex" process of negotiating an over-arching deal to advance the mutual prosperity of the US and UK people, he suggested the issue ranked low down on his list of current priorities.
Speaking more broadly, Mr Fox said discussions about global trade too often focused around talk about the interests of producers and jobs rather than the needs of consumers as people.
"We have to make the case for free trade and consumer gains," he said.
On Sunday, he conceded that reciprocal access to markets for agri-food products were one of the hardest-fought elements of trade deals and often among the last areas to be agreed.
There have been reports of disagreement in the Cabinet over the issue of chicken imports.
Environment Secretary Michael Gove has said the UK will retain existing standards of environmental and animal welfare outside of the EU and that his goal was to improve them further.
Speaking last week, he said there would be "no compromise" on standards and that he believed being a world leader in free trade and animal welfare should not be incompatible.
Free market economists have called for the UK to permit imports of chlorinated chicken as a goodwill gesture to help facilitate a comprehensive trade deal.
The Adam Smith Institute said there was no evidence that eating chlorinated chicken in moderation posed any risk to human health.
In a report published on Monday, it said lifting restrictions would be good for hard-pressed consumers as a kilo of chicken was 21% cheaper in the US than its UK equivalent.
"Trade critics like to suggest that signing a deal with the USA will mean that Brits will be forced to eat unsafe produce," said its author Peter Spence.
"In reality, chlorinated chicken is so harmless that even the EU's own scientific advisers have declared that it is "of no safety concern."
"Agreeing to US poultry imports would help to secure a quick US trade deal, and bring down costs for British households. European opposition to US agricultural exports has held up trade talks for years."
Asked whether the government was guaranteeing to maintain EU-level food standards after Brexit, a Downing Street spokesman said: "Our position when it comes to food is that maintaining the safety and public confidence in the food we eat is of the highest priority
"Any future trade deal must work for UK farmers, businesses and consumers."

Liam Fox is to raise concerns in cabinet at the failure of his party to highlight the "totemic" issue of an independent trade policy in a nationwide leaflet for the European elections.
The international trade secretary confirmed that he is facing an "argument" in cabinet to prevent Theresa May conceding a customs union to the Labour party.
In an interview with BBC Newsnight Dr Fox also said he expects voters to use the European Parliamentary elections to register a protest at the UK's failure to leave the EU.
The cabinet minister added that if the UK fails to ratify the prime minister's Brexit deal by the EU's October deadline then the UK should be prepared to leave the EU without a deal rather than revoking article 50.
Dr Fox was speaking to Newsnight during a visit to Iceland to drum up new trade deals with countries outside the EU after Brexit.
Commenting on the US-China trade talks taking place today in Washington, Fox also said "in a trade war, there are never any winners. There are only casualties"
The international trade secretary indicated he had concerns after the Times reported that the Tory election leaflet for the European elections failed to make any mention of an independent trade policy.
Downing Street has said that one of the benefits of leaving the EU - and thereby leaving the customs union - will be the ability of the UK to sign its own trade deals.
The leaflet said the prime minister is working "tirelessly" to pass a "workable deal" which would allow the UK to take back control of its money, laws and borders; to leave the Common Fisheries Policy and the Common Agricultural Policy; and to protect jobs, security and the UK.
He said: "Well I certainly will be wanting to be raising at cabinet that we retain that as a central plank of our European policy: that having an independent trade policy, enabling Britain to navigate the shifting seas in trade policy, is an essential prerequisite for taking back control."
Dr Fox added: "I haven't seen the leaflet. But I would say that [an independent trade policy] was one of the totemic elements of leaving the EU. And the prime minister has been very clear that an independent trade policy is one of the key asks in this.
"It has to be a real independent trade policy not something that is called an independent trade policy but isn't. [That] is why I can't accept membership of a customs union on a permanent basis because that would not be an independent trade policy."
An independent trade policy is a sensitive issue at the moment for Brexiteers because Labour is demanding in the cross party talks that the UK should agree a permanent customs union with the EU.
Senior Tories say that the prime minister is offering Labour a customs arrangement which would preserve core elements of the customs union until the 2022 election.
Asked if he would resign if the prime minister conceded a customs union, Dr Fox said: "Oh I have no intention of losing that argument. It is far too important.
"That is why I decided to remain in the cabinet and fight for those elements I believe in, including that a customs union would not be a good idea for the UK.
"Any argument around a customs union I want to be there at the table making the case why it is bad for the UK."
In his interview Dr Fox said Britain should be prepared to leave the EU next October if the EU refuses to extend article 50 again.
At that point the UK would be faced with the choice of leaving with no deal or halting Brexit by revoking article 50.
"The EU may decide that it is time for us to leave and they don't want any extension beyond that period.
"The longer we take in this process the more the chances are of revocation and simply defying the voters and not having Brexit at all or leaving without a deal.
"I don't find leaving without a deal particularly palatable but I find it much more palatable than not leaving at all."
Dr Fox said he expects Conservative voters to register a protest in the European elections though he confirmed he would be voting for his party.
"Voters will rightly be frustrated that they are being asked to vote for an institution they have already voted to leave," he said.
"So I wouldn't be surprised if voters use it as a protest."
In a swipe at Nigel Farage's Brexit party, he said: "It is very easy to be a one policy party when you don't have any responsibility for actually being the government."
The international trade secretary said he hoped Brexit would provide an opportunity to improve links with Iceland which is not in the customs union but which is in the single market through the European Free Trade Association.
He said: "Iceland is a very important partner for the UK, it is an important NATO partner, potentially in terms of energy security and of course it is estimated that up to 95% of British fish and chip shops are dependent upon cod and haddock produced by Iceland."

A cabinet Brexiteer has voiced fears that Remain supporters in parliament will seek to overturn the referendum result over the next week.
Liam Fox told BBC Newsnight that a large number of MPs want to keep the UK "locked in the EU", adding there needs to be an end to the "self-induced pessimism" which is denying the opportunities offered by Brexit.
Dr Fox also called on the EU to show greater flexibility as he called on Brussels to move away from defending "the purity of the European project".
And the cabinet minister, who was close to Margaret Thatcher, hinted that he would have endorsed Theresa May's Brexit deal.
Dr Fox said it would be wrong to second guess the late prime minister. But he added: "Mrs Thatcher made a lot of compromises in terms of our relationship with Europe.
"This is the time for Britain to reclaim our freedom and to be able to use that in a positive way to help shape the prosperity, the stability and the security in which future generations of Britons will live."
The international trade secretary, who was speaking to Newsnight during a visit to the headquarters of the World Trade Organisation in Geneva, voiced fears that Remain MPs may seek to wrest control of Brexit from the government next week.
Theresa May is due to hold a second "meaningful" vote on her Brexit deal next Tuesday.
If that falls there will be a vote on whether to support a no deal Brexit. If that is rejected, MPs will be given the chance to vote on whether to extend article 50, with the possibility of pro-Europeans seeking to table amendments to push for a softer Brexit.
Dr Fox said he supports the prime minister's deal because it is the best way of honouring the referendum while leaving the EU in an orderly way. But he added: "The thing that I fear is that...there will be a risk that we might not deliver Brexit at all.
"In Parliament there are a large number of MPs who do not see it as their primary objective to deliver the referendum and would want to keep us locked to the EU."
The minister criticised commentators and politicians who have railed against Brexit.
He said: "This mood of self-induced pessimism that has pervaded a great deal of the commentariat in recent times, and indeed some of the political system, is hugely damaging.
"It is time we actually took a positive view of where Britain is and what Britain's opportunities could be. We are not some insignificant little country. We are the fifth biggest economy in the world."
Dr Fox acknowledged that the UK's negotiations with the EU were tough and would go close to the wire. But he called on the EU to show greater flexibility.
The minister said: "There needs to be a concentrating of minds not on the purity of the European project but on jobs, prosperity and trade for the real citizens of Europe."
Dr Fox also pleaded with Tory Brexiteers opposed to the prime minister's deal to show flexibility. "You can never allow the perfect to become the enemy of the good. Many of us have made compromises throughout this process."
Dr Fox visited the WTO in Geneva amid reports that the cabinet has agreed to lift up to 90% of the UK's trade tariffs in the event of no deal.
He declined to confirm the reports in the FT and on Sky News but added: "What we will want to is, in the event of no deal, show that we have a clear idea of how we can maximise the opportunities and mitigate the difficulties. We are well agreed on that."
The international trade secretary, who met delegations from the Commonwealth and the Caribbean, said he sensed strong interest in the UK beyond Brexit. "There is a world beyond Europe and there will be a time beyond Brexit.
"We need to start to discuss what the opportunities are for the UK as we move into that new world what role we will have in shaping the global trading future."
You can watch Newsnight on BBC 2 weekdays 22:30 or on iPlayer. Subscribe to the programme on YouTube or follow them on Twitter.

Liam Fox says the chance of a no-deal Brexit is growing, blaming the "intransigence" of the European Commission.
The international trade secretary and Brexiteer put the chance of failing to come to an agreement at "60-40".
He told the Sunday Times that Brussels' chief negotiator had dismissed the UK's Chequers proposals simply because "we have never done it before".
No 10 insists the government remains confident it can get a good deal.
Mr Fox told the paper that he had not thought the likelihood of no-deal was higher than 50-50, but the risk had increased.
He said the EU had to decide whether to act in the economic best interests of its people, or to go on pursuing an approach determined by an obsession with the purity of its rules.
"I think the intransigence of the commission is pushing us towards no deal," he said.
The government has been touting its plans for Brexit agreed at Chequers - the prime minister's country residence in Buckinghamshire - to the EU and its leaders, including the French President Emmanuel Macron, whom Theresa May met on Friday.
But Mr Fox claimed Michel Barnier, the EU's chief negotiator, had already dismissed the proposals, which "makes the chance of no deal greater".
He said: "We have set out the basis in which a deal can happen but if the EU decides that the theological obsession of the unelected is to take priority over the economic wellbeing of the people of Europe then it's a bureaucrats' Brexit - not a people's Brexit - then there is only going to be one outcome."
Mr Fox said if the EU did not like the proposal, they should "show us one that they can suggest that would be acceptable to us".
He added: "It's up to the EU27 to determine whether they want the EU Commission's ideological purity to be maintained at the expense of their real economies."
On Friday, the governor of the Bank of England, Mark Carney, warned that the possibility of a no-deal Brexit was "uncomfortably high".
Mr Carney said that if a no-deal Brexit were to happen, it would mean disruption to trade and economic activity, as well as higher prices for a period of time.
But he said that the UK financial system was robust and could withstand any post-Brexit shocks.
The comments led to a decline in the pound on the currency markets and saw him labelled as "the high priest of Project Fear" by Leave-backing MP Jacob Rees-Mogg.
Meanwhile, another prominent Brexiteer, former minister Priti Patel, has called on Mrs May to have the "backbone and confidence" to back Britain in the negotiations with the EU.
Writing for the Telegraph's website, she said the UK was in a "strong position" when it came to a future trade deal because "we are dynamic, competitive and growing" - while the EU "desperately needs our money".
But unlike Mr Fox, Ms Patel does not back the Chequers deal, which has already led to a number of resignations from the government - including David Davis as Brexit secretary and Boris Johnson as foreign secretary.
She wrote: "It will leave us half in and half out, still bound to EU regulations and constraints.
"[It will be] the worst of both worlds - effectively out of Europe but still run by Europe."
The UK and EU say they want agreement before the exit on 29 March 2019.

The Liberal Democrats' chief whip says he "messed up" by allowing party leader Sir Vince Cable and his predecessor Tim Farron to skip Monday night's knife-edge vote on Brexit.
They could have cut the government's winning margin on the Customs Bill from three votes to just one.
Mr Farron said he had "called it wrong" and was sorry for what had happened.
And chief whip Alistair Carmichael said he had expected the vote to be "lost by hundreds".
In a statement tweeted by Sir Vince, Mr Carmichael said the government's winning margin should have been just one.
"By the time it became apparent that the vote was going to be close - it was too late to get two of our MPs, Vince and Tim, back in time to vote," he said.
"I'm taking responsibility and redoubling my efforts to stop Brexit."
A party source described Sir Vince's absence as a "bit unfortunate" and that he was elsewhere at a confidential political meeting "outside of the parliamentary estate".
Mr Farron was booked to give a talk, Illiberal Truths, about the furore over whether he believed gay sex was a sin during the last general election.
He tweeted that the Conservatives "don't deserve any luck".
All the party's other MPs - with the exception of new mum Jo Swinson who was 'paired' with an MP who didn't vote for the other side - cast their ballot against the government on amendments to legislation defining the UK's customs arrangements with the EU after it leaves in March 2019.
The amendments, tabled by Eurosceptic Tory MPs, were accepted by ministers - prompting a backlash by pro-European Tories, 14 of whom ended up voting against the government.
With Labour also voting against, the government scraped home in two votes by a margin of three.
The Lib Dems have been calling for a referendum on the final Brexit deal, with senior figures backing the cross-party People's Vote campaign.

The Liberal Democrats are on a mission to go from "protest back to power", the party's departing leader, Sir Vince Cable, has said.
In a speech in York, Sir Vince called for the party to continue arguing for the benefits of staying in the EU.
He also accused Prime Minister Theresa May of prioritising Conservative Party unity over maintaining peace in Northern Ireland.
Sir Vince, 75, will step down in May after leading the Lib Dems since 2017.
Speaking on Sunday at the party's spring conference, Sir Vince said "we are Remain", adding: "Whatever happens in the next few weeks of parliamentary twists and turns, we must argue - since no-one else can be relied upon to do so - that none of the several mutually exclusive versions of Brexit on offer - soft or hard - are as good as the deal we currently have."
Next week, Mrs May is expected to bring her withdrawal agreement back to the Commons for a third time after it was twice voted down by large margins.
Mrs May's efforts to win over Tory Eurosceptics to back the deal have focused on attempts to revise the backstop, the measures in the Brexit deal aimed at preventing the return of a hard border in Ireland.
"The intensity of the campaign to remove it speaks volumes about the underlying motives of those who demanded Brexit and now demand a 'clear Brexit'," Sir Vince said.
"They simply deny our history, which is entwined with that of Ireland."
Sir Vince also targeted Northern Ireland Secretary Karen Bradley personally for criticism, following a series of gaffes.
Ms Bradley previously said that deaths caused by the security forces in Northern Ireland during the Troubles were "not crimes" - comments she ended up apologising for.
She also admitted to initially not understanding that nationalists did not vote for unionist parties during elections.
"It really is quite shocking that this government is so lacking in talent that it employs a secretary of state for Northern Ireland who says she doesn't understand sectarian voting patterns and then compounds this public declaration of ignorance with a blatantly and naively one-sided view of the killings in the Troubles," Sir Vince said.
"Ms Bradley has revealed an ugly truth: that peace in Ireland matters less than peace in the Conservative Party."
Sir Vince, who clashed repeatedly with Mrs May over immigration policy while they sat around the Cabinet table during the coalition years, used his speech to return to the issue, saying it highlights a divide in British politics.
"Our mission to move from survival to success, from protest back to power, takes place in a world where liberal values are under siege and in retreat.
"Nothing quite defines liberalism like its opposite, illustrated by Theresa May's policies on immigration."
The Lib Dems have 11 MPs - down from the 57 they had in 2010.
The party has struggled electorally since 2010, when it formed a coalition government with the Conservatives.
Sir Vince, a former business secretary under the Coalition government, will step down after the English local elections in May.
Leading candidates to replace him include the current deputy leader, Jo Swinson, relative newcomer Layla Moran and former environment secretary Ed Davey.

The Liberal Democrats have pledged to cancel Brexit if they come to power at the next general election.
Members voted for the new policy at their party conference in Bournemouth by an overwhelming majority.
Previously, the party has backed another referendum or "People's Vote", saying they would campaign to Remain.
After the vote, their leader Jo Swinson, said: "We will do all we can to fight for our place in Europe, and to stop Brexit altogether."
The commitment only comes into force if the party wins the election as a majority government.
Ms Swinson also confirmed that before an election is called, the Lib Dems would continue to work with other opposition parties to campaign for a further referendum, and to prevent a "dangerous" no-deal Brexit.
She told BBC Radio 4's Today programme: "We still want to have a People's Vote. We've been arguing for that for the last three-and-a-half years - [to put] the Brexit deal to the public in a referendum.
"[But] when we have an election, if we haven't had a People's Vote, people will be looking to resolve the issue of Brexit, and there are so many people in this country who are so sick of hearing about it.
"They want to get on with their lives and want the government to get on with making their lives better."
In his first speech to conference as a Lib Dem MP, Chuka Umunna - who left Labour over its Brexit stance - said it would give the party a "clear, unequivocal position".
He said: "This [policy] will stop this national embarrassment and enable us to focus on the things that really matter."
But fellow Lib Dem MP Norman Lamb said the policy saw his party "playing with fire".
He told the Today programme that the polarisation between Leave and Remain was "incredibly dangerous", adding: "If we take this to the very limit in a situation where one side is vanquished entirely, I think there's a real danger that we break the social contract in our country.
"And I think that we all have a responsibility of reuniting the country in a common endeavour."
The government says it is trying to get a deal with the EU so it can leave on 31 October - the current deadline agreed with the EU.
Home Secretary Priti Patel said the "entire machinery of government" was focused on securing that deal.
The PM is due to meet European Commission president Jean-Claude Juncker in Luxembourg later, as negotiations aimed at securing a deal continue.
MPs passed a new law earlier this month that forces Boris Johnson to ask the EU for an extension to the deadline if a deal isn't agreed by 19 October - two days after a key EU summit.
But the prime minister has said he would rather be "dead in a ditch" than ask for a delay, and the UK will leave the EU at the end of next month "whatever happens".
The Lib Dems' motion said that if the party became the government at the next general election, it would revoke Article 50 - the law that ensures the UK leaves the EU.
Earlier, Ms Swinson told the BBC's Andrew Marr show: "If people put [the Lib Dems] into government... the stop Brexit party, then stopping Brexit is exactly what people will get.
"Everybody can see we are stuck, that Brexit is in a mess. There needs to be a way out of that."
Moving the motion in Bournemouth, Sir Vince Cable said: "Brexit will make us poorer and risks breaking up our United Kingdom.
"We must stop it and we will."
He added: "Jo [Swinson] is ready to steer us back into government as our new captain.
"And now, I am full of confidence and hope for our party and for our country."
Analysis by BBC political correspondent Jonathan Blake
In Brexit terms, revoking Article 50 could be considered the nuclear option, stopping dead the process of leaving the EU.
It's just what the Liberal Democrats want and now they've adopted a policy to do exactly that - if they win a general election.
But the most important word in the last sentence is "if".
If they don't find themselves in government they will, we can assume, revert to campaigning for a further referendum as the best way to reverse the result of the last one.
So, this policy allows the party to send a message to voters that they are as opposed to Brexit as it's possible to be.
But it's not without risk for a party with the word "democrat" in its name to promise to overturn the result of a referendum without putting that question to the electorate again.
The Lib Dems are enjoying a resurgence on the back of their anti-Brexit stance.
The party currently has 18 MPs, having been boosted by a victory in the Brecon and Radnorshire by-election, along with defections from both Labour and the Conservatives over the summer.
The latest to join the ranks is former Conservative Sam Gyimah, who had the Tory whip removed earlier this month when he voted to block a no-deal Brexit.

Lib Dem leader Jo Swinson says she hopes to convince members to back a policy of scrapping Brexit without another referendum, as the party's conference begins in Bournemouth.
Ms Swinson says holding the referendum got the UK "into a mess".
And she believes revoking Article 50 - the formal process to leave the EU - is the only satisfactory way out.
Ms Swinson said the party's anti-Brexit message should be "unequivocal" in a general election campaign.
She told the BBC: "The Liberal Democrats are crystal clear. We want to stop Brexit... If a Liberal Democrat majority government is elected, then we should revoke Article 50 and I think it's about being straightforward and honest with the British public about that."
Up until now, the party's policy on Brexit has been to campaign for another referendum - in which it would again call for the UK to stay in the EU.
But if Lib Dem members vote to back their leader's policy proposal on Sunday, revoking Article 50 would be written into the next election manifesto.
Speaking on BBC Radio 4's Today programme, Lib Dem deputy leader Ed Davey said a referendum would have been the best way to solve the problem, but "people want an end to this, and the only way you can stop Brexit in a democratic exercise like a general election is to say you would revoke".
Meanwhile, amid reports that a new version of Theresa May's Brexit deal could be supported by MPs, former Lib Dem leader Sir Vince Cable said the party would insist that it be put to a referendum, with an option to remain in the EU.
In an interview with the Guardian, Ms Swinson ruled out any kind of coalition with the Conservatives or Labour.
She said neither Conservative leader Boris Johnson nor Labour's Jeremy Corbyn were fit to be prime minister.
Mr Johnson did not care about anyone but himself, she said, and she criticised Mr Corbyn's failure to tackle anti-Semitism in his own party.
Parliament has so far denied Prime Minister Boris Johnson's request for an autumn election, because opposition parties wanted to first make sure a bill designed to avoid a no-deal Brexit became law.
But since the bill, which seeks to force Mr Johnson to ask for an extension to the deadline, has been given Royal Assent, opposition MPs are preparing to start their general election campaigns.
Revoking Article 50 would effectively undo the legal mechanism under the EU's Lisbon Treaty that was triggered to start Britain's withdrawal from the European Union. Lord John Kerr, the British diplomat who was involved in drafting Article 50, has publicly said the clause is reversible.
Lib Dem environment spokeswoman Wera Hobhouse, who was one of the first delegates to address delegates at the Bournemouth International Centre, criticised the government's record on the climate.
She said while the Tories had committed the UK to net-zero emissions by 2050, its policy on fracking was "madness" and they were action like "climate change deniers" with a reported plan to cut fuel duty.
Ms Swinson is expected to take questions from delegates on Sunday, following a speech by her predecessor Sir Vince Cable.  It is likely to be Mr Cable's last conference as a Lib Dem MP as he has said he will not contest his Twickenham seat at the next election.
Ms Swinson's main speech will be held on Tuesday, the last day of the conference, after a tribute to the party's former leader, Paddy Ashdown, who died in December.
Chuka Umunna, the former Labour MP who joined the Lib Dems three months ago, will speak on Monday in his role as foreign affairs spokesman.
The Lib Dems are enjoying a resurgence on the back of its anti-Brexit stance. The party currently has 17 MPs, having been boosted by a victory in the Brecon and Radnorshire by-election and defections from both Labour and the Conservatives over the summer.

Neither the prime minister nor the Labour leader has anywhere to hide.
After nine years in government it's not surprising that the Conservatives have lost a significant chunk of seats.
But the sheer number that have disappeared and the loss of control of authorities will hurt - especially with so many activists identifying Theresa May's handling of Brexit as a root of the problem, not just a general malaise.
The perceived personal nature of the failure is more of an indignity than an encounter with a heckler in tweeds.
And for Jeremy Corbyn, it IS surprising and disappointing that Labour has simply failed to make any significant capital from such a divided and chaotic government.
However ardently his devotees swear loyalty, the party has fallen back - on this set of results at least - seeming further rather than closer from winning power in a general election he so often claims to crave.
Take a breath. Local ballots do not translate directly into the next general election. It bears repeating time and again that specific rows over green belt building, local party spats, even simple quirks of geography all apply too.
But such an enormous set of results does give a sense of the public's political taste at this moment. And it provides a bitter flavour for the two big UK parties - locked in an uncomfortable embrace with historically feeble levels of support.
The public will also have given both of them anxiety about the potential of the Lib Dems to creep back into their territory after a strong show.  And the sour mood around Brexit adds more pressure to Labour and the Tories in their own ranks too.
For Mrs May it directly and overtly gives ammunition for convinced Tory Eurosceptics to demand a more rapid departure from the EU, whatever happens.
The delay, they believe has been toxic, so the solution is to speed on. And for Labour's many supporters of a second referendum, the significant advance of the Lib Dems and the Greens is evidence that a clear demand for another say is the only way to carve out a convincing identity.
That geographical pattern is very  marked, although unwise maybe to assume it can last, or a howl for another referendum is what it overwhelmingly means.
Because while our departure from the EU has just shaped yet another chapter of our politics in an unconventional way, two of the old rules do still apply.
After months of grisly pantomime, the rejection of both parties may well also be a simple judgement on both main parties' competence.
Voters quite plainly like politicians who look like they know what they are doing. And the public does not like parties that spend vast amounts of time fighting amongst themselves.
Whether government or opposition, we want them to care about us, rather than be expected to care  about them.
No surprise for today at least, that the Labour and Tory leaderships are both outwardly trying to push harder for a joint deal that could find a way out for them both - damned or saved together.
But their local election anguish doesn't make a deal any easier to achieve.
So our two big political parties are both finding there's been a cost to conflict and messy internal compromise.
And will look ahead nervously to the European elections when two new parties created specifically to advance clear ways out of the Brexit stalemate could divide the public more cleanly, and mete out a much more painful punishment to them.

The Conservatives have lost 1,334 councillors, with Theresa May saying voters wanted the main parties to "get on" with Brexit.
Labour also lost 82 seats in the English local elections, in which it had been expected to make gains.
But the strongly pro-EU Lib Dems gained 703 seats, with leader Sir Vince Cable calling every vote received "a vote for stopping Brexit".
The Greens and independents also made gains, as UKIP lost seats.
All 248 English councils holding elections have now announced their full results.
While the scale of the Conservative election losses is larger than expected, Labour had predicted it would gain seats, having suffered losses the last time these council seats were contested, in 2015.
The Green Party has added 194 councillors, while the number of independent councillors has risen by 612.
UKIP, which enjoyed large gains in 2015, lost 145 seats.
Results from Northern Ireland's 11 councils are also being announced. No local elections are taking place in Scotland and Wales.
After nine years in government it's not surprising that the Conservatives have lost a significant chunk of seats.
But the sheer number that have disappeared and the loss of control of authorities will hurt - especially with so many activists identifying Theresa May's handling of Brexit as a root of the problem, not just a general malaise.
The perceived personal nature of the failure is more of an indignity than an encounter with a heckler in tweeds.
And for Jeremy Corbyn, it is surprising and disappointing that Labour has simply failed to make any significant capital from such a divided and chaotic government.
However ardently his devotees swear loyalty, the party has fallen back - on this set of results at least - seeming further, rather than closer, from winning power in a general election he so often claims to crave.
MPs have yet to agree on a deal for leaving the European Union, and, as a result, the deadline of Brexit has been pushed back from 29 March to 31 October.
While local elections give voters the chance to choose the decision-makers who affect their communities, the national issue has loomed large on the doorstep.
Mrs May, appearing at the Welsh Conservative conference, said voters had sent the "simple message" that her party and Labour had to "get on" with delivering Brexit.
"These were always going to be difficult elections for us," the prime minister added, "and there were some challenging results for us last night, but it was a bad night for Labour, too."
A heckler shouted at the prime minister: "Why don't you resign?" He was then ushered out of the conference hall in Llangollen, North Wales, as the audience chanted: "Out, out, out."
BBC political correspondent Iain Watson said that while the Conservatives had lost "more than 10 times as many councillors", it was "remarkable" that Labour, "around the mid-term of a not-very-popular government - has not made net gains".
Speaking in Greater Manchester, Labour leader Jeremy Corbyn said he "wanted to do better" and conceded voters who disagreed with its backing for Brexit had deserted the party.
But Lib Dem leader Sir Vince, attending a rally in Chelmsford, Essex, where his party took control of the council, said it had been a "brilliant" result and that "every vote for the Liberal Democrats was a vote for stopping Brexit".
The BBC projects that, if the local election results it analysed were replicated across Britain, both the Conservatives and Labour would get 28% of the total vote.
The data, based on 650 wards in which detailed voting figures were collected, suggests the Lib Dems would get 19% and other parties and independents 25%.
Polling expert Prof Sir John Curtice said the days of the Conservatives and Labour dominating the electoral landscape, as happened in the 2017 election when they won 80% of the vote between them, "may be over".
He said it was only the second time in history that the two main parties' projected national share of the vote had fallen below 30%.
The only other occasion was in 2013, when UKIP performed strongly in local elections.
Prof Curtice also said the Conservatives and Labour had both lost ground since last year's local elections when both were estimated to be on 35%.
While the Lib Dem figure was the highest since 2010, when they agreed to join the coalition government with the Conservatives, he said it was still well below the 24% the party regularly achieved in the 1990s and 2000s.
Green Party co-leader Sian Berry told the BBC the Greens were not simply benefiting from a protest vote over Brexit - their gains reflected "huge new concerns" about climate change as well as the strength of their local campaigning on a range of issues.
For UKIP, Lawrence Webb, a former London mayoral candidate who is standing in this month's European elections, said the party's "fortunes were on the up", despite the fall in its number of councillors.
This is the biggest set of local elections in England's four-year electoral cycle, with more than 8,400 seats being contested. A further 462 seats are up for grabs in Northern Ireland.
Six mayoral elections have also taken place, with Labour's Jamie Driscoll winning the contest to become the first ever North of Tyne mayor.
Labour candidates also won in Leicester and Mansfield but the party out lost to independents in Middlesbrough and Copeland.
Either search using your postcode or council name or click around the map to show local results.

The local election results are disappointing for both the Conservatives and for Labour, while the Liberal Democrats, Greens and independents prospered, writes Prof Sir John Curtice and colleagues on the BBC's local elections team.
"A plague on both your houses." That seems to have been the key message to emerge from the ballot boxes.
On the basis of the detailed voting figures in 40 local authorities, we estimate that if the pattern of voting in the local council elections were to be replicated across the whole of Great Britain, both the Conservatives and Labour would have won 28% of the vote. This is only the second time that this calculation has put both those parties below 30%.
The elections always looked set to be difficult for the Conservatives. The party was defending seats that were mostly last up for grabs four years ago, on the same day David Cameron won the 2015 general election. That, coupled with the party's recent freefall in the polls, clearly pointed to significant Conservative losses.
And that proved to be the case. The party has suffered net losses of more than 1300 seats. On average the party's share of the vote was down by six points, both compared with 2015 and with last year's local election results.
However, despite the government's difficulties, Labour also slipped back - on average, by no less than seven points compared with last year's local election results. As a result, the party has found itself suffering net losses of around 80 seats, when opposition parties are normally expected to post gains.
The party's performance would seem to confirm the message of a number of polls that Labour's support has been slipping in the wake of the Brexit impasse, a fall in Jeremy Corbyn's popularity, and a continuing row about anti-Semitism. Compared with last year, the party lost ground more heavily in Leave-voting areas than in Remain-voting ones, a pattern that it shared with the Conservatives (who in previous years have tended to perform better in such areas). This has been seized on by pro-Leave Labour MPs as evidence that the party should reach an agreement with the government which would pave the way for the UK to leave the EU.
What the two parties also had in common was a tendency for their support to fall more heavily in their heartlands. Labour's vote fell back most heavily in the north, the Conservatives in the south. Equally, Labour's vote fell more heavily in wards where it was previously strong, while the Conservative vote fell most heavily where they were strongest.
It was as though voters vented their frustration with the Brexit process by punishing whichever party represented the political establishment locally.
This mood perhaps also helps account for the remarkable success of independent candidates. Those not standing on a party label were on average winning as much as a quarter of the vote where they stood. More than 900 independent councillors have been elected - a net gain of more than 500.
Meanwhile the Liberal Democrats, who before they entered into coalition with the Conservatives in 2010 were often a vehicle for protest votes, also appear to have profited from voters' disenchantment with the two largest parties.
The party, which has made net gains of more than 600 seats, advanced particularly strongly in Conservative-held wards where it was previously in second place. Double digit swings from the Conservatives to the Liberal Democrats were common in such seats. The party seemed to be successful in reinvigorating some of the bastions of local strength where its support had been badly eroded in the wake of the coalition government. This pattern added significantly to the tally of Conservative losses.
In contrast, and despite the party's pro-Remain stance, there was only limited evidence that the Lib Dems' advance was stronger in areas that voted heavily for Remain in the 2016 referendum. For example, while support for the party rose on average by three points on last year in areas where more than half voted for Remain, it also increased by two points in areas where the Remain vote was less than 45%.
Thanks in part to the fact that in 2015 the Liberal Democrats had recorded its worst ever local election performance, the party was able to make so many gains, due to an increase in its vote since then, of eight points. More significant, perhaps, was the fact that its vote was also up by three points on last year's local elections.
When the party's performance is projected into a national vote, it is estimated to be worth 19% of the vote. This represents its best local election performance since the party entered into coalition in 2010, but was still well below the party's performance in any round of local votes between 1993 and 2010. Overall, the party's performance is best seen as evidence of a partial recovery from the depths to which the party sank during the coalition years.
At the same time, the Greens had one of their best local election results ever. The party made net gains of more than 180 seats. The Greens posted an average of 12% of the vote in the wards they contested, up five points on their performance where they stood four years ago. That equals the party's previous highest average, 12% in 2009, when local elections were held on the same day as European Parliament elections. The party may have been helped by the recent protests about climate change.
Fighting just one in six wards, there was little opportunity for UKIP to make much impact on these elections. Where it did stand, the party's vote was down by four  points on its relative high point of 2015, but up eight points on its poor position last year. However, the challenge from the Eurosceptic parties may be more formidable in the European elections in three weeks time, when Nigel Farage's Brexit Party is on the ballot paper.
About this piece
This analysis piece was commissioned by the BBC from an expert working for an outside organisation.
Sir John Curtice is professor of politics at Strathclyde University, senior fellow at NatCen Social Research and The UK in a Changing Europe. He is also chief commentator at WhatUKthinks.org.
He worked with Stephen Fisher, associate professor of political sociology, University of Oxford; Robert Ford, professor of politics, University of Manchester and Patrick English, associate lecturer in data analysis, University of Exeter.

Labour has suffered a net loss of council seats - starting from the low base of 2015 in many cases.
The Conservatives have lost more than 10 times as many councillors, but what is remarkable is that the main party of opposition - around the mid-term of a not-very-popular government - has not made net gains.
It seems reasonable to assume that some votes have been lost by Labour in Leave areas because - as the leader of Sunderland City Council Graeme Miller has said - the party hasn't decisively ruled out another referendum.
(It has retained it as an option, if the Conservatives are unwilling to change their deal).
But if you take a close look at the figures in Sunderland, the complexity of Labour's political problems are revealed.
Its vote fell by nearly 17 points there - while UKIP's went up by 4.5.
The pro-Remain Lib Dems saw their vote rise by nearly 10 points and the Greens by 8.5.
Indeed, the combined vote of the Lib Dems and Greens was 21.4%, not far off UKIP's 23.9%.
The swing from Labour to the Lib Dems was about 13%  and to the Greens 10%.
Those in Labour's ranks who wanted a stronger commitment to another referendum on any Brexit deal are arguing now that the party is losing support in some Leave areas by failing to appeal enough to those who voted Remain.
Defections to the Lib Dems and the Greens suppressed the Labour vote, and further flatters UKIP's performance.
In leave-supporting Derby, where Jeremy Corbyn's party lost six seats and UKIP gained two, the swing from Labour to Lib Dems was 6%.
But those who support Labour's current policy - a heavily caveated commitment to a referendum on Brexit under certain circumstances rather than a public vote in all circumstances - say this is too simplistic an analysis.
In truth, we can't discern the underlying motives of Labour/Lib Dem switchers in every part of the country unless we ask them.
There are genuinely local factors at play in some areas - unsurprising, perhaps, as these are indeed local elections.
And some on Labour's left have another theory. They say the party is vulnerable to a protest vote because some Labour councils have had to cut services due to constrained budgets.
In some cases the Lib Dems are the beneficiaries
Others on the left say the party can't get a hearing for its anti-austerity message as the Brexit debate muffles all else.
They are actually quite keen for their party leadership to reach a deal with the government soon to get Brexit over the line and - they believe - this will then neutralise the political toxicity of the issue.
But there is little doubt politicians will proclaim to know the will of the people, without necessarily exploring deeper motivations - and the results will be interpreted in a way which advances their own arguments.

The BBC has obtained a more localised breakdown of votes from nearly half of the local authorities which counted EU referendum ballots last June.
This information provides much greater depth and detail in explaining the pattern of how the UK voted. The key findings are:
A statistical analysis of the data obtained for over a thousand individual local government wards confirms how the strength of the local Leave vote was strongly associated with lower educational qualifications.
Wards where the population had fewer qualifications tended to have a higher Leave vote, as shown in the chart. If the proportion of the local electorate with a degree or similar qualification was one percentage point lower, then on average the leave vote was higher by nearly one percentage point.
Using ward-level data means we can compare voting figures in this way to the local demographic information collected in the 2011 census. Of the main census statistics, this is the one with the greatest association with how people voted.
In statistical terms the level of educational qualifications explains about two-thirds of the variation in the results between different wards.
The correlation is strong, whether based on assessing graduate and equivalent qualifications or lower-level ones.
This ward-by-ward analysis covers 1,070 individual wards in England and Wales whose boundaries had not changed since the 2011 census, about one in nine of the UK's wards. We had very little ward-level data from Scotland, and none from Northern Ireland.
It should be noted, however, that many ward counts also included some postal votes from across the counting area, and therefore some variation between wards will have been masked by the random allocation of postal votes for counting. This makes the results less accurate geographically, but we can still use the information to explore broad national and local patterns.
Adding age as a second factor significantly helps to further explain voting patterns. Older populations were more likely to vote Leave. Education and age combined account for nearly 80% of the voting variation between wards.
Ethnicity is a smaller factor, but one which also contributed to the results. Adding that in means that now 83% of the variation in the vote between wards is explained. White populations were generally more pro-Leave, and ethnic minorities less so.  However, there were some interesting differences between London and elsewhere.
The ethnic dimension is particularly interesting when examining the outliers on the graph that compares the Leave vote to levels of education.
There are numerous wards towards the bottom left of the graph where electorates with lower educational qualifications nevertheless produced low Leave and high Remain votes. This is where the link between low qualifications and Leave voting breaks down.
It turns out that these exceptional wards have high ethnic minority populations, particularly in Birmingham and Haringey in north London.
In contrast, there are virtually no dramatic outliers on the other side of the line, where comparatively highly educated populations voted Leave. Only one point on the graph stands out - this is Osterley and Spring Grove in Hounslow, west London, a mainly ethnic minority ward which had a Leave vote of 63%. While this figure does include some postal votes, they are not nearly enough to explain away this unusual outcome.
In fact, in Ealing and Hounslow, west London boroughs with many voters of Asian origin, the ethnic correlation was in the other direction to the national picture: a higher number of Asian voters was associated with a higher Leave vote.
This powerful link to educational attainment could stem from the lower qualified tending to feel less confident about their prospects and ability to compete for work in a competitive globalised economy with high levels of migration.
On the other hand some commentators see it as primarily reflecting a "culture war" or "values conflict", rather than issues of economics and inequality. Research shows that non-graduates tend to take less liberal positions than graduates on a range of social issues from immigration and multi-culturalism to the death penalty.
The former campaign director of Vote Leave, Dominic Cummings, argues that the better educated are more prone to holding irrational political opinions because they are more driven by fashion and a group mentality.
Of course this assessment does not imply that Leave voters were almost all poorly educated and old, and Remain voters well educated and young. The Leave side obviously attracted support from many middle class professionals, graduates and younger people. Otherwise it couldn't have won.
While there was undoubtedly a lot of voting which cut across these criteria, the point of this analysis is to explore how different social groups most probably voted - and it is clear that education, age and ethnicity were crucial influences.
After these three key factors are taken into account, adding in further demographic measures from the census does little to increase the explanation of UK-wide voting patterns.
However, this does not reflect the distinctively more pro-Remain voting in Scotland, since we are short of Scottish data at this geographical level. It is clear as well that in a few specific locations high student numbers were also very relevant.
To a certain extent, using the level of educational qualifications as a measure combines both class and age factors, with working class and older adults both tending to be less well qualified.
But the association between education and the voting results is stronger than the association between social or occupational class and the results. This is still true after taking the age of the local population into account.
This suggests that voters with lower qualifications were more likely to back Leave than the better qualified, even when they were in the same social or occupational class.
The existence of a significant connection between Leave voting and lower educational qualifications had already been suggested by analysis of the published referendum results from the official counting areas.
The data we have obtained strengthens this conclusion, because voting patterns can now be compared to social statistics from the 2011 census at a much more detailed geographical level than by the earlier studies.
The BBC analysis is also consistent with opinion polling (for example, from Lord Ashcroft, Ipsos Mori and YouGov) that tried to identify the characteristics of Leave and Remain voters.
The data we have collected can be used to illustrate the sort of places where the Leave and Remain camps did particularly well: it is hard to imagine a more glaring social contrast than that between the deprived, poorly educated housing estates of Brambles and Thorntree in Middlesbrough, and the privileged elite colleges of Market ward in central Cambridge.
It is important to bear in mind, however, that most of the voting figures mentioned below also include some postal votes, so they should be treated as approximate rather than precise.  It is also important to note that the examples are limited to the places for which we were able to obtain localised information, which was only a minority of areas. The rest of the country may well contain even starker instances.
Of the 1,283 individual wards for which we have data, the highest Leave vote was 82.5% in Brambles and Thorntree, a section of east Middlesbrough with many social problems. Ward boundaries have changed since the 2011 census, but in that survey the Thorntree part of the area had the lowest proportion of people with a degree or similar qualification of anywhere in England and Wales, at only 5%. And according to Middlesbrough council, the figure for the current Brambles and Thorntree ward is even lower, at just 4%.
Second highest was 80.3% in Waterlees Village, a poor locality within Wisbech, Cambridgeshire. This area has seen a major influx of East European migrants who have been doing low-paid work in nearby food processing factories and farms, with tensions between them and British residents.
Other wards with available data which had the strongest Leave votes were congregated in Middlesbrough, Canvey Island in Essex, Skegness in coastal Lincolnshire, and Havering in east London.
The highest Remain vote was 87.8% in Market ward in central Cambridge, an area with numerous colleges and a high student population, in a city which was strongly pro-Remain.
This was followed by Ashley ward  (85.6%) in central Bristol, a district featuring ethnic diversity, gentrification and alternative culture.
Next highest was Northumberland Park (85.0%) in Haringey, north London, which has a substantial black population.
Other wards with available data which had the strongest Remain votes were generally located in Cambridge, Bristol and the multi-ethnic London boroughs of Haringey and Lambeth.
The count for Ashburton in Croydon, south London, split 50-50 exactly, with both Leave and Remain getting 3,885 votes, but that did include some postal ballots.
As for being nearest to the overall result, the combined count of Tulketh and University, neighbouring wards near the centre of Preston, was 51.92% for leave, very close to the UK wide figure of 51.89%. The individual ward of Barnwood in Gloucester had Leave at 51.94%. Both figures however contain some postal votes.
Given that a few councils provided even more detailed data down to the level of polling districts, it is possible to identify some very small localities that were nicely representative of the national picture.
The 527 voters in the neighbouring districts of Kirk Langley and Mackworth in Amber Valley in Derbyshire, whose two ballot boxes were counted together, produced a leave proportion of 51.99%. And this figure is not contaminated by any postal votes.
So journalists (or anyone else for that matter) who seek a microcosm of the UK should perhaps visit the Mundy Arms pub in Mackworth, the location for that district's polling station.
Similarly, the 427 voters in the combined neighbouring polling districts of Chiddingstone Hoath and Hever Four Elms to the south of Sevenoaks in Kent delivered a leave vote of 51.6% (again, without any postal votes).
The data obtained points to 269 areas of various sizes (wards, clusters of wards or constituencies) which had a different Leave/Remain outcome compared to the official counting area of which they were part.
This consists of 150 areas which backed Remain but were part of Leave-voting counting areas; and 119 in the other direction.
The detailed information therefore gives us an understanding of how the electorate voted which is more variegated than the officially published results.
Every one of Scotland's 32 counting areas came down on the Remain side. Yet, despite the fact that most Scottish councils did not give us much detailed information, we can nevertheless identify a few smaller parts of the country which actually backed Leave.
A cluster of six wards in the Banff and Buchan area in north Aberdeenshire had a strong Leave majority of 61%. There is much local discontent within the fishing industry of this coastal district about the EU's common fisheries policy.
An Taobh Siar agus Nis, a ward at the northern end of the Isle of Lewis in Na h-Eileanan an Iar (Western Isles), also voted Leave, if very narrowly.
And at a smaller geographical level, in Shetland the 567 voters in the combined polling districts of Whalsay and South Unst had an extremely high Leave vote of 81%. The island of Whalsay is a fishing community, where EU rules have been controversial and in 2012 numerous skippers were heavily fined for major breaches of fishing quotas.
Ealing and Hounslow are neighbouring multi-ethnic boroughs in the west of London with large Asian populations, where - in contrast to the national picture - non-white ethnicity was associated with voting Leave, particularly in Ealing. Both boroughs shared a varied internal pattern of prosperous largely white areas voting strongly Remain, poorer largely white areas preferring Leave, and the Asian areas tending to be more evenly split.
Ealing voted 60% Remain, with Southfield ward hitting 76%, but in contrast the Southall wards which are over 90% ethnic minority were close to 50-50.
In Hounslow the richer wards in Chiswick in the east of the area voted heavily Remain (73%), but the poorer largely white wards at the opposite western end in Feltham and Bedfont voted Leave (64-66%). Osterley and Spring Grove was also 63% Leave, the highest Leave vote in any individual ward in the UK with a non-white majority for which we have data.
The south London borough of Bromley narrowly voted Remain. Those parts which did not do so by a significant margin were the Cray Valley wards, largely poor white working class areas; and Biggin Hill and Darwin wards, locations to the south which contain more open countryside and lie outside the built-up commuter belt.
In Croydon in south London, places which voted Leave by substantial amounts were New Addington and Fieldway, neighbouring wards with large council estates.
Beyond the areas with the strongest backing for Leave and Remain, examining the detailed breakdown of votes in various places gives greater insight into the pattern of support for the two sides - as can be seen from the following examples.
In several places (for example, Birmingham, Bristol, Nottingham, Portsmouth) there was a strong contrast between the Leave-voting populations of large, rundown, predominantly white, housing estates in the urban periphery, versus Remain-voting populations in inner city areas with large numbers of ethnic minorities and sometimes students.
Birmingham had several wards with large Remain votes, although the city as a whole narrowly voted Leave.  These pro-Remain wards tended to be the more highly educated, better off localities, or minority ethnic areas which strongly backed Remain despite low levels of educational qualifications. I have written about this before.
In Blackburn with Darwen, Bastwell ward had the highest Remain vote at 65%, compared to only 44% in the area as a whole. This ward has an ethnic minority proportion of over 90%. Other Blackburn wards which voted Remain were also ones with high minority populations.
Bradford voted to Leave (54%), but the area included some starkly contrasting places which went over 60% Remain: the prosperous, genteel, spa town of Ilkley, and strongly ethnic minority wards in the city, such as Manningham and Toller.
Bristol voted strongly Remain on the whole (62%), but there were some striking exceptions, particularly the large, deprived, mainly white estates to the south of the city. Hartcliffe and Withywood backed Leave at 67%. Similar neighbouring wards (Hengrove and Whitchurch Park, Filwood, Bishopsworth and Stockwood) also voted Leave, as did the more industrial area of Avonmouth and Lawrence Weston to the north west of the city.
As a county Cornwall voted to Leave. But one of its six parliamentary constituencies, Truro and Falmouth, voted 53% to Remain, possibly linked to a significant student population.
In Lincoln, which voted 57% to Leave, Carholme ward stands out as very different - it voted 63% to Remain. This ward includes Lincoln University, and 43% of the residents are students
Middlesbrough voted 65% to Leave. As already noted, it had several wards with extremely high leave votes of over 75%. But one ward, Linthorpe, voted very narrowly to Remain - a comparatively well-to-do inner suburb which includes an art college; and another ward, Central, which contains Teesside University, nearly did.
Mole Valley in Surrey exhibited a dramatic contrast between two neighbouring districts with very different demographics and housing. The highest Remain vote was in the very prosperous location of Dorking South, which voted 63% Remain, but the neighbouring ward of Holmwoods, dominated by large estates on the edge of the town of Dorking, voted 57% Leave, the area's highest Leave vote.
Nottingham voted narrowly to Leave, but the inner city ward of Radford and Park voted 68% Remain. This has both a comparatively high proportion of ethnic minorities and considerable numbers of students from two nearby universities. There was a lot of variation within the area. Bulwell - a market town to the north of the city with many social problems - voted 69% Leave
There was also a high Leave vote in the housing estate locations of the Clifton wards in the south of Nottingham.
Oldham voted to Leave at 61%, but Werneth, the city ward with the highest ethnic minority population, voted Remain (57%). Other wards with high minority populations also voted Remain.
In Oxford the cluster of polling districts which included Blackbird Leys and other deprived estates on the southern edge of the city voted to Leave at 51%. In contrast the central areas containing colleges, university buildings and student accommodation voted to Remain at over 80%.
Plymouth voted 60% Leave, but Drake ward which includes the university had the city's highest Remain vote at 56%.
Portsmouth was another place with wide variation. Paulsgrove ward, with its large estate on the edge of the city, had the highest Leave vote at 70%, whereas at the other end of the spectrum Central Southsea, an inner city ward and student area, voted 57% Remain.
Rochdale voted 60% Leave. The place which bucked this trend by voting 59% Remain, Milkstone and Deeplish, was the most predominantly ethnic minority ward. Central Rochdale had the second highest Remain vote and is the other ward that is mainly not white.
Walsall voted strongly Leave (68%). The only ward which voted Remain, Paddock, is both a comparatively prosperous and multi-ethnic locality.
A few councils released their data at remarkably localised levels, down even to individual polling districts (ie ballot boxes) in the case of Blackburn with Darwen and Bracknell Forest, or clusters of two/three/four districts, in the case of Amber Valley, Brentwood, Sevenoaks, Shetland, South Oxfordshire, and Tewkesbury.
This provides very local and specific data, in some cases just for neighbourhoods of hundreds of voters.
At its most detailed this reveals that the 110 people who cast their votes in the ballot box at St. Alban's Primary School in central Blackburn split 56-52 in favour of Remain, with two spoilt papers.
It also discloses stark contrasts in some neighbouring locations. The 953 people who voted at Little Harwood community centre in north Blackburn had a Leave vote of only 31%, while the 336 electors who voted in the neighbouring ballot box at Roe Lee Park primary school produced a Leave percentage over twice as high, at 64%.
The very detailed data we obtained also provides some rare evidence on the views of postal compared to non-postal voters. Campaign strategists have often deliberated on whether the two groups vote differently and should be given separate targeted messages.
Most places mixed boxes of postal and non-postal votes for counting, so generally it's not possible to draw comparative conclusions. However there were a few exceptions which recorded them separately, or included a very small number of non-postal votes with the postals.
These figures indicate that postal voters were narrowly less likely to back Leave than voters in polling stations. Data covering five counting areas with about 260,000 votes shows that in these places the roughly one in five electors who voted by post backed Leave at 55.4%, one percentage point lower than the local non-postal support for Leave of 56.4%.
The counting areas involved are Amber Valley, East Cambridgeshire, Gwynedd, Hyndburn and North Warwickshire.
Since the referendum the BBC has been trying to get the most detailed, localised voting data we could from each of the counting areas.  This was a major data collection exercise carried out by my colleague George Greenwood.
We managed to obtain voting figures broken down into smaller geographical units for 178 of the 399 referendum counting areas (380 councils in England, Wales and Scotland, with a separate tally in Gibraltar, while in Northern Ireland results were issued for the 18 constituencies).
This varied between data for individual local government wards, wards grouped into clusters, and constituency level data. In a few cases the results supplied were even more localised than ward level. Overall the extra data covers a wide range of different areas and kinds of councils across the UK.
Electoral returning officers are not covered by the Freedom of Information Act, so releasing the information was up to the discretion of councils. While some were very willing, in other cases it required a lot of persistence and persuasion.
Some councils could not supply any detailed data because they mixed all ballot boxes prior to counting; some did possess more local figures but simply refused to disclose them to us. Others did provide data, but the combinations in which ballot boxes were mixed before counting were too complex to fit ward boundaries neatly.
A few places such as Birmingham released their ward by ward data following the referendum on their own initiative, but in most cases the information had to be obtained by us requesting it directly, and sometimes repeatedly, from the authority.

The government's infrastructure adviser has announced he is quitting his role, describing Brexit as a "populist and nationalist spasm".
Lord Adonis said Prime Minister Theresa May was "pursuing a course fraught with danger" over the UK's EU departure.
The ex-Labour minister is already a high-profile campaigner against Brexit.
A government source said: "He's been moving closer towards the exit door with each new onslaught he makes against Brexit."
The source added: "He's now walked through the door before he was pushed."
But Lord Adonis later insisted it had been his decision to leave, as his "differences with the government had become too great".
Lord Adonis, who was transport secretary under Gordon Brown between 2009 and 2010, has chaired the National Infrastructure Commission since 2015.
The commission produces a report in every Parliament advising the government on spending in areas such as transport connections and energy.
Lord Adonis sparked anger earlier this year when he compared Brexit to the appeasement of the Nazis in the 1930s, and has repeatedly called for last year's referendum vote to be reversed.
In his resignation letter, he accused Mrs May of "allying with UKIP and the Tory hard right to wrench Britain out of the key economic and political institutions of modern Europe", saying the UK was "hurtling towards the EU's emergency exit with no credible plan for the future of British trade and European co-operation".
"If Brexit happens, taking us back into Europe will become the mission of our children's generation, who will marvel at your acts of destruction," he said.
"A responsible government would be leading the British people to stay in Europe while also tackling, with massive vigour, the social and economic problems within Britain which contributed to the Brexit vote."
Lord Adonis said he planned to oppose "relentlessly" the government's EU (Withdrawal) Bill in the House of Lords.
As well as Brexit, he said the recent decision to end the East Coast rail franchise three years early, would also have forced him to quit, describing it as a bailout costing hundreds of millions of pounds.
MP Iain Duncan Smith said the departure of Lord Adonis was "long overdue".
He added: "It's a bit rich for him to pontificate on what he calls populism, but what most would refer to as democracy, when he himself has never been elected by a public vote. He has instead relied on preferment from others."
Liberal Democrat leader Sir Vince Cable described Lord Adonis's resignation as "a great shame", saying it showed that Brexit was being "badly mishandled".
He added that the Lib Dems would work with Lord Adonis "in fighting to end the hard Brexit that the government is recklessly pursuing".
A Labour spokesman said the government couldn't even "command the confidence of its own advisers".

Former Bank of England governor Lord King has blasted Brexit preparations as "incompetent".
The Brexit supporter said it "beggared belief" that the world's sixth-biggest economy should be talking of stockpiling food and medicines.
This left the government without a credible bargaining position, he said.
A spokesperson for the Department for Exiting the European Union (DExEU) said that getting a good deal with the EU was "by far, the most likely outcome".
Lord King said that "a government that cannot take action to prevent some of these catastrophic outcomes illustrates a whole lack of preparation".
"It doesn't tell us anything about whether the policy of staying in the EU is good or bad, it tells us everything about the incompetence of the preparation for it."
In a BBC interview to discuss the 10 years since the economic crisis - due to be aired next week - Lord King spent a significant amount of time saying the 11th hour preparation for a no-deal Brexit has undermined the government's negotiating position.
He added: "We haven't had a credible bargaining position, because we hadn't put in place measures where we could say to our colleagues in Europe, 'Look, we'd like a free-trade deal, we think that you would probably like one too, but if we can't agree, don't be under any misapprehension, we have put in place the measures that would enable us to leave without one.'"
In response, the government said it was "focused on negotiating a deal of unprecedented scope and ambition".
"We have already made significant progress," the DExEU spokesperson added. "The vast majority of the Withdrawal Agreement has now been agreed, and we are making further progress on the outstanding separation issues".
But Lord King predicts that we will find ourselves with what's been dubbed as Brino - Brexit in name only - which he said was the worst of all worlds. It's also a state of affairs that he fears could drag on for years.
"I think the biggest risk to the UK, and this is what worries me most, is that this issue isn't going to go away, you know the referendum hasn't decided it, because both camps feel that they haven't got what they wanted."
Lord King expressed regret and surprise that it was more difficult for a single country to present a united front than the other 27 EU members.
He said: "They must have been really worried that they had 27 countries to try to corral, how could they have a united negotiating position, they were dealing with a country that was one country, made a clear decision, voted to leave, it knew what it wanted to do, how on earth could the EU manage to negotiate against this one decisive group on the other side of the Channel?
"Well, the reality's been completely the opposite. The EU has been united, has been clear, has been patient and it's the UK that's been divided without any clear strategy at all for how to get to where we want to go."
He also said he found the current level of debate around Brexit "depressing" and said it obscured the real challenges ahead.
"The biggest economic problems facing the UK are, we save too little, we haven't worked out how to save for retirement, the pension system is facing I think a real challenge, we haven't worked out how to save enough for the NHS and finance it, we haven't worked out how we're going to save enough to provide care for the elderly.
"These are the big economic challenges we face, but are they being discussed at present in an open way?
"No, because the political debate has been completely taken up by Brexit," he said. "It's a discussion where both sides seem to be throwing insults at each other."
Lord King might argue he is being much more even-handed, with stinging criticism for all involved.
His comments come as Manchester Mayor Andy Burnham calls for Brexit to be postponed, if a no-deal scenario seems likely.
In a speech on Wednesday, the former Labour minister will say that although "a price would undoubtedly be paid in terms of social cohesion," a suspension of the process would be necessary to avoid damaging jobs.

Italian former journalist David-Maria Sassoli has been selected as the new president of the European Parliament.
Mr Sassoli, 63, received the support of 345 out of a total of 667 MEPs in the second round of voting in Strasbourg.
The centre-left politician beat three other candidates and will assume the role of assembly speaker immediately.
The vote comes a day after EU leaders agreed nominations for the bloc's top jobs, with a woman for the first time proposed as European Commission chief.
In a speech following Wednesday's result, Mr Sassoli spoke of an "imperfect" union in need of reform, calling for the EU to return to the spirit of its founding fathers, who swapped warfare and nationalism for peace and equality.
"We need to strengthen our capacity to play a leading role in democracy," he said, focusing particularly on the need for reform to the EU's system for asylum seekers. "You can't continue to kick this down the road. We don't want citizens asking 'where's Europe' every time an emergency happens."
He then described Brexit as "painful", adding: "The European Parliament will guarantee the independence of European citizens - only they are able to determine their history."
Mr Sassoli replaces another Italian, ex-army officer Antonio Tajani.
The night before, marathon talks over who will take over the EU's top jobs came to a close with the surprise choice of German Defence Minister Ursula von der Leyen to replace Jean-Claude Juncker.
Her nomination has to be approved by a majority of MEPs in a vote to be held in Strasbourg on 15 July.
Mrs von der Leyen was due to visit MEPs on Wednesday to discuss her nomination. If her candidacy is rejected, national leaders will have a month to nominate a replacement.
On the face of it, it's a historic double first for Europe, the nomination of two women, Ursula von der Leyen and Christine Lagarde, to lead the European Commission and the European Central Bank respectively.
For some media, however, it's very much a return to business as usual after turbulent times.
It amounts to a successful operation by French President Emmanuel Macron and German Chancellor Angela Merkel to "solder the Franco-German tandem back together again", according to right-leaning French daily Le Figaro.
Italy's left-leaning daily Il Messagero detects a level of cynicism worthy of the historical film The Leopard. In that film, a noble family grapples with revolutionary times by adopting the principle that "for things to remain the same, everything must change".
"Behind the new feminine face of the community leadership," the paper writes, "is a Leopard-style operation in the sense that the change is a return to the Franco-German monopoly über alles", Il Messagero deliberately uses the German term for "above all else", with its Nazi-era connotations.
Christine Lagarde, the French current head of the International Monetary Fund (IMF), has been nominated as the first woman to lead the European Central Bank (ECB).
Belgian liberal Prime Minister Charles Michel has been chosen to replace European Council President Donald Tusk.
Spain's foreign minister Josep Borrell is nominated as EU foreign policy chief. A Catalan economist, he held the post of European Parliament president from 2004-2007.
On Wednesday, members of the European Parliament elected in May voted in a secret ballot for their choice of one of four candidates.
Ahead of the vote, contenders for the position were each given a few minutes to pitch their ideas to fellow MEPs in the Strasbourg assembly:

A Conservative MP has been suspended from the party after it emerged she used a racist expression during a public discussion about Brexit.
Anne Marie Morris, the MP for Newton Abbot, used the phrase at an event in London to describe the prospect of the UK leaving the EU without a deal.
She told the BBC: "The comment was totally unintentional. I apologise unreservedly for any offence caused."
The Conservative Party later confirmed she had had the whip withdrawn.
Announcing the suspension, Theresa May said she was "shocked" by the "completely unacceptable" language.
"I immediately asked the chief whip to suspend the party whip," she said in a statement.
"Language like this has absolutely no place in politics or in today's society."
The BBC understands the prime minister and Conservative Chief Whip Gavin Williamson met to discuss the matter once Mrs May finished her Commons statement on last weekend's G20 summit.
According to a recording published on the Huffington Post website, Ms Morris was discussing the impact of Brexit on the UK's financial services industry at an event organised by the Politeia think tank, which was attended by other MPs.
Suggesting that just 7% of financial services would be affected by Brexit, she reportedly said: "Now I am sure there will be many people who will challenge that but my response and my request is look at the detail - it isn't all doom and gloom."
She went on: "Now we get to the real nigger in the woodpile, which is in two years what happens if there is no deal."
The phrase originated in the American Deep South in the mid-19th Century and is thought to have referred to slaves having to conceal themselves as they sought to flee north and secure their freedom.
It was subsequently used in the 20th Century - including by a number of leading novelists - as a metaphor to describe a hidden fact or problem.
The Lib Dems had called on Theresa May to withdraw the whip from Ms Morris, who was first elected to Parliament in 2010 and was subsequently re-elected in 2015 and earlier this year.
Leader Tim Farron said he was "shocked" and called for her to be suspended from the parliamentary party.
"This disgusting comment belongs in the era of the Jim Crow laws and has no place in our Parliament," he said.
Labour's Andrew Gwynne said Ms Morris had used "outrageous and completely unacceptable" language.
Green Party leader Caroline Lucas called on Ms Morris to resign as an MP, telling Sky News: "There is no place for her in the House of Commons."
She also claimed that other Conservative MPs at the meeting "apparently did not bat an eyelid" at Ms Morris's language.
"At the very least, there ought to be a conversation between Theresa May and the others in that room so that they're very clear going forward that if ever that kind of language is heard in the earshot, it has to be condemned immediately," Ms Lucas said.
Labour MP Chuka Umunna tweeted: "Speechless, not just at the remark being made but also at the reported lack of a reaction from the Tories there. Utterly appalling."
Politeia's website said MPs Sir William Cash, Kwasi Kwarteng and John Redwood also took part, though Mr Kwarteng told the BBC he was not there. The BBC has contacted the other MPs for comment.
Ms Morris did face criticism from Tory colleagues, one of whom, Heidi Allen, tweeted: "I'm afraid an apology is not good enough - we must show zero tolerance for racism. MPs must lead by example."
Fellow Conservative MP Helen Grant tweeted: "Inconceivable for an MP using that expression to be incognisant of its history, impact and complete unacceptability. So ashamed!"
In 2008, Conservative peer and party spokesman Lord Dixon-Smith apologised for using the same phrase in the House of Lords, saying that it was not appropriate and that he had "left his brains behind".
The peer was not dismissed.

A Labour MP has claimed it was "the better educated people" who voted remain in the EU referendum.
Barry Sheerman, who has held the Huddersfield seat since 1979, made his comments during  the BBC's Sunday Politics programme.
Mr Sheerman said: "You can actually see the pattern, nearly all the university towns voted remain."
Pudsey Conservative MP Stuart Andrew, who was also taking part in the debate, described the remarks as "snobbery".
Mr Sheerman made the comment during a discussion of the letter sent last week to universities by Tory MP Chris Heaton-Harris asking for the names of professors teaching courses involving Brexit.
The Labour MP claimed Mr Heaton-Harris was indulging in "McCarthyite sort of tactics".
In response, Mr Andrew described sending the letter as "probably not" the best thing to do, but denied the letter was an attempt to intimidate lecturers.
He said Mr Heaton-Harris "was genuinely trying to find out was was being discussed in our universities".
Mr Sheerman claimed the letter was an attempt to "frighten campuses".
"This man who went to Wolverhampton Polytechnic, who does he think he is trying to frighten my university in Huddersfield," said Mr Sheerman.
"The truth is that when you look at who voted to remain, most of them were the better educated people in our country."
Mr Andrew said: "I am astounded by this snobbery.
"The fact that Chris went to some polytechnic is some problem."
Information about BBC links to other news sites

MPs have voted to back the government's plan to start formal talks on Brexit by the end of March next year.
They also supported a Labour motion calling for Parliament to "properly scrutinise" the government in its proposals for leaving the EU.
The votes followed a compromise between Labour and the Conservatives, who had argued over the questions to be put.
The House of Commons' decisions are not binding on ministers.
MPs backed Labour's motion, saying the government should publish a plan and it was "Parliament's responsibility to properly scrutinise the government" over Brexit, by 448 votes to 75 - a margin of 373.
This followed another vote over the government's amendment to the motion, which added the proviso that its timetable for triggering Article 50 of the Lisbon Treaty, getting formal talks with the EU under way, should be respected.
MPs backed this by 461 votes to 89 - a margin of 372.
Analysis - Alex Forsyth, BBC political correspondent
Within minutes of the vote, one dedicated Brexiteer had labelled it an historic moment. Iain Duncan Smith said for the first time the majority of parliamentarians had voted to leave the EU.
Technically MPs have only backed the government's plan to start the process of leaving by the end of March next year. Nonetheless it is a statement of Parliament's intent.
Some have accused pro-Remain MPs of wanting to backtrack on Brexit, but tonight's result shows most parliamentarians are willing to respect the result of the referendum.
Instead the arguments are over exactly what Brexit will mean and the extent to which Parliament will have a say in shaping that.
In that respect, both the government and the opposition will claim victory over tonight's result: Labour for getting the government to agree to publish a Brexit plan of sorts which will be subject to scrutiny, ministers for getting MPs' backing for their timetable.
This was not a binding vote, but for both sides it counts. With further parliamentary skirmishes inevitable, positioning and political power play are vital - especially when the stakes are so high.
After Labour proposed its motion, Prime Minister Theresa May had reportedly faced a rebellion by up to 40 Conservative MPs.
So, on Tuesday she offered to support it, in return for the Labour leadership backing a compromise government amendment to support the Brexit timetable.
During Wednesday's debate, Labour's shadow Brexit secretary Sir Keir Starmer said the government had refused "on every occasion" to give details of its plans, saying information about its negotiating stance was important because it "sets the scene" for Brexit.
He said there must not be "a situation where the government seeks a vote in a vacuum, or produces a late, vague plan".
But Brexit Secretary David Davis responded: "The simple fact is that the mandate (in June's referendum) was to leave the European Union - full stop. We need to keep that in mind when we are going through that process."
He added: "This is a negotiation; it's not a policy statement. And, therefore, where you are aiming for may not be the exact place you end up."
The government's amendment was opposed by 23 Labour MPs and one Conservative - former chancellor Ken Clarke.
Five Liberal Democrat MPs, three Plaid Cymru MPs and 51 SNP MPs also voted against it.
And Labour's motion was opposed by nine of its own MPs:
Ms Siddiq, Ms West and Mr Zeichner all serve in party leader Jeremy Corbyn's frontbench team.
The government's Brexit timetable means the UK will leave the EU in 2019, with negotiations lasting up to two years.
In June's referendum, UK voters backed leaving the EU by 51.9% to 48.1%.

Parliament can stop the UK leaving the EU without negotiating a deal, shadow chancellor John McDonnell has said.
There was not a Commons majority for such an outcome, he told the BBC, and Labour would work with other parties to stop the "damage" it would cause.
He urged ministers to "come to their senses" and publish legal advice about what was owed in financial liabilities.
Transport Secretary Chris Grayling said the UK will "succeed come what may" but he was confident of a "sensible deal".
Dismissing Mr McDonnell's comments as "complete nonsense", he told the Andrew Marr show on BBC One that it was a "legal reality" that the UK would be leaving at the end of March 2019 after Article 50 was triggered earlier this year.
Meanwhile, Brexit minister Robin Walker has suggested the three million citizens of other EU countries currently living in the UK will be able to stay regardless of the outcome of the negotiations, telling Pienaar's Politics on BBC Radio 5 live "yes, people will be allowed to stay".
Prime Minister Theresa May has said she believes the two sides will reach a deal but the UK must prepare for all eventualities.
As it stands, the UK will leave the EU in March 2019 whether it agrees a deal on the terms of withdrawal or not.
But Mr McDonnell said he could "not countenance" such a situation and Parliament had the power to force the government to conceded a "meaningful vote" on the terms of exit, by amending the EU Withdrawal Bill or other relevant legislation related to Brexit.
"I don't think no deal is a realistic option," he said. "There are enough sensible people in the House of Commons to say 'this cannot happen, we cannot damage our country in this way'."
Urging ministers to stop "fighting" among themselves and focus on what was best for the economy, he added: "They should come to their senses, behave responsibly and look after the interests of the country."
He called on ministers to publish legal advice about the size of the so-called divorce bill, saying the UK should honour its obligations but the final figure should not be anywhere near the £60bn quoted in some quarters.
The government has appointed a Brexit "contingency minister" and will spend £250m this year on preparing for the UK's exit, including the possibility of it leaving without an official deal.
Speaking on the same programme, Mr Grayling said talks were always going to be "long and challenging" and it was fanciful to suggest the two sides would "shake hands and do a deal in half an hour".
While he believed that the two sides would ultimately reach agreement, he said Labour was wrong to argue for a deal in any circumstances and he was not personally afraid of the UK leaving the EU without one.
"Britain will succeed come what may but I don't think we will come to that. I think we will agree a sensible trading partnership... because it is in both of our interests for this to happen."
He rejected suggestions that flights would be grounded - as one major airline has suggested - in the event of a no-deal Brexit, insisting "people will be able to carry on making their bookings".
Asked about reported cabinet divisions, Mr Grayling said ministers were "not clones" but there was a spirit of collaboration and Philip Hammond, criticised in recent days for being too gloomy, should remain as chancellor.
Amid talk of supporters of a "soft Brexit" joining forces to put pressure on the government, ex-Tory education secretary Nicky Morgan said most MPs wanted "a sensible deal that protects our economy and supports jobs".
While the UK would be "resilient" whatever happened, she told ITV's Peston on Sunday that she was dismayed that some of her colleagues were talking up a no-deal Brexit as a "favourable outcome".

Parliament will not allow the UK to leave the European Union without a negotiated agreement, shadow Brexit secretary Sir Keir Starmer has claimed.
Asked during a BBC interview whether MPs could prevent a no-deal exit, he replied "absolutely".
Labour leader Jeremy Corbyn suggested on Friday Brexit could not be stopped because the people had voted to leave.
But Sir Keir said if 400 or so MPs were opposed to a no-deal exit, they would be able to force the government's hand.
The BBC's political editor Laura Kuenssberg said no-one really knew what would happen if Parliament voted down any agreement reached between the UK and the EU in the coming weeks and it could open a "Pandora's Box".
One former cabinet minister, John Whittingdale, has suggested that Theresa May would have to step down if she "staked her credibility" on a deal which did not command the confidence of MPs.
The UK is due to leave the EU on 29 March 2019.
The two sides are trying to hammer out an agreement on the terms of the UK's exit in the coming days which could be put to a special summit of the 28 EU leaders at the end of November.
The EU's negotiator Michel Barnier told European ministers on Monday that intense negotiating efforts were continuing but no agreement had been reached and the EU must prepare for every possible scenario.
Arriving for the meeting in Brussels, Brexit minister Lord Callanan said the UK was trying hard to get a deal but claimed it had not set a "particular deadline" and we "have to take time to make sure its right".
But the BBC's assistant political editor Norman Smith said if no agreement was reached imminently, the reality was that things would get "more ominous" for Mrs May.
While the UK's no deal preparations would have to be intensified, he said there were fears it would be harder to get MPs' support if the crunch Commons vote on accepting or rejecting the deal did not happen until the start of 2019.
Labour leaders have said they are unlikely to support any agreement as it stands, with Sir Keir telling BBC Radio 4's Today that "there is no duty to vote for the wrong deal".
The opposition has said it will press for a general election in the event of Parliament rejecting a deal but - if that does not happen - "all options" should remain on the table, including the possibility of a new Brexit referendum.
Asked whether MPs would be able to force such an outcome, he said they would use the parliamentary process to "assert themselves" and, at the very least, "indicate" what should happen in the event of a deadlock.
He suggested Mrs May herself would not be prepared to see the UK leave without a deal.
"I am confident that the majority in Parliament will not countenance a no deal," he told BBC Radio 4's Today. "So the question is can Parliament stop no deal if it becomes necessary? Absolutely.
"If there was a motion that 400-plus MPs supported saying we do not countenance a no-deal, then the prime minister would have to go forward in the teeth of Parliament.
"Of course I am critical of the prime minister on a number of fronts but I don't think she would simply take us out of the EU without a deal in the teeth of the vast majority in Parliament.
"She has got a deep sense of duty. She knows the ruptures that would cause, not just on trade, but on security and counter-terrorism. She knows that."
Sir Keir acknowledged continuing divisions within Labour over the question of another referendum but insisted that the party had decided at its conference in September that it should not be ruled out.
"On this question of options on the table, we had a long, long discussion about it and we did agree all options to remain on the table including the option of a public vote.
"The Labour Party has had a healthy discussion. But did we reach an agreement? Yes we did. Are we sticking to it? Yes we are. Neither Jeremy nor anyone else has altered that position, that is the position of the Labour Party."

Pro-European Conservative MPs could join forces with Labour to block the kind of Brexit Theresa May wants, a Tory rebel has warned the PM.
Anna Soubry claimed there would be a Commons majority against leaving the single market and customs union.
Labour's Chuka Umunna, appearing alongside Ms Soubry on the Andrew Marr show, agreed with her comments.
MPs have been promised a "meaningful vote" on the terms of Brexit before it happens in March next year.
"If this government doesn't get this right," said Ms Soubry, "the majority of members of parliament, putting their constituents first, will find themselves unable to vote for a withdrawal agreement."
Theresa May is set to deliver a major speech within the next three weeks outlining the future relationship Britain wants to have with the EU.
The prime minister has ruled out continued membership of the single market and customs union.
But Ms Soubry, one of 11 pro-European Conservative MPs who defeated the government in December on the right to get a vote on any final Brexit deal, said the PM's stance was a "huge mistake".
"Not only is it bad for our economy but it also fundamentally undermines the [Northern Ireland] peace process that was achieved and this is really important," she told Andrew Marr.
She said she wanted the UK to remain in the European Free Trade Area, like Norway, which would allow access to the single market without being a member of the EU.
Asked by Andrew Marr if they believed they had a majority in the House of Commons to defeat "the kind of Brexit the prime minister wants", Ms Soubry said: "If she's not careful, yes."
Mr Umunna said: "There is no majority in the House of Commons for us simply to jump off a cliff."
When Andrew Marr suggested to Ms Soubry that she was politically closer to Mr Umunna than she was to leading Brexiteer and Conservative colleague Jacob Rees-Mogg, she said: "I'm not denying that."
Asked if she thought Brexit would definitely happen, Ms Soubry said: "I genuinely don't know what is going to happen."
Responding to whether it might be stopped, she said: "Well I'll tell you who might stop it, and that's the people of this country.
"We won't stop it. It is the people. We gave the people a referendum to start this process."
Mr Umunna said he also backed another referendum on the terms of the Brexit deal - something his party leader Jeremy Corbyn has appeared to rule out.
He claimed the Labour leader - who last month rejected calls to attend a cross-party summit on avoiding a "hard Brexit" - was "open minded" about staying in the single market.
"I cannot conceive of circumstances where Labour MPs are marshalled to go through the lobby and vote against us staying in the customs union and the single market, with the likes of Jacob Rees-Mogg, Boris Johnson and Michael Gove," said Mr Umunna.
Both MPs insisted they were acting in the "national interest," which they said transcended party politics.
Labour's shadow chancellor John McDonnell said another Brexit referendum would cause divisions and a "better route" would be to have a general election.
"Better we have a general election. On the issue, and all the other issues, because you then have a wider debate as well," he told told ITV's Peston On Sunday.
Lib Dem leader Sir Vince Cable, who is campaigning for another referendum, said: "It is good to see cross-party cooperation between Tory and Labour rebels."
He said he was "optimistic that the rebellions in both Tory and Labour parties will spread in coming weeks", and that his party was working with them in the House of Lords.

There is a risk MPs could "steal Brexit from the British people" if Theresa May's proposed deal is rejected, a senior cabinet minister has warned.
Liam Fox said there was "natural Remain majority" in Parliament and any attempt to overturn the 2016 referendum vote would be a "democratic affront".
It came after MPs voted to exert more influence should the PM's deal fall.
Ministers will again battle to win over MPs to Theresa May's withdrawal deal after three government defeats.
Security will be the focus of the second of five days of debate in the Commons, where Tuesday's marathon session extended into the early hours.
Ahead of Prime Minister's Questions at noon, the government published its Brexit legal advice - a move which came after MPs voted to find the government in contempt of Parliament for ignoring a Commons vote demanding publication.
The PM's deal has been endorsed by EU leaders but must also be backed by the UK Parliament if it is to come into force. MPs will decide whether to reject or accept it next Tuesday, 11 December.
The UK is due to leave the European Union on 29 March, 2019. Ministers say that if MPs reject their deal they increase the chances of the UK leaving without a deal, or not leaving the EU at all.
Ministers will plough on with attempts to win over MPs on Wednesday, with eight hours of debate on the security and immigration aspects of the withdrawal agreement.
Meanwhile, Mrs May is expected to continue trying to convince small groups of her MPs to back the plan in private meetings.
Mrs May will face Labour leader Jeremy Corbyn at prime minister's questions, at noon, before the Brexit debate gets under way.
Senior Brexiteers in the cabinet have warned that the UK may not leave the EU if Mrs May's deal is voted down.
International Trade Secretary Liam Fox suggested the PM's deal was the only way of guaranteeing the UK leaves the EU, as scheduled, on 29 March 2019.
"When you are in prison and someone offers you a key, you take it," he told a committee of MPs.
While a no-deal exit would be "disorderly", he suggested the UK being kept in the EU against the will of the British people would be even more damaging.
"I think that there is a real danger that the House of Commons which has a natural remain majority may attempt to steal Brexit from British people which would be a democratic affront."
Environment Secretary Michael Gove said the deal on the table was in the best interests of the country.
"Everyone has to think at this momentous moment - do we want to ensure that Brexit gets over the line? Do we want to deliver on the verdict of the 17.4 million people who voted to leave the European Union because if we don't back the prime minister, we risk there being no Brexit and that I think would be a fatal blow to faith in democracy."
But a former Conservative chief whip has said he expects the PM to lose the vote.
Mark Harper, who backed Remain in the referendum told the Daily Telegraph he would vote against the withdrawal agreement, and predicted the deal would be rejected by 80 of his party colleagues.
He urged the prime minister to renegotiate the deal, insisting the current plan would leave the UK worse off.
First, the government lost a bid to have the legal advice issue dealt with separately by the Privileges Committee of MPs.
In a second defeat, ministers were found in contempt of parliament and forced to concede they would have to publish that advice in full, having previously argued this would break convention and was not in the national interest.
Most significantly, the third defeat was over changes to the parliamentary process in the event that the Commons votes down Mrs May's deal.
Instead of being confined to merely "taking note" of what the government tells them, MPs would also be able to exert more influence by voting on what they want the government to do next.
This could potentially see Parliament wrest control of the Brexit process from ministers if, as expected, MPs push for a "Plan B" alternative to Mrs May's deal and seek to prevent any chance of Britain leaving the EU without a deal in place.
Former Attorney General Dominic Grieve, who brought the motion, told Channel 4 News it would "allow the UK time to consider its options", including re-starting negotiations with the EU or giving the public the final say.
Liberal Democrat leader Sir Vince Cable said: "The Commons is now very likely to defeat the government again next week on the Brexit deal, at which point the country must be given a 'People's Vote', and asked to choose between the deal or remaining in the EU."
By BBC Political Editor Laura Kuenssberg
Former Remain rebels now have a possible route to get what they want if the PM's plan is rejected, as there is a possible - I emphasise the possible - way to get a vote with a majority for a Norway-style agreement or, less likely, a push for another referendum.
That won't go unnoticed by Brexiteers too, who may feel (some of them at least) that Mrs May's deal might be their best bet in that case, rather than risk that softer, squidgier Brexit.
It's possible therefore that Tuesday's shenanigans have made it less likely that the prime minister will face a terrible defeat next week because a few wobbly rebels on both sides might come in line.
When she finally kicked off the debate about the deal itself, Mrs May insisted the UK would enjoy a "better future" outside the EU.
She said the "honourable compromise" on offer was "not the one-way street" many had portrayed it to be and that the EU had made it clear that the agreement would not be improved on.
"I never said this deal was perfect, it was never going to be. That is the nature of a negotiation," she said.
"We should not let the search for a perfect Brexit prevent a good Brexit."
Labour leader Jeremy Corbyn said it was a bad deal for the UK and that his party would seek a vote of no confidence in the government if it was thrown out by MPs.
"I hope and expect this House will reject that deal," he said.
"At that point, the government has lost the confidence of the House. Either they have to get a better deal from the EU or give way to those who will."
Nigel Dodds, leader of the DUP in Westminster, said the agreement "falls short" of delivering Brexit "as one United Kingdom" and would mean entering "a twilight world where the EU is given unprecedented powers over the UK".
Ex-Foreign Secretary Boris Johnson dismissed the deal as a "paint and plaster pseudo-Brexit" and said its supporters would be "turning their backs" on the 17.4 million Leave voters.
The leader of the SNP at Westminster, Ian Blackford, said the "cold, hard truth" was that the deal represented "a moment of self-harm in our history".
"It is not too late to turn back," he said. "Fundamentally, there is no option that is going to be better for our economy, jobs, and for our communities than staying in the European Union."
However, in closing the debate shortly after 01:00 GMT on Wednesday, Brexit Secretary Stephen Barclay argued the deal would bring "real changes which will improve the livelihoods of people up and down the country".

MPs will get another chance to vote for an early election on Monday, the government has announced.
It comes after the House of Commons rejected Boris Johnson's plan for a snap election on 15 October in a vote on Wednesday.
Shadow chancellor John McDonnell said Labour wanted an election, but its priority was stopping a no-deal Brexit.
The PM later said he would rather be "dead in a ditch" than go to Brussels to ask for a further delay to Brexit.
He added that he wanted to give the country a choice.
"We either go forward with our plan to get a deal, take the country out on 31 October which we can or else somebody else should be allowed to see if they can keep us in beyond 31 October," Mr Johnson said.
Meanwhile, the prime minister's brother Jo Johnson - who backed Remain in the 2016 EU referendum - has quit as Tory MP and minister, saying he is "torn between family and national interest".
And independent MP Luciana Berger, who left the Labour Party for Change UK earlier this year, has joined the Liberal Democrats, saying she is acting "in the national interest, to offer a vital, positive alternative to Johnson and Corbyn".
The fresh vote on an early election is scheduled just before Parliament is due to be prorogued - or suspended - from next week until 14 October.
Announcing the vote, Commons leader Jacob Rees-Mogg said the suspension would begin on Monday, Tuesday or Wednesday but did not say precisely when.
The government-controlled commission responsible for setting the date has not yet made a decision, he added.
Opposition parties are holding talks about how to respond to the prime minister's call for a mid-October election, amid concern over whether it should be delayed until after an extension has been agreed to prevent a no-deal Brexit on 31 October.
A bill aimed at preventing a no-deal Brexit was approved by the Commons on Wednesday and a deal was agreed in the early hours of Thursday that Tory peers would not attempt to filibuster - talk it out - in the Lords.
The government says this bill will now complete its passage through the Lords on Friday.
Number 10 said the bill "would in essence overturn the biggest democratic vote in our history - the 2016 referendum". It added: "The PM will not do this."
Labour and other opposition MPs say they will not back the prime minister's call to have a general election while the option of a no-deal Brexit on 31 October remains open to Mr Johnson.
Mr McDonnell told the BBC that Labour would only agree once it had ensured the legislation to protect against a no-deal Brexit, but he would prefer to have an election "later rather than sooner".
He said Labour was "consulting" with other opposition parties "to determine the date" of a general election.
"The problem that we've got is that we cannot at the moment have any confidence in Boris Johnson abiding by any commitment or deal that we could construct," he said. "So we are now consulting on whether it's better to go long, therefore, rather than to go short."
He acknowledged there were splits in Labour about the timing of a general election, saying the leadership was in contact with legal experts and other opposition parties about what to do.
Liberal Democrat leader Jo Swinson said she believed Mr Johnson could try to press ahead with a no-deal Brexit, despite the legislation.
"I do have confidence that the bill will get through the House of Lords," she said.
"But in the current circumstances where we find ourselves, where we've got a prime minister seemingly prepared to do anything to rip up the traditions of parliamentary democracy, then I also think that we need to be very aware of the risks."
Meanwhile, Brexit Party leader Nigel Farage has warned Mr Johnson that he "cannot win an election, whenever it comes, if the Brexit Party stands against him".
However, if they were to make a pact during a general election "with a clear policy, we'd be unstoppable", he told BBC Breakfast.
Elsewhere, legal challenges against Mr Johnson's plan to shut down Parliament next week are taking place.
The High Court in England will consider a judicial review request from Gina Miller, the businesswoman who successfully challenged the government over the triggering of the Article 50 process to start the Brexit countdown. She will be joined by former Prime Minister Sir John Major.
In Scotland, there is an appeal against a ruling that said the prime minister had not broken any laws by asking the Queen to suspend Parliament.
And in Belfast, a judicial review against the government by a campaigner arguing that no deal could jeopardise the Northern Ireland peace process, has been fast-tracked and will be heard later.
In the Lords, peers sat until 01:30 BST, holding a series of amendment votes that appeared to support predictions of a marathon filibuster session - designed to derail the bill.
But then Lord Ashton of Hyde announced that all stages of the bill would be completed in the Lords by 17:00 BST on Friday.
The proposed legislation was passed by MPs on Wednesday, inflicting a defeat on Mr Johnson.
The bill says the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit - and after that he will have to request an extension to the UK's departure date to 31 January 2020.
However, an extension would require the agreement of the EU, a point which Brussels correspondent Adam Fleming says is being made "quite strenuously" by EU officials.
And Michel Barnier, the chief European Brexit negotiator, is reported to have told European diplomats that negotiations with London over the terms of Britain's withdrawal from the EU are in a state of paralysis.
He also advised that the UK appeared intent on reducing the level of ambition in the political declaration that will steer the next stage of the negotiations.
Responding to the comments, Downing Street said it rejected Mr Barnier's assessment.
The PM's official spokesman said: "Both sides agree to continue talks tomorrow after constructive discussions yesterday and we have seen from EU leaders that there is a willingness to find and agree solutions to the problems we have with the old deal."

MPs are voting on whether to allow the government to get negotiations for Brexit under way.
With Labour also backing the European Union Bill, the Commons is expected to pass it by a large majority, with the result expected at about 1930 GMT.
But several Labour MPs are expected to rebel by voting against it. Rachael Maskell and Dawn Butler have just quit Jeremy Corbyn's front bench to do so.
The SNP also opposes the bill, which has been debated for two days.
If it passes, it will undergo more scrutiny in the Commons and Lords before passing into law.
MPs voted down an SNP amendment aimed at scuppering the bill.
Prime Minister Theresa May says she wants to trigger Article 50 of the Lisbon Treaty, enabling negotiations with the EU to get under way, by 31 March.
Labour shadow environment secretary Rachael Maskell and equalities spokeswoman Dawn Butler announced they were resigning from leader Jeremy Corbyn's team so that they could vote against the European Union Bill.
During the debate earlier, former Chancellor George Osborne said the government had chosen "not to make the economy the priority in this negotiation, they have prioritised immigration control", while the EU's priority would be to "maintain the integrity of the remaining 27 members of the European Union".
He predicted the talks with the EU would be bitter, and a trade-off between "access and money".
Mr Osborne said he had "passionately" campaigned for a Remain vote in the EU referendum and had sacrificed his position in government for the cause.
But he said for Parliament not to allow Article 50 of the Lisbon Treaty to be invoked would "alienate people who already feel alienated" and could cause a "deep constitutional crisis".
Before that, MPs were told that European Commission chiefs plan to ask the UK to pay up to 60bn euros for its separation from the EU.
Sir Ivan Rogers, the UK's former ambassador to the EU, told a Commons committee that the commission's chief negotiator, Michel Barnier, and other key figures were "openly" saying the UK's total financial liabilities would be in the order of 40 to 60bn euros.
He said the "unreasonable" figure represented a "predictably hard line".
In other Brexit news, Prime Minister Theresa May confirmed a White Paper setting out her Brexit strategy would be published on Thursday.
The official document, which will include a desire to secure the status of EU nationals in the UK and Britons abroad, is separate to the Brexit bill being debated by MPs.
Mr Corbyn faces a rebellion by a number of his MPs, including several frontbenchers, while the SNP and Liberal Democrats are also promising to oppose ministers.
The Labour leader has imposed a three-line whip - the strongest possible sanction - on his MPs to back the bill, which is only two lines long.
If the vote goes the government's way, the bill will return to the Commons next week for the committee stage, when opposition parties will try to push through a series of amendments.
The bill was published last week, after the Supreme Court decided MPs and peers must have a say before Article 50 could be triggered.
It rejected the government's argument that Mrs May had sufficient powers to trigger Brexit without consulting Parliament.

Boris Johnson has refused to moderate his language during a heated debate in the Commons, despite a barrage of criticism from opposition benches.
Labour's Paula Sherriff referred to Jo Cox, the MP murdered in 2016, as she pleaded with him to refrain from using "dangerous" words like "surrender".
He described her intervention as "humbug" and repeated the word again.
The SNP's Nicola Sturgeon said there was "a gaping moral vacuum where the office of prime minister used to be".
BBC political editor Laura Kuenssberg described scenes in Parliament as an "absolute bear pit".
Mr Johnson was repeatedly challenged over his use of the word "surrender" to describe legislation passed earlier this month which aims to block a no-deal Brexit on 31 October.
Ms Sherriff, the Labour MP for Dewsbury, told the Commons the prime minister had "continually used pejorative language to describe an Act of Parliament passed by this House".
Pointing to a plaque in the chamber, commemorating Mrs Cox, who was murdered by a right-wing extremist, she said:  "We should not resort to using offensive, dangerous or inflammatory language for legislation that we do not like, and we stand here under the shield of our departed friend with many of us in this place subject to death threats and abuse every single day."
"They often quote his words 'Surrender Act', 'betrayal', 'traitor' and I for one am sick of it.
"We must moderate our language, and it has to come from the prime minister first."
In response, Mr Johnson said: "I have to say, Mr Speaker, I've never heard such humbug in all my life."
Tracy Brabin, who was elected as MP for Batley and Spen after Ms Cox was murdered, also urged the prime minister to moderate his language "so that we will all feel secure when we're going about our jobs".
Mr Johnson replied that "the best way to honour the memory of Jo Cox and indeed the best way to bring this country together would be, I think, to get Brexit done".
Mrs Cox's husband, Brendan, later tweeted he felt "sick at Jo's name being used in this way".
The best way to honour her is to "stand up for what we believe in, passionately and with determination", he tweeted.
Liberal Democrat leader Jo Swinson said the prime minister was an "utter disgrace" for his response to the questions on his language.
She told MPs: "I today have reported to the police a threat against my child. That has been dismissed as 'humbug'.
"This is a disgraceful state of affairs and we must be able to find a way to conduct ourselves better."
Leader of the Independent Group for Change, Anna Soubry, said it "takes a lot to reduce this honourable member to tears" but she said she is "not alone tonight".
"There are others I believe who have left the estate, such has been the distress," she told MPs.
"In this, the most peculiar and extraordinary of political times, the language that is used is incredibly important.
"We have evidence, whatever side of the debate you are on, when you use word like 'surrender', 'capitulation', and others use the word 'traitor' and 'treason', there is a direct consequence.
"It means my mother receives a threat to her safety. It means my partner receives a death threat."
Labour leader Jeremy Corbyn urged the Speaker to unite the party leaders "to issue a joint declaration opposing any form of abusive language or threats and to put this message out to our entire community that we have to treat each other with respect".
Speaker John Bercow said he was "very open to convening a meeting of senior colleagues for the purpose of a House-wide public statement".
Conservative MP Stephen Crabb told BBC Newsnight that he was "shocked by the way [the PM] responded to the remarks about Jo Cox".
He said Mr Johnson had "strong support among Conservative MPs... but he also has a duty as prime minister to try to bring unity to our country and reduce the level of poison in our politics".
Culture Secretary Nicky Morgan said the prime minister was "aware and sympathetic" to the threats MPs have received.
"But at a time of strong feelings we all need to remind ourselves of the effect of everything we say on those watching us," she tweeted.

MSPs have voted to say Holyrood "does not consent" to UK Brexit legislation.
The Withdrawal Agreement Bill - which will take the UK out of the EU - is currently passing through Westminster.
The UK government wanted MSPs to give their formal consent to the bill, but all parties bar the Conservatives ultimately spoke out against it.
Scottish Brexit secretary Mike Russell said voters north of the border had repeatedly said "very clearly" that "they do not want to leave the EU".
His motion rejecting the Brexit legislation passed by 92 votes to 29, with Labour, the Greens and Lib Dems all backing the SNP administration.
Scottish Secretary Alister Jack has indicated that the bill will proceed regardless, saying the UK government would "respect the democratic outcome" of the 2016 referendum.
The Scottish government has long refused to put forward Brexit legislation for consent votes at Holyrood, after the original EU Withdrawal Act passed into law despite opposition from MSPs.
Members instead debated a memorandum detailing the Scottish government's opposition to the legislation, which states that "the best option for the UK as a whole, and for Scotland, is to remain in the EU, as voted for by the people of Scotland".
Presiding Officer Ken Macintosh said he would write to counterparts in the UK's other parliaments to note that Holyrood had withheld its consent for the legislation.
Mr Russell led the debate for the SNP, saying that "Scotland has rejected Brexit, and those who espouse Brexit are also being rejected by Scotland".
He said: "Scotland has had enough of being spoken for and enough of being spoken over. It's had enough of Brexit, and we should say that loudly and clearly as a country and a parliament."
Scottish Conservative constitution spokesman Adam Tomkins said the SNP would have opposed the bill no matter what it contained, adding: "You cannot be opposed to a no-deal Brexit and at the same time oppose any and every available deal that would avoid it."
Scottish Labour's Alex Rowley said there was a "very real prospect" of the UK exiting the EU without a trade deal after the transition period, saying: "While Brexit will now happen, it will not be over with for a very long time."
Patrick Harvie said there was "no way the Scottish Greens could back this bill", adding that "the unspoken reality of course is the the UK government honestly doesn't give a damn if MSPs give consent or not".
And Lib Dem leader Willie Rennie said he would "continue to make the case to stop Brexit", saying the UK's exit from the EU had already "divided our country, damaged our economy and diminished our place in the world".
At Westminster, Scottish Secretary Alister Jack was asked whether the UK government would "respect" MSPs' rejection of the legislation.
He replied: "What we are respecting is the democratic outcome of referendums, which the SNP does not respect.
"The referendum in 2016 was a United Kingdom referendum, and we voted to leave the European Union. We are respecting that."
Under the Sewel convention, Westminster would "not normally" legislate across devolved areas without the consent of MSPs.
However Mr Jack insisted that the Brexit legislation was not normal, adding: "This is a constitutional matter, and they are not normally under the remit of the Scottish Parliament".
Scottish and UK ministers are set to meet for Brexit talks at a Joint Ministerial Council summit in London on Thursday.

French President Emmanuel Macron has suggested the UK could get a special trade deal with the EU after Brexit.
But he warned that Britain would not have full access to the single market without accepting its rules.
Speaking to Andrew Marr, he warned - as Brussels has already done - that the UK could not "cherry-pick" the elements it liked.
A deal might fall somewhere between the single market and a trade agreement, he said.
Mr Macron's comments came during his first visit to the UK since becoming French president, where he held talks with Prime Minister Theresa May.
In the interview, to be broadcast on Sunday, the leader said the UK should not gain access to the single market without accepting its "preconditions", which include freedom of movement across the EU, budget contributions and the jurisdiction of the European Court of Justice.
"There should be no cherry-picking in the single market because that's a dismantling of the single market," he said.
"As soon as you decide not to join the [EU] preconditions, it's not a full access.
"What is important is to not make people believe that it is possible to [have your cake and eat it]."
He said the UK could have "deeper relations" with the EU than other countries, as with Norway, but ruled out full single market access as "you decided to leave".
Speaking in a separate interview, with German newspaper Bild, Mrs May insisted any new deal between the UK and the EU was "not about cherry-picking".
"We want to negotiate a comprehensive free trade agreement and a security partnership," she said.
"Because we don't start from the position of, say, Canada or Norway - there are significant and long-grown economic links between us.
"What I want and hope is that the importance of a lasting good relationship for people on both sides of the Channel is recognised."
By BBC Europe editor Katya Adler
Essentially President Macron is looking for a negotiated Brexit deal that is in France's interest. And this is what the British government is hoping: that each EU country will now push its own agenda in trade talks, allowing the UK to get the bespoke deal it wants.
But the cold water on that argument is that every EU member benefits from the European single market. They don't want rules to be broken just for the UK if that might hurt them in the long run.
President Macron believes EU interests are France's interests. He aims to "make France great again" and wants his country to be the most influential in Europe (taking from Germany, which is now hobbled by domestic political problems).
He won't endanger his grand plan by advocating special deals for the UK that might damage the EU as a whole.
Mr Macron said access to the EU for the UK's financial services sector was "not feasible" if the UK did not accept the obligations of the single market.
But he insisted he did not want to "unplug" the City from the EU, adding: "It doesn't make sense, because it's part of the whole financing of our European Union."
He told Marr it was not too late for the UK to change its mind about remaining - describing the 2016 referendum as a "mistake".
"I do respect this vote, I do regret this vote, and I would love to welcome you again," he said.
"It's a mistake when you just ask 'yes' or 'no' when you don't ask people how to improve the situation and explain how to improve it."
Mr Macron said he believed the Brexit vote mainly came from the middle and working classes, and older people, who "decided that the recent decade was not in their favour".
"When I look at your debate it was too much favourable just for the City and less favourable for the rest of the country," he said.
But, speaking to Bild, Mrs May once again flatly denied there would be a second referendum: "Parliament gave the British public the choice and they made their decision. I think it's important that politicians then deliver on that."
On his first visit to the UK this week, President Macron signed a treaty with the Prime Minister to speed up the processing of migrants in Calais.
Mrs May praised the "uniquely close relationship" between the two nations.
She said both leaders remained committed to the Le Touquet border agreement which established French border controls in Britain and UK controls in Calais. The UK also announced an extra £44.5m to be spent on beefing up Channel border security.
The visit was punctuated by a smiling selfie taken of Mr Macron and Mrs May, at an evening reception in the Victoria and Albert Museum.
During the trip there was chatter about whether UK Foreign Secretary Boris Johnson had discussed building a bridge across the English Channel, between France and the UK.
But Downing Street has said there are "no specific plans" for such a project.
The full interview with French President Emmanuel Macron will be broadcast on The Andrew Marr Show on Sunday at 09:00 GMT. You can watch it on BBC iPlayer after it is broadcast.

The EU will decide at the end of the week whether a Brexit deal is going to be possible, French President Emmanuel Macron has told Boris Johnson.
President Macron said talks should now proceed swiftly to see if an agreement could "respect" EU principles.
Mr Johnson said the EU should not be "lured" into thinking there would be a delay to Brexit beyond 31 October.
The PM will hold further calls with EU leaders on Monday to discuss his latest proposals for the Irish border.
Downing Street said Mr Johnson was expected to hold phone calls with the leaders of Sweden, Denmark and Poland, after speaking to Mr Macron on Sunday.
The prime minister told the French president over the phone he believed a deal could be achieved, but that the EU must match compromises made by the UK.
A French government official said President Macron told Mr Johnson "that the negotiations should continue swiftly with Michel Barnier's team in coming days, in order to evaluate at the end of the week whether a deal is possible that respects European Union principles".
The comments come ahead of a key few days of negotiations as both parties try to find a new agreement in time for a summit of European leaders on 17 and 18 October.
On Monday, Mr Johnson's Europe adviser, David Frost, will hold further discussions with the European Commission, while Brexit Secretary Stephen Barclay will visit EU capitals.
Arrangements for preventing a hard border on the island of Ireland continue to be a sticking point, with the EU calling for "fundamental changes" to the UK's latest proposals.
A senior Number 10 source said: "The UK has made a big, important offer but it's time for the Commission to show a willingness to compromise too. If not the UK will leave with no deal."
It's good to talk.
But was there a meeting of minds between the prime minister and the French president?
Boris Johnson's aim was to disabuse President Macron of any suspicion that parliament simply wouldn't allow the UK to leave the EU at the end of the month without a deal.
So this really could be the 'final opportunity' to seal one.
The prime minister will deliver a similar message to other EU leaders.
So far, though, Mr Johnson's proposals are yet to open the door to more intensive negotiations.
From the Elysee Palace's account of the call, Macron's message to the PM seemed to be: First, work through the EU negotiator, Michel Barnier - don't work on individual leaders.
And second, if you don't move a bit more towards the EU's position  by the end of the week, then it's no deal.
So far, then, any talks seem to resemble the denouement of Reservoir Dogs - more stand-off than mutual understanding.
Under the Benn Act, passed last month, the prime minister must write to the EU requesting a Brexit extension if no deal is signed off by Parliament by 19 October, unless MPs agree to a no-deal Brexit.
Government papers submitted to a Scottish court said that Mr Johnson will comply, despite his assertion that there will be "no more dither or delay".
The Number 10 source called the legislation a "surrender act" and said its authors were "undermining negotiations".
"If EU leaders are betting that it will prevent no deal, that would be a historic misunderstanding," they said.
Under Mr Johnson's proposals, which he calls a "broad landing zone" for a new deal with the EU:
Mr Johnson has claimed his plans will be supported by Parliament.
At the weekend he said his untested plan to use technology to eliminate customs border checks would take the UK out of EU trade rules while respecting the Northern Ireland peace process.
He claimed MPs from "every wing of the Conservative Party", Northern Ireland's Democratic Unionist Party and from Labour have said "our proposed deal looks like one they can get behind".
Speaking on the BBC's Andrew Marr Show, Brexit Secretary Stephen Barclay said talks were under way with Labour and other opposition MPs aimed at securing their support for a new deal.
He said ministers were "considering" the idea of putting the PM's proposals to a vote in Parliament to test support for them ahead of the EU summit.
Meanwhile, Jeremy Corbyn is set to meet the leaders of other opposition parties to scrutinise the government's new Brexit proposals.
The cross-party meeting between Labour, the SNP, Lib Dems, Greens and others on Monday will decide the next steps to "hold the government to account".
Monday 7 October - Opposition leaders meet to discuss the PM's border proposals. In Edinburgh, the Court of Session could rule on the sanctions Boris Johnson would face if he contravened the law compelling him to seek a Brexit delay.
Tuesday 8 October - Last working day in the House of Commons before it is due to be prorogued - suspended - ahead of a Queen's Speech to begin a new parliamentary session.
Monday 14 October - The Commons is due to return, and the government will use the Queen's Speech to set out its legislative agenda. The speech will be then be debated by MPs throughout the week.
Thursday 17 October - Crucial two-day summit of EU leaders begins in Brussels. This is the last such meeting currently scheduled before the Brexit deadline.
Saturday 19 October - Date by which the PM must ask the EU for another delay to Brexit under the Benn Act, if no Brexit deal has been approved by Parliament and they have not agreed to the UK leaving with no-deal.
Thursday 31 October - Date by which the UK is due to leave the EU, with or without a withdrawal agreement.

Former prime minister Sir John Major has told the BBC he would seek a judicial review in the courts if the new prime minister tried to suspend Parliament to deliver a no-deal Brexit.
Sir John said such a move would be "utterly and totally unacceptable".
Using a judicial review, anyone can apply to challenge the lawfulness of decisions made by the government.
Boris Johnson - the frontrunner in the Tory leadership race - has refused to rule out proroguing Parliament.
A source close to Boris Johnson told the BBC's assistant political editor Norman Smith that Sir John "has gone completely bonkers" and had "clearly been driven completely mad by Brexit".
They said the threat of court action was "absurd" and risked dragging the Queen into politics.
The UK had been due to leave the EU on 29 March, but this date was delayed after MPs repeatedly rejected Theresa May's deal. Currently, the date for exit is 31 October.
If that date is reached without a deal being agreed on the separation process, then the UK will leave without one.
MPs have consistently voted against this option, but the prime minister could try to get around that by closing Parliament - proroguing - in the run-up to Brexit day, denying them an opportunity to block it.
Prorogation ends a parliamentary session, meaning MPs can no longer vote on legislation. A new session opens with the State Opening of Parliament and the Queen's Speech.
The question of prorogation was raised during a lTV debate between Mr Johnson and his rival in the race to lead the Conservative Party Jeremy Hunt.
Mr Hunt categorically ruled it out but Mr Johnson said he would "not take anything off the table".
Speaking to Radio 4's Today programme, Sir John said: "In order to close down Parliament, the prime minister would have to go to Her Majesty the Queen and ask for her permission."
He said it would be "inconceivable" the Queen would refuse his request and that she would be put "amidst a constitutional controversy".
"The Queen's decision cannot be challenged in law, but the prime minister's advice to the Queen can, I believe, be challenged in law - and I for one would be prepared to seek judicial review to prevent Parliament being bypassed," he said.
Sir John also criticised the "artificial" Brexit deadline of 31 October which he said "had a great deal more to do with the election of leader for the Conservative Party than the interests of the country".
"National leaders look first at the interests of the country - not first at the interests of themselves," he added.
Conservative MP and Boris Johnson supporter Chris Philp described Sir John's threat as "a stunt" adding "I don't think it is a serious proposition".
He told BBC Radio 5 Live: "Prorogation is not the plan A or even plan B or plan C.  The main plan is to get a deal agreed with the European Union."
However, Labour peer and Remain supporter Lord Falconer said Sir John had "accurately set out the legal position".
The former justice secretary said that "to advise the Queen to prevent Parliament from doing its job would be to cut out the most basic part of our constitution and therefore would be unlawful."
Sir John's comments give you an idea of the distrust, hostility and division now gripping the Tory party in this contest.
That prospect of a judicial review opens up an entirely new front in the campaign to halt no deal.
We know already a number of Tory MPs - like Dominic Grieve - are trying to devise parliamentary mechanisms to thwart no deal - so far with no success.
Now we have John Major opening up an entirely new judicial route to stop Boris Johnson from proroguing parliament.
It points to the key dividing line in the party. It is not the backstop, not the Northern Ireland border, not the date we leave.
The real dividing line is over attitudes to no deal. It is clear Boris Johnson's supporters are pretty sanguine about it.
On the other hand figures like John Major and Philip Hammond believe there are profound risks - and that is the crunch dividing line.

The government should rethink its Brexit strategy, following last week's election, according to the engineering industry organisation, the EEF.
It said without a more pro-business stance, the resulting political instability may force more firms to alter their plans "away from the UK".
The EEF is the latest business organisation to call for a rethink of the government's Brexit plans.
It wants access to the single market to be at the heart of Brexit negotiations.
The EEF said even before the election firms were already altering or thinking about changing their business plans because of the Brexit vote.
Terry Scuoler, EEF chief executive, said the government had already "wasted a year" and needed to "move away from its previous rhetoric and start repairing relations with EU partners".
For the EEF that meant putting access to the single market and staying in a customs union at the centre of the government's negotiations and involving business groups in the talks over trade.
It is also calling for a "suitable" transition period to be "firmly back on the table" as part of the Brexit talks.
On Monday Carolyn Fairbairn, director-general of the CBI, called for the government to "reset" Brexit negotiations, which are due to start next week.
Meanwhile, the uncertainty caused by the general election has led business confidence to sink "through the floor", according to the Institute of Directors.
A snap poll of 700 members of the lobby group found a "dramatic drop" in confidence following the hung parliament.
The main priority for the new government should be striking a new trade deal with the European Union, according to the IoD.
Business groups such as the CBI and EEF believe the election result has weakened the hand of those wanting a "hard Brexit", which would involve leaving not just the EU but also the single market, customs union and escaping the jurisdiction of the European Court of Justice.
They favour a deal that would give British business much the same access to the rest of the EU as they enjoy now and seem to be freshly emboldened to press their case.

Martin Selmayr has been appointed Secretary-General of the Commission, the organisation that monitors whether countries are sticking to EU rules, dreams up new laws and runs the Brexit talks day-to-day.
Normal service in the Brussels bubble temporarily came to a halt when journalists became consumed by the saga.
The 40-something former lawyer and media executive from Germany joined the European Commission as a press officer in 2004.
He helped run Jean-Claude Juncker's successful campaign to be selected as president of the commission in 2014 and later became his head of cabinet, Brussels-speak for chief of staff.
He has earned multiple nicknames, like the Monster or the Beast of the Berlaymont, the name of the building where he works.
It depends who you ask.
Admirers, like his mentor the German MEP Elmar Brok, describe a hard-working strategic genius with political nous, who gets much better results than your average official.
Detractors say his take-no-prisoners attitude goes too far. Asked about his fierce reputation, Mr Selmayr himself said: "You can't run the European Commission like a Montessori school," referring to the education system that favours child development over passing exams.
Brussels-based journalists love to talk about him. Endlessly.
Selmayr-slanging has reached new heights.
At a surprise press conference in February, Jean-Claude Juncker announced he had been keeping a secret: the commission's top civil servant, the secretary-general, was retiring. Martin Selmayr would take his place.
It emerged that Mr Selmayr had applied for the role of deputy secretary-general, got that job and was then instantly promoted.
But there's more.
It has been suggested that the only other candidate in the race to become deputy withdrew their application, meaning Mr Selmayr had a clear run to the top.
It has been alleged that members of the European Commission were offered more generous severance packages as inducements to smooth Mr Selmayr's path, which is vigorously denied.
It is claimed that he even plans to knock down walls in the commission's management suite to cement his power.
The European Commission's spokespeople have endured hours of questioning about the promotion. And I mean hours.
Many of the stories are "post-truth", they claim. Especially the one about commissioners' retirement pay-offs.
And they say the recruitment process was followed "religiously" which prompted a social-media meme of Mr Selmayr dressed as a nun (I told you journalists were obsessed).
The European Parliament holding a debate about it on Monday. A motion calls for a formal inquiry into the appointment and more transparency in the recruitment process in general.
"The way Martin Selmayr was appointed puts the European institutions into disrespect. If this procedure was corresponding to the rules, the rules have to be changed," said Green MEP Sven Giegold.
To MEPs outside the most powerful parliamentary groups it looks like jobs for the boys.
To campaigning reporters it smells bad. To less zealous journalists it is great gossip.
To Brexiteers it is a "coup" that proves the EU's structures are opaque and undemocratic.
To me, it is the latest twist in a long-running tussle over where power lies in Europe: with the member states or with an increasingly political commission that seeks to protect the very idea of the EU.

Italian PM Matteo Renzi's referendum defeat on Sunday has left Italy facing political and economic uncertainty.
Mr Renzi announced he was stepping down after his constitution reform plan was rejected by voters.
He met President Sergio Mattarella and will offer him his resignation later. Mr Mattarella must decide whether to appoint a new PM or hold elections.
There are concerns the instability may trigger a deeper crisis for Italy's already vulnerable banking sector.
A consortium organising a possible bailout for one leading bank, Banca Monte dei Paschi di Siena, is meeting on Monday to consider whether to pursue the rescue bid.
With most ballots counted, the No vote leads with 60% against 40% for Yes, with a 70% turnout.
Mr Renzi staked his political future on his attempt to change Italy's cumbersome political system. He wanted to strengthen central government and weaken the Senate, the upper house of parliament.
His opponents - including some within his own party - had argued that the reforms would give the prime minister too much power. The electorate agreed.
But the referendum was more than a vote on constitutional reform, it was widely regarded as a chance to reject establishment politics.
It was a resounding victory for the No camp, a medley of populist parties headed by the Five Star Movement, which capitalised on Mr Renzi's declining popularity, years of economic stagnation, and the problems caused by tens of thousands of migrants arriving in Italy from Africa.
EU leaders won't have slept much on Sunday night. Angst about Italy makes an uncomfortable bedfellow and there's plenty for them to worry about.  Particularly in Brussels.
Prime Minister Renzi was the only premier left in Europe with a vision for the EU's future. Angela Merkel is too busy crisis-managing while much of France is in thrall to Front National eurosceptics.
But Matteo Renzi is no more. The self-styled reformer with his promise to stabilise politics and kick-start the Italian economy has managed quite the reverse.
Italy wakes up on Monday to the threat of a banking crisis, political turmoil, and a group of anti-establishment populists banging on the doors of government. Eurozone beware and EU be warned. Italy is the euro currency's third largest economy and it's in for a bumpy ride. And there are more unpredictable votes to come in 2017: in France, Germany, the Netherlands and perhaps here in Italy too.
The No vote's victory was even bigger than the last opinion poll in November had predicted.
Five Star says it is getting ready to govern Italy. Its leader Beppe Grillo said an election should be called "within a week".
Another opposition leader Matteo Salvini, of the anti-immigrant Northern League, called the referendum a "victory of the people against the strong powers of three-quarters of the world".
Mr Renzi will hand in his resignation to President Sergio Mattarella after the final cabinet meeting.
The president may ask him to stay on at least until parliament has passed a budget bill due later this month.
In spite of the pressure from the opposition, early elections are thought to be unlikely.
Instead, the president may appoint a caretaker administration led by Mr Renzi's Democratic Party, which would carry on until an election due in the spring of 2018.
Finance Minister Pier Carlo Padoan is the favourite to succeed Mr Renzi as prime minister.
The result is being seen as a blow to the EU, although there is no question of Italy following the UK out of the door.
Both Five Star and the Northern League are opposed to the eurozone but not to membership of the EU itself.
Jeroen Dijsselbloem, who heads the group of 19 eurozone countries, denied any impending crisis.
"It doesn't really change the situation economically in Italy or in the Italian banks. The problems that we have today are the problems that we had yesterday," he said.
Meanwhile a spokesman for Chancellor Angela Merkel said she "took note with regret" of Mr Renzi's resignation but Germany would offer to work closely with the next Italian government.
But the leader of far-right Front National in France, Marine Le Pen, tweeted: "The Italians have disavowed the EU and Renzi. We must listen to this thirst for freedom of nations."
Markets seemed to have taken Mr Renzi's departure in their stride. Stocks and the euro fell in early trading in Asia but there were no signs of panic, as the possibility of his resignation had already been factored in.
But the referendum result could have longer-term implications.
There have been growing concerns over financial stability in the eurozone's third largest economy.
Italy's economy is 12% smaller than when the financial crisis began in 2008.
The banks remain weak and the country's debt-to-GDP ratio, at 133%, is second only to Greece's.
There is a risk that the failure of a major bank could set off a wider crisis, but repairing the banks becomes more difficult amid political uncertainty.
One of the threatened banks is the world's oldest and Italy's third-largest, Banca Monte dei Paschi di Siena, which has been ordered by the European Central Bank to reduce its holdings of bad debt.
The bank is trying to raise new capital to the tune of €5bn (£4.2bn; $5.3bn), but a consortium which had hoped to organise a rescue plan will meet on Monday morning to review its options.
With Mr Renzi gone, and populist parties on the rise, the question is whether Italy can keep a lid on the problems.

Theresa May's speech was another key milestone in the Brexit process and for once business leaders did not leave totally disappointed.
What business will most appreciate is that this was not a complacent speech.
It acknowledged the scale and complexity of the task in hand and made some pragmatic concessions to the realities of trade with the EU.
Most of those concessions will please the business community, but some may not satisfy members of her party.
Perhaps the most eye-catching passage for business was the prime minister's indication that the UK would be prepared to pay to remain a member of some European regulatory agencies, such as the European Medicines Agency or the European Aviation Safety Authority.
As the regulations change, the UK parliament could choose to enact an identical law - or not - but failing to do so would be in the knowledge that it might affect our membership of the agency.
So parliament remains sovereign but in practice would probably not use that sovereignty in case we got booted out of the agency. That will sound suspiciously like rule taking to some Brexit firebrands.
She also accepted that on goods regulations, UK standards would have to be at least as high as the EU's - so, no bonfire of regulation that frankly no one in the business world wanted anyway.
On services, which accounts for about three quarters of the UK economy, she conceded that services had never been included in any meaningful way in previous deals and this accepted this part would be tough.
The tone was strongest on financial services. She said that London was the most important financial centre in the world and the UK taxpayers take the risk of being its home - so the UK could never be a rule taker.
She called for a collaborative, objective framework that was mutually agreed and permanent. That would mean "equivalence" (which the EU already grants to some third countries) is probably not good enough as it can be terminated at short notice. She said Phillip Hammond would expand upon the UK's ideas on this shortly.
On customs, it seems that a new "partnership" with the EU has become the favourite option. This would require the UK to enforce both its own customs arrangements and act as agent for the EU when goods arrive in the UK bound for the EU.
This option sounds mindbogglingly complex and business will need to see much more detail to be convinced that the government has a solid answer to a very important question for them - and the future of the border on island of Ireland.
As Adam Marshall of the BCC said: "The prime minister was clearer and more realistic than ever before on the political choices and economic trade-offs ahead."
The financial services lobby group, TheCityUK, praised her for making "a detailed and practical proposition and it should put to rest any suggestion that the UK has not made its intentions and ambitions clear".
Was it cherry picking? To an extent - but she had a neat if simplistic answer to this. Every trade deal involves a bit of cherry picking and the EU does it too in its differing approaches to its deals with South Korea and Canada.
The EU's chief negotiator Michel Barnier tweeted:
Mrs May also said the two sides were close to agreement on an implementation period. Some members of her own party would rather not agree to that until they know what they are implementing - but it will be music to the ears of many businesses who are close to pulling the trigger on contingency plans in case of a no deal scenario.
That threat seemed to be in retreat in the prime minister's tone. While Nigel Farage called it a negotiating mistake, it will be a relief to most businesses.

Theresa May has held talks about Brexit with Northern Ireland's five main political parties at Stormont.
The PM was on a two-day visit to try to reassure people she can secure a Brexit deal that avoids a hard border.
Speaking on Wednesday, European Council President Donald Tusk said the EU would "insist" on the Irish backstop.
Mr Tusk also said that there was a "special place in hell" for "those who promoted Brexit without even a sketch of a plan of how to carry it safely".
He was speaking after talks with Taoiseach (Irish PM) Leo Varadkar in Brussels.
In response to Mr Tusk's remarks, Northern Ireland Secretary Karen Bradley said "it is a delicate time and it is important we all consider our words carefully".
Mrs May is due to meet European Commission President Jean-Claude Juncker on Thursday in an effort to secure changes to her Brexit deal.
The EU has maintained it will not renegotiate the withdrawal agreement, including the Irish border backstop.
On Tuesday, Mrs May told business leaders in Belfast that she wants changes to the controversial backstop but she suggested that she is not seeking to remove it from her Brexit deal.
Analysis by Laura Kuenssberg, BBC News Political Editor
Tomorrow she will be in Brussels, asking again for the EU to amend the policy, seeking either a time limit or a legal upgrade to the promise that both sides will only use it if they really, really, really have to, and they don't expect it to last for ever.
In short, Wednesday has been a chance for the PM to test out what she'll ask for; tomorrow is an opportunity to sell it as hard as she can in Brussels.
Remember she has asked for these changes before and been turned down.
And she's heard before from both sides in Northern Ireland how dug in their positions are.
So can she do anything other than take one more turn around the same carousel while the clock ticks down?
Mrs May held meetings about Brexit and Northern Ireland's political deadlock with Stormont's five biggest political parties:
It sparked a snap election but, since then, various talks processes have collapsed and the Northern Ireland Secretary Karen Bradley had to take control of financial matters and pass Stormont's budget bills through Westminster.
DUP
Leader Arlene Foster reiterated the party's opposition to the backstop and said Mrs May must "stand strong" in her talks with the EU.
Mrs Foster also said Mr Tusk's comments were "deliberately provocative and disrespectful" and that the pressure is mounting among EU leaders.
Brexit spokesperson Sammy Wilson responded to Mr Tusk's comments by calling him a "devilish euro maniac", and accused the European Council president of having "fanned the flames of fear" to try and overturn the referendum result.
President Mary Lou McDonald said Donald Tusk's words were "accurately reflecting the outrage" people in NI feel about how Brexit has been handled.
She added that the party's meeting with the PM was direct, but offered nothing new and she accused Mrs May of having "no honour".
Ms McDonald also reiterated the party's support for the backstop and that a border poll should take place if there is a no-deal Brexit.
The idea of a border poll was met sceptically on Tuesday by Tony Lloyd, Northern Ireland's shadow secretary of state, who said it was "not the most obvious thing we should rush into".
UUP
Leader Robin Swann said his party would not accept a time-limited backstop, something the PM suggested when his party met her.
He added that Mrs May wanted to focus on Brexit and the UUP had to "drag" her to a place where they could raise the restoration of Stormont.
Mr Swann said his party told her they wanted direct rule implemented in Northern Ireland if there is a no-deal Brexit.
SDLP
Leader Colum Eastwood said that his party had told Mrs May that it is now time to "put up or shut up".
He said it was clear the backstop was the only viable solution, save keeping the UK in the single market and the customs union.
He added that he had been "infuriated" when the government voted in favour of an amendment last week that called for alternative arrangements to replace the backstop.
Alliance Party
Leader Naomi Long said the time for "assurances" about Brexit from the government was over, describing her party's talks with Mrs May as "constructive but very direct".
Ms Long reiterated that the party had heard nothing new from Mrs May and that it still backed the Brexit deal that included the backstop.
The backstop is a commitment to avoid physical barriers or checks on the border between Northern Ireland and the Republic of Ireland, if no UK-EU trade deal is agreed before the Brexit transition period ends.
Many people fear the return of customs checks would put the peace process at risk.
In Tuesday's speech in Belfast, Mrs May said: "There is no suggestion that we are not going to ensure in the future there is provision for this insurance policy... the backstop."
However, she indicated she would seek changes to address concerns raised by MPs about its "potential indefinite nature" when they overwhelmingly rejected her Brexit deal.
Last week, MPs voted for an amendment tabled by Conservative grandee Sir Graham Brady - and backed by the PM - which "requires the Northern Ireland backstop to be replaced with alternative arrangements to avoid a hard border".
Many fear the "temporary single customs territory" created under the backstop plan would keep the UK tied to EU rules in the long term.
Downing Street has insisted the government is still considering alternatives.
On Wednesday, the Alternative Arrangements Working Group, comprised of Leave and Remain MPs, will conclude three days of talks aimed at finding other Brexit options that would avoid a hard border.
MPs have been looking at "alternative arrangements" to the backstop, which Mrs May has said she will discuss with EU leaders. They include:
The UK is due to leave the EU at 23:00 GMT on Friday 29 March, when the two-year limit on withdrawal negotiations enforced by the Article 50 process expires.
If MPs approve a deal with Brussels, the parties will then have until the end of 2020 to negotiate a future trade deal.
If that is not in place by the end of this transition period, the backstop kicks in.
Without a deal, however, there would be no backstop and no transition period.
The prime minister has said she is "determined" to deliver Brexit on time but a number of cabinet ministers have indicated they would be willing to agree to a short extension to finalise legislation for Brexit.

Theresa May has warned opponents of her Brexit deal that they risk "letting the British people down" as Labour said the prime minister faced a "humiliating defeat" in Tuesday's crunch vote.
She urged critics to give the deal "a second look", insisting new assurances on the Irish border had "legal force".
She said the "history books" would judge if MPs delivered on Brexit while safeguarding the economy and security.
But Jeremy Corbyn said the PM had "completely and utterly failed".
And the SNP said the PM was "in fantasy land and the government should stop threatening no-deal".
MPs will vote on the terms of the UK's withdrawal from the EU and declaration on future relations on Tuesday evening.
Labour and the other opposition parties will vote against the deal while about 100 Conservative MPs, and the Democratic Unionist Party's 10 MPs, could also join them.
Both Mrs May and Mr Corbyn met their backbenchers after the PM's Commons statement on Monday night - the PM to appeal once more for their support and the Labour leader to reiterate his plan to call for a general election if the deal is rejected.
Mr Corbyn also told his MPs a no-confidence vote in the prime minister would be "coming soon", according to BBC political correspondent Iain Watson.
Assistant whip Gareth Johnson has become the latest member of the government to quit his job over the deal, saying in his resignation letter to the PM that it would be "detrimental to our nation's interests".
He added: "The time has come to place my loyalty to my country above my loyalty to the government."
Ahead of the vote, Mrs May briefed MPs on the controversial issue of the "backstop" - the fallback plan to avoid any return to physical Northern Ireland border checks.
She said her "absolute conviction" was that the UK and EU would be able to finalise their future relationship by the end of 2020, meaning the backstop would never be needed.
She published a joint letter from European Council President Donald Tusk and European Commission President Jean-Claude Juncker in which they stressed their "firm commitment" to working towards such an agreement - and said if the backstop were to be used it would be for the "shortest possible period".
However, they said they could not add anything to change the terms of the deal negotiated with Mrs May.
The PM told MPs: "I say to members on all sides of this house, whatever you may have previously concluded, over these next 24 hours, give this deal a second look.
"It is not perfect, but when the history books are written, people will look at the decision of this House tomorrow and ask 'did we deliver on the country's vote to leave the EU, did we safeguard our economy, security or union or did we let the British people down'."
Five Conservative Brexiteer MPs who have been critics of the withdrawal agreement have now said they will support the government in the vote on Tuesday, including Sir Geoffrey Clifton-Brown and former Public Accounts Committee chairman Sir Edward Leigh.
But former Labour leader Ed Miliband said the PM must make the government "the servant of the House" if the deal was rejected, giving Parliament an "open and honest process" to express their will.
By Alex Forsyth, BBC political correspondent
The letter from Presidents Juncker and Tusk was deliberately released at the moment No 10 hoped it might have the most impact - the eve of the crucial Brexit vote.
But regardless of the timing, the attempt to reassure hasn't done enough to convince many senior Brexiteers to swing behind the prime minister's deal.
The contentious Northern Ireland backstop remains the biggest sticking point, and nothing short of a legally watertight guarantee that it can't go on indefinitely will be enough for many of those with concerns.
At this stage, the EU has made clear it won't reopen the negotiated Withdrawal Agreement to include such a guarantee.
So, however warm the words of reassurance offered today, it seems they won't be enough to persuade many opponents to Mrs May's deal to change their mind.
The so-called Irish backstop will see the UK and EU share a single customs territory until they settle their future relationship or come up with another solution to stop a hard border.
Many Tory MPs, as well as the Democratic Unionists, are adamantly opposed to it.
The EU has given fresh written assurances about how the backstop might be triggered and how long it would last. The key points, in the letter from top officials Donald Tusk and Jean-Claude Juncker to the PM, are:
"Were the backstop to enter into force in whole or in part, it is intended to apply only temporarily, unless and until it is superseded by a subsequent agreement," they said.
"The Commission is committed to providing the necessary political impetus and resources to help achieving the objective of making this period as short as possible," it said.
Attorney General Geoffrey Cox said the assurances offered "legal force" to the UK, but admitted they did not alter the "fundamental meanings" in the Withdrawal Agreement - namely that the UK is indefinitely committed to the backstop if it comes into force, as neither side can unilaterally withdraw from it.
Mr Corbyn said it amounted to nothing more than "warm words and aspirations" while the DUP's deputy leader Nigel Dodds said there were no "legally binding assurances" as talked about by the PM in December.
"In fact, there is nothing new," he said.
Here is what is likely to happen:
The UK will leave the EU on 29 March unless there is a new act of Parliament preventing that.
Three senior Conservative backbenchers - Nick Boles, Sir Oliver Letwin and Nicky Morgan - have proposed a "European Union Withdrawal Number 2 Bill" if she fails a second time, giving ministers three weeks to get a plan B through Parliament.
If this doesn't work, they propose that the Liaison Committee - made up of the chairmen and chairwomen of all the Commons select committees - should be given "the responsibility to try and come up with its own compromise deal, which would have to go back to the House for a vote".
Downing Street has said it is "extremely concerned" about the plot, which it says could potentially overturn centuries of Parliamentary precedent.
A cross-party group of anti-Brexit politicians have also published proposed legislation to bring about a second referendum on leaving the EU, asking the public whether they want to remain in the EU or leave under the prime minister's deal.
The MPs behind the draft legislation point out that Article 50 - the two-year process by which an EU member leaves the bloc - would have to be extended in order for another poll to take place, meaning the UK would remain a member beyond 29 March.

Theresa May's former chief of staff has told the BBC she always saw Brexit as a "damage limitation exercise".
In his first TV interview, Nick Timothy suggested the PM and other ministers' attitude meant the government has "not been prepared to take the steps" needed to make the most of Brexit.
And he warned the government's mishandling of it risked "opening up space for a populist right wing party".
His comments are in forthcoming BBC Two documentary Inside the Brexit Storm.
Mr Timothy, who is considered to have been one of Theresa May's most influential advisers, said that the prime minister should have been clearer that different sides of the Tory Party would have to compromise much earlier on.
"One of the difficulties she's had is that she's tried to take every part of the party with her at different points.
"It would have been better to be clearer that not everybody in the party was going to get what they wanted."
He added: "I think one of the reasons we are where we are is that many ministers, and I would include Theresa in this, struggle to see any economic upside to Brexit.
"They see it as a damage limitation exercise.
"If you see it in that way then inevitably you're not going to be prepared to take the steps that would enable you to fully realise the economic opportunities of leaving."
Mr Timothy, a Brexiteer, also said that many MPs write off Leave voters as "being racist, stupid or too old to have a stake in the future", and warned that the government's mishandling of Brexit risked "opening up space for a populist right wing party…this is one of the dangers of where we are right now".
Mr Timothy, who many MPs consider to have been responsible for some of the mistakes of the 2017 general election campaign also said that Theresa May's premiership had "not been bad, but unlucky".
In response, Business Secretary Greg Clark told BBC Midlands Today: "I think Theresa May and ministers right from the outset recognised that there'd been this big debate about Brexit in the referendum and the British people made their decision and it needed to be implemented, but to be done so in a way that made sure that we could continue to enjoy the prosperity that we've had."
The interview with Nick Timothy is part of Inside the Brexit Storm, a behind-the-scenes programme following the BBC 's Laura Kuenssberg through the twists and turns of the Brexit process to be transmitted shortly.

Theresa May has said she will put together a government with the support of the Democratic Unionists to guide the UK through crucial Brexit talks.
Speaking after visiting Buckingham Palace, she said only her party had the "legitimacy" to govern, despite falling eight seats short of a majority.
Later, she said she "obviously wanted a different result" and felt "sorry" for colleagues who lost their seats.
But Labour said they were the "real winners".
The Lib Dems said Mrs May should be "ashamed" of carrying on.
The Tories needed 326 seats to win another majority but they fell short and must rely on the DUP to continue to rule.
In a short statement outside Downing Street after an audience with the Queen, Mrs May said she would join with her DUP "friends" to "get to work" on Brexit.
Referring to the "strong relationship" she had with the DUP but giving little detail of how their arrangement might work, she said she intended to form a government which could "provide certainty and lead Britain forward at this critical time for our country".
"Our two parties have enjoyed a strong relationship over many years," she said.
"And this gives me the confidence to believe that we will be able to work together in the interests of the whole United Kingdom."
It is thought Mrs May will seek some kind of informal arrangement with the DUP that could see it "lend" its support to the Tories on a vote-by-vote basis, known as "confidence and supply".
Later, she told reporters that she had "wanted to achieve a larger majority but that was not the result".
"I'm sorry for all those candidates... who weren't successful, and also particularly sorry for MPs and ministers who'd contributed so much to our country, and who lost their seats and didn't deserve to lose their seats.
"As I reflect on the results, I will reflect on what I need to do in the future to take the party forward."
DUP leader Arlene Foster confirmed that she had spoken to Mrs May and that they would speak further to "explore how it may be possible to bring stability to this nation at this time of great challenge".
While always striving for the "best deal" for Northern Ireland and its people, she said her party would always have the best interests of the UK at heart.
Scottish Conservative leader Ruth Davidson has since sought assurances from Mrs May that any deal with the DUP will not affect LGBTI rights across the UK. Northern Ireland is the only part of the UK where same-sex marriage is not legal.
A source close to Ms Davidson, who is gay, told the BBC: "The PM needs to remember there are more Scottish Conservatives than DUP MPs."
Who are the DUP?
The DUP are pro-union (not Europe but UK), pro-Brexit and socially conservative.
The party, which returned 10 MPs to Westminster, has garnered a reputation for its strong, sometimes controversial views.
It opposes same-sex marriage and is anti-abortion - abortion remains illegal in Northern Ireland, except in specific medical cases.
One MP is a devout climate change denier, while a former MP once called for creationism - the belief that human life did not evolve over millions of years but was created by God - to be taught alongside evolution in science classes.
During the election campaign, the DUP's Emma Little-Pengelly was endorsed by the three biggest loyalist paramilitary organisations.
Who's in the Cabinet?
In an ongoing Cabinet reshuffle, five cabinet ministers are certain to stay: Defence Secretary Sir Michael Fallon; Brexit Secretary David Davis; Home Secretary Amber Rudd; Chancellor Philip Hammond and Foreign Secretary Boris Johnson.
Mr Hammond said, in a tweet, that he was "pleased to be reappointed so we can now get on and negotiate a Brexit deal that supports British jobs, business and prosperity". Mr Johnson tweeted that he was "delighted", adding "lots of great work to do for greatest country on earth".
However, those rarely seen on the campaign trail, including Andrea Leadsom, Priti Patel and Liam Fox, could be out, says BBC political correspondent Eleanor Garnier.
Comebacks from Iain Duncan Smith, Michael Gove and prominent leave campaigner Dominic Raab were being floated, she adds.
Where does this leave Labour?
Labour leader Jeremy Corbyn has denounced Mrs May's plan to head up a minority government, calling for her to "make way" for a government that would be "truly representative of the people of this country".
He said Labour was ready to form a minority government of its own, after far exceeding expectations by picking up 30 seats in England, Wales and Scotland.
But even if it joined together in a so-called progressive alliance with the SNP, Lib Dems, Green Party and Plaid Cymru, it would only reach 314 seats - short of the 326 figure needed.
"We are ready to serve the people who have put their trust in us," he said, while stressing he would not enter into any "pacts or deals" with other parties.
Former Labour cabinet minister Lord Mandelson said the "surprise" result was a political "earthquake",  and he'd been "wrong" to criticise Mr Corbyn's leadership of the party.
There are three posts that Mr Corbyn now needs to fill in the shadow cabinet, but sources say an announcement is not likely until Sunday at the earliest.
Streatham MP Chuka Umunna, a leading figure on the right of the party, has said he would accept a role in the shadow cabinet.
What about Scotland?
The SNP remains the largest party in Scotland but lost 21 seats to the Tories, Labour and the Lib Dems.
Leading figures in the party such as Alex Salmond and Angus Robertson were defeated.
First Minister Nicola Sturgeon said her party's plans for a second independence referendum were "undoubtedly" a factor in the results, and she would "reflect carefully".
Ruth Davidson - whose Scottish Conservatives went from one seat to 13 - said Ms Sturgeon should now take a second referendum "off the table".
How did the parties fare?
The BBC's Laura Kuenssberg said the PM has returned to No 10 a "diminished figure", having ended up with 13 fewer seats than when she called the election in April.
She had called the election with the stated reason that it would strengthen her hand in negotiations for the UK to leave the EU - the talks are due to start on 19 June.
But the Tories are on 318 seats, ahead of Labour on 262 following its late win in Kensington, the SNP 35 and the Lib Dems on 12. The DUP won 10 seats.
As it stands, the Tories and the DUP would have 328 MPs in the Commons, giving it a wafer-thin majority although as Sinn Fein will not be taking its seven seats, the new administration will have slightly more room for manoeuvre.
Reaction to Theresa May's performance
After losing her majority, Mr Corbyn called on the prime minister to quit and Lib Dem leader Tim Farron said she should resign "if she has an ounce of self-respect".
Some in her own party have also called for her resignation, with Anna Soubry saying she should consider her position after a "disastrous" campaign.
However, other MPs have urged her to stay on - Iain Duncan Smith said a leadership contest would be a "catastrophe".
Tory MP Philip Davies said his party had made "a pig's ear" of the campaign, and fellow Tory MP Nigel Evans said his party had "shot ourselves in the head".
Mrs May's former director of communications, Katie Perrior, said the party should never have run a Presidential-style campaign when the leader is "shy" and doesn't like doing interviews.
The Green Party, which held its one seat at the election but saw its total vote halve, said a Conservative government propped up by the DUP would be a "coalition of chaos".
"The DUP, I don't think, are the kind of people you want calling the shots," co-leader Jonathan Bartley said.
Downing Street said Mrs May received congratulatory calls from French President Emmanuel Macron, who said he was pleased that she would continue to be a close partner, and US President Donald Trump, who agreed with her that they looked forward to close co-operation.
Where does this leave Brexit and the Conservative manifesto?
Britain's exit from the European Union has been plunged into uncertainty, says BBC diplomatic correspondent James Landale.
The government - and the DUP - may have to rethink their strategy, and the EU will be dismayed to be facing a divided British parliament in a divided Britain, he adds.
European Council president Donald Tusk says there is now "no time to lose" over Brexit and the European Parliament's chief negotiator, Guy Verhofstadt, said the result was an "own goal" which made negotiations more "complicated".
BBC analysts says the Conservative's election manifesto may also be in jeopardy.
Policies, such as new grammar schools and social care reforms, are likely to get ditched, they say. Without a majority in the Commons, members of the Lords might feel entitled to block them.
Also, within the Conservative party, there is a widespread perception that the manifesto was a disaster which they need to distance themselves from, they add.
Other big shocks and surprises
In a night of high drama, former Lib Dem leader Nick Clegg lost his seat while current leader Tim Farron clung on by less than 800 votes in his Cumbrian constituency.
Vince Cable and Jo Swinson are among the Lib Dems returning to the Commons after winning back their former seats.
UKIP leader Paul Nuttall quit after his party failed to win any seats and saw its vote collapse across the country. Former party chairman Steve Crowther will lead the party on an interim basis.
Gerry Adams, president of Sinn Fein, which gained three seats taking its total to seven, said it had been a "very good election for republicanism", and appealed for "calm reflection" on how to go forward.
In more results from the night:

Prime Minister Theresa May has urged the first ministers of Scotland and Wales to back her Brexit deal.
At a Downing Street summit, the leaders of the devolved administrations discussed the UK's impending exit from the European Union.
Mrs May said her plan "delivers for the whole of the UK", urging others to "pull together" behind it.
But Scottish First Minister Nicola Sturgeon said MPs should study other plans, such as a new Brexit referendum.
Members in both the Scottish Parliament and Welsh Assembly have overwhelmingly voted against Mrs May's deal.
MPs are set to hold their "meaningful" vote on the withdrawal agreement, hammered out with European negotiators, in January 2019.
Ministers from around the UK gathered for the meeting in London on Wednesday afternoon, with Brexit high on the agenda. Mrs May and a team of her ministers were joined by Ms Sturgeon and the newly appointed Welsh First Minister Mark Drakeford.
There was also discussion of immigration after the government published a White Paper of its plans for rules after the UK leaves the EU.
Mrs May has been facing a battle to win support for her Brexit plans, with critics on her own back benches as well as across the opposition.
The prime minister said she was "confident that what we have agreed delivers for the whole of the UK".
She said: "This deal honours the result of the referendum - taking back control of our money, laws and borders, protecting jobs and livelihoods, and freeing the UK to strike new trade deals with countries around the world.
"That's why it is more important than ever that the devolved administrations get behind this deal and listen to businesses and industry bodies across all four nations who have been clear that it provides the certainty they need."
Following the meeting, Ms Sturgeon said SNP MPs would not be voting for Mrs May's deal, and called on the prime minister to extend the current Brexit deadline of 29 March.
She said: "We have argued that Article 50 should be extended, so that no-deal is absolutely taken off the table and that time is then given for parliament to look at the alternatives to the deal.
"Our preference of course is for another EU referendum, to give people across the UK the opportunity, knowing what they now know after the last two and a half years, to change their minds."
Ms Sturgeon also said she had made her views about immigration "very clear to the prime minister" at the meeting.
She said: "This paper says that the proposals would reduce EU migration into Scotland by 85%. So it would be devastating for jobs, the economy, for living standards, the income of the country, and it would also deprive us of people who make a big and positive contribution to life in Scotland."
Home Secretary Sajid Javid has argued that the new system would be based on the skills, rather than origin, of migrants and show the UK was "open for business".
Mr Javid said the plans did not include a "specific target" for reducing numbers coming into the UK but would bring net migration down to "sustainable levels".
Meanwhile, the SNP, Liberal Democrats, Plaid Cymru and the Greens tabled a vote of no confidence in the UK government following a meeting on Tuesday evening.
The parties want the government to debate the motion before parliament rises for the Christmas recess, but it is thought the government is only obliged to give time to motions tabled in the name of the Leader of the Opposition - Labour's Jeremy Corbyn - who has so far failed to do so.
And Chancellor Phillip Hammond has confirmed the Scottish government will be allocated £55m for Brexit preparations in 2019/20, as part of its £2bn spend.
The Welsh Government will receive £31m while the Northern Ireland Executive will be granted £20m.

This summit was, in some ways, quite predictable.
Not a crisis moment like Salzburg. Not a success where Theresa May could walk away with something that felt like a significant achievement.
As we know, both sides, in principle, want a deal. So last night and through this afternoon the EU and the UK agreed to keep the show on the road.
But as we move towards what the legal deadlines imply are the closing moments of this whole process, some of its moments are becoming pretty strange.
The prime minister had a hint of warmth from some parts of the EU empire for the idea of drawing out the implementation period, to give more time to work out the long term fixes.
But even so, the politics put such a straitjacket on proceedings that she can't even quite manage to be completely clear about that.
So we heard today about a proposal that's not a proposal but an "idea that's emerged". An extension to an extension that's not a request for a longer transition period but a desire perhaps to have the option.
It might sound like Kafka. But it's the words of a government struggling to keep a set of almost impossible promises.
The sound of a prime minister desperately trying to keep to the contradictory pledges that she has made in order to survive.
The circumstances for Theresa May in Brussels have not got worse in the last 24 hours. But they are hardly better. And when she gets home, a nightmare awaits.
There's upset about the parliamentary games ministers are proposing.
And irritation and disbelief at the proposal of an extension.
One former loyal Remainer Brexit minister, Lord Bridges, told me the idea of a longer transition is dead on arrival.
Each new compromise brings a confrontation with her party.
When Theresa May's promises are broken, ministers know there's a risk that it will break her government, and her leadership too.

The talking in Brussels is done. After nearly two years of negotiations, arguments - and the inevitable moments where it felt like the process would explode - there is, now, a deal.
It's a compromise. It was always going to be. It's not a happy compromise either. People on both sides of the Brexit argument are already screaming their protests.
And although the prime minister must be relieved, she didn't exactly say that she was pleased about the deal when I asked her at a news conference this lunchtime.
Instead, she said she was sure the country's best days are ahead.
But however she really feels about it - and with this prime minister it is hard to tell - her strategy for the next couple of weeks is crystal clear. Her case? This is all there is.
With the explicit backing of almost every European leader who has opened their mouth today, this is the "only deal", the "best possible deal", "the max".
The message to MPs from Theresa May and her counterparts: don't kid yourselves if you think something else might magically appear if you vote it down.
And the message to the public? Just let me get on with it, then we can all stop talking about Brexit - please.
Again today she used the platform to "talk directly to the British public", to explain how her (now rather pink) red lines, on "money, laws and borders", have been followed.
It's her Brexit with caveats, with a lot to be sorted out about the future, in the future. You can remind yourself what's actually in the deal here.
And No 10 is all too aware that dozens and dozens of their own MPs hate it. Theresa May has reached her imperfect compromise at a moment when in Parliament both sides are hardening against the idea of compromising at all.
For two years Theresa May has survived by tacking one way, then another. But now the deal is on paper, in black and white, that approach can't go on.
A senior government figure said privately that No 10 was past the point of trying to please everyone. And of course, everyone in government is all too aware that it is likely that the deal will be rejected by Parliament in any case.
But the only potential route through for the prime minister is through the middle, to look like, as one senior Whitehall official describes it, "the adult in a world of children".
However the prime minister looks, however she sounds in the next fortnight, the levels of unhappiness at home are so profound that her pleas may fall on deaf ears.
If the deal falls, she - and her government - may fall with it. Scrape it through then she'll have pulled off a feat far harder than getting the actual deal done.
PS: Here's a great explanation from my colleague Ben Wright about what might happen if the vote, which we expect on 12 December, doesn't pass the deal.

Labour should 'get on with' changing its Brexit policy to support a second referendum, the shadow chancellor has told the BBC.
John McDonnell said Jeremy Corbyn was "rightfully" trying to build consensus, but added the party needed to reach a position "sooner rather than later".
"I want to campaign for Remain," he said.
He also denied he had called for the Labour leader's advisors to be sacked, as reported in the Sunday Times.
Labour had previously promised a vote on Brexit in certain circumstances, specifically if it could not get its own deal with the EU passed by MPs or if there was no general election.
Following the party's poor performance in the European elections in May, Mr Corbyn appeared to go further, suggesting there "had to be a public vote" on any deal agreed with Brussels.
He has recently come under pressure from his own MPs to confirm that the party would call for another referendum, and would campaign to remain in the EU.
Speaking on the Andrew Marr Show, Mr McDonnell confirmed that he, personally, would campaign to Remain if there was a second referendum.
He said he wanted to "get on with it", but added that Mr Corbyn was "much wiser" and wanted to "build consensus and then go for it".
"That's what he's doing at the moment," he added.
"Jeremy and I go back 40 years, we're the closest of friends. We've minded each other's back throughout that period. Yes, we'll disagree on things, and then we'll come to an agreement."
Asked if he and shadow home secretary Diane Abbott had called for Mr Corbyn's advisors - Karie Murphy and Seumas Milne - to be sacked, Mr McDonnell replied such stories were "rubbish".
Meanwhile, Labour's Barry Gardiner told Sky News' Sophy Ridge that his party is in talks with Conservative MPs who might support a no-confidence motion in the government in order to stop a no-deal Brexit. Conservative MP and ex-minister Sam Gyimah suggested "30 plus" Tory MPs would seek to stop a no-deal Brexit.
Mr McDonnell was also asked about reports in the Sunday Times that up to half a dozen Labour staff have ignored non-disclosure agreements (NDA) to speak to BBC journalists working on a Panorama programme about Labour and anti-Semitism.
According to the Times, Labour, through the law firm Carter Ruck, has warned there could be legal action against those staff members.
Mr McDonnell said the Labour Party was "reminding them of their confidentiality agreement".
He argued this was important in cases where employees "are dealing with individual cases, individual information and individual members".
However, he added the party would "always protect anyone subject to harassment".
A number of Labour MPs criticised the reported action, including deputy leader Tom Watson who said "using expensive media lawyers in an attempt to silence staff members is as futile as it is stupid".
Labour MP Wes Streeting tweeted "Labour opposes NDAs, yet seems to impose them. I'm protected by parliamentary privilege. I'll whistleblow in the House of Commons for anyone who needs me to do so. Sunlight is the best disinfectant. No more excuses or hiding places. You should promise the same Jeremy Corbyn."
Mr Gardiner, shadow international trade secretary, has attacked the forthcoming Panorama programme - which will be aired next week - as neither balanced or impartial.
In response the BBC said: "The Labour Party is criticising a programme they have not seen.
"We are confident the programme will adhere to the BBC's editorial guidelines. In line with those, the Labour Party has been given the opportunity to respond to the allegations."
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Labour would vote against a government plan designed to resolve the impasse in the Brexit negotiations on Northern Ireland, the shadow chancellor said.
John McDonnell has told Newsnight that Labour would reject any customs arrangement with the EU unless it was established on a permanent basis.
Theresa May hopes to avoid a hard border in Northern Ireland through a temporary UK-wide customs arrangement.
Mrs May plans to have an agreement with EU leaders by the end of this month.
Such a move from Labour would raise the chances of Parliament rejecting her withdrawal agreement.
It is understood the prime minister believes that an agreement with EU leaders needs to be reached no later than the final week of November to allow it to pass parliamentary hurdles in Westminster and Strasbourg.
That means a deal needs to be agreed with the EU's chief negotiator Michel Barnier by around 21 November to give the EU a week to prepare for an emergency summit of EU leaders.
Mrs May is due to brief the cabinet on Brexit on Tuesday morning.
The prime minister's customs arrangement is known informally in No 10 as a customs union.
Downing Street is facing calls from ministers for the UK to be allowed to end it unilaterally, a demand that has been rejected by the EU and Dublin.
The No 10 initiative for an all-UK customs arrangement is designed to replace an EU proposal to create separate customs territories for Northern Ireland and Great Britain. The prime minister has rejected this on the grounds that it would lead to an internal UK border down the Irish Sea.
Asked by Newsnight whether Labour could vote for a deal in which the whole of the UK was placed in a customs union with the EU for a temporary period, Mr McDonnell said: "I can't see it because I think it would be the worst of all worlds. What I'm getting from business leaders, trade union leaders and others is they want permanence, they want stability."
Labour, which has advocated UK membership of a customs union for the past year, has said that it would vote down the prime minister's Brexit deal unless it passes six tests set by the party.
These include delivering the "exact same benefits" as the UK enjoys as a member of the single market and the customs union.
The shadow chancellor's remarks to Newsnight show that he wants permanent membership of a customs union to apply in all circumstances. This includes what is intended by No 10 to be a temporary "backstop" period after the end of the transition period in December 2020, if a future trading relationship has not been finalised by then.
"If the government says 'well a customs union for a couple of years or maybe customs union until we decide there won't be one,' well actually, that doesn't give the stability for investment for anyone," McDonnell said.
"What I'm worried about is Theresa May comes back from Europe waving a piece of paper - and it won't be Winston Churchill, it'll be more like Neville Chamberlain. What we'll see is peace in our time that will then disintegrate over time.
"I'd rather she just came back and told us. If she can get a deal that protects jobs and the economy we'll vote for it, but it can't be half in half out.
"If she can't deliver, we can't vote for it - move to one side and let us do the negotiations."
The shadow chancellor indicated that if Parliament rejects a Brexit deal proposed by Theresa May, the EU might be prepared to renegotiate with a new UK government.
Labour believes that if Parliament votes down a Brexit deal a general election should be held.
"All the messages that we get back over this whole period is that our European partners desperately want what we want: a deal that will protect their jobs and their economies in the same way that we want to," he said.
"If they recognise the deal is unacceptable to Parliament I think that opens up a vista of the opportunity of real negotiations... In the EU you negotiate on the basis of mutual interest and mutual respect. You don't negotiate on the basis of banging on the table, threatening to walk out every five minutes."
Watch the full interview on Newsnight on Monday, 22:30 on BBC Two or online.

German Chancellor Angela Merkel has suggested an alternative to the Irish border backstop - a key Brexit sticking point - could be found within 30 days.
Speaking at a news conference alongside Prime Minister Boris Johnson in Berlin, she stressed it would be up to the UK to offer a workable plan.
The PM said he was "more than happy" with that "blistering timetable".
He accepted the "onus" was on the UK, but said he believed there was "ample scope" for a new deal to be reached.
In his first overseas visit to a fellow leader, Mr Johnson is meeting Mrs Merkel after he told the EU the backstop - which aims to prevent a hard Irish border after Brexit - must be ditched if a no-deal exit was to be avoided.
He will meet French President Emmanuel Macron on Thursday, before attending the G7 summit on Saturday alongside other leaders including US President Donald Trump.
The EU has repeatedly said the withdrawal deal negotiated by former PM Theresa May, which includes the backstop, cannot be renegotiated.
And - despite Mrs Merkel's comments - that message was echoed by Mr Macron on Wednesday evening.
"Renegotiation of the terms currently proposed by the British is not an option that exists, and that has always been made clear by [EU] President Tusk," he told reporters in Paris.
At the news conference, the German chancellor said a realistic alternative to the plan would require "absolute clarity" on the post-Brexit future relationship between the UK and the EU.
"The backstop has always been a fall-back option until this issue is solved," she said.
"It was said we will probably find a solution in two years. But we could also find one in the next 30 days, why not?"
Mr Johnson replied: "You rightly say the onus is on us to produce those solutions, those ideas [...] and that is what we want to do.
"You have set a very blistering timetable of 30 days - if I understood you correctly, I am more than happy with that," he added.
He added that alternatives to the backstop had not been "actively proposed" under his predecessor Theresa May - but he was pressed by Mrs Merkel to spell out what such alternatives might look like.
The prime minister has insisted he wants the UK to leave the EU with a renegotiated withdrawal deal, but the UK must leave on 31 October "do or die".
If implemented, the backstop would see Northern Ireland staying aligned to some rules of the EU single market, should the UK and the EU not agree a trade deal after Brexit.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
These arrangements would apply until both the EU and UK agreed they were no longer necessary. Brexit supporters fear this could leave the UK tied to the EU indefinitely.
Mr Johnson called the backstop "anti-democratic" and "unviable".
Should we be optimistic about the scope for a Brexit breakthrough after Angela Merkel suggested a solution to remove the need for the backstop could be found - possibly even within just 30 days?
Boris Johnson will certainly be pleased the German chancellor has left a door open.
But don't get carried away. There's a reason Europe is so adamant the backstop has to stay in the Brexit deal - it just doesn't believe there is a workable alternative available right now.
Boris Johnson says it's his job to find a solution and accepted a deadline of 30 days to come up with one.
The pressure is firmly on the UK to find that solution - and it's going to be a huge challenge to put it mildly.
Meanwhile, Jeremy Corbyn has cancelled a trip to Ghana later this week, urging opposition MPs to meet urgently to discuss ways to prevent a no-deal Brexit.
SNP Westminster leader Ian Blackford has confirmed he would attend the meeting next Tuesday, but warned the Labour leader that "all options must be on the table".
Mr Corbyn has proposed that in order to prevent a no-deal exit, opposition MPs should help him defeat the government in a no-confidence motion and install him as a caretaker PM.
If he wins the vote, he plans to delay Brexit, call a snap election and campaign for another referendum.
But the Liberal Democrats, and some potential Tory allies opposed to a no-deal exit, have indicated they won't back a plan that leads to Mr Corbyn in No 10.

The government needs to seek the "maximum possible consensus" on Brexit in the light of the general election result, Michael Gove says.
The new environment secretary, a leading figure in the campaign to leave the EU, said the referendum result should be "honoured in the right way".
The Tories no longer have a Commons majority with EU negotiations set to begin next week.
There have been calls for a cross-party commission to seek agreement.
In the Daily Telegraph, Former Conservative leader William Hague said a "change of style and substance" was now needed, suggesting a commission, also including business leaders and trade unions, to find areas of agreement.
Scottish First Minister Nicola Sturgeon has also called for a cross-party approach, and Labour's Yvette Cooper said a commission was needed to avoid Brexit being "caught up in the inevitable Hung Parliament political rows".
Theresa May set out the government's strategy last year and started the clock on the UK's final departure from the EU in March.
Downing Street has said there will be no changes to this approach, despite the Tories looking like they will have to rely on the Democratic Unionist Party - which backs Brexit but has specific demands including close trade with the EU - to stay in power.
Mr Gove noted that most votes at the election had been cast for either the Conservatives or Labour, who both support leaving the EU and ending freedom of movement, but added: "It is important to recognise we were not returned with a majority."
The government should "proceed with the maximum possible consensus", he told BBC Radio 4's Today programme, and "make sure that Remainers' concerns are part of our conversation".
Following reports of talks between some Remain-backing Conservative and Labour MPs, he rejected a "softening" of the government's approach, but said there were a "significant number of questions as we leave about the shape that we want our country to take".
But he played down Lord Hague's suggestion of a commission - "this idea is very much his copyright", he added.
Another ex-Tory leader, Iain Duncan Smith, dismissed suggestions of a change in the Conservatives' approach as "made-up nonsense".
He told the BBC the DUP had supported the government's strategy before the general election and "the vast majority of the Conservative Party believes this is a settled issue".
Aside from Brexit, it has also been reported that the DUP's opposition to some austerity measures could trigger a rethink in the government's economic strategy.
Asked about this, Mr Gove said ministers had to "reflect on what the election result told us about the way that people want to see the economy managed in the future".
He said there was a need to ensure public spending was kept at a sustainable level but stressed that "we also need to take account of legitimate public concerns about ensuring that we properly fund public services in the future".
The former education secretary, who clashed with Mrs May when both were ministers and was then sacked by her when she arrived in Downing Street, declared himself a "huge fan" of the PM.
He also rejected criticism of his environmental credentials by some campaigners, saying he had spoken in 2006 in favour of a bill making it easier to fight climate change and attributing his later voting record to having been following the whip in government.
"My own approach has always been to argue for strong action to deal with man-made climate change," he added.

The government has published a new law that says it must treat animals as "sentient beings" when it makes laws.
Environment Secretary Michael Gove promised to "make Brexit work not just for citizens but for the animals we love and cherish too".
The draft law also increases the maximum sentence for serious animal cruelty to five years in jail.
The Green Party said the government had done a "screeching U-turn".
The move follows last month's animal sentience "fake news" row involving a celebrity-backed social media campaign.
After MPs voted not to incorporate part of an EU treaty recognising that animals could feel emotion and pain into the EU Withdrawal Bill, some widely-shared reports and petitions suggested it had been a vote against the idea of animal sentience itself.
High-profile figures such as explorer Ben Fogle shared the stories. He later apologised for posting "misleading threads" but defended sharing details on "important stories".
In the aftermath Mr Gove hit out at the way social media "corrupts and distorts" political reporting and promised new UK legislation to ensure the principle of animal sentience is recognised.
The draft bill says the government "must have regard to the welfare needs of animals as sentient beings in formulating and implementing government policy".
Mr Gove said: "Animals are sentient beings who feel pain and suffering, so we are writing that principle into law and ensuring that we protect their welfare.
"Our plans will also increase sentences for those who commit the most heinous acts of animal cruelty to five years in jail.
"We are a nation of animal lovers so we will make Brexit work not just for citizens but for the animals we love and cherish too."
Speaking in a House of Commons debate, Environment Minister Therese Coffey said that "contrary to the fake news that was spread recently" the "direct effect of animal sentience" was already recognised "throughout the statute book" but the new measure would put animals' capability of feeling pain or pleasure "more clearly than ever before in domestic law".
David Bowles, the RSPCA's head of public affairs, said the plans were "potentially great news" for animals post-Brexit.
He said: "To include the recognition of animal sentience as well as increasing animal cruelty sentencing to five years into the new 2018 Animal Welfare Bill is a very bold and welcome move by the government."
Green Party MP Caroline Lucas, whose amendment to the EU bill sparked the debate about animal sentience, said the government had "performed a screeching U-turn" after previously insisting it was covered by existing UK law.
"There's absolutely no doubt in my mind that this legislation wouldn't have emerged now without the pressure of thousands of people who have taken action after the government voted against my amendment," she said.
Labour's Sue Hayman, shadow environment, food and rural affairs secretary, said: "This is a rushed and haphazard attempt to backtrack on the government's mistake of not including animal sentience in the EU Withdrawal Bill.
"There are serious questions about whether this Bill is equivalent to current EU standards given that it does not appear to cover wild animals - giving this Tory government freedom to pursue their pro-fox hunting and reckless badger culling agenda across England."

The UK should not accept imports of chlorinated chickens as part of any future trade deal with the US, Michael Gove has said.
The environment secretary told the BBC that the UK would not "compromise" on or "dilute" its animal welfare standards in the interests of trade.
The EU currently bans chlorine-washed chickens on welfare grounds.
International Trade Secretary Liam Fox has questioned this but downplayed the potential for UK-US disagreement.
It will be up to the UK to decide whether to retain the ban once it leaves the EU in March 2019.
Labour said the government's "casual and inconsistent" approach risked undermining British farmers.
On a visit to Washington on Monday, Mr Fox said chlorinated chicken was just one detail in one sector that would only be addressed at the end of discussions about a free trade deal - which are likely to be years away.
He has suggested there are no food safety issues regarding chlorine-washed chickens, a view shared by many UK experts.
In the US, it is legal to wash chicken carcasses in strongly chlorinated water.
Producers argue that it stops the spread of microbial contamination from the animal's digestive tract to the meat, a method approved by US regulators.
But the practice has been banned in the EU since 1997, where only washing with cold air or water is allowed.
The EU argues that chlorine washes could increase the risk of bacterial-based diseases such as salmonella on the grounds that dirty abattoirs with sloppy standards would rely on it as a decontaminant rather than making sure their basic hygiene protocols were up to scratch.
There are also concerns that such "washes" would be used by less scrupulous meat processing plants to increase the shelf-life of meat, making it appear fresher than it really is.
Agriculture is likely to be one of the sticking points in talks over a deal, amid concerns about differing farming and welfare practices, such the use of growth hormones given to cows and cattle.
Asked whether lifting the ban on chlorinated chickens was a price to be paid for sealing a post-Brexit deal with the US, Mr Gove told BBC Radio 4's Today: "No. I have made it perfectly clear we are not going to dilute our high environmental standards or our animal welfare standards in the pursuit of a trade deal.
"We need to ensure that we do not compromise those standards. And we need to be in a position as we leave the European Union to be leaders in environmental and in animal welfare standards."
On whether poultry could scupper a US trade deal, he added: "The Trade Secretary, quite rightly, pointed out that, of course, this issue is important, but we mustn't concentrate just on this one issue when we look at the huge potential that a trade deal can bring."
While membership of the EU meant the UK had to accept some environmental obligations "which do not work in the interests of the environment", he said the UK had been a world leader in environmental standards for decades and that would continue after Brexit.
Mr Fox, who concluded a four-day trip to the US on Wednesday, has said the UK will not be lowering its food safety or animal welfare standards after Brexit but decisions on US chicken imports and other consumer protection issues should be based on scientific advice.
"There is no health issue with that - the European Union has said that it is perfectly safe," he said. "The issue lies around some of the secondary issues of animal welfare and it's perfectly reasonable for people to raise that, but it will come much further down the road."
A Lords report on Wednesday warned that UK farmers' livelihoods could be threatened by an influx of cheaper food imports from the US. It said there was evidence that UK consumers would be willing to pay more for food reared to higher standards but it remained to be seen if this would happen in practice.
For Labour, shadow environment secretary Sue Hayman said the cabinet was in disarray over the issue.
"Theresa May must set the record straight by publicly supporting British poultry farmers and committing to protect the British public from substandard food produce in a race-to-the-bottom Brexit," she said.
But Conservative MP John Redwood said British farmers were already losing out to cheaper competition from the European continent, where welfare standards - both in terms of the rearing and transport of animals - were not as high as in the UK.
"When we leave the EU we will be free to set our own standards, which will be higher than EU minimum requirements," he wrote on his blog. "This makes animal welfare an odd argument for people to use who want us to stay in the EU system."

The EU's chief Brexit negotiator Michel Barnier has said he is "strongly" opposed to key parts of Theresa May's proposals for a future trade deal.
This morning the prime minister said she would not compromise on the UK government's Chequers plan.
But Mr Barnier said plans for a "common rulebook" for goods but not services were not in the EU's interests.
"Our own ecosystem has grown over decades," he said. "You can not play with it by picking pieces."
While he has previously expressed criticism about Mrs May's Chequers plan, sources close to Mr Barnier told the BBC he has not been this explicit before.
In response, the UK government insisted its plans were "precise and pragmatic" and would work for the UK and the EU.
The negotiations between the UK and the EU have an informal October deadline, but Mr Barnier said this could be extended to mid-November.
In an interview with the German newspaper Frankfurter Allgemeine Zeitung, Mr Barnier said Mrs May's plans "would be the end of the single market and the European project".
"The British have a choice," he said.
"They could stay in the single market, like Norway, which is also not a member of the EU - but they would then have to take over all the associated rules and contributions to European solidarity. It is your choice.
"But if we let the British pick the raisins out of our rules, that would have serious consequences.
"Then all sorts of other third countries could insist that we offer them the same benefits."
He said another problem was that many goods now come with services attached - meaning they were hard to separate in a trade deal.
"We have a coherent market for goods, services, capital and people - our own ecosystem that has grown over decades," he said.
"You can not play with it by picking pieces. There is another reason why I strongly oppose the British proposal.
"There are services in every product. In your mobile phone, for example, it is 20 to 40 percent of the total value."
Mr Barnier's comments were published on the same day Mrs May wrote in the Sunday Telegraph that she was "confident" a "good deal" could be reached.
But she said it was right for the government to prepare for a no-deal scenario - even though this would create "real challenges for both the UK and the EU" in some sectors.
Foreign Secretary Jeremy Hunt has warned a no-deal Brexit would be a "big mistake for Europe", although Britain "would survive and prosper".
Various business groups have warned about the possible impact on the UK of no-deal Brexit.
The World Trade Organization - under whose rules the EU and UK would trade if no deal was agreed - said it "would not be end of the world... but it's not going to be a walk in the park".
Responding to Mr Barnier's remarks, a government spokeswoman said: "We are confident that we have put forward a proposal that is precise, pragmatic and that will work for the UK and the EU.
"This proposal achieves a new balance of rights and obligations that fulfils our joint ambition to establish a deep and special partnership once the UK has left the EU while preserving the constitutional integrity of the UK. There is no other proposal that does that.
"Our negotiating teams have upped the intensity, and we continue to move at pace to reach - as Mr Barnier says - an ambitious partnership, which will work in the mutual interests of citizens and businesses in the UK and in the EU."
The so-called Chequers plan was agreed at the prime minister's country residence in July. It led to the resignations of Brexit Secretary David Davis and Foreign Secretary Boris Johnson.
Mr Barnier has previously criticised the proposals, ruling out allowing the UK to collect customs duties on behalf of the EU.
The UK is due to leave the EU on 29 March but has yet to agree how its final relationship with the bloc will work.

The UK's David Davis and his EU opposite number have discussed the thorny issue of a post-Brexit "backstop" plan for the Northern Ireland border.
Mr Davis met Michel Barnier in Brussels for what the UK side described as a "stock-take" of progress made so far.
The EU has set out several objections to the UK's proposals, saying they would lead to a "hard border" in Northern Ireland.
It has also raised fraud concerns.
The UK published its "backstop" plans last week, after a reported tussle over the wording between Mr Davis and Prime Minister Theresa May.
The aim of the backstop is to avoid border checks if the UK and the EU have not finalised a new trade relationship by December 2020, when the post-Brexit transition period is due to end.
The government's suggestion to avoid a physical border is that the UK temporarily aligns with the EU's customs union.
But last week Mr Barnier raised questions about how this would work, and now, in a series of internal slides published by the European Commission, the EU has criticised the proposal.
The UK's so-called "temporary customs partnership" would involve a "piecemeal application" of EU rules, and poses "serious risks of fraud", they say.
The EU documents also claim the UK plans would lead to a hard border between Northern Ireland and the Republic because they do not cover regulatory checks.
And on the UK's insistence that the arrangement should be time-limited, the EU questions whether this can be a proper backstop, and says it would be a "complex and unprecedented arrangement" for a short duration.
The EU's own backstop proposals - already rejected by the UK government - would be a "timely and workable solution", the commission claims.
The UK says its plan, which would only apply in "specific and narrow circumstances" delivers on a commitment made in December to avoid a hard border in Northern Ireland.

Michel Barnier has said Theresa May's plan for a future trade relationship with the EU could weaken the single market and create burdens for business.
The EU Brexit negotiator said the White Paper opened "the way to a constructive discussion" but must be "workable".
He questioned whether UK plans for a common rulebook for goods and agri-foods were practical.
Earlier, Theresa May urged the EU to "evolve" its position on Brexit and not fall back on unworkable proposals.
Mrs May is hoping the White Paper - which sparked two cabinet resignations - will allow the two sides to reach a deal on post-Brexit relations by the autumn, so the UK can avoid leaving the EU without a deal in March next year.
The White Paper proposes close ties in some areas, such as the trade in goods, but Mrs May says it will end free movement and the jurisdiction of the European Court, and allow the UK to strike trade deals with other nations.
Critics at Westminster say it is an unworkable compromise which would leave the UK being governed by the EU in many areas, but with no say in its rules.
Mr Barnier did not reject the White Paper out of hand, saying "several elements" of it were "very useful".
But there were parts that Brussels did not understand which would need further clarification.
He said his main aim was to protect the integrity of the EU single market, and the UK proposals - which would see frictionless trade in goods but not services - risked undermining that.
"We are not going to negotiate on the basis of the White Paper because that's the British paper but we could use many elements of the White Paper," said Mr Barnier.
"There's not an awful lot of justification for the EU running the risk of weakening the single market.
"That is our main asset. There's no justification for us to create additional burdens on business just because the UK wants to leave."
Mr Barnier questioned the UK's plans for a "common rulebook" for EU-UK trade as it only referred to goods checked at the border, not areas like pesticide use, adding: "How can we protect consumers in Europe?"
He also questioned whether the plans were workable without additional bureaucracy and said there were "practical problems" about how tariffs would be determined and collected - under the UK's plan, EU member states would collect tariffs on the UK's behalf and vice versa.
But Mr Barnier suggested the EU's controversial "backstop" proposal aimed at avoiding a hard Irish border could be changed: "There will be a deal if there is an agreement on the backstop.
"It's not necessarily our backstop. We can work on this, amend it, improve our backstop ... But we need an operational backstop now, in the Withdrawal Agreement, and not later."
Leading Brexiteer Jacob Rees-Mogg described Mr Barnier's speech as "aggressive" in a tweet:
On a visit to Belfast on Friday, Theresa May said the "seamless border" between Northern Ireland and the Irish Republic was "a foundation stone on which the Belfast [Good Friday] Agreement rests" and the concept of a hard border was now "almost inconceivable".
But she reiterated her opposition to the EU's "backstop" proposal, that would see Northern Ireland effectively staying in the single market for goods and the customs union, as "something I will never accept and I believe no British prime minister could ever accept".
And she dismissed suggestions made by former foreign secretary Boris Johnson that technology could be used to avoid the need for a hard border: "No technology solution to address these issues has been designed yet or implemented anywhere in the world, let alone in such a unique and highly sensitive context as the Northern Ireland border."
She said the White Paper was a "significant development" of the UK's position and offered a "coherent package".
"It is now for the EU to respond - not simply to fall back on to previous positions which have already been proven unworkable, but to evolve their position in kind.
"And, on that basis, I look forward to resuming constructive discussions."
Ireland's Foreign Minister Simon Coveney told Ireland's RTE radio there had been a "lukewarm" response in Brussels to the UK White Paper.
He added: "We don't have any British proposal in terms of a functioning backstop in its entirety. We have bits and pieces of ideas."

Environment minister George Eustice has quit the government over Theresa May's promise to allow MPs a vote on delaying Brexit, if her deal is rejected.
The MP said it would be "dangerous" to go to the EU "cap in hand at the 11th hour and beg for an extension".
He feared it could mean a long delay or that Brexit "may never happen at all" and said the UK must be prepared to walk away without a deal.
The PM said she was focused on leaving the EU with a deal on 29 March.
Mr Eustice is a longstanding Brexiteer, who stood as a UKIP MEP candidate before joining the Conservatives.
He told the BBC he would back the withdrawal deal the prime minister has negotiated with the EU, despite some reservations.
"I do think it's preferable to have an orderly Brexit and crucially, it's preferable to get Brexit done," he said.
"We have to get legally out of the European Union as quickly as possible within this window. If we don't and we end up with a long delay of two years, as some would like, then I really do fear we will be in a disastrous situation and Brexit may never happen at all."
Former Brexit Secretary Dominic Raab, who himself quit the government in November, suggested any delay to Brexit would reward the EU for its "intransigence" and reduce the chances of getting a deal.
"The issue with delay is at this point in time it weakens our leverage - why would the EU make concessions now?" he told BBC Radio 4's Today.
"I think from the EU's point of view it signals to them that actually their intransigence pays off and that's the wrong message for the UK to be sending to Brussels at this moment."
Mr Eustice, the MP for Camborne and Redruth in Cornwall, is the 14th member of Theresa May's government to resign over Brexit and said he was doing so with "tremendous sadness".
But in his resignation letter, he said he feared that the EU would end up "dictating the terms of any extension requested and the final humiliation of our country".
He added: "We cannot negotiate a successful Brexit unless we are prepared to walk through the door."
By the BBC's Deputy Political Editor John Pienaar
George Eustice resigned because he believes Mrs May's been manoeuvred into putting Brexit itself in doubt.
For him, the breaking point was allowing MPs to vote on whether to rule out a no-deal Brexit, he's one of many Brexiteers who are convinced the danger of a disruptive exit might add to the pressure on the EU to make concessions.
And he's especially upset about Mrs May promising a vote on whether to delay Brexit beyond 29 March, if only for a short time.
The prime minister was driven to volunteer those concessions by the fear of being defeated in the Commons this week, and having to concede them anyway.
Her de-facto deputy David Lidington, and Chief Whip Julian Smith, warned Mrs May plainly that she had no choice.
A core of ministers, senior, junior and their parliamentary aides, were willing to sacrifice their jobs if necessary to bring about that defeat.
She gave in, and hated doing so.
But the fear of George Eustice - shared by other Brexiteers is that once Brexit is delayed, the government loses control.
Read John's blog
Mr Eustice's resignation comes after Theresa May's decision on Tuesday to allow MPs a vote on delaying the UK's departure from the EU, or ruling out a no-deal Brexit, if they again reject the withdrawal deal she has negotiated with the European Union.
The UK scheduled departure date from the EU is still 29 March - but that could be delayed if Theresa May fails to get her deal through Parliament in a vote she has promised will take place on or before 12 March.
In her reply, the prime minister said she was sorry he was resigning and praised his work as the longest serving minister at the Department for Food, Environment and Rural Affairs since the department was created, in 2001.
She said: "I agree with you that Parliament must now come together and honour the referendum result by voting for a deal which will give businesses and citizens the certainty they need and deserve.
"Our absolute focus should be on getting a deal that can command support in Parliament and leaving on 29 March.
"It is within our grasp and I am grateful to have your continued support in that important mission."
Praising Mr Eustice on Twitter, his former boss Environment Secretary Michael Gove said he would be "very much missed".
And former foreign secretary Boris Johnson praised the MP as "brave and right":
But the SNP's Westminster leader Ian Blackford said: "Another day, another resignation from the UK government. Any illusion to strong and stable ended before it began but this is beyond parody."

Jo Johnson has quit as transport minister and called for the public to have a fresh say on Brexit.
The MP, who is Boris Johnson's brother but voted Remain in the referendum, said the  deal being negotiated with the EU "will be a terrible mistake".
Arguing Britain was "on the brink of the greatest crisis" since World War Two, he said what was on offer wasn't "anything like what was promised".
Downing Street thanked him for his work but ruled out another referendum.
Jo Johnson voted to remain in the EU in the 2016 referendum while his brother Boris, who quit as foreign secretary in July, was a leading Brexiteer.
His brother praised his decision, saying they were "united in dismay" at the PM's handling of the negotiations.
Cabinet ministers have been invited this week to read the UK's draft withdrawal deal with the EU. Theresa May has said the withdrawal deal is 95% done - but there is no agreement yet on how to guarantee no hard border in Northern Ireland.
On Friday the DUP, whose support Theresa May relies on for votes in the Commons, said they cannot support any deal which included the possibility that Northern Ireland would be treated differently from the rest of the UK.
Mr Johnson, the MP for Orpington in Greater London, said the choice being finalised was either:
He described this as "a failure of British statecraft unseen since the Suez crisis" but said even a no-deal Brexit "may well be better than the never-ending purgatory" being put forward by the prime minister.
But in a warning to his brother and fellow Brexiteers, he added: "Inflicting such serious economic and political harm on the country will leave an indelible impression of incompetence in the minds of the public."
The "democratic thing to do is to give the public the final say", he argued.
Analysis by BBC political editor Laura Kuenssberg
For some time, Jo Johnson has struggled with the unfolding reality of Brexit.
A well-respected and liked member of the government, he has decided that what was promised to people during the referendum campaign is now so different to what is on the table that he has quit the government instead.
He's not the first, nor the best-known minister to resign over Brexit. But to leave at this moment, right when Theresa May is trying to stitch together a final deal, could have a serious impact.
Read Laura's full blog
He added: "This would not be about re-running the 2016 referendum, but about asking people whether they want to go ahead with Brexit now that we know the deal that is actually available to us, whether we should leave without any deal at all or whether people on balance would rather stick with the deal we already have inside the European Union.
"Britain stands on the brink of the greatest crisis since the Second World War. My loyalty to the party is undimmed. I have never rebelled on any issue before now.
"But my duty to my constituents and our great nation has forced me to act."
In response, a Downing Street spokesman said: "The referendum in 2016 was the biggest democratic exercise in this country's history. We will not under any circumstances have a second referendum.
"The prime minister thanks Jo Johnson for his work in government."
Mr Johnson is the sixth minister in Theresa May's government to resign specifically over Brexit, following David Davis, Boris Johnson, Philip Lee, Steve Baker and Guto Bebb.
For Labour, Shadow Brexit Minister Jenny Chapman said Mrs May had "lost all authority and is incapable of negotiating a Brexit deal within her own party, let alone with the EU".
But asked in an interview with the German magazine Der Spiegel whether he would stop Brexit if he had the chance, Jeremy Corbyn replied: "We can't stop it, the referendum took place."
Lib Dem leader Sir Vince Cable, whose party supports calls for a "People's Vote" on the final deal, said: "We warmly welcome Jo Johnson's support of the campaign to give the people the final say on the deal and a chance to exit from Brexit.
"This is a fascinating situation in which Jo and his sister are united in opposing their brother Boris and his Brexit plans."
Brexiteer Tory MP Andrea Jenkyns tweeted that she did not agree with him about another referendum - but his intervention highlighted unease on both sides of the debate, with the PM's efforts to secure a deal.
And pro-Remain Conservative Anna Soubry supported his decision and said it was time for another referendum.
David Davis, who quit as Brexit Secretary over Mrs May's Chequers Brexit plan, tweeted:

The cabinet is divided over how to handle the process of asking MPs to vote on alternative Brexit plans.
The government has promised to give the Commons the chance to vote on different versions of Brexit if the prime minister's deal is rejected again.
But the BBC's Laura Kuenssberg said it had not been decided in government whether the votes should be binding or not and what role ministers would play.
MPs believe the process can help break the current parliamentary deadlock.
It has been reported MPs could potentially consider up to six options, including remaining in the customs union and single market, a no-deal exit or cancelling Brexit, to gauge support for alternative courses of action.
Cabinet minister Greg Clark said it would be the "right step" if the prime minister's deal failed again.
He told Nick Robinson's Political Thinking podcast it was not good enough for any plan to "get over the line" and there needed to be as wide a consensus as possible behind the terms of withdrawal and the UK's future relations with the EU.
"Something that passes with a majority of one or two, I think, is not doing what we need to do which is to try to build as many people as possible together," he told Nick Robinson's Political Thinking Podcast.
In the coming days, as many as six other options, in addition to Mrs May's deal, could be voted on:
Labour leader Jeremy Corbyn, who wants his alternative plan for a customs union and guarantees on workers rights to be among those voted on, said there was support for a different way forward.
Conservative MP Sir Oliver Letwin, who is spearheading the move with senior Labour MPs including Hilary Benn, said he believed enough MPs would back an amendment to a government motion on Monday to trigger the so-called "indicative" votes later in the week.
But Conservative Brexiteer Marcus Fysh said the idea of giving MPs a menu of options after two years of negotiations was "ludicrous and childish", while ex-minister Steve Baker said it would end in "national humiliation".
The EU has given the UK until 12 April to decide on a way forward in an attempt to break the current impasse.
By the BBC's parliamentary correspondent Mark D'Arcy
If the Letwin amendment passes on Monday, it could allow a rough and ready version of the "indicative votes" process MPs have been discussing for some time now.
Alongside the PM's deal, as many as six other options could be voted on, including:
It is possible other options which could command reasonable levels of support might be added to the mix.
At the end all would be voted on simultaneously. MPs would fill out a ballot paper on each, voting for or against, and the relative support could then be seen.
Crucially, all the ballot-filling would be done at the same time; it would not be a case of MPs voting on one option, hearing the result, and then voting on the next. So there would be no tactical voting between options.
On Thursday, EU leaders agreed to push back the date of Brexit from 29 March until 22 May if Parliament approves the withdrawal agreement at the third time of asking.
However, they said the UK would need to come up with a plan B within three weeks if MPs throw out Mrs May's deal yet again.
Sir Oliver and Mr Benn hope that Plan B could emerge from indicative votes - with MPs effectively asked to choose from a menu of different options, to see which one gets the most backing.
MPs will debate the next steps for Brexit on Monday, as the government scrambles to persuade enough of them to back the prime minister's deal to hold another vote on it later in the week.
The indicative votes would not be binding on ministers.
But they would signal the degree of support among MPs for alternative options for the UK's future relationship with the EU.
After meeting ministers on Friday, Sir Oliver said he believed those searching for a cross-party compromise "have the numbers" to guarantee indicative votes will go ahead on Wednesday.
"We are seeking to crystallise a majority in some form of proposition so we have a way forward," he said.
MPs narrowly failed in an attempt to seize control of the Parliamentary agenda earlier this month to get indicative votes on to the Commons agenda.

A cabinet minister says he is "confident" his colleagues will settle their differences over Brexit at a crunch summit at Chequers on Friday.
James Brokenshire said there were "strong views" on both sides but predicted the away-day would yield a "clear direction" from the UK.
Ministers are under increasing pressure to spell out what type of relationship with the EU the UK should pursue.
EU chiefs demanded clarity from the UK at last week's Brussels summit.
Theresa May has promised more details in a White Paper that will be published after Friday's cabinet get-together at her official country residence.
The UK is leaving the EU on 29 March 2019, and negotiations are taking place on what their future relationship will look like.
But there is disagreement on the UK side about what sort of trading relationship to pursue with the EU, and how closely aligned they should be in years to come.
Speaking on the BBC's Andrew Marr Show, Mr Brokenshire, the secretary of state for local government and housing, said: "I think there's no doubt that there are strong views on either side and that's what I would expect as we lead into the discussions on Friday.
"But, equally, I remain confident that we will come out from that meeting with that clear direction, the White Paper that will follow, and actually setting out our vision for our future with our EU partners."
After Brexit day in March 2019, a temporary transition period is planned until the end of 2020 to allow an "orderly withdrawal" for the UK.
Business Secretary Greg Clark did not rule out an extension to this arrangement, telling Sky News the government had to be "guided by the evidence" and avoid "frictions" at the border.
He said the government would assess how long a new customs system would take to put in place, adding that "it seems to me that any reasonable person would have to be guided by the facts and the evidence".
Ministers have yet to agree on how to replace the UK's membership of the EU customs union - on Saturday it was revealed Environment Secretary Michael Gove had physically torn apart a report on Theresa May's preferred "partnership" arrangement.
Brexiteer Conservative MPs have said they will not accept any extension to the transition phase.
More than 30 have signed a letter to Mrs May urging her to face down people trying to "undermine" the 2016 vote to leave the EU.
Their other demands include not replicating the EU's customs union and an end to the free movement of EU citizens.
"Our departure must be absolute," the MPs say.
"We must not remain entangled with the EU's institutions if this restricts our ability to exercise our sovereignty as an independent nation.  Anything less will be a weakening of our democracy. Britain must stand firm."
Conservative MP Andrea Jenkyns, who delivered the letter to the PM, tweeted: "We must be clear to those in the cabinet and on the back benches, we will not sit back & allow a small minority to dominate."
Eurosceptic former Tory leader Iain Duncan Smith said Theresa May "probably doesn't need letters... to tell her what to do".
He added: "I just think we simply have to get behind her and say, 'let's get her over there and tell the European Union they need to do a trade agreement with us and do it pretty quickly'."
But pro-EU Labour MP Alison McGovern said there was a "serious" price attached to the government's negotiating red lines like leaving the EU's single market and customs union.
And she said the Chequers meeting was vital.
"We now need to know what it is the cabinet is trying to achieve - so this cannot be more important."
There are also Brexit divisions within the Labour Party, with Jeremy Corbyn urged by some of his MPs to back staying in the EU's single market or support another referendum on the final deal.
Campaigners for a so-called "People's Vote" have published a survey of members of Unite - the trade union that is Labour's biggest donor - where a majority were in favour of a second referendum.
Of almost 1,000 polled by YouGov, 57% backed a second referendum compared with 34% who were against, while respondents believed, by a margin of by a margin of 58% to 21%, that leaving the single market would make Britain worse off.
The People's Vote campaign said its survey provided "clear evidence that workers are turning decisively against the bad Brexit deal emerging from political machinations in Westminster and botched negotiations in Brussels".
Mr Corbyn told the BBC's Sunday Politics: "It's not our policy to have a second referendum - it's our policy to respect the result of the referendum but to have serious negotiations with the EU to gain a customs union and access to the single market to protect jobs in this country."
He added that one of the reasons people voted to leave the EU was because of the UK's "deeply unequal society where many former industrial areas lose out very badly because they haven't had the investment they need".

The government says it will not publish a leaked report document predicting an economic hit from Brexit.
Brexit Minister Steve Baker said the document was at a "preliminary" stage and releasing it in full could damage the UK's negotiations with the EU.
According to BuzzFeed, the report said growth would be lower in each of three different Brexit outcomes than if the UK had stayed in the EU.
Labour has called for it to be published and debated in Parliament.
According to Buzzfeed, the leaked document, titled EU Exit Analysis - Cross Whitehall Briefing and drawn up for the Department for Exiting the EU, suggests almost every part of the economy would suffer.
It looked at scenarios ranging from leaving with no deal to remaining within the EU single market.
Responding to an urgent question in the Commons, Mr Baker said the document was "not anywhere near being approved by ministers" and that ministers in his team had only just seen it.
He described the document as a "preliminary attempt to improve on the flawed analysis around the EU referendum" and said it did not assess the government's preferred option of a bespoke free trade deal.
It "does not yet take account of the opportunities of leaving the EU", he said, adding that civil service forecasts were "always wrong, and wrong for good reasons".
Responding to calls for it to be published, Mr Baker said MPs would get as much information as possible before they vote on the final Brexit deal but said: "We don't propose to go into these negotiations having revealed all of our thinking."
And as Brexiteer MPs hit out at the leaking of the document, he said there was "clearly" a campaign to overturn the 2016 EU referendum by some people in the media and the House of Commons.
One Conservative MP, Antoinette Sandbach, told Mr Baker she took exception to being told it was not in the national interest for her to see the document.
And responding for Labour, Brexit spokesman Sir Keir Starmer said the emergence of the report was "piling absurdity on absurdity" with the government having previously denied the existence of Brexit impact assessments.
Scottish First Minister Nicola Sturgeon said: "For months, Theresa May's government have refused to produce any detailed analysis of the potential impact of various Brexit scenarios - now we know why they have so desperately engaged in a cover-up."
The BBC understands the Treasury contributed to the document but sources say it is part of a much wider range of work going on in Whitehall.
The report suggests UK economic growth would be 8% lower than current forecasts, in 15 years' time, if the country left the bloc with no deal and reverted to World Trade Organisation rules.
It says growth would be 5% lower if Britain negotiated a free trade deal and 2% lower even if the UK were to continue to adhere to the rules of the single market.
All scenarios assume a new deal with the US.
Conservative MP Philip Davies blamed the report on "London-centric remoaners" in the civil service "who didn't want us to leave the European Union in the first place and put together some dodgy figures to back up their case".
Earlier Conservative MP and leave campaigner Iain Duncan Smith told BBC Radio 4's Today programme the document should be taken "with a pinch of salt" as almost every single forecast on Brexit has been wrong.
A government source said the report "contains a significant number of caveats and is hugely dependant on a wide range of assumptions".
The FDA, which represents senior civil servants, reacted angrily to Mr Baker's dismissal of the leaked study.
"We have just witnessed the extraordinary scene of a serving minister telling the House that, whatever analysis his own department comes up with, he simply won't believe it," said the union's general secretary Dave Penman.
Meanwhile, International Trade Secretary Liam Fox has denied telling Tory Brexiteers to prepare for disappointment.
Speaking to The Sun about pressure on Prime Minister Theresa May, he criticised Tory MPs involved with negative briefings, saying "nothing that would happen would change the parliamentary arithmetic".
"We don't have a working majority, other than with the support of the Democratic Unionists, and we need to accept the reality of that. I know that there are always disappointed individuals but they're going to have to live with disappointment."
Mr Fox told the BBC his warning was to Mrs May's critics that they will be "disappointed" in their efforts to topple her or secure cabinet positions for themselves.

The government has avoided a major defeat on its Brexit bill by 324 votes to 298 after a late concession.
Ministers saw off a move to give MPs the decisive say on what happens over Brexit if they do not agree with the deal negotiated by the UK government.
Following a meeting with Theresa May, Tory MPs said they had been promised "input" into what the government would do if the UK faced a no-deal scenario.
But one minister told the BBC he would commit only to "further discussions".
Solicitor General Robert Buckland said the government remained "open-minded", but this may or may not result in it coming forward with new proposals in the coming days.
The BBC's political editor Laura Kuenssberg said she had been told by a government source that no actual concessions had been agreed and the only agreement was to keep talking.
Tuesday's Commons debate marked the start of the government's attempts to undo most of the changes to its EU Withdrawal Bill that were put forward by the House of Lords.
The most contentious was the bid to give Parliament the power to tell the government what to do if the Brexit deal was voted down or no agreement was reached.
While in the end, only two Tory MPs - Ken Clarke and Anna Soubry - voted against the government, there were clashes over how much of a say Parliament should get as the UK leaves the EU, with one side accusing the other of trying to "wreck" Brexit - and being accused in turn of being "zealots" who wanted to sideline Parliament.
Seeking to placate would-be Conservative rebels, government frontbenchers offered to meet them to discuss their concerns, and agreed to "engage positively" on a "compromise" put forward by one of them, former attorney general Dominic Grieve.
Details of precisely what this will involve will be agreed in the coming days when the bill is due to return to the House of Lords and ministers could table a fresh amendment.
Analysis by BBC Parliamentary correspondent Mark D'Arcy
The government would not have sought a deal if it thought it had the votes to win, and they clearly blinked.
The decision to seek a compromise marked an important victory for the soft Brexit/Remainer/"realist" Tory rebels, who have been promised an amendment giving them most of what they want.
Read Mark's full blog
Mr Grieve said he had "confidence and trust" in Theresa May to address the concerns of more than a dozen MPs who are reported to have held last-minute talks with the prime minister in her Commons office during the debate.
He said if the UK and EU were unable to agree a deal in the autumn, or if MPs rejected the deal on offer as inadequate, there would be a "national crisis", with the real prospect of the UK leaving in March 2019 without an agreement.
In such a situation, he said, Parliament should be able to flex its muscles by requiring ministers to come forward with a plan of action, which MPs would be able to debate and vote on.
Several Tory MPs, including Heidi Allen, have suggested ministers have accepted this.
But the government is not believed to be willing to agree to Mr Grieve's call for MPs to effectively take control of negotiations in the last resort if no deal is agreed by February 2019.
Jacob Rees-Mogg, chair of the influential European Research Group of MPs, told the BBC a concession of this kind would have been "revolutionary" as the Commons could not override the government when it came to negotiating international treaties.
The leading Brexiteer said Mrs May had "paid attention to both sides" and the unity displayed by his party would strengthen the PM's hand in negotiations in the run-up to June's EU leaders' summit.
Fellow Brexiteer Sir Bill Cash said he was pleased the Lords amendment, which he said would have given Parliament an effective veto over Brexit, had been "soundly and significantly defeated".
Labour, five of whose MPs defied the leadership by voting with the government, said the prime minister may have avoided a "humiliating defeat" but the fight to ensure Parliament had a "proper role" in shaping the outcome of negotiations would continue.
"We will wait and see the details of this concession and will hold ministers to account to ensure it lives up to the promises they have made to Parliament," said the party's Brexit spokesman Sir Keir Starmer.
Earlier, the government suffered its first ministerial resignation over Brexit as Phillip Lee quit the Ministry of Justice so he could speak out freely.
Mr Lee said Parliament was being sidelined, and called for another referendum to be held when the final direction of Brexit became clear.
Revealing he had abstained in the Commons vote on Parliament's role, he said he was "delighted" at the government's concession, adding: "This justifies my decision to resign and makes it a lot less painful."
The government, meanwhile, has reversed a series of other changes made by the Lords to the EU Withdrawal Bill, including reinstating the precise day of departure - 29 March 2019 - in the proposed legislation.
A government amendment on the Irish border, guaranteeing there will be no new border arrangements without the agreement of the UK and Irish authorities, was also approved by MPs.

Now he's gone and done it.
For a long time it had been clear Boris Johnson was not happy with the prime minister's Brexit strategy.
His dissatisfaction was more than just the odd off-colour remark, although goodness knows there were enough of those.
His departure is a huge story and turns what might have been a couple of days of significant turmoil, into a significant crisis for Theresa May and the whole Brexit project.
He was Brexit's main cheerleader, the politician most associated with making it happen, and one of the best known politicians in the country, for good or ill.
It's enough of a mess on its own.
But a well-connected source has just told me it could be more serious than that.
They said it is a concerted push to force the prime minister to drop her Chequers compromise.
"If she doesn't drop Chequers there will be another," they said, "then another, then another, then another."
But if she can't force a compromise through her party that itself took months to stitch together, the prime minister's authority would be significantly diminished.
As Mr Johnson is hemmed in by paparazzi and camera crews outside his official residence that will soon be no longer his home, Theresa May is also a hostage with no obvious means of escape.

"Extensive" planning is under way to prepare the health service for a no-deal Brexit scenario, the NHS England chief executive says.
Simon Stevens said immediate planning was taking place around the supply of medicines and equipment.
"Nobody's pretending this is a desirable situation, but if that's where we get to it will not have been unforeseen," he said.
Ministers say they do not want a "no-deal" scenario.
"I believe that is an option that can be very firmly avoided," Housing Secretary James Brokenshire told the BBC's Andrew Marr Show.
The UK is due to leave the EU in March 2019, and negotiations are taking place about what their future relationship will look like.
In recent days there have been several warnings that time is running out to reach agreement before the autumn, so that a deal can be ratified by politicians.
Theresa May's cabinet will gather at Chequers on Friday to try to agree a "clear direction" that the UK wants to follow in trade talks.
Last October Mr Stevens told MPs he had not been asked by the government to examine the potential impact of the UK leaving in March 2019 with no deal in place.
Asked about this scenario, he told Andrew Marr: "There is immediate planning which the health department, with other parts of government, are undertaking around securing medicine supply and equipment under different scenarios.
"That will obviously crystallise when it's clear later this autumn what the UK's position will be."
He also said every hospital had been asked to "reach out" to EU nationals working there with information about how to apply to stay in the UK.
There have been warnings about the UK leaving Euratom, which regulates Europe's nuclear industry, including the supply of medical isotopes which are essential for various types of cancer treatment.
Prime Minister Theresa May has called for the UK to have a "close association" with Euratom after Brexit.
She has also said the UK will seek "associate membership" of the European Medicines Agency, which evaluates and supervises medicines and helps national authorities authorise the sale of drugs across the EU's single market.

The NHS in England is preparing to stockpile medicines and blood products in case of a "no deal" Brexit, Health Secretary Matt Hancock has said.
He said he was confident a deal would be reached but it was "responsible" to prepare for all outcomes.
He told the Health Select Committee he had met medical industry leaders to "accelerate" preparations since taking over as health secretary two weeks ago.
The government is stepping up planning for a "no deal" Brexit.
But ministers have so far rejected talk of shortages and queues of lorries at ports if the EU and UK can not reach a deal by March next year, when the UK officially leaves the bloc.
Both the government and the EU have insisted they want to avoid a "no deal" Brexit but key differences remain as they enter the critical phase of talks. The UK is sticking by its insistence that "no deal is better than a bad deal".
Mr Hancock said: "We are working right across government to ensure that the health sector and the industry are prepared and that people's health will be safeguarded in the event of a no-deal Brexit.
"This includes the chain of medical supplies, vaccines, medical devices, clinical consumables, blood products.
"And I have asked the department to work up options for stockpiling by industry.
"We are working with industry for the potential need for stockpiling in the event of a no-deal Brexit."
The health and social care secretary said such planning carried a "cost implication".
"We are also focusing on the importance of a continuous supply of medicines that have a short shelf life - so some of the medicines most difficult to provide in a no-deal scenario where there is difficult access through ports will need to be flown in.
"I hope that even under a no-deal scenario that there will still be smooth movement in through ports."
He said the government would also be setting out "contingency plans" for people booking holidays in EU countries who might need medical insurance in the event of a no deal scenario.
Labour's shadow health minister Justin Madders said: "We need a Brexit deal which puts patients first but now we know that the NHS is having to stockpile medicines because of this government's chaotic handling of Brexit.
"This is the terrifying reality of this government's failure to prioritise the NHS in the Brexit negotiations."
Simon Stevens, NHS England's chief executive, said earlier this month that "extensive" planning for a no deal Brexit was under way, around the supply of medicines and equipment.
Government departments are planning to issue guidance to businesses and consumers over the summer break on how to cope with a no deal Brexit.
Brexit Minister Lord Callanan dismissed claims there were plans to stockpile food.
"I am not aware of any plans for stockpiling food. It seems to me to be a fairly ridiculous scare story," he told the House of Lords.
"There are many countries outside of the European Union that manage to feed their citizens perfectly satisfactorily without the benefit of EU processes."
Brexit Secretary Dominic Raab told MPs the government would take steps to ensure an "adequate food supply".

The UK's new Brexit secretary has offered to meet Michel Barnier throughout August to "intensify" talks and "get some energy" into them.
Dominic Raab said his first meeting with the EU's chief negotiator in Brussels had been "constructive".
He replaced David Davis, who quit in protest at Theresa May's trade policy.
It comes as the IMF says some EU countries will suffer significant economic damage if the UK leaves without a trade deal.
Both the UK and EU are stepping up preparations for a "no deal" Brexit.
The two sides insist it is not what they want - and that reaching a deal by the autumn is still very much on the cards.
But they have yet to agree how their final relationship will work, with key issues around cross-border trade unresolved, and the UK's official departure date of 29 March 2019 fast approaching.
The UK government is standing by its belief that "no deal is better than a bad deal" - and is set to issue advice to businesses on how to cope with that eventuality.
The European Commission has issued a paper instructing other EU states to prepare for a no-deal Brexit.
Possible consequences, the paper says, include disruption to the aviation industry and goods from the UK being subject to custom checks.
According to the IMF analysis, the organisation's first since the UK voted to leave the EU in June 2016, 0.7% of the EU workforce could lose their jobs and economic growth could fall by 1.5%.
Ireland, which has the closest trade ties with the UK, would be the worst hit, according to the IMF report.
Taoiseach (Irish prime minister) Leo Varadkar has said his government is making contingency plans for "the unlikely event of a no-deal hard Brexit".
Mr Varadkar said that - even if there is a deal - Ireland will need 1,000 new customs officers and veterinary inspectors to deal with changes in trade rules with the UK.
By BBC Reality Check correspondent Chris Morris
If both sides come to the conclusion several months before the end of March that there will be "no deal", they can at least make some contingency plans to deal with that.
But if there is a last-minute hitch, time will have run out. So, from the EU's perspective, thinking about "no deal" means "preparing for the worst and hoping for the best".
Much of the UK government would probably look at it in the same way - but there are many Brexiteers who think that "no deal" would be perfectly acceptable as long as sufficient preparations have been made.
Read Chris's full piece
Speaking to MPs before setting off for Brussels, Mr Raab said he hoped Mr Barnier would "fully support" the proposals for post-Brexit trade with the EU in the government's White Paper.
And addressing the press as he began his first meeting with Mr Barnier, the MP -  who was a leading figure in the 2016 campaign to leave the EU - vowed to get "best deal for Britain" and to tackle talks with "renewed energy, vigour and vim".
Mr Barnier said it was a "matter of urgency" to agree on a "backstop" plan to prevent a hard border in Northern Ireland if no deal is agreed - and said a "close partnership" on security was "more important than ever given the geopolitical context".
Mr Raab's trip to Brussels comes with debate raging within the Conservative Party about what Brexit should look like.
On Wednesday, former Foreign Secretary Boris Johnson - who also quit over the proposals presented to the cabinet at Chequers - used his resignation speech to accuse Theresa May of "dithering" over the UK's strategy for leaving the EU.
"It is not too late to save Brexit", he said, calling for the government to "change tack".
Former Remain supporters, on the other hand, were furious when the government changed its Customs Bill this week to comply with the demands of a Eurosceptic group of Tory MPs.
The EU says it will analyse the Chequers proposals, which were set out in full in a White Paper, before coming up with a response.

The EU's chief Brexit negotiator has described how a Brexit backstop would affect movement of goods between Great Britain and Northern Ireland.
The backstop will apply if the Irish border cannot be kept frictionless in the context of a wider deal.
Michel Barnier said animals and some food products would have to be checked at ports.
However he said other products could be dealt with by scanning barcodes on lorries or shipping containers.
There could also be "market surveillance" checks carried out in Northern Ireland by officials, like trading standards officers.
Mr Barnier said checks would be carried out "in the least intrusive way possible".
"I understand why such procedures are politically sensitive but... Brexit was not our choice, it is the choice of the UK," he said.
"Our proposal tries to help the UK in managing the negative fallout of Brexit in Northern Ireland in a way that respects the territorial integrity of the UK."
The DUP have repeatedly warned they will not support any Brexit deal that could lead to new economic barriers between Northern Ireland and the rest of the UK.
Earlier this week the party leader Arlene Foster said:  "The United Kingdom single market must be protected with no new borders between Northern Ireland and Great Britain being created.
"From day one this has been the DUP's only red line."
The backstop arrangement is effectively an insurance policy to avoid a hard border in Northern Ireland.
It is what will happen if a deal is agreed but the border cannot be kept as frictionless as it is now.
The UK is due to leave the EU on 29 March 2019.

MPs could end up supporting another Brexit referendum if "none of the other options work", Tony Blair has said.
The ex-prime minister said there could be majority support for a new EU poll if Parliament ended up "gridlocked".
He urged Theresa May to "facilitate" the process by "running all options" by MPs first, including Norway and Canada-style alternatives as well as her deal.
But Labour frontbencher Angela Rayner says another referendum could increase division in the UK.
The shadow education secretary told the BBC's Question Time that holding a further Brexit vote would "undermine democracy".
"People made the decision and you can't keep going back saying, 'Would you like to answer it a different way?'"
And Hilary Benn, the Labour MP who chairs the Commons Brexit committee, has also distanced himself from calls within his party for another vote, telling BBC Radio 4's Political Thinking podcast that politicians have a "responsibility to give effect to the result of the last referendum".
But he told presenter Nick Robinson: "If the deal goes down… it may be that the prime minister decides, 'Well, I'm taking my deal to the country.'"
The government is opposed to any further referendum, saying the public made a clear choice when they voted in 2016 to leave by a margin of 51.9% to 48.1%.
Labour's position, which was approved by members at its party conference, is not to rule out any options if Parliament cannot agree a Brexit deal.
Shadow Brexit secretary Sir Keir Starmer said Labour's goal was to force a general election but if this was not possible, another referendum "had to be available" as an option.
The prime minister abandoned plans to hold a vote earlier this week on the withdrawal deal she has negotiated with the EU after admitting it would be heavily defeated.
She is currently in Brussels appealing to fellow EU leaders to soften their stance on the Irish backstop.
The PM insists her deal can pass if the EU is willing to give "political and legal assurances" on how the backstop - a contingency plan to ensure there is no hard border on the island of Ireland while the two sides settle a future trade deal - might come into force and how long it would last.
Mr Blair said he admired Mrs May's determination but suggested that, with so many MPs opposed to the backstop and other parts of the deal, this was becoming a weakness and she must realise she was "in a hole... and there is literally no point in carrying on digging".
Ahead of a speech in London later setting out the case for a "People's Vote", he said giving the final say to the people would become the "logical" outcome if every other option were to be exhausted.
"There will be a majority in Parliament, in the end, for a referendum if no other option of Brexit works," he told BBC Radio 4's Today programme.
"The real reason we should have another referendum is that we have had 30 months of negotiation and let's be clear, we are in crisis mode on this.
"The government is in a mess. Parliament cannot agree. Our knowledge has been vastly enlarged of what leaving the European Union will mean.
"If you look at all of this mess how can it be undemocratic to say to the British people, 'OK in light of all of this, do you want to proceed or do you want to stay?'"
Both the UK and EU are stepping up no-deal planning in case no agreement can be reached ahead of the UK's scheduled departure on 29 March.
Some Tory MPs, reportedly including some ministers, support a "managed no deal", in which the UK would reach agreements with the EU in key sectors, such as transport, and the UK would move to trade with the EU on World Trade Organization rules.
Cabinet Office Minister David Lidington said this was "not the government's policy" and ministers were focused on getting Commons backing for the deal in a vote now expected in mid-January.
Asked whether Parliament should hold a series of indicative votes on what the future course of action should be, he said the government first had to deliver on its promise that MPs would finish their debate on the proposed Brexit deal and vote on it.
Were the proposed deal to be defeated, he said the cabinet and prime minister would need to take stock and "go to Parliament accordingly".

Former Conservative MP Nick Boles has accused the cabinet of being "cowardly and selfish" for failing to challenge Theresa May's approach to Brexit.
Mr Boles, who quit the parliamentary party on Monday, said the PM had "misunderstood and mismanaged" the whole process of leaving the EU.
And he told the BBC's Laura Kuenssberg no-one in the cabinet "had earned the right" to succeed her.
The Tory Party "did not really exist any more", he also suggested.
Mr Boles was part of a cross-party group of MPs co-ordinating efforts to find a compromise in Parliament around a Brexit proposal that would retain access to the single market.
After his Common Market 2.0 plan was rejected by MPs for the second time on Monday, he accused his party of "failing to compromise".
He said he could no longer represent them in the Commons and would sit as an independent.
Mr Boles, the MP for Grantham and Stamford, told the BBC his former party was gripped by a combination of "cowardice and dogma".
He said the prime minister had been totally preoccupied with the wishes of her party and had never attempted to "construct or understand what a deal would look like to bring the country together".
Senior ministers had shown a "collective failure to lead and unite" and had "all put their interests first".
"There are fine people in cabinet but this is the worst cabinet in recorded history," he said. "None has earned the right to lead the country after Brexit."
He suggested Brexit would be the equivalent of a "meteor strike" on the British political system and none of the major parties would be immune from the repercussions.
But he also admitted that MPs who wanted closer economic links with the EU had failed to coalesce early enough around an alternative to the PM's deal and had "missed the boat".
The MP quit his local constituency party last month amid a campaign by some party members to deselect him as their candidate for the next election.

Tory MP Nick Boles is resigning from his local Conservative association after clashing with them over Brexit.
Mr Boles, who wants to remain as MP for Grantham and Stamford, has spoken out about leaving the EU with no deal.
Local activists had wanted to deselect him as their candidate in the next general election because of his stance.
In his letter, seen by the BBC, he said he was resigning with immediate effect and that a "division had opened up" between him and the local association.
He wrote: "I regret that my relationship with you should end in this way. But a politician without principles is worthless.
"I am in no doubt about my duty, which is to be true to my convictions and to dedicate the rest of my time in Parliament to the best interests of the people I was elected to serve."
Mr Boles said he wanted to continue to "take the Conservative whip" at Westminster if it is offered "on acceptable terms" - meaning he would still vote with the party.
Councillor Martin Hill, vice president of the Grantham and Stamford Conservative Association, told members they had been "betrayed by their parliamentary representative" and called on him to take the "honourable course" and quit as an MP.
He wrote: "As you are all aware, Nick has been at odds with the local party and the prime minister for some time, so this announcement does not come as a complete surprise, but the timing does leave a lot to be desired."
He said the process of selecting a new candidate would start at the group's AGM later this month.
Chief Whip Julian Smith said Mr Boles was a "valued member of the Conservative parliamentary party which I hope will continue to benefit from his ideas and drive".
His announcement comes after a busy week in Westminster, when MPs voted to seek a delay to the UK's departure from the EU, due to take place on 29 March.
The third "meaningful vote" on Prime Minister Theresa May's deal is expected to take place next week. If it is agreed, she has promised to seek a short extension to the departure date. But if it doesn't gain support, she has warned a longer extension may be needed - and the UK might have to take part in European elections.
To find out how your MP voted this week, use the look-up below.
Click here if you cannot see the look-up. Data from Commons Votes Services.
Mr Boles had voted in favour of extending Article 50 in the Commons this week, and in favour of Mrs May's Brexit deal.
In his letter, he said: "While I have consistently argued that Brexit must be delivered, and have voted for the prime minister's deal every time she has brought it to the House of Commons, I am certain that crashing out of the EU without a deal would do great harm to the British people and have done everything in my power to prevent it."
Mr Boles said he was "proud" of his role in the cross-party campaign to force Mrs May to request an extension to Article 50 beyond 29 March and block a no-deal Brexit.
"In securing substantial Commons majorities in favour of both propositions last week, I believe we have done the country a great service," he added.
Mr Boles is keen on a closer Norway-style relationship with Europe after leaving the EU.
But Mr Hill told the BBC: "Talk to the man and woman on the street and they're also quite angry that their MP seems to be going back on what he promised to do at the general election. He signed up to the manifesto about coming out of the single market and the customs union."
Meanwhile, pro-Brexit marchers, led by former UKIP leader Nigel Farage, have begun a two-week journey from Sunderland to London.
About 100 people had assembled to start the march. They were joined by counter-protesters, including those from anti-Brexit campaign Led by Donkeys.
Mr Farage aims to walk 100 of the 270-mile March to Leave, which is due to arrive in the capital on 29 March.
Separately, shadow chancellor John McDonnell has said politicians will move "heaven and earth" to prevent the UK from leaving the EU without a deal.
Speaking before an event in Gravesend, Kent, Mr McDonnell said "quite a number" of MPs would be prepared to support a compromise deal, with the guarantee the deal goes back to the people for a final say on Brexit.
Any final say should not be on the deal Mrs May has agreed, "because it's not credible", he said.

Scotland's first minister has told the BBC she wants to find a referendum date that both sides can agree on.
Nicola Sturgeon said she was "up for continued discussion" with Theresa May on the matter.
The prime minister insisted this week that "now was not the time" to hold a second independence referendum.
And she indicated that the UK government would not give approval to the SNP's preferred timetable of between autumn 2018 and spring 2019.
Ms Sturgeon believed it was imperative for a vote on Scotland's constitutional future to take place once a deal had been agreed on the UK exiting the European Union.
The  focus on a Scottish independence referendum comes as the SNP meet for its spring conference in Aberdeen.
On the first day of the gathering, the party's deputy leader Angus Robertson said it would be "totally unacceptable" for Westminster to deny a referendum before Brexit was finalised.
In his speech, the SNP MP said: "Let there be no doubt - Scotland will have its referendum and the people of this country will have their choice. They will not be denied their say."
Ahead of her keynote speech on Saturday, Ms Sturgeon spoke to the BBC's Sarah Smith.
She said: "We [Ms Sturgeon and Mrs May] have got a disagreement. What I am saying today is let us try and work our way through that disagreement.
"Now, I am no paragon of virtue about these things - it takes two to have a relationship, I absolutely accept that. But I have tried really really hard to find compromise with the PM over the last few months."
Ms Sturgeon added: "So let her [Mrs May] set out when she thinks it would be right and then let's have a discussion about it - who knows we might be a matter of weeks or months apart.
"I am up for continued discussion, but people will recognise in any walk of life - not just in politics - you can't have discussion and reach compromise with people who are not prepared to enter into discussion and are not prepared to countenance compromise and that so far has been my experience of the PM."
By BBC Scotland's political editor Brian Taylor
I do not believe that the first minister is attracted to the idea of a non-consensual referendum. I believe she would see it as gesture politics, not the actions of a long-standing elected government. I believe further she would question what it would achieve, given that it might face a boycott from supporters of the Union.
So might she engineer an early Holyrood election? Might she seek an overall majority in the Scottish Parliament in order, presumably, to bring the Prime Minister to the negotiating table?
She might. It is feasible. But, again, I think it is highly unlikely.
Broadly, there are three objections:
By the BBC's Scotland editor Sarah Smith
Speaking to me today, Ms Sturgeon indicated she might be prepared to discuss the timing of another vote with Mrs May.
The Scottish government want a referendum between Autumn 2018 and Spring 2019.
It looks like they would be prepared to negotiate a different, later, date.
However, it is not yet clear that the UK government are prepared to talk about a date.
The PM did say "now is not the time" for another referendum. She didn't say never. So, will she talk about holding a vote in the future?
That seems to be the question today.
The SNP conference got under way just 24 hours after the Scottish and UK governments clashed over a second referendum.
Ms Sturgeon insisted that a referendum should go ahead on her timescale.
It followed Mrs May rejecting calls for a second independence vote before Brexit.
Meanwhile, Mrs May used a speech in Wales to defend the UK.
She said the "precious bond" between England, Scotland, Wales and Northern Ireland was much more that just "constitutional artefact".
Mrs May went on to tell a gathering of Conservatives in Cardiff that a second Scottish independence referendum would be "bad for Scotland, bad for the United Kingdom, and bad for us all".
The prime minister added: "The coming negotiations with the EU will be vital for everyone in the United Kingdom.
"Every person, every family, every business, every community the length and breadth of the United Kingdom - England, Scotland, Wales and Northern Ireland.
"As the prime minister of this United Kingdom, I will always ensure the voices and interests of England, Scotland, Wales and Northern Ireland are represented as we negotiate to leave the EU."
Mrs May had already accused the SNP of forcing a "fundamentally unfair" independence referendum that would damage Brexit negotiations.
Writing in the Times, she said: "The SNP is trying to force the UK government to agree to something that is fundamentally unfair to the Scottish people.
"It wants to ask them to make a crucial decision without the necessary information.
"They would not know what the new partnership with the EU would look like, or what the alternative of an independent Scotland would be. It would simply not be fair."
The article follows a television interview on Thursday, in which she said "all our energies" should be focused on negotiations with the European Union.
At the SNP conference later, Deputy First Minister John Swinney will address domestic Scottish matters as the parties in Scotland prepare for May's local government elections.
Mr Swinney said the spring conference, which will be attended by 2,500 delegates, would "underline our party's top priorities of education, the economy and our public services".

Ex-UKIP leader Nigel Farage has launched his new Brexit Party, saying he wants a "democratic revolution" in UK politics.
Speaking in Coventry, he said May's expected European elections were the party's "first step" but its "first task" was to "change politics".
"I said that if I did come back into the political fray it would be no more Mr Nice Guy and I mean it," he said.
But UKIP dismissed the Brexit Party as a "vehicle" for Mr Farage.
The launch comes after Prime Minister Theresa May agreed a Brexit delay to 31 October with the EU, with the option of leaving earlier if her withdrawal agreement is approved by Parliament.
This means the UK is likely to have to hold European Parliament elections on 23 May.
Mr Farage said the Brexit Party had an "impressive list" of 70 candidates for the elections. Among those revealed at the launch was Annunziata Rees-Mogg, sister of leading Conservative Brexiteer MP Jacob Rees-Mogg.
Mr Farage said: "This party is not here just to fight the European elections... this party is not just to express our anger - 23 May is the first step of the Brexit Party. We will change politics for good."
He said he was "angry, but this is not a negative emotion, this is a positive emotion".
The party had already received £750,000 online over 10 days, he said, made up of small donations of up to £500.
Ms Rees-Mogg said she had stuck with the Conservatives "through thick and thin", but added: "We've got to rescue our democracy, we have got to show that the people of this country have a say in how we are run."
Annunziata Rees-Mogg joined the Conservative Party, at the age of five, in 1984. She says she canvassed for the party from the age of eight.
The sister of Conservative Brexiteer MP Jacob Rees-Mogg, Ms Rees-Mogg stood unsuccessfully as a Conservative candidate in the 2005 and 2010 general elections.
The freelance journalist has written for the Daily Telegraph, MoneyWeek and the European.
Earlier, Mr Farage told BBC Radio 4's Today programme: "In terms of policy, there's no difference (to UKIP), but in terms of personnel there is a vast difference.
"UKIP did struggle to get enough good people into it but unfortunately what it's chosen to do is allow the far right to join it and take it over and I'm afraid the brand is now tarnished."
He promised the Brexit Party would be "deeply intolerant of all intolerance" and would represent a cross-section of society.
UKIP leader Gerard Batten tweeted that Mr Farage's suggestion that there was no difference in policy between UKIP and the Brexit Party was "a lie".
He said: "UKIP has a manifesto and policies. Farage's party is just a vehicle for him."
He said the Brexit Party's "only purpose is to re-elect him (Mr Farage)" and was a "Tory/Establishment safety valve".
The Electoral Commission has issued European Parliamentary elections guidance for returning officers to advise them "on the rules should the elections go ahead" and to ensure they "have as much certainty as possible in developing contingency plans".

Brexit Party leader Nigel Farage has said he is open to an electoral pact with the Conservative Party - if Boris Johnson is genuine about taking the UK out of the EU on 31 October.
Mr Farage said Mr Johnson would need to call an election if he wanted a no-deal Brexit, in order to "change the arithmetic" in the Commons.
He said there was then a "possibility" of a pact between the parties.
But he added: "I don't believe a single word the Conservative Party tell us."
An electoral pact usually involves not fielding candidates in specific areas, in order to allow another party a better chance of winning.
A pact between the Brexit Party and the Conservatives could avoid splitting the pro-Brexit vote - but Mr Johnson has previously said he does not believe the Tories should do deals with any other party.
The Brexit Party was the clear winner in the UK's European elections in May, taking almost 32% of the vote in Great Britain, with the Conservatives winning only 9%.
Mr Farage said: "Theresa May told us 108 times we were leaving on March 29 and we didn't, so just because Boris says we're leaving on the 31 October doesn't mean we're going to."
"We would need to believe them and at the moment that's not very easy," he added.
Mr Johnson - who was elected Tory leader and the UK's next prime minister on Tuesday - has pledged the UK will leave the EU on 31 October "do or die", and with or without a deal.
Asked at a Tory leadership hustings last week whether he could work with the Brexit Party, Mr Johnson said: "I don't believe that we should do deals with any party."

Former UKIP leader Nigel Farage says he is close to backing a second EU referendum to end the "whinging and whining" of anti-Brexit campaigners.
Mr Farage told Channel 5's The Wright Stuff a fresh vote could "kill off" the Remain campaign for a generation.
He later clarified his remarks saying it was the "last thing" he wanted but Leave voters had to be prepared and he was confident they would win again.
Pro-EU campaigners said "support is growing" for another referendum.
And co-founder of the Leave.EU referendum campaign group, Arron Banks, said that to avoid sleepwalking "into a faux Brexit" people should "go back the polls and let the people shout from the rooftops their support of a true Brexit".
But Mr Farage's former UKIP colleagues dismissed his suggestion.
And Downing Street said: "We will not be having a second referendum."
Mr Farage was one of the leading figures in the Leave campaign, which won the referendum with 51.9% of votes.
The result in June 2016 means that the UK is leaving the European Union, with the date for departure set as 29 March 2019. Negotiations are currently taking place between the UK and the EU about a post_Brexit relationship.
During a debate about Brexit on the Channel 5 programme, Mr Farage said: "What is for certain is that the [Nick] Cleggs, the [Tony] Blairs, the [Lord] Adonises will never ever, ever, give up.
"They will go on whinging and whining and moaning all the way through this process.
"So maybe, just maybe, I'm reaching the point of thinking that we should have a second referendum on EU membership... and we may just finish the whole thing off.
"And Blair can disappear off into total obscurity."
He said "the percentage that would vote to leave next time would be very much bigger than it was last time round".
His UKIP colleagues did not agree:
The party's former deputy chairwoman Suzanne Evans described his comments as "epically stupid".
"Even putting aside the astronomical and completely unjustified public cost of a second referendum, Farage's comments are an open goal for the Remain camp," she wrote on the Brexit Central website.
But the other side of the Brexit debate were more enthusiastic.
Labour MP Chuka Umunna, of the Open Britain campaign for close ties with the EU, said: "For perhaps the first time in his life, Nigel Farage is making a valid point.
"In a democracy like ours, the British people have every right to keep an open mind about Brexit."
The Lib Dems vowed that in any referendum, they would be "leading the charge" to keep Britain in the EU.
The party's Brexit spokesman Tom Brake said: "But Farage shouldn't be so confident of winning, people are now far more aware of the costs of Brexit and the fabrications of the Leave campaign.... what will the Leave campaign bus have written on it next time: 'let's not fund our NHS, but pay a £39bn Brexit divorce bill instead'?"
Speaking on his LBC radio show later on Thursday, Mr Farage said that his meeting with Michel Barnier in Brussels on Monday had convinced him that the EU's chief Brexit negotiator was "not going to give us a good deal."
He believed it would be rejected by Parliament, where he counted more Tory rebels than Labour Brexiteers ready to defy their own side.
"I am saying this to Leavers: Don't be complacent," he said.
"There may well be one last dramatic battle that will take place in all this."

"Another big seismic shock" could hit British politics at the next election, Nigel Farage has warned Theresa May if Brexit is not delivered by 2020.
The interim UKIP leader said he suspected the Conservative Government "is not fit for the legacy of Brexit".
He made the remarks at a reception in London's Ritz Hotel to celebrate his contribution to the Brexit victory.
In a nod to Donald Trump's call for him to be UK ambassador to the US, he handed out Ferrero Rocher chocolates.
The sweet treats were famously offered in an advert set at an "ambassador's reception" and included the oft-quoted line: "You are really spoiling us."
Downing Street has already rejected Mr Trump's claim that Mr Farage would do a "great job" as ambassador by saying "there is no vacancy".
And Chancellor Philip Hammond said Mr Farage should not "hold his breath" if he expected a call for him to help with UK-US relations.
Mr Farage was introduced for his speech by Leave.EU spokesman Andy Wigmore, with a call for attention from "Ladies, Gents, Lords and... diplomats".
Mr Farage told the gathering: "We've got a problem. In America the revolution is total. Not only have the people spoken and won, but the old administration, Obama and all those ghastly people, are out and the Trump people are in.
"In this country, the people have spoken, but the same players have just been shuffled around the chess board and we are still being run by the career professional political class.
"I am not sure what is going to happen over the course of the next couple of years but I suspect there's another big seismic shock in British politics perhaps going to come at the next election.
"I suspect that the Conservative Party is not fit for the legacy of Brexit. I suspect there is going to be a genuine realignment of British politics over the course of the next three or four years.
"It is unfinished business - the people have spoken but the establishment don't want to listen. There are great battles to be fought and I'm going to go on fighting those battles."
The reception at the Ritz was hosted by millionaire Arron Banks, who was thanked by Mr Farage for bankrolling the Leave.EU campaign.
 On speed dial?
Also present were Conservative MPs Jacob Rees-Mogg and Peter Bone, Labour Leave campaigner and donor John Mills and UKIP leadership candidate Paul Nuttall.
Asked if he would back Mr Farage to be the UK ambassador to the US, Mr Rees-Mogg said: "Mr Farage's relationship with Mr Trump could be beneficial for the country but I am not sure he should be Ambassador Extraordinary and Plenipotentiary.
"Mr Farage is certainly extraordinary in his own way but I think that being plenipotentiary as well may be a bit too much."
Mr Hammond also dampened any ambassadorial ambitions Mr Farage might have in an interview with ITV's Good Morning Britain.
"It isn't for other countries to decide who we appoint as ambassadors - and if I ever need any advice from Nigel Farage, I've got his number and I'll give him a call," he said. "Tell him not to hold his breath."
Mr Farage, who has denied reports that he plans to emigrate to the US, recalled that he had joined Mr Banks and other leading Brexiteers at the Ritz on the morning after the 23 June referendum for a victory breakfast of Champagne and kippers - a reference to the nickname for UKIP supporters.
He said: "When people look back in 100 or 200 years, 2016 will be seen as one of the great historic years - a year of big political revolution.
"Brexit was the first brick knocked out of the establishment wall and then look what we got on 8 November. The election of 'The Donald' was something of a completely different order."
To cheers he said: "For those of you who aren't particularly happy with what happened in 2016, I've got some really bad news for you - it's going to get a bloody sight worse next year."

UKIP leader Nigel Farage has warned of disturbances on the streets if Parliament tries to block Brexit.
He told BBC One's Andrew Marr Show there would be "political anger the likes of which none of us in our lifetimes have ever witnessed".
The comments follow the High Court ruling that MPs and peers must have a vote ahead of the government triggering official talks with the European Union.
The campaigner who brought the case said it had given "clarity".
Mr Farage is in charge of UKIP on an interim basis, as the party looks for its next full-time leader, following the resignation of Diane James after just 18 days in the job.
The judges who ruled on Thursday that the government must seek MPs' approval to invoke Article 50 of the Lisbon Treaty - getting formal Brexit negotiations with the EU under way - have been criticised in some newspapers, the Daily Mail calling them "enemies of the people".
Mr Farage said: "We may have seen Bob Geldof and 40,000 people in Parliament Square moaning about Brexit.
"Believe you me, if the people in this country think they're going to be cheated, they're going to be betrayed, then we will see political anger the likes of which none of us in our lifetimes have ever witnessed in this country. Those newspaper headlines are reflecting that."
Asked by Andrew Marr if there was a danger of "disturbance in the streets and so on" if Parliament thwarted Brexit, Mr Farage replied: "Yes, I think that's right."
He added: "The temperature of this is very, very high.
"Now, I'm going to say to everybody watching this who was on the Brexit side - let's try and get even, let's have peaceful protests and let's make sure in any form of election we don't support people who want to overturn this process."
Also appearing on Andrew Marr, investment manager Gina Miller, who brought the High Court case against the government, insisted the UK had a representative democracy which ensured politicians had to debate issues.
"Do we want a country where we have no process?" she asked, adding: "The case is that [Mrs May] cannot use something called the Royal Prerogative to do it because we do not live in a tin-pot dictatorship."
She told Mr Farage: "That's what you argued for the whole way through [the Brexit referendum campaign] - parliamentary sovereignty."
He replied: "No, no. This is not about whether Parliament is sovereign; it's about whether the British people are sovereign."
Liberal Democrat leader Tim Farron criticised Mr Farage over his warnings of disturbances, saying "all responsible politicians" must distance themselves from UKIP's leader.
He said: "This is the politics of the gutter. All that has happened is that British judges in a British court have interpreted British laws.
"Nigel Farage should welcome that. British citizens aren't talking about taking to the street, only Nigel Farage is.
"Responsible leaders have a duty to calm tempers, heal division and work together to keep Britain open, tolerant and united."
Meanwhile, Mr Farage told Andrew Neil he was "sick" of and "finished" with party politics but would continue campaigning on "issues" after leaving frontline politics.
Several contenders have quit the leadership contest, leaving Suzanne Evans, Paul Nuttall and John Rees-Evans.
Mr Farage described the situation as a "soap opera" over a "terrible few weeks", but said the party was still well-placed in the opinion polls.

There was a definite "battle of the tones" at the seal-the-deal Brexit summit with Theresa May.
EU leaders were determinedly sombre, while the UK prime minister had to sound upbeat and positive about her country's Brussels-free future.
It shouldn't be under-estimated. Sunday was a huge day for the EU, signing off on the divorce papers of a departing key member state for the first time in the history of the bloc.
In the eyes of many, Brexit counts as an EU failure. At the summit, French President Emmanuel Macron reminded the press of the fragility of European Union. Which is why, time and again, EU leaders in Brussels continue to make so much of the (unusual) show of unity the Brexit process has provoked in EU ranks.
For now, of course, all European eyes turn to the UK to see if the hard-negotiated Brexit deal passes through the House of Commons.
If it doesn't, the President of the European Commission, Jean-Claude Juncker, insists there will be no deal.
"This is the deal. This is THE deal," he told me emphatically, ruling out the possibility of renegotiating the Brexit texts.
If he's true to his word, and parliament votes down the divorce deal, then all 19 months of painful EU-UK negotiations were for naught. And both sides could find themselves staring at the cost and potential chaos of what the EU's chief Brexit negotiator Michel Barnier calls a non-orderly Brexit.
EU leaders are hell-bent on avoiding that.
So much so, that as much as  EU leaders regret Brexit, and as often as they have spoken at every EU summit so far since the Brexit vote about the door still being open for the UK to change its mind, there was none of that talk on Sunday. Instead, they were fully on message with Theresa May - to help her sell her deal back home.
Dutch Prime Minister Mark Rutte remarked that Mrs May had "fought hard" and that the result was a good deal. Meanwhile, Mr Barnier said these had been "extraordinary", "complex" and "difficult" negotiations, resulting in an "unprecedented and ambitious partnership".
All that talk of fair and fabulous deals somehow rings rather hollow, though, when the EU has made clear from the start that it would never concede a deal to the UK that made life look as good - or even better - outside, rather than inside, their club.
But of course, this is not the final deal. The story of the EU and UK's tempestuous relationship is far from over.
Maybe there will be a second vote on the Brexit deal in the UK parliament, or a second referendum, or a general election. Until we know, we cannot be 100%  sure how the EU will react.
But if, as seems likely, Brexit does indeed go ahead, it is only then that the detailed negotiations for a future EU-UK trade deal begin in earnest.
And Mr Macron reminded us all at the Sunday summit of the horse-trading, arm-twisting and conflicting national interests of EU countries that will challenge those negotiations.
The French president essentially threatened the success of a future EU-UK trade deal if the UK didn't guarantee access for French fishermen to UK waters after Brexit.
Now this should shock no-one. Fish, Gibraltar, the EU trying to tie the UK to its competition rules, even the Irish border backstop are all issues that were dealt with just enough to complete the Brexit deal texts but, in reality, the can was kicked down the road to the future trade negotiations.
To sum up: these 19 months of endless wrangling over the Brexit divorce deal... they were a just a taster of what is yet to come.

Downing Street say there are no plans to use the Army to maintain food and other supplies in the event of the UK leaving the EU with no Brexit deal.
No 10 is expected to publish around 70 separate papers with advice about the implications of no deal.
The papers are due to be published in August and September - and will contain information for different industries.
They are also expected to contain advice for consumers - for example about travelling around the EU.
However No 10 dismissed newspaper reports that the Army might be called in to ensure food and medical supplies are maintained in more remote communities.
A spokesman said: "This is about putting in place sensible preparations in the unlikely event of no deal."
"There are no plans to involve the Army. I don't know where that speculation came from."
The prime minister's spokesman added: "We have been absolutely clear that it's in the interests not just of ourselves but the EU to get a deal.
"In the event of 'no deal' there will of course be consequences for the European Union."
The spokesman added that the plans were aimed at ensuring an "orderly" Brexit even if there is no agreement with Brussels.
"We are working towards getting a deal but the prime minister is clear that we will put in place all the necessary steps to ensure the UK has a bright future."
The spokesman also dismissed suggestions that the original plan to publish the papers over the course of the summer had been shelved.
This had provoked alarm among some Brexiteers who described it as "Project fear Mark 2" designed to frighten people away from accepting no deal.
The prime minister is on holiday in the Italian Lakes, leaving her effective deputy David Lidington as the senior government figure in the UK.
Downing Street defended ministers taking holidays despite the tense state of the Brexit talks, saying: "The prime minister and other ministers are always fully engaged with their briefs."

Downing Street has dismissed any prospect of a return to a "hard border" on the island of Ireland after Brexit.
It followed the leak of a letter from Boris Johnson in which he appeared to contemplate future customs border checks after the UK leaves the EU.
In the letter, obtained by Sky News, the foreign secretary tells Theresa May 95% of traffic would still pass unchecked if there was a hard border.
It comes as the EU is set to publish a draft of its Brexit withdrawal treaty.
The 120-page document, to be unveiled on Wednesday, will refer to three possible options for avoiding physical infrastructure on the Irish border but the only one to be fleshed out will be the government's least-favourite: Northern Ireland staying aligned with European rules and regulations.
The document, marking another major milestone on the UK's road to Brexit, will encapsulate in legally binding text agreements already reached on Ireland, citizens' rights and the UK's so-called "divorce bill".
The BBC's Brussels reporter Adam Fleming said it would form the basis of further negotiations with the UK in areas like the transition and could still be tweaked by the 27 remaining member states.
According to reports by Irish broadcaster RTE, the text - which EU negotiator Michel Barnier has said will not contain any surprises - will say that Northern Ireland may be considered part of European Union customs territory after Brexit, alluding to a single regulatory space on the island of Ireland with no internal barriers.
Earlier on Tuesday, the foreign secretary was criticised by opponents for suggesting in a BBC interview the issue of the border could be managed as easily as London's congestion charging zone.
In his letter to the prime minister, Mr Johnson seeks to play down the "exaggerated impression" of "how important checks are" at EU external borders.
He also appears to contemplate a hard border between Northern Ireland and the Republic of Ireland, writing: "Even if a hard border is reintroduced, we would expect to see 95% + of goods pass the border [without] checks."
He may have thought he was being helpful. Boris Johnson was offering his views on how to deal with the thorny issue of the Irish border.
But today he seemed to put both feet in it.
First foot. He seemed to trivialise centuries of Irish history by suggesting the status of the Irish border was no more important than a borough boundary in London, where the congestion charge is policed electronically.
Second, while his paper didn't contemplate new infrastructure between Northern Ireland and the Republic he used the potentially toxic phrase "if" in connection with a hard border.
This allowed opponents to suggest he - maybe even the government - was contemplating a regime of border checks that would be anathema to republicans and nationalists - and why No 10 moved so quickly to confirm the policy hadn't changed.
As the old wartime adage goes "Loose Lips Sink Ships".
Mr Johnson's loose language is unlikely to cost lives but could erode much needed goodwill just as the EU draws up a legal text on the post-Brexit Irish border which will also prove controversial.
Following the letter's emergence, Labour called for Mr Johnson - one of the leading Brexiteers in the cabinet - to be dismissed "before he can do any more damage".
"This man's ego, and his Brexit at any cost strategy cannot be allowed to jeopardise peace," said shadow Northern Ireland secretary Owen Smith.
A spokesman for Mr Johnson said the letter was "designed to outline how a highly facilitated border would work and help to make a successful Brexit".
"The letter points out there is a border now, and the task the (cabinet Brexit) committee face is stopping this becoming significantly harder," he said.
"It shows how we could manage a border without infrastructure or related checks and controls while protecting UK, Northern Ireland, Irish and EU interests."
He added: "We will not accept any physical infrastructure at the border, and will instead seek alternatives that allow us to leave the customs union and take back control of our money, borders, laws and trading policy."
No 10 said it had made it clear "on numerous occasions" the UK government will not contemplate a hard border after the UK leaves the EU on 29 March 2019.

Downing Street has sought to play down a warning from a government source that the House of Lords could be abolished if peers try to block the Brexit bill.
The bill - to give the government the authority to trigger Article 50 - was approved by 494 votes to 122 in the Commons, and now moves to the Lords.
A government source said the Lords will face an "overwhelming" public call to be abolished if it opposes the bill.
Brexit Secretary David Davis called on peers to "do their patriotic duty".
Prime Minister Theresa May wants to invoke Article 50 - the starting gun on the two-year process of the UK leaving the EU - by the end of March.
However, after a Supreme Court ruling last month, she first requires Parliament's permission.
Mr Davis said the government had seen off a series of attempts to amend the European Union (Notification of Withdrawal) Bill before MPs overwhelmingly voted on Wednesday in favour of passing it unamended.
The bill must now be approved by peers, who will begin debating it after the Lords returns from recess on 20 February.
The Liberal Democrats have vowed to continue trying to amend the legislation after it comes to the Lords, while pro-Europe Tory and Labour peers may also try and make changes to the bill.
Mr Davis said he expected the House of Lords to "do its job and to do its patriotic duty and actually give us the right to go on and negotiate that new relationship".
However, a government source told BBC political editor Laura Kuenssberg on Wednesday: "If the Lords don't want to face an overwhelming public call to be abolished they must get on and protect democracy and pass this bill."
On Thursday morning a No 10 source distanced Downing Street from that view, saying peers had an important role in scrutinising and debating the bill "and we welcome them exercising this role".
BBC assistant political editor Norman Smith said:  "It suggests ministers are mindful that threatening peers may simply fuel opposition - and prompt a constitutional clash - that would be a massive distraction from delivering Brexit."
Shadow business secretary Clive Lewis was one of 52 Labour MPs to defy party orders to back the bill in the Commons and he resigned from the front bench.
He said he could not back the bill, given his Norwich constituency voted 56.2% to 43.8% to remain in the EU in June's referendum.
Eleven Labour junior shadow ministers and three party whips also voted against the bill.
Leader Jeremy Corbyn said he understood the difficulties the vote presented some of his MPs but said they had been ordered to back the Article 50 because the party would not "block Brexit".
Mr Corbyn will make decisions on whether to sack frontbenchers who defied the whip and who will replace the shadow cabinet ministers who resigned in the next few days, a Labour source said.
Shadow home secretary Diane Abbott, who last week blamed a migraine for a failure to attend a key vote on the bill, backed the triggering of Article 50.
She told BBC's Newsnight: "I respect the result of the referendum and no-one wanted to thwart it in a perverse kind of way.
"But we need to be clear, this is not a Tony Benn Brexit, this is Donald Trump Brexit, and it's got a very ugly side."
Former Chancellor Ken Clarke was again the only Conservative to vote against the two-clause bill.
Earlier the bill survived several attempts to change its wording and add extra conditions.
These included Labour MP Harriet Harman's bid to protect the residence rights of EU citizens in the UK, which was outvoted by 332 votes to 290, with three Conservative MPs rebelling.

Suggestions that freedom of movement will continue after the UK leaves the EU are wrong, Downing Street has said.
On Friday, Chancellor Philip Hammond warned full controls could take "some time", prompting speculation free movement may continue in all but name after the UK leaves in March 2019.
But amid claims of splits in cabinet, No 10 has moved to make clear free movement will end when the UK leaves.
It said: "It would be wrong to suggest it... will continue as it is now."
Downing Street's move followed days of uncertainty over future immigration policy during any transitional phase after Brexit.
The PM's spokesman said plans for a registration system for migrants arriving after March 2019 had been set out last week, and Prime Minister Theresa May had raised, as long ago as January, the prospect of a transition period before the post-Brexit system was implemented.
At the moment, citizens from the other 27 EU member states have the right to come and work and live in the UK.
Ministers have said Brexit will enable the UK to control who comes to the country and in what numbers but there has been debate within government about how quickly this will happen and what its impact will be.
Mr Hammond has said the cabinet is united behind the need for a transitional period of up to three years after Brexit, a period of time in which he said many arrangements would "remain very similar to how they were the day before we exited the European Union".
He has said his goal is to minimise the level of disruption to British business and consumers, by retaining access to European markets both for goods and workers.
But International Trade Secretary Liam Fox has warned that allowing unregulated EU immigration to continue would be a betrayal of last year's referendum result, while a former Brexit minister, David Jones, suggested some ministers were being "kept out of the loop" by No 10 and the Treasury.
No 10 said the shape of post-Brexit immigration controls would become clearer in due course, with legislation due to be presented to Parliament later this year.
"It would be wrong to speculate on what these might look like or to suggest that freedom of movement will continue," the spokesman said.
"Free movement will end in March 2019. We've published proposals on citizen's rights. Last week the home secretary set out a registration system for EU nationals arriving post March 2019."
By assistant political editor Norman Smith
We've had days of rival ministers setting out their different views, with former Remain ministers the loudest - the chancellor saying there might have to be a three year transitional period after the UK leaves and the home secretary saying EU migrants will still be able to come to the UK  provided they register.
Downing Street has now decided that enough is enough and that it is time to stop the bickering. Number 10 says the plan is as Theresa May set out in her big speech at the start of the year. But will this attempt by No 10 to reassert control work?
There are two reasons why this might prove tricky.
The first is the diminution in Mrs May's authority after the election; the second is that there remain very profound differences between the ideologues, who believe the UK must leave to regain sovereignty, and the pragmatists who think the UK's economic well-being comes first.
Downing Street also rejected the possibility of an "off-the-shelf" trade deal with the EU such as that enjoyed by Norway and other members of the European free trade association - which grants them access to the single market. The idea has been floated by Mr Hammond among others.
Cabinet ministers have also sought to play down talks of rifts and factions within Theresa May's top team over the terms of any transitional deal.
Defence Secretary Sir Michael Fallon said future immigration rules would be decided as part of the current Brexit negotiations and dismissed suggestions there were "arguments raging around the cabinet table" while Health Secretary Jeremy Hunt insisted the NHS must still be able to recruit new staff from across Europe.
Lib Dem leader Vince Cable has claimed there is a "deep, unbridgeable chasm" between what he has characterised as Brexit "fundamentalists and pragmatists" within the government while Labour's Peter Dowd said the government had "broken down into farce".

A clock counting down to the moment the UK leaves the EU on 31 January will be projected on to Downing Street as part of government plans to mark Brexit Day.
The clock will tick down to 23:00 GMT, while Prime Minister Boris Johnson will give a "special" address to the nation in the evening, the government said.
A special 50p coin will also enter circulation to mark the occasion.
But the plans do not include Big Ben chiming, after Commons authorities said the cost could not be justified.
A campaign to find the £500,000 needed to make Big Ben ring when the UK leaves the EU has raised more than £200,000, but the House of Commons Commission cast doubt on whether it was permitted to use public donations to cover the costs.
Millionaire businessman Arron Banks and the Leave Means Leave group donated £50,000 to the campaign.
Downing Street has said the prime minister will chair a cabinet meeting in the north of England during the day, to discuss spreading "prosperity and opportunity".
He will then make a special address to the nation in the evening.
Mr Johnson is expected to be one of the first people to receive one of the newly-minted 50p coins, which will bear the motto "peace, prosperity and friendship with all nations".
Buildings around Whitehall will be lit up to mark Brexit, with the government saying that, "in response to public calls, the Union Jack will be flown on all of the flag poles in Parliament Square".
The government says it will use the "significant moment in our history" to "heal divisions, re-unite communities and look forward to the country that we want to build over the next decade."
However, hopes have faded that Big Ben - which is currently out of action due to renovation work going on at the Houses of Parliament - will chime to mark the moment the UK leaves the EU.
Earlier this week, Mr Johnson told BBC Breakfast he wanted the public to raise funds to ensure this can happen.
But Downing Street later distanced itself from the campaign, with a spokesman saying the prime minister's focus was on the government plan for marking the day, and that Big Ben was a matter for MPs.
The House of Commons Commission estimates the cost will be up to £500,000, and it has raised concerns over the "unprecedented approach" of using donations to fund the project.
It says this would involve bringing back the chiming mechanism and installing a temporary floor, resulting in delays to the conservation work.
The campaign group Stand Up 4 Brexit set up an online appeal to raise the money, collecting more than £200,000 by Friday evening.
Conservative MP Mark Francois told BBC Radio 4's The World at One that the pro-Brexit Leave Means Leave campaign and Mr Banks had donated £50,000.
He queried whether the cost of getting the bell to ring again was really £500,000, adding that he believed officials had "deliberately inflated the figure" because "they don't want to do it".
It comes as Downing Street has said EU citizens will not automatically be deported if they fail to sign up to the settled status scheme by the 2021.
Under the settlement scheme, EU citizens living in the UK can apply to stay in the country after Brexit.
So far the number of applicants to the scheme has hit more than 2.7 million.

So, is the EU jumping up and down with glee at the prospect of indicative votes in Westminster on Wednesday?
For months, even years now, Brussels has been urging the UK to "tell us what you want, what you really, really want!"
And yet there is no sudden outbreak of Brexit joy across the Channel.
EU governments know well enough by now that Wednesday's votes may not end up providing a clear picture of Brexit.
Even if they did, European Commission chief Jean-Claude Juncker will point out that the EU's only "interlocutor" – or opposite number – remains Her Majesty's government, led by Theresa May, and not UK MPs.
Would she be willing to shuttle as a go-between on behalf of Parliament, which has chosen to ignore her negotiated Brexit deal?
Not likely.
So the EU sees yet more uncertainty ahead.
And that's bad for business, off-putting for international investors, it costs a fortune in no-deal planning and can affect opinion polls in European countries most affected by Brexit.
Which is not to say the EU prioritises certainty enough to pursue a no-deal Brexit.
Some in the European Commission may feel that way, along with a number of European diplomats based here in Brussels.
They say they are fed-up with the UK's Brexit chaos infecting the rest of the continent. They speak with yearning of EU life after Brexit, and describe a no-deal scenario as "damaging" and "suboptimal" – but ultimately something the EU will survive.
One of the favourite statistics doing the rounds it that, while the UK relies on the EU for 49% of its trade, only around 10% of EU trade is with the UK.
But this "bring-it-on" attitude towards no deal is very much absent in European capitals.
As we saw at last week's summit, EU leaders believe it in their interest to avoid a no-deal Brexit. Or, at the very least, to avoid being blamed in the worst-case scenario.
As one high-level Brussels official put it: "We want to be seen to have made the maximum effort so that, if the UK doesn't find a Brexit solution, it's not because of us."
It's also a fool's errand to go searching for rifts between EU countries over Brexit at this stage.
MEPs are not very relevant here. It's the national leaders of the 27 EU countries that count. And amongst them, as (pretty much) always, it's the net payers into the EU budget that hold most influence.
Germany and France above all.
Angela Merkel and Emmanuel Macron also have their domestic audiences in mind when they speak about Brexit. Their parties are contesting fast-approaching elections for the European Parliament too, and their political styles are intentionally very different.
At last week's summit, for example, Emmanuel Macron was happy to play "bad cop" on Brexit, according to one EU diplomat I spoke to. Angela Merkel generally prefers to appear more conciliatory.
Tempting as it may be to look for clear black and whites in the EU, when UK politics is such a mess, European opinion is nuanced too. But the big players are not pulling in wildly different directions.
They are united in preferring to avoid a no-deal Brexit if they can, in wishing that Parliament would pass the prime minister's negotiated Brexit deal - sooner rather than later - and in hoping for a close relationship with the UK on the other side.
An inconclusive second referendum or general election would be a nightmare for the EU – keeping Brexit looming over EU affairs for the foreseeable future.
Revoking Article 50 is described in Brussels as "the nuclear option" and is viewed as very unlikely as things stand.
For now the EU does as Theresa May does: it takes one Brexit week, one Brexit day at a time.
Brussels has told the prime minister if she is unable get her deal passed through parliament by 12 April, she needs to give them several days' warning as to what her Plan B might be.
Few in the EU think she has one.
EU leaders are pencilling in a possible Brexit summit around that time, in order for the prime minister to request a longer Brexit delay – or another short one until 22 May, to get the deal passed or to make last-minute preparations for a no-deal Brexit.
Ask EU diplomats and officials about their plans beyond that and they start to go a bit cross-eyed.

Scottish ministers have rejected the latest bid to settle the dispute over post-Brexit powers, despite the Welsh and UK governments striking a deal.
The UK government is to publish changes to the EU Withdrawal Bill in an effort to end the long-running row with the devolved administrations.
Welsh ministers reached an agreement with their UK counterparts on Tuesday.
But the Scottish government said there was still a "key sticking point" and called for further changes to be made.
First Minister Nicola Sturgeon has written to Prime Minister Theresa May accepting that "substantial progress" had been made in talks, and setting out potential ways to settle the "remaining issue".
Scottish Secretary David Mundell said he was disappointed by the Scottish government's decision, but said his "door remains open" for further talks.
The UK and devolved administrations have been entangled in a long-running dispute about how powers currently exercised from Brussels will work post-Brexit.
All agree that some powers should be built into UK-wide frameworks, so the same rules and regulations in areas such as food labelling are used across the country.
But there has been disagreement over whether the devolved administrations should only be consulted about any changes, or whether they need to formally give their consent.
Ministers from Edinburgh and Cardiff had previously coordinated opposition to what they termed a "power grab", issuing joint statements and passing their own Brexit bills on the same day.
However the Welsh government confirmed on Tuesday that it had reached an agreement with the UK government after "compromise on both sides".
Finance Secretary Mark Drakeford said the deal meant powers that were currently devolved "remain devolved" .
And he said that "all powers and policy areas rest in Cardiff, unless specified to be temporarily held by the UK government".
He added: "These will be areas where we all agree common, UK-wide rules are needed for a functioning UK internal market."
Scottish Brexit minister Mike Russell told MSPs that there was still a "key sticking point" for his government on a "fundamental point of principle" over devolution.
He said ministers had given the latest amendments "serious and respectful consideration", but said they "continue to give Westminster the power to prevent the Scottish Parliament from passing laws in certain devolved policy areas".
He said: "The effect of the UK government's latest proposal remains this: the Scottish Parliament's powers could be restricted without consent. This is not something the Scottish government could recommend the Parliament approves."
In her letter to the prime minister, Ms Sturgeon suggested two methods of settling the dispute - by deleting the offending clause from the UK government's EU Withdrawal Bill altogether, or by sticking with the present system of the UK government seeking the express consent of Holyrood for legislating in devolved areas.
Further talks between ministers are expected next week, with Mr Russell setting a deadline of the final reading of the Withdrawal Bill in the House of Lords - the middle of next month - for changes to be agreed.
If they are not, then ministers will not put forward the Withdrawal Bill for a consent vote at Holyrood. MSPs have already prepared for this possibility by passing their own legislation as a stop-gap measure, although UK law officers have formally challenged it in the Supreme Court.
The UK government views the position put forward by Mr Russell as potentially giving devolved ministers a "veto" over certain powers.
Lord Keen, the advocate general for Scotland, told peers earlier in the year that needing formal consent for changes to power-sharing frameworks would be "a fundamental change in the devolved competence".
He said: "If we have a black and white, sharp-edged consent mechanism for the devolved administrations, then we have the basis for what has been termed the veto problem.
"We have the situation in which, beyond the existing devolved competence, any one of these assembles could proceed to legislate within its devolved competence in a manner that impacted upon those in another country within the United Kingdom. We cannot go down that road."
The Scottish Conservatives said the fact the Welsh government had struck a deal meant the SNP was "utterly isolated and exposed".
The party's constitution spokesman, Adam Tomkins, said the Scottish government had rejected the deal for "narrow political reasons", namely "obsession with a second independence referendum".
Labour's Brexit spokesman Neil Findlay said it "would be wrong for the SNP government to play politics with devolution in order to further their goal of independence".
UK government sources told BBC Scotland they were convinced that they had reached a deal with Mr Russell, only for Ms Sturgeon to "scupper" it at the last moment.
Mr Russell flatly denied that he had been "overruled" by the first minister, saying he stood "foursquare behind" the government's position on devolved powers and insisting his relationship with Ms Sturgeon was "fine".
The Greens meanwhile continued to oppose the Brexit legislation outright, with co-convener Patrick Harvie saying MSPs "must dig our heels in and refuse to give consent to the EU Withdrawal Bill".
And the Lib Dems said Mr Russell had "behaved in a misleading fashion" by claiming not to know what was going on between the Welsh and UK governments.
Mr Russell had told MSPs that Scottish and Welsh ministers would continue to work together regardless of what decisions they took over the deal.

The former boss of supermarket chain Waitrose has warned that a "no deal" Brexit would push up the cost of fruit, vegetables, meat and dairy products.
Lord Price, a former Conservative trade minister, said fresh food could not be stockpiled like packets or tins.
The government says it will act to secure food supplies if the UK leaves without a deal in March.
It comes as Brexit Secretary Dominic Raab resumes talks with EU negotiator Michel Barnier in Brussels.
Both sides are focused on getting a deal by October that can be ratified by the UK Parliament and the EU member states before Britain officially leaves on 29 March next year.
But they are also stepping up preparations for the consequences of talks breaking down without a deal.
Lord Price, who quit the government in September, said: "What you will see is, rather than a pinch on supply - although that is highly likely - a pretty significant increase in the cost of fruit and veg, the cost of meat and the cost of dairy products."
He said the UK only produces about 25% of the fruit and vegetables it consumes and, while the winter season for imports from places like South America and New Zealand could be extended slightly to cover the UK's EU departure, supermarkets would have to find new supply routes.
"They may think about air freight, they may think about shipping," he told BBC Radio 4's Today programme.
"But all these things are going to add cost and they are going to add to the cost of a tariff that will be applied because the EU has pretty penal tariffs on food, to protect European farmers."
France's European affairs minister Nathalie Loiseau told Today a "no deal" Brexit would mean "traffic jams in Calais and in each and every European port welcoming goods and people coming from the United Kingdom".
She added: "We would all suffer. The worst would be for the United Kingdom."
Some UK ministers have dismissed talk of food shortages in the shops in the event of there being no deal.
"I am not aware of any plans for stockpiling food. It seems to me to be a fairly ridiculous scare story," Brexit Minister Lord Callanan told the House of Lords last week.
"There are many countries outside of the European Union that manage to feed their citizens perfectly satisfactorily without the benefit of EU processes."
Brexit Secretary Dominic Raab told MPs on Tuesday the government would take steps to ensure an "adequate food supply".
In an interview with Channel 5's 5 News on Wednesday, Prime Minister Theresa May did not deny that stockpiling was happening, saying the government is being "responsible and sensible" while still trying to get a good deal with the EU.
Mrs May has taken personal control of Brexit negotiations, which are being run by a unit in the Cabinet Office reporting directly to her.
Mr Raab is holding face-to-face talks with Mr Barnier at the end of the latest round of Brexit negotiations, along with senior civil servant Olly Robbins.

Both the UK and EU have expressed frustration at the pace of Brexit talks amid disagreement over the size of the UK's "divorce bill".
EU negotiator Michel Barnier said the UK did not feel "legally obliged to honour its obligations" after Brexit.
He said "no decisive progress" had been made on key issues, following the third round of talks.
But Brexit Secretary David Davis said the UK had a "duty to our taxpayers" to "rigorously" examine the EU's demands.
And he urged the EU to be "more imaginative and flexible" in its approach.
During a joint press conference, Mr Barnier acknowledged there had been some "fruitful" discussions on the issues surrounding the relationship between the Republic of Ireland and Northern Ireland, but he struck a pessimistic tone overall.
He stressed that he was "impatient… I am not angry… I am impatient and determined" about the progress of negotiations, adding that "time is flying" and the EU was willing to intensify the "rhythm" of talks.
Behind their polished podium performances, it's clear there are major gaps between the stance of Michel Barnier and David Davis which are not being bridged.
Money is the big sticking point of course, although the phraseology around the issue is a little more elegant than that, and the language at these moments can give you a real feel for the underlying atmosphere.
Mr Barnier says that after this week "it's clear that the UK doesn't feel legally obliged to honour its obligations".
Mr Davis claims it's natural that the UK would want to "interrogate rigorously" any demand placed on its taxpayers. But he is also careful to note that Britain is a country that meets its obligations - moral as well as legal; it just expects them to be properly specified.
The UK wants to begin trade talks as soon as possible, but Brussels insists that discussions about the future relationship after Brexit can only begin once "sufficient progress" has been made on the arrangements for withdrawal - including on the so-called "divorce fee".
Mr Barnier said that at the current rate of progress, he was quite far from being able to recommend opening parallel talks on a future trade relationship with the UK.
He cited two areas where "trust" needed to be built between the two sides - on citizens' rights and the financial settlement, stressing that 27 members of the bloc should not have to pay for obligations taken by 28.
Claiming there had been a shift in the UK government's approach, he said: "In July the UK recognised that it has obligations beyond the Brexit date but this week the UK explained that these obligations will be limited to the last payment to the EU project before departure."
No figure has yet been put on the payment, but European Commission president Jean-Claude Juncker has suggested it could come in at around 60 billion euro (£55bn), while unconfirmed reports have put it as high as 100 billion euro (£92bn).
Mr Davis defended the "rigorous" line-by-line examination of the EU's demands carried out by British officials in response to the "unspecified but undoubtedly large" sum demanded by Brussels.
He added: "It will, of course, lead to difficult exchanges - nobody will pretend it was anything but a tough exchange this week - but I think the British taxpayer would expect nothing less."
Mr Davis also told reporters the talks had exposed how the UK approach was "substantially more flexible and pragmatic than that of the EU".
"This week we have had long and detailed discussions across multiple areas and I think it's fair to say we have seen some concrete progress, and Michel referred to one but there's more than that," he said.
"However, as I said at the start of the week, it's only through flexibility and imagination that we will achieve a deal that works truly for both sides.
"In some areas we have found this from the [European] Commission's side, which I welcome, but there remains some way to go."
He added: "Beyond the debates about process and technicalities, at the heart of this process, must be a desire to deliver the best outcome for the people and the businesses of the European Union and the United Kingdom," he added - particularly on citizens' rights.

It is "obvious" there will be a hard border in Ireland in the event of a no-deal Brexit, the European Commission's chief spokesman has said.
Margaritis Schinas made the comments at the commission's daily media briefing.
If he was pushed to speculate what might happen in a no-deal scenario, he said, it was "pretty obvious you will have a hard border".
However, the Irish government has repeated its stance that it will "not accept a hard border on this island".
In a statement, the office of Taoiseach (Irish Prime Minister) Leo Varadkar said: "Regardless of Brexit, the British government will always have responsibilities as co-guarantor of the Good Friday Agreement to ensure that, even in a no deal, there will not be a return to a border."
In June 2016 the UK voted to leave the EU and negotiations have been taking place since then on the terms of the UK's withdrawal.
Unless the EU and UK strike a deal that is accepted by the British parliament, the default position will be for the UK to leave the EU without a deal on 29 March.
Mr Varadkar's statement added that avoiding a hard border would be "more difficult to achieve without the withdrawal agreement and would require very difficult discussions with our EU partners".
"Working out suitable customs and trade arrangements compatible with our EU membership will require detailed discussion with the commission, while the UK will also need to live up to its responsibilities.
"We are under no illusions about how challenging that would be," Mr Varadkar's office added, but it also reiterated its position that the Irish government is "not planning" for a hard border.
Speaking later in the Dáil (Irish parliament) Mr Varadkar said the Irish government would have "a real dilemma" if the UK leaves without a deal:
"We would have to negotiate an agreement on customs and regulations that meant full alignment so there would be no hard border.
"We already have that agreement, and that is the backstop," he said.
He also said that in a no-deal scenario Ireland would have obligations to protect the single market, the United Kingdom would have obligations to protect World Trade Organisation rules and both states would have an obligation to honour the Good Friday Agreement, protect the peace process and honour their commitments to the people of Northern Ireland that there will not be a hard border.
Last week, the UK prime minister said the EU had made it "clear there will be no flexibility on border checks in no deal".
"The Irish government will be expected to apply EU checks in full," added Theresa May.
Mr Schinas told reporters at Tuesday's briefing: "If you'd like to push me and speculate on what might happen in a no-deal scenario in Ireland, I think it's pretty obvious - you will have a hard border.
"And our commitment to the Good Friday Agreement and everything that we have been doing for years with our tools, instruments and programmes will have to take, inevitably, into account this fact.
"So, of course we are for peace; of course we stand behind the Good Friday Agreement but that's what a withdrawal... that's a no-deal scenario, that's what it [would] entail.
"So I will not now speculate on this plan B because, as I said seconds ago, we are for plan A, which is set by the withdrawal agreement and the political declaration as a package."
Northern Ireland's Democratic Unionist Party (DUP) has described Mr Schinas's comments as "a lot of bluff".
The party's Brexit spokesman, Sammy Wilson, said he believed the EU was trying to "up the ante" as the Brexit deadlock continues.
He said his party would not be scared into voting for the deal that includes the current Irish "backstop" - the controversial insurance policy designed to prevent a hard border if the UK leaves the EU without securing an all-encompassing deal.
The DUP MP acknowledged there would be pressure on the Irish government now, but he urged the British government not to listen to what the EU has said about a hard border.
"Good luck to them (the EU) if they think they can put a hard border up," Mr Wilson added.
"We'll see it for bluff come 1 April, if there is no deal."
It is written into law that the UK will be leaving  the EU on March 29, but the deadline could be extended
Last week, the withdrawal agreement was overwhelmingly rejected by Westminster,, with MPs voting against Mrs May's preferred deal by 432 votes to 202.
It was the largest defeat for a sitting British government in history.
Mrs May was asked to come up with an alternative option and MPs are now due to vote on an amended version of her deal on 29 January.
On Monday, the prime minister told the House of Commons she will go back to EU leaders in a bid to secure changes to the Irish backstop.
However, there is little consensus in the Commons for any one solution to Brexit, and so MPs are currently putting forward a range of other options ahead of the 29 January vote.
Among the amendments suggested so far are plans to prevent a no-deal Brexit and to extend the deadline for leaving the EU.
Northern Ireland Affairs Committee chairman Andrew Murrison has submitted an amendment which seeks to time-limit the backstop.

A no-deal Brexit is "no problem", Nigel Farage has said at a rally of the Leave Means Leave campaign group.
The former UKIP leader told an audience in Bolton the current government negotiations on Brexit could plausibly end in an agreement.
But "far from being a cliff edge", the UK would prosper without one, he said.
Ex-Brexit Secretary David Davis told the rally the PM's plans were a "weak compromise" and the government had to deliver Brexit "without dilution".
Mr Farage said the majority of the "political class" did not respect the Brexit vote and the "endless negative narrative" needed to be countered "again".
"They do not want to give us Brexit," he told the rally at the University of Bolton Stadium, the first in a number of Leave Means Leave events across the country.
The MEP said of the EU: "They are a bunch of gangsters. We will explain a free trade deal is possible, if that's what the gangsters in Brussels want.
"If they don't, that is fine, if they don't we will leave with no deal. No deal, no problem."
Theresa May's plan for Brexit - known as the Chequers agreement - was rejected by EU leaders as unworkable at a summit in Salzburg on Thursday.
Mrs May later said the EU's rejection of her plan without offering an alternative was "unacceptable" and made it clear she was ready to walk away from the negotiations rather than accept a "bad deal".
Mr Farage criticised the Chequers proposals, saying they were "dead" and do not work for the EU or the UK.
Mr Davis had been leading the UK negotiations to leave the EU but quit the cabinet in July, saying he did not "believe" in the Chequers plan.
He told Saturday's rally: "We have nothing to fear and that is the reason why we should only accept a clean and clear Brexit, not some fudge."
Mr Davis also said he viewed the EU's treatment of Mrs May "with contempt", adding: "Bad manners and discourtesy are not the hallmarks of great men."
He continued: "And if you think you can bully our country, all I can suggest is that you read some history books."
Labour MP Kate Hoey also spoke at the rally, saying: "We don't need another vote - we just want to leave."
"Our vote matters and we won't allow it to be stolen from us," she said.
She also said Brussels had never negotiated Brexit in "good faith".
"They underestimate how strong we are when we are up against it," she added.
It was a full house at the University of Bolton Stadium. An audience of more than 2,000 people squeezed into what was decked out like a ballroom. A stall selling Leave Means Leave baseball hats did excellent trade.
In Bolton, 58% voted to leave the EU in June 2016 and, as they queued to get in, many told how passionate they were to secure the kind of Brexit they voted for.
They said they felt the result of the referendum was not being taken seriously enough.
The audience had come from around the country, some waved union flags; others wore them.
The loudest of the applause was reserved for Nigel Farage who started by saying: "I didn't think I'd have to do this again." That got laughs.
Earlier he took an open top bus into Bolton to speak to shoppers and market traders, the media in tow.
It all felt a bit like going back to the referendum campaign.

A no-deal Brexit threatens the UK's food security and will lead to higher prices and empty shelves in the short-term, retailers are warning.
Sainsbury's, Asda and McDonald's are among those warning stockpiling fresh food is impossible and that the UK is very reliant on the EU for produce.
The warning comes in a letter from the British Retail Consortium and is signed by several of the major food retailers.
It comes ahead of crucial votes in Parliament on Tuesday.
Retailers have told me that they fear shelves would be left empty if there were significant disruptions to supplies.
The letter from the retailers, and seen by the BBC, says there will be "significant risks" to maintaining the choice, quality and shelf life of food.
"We are extremely concerned that our customers will be among the first to experience the realities of a no deal Brexit," the letter says.
MPs will consider a series of amendments to Theresa May's plans that could shape the future direction of Brexit.
While it will not be MPs' final verdict on the deal, they will vote on the amendments and, if one is passed, it will illustrate what changes to the deal might be enough to get a modified version of the deal through Parliament.
Retailers have been reluctant to intervene in the Brexit debate but are doing so now as the UK's departure date from the EU approaches.
In the letter, they urge MPs to work together "urgently to find a solution that avoids the shock of a no-deal Brexit".
The letter uses the government's own estimate that freight through Calais may fall 87% from current levels, threatening the availability and shelf life of many products.
It expresses worry over tariffs, with only 10% of the UK's food imports currently subject to World Trade Organisation (WTO) rules.
If the UK were to revert to WTO rules, the retailers warn that would "greatly increase import costs that would in turn put upward pressure on food prices".
The other signatories to the letter include the chief executives of M&S, KFC, Co-Op, and Lidl.
The letter spells out the UK's food relationship with Europe, with nearly one third of the food in the UK coming from the EU.
"In March, the situation becomes more acute as UK produce is out of season," the letter says.
At that time of year, 90% of lettuces, 80% of tomatoes and 70% of soft fruit sold in the UK is grown in the EU, the letter says.
"As this produce is fresh and perishable, it needs to be moved quickly from farms to our stores," the retailers say.
Their letter says that stockpiling fresh food is impossible and that the complex, just-in-time supply chain through which food is imported into the UK will be "significantly disrupted" in the event of a no-deal Brexit.
It adds it is difficult to stockpile any more produce as "all frozen and chilled storage is already been used".
"While we have been working closely with our suppliers on contingency plans, it is not possible to mitigate all the risks to our supply chains and we fear significant disruption as a result if there is no Brexit deal," the retailers say in the letter to MPs.
The retailers say that while they are looking for alternate supply routes, there are limited options and not enough ferries.
A spokesperson for the Department for Environment, Food and Rural Affairs said: "The UK has a high level of food security built upon a diverse range of sources including strong domestic production and imports from other countries. This will continue to be the case whether we leave the EU with or without a deal."
They added the government had "well established" ways of working with the food industry to prevent disruption.
The letter comes after a report from MPs on the Exiting the EU Committee said the government must rule out a no-deal Brexit.
Committee chairman Hilary Benn said: "The suggestion that the UK might opt for a no-deal outcome but assume that the EU will continue to act in a co-operative manner to avoid disruption, cannot seriously constitute the policy of any responsible government."
However, a Tory member of the committee, Craig Mackinlay, said he "disowned" the report findings as "just more Project Fear from a group of MPs who have never wanted the UK to leave the EU".
A number of amendments are being voted on by MPs on Tuesday - although the Irish deputy PM says changes to the backstop - aimed at preventing a hard border - would not be acceptable.
The backstop is the "insurance policy" in the withdrawal deal, intended to ensure there will be no return to a visible border between Northern Ireland and the Irish Republic after the UK leaves the EU.

Concerns have been raised over the readiness of a British firm contracted by the government to run extra ferries in the event of a no-deal Brexit.
Seaborne Freight was awarded a £13.8m contract this week to run a freight service between Ramsgate and Ostend.
The firm has never run a ferry service and a local councillor said it would be impossible to launch before Brexit.
The government said it had awarded the contract in "the full knowledge that Seaborne is a new shipping provider".
The Department for Transport said that "the extra capacity and vessels would be provided as part of its first services".
"As with all contracts, we carefully vetted the company's commercial, technical and financial position in detail before making the award," it added.
Conservative Kent county councillor Paul Messenger said it was impossible for the government to have carried out sufficient checks on the firm.
"It has no ships and no trading history so how can due diligence be done?" he asked.
Mr Messenger said he didn't believe that it was possible to set up a new ferry service between Ramsgate and Ostend by 29 March - the date when the UK is due to leave the European Union.
The narrow berths for ships at the Port of Ramsgate mean there are only a few suitable commercial vessels, most of which are currently already in service, he said.
Ferry services have not operated from Ramsgate Port since 2013 after cross-channel operator TransEuropa collapsed, owing around £3.3m to Thanet District Council.
Mr Messenger said he was "perplexed" at the choice of Seaborne Freight to run the service.
"Why choose a company that never moved a single truck in their entire history and give them £14m? I don't understand the logic of that," he said.
But Seaborne Freight, which was formed less than two years ago to revive the Ramsgate-Ostend line, insisted it will launch its freight service between Ramsgate and Ostend before 29 March.
Chief executive Ben Sharp said the firm had been founded by seasoned shipping veterans.
He declined to give details on which ships it planned to use for the service, saying the information was commercially sensitive, but said they planned to start operations with two ships before "very quickly" increasing to four by late summer.
He said dredging in Ramsgate Port would start on 4 January in preparation for the freight service.
The firm said it had originally intended to start the service in mid-February but this had now been delayed until late March for operational reasons.
It said directors and shareholders had been working during the past two years to restart the service.
"This phase has included locating suitable vessels, making arrangements with the ports of Ostend and Ramsgate, building the infrastructure, as well as crewing the ferries once they start operating," the firm's statement added.
The government has also awarded additional, much larger ferry contracts to French company Brittany Ferries and Danish shipping firm DFDS, worth £46.6m and £42.5m (€47.3m) respectively.
The new contracts are part of the government's contingency planning, which aims to ease the potential for severe congestion at main port Dover if the UK leaves the European Union without a deal.
The department has warned that increased border checks by EU countries in the case of a no-deal Brexit could "cause delivery of critical goods to be delayed", and "significant wider disruption to the UK economy and to the road network in Kent".
By Joe Miller, BBC business correspondent
The government has for some time now acknowledged that in the event of a no-deal Brexit, contingency plans at ports other than Dover would need to be in place.
But it appears that Transport Secretary Chris Grayling's department only started awarding contracts to shipping firms a few weeks ago, with no time left, it says, for a full public tender process.
And while the two large international firms enlisted to provide extra capacity have existing fleets and large operations, Seaborne does not, and has given few details on how it will get a service up and running in a matter of months.
The Department for Transport also wasn't too keen on making much noise about these plans - it quietly posted notices of the awards on an EU portal on Christmas Eve, and the BBC was only alerted to them by a data firm, Tussell.
And it's worth noting that without the award to Seaborne, the government would be in a position where the two beneficiaries of a no-deal Brexit were a Danish and a French firm - based, of course, in the EU.
The Department for Transport says the new contracts will provide "significant extra capacity" to UK ports in the event of a no-deal Brexit,
The BBC understands that the three firms chosen are likely to retain a portion of their award even if their services are no longer needed, due to a deal being reached with Brussels.
However, in that event, the government would then seek to sell the extra capacity back to the market.
Labour MP Tonia Antoniazzi, a supporter of the Best for Britain campaign for a second referendum, said: "Never has it been clearer that our government is selling us down the river over Brexit.
"A firm that has never run a ferry service before has been awarded a multi-million pound contract and they don't even have any ships. This idea should have been sunk before it saw the light of day."
Ed Davey, home affairs spokesperson for the Liberal Democrats, said reports that the government had signed a contract with "a ferry company with no ferries" summed up the government's "farcical" approach to Brexit.
The UK is due to leave the EU on 29 March - following the result of the 2016 referendum.
It and the EU have agreed a withdrawal agreement - or "divorce deal" - and a political declaration outlining ambition for future talks - but it needs to be agreed by Parliament for it to come into force.
A vote by MPs on the deal had been scheduled for 11 December, but Prime Minister Theresa May postponed it until January when it became clear her deal would be rejected, leading to widespread anger in the Commons.

The government is now "working on the assumption" of a no-deal Brexit, Michael Gove has said.
Mr Gove said his team still aimed to come to an agreement with Brussels but, writing in the Sunday Times, he added: "No deal is now a very real prospect."
The prime minister has made Mr Gove responsible for preparing for no-deal.
Treasury sources say they expect more than £1bn of extra funding to be made available later this week for no-deal planning and preparation.
Writing in the Sunday Telegraph, Chancellor Sajid Javid said there would be "significant extra funding" for 500 new Border Force officers and "possible" improved infrastructure at British ports.
Prime Minister Boris Johnson has told Mr Gove to chair no-deal meetings seven days a week until Brexit is delivered, according to the Sunday Times.
Mr Gove said tweaks to Theresa May's withdrawal agreement - which was approved by the EU but resoundingly rejected by Parliament - would not be enough.
"You can't just reheat the dish that's been sent back and expect that will make it more palatable," he wrote.
He added he hoped EU leaders might yet open up to the idea of striking a new deal, "but we must operate on the assumption that they will not".
"While we are optimistic about the future, we are realistic about the need to plan for every eventuality."
Mr Gove highlighted a major flaw of Mrs May's deal as the Irish backstop plan - a measure designed to prevent the introduction of a hard border on the island of Ireland.
So far the backstop has proved a sticking point in the Brexit negotiations.
A no-deal Brexit would mean the UK leaving the EU and cutting ties immediately, with no agreement in place.
The UK would follow World Trade Organization rules if it wanted to trade with the EU and other countries, while also trying to negotiate free-trade deals.
But with Britain outside the EU, there could be physical checkpoints to monitor people and goods crossing in and out of the UK.
Speaking to Sky's Sophy Ridge, Labour leader Jeremy Corbyn said he would do everything to prevent a no-deal Brexit.
He reiterated his call for a new referendum - insisting he would still hold one if Labour were in power - and said, in the event of a no-deal Brexit, Labour would campaign to remain in the EU.
Mr Corbyn also said he would look at whether to call a no-confidence vote in the government after Parliament returns in September.
Liberal Democrat leader Jo Swinson told Sky that, in the event of a general election, her party's message would be: "Stop Brexit, stop Boris and start renewing our country."
Mr Gove is one of several new ministers pressing on with Brexit preparations since joining Mr Johnson's cabinet earlier this week.
Newly appointed Chief Secretary to the Treasury, Rishi Sunak, told Sky: "We're turbo-charging preparations for no-deal, that is now the government's number one priority."
He said if the EU would not reopen discussions about the Irish backstop plan then "it's right that we prepare properly, with conviction, and importantly with the financial resources that the Treasury will now supply properly".
Who is in charge of what?
Meanwhile, there have been reports of more dissatisfaction within the Conservative Party, as MPs opposed to a no-deal Brexit continue to consider ways to avoid it.
The Observer alleges former chancellor Philip Hammond held private talks with Labour's Brexit spokesman Sir Keir Starmer before Mr Johnson became prime minister.
The pair met shortly after Mr Hammond resigned from the government, the paper said.
Mr Starmer told the paper that work to build "a strong cross-party alliance" to prevent a no-deal Brexit would "intensify over the summer".
But despite several Tory MPs voicing their opposition to Mr Johnson in his first week in Downing Street, an opinion poll has suggested a recent boost in support for the party.
Since Mr Johnson took office on Wednesday the Conservatives have gained 10 points to stand at 30%, a survey for the Mail on Sunday showed.

The M26 in Kent is being shut overnight while work is done to see if it can be used as a "parking lot" for lorries, in the event of a no-deal Brexit.
It will be closed from 2200 BST until 0530 BST until 15 October and again between 19 November and 21 December.
Local Tory MP Tom Tugendhat questioned why work began with "no consultation" - despite assurances none was planned.
Transport Secretary Chris Grayling said was part of "no-deal" contingency plans but he thought it would not be needed.
The M26 is a 10-mile stretch of road connecting the M25 at Sevenoaks and the M20 near West Malling.
Sections of the M20 in Kent can be closed under Operation Stack, when lorries are forced to queue because of disruption to rail or ferry journeys.
And there have been concerns that a no-deal Brexit could mean lorries getting stuck at the nearby port of Dover because of customs delays.
Mr Tugendhat, MP for Tonbridge and Malling, which covers the eastern half of the M26, told the Commons he had been assured that works were not planned as recently as last week - only to find out on Wednesday night that they were going ahead.
He told MPs: "It's come to a pretty pass when a member finds out that works have begun on a motorway to turn that motorway into a parking lot without consultation either with the local community or with surrounding members.
"The M26 works started last night. I wrote (to Mr Grayling) in April, asking whether or not this would happen.
"I was assured the works were not planned and only yesterday (Wednesday) was it confirmed to me that Highways England had said that is exactly what was planned, despite having told me the reverse a week earlier."
Mr Grayling replied that he would be happy to meet the MP to discuss the issue, but added: "I do not expect any of the contingencies that we have in place for a no-deal Brexit to be needed because I'm confident we will reach a sensible agreement."
Operation Stack is currently used on closed sections of the M20 in Kent, where lorries park while waiting to cross the English Channel when traffic is disrupted.
A new strategy, Operation Brock, due to start in early 2019, plans to use a contraflow to keep the roads open when problems arise.
Paul Carter, the Conservative leader of Kent County Council, said turning sections of the M26 into a lorry park would be complex and cause "significant problems".
"It is possible to close part of the M26 but my mantra is that we must keep our roads open to the public no matter what is thrown at us," he told Kent Online.
Highways England said traffic was relatively light on the M26 overnight and drivers were being informed of alternative routes during the closure period.
"As part of wider resilience planning, Highways England has been asked by the Department for Transport to develop plans to utilise the M26 to hold heavy goods vehicles, should further capacity be required in the future," a spokesman added.
"We will be undertaking site surveys on the M26 during October leading to the installation of two gates in the central reservation to support the safe management of freight in the future, if needed."

Preparing for the possibility of a no-deal Brexit should be "the top priority" for civil servants, Boris Johnson has told them in a letter.
The PM said he would prefer to get a deal with the EU, but he said he recognised this "may not happen".
Earlier Jeremy Corbyn had urged the UK's top civil servant to intervene to prevent a no-deal Brexit happening during a general election campaign.
It comes amid speculation MPs could back a no-confidence motion in the PM.
In his letter to civil servants, Mr Johnson said the UK must be prepared to leave the EU by the latest Brexit deadline of 31 October "whatever the circumstances".
"That is why preparing urgently and rapidly for the possibility of an exit without a deal will be my top priority, and it will be the top priority for the civil service too."
It is understood that government special advisers also received an email last night from the PM's senior adviser Eddie Lister instructing them not to take annual leave until after 31 October.
Mr Johnson's message to civil servants follows a similar letter sent by Chancellor Sajid Javid earlier this month to HM Revenue and Customs.
Mr Javid also ordered the tax authority to make preparing for no-deal its "absolute top priority", including helping the public to prepare for the possibility.
He said this should include making sure IT systems are ready, helping businesses with a helpline, and contacting traders directly.
In his letter to Cabinet Secretary Sir Mark Sedwill, Mr Corbyn said it would be an "anti-democratic abuse of power" if the PM allowed a no-deal to occur by default during a general election campaign, if the government was defeated in a vote of no confidence.
Shadow chancellor John McDonnell has said it is "almost inevitable" that Labour would push for such a vote when the Commons returns from its summer recess on 3 September.
It is thought MPs opposed to no-deal could back the vote in a bid to prevent the UK leaving the EU without an agreement - leading to a general election being called.
Election rules say Parliament should be dissolved 25 working days before polling day - so some people are concerned Mr Johnson could allow a no-deal Brexit to happen while MPs are not sitting.
According to the Sunday Telegraph, Mr Johnson's senior adviser at No 10, Dominic Cummings, has told MPs even losing such a vote could not stop the PM taking the UK out of the EU on 31 October.
He reportedly said Mr Johnson could call an election for after the deadline, with Brexit taking place in the meantime.
Theresa May's Brexit deal was rejected three times by MPs and, as things stand, the UK will leave the EU on 31 October whether it has agreed a new one or not.
Mr Johnson has urged the EU to make changes to the deal, but has said the UK must leave by this deadline with or without an agreement.
Many of those who voted against the deal had concerns over the backstop, which if implemented, would see Northern Ireland staying aligned to some rules of the EU single market.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
These arrangements would apply unless and until both the EU and UK agreed they were no longer necessary.
On Thursday Mr Johnson again urged the EU to compromise on the Irish border backstop plan, designed to guarantee there will not be a hard Irish border after Brexit.
However, the EU has continued to insist that the withdrawal deal agreed by Mrs May last year, including the backstop, cannot be renegotiated.
Meanwhile, a transport minister has said he supports the government position of leaving the EU in all circumstances, following comments he made about a no-deal Brexit.
George Freeman told HuffPost UK's Commons People podcast it would be an "absolute disaster" for the UK in the long term if it only traded with the EU on WTO [World Trade Organization] terms, without its own free trade deal with the bloc.
But he later tweeted to say he "totally supports" the position that the UK should leave with no deal on 31 October, "if the EU is unwilling to negotiate".
In response, Downing Street told the BBC that Mr Freeman has the "full support of the prime minister".

Bodies may remain uncollected and children might miss exams due to gridlocked roads in the event of a no-deal Brexit, a council has warned.
In a damning report, Kent County Council warned about the effect on other key services.
It said refuse could blight the streets and food deliveries could be disrupted as the county copes with 10,000 lorries parked or stacked on its roads.
A government spokesman said it was providing support to local authorities.
The 17-page report - an update on no-deal contingency planning -  laid bare the possible Brexit scenarios for the county, with "prolonged disruption" predicted to affect several vital services.
It could result in staff shortages in areas such as social care, as well as problems for people trying to get to hospital and disruption to the delivery of medicines, the council said.
The coroner service "could face difficulties with the transport of the deceased to post mortem or body storage facilities... and travel by pathologists to mortuary to conduct post mortems".
It goes on to say: "Schools could be compromised if staff and pupils cannot effectively travel to exams."
Talking about waste management, the report said: "District and borough collection services may be delayed and disrupted if there is significant traffic congestion, which could lead to a build up of waste awaiting collection."
Changes in the border at the cross-Channel terminals are likely to cause traffic congestion, with Kent's roads forecast to feel the brunt.
The council warned it could exceed that of the problems experienced in 2015, when almost 7,000 HGVs were contained on the M20 in Kent as part of Operation Stack.
Richard Burnett, chief executive of the the Road Haulage Association, said the customs process in the event of a no-deal was "alarming".
He said: "If there's a slowing of that... people won't get the stuff when they want it because it won't be there.
"That's going to be catastrophic for us and the nation."
A government spokesman said: "We have been working closely with Kent County Council - and all other local authorities - to make sure they have the support and resources they need to cope with Brexit in any scenario.
"That includes keeping the county's vital road networks moving so that local people, businesses, schools, and visitors face as little disruption as possible."
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Britain leaving the European Union has been described as akin to attempting to remove an egg from an omelette.
Today's "no deal" papers reveal the complicated exercise could carry significant costs for consumers and businesses if Britain and the EU fail to agree on a transition period and a subsequent trading agreement.
Those increased costs would be very likely to have a negative impact on the economy and could mean higher prices in the shops as firms pass on the higher costs of doing business.
Which is why the government keeps insisting that it is pushing for a "successful" deal with the EU.
And the EU says that is also its preferred outcome - Britain is a major customer for many EU goods and services.
Many firms I speak to are not preparing for a "no deal" because they simply do not believe that it will happen, such is the disruption that could be caused.
The details on "no deal" published by the government are sobering.
Just take one - trade across the border between the UK and the EU post-Brexit if there is no agreement.
If there is no deal and Britain reverts to "third country" status, the government has provided a long list of preparations firms that export and import to and from the EU will be required to undertake.
Customs declarations would be needed, tariffs (import and export taxes) "may also become due" and the government also says firms are likely to need to invest in new computer systems to track goods.
"If the UK left the EU on 29 March 2019 without a deal there would be immediate changes to the procedures that apply to businesses trading with the EU. It would mean that the free circulation of goods between the UK and EU would cease," the government says.
The import and export of food would be particularly affected.
Food companies would have to register with a new (and as yet non-existent) UK authority which would be needed to replace the EU's "TRACES" system that tracks the trade and certification process for animals, food, feed and plants across Europe.
"The new burdens potentially facing food and drink exporters and importers set out today will frighten many SME [small and medium-sized] food businesses," the Food and Drink Federation's chief executive, Ian Wright, said.
That is the crux of the problem.
Leaving the single market and the customs union without a deal means significantly higher barriers to trade with the EU.
And higher costs for firms that are engaged in that trade.
Consumers could find going on holiday and making card payments for EU products more expensive because Britain would no longer be part of the EU's payments process.
Some of the overall costs to the economy might be mitigated over the medium term by increased trading opportunities with nations outside the EU.
And the government has signalled that in some areas - such as the need for upfront payments of VAT on imports - it is doing its best to smooth the impact on cash flow by allowing for delayed payment systems.
That has been welcomed by business groups.
But what is key from the documents published today is pretty straightforward.
The costs of a no-deal situation are likely to be substantial.
And consumers and businesses would be the ones paying the bill.

Dover and other Channel ports face disruption for up to six months if the UK leaves the EU without a deal, ministers have said.
The "worst case scenario" warning comes after analysis of likely traffic flows, if customs checks are delayed.
Lorries carrying medicine could get priority at ports and planes used to fly in drugs, ministers said.
But Tory Brexiteer Andrew Bridgen said it was "Project Fear on steroids," ahead of Tuesday's big Brexit vote.
He told the BBC: "It's the last throw of the dice from the prime minister who is desperate to get MPs to vote for her withdrawal agreement."
The prime minister's claim that the alternative to the withdrawal agreement she has negotiated with the EU is a no-deal Brexit, has so far failed to convince many of her own MPs.
Health Secretary Matt Hancock was among ministers trying to promote the deal on Friday, ahead of Tuesday's Commons vote, which the PM is widely expected to lose.
He told the BBC: "I don't know how likely 'no deal' is. It is what happens automatically unless Parliament passes something else.
"I very strongly feel that the best thing for the country, not just for the health service but for the country as a whole, is for Theresa May's deal to pass."
Updated advice to government departments from officials warns there could be six months of reduced access and delays at Dover and Folkestone, if the UK leaves the EU on 29 March 2019 without a deal.
By BBC Health Editor Hugh Pym
Drug companies were told in August by the government to create stockpiles in the UK with six weeks worth of supplies.
That has largely been achieved although there has not been so much progress with medical devices.
But pharma bosses believe the government should do more to ensure continuity of supply and ministers should give more detail of plans to fast-track lorries through ports.
Some may be suspicious about the timing of this with political debate over Brexit raging - government sources say the warning is based on analysis of trading patterns by officials which could not be withheld from Whitehall departments.
Mr Hancock has written to health leaders, telling them to check their plans for ensuring the continued supply of medicines.
Current advice is that there should be a six-week stockpile of medicines in the UK to cover the possibility of disruption after a no-deal Brexit. About 90% of medicines imported by the UK and the Republic of Ireland come in through Dover.
The health secretary said the "worst-case planning assumption" meant that "whilst the six-week stockpiling activities remain a critical part of our contingency plans, this now needs to be supplemented with additional actions".
He said the NHS should prepare to use alternative routes in the event of disruption on cross-channel routes, including the use of planes to fly in supplies.
He wrote that if France or other EU countries imposed additional border checks in a no-deal scenario, the impact was "likely to be felt mostly on the short straits crossings into Dover and Folkestone" affecting both exports and imports, with "significantly reduced access" for up to six months.
"This is very much a worst-case scenario. In a 'no deal' exit from the EU we would, of course, be pressing member states hard to introduce pragmatic arrangements to ensure the continued full flow of goods which would be to their benefit as well as ours."
Mike Thompson, chief executive of the Association of the British Pharmaceutical Industry (ABPI), said the government warning was "stark" adding that "stockpiling more medicines is not the solution to this problem".
He welcomed the intention to prioritise the flow of medicines and vaccines, but added, with just four months to go, "we need the government to take immediate action to open up alternative supply routes between the UK and Europe and tell companies so that they can make plans".
Kent County Council has warned that dead bodies may remain uncollected and children might miss exams due to gridlocked roads in the event of a no-deal Brexit.
In an update on its contingency planning, the local authority said refuse could blight the streets and food deliveries could be disrupted as the county copes with 10,000 lorries parked or stacked on its roads.
Council leader Paul Carter said preparations had been made for potential difficulties but added: "We now need far more input and information from national government in how they are going to work with us.
"There must be a national freight transport plan which, when necessary, can hold lorries back from coming into Kent in the first place should the need arise."
The withdrawal deal negotiated between the UK and EU has been endorsed by EU leaders but must also be backed by Parliament if it is to come into force.
With many of her own MPs opposing the deal, particularly the controversial issue of the "backstop", aimed at preventing the return of a hard border between Northern Ireland and the Republic of Ireland, Mrs May is expected to lose Tuesday's vote on the deal.
One senior minister has told the BBC "the only political common sense is to delay" it - but Downing Street has said it will go ahead as planned.

Northern Ireland may be considered part of European Union customs territory post-Brexit, Irish national broadcaster RTE is reporting.
It is part of a draft legal text to be published by the European Commission on Wednesday, RTE reports.
The text will allude to a single regulatory space on the island of Ireland with no internal barriers, adds the broadcaster.
The report cites "a well-placed EU source".
The scenario would reflect the so-called "default" or "backstop" option contained in the December agreement between the EU and the UK on how to avoid a hard border on the island of Ireland.
On Wednesday, the EU is expected to publish a text which will translate the political pledges made by both sides at the end of 2017 into legally-binding treaty language.
It will concern only divorce-related issues - not the future relationship.
Three separate well-placed sources have confirmed the general content of the draft to RTE News.
According to RTE's sources, the draft text will also state that, under the backstop option, joint EU-UK customs teams will be required to apply checks on goods coming from the UK into the new regulatory space, but will not specify where those checks will take place.
The text will also say that the two other options preferred by the UK to avoid a hard border are also available, and that if agreement is reached on those options, the above scenario would not apply.
Those options include avoiding a hard border through a future EU-UK free trade agreement, or through specific proposals made by the UK government.
It is understood that the draft will not spell out that Northern Ireland remains in the EU single market.
However, that will be implied by a series of annexes which will say that individual pieces of EU single market legislation "will be applicable".
The text will have considerable detail on how the movement of goods, north and south, will be facilitated without any border checks, RTE also reports.
The Democratic Unionist Party (DUP) has made clear if the Irish Sea became a de facto trade border, it would withdraw its support for the Conservative government.
"It would represent a break-up of the United Kingdom," the party's Sammy Wilson said.
"For the Irish government, which prattles on all of the time about the importance of the Belfast Agreement, - part of the Belfast Agreement was that there can be no change in the constitutional position of Northern Ireland without the consent of the people of Northern Ireland.
"Yet here we now have the EU, prompted by the Irish government, seeking to bring about that constitutional change."
The DUP's 10 MPs are helping to keep Prime Minister Theresa May in power as part of a confidence and supply deal.
"But if reports are true that it has something around the north remaining within the customs union, this of course is to be welcomed. But it's only a start," he said.
"We need to have membership, not just of the customs union, but of the single market and we need to ensure our human rights are protected under the European courts of justice."
EU negotiator Michel Barnier said earlier that there would be "no surprises" in Wednesday's 120-page document.
He said it was the EU's responsibility to include the "backstop" option of Northern Ireland maintaining full regulatory alignment with the Republic in areas of existing North-South co-operation if no other solutions could be made to work.
While all three options would be mentioned in the 120-page document, he said it would be the backstop one which would be "operationalised" into legally binding text.
The other options would be worked on as soon as the UK provided more details, he said.
The paper would also set out the EU's position on the post-Brexit transition period, and would cover citizens' rights and financial issues too, he said.
Meanwhile, the prime minister's office has categorically dismissed any prospect of a return to a "hard border" in Ireland as a consequence of Brexit.
The statement followed the leak of a letter to the prime minister from Foreign Secretary Boris Johnson, in which he appeared to contemplate the possibility of future customs border checks, after the UK, including Northern Ireland leaves the EU customs union.
A spokesman said: "We have made it clear on numerous occasions we will not contemplate a hard border on the island of Ireland".
The leaked letter, obtained by Sky News, quoted Mr Johnson telling the prime minister the return of a hard border on the island of Ireland would continue to leave 95% of traffic to pass unchecked.
Earlier, Mr Johnson was criticised after he likened the challenge of avoiding a hard border in Northern Ireland to the boundaries between different boroughs of London - implying a system similar to London's congestion charge could operate along the border.
The foreign secretary said it was a "very relevant comparison" because money was "invisibly" taken from people travelling between Camden and Westminster when he was London mayor.

Brexiteers will have some concerns with Theresa May's latest Brexit speech but "now is not the time to nitpick", Tory MP Jacob Rees-Mogg has said.
Writing in the Daily Telegraph, the prominent Eurosceptic praised the prime minister and urged the EU to respond with "wisdom and not aggression".
On Friday, Mrs May warned "no-one will get everything they want" from talks.
EU officials are now scrutinising Mrs May's speech ahead of a fresh round of negotiations next week.
Health Secretary Jeremy Hunt, told the BBC's Today programme the prime minister had shown in her speech it was possible to have "frictionless trade" with the European Union while leaving the single market and the customs union.
Speaking at London's Mansion House, Mrs May set out the UK's hopes for a future EU economic partnership, calling for "pragmatic common sense" in negotiations.
Single market access would be "less than it is now", she said, and the UK would have to pay into some EU agencies.
But she said she would not threaten to walk out of talks and in a message to the EU added: "Let's get on with it."
She said all sides of the argument had to now face "hard facts".
Mr Rees-Mogg praised her "good speech", saying it delivered on the government's promise to take the UK out of the customs union, the single market and the European Court of Justice.
"There are inevitably a few small points that will concern Leave campaigners but we must all recognise that everyone will have to give up something to get a deal, so now is not the time to nitpick," he wrote.
Mrs May's address was also cautiously welcomed by pro-European Conservatives.
Writing in the same paper, Tory Remainer Nicky Morgan said her speech was a "welcome dose of realism".
"The EU can't say they don't know what the UK wants anymore," she added.
Mr Hunt told the BBC Mrs May had successfully brought Leavers and Remainers together.
She had explained in the speech, he said, how there would be "pragmatic alignment of our regulations" that would be of the same high standards as in European countries, but on a voluntary basis.
Parliament would have the final say and the UK could always choose to have less market access.
He said he was certain the negotiations would "go to the wire".
Speaking on BBC's Newsnight the vice-president of the European Parliament, the Irish MEP Mairead McGuinness, said the speech showed the realities of Brexit "were dawning" in the UK.
She said some of Mrs May's proposals amounted to the UK wanting "to be part of the European Union" Not time to nitpick on Brexit - Rees-Moggin all but name.
Irish prime minister Leo Varadkar said he feared the constraints of leaving the customs union and the single market have not been fully recognised by Mrs May's government.
"Brexit is due to happen in a little over 12 months, so time is short," he said.
In her speech, Mrs May said she was confident remaining differences over a draft EU legal agreement could be resolved, allowing trade talks to get under way.
She said life would be different for the UK outside the EU's single market: "In certain ways, our access to each other's markets will be less than it is now."
The UK could not expect to "enjoy all the benefits without all of the obligations" of membership.
Another "hard fact" would be the UK would still continue to be affected by EU law and some decisions of the European Court of Justice - such as the ECJ rules on whether EU agreements are legal.
However, she stressed the "jurisdiction of the European Court of Justice in the UK must end".
The UK may choose to remain "in step" with EU regulations in areas like state aid and competition, in order to get "good access" to markets, she said.
The hard fact for the EU was that the UK would want its own bespoke trade deal, not an "off-the-shelf model".
BBC political correspondent Alex Forsyth said "the real test will be whether this speech was enough to convince critics that Mrs May's ambition for Brexit is credible and achievable without alienating her own MPs".

Now what? The prime minister didn't delay the vote because she wanted to.
She and her team made the decision because the option of a horrendous defeat was more grim than the humiliation of delay.
Cabinet ministers were arguing that even in these strange political times, some of the traditional political rules do still apply - don't call a vote that you can't win, and don't ask a question that you don't know the answer to.
So Theresa May made it through another day. What now though? The very act of postponing the vote, in and of itself, has been another knock to the PM's credibility.
Anyone listening to even a fraction of Monday's debate, while the PM stood there taking question after question after question, could not help but conclude that.
The questioning was not just hostile, but also incredulous. The implication - how on earth, despite all the difficulties, has Theresa May allowed it to come to this?
Tonight she is on her way to press the flesh once more with other European leaders. She'll see the normally friendly Dutch, the important Germans, and then is likely to arrive in Brussels to see the EU top brass.
It's pretty clear already though that they are not in the market for making big changes - helpful verbal clarifications, or linguistic gymnastics perhaps - but a dramatic renegotiation of the divorce deal - forget it.
What is the point then? Having one more heave might blunt at least some of the criticism. If Tory MPs have been saying she has to have another go, well, she is having another go, and some of those who were calling for that old chestnut "she must do more", may be satisfied.
But as things stand, it seems unlikely that she'll be able to return to Parliament with anything that's very different to the agreement as negotiated. One source closely involved in the talks told me "there is never going to be a withdrawal agreement without a backstop".
And it feels right now that Brexiteer and Remainer MPs are so entrenched in their positions that if there can't be a dramatic change, the numbers whenever a vote's called are very much against her.
If there is no prospect of a real change then all that's been achieved is to postpone a likely defeat.
And again that puts all the choices that will then become urgent and immediate about a real Plan B for the prime minister on hold.
Right now she is trying to maintain her case that it's her deal or no deal, or no Brexit, ruling out another referendum again, at least under her leadership, and trying again to stick to the course.
In blunt terms, though, perhaps it's as a senior Tory MP told me - the decision is just about trying to "protect her bunker".
For today, to delay was to survive. And even though Parliament, and no doubt many more members of the public, more importantly, will be aghast at yet another delay in this long drawn-out saga, there is no plan, nor anything ready or with enough agreement from enough MPs to take its place.

A giant 13-mile "lorry park" on the M20 could last for years if there is a no-deal Brexit, a council has warned.
An assessment by Dover council has expressed concern over how ports would cope with the potential situation.
The document is critical of the slow pace of work on a "temporary" scheme, named Operation Brock, and said "there does not appear to be a Plan B".
A government spokesman said it was working with "a range of partners on contingency plans".
Operation Stack is currently used on closed sections of the M20 in Kent, where lorries park while waiting to cross the English Channel when traffic is disrupted.
The new strategy, Operation Brock, plans to use a contraflow to keep the roads open when problems arise.
The Dover council report stated: "A 13-mile stretch of the coast-bound section of the M20, between junction eight near Maidstone and junction nine near Ashford, will be earmarked to hold heavy goods vehicles, in what will effectively become a giant temporary lorry park holding around 2,000 lorries.
"It is likely a permanent solution will not be in place for many years if enacted through current planning processes and procedures."
The report, released under a Freedom of Information request, said "there could be gridlock around the town" if Brexit "ends up creating regulatory and tariff barriers between the UK and the EU".
"Customs checks on imports from outside the common market can take between five minutes to 45 minutes per vehicle," it added.
"Port officials have warned that increasing the average time it takes to clear customs by as little as two minutes could lead to 17-mile traffic jams."
A government spokesman said: "As the prime minister has set out, after Brexit we will not only seek to forge new trade relationships with partners around the world but also maintain frictionless trade in goods between the UK and EU.
"While we remain confident of reaching an agreement with the EU to achieve this, it is only sensible to prepare for a range of scenarios.
"That is why the Department for Transport is working closely with a range of partners on contingency plans to ensure freight can continue to move as freely as possible between the UK and Europe."
The spokesman also insisted that work on Operation Brock would have taken place regardless of Brexit to improve contingency arrangements for a range of scenarios which could result in cross-Channel disruption.
Highways England said it recently consulted on a permanent solution and is considering responses.
In the meantime, it said Operation Brock would create up to 2,000 on-road lorry holding spaces between junctions 8 and 9 on the M20.
It said it would offer "significant benefit" compared to Operation Stack, as it would keep traffic flowing in both directions.
Deployment of the temporary solution is planned for a maximum duration of up to six months, it added.
Conservative MP for Dover Charlie Elphicke tweeted that the report underlined the case for investment in border infrastructure and roads.
He added: "The government has not done enough to prepare in the two years since the EU referendum."
Kent County Council set out its position on preparations for Brexit earlier this month.
It warned that any increased border and customs checks could lead to delays and long queues of port freight traffic.
It added: "We need to avoid the dire consequences experienced in 2015 which impacted on the Kent economy and and more broadly on the national economy."
It said there needed to be a "robust, workable implementation plan that utilises all available resources" and urged the government to consider making further resources available.
Additional powers in legislation should also be considered, it added, to ensure that all agencies have the necessary authority to take action to ensure the free-flow of traffic.
More than 10,000 freight vehicles pass through Dover on peak days as it handles one sixth of the UK's total trade in goods with a value of £119bn per year.
In 2015, queues of 4,600 lorries stretched back 30 miles and the daily cost to the UK economy was estimated at £250m.
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Almost £29m has been granted to Kent County Council for infrastructure improvements ahead of Brexit day on 29 March.
Council transport boss Mike Whiting said the grant would make Kent's roads ready for the effects of a no-deal Brexit as part of Operation Brock.
Carriageway strengthening is the priority but £5m will go on improving the disused Manston Airport.
The grant is based on 10,500 lorries using the Port of Dover daily.
Mr Whiting said: "This is very much an insurance policy, if there is no deal we want Kent to be as prepared as possible.
"It's a very tight timetable - it's an enormous task."
Heidi Skinner at the Freight Transport Association (FTA) said the funding was "welcome news".
She added: "A no-deal departure from the EU will present significant challenges, and this investment for the transport network will provide welcome protection for the vital link for the UK's trading relationships - 17% of the UK's trade goes through Dover.
"The transport infrastructure must be robust enough to meet the demands of the supply chain."
Dover Tap (Traffic Assessment Project) controls traffic bound for the port by separating lorry drivers on the A20 into a queue on the left-hand lane.
Under Operation Brock, when the volume of traffic becomes too large, a section of the M20 would become a contraflow system on one side of the carriageway. Lorries would queue on the opposite carriageway.
Road improvements will prioritise alternative routes used by HGVs when Tap and the Manston airfield options are deployed, such as the A299.
The A20 and A25 will be improved, ready for closures to the M26.
The A256 is also set to have a Tap in place, as per the Operation Brock trial run.
The £5m ring fenced for Manston will create a new access point and more hard standing areas.
A Department of Transport spokeswoman said it was working to "ensure that in the event of a no-deal, both local traffic and freight can continue to flow".
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Boris Johnson says he has been "a model of restraint" when it comes to language around the Brexit debate.
The PM was accused of dismissing abuse fears of female MPs as "humbug" during a heated Commons debate this week.
Mr Johnson said there had been a "misunderstanding" over his intention - which he apologised for.
But he claimed there was a "cloud of indignation" around the use of terms like "surrender" to distract from MPs' desire to frustrate Brexit.
Labour's Angela Rayner said Mr Johnson should be "absolutely, utterly ashamed of himself".
The shadow education secretary said the PM had "a direct strategy to divide our country", which she called "really damaging", but added that MPs on both sides of the Commons needed to "dial down that language and act responsibly".
Mr Johnson spoke to the BBC's Andrew Marr ahead of the start of the Conservative Party conference in Manchester.
The annual gathering follows a turbulent week for the PM - facing stormy scenes in Westminster after a ruling by the Supreme Court that his suspension of Parliament was unlawful.
Rows later broke out over Mr Johnson's Commons conduct - and that of his Attorney General Geoffrey Cox - and questions are also continuing over his links with US businesswoman Jennifer Arcuri.
But he will use the conference to try to focus on delivering Brexit and making funding promises for public services.
On the opening day, ministers have promised to spend billions on hospital projects across England in the next decade.
But opposition MPs back in London could stage a no-confidence vote in the government some time this week.
No 10 failed to secure a recess for the conference, meaning Tory MPs could face travelling between Manchester and Westminster for crucial votes while it takes place.
Labour leader Jeremy Corbyn is also expected to bring opposition leaders together at a meeting on Monday to plan their next steps to avert a no-deal Brexit.
Mr Corbyn has said he would be ready to become a caretaker PM if Mr Johnson was forced from No 10.
Greater Manchester Police said they were expecting tens of thousands of protesters to attend two rallies on Sunday against Brexit and austerity.
A small number of demonstrators also gathered outside the conference venue on Saturday night when Mr Johnson arrived with his partner, Carrie Symonds.
Speaking to Andrew Marr, Mr Johnson defended his decision to repeatedly refer to the Benn Act - which is designed to force the PM to seek an extension rather than lead the country into a no-deal Brexit - as "the surrender bill".
Last week, Labour's Paula Sheriff said threats made to her and other MPs often quoted his "dangerous" language of "surrender" and "betrayal".
She also referred to the murder of Labour MP Jo Cox in 2016, but Mr Johnson replied: "I've never heard such humbug in all my life."
The PM said any such threats were "deplorable" but he did not regret "using the word surrender to describe the surrender act".
"Military metaphors are old, standard, Parliamentary terms," he continued.
"I think everybody should calm down," he said, but asked whether that included him, he added: "I think I've been the model of restraint."
The Jo Cox Foundation - set up in memory of the murdered MP - has called on all political parties to agree to a code of conduct to help protect MPs.
Cardinal Vincent Nichols, the UK's most senior Catholic clergyman, warned some of the language being used could encourage violent extremists.
He told BBC Radio 4's Sunday programme political leaders had a particular responsibility to be respectful in public discourse.
Commons Speaker John Bercow will hold an emergency meeting on Monday with party leaders over the use of "inflammatory language" in Parliament.
When Mr Johnson talks about the "surrender bill", he is referring to the European Union (Withdrawal) (No. 2) Act, also known as the Benn Act after Labour MP Hilary Benn, who introduced the legislation to the Commons.
The act - which became law earlier this month - stipulates the prime minister will have until 19 October to either pass a deal in Parliament or get MPs to approve a no-deal Brexit.
Once this deadline has passed, he will have to request an extension to the UK's departure date to 31 January 2020 from the EU.
If the EU responds by proposing a different date, the PM will have two days to accept that proposal. But during this two-day period, MPs - not the government - will have the opportunity to reject the EU's date.
On Brexit, Mr Johnson said he still thought there was a "good chance" of getting a deal with the EU and the government was "working incredibly hard".
Success depended on "the common sense of our EU partners", he argued, but said talks were "not being helped" by the Benn Act.
"If they suspect or think there is a realistic chance the UK can be kept in [the EU], that clearly takes away a lot of our negotiating freedom."
The PM insisted that "of course" the UK could still leave without a deal on 31 October despite the act - although he would not be drawn on how that could happen.
Mr Johnson also ruled out bringing back the withdrawal agreement negotiated between Theresa May and the EU, and dismissed suggestions he could resign rather than ask for an extension.
There's no sign whatsoever of Boris Johnson retreating from his strategy - the approach he's taken since he moved into Downing Street. And as far as many people in his team, and the wider party, are concerned their only real path to success is to stick to trying get Brexit done by 31 October.
The tricky thing is, though, that it looks very unlikely - maybe even impossible. And there are plenty of people in Westminster who say they're prepared to do everything necessary to stop Mr Johnson doing what he wants to do - taking the UK out without a deal on that date if one isn't agreed.
Party conferences are pretty much always like being in a parallel universe, but this week is going to be something else.
Parliament will still be sitting while the Conservatives are gathering here in Manchester and it could certainly be a surreal and bumpy few days.
Meanwhile, the Sunday Times has fresh allegations about the American businesswoman at the centre of claims about her links to the prime minister.
The paper claims Jennifer Arcuri told four friends that she had an affair with Mr Johnson while he was mayor of London.
On Friday, the Greater London Authority (GLA) referred Mr Johnson to the police watchdog over allegations Ms Arcuri, a US technology entrepreneur, received favourable treatment because of her friendship with him.
She joined trade missions led by Mr Johnson while he was mayor and her company received several thousand pounds in sponsorship grants.
The Independent Office for Police Conduct will now consider whether there are grounds to investigate the prime minister for the criminal offence of misconduct in public office.
But Mr Johnson insisted he had "no interest to declare" when pressed by Andrew Marr over whether he made his personal relationship with her known at the time.
"Everything was was done with full propriety," he added.
The PM also appeared to claim the story was politically motivated, saying someone in his position "expects a lot of shot and shell".
As well as promises on hospitals, the government is also announcing a new approach to NHS mental health treatment to be trialled in 12 areas of England - with housing and job support alongside psychological help.
Chancellor Sajid Javid is expected to speak on Monday and Home Secretary Priti Patel - talking about tackling crime - on Tuesday.
Animal welfare policies, environmental plans - including a proposed £1bn fund to boost the electric motor industry and a pledge to plant one million new trees - are on the agenda.

Theresa May will have to "listen to other parties" as she reviews her Brexit strategy in the wake of the election, David Cameron has said.
The Financial Times reported the former PM saying there would be pressure for a "softer" exit from the EU after his party did not win an election majority.
Speaking in Poland, he said his successor should "consult more widely" both inside Parliament and beyond.
It comes as Mrs May tries to seal a deal with the DUP to govern.
Downing Street has so far rebuffed calls for major changes to its Brexit blueprint and ruled out the prospect of cross-party talks ahead of the start of official negotiations with the EU next week.
Speaking in Paris after meeting French President Emmanuel Macron, Mrs May said there was a "unity of purpose" to get on with the process, reiterating that she wanted to maintain a "close relationship" with the EU.
She is currently trying to negotiate the terms of a deal with the Democratic Unionists that will give her a majority in the Commons and enable her to pass a Queen's Speech - in which Brexit legislation will figure prominently.
The Conservatives are having to seek a guarantee of support from the Northern Ireland party after failing to win enough seats to govern on their own.
The two sides will continue what sources have described as "positive" talks on Wednesday, with the expectation that an agreement on a so-called "confidence and supply agreement" is imminent.
Amid calls from opposition MPs for a rethink on Brexit, ministers have pointed out that the Conservative and Labour leaderships both agree that the UK needs to leave the single market to end free movement.
But the PM is facing growing calls for other options to be put back on the agenda, including potentially remaining in the customs union, accepting a transitional role for the European Court of Justice, ruling out leaving without a deal and seeking some concessions on immigration.
According to the Financial Times, Mr Cameron, who campaigned for a Remain vote and quit after losing the referendum, told a business conference in Lodz the Tories' failure to win a majority had changed the outlook.
"It's going to be difficult, there's no doubt about that, but perhaps an opportunity to consult more widely with the other parties on how best we can achieve it," he said.
"Over Brexit, she is going to have to talk more widely, listen to other parties."
He said there would be pressure from Ruth Davidson's new group of Scottish Conservative MPs - 13 of whom were elected to Parliament - to revisit aspects of Brexit to place greater emphasis on economic considerations.
"There's no doubt that there is a new player on the stage. Scotland voted against Brexit. I think most of the Scottish Conservatives will want to see perhaps some changes with the policy going forward."
Leading Brexiteers in the government have insisted that there will no U-turn on the single market and they remain hopeful of getting a deal that will secure the maximum market access.
Steve Baker, a Eurosceptic backbencher who has been made a minister in the Brexit department, said his aim was as "softest exit consistent with actually leaving and controlling laws, money, borders and trade".
The Times is reporting that Chancellor Philip Hammond is pushing for the UK to remain in the customs union to minimise the impact of withdrawal on trade.
Labour MP Hilary Benn, who is seeking re-election as chair of the Brexit select committee, told BBC's Newsnight this was "the first and clearest sensible step to take" to support business.
Speaking on Tuesday, French President Emmanuel Macron said the possibility of the UK remaining in the EU remained an option until Brexit negotiations have concluded.
Both the Conservatives and Labour have categorically ruled this option out.
Speaking on BBC Radio 4's Today programme, the former Chancellor Kenneth Clarke said that the French President was "wrong" and that the UK was now destined to leave the EU.
Former UKIP leader Nigel Farage said the British people had expressed a clear view last year that uncontrolled immigration from the EU must come to an end.
He tweeted: "Westminster politicians are positioning for a 'soft Brexit'. That would mean the continuation of open borders."
But Lib Dem leader Tim Farron, whose party has proposed a cross party joint cabinet committee on Brexit, said Mr Macron's comments "show there is a chance for the British people to reject a bad Brexit deal and stay in the EU if that is what they decide".
As the PM fights to regain the initiative after her election setback, a former colleague of hers has warned the Conservatives are on "death row" and face "years of opposition" if they don't broaden their appeal.
In an article for the Sun, Robert Halfon - who was sacked as a skills minister on Tuesday - said the party's manifesto had been "devoid of ideas" to help working families burdened by years of austerity.
Among other ideas, he said the party should change its name to the Conservative Workers Party and develop a campaigning arm along the lines of Momentum or Vote Leave.

The government has published its blueprint for UK relations with the EU, with Theresa May saying it "delivers on the Brexit people voted for".
The long-awaited White Paper is aimed at ensuring trade co-operation, with no hard border for Northern Ireland, and global trade deals for the UK.
But Tory Brexiteer Jacob Rees-Mogg said it was a "bad deal for Britain".
And US President Donald Trump said the proposals would "probably kill" a trade deal with his country.
The White Paper fleshes out the Chequers agreement that sparked the resignations of Boris Johnson and David Davis.
The UK is hoping the EU will back the proposals so an exit deal can be struck by the autumn, ahead of the UK's official departure from the EU in March.
New Brexit Secretary Dominic Raab, formerly a leading figure in the Leave campaign, said the White Paper was a blueprint for a "principled, pragmatic and ambitious future partnership between the UK and the EU".
"Now, it is time for the EU to respond in kind, we approach these negotiations with a spirit of pragmatism, compromise and, indeed, friendship, I hope. I trust that the EU will engage with our proposals in the same spirit," he told MPs.
Asked in Brussels about US President Donald Trump's claim that the British people were not getting the Brexit they voted for, Mrs May said: "We have come to an agreement on the proposal we are putting to the European Union which absolutely delivers on the Brexit we voted for.
 "They voted for us to take back control of our money, our law and our borders. That is exactly what we will do."
Leading Tory rebel Jacob Rees-Mogg said: "There are very few signs of the prime minister's famous red lines.
"It is a pale imitation of the paper prepared by David Davis, a bad deal for Britain. It is not something I would vote for, nor is it what the British people voted for."
Former Conservative leader Iain Duncan Smith told ministers he had "deep misgivings" about the White Paper.
"I voted to leave not to half leave," he said.
The EU's chief negotiator Michel Barnier said he would analyse the details with the European Parliament and member states and was "looking forward" to negotiations with the UK next week.
Guy Verhofstadt, the European Parliament's chief Brexit negotiator, said he welcomed the UK's proposal for a future "association agreement" with the EU - an idea he has been promoting for some time.
He added: "We will analyse the White Paper in light of our priorities: citizens' rights, an operational backstop for Ireland and a deep economic relationship based on the integrity of the union and internal market."
CBI director general Carolyn Fairbairn said "many of the intentions are reassuring" but "there are gaps in these proposals and more detail is needed on EU VAT, some services sectors and the new customs system".
"It's vitally important UK negotiators get their heads down and work with businesses to grapple with the detail and get it right," she added.
Federation of Small Businesses national chairman Mike Cherry said: "With just 37 weeks before we leave the European Union, we need to see tangible and comprehensive details on these proposals and how they will impact small businesses."
Former chief executive of UK Trade and Investment Sir Andrew Cahn told the BBC the City would be hurt by the lack of a deal on financial services, stating: "It means the City is going to have to change. It's going to have to change quite radically.
 "We will clearly lose business, some business, to Europe. But I think the City will adjust and find a way forward."
Len McCluskey, general secretary of the Unite union, said the White Paper was "a fudge, which pleases no one and is politically undeliverable".
Some MPs are already calling it a "hard Brexit" for services, even though, overall, the deal suggests much closer ties to the rest of the EU than many Brexiteers had desired.
For the prime minister and the government it's an important step in spelling out the reality of leaving - more political freedom does, this paper suggests, come at a cost.
And it is a compromise, which by its very nature, can't please everyone.
Read Laura' full blog
Dominic Raab's first speech as Brexit Secretary was halted shortly after it had begun, as MPs shouted that they had not seen the White Paper.
Mr Raab said the paper would be made available "as soon as is practicably possible".
Former Labour minister Ben Bradshaw could be seen throwing copies of the document to MPs on his own bench.
At which point, Speaker Bercow decided to suspend sitting for five minutes to give MPs time to read it.
Labour's Shadow Brexit Secretary Sir Keir Starmer said Mr Raab had "not got off to a very good start", adding: "The utter shambles of the last 20 minutes that led to the suspension of the House during a statement is clear evidence of why the government is in such a mess."
Sir Keir told MPs: "Across business communities, among trade unions and I genuinely believe across this House there is growing unity that the UK should remain economically close to the EU - and that means negotiating a comprehensive customs union with the EU27, and a single market deal with the right balance of rights and obligations tailored to the UK."
Labour MP Chuka Umunna, who, is campaigning for a referendum on the final EU deal - in contrast to his party's leadership - said the White Paper was "totally unworkable and a bad deal for Britain".
It sets out four areas of future co-operation:
The document repeatedly acknowledges that the UK will have more barriers to trade in some areas than there are today.
It sets out plans for what is described as an "association agreement",  with "joint institutional arrangements" between the EU and the UK.
The paper says that the UK will end the free of movement of people, but suggests EU citizens would be allowed to come to the UK without visas to do "paid work in limited and clearly defined circumstances".
No more detail of this was given by officials on Thursday morning, says BBC Political Editor Laura Kuenssberg, but they rejected suggestions that it could open the door to freedom of movement for workers.
The paper also suggests that there could be "reciprocal" arrangements with the EU for the payment of certain limited benefits or social security.
Again, officials denied that this would mean widespread access to the UK benefits systems for EU nationals after Brexit, says our correspondent.
Both of these elements will be subject to the upcoming negotiation.
As the Chequers agreement set out on Friday, the UK would accept a "common rule book" for trade in goods, but not services.
The government's aim is to preserve free trade in that part of the economy and avoid a hard border in Northern Ireland.
The White Paper also proposes the setting up of a "governing body", made up of UK and EU ministers, and then a "joint committee" of officials, which would enforce the agreement.
Officially, the jurisdiction of the European Court of Justice in the UK would come to an end.
British citizens or businesses would no longer be able to take issues to the European Court of Justice - and the court would no longer be able to make judgements on UK cases.
But the White Paper accepts that the European Court of Justice will be "the interpreter of EU rules" that the UK has agreed to follow in the "common rule book".
The White Paper also sets out in more detail the government's proposed customs system, the Facilitated Customs Arrangement for goods and agri-foods, where it plans for the UK to collect some EU tariffs.
The paper confirms that the UK will not seek "mutual recognition" in the services sector, which makes up the vast majority of the economy.
A leaked version of an earlier draft of the White Paper, put together by the Brexit department under David Davis, envisaged that there would be such an arrangement.
Some MPs have already expressed concern that by pursuing a looser arrangement with the rest of the EU on services it means a "hard Brexit" for the majority of the economy while the goods sector stays closely tied to the single market, although technically not inside it.

Jo Johnson, the younger brother of Prime Minister Boris Johnson, is resigning as an MP and minister, saying he is "torn between family loyalty and the national interest".
The business minister and Tory MP for Orpington, south-east London, cited an "unresolvable tension" in his role.
BBC political editor Laura Kuenssberg said it was "unbelievable timing".
Mr Johnson voted Remain in the 2016 EU membership referendum, while his brother co-led the Leave campaign.
Mr Johnson's resignation follows the removal of the Tory whip from 21 MPs this week for supporting moves to prevent a no-deal Brexit.
Our political editor tweeted that Mr Johnson was "understood to be upset about the purge of colleagues" and that the brothers were "in very different places" on Brexit.
Speaking at an event in West Yorkshire, Boris Johnson called his brother a "fantastic guy" and a "brilliant minister".
But he added that he had a "different approach to me about the European Union".
Jo Johnson resigned as a minister last year in protest at Theresa May's Brexit deal with the EU. But he re-entered government during the summer, after Conservative Party members elected his brother as leader.
Jo Johnson's resignation also comes as the government announced it would give MPs another chance to vote for an early election on Monday.
The fresh vote on an early election is scheduled just before Parliament is due to be prorogued - or suspended - from next week until 14 October.
A Downing Street spokesman said: "The PM, as both a politician and brother, understands this will not have been an easy matter for Jo. The constituents of Orpington could not have asked for a better representative."
Former cabinet minister David Gauke, one of the MPs who lost the Conservative whip, tweeted: "Lots of MPs have had to wrestle with conflicting loyalties in recent weeks. None more so than Jo. This is a big loss to Parliament, the government and the Conservative Party."
Labour's shadow education secretary Angela Rayner said: "Boris Johnson poses such a threat that even his own brother doesn't trust him."
Brexit Party leader Nigel Farage said the resignation showed the "centre of gravity in the Conservative party is shifting rapidly".
But, in a tweet, Rachel Johnson, the Remain-supporting sister of Boris and Jo Johnson, said "the family avoids the topic of Brexit, especially at meals, as we don't want to gang up on the PM".
Jo Johnson appeared at several of his brother's campaign events during the Conservative Party leadership contest.
In 2013, Boris Johnson predicted Jo Johnson was himself "very likely" to become prime minister, telling The Australian newspaper: "He'd be brilliant."
At the last general election, Jo Johnson held the Orpington seat by a 19,461 majority.
He is expected to stand down at the next general election, rather than leaving Parliament immediately and prompting a by-election.
Northern Ireland Minister Nick Hurd also announced that he would not stand as an MP in the next election.
He said politics had become "dominated by the ongoing division over Brexit". He also said his life had been "changed profoundly by the birth of my two youngest children".

Boris Johnson has said he would "rather be dead in a ditch" than ask the EU to delay Brexit beyond 31 October.
But the PM declined to say if he would resign if a postponement - which he has repeatedly ruled out - had to happen.
Mr Johnson has said he would be prepared to leave the EU without a deal, but Labour says stopping a no-deal Brexit is its priority.
The prime minister's younger brother, Jo Johnson, announced earlier that he was standing down as a minister and MP.
Speaking in West Yorkshire, Boris Johnson said Jo Johnson, who backed Remain in the 2016 referendum, was a "fantastic guy" but they had had "differences" over the EU.
Announcing his resignation earlier in the day, the MP for Orpington, south-east London, said he had been "torn between family loyalty and the national interest".
During his speech at a police training centre in Wakefield, the prime minister reiterated his call for an election, which he wants to take place on 15 October.
He argued it was "the only way to get this thing [Brexit] moving".
"We either go forward with our plan to get a deal, take the country out on 31 October which we can or else somebody else should be allowed to see if they can keep us in beyond 31 October," Mr Johnson said.
He told the audience he hated "banging on about Brexit" but accused MPs of having "torpedoed" the UK's negotiating position with the EU by voting for a Labour-backed bill designed to block a no-deal exit on 31 October.
The legislation would force the prime minister to delay Brexit until January 2020, unless MPs approve either a new deal or a no-deal exit by 19 October.
However, Labour leader Jeremy Corbyn has accused the PM of having "no plan to get a new deal".
Liberal Democrat leader Jo Swinson said the prime minister's comments were "deeply troubling", and the PM would soon be legally forced to seek a Brexit delay.
The House of Commons rejected Mr Johnson's plan for a snap election in a vote on Wednesday.
But the government has announced that MPs will get another chance to back this plan next Monday.
The fresh vote on an early election is scheduled just before Parliament is due to be prorogued - or suspended - from next week until 14 October.
Opposition parties are holding talks about how to respond to the prime minister's call for a mid-October election, amid concern over whether it should be delayed until after an extension has been agreed to prevent a no-deal Brexit on 31 October.
Meanwhile, Brexit Party leader Nigel Farage has warned Mr Johnson that he "cannot win an election, whenever it comes, if the Brexit Party stands against him".
However, if they were to make a pact during a general election "with a clear policy, we'd be unstoppable", he told the BBC.
Yvette Cooper, Labour MP and chairwoman of the Home Affairs Committee, criticised the PM for using police officers as a backdrop to his speech.
"This is an abuse of power by Boris Johnson, making so many police stop their training and work to be part of his political stunt," she said.
West Yorkshire Police chief constable John Robins said he was pleased the force was "chosen as the focal point of the national recruitment campaign" and welcomed Mr Johnson's pledge to increase police funding.
One of the student officers standing behind the prime minister appeared to become unwell during his speech and question-and-answer session.
Twenty minutes in, she sat down with her head bowed, at which point Mr Johnson apologised and said: "That is the signal for me to actively wind up."

"I'm not sure that we can look the nation in the eye and say that was a good day."
That's how a Conservative MP has described the torrid scenes in the Commons in the last 24 hours.
Did the prime minister alight on the frustration of many members of the public who may feel that Parliament has simply failed to keep the promise it made to carry out their wishes expressed in the referendum - yes.
Did Boris Johnson confirm his determination to push on with keeping the vow he made to take the UK out of the EU at the end of next month - yes.
But did the scenes in Parliament suggest that his determination tips into a potentially destructive disdain - yes, to that too.
Boris Johnson's decision has long been clear - he would seek to use everything within his grasp to stick to the Brexit deadline he set.
If that meant knocking some plaster off the ceiling, rattling some cages in a fractious and perhaps failing Parliament, so be it.
It is not as if, his allies argue, this Parliament has any measurable or reliable level of support from the public at large.
Their calculation is that swathes of voters, whatever they chose in 2016, have simply had enough of MPs' inability to decide.
After three years of political strife, following a clear, if narrow, result in the referendum, it is of course the case there are plenty of voters who blame politicians collectively for the mess we all witness.
So, as Boris Johnson and Number 10 have been obviously doing since taking office, Parliament's failure is a political target.
Whatever you think of that interpretation, for most of tonight's debate, this still relatively new prime minister was combatively, precisely on his chosen message.
Accordingly, he decided to stir his benches with rancour rather than make any effort to soothe nerves on all sides, let alone show remorse for his defeat.
Yet, even for a politician whose tactics include provocation, it is worth asking if he went too far.
Outrage is a common currency these days, but MPs' jaws dropped as he ramped up the rhetoric in responses to questions - suggesting first that it was "humbug" for a Labour MP to demand he temper his language, to try to protect MPs' safety.
Then, he went on to say that the appropriate legacy for the MP who was murdered during the referendum, Jo Cox, was for MPs to complete the Brexit process.
No surprise that Labour MPs howled in protest, some left the Commons in disbelief.
And there may be few Tory MPs willing, as the day goes on, to defend how far he went.
The cabinet minister Nicky Morgan too, who expressed her concern on Twitter, is not the only Tory MP who was unhappy at what happened.
There is pushback from the other side, of course.
One minister said, in sadness rather than anger, that Labour was deploying "double standards" after several years of calling the Leave side "racists and criminals".
There should be no surprise there was reaction like this.
Others in government believe that we are seeing the raw conflict that had to play out, the fight Theresa May delayed but couldn't make disappear.
And, rightly or wrongly, politics moves so fast in this era, it's impossible to tell if tonight's cries of horror in SW1 will fade fast to nothing, or indeed, how far they have reached beyond Westminster's bubble.
As ever, forgive but note the caveat that the situation is ever shifting and could transform within days.
For now, though, it is almost impossible to imagine this group of politicians being able to agree on much.
The attitude Boris Johnson displayed has made the divisions more stark.
And in the unlikely event this prime minister strikes a deal, it seems harder in this moment to imagine that he'd have more than a handful of Labour MPs on side.
And if you were hoping that, eventually, our politicians were moving towards a way of working together, Parliament tonight was a place of fear and loathing, not a place of debate and discussion that could provide a solution for us all.

The prime minister's decision to suspend Parliament has prompted an angry backlash from MPs and opponents of a no-deal Brexit.
It sparked protests across the country, a legal challenge and a petition with more than a million signatures.
The government said the five-week suspension in September and October will still allow time to debate Brexit.
Commons leader Jacob Rees-Mogg said the outrage was "phoney", and that the move was "constitutional and proper".
"The candyfloss of outrage we've had over the last 24 hours, which I think is almost entirely confected, is from people who never wanted to leave the European Union," he told BBC Radio 4's Today programme.
"This is the greatest period of anger for them, or of confected anger, because after 31 October we will have left," he added.
Conservative peer Lord Young of Cookham has resigned from his role as government whip in the House of Lords in protest at suspension, known as prorogation.
In his resignation letter, he said the timing and length of the suspension "risks undermining the fundamental role of Parliament at a critical time in our history".
Meanwhile, Ruth Davidson has also confirmed she is quitting as leader of the Scottish Conservatives after eight years in the job.
In a statement she said "much had changed" both politically and personally during that time, which had led her to tender her resignation.
Ms Davidson - who backed Remain in the 2016 EU referendum - added she had never sought to hide the "conflict" she felt over Brexit, and urged Mr Johnson to get a Brexit deal.
On Wednesday, Prime Minister Boris Johnson said a Queen's Speech would take place after the suspension, on 14 October, to outline his "very exciting agenda".
Cabinet minister Michael Gove said the suspension, which was approved by the Queen on Wednesday, was "certainly not" a political move to obstruct opposition to the UK leaving the EU without a deal.
Mr Rees-Mogg said this parliamentary session had been one of the longest in almost 400 years, so it was right to suspend it and start a new session.
MPs voted by 498 votes to 114 to leave the EU by triggering Article 50 in February 2017. That began the countdown to the UK's departure, which is now just over two months away.
But Ruth Fox - director of parliamentary experts the Hansard Society - said this prorogation was "significantly longer than we would normally have" for the purpose of starting a new parliamentary session.
Ms Fox said that depending on the day the suspension began - and on whether MPs would have voted to have a party conference recess at all - the prorogation could "potentially halve" the number of days MPs have to scrutinise the government's Brexit position.
The prime minister says he wants to leave the EU at the end of October with a deal, but is willing to leave without one rather than miss the deadline.
On Wednesday, Labour leader Jeremy Corbyn described Mr Johnson's move as "a smash-and-grab on our democracy" in order to force through no-deal by leaving MPs without enough time to pass laws in Parliament.
Anti-Brexit campaigner Gina Miller - who previously won a legal battle against ministers over Article 50 - has made a judicial review application to the courts about Mr Johnson's decision.
Shadow international trade secretary Barry Gardiner said Labour would be looking at calling for an emergency debate.
"We will seek to try and put through the appropriate legislation in this constrained timetable that the government has now put before us," he said.
Conservative MP Ken Clarke called Mr Johnson's move "outrageous conduct", while David Lidington, who served as Cabinet Office Minister under former PM Theresa May, said it would limit the ability of MPs to hold the government to account.
The leader of the Liberal Democrats, Jo Swinson, told BBC Newsnight that the prime minister "is prepared to deny people their voice through their representatives in Parliament to force through a no-deal Brexit".
Others, though, have defended the plan.
Former Cabinet Office minster Damian Green tweeted that there was time to ratify a deal with the EU before 31 October, saying: "This is all normal Parliamentary democracy, which shows that the talk of coups and dictatorship is massively overblown."
The leader of the DUP, Arlene Foster, also welcomed the decision, but said the terms of her party's agreement with the Conservatives would now be reviewed.
On Wednesday evening, protesters gathered in Westminster chanting "stop the coup", carrying anti-Brexit placards and EU flags.
The demonstration - organised hours beforehand - started outside Parliament before spreading towards Downing Street.
Meanwhile, an e-petition on the government's website demanding Parliament not be suspended reached more than a million signatures in less than a day.
A snap YouGov poll conducted on Wednesday suggests 47% of British adults thought the decision was unacceptable, with 27% saying it was acceptable and 27% unsure.
But it suggested the suspension was supported by 51% of people who voted Leave, with 52% of Conservative voters also approving of the move.
Richard Miles was one of a number of voters in Harborne, Birmingham, who said they supported the prime minister's decision.
He told the BBC: "[MPs] just want to undermine the democratic vote that has already taken place [the referendum]. It's very very dangerous what they're doing."
Three Conservative members of the Queen's Privy Council took the request to suspend Parliament to the monarch's Scottish residence in Balmoral on Wednesday morning on behalf of the prime minister.
It has now been approved, allowing the government to suspend Parliament no earlier than Monday 9 September and no later than Thursday 12 September, until Monday 14 October.
Mr Johnson wrote to MPs to outline his plan, calling on Parliament to show "unity and resolve" in the run up to 31 October so the government "stands a chance of securing a new deal" with the EU.
Scotland's top civil court is considering a challenge to the suspension of Parliament, led by the SNP's justice spokeswoman, Joanna Cherry.
It is not possible to mount a legal challenge to the Queen's exercise of her personal prerogative powers.
Campaigner Gina Miller has made an application to the courts, seeking permission for a judicial review of the PM's decision.
She told the BBC the case would question Mr Johnson's advice to the Queen and challenge whether he was using his powers to suspend Parliament and call a Queen's speech legally.
Former Prime Minister John Major had previously threatened to go to the courts to stop Mr Johnson if he shut down Parliament to deliver a no-deal Brexit.
After the announcement, Sir John said he had "no doubt" Mr Johnson's motive was to "bypass a sovereign Parliament that opposes his policy on Brexit", and he would continue to seek legal advice.
However you dress this up, with pinstripe politesse and all the eloquence of the new leader of the House of Commons, welcome to the new reality.
There is a band of Brexiteers at the top of government who are committed to sticking to their Brexit deadline whatever it takes - even if it means tearing up conventions that many other people see as valuable.
We are going to see others spluttering in their wake: "They wouldn't dare do that, would they?"
But, oh yes, they would.
It is worth saying some of those who are most outraged have been pretty good at bending the rules themselves.
But this move by the government does not go without considerable risk - and it hastens the very likely possibility of an election.
As one member of the cabinet said to me on Wednesday, everybody knows it is coming, it is just a question of when.
But the real question, as ever for the broader Brexit process, is what will be left of our political conventions when one day, eventually, this is all over.
Shutting down Parliament - known as prorogation - happens after the prime minister advises the Queen to do it.
BBC royal correspondent Jonny Dymond said it was established precedent to prorogue Parliament before a Queen's Speech. But the suspension is generally shorter and rarely takes place at such a constitutionally charged time.
Parliament is normally suspended - or prorogued - for a short period before a new parliamentary session begins, during which time no debates and votes are held.
It is different to "dissolving" Parliament, where all MPs give up their seats to campaign in a general election.
If this prorogation happens as expected, it will see Parliament closed for 23 working days.
MPs cannot block prorogation.
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Parliament will be suspended just days after MPs return to work in September - and only a few weeks before the Brexit deadline.
Boris Johnson said a Queen's Speech would take place after the suspension, on 14 October, to outline his "very exciting agenda".
But it means the time MPs have to pass laws to stop a no-deal Brexit on 31 October would be cut.
House of Commons Speaker John Bercow said it was a "constitutional outrage".
The Speaker, who does not traditionally comment on political announcements, continued: "However it is dressed up, it is blindingly obvious that the purpose of [suspending Parliament] now would be to stop [MPs] debating Brexit and performing its duty in shaping a course for the country."
Labour leader Jeremy Corbyn said: "Suspending Parliament is not acceptable, it is not on. What the prime minister is doing is a smash and grab on our democracy to force through a no deal," he said.
He said when MPs return to the Commons next Tuesday, "the first thing we'll do is attempt legislation to prevent what [the PM] is doing", followed by a vote of no confidence "at some point".
Hundreds of protesters gathered in Westminster on Wednesday evening chanting "stop the coup" and carrying anti-Brexit placards and EU flags.
The demonstration, which was organised hours beforehand, started outside Parliament before spreading towards Downing Street.
At the scene, BBC correspondent Richard Galpin described the atmosphere as peaceful and lively.
He said "good-natured" protesters on College Green broke through barriers which had been in place to separate live TV crews from members of the public - before traffic on Parliament Square was blocked by some people who sat down in the road.
Several protesters he spoke to indicated this was only the beginning of the disruption, with more demonstrations being organised for the weekend.
Three Conservative members of the Queen's Privy Council took the request to suspend Parliament to the monarch's Scottish residence in Balmoral on Wednesday morning on behalf of the prime minister.
It has now been approved, allowing the government to suspend Parliament no earlier than Monday 9 September and no later than Thursday 12 September, until Monday 14 October.
Leader of the House Jacob Rees-Mogg, who was at the meeting with the Queen, said the move was a "completely proper constitutional procedure."
Earlier, Mr Johnson said suggestions the suspension was motivated by a desire to force through a no deal were "completely untrue".
He said he did not want to wait until after Brexit "before getting on with our plans to take this country forward", and insisted there would still be "ample time" for MPs to debate the UK's departure.
"We need new legislation. We've got to be bringing forward new and important bills and that's why we are going to have a Queen's Speech," Mr Johnson added.
Shutting down Parliament - known as prorogation - happens after the prime minister advises the Queen to do it.
The decision to do it now is highly controversial because opponents say it would stop MPs being able to play their full democratic part in the Brexit process.
A number of high profile figures, including former Prime Minister John Major, have threatened to go to the courts to stop it, and a legal challenge led by the SNP's justice spokeswoman, Joanna Cherry, is already working its way through the Scottish courts.
After the announcement, Sir John said he had "no doubt" Mr Johnson's motive was to "bypass a sovereign Parliament that opposes his policy on Brexit", and he would continue to seek legal advice.
BBC royal correspondent Jonny Dymond said it was established precedent to prorogue Parliament before a Queen's Speech, albeit generally more briefly, and rarely, if ever, at such a constitutionally charged time.
He said it was "Her Majesty's Government" in name only and it was her role to take the advice of her ministers, so she would prorogue Parliament if asked to.
It is not possible to mount a legal challenge to the Queen's exercise of her personal prerogative powers.
But anti-Brexit campaigner Gina Miller - who previously won a legal battle against ministers over Article 50 - has made a judicial review application to the courts about Mr Johnson's decision.
She told the BBC's Clive Coleman: "If the intention of using this prorogation - and the effect - is that it limits Parliament sovereignty, then we believe that's illegal and unconstitutional."
This has been an extraordinarily long Parliamentary session, and governments have the right to shut up shop and return to announce their proposals in a new one, with all the golden carriages, fancy Westminster costumes, banging of doors and splendour that goes with it.
But that new timetable means Parliament will be suspended for longer than had been expected - it's only a matter of days, but those are days that might matter enormously.
Boris Johnson secured his place in No 10 by promising he'd do whatever it takes to leave the EU at Halloween, so this decisive and intensely risky plan will satisfy many of those who backed him.
But some others in his government are worried - moving now, even with the accompanying controversy, he sets the stage and the terms for an epic fight with MPs on all sides.
The PM says he wants to leave the EU on 31 October with a deal, but it is "do or die" and he is willing to leave without one rather than miss the deadline.
That position has prompted a number of opposition MPs to come together to try to block a possible no deal, and on Tuesday they announced that they intended to use parliamentary process to do so.
But with Parliament set to be suspended, opponents have only a few days next week to push for their changes.
Senior Tory backbencher and former attorney general Dominic Grieve said the move by Mr Johnson could lead to a vote of no confidence - something opposition parties have left on the table as another option to stop no deal.
"There is plenty of time to do that if necessary [and] I will certainly vote to bring down a Conservative government that persists in a course of action which is so unconstitutional," he said.
Scotland's First Minister Nicola Sturgeon said MPs must come together to stop the plan next week, or "today will go down in history as a dark one indeed for UK democracy".
Mr Johnson has written to MPs to outline his plan, adding: "There will be a significant Brexit legislative programme to get through but that should be no excuse for a lack of ambition!"
He mentioned the NHS, tackling crime, infrastructure investment and the cost of living as important issues.
He also called on Parliament to show "unity and resolve" in the run up to the 31 October so the government "stands a chance of securing a new deal" with the EU.
But a senior EU source told the BBC's Brussels correspondent Adam Fleming the bloc's position was clear and was not contingent on the machinations of the UK Parliament.
There has been considerable anger at Mr Johnson's move from across the political spectrum.
Former Tory Chancellor Philip Hammond called it "profoundly undemocratic".
The leader of the Liberal Democrats, Jo Swinson, said it was a "dangerous and unacceptable course of action".
"He knows the people would not choose a no deal and that elected representatives wouldn't allow it. He is trying to stifle their voices," she said.
The leader of the SNP in Westminster, Ian Blackford, accused Mr Johnson of "acting like a dictator", while First Minister of Wales Mark Drakeford said he wanted to "close the doors" on democracy.
Others, though, have defended the plan.
Conservative Party Chairman James Cleverly said setting out a legislative programme via a Queen's Speech was what "all new governments do".
US President Donald Trump tweeted his support for Mr Johnson, saying it "would be very hard" for Mr Corbyn to seek a no-confidence vote against the PM, "especially in light of the fact that Boris is exactly what the UK has been looking for".
Brexit Party MEP Alex Phillips said MPs "only had themselves to blame" for the move.
She told BBC News: "They have made themselves the obstacle in front of delivering the referendum result. Boris Johnson is saying he now needs to remove that obstacle, and quite right too."
The leader of the DUP, Arlene Foster, also welcomed the decision to suspend Parliament and have a Queen's Speech, but said the terms of her party's confidence and supply agreement with the Conservatives would now be reviewed.
"This will be an opportunity to ensure our priorities align with those of the government," she added.
Parliament is normally suspended - or prorogued - for a short period before a new session begins. It is done by the Queen, on the advice of the prime minister.
Parliamentary sessions normally last a year, but the current one has been going on for more than two years - ever since the June 2017 election.
When Parliament is prorogued, no debates and votes are held - and most laws that haven't completed their passage through Parliament die a death.
This is different to "dissolving" Parliament - where all MPs give up their seats to campaign in a general election.
The last two times Parliament was suspended for a Queen's Speech that was not after a general election the closures lasted for four and 13 working days respectively.
If this prorogation happens as expected, it will see Parliament closed for 23 working days.
MPs have to approve recess dates, but they cannot block prorogation.

Demonstrations have been taking place across the UK against Boris Johnson's decision to suspend Parliament in the run-up to Brexit.
Thousands of protesters took to the streets in cities including Manchester, Leeds, York and Belfast.
Parts of central London were brought to a standstill, as people chanted: "Boris Johnson, shame on you."
A small group of counter-protesters, marching in support of the prime minister, also arrived in Westminster.
Mr Johnson's plan to prorogue Parliament prompted an angry backlash from MPs and opponents of a no-deal Brexit when he announced it on Wednesday.
If the prorogation happens as expected, Parliament will be closed for 23 working days.
Critics view the length and timing of the suspension - coming just weeks before the Brexit deadline on 31 October - as controversial.
Protests were held place in more than 30 towns and cities across the UK, including Edinburgh, Belfast, Cambridge, Exeter, Nottingham, Liverpool, Manchester and Birmingham.
In London, demonstrators stopped traffic in Whitehall and the West End.
They also staged a sit-down protest in the roads around Trafalgar Square, before marching to Buckingham Palace shouting: "Whose democracy? Our democracy."
The Met Police said it had made three arrests but gave no further details.
The Green Party said London Assembly member Caroline Russell was among those arrested.
Sian Berry, co-leader of the Green Party, tweeted she was "proud of Caroline standing up for democracy".
NHS pharmacist Bridie Walton, 55, said she had never been to a demonstration before, but joined the protest in Exeter to oppose Mr Johnson's plan.
"These are the actions of a man who is afraid his arguments will not stand scrutiny," she said.
In Liverpool, Paula Carlyle said she was "proud" to stand alongside protesters "who voted both Remain and Leave".
"We will not be silenced," she said. "Without us you have no power and we will continue to show ours until Mr Johnson is stopped."
In Oxford, crowds holding banners gathered outside Balliol College, where Mr Johnson studied at university.
Named "Stop the Coup", the protests are organised by anti-Brexit campaign group Another Europe is Possible.
Small protests also took place in Amsterdam, Berlin and the Latvian capital Riga.
Speaking at a rally in Glasgow, Labour leader Jeremy Corbyn said the protesters' message to the prime minister was: "No way do you take us out without a deal."
"Demonstrations are taking place everywhere because people are angered and outraged about what is happening," he added.
Shadow chancellor John McDonnell and shadow home secretary Diane Abbott both addressed crowds in London.
Speaking from a stage near Downing Street, Ms Abbott told protesters: "We cannot allow Boris Johnson to shut down Parliament and to shut down the voice of ordinary British people."
Meanwhile in Bristol, former Liberal Democrat MP Stephen Williams said by suspending Parliament, Mr Johnson had left MPs "with about four days to make the most important decision of any of our lifetimes".
Chancellor Sajid Javid, speaking on BBC Radio 4's Today programme, defended the prime minister's decision to suspend Parliament.
He said: "It's quite usual this time of year for Parliament to go in to a recess. It's perfectly correct and appropriate to prorogue Parliament.
"I think it's absolutely right that this prime minister and his government get the chance to set up their agenda."
It's a far cry from the numbers that we saw marching through Westminster earlier this year. I think we'd probably measure this one in the thousands [in central London].
But there are deeply-held passions here, different kinds of passions. Some are here because they don't like Boris Johnson's government, some because they are worried about proroguing Parliament, some because they don't want no deal, some because they don't want Brexit at all.
There's been a lot of talk about democracy from the people I've spoken to here today, but actually I think what it comes down to is a country which is riven by very different definitions about what democracy actually means.
The Jo Cox Foundation, which was set up in the wake of the Labour MP's murder in 2016, warned that anger over Brexit "should not spill over into something more dangerous".
Meanwhile, a petition against the prime minister's plan to suspend Parliament has received more than 1.5 million signatures.
And on Friday, former Tory Prime Minister Sir John Major announced he will join forces with anti-Brexit campaigner Gina Miller to oppose the decision to suspend Parliament in the courts.
He believes Mr Johnson's move to suspend Parliament is aimed at preventing MPs from opposing a no-deal Brexit.
The prime minister has dismissed suggestions that suspending Parliament is motivated by a desire to force through a no deal, calling them "completely untrue".
Foreign Secretary Dominic Raab said: "The idea this is some kind of constitutional outrage is nonsense."

A Tory MP's suggestion that the economic impact of a no-deal Brexit on the Republic of Ireland could encourage the EU to drop the backstop has been widely criticised.
However, Priti Patel said her comments "have been taken out of context".
A government report, leaked to the Times, indicated that there could be food shortages in Ireland in the event of a no-deal Brexit.
It said the economic impact on Ireland would be worse than in the UK.
The report indicated that there would be a 7% drop in GDP for Ireland.
The equivalent UK drop would be 5%.
Speaking to The Times, Conservative MP Priti Patel said such warnings should have been used in negotiations as leverage against the Republic of Ireland to encourage them to drop the backstop.
"This paper appears to show the government were well aware Ireland will face significant issues in a no-deal scenario. Why hasn't this point been pressed home during negotiations?
"There is still time to go back to Brussels and get a better deal."
Speaking to the Irish Examiner, the Tanáiste (Ireland's deputy prime minister) Simon Coveney said Ms Patel's comments were "ridiculous".
Her words were interpreted by some as insensitive given Ireland's history.
Alliance Party leader Naomi Long tweeted: "This kind of comment from MPs like Priti Patel demonstrate not only profound ignorance of and insensitivity about our history but also reckless indifference to the impact on relations today."
Elsewhere on Twitter, SDLP MLA Claire Hanna delivered a sharp rebuke to Ms Patel's comments.
"The warped and spectacularly ignorant mind of Brexit, alongside the evil approach to Ireland is the failure to grasp that this is about the most food secure island in the world," the South Belfast MLA wrote.
Priti Patel resigned as UK international development secretary in November last year amid controversy over her unauthorised meetings with Israeli officials.
The BBC asked Ms Patel for a response to the criticism but none was received.

Protesters seeking a referendum on the final Brexit deal have attended a rally which organisers say was the biggest demonstration of its kind.
Young voters led the People's Vote march to London's Parliament Square, which supporters say attracted approximately 700,000 protesters.
It also had support from a number of MPs who want a fresh vote.
This is something which has already been ruled out by Prime Minister Theresa May.
The People's Vote campaign said stewards on the route estimated 700,000 were taking part.
The Metropolitan Police said it was not able to estimate the size of the crowd.
Mayor of London Sadiq Khan - who started the march - was among those who addressed Parliament Square, along with representatives from the main political parties. Celebrity speakers included Steve Coogan, Delia Smith and Deborah Meaden.
London Mayor Mr Khan told the crowd: "What's really important is that those that say that a public vote is undemocratic, is unpatriotic, realise that in fact, the exact opposite is the truth.
"What could be more democratic, what could be more British, than trusting the judgement of the British people."
The march was held at the same time as a pro-Brexit rally in Harrogate, organised by the group Leave Means Leave and led by former UKIP leader Nigel Farage.
Mr Farage said: "The evidence suggests about a third of those that voted remain now say we're democrats and think the government should simply get on with it.
"And that's our message - get on with it, fulfil your promises to us, you said if we voted to leave it would happen, it needs to."
People gathered on Park Lane for hours before the march.  Many held home-made signs and banners with slogans like "the wrexiteers", "Brexit stole my future" and "Even Baldrick had a plan".
As the crowds began to form, the sheer scale of the protest became clear. Thousands of people stretched filled the street, some were singing, others were playing instruments, while many plastic whistles blared out.
There were lots of young families there, some with children wrapped in EU flags. Many told me they'd gone because they were worried about their families' future.
Some people marched in groups - there were NHS staff, political parties, members of the LGBT community and dog owners. Many took the opportunity to dress up their pets for the protest.
The start of the march was delayed due to the number of people there.  It was a good natured and friendly march through some of London's most famous streets before the hundreds of thousands of people arrived at Parliament Square.
By that stage the march was so large that not everyone could fit in the square and demonstrators spilled out onto nearby streets.
The marchers are hoping people power will persuade the British government to hold a referendum on the final Brexit deal. They will have to wait and see if the government was listening.
The British public voted to leave the EU by a margin of 51.89% to 48.11% in a referendum in June 2016.
The UK is scheduled to leave on 29 March 2019, under the terms of the two-year Article 50 process.
Labour's Lord Adonis, a campaigner for People's Vote - which wants a referendum on the outcome of the negotiations with the EU - said: "Brexit's becoming a dog's dinner.
"This week's fresh chaos and confusion over Brexit negotiations has exposed how even the best deal now available will be a bad one for Britain."
Richard Tice, founder of Leave Means Leave and former co-chair of Leave.EU, told BBC Breakfast: "The idea that you should have a second referendum would be incredibly damaging - most of all to the trust in democracy from people up and down this country."
Some 150 coach loads of people from across the UK - including as far away from London as Orkney - travelled to the March for the Future, which started in Park Lane.
TV chef Delia Smith told the crowds that Brexit was "the most important issue in our lifetime", adding: "My message to MPs is please sort this out. Let the people you serve have their say."
Lord of the Rings star Andy Serkis attended with his wife Lorraine Ashbourne and 14-year-old son Louis.
"The will of the people is now, it's people expressing their points of view in a more informed state," he said.
And First Minister of Scotland Nicola Sturgeon sent a message of support to the rally, saying the SNP would support a vote that would give the option of staying in the EU.
#PeoplesVoteMarch was trending on Twitter on Saturday, with lots of young people - some of those who were not eligible to vote in the 2016 referendum - heading on the march.
Emily Longman, 20, one of the students leading the march behind a People's Vote banner, was four months too young to vote in the 2016 referendum.
She studies Spanish and is due to study abroad next year, but said "no-one knows what will happen with Erasmus funding".
Aleta Doyle, 46, from Peterborough, who attended with her 12-year-old son Leo, said she was marching "for my children's future and European unity".
And Leo Buckley, 16, from Hampshire, said: "Young people stand to lose the most. I'm going to be poorer and not have the same career opportunities."
At the other end of the age spectrum, Joe Trickey from Croydon celebrated his 83rd birthday at the march. He said: "I believe very strongly in the EU as a place of peace and strength."
Dr Mike Galsworthy, from NHS Against Brexit, told BBC News: "Whether you voted leave, or whether you voted remain - when a contract comes back, you do have the right to read the small print and say actually 'no, no. no, this isn't what we want to be signing up for'."
Campaign supporter Alastair Campbell, former Downing Street director of communications, said: "The Brexit that was promised, and the Brexit that was campaigned successfully for, doesn't exist."
He added: "I don't think you can re-run the referendum. I think we have to accept that we lost that debate. I think the question has to be on the nature of the deal."
Saturday's event followed a march in London in June, on the second anniversary of the Brexit vote.

MPs will have "multiple" opportunities to give the public the final say over whether the UK leaves the EU, the People's Vote campaign group has said.
Theresa May has ruled out a referendum on the outcome of the Brexit negotiations under any circumstances.
But People's Vote said there were six plausible scenarios in which Parliament could legislate for another vote.
It said there should be a choice for voters between leaving with or without a deal or staying on current terms.
The prime minister says the UK made its choice to leave in 2016 and that her plan for future co-operation with the EU - based on the Chequers blueprint agreed in July - respects the referendum result.
She has said the choice facing Parliament is between leaving with or without a comprehensive agreement.
But in a report called Roadmap to a People's Vote the group campaigning for a referendum on any Brexit deal said there were no practical or legal barriers to giving the public the final say through a referendum and urged MPs not to hide behind "logistical arguments".
The British public voted to leave the EU by a margin of 51.89% to 48.11% in a referendum in June 2016.
The UK is scheduled to leave on 29 March 2019, under the terms of the two-year Article 50 process.
Negotiations on the terms of the UK's withdrawal, the so-called divorce settlement, as well as the shape of future relations between the two sides are now at a critical stage.
European leaders meeting in Salzburg on Wednesday are expected to agree to hold a special summit in November at which any deal sealed in the next six weeks could be approved.
Parliament will then be expected to vote on the terms of any agreement before the end of the year.
People's Vote said this Commons showdown, when it happened, could be a catalyst for securing a referendum.
The six ways it believes a referendum could be delivered are:
Lord Kerr, the former top civil servant who wrote the report, said MPs who wanted a referendum faced a "high bar" given the government's control of the Parliamentary timetable.
But he pointed out that Mrs May, who relies on the Democratic Unionist Party for her slim Commons majority, had already suffered two Brexit defeats and if Parliament did not act "it will not be due to procedural impediments or a lack of time but because MPs have not chosen to take these opportunities".
The cross-bench peer said the government could easily seek an extension of the Article 50 process to allow for a referendum by "withdrawing" the letter sent on 29 March 2017 notifying the EU of its intention to leave.
"The die is not irrevocably cast," he wrote.
"There is still time. If there is a majority in Parliament for a People's Vote, there are multiple routes to securing one and, as the process unfolds, more opportunities for the House of Commons to assert its will may emerge."
In terms of what question would be asked, People's Vote said it did not rule out having three options on the ballot paper - namely any deal agreed by the two sides, leaving without a deal or staying in on current terms.
But it said this was unlikely to get the backing of MPs and a "binary choice" between two options would be clearer, simpler and quicker.
While there was a case for giving 16-year olds the vote and allowing EU nationals living in the UK to take part, it said there might be "practical limits" on any changes to the franchise given the timescale involved.
The Lib Dems, the SNP and a growing number of Labour MPs back the idea of a referendum but Jeremy Corbyn has not committed to one as yet and only a handful of Tories support it.

Labour has narrowly seen off a Brexit Party challenge to hold on to its Peterborough seat in a by-election.
Union activist Lisa Forbes retained the constituency for Labour, taking 31% of the vote and beating the Brexit Party's Mike Greene (29%) by 683 votes.
Labour leader Jeremy Corbyn called it an "incredible" win for the "politics of hope over the politics of fear".
But Nigel Farage, who founded the Brexit Party less than two months ago, called its showing "very significant".
The Conservatives came third with 21%, while the Liberal Democrats were fourth with 12%, followed by the Green Party on 3%.
The Peterborough by-election was called after Fiona Onasanya - who won for Labour in 2017 but was convicted of lying over a speeding offence and thrown out of the party - became the first MP to be ousted under recall rules.
In her victory speech, Ms Forbes said, to cheers from her supporters, that "the politics of hope can win regardless of the odds".
"Despite the differing opinions across our city, the fact that the Brexit Party have been rejected here in Peterborough shows that the politics of division will not win," she said.
The Brexit Party had been the bookmakers' favourite to take the Cambridgeshire seat - which would have been its first at Westminster - following its success in the recent European elections.
Joining Labour's victory celebrations on a visit to the city, Mr Corbyn said: "All the experts wrote Lisa Forbes off. All the experts wrote Labour off. Write Labour off at your peril."
The Labour leader said the party had triumphed due to its anti-austerity message and its opposition to a "cliff-edge" no-deal Brexit that would threaten jobs and investment.
He challenged whoever succeeds Theresa May as Conservative leader to call an immediate general election.
Despite the Brexit Party's failure to take the seat, leader Mr Farage said he was "pretty buoyed", as it had "come from nowhere and produced a massive result".
He rejected claims that its focus on a single issue limited its appeal, telling BBC Radio 4's Today programme we have a "very strong, simple message that people believe in".
Mr Farage later handed in a letter to Downing Street calling for his party's MEPs to be included in the UK's Brexit negotiating team.
He told reporters he believed the NHS should be included in future US trade negotiations despite the political outcry when Donald Trump raised the possibility earlier this week - comments which the US president subsequently appeared to row back on.
The Brexit Party has made a huge impression - but history is written by the winners.
Had Nigel Farage's party actually won this narrowly, he would have had much more momentum to argue not just to get Brexit done by the end of October, but to have huge influence potentially over how the Conservatives choose their leader.
Had Labour lost narrowly, there would have been a big demand from the rank and file for Jeremy Corbyn to sharpen his Brexit act and to call for a referendum under all circumstances. That has not happened either.
The conclusion that the Labour leadership is drawing from this is that people actually wanted to talk about things other than Brexit.
By talking about council cuts, crime, and education, they managed not to fight on the same territory as their opponents and were able to carve out their own distinctive message, get out their core vote and sneak over the line.
Conservative leadership candidate Boris Johnson tweeted his "commiserations" to Tory candidate Paul Bristow, who, he said, "did not deserve to come third", while fellow contenders Dominic Raab, Matt Hancock and Jeremy Hunt said the result showed the threat from Labour.
Conservative Party chairman Brandon Lewis said the "clear message" from its poor performance in Peterborough as well as in recent council and European elections was the public wanted the government to deliver on the Brexit referendum result.
Polling expert Professor Sir John Curtice said the Peterborough by-election had not been as "dramatic" as the UK-wide European elections last month, in which the Brexit Party and Liberal Democrats came first and second.
But he added that the combined results had been "enough to disturb the regular rhythms of two-party politics".
Ms Forbes caused controversy during the campaign when she liked a social media post which said Theresa May had a "Zionist slave masters agenda".
Labour said she had liked a video expressing solidarity with the victims of March's terror attacks on mosques in the New Zealand city of Christchurch "without reading the accompanying text, which Facebook users know is an easy thing to do".
"She has fully accounted for this genuine mistake and apologised," a party source said.
But the Jewish Labour Movement called for Ms Forbes to have the Labour whip suspended, meaning she would have to sit in the Commons as an independent MP.
Meanwhile, Labour Against Antisemitism asked for her to be suspended from the party, calling her election a "dark day" for Labour.

The UK will need a transition period to help businesses adjust after Brexit, the chancellor and the international trade secretary have said.
In a joint Sunday Telegraph article, Philip Hammond and Liam Fox stressed any deal would not be indefinite or a "back door" to staying in the EU.
Their comments are being seen as an attempt to show unity between rival sides in Theresa May's cabinet.
The Liberal Democrats said Mr Hammond had "been brought back in line".
"What this is about is getting Philip Hammond back on track with a hard Brexit program," Tom Brake, the party's foreign affairs spokesman, said.
"What we don't know from this letter is exactly how this is going to work. It's also not clear how long the transition period is going to be."
The letter comes as ministers start to set out their detailed aims for Brexit.
A series of papers is being published, including one this week covering what will happen to the border between Northern Ireland and the Republic after the UK has left the EU.
Writing in the Sunday Telegraph, Mr Hammond and Mr Fox said the UK definitely would leave both the customs union and the single market when it exits the EU in March 2019.
They said a "time-limited" transition period would "further our national interest and give business greater certainty" - but warned it would not stop Brexit.
"We are both clear that during this period the UK will be outside the single market and outside the customs union and will be a 'third-country' not party to EU treaties," they said.
They said the UK's borders "must continue to operate smoothly", that goods bought on the internet "must still cross borders", and "businesses must still be able to supply their customers across the EU" in the weeks and months after Brexit.
The two leading politicians said the government wanted to ensure there would not be a "cliff edge".
Labour MP Ben Bradshaw said leaving the single market and the customs union would be a "dreadful mistake for the future of our economy, for jobs and prosperity in Britain".
BBC political correspondent Ben Wright said Mr Hammond - who is seen to favour a "softer" approach to Brexit - and Mr Fox, one of the most prominent pro-Brexit ministers, had "previously appeared at loggerheads" over the government's strategy on leaving the EU.
Mr Hammond has raised the prospect of a Brexit deal that saw little immediate change on issues such as immigration - something Brexiteers have rejected.
Our correspondent said their article was an attempt to "prove cabinet unity on Brexit".
Conservative MP and Brexit minister David Jones said the letter showed Mr Hammond had "rowed back from his previous position".
But Stephen Gethins, from the SNP, said there was "no masking the fact there are deep divisions within cabinet over Brexit  - and still no apparent plan almost 14 months on from the vote".
Meanwhile, former Labour Foreign Secretary David Miliband has called for politicians on all sides to unite to fight back against the "worst consequences" of Brexit.
He described the outcome of last year's referendum as an "unparalleled act of economic self-harm".
Writing in the Observer, he said: "People say we must respect the referendum. We should. But democracy did not end on June 23, 2016.
"The referendum will be no excuse if the country is driven off a cliff."
Negotiations between Brexit Secretary David Davis and EU officials are set to resume at the end of this month.
Mr Davis said the publication of the papers outlining the government's aims for Brexit would mark "an important next step" towards delivering the referendum vote to leave the EU.

Wednesday sees the next stage in the difficult process of the government agreeing its approach to trade with the European Union.
Theresa May will host a meeting of her Brexit cabinet - the inner sanctum that attempts to thrash out the knottiest issues left on the table.
One is the future customs relationship between the UK and EU.
That will be a vital part of any future trade deal as the UK exports 50% of its goods to the EU.
The government has said it wants to leave the EU single market and the customs union and at the same time retain an open border between Northern Ireland and the Republic.
The big and highly complicated question is how?
I am told that the chancellor will use the meeting tomorrow to argue in favour of a close "customs partnership" with the EU, or at least not rule it out at this early stage.
Senior sources have told me that Philip Hammond sees advantages in the proposal that would mean the UK could set its own tariffs but would also be obliged to mirror European Union customs rules.
He is likely to receive support from the business secretary, Greg Clark.
The arrangement would mean the UK collecting tariffs on behalf of the EU for any goods coming to the UK that were subsequently destined for any other union member state.
Businesses would claim back any tariff rebates from the government if the goods stayed in the UK.
Although technically difficult - some say impossible - officials believe such a partnership could "solve" the Irish border question as there would be no hard customs border between the UK and the EU.
It still leaves open the problem of what happens if there are substantive regulatory differences between the UK and the EU beyond tariff arrangements.
Whitehall sources I have spoken to say a customs partnership would help the many British businesses that only export to the EU.
It would also leave the UK free to sign trade deals with other countries, a key plank of the government's Brexit strategy.
Sources said a fourth advantage is that it would be for the UK to sort out the very difficult technical and infrastructure issues alone as they would all fall on the British side of the border.
Mr Hammond's position is likely to cause controversy within the Conservative Party.
Brexit-backing MPs believe the partnership model may be used as a back door route to rejoining the customs union.
"Some of the people proposing it know such an immensely complicated - and untried - arrangement is guaranteed to end in chaotic failure," said David Jones, the former Brexit minister, last month.
"At which point they will conclude we have no choice but to rejoin the fully fledged customs union."
The second option put forward by the government - and to be discussed at Wednesday's Cabinet meeting - is called "maximum facilitation" or a "highly streamlined customs arrangement".
Under the "maxfac" model - supported by many pro-Brexit MPs - any customs checks needed at borders between the EU and the UK once Britain has left the EU would be as friction free as possible.
Technology and trusted trader status licences would be used to smooth the flow of goods and services, its proponents argue.
Its backers also say it would be a more definitive break with the EU and is more technically feasible as it would in part be operationally based on arrangements Britain already has with non-EU nations.
Critics say it would not solve the Irish border question as there would still need to be tariff checks.
The whole debate on Wednesday will ultimately be a rather surreal affair.
Senior figures I have spoken to admit that both models are untried, possibly unworkable and it could take years to build either system.
The EU is yet to be convinced that they are viable alternatives to its own "backstop" solution to the Irish border question - placing a customs border in the Irish Sea and approaching the whole island of Ireland as a single trading entity.
Theresa May has said that the government would never agree to such a plan.
What is clear is that there is still a very significant amount of work to be done if any customs policy is to be agreed by both the government and the EU, which wants there to be "substantial progress" by June.
Without agreement, the conclusion of Britain's overall withdrawal deal - due to be signed in October or December - would be in jeopardy.

The chancellor has labelled the European Union's Brexit negotiators as "the enemy" - a remark he subsequently described as a "poor choice of words".
During a television interview, Philip Hammond also called the negotiators "the opponents" and said they should "behave like grown-ups".
But he tweeted later: "I was making the point that we are united at home. I regret I used a poor choice of words."
Mr Hammond is in Washington for an International Monetary Fund meeting.
He has been criticised for saying that the Brexit process has created uncertainty, and this week a former chancellor claimed he was trying to sabotage the talks.
During a series of media interviews in Washington, Mr Hammond told Sky News that "passions are high" in the party "but we are all going to the same place".
But he added: "The enemy, the opponents, are out there on the other side of the table. Those are the people that we have to negotiate with to get the very best deal for Britain."
Despite his regrets, Mr Hammond's comments drew fire from political opponents. Shadow Chancellor John McDonnell said it was an "inept approach from a failing government. Insulting the EU is not the way to protect our economic interests".
During his interviews, the chancellor also has described as "bizarre" and "absurd" accusations he is talking down the economy.
Mr Hammond said he was a realist and that he wanted to "protect and prepare" the economy for the challenges ahead.
The chancellor said: "It is absurd to pretend that the process we are engaged in hasn't created some uncertainty. But the underlying economy remains robust.
"I am committed to delivering a Brexit deal that works for Britain," he added.
He refused to answer how he would vote if another referendum was held now. "We've had the referendum," he said. "You know how I voted in it."
This week, former Conservative Chancellor Nigel Lawson called for Mr Hammond to be sacked, saying he was unhelpful to the Brexit process.
Lord Lawson said: "What he [Mr Hammond] is doing is very close to sabotage".
Responding to these comments, Mr Hammond said: "Lord Lawson is entitled to his view on this and many other subjects and isn't afraid to express it, but I think he's wrong."
The chancellor, who has been accused of being too pessimistic about Brexit, told the Treasury Committee of MPs this week that a "cloud of uncertainty" over the outcome of negotiations was "acting as a dampener" on the economy.
But speaking on Friday, Mr Hammond said he was optimistic about the UK's economic future and was in Washington to promote it.
"What I'm doing here in Washington is talking Britain up, talking about Britain's future as a champion of free trade in the global economy, seeking further moves on liberalisation on trade in services which will hugely benefit our economy."
He added that Britain had "a very bright future ahead", but added that it was "undoubtedly true" that the process of negotiations had created uncertainty for business.
"If you talk to businesses, they would like us to get it done quickly so that they know clearly what our future relationship with the European Union is going to look like."
Mr Hammond said the Cabinet was united behind Prime Minister Theresa May's recent speech in Florence setting out her Brexit plans.
"We know what our proposal is, we put it on the table effectively. Now we want the European Union to engage with it… challenge us… but let's behave like grown-ups." he said.
Mr Hammond said the government would not spend taxpayers' money preparing for a "no-deal" Brexit until the "very last moment".
He said he would not take money from budgets for other areas such as health or education just to "send a message" to the EU.
One former minister, David Jones, has said billions of pounds should be set aside in November's Budget for a "no deal" scenario.
He argued that if this did not happen it would be seen as a "a sign of weakness" by EU leaders, who would think the UK was not serious about leaving the EU without a deal.

Chancellor Philip Hammond has indicated he may vote to bring down the next PM to stop a no-deal Brexit.
Asked whether he would back a motion of no-confidence in the government, he said he could "not exclude anything".
Mr Hammond also said he would do "everything in my power" to stop a future prime minister suspending Parliament to get a no-deal Brexit.
He was one of four cabinet ministers who abstained from a vote blocking the possibility of this happening.
The Commons vote was brought forward on Thursday by MPs who fear the next Conservative leader and prime minister will make the move - known as "prorogation" - to push through a no-deal Brexit and cut them out of the process.
Foreign Secretary Jeremy Hunt has discounted the possibility if he becomes prime minister, but his rival in the Conservative Party leadership race, Boris Johnson, has refused to give the same assurance.
In an interview with Le Monde and Süddeutsche Zeitung, Mr Hammond said he would "take steps to avoid an exit without agreement apart from an explicit parliamentary approval".
Speaking on Tuesday at the G7 conference in Paris, he told the French and German newspapers: "There should be a new and sincere attempt to reach a consensus.
"If we do not find a solution with the members, we may have to ask the British to give their opinion again, in one form or another."
Asked if he would rule out supporting a motion of no confidence - which, if successful, would bring down the government - he said: "I do not exclude anything for the moment."
It is a chance for MPs to hold a vote on whether they want the government to continue - and it has the power to trigger a general election.
Any MP can propose a motion of no confidence, but that doesn't mean it would be debated.
However, if the leader of the opposition introduces the motion, convention means the government will provide time for a debate to take place.
Mr Hammond also said another extension to Brexit was "absolutely necessary" in practice, as there was not enough time to renegotiate with the EU ahead of 31 October deadline.
He added: "If the next government is sincere in its desire to reach an agreement with Europe, it must try to get more time. If it does not, the British parliament will insist on getting a new postponement.
"I will remain a member of the House of Commons. I will do everything in my power from my position to make sure that parliament blocks a Brexit without agreement."
By Jessica Parker, political correspondent
The so-called "awkward squad" - a group of Conservative Eurosceptic MPs - has for a long time made life tricky for David Cameron and Theresa May.
With the pro-Brexit Boris Johnson apparently on the cusp of becoming PM, the expectation is that a chunk of the group could get government jobs. And the rest will surely hold fire on their new boss, at least for a while.
Taking their place… the "Gaukeward squad", named after current Justice Secretary David Gauke.
The current projection is that it will be made up of Mr Gauke, Chancellor Philip Hammond and a good handful of other Tory MPs who avidly oppose a no-deal Brexit.
Just how Gaukeward will they be? Mr Hammond's comments on potentially supporting a no-confidence vote suggest he - in principle at least - is willing to go pretty far to make his point.
But is this just tough talk in order to let off some loud warning shots? We won't know until the crunch moment - if and a when Parliament finds itself confronted with the very real and immediate prospect of a no-deal Brexit.
Mr Hammond said Mr Johnson, the frontrunner in the Tory leadership race,  was "a more complex personality than it sometimes seems", and was "a mainstream Conservative on all topics except Brexit".
But he pleaded for the EU to have patience with some of Mr Johnson's Brexit-backing supporters in the Conservative Party who were being "deliberately noisy, rude and inconsiderate... to make the Europeans so tired that they ask us to leave".
He added: "Please, do not listen to the the few noise-makers."
Pro-Remain Tory Dominic Grieve told the BBC that he thought a "substantial number" of his party would be willing to support a vote of no confidence in the government to stop a no-deal Brexit.
He said: "I'm going to be working with colleagues who share my view that no deal would be very bad for the country to try to make sure that the government cannot push us into no deal without Parliament having consented to it."
Health minister Stephen Hammond - who abstained in Thursday's vote - said he would not rule out supporting a no-confidence vote in his own government if its policy became pursuing a no-deal Brexit, telling BBC Radio 4's Today programme: "A lot of people were taught that you must put the interest of the country before yourself."
But leading Brexiteer and Tory MP Jacob Rees-Mogg told the same programme those trying to prevent it were "not saying what they believe", and their intention was to "snub the British voters" and stop Brexit altogether.
He did, however, say prorogation was a possibility "for a day or two" to stop parliamentary procedures being "upended" by backbenchers trying to block the UK leaving the EU.
If MPs fail to support a Brexit deal agreed between UK and EU by 31 October, the legal default is to leave with no deal on that date.
Both contenders to be the next prime minister said they want to keep to the date and renegotiate with the EU, leaving with a deal.
But Mr Hunt and Mr Johnson have also said they would keep no deal on the table to strengthen negotiations, despite Parliament voting to rule the option out.
The EU has consistently said the withdrawal agreement is closed and cannot be changed.
The incoming president of the European Commission, Ursula von der Leyen, has said she hopes the UK remains in the EU, but it was up to British authorities to "sort its side of things on Brexit".
Asked about Mrs von der Leyen's position, German Chancellor Angela Merkel said on Monday she understood that "if the UK wishes for more time [e.g. another delay to Brexit], then they would have more time", but it was "up to the UK".
She praised her "cooperative relationship" with Theresa May, adding: "She has not had an easy time dealing with this difficult question. I always found her to be a reliable and collegial partner, and I thank her for that."
But she added: "We now have the position that there will be a new PM, and then we have to watch what that person decides."

The government will set a new Budget if it is unable to reach a Brexit deal with the EU, the chancellor has said.
Philip Hammond said a no-deal Brexit would require a "different response", with "fiscal buffers" being maintained to provide support for the economy.
Mr Hammond was speaking on the eve of his Budget, which he will present to the Commons on Monday.
He also hinted at more funds for the universal credit rollout, after claims that millions of homes will lose money.
The spending plans take place at a time of uncertainty over Brexit, with no deal in place five months before the UK's departure date.
Questioned about the impact of a no-deal Brexit, Mr Hammond told Sky News' Ridge on Sunday programme: "We would need to look at a different strategy and frankly we'd need to have a new Budget that set out a different strategy for the future."
Mr Hammond said the Budget forecasts to be used on Monday were based on an "average-type free trade deal" being agreed between the two sides.
But if the UK leaves without a deal, the government would have to "revisit where we are", he told the BBC's Marr Show.
The chancellor added: "I have got fiscal reserves that would enable me to intervene."
Labour's shadow chancellor John McDonnell said he was "deeply worried" that the government was edging towards a no-deal Brexit.
Prime Minister Theresa May has recently promised "an end to austerity", the cuts made to public spending since 2010.
Asked about this pledge, Mr Hammond said detailed information would have to wait for next year's spending review.
"Once we get a good deal from the European Union and the smooth exit from the EU we will be able to show the British people that the fruits of their hard work are now at last in sight," he said.
A deal based on the government's preferred model - which has been criticised by the EU and some Tory MPs - would "minimise the negative effect" of leaving, he said.
But Mr Hammond warned he could not say at this stage whether the overall impact would be positive or negative for the UK.
Labour has dismissed the government's austerity promise.
Mr McDonnell said Labour would spend £50bn to "start the process" of reversing spending cuts, a process he said would take until the end of the next Parliament.
This would be done in a "realistic and responsible" way, he said.
The government has also been under pressure to commit extra funds to the flagship universal credit reform, amid reports that millions of households face losing money under the new system.
Conservative MPs have been among those demanding more money to protect people moving onto the new payment, which replaces six benefits and merges them into a single payment.
Asked about this, Mr Hammond told the BBC's Marr Show he had used previous Budgets to put money into the project, adding: "When we see things that need addressing, we address them."
Labour says the universal credit should be scrapped, and Mr McDonnell called for the Budget to be voted down if the government does not agree to halt its repeatedly delayed rollout across the UK.
Other expected Budget announcements include a £30bn package for England's roads, £900m in business rates relief for small business and £650m to rejuvenate high streets.

A former government minister has lost a vote of no confidence in him by his local Conservative association.
Phillip Lee, MP for Bracknell, said the move had been "inspired" by the single issue of Brexit.
Bracknell Conservative Association called the vote after 53 members signed a petition.
The ex-justice minister, who supported Remain in the 2016 EU referendum, said the government's approach would damage businesses in his constituency.
Dr Lee then became the first government minister to resign over Brexit.
Association chairman Gerry Barber said: "The result of the vote was that a majority of members present were in agreement with the motion, which was therefore passed, and the result has been communicated to Dr Lee and to the full membership.
"I will be discussing the meeting with Phillip later this week."
Dr Lee said he would not be "forced into taking a decision" on his future by an "orchestrated, destructive campaign from outside the party".
He previously claimed more than half those who signed the petition had joined the association less than a year ago.
He said: "In the future, I may or may not decide that I can continue serving as a Conservative Member of Parliament, and the Bracknell Conservative Association may or may not decide that they wish to readopt me as the Conservative Party's candidate.
"But one thing is for sure, we will not be forced into taking a decision one way or the other by this orchestrated, destructive campaign from outside the party."
Those behind the campaign had "done nothing but spread hatred, intimidation and distrust over a single issue", Dr Lee said.
"[But the] people of the Bracknell constituency can rely on my absolute commitment to serving our area's best interests in Parliament, without fear or favour, and then take into account my full record at the next general election."
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The UK is to offer Gibraltar continued barrier-free access to finance markets after Brexit, the BBC understands.
The UK is negotiating for Gibraltar to be treated the same as Britain when it leaves the EU in March 2019.
But the EU insists Madrid can stop a transitional deal or future trade relationship applying to Gibraltar unless there is a Spain-UK agreement.
Gibraltar fears Spain could use this veto to force talks about the Rock's constitutional future.
At the very least, it fears there could be talks about closer cooperation with Spain.
If Britain refused, then Gibraltar could fall out of the EU next March without a transitional deal and lose its access to the British financial markets.
Ministers are to give the commitment to financial market access at a meeting in London of the so-called Joint Ministerial Council with the Gibraltar government.
Gibraltar is hoping to get some formal reassurance that it will retain access come what may.
This matters not just because most of its financial trade is with the UK but also because its insurance sector is important to Britain.
The Gibraltar government says that one in five British drivers insure their cars with firms based in Gibraltar. For insurers to offer annual policies with certainty, they need some kind of reassurance before the end of this month.
The Lib Dem leader, Sir Vince Cable, told the BBC Theresa May should make rejecting Spain's veto a red line in her negotiations.
The prime minister, he said, had ignored the people of Gibraltar and taken her eye off a key national interest.
He said: "If the government is going to take a tough line on Brexit in these negotiations, this is one of the things they should be tough about.
"Currently they have been very, very weak and created an enormous sense of anxiety and insecurity".
He added: "It is an issue of fundamental principle. Gibraltar has been attached to the UK for two centuries.
"We have seen off repeated demands by Spain to have control over the Rock. We should not allow Brexit to be used as a cloak for giving away what is a substantial British commitment."
A UK government spokesmansaid: "The EU's guidelines are a matter for the EU and the other member states.
"The prime minister has said that as we negotiate these matters we will be negotiating to ensure that the relationships are there for Gibraltar as well.
"We are not going to exclude Gibraltar from our negotiations for either the implementation period or the future agreement."
Former Labour Europe minister Lord Hain suggested that one solution to any co-sovereignty suggestions could be turning Gibraltar into a "micro state" like Andorra, the Vatican City and San Marino.
But Gibraltar's Chief Minister Fabian Picardo said this was not an option and insisted sovereignty could not be bartered away.
"We're very linked to the UK, we see the world through British eyes and we don't want to change that," he told BBC Radio 4's Today programme.
"But at the same time, we believe we should be engaging more closely with Spain. I think we can create, even despite Brexit, a rainbow of opportunities for people who live in the bay of Gibraltar and the wealth that Gibraltar creates."
Samantha Barrassa, who runs the Gibraltar Financial Services Commission insisted the UK market "is important" to the financial services sector in Gibraltar, with services companies employing thousands of people in the UK.
But former Spanish EU minister Diego Lopez Garrido said it was "unacceptable that Britain says 'no matter about Gibraltar - business as usual. Nothing to talk (about).'"
"The British government should negotiate with the Spanish government about Gibraltar."
And Charles Powell, from the Elcano Royal Institute think-tank, said Britain now has to accept the European Commission will be on Spain's side in the future because it is an EU member, while the UK will not be, post-Brexit.
He said the Spanish public "cannot understand this obsession with Gibraltar and this total lack of concern about the Brits who live in Spain and the consequences Brexit will have on them".

The pound's fall against the dollar and the euro has deepened following Theresa May's assertion after an EU summit that "no deal is better than a bad deal".
Sterling was already trading lower after EU leaders warned the UK must make compromises on trade and the Irish border to secure a Brexit trade deal.
After the Prime Minister said the UK and EU were at an "impasse" the pound fell further.
The pound dropped from 1% to 1.5% lower against the dollar to $1.3068.
By the end of US trading, the pound was on track for its biggest daily drop against the dollar so far this year.
Against the euro, the pound was down 1.1% at €1.1144 after Mrs May's statement.
"The rhetoric that 'no deal is better than a bad deal' is startling, and undermines recent hopes that a deal could be finalised soon," said Hamish Muress, currency analyst at OFX.
Business bodies reacted with alarm to the latest development.
The British Chambers of Commerce (BCC) warned that the possibility of the UK leaving the EU without a trade deal was a big concern for firms.
"Many firms are hugely worried about a messy and disorderly outcome, and the potential impact on their ability to trade and grow. Others could be caught flat-footed. Both sides must make every effort to avoid this scenario," said BCC director general Adam Marshall.
Carolyn Fairbairn, director general of the CBI, said negotiators on both sides had to change tack.
"The stakes could not be higher. Jobs, wages and living standards are at risk, on both sides of the Channel.
"With time slipping away, employers and employees alike need to see constructive dialogue. Pragmatism must come before politics. Every day lost in rhetoric is lost investment and lost jobs," she added.
Mrs May's statement followed a cool reception for her Chequers plan at a summit of EU leaders in Salzburg.
She said the two sides were still "a long way apart" on the post-Brexit economic relationship.
The two options being offered by the EU - for the UK to stay in the European Economic Area and customs union or a basic free trade agreement - were not acceptable, she said.
She said EU leaders needed to come up with new alternatives to her Brexit proposals if both sides were to break the current deadlock.
"It is not acceptable to simply reject the other side's proposals without a detailed explanation and counter-proposals," Mrs May said.

The pound has risen after MPs voted to reject Theresa May's Brexit deal by 230 votes.
The vote opens up a range of outcomes, including no deal, a renegotiation of Mrs May's deal, or a second referendum.
Sterling rose 0.05% to $1.287 after declines of more than 1% earlier in the day.
The currency slumped 7% in 2018 reflecting uncertainty about the terms of the UK's exit from the European Union.
MPs voted by 432 votes to 202 to reject the deal, the heaviest defeat for a sitting government in history.
"A defeat has been broadly anticipated in markets since the agreement with the EU was closed in November 2018 and caused several members of the government to resign," said Richard Falkenhall, senior FX strategist at SEB.
But business groups said their members' patience was wearing thin.
"There are no more words to describe the frustration, impatience, and growing anger amongst business after two and a half years on a high-stakes political rollercoaster ride that shows no sign of stopping," said Adam Marshall, director general of the British Chambers of Commerce.
He implored MPs to come to an agreement, and was joined in this plea by business groups including the Federation of Small Businesses, the Institute of Directors and the Confederation of British Industry.
Some investors see the chances of a no-deal Brexit diminishing as parliament exerts more authority over the process.
"The probability of a no deal has diminished while the chances of a delay in Article 50, a second referendum or even, at the margin, no Brexit at all, have all increased. The consequence of those scenarios has encouraged sterling to rally despite the PM suffering the worst parliamentary result in a century," said Jeremy Stretch of CIBC Capital Markets.
On Friday, hedge fund manager Crispin Odey, a major donor to the Brexit campaign, said he now expected the project to be abandoned altogether and that he is positioning for the pound to strengthen.
The markets were prepared for her to lose - but the scale of her defeat took most by surprise.
But more surprising still was the fact that the pound - the first financial responder to political events - gained in value after the vote - despite many, most, confidently predicting a crushing defeat would send it down.
So what to make of it? Using the benefit of hindsight, some are saying that the recent display of animosity in the House of Commons to the idea of a no-deal Brexit, something markets are most wary of - has convinced them that outcome is very unlikely.
The other new line is that this crushing defeat for her Brexit deal, makes no Brexit - at least not on 29 March - a growing possibility. That's financial markets, which respond in seconds.
Real businesses are not so sure.  With 72 days to go before the UK is due to leave the EU another milestone has come and gone with the future no clearer and planning for no deal more urgent.
But others are concerned the rejection of Mrs May's plan makes a no-deal Brexit more likely as other options become fewer in number.
"A no-deal Brexit means the public will face higher prices and less choice on the shelves," said Helen Dickinson, chief executive of the British Retail Consortium.
"British businesses desperately need certainty about the UK's future trading relationship with the EU and will be severely disadvantaged by a no deal. The time for Parliamentary games is over."
While there is speculation that Britain's exit from the EU must now be suspended as the most-developed plan has been scrapped, businesses may not be counting on this, particularly complicated ones like banks.
"Firms in the finance industry have put contingency plans in place to minimise disruption for their customers in a 'no deal' scenario but critical cliff-edge risks remain, including on the transfer of personal data and the operation of cross-border contracts," said Stephen Jones, chief executive of UK Finance.
Omar Ali, UK financial services leader at accountants EY, added: "Firms have no choice but to fully implement their no-deal plans."

President Donald Trump has predicted a "tremendous increase" in UK-US trade, after talks with Theresa May.
He also said the US and UK were "joined at the hip" on military matters, while Mrs May said they stood "shoulder to shoulder" in facing shared threats.
In a series of warm exchanges in Davos, Switzerland, President Trump also told the UK PM:  "We love your country."
He also rejected "false rumours" of differences, saying that the two leaders "like each other a lot".
And Downing Street said later that they had asked officials to work on "finalising the details of a visit by the president to the UK later this year".
It was their first meeting since clashing over the US president's retweets of far-right videos in November.
And earlier this month Mr Trump cancelled a visit to the UK, criticising the location of the new US embassy in London.
But after their meeting, Mr Trump told Mrs May at their news conference: "I have great respect for everything you are doing, we love your country, I think it's really great."
The two leaders met in Davos, at the World Economic Forum, with post-Brexit trade relations between the two countries high on the agenda.
Mr Trump said: "One thing that will be taking place over a number of years will be trade. Trade is going to increase many times.
"I look forward to that... the discussions... that will be taking place are going to lead to tremendous increases in trade between our two countries which is great for both in terms of jobs. We look forward to that and we are starting that process, pretty much as we speak."
He added the US would be "there to fight for you - you know that" and the two were "joined at the hip when it comes to the military".
Mrs May replied that the "really special relationship" between the UK and US continued and they stood "shoulder to shoulder because we are facing the same challenges across the world".
"Alongside that working for a good trade relationship for the future which will be for both our benefits, so the UK and the US both do well out of this - and it's been great to see you today."
In response to reporters' questions, both leaders said they would "talk about" his state visit to the UK - offered by Mrs May when she visited him in Washington shortly after he became US president. No date has been set.
Downing Street later confirmed that the visit officials were discussing this year would be a working, not a state, visit.
But BBC North America editor Jon Sopel said the British would be pleased with the press call. The mood music had been good and the Americans were talking positively about a trade deal.
A Downing Street spokesman said the two leaders had also discussed the Bombardier trade dispute and that Mrs May had "reiterated" the importance of the firm to Northern Ireland, Iran, Syria and Brexit negotiations.
The UK prime minister had earlier addressed the World Economic Forum about the need to put more pressure on tech giants to deal with extremist content and tackle child abuse and modern slavery on social networks. She said shareholders should use their influence to "ensure these issues are taken seriously".
"No-one wants to be known as the terrorist platform, or the first-choice app for paedophiles," she said.
She said some progress had been made but more must be done "so that ultimately this content is removed automatically".
She acknowledged people's concerns about the impact of technology on jobs - pointing to Uber as an example of a company that had "got things wrong along the way".
The ride-hailing firm should not be shut down but should address concerns about safety and workers' rights and enforce standards "that can make this technology work for customers and employees alike", she said.
Mrs May said that employment law must keep pace with the way technology is changing jobs and while it must protect the "flexibility" companies valued, it must not be "a one way street deal that can become exploitative."
The UK is in the process of leaving the European Union - the day set for Brexit is 29 March, 2019, so is expected to negotiate its own trade deals in future, rather than being part of the deals drawn up on behalf of  all EU member states.

Prime Minister Boris Johnson has carried out a reshuffle of ministers in cabinet positions, two months after winning the general election.
There was speculation ahead of the reshuffle about how diverse the new Cabinet would be, particularly considering women and people from ethnic minority backgrounds.
Who's in what job? Here's a guide to the people that make up Mr Johnson's cabinet, with the latest new faces and who's changed places.
Note: BAME (Black, Asian and Minority Ethnic) is a term widely used in the UK to describe people of non-white descent, as defined by the Institute of Race Relations.
This is the second reshuffle for Mr Johnson, who became prime minister last July after winning a Conservative leadership election.
Big names to have left cabinet on Thursday included Chancellor Sajid Javid, Attorney General Geoffrey Cox and Business Secretary Andrea Leadsom.
The make-up of the cabinet has also changed. The proportion of women in it has increased - but the actual number has fallen from eight to seven because some positions were closed.
Members of the cabinet are more than 10 times more likely to have gone to a private school than members of the public.
Under Mr Johnson's predecessor, Theresa May, 70% of cabinet had not been privately educated, whereas almost 70% of Mr Johnson's new cabinet have.
According to the Sutton Trust social mobility charity, every prime minister since 1937 who attended university was educated at Oxford - except for Gordon Brown.  Half of Mr Johnson's cabinet went to Oxford or Cambridge universities.
This compares with 27% of all Conservative MPs and 18% of Labour MPs.
Sir Peter Lampl, founder and chairman of the Sutton Trust, said December's election led to a seismic shift in the political landscape and Conservative MPs now represent a more diverse range of constituencies than before.
"Yet in terms of educational background, the make-up of Johnson's cabinet is still over 60% from independent schools," he said. "Today's findings underline how unevenly spread the opportunities are to enter the elites and this is something Boris Johnson must address."
Michael Gove is by far the most experienced of Mr Johnson's new top team. The ministers who have had 204 days of cabinet experience are new faces appointed by the PM when he took power in July last year.
Click here if you cannot see the Cabinet Guide.
Theresa May has set out her desire to create a "more united" Britain, in a speech in Cardiff.
The prime minister told the Conservatives' spring conference that Britons are "at heart one people" be they Welsh, English, Scottish or from Northern Ireland.
It follows Nicola Sturgeon's demands for a second independence referendum for Scotland.
Mrs May has already rejected the call from Scotland's first minister.
Scotland voted to remain in the UK in 2014 but the SNP administration in Edinburgh wants a fresh vote as the UK plans to leave the European Union.
Scottish voters opted by a majority to remain in the EU, with England and Wales voting to leave.
Mrs May said on Thursday it was "not the right time" for another independence referendum.
In her conference speech on Friday, the prime minister described her triggering of the Article 50 process for Brexit as one of the "great national moments that define the character of a nation".
With a "road before us" that "may be uncertain at times", the UK could "look forward with optimism and hope, or give in to the politics of fear and despair", she said.
"I choose to believe in Britain and that our best days lie ahead," she said.
The Brexit vote in 2016 was also a vote for changing the way the country works, Mrs May added.
"It means forging a more united nation, as we put the values of fairness, responsibility and citizenship at the heart of everything we do, and we strengthen the bonds of our precious union too," she told the conference.
"It means building a stronger, fairer Britain that our children and grandchildren will be proud to call home."
The union is "more than just a constitutional artefact," she added. "It is a union between all of our citizens, whoever we are and wherever we're from."
The prime minister also promised to take account of competing demands from Wales, Scotland and Northern Ireland as the negotiations begin on leaving the EU, saying: "We are four nations but at heart we are one people."
Opening the conference earlier, Welsh Conservative leader Andrew RT Davies said Labour ministers' plans to scrap the right to buy council homes in Wales would end "one of the greatest aspirational policies this country has ever seen".
Meanwhile education spokesman Darren Millar joked about being dubbed "Millar the Cereal Killer" because of his opposition to free school breakfasts.
The AM for Clwyd South said he had been compared to "Thatcher the so-called Milk Snatcher", before saying he was proud to have been compared to the former prime minister.
Analysis by BBC Wales political editor Nick Servini
This was a Theresa May speech delivered to an audience of the Welsh Tory faithful, but in reality was directed further afield and in particular to a Scottish audience contemplating the prospect of another independence referendum.
The gloves came off as the prime minister visibly became more animated as she called the SNP and Plaid Cymru "obsessives" with tunnel vision.
In fact, Jeremy Corbyn was barely mentioned as nationalist-bashing became the tactic of choice instead from a roll-call of senior party figures.
This conference may have been in Cardiff but there was little to give it a Welsh dynamic, with the focus turned to May's twin battle of Brexit negotiations while trying to hold Britain together.

Theresa May is being urged to walk away from Brexit negotiations this week if EU leaders refuse to start trade talks.
The call comes from a group of pro-Brexit Tory and Labour politicians, including former Chancellor Lord Lawson, as well as business leaders.
The prime minister is to push for the deadlocked talks to move to the next phase at a meeting of EU leaders in Brussels on Thursday.
But EU officials are not expecting any movement at the summit.
But European Council President Donald Tusk is expected to propose to the 27 EU leaders that they begin talks amongst themselves about Britain's future relationship with the EU, when it leaves the bloc in March 2019.
In a letter to Theresa May, organised by the Leave Means Leave campaign, the leading Brexiteers say the government "has been more than patient" towards the EU and "decisive action" was now needed to end the "highly damaging" levels of uncertainty facing businesses.
In the event of no progress at Thursday's European Council meeting, the letter says, Mrs May should formally declare that the UK is working on the assumption that it will be reverting to World Trade Organisation (WTO) rules on 30 March, 2019.
Early notification of such a move would allow the UK to "concentrate our resources on resolving administrative issues" and prepare to "crystallise the economic opportunities" of Brexit, it adds.
The letter is signed by Lord Lawson, Conservative former ministers Owen Paterson and Peter Lilley, Labour MPs Kate Hoey, Graham Stringer and Kelvin Hopkins, Wetherspoons pub boss Tim Martin and home shopping magnate and Labour donor John Mills, as well as pro-Brexit academics and former military figures.
The UK government says it does want to leave the EU without a deal in place and is targeting a new free trade arrangement to replace its current single market membership.
But speaking on BBC Radio 4's Today programme, Mr Paterson said it appeared unlikely that a trade deal would be struck with the EU "because they are flatly refusing to talk about it".
Instead, he said, there was a "complete obsession with money" - the amount the UK is required to pay as it leaves the EU.
It was "inevitable at the moment, it is an ineluctable certainty we are going to end up with WTO at the end of this anyway" so it was better to "state that now" and give business time to prepare, he added.
But Labour's Brexit spokesman Sir Keir Starmer said: "This is the first phase of the first set of negotiations and talking of walking away at this stage is irresponsible."

More than 60 Brexit-supporting Tory MPs have written to Theresa May to insist the UK make a clean break with the EU.
The MPs say the UK must not be stopped from negotiating trade deals with other countries, once it leaves the EU, and must gain full "regulatory autonomy".
The letter was sent by the European Research Group of Tory backbenchers, headed by Jacob Rees-Mogg.
Opposition critics accused the PM of being "too weak" to confront the "hard Brexiteers" in her own party.
The letter, signed by 62 MPs including several ex-ministers and former Conservative Party leader Iain Duncan Smith, includes a number of "suggestions" for securing a successful Brexit.
It backs the PM's vision for Brexit, as set out in her Lancaster House speech in January 2017, including leaving the customs union and single market.
But it says she "must" ensure the UK can change its laws without authorisation from the EU from the moment it leaves in March 2019.
The MPs also insist the UK must be "free to start its own trade negotiations" during the planned two-year transition period that would kick in after Brexit day.
And it urges the UK government to resist EU efforts to set the timetable for Brexit negotiations.
"The UK should negotiate as an equal partner. Ministers may not want or be able to accept the EU's timing and mandates as fixed, and should be able to set out alternative terms including, for example, building an agreement based on our World Trade Organisation membership instead," says the letter.
It comes ahead of a crunch cabinet meeting on Thursday to thrash out an agreement on how to proceed in negotiations with the EU.
The government is also set to publish its its response to the EU's proposals for how the two-year transition period after Brexit should work later on Wednesday.
The UK wants a mechanism to object to new European legislation introduced during the implementation phase.
The prime minister had suggested that EU nationals who arrive during the transition period should not have the right to settle permanently in the UK.
Analysis by BBC political editor Laura Kuenssberg
With no majority, she knows that she needs to keep the dozens and dozens of Brexit-backing Tory MPs broadly with her for her own government's survival.
They have accepted some shifts from the government that they used to find intolerable - a Brexit departure lounge of a couple of years rather than a sharp exit, and a bill of tens of billions.
But they are not, as this letter makes clear, up for swallowing many more compromises when it comes to getting trade deals done immediately after Brexit.
Read Laura's full blog
Labour claimed the MPs' letter "exposes the deep divisions that run through the heart of this Tory government".
Shadow Brexit minister Paul Blomfield  said: "It is clearer than ever that Theresa May cannot deliver the Brexit deal Britain needs.
"She is too weak to face down the fanatics in her own party and to deliver a final deal that protects jobs and the economy."
The SNP's Stephen Gethins said: "It is clear from this list of demands that the Tories don't want either a transition deal or a ‎future relationship with the EU."
Former Lib Dem leader Tim Farron said it appeared the prime minister had "one arm tied behind her back by the Tory militants who are now nakedly acting like a party within a party".
In other Brexit news, a group of pro-Leave economists claim to have "comprehensively debunked" leaked government forecasts predicting a hit to the UK economy outside the EU.
The Whitehall forecasts - which predicted lower growth across the UK as a result of Brexit - sparked a row when they emerged last month.
Now Economists for Free Trade have published their "alternative" calculations, saying the civil servants' version ignored what they said were the "clear objectives" set out by Mrs May of free trade with Europe and the rest of the world.
Using government models, this would suggest a 2% rise in GDP over 15 years, the group claimed.
Mr Duncan Smith said the report "deserves to be taken very seriously".
Mrs May is meeting Dutch Prime Minister Mark Rutte for talks in Downing Street and is expected to update him on Brexit progress.

A campaign group fighting to keep the UK in the EU has received £400,000 from billionaire investor George Soros.
Mr Soros made his donation to Best for Britain through one of his foundations.
The Daily Telegraph says the group will launch advertising later this month to rally public opinion and convince MPs to vote against the final Brexit deal.
Best for Britain chairman Lord Malloch-Brown, a former Labour minister, said Mr Soros was a "valued" supporter but small donors had contributed more.
Mr Soros, a Hungarian-born US citizen, made a fortune in 1992 betting against sterling on Black Wednesday, forcing then-PM John Major to take the pound out of the European Exchange Rate Mechanism.
He has previously suggested it was possible that the UK would apply to rejoin the European Union soon after Brexit.
According to the Telegraph, the donation was made through Mr Soros's Open Society Foundation
Best for Britain was co-founded by Gina Miller, who took the UK government to court in 2016 over its triggering of the Article 50 process to leave the EU. A judge ruled Parliament must give its consent before Theresa May can start official talks on the terms of the UK's exit. Mrs Miller left Best for Britain last June.
Lord Malloch-Brown confirmed Mr Soros's contribution but said some of the campaign's other major donors had given more.
He added Best for Britain had followed rules governing financial contributions.
He said: "We have never hidden our agenda; we have been campaigning hard to win a meaningful vote on Brexit, which we did, and to keep all options on the table, including staying in the European Union."
He said the campaign was a "democratic and patriotic effort to recover our future and we welcome support for our efforts from many quarters".
The involvement of Mr Soros was reported in the Daily Telegraph in a story co-written by Theresa May's former chief of staff Nick Timothy.
In an article in the paper, Mr Timothy maintained the objective of the campaign was "to convince MPs to vote against the deal Theresa May negotiates with Brussels, regardless of its content".
He said: "Malloch-Brown and his backers believe that, if Parliament rejects the Brexit deal, the government will fall, and Brexit can then be stopped."

Protesters have thrown dead fish into the Thames outside Parliament as they oppose the Brexit transition deal.
The fishing industry and many coastal MPs are unhappy that the UK will not regain control of the country's fishing waters on Brexit day, 29 March 2019.
Instead it will be subject to EU rules for 21 months until December 2020.
Michael Gove has said he shares the "disappointment" but urged people to keep their "eyes on the prize" of getting full control of UK waters back.
In a sign of government unease about the reaction, Theresa May met MPs with fishing ports in their seats on Tuesday in an attempt to explain their approach.
Speaking from the fishing trawler, former UKIP leader Nigel Farage told Sky News the government did not have the "guts" to stand up to the EU.
"They told us they would take back control in 2019 - that is not happening. We are now told at the start of 2021 it may happen," he said.
"I don't think this government has got the guts or the strength to stand up and take back our territorial waters."
Conservative backbencher Ross Thomson, who is MP for Aberdeen South, said he was "really disappointed" fishing communities will not regain control of UK waters as soon as it leaves the 27-nation bloc.
Speaking from the fishing trawler, he said: "Literally within seconds of our leaving (the EU), we're handing all of that back."
Mr Thomson, who was among the delegation of MPs to see Mrs May, said that while it was a "productive" meeting, "we were very, very clear that we'll only support an end deal if it delivers for our fishing communities - and we have been absolutely clear that this is a red line for us".
Mrs May is hoping the deal will be signed off at a meeting of leaders at the European Council summit in Brussels this week, clearing the way for crucial talks on post-Brexit trade to begin in earnest.
But 14 MPs, including leading backbench Brexiteer Jacob Rees-Mogg, said the proposal for Britain effectively to remain in the EU's Common Fisheries Policy for almost two years after Brexit day in March 2019, with no say over the allocation of quotas, would not command the support of the Commons.
"These demands are completely unacceptable and would be rejected by the House of Commons," they said.
Speaking from the quayside in Westminster, Mr Rees-Mogg said the EU "desperately needs our money" so the negotiating strength was with the UK.
He added: "Am I pleased with the transition deal? No, I can't begin to pretend to be. I don't like the transition deal, but I can live with it."

12:00 GMT: I've just been speaking to Dominic Raab, the now former Brexit Secretary. His verdict on the prime minister's deal is damning.
He told me that because of the way the agreement treats Northern Ireland and the rest of the country differently - and the way the country couldn't decide on its own to leave the so-called backstop - that the draft deal is a betrayal of people's trust.
Mr Raab, who says he told the chief whip straight after cabinet yesterday that he would quit, says the prime minister can still change course, and should be ready to walk away with no deal.
He insists the short-term disruption that might entail - which many of his colleagues think would be catastrophic - would be worth it. Better in his view to tolerate short-term pain, than lock ourselves into a dreadful arrangement for years and years to come.
That prospect horrifies others in the government, and on the backbenches too. But it's a risk worth taking he says - claiming it's the best way to proceed, to be willing to risk no deal in the face of what he describes as the EU's "blackmail".
The alternative for the prime minister, carrying on like this, he says, is inevitable defeat in the Commons and who knows what would happen then. Might he put himself forward if it all falls apart?
His answer was it is "irresponsible" to be talking about that right now. But notably, not ruling himself out and knowing, perhaps in a few days' or weeks' time, he might have to give a very different answer.
10:00 GMT: A resignation in itself is not a surprise - but the departure of the Brexit secretary might be the domino that causes everything else to fall.
It's not just that it was his job to make the policy work. It's because he has just given unhappy Brexiteers someone to rally round, and someone who sees himself as a potential challenger to the PM.
After his departure, it becomes extremely difficult for other Brexiteers unhappy about the deal to stay on.
And in the last few minutes Work and Pensions Secretary Esther McVey has decided to leave the government.
There is speculation about International Development Secretary Penny Mordaunt too, although sources close to her say a departure today is far from definite.
Meanwhile, No 10 is busy trying to explain its policy this morning to opposition politicians and then to Parliament in the next hour.
But there have been three resignations from government - Northern Ireland minister Shailesh Vara was the first to quit - and it's not even 10:00 GMT.
It's too early to say if this morning's storm will be a hurricane that will sweep the policy, and maybe the prime minister away.

When British Prime Minister Theresa May first trailed the Conservative Party's proposals for EU citizens living in the UK at last week's EU summit, the initial response from her fellow leaders was hardly enthusiastic.
Now they've seen the details, they haven't changed their tune.
There is actually a fair amount of common ground between the two sides, but the details - naturally - matter.
The EU's goal on citizens' rights, said its chief Brexit negotiator Michel Barnier, is "the same level of protection as [is offered] in EU law".
"More ambition, clarity and guarantees needed than in today's UK position," Mr Barnier tweeted.
This is a crucial point for the European negotiating team.
However pleased it may be that the UK has finally produced a detailed policy document on one aspect of Brexit, this proposal falls short of what it wants in several respects.
The EU's Essential Principles on Citizens' Rights argued that the rights of EU citizens in the UK, and British citizens elsewhere in the EU, should not change as a result of Brexit.
All their rights should be respected.
The British proposal, on the other hand, entails the loss of some of those rights - the legal protection of the European Court of Justice (ECJ), for example, or the unconditional right to bring family members into the UK from third countries.
The cut-off date for eligibility for settled status also needs to be clarified. The UK proposal suggests that the cut-off could be as early as 29 March 2017, the day when Article 50 was triggered.
But it is unlikely that the EU would be willing to agree to any date that has already passed. It would mean - in effect - that some citizens would lose some of their rights while the UK was still a member of the EU.
Opposition to such an idea would be seen in many EU capitals not just as a point of principle, but as a matter of EU law.
It is more likely that British negotiators will eventually agree to settle on their other suggested date - the date on which the UK actually leaves the EU, which is currently due to be 29 March 2019.
If the UK shows flexibility on the cut-off date, it will expect equal flexibility on other matters from the EU. But trust between the negotiating teams appears to be in rather short supply.
It will need to be established quickly because a similar mood of compromise will be needed to reach agreement on the legal system that will underpin any agreement.
The British side insists that the ECJ will have no jurisdiction in the UK after Brexit. The EU insists that the ECJ must continue to offer legal protection for their citizens in the UK, just as it does now.
The obvious answer to this conundrum is to create a joint UK-EU arbitration panel that will ensure that the terms of an agreement are respected under international law. But this will require both sides to alter fairly entrenched positions.
Well, the UK proposal does contain a few carrots.
It accepts that child benefit payments will still be paid for the children of EU workers in the UK whose families live abroad. This was a right that David Cameron tried but failed to abolish.
It advocates a "grace period" of two years to allow EU citizens to get their status in order. It is an idea that could dovetail conveniently with the need for transitional arrangements, to ensure that the British exit from the EU takes place without sudden shocks.
As for British citizens who have retired abroad, the UK proposal offers the reassurance that the government will continue to export and "uprate" the UK state pension within the EU.
So if, for example, you live in Spain, you will still get annual pension increases - something that is not always guaranteed if you live elsewhere in the world.
There is also a promise to simplify bureaucratic procedures for people applying for settled status in the future. But many of them will be furious that they have just spent time and money to obtain permanent residence in the UK, only to find out that they need to start again from scratch.
"How can you promise to give people certainty and then tell tens of thousands that their permanent residence is going to be invalidated?" says Ian Robinson, a partner at the immigration law firm Fragomen.
"It would have been just as easy to continue to recognise permanent residence already granted but just stop accepting new applications," Mr Robinson adds.
The UK may argue that its proposal at least tries to offer something to everyone. But so far it doesn't do enough to satisfy the EU.
So even if the basis for a deal can be envisaged on this one aspect of Brexit, there is plenty of bridge-building still to be done.
When the UK proposal was first trailed, it was described as a generous offer. That was quickly amended to a "fair and serious" one.
Because the EU doesn't see this as a generous offer, and it has been prepared to say so. It involves millions of EU citizens losing some of the rights they currently enjoy, and for EU leaders that is no cause for celebration.
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The claim: Prime Minister Theresa May says there is no turning back from the triggering of Article 50, which starts the process of leaving the EU.
Reality Check verdict: The government is clear that it respects the result of the referendum, so it argues that any debate is theoretical. However, the question of whether Article 50 is irrevocable is the subject of legal dispute.
Article 50 of the Lisbon Treaty was written with a deliberate lack of clarity - it does not say whether it can be revoked once it has been triggered.
As a result, the UK government has been unable to make any definitive legal statements on the issue.
The Justice Secretary, Liz Truss, has said "My understanding is that it is irrevocable," while the Brexit Secretary, David Davis, said in December 2016: "Is it irrevocable? I don't know."
In the recent UK Supreme Court case on Article 50, both sides assumed that it was irrevocable and the court judgement concluded: "We are content to proceed on the basis that that is correct, without expressing any view of our own."
So this is not an issue that has been formally tested in a UK court.
But European Council President Donald Tusk has said that he believes Article 50 can be reversed.
When asked if the UK could unilaterally withdraw its Article 50 notification during the next two years, he said, "Formally, legally, yes."
Lord Kerr - the former British ambassador to the EU, who helped draft Article 50 - agreed.
"You can change your mind while the process is going on," he said.
He acknowledged that this might annoy the rest of the EU, and be seen as a huge waste of time.
"They might try to extract a political price," Lord Kerr said, "but legally they couldn't insist that you leave."
The distinction between political and legal opinion on this issue is critical. The politics might become way too complicated if the UK tried to change its mind.
But who might have the final legal say on what could yet become a critical question?
Article 50 is a piece of European law, so the ultimate arbiter on this issue is the European Court of Justice.
There is an ongoing case in Dublin at the moment that is seeking to refer the question of irrevocability to the European Court to get a definitive answer.
One other point is worth bearing in mind: everyone is talking about a two-year period for negotiating under Article 50, at the end of which the UK would leave the EU.
But Article 50 does provide for that two-year period to be extended, if all 28 EU countries, including the UK, agreed.
No-one is advocating that, but it remains a legal possibility.
The argument that Article 50 cannot be reversed once it has been triggered has not been tested in court.
The rest of the EU has said it does not want the UK to leave, but - politically speaking - it would be very difficult to revoke notification of Article 50, and the current UK government says it has no intention of doing so.

Former Prime Minister Tony Blair has launched a campaign to try to persuade the British people to change their minds about leaving the European Union. It comes just weeks before the government intends to trigger the departure mechanism. In a speech in London, he said that he respected the will of the people, but voters hadn't been given details about the terms on which Britain would exit the EU.
Mr Blair argued that what he called the "cost" of Brexit was only now becoming clear. The referendum vote, he said, was based on "imperfect knowledge" which would now become "informed knowledge".
It's true that we don't yet know the details of the UK's future relationship with the rest of the EU - that will depend on the deal that is negotiated - but lots was said during the referendum campaign about what Brexit would mean in more general terms. In particular, leading figures in both campaigns said leaving the EU would entail leaving the single market.
Mr Blair suggested that immigration was the main issue that propelled Leave to victory in the referendum campaign. But, he argued, the effect of quitting would probably have only a modest impact on overall immigration levels.
He pointed out that just over half of migration into the UK comes from outside the EU. That's confirmed by official statistics from the ONS. In the year to June 2016 net migration - the difference between the number of people who arrived and the number of people who left - was 196,000 from outside the EU, compared with 189,000 from inside the EU.
The same is true for the gross migration statistics - ie just looking at how many citizens from different parts of the world arrived in the UK.
Again, there were slightly more from outside the EU (289,000) than from inside (284,000) along with a smaller number of British citizens returning to live in the UK (77,000). And only an estimated 82,000 or 12.6% of the 650,000 total were EU citizens who arrived looking for work.
Theresa May has ruled out introducing a points-based migration system but the government hasn't published details of what it does want to implement. If the new system continues to allow in EU migrants with job offers, as well as students and people coming to join spouses, then Mr Blair's 12% would be, broadly speaking, correct.
There could be a bigger impact if the government opts for a capped number of work permits. But about half of total migration will be unaffected no matter what arrangements are made with the EU.
This isn't really a fair quotation. It's a reference to an interview given by Philip Hammond on ITV's Peston on Sunday on 26 June.
Mr Hammond said: "I believe it's essential that we protect our access to the single European market. Whether we like it or not, our economy, over 40 years, has become shaped by that access, and to lose that access now would be catastrophic."
But note that he was talking about access to the single market. That's not the same as membership. You don't have to be a member of the single market to have access to it, although the level of access that Britain would have after leaving the single market would depend on what trade relationship was negotiated.
It's true that the pound has fallen against the dollar and the euro since the referendum, although not by quite as much as Mr Blair said. It has recovered from its lowest point. Against the dollar, the pound is currently down about 16% compared with its pre-referendum level. Against the euro, it's about 10.5% down.
It's also worth noting that the pound/euro exchange rate was at a similar level to now between 2009 and the middle of 2011, so it's hardly unprecedented. Against the dollar, though, the pound has hit multi-decade lows in recent months.

This was a wide-ranging speech setting out Labour's views of Britain's place in the world after Brexit. But the main focus was on the UK's future economic relationship with the European Union. The BBC's Reality Check correspondent Chris Morris has been looking at a few key quotes from the speech.
This was the key passage of Jeremy Corbyn's speech - putting clear water between Labour and the government.
He wants to stay in a customs union to avoid the imposition of tariffs on goods traded within Europe, and to help solve the Brexit conundrum at the Irish border.
As a member of the EU, the UK is currently in the customs union, which means that all countries impose a common external tariff - in effect the same tax - on goods being brought in from elsewhere in the world. Once those goods have crossed the external border, there are no further tariffs to move them around inside the customs union.
Mr Corbyn wants to replicate most of that in a new customs union, which would certainly help companies who rely on moving goods across EU borders several times in their manufacturing process.
But it wouldn't entirely solve the problem in Ireland, because some of the border issues - such as food safety or animal welfare - involve regulations that are nothing to do with the customs relationship.
Here Mr Corbyn addresses the government's primary reason for opposing the formation of a new customs union: that it would stop the UK doing trade deals around the world.
He says he wants to ensure that the UK will be able to negotiate new trade deals "in the national interest".
Although he is not explicit about what this involves in practice, it appears to mean that Labour wants the UK to be involved in negotiating those trade deals alongside the EU. He is not suggesting that the UK would be an entirely separate entity in international trade.
Membership of a customs union constrains your ability to sign your own trade deals, because you can't alter external tariffs. But you can negotiate on services, or on harmonising regulations with other countries.
Mr Corbyn argues that this is a compromise worth making, and it is another significant departure from government policy. The Conservatives accuse him of wanting to have his cake and eat it - a familiar theme.
This is Mr Corbyn's political pitch, trying to peel enough Tory MPs away from the government to be able to defeat it in Parliament on the question of a customs union. He is trying to position Labour in the middle ground - supporting what appears to be a softer version of Brexit rather than what he would see as a hard ideological one.
Of course anything Labour proposes, just like anything the government has proposed, does not have to win the approval of Parliament alone. It would also have to be negotiated with the rest of the EU, which remains suspicious of any UK effort to cherry-pick the best bits.
Mr Corbyn was very clear about this - attacking the government for starting with what he called rigid red lines on immigration and only afterwards working out what it meant for the economy. He says it is very clear that free movement of people from the EU would come to an end.
There would, he says, be reasonable management of immigration, but the economy should always come first.
This is a delicate balancing act. Without free movement of people, the UK will not get the same access to the single market that it has now.
On the other hand, Labour can't ignore the "take back control" message entirely. But it is interesting to note that there was no mention at all in this speech of the future role of the European Court of Justice.
It has always been clear that Jeremy Corbyn has never been a massive EU enthusiast. He says he campaigned for "Remain with reform" - which sounds suspiciously like David Cameron.
But he was trying to appeal to both Remain and Leave voters in this speech, arguing that Brexit would lead neither to disaster nor to a land of milk and honey.
Like the prime minister, he is trying to claim the Brexit middle ground. But, also like the prime minister, that doesn't mean he can sit on the fence, with little more than a year to go before Brexit is due to happen.
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After months of talking we've finally got our first look at a draft of the agreement which is designed to take the UK out of the European Union. This is a long and complex legal document. It is the European Commission's draft of a withdrawal agreement, which still has to be discussed with the 27 EU member states and the European Parliament before it gets formally sent to the UK authorities for negotiation.
The document is based on the joint report that was agreed by EU and UK negotiators in December but it goes into more detail and translates some of the commitments made into formal legal text.
Here are a few excerpts, with the key phrases in bold type.
Most of the headlines are being generated by what the document says about steps that need to be taken to avoid the reimposition of a hard border in Ireland.
In effect, it creates a customs union between Northern Ireland and the EU - in fact it says specifically that Northern Ireland "shall be considered to be part of the customs territory of the Union".
That of course leads back to the question of whether there would have to be a customs border between Northern Ireland and the rest of the UK instead - something the government has already rejected emphatically.
But it is important to stress that Michel Barnier, the EU's chief negotiator, describes the text on Ireland as a "backstop". Three options were set out in the agreement in December but no progress has been made on the other two.
If another solution can be found for the Irish border during overall negotiations on the future relationship between the UK and the EU, the backstop can be deleted.
But if the proposal on the Irish border did come into effect, EU institutions would be given the authority to enforce it, and Northern Ireland would be under the jurisdiction of the European Court of Justice (ECJ).
It is another red line for the government, and another sign of how difficult it is going to be to find a solution at the Irish border.
Other roles for the ECJ, with potential influence over the UK for many years, are also scattered throughout the text - including the proposal that it should be the ultimate arbiter of the withdrawal agreement itself. All of this is rejected by the UK.
There is a huge amount of detail in this text about the rights of EU citizens in the UK and UK citizens elsewhere in the EU after Brexit. But here is something that will dismay a lot of Brits living elsewhere in Europe - their rights will apply only in the country in which they live.
They will lose the right to further free movement in the future. It is only a draft but many UK citizens who have chosen to live elsewhere in the EU fear their rights are being forgotten.
This punishment clause has caused controversy before and will probably do so again. Basically, if the UK misbehaves during a transition period after Brexit, some of its rights to participate fully in the single market could be suspended.
Any suspension, the text suggests, would not exceed three months but could be renewed. It's not exactly what businesses desperate for some certainty want to hear.
Vassal state, anyone?
Finally, a reminder of how much still has to be done. The UK will lose access to a whole series of databases and networks that it has become accustomed to using.
The text does say there can be some exceptions but access to any of them will have to be negotiated (in the field of internal security and police co-operation, for example).  This is another reason why a transition period is important, because it will give more time for this kind of detailed work to be done.
But Michel Barnier has said that technical negotiations this week have confirmed that several clear differences of opinion remain about the terms and conditions for a transition - and, in his words, "transition is not a given".


The Labour Party is going into the 2019 general election with a promise to "get Brexit sorted" in six months.
So, what exactly is its plan?
If it wins the election, Labour wants to renegotiate Prime Minister Boris Johnson's Brexit deal and put it to another public vote.
Rather than backing either Leave or Remain during the election campaign, the party will remain neutral until a later date.
Should a referendum under a Labour government be held, voters would be able to choose between a "credible Leave option" and Remain.
The party would organise the referendum within six months and decide which position to back at a special conference in the build up.
Experts at the Constitution Unit at University College London say it would take a minimum of 22 weeks to organise another referendum.
Labour's Brexit stance was adopted after Labour's delegates voted for it at the party conference in September.
Delegates rejected a motion which called on the party to back Remain outright in all circumstances.
It was voted down despite receiving support from senior figures - such as shadow Brexit secretary Keir Starmer and shadow foreign secretary Emily Thornberry.
Until July, Labour had resisted outright support for another referendum. Its deputy leader, Tom Watson, said "ambiguity" over the party's Brexit policy had cost it votes at the European elections in May.
Mr Corbyn says Labour will negotiate a Brexit deal which maintains a very close trading relationship with the EU. This would be achieved by staying in a customs union and keeping close alignment to the single market.
That would mean the UK would be able to continue trading with the EU without tariffs (taxes on imports) being applied.
However, being in a customs union would prevent the UK from striking its own trade deals with other countries on goods, such as the US.
Under the deal negotiated by Mr Johnson, the UK would leave both the single market and customs union. This would require checks to take place on some goods travelling between Great Britain and Northern Ireland.
Labour believes it would take no longer than three months the renegotiate the current Brexit deal.
Just like the Conservative Party, Labour has had to deal with internal divisions over its Brexit policy.
Many Labour MPs who represent parts of the country where most people voted Leave have previously expressed unhappiness with the party's shift on supporting a referendum.
More than 25 Labour MPs wrote to Mr Corbyn in June, saying another public vote would be "toxic to our bedrock Labour voters" and urged the party leadership to back a Brexit deal.
On the other hand, shadow chancellor John McDonnell and shadow foreign secretary Emily Thornberry, are among those to say remaining would be the best thing for the UK - even if the other option is a Labour-negotiated Brexit deal.


Peers have been urged to "respect" voters' decision to leave the EU as they began debating the Brexit bill.
With Prime Minister Theresa May taking the unusual step of sitting in the Lords to watch the opening speeches, Leader of the House Baroness Evans said peers must not "frustrate" Brexit.
But Labour said "reasonable changes" could take place to the bill.
MPs have already backed the proposed law, authorising Mrs May to inform the EU of the UK's intention to leave.
The government does not have a majority in the House of Lords where a record 190 peers are due to speak over two days.
The sitting was extended to midnight on Monday to allow more peers to speak and the debate will continue on Tuesday.
Opposition and crossbench peers are seeking guarantees about the rights of EU citizens in Britain and the role of parliament in scrutinising the process.
Mrs May has said she wants to invoke Article 50 of the 2009 Lisbon Treaty - the formal two-year mechanism by which a state must leave the EU - by the end of March, and the government has warned the House of Lords not to frustrate the process.
The prime minister decided to sit in the Lords chamber itself to listen to the start of the debate. Her official spokesman said this was "in recognition of the importance of this bill as it proceeds through the Lords".
Opening proceedings, Lady Evans said the government had promised to deliver on the result of last year's referendum, in which 51.9% of voters backed Brexit.
She said: "This bill is not about revisiting the debate." She added: "Noble Lords respect the primacy of the elected House and the decision of the British people on 23 June last year."
Lady Evans also said: "This bill is not the place to try and shape the terms of our exit, restrict the government's hand before in enters into complex negotiations or attempt to re-run the referendum."
For Labour, Lords opposition leader Baroness Smith of Basildon said the government would not be given a "blank cheque" and that "if sovereignty is to mean anything, it has to mean parliamentary responsibility".
She promised to make ministers consider "reasonable changes" and this was not "delaying the process" but "part of the process" of Brexit.
But Lord Newby, leader of the Liberal Democrats in the Lords, said the bill could be changed and sent back to the House of Commons for reconsideration, arguing there was a "world of difference between blocking... and seeking to amend it".
The government's approach was "little short of disastrous" and "to sit on our hands in these circumstances is unthinkable and unconscionable", he added.
UKIP's Lord Stevens of Ludgate said the prime minister "should be congratulated" for "honouring" the commitment to leave the EU, following the referendum.
But he told peers it was better to "leave the EU quickly", rather than enter negotiations with member states on a post-Brexit deal.
And Labour peer Lord Howarth of Newport, who backed Brexit, said: "All of us should respect the democratic decision to leave. If we do not, public disaffection from politics will become a crisis. Those who meditate a second referendum are playing with fire."
By Ben Wright, political correspondent
Peers will not block Brexit. But nor are they likely to wave this bill through without asking the Commons to think again about a number of issues.
Peers are certainly keen to have their say in this week's two-day debate.
The committee stage scrutiny - and possible votes - will come the week after.
And with many non-party cross-benchers in the picture the government cannot be certain of defeating all the changes peers will be pushing for. That would mean the Commons could have to consider the bill again.
However, there is no sign the unelected Lords want to go into battle with MPs and the government over Brexit - or meddle with the referendum's mandate.
Labour has said it will not frustrate Theresa May's plan to trigger the start of Brexit by the end of next month.
The government has set aside five days in total to discuss the various stages of the EU (Notification of Withdrawal) Bill - starting with its Second Reading, in which peers debate the general principles of the bill.
The Second Reading debate is due to conclude on Tuesday evening - possibly with a vote, but only if peers break with their usual practice of allowing government legislation through unopposed at this stage.
Although amendments are not voted on at this stage, speeches will be closely watched for signs of the mood of peers on the two key ones of parliament having a "final meaningful vote" on the draft Brexit agreement - and guaranteeing the rights of EU citizens in the UK.
Detailed scrutiny of the bill at committee stage is due to take place on 27 February and 1 March. If the bill is not amended, then it could theoretically be approved by the Lords at Third Reading on 7 March, becoming law shortly afterwards.
If peers do make changes to the bill, it would put them on a collision course with MPs - who overwhelmingly passed the bill unaltered and would be expected to overturn any Lords amendments.
Although the Conservatives have the largest number of peers in the Lords, with 252 members, they are vulnerable to being outvoted if opposition peers - including 202 Labour peers and 102 Lib Dems - join forces.
Much will hinge of the actions of the 178 crossbenchers in the Lords - who are not aligned to any party and do not take a party whip.
Once Article 50 is invoked, there will be up to two years of talks on the terms of the UK's departure and its future relationship with the EU unless all 28 member states agree to extend the deadline.

Ministers have sought to reassure peers about the status of EU citizens in the UK after Brexit as they face possible defeat over the issue in the Lords.
Home Secretary Amber Rudd has written to peers to say the UK cannot offer a unilateral guarantee on residency but it will be a priority once talks begin.
She also said peers would have a say on future changes to migration rules.
The Lords could inflict a defeat on the government when amendments to the Brexit bill are debated on Wednesday.
Earlier this month, MPs passed unamended a bill which would give Theresa May the power to begin the Brexit process.
They accepted assurances from ministers that protecting the rights of the 3 million EU nationals living in the UK would be a priority for ministers.
But many peers want the government to go further and state that all EU nationals lawfully in the UK at the time the UK exits the EU should be allowed to stay.
In a letter to peers, Ms Rudd said such a guarantee, however "well-intentioned", would not help the hundreds of thousands of UK citizens living on the Continent as it could leave them in potential limbo if reciprocal assurances were not given by the EU's 27 other member states.
BBC political editor Laura Kuenssberg
The letter is not that different to what was sent to MPs previously to try to ease their minds, as the Article 50 legislation made its way through the House of Commons.
It does though appear to kill off the idea that Theresa May will arbitrarily set a cut off date for EU immigration without having to get MPs or peers onside first. But it is unlikely to spare the government's blushes tomorrow. Without a further more dramatic concession, they are set to lose.
That will set in train the first 'ping' of the potential 'ping pong' - the Parliamentary process where the Lords reject something in the red chamber, sending it back down the corridors to the green benches - daring, imploring perhaps, backbenchers to join with them and push back at the government.
There is no sign at the moment that ministers want to budge on this issue
"We need to act fairly and provide certainty for both groups of people as quickly as possible and that will remain the government's position," she wrote.
She suggested the inability to reach a mutual agreement was more a question of timing than principle and the UK and EU had a "common goal" in doing so if, as expected, the UK notifies the EU of its intention to leave by the end of March.
"There is absolutely no question of treating EU citizens with anything other than the utmost respect," she wrote.
"That's why we will be making securing their status a priority as soon as we trigger Article 50 and the negotiations begin.
"I know some colleagues are concerned about how long this might take to resolve, but the government remains committed to providing reassurance to EU nationals here and UK nationals in the EU as a priority once Article 50 has been triggered."
Ms Rudd said that any changes to the status of existing EU residents and those coming from Europe in future would have to be approved by Parliament.
"This will be done through a separate Immigration Bill and subsequent secondary legislation so nothing will change for any EU citizen, whether already resident in the UK or moving from the EU, without Parliament's approval."
She added: "This isn't just about ensuring British businesses and our public sector have access to the right workers.
"We owe it to those many European citizens who have contributed so much to this country to resolve this issue as soon as possible and give them the security they need to continue to contribute to this country."
Last week, peers gave an unopposed second reading to the European Union (Notification of Withdrawal) Bill.
But the government - which does not have a majority in the Lords - is potentially more vulnerable to defeat now that specific amendments are being discussed.
The Supreme Court ruled in January that the government requires the prior approval of both Houses of Parliament before it can trigger Article 50.

Sam Gyimah has become the first Tory leadership candidate to back a further referendum on Brexit.
The former universities minister is the 13th candidate to join the race, which will also choose the UK's next PM.
Mr Gyimah - who quit over Theresa May's Brexit plan - said he would vote Remain in such a poll, but would not "actively campaign" if he became prime minister.
Meanwhile, other contenders to succeed Mrs May have been setting out their Brexit plans.
Former Commons Leader Andrea Leadsom said she would seek a "managed exit" by 31 October - the deadline the EU has set for leaving the bloc.
She told the BBC's Andrew Marr Show that Mrs May's negotiated plan was "dead", as the EU would not re-open it and Parliament would not vote for it.
Mrs Leadsom said she would instead introduce legislation to guarantee citizens' rights, ramp up preparations for all Brexit scenarios and explore alternatives to the Irish border backstop plan.
Home Secretary Sajid Javid, who is also running in the Tory leadership race, said he "passionately" wanted to leave the EU with a deal, but it was "responsible" to prepare for a no-deal exit.
His pitch for the top job was a "modern digitised border" between Northern Ireland and the Republic of Ireland, which he said would "unlock a Brexit deal".
Appearing on the Andrew Marr Show, Mr Javid said he would try to renegotiate the Irish border backstop plan and offer to pay Ireland for work towards a digital border, saying it was "morally right".
He also said there should not be another general election before Brexit is delivered, but admitted he "may not be able to stop it" if the government were defeated in a vote of no confidence.
The winner of the contest to lead the Conservative Party will become the next prime minister.
Mr Javid is one of the leadership candidates who have said they are prepared to leave the EU without a deal if necessary.
But his rival, Health Secretary Matt Hancock, said leaving without a deal is "not an available choice" to the next PM, as Parliament "will never allow it to happen".
In a letter to MPs, he set out his strategy for delivering Brexit, including a pledge to negotiate an "end point" to the backstop plan.
He also says he would unilaterally guarantee the rights of EU citizens, and set up an "Irish Border Council" to explore how technology can be used to avoid a hard border.
The backstop is a backup plan to maintain an open border on the island of Ireland in case the UK leaves the EU without an all-encompassing deal.
The EU's chief negotiator Michel Barnier has previously insisted the backstop plan would not be renegotiated, saying it is "part and parcel" of the UK's Brexit deal.
On Sunday, Irish European Affairs Minister Helen McEntee said the backstop plan and withdrawal agreement will not be changed.
"Much of what is in the withdrawal agreement was asked for by the UK," she tweeted.
"They were not bystanders in the two years it took to negotiate. Bit of realism needed."
Rory Stewart - who has also launched his own leadership bid - said candidates should "stop pretending that there is some different deal out there", and focus instead on getting the current agreement through Parliament.
"There is literally no evidence at all that Europe will give us a different deal", the international development secretary wrote on Twitter.
Speaking to BBC News, Mr Gyimah said he was putting himself forward to "broaden the race" for the Conservative leadership.
The East Surrey MP said existing candidates had either been pledging to "reawaken the deal that is dead" or "bunching around" the option of a no-deal exit.
Mr Gyimah quit the government last December over Mrs May's Brexit plan, saying that he intended to vote against the deal and advocate another referendum.
He added that another referendum could be a way to "break through" the impasse in Parliament, although he said that a no-deal Brexit would be an "abject failure".
Conservative MPs will take part in a series of votes to narrow down all the candidates to a final two.
These two MPs will then face a vote of the full party leadership.
Most members of political parties in the UK are pretty middle-class, but Conservative Party members are the most middle-class of all: 86% fall into the ABC1 category.
Around a quarter of them are, or were, self-employed and nearly half of them work, or used to, in the private sector.
Nearly four out of 10 put their annual income at over £30,000, and one in 20 put it at over £100,000. As such, Tory members are considerably better-off than most voters.

DUP MP Sammy Wilson has warned that his party's deal to support the Conservative government could be jeopardised by the Brexit negotiations.
He said any attempt to "placate Dublin and the EU" could mean a withdrawal of DUP support at Westminster.
He was responding to reports of a possible strategy to deal with the Irish border after Brexit.
Former DUP leader and first minister Peter Robinson also responded, saying "the south needs to wind its neck in".
He said Dublin politicians had taken to "lecturing the UK," doing "significant harm to north/south relations".
"Sensible solutions can be found and positive outcomes are more likely to be reached if a spirit of friendship and mutual understanding exists," he said.
A story, published earlier in the Times newspaper, reported that British and EU officials could be about to seek separate customs measures for Northern Ireland after the UK leaves the European Union.
This could avoid any divergence in trade rules between Northern Ireland and the Republic.
Mr Wilson said that the UK government would "have to recognise that if this is about treating Northern Ireland differently, or leaving us half in the EU, dragging along behind regulations which change in Dublin, it's not on".
Earlier on Thursday, DUP leader Arlene Foster said that the government had a "clear understanding that the DUP will not countenance any arrangement that could lead to a new border being created in the Irish Sea".
Mr Wilson said the proposal mooted in The Times report was unworkable, and revealed the DUP would be seeking clarification from the government on its accuracy.
The DUP struck a deal with the Conservative government in June, agreeing to support Tory policies at Westminster, in return for an extra £1bn in government spending for Northern Ireland.
Mr Wilson said his party will be "making clear to the government we have a confidence and supply arrangement with them".
The East Antrim MP added that "if there is any hint that in order to placate Dublin and the EU, they're prepared to have Northern Ireland treated differently than the rest of the UK, then they can't rely on our vote".
Mr Wilson was speaking in a BBC interview in his East Antrim constituency on Thursday afternoon.
The DUP has consistently opposed calls for Northern Ireland to be granted "special status" within the EU, in a bid to resolve border issues.
The party has accused Irish nationalists of using the special status campaign as "an opportunity separate Northern Ireland from the rest of the United Kingdom, with a border in the Irish Sea".
Under the type of plan mooted in The Times report, regulations relating to customs would be harmonised on both sides of the Irish border.
It would allow a freer flow of traffic and goods, in line with the UK's aim of making the crossing as "frictionless" as possible.

Parliament has been sitting on a Saturday for the first time in 37 years to debate and vote on Boris Johnson's Brexit deal.
MPs have supported a motion tabled by Independent MP Sir Oliver Letwin that "withholds approval" for Boris Johnson's Brexit deal until legislation implementing it has been passed.
It was very close - the government lost by just 16 votes, by 322 to 306.
It was due to be followed by a vote on the main government motion - whether or not to back the deal. But the motion, as amended, was approved by MPs without a vote, as the government effectively accepted defeat.
A cross-party amendment on preventing a no-deal Brexit and holding a second referendum was not put to the vote either, after the government pulled the motion it was attached to.
Under the terms of the so-called Benn Act, the prime minister must send a letter to Brussels requesting a three-month Brexit delay by 2300 BST.
But Prime Minister Boris Johnson said: "I will not negotiate a delay with the EU and neither does the law compel me to do so."
He added: "I continue in the very strong belief that the best thing for the UK, and for the whole of Europe is for us to leave with this new deal on 31 October, and to anticipate the questions that are coming from the benches opposite, I will not negotiate a delay with the EU."
A Number 10 source said: "Parliament has voted to delay Brexit yet again.
"The prime minister will not ask for an extension - he will tell EU leaders there should be no delays, they should reject Parliament's letter asking for a delay, and we should get Brexit done on 31 October with our new deal so the country can move on."
The House of Commons Twitter account posted that the government now "must ask for an extension of Article 50 under the Benn Act and set out how it intends to proceed".
Labour leader Jeremy Corbyn told MPs: "Today is an historic day for parliament because it said it will not be blackmailed by a prime minister who is apparently prepared once again to defy a law passed by this parliament.
"I invite him to think very carefully about the remarks he just made about refusing, apparently, to apply for the extension which the EU number two Act requires him to do."
SNP justice and home affairs spokesperson Joanna Cherry tweeted: "So Boris Johnson loses again today but is threatening not to comply with BennAct or promises made to Scottish court.
"Just as well we are due back in court on Monday & Mr Speaker has just confirmed to me that he'll sign Extension letter if court so requires."
No. The government plans to push ahead with the legislation enacting the treaty agreed by Boris Johnson in Brussels - the Withdrawal Agreement Bill on Monday.
They also want to hold another "meaningful vote" on the Brexit deal on Monday.
Commons Speaker John Bercow will not allow the government to ask the same question of MPs again - but he said he would give the matter consideration before giving a ruling on it on Monday.
By BBC Parliamentary Correspondent Mark D'Arcy
If John Bercow allows the "meaningful vote", Labour MPs in pro-Brexit seats will be under massive pressure.
They would much rather go straight to a Withdrawal Agreement Bill, where they can tinker with the detail to their heart's content - possibly allying with dissident Tories to write a customs union into it.
And for the government, putting down a bill without the support of the DUP would be fraught with danger.
An early indicator will be whether the government can win the programme motion necessary to ensure the Bill gets through in quick time.
Read Mark's full blog

British and French fishermen have clashed in the Channel, over alleged "looting" of the scallop fishing grounds there by British boats. Tense exchanges were filmed on Tuesday, off the coast of Normandy, after years of carefully managed truce between the two sides.  What lies behind the fresh tensions, and what impact will Brexit have on relations between them?
In times of cross-Channel tension, it's been a handy and well-worn reflex in some quarters to blame the meddlesome bureaucracy of the EU - its agricultural subsidies; its detailed trading standards; its fishing quotas.
For more than a decade, the friction between British and French fishermen around the Bay of Seine, off the coast of Normandy, has been over scallops.
The French fishing industry is bound by an agreement with its government in Paris not to fish for scallops in the area between May and October, in order to conserve fish stocks. The British - who are also allowed to fish the area under EU access rights - are under no such restrictions from their own government.
Et voilà: an ongoing battle that's been wearily termed "the scallop wars".
For the past few years, a carefully constructed truce has kept the peace over this watery battlefield. The British agreed to ban their larger fishing vessels from the area until October, in keeping with French restrictions, on the understanding that smaller British boats could fish there all year round.
But with the big boats out of the way during the summer months, the Regional Committee for Maritime Fishing in Normandy says that the number of smaller boats coming across the Channel is growing. This year, they asked that all British boats stay away from the scallop fishing grounds until they could share the catch, from October onwards.
But smaller British fishermen are already feeling hard done by, because the vast majority of their EU fishing quotas go to larger British industrial fishing fleets, and many struggle to make a profit. Scallops, on the other hand, are not restricted by standard EU quotas.  Larger vessels have limits on the number of days they can fish for them, but boats under 10m (32ft) have an open invitation - a small but important symbolic advantage.
So, their answer to the new terms of the truce?  Non.
With no gentlemen's agreement in place, British vessels have had free rein to stir up the stormy waters of Normandy's scallop grounds. And in the early hours of Tuesday morning, the French took things into their own hands.
So far, no-one has been hurt, but the dispute remains unresolved. Both sides have agreed to meet, to try to find a solution.
One local fisherman told Le Monde newspaper that a hard Brexit would solve it once and for all - by denying the British automatic access to fish in EU waters.
But the rules restricting French scallop fishermen in the Bay of Seine have nothing to do with the EU. And even if their British rivals leave the bloc, France's fisheries ministry points out, that area is open to other EU members who have the freedom to fish there all year round.
Even for British fishermen - who are reported to have voted overwhelmingly for Brexit, with the aim of regaining control over their own national fishing grounds - Brexit may not be the cure-all.
EU vessels will no longer have automatic access to British fishing waters after Brexit, but the war over quotas between big industrial vessels and local fishermen is an internal British one.
It's the authorities in London, not Brussels, who set the rules under which industrial fishing companies dominate the market, and allow the "leasing" of fishing quotas by big companies, while some other EU governments, like France, do not.
Brexit may look like a handy solution for fishermen on both sides of the Channel, but - as one journalist put it recently - it could well be a red herring.

The Scottish and Welsh governments are to be allowed to have a say in the Supreme Court battle over how Brexit should be triggered.
The government is appealing against a High Court ruling that MPs must get a vote on triggering Article 50.
The Supreme Court confirmed that Wales and Scotland's senior law officers will be allowed to take part in the appeal.
UK PM Theresa May said on Friday that work was "on track" to begin the formal process of Brexit by April 2017.
At a joint press briefing with German Chancellor Angela Merkel, following a meeting with EU leaders in Berlin, Mrs May said: "We stand ready to trigger Article 50 by the end of March 2017 and I want to see this as a smooth process, an orderly process, working towards a solution that's in the interests of both the UK and also in the interests of our European partners."
McCord Brexit case can go to Supreme Court
The judges ruling on Brexit case
She was speaking after the Supreme Court confirmed that Scotland's senior law officer, the Lord Advocate, had been invited to address the court on the relevance of points of Scots law. The Counsel General for Wales will make arguments about the importance of parliamentary sovereignty and the rule of law.
The Supreme Court hearing is expected to start on 5 December and last four days, with the decision expected in the new year.
Analysis
Tom Bateman, BBC political correspondent
The government has been clear in its belief that the referendum result gives it the authority to use its executive powers to trigger the EU exit process.
But the Scottish government believes this is unlawful, claiming that invoking Article 50 would involve a "fundamental alteration" in the UK's constitutional arrangements and the rights of Scottish people - who voted to remain in the EU - about which the Hollyrood parliament should be consulted.
It is far from clear how much legal weight these arguments will carry in this complex constitutional case in front of 11 Supreme Court judges.
But the politics are easier to predict: If the government's appeal fails, Parliament is likely to become the next battleground over the timing and - potentially - the terms of Brexit.
It is a fight Downing Street is desperate to avoid - amid the increasingly toxic atmosphere between those tussling for control of Britain's departure from the EU.
A government spokesman said it was "a matter for the Supreme Court which applications to intervene are accepted".
"The UK government's position remains the same, and we will be taking strong legal arguments to court next month," he said.
Scotland's Brexit minister Michael Russell welcomed the decision, but added: "We continue to call on the UK government to drop the appeal and to accept that Parliament has the right to determine the triggering of Article 50.
"We recognise the decision of people in England and Wales to support Brexit, but the views of people in Scotland cannot simply be brushed aside."
The Independent Workers Union of Great Britain, which describes itself as "fighting for the rights and welfare of some of the most vulnerable and under-represented workers in the UK", has also been given permission to make submissions to the Supreme Court.
The Attorney General for Northern Ireland has made a reference to the court on devolution issues and did not need permission to intervene. Separately another Brexit case brought by victims' campaigner Raymond McCord in Belfast has also been referred to the Supreme Court.
Earlier this month three High Court judges ruled that the prime minister did not have the power to use the royal prerogative to trigger Article 50 of the Lisbon Treaty to start the two-year process of negotiating Brexit, without the prior authority of Parliament.
Mrs May and her ministers are now asking the Supreme Court to overturn that unanimous decision.
Labour has said it will not attempt to delay or scupper this process if a vote goes ahead.
But Lib Dem leader Tim Farron has said his party will vote against triggering Article 50, unless they are promised a second referendum on the UK's Brexit deal with EU leaders. Some Labour MPs have said they are also willing to oppose it.
Scotland's first minister, Nicola Sturgeon, believes that the consent of the Scottish Parliament and the UK's other devolved parliaments and assemblies should also be sought before Article 50 is triggered.
Mick Antoniw AM, Counsel General for Wales, said previously: "This case raises issues of profound importance not only in relation to the concept of parliamentary sovereignty, but also in relation to the wider constitutional arrangements of the United Kingdom and the legal framework for devolution."
The legal challenge over Brexit was brought by investment fund manager and philanthropist Gina Miller, along with London-based Spanish hairdresser Deir Dos Santos and the People's Challenge group, set up by Grahame Pigney and backed by a crowd-funding campaign.
After Lord Toulson's retirement this summer, the appeal will be heard by all 11 remaining Supreme Court justices, led by their President Lord Neuberger.

The UK government is to reject calls for a Scottish independence referendum before Brexit after Theresa May said "now is not the time".
The prime minister said the focus should be on getting the best Brexit deal for the whole of the UK.
Scottish Conservative leader Ruth Davidson said Nicola Sturgeon's demand for a vote by the spring of 2019 would be rejected "conclusively".
Ms Sturgeon said blocking a referendum would be a "democratic outrage".
Ms Sturgeon, the Scottish first minister, told BBC Scotland: "It is an argument for independence really in a nutshell, that Westminster thinks it has got the right to block the democratically elected mandate of the Scottish government and the majority in the Scottish Parliament.
"You know history may look back on today and see it as the day the fate of the union was sealed."
Ms Sturgeon has called for a referendum to be held in the autumn of 2018 or the spring of the following year, to coincide with the conclusion of the UK's Brexit negotiations with the EU.
But Mrs May said her message to Ms Sturgeon was clear - "now is not the time".
The prime minister added: "I think we should be working to get the right deal for Scotland and the UK with our future partnership with the European Union.
"It would be unfair to the people of Scotland that they would be being asked to make a crucial decision without the information they need to make that decision."
The prime minister also said the country should be "working together, not pulling apart".
Ms Davidson later told a media conference in Edinburgh that the people of Scotland should have the right to see how the UK was working after leaving the EU before deciding whether or not they wanted independence.
She added: "People should only be asked to make a judgment on whether to leave or remain within a 300-year-old union of nations when they have seen for themselves how that union is functioning following Brexit.
"They should also know what the alternative entails and we have seen no clarity from the SNP on even the basic questions of their proposition."
Scottish Secretary David Mundell said: "The proposal brought forward is not fair, people will not be able to make an informed choice.
"Neither is there public or political support for such a referendum.
"Therefore we will not be entering into discussions or negotiations about a Section 30 agreement and any request at this time will be declined."
By BBC Scotland political editor Brian Taylor
The Tory triumvirate - PM, secretary of state, Scottish leader - stress that a referendum might be feasible once Brexit is signed, sealed and settled. David Mundell seemed particularly keen to stress that point.
However, if they won't contemplate Section 30 meantime, then the time needed for legislation, consultation and official preparation would suggest that - by that calendar - any referendum would be deferred until 2020 or possibly later. Possibly after the next Holyrood elections.
Options for the FM? She could sanction an unofficial referendum, without statutory backing. Don't see that happening. It would be a gesture - and Nicola Sturgeon, as the head of a government, is generally averse to gestures. Unless they advance her cause.
She could protest and seek discussions. Some senior Nationalists believe this to be a negotiation ploy by the PM, the prelude to talks.
Will the first minister proceed with the vote next week at Holyrood, demanding a Section 30 transfer in which the Greens are expected to join with the SNP to create a majority? I firmly expect her to do so, to add to the challenge to the PM.
Scotland voted by 55% to 45% to remain in the UK in a referendum in September 2014 - but Ms Sturgeon says a second vote is needed to allow the country to choose what path to take following last year's Brexit vote.
MSPs are due to vote next Wednesday on whether to seek a section 30 order from the UK government, which would be needed to make any referendum legally binding.
The parliament currently has a pro-independence majority, with the Scottish Greens pledging to support the minority SNP government in the vote.

Here is the full text of First Minister Nicola Sturgeon's letter to Prime Minister Theresa May, asking for a Section 30 order to allow Holyrood to legislate for a referendum on Scottish independence.
Dear Theresa,
When we met in Glasgow on Monday, I wished you well for the negotiations that lie ahead now that you have formally invoked Article 50 of the Lisbon Treaty. I want to reiterate those good wishes now.
I very much hope that you succeed in realising your ambitions for the terms of the UK's future relationship with the EU. A good deal for the UK is clearly in Scotland's interests whatever constitutional future we choose.
It is for that reason that I intend that the Scottish government will play a full and constructive role in securing such an outcome.
I expressed my frustration on Monday that the process leading up to the invoking of Article 50 had failed to involve the devolved administrations in any meaningful way - a view that I know is shared by the First Minister of Wales.
Far from securing a UK-wide approach ahead of invoking Article 50 - as you committed to do last July - the voices of the devolved administrations were largely ignored and all attempts at compromise rejected, in most cases with no prior consultation.
As we move forward into a new phase, we need to agree a more direct role and influence for the devolved administrations, reflecting the key interests that are at stake for all of us.
However, whatever outcome is secured, it seems inevitable that it will remove the UK, not just from the EU, but also from the single market.
As you are aware, that is not an outcome that the people of Scotland voted for. It is also an outcome that will have significant implications for our economy, society and place in the world.
In these very changed circumstances, the people of Scotland must have the right to choose our own future - in short, to exercise our right of self determination.
Indeed I noted the importance you attached to the principle of self determination in your letter to President Tusk.
As you are aware, the Scottish Parliament has now determined by a clear majority that there should be an independence referendum.
The purpose of such a referendum is to give people in Scotland the choice of following the UK out of the EU and single market on the terms you negotiate, or becoming an independent country, able to chart our own course and build a genuine partnership of equals with the other nations of the UK.
A copy of the motion passed by Parliament on 28 March 2017 is attached.
The decision of the Scottish Parliament has been made in line with the tradition of popular sovereignty in Scotland - that the people of Scotland should be able to determine the form of government most suited to their needs - and with the clear commitment in the manifesto on which my government was re-elected last May.
I am therefore writing to begin early discussions between our governments to agree an Order under section 30 of the Scotland Act 1998 that would enable a referendum to be legislated for by the Scottish Parliament.
I have, of course, noted and carefully considered your public position.
However, it seems that we are in agreement on the essential matters.
For example we agree that now is not the time for a referendum.
You confirmed to me on Monday, and repeated in your letter invoking Article 50, that you intend the terms of both the UK's exit from the EU and of a future trade deal to be agreed before March 2019 and in time for ratification by other member states - in other words, between the autumn of next year and the spring of 2019.
As you are aware, this is the timescale endorsed by the Scottish Parliament for a referendum.
As I have said previously, if the timetable you have set out changes, we will require to consider the implications for the timing of a referendum. However, it seems reasonable at this stage to work on the basis of your stated timetable.
We are also in agreement that - unlike the EU referendum - the choice must be an informed one. That means that both the terms of Brexit and the implications and opportunities of independence must be clear in advance of the referendum.
It is also worth noting that the clear precedent of the 2012 Edinburgh Agreement should make reaching agreement on this occasion a relatively straightforward process - addressing any concern you may have that discussions would be time-consuming for your government when they are also preparing for EU negotiations.
In light of the above, there appears to be no rational reason for you to stand in the way of the will of the Scottish Parliament and I hope you will not do so.
However, in anticipation of your refusal to enter into discussions at this stage, it is important for me to be clear about my position.
It is my firm view that the mandate of the Scottish Parliament must be respected and progressed.
The question is not if, but how.
I hope that will be by constructive discussion between our governments.
However, if that is not yet possible, I will set out to the Scottish Parliament the steps I intend to take to ensure that progress is made towards a referendum.
Again, I wish you well for all that lies ahead and stand ready to discuss both a section 30 order and the Scottish government's role in securing the best outcome for all parts of the UK.
I am copying this letter to the Presiding Officer of the Scottish Parliament and to Bruce Crawford, convener of the Parliament's Finance and Constitution Committee.
Nicola Sturgeon
'No rational reason' to block indyref2

Seven MPs have resigned from the Labour Party in protest at Jeremy Corbyn's approach to Brexit and anti-Semitism.
They are: Chuka Umunna, Luciana Berger, Chris Leslie, Angela Smith, Mike Gapes, Gavin Shuker and Ann Coffey.
Ms Berger said Labour had become institutionally anti-Semitic and she was "embarrassed and ashamed" to stay.
Mr Corbyn said he was "disappointed" the MPs had felt unable to continue working for the policies that "inspired millions" at the 2017 election.
Shadow Chancellor John McDonnell said the "honourable thing for them to do" would be to stand down as MPs and seek to return to Parliament in by-elections.
Labour's deputy leader Tom Watson, in a video message on Facebook, urged the "hard left" to stop celebrating the departure of the seven MPs, saying it was "a moment for regret and reflection not for a mood of anger or a tone of triumph".
"Betrayal narratives and shouting insults at the departed might make some feel better briefly but it does nothing to address the reasons that good colleagues might want to leave," said Mr Watson.
He said Luciana Berger's decision to quit was a "wake-up call for the Labour Party" over anti-Semitism, saying: "We were slow to acknowledge we had a problem and even slower to deal with it."
Labour had to "broaden out" and become more tolerant, he said, adding: "I love this party. But sometimes I no longer recognise it, that is why I do not regard those who have resigned today as traitors."
The seven MPs, who all back a further EU referendum, are not launching a new political party - they will sit in Parliament as the Independent Group.
But Chuka Umunna said they had "taken the first step" and urged other Labour MPs - and members of other parties - to join them in "building a new politics".
"It is time we dumped this country's old-fashioned politics and created an alternative that does justice to who we are today and gives this country a politics fit for the here and now - the 21st Century," he said at a launch event in central London.
He said there would be "no merger" with the Liberal Democrats, who have 11 MPs, and the group wanted to "build a new alternative".
The group rejected comparisons with the Social Democratic Party - which broke away from the Labour Party in the early 1980s but eventually merged with the Liberal Party - saying it was a different era and they would not be contesting by-elections.
In a founding statement on its website, the group sets out its approach to the economy, public services and security, as well as Brexit.
One of the seven MPs, Angela Smith, has, meanwhile, had to apologise after being criticised for a comment about skin colour on BBC Two's Politics Live programme.
In a discussion about race, the MP appeared to say: "It's not just about being black or a funny tinge."
She has since posted a video on Twitter apologising for the comment, adding: "I am very upset that I misspoke so badly."
By BBC Political Correspondent Iain Watson
Defections to the Independent Group are likely to increase - but it will need to attract some of those beyond Labour to become a proper "centre party".
Two more MPs were undecided about whether to be at the launch, one of them was 90% but clearly not 100% there.
And more still may be persuaded to go unless they see a more robust response to anti-Semitism.
But strong supporters of the Blair/Brown governments such as Peter Kyle and Ben Bradshaw are staying to fight their corner on Brexit and it's likely in the short term the numbers who do go will be small.
This is no simple centrists v left, or indeed, ultra left split.
However, the reaction of left-wing activists to today's drama could be crucial.
If they feel fired up to de-select those who share the politics of the defectors but who have no intention of leaving Labour, the splinter could yet become a more sizeable split.
Each of the seven took turns to explain their personal reasons for quitting the party.
Ms Berger said: "I am leaving behind a culture of bullying, bigotry and intimidation."
Chris Leslie said Labour under Mr Corbyn had been "hijacked by the machine politics of the hard left".
Mike Gapes said he was "sickened that Labour is now perceived by many as a racist, anti-Semitic party" and "furious that the Labour leadership is complicit in facilitating Brexit".
Senior Labour figures, including former leader Ed Miliband and London Mayor Sadiq Khan, expressed their dismay at the split, with Mr Khan saying on Facebook that the seven MPs were friends of his but he would not be joining their new group and it was a "desperately sad day".
In a statement, Jeremy Corbyn said: "I am disappointed that these MPs have felt unable to continue to work together for the Labour policies that inspired millions at the last election and saw us increase our vote by the largest share since 1945."
GMB leader Tim Roache described the MPs' actions as "unforgiveable", adding that they were "hardly the Magnificent Seven".
Unite general secretary Len McCluskey, a close ally of Mr Corbyn, said there was a "strong whiff of hypocrisy" about the resigning MPs because they had stood on a manifesto at the 2017 general election that "promised to respect the 2016 referendum taking us out of Europe".
Jon Lansman, the founder of the pro-Corbyn Momentum campaign group, said he had "personal sympathy" for Ms Berger because of the "hate and abuse" she had suffered.
But he said the other six MPs were malcontents opposed to Mr Corbyn's leadership, telling BBC Radio 4's World at One: "These are people who are not heavyweights and do not have clear policies."
Liberal Democrat leader Sir Vince Cable said the split was "not unexpected, or unwelcome" and his party was open to "working with like-minded groups and individuals in order to give the people the final say on Brexit, with the option to remain in the EU".
Conservative Party Chairman Brandon Lewis said the resignations had confirmed that Labour "has become the Jeremy Corbyn Party - failing to take action on everything from tackling anti-Jewish racism to keeping our country safe".
Former UKIP leader Nigel Farage, whose new Brexit Party launched earlier this year, tweeted: "This moment may not look very exciting but it is the beginning of something bigger in British politics - realignment."
The resignation of seven Labour MPs leaves Jeremy Corbyn with 248 MPs under his leadership. For now, the new group will sit as independents, but could soon form a new political party.
Five other MPs are already sitting as independents after leaving the Labour Party for various reasons, but they are not part of an organised group.
Separately, Peterborough MP Fiona Onasanya was kicked out of the party when she was jailed in January.
There are two other independent MPs - former Lib Dem Stephen Lloyd, who quit his party because he disagrees with them on Brexit, and North Down MP Lady Sylvia Hermon - a former Ulster Unionist.
Not necessarily.
Parties are membership organisations that are registered with the Electoral Commission and stand candidates in elections. They also have a leader.
One major advantage of forming a party - rather than just a Parliamentary group - is that you qualify for government money to help with research, which may be a factor in the new group taking the next step.
Under the rules of Parliament, none of the MPs who have resigned from Labour today have to put themselves forward for re-election in their constituencies.

Jo Stevens has quit as Jeremy Corbyn's shadow Welsh secretary after he forced Labour MPs to back the Article 50 bill.
The Cardiff Central MP said she believed Brexit was "a terrible mistake" and said she "cannot reconcile my overwhelming view" that to endorse the bill would make it inevitable.
She is the first member of the shadow cabinet to quit over the issue.
Party leader Mr Corbyn said MPs in pro-EU constituencies were "understandably torn" over the vote.
Her resignation follows that of Tulip Siddiq, who quit as shadow early years minister on Thursday after the Labour leadership imposed a "three-line whip".
Frontbench members of parties are generally expected to resign from their posts if they choose to defy a three-line whip, which is the strongest form of discipline political party leaders can impose.
Ms Stevens set out her opposition to triggering Article 50 in a resignation letter.
She wrote that the government had offered "no guarantees" that "single market access, employment, environmental and consumer rights, security and judicial safeguards" would be protected after Brexit.
Labour's Brexit bind is not hard to grasp.
The vast majority of Labour MPs campaigned to keep Britain in the EU. But most now represent constituencies that voted to leave.
And as Parliament prepares to vote on triggering divorce talks with Brussels, Labour MPs are being ordered to approve the start of Brexit by a party leader who spent his backbench career ignoring similar demands for discipline.
The Cardiff Central MP also said a lack of "guarantees for the people of Wales" contributed to her decision to defy her party leadership.
Cardiff voted to remain in the EU during the 2016 referendum, and remains a target of the pro-EU Liberal Democrats.
Jeremy Corbyn responded to Ms Stevens's resignation saying: "I understand the difficulties that Jo, and other MPs, have when facing the Article 50 Bill. Those MPs with strong Remain constituencies are understandably torn."
He continued: "We have said all along that Labour will not frustrate the triggering of Article 50 and to that end we are asking all MPs to vote for the Bill at its second reading next week."
Two Labour whips - MPs in charge of parliamentary party discipline - have said they will vote against the EU (Notification of Withdrawal) Bill, despite the order to support it.
Jeff Smith and Thangam Debbonaire have said they will vote against it although neither have resigned their posts as party whips.
Another shadow minister Daniel Zeichner has also said he will vote against the bill, as will other MPs including former Culture Secretary Ben Bradshaw.
The European Union (Notification of Withdrawal) Bill was introduced after the Supreme Court ruled that parliament - not just the government alone - must vote to trigger Article 50 of the Lisbon Treaty, which starts the formal process of the UK leaving the EU.
Mr Corbyn has said he understands the pressures faced - many Labour MPs represent constituencies which voted to remain in the European Union - but called on them to "unite" around "important issues".
Shadow Home Secretary Diane Abbott said voting against the bill would "be very undermining of democracy".
"MPs voted for a referendum, there was an extraordinary high turn out - 72% - 17m people voted to leave. Many of them in some of our poorest areas," she told the BBC.
She added: "How would it look if a bunch of politicians and commentators in London turned round and said: 'We know you voted to leave but we're just going to ignore you?'"
But senior Labour backbencher Meg Hillier told the BBC some of her east London constituents were "horrified" at Mr Corbyn's stance.
"Certainly in Hackney the rage in the room was palpable - and people are really concerned. My constituency voted 78% to remain [in the EU] and while a lot of those people recognise the outcome of the referendum, we just don't want a blank cheque."
Prime Minister Theresa May has promised to begin the formal process of quitting the European Union by the end of March.
The bill is due to be initially debated by MPs on Tuesday - in a sitting that may last until midnight - and clear the Commons on 8 February, after which it will move to the House of Lords.
The Liberal Democrats have vowed to oppose Article 50 unless there is a guarantee of another referendum on the final Brexit deal that is agreed with Brussels, while the SNP has vowed to table 50 amendments to the legislation.

The Irish foreign minister says he is of "one mind" with the EU's Brexit negotiators.
Simon Coveney made the comments after meeting with Michel Barnier in Brussels on Monday.
On Wednesday, the EU is expected to publish a text which will translate December's deal between the UK and EU into a legally binding agreement.
Mr Coveney said people could expect a document that was "faithful and true" to the pledges made at the end of 2017.
Meanwhile, Ireland's taoiseach (prime minister) has said full regulatory alignment should be "spelled out" in this week's draft EU withdrawal agreement.
Leo Varadkar held a telephone conversation with the Prime Minister on Monday evening.
In the December deal, the UK pledged there would be no hard Irish border in any post-Brexit circumstances.
Since then, however, the two sides have had different interpretations of what was agreed.
The sticking point concerns a UK pledge to follow EU rules relating to cross-border co-operation.
The UK agreed that, in the absence of an overall deal, it will continue to fully align with the rules of the customs union and single market that are necessary for cross-border co-operation and the protection of the all-island economy.
Mr Barnier has said there would be "a large number of rules where this coherence or alignment" would be needed.
However, UK ministers, including the Brexit Secretary David Davis, have suggested the areas requiring alignment would be minimal.
The UK's preference is to solve the border issue in the context of an overall trade deal.
On Monday, the tánaiste (Irish deputy prime minister) said the legally-binding document, due to be released later this week, would focus on the "backstop" of Northern Ireland remaining aligned with EU rules, because the UK had not yet given information about its preferred solutions for avoiding a hard border.
Mr Coveney said he had a "very good meeting" with Mr Barnier, adding: "It's true to say the Irish government and the Barnier task force are of one mind in terms of how the text should look this week."
When asked if there would be an option A or B concerning the Irish border issue contained within Wednesday's document, Mr Coveney said: "The problem with putting any text around option A or option B is that we don't know what they are yet.
"So, what was agreed in December is that, in the absence of a text on A and B, that we would have a default position so that we would understand how, in the absence of a political agreement on an alternative, the issues of Ireland and Northern Ireland could be resolved in terms of maintaining a largely invisible border to protect the all-island economy on the island of Ireland.
"And so, you can't put a text around an option A until you have an option A. We don't have one yet."
Being outside a customs union has two main issues, tariffs & rules of origin. Does that product really originate from where you claim and thus qualify for low or no tariffs?
Both options will impose real costs on businesses but needn't necessarily mean systematic checks at the border. There would still have to be spot checks but technical and administrative arrangements can minimise these.
But if you stay in a customs union these problems disappear.
That said simply being in a customs union won't eliminate all border checks. That's because the current frictionless border involves the interplay of the customs union and the single market.
In very simple terms the single market deals with product standards: Do these products crossing our borders comply with our standards and therefore can they be sold to our consumers?
The EU is very strict on this, particularly on agri-food products.
Products of animal origin from outside the single market are subject to systematic checks at designated border inspection posts - this applies even to countries with which the EU has a trade deal.
So short of an unprecedented deal for mutual recognition on agri-food standards Northern Ireland and by extension the UK, would have to stay locked into single market rules & enforcement mechanisms to avoid checks.
Also on Monday, the Labour leader Jeremy Corbyn said he favours the UK staying in a customs union with the EU.
Shadow Brexit Secretary, Sir Keir Starmer, told BBC One's Andrew Marr Show the UK will leave the customs union in March 2019 - but Labour would seek to negotiate a new treaty that will "do the work of the customs union".
Sir Keir said this was "the only way realistically to get tariff-free access" to EU markets for UK manufacturers and to avoid the return of a "hard border" in Northern Ireland.
On Friday, Prime Minister Theresa May is due to give a major speech outlining the future relationship the UK would like with the EU.

Party President Mary Lou McDonald made the comments after she and her party colleagues met Michel Barnier in Brussels.
It follows comments from Prime Minister Theresa May that she did not want to see a hard border between Northern Ireland and the Republic of Ireland.
Ms McDonald said the issue was now "in Mrs May's court".
She said the British government had to come up with Plan A and Plan B, and there could be be no overall agreement on Brexit unless the issue of the border was solved.
She said there was now a challenge for Mr Barnier to "hold steady", but that "he gets it" on the issue of Brexit and the border.
Mrs May has also said she did not want a customs border between Northern Ireland and the rest of the UK.
The prime minister was responding to a legal text published by the EU as part of the Brexit negotiations with the UK.
The EU's draft legal agreement proposes a "common regulatory area" after Brexit on the island of Ireland - in effect keeping Northern Ireland in a customs union - if no other solution is found.
The party wants to know how Brexit will affect cross-border workers and will insist that the 1998 Good Friday Agreement must be protected.
The Irish border question is at the heart of EU-UK discussions and although a number of options have been tabled, there is no agreed plan of what life will look like after Brexit.
On Tuesday, he will get a very different perspective when he hosts the DUP leader Arlene Foster and her deputy Nigel Dodds in Brussels.
The DUP opposes special status for Northern Ireland and are against staying in the customs union or single market.
The party insists that recent EU proposals would break up the UK.
Nigel Dodds has said an internal border would be "catastrophic" for Northern Ireland to be "cut off" from UK.
Last week, Taoiseach (Irish prime minister) Leo Varadkar said he remained "concerned that some of the constraints of leaving the customs union and the single market are still not fully recognised".
He added: "We will now need to see more detailed and realistic proposals from the UK. Brexit is due to happen in a little over 12 months, so time is short."

The UK's ambassador to the European Union, Sir Ivan Rogers, has resigned. Here is his message to staff in full. We have highlighted key passages in bold, and added BBC political reporter Justin Parkinson's commentary in italics.
Dear All,
Happy New Year! I hope that you have all had/are still having, a great break, and that you will come back refreshed and ready for an exciting year ahead.
I am writing to you all on the first day back to tell you that I am today resigning as Permanent Representative.
As most of you will know, I started here in November 2013. My four-year tour is therefore due to end in October - although in practice if we had been doing the Presidency my time here would have been extended by a few months.
As we look ahead to the likely timetable for the next few years, and with the invocation of Article 50 coming up shortly, it is obvious that it will be best if the top team in situ at the time that Article 50 is invoked remains there till the end of the process and can also see through the negotiations for any new deal between the UK and the EU27.
It would obviously make no sense for my role to change hands later this year.
I have therefore decided to step down now, having done everything that I could in the last six months to contribute my experience, expertise and address book to get the new team at political and official level under way.
This will permit a new appointee to be in place by the time Article 50 is invoked.
Importantly, it will also enable that person to play a role in the appointment of Shan's replacement as DPR. (Shan Morgan was Deputy Permanent Representative)
I know from experience - both my own hugely positive experience of working in partnership with Shan, and from seeing past, less happy, examples - how imperative it is that the PR and DPR  operate as a team, if UKREP is to function as well as I believe it has done over the last few years.
I want to put on record how grateful I am to Shan for the great working relationship we have had.
She will be hugely missed in UKREP, and by many others here in Brussels, but she will be a tremendous asset to the Welsh government.
From my soundings before Christmas, I am optimistic that there will be a very good field of candidates for the DPR role.
But it is right that these two roles now get considered and filled alongside each other, and for my successor to play the leading role in making the DPR appointment.
I shall therefore stand aside from the process at this point.
I know that this news will add, temporarily, to the uncertainty that I know, from our many discussions in the autumn, you are all feeling about the role of UKREP in the coming months and years of negotiations over "Brexit".
I am sorry about that, but I hope that it will help produce earlier and greater clarity on the role that UKREP should play.
My own view remains as it has always been. We do not yet know what the government will set as negotiating objectives for the UK's relationship with the EU after exit.
Justin Parkinson: This could be read as a hurry-up to the UK government to decide what it actually wants from Brexit talks, expected to start as early as April. This differs from criticism from some MPs that not enough is being divulged - Sir Ivan is implying a lack of direction at the heart of government, rather than vagueness in its public message. And he is suggesting that UK diplomats in Brussels need to be better informed.
There is much we will not know until later this year about the political shape of the EU itself, and who the political protagonists in any negotiation with the UK will be.
But in any negotiation which addresses the new relationship, the technical expertise, the detailed knowledge of positions on the other side of the table - and the reasons for them, and the divisions amongst them - and the negotiating experience and savvy that the people in this building bring, make it essential for all parts of UKREP to be centrally involved in the negotiations if the UK is to achieve the best possible outcomes.
Serious multilateral negotiating experience is in short supply in Whitehall, and that is not the case in the Commission or in the Council.
JP: Sir Ivan is suggesting there's a danger the UK could be outclassed in the Brexit talks - and lose out as a result. Diplomats must be better prepared, he is apparently arguing.
The government will only achieve the best for the country if it harnesses the best experience we have - a large proportion of which is concentrated in UKREP - and negotiates resolutely.
Senior ministers, who will decide on our positions, issue by issue, also need from you detailed, unvarnished - even where this is uncomfortable -  and nuanced understanding of the views, interests and incentives of the other 27.
JP: Sir Ivan is saying that only civil servants, rather than campaigners and activists, can provide a true picture of the complexities ahead.
The structure of the UK's negotiating team and the allocation of roles and responsibilities to support that team, needs rapid resolution.
The working methods which enable the team in London and Brussels to function seamlessly need also to be strengthened.
The great strength of the UK system - at least as it has been perceived by all others in the EU - has always been its unique combination of policy depth, expertise and coherence, message co-ordination and discipline, and the ability to negotiate with skill and determination.
UKREP has always been key to all of that. We shall need it more than ever in the years ahead.
As I have argued consistently at every level since June, many opportunities for the UK in the future will derive from the mere fact of having left and being free to take a different path.
But others will depend entirely on the precise shape of deals we can negotiate in the years ahead.
Contrary to the beliefs of some, free trade does not just happen when it is not thwarted by authorities: increasing market access to other markets and consumer choice in our own, depends on the deals, multilateral, plurilateral and bilateral that we strike, and the terms that we agree.
JP: Sir Ivan does not name those he is effectively accusing of over-optimism and naivety, but this could be read as a criticism of pro-Brexit ministers - those said to favour a "hard Brexit", under which the UK could leave the European single market and customs union and be subject to the rules of the World Trade Organization. There is much hard work ahead, it suggests.
I shall advise my successor to continue to make these points.
Meanwhile, I would urge you all to stick with it, to keep on working at intensifying your links with opposite numbers in DEXEU [Department for Exiting the EU] and line ministries and to keep on contributing your expertise to the policy-making process as negotiating objectives get drawn up.
The famed UKREP combination of immense creativity with realism ground in negotiating experience, is needed more than ever right now.
On a personal level, leaving UKREP will be a tremendous wrench. I have had the great good fortune, and the immense privilege, in my civil service career, to have held some really interesting and challenging roles: to have served four successive UK prime ministers very closely; to have been EU, G20 and G8 Sherpa; to have chaired a G8 Presidency and to have taken part in some of the most fraught, and fascinating, EU negotiations of the last 25 years - in areas from tax, to the MFF to the renegotiation.
Of all of these posts, I have enjoyed being the Permanent Representative more than any other I have ever held.
That is, overwhelmingly, because of all of you and what you all make UKREP: a supremely professional place, with a fantastic co-operative culture, which brings together talented people whether locally employed or UK-based and uniquely brings together people from the home civil service with those from the Foreign Office.
UKREP sets itself demanding standards, but people also take the time to support each other which also helps make it an amazingly fun and stimulating place to work.
I am grateful for everything you have all done over the last few years to make this such a fantastic operation.
For my part, I hope that in my day-to-day dealings with you I have demonstrated the values which I have always espoused as a public servant.
I hope you will continue to challenge ill-founded arguments and muddled thinking and that you will never be afraid to speak the truth to those in power.
I hope that you will support each other in those difficult moments where you have to deliver messages that are disagreeable to those who need to hear them.
JP: The most-reported part of Sir Ivan's email, this implies that more planning is needed, and that ministers are unwilling to listen to the advice civil servants are offering. It gives a strong hint that his colleagues feel intimidated.
I hope that you will continue to be interested in the views of others, even where you disagree with them, and in understanding why others act and think in the way that they do.
I hope that you will always provide the best advice and counsel you can to the politicians that our people have elected, and be proud of the essential role we play in the service of a great democracy.
Ivan

Britons are being offered an "unreal and over-optimistic" vision of what Brexit will look like, Sir John Major has warned.
The former Tory prime minister also called for "more charm and a lot less cheap rhetoric" from the UK government towards the rest of the EU.
And he said the costs of leaving would be "substantial" and "unpalatable".
Downing Street said the government was determined to make a success of the UK's departure from the EU.
Conservative former cabinet minister Iain Duncan Smith said it was a "peculiar speech in the sense that it looked backwards the whole time".
He told BBC Newsnight: "It was almost like a re-fight of the referendum... strangely bitter really, and almost really the speech of someone who simply refuses to accept that the British people should have made a decision such as they did."
Prime Minister Theresa May plans to invoke Article 50 of the Lisbon Treaty, which begins two years of formal negotiations, by the end of March.
She has already confirmed the UK will not remain a member of the EU single market but will instead seek a new free trade deal with the remaining members.
In a speech in London, Sir John, who campaigned for a Remain vote in June's referendum, claimed there was "little chance" the advantages of being part of the EU single market could be replicated once the UK leaves.
"I have watched with growing concern as the British people have been led to expect a future that seems to be unreal and over-optimistic," he said.
"Obstacles are brushed aside as of no consequence, whilst opportunities are inflated beyond any reasonable expectation of delivery."
For Theresa May, also an unflashy leader who was propelled to No 10 by a surprising political moment, Europe will be defining in a way no others could even have anticipated.
In Sir John's carefully calibrated speech, there are plenty of messages for her, some of which may be welcome, some not.
First off, having campaigned to stay in the European Union, with sober warnings particularly about the consequences for the Northern Irish peace process, it's no surprise that Sir John says that in his view, Brexit will be a "historic mistake".
It is notable, although again not surprising, that he cautions that the UK will be a diminished diplomatic force in the world after we walk away from the EU, with a warning too that we will be less useful to our most important ally, the US, as a consequence.
Also, even as the PM who lived through the Commons trauma of trying to deliver the Maastricht Treaty, it is logical that he calls for Parliament to have a full role in shaping the negotiations over our place in Europe.
What may be harder for No 10 to dismiss is Sir John's obvious political concern about how the public is being treated in the months after the referendum decision.
Sir John said Brexit talks require "statesmanship of a high order" and warned of a "real risk" of the exit deal falling "well below the hopes and expectations" that have been raised, saying he doubted the "rosy confidence being offered to the British people".
"In my own experience, the most successful results are obtained when talks are conducted with goodwill: it is much easier to reach agreement with a friend than a quarrelsome neighbour.
"Behind the diplomatic civilities, the atmosphere is already sour. A little more charm, and a lot less cheap rhetoric, would do much to protect the UK's interests."
He also said the "cheerleaders" for Brexit had shown a "disregard that amounts to contempt" towards those that backed the losing side.
And he said the UK would become "far more dependent" on the US after it leaves the EU, describing President Donald Trump as "less predictable, less reliable and less attuned to our free market and socially liberal instincts than any of his predecessors".
Sir John, who as prime minister between 1990 and 1997 oversaw the start of the Northern Ireland peace process, warned that "uncertainties over border restrictions" after Brexit were "a serious threat to the UK, to the peace process and for Ireland, North and South".
The ex-PM, who faced battles with Eurosceptic MPs during his time in Downing Street, also said Mrs May would have to "face down" people calling for "total disengagement" from Europe.
But the Leave Means Leave campaign hit back, recalling Sir John's famous "don't bind my hands" plea to Tory Eurosceptics ahead of EU talks and saying he was now "seeking to do just this to the British prime minister ahead of negotiations with the EU".
Conservative MP Jacob Rees-Mogg added: "It was a craven and defeated speech of a bitter man who was heavily defeated by the electorate for his own failings in Europe in 1997, was defeated again last June and now wishes to take out his failures on Mrs May."

Downing Street has called the UK's new ambassador to the European Union a "seasoned and tough negotiator", who will bring "energy" to Brexit talks.
Sir Tim Barrow takes on the role with discussions with the EU expected to start soon and promised to work for the "right outcome".
He replaces Sir Ivan Rogers, who quit earlier this week, accusing ministers of "muddled thinking".
Some MPs have accused Sir Ivan of being "half-hearted" towards Brexit.
Meanwhile, Prime Minister Theresa May is expected to give what is being billed as a "major" speech on Brexit within the next few weeks.
Sir Tim, UK ambassador in Moscow from 2011 to 2015 and an adviser to several previous foreign secretaries, said he was "honoured" to be appointed permanent representative to the EU and promised to work for "the right outcome" for the UK after Brexit.
Downing Street said he had "extensive experience of securing UK objectives in Brussels" and would "bring his trademark energy and creativity to this job".
John Pienaar, BBC deputy political editor
The resignation of Sir Ivan Rogers has revealed more than the difficulty and complexity of Britain's EU divorce.
It has highlighted wider strains in Whitehall between some mandarins and some ministers, up to and including Theresa May.
Mandarins and ambassadors perennially advise more junior mandarins on the importance of speaking truth to power.
On this occasion, Sir Ivan's leaked farewell memo can fairly be read as a protest and a warning. Concern is growing among some high-ranking officials that ministers don't understand or won't admit the scale of the task they're facing.
Foreign Secretary Boris Johnson and Brexit Secretary David Davis both welcomed Sir Tim's appointment and Tom Fletcher, a former UK ambassador to Lebanon, told BBC Radio 4's Today programme: "It's the toughest negotiation in our lifetimes and I think he is up to it. I have seen him in Brussels. He knows the corridors, he knows the characters.
"But actually more importantly I saw him in Moscow where he was incredibly resilient as ambassador there, dealing with (Vladimir) Putin in a very testing time in our relationship and Tim had a reputation of being bulletproof out there."
Former UKIP leader Nigel Farage was less enthusiastic, tweeting: "Good to see that the government have replaced a knighted career diplomat with... a knighted career diplomat."
However, BBC diplomatic correspondent James Landale said Sir Tim's record was less likely to be criticised by Brexit supporters than those of some other potential candidates, as it "would be very hard to say that Sir Tim Barrow is an out-and-out pro-European".
Brexit negotiations could begin as early as this April, with the UK government promising to invoke Article 50 of the Lisbon Treaty - which triggers the process - by the end of March.
Erna Solberg, the prime minister of Norway - which is not in the EU but is part of its single market and allows free movement of EU workers - said she feared a "very hard Brexit", involving leaving the single market and the customs union.
She also said: "And we do feel that sometimes when we are discussing with Britain, that their speed is limited by the fact that it is such a long time since they have negotiated (outside the EU)."
In his resignation email to fellow UK diplomats in Brussels, Sir Ivan urged them to challenge "ill-founded arguments and muddled thinking" and "never be afraid to speak the truth to those in power". He said he did not yet know the government's negotiating plans for Brexit.
Sir Ivan had previously warned ministers that EU-UK trade talks could take a decade to complete, advice revealed by the BBC last month.
Pro-EU MPs have described the loss of his experience shortly before Brexit talks as a blow to the government's negotiating strategy, but anti-EU MPs have played down the importance of his resignation.
Labour has demanded a statement from the government when Parliament returns from its Christmas and New Year break next Monday.
Former cabinet minister Iain Duncan Smith, who backed Brexit, was among those criticising Sir Ivan, saying that when a civil servant "starts going public", ministers "can no longer trust that individual".
But pro-EU Conservative MP Sir Nicholas Soames tweeted: "IDS attack on Ivan Rogers unforgivable am ashamed a colleague could be so ignorant and rude about an Official of such distinction #buttonup."

It's good and sensible to plan.
If they weren't taking it seriously, as the government was very regularly criticised for failing to do, careering into a 'no deal' scenario would be pretty irresponsible, and planning properly for no deal has also been prized by Brexiteers as evidence that the PM might actually walk away if the offer on the table is simply not good enough.
A literal snapshot of some of that planning today has given a slice of insight into the kind of preparation that's taking place inside the Treasury, so called 'Operation Yellowhammer'.
As an intellectual exercise, none of this brief excerpt is completely surprising.
It demonstrates the political reality that in government there is concern about what might happen to the financial system, as well as transport, air and rail.
But it is still a message to government departments they should try to find cash to spend on "no deal" preparations from existing budgets, rather than the big cash pot that's been allocated so far.
That could give yet another reason for Brexiteers to get riled. But in this hot political climate, that's not hard to do. The Treasury officially won't comment on the leak.
Here is the text of the snap, captured by the sharp-eyed Westminster photographer @politicalpics:
HMT briefing - Operation Yellowhammer - 04 September 2018
Operation Yellowhammer: no deal contingency planning
 Summary of issue
•This meeting will consider progress on the Government's plans for mitigating the immediate impacts of a No Deal Brexit.
•The Civil Contingencies Secretariat held a two-day workshop last week to review departments' plans, assumptions, interdependencies and next steps.
 HMT objectives
1.Emphasise the importance of building XWH [cross Whitehall] communications architecture that can help maintain confidence in the event of contingency plans being triggered - particularly important for financial services.
2.Explain that departments should be raising Yellowhammer costs through the normal channels - through their spending teams for in-year pressures, and in their bids for 19/20 Brexit allocations for spending that year. Their first call should be internal prioritisation.
3.Reaffirm the need for consistent planning assumptions across plans […] aviation and rail access to the EU.
4.Remind departments of the need to consider the financial […] commercial firms that play a role in their contingency plans.

Listen carefully. The strange sound of rushing air you can hear in the background, as Britain continues its slow march towards Brexit, is a deep collective sigh of relief.
Ministers, officials and business leaders - the latter group puffing out their cheeks more than anyone - wanted, needed, to see their wish of a Brexit transition period fulfilled.
So one obstacle cleared, or more accurately, skipped around.
The danger that's kept much of business and many MPs at Westminster awake at night, fear of the UK tumbling off a cliff edge into its post-Brexit future next March, has receded. Not disappeared. Receded.
Now Theresa May and the UK negotiating team can focus on the task ahead. Urgently.
A sigh of relief is time consuming, and there's no time or breath to spare.
Team-UK will need plenty of both as it confronts the next stage of the process; contemplates wholly unresolved issues like the Irish border - in truth barely even addressed in negotiations - and the talks about talks which have yet to begin on the future trading relationship.
The uncomfortable truth is that the issue of the Irish border, or the conflict to come over the shape of a future trade deal, could yet blow the Brexit plan into fragments, and see the prime minister and perhaps even her government disappear into the resulting political crater.
Brexiteer ministers and MPs are having none of it.
They sound optimistic because they are. And, who knows? It could all work out in the end.
Among business leaders, especially in the City, there is mild surprise that firms have defied earlier apocalyptic predictions.
Even former Remain-supporting MPs have noted a certain cautious confidence that the infrastructure of the Square Mile - the concentration of legal and technical expertise, to say nothing of schools, homes and the rather appealing lifestyle available in London (to those who can afford it) might just see the City through.
And, who knows? EU negotiators might just give a little on the mutual recognition of rules and standards companies crave.
That's the optimistic view. Remember, Brussels has already dangled the thought there could be no tariffs imposed on exports of goods. It's a start.
Others remain deeply worried. The head of the CBI, Carolyn Fairbairn, told me a trade deal comparable to the EU's agreement with Canada would be disastrous.
Services denied access, exporters forced to deal with costly and wearying paperwork and checks on the rules of origin of goods and the like.
But maybe, somehow, Theresa May may yet pass on the legacy of a politically arduous but complete Brexit.
Those trade discussions will be hazardous. The prime minister has conceded Britain cannot expect to win everything it wants by way of market access, has even conceding access to markets here and in Europe will be diminished.
Dissident Tory MPs insist their determination to resist what they would see as a poor deal has grown.
More ominously for the government, they are also convinced their numbers have grown to the point they could defeat Theresa May by joining with Jeremy Corbyn's repositioned Labour Party in the coming vote on whether the government should seek to remain inside the EU customs union.
If that vote - possibly some time after 3 May's English local elections - is lost, ministers can be expected to shrug it off.
The dissidents fully expect the government to try.
But a defeat would also be a dangerous marker ahead of the later promised "meaningful vote" on the outline of a trade deal - if one exists - in the Autumn.
Lose that vote, and the prime minister's authority will suffer a huge and perhaps mortal blow.
Could she survive?
Certainly government whips would use the prospect of a prime ministerial defenestration - and even the spectre of Jeremy Corbyn in Downing Street - to pile pressure on potential rebels.
As for the Irish border issue, the calculation among Brexiteers and the MPs of the Democratic Unionist Party (who were kept in close and constant touch with the government's thinking ahead of the March EU summit) is that if and when it comes to the crunch, Dublin will blink first.
Britain has not accepted the "backstop" option in the EU withdrawal text that says Northern Ireland will remain in a customs union if all other ideas for avoiding a hard border with the Republic fail.
Some still undefined backstop, yes, just not that one.
UK negotiators will now take their published plan to enforce rules away from the border to Brussels.
Brexit Secretary David Davis would also like to see most Irish traders exempted from border controls altogether.
An alternative is for the UK to enforce the EU's external border, and allow those trading with the UK on lower tariffs, or none at all, to reclaim duties paid.
Overall, the guiding ambition remains a frictionless trade deal with the EU that renders border controls redundant.
So far, Brussels has sounded cool on all of it. Something has to give.
And with the DUP adamant they will never, ever, live with a settlement that separates out Northern Ireland, and with Tory colleagues equally adamant that the UK must leave the customs union and the single market, it cannot be the prime minister.
This obstacle too may yet conceivably send the Brexit plan up in smoke. Another mushroom cloud. Another crater.
 In the meantime, those most sceptical about the value of Brexit believe the government should give up any idea of being willing to walk away from negotiations with no deal.
Dissidents insist Parliament would never allow that in any case.
Ministers such as David Davis insist they must be prepared for any eventuality, and whatever happens in negotiations, or even in Parliament, Brexit will happen.
There is, in the end, more at stake here than Mrs May's future or that of her administration.
There is also no shortage of undeclared potential candidates quietly dreaming of taking over her job.
Sometimes, actually quite often, you have to wonder why?

When it comes to Brexit, there are two parties here in Liverpool this week.
First, former Remainers, thrilled by Labour's flirting with the idea of another referendum - cheering to the rafters, delighted by the prospect of another vote. Their new hero is the shadow brexit secretary, Sir Keir Starmer - who has cajoled the party leadership to sharpen the lines of its ambiguity.
Then the other flank - Jeremy Corbyn himself, visibly lukewarm about the idea, saying not much has really changed.
Members and some MPs are deeply anxious that even sketching out the possibility of another referendum sticks two fingers up to millions of voters who want to leave the EU.
Labour might ultimately be punished by voters who are desperate for the party to try to stop us leaving the EU.
But the party could lose out just as painfully at the hands of many members of the public who chose Brexit in the referendum.
What message does Labour send to them if they eventually want another go?
The party has managed to craft a new formal position that leaves several Brexit options open.
And the leader was cautious in how he approached it today, refusing to say on which side he would campaign if there were another Brexit vote.
But the new emphasis at the party conference in Liverpool also leaves them open to attack.
Mr Corbyn seemed frustrated today, at having to engage in the hypothetical - but that is politics right now.
The biggest question for all its players on Brexit  - is "what if?".
What if Theresa May can't do a deal with the EU?
What if the deal fails in Parliament?
And what happens if our politicians fail to meet the challenge that the public set them in 2016?

"The test of a first-rate intelligence," F. Scott Fitzgerald wrote in The Crack-Up, "is the ability to hold two opposed ideas in the mind at the same time, and still retain the ability to function."
Today the British government and the European Union are making a fist of passing that test.
Reading the joint report between the UK and the EU, it is clear that the most important section when considering the economics of Brexit is the section on Ireland.
The document commits both sides to an open border between Northern Ireland and the Republic, and that there will be "no new regulatory barriers" between Northern Ireland and the rest of the UK.
It also commits to the UK leaving the EU's single market and customs union.
These two positions appear to be in contradiction.
If Britain does become a "third country" - that is trading with the EU as other non-EU countries outside the single market and the customs union do - then border controls will be necessary.
And that open border will become very much more closed.
There is at least a partial way around this conundrum.
And it necessitates the comprehensive free trade deal the British government has said it wants.
And at least closely mirroring customs arrangements we presently adhere to as members of the EU's customs union.
That equates for many with a "soft Brexit" and is the trajectory many economists argue would be best for the UK economy.
This is because, if there is no free trade agreement, it is difficult to see how Theresa May's government could maintain "full alignment with the rules of the internal market and the customs union which support north-south co-operation [on the island of Ireland]" which the joint report commits the PM to.
And still say that Britain has left the EU.
This document has been described as the "withdrawal deal".
But it is actually far more importantly a signal of what the future might hold.
And that appears to be a relationship where the UK closely follows the EU's single market and customs union rules despite not being a formal member of either.
Which might very well constrain Britain's ability to sign free trade deals with other countries outside the EU.
The government will have to find a way through that if it is not to make Liam Fox's job as international trade secretary redundant.
And in its deliberate ambiguity (every side needs to be able to claim victory) today's joint agreement leaves that debate for another day.
The EU has said it wants to move urgently onto discussing and agreeing transition arrangements to be applied once Britain has officially left the union in March 2019.
That now looks like being Phase II of this process.
And from there, onto mapping out an agreement on free trade which will be put in place after the transition period has expired.
That's Phase III.
That has been seen as good news by businesses which need clarity on the trade rules they will be required to play by.
And the more "frictionless" that trade is, many believe, the better for the economy.
What today's deal has revealed is that there is a genuine desire - it appears from both sides - to get that free trade deal nailed down.
"One should be able to see that things are hopeless and yet be determined to make them otherwise," Fitzgerald wrote.
Today, the UK and the EU have moved the process of Brexit significantly forward.
Even if the end point is still shrouded in much uncertainty.

Liberal Democrat, some Labour and SDLP MPs have told the BBC they are prepared to vote against triggering Article 50.
Lib Dem leader Tim Farron said his party would oppose it, unless they were promised a second referendum on the UK's Brexit deal with EU leaders.
Several Labour MPs are also willing to vote against it, despite the Labour Party pledging not to do so.
The government says Lib Dem and Labour MPs are "trying to thwart and reverse the referendum result".
With the support of Conservative MPs and the support or abstention of most Labour MPs, the bill is well placed to pass through the Commons.
But the opposition of some MPs is likely to embolden critics in the House of Lords.
The Liberal Democrats have long called for a referendum on the outcome of the government's negotiations with EU, but only now have they said they will definitely vote against Article 50 if their demand is not met.
Mr Farron, whose party has eight MPs in the Commons, told BBC Radio 4's Today: "Article 50 would proceed but only if there is a referendum on the terms of the deal and if the British people are not respected then, yes, that is a red line and we would vote against the government."
For Labour, shadow minister Catherine West, former leadership contender Owen Smith and south London MP Helen Hayes all made clear they were prepared to vote against Article 50 - which begins formal exit negotiations with the EU - if amendments were not accepted.
Former Labour minister David Lammy and shadow transport minister Daniel Zeichner have said they would oppose Article 50. Opposition whip Thangam Debbonaire said she would also vote against it, if a vote were held imminently.
The SNP's 54 MPs may join them. First Minister Nicola Sturgeon has said they will not vote for anything that undermines the will of the Scottish people, and has previously said they will vote against a bill to write EU provisions into British law to prepare for Brexit.
Dulwich Labour MP Hayes said she was prepared to defy Labour whips to oppose the measure unless the government promised a second referendum.
She said: "I had somebody in my surgery last week who was in tears because of Brexit and I see genuine distress amongst my constituents about what this path means.
"I would not be representing them if I voted to trigger Article 50 on the basis of no information from the government about the path that they would then take us on."
In posts on Twitter and Facebook earlier this week, shadow Foreign Office minister Catherine West wrote: "As I have said before, I stand with the people of Hornsey & Wood Green, and I will vote against Brexit in Parliament."
Owen Smith confirmed to Today that if his bid for a second referendum failed, he was likely to oppose the bill.
The SDLP's three MPs will also oppose the measure.
Ministers said MPs voting against Article 50 would effectively be trying to re-run the referendum in the hope of a "different answer".
"Parliament voted by a margin of six to one to put the decision on whether to remain in or leave the EU in the hands of the British people," said Brexit minister David Jones.
"Only the Conservatives can be trusted to respect the outcome of the referendum and make a success of Brexit."
Last week the High Court ruled Parliament must be consulted about leaving the European Union.
Unless the Supreme Court overturns the judgement in December, a bill to invoke Article 50 is expected in the new year.
Labour made clear its official position would be not to frustrate the process of leaving the EU after a newspaper report said the party leader Jeremy Corbyn intended to force a general election unless ministers caved in to demands.
After the story broke Labour sources said that while it would seek to amend the bill, it would provide "unconditional" support.
Shadow Brexit secretary Keir Starmer said Labour would not frustrate the process and would not vote down Article 50.
However, Labour and Liberal Democrat peers will try to amend the bill in the House of Lords. So too will one Conservative peer - Baroness Wheatcroft.

Sony will move its European headquarters from the UK to the Netherlands to avoid disruptions caused by Brexit.
The company said the move would help it avoid customs issues tied to Britain's exit from the EU.
Despite the move, Sony won't shift personnel and operations from the existing UK operations.
It is the latest Japanese company to flag a move to the continent in response to Brexit.
And on Tuesday appliance maker Dyson announced it was moving its headquarters to Singapore, from Malmesbury in Wiltshire, although it said it had nothing to do with Brexit.
The UK is on course to leave the European Union in March, but there is uncertainty over the process following the vote in the UK parliament to reject a deal agreed by the British prime minister with the EU.
On a recent trip to the UK, Japan's Prime Minister Shinzo Abe expressed concern over a no-deal Brexit.
He said it could hurt Japanese companies, which employ up to 150,000 people in the UK.
In a statement Sony said the move would mean "we can continue our business as usual without disruption once the UK leaves the EU. All our existing European business functions, facilities, departments, sites and location of our people will remain unchanged from today."
Sony spokesperson Takashi Iida said the move would make Sony a "company based in the EU" so the common customs procedures will apply to Sony's European operations after Britain leaves the bloc.
Sony's rival Panasonic has already moved its headquarters to Amsterdam, mostly because of tax issues potentially created by Brexit.
Both companies say the decision is unlikely to have a major impact on jobs in the UK.
When Panasonic announced its move, it said "fewer than approximately 10" people would be affected out of a staff of 30.
Several Japanese firms, including Daiwa Securities and Sumitomo Mitsui Financial Group, have said they plan to move their main EU bases out of London.
Nomura Holdings has set up new offices for certain operations in Paris and Frankfurt as part of its Brexit preparations, but says it headquarters remain in London.
Japanese bank Norinchukin announced earlier this month that it would set up a wholly-owned subsidiary in the Netherlands in response to Brexit and other economic changes in Europe.
A number of Japanese carmakers have also expressed concern over the impact of a hard Brexit.
Toyota has warned that a no-deal Brexit would affect investment and would temporarily halt output at its plant in Burnaston.
Honda  has already planned a six day halt in April to plan for "all possible outcomes caused by logistics and border issues".

Spain hopes to reach an agreement with the UK over Gibraltar by the summer, its foreign minister has said.
Alfonso Dastis said Spain would "defend our position" but the two sides were "working towards" an agreement as soon as possible.
The UK says "informal" talks are going on about Gibraltar's post-Brexit future with Spain.
Spain has a long-standing territorial claim on Gibraltar, a UK overseas territory on the Iberian Peninsula.
Mr Dastis has previously said that sovereignty would not be an issue in Brexit negotiations.
Instead Madrid wants joint management of Gibraltar's airport and more co-operation on tax fraud and border controls.
Asked if he was hopeful agreement could be reached before October - when the UK and EU hope to reach a Brexit deal that can then be ratified by EU states - Mr  Dastis told the BBC: "We are definitely determined to defend our position so I don't exclude anything.
"But we are definitely working towards having an agreement before October, even if possible by the summer, and we hope... that there is also, from the British side, a position which works towards that end."
The EU has said that no future Brexit trade deal may apply to Gibraltar without a bilateral agreement between Spain and the UK.
Mr Dastis said the two sides had met three or four times already this year: "We are having very constructive conversations."
Spain wants joint management of Gibraltar's airport, which is located on a disputed strip of land connecting Gibraltar to the Spanish mainland.
Mr Dastis said that while Spain "cannot accept" British jurisdiction over the land, it wanted to use the airport "to the benefit of the population of Gibraltar".
Asked what joint management would mean, he said: "We will have to work out what the exact terms will be.
"We have tried twice. Once it was rejected by the UK, the second time it was rejected by us - maybe third time lucky?"
Responding to Mr Dastis's comments, a spokesman for the UK government said: "We are having a wide range of discussions with member states, including Spain, about our departure from the EU, including the practical implications for Gibraltar.
"Discussions are continuing with the Government of Gibraltar and our European partners on how to address the specific challenges and opportunities here."
The Government of Gibraltar did not respond directly to Mr Dastis's comments, but in a speech last week, its chief minister Fabian Picardo said Gibraltar had agreed "key fundamentals" with the UK for after Brexit - including the continuation of current trade arrangements.
He added that Gibraltar would seek to establish "new lines of co-operation with the EU" and in particular, Spain, "not because we feel threatened, but because that is our nature".
"And we will continue to seek to construct new synergies for the future and avoid unnecessary confrontation because it has always been our approach."
He added that while Spain had a list of "historic irritants" it wanted to resolve, Gibraltar had its own list of issues that it wanted addressed - including removing Gibraltar from "financial services blacklists" and better traffic flows at the border.
"One of these is also, for us, the future arrangements that might be agreed by us for the exploitation of our £84m airport pursuant to an agreement with Spain, as well as the ability to access the EU Single Sky [an initiative aimed at streamlining air traffic management in the bloc] , even after we leave the EU".
Gibraltar was ceded to Great Britain in the 1713 Treaty of Utrecht but Spain has continued to press its claim - which is rejected by both the UK and Gibraltar itself.
Gibraltarians rejected by 99% to 1% the idea of the UK sharing sovereignty with Spain in a vote in 2002 and in a previous referendum in 1967.
But Gibraltar voted by 96% to stay in the EU in the 2016 referendum.

A Standard Chartered bank executive says tough demands by EU regulators could mean more jobs being moved from the UK overseas than currently thought.
Europe and Americas boss Tracy Clarke says the relatively small size of the bank in the EU market means it would not "be moving hundreds of people".
But she says the impact on banks with large EU services may be "significant".
Standard Chartered is to spend about £15m turning its Frankfurt office into a European base due to Brexit.
The bank plans to create a subsidiary at its German branch in order to maintain access to the European market after the UK withdraws from the European Union.
It has been waiting nearly nine months for EU officials to approve the relevant banking licence, which it originally expected to receive by the spring.
Ms Clarke told the Press Association: "Because we were one of the first [to apply for a licence] there was no precedent for us, or for them. It's been a learning process on both sides."
The European Central Bank has said it will not tolerate so-called brass plate operations - that is where companies have a presence in a host country in name only.
Mr Clarke says it means banks such as the UK-headquartered Standard Chartered may end up moving more jobs due to Brexit than originally planned, in order to meet European banking compliance rules.
"For us, it still won't be hundreds more people because of the size and scale of our business, so you might be talking a few more for us.
"But if they're taking this approach with all other banks who are much bigger than we are in terms of their European business, that could be more significant," she warned.
The ECB would not comment on Standard Chartered but said it is "keen to prevent banks from creating empty shells when granting licences to international banks setting up new subsidiaries in the euro area in the context of Brexit".
It added there were a number of criteria to be considered when assessing licence applications, including that subsidiaries have adequate local management capabilities, and can provide accurate data on their local activities.

Stephen Barclay has been picked as the new Brexit secretary, as Theresa May seeks to fill her cabinet after several of her top team quit.
The MP for North East Cambridgeshire - who is a Leave supporter - had been a health minister since January.
He replaces Dominic Raab, who resigned on Thursday over Mrs May's withdrawal agreement for Brexit.
A No 10 spokesman indicated that Mr Barclay would focus on the domestic preparations rather than negotiations.
Mr Barclay's promotion comes after a tumultuous few days for Mrs May, after two senior ministers and several other junior ministers and aides quit following the publication of the proposed Brexit agreement.
And some Conservative Brexiteers who are unhappy with the deal have also been submitting letters of no-confidence in Mrs May. If 48 letters are sent, then a vote will be triggered and Mrs May could face a challenge to her leadership.
But shortly before Mr Barclay's appointment, two leading Brexiteers in the cabinet, Environment Secretary Michael Gove and International Trade Secretary Liam Fox publicly threw their support behind her.
In a tweet, Mr Barclay said he was "looking forward" to getting to work.
Mr Barclay becomes the third Brexit Secretary since the role was created, after Mr Raab and David Davis - who resigned over Mrs May's Brexit plans in July.
He has been congratulated on Twitter by Chief Secretary to the Treasury Liz Truss, who said he was "a star" when he worked in her department.
But Labour's shadow Brexit secretary Sir Keir Starmer said: "Stephen Barclay's appointment changes absolutely nothing.
"After two years of negotiation, the prime minister has failed to deliver a Brexit deal that can command the support of Parliament.
"A new face in the Brexit department will do nothing to bring this divided government back together."
Environment Secretary Michael Gove - who the BBC understood had at one point been contemplating his position before rallying behind Mrs May - is understood to have turned down the role of Brexit secretary following Mr Raab's departure.
Stephen Barclay - or Steve Barclay as he calls himself on Twitter - is a former banker and has also held the posts of City minister and a whip at the Treasury.
BBC assistant political editor Norman Smith said Mr Barclay was not a household name and it was a big promotion for him.
But he also described the 46-year-old as ultra-loyal, having never rebelled against the government.
Vicky Ford, a fellow Tory MP and a friend of Mr Barclay, told BBC Radio 4's PM programme he is known for listening "very, very hard and getting things done".
Mr Barclay, who is said to be a close friend of Theresa May's chief of staff Gavin Barwell, is married and has two children.
Meanwhile, Amber Rudd has been named the new work and pensions secretary - replacing Esther McVey, the second senior minister who resigned over the PM's Brexit plans on Thursday.
Ms Rudd said she was "delighted" to be given the role, and saw it as her job to "try to iron out" the issues with Universal Credit.
In her first interview in her new job, Ms Rudd called on any colleagues planning to submit letters of no-confidence in Mrs May to "think again".
"This is not a time for changing our leader," she said.
"This is a time for pulling together, for making sure we remember who we are here to serve, who we are here to help: that's the whole of the country."
Stephen Hammond will take over from Mr Barclay at the department for health and social care.
The government also announced replacements for two junior ministers who resigned over Mrs May's deal.
John Penrose will join the Northern Ireland office, replacing Shailesh Vara, and Kwasi Kwarteng will go to the Department for Exiting the EU, replacing Suella Braverman.
Mrs May agreed a draft withdrawal agreement for Brexit with her cabinet on Wednesday, which had already been signed off by negotiators from both the UK and EU.
But the deal led to a backlash from some Brexit-supporting MPs, including Mr Raab and Ms McVey.
Around 20 Tory MPs have publicly called for a vote of no confidence in the prime minister, with more thought to have written to the chairman of the backbench 1922 Committee to call for a vote on her leadership.
But Mrs May responded to critics saying she will stay in No 10 and see the deal through.

Lib Dem MP Stephen Lloyd has quit the party's group in Parliament so he can vote for Theresa May's Brexit deal.
The Eastbourne MP says he remains a member of the party, but wants to keep his promise to voters to respect the result of the referendum.
"I have decided that the only honourable thing for me to do is resign the party whip in Parliament," he said.
His departure reduces the number of Lib Dems MPs to 11. The party opposes Brexit and backs a further referendum.
The party's position is that they will vote against the Brexit deal Theresa May has negotiated with the EU, when MPs vote on it next Tuesday.
In a statement Mr Lloyd said: "I have come to the conclusion that I cannot honestly uphold the commitment I made... to accept the result of the referendum, vote for the deal the prime minister brought back from the EU and not back calls for a second referendum - whilst supporting the Lib Dem parliamentary party's formal position of voting against Theresa May's deal and advocating a 'People's Vote'.
"Although I have resigned the Whip, I continue to be a member of the Liberal Democrats, have nothing but respect and affection for the party leader, Sir Vince Cable MP, my Parliamentary colleagues and the Lib Dems.
"I will not cease fighting hard for liberal values, both locally and nationally."
While Mr Lloyd campaigned for a Remain vote in the 2016 EU Referendum, Eastbourne backed Leave by 57% - higher than the national average of 52%. In the 2017 snap election, Mr Lloyd beat his Conservative rival Caroline Ansell by 1,609 votes, having lost it to her in 2015.
A Liberal Democrat statement said: "We respect what we know was a difficult decision for Stephen ahead of next week's vote and are sorry to see him go. Liberal Democrats are clear that we will be voting against Theresa May's deal.
"The Liberal Democrats have campaigned for an exit from Brexit and a people's vote where people can choose to remain in the European Union...  we will continue to fight for this in Parliament."

Liam Fox and David Davis have called for an end to pessimism over Brexit and for the British public to "keep their eyes on the prize" on offer.
The international trade secretary hit out at "negative" attitudes in certain quarters and urged people to be more upbeat about the UK's prospects.
"We are not passengers in our own destiny," he told the Tory conference.
In his speech, Mr Davis said the UK would still be "good Europeans" in all respects after leaving.
Mr Davis, Mr Fox and foreign secretary Boris Johnson - dubbed the three Brexiteers - all made eagerly-awaited speeches to conference on Tuesday afternoon.
Earlier on Tuesday, MEPs in the European Parliament claimed cabinet divisions were hampering the UK's approach to negotiations and urged EU leaders to postpone a decision on extending the talks to discuss trade.
While the negotiations were proving difficult and at times fractious, Mr Davis said his job was to keep calm and he urged Tory activists to "keep their eyes on the prize" on offer following the UK's exit from the EU.
Brexit, he said, was a "one-off time-limited extraordinary opportunity" to shape the country's future.
"An opportunity to make sure that all the decisions about the future of this country are taken by our parliament, our courts, our institutions," he said.
"Decisions about how to spend our taxes - made here in Britain. Decisions about who comes into the country - made here in Britain. All our laws - made here in Britain.
"We need to get Britain standing on its own two feet - facing outwards to the world."
Criticising what he said was Labour's flip-flopping on Europe, he said the Brexit talks were perhaps the most "complex" negotiations ever and that one mistake could cost the UK billions in lost business.
While he was committed to getting a deal with the EU, he said the UK was prepared for alternative scenarios and contingency planning was taking place for no agreement being reached.
While he was prepared to work with other parties to improve the government's EU Withdrawal Bill, which will convert existing EU laws into British law, he said he would not let the bill be "wrecked".
He countered claims that the UK was not a "good European", saying the UK was at the forefront of defending Europe's borders, taking the lead in tackling terrorism and a leading sponsor of humanitarian aid.
Mr Fox said all the UK's international partners wanted to do business with it but he warned advanced economies which had benefited from free markets and unrestricted trade not to "pull up the drawbridge", amid what he said was a worrying growth in protectionism.
"We need to stop the negative, undermining, self-defeating pessimism that is too prevalent in certain quarters and be bold, be brave and rise to the global challenges, together," he argued.
Labour's shadow international trade secretary, Barry Gardiner, said: "Fox has had more than a year to bring forward a trade white paper that sets out a proper road map for business export and inward investment.
"Today would have been a sensible time to introduce some of its key ideas. Instead we got meaningless bravado from the government's most policy-light minister."

A £1.6bn government fund has been launched to boost less well-off towns in England after Brexit.
The pot is split into £1bn, divided in England using a needs-based formula, and £600m communities can bid for.
More than half of the money, to be spread over seven years, will go to the north of England and the Midlands.
Labour called it a bribe to influence MPs to back the PM's Brexit deal and critics say it does not cover cuts to local authority funding.
The Department of Housing, Communities and Local Government said there will be additional announcements "in due course" for Wales, Scotland and Northern Ireland.
In January, MPs rejected the withdrawal deal Theresa May has reached with the EU by 230 votes - the biggest defeat for a sitting government in history.
To win another vote, which Mrs May has promised will be on or before 12 March, she could find herself relying on the votes of Labour MPs from Leave-voting parts of the country.
John Mann, MP for Bassetlaw, a former coal mining area in Nottinghamshire, told the PM last month to "show us the money" with "transformative investment" in areas that voted to leave.
The Labour MP, who backed Mrs May's Brexit deal at the first vote, denied it amounted to "transactional politics".
But John McDonnell, Labour's shadow chancellor, said the fund "smacks of desperation from a government reduced to bribing MPs to vote for their damaging flagship Brexit legislation".
The BBC's assistant political editor Norman Smith said the money will be targeted on coastal communities, market towns, and de-industrialised towns, which meets the demands of some Labour MPs, who say regeneration funding tends to go to big cities.
The funding will go to specific projects like a new university campus or railway station, our correspondent added.
Dismissing the claim that the funding aimed to entice Labour MPs, Housing and Communities Secretary James Brokenshire insisted the cash would be made available even if the withdrawal agreement was rejected and denied the funding was a bribe.
He told BBC Radio 4's Today programme: "This funding is there regardless of the outcome, but obviously we want to see a deal happening, we believe that is what is in the best interests of our country."
He said the money would "supplement the work of councils" and could be "transformative" and was there "to see that towns grow".
However, Labour MP Alex Sobel, of the cross-party People's Vote campaign, which wants a new referendum on Brexit, said it was "a drop in the ocean" compared with the cost of leaving the EU.
He said the annual loss to local economies would be more than enough to wipe out any potential return from this scheme.
Labour's Ruth Smeeth, the MP for Leave-supporting Stoke-on-Trent, described the amount of money as "extraordinarily pathetic".
Speaking on BBC Radio 4's Westminster Hour programme, she said: "If you're talking about national renewal, this is less money than is being taken out of my economy by the introduction of [new welfare system] universal credit over the next four years."
Labour and Stoke-on-Trent Central MP Gareth Snell said the announcement was a "huge disappointment", tweeting: "The entire allocation for the West Midlands over four years is less than the total value of cuts faced by Stoke-on-Trent City Council alone over the same period."
Anna Turley, Labour MP for Redcar, has described the funding as "a shameless little bung."
She told BBC Radio 5 Live that £90m had been lost from her local council over nine years of austerity and the money was "bobbins" and was "shameless and embarrassing".
And Labour's Rhondda MP Chris Bryant tweeted: "And not a penny for Wales. The trouble with bribes is they embody injustice."
But the prime minister insisted: "Communities across the country voted for Brexit as an expression of their desire to see change - that must be a change for the better, with more opportunity and greater control.
"These towns have a glorious heritage, huge potential and, with the right help, a bright future ahead of them."
She said prosperity had been "unfairly spread" for "too long".
By BBC political correspondent Iain Watson
A month ago John Mann - who voted to leave the EU - told the BBC there was a "good dialogue" going on with the government.
And he was hopeful Mrs May would come back with "something significant" for his, and other, areas outside London.
He and a group of Labour MPs from Leave areas were demanding the protection of employment rights after Brexit - and assurances poorer areas wouldn't lose out when EU regional funding ended.
The cash on offer from the government is equivalent to less than 2% of English local authority spending.
Theresa May says she is simply making good a promise she made in her first speech as prime minister to help "ordinary working class families".
But the Labour leadership see this as a "bribe" to tempt some of their own MPs to break ranks and back Mrs May's deal.
The former Conservative, now Independent, MP Anna Soubry claims it's an attempt to buy votes.
But the government insists the true beneficiaries will be residents of coastal and industrial communities who feel left behind.
The £1.6bn Stronger Towns Fund will be broken down into £600m, which communities in any part of England can bid for, and £1bn allocated using a needs-based formula to the following areas:
"The formula allocations are based on a combination of productivity, income, skills, deprivation metrics and proportion of the population living in towns," a department spokesperson said.
"This targets funding at those places with economies that are performing relatively less well to the England average."
London is not included in the list, but towns within Greater London can bid for a share of the £600m pot, the department spokesperson added.
The government said communities would be able to draw up job-boosting plans for their town, with the support and advice of their Local Enterprise Partnerships.
It added that it would also seek to ensure towns in Wales, Scotland and Northern Ireland would benefit from the new funding.

Scotland's first minister has signed a letter formally asking for powers to hold a second Scottish independence referendum.
The Scottish Parliament voted by 69 to 59 on Tuesday in favour of seeking permission for another referendum.
Nicola Sturgeon argues Scotland should have the choice on what path to follow in the wake of the Brexit vote.
The UK government has already indicated that any referendum should wait until the Brexit process has been completed.
Prime Minister Theresa May, who met Ms Sturgeon for talks in Glasgow on Monday, has repeatedly insisted that "now is not the time".
She argues that the focus should be on getting the best Brexit deal for the whole of the UK, and Scottish voters can only make an informed choice once the terms are clear.
By Sarah Smith, Scotland editor
Sitting on the sofa, her shoes kicked off, putting the final touches to that letter
It couldn't be more different from the very formal portrait of Theresa May signing the Article 50 letter in Downing Street. Very different images - and that is no accident.
But while the picture may look quite casual, the contents of this letter are  not.
In it the first minister asserts that she has a clear mandate to ask for another referendum since the Scottish parliament voted to back her on Tuesday.
And she repeats her request for a vote in 18-24 months time. She says by then the shape of the Brexit deal will be clear.
But she knows what the prime minister is going to say in reply.
Constitutional matters are reserved to Westminster so the Scottish government must ask for the powers to hold such a vote to be transferred to Holyrood under a Section 30 order, as was done before the 2014 referendum.
The Scottish government released a photo of Nicola Sturgeon drafting the letter to Theresa May, with her feet curled up on a sofa at her official residence, Bute House in Edinburgh.
The letter is expected to be sent to Downing Street on Friday.
Ms Sturgeon is seeking a referendum between the autumn next year and spring 2019 - but has indicated she would be willing to negotiate the timing.
If, as expected, the request is declined, Ms Sturgeon has said she will set out her government's next steps in April, when MSPs return to the Scottish Parliament after the Easter recess.
The two-day debate at Holyrood on an independence referendum began last week but was suspended as news of the terror attack at Westminster emerged.
When it resumed on Tuesday, the minority SNP government was backed by the pro-independence Scottish Greens in the vote, with the Conservatives, Labour and Lib Dems opposed.
Scottish voters rejected independence by 55% to 45% in a referendum in 2014, but Ms Sturgeon believes the UK voting to leave the EU is a material change in circumstances which means people should again be asked the question.
While the UK as a whole voted to leave, Scotland voted by 62% to 38% to remain in the EU.
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When Boris Johnson, the Foreign Secretary, described the Treasury as the "heart of Remain" he was only partially correct.
When a Cabinet minister said directly to me when asked about relations with Philip Hammond, "Well, he's a Remainer", that person missed the target.
Mr Hammond and the Treasury have long since given up on any idea that the UK can remain a member of the European Union.
But, at heart, the most powerful department in government - and many forget that is still true despite the "spreadsheet Phil" dismissal of his critics - believes that the closest possible relationship with the European Union is the only way to reduce the potential of lasting economic damage to Britain post-Brexit.
Whilst others such as Mr Johnson and David Davis, the Brexit Secretary, have dominated the headlines, the Treasury has played it differently.
Submarine would be a good descriptor.
Under the surface, the department has focused its most senior people on persuading departments across government of two things.
First, that the economic and trading links between Britain and the rest of the EU are so deep and intractable that a sharp and irrevocable split would carry perilous risk.
From that argument came agreement to a "transition period" following the UK's official departure from the EU next March.
Second, that open economies such as Britain depend on goods being traded freely across borders and that the way to achieve this with the UK's biggest customer, the EU, was via some form of customs deal.
From that argument came the "facilitated customs arrangement" the Cabinet is discussing at Chequers today.
A system that ties the UK so closely to EU regulations and processes that free-trade deals with other counties, such as America, become difficult to the point of impossible.
In its arguments for the softest of soft Brexits, the Treasury has had some allies.
The first is not a person, but a thing - the border between Northern Ireland and the Republic.
Only via close alignment with the EU can there be any hope that the border can be kept free of customs checks, a key requirement, given the Good Friday agreement, of both the UK government and the EU.
The second is Greg Clark, the Business Secretary, who spoke yesterday of the need to listen "with the greatest respect" to companies such as Jaguar Land Rover when it said that billions of pounds of investment were at risk and jobs could be lost if barriers were suddenly thrown up between Britain and the EU.
In his interview with me in Newcastle yesterday, Mr Clark also executed a subtle but significant change of language.
Not that, when it came to goods, Britain would attempt a deal with the EU as friction free "as possible".
But that it would attempt a deal that was friction free, period.
That means some form of customs union on goods with the EU.
Third is economic growth, which the Bank of England has said is up to two percentage points below where it was expected to be had Brexit uncertainty not weighed on business investment decisions and consumer spending power.
The real world effects of the referendum, the Bank said, were "material".
Of course, the Treasury has not yet "won" anything.
The Cabinet has not agreed to the latest Brexit plan.
Opponents of Mr Hammond's approach say that "close alignment" means the result of the referendum has not been respected and opportunities to exploit new global trade deals could be lost.
The "facilitated customs arrangement" relies on technological gymnastics so intricate the systems do not yet exist and no other country in the world has attempted to follow a similar path.
The European Union is wary of any deal that could be portrayed as giving Britain "preferential treatment".
The "having cake and eating it" problem still remains.
But, given that just over a year ago the headlines were talking of Theresa May's plans to sack the Chancellor, Mr Hammond will be at Chequers knowing that the Treasury's submarine approach appears to have secured at least the beach-head towards the softest of soft Brexits.

The Supreme Court has dismissed the government's appeal in a landmark case about Brexit, meaning Parliament will be required to give its approval before official talks on leaving the EU can begin.
The ruling is a significant, although not totally unexpected, setback for Theresa May.
What will the prime minister do next and what impact will the ruling have on the process of leaving the EU, following last year's referendum vote?
The highest court in the UK dismissed the government's argument that it has the power to begin official Brexit negotiations with the rest of the EU without Parliament's prior agreement.
By a margin of eight to three, the 11 justices upheld November's High Court ruling which stated that it would be unlawful for the government to rely on executive powers known as the royal prerogative to implement the outcome of last year's referendum.
It said a law would have to be passed to authorise Article 50 but the precise form such legislation should take was "entirely a matter" for Parliament.
Attorney General Jeremy Wright said the government would "comply with the judgement of the court and do all that is necessary to implement it".
In a statement to Parliament setting out details of the government's legislative response, David Davis said he intended to publish an outline bill "within days".
The BBC's political editor Laura Kuenssberg said the details could be announced as early as Thursday, with a view to staging the first vote next week and getting it through the Commons within a couple of weeks.
We will get more details from the government later this week, with draft legislation already said to have been prepared in preparation for the appeal being rejected.
The new bill is expected to be short, with the government's lawyer suggesting during the hearing that "one-line" legislation could be put forward.
Both the House of Commons and House of Lords will have to vote in favour of it.
Separately, the government has agreed to produce an official policy document known as a White Paper explaining its objectives for the upcoming Brexit negotiations.
Ministers initially resisted the move, saying it would take too long, but Theresa May has agreed to it. The concession is being seen as a victory for opposition parties and a group of former Tory ministers who oppose a so-called "hard Brexit" and want to examine the government's plans in greater detail.
The bill will be given special priority by Parliament, whose order of business is still largely controlled by ministers.
While Tory MPs would like to see it fast-tracked through Parliament, many Labour, Lib Dem and SNP MPs will want as much time as possible to discuss a variety of issues and to make amendments.
The SNP responded to the ruling by saying it would table 50 "serious and substantive" amendments.
Labour said it too would seek to amend the bill but would not "frustrate" the Brexit process.
However it pans out, BBC Parliamentary correspondent Mark D'Arcy says the bill could pass through the Commons before the half-term recess in the middle of February, giving ample time for the Lords to then consider it and for it to become law before the end of March.
While there are some MPs who want the process to be delayed, they are vastly outnumbered by those who want the government to get on with it so that the UK will have left the EU by the time of the next election - scheduled for May 2020.
In theory, yes there is. But in reality it is extremely unlikely to happen.
Few, if any, Conservative MPs are likely to vote against Article 50. In fact, only one - the europhile former chancellor Ken Clarke - has said he will do so.
Given that the Tories have a working majority of 15 in the Commons, this means that the bill is guaranteed to pass - especially since a majority of Labour MPs have said they will not stand in the way of the process and many will actually vote for Article 50.
Although the Lib Dems, the SNP and some Labour MPs are likely to vote against, this will make little difference. What will be more interesting is if a coalition of pro-European Conservatives and opposition MPs join forces to win concessions, over the extent of Parliamentary scrutiny of the two-year process.
Events in the Lords - where the government does not have a working majority and there are 178 non-affiliated cross-bench peers - could be more unpredictable. Mark D'Arcy says there are murmurings of an organised attempt to resist Article 50 and a "doomed last stand" by diehard Remainers.
But amid warnings that any attempt to block Brexit could trigger a general election, in which the future of the Lords would be a major issue - it is likely that the skirmishes will amount to just that and the government will eventually get its way.
The Supreme Court case wasn't just a battle over the powers of the executive and the legislature.
The justices heard a number of separate but related challenges to the government's Brexit approach, centred around the involvement of the devolved administrations in Scotland, Wales and Northern Ireland.
But the court unanimously ruled that devolved administrations did not need to be consulted, and did not have a right to veto Article 50.
The government has previously said Scotland, Wales and Northern Ireland will be kept fully involved.

Boris Johnson's decision to suspend Parliament for five weeks was unlawful, the Supreme Court has ruled.
Judges said it was wrong to stop MPs carrying out duties in the run-up to the Brexit deadline on 31 October.
The PM, who has faced calls to resign, said he "profoundly disagreed" with the ruling but would "respect" it.
The Labour conference finished early following the ruling and MPs are returning to Westminster ready for Parliament to reconvene on Wednesday.
A senior government official said the prime minister spoke to the Queen after the Supreme Court ruling, but would not reveal the details of the conversation.
It comes after the court ruled it was impossible to conclude there had been any reason  "let alone a good reason - to advise Her Majesty to prorogue Parliament for five weeks".
Mr Johnson, who returns to London from New York on Wednesday, also chaired a 30-minute phone call with his cabinet.
A source told the BBC that the Leader of the Commons Jacob Rees-Mogg said to other cabinet ministers on the call that the action by the court had amounted to a "constitutional coup".
The prime minister insisted he wanted to outline his government's policies in a Queen's Speech on 14 October, and to do that, Parliament must be prorogued and a new session started.
But critics said he was trying to stop MPs scrutinising his Brexit plans and the suspension was far longer than necessary.
During a speech in New York, the PM said he "refused to be deterred" from getting on with "an exciting and dynamic domestic agenda", and to do that he would need a Queen's Speech.
The court ruling does not prevent him from proroguing again in order to hold one, as long as it does not stop Parliament carrying out its duties "without reasonable justification".
A No 10 source said the Supreme Court had "made a serious mistake in extending its reach to these political matters", and had "made it clear that its reasons [were] connected to the Parliamentary disputes over, and timetable for" Brexit.
But Supreme Court president Lady Hale emphasised in the ruling that the case was "not about when and on what terms" the UK left the EU - it was about the decision to suspend Parliament.
Delivering the justices' conclusions, she said: "The decision to advise Her Majesty to prorogue Parliament was unlawful because it had the effect of frustrating or preventing the ability of Parliament to carry out its constitutional functions without reasonable justification."
Lady Hale said the unanimous decision of the 11 justices meant Parliament had effectively not been prorogued - the decision was null and of no effect.
Speaker of the Commons John Bercow said MPs needed to return "in light of the explicit judgement", and he had "instructed the House of Commons authorities to prepare... for the resumption of business" from 11:30 BST on Wednesday.
He said prime minister's questions would not go ahead, but there would be "full scope" for urgent questions, ministerial statements and applications for emergency debates.
Short of the inscrutable Lady Hale, with the giant diamond spider on her lapel, declaring Boris Johnson to be Pinocchio, this judgement is just about as bad for the government as it gets.
Mr Johnson is, as is abundantly clear, prepared to run a general election campaign that pits Parliament against the people. And so what, according to that view of the world, if that includes the judges as part of the establishment standing in his way?
But there is a difference between being ruthless and reckless.
And the scope and strength of this judgement cannot just be dismissed as some pesky judges sticking their noses in.
Reacting to the ruling, Mr Johnson said it was an "unusual judgement", adding: "The prerogative of prorogation has been used for centuries without this kind of challenge.
"There are a lot of people who basically want to stop this country from coming out of the EU and we have a Parliament that is unable to be prorogued and doesn't want to have an election. I think it is time we took things forward."
The PM said getting a deal was "not made much easier with these sort of things in Parliament or the courts", but insisted the UK would still leave on 31 October.
Labour leader Jeremy Corbyn was due to close the Labour Party conference in Brighton with a speech on Wednesday, but brought it forward to Tuesday afternoon so he could return to Westminster.
He told cheering delegates: "Tomorrow Parliament will return. The government will be held to account for what it has done. Boris Johnson has been found to have misled the country. This unelected prime minister should now resign."
Lawyers for the government had argued the decision to prorogue was one for Parliament, not the courts.
But the justices disagreed, unanimously deciding it was "justiciable", and there was "no doubt that the courts have jurisdiction to decide upon the existence and limits of a prerogative power".
The court also criticised the length of the suspension, with Lady Hale saying it was "impossible for us to conclude, on the evidence which has been put before us, that there was any reason - let alone a good reason - to advise Her Majesty to prorogue Parliament for five weeks".
A spokesperson from the Attorney General's office said the government had acted in "good faith and in the belief that its approach was both lawful and constitutional".
"These are complex matters on which senior and distinguished lawyers have disagreed," a statement said.
"The Divisional Court led by the Lord Chief Justice agreed unanimously with the government's legal position, as did the Outer House in Scotland.
"We are disappointed that in the end the Supreme Court took a different view. We respect the judgment of the Supreme Court."
Wow! This is legal, constitutional and political dynamite.
It is worth just taking a breath and considering that a prime minister of the United Kingdom has been found by the highest court in the land to have acted unlawfully in shutting down the sovereign body in our constitution, Parliament, at a time of national crisis.
The court may have fallen short of saying Boris Johnson had an improper motive of stymieing or frustrating parliamentary scrutiny, but the damage is done, he has been found to have acted unlawfully and stopped Parliament from doing its job without any legal justification.
And the court has quashed both his advice to the Queen and the Order in Council which officially suspended parliament.
That means Parliament was never prorogued and so we assume that MPs are free to re-enter the Commons.
This is the most dramatic example yet of independent judges, through the mechanism of judicial review, stopping the government in its tracks because what it has done is unlawful.
Be you ever so mighty, the law is above you - even if you are the prime minister.
Unprecedented, extraordinary, ground breaking - it is difficult to overestimate the constitutional and political significance of today's ruling.
The ruling was made after a three-day hearing at the Supreme Court last week which dealt with two appeals - one from campaigner and businesswoman Gina Miller, the second from the government.
Mrs Miller was appealing against the English High Court's decision that the prorogation was "purely political" and not a matter for the courts.
The government was appealing against the ruling by Scotland's Court of Session that the prorogation was "unlawful" and had been used to "stymie" Parliament.
The court ruled in favour of Mrs Miller's appeal and against the government's.
Speaking outside the court, Mrs Miller said the ruling "speaks volumes".
"This prime minister must open the doors of Parliament tomorrow. MPs must get back and be brave and bold in holding this unscrupulous government to account," she added.
The SNP's Joanna Cherry, who led the Scottish case, called for Mr Johnson to resign as a result of the ruling.
"The highest court in the United Kingdom has unanimously found that his advice to prorogue this Parliament, his advice given to Her Majesty the Queen, was unlawful," she said.
"His position is untenable and he should have the guts, for once, to do the decent thing and resign."
Former Prime Minister Sir John Major - one of the sponsors of the prorogation appeal - said it gave him "no pleasure to be pitted against a government and prime minister of my own party".
"No prime minister must ever treat the monarch or Parliament in this way again."
Mr Johnson was backed by US President Donald Trump at a joint press conference at the United Nations in New York.
"I'll tell you, I know him well, he's not going anywhere," said Mr Trump, after a US reporter quizzed the prime minister on whether he was going to resign.
But reaction at home was far more negative. Scotland's First Minister, the SNP's Nicola Sturgeon, said the ruling was the most significant constitutional judgement in her lifetime, and it would be "unthinkable" for Mr Johnson to remain in office.
Wales' First Minister, Labour's Mark Drakeford, said the court's decision had been a "victory for the rule of law" and the PM had "tried to play fast and loose with our constitution".
In Northern Ireland, the leader of the DUP, Arlene Foster, said the ruling must be respected, while Sinn Fein's vice president, Michelle O'Neill, said Mr Johnson should resign.
Other figures have taken to Twitter to support the court's decision, including former Tory minister Amber Rudd, who resigned her post - and the party whip - over the government's approach to Brexit.
The leader of The Brexit Party, Nigel Farage, said Mr Johnson must, "as a matter of honour", offer his resignation to MPs in Parliament on Wednesday.
The decision to prorogue Parliament had been a "disaster", he added, and there must be a general election "before very long because Parliament and the government have ceased to function".
Former Attorney General Dominic Grieve, who has been an outspoken critic of the suspension, said he was "not surprised" by the judgement because of the "gross misbehaviour by the prime minister".
He told the BBC's Victoria Derbyshire programme he was "delighted" the Supreme Court had "stopped this unconstitutional act in its tracks".
But Tory MP Andrew Bridgen said the court's decision was "the worst possible outcome for our democracy" and "an absolute disgrace".
He told the same programme: "What we've got is a Parliament that's completely out of step with sentiment of the country."
Fellow Tory MP and chairman of the pro-Brexit European Research Group Steve Baker said the ruling was an "earthquake moment".
He described the Commons as a "rotten Parliament" facing a "crisis", and called for a general election so a government with a majority could move forward.
Prorogation is a power that rests with the Queen, carried out by her on the advice of the prime minister.
And at the end of August - shortly before MPs returned from their summer recess - Mr Johnson called Her Majesty to advise she suspend Parliament between 9 September until 14 October.
MPs had been expecting to be in recess for some of these weeks for their party conferences.
But unlike prorogation, a recess must be agreed by a vote, and a number of MPs said they would have voted against it to ensure they could scrutinise Mr Johnson's Brexit plans.
The decision to prorogue prompted an uproar from the Commons, especially from MPs who had planned to take control of Parliament to force through a law to block a no-deal Brexit after Mr Johnson said the UK would leave the EU with or without a deal on the Halloween deadline.
Despite only sitting for a week, they did manage to pass that law ahead of prorogation and it received royal assent on 9 September.
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The Supreme Court ruling that the prime minister's suspension of Parliament was void and his advice to the Queen unlawful, raises all sorts of questions for the EU - will their Brexit negotiating partner Boris Johnson stay in his job? When might the UK hold a general election?
Privately the court ruling has been described to me by EU sources as "an embarrassment" and "a humiliation" for Boris Johnson but this isn't the first time the EU has found itself faced with similar questions about possibly imminent elections and Mr Johnson's longevity as prime minister.
Yet then, as now, the EU has taken the decision to put its metaphorical hands over its metaphorical ears in an attempt to block out the noise.
Why? Because EU leaders view the Supreme Court ruling and what follows next in the UK as an unpredictable domestic political affair. They regard themselves as onlookers to that drama - which is why German Chancellor Angela Merkel and French President Emmanuel Macron have stayed silent, and why the European Commission refused to comment on the ruling on Tuesday, however hard UK journalists pushed.
Brussels prefers to focus on where it can play a part - negotiations. And there, in the short term at least, Tuesday's ruling changes little. EU leaders still want a Brexit deal and, under EU law, their negotiating partner is Her Majesty's government, still headed by Boris Johnson.
EU-UK technical talks are pressing ahead on Wednesday in Brussels, regardless of what might be going on in a parallel universe in London, when MPs are reunited with the prime minister in Parliament.
But is the Supreme Court ruling a demotivating factor for the EU in engaging with the Johnson government?
In fact, EU politicians say the most demotivating factor for them is the lack of a guarantee that the majority of MPs would definitely approve a new Brexit deal, even if they made big compromises.
But, although EU leaders says they are "open" to another Brexit extension, such is the impatience with the more than three-year-long Brexit debate, they would love to agree a new deal with Boris Johnson by mid-October as he hopes to do.
And yet, scepticism is rife in Brussels.
One diplomat from a country traditionally very close to the UK told me: "The prospects of an October deal already weren't good. They're now complicated further by UK domestic issues. Time, as we always say, is running out."
EU diplomats argue that the current UK ideas on how to replace the Irish backstop in a new Brexit deal may be a start. But as the EU's chief Brexit negotiator, Michel Barnier, said on Tuesday in Berlin, in EU eyes the UK proposals fall far short of the "technically detailed, legally operable, concrete solutions" they are calling for.
Pushback from journalists and/or the UK government that the EU needs to compromise, too, is rejected at this stage in Brussels.
The stock reply is that before anyone in the EU thinks of compromise, they need realistic UK proposals to negotiate over.
As for assertions by UK Foreign Secretary Dominic Raab and others that the EU always blinks at five minutes to midnight, EU contacts say this shows a misunderstanding of how the EU works.
One EU diplomat from a small member state commented to me: "We only compromise when that compromise doesn't cause us great harm."
Brussels believes it couldn't protect the single market, the Northern Ireland peace process or EU member state Ireland if it agreed to current UK proposals on how to replace the backstop.
And EU sources claim the two sides are still too far apart for it to make sense to "go into a tunnel" of intense negotiations with a media blackout at this stage.
EU governments admit that a new Brexit extension would be likely to take the pressure off both sides to make the compromises necessary to agree a new deal.
However, the bottom line is that Europe's leaders are unsure whether Boris Johnson would be willing to make Brexit compromises anyway, if he knows that he's heading into a general election.

Before everything gets swept up in a force 10 political storm, stop for a moment to think about what has just happened.
The highest court in the land has just ruled that the serving prime minister broke the law. He gave the Queen advice that was unlawful.
Therefore his decision to suspend Parliament was also against the law, so is now null and void.
Short of the inscrutable Lady Hale, with the giant diamond spider on her lapel, declaring Boris Johnson to be Pinocchio, this judgement is just about as bad for the government as it gets.
Mr Johnson is, as is abundantly clear, prepared to run a general election campaign that pits Parliament against the people. And so what, according to that view of the world, if that includes the judges as part of the establishment standing in his way?
But there is a difference between being ruthless and reckless. And the scope and strength of this judgement cannot just be dismissed as some pesky judges sticking their noses in.
Just a few weeks ago, the advice of government lawyers was said to be that it was unlikely the judges would want to step into such explosive territory. They were wrong. For the very many people in the Conservative Party who have doubts about Boris Johnson but wanted to give him the chance, this is a nightmare.
But back to that political storm which is, no surprise, already raging. To shouts of "Johnson out! Johnson out!" on the Labour conference floor, Jeremy Corbyn said the prime minister should consider his position - in other words, he should quit.
The SNP and Liberal Democrats are calling on him to go now too.
The prime minister is in New York at the United Nations, and his team is yet to respond. But the idea that he would walk is far-fetched (for now). What seems certain, though, is that MPs will be sitting again in Parliament on Wednesday.
The Commons Speaker has already said they should convene urgently. Some MPs have, out of principle, already gone back to sit on the green benches. It is a different question, of course, to ask, for what purpose, what will they discuss.
There isn't suddenly going to be a majority in Parliament for a way out of this mess. And Boris Johnson will inevitably try to use this to his political advantage.
Do not underestimate how aggressive Number 10 might be willing to be in response to the judgement. It is possible they will fly straight back from New York to face the music - armed with what strategy is harder to read.
But the decision to suspend Parliament may just have blown up in Number 10's face.
In his two months in power, Boris Johnson has lost his first six Commons votes, broken the law by suspending Parliament, and misled the monarch.
Even for a politician who seems to enjoy breaking the rules, that is a serious charge that, only two months into office, even the most brazen Johnson backer cannot simply shrug off.

Westminster is buzzing with talk of splits, general elections, second referendums and even the formation of new political parties as Brexit strains traditional loyalties to breaking point.
With votes on any deal struck by Theresa May with the EU expected to happen this autumn, here is a guide to the main factions in the Commons:
Government ministers, basically - there are just over 100 them out of a total of 316 Tory MPs - and those backbenchers who support Theresa May's Brexit policies, or at least are not willing to vote against them and threaten her leadership.
Most Tory MPs fall into this category but it is not enough for Mrs May to be sure of winning key Commons votes, even with the support of the DUP's 10 MPs, who unlike Mrs May backed Leave in the EU referendum.
Ten members of Mrs May's government have quit in recent months - most of them because they are against her Chequers plan for post-Brexit trade, although Defence Minister Guto Bebb quit because he is in favour of it. Mr Bebb thought she had caved in to the hard Brexiteers (see below) over customs legislation. He has now joined the People's Vote campaign (see below).
Sixty Conservative MPs, headed by Jacob Rees-Mogg (pictured above), are members of the European Research Group - a pro-Brexit lobby, who are against Theresa May's plans for trading arrangements with the EU.
They are well-organised and highly motivated and the PM's continued survival in Number 10 is, largely, in their hands.
The rebel ranks were swollen by ex-Foreign Secretary Boris Johnson, former Brexit Secretary David Davis and his deputy Steve Baker, who all quit in protest at her blueprint for post-Brexit trade with the EU hammered out at her country residence Chequers, in July.
Mr Baker claims as many as 80 Conservative MPs are prepared to vote against the Chequers plan. He has warned about a "catastrophic split" in the Conservative Party if it is not able to unite around a different vision. Mr Johnson has thrown grenades - and a "suicide vest" - into the debate from the pages of national newspapers, with increasingly strident attacks on the Chequers proposal, prompting an angry backlash from Theresa May loyalists.
The Dominic Grieve gang. Like most of his cohorts, who number about a dozen and include former minister Nicky Morgan (seated behind Mr Grieve in the picture above) who led an unsuccessful rebellion in the customs vote, the former attorney general is not a natural rebel.
Mr Grieve and his supporters inflicted the government's first Brexit defeat, in December, securing a "meaningful vote" for MPs on the final deal with Brussels, but some wonder whether his gang have the killer instinct of their pro-Brexit rivals when that final showdown happens in the autumn. Mr Grieve has said he will quit the party if Boris Johnson becomes prime minister, in reaction to a row over the former foreign secretary's comments about the burka.
Conservative MP Anna Soubry, a close ally of Labour's Chuka Umunna in the People's Vote campaign for another EU referendum (see below), has called in the past for the creation of a new centre-ground party.
She also backed a call by fellow Conservative Sir Nicholas Soames - a longstanding pro-European and the grandson of Sir Winston Churchill - for a "government of national unity", made up of senior figures from different parties to sort out Brexit, although that idea seems to have disappeared from the radar.
But it is the leader of the Liberal Democrats, the UK's traditional centre party, who has emerged as the biggest cheerleader for a new centre party.
Sir Vince Cable is openly encouraging disaffected anti-Brexit Labour and Tory MPs to form new groups and work with the Lib Dems to colonise what he believes is the vast territory that has opened up in British politics as Labour moves to the left under Jeremy Corbyn and Tory Brexiteers push their party to the right.
Sir Vince, who has said he will stand down as Lib Dem leader once Brexit has been "resolved or stopped", admits his party, with just 12 MPs, has struggled to achieve the rapid growth in support it wanted despite being the only national party campaigning for a second referendum and has set out plans to transform into a "movement for moderates".
Former Education Secretary Justine Greening is the most senior Conservative to have called for a referendum on the final Brexit deal. She was backed by Heidi Allen and Anna Soubry, and another prominent backbencher, Sarah Wollaston, has also joined the People's Vote campaign. along with Phillip Lee and Guto Bebb.
Jeremy Corbyn's supporters insist the party has never been more united behind its leader - despite a bitter and divisive row about anti-Semitism that dragged on for months over the summer.
The vast majority of the shadow cabinet - about 30 MPs - and most of the 47 new Labour MPs elected last year, in addition to a handful of long-serving left wing backbenchers, are fiercely loyal to the leader and back his Brexit stance.
But many, maybe even the majority, of the 257 Labour MPs, including the self-styled "moderates" who served in government during the Blair/Brown era, remain unhappy with the direction the party is going in.
Some Corbyn critics have faced no confidence votes from their local parties, a sign they could face de-selection before the next general election.
Jeremy Corbyn's backing for Brexit and refusal to throw his weight behind calls for a second referendum, after campaigning for Remain in the referendum, are a major sore point among "moderate" Labour MPs, who suspect he remains a Eurosceptic at heart.
The cross-party People's Vote campaign for a second referendum is backed by about 30 Labour MPs, including prominent figures such as Chuka Umunna (pictured above), Chris Leslie and Stephen Doughty.
They outnumber members of other parties in the group, which also includes Lib Dems, Green MP Caroline Lucas, five Conservative MPs and Plaid Cymru's four MPs.
These MPs tend to eschew party labels when commenting on Brexit. The Labour members are in open revolt against their party leadership's opposition to a second referendum - but they insist they are not operating as a party within a party.
Chuka Umunna has written to members of his local party in Streatham, South London, to deny speculation he is involved in talks about the formation of a new party. The idea that the People's Vote is the forerunner of a such a party is "patently absurd", he writes.
But he has also claimed Jeremy Corbyn's supporters are trying to force "moderate" MPs like himself out of Labour, something the party leadership says is simply not the case.
Like the members of the People's Vote campaign, the SNP's 35 MPs, led by Ian Blackford (pictured) are against Brexit and want the UK to stay in the EU single market and customs union.
They have said they won't stand in the way of a second referendum but have not committed to voting for one. One reason for this is that Scotland voted for Remain in 2016 and it did not make any difference to the result.
They are likely to vote against anything resembling a "hard Brexit".
Kate Hoey (pictured), John Mann, Frank Field and Graham Stringer - along with the currently independent Kelvin Hopkins - voted with the government in key Brexit votes, helping to ensure Theresa May's survival.
This is the core of a group who say they are standing up for the millions of Labour supporters who voted to Leave the EU.
Mr Field has resigned the Labour whip in Parliament - and is fighting to remain a member of the party - after claiming it has become a "force for anti-Semitism in British politics".
The MP's opponents say he jumped before he was pushed after losing a confidence vote organised by local activists in Birkenhead angry at his support for the government in Brexit votes, which they believe robbed Labour of the chance to force a general election it could have won.
Ms Hoey is also facing calls to be expelled from Labour and has lost a confidence vote in her local Vauxhall Labour Party. Graham Stringer won a confidence vote in his Blackley and Broughton Labour branch.

Forget for a moment the "will they, won't they" numbers game.
Unless and until the head honcho of the Tories' backbench committee receives 48 letters there won't be a vote of no confidence in the prime minister.
As far as we know tonight the total has not yet been reached.
One of those who has submitted their letter told me in no uncertain terms "where are the others?" - frustrated that many of his colleagues seem to have promised to be part of the action, but reinforcements are yet to arrive.
If and when that threat can more clearly be seen to have retreated, there's a lot to be said about the true power of backbench Brexiteers. But as of the time of writing we are not there yet and who knows, in a matter of hours, the putsch could suddenly be back on.
Something very worrying however for Number 10 has just happened for real, more important in this moment than the potential threat from their own backbenches.
The DUP, crucial to Theresa May holding on to power, has just abstained in votes on the finance bill. In other words, they decided not to back the prime minister on the Budget.
Why? We know that the DUP is furious about the compromises that Number 10 has made to get their draft deal with the EU.
And they want to show, loudly and clearly, that they are not on board.
A senior DUP source has just told me tonight's votes were deliberately designed to "send a message to Theresa May that if she wants to continue down the road of the withdrawal agreement and its effect on the Union then there will be repercussions in the Commons".
"She could be leading them to a very bad place," they continued. "Tory MPs need to realise that their jobs, their majorities, their careers depend on a good working relationship with the DUP and May doesn't appear to be listening."
Ouch. The DUP says this is not the end of the arrangement of so called "confidence and supply" agreement, where the government can formally rely on support from the Northern Irish unionists' 10 votes.
But the fabric of that arrangement is certainly torn... And once faith is broken between the two, it's hard to see how it could be restored.
Remember, there's a really straightforward reason why this matters so much. Theresa May does not have enough votes on her own to pass the Brexit deal.
The partnership with the DUP was set up to try to make sure she could. If it collapses completely then her central task becomes yet more seemingly impossible, even if those 48 letters never come.

Ministers want you to ignore the Tory psychodrama, but frankly, that is what it feels like we are stuck in the middle of.
This is an attempt at a basic summary of what happened - from what I've been told - after a barmy afternoon.
For this to make sense, here's a reminder of what happened earlier in the week.
By about 1400 BST the haggling between Dominic Grieve and the solicitor general, representing the government, was pretty much concluded to Grieve's satisfaction.
The Remain-leaning potential rebels had a version of the promised compromise that saved Theresa May's bacon earlier in the week. And they were happy with it.
By 1600 BST, that was not the case.
Those pushing for a change were told the government wanted something else, to make the motion "unamendable".
Forget the technicalities, that would basically mean the final "meaningful" vote would, in effect, be a take-it-or-leave-it vote, a potential vote of no confidence in the prime minister.
I'm told they made it crystal clear they would never accept it.
But then, "inexplicably", that ended up in the final version that was published, before they had seen it.
Their suspicion: Brexiteers had put the kybosh on it all.
A senior Brexiteer told me that they were not the ones who had put a spanner in the works. They say they only saw it at the last minute, and weren't involved in haggling over the deal.
Others beg to differ though, suggesting that they were told the problem was that "Jacob [Rees-Mogg], needed to see it" and it has been suggested that Brexit Secretary David Davis was instrumental in changing the plan.
What does that all mean though?
The hardcore Remainer rebels are apoplectic, feeling they have been betrayed by the prime minister, who has broken the promise she gave them to avoid defeat.
And it sets the scene for another showdown in Parliament next week when the prime minister may find out which side of her party has the stronger resolve.
What happened today is likely to have pushed the two sides further apart.
This whole process is meant to be about the political divorce between the EU and the UK.
At times it is the negotiation between the two sides of the Tory party that are more bitter than any of that could be.

The UK and EU have agreed on a "large part" of the agreement that will lead to the "orderly withdrawal" of the UK.
Negotiators Michel Barnier and David Davis said the deal on what the UK calls the implementation period was a "decisive step" in the Brexit process.
But issues still to be resolved include the Northern Ireland border.
And Scotland's fishing industry has reacted angrily to the deal, which will see the UK "consulted" on quotas and access to its waters until 2021.
Brexit Secretary Mr Davis said Monday's transition agreement, which is conditional on both sides agreeing a final withdrawal treaty, would smooth the path to a future permanent relationship.
Mr Barnier said the legal text marked a "decisive step" but added that it was "not the end of the road".
The key aspects of the agreement announced in Brussels are:
The EU says this so-called "backstop option" for Northern Ireland was a key part of December's phase one agreement with the UK and must continue to apply "unless and until another solution is found".
Theresa May has suggested this outcome - which is favoured by Dublin - would be unacceptable as it would effectively shift the existing land border to the Irish Sea and compromise UK sovereignty.
In a letter to the European Council President Donald Tusk, the prime minister said "more work" was needed on certain commitments included in December's agreement and she continued to believe safeguards for Ireland could be agreed as part of the overall future economic and security partnership.
Should this not prove possible, she said she was committed to discussing "additional specific solutions" in parallel with the existing legal process for the UK's withdrawal.
Both the UK and the EU hope the terms of an agreement on the transitional period can be signed off by Mrs May's fellow 27 leaders at the EU summit this week.
The UK has said it had secured a number of improvements to the text, including an explicit reference to Gibraltar being covered by the agreement and the creation of a joint committee to oversee the process.
"We must seize the moment and carry on the momentum of the last few weeks," Mr Davis said. "The deal today should give us confidence that a good deal for the UK and EU is closer than ever before."
Labour's shadow Brexit secretary Keir Starmer said the agreement was "a step in the right direction" but Scotland's First Minister Nicola Sturgeon tweeted that the agreement for fishing during the implementation period was "shaping up to be a massive sell-out of the Scottish fishing industry by the Tories".
She added: "The promises that were made to them during #EUref and since are already being broken - as many of us warned they would be."
Bertie Armstrong, chief executive of the Scottish Fishermen's Federation, said the agreement fell "far short of an acceptable deal" giving the UK full control of its waters from the moment it leaves.
"We will leave the EU and leave the Common Fisheries Policy, but hand back sovereignty over our seas a few seconds later," he said. "Our fishing communities' fortunes will still be subject to the whim and largesse of the EU for another two years."
Downing Street said that because fishing quotas are worked out on an annual basis, for the period from 2020 onwards, the UK would be "negotiating fishing opportunities as an independent coastal state deciding who can access our waters and on what terms".
Monday's document clearly states the European Court of Justice will have "jurisdiction" over matters relating to EU law and EU citizens during the transition - once regarded as a "red line" by many Brexit-supporting MPs.
As well as questions about Northern Ireland, there are unresolved issues about what role, if any, the ECJ will have after the transition and other governance issues.
The UK and EU hope that if a transition deal is agreed, then negotiations can focus on what sort of permanent future relationship the two sides will have - with the aim of a deal being agreed in the autumn to allow time for EU member states and the UK Parliament to ratify it before Brexit next March.

With rumour swirling, gossip in the air about the cabinet, it is hard to work out what is really going on. Since Mrs May didn't really win the prize she was expecting, ministers have become an unruly lot. Tomorrow, they're all going to get a telling off (with apologies to the truth).
Why is she so cross?
David wants her job, although he says that he doesn't and isn't thinking about it, it's only his friends getting excited.
Boris wants the job too, although he says he doesn't want it yet, and guess what, it's only his friends getting a bit excited.
This excitement sometimes involves those friends saying rude things about the other one.
Neither of them, nor any of their friends, want Philip to get the job.
Some of Philip's friends want him to get the job, but maybe he's not so sure. What he really wants is to stay in charge of the money, whoever has the big job.
Philip doesn't trust or like Michael very much.
Neither, really, does Theresa like Michael very much. But lots of people think he is clever and he likes Brexit.
So does Boris, who used to like Michael a lot.
Then Michael was really mean to Boris and it hurt his feelings a lot. They'll probably never go to each other's houses again for dinner but they may not quite feel like poisoning the other's dinner.
Then there's Liam, who also likes Brexit a lot.
He likes running for the big job. He says he doesn't want that opportunity to come up, but if it does, he might well have another go because he likes doing it so much.
There's also Andrea, who smiles a lot and likes Brexit, a lot. She didn't really enjoy going for the big job last time, but if it happens again, the chance to run again might make her smile, a lot.
Then there's the newer gang, like Priti, who also likes Brexit and might like to try for the big job one day.
So might Sajid, who doesn't really like Brexit that much, but might want to join in the big race too.
And don't forget Amber, who Philip and David are apparently trying to get into their gang - but it's tricky because she doesn't like Brexit and could also fancy having a go at the top post too one day, although she'd probably need to make a few more friends in her home town.
And there's Patrick, who didn't like Brexit either. No one really wants to be friends with him at the moment. He was meant to be in charge of trying to win the big prize but that didn't quite go according to plan.
Then there are Greg, Karen, Justine, Michael number two, David number two, Jeremy,David number three, Alun and yes, David number four.
None of them really like Brexit very much.
Most of them (apart from David number three) would also like Philip (remember him?) to write some bigger cheques for their departments.
But he isn't really in the mood to do that, remember. He wants to stay in charge of the money, whoever has the big job.
Then there is James, who also didn't like the idea of Brexit but has an almost even harder project in Belfast.
There are also Liz and Brandon. She used to have to worry about cheese, he now has to worry about immigration.
Neither of them really liked Brexit either but are, you guessed it "getting on with the job".
And Chris, who really loves the idea of Brexit and is in charge of trains. He says he doesn't want Philip or Boris or David (number one) to be making trouble.
There's also Natalie, who has to explain to another lot who get to wear red velvet cloaks (honest) what all of the above are trying to achieve. (That's a good question)
Then there is Damien, who really didn't like the idea of Brexit but who is really important because Theresa isn't cross with him.
In fact, she trusts him and my goodness, that doesn't happen very often.
Last of course there is Theresa who, while being cross with this lot, is probably still cross with herself, and most likely peeved with Nick and Fi, but that's another story.
The public might well think they all must try much harder.

After many months of rumours that he would pull the plug, David Davis has actually quit as Brexit Secretary.
His unhappiness in government has been no secret for some time, but after the prime minister's Chequers agreement with cabinet ministers to pursue closer ties with the EU than he desired, he found his position untenable.
After a visit to Downing Street on Sunday he concluded that he had no choice but to walk. Junior ministerial colleague Steve Baker has also quit alongside him from the Brexit department. David Davis' move, while not completely surprising, throws doubt on to how secure the government's Brexit strategy is.
Some of Theresa May's colleagues had urged her to face down her Brexiteer ministers but Number 10 had hoped to keep them all on side, and a carefully designed strategy to move them to her position brokered an agreement in cabinet at the end of their day-long meeting at Chequers on Friday .
But Mr Davis, who was meant to be responsible for Brexit policy, felt,  according to colleagues, that he was "wondering if he really had a proper job" after Number 10 chose to follow a very different path to the now former Brexit secretary's intention.
Mr Davis has been frustrated for some time after the most senior official at the Department for Exiting the EU - Olly Robbins - was moved into Number 10 to work directly for Theresa May.
To some former Remainers, Mr Davis' departure could even be considered a temporary relief. One of his fellow ministers remarked, "it's just a personal outburst", adding: "He is not exactly the cleverest, he has always struggled to muscle into any of the complicated arguments."
But conditions in the Tory party are febrile. Theresa May had carefully constructed her cabinet with a balance of Brexiteers and former Remainers. With no majority, and unhappiness on the back benches, it adds instability at a time when the prime minister was pursuing calm.
And when she was hoping to project an image to Brussels of authority and stability, it is a headache she could well do without. He could provide a rallying point from outside government for those forces in the Tory party who believe the Brexit plan the prime minister is pursuing is not the Brexit that a clear but narrow majority of the public chose.
Westminster being Westminster, eyes will immediately turn to who will replace him. The most likely candidate it seems at this stage is Michael Gove who has pitched himself as the Brexiteer that "remainers can do business with".
His public appearances defending the Brexit policy over the weekend make him certainly near the top of the list for one of the most important jobs in government.

The good, the bad and the ugly - the story of this summit so far.
Theresa May can claim something already. EU leaders have agreed that the negotiations can continue, officials can get back to the extremely difficult task of solving conundrums that have been preoccupying them for two years.
For EU leaders to have said any less than that would have been a horror show for Number 10.
But the bad? After listening to Theresa May and then talking amongst themselves after she left, her counterparts decided that there simply hasn't been enough progress to be able to reach anything like a deal.
The prime minister did not turn up with "new facts" that could have changed the dynamic. Yes, the two sides have moved closer together on many of the sticking points in the last few weeks. But the division over Ireland is still plain and there is no way out of it yet.
The ugly? Well a senior EU official revealed after the dinner that the prime minister told the others that she was "ready" to consider a longer implementation period after Brexit than is currently planned - essentially she'd think about both sides having longer to work out all the complexities of how the relationship between the EU and UK will work well after Brexit.
To many people that will sound perfectly sensible. But to others, including many Tory MPs, it would mean the UK being trapped in the status quo until 2022.
And more to the point, potentially having to promise to pay the EU billions more, without quite knowing for what.
Number 10 won't confirm the prime minister's comments. But the president of the European Parliament said on the record that it had been discussed. And sources at Downing Street repeatedly refused to rule it out.
But there's one giant problem. It's hard to see how it could get through the House of Commons. One former Remainer MP told me "it just wouldn't fly".
Iain Duncan Smith, the prominent Brexiteer, said "why are we agreeing to extend for another year when we have nothing back in return".
Nick Boles, an influential former minister, wrote on Twitter, "good luck with that".
Remember getting Brussels on board is one thing. Theresa May has a harder job at home. And if she is looking for big rebellions, staying tied to the EU for longer is one way of making that happen.

Maybe it was the moment when the former education secretary, Justine Greening, intervened on her former ministerial colleague, Dominic Grieve, that the government realised the game was up.
She was so supportive towards the former attorney general, as he argued for Parliament to have a "meaningful vote" on the terms of the Brexit deal, that it seemed probable she would join the Euro-rebels in voting for it….
For some time the government Chief Whip Julian Smith had been flitting round the Chamber talking to his troops - then he went and had a word with the Solicitor General, Robert Buckland, the government's in-house legal eagle, who is dealing with the techie legal aspects of the EU (Withdrawal) Bill.
Soon after, Mr Buckland intervened on Mr Grieve to suggest talks over a compromise deal. It appeared that the head count had been done, and the concession followed.
Most dangerous
The meaningful vote is probably the most dangerous of the Lords amendments to the EU (Withdrawal) Bill - because it tees up an unpredictable vote on the final terms of Brexit, towards the end of this year, and opens up the possibility that MPs could demand that ministers change policy, in the event the terms were rejected by the House, or no deal was reached in the talks with the EU….. they could even demand (drumroll) a second referendum…
The government would not have sought a deal if it thought it had the votes to win, and they clearly blinked.
The decision to seek a compromise marked an important victory for the soft Brexit/Remainer/"realist" Tory rebels, who have been promised an amendment giving them most of what they want.
As I write the full terms of the deal have yet to be revealed, but there is briefing ministers have conceded that a motion, which could be amended, would be put before MPs, in event a final divorce deal is voted down.
In other words, in the event of a divorce deal that the Commons refused to accept, MPs would be able to set a new course for Brexit.
This whole idea was denounced by Brexiteers as a Trojan horse for Remainers, and for a second referendum, so that concession could well produce some blowback. But for now, the government seems to have prevented an embarrassing defeat, and the Tory rebels have avoided the unpleasantness of colluding in the defeat of their Prime Minister.
One of the leading Tory rebels has told the BBC "the government has bent not broken" but it leaves the "fight for another day".
But ministers now know that a narrow but decisive Commons majority can be assembled against them on critical Brexit issues, and that its next outing could well be on a more substantive vote on a customs union.
Will that knowledge mean a softer Brexit strategy will now emerge?

There is one vital paragraph to pay particular attention to in the speech by Philip Hammond on Wednesday.
Its significance should not be under-estimated for it is about one of the few sectors where the UK has a substantial trade surplus with the European Union - financial services.
It is the sector which Britain wants to be a key part of any ambitious free trade deal with the EU.
And the EU, so far, suggests it won't be.
In his speech on UK-EU co-operation post-Brexit, the Chancellor will refer to past attempts at forging a free trade agreement between the US and Europe.
"The EU itself pursued ambitious financial services co-operation in its proposals for TTIP [the now aborted Trans-Atlantic Trade and Investment Partnership]," Mr Hammond will say.
"Which it described as a partnership that would be: 'more than a traditional free trade agreement'."
Mr Hammond is arguing that if the EU tried it before with a nation which doesn't have regulatory alignment on financial services - America - then surely it can do so with a country that it at present does - the UK.
But the Chancellor is also saying a lot more than that.
Because the person who proposed "regulatory co-operation" on financial services as part of the EU-US free trade negotiations was one Michel Barnier.
The European Commission's chief Brexit negotiator was then - in 2014 - head of the EC's internal markets and services division.
"We want to include regulatory cooperation on financial services in the TTIP," he said at the time.
What he described as "inter-operable" regulation would mean close alignment without the need for either side to be a "rule taker".
Some in government suggest that this formulation runs counter to the mood music Mr Barnier has created around the chances of financial services being part of any free trade deal between the UK and the EU.
"I remind you that I'm not aware of any free-trade deal in the past between the European Union and third countries that would have allowed privileged access for financial services," Mr Barnier told a news conference in Brussels in December.
That came a few days after an interview with several European newspapers in which Mr Barnier said: "There is not a single trade agreement that is open to financial services. It doesn't exist."
Well, Mr Hammond is suggesting in his speech, the EC proposed it should exist between the EU and the US before the TTIP deal ran into the sand of President Donald Trump's America First policy on free trade.
The EC can counter that the two scenarios do not bear comparison.
Regulatory co-operation is very different from being a member of a financial services single market as the UK is at present.
And if Britain thinks it is going to replicate that, it has another think coming.
Passporting agreements - which allow banks to operate freely across EU borders with a single national licence - are not going to be extended to the UK outside the EU.
There may be some regulatory "equivalence" agreements between the UK and the EU on financial services, allowing for some banking operations to continue between the two sides.
As Mr Hammond says, that is mutually beneficial.
But, the EU is arguing at this stage, that is a long way from a comprehensive free trade deal on financial services.
The Chancellor has taken up a strong and oppositional stance against those who say that because there has never been a free trade deal including financial services agreed by the EU - which is true - there never will be.
The "sceptics" as Mr Hammond describes them.
The Chancellor - and in this he is supported by the Governor of the Bank of England, Mark Carney - argues the two statements do not logically follow.
For if they did, the EU would only do exactly the same trade deal time after time.
Which is not true when you look at the relationship between the EU and, say, Switzerland, Canada and Turkey, Mr Hammond argues.
Each of those arrangements is "bespoke" the Chancellor says.
Mr Barnier has a straightforward retort.
This may not be an issue of having your cake and eat it.
Theresa May appears to accept, for example, that some City access to the EU will be curtailed.
But it is no time to compare apples - TTIP - and pears - a comprehensive free trade deal including financial services between the UK and the EU.

The ramifications might be seismic, but the question at issue in this momentous legal dispute could not have been clearer.
The Lord Chief Justice Lord Thomas put it in this way: "The sole question in this case is whether, as a matter of the constitutional law of the United Kingdom, the Crown - acting through the executive government of the day - is entitled to use its prerogative powers to give notice under Article 50 for the United Kingdom to cease to be a member of the European Union."
He stressed that it was a "pure question of law" with "no bearing" on the merits of the UK withdrawing from the EU.
Many of today's papers took issue with that.
In beginning his judgment, Lord Thomas firmly asserts the critical importance in our law of the sovereignty of parliament: "The most fundamental rule of UK constitutional law is that the Crown in Parliament is sovereign and that legislation enacted by the Crown with the consent of both Houses of Parliament is supreme."
He quotes a predecessor, Lord Bingham, who said: "The bedrock of the British constitution is... the supremacy of the Crown in Parliament."
He then turns to the Crown's prerogative powers.
These are a collection of executive powers derived from the Crown from medieval times.
Once exercised by all-powerful kings and queens, they have been dramatically reduced over centuries and the residue are now vested in the hands of ministers.
Exercising them is controversial because they have the effect of by-passing our "supreme" Parliament.
Lord Thomas says: "An important aspect of the fundamental principle of Parliamentary sovereignty is that primary legislation is not subject to displacement by the Crown through the exercise of its prerogative powers."
So, prerogative powers are strictly limited and in the relationship between them and Parliament it is Parliament that very firmly has the upper hand, because, "This subordination of the Crown [ie the executive government] to law is the foundation of the rule of law in the United Kingdom", he says.
In other words, Parliament is king - top dog of the constitution.
The government cannot use executive powers to override legislation. Only legislation can override legislation.
That, in essence, was the argument of Gina Miller, the investment manager who was the lead claimant in the case.
So when can ministers use prerogative powers?
It is agreed and part of our law that they can be used in international relations and the making and unmaking of international treaties.
That is permissible because generally exercising these powers in this arena has no effect on domestic law, so there is no collision with parliamentary legislation, and parliamentary sovereignty is not affected.
The government argued that using prerogative powers to trigger Article 50 was a "classic exercise of the royal prerogative", and that if Parliament had not wanted it used it would have said so in the 2015 European Union Referendum Act.
Where the government came a cropper is that it fully accepted that triggering Article 50 by using prerogative powers would have the effect of changing domestic law.
By enacting the 1972 European Communities Act (the 1972 Act), which took the UK into what was then the European Economic Community, now the EU, Parliament made EU law part of our law.
Rights enjoyed by you and me were written into our law via the 1972 Act.
However, the government argued that Parliament must have intended that ministers would keep the prerogative power to withdraw from EU treaties and so would continue to have the power to choose whether EU law - including the rights given to us under it - should continue to have effect in domestic law.
Gina Miller's lawyers argued that once Article 50 is triggered some rights, such as the right to vote in EU elections and to petition the European Court of Justice, would be extinguished forever.
They claimed that it was not enough for the government to assert that many rights would be restored later in the Great Repeal Bill.
The court categorically disagreed with the government.
Lord Thomas concluded that, "Parliament intended EU rights to have effect in domestic law and that this effect should not be capable of being undone or overridden by action taken by the Crown in exercise of its prerogative powers."
Slam dunk!
"The Crown cannot, through the exercise of its prerogative powers, alter the domestic law of the United Kingdom and modify rights acquired in domestic law under the ECA 1972 or the other legal effects of that Act.
"We agree with the claimants that, on this further basis, the Crown cannot give notice under Article 50(2)."
Slam, slam, dunk, dunk.
The judgment did not go on to say specifically that an act of Parliament is needed to give ministers the authority to trigger Article 50.
The judges were understandably keen to keep some constitutional distance and not be seen to be telling Parliament precisely how to exercise its sovereignty.
However, it is almost impossible to see how Parliament could give its authority to ministers to serve notice under Article 50 without full-blown primary legislation, ie an act of Parliament.
What is now an epic legal battle reveals arguably the great constitutional clash of our time.
A government used to getting its way has been stopped in its tracks by independent judges, unelected and who some regard as unaccountable, but who through the mechanism of judicial review can defy ministers, if what they are proposing is unlawful.
The judges may have been deciding a purely legal point, but it is a legal point with massive political consequences.
These tectonic plates of our constitution will grind up against each other again next month when the government appeals to the Supreme Court.
For the first time ever, all 11 permanent justices, including those from Northern Ireland and Scotland, are likely to sit - underlining the importance of what is at stake.
If the High Court's ruling is overturned, the government's problems in triggering Article 50 probably disappear.
If it is upheld and the government is forced to bring in an act of Parliament to give it the authority to trigger our withdrawal from the EU, the timing and manner of Brexit is thrown into confusion.
There is an intriguing further option.
The Supreme Court could in theory refer the question of the construction of Article 50 to the European Court of Justice, which is in effect the EU's Supreme Court.
But asking that court to adjudicate on the mechanism for the UK departing the EU, and by implication consider issues relating to the sovereignty of Parliament, would be so drenched in irony it would be almost unthinkable.

Forget what might happen when the tellers read out the numbers on Tuesday night, let's think about what's at stake.
With Brexit, it's nearly always subjective, but according to MPs and ministers of different flavours, these are some of the factors that matter and that the result might influence.
Disagree at will of course - you may read these and scoff, or you may even have your own.
But the meaningful vote may well end up having multiple meanings...
1) Let's start with the least likely outcome. A miracle could take place overnight and scores of MPs might suddenly find themselves swinging behind the prime minister's plan.
The vote goes through, she shouts hurray, and the process moves on smoothly.
We leave the EU as planned in less than three months, and Theresa May's place in history is secure (no laughing at the back).
2) The defeat is disastrous and a combination of pressure from some ministers and MPs forces the PM to reach across the aisle.
Depending on the scale of the defeat, and the reaction of Labour front and backbenchers, Westminster might be ushered into a different phase of bargaining across the benches.
One Labour MP told me today: "At some stage I will vote for the deal, but I will need something specific to show for it. We are about to enter an era of transactional politics."
Cross-party working may not be some kind of high-minded pursuit.
3) The scale of the likely loss might prompt the kind of parliamentary takeover that's been much discussed in the last couple of days.
Arguably this might be one of the most long-lasting impacts.
Rewriting the parliamentary rulebook may inevitably be largely of interest to nerds like me, but the kind of suggestions these extraordinary times are prompting might reshape the relationship between the government and MPs for years to come - and that matters.
4) Given that the balance in Parliament is definitely for a softer Brexit with closer ties to the EU, (arguably) the defeat on Tuesday might lead to a less dramatic break with the EU than the deal on the table promises.
One member of the cabinet tonight told me: "The longer this goes on, the softer Brexit gets."
Before you scream, I know that is not a view that is shared universally. But it is sincerely held by plenty of people around the place who point rather frustratedly to the irony.
As another member of cabinet said: "The hardline Brexiteers will push us toward a softer Brexit by digging in their resistance."
5) Technically speaking, if you don't assume (and assumptions are dangerous) that Parliament can and would block no deal, the rejection of the plan would move us closer to leaving without a deal.
That's not just because Eurosceptics are showing very little sign of budging, but remember the process is on a clock.
Article 50 has to come to a conclusion by the end of March and, as the law currently stands, we are leaving with or without an agreement.
Some other ministers in the cabinet believe very firmly once the vote is lost the PM has not much choice other than to up no-deal prep again in the hope, not of going that way, but of trying for another EU concession.
One told me it is the "only logical conclusion" to keep going steadily and hope the EU will break - a continuation of the high-stakes poker game.
6) Jeremy Corbyn will either delight or disappoint his ranks by having the bottle to force a confidence vote, or delaying again, waiting for a magic moment.
But he seems unlikely to take the bold step many of his members want and to move to offering another referendum.
7) For those campaigning for another European referendum, too, the scale of the defeat, and Tuesday night's front bench responses to it, are vital.
The outcome of the vote will affect whether we leave the EU on time, and less likely, whether we could be given another say on whether we leave at all.
And when those truths eventually reveal themselves, they in turn could have an impact on the fabric of the UK itself.
What happens in Northern Ireland, or to the case for Scottish independence, are part of what is at stake in the long term.
8) Lastly, after more than two years of endless discussions, as and when the vote goes down on this hard-fought compromise, Westminster's factions and rival camps might finally have to do more than talk amongst themselves, and actually bend or break.
The divisions are so intense in both the main political parties that it could also be the moment some of the divisions turn into real splits.
That really would be history happening in front of our eyes.

Theresa May has been applauded by Tory MPs after making a "heartfelt" appeal for unity over Brexit and urging her critics to get behind her.
The prime minister has been addressing all her MPs in Parliament, many of whom are seeking a change of approach.
Asked by one MP what concessions she had made to the EU, she set out areas where the EU had itself given ground.
Former minister Amber Rudd said the PM "won the room" while another MP said it was a "petting zoo, not a lion's den".
The sound of desks and doors being thumped could be heard coming from the Commons room where the 1922 committee - an elected body of MPs which represents backbenchers and also oversees leadership contests - met privately.
Comments by unnamed Tory MPs over the weekend suggested the PM would be fighting for her political life at the meeting and was on the edge of the "killing zone".
However, Tory MP Michael Fabricant told journalists waiting outside that the atmosphere inside the meeting was "not a lion's den but a petting zoo".
Attorney General Geoffrey Cox said the PM's remarks were "very good" while former home secretary Amber Rudd said Mrs May "was able to win the room, despite being frank about difficulties still there".
"She looked like she really meant it," she told the BBC. "It felt heartfelt."
And Basildon MP John Baron said "the mood was, let's get behind the PM and get this over the line".
But not all MPs were happy, one suggesting the odds of her surviving another week were 50:50 while another said what mattered was the mood in the party not orchestrated shows of support.
Mrs May is reported to have told MPs that she had won a number of concessions from the EU, including the role of the European Court of Justice in enforcing the rights of EU citizens in the UK.
She also rejected suggestions that her top European adviser, Olly Robbins, was "freelancing" when the UK agreed to consider extending the post-Brexit transition period beyond 2020.
Talks on the UK's exit from the EU are said to be 95% complete, but have stalled over the Irish border issue.
The UK prime minister has said that having the option of extending the transition could provide the "safety net" or "backstop" needed to guarantee no new visible border checks where Northern Ireland meets the Republic.
But her plans have come in for criticism among Tory ranks, with a social media campaign called "Standup4Brexit" claiming to have 50 MPs backing its call for Mrs May to "chuck" her current strategy.
The prime minister has said any temporary measure used to avoid a hard border would have to end by the next general election, which is due in 2022.
At the weekend, anonymous quotes about Mrs May in the Sunday newspapers sparked a backlash from MPs of all parties.
The Sunday Times quoted a Tory backbencher saying: "The moment is coming when the knife gets heated, stuck in her front and twisted. She'll be dead soon."
Another said she should "bring her own noose" to the 1922 Committee meeting. Tory MPs said those behind the quotes were "spineless cowards" who should be thrown out of the party.
Meanwhile, EU politicians in Strasbourg have been debating Brexit, with European Council President Donald Tusk saying more time was needed to find a solution.
"Therefore, there is no other way but to continue the talks," he told MEPs.
Mr Tusk said Mrs May had mentioned the option of extending the transition period planned after Brexit, saying that if it helped reach a deal, "I'm sure that the leaders would be ready to consider it positively".
Irish Sinn Fein MEP Lynn Boylan said the UK government was trying to "understate" the issue of the Irish border, and is "yet to understand" a deal cannot be reached without agreement on an Irish backstop.
And Spanish MEP Esteban Gonzalez Pons called for an extension of the transition phase to allow time for a second, "definitive", referendum.
But former UKIP leader Nigel Farage blamed the UK civil service for the delays in reaching a deal, saying senior officials were "out to sabotage Brexit".

Theresa May has accused European politicians of making "threats" against Britain to try to influence the general election result.
The PM launched a stinging attack on the "bureaucrats of Brussels" in a speech outside 10 Downing Street after meeting the Queen.
She said some in Brussels wanted Brexit talks to fail.
Labour leader Jeremy Corbyn said she was "playing party games with Brexit" to try to win the general election.
Scottish First Minister Nicola Sturgeon said it was "irresponsible" of her to "poison" the atmosphere with the EU.
A senior EU source told the BBC the PM's suggestion that officials were trying to affect the election result was "pure fantasy".
Parliament was dissolved at midnight, meaning the election is formally under way, and the PM made her speech after visiting the Queen at Buckingham Palace.
She said events of the past few days had shown "just how tough" Brexit talks are likely to be.
"Britain's negotiating position in Europe has been misrepresented in the continental press," she said, in a reference to a German newspaper's account of her dinner with the EU Commission chief.
"The European Commission's negotiating stance has hardened. Threats against Britain have been issued by European politicians and officials.
"All of these acts have been deliberately timed to affect the result of the general election that will take place on 8 June."
Mrs May said she wanted to reach a Brexit deal, and for the EU to succeed: "But the events of the last few days have shown that - whatever our wishes, and however reasonable the positions of Europe's other leaders - there are some in Brussels who do not want these talks to succeed."
The PM also warned of "serious" consequences if the Brexit talks failed, which would be felt by "ordinary, working people across the country".
"If we don't get the negotiation right, your economic security and prosperity will be put at risk and the opportunities you seek for your families will simply not happen.
"If we do not stand up and get this negotiation right we risk the secure and well-paid jobs we want for our children and our children's children too.
"If we don't get the negotiation right, if we let the bureaucrats of Brussels run over us, we will lose the chance to build a fairer society with real opportunity for all."
She was criticised by Ms Sturgeon, who tweeted: "UK needs best possible Brexit deal and has limited leverage, so for PM to poison atmosphere for partisan reasons is deeply irresponsible.... Having called election for reasons of party not national interest, PM now seems intent on fighting campaign in same way."
Mr Corbyn added: "By winding up the public confrontation with Brussels, the prime minister wants to wrap the Conservative party in the union jack and distract attention from her government's economic failure and rundown of our public services.
"But Brexit is too important to be used as a political game in this election."
Lib Dem Nick Clegg attacked her "desperate, bizarre statement", and UKIP's Patrick O'Flynn said millions of his party's voters remained worried the UK would leave the EU "with the worst possible terms".
Analysis by BBC political editor Laura Kuenssberg
Theresa May just used one of the most powerful microphones in the country for blunt diplomacy indeed.
It's worth pointing out she made careful aim at the EU institutions, rather than the individual leaders, with whom she'll have to deal one on one.
But forget that nuance for a moment - this was quite some statement, quite an accusation to make. It seems the prime minister is intent on playing the Brexit card for all it's worth in the next election.
Mrs May's statement came during a day in which the UK's Brexit secretary and the EU's chief Brexit negotiator Michel Barnier had appeared at odds over the size of the "Brexit bill" the UK would owe when it left the European Union.
The Financial Times claimed the likely bill had risen sharply from 60bn to 100bn euros, basing its calculations on new data from across Europe.
Mr Barnier said there was no agreed figure but the UK and EU had entered into "mutual commitments" which must be honoured.
Mr Davis said the UK would pay what was legally due, in line with its rights and obligations, but "not just what the EU wants".
On Tuesday, Mrs May told the BBC she would be a "bloody difficult woman" towards Mr Juncker during Brexit talks.
Asked about her comment, Mr Juncker's chief of staff Martin Selmayr said: "President Juncker said today that she is an impressive woman and that she is a very impressive negotiator."
He added: "Brexit will never become a success, of course, because it is a sad and sorry event. But as I have set out, it can be managed in a professional and pragmatic way."
The dissolution of Parliament means there are no MPs - only candidates - until polling day.
However, government ministers retain their roles and continue their work.
MPs are allowed access to Parliament for just a few days in order to remove papers from their offices, but facilities provided by the House of Commons are no longer available to them.  It was the shortest Parliament since 1974.

Theresa May has promised to set a timetable for the election of her successor after the next Brexit vote in the first week of June.
The agreement follows a meeting between the prime minister and senior Tory MPs who are demanding a date for her departure from Downing Street.
If she loses the vote on her Brexit plan, already rejected three times, sources told the BBC she would resign.
Meanwhile, Boris Johnson has said he will run for leader once Mrs May goes.
The prime minister survived a confidence vote by Conservative MPs at the end of last year and party rules mean she cannot formally be challenged again until December.
But Mrs May has come under increasing pressure to leave Downing Street this summer, amid the Brexit impasse and poor results for the Conservatives in the recent local elections in England.
BBC political editor Laura Kuenssberg said senior sources had told her it was "inconceivable" the prime minister could remain in office if MPs rejected her Brexit plans for a fourth time.
"Discussing an election timetable" doesn't sound that exciting.
But the paragraph tucked into the short formal letter from Sir Graham Brady to Tory MPs all but marks the end of Theresa May's premiership and the beginning of the official hunt for the next leader of the country.
After the lines in the short note restate the prime minister's determination to get Brexit done, it confirms in black and white that after the next big vote, in the first week of June, the prime minister will make plans with the party for choosing a successor.
Right now, the expectation is that vote will be lost (although it is not impossible, of course, that Number 10 could turn it round).
And the conversation that's been arranged won't just be a gentle chat about what to do next.
Senior sources have told me that means, even though the letter doesn't spell it out, that if her Brexit plan is defeated again, Mrs May will announce she is going.
The chairman of the 1922 committee of Conservative MPs, Sir Graham Brady, said he had reached an agreement over the prime minister's future during "very frank" talks in Parliament.
He said the committee's executive and Mrs May would meet again to discuss her future following the first debate and vote on the Withdrawal Agreement Bill in the week beginning 3 June.
Sir Graham said there was now "greater clarity" about the situation.
Asked if that meant the prime minister would quit immediately if MPs rejected her Brexit plans once more, he said that scenario went "beyond" what had been agreed.
MPs have rejected the prime minister's Brexit agreement with the EU three times.
But she will have another go at gaining their support in the week beginning 3 June, when the Commons votes for the first time on the EU Withdrawal Agreement Bill - legislation needed to implement her deal with the EU.
Former foreign secretary Boris Johnson has joined the growing list of Conservatives who say they will stand for leader when Mrs May announces her departure.
He told a business conference in Manchester: "Of course I am going to go for it."
Conservative MP Grant Shapps welcomed the announcement that a timetable would be set out for Mrs May's departure, suggesting it would inject greater ambition and dynamism into the Brexit process.
The former party chairman told BBC News the Brexit bill had no chance of passing in its current state but holding another vote would allow Mrs May to demonstrate she had "tried everything".
"It is right to bring this whole saga to a conclusion," he said.
But fellow Tory Phillip Lee, who backs another Brexit referendum, said replacing the prime minister would not "solve the crisis" the UK found itself in or build a parliamentary majority for the terms of the UK's departure.
"Forcing the PM's resignation and spending this summer locked in a leadership election where candidates trade ever more fantastic visions of unicorn Brexits…is neither in the interests of the Conservative Party nor of the United Kingdom," he said.
Last month, the 1922 Committee executive narrowly decided against changing the party's leadership rules to allow an early challenge to Mrs May.
Local Tory associations have confirmed they will hold a vote of confidence in her leadership on 15 June, although its result will not be binding.
Much of the anger in the Conservative parliamentary party is focusing on the prime minister's talks with Labour, aimed at reaching a cross-party compromise to get her deal through the Commons.
BBC Newsnight political editor Nick Watt said he understood the talks will "soon be drawing to a close" adding that Tory whips had "given up on this phase of the negotiations and are looking to pack the legislation with goodies for Brexiteers".
Labour leader Jeremy Corbyn said his party would not support the Withdrawal Agreement Bill unless it guaranteed membership of a customs union with the EU, and protected workers' rights, consumer rights and environmental rights.
Meanwhile, Liberal Democrat leader Sir Vince Cable said his party would "happily support" the legislation, provided it was subject to a "confirmatory public vote".

It has become something of a weekend ritual that hardline Brexiteers breathe fire and brimstone and declare they are on the verge of triggering a vote of confidence in Theresa May.
On Monday mornings the chairman of the 1922 committee Sir Graham Brady inspects his office safe and finds a pile of letters in the corner falls short of the magic number - 48 - needed to trigger a vote.
And so the prime minister limps on for another week until the ritual starts out all over again.
This time, however, there is a different feel. Theresa May managed to achieve the extraordinary feat last week of uniting Remain and Leave Tories in despair after she floated the idea of extending the transition period after the UK leaves the EU. There are now Remain Tories saying the time has come for her to go.
Until now three factors have ensured that the prime minister has been safe from the sniping. If any of these change then the weekend ritual may have a different ending when Sir Graham opens his safe in the coming weeks.
The three factors are:
For the moment these three factors are likely to mean that Theresa May will hang on. But the mood is changing. If you examine the three factors in reverse you can see how events could move against the prime minister:
The odds are that Theresa May will soldier on for the moment. She did after all exceed expectations in her recent Conservative party conference speech.
But Margaret Thatcher was cheered at the end of her speech to the 1990 conference. The following month she was out.

Theresa May has asked MPs to make an "honourable compromise" as she seeks to persuade them to back her Brexit deal at the third time of asking.
Writing in the Sunday Telegraph, the prime minister said failure to support the deal would mean "we will not leave the EU for many months, if ever".
Mrs May is expected to bring her withdrawal agreement back to the Commons next week for a third vote.
It comes after MPs this week rejected her deal and voted to delay Brexit.
Former Cabinet minister Esther McVey, who resigned over the Brexit agreement, told Sky's Sophie Ridge programme that she would "hold my nose" and vote for the deal after rejecting it twice herself, as it was now a choice between "this deal or no Brexit".
And a letter signed by 15 Tory MPs from Leave-backing constituencies, including former Brexit Secretary David Davis, also urged colleagues to back the deal.
But International Trade Secretary Liam Fox warned the vote could be pulled, telling Sophie Ridge it was "difficult to justify having a vote if we knew we were going to lose it".
The EU will decide the terms and conditions of any extension. Legally, the UK is still due to leave the EU on 29 March.
Meanwhile, Labour leader Jeremy Corbyn has written to MPs across the Commons inviting them for talks to find a cross-party compromise.
He also told Sky that while he "has to see the wording of it", Labour MPs would be told to vote in favour of an amendment calling for another referendum next week, and he said he may propose another vote of no confidence in the government if the PM's deal is voted down again.
Mrs May says if Parliament votes for her withdrawal deal before an EU leaders' summit on Thursday, the UK will seek a short delay to Brexit to pass the necessary legislation.
"That is not an ideal outcome - we could and should have been leaving the EU on 29 March," she said.
"But it is something the British people would accept if it led swiftly to delivering Brexit. The alternative if Parliament cannot agree the deal by that time is much worse."
If a deal is not agreed before Thursday, EU leaders are contemplating a much longer delay.
Mrs May said it would be a "potent symbol of Parliament's collective political failure" if a delay to Brexit meant the UK was forced to take part in May's European elections - almost three years after voting to leave the EU.
On Tuesday, MPs overwhelmingly rejected Mrs May's withdrawal agreement for a second time - by 149 votes.
In her article, Mrs May said she had more to do to convince dozens of Tory MPs to back the deal - as well as getting Northern Ireland's Democratic Unionist Party to drop their opposition.
She wrote: "I am convinced that the time to define ourselves by how we voted in 2016 must now end.
"We can only put those old labels aside if we stand together as democrats and patriots, pragmatically making the honourable compromises necessary to heal division and move forward."
The DUP, which has twice voted against the agreement, said there were "still issues to be discussed" and it remained in talks with the government.
The 10 votes provided by the DUP, which props up the Conservative government, are thought to be key to the prime minister securing her deal.
In the letter from Conservative MPs asking others to back the deal, the group claimed there were people "who will stop at nothing to prevent Britain leaving the EU", adding they would vote for the deal to ensure Brexit went ahead.
"We urge colleagues who, like us, wish to deliver Brexit, to vote for the deal and ensure we leave the EU as soon as possible," they said.
"We need to leave now, take the risk of 'no Brexit' off the table, and then continue to fight for the best future relationship as an independent nation."
Mr Corbyn has offered talks with opposition leaders and backbench MPs in an effort to find a Brexit compromise which could replace Mrs May's plan.
The Labour leader has invited Liberal Democrat leader Sir Vince Cable, DUP deputy leader Nigel Dodds, SNP Westminster leader Ian Blackford, Plaid's Liz Saville Roberts and Green MP Caroline Lucas.
In his letter, he called for urgent meetings to find a "solution that ends the needless uncertainty and worry" caused by Mrs May's "failed" Brexit negotiations.
Meanwhile, Tory MP Nick Boles has pledged to stay in the Conservative Party, despite quitting his local association over an ongoing row about Brexit.
He told the BBC's Andrew Marr that he would be meeting with the chief whip on Monday to find a way forward, but that he was "not going to be bossed around" by local members.
Mr Boles, who campaigned to stop a no-deal Brexit, said: "I will be my own kind of Conservative. Not an ideological reactionary Conservative."

Theresa May had to battle losing her voice and being interrupted on stage by a comedian as she sought to reassert her Conservative leadership.
Mrs May, who at one point was handed a throat sweet by the chancellor, did make it to the end of a speech in which she vowed to "renew the British dream".
She announced plans for more council houses and a cap on energy prices.
But they were overshadowed by the problems she had delivering the set-piece speech in Manchester.
BBC political editor Laura Kuenssberg said the annual conference "was meant to be about restoring Theresa May's authority - it may prove instead to have been further undermined".
Mrs May was interrupted early on in her speech by comedian Simon Brodkin - also known as Lee Nelson - who managed to make it to the podium to hand her a P45, a redundancy notice, saying to her that "Boris asked me to give you this".
After he was removed and she got encouraging cheers from the audience she joked that the only P45 she wanted to give out was to Jeremy Corbyn.
But she struggled to finish the speech because of a croaky voice, having to stop several times to drink water.
Sources close to the prime minister have said that the PM had caught the "conference cold", and that her many interviews and meetings this week have taken their toll on her voice.
They say the prankster who interrupted her speech has been arrested for a breach of the peace and there will be a thorough investigation of security.
To add to her woes, some of the letters fell off the conference stage backdrop. By the end it read: "Building a country that works or everyon."
In normal political times, it is probably the case that what one minister described as a "tragedy" today would have led to a prime minister being forced out or quitting.
But these aren't normal times. Allies of Theresa May say today she has shown her resilience and determination in spades, demonstrating exactly why she deserves to stay in the job.
A senior colleague of hers told me she importantly did manage to put forward a coherent vision and talked about her personal beliefs. More than that, for those who want her gone there are three obstacles.
Scottish Conservative leader Ruth Davidson said of the prime minister's performance: "If ever there was a metaphor for battling through adversity, that was it."
In the speech itself, Mrs May delivered a call for a "modern, compassionate Britain" and focused on her personal commitment to social justice and fairness.
She also apologised to activists in Manchester for an election campaign that had been "too scripted, too presidential".
And she said the "British dream" that "life should be better for the next generation" was out of reach for too many people, something she vowed to dedicate her premiership to fixing.
Mrs May began her speech by outlining the reasons why she joined the Conservative Party more than 40 years ago, stressing that the things that have made her most proud in politics have not been the positions she has held, but "knowing that I made a difference - helped those who cannot be heard".
She announced that there would be an independent review of the Mental Health Act, to tackle injustice, and would press for justice to be done for the families of those killed and injured in the Grenfell Tower tragedy.
"That's what I'm in this for," she said.
Turning to Brexit, Mrs May said she was "confident that we will find a deal that works for Britain and Europe". She also reassured European citizens living in the UK that "you are welcome here" and urged negotiators to reach agreement on this policy "because we want you to stay".
Mrs May said it had "always been a great sadness for Philip and me that we were never blessed with children", but she said this did not stop her wanting to help young people on to the housing ladder.
Hailing plans to "reignite home ownership" in Britain, she said the government plans to invest an additional £2bn in affordable housing, taking the total budget up to almost £9bn.
If ministers made the land available and gave young people the skills to build the houses, she challenged house builders to ensure they "build the homes our country needs".
Simon Brodkin is an English comedian more commonly known by his TV character name Lee Nelson. Handing the prime minister a P45 was far from his first.
His most famous interruption came at Glastonbury in 2015 when he ran onstage as Kanye West was performing. He pulled a similar stunt on The X Factor in 2014, running onstage as the Stereo Kicks were playing.
He also threw US dollar bills over former Fifa president Sepp Blatter during the football organisation's bidding scandal.
The BBC's assistant political editor Norman Smith said the focus on council housing underlines Mrs May's readiness to intervene and use the public sector to build houses in a way not seen since the 1950s.
Mrs May announced that the government will next week publish draft legislation to impose a cap on energy prices. Downing Street says it will apply to all standard variable rates.
Having seen her Commons majority vanish after June's general election and facing calls to sack Foreign Secretary Boris Johnson over his interventions on Brexit, Mrs May attempted to use the conference to unite the party behind her "mission" to transform Britain.
She said it would not be easy, but "it has never been my style to hide from a challenge, to shrink from a task, to retreat in the face of difficulty, to give up and turn away."
"And it is when tested the most that we reach deep within ourselves and find that our capacity to rise to the challenge before us may well be limitless."
The disruptions to the speech dominated discussion afterwards, but for Labour, shadow chancellor John McDonnell saying that there had been £15bn of pledges made by the end of the speech showing "the Tory magical money tree returns".
Lib Dem leader Sir Vince Cable called it "the speech of a brave prime minister struggling on, while her disloyal Cabinet colleagues openly plot against her".

Theresa May has tried to reassure businesses fearing a sudden change in rules once the UK leaves the EU.
Speaking at the CBI conference, Mrs May promised early agreement on the status of UK nationals in Europe and EU nationals in the UK.
"People don't want a cliff-edge; they want to know with some certainty how things are going to go," she said.
Several business lobby groups have pushed for an interim deal to let them trade in the same way post-Brexit.
Mrs May said she understood companies' concerns and was "conscious that there will be issues that will need to be looked at".
"That will be part of the work that we do in terms of the negotiation that we are undertaking with the European Union," she added.
She also pledged to provide clarity on the government's plans where possible, but said there would not be "a running commentary on every twist and turn".
Downing Street declined to say whether Mrs May's comments about avoiding a "cliff-edge" meant she was seeking a transitional deal to cover the period between the UK's departure from the EU and the start of a new trade deal.
"She was reflecting the views we have expressed already about how we secure the best deal for the UK and how we seek to provide certainty where we can to businesses and people across the UK of the steps moving forward," the PM's official spokeswoman said.
In the wide-ranging speech, Mrs May also pledged to:
The prime minister also insisted she still favoured worker representation on company boards, dismissing suggestions that comments she made during the speech marked a watering-down of the idea.
There have been widespread reports since the summer that Mrs May wanted to see workers on boards as part of a corporate governance shake-up, an idea that had caused unease among companies and, according to the Financial Times, disagreements in Cabinet.
However, the prime minister told the CBI that there were "other routes" to providing worker representation on boards, including advisory councils or panels.
"It will be a question of finding the model that works," she said.
Mrs May promised to shake-up governance as part of her Conservative Party leadership campaign in July, and repeated the promise at last month's party conference when she said she planned to have "not just consumers represented on company boards, but workers as well".
And later, on Sky News, when asked if her conference speech marked a watering down of the idea, Mrs May said. "No, what I've always said is that we want to look at ways in which we can improve corporate governance, looking at a number of areas, including workers' representation on boards. You can do that in a number of ways.
"We want to work with business on this and that's why we'll be consulting later this year on the various ways in which we can do it to find a model that works," she said.
Did the PM arrive at the CBI conference with an olive branch or just another stick? A little bit of both.
Business groups have been wary of Theresa May ever since her blistering attack on the massive pay differentials, tax avoidance and treatment of workers she identified in some corners of British business.
Today, she offered a more conciliatory tone. As well as weakening her commitment to put workers on company boards, saying only their voice should be represented - she insisted her agenda was unequivocally pro-business.
However, there was no escaping the big question as spelled out by the CBI's President, Paul Dreschler: "What happens the day after we leave the EU? Government has a responsibility to keep uncertainty to a minimum. We understand, in negotiations, the need for discretion, we're not asking for a running commentary but we are looking for clarity and above all a plan."
Business folk were pleased to hear her say, when questioned, that she understood their fears over a potential cliff edge of trading and regulatory uncertainty the day after Britain leaves the EU but weren't so pleased she declined to reassure them with details of her plan.
If business leaders were hoping to be treated to the same fireside chat that seemed to comfort the boss of Nissan, they would have left disappointed.
£2bn of new money for research and development was welcomed and business leaders seemed to accept the essential premise of the grand bargain she is offering - the government invests to boost productivity and cut corporation tax in exchange for help in tackling the worst excesses of capitalism.
'Clear promise'
However, trade unions said they were disappointed by Mrs May's remarks.
TUC general secretary Frances O'Grady said: "Theresa May made a clear promise to have workers represented on company boards. The proposals in her speech do not deliver on this.
"This is not the way to show that you want to govern for ordinary working people."
But CBI director-general Carolyn Fairbairn said "different approaches will work for different businesses" on employee engagement.
"A starting point is firms being able to outline and explain what approach they are taking - whether that's employees on boards, employee committees, dedicated representatives, or other models that genuinely address the issue."
What May did and didn't say at CBI
What is the Autumn Statement?
A difficult trick to pull off
Views from UK business
Financial upheaval ahead for families
Mrs May also promised to boost productivity and cut corporation tax in exchange for help from businesses in tackling issues such as executive pay and shareholder accountability.
"Just as the government must open its mind to a new approach, so the business community must too," she said.
The promises made by the prime minister include a "patient capital review" to help firms secure long-term investment. The review will be chaired by Sir Damon Buffini, the former head of private equity group Permira.
Mrs May also said the government would review the support given to innovative firms through the tax system "because my aim is not simply for the UK to have the lowest corporate tax rate in the G20, but also one that is profoundly pro-innovation."
Corporation tax is already due to fall from its current 20% rate to 17% by 2020.
Labour leader Jeremy Corbyn addressed the conference later in the day criticising the government's "shambolic"  approach to Brexit which he said was hampering business's ability to plan. He set out Labour's approach to working with business, which he said would be characterised by "good intervention".
He said Labour's policies would involve "some increase in corporation tax" and said the suggestion that the UK should aim to reduce corporation tax to 15% or below was "reckless short-term grandstanding."
He called for more investment in housing, research and development and infrastructure, a higher minimum wage and measures to prevent undercutting of workers' pay and conditions.

Prime Minister Theresa May has called off Tuesday's crucial vote on her Brexit deal so she can go back to Brussels and ask for changes to it.
As it stands the deal "would be rejected by a significant margin" if MPs voted on it, she admitted.
But she said she was confident of getting "reassurances" from the EU on the Northern Ireland border plan.
But European Council President Donald Tusk said the remaining 27 EU countries would not "renegotiate" the deal.
While EU leaders would be willing to "discuss how to facilitate UK ratification" of the withdrawal agreement at Thursday's summit in Brussels, he suggested the controversial Northern Irish backstop, which the DUP and many Tories want removed, would remain in place.
The prime minister's U-turn came after she and senior ministers had spent days insisting the vote would go ahead, despite the scale of opposition from MPs being obvious.
It prompted angry scenes in the Commons, with MPs from all sides complaining that the government had denied them the right to have any say in the move.
Labour's Jeremy Corbyn, who accused Mrs May of "losing control of events" and "disregarding" MPs, was granted an emergency debate in the Commons on Tuesday while Commons Speaker John Bercow said the government's handling of the issue had been "regrettable".
And Lloyd Russell-Moyle, the Labour MP for Brighton Kemptown, was expelled from the Commons after grabbing the ceremonial mace and trying to take it out of the chamber.
He was stopped by an officer of the House who returned it to its place on the table.
Theresa May refused to say when the Commons vote on her deal would now be held - saying it would depend how long fresh talks with the EU last.
Some MPs called for it to come back to the Commons before Christmas, but Mrs May would only say the final deadline for the vote was 21 January.
She said the the UK's departure date from the EU - 29 March next year - was written into law and the government was "committed" to delivering on it.
Conservative Remainer Justine Greening said she hoped the PM would not wait until 28 March before holding the vote.
Labour leader Jeremy Corbyn had been hoping to force a general election if Mrs May had lost Tuesday's planned vote, by tabling a vote of no confidence.
In his reaction to Mrs May's announcement that the vote would be delayed, he urged the PM to stand down because her government was now in "chaos".
But Labour has rejected calls from the SNP, the Lib Dems and some of its own MPs, to hold a vote of no confidence in the prime minister on Tuesday.
A Labour Party spokesperson said: "We will put down a motion of no confidence when we judge it most likely to be successful.
"It is clear to us that Theresa May will not renegotiate the deal when she goes to Brussels, and will only be asking for reassurances from EU leaders.
"When she brings the same deal back to the House of Commons without significant changes, others across the House will be faced with that reality.
"At that point, she will have decisively and unquestionably lost the confidence of Parliament on the most important issue facing the country, and Parliament will be more likely to bring about the general election our country needs to end this damaging deadlock."
Dozens of Conservative MPs had been planning to join forces with Labour, the SNP, the Lib Dems, Plaid Cymru and the DUP to vote down Mrs May's deal.
The Tory rebels and the DUP do not like the Northern Ireland "backstop", a legally-binding proposal for a customs arrangement with the EU, which would come into force if the two sides cannot agree a future relationship which avoids the return of a visible Northern Ireland border.
Tory MPs say it is unacceptable because it would result in new regulatory barriers between Northern Ireland and the rest of the UK and could continue indefinitely, because the UK would not be able to leave without the EU's approval.
The prime minister vowed to put the deal to a vote but said there was no point at this stage because it would have been defeated.
She told MPs she would be speaking to EU leaders ahead of a summit later this week, about the "clear concerns" expressed by MPs about the backstop.
And she would also be "looking closely at new ways of empowering the House of Commons to ensure that any provision for a backstop has democratic legitimacy".
Mrs May wants to enable MPs to place obligations on the government "to ensure that the backstop cannot be in place indefinitely".
She again rejected all other alternatives that have been proposed to her deal - including a further referendum and leaving without a deal.
Her deal "gives us control of our borders, our money and our laws - it protects jobs, security and our Union", she said.
"It is the right deal for Britain. I am determined to do all I can to secure the reassurances this House requires, to get this deal over the line and deliver for the British people," she added.
Asked by Lib Dem leader Sir Vince Cable if EU leaders would be ready to ditch the backstop, she said they had shown they were aware of MPs' concerns that the backstop should be temporary.
"A number of European leaders I've spoken to have indicated that they are open to discussions to find a way to provide reassurance to members of this House on that point," she added.
Leading Conservative Brexiteer Jacob Rees-Mogg said in a statement that Mrs May lacked the "gumption" to put her "undeliverable" deal before MPs.
"This is not governing, it risks putting Jeremy Corbyn into government by failing to deliver Brexit. We cannot continue like this. The prime minister must either govern or quit."
Mr Rees-Mogg is trying to get enough Tory MPs to submit letters of no confidence in the PM to trigger a leadership contest.
Graham Brady, who receives those letters as chairman of the backbench 1922 Committee, said some MPs were angry and others were "fidgety" but many were glad not to be "going through the motions of a needless defeat".
"We've just seen the PM doing the right thing but also quite bravely standing up... and making her case to an angry opposition," he added.
The deputy leader of the DUP - the Northern Ireland party whose backing Theresa May needs to win key votes - Nigel Dodds, said the situation was "quite frankly a bit of a shambles" and the PM was paying the price for crossing her "red lines" when it came to Northern Ireland.
He told Mrs May: "Come back with the changes to the withdrawal agreement or it will be voted down."
DUP leader Arlene Foster said she had told the prime minister in a phone call that the "backstop must go".
Theresa May's deal has been agreed with the EU - but it needs to be backed by the UK Parliament if it is to become law ahead of the UK's departure.
Mrs May has also been speaking to EU leaders about re-opening the withdrawal agreement, something both sides have previously ruled out.
European Commission spokeswoman Mina Andreeva said the EU would not renegotiate the Withdrawal Agreement.
"As President Juncker said, this deal is the best and only deal possible," she said.
The BBC's Brussels reporter Adam Fleming said Mrs May was "trying get more legal oomph behind the language" in the withdrawal agreement about the EU using "best endeavours" to get a trade deal which would remove the need for the backstop to be used.

Theresa May has attacked one of her predecessors - accusing Tony Blair of "undermining" the Brexit talks by calling for another referendum.
She called his comments an "insult to the office he once held" and said MPs could not "abdicate responsibility" to deliver Brexit by holding a new poll.
In London last week, Mr Blair said MPs might back a new vote if "none of the other options work".
In response to Mrs May, he insisted that a new referendum was democratic.
"Far from being anti-democratic it would be the opposite, as indeed many senior figures in her party from past and present have been saying," he said.
On Thursday about 10 Labour MPs met David Lidington - who is Mrs May's de facto second-in-command - to argue for another public vote.
Sources close to Mr Lidington said it was "pretty standard stuff" and he was not "planning for or advocating a second referendum".
Many senior Labour figures are deeply uneasy about endorsing another referendum.
The government is also opposed to any further referendum, saying the public made a clear choice when they voted in 2016 to leave by a margin of 51.9% to 48.1%.
BBC political correspondent Chris Mason said Mrs May's criticism of the former Labour prime minister was striking for its anger.
Mrs May said: "For Tony Blair to go to Brussels and seek to undermine our negotiations by advocating for a second referendum is an insult to the office he once held and the people he once served.
She added: "We cannot, as he would, abdicate responsibility for this decision.
"Parliament has a democratic duty to deliver what the British people voted for."
Meanwhile, the PM's chief of staff, Gavin Barwell, has responded to reports in the Mail on Sunday that he told colleagues another referendum was "the only way out of this", saying on Twitter: "Happy to confirm I am not planning a 2nd referendum with political opponents (or anyone else, to anticipate the next question)."
International Trade Secretary Liam Fox, who campaigned to leave the EU, said that if another referendum was held "people like me will be immediately demanding, it's best of three. Where does that end up?"
MPs were due to vote on Mrs May's Brexit deal last Tuesday, but it was postponed when the prime minister admitted it would have been "rejected by a significant margin".
After postponing the vote in Parliament, Mrs May travelled to Brussels to make a special plea to European Union leaders, in a bid to make her deal more acceptable to MPs.
However, the EU said there could be clarification but not renegotiation.
The Labour leadership has been under pressure to call a vote of no confidence in the government.
But Labour frontbencher Andrew Gwynne told the BBC's Andrew Marr: "We can't move to the next stage until Parliament has decided whether or not to back the prime minister's deal."
He said the party would be using "parliamentary tactics" to try to bring the MPs' "meaningful vote" on the deal - which was delayed by the government last week in expectation of a heavy defeat - forward to this week.
Asked whether his party would campaign for Brexit under a Labour deal if there were to be another referendum on the issue, he said: "Let's wait and see. These things are moving very quickly.
"We are a democratic party and we will put our decision to the party members in a democratic way before we decide what the next steps are."
Many of Mrs May's Conservative MPs are concerned that the "backstop" - which is aimed at preventing a hard border in Northern Ireland - would keep the UK tied to EU rules and limit its ability to strike trade deals.
Education Secretary Damian Hinds has told the BBC a second referendum would not end the deadlock over Brexit but might simply extend the impasse.
Speaking on BBC Breakfast, he urged politicians to back the PM's plan, describing it as "balanced" and the "best of both worlds".
Mr Hinds accused some in Parliament of "wishful thinking" in believing they will get something closer to their own view by rejecting Mrs May's deal, adding: "There is really no reason to believe that's true."
Meanwhile, in an interview with the Sunday Telegraph, Foreign Secretary Jeremy Hunt has said the UK will "flourish and prosper" even if it leaves the EU with no deal.
"We've faced much bigger challenges in our history," he said.
"But we shouldn't pretend that there wouldn't be disruption, there wouldn't be risk, and there wouldn't be impact and that's why as a responsible government we have to make all the preparations necessary
He also said he wanted a "crack" at succeeding Mrs May after the PM takes the country through "this challenging next few months".
His comments come after Mrs May made it clear she would step down before the next general election - due in 2022.

Prime Minister Theresa May could set a date for her resignation in the coming days, the chairman of the Conservative backbench 1922 Committee has said.
The PM said she will step down when her Brexit deal is ratified by Parliament - but some MPs want a fixed date.
Sir Graham Brady said he expected a "clear understanding" of that timetable once she has met the committee, which she would do on Wednesday.
He also said he expected Brexit talks with Labour to "peter out" within days.
And Sir Graham also refused to rule out running himself to replace Mrs May.
Speaking to BBC Radio 4's The Week in Westminster, he said the 1922 Committee had asked her to give "clarity" about her plans for the future, and she had "offered to come and meet with the executive".
"It would be strange for that not to result in a clear understanding [of when she will leave] at the end of the meeting," he added.
The 1922 Committee represents backbench Tory MPs and oversees the party's leadership contests.
On why the PM had so far been unwilling to set a date to step down, Sir Graham said: "I do understand the reticence about doing it.
"I don't think it's about an intention for staying indefinitely as prime minister or leader of the Conservative Party.
"I think the reticence is the concern that by promising to go on a certain timetable, it might make it less likely she would secure Parliamentary approval for the withdrawal agreement, rather than more likely."
He was also asked about the cross-party talks between the government and Labour over Mrs May's Brexit deal, which has been rejected three times.
Sir Graham said: "I find it very hard to see how that route can lead to any sensible resolution.
"If the customs union is agreed without a second referendum then half the Labour Party won't vote for whatever comes through regardless, and if a customs union is agreed then most of the Conservative Party isn't going to support it.
"So, I can't see that is a very productive route to follow, and I may be wrong, but I suspect it will peter out in the next few days without having come to any significant conclusion."
When quizzed about running for the party leadership, Sir Graham said: "It would take an awful lot of people to persuade me.
"I'm not sure many people are straining at the leash at the moment to take on what is an extraordinarily difficult situation."
In March, Mrs May pledged to stand down if and when Parliament ratified her Brexit withdrawal agreement, but did not make it clear how long she intends to stay if no deal was reached.
Pressure has grown on her since the Tories' local election drubbing, and there have been warnings the party faces a meltdown in elections to the European Parliament as well.
The UK had been due to leave the EU on 29 March, but the deadline was pushed back to 31 October after Parliament was unable to agree a way forward.

A "backstop" plan to keep the UK aligned with the EU's customs union after 2020 would only apply "in a very limited set of circumstances", Theresa May has said.
The proposal was drawn up to avoid a hard border in Northern Ireland if the UK and EU cannot agree new arrangements in time.
Earlier Boris Johnson said Brexiteers need not worry about a "betrayal".
He said Mrs May would be "true to her promises" and deliver a deal.
The UK is leaving the EU in March 2019, which will be followed by a temporary transition phase until the end of 2020.
But ministers have yet to agree what they want to replace the UK's membership of the EU's customs union, which allows for tariff-free trading between members.
With no decision reached between the two alternative proposals the UK is considering, senior ministers signed off on a third, temporary, "backstop" option - which government sources say is very unlikely to be needed - at a meeting last week.
It would see the UK match EU tariffs in order to avoid border checks.
The government says this would allow the UK to sign and implement its own trade deals, something which it cannot do in the customs union.
But some Brexiteers who want a clean break from the EU fear it could turn into a long-term arrangement - last week backbench MP Jacob Rees-Mogg warned that people did not vote for a "perpetual purgatory".
Speaking in Macclesfield, Mrs May said the EU's own "backstop" - keeping Northern Ireland in the customs union - had been unacceptable so the UK had drawn up an alternative.
"Nobody wants this to be the solution that is achieved," she said.
"If it's necessary it will be in a very limited set of circumstances for a limited time."
The prime minister said she wanted to solve the customs issue "through our overall relationship with the European Union".
Earlier, speaking to reporters during a tour of Latin America, Mr Johnson - who led the campaign to leave the EU in 2016 - said: "Brexiteers fearing betrayal over the customs backstop must understand that the PM has been very clear that neither option is an outcome we desire - we want a deal with the EU and she will deliver it.
"I'm convinced that the prime minister will be true to her promises of a Brexit deal that sees Britain come out of the customs union and single market, have borders as frictionless as possible, reject European Court of Justice interference, control immigration and free to conduct unhindered free trade deals across the world.
"We must now give the prime minister time and space to negotiate this Brexit vision."
One of Mr Johnson's fellow Brexit campaigners, Environment Secretary Michael Gove, said the "whole point" of the backstop arrangement was "that it's intended not to be implemented but is there just in case".
The "strictly time-limited" arrangement would ensure a free flow of goods across the Irish border if the UK and EU cannot agree alternative arrangements, he said.
Democratic Unionist Party leader Arlene Foster said there had to be clarity about how long any such arrangement would last, telling an event in London "there has to be a backstop to the backstop".
None of the UK's customs proposals have been agreed with the EU yet.
Most Brexiteers are against Mrs May's preferred option of a "customs partnership", under which the UK would collect tariffs set by the EU customs union on goods coming into the UK.
If the goods subsequently ended up in the EU the UK would pass the collected tariffs on to the EU. If the goods stayed in the UK, firms would be able to claim back the difference if the UK tariff on those goods was lower.
The alternative proposal would rely on technology and advance checks to minimise, rather than remove, customs checks. The EU has expressed doubts about whether either option would work.
Mr Johnson's five-day visit, taking in Peru, Argentina and Chile, is designed to pave the way for post-Brexit deals.
"Already during my time in South America I've been bowled over by the optimism and excitement from nations keen to forge deeper ties and new trading relationships with the UK," he said.

Theresa May's Brexit withdrawal bill will not be published or debated until early June, the government says.
The prime minister is under pressure to resign following a backlash from her own MPs against her pledged "new deal" on Brexit.
Andrea Leadsom quit as Commons Leader, saying she could not announce the bill which had "new elements that I fundamentally oppose".
She has been replaced by Treasury minister Mel Stride.
Downing Street has confirmed that the prime minister met Foreign Secretary Jeremy Hunt and Home Secretary Sajid Javid at No 10 on Thursday morning and would "give full consideration their views" about the bill.
Mrs May had told the Commons that the Withdrawal Agreement Bill - the legislation needed to implement the agreement between the UK and EU - would be published on Friday so MPs would have "the maximum possible time to study its detail".
Mrs Leadsom had been due to announce when it would be introduced to Parliament on Thursday, but resigned on Wednesday night.
Standing in for her, government whip Mark Spencer told MPs: "We will update the House on the publication and introduction of the Withdrawal Agreement Bill on our return from the Whitsun recess."
He added that the government planned to publish the bill in the first week of June.
"We had hoped to hold second reading on Friday 7 June," he added. "At the moment, we have not secured agreement to this in the usual channels. Of course we will update the House when we return from recess."
Second reading is when MPs get a first chance to debate legislation, before deciding whether it should proceed to detailed scrutiny.
Responding for Labour, shadow Commons leader Valerie Vaz said: "The prime minister has once again put her own political survival ahead of the national interest.
"It is clear that the prime minister does not command a majority in her approach to Brexit and she has failed to accept this political reality."
US President Donald Trump is due to make a three-day state visit to the UK from 3 to 5 June.
Asked who would be in 10 Downing Street when he arrives, Mr Hunt said: "Theresa May will be prime minister to welcome him and rightly so."
It is possible for Mrs May to quit as Conservative leader before Mr Trump's visit, but continue as prime minister on a caretaker basis.
Mrs Leadsom said on Thursday she had "no doubts that I made the right decision" adding: "I felt I couldn't, in all conscience, stand up and deliver the business statement today with a Withdrawal Agreement Bill in it that I couldn't support elements of."
She did not answer questions about whether she was planning to run for the leadership.
The UK needs to pass a law to implement the withdrawal agreement - the part of the PM's Brexit deal which will take the country out of the EU - in UK law.
In a mini-reshuffle prompted by Mrs Leadsom's resignation, Mel Stride, who had been Financial Secretary to the Treasury, has replaced her as Commons leader.
He has been replaced on the Treasury team by Jesse Norman, whose previous role as a transport minister has been filled by Michael Ellis. Rebecca Pow has been made a junior minister at the Department for Digital, Culture, Media and Sport, replacing Mr Ellis.
On Wednesday, members of the Conservatives' backbench 1922 Committee held a secret ballot on whether to change party rules, to allow the prime minister to face a vote of no confidence immediately.
Mrs May is due to meet the chairman of the committee, Sir Graham Brady, on Friday.
The results, in sealed envelopes, will be opened if Mrs May does not agree to stand down by 10 June.
Mrs May survived a no-confidence vote of Conservative MPs in December. Under existing rules, she cannot be challenged again until December this year.

Ministers say no part of the UK will be treated differently in the Brexit talks as Labour branded their approach an "embarrassment".
No agreement has been reached with the EU after a DUP backlash against proposals for the Irish border.
Brexit Secretary David Davis told MPs the government was close to concluding the first phase of talks.
DUP leader Arlene Foster said the text of the deal was a "big shock" and "it was not going to be acceptable."
She told the Republic of Ireland national broadcaster RTÉ that her party only saw the text on Monday morning, despite asking to see it for five weeks.
Theresa May, speaking as she welcomed Spanish Prime Minister Mariano Rajoy to Downing Street, said talks with the EU had " made a lot of progress".
"There are still a couple of issues we need to work on. But we'll be reconvening in Brussels later this week as we look ahead to the December European Council," she said.
Mrs Foster was invited to hold talks with Mrs May in London on Tuesday, but the party's Westminster leader met the government's chief whip instead.
The meeting lasted for several hours, but sources suggested to the BBC's political editor Laura Kuenssberg that there was not much sign of a breakthrough yet, with a DUP insider saying the deal needed "radical surgery", rather than a few word changes.
A phone call between Mrs May and Mrs Foster had then been expected this evening, but sources added that it would not go ahead, suggesting it had never been arranged.
The UK is due to leave the EU in March 2019 and Mrs May is under pressure to reach agreement on the Northern Ireland border so negotiations can move forward.
The prime minister needs the support of the DUP - the Democratic Unionist Party - which is Northern Ireland's largest party and has 10 MPs at Westminster, because she does not have a majority to win votes in the House of Commons.
Responding to an urgent question from Labour in the Commons on Tuesday, Mr Davis defended the controversial proposal for "regulatory alignment" between Northern Ireland and the Republic of Ireland - intended to avoid the need for border checks after Brexit - saying this would apply to the whole of the UK.
The DUP is unhappy about any agreement which treats Northern Ireland differently.
It would not mean "having exactly the same rules" as the EU, Mr Davis said, but would involve "sometimes having mutually recognised rules".
Backbencher Jacob Rees-Mogg warned that having "regulatory divergence" from the EU after Brexit was a "red line".
Labour's Brexit spokesman Sir Keir Starmer said that when the DUP objected to the draft agreement, "fantasy met brutal reality", adding: "The DUP tail is wagging the Tory dog."
Mr Starmer also called for the government to drop its plan to enshrine the 29 March 2019 Brexit date in UK law.
Meanwhile, former Tory leader Iain Duncan Smith suggested the UK should walk away from the negotiations if the EU does not change its position.
But Tory MP and former cabinet minister, Nicky Morgan, said his comments were "madness" and walking away would "betrays the futures of millions of young people and those who never wanted to leave in the first place".
Dublin - which as an EU member is part of its single market and customs union - has been calling for written guarantees that a "hard border" involving customs checks on the island of Ireland will be avoided after Brexit
It is concerned this could undermine the 1998 peace treaty - the Good Friday Agreement that brought an end to 30 years of sectarian conflict in Northern Ireland.
Mr Davis said that while the "integrity" of the single market and customs union must be respected after Brexit, it was "equally clear we must respect the integrity of the United Kingdom" and individual nations could not have separate arrangements.
Mrs May needs to show "sufficient progress" has been made so far on "divorce" issues before European leaders meet on 14 December to decide whether to allow talks on future trade relations to begin.
The three issues that need to be resolved are the Northern Ireland border, citizens' rights and the amount of money the UK will pay as it leaves.
Talks between Mrs May and European Commission president Jean-Claude Juncker broke up without agreement on Monday, after the DUP objected to a draft agreement on the future of the Irish border.
Key to the row is how closely aligned Northern Ireland's regulations will be with those of the Republic of Ireland, and the rest of the EU, in order to avoid a "hard" border.
Ireland's deputy prime minister Simon Coveney said Dublin would not budge from its position on the border.
The EU is treating the row as a "domestic British political issue", BBC Brussels correspondent Adam Fleming said.
"The show is now in London," said a European Commission spokesman.
Downing Street has insisted the border was not the only outstanding problem and disagreement remains over the role of the European Court of Justice in overseeing EU citizens' rights in the UK after Brexit.

Another gathering in Downing Street has come and gone, imagined at one point to be a "crunch meeting" at which Cabinet colleagues might thrash out their differences on the destination of Brexit.
In fact, it was nothing of the kind. The only crunching to be seen or heard was the gentle crump of the metaphorical tin can labelled "Britain's future after Brexit" being kicked, unopened, further down the road.
Did we seriously expect anything else?
Boris Johnson, and Brexiteers like him, believe that Brexit opens up a world of new opportunities.
Former Remainers including Phillip Hammond, the chancellor, are believed to quietly fear it could usher in an era of national decline.
There is no reconciling these views.
So ministers on both sides, and colleagues in between, have chosen with lesser or greater enthusiasm to embrace the government's stated ambition to pursue the goal of "frictionless trade" with the EU, with few if any tariff or non-tariff barriers, while simultaneously shuffling off the obligations that go with membership of the EU customs union and single market.
No matter that the chancellor is suspected by many in Whitehall and at Westminster to fear this is unachievable, and to secretly nurse the dream of an eventual rethink, or perhaps the hope that a Brexit transition might somehow go on and on.
Never mind that some senior Brexiteers are known to be quietly enthusiastic about the possibility of Brexit negotiations ending with no-deal with the EU, and with Britain trading in future on World Trade Organisation rules, until agreements can be struck with nations around the world.
For now, the goal of a future in which the UK both has its cake and eats it serves as the fulcrum upon which two opposing views can balance.
When Amber Rudd told Brexiteers via the BBC's Andrew Marr Show the cabinet was "more united than they think", this was surely what she meant.
Meanwhile, the paper published by HMRC officials last August set out practical means of managing cross-border trade, while leaving the tricky business of striking a trade deal with the EU, or failing to do so, to their political masters.
The practical talk in cabinet, I'm told by one senior minister, encompassed the UK's future relationship with the EU on the point of alignment of trading rules and regulations.
There's broad agreement among ministers that Britain should set its own rules and standards, and not automatically accept diktats from Brussels.
Yet it is also recognised that trade with Europe requires compliance with the standards enshrined in those same rules.
The distinction may seem rather Jesuitical to some.
But to Brexit enthusiasts, and to 10 Downing Street, it is a matter of sovereignty and goes to the heart of Brexit as an idea.
British and EU trading standards are perfectly aligned now, it's argued, and there's no intention on the British side to lower those standards, still less to go down the route to what Brussels calls "social dumping" and reduce workers' rights.
Arguments over any divergence in regulations could go to some form of arbitration.
"The Treasury just wants to stay in or close to a customs union," said a minister, "but they won't win that one".
And what about the European Commission?
"They just want to stay in control."
So, the moment of decision awaits further down the road.
Brexiteer ministers insist talk in Brussels that the UK cannot cherry pick, cannot enjoy free access to markets without accepting free movement of people and the jurisdiction of the European Court is merely a negotiating position.
"It's the starting position, not the end. Michel Barnier (the EU's chief negotiator) does not speak for the entire European Union...can you imagine the Netherlands wanting to put up barriers?"
Theresa May told MPs at Prime Minister's Questions: "As I have said right from the very beginning, we will hear noises off and all sorts of things being said about positions, but what matters is the position that we take in the negotiations as we sit down to negotiate the best deal.
"We have shown that we can do that; we did it December and we will do it again."
In other words, "trust me".
But the pressure on Mrs May to mark out her own preferred destination keeps mounting - especially from Brexiteers who'd like her to tell Brussels to accept Britain's terms or live with no deal at all.
The moment she does so the Cold War in her party between rival ministers and rival factions would likely warm up very quickly.
There is also a more urgent problem: securing a Brexit transition at the European Council on 22 March.
Without an agreement, Britain will suddenly be (forgive the mixed metaphor) looking down the barrel of a Brexit cliff-edge.
Fears among business leaders would reach a new pitch, threatening investment and jobs. And the government would need to prepare itself, and warn the businesses it has been trying to reassure that a hard Brexit was at least a real possibility.
Obstacles to a transition deal have not yet been resolved.
They include the rights of EU migrants who arrive in Britain after the transition. There is still no clear or detailed answer to the problem of the border on the island of Ireland.
Downing Street says trading regimes will remain aligned. Dublin is widely believed to want to push the UK to maintain a customs union. Any new, or old obstacle, could appear, or reappear. Who knows? Gibraltar?
Ultimately, the mythical tin can marked "Britain's future after Brexit" must come home to roost (to mix another metaphor).
In the Autumn, clear positions will be required on both the UK and EU side if there is to be a document - at the very least setting out "heads of agreement" on the future relationship.
At that point Parliament will have its say.
A "meaningful vote" is promised. On its outcome rests Brexit, Tory unity, Theresa May's future and conceivably that of the government.
A cabinet minister observed recently that the prime minister seemed to be privately philosophical about the state of her premiership and her government: "She said 'it goes with the territory'"
Perhaps, in another life, Mrs May commanded a bomb disposal unit.

Theresa May has promised MPs a vote on delaying the UK's departure from the EU or ruling out a no-deal Brexit, if they reject her deal next month.
Mrs May made a statement to MPs about Brexit on Tuesday, amid the threat of a revolt by Remain-supporting ministers.
The PM has promised MPs a meaningful vote on her Brexit deal by 12 March.
But Labour leader Jeremy Corbyn accused the prime minister of another "grotesquely reckless" Brexit delay.
The prime minister said she will put her withdrawal agreement  - including any changes she has agreed with the EU - to a meaningful vote by 12 March.
If that fails, MPs will be offered two separate votes:
"Let me be clear, I do not want to see Article 50 extended," she told MPs.
"Our absolute focus should be on working to get a deal and leaving on 29 March."
Any extension should not go beyond the end of June and "would almost certainly have to be a one-off", she added.
Mrs May said an extension "cannot take no deal off the table", adding:  "The only way to do that is to revoke Article 50, which I shall not do, or agree a deal."
Extending Article 50 would require the unanimous backing of the other 27 EU member states and, she said, she had not had conversations about it with them.
Mrs May repeatedly declined to say whether she would vote against a no-deal Brexit, and whether Tory MPs would be whipped to vote for or against it.
By the BBC's deputy political editor John Pienaar
Theresa May's big concession - and it was a significant tactical retreat - was about buying herself more time.
So now, under the threat of maybe 15 to 20 ministers rebelling, the prime minister's promised MPs an opportunity next month to rule out a no-deal Brexit, and force a "limited" delay in leaving the EU.
Without that promise, there's every chance those unhappy ministers would have joined other MPs in voting to rule out no-deal and delay Brexit anyway.
She did not offer ministers freedom to vote as they choose. So now the (potential) rebels must decide whether to hold fire for a fortnight, while she tries to get terms in Brussels she can sell to the Commons - hoping Brexiteers ultimately back her deal as the best Brexit available.
Call it "running down the clock", or "kicking the can down the road", if you like.
But kicking and running has been Mrs May's best hope for months.
Several Remain-backing ministers were threatening to resign, so that they could vote for a cross-party amendment aimed at ruling out a no-deal Brexit, when MPs vote on a government motion on Wednesday.
Conservative Caroline Spelman and Labour's Jack Dromey said they "welcomed" the PM's statement but they would still table amendments paving the way for a bill to extend Article 50.
They will then "seek assurances from ministers during [the] debate to secure confirmation of the prime minister's commitments, which we hope will mean we will not push our amendments to a vote", the pair said in a joint statement.
Another of the MPs behind the amendment, Conservative Sir Oliver Letwin, had earlier said there was no need for it now, because the prime minister's statement "does what is needed to prevent a no-deal exit on 29 March".
But opponents of Mrs May who support another EU referendum said she had still not ruled out a no-deal Brexit.
The Independent Group's Anna Soubry, who quit the Conservatives in protest at their Brexit policy, said it was a "shameful moment" and "nothing has changed".
Jacob Rees-Mogg, the chairman of the European Research Group of Leave-backing Conservative MPs, said: "My suspicion is that any delay to Brexit is a plot to stop Brexit.
"This would be the most grievous error that politicians could commit."
Speaking after a meeting with Theresa May, DUP Leader Arlene Foster said the PM had to deliver on her commitment to get legally-binding changes to her EU withdrawal agreement.
"Experience in Northern Ireland has shown that extending deadlines does nothing to encourage a deal," she said.
The EU had it "in their hands" to avoid a no-deal Brexit, she added, and come up with a deal which MPs can support.
"It's time for Dublin and Brussels to be in a deal-making mode," she said.
Jeremy Corbyn said he had "lost count" of the prime minister's explanations for her "grotesquely reckless" Brexit delays.
"The prime minister continues to say it is her deal or no deal, but this House has decisively rejected her deal and has clearly rejected no deal," he told MPs.
"It is the prime minister's obstinacy that is blocking a resolution."
Mr Corbyn says Labour will get behind another EU referendum if the party can't get its own Brexit proposals through Parliament on Wednesday.
If Mrs May's Brexit deal gets through Parliament next month, Labour wants it to be put to a public vote - with remaining in the EU as the other option.
The SNP's Westminster leader Ian Blackford said Mrs May "could not be trusted" not to "dodge" another meaningful vote.
He said: "It's the height of irresponsibility for any government to threaten its citizens with these consequences.
"Rule out no deal, extend Article 50, but do it today - this should not be left until the middle of March."
But Mrs May surprised the House by quoting a TV advert in her response: "If he wants to end the uncertainty and deal with the issues he raised...then he should vote for a deal. Simples."

Theresa May has officially stepped down as the leader of the Conservative Party, but will remain as prime minister until her successor is chosen.
She has handed in her private resignation letter to the backbench 1922 Committee, two weeks after announcing her intention to leave.
Eleven Conservative MPs are vying to replace her as party leader and, ultimately, prime minister.
The winner of the contest is expected to be announced in the week of 22 July.
Mrs May, who has said it was a matter of deep regret that she had been unable to deliver Brexit, remains acting party leader during the leadership election process.
Meanwhile, the Conservatives fell to third place in the Peterborough by-election, behind winners Labour and the Brexit Party in second place, in what is traditionally a Tory-Labour marginal seat.
Mrs May's time as leader has been dominated by Brexit, with her party divided over the issue, and the failure to get her deal through Parliament.
The UK was originally meant to leave the European Union on 29 March but that was then pushed back to 12 April and eventually 31 October.
When Mrs May announced her resignation, she said it was time for a new prime minister to try to deliver Brexit.
BBC political correspondent Nick Eardley said Mrs May is expected to announce a number of domestic policies before her final departure, with sources saying she is aiming for an announcement a week on issues like the environment and women in the workplace.
On Friday, Mrs May handed in her resignation letter to the 1922 Committee of backbench Conservative MPs. Number 10 said the letter was short and formal.
The committee said it was now inviting nominations from those Conservative MPs "who wish to stand for election as the next party leader".
Leadership nominations close at 17:00 on Monday, a statement said.
By Tom Edgington, BBC Reality Check
Constitutionally speaking, Theresa May keeps the same powers. But in the eyes of MPs she may lack the authority to introduce any radical policies between now and handing the reins over to a new prime minister.
While Mrs May is still free to make policy or funding announcements, any pledges would eventually need to be made into law. According to Catherine Haddon, from the Institute for Government think tank, there's no guarantee MPs would give Mrs May's announcements the green light - especially with such a small working majority.
Aside from policy, Mrs May will continue to represent the UK abroad and she is still free to make public appointments and make changes to her team of ministers.
She will be able reward some of those she has worked with - including knighthoods and appointments to the House of Lords. But the resignation honours list has been controversial in the past - so it will be interesting to see how many appointments Mrs May makes.
Leadership candidates need eight MPs to back them. MPs will then vote for their preferred candidates in a series of secret ballots held on 13, 18, 19 and 20 June.
The final two will be put to a vote of members of the wider Conservative Party from 22 June, with the winner expected to be announced about four weeks later.
Speaking to BBC Politics Live, leadership contender Sam Gyimah said he had considered dropping out of the Conservative Party leadership race but insisted he would "get to the starting line" by Monday.
Three of his rivals, former Work and Pensions Secretary Esther McVey, former Government Chief Whip Mark Harper and International Development Secretary Rory Stewart, have also said they have the eight nominations needed.
While the contest does not officially start until Mrs May steps down, candidates have already been jostling for position.
How the next prime minister gets a Brexit deal through Parliament and whether they would countenance a no-deal exit has been the dominant question of the campaign so far.
The winner of the contest to lead the Conservative Party will become the next prime minister.
Dominic Raab's suggestion at a hustings on Wednesday that he would be prepared to shut down Parliament - the process known as prorogation - to ensure the UK leaves the EU on 31 October has been criticised by his rivals. And Commons Speaker John Bercow said on Thursday it was "simply not going to happen".
Conservative leadership contender Michael Gove has said the UK must not be bound by a "fixed" date if it needs slightly more time to get a deal.
Others, such as Mr Raab and Boris Johnson, insist the UK must leave on 31 October, whether it has approved a deal with Brussels or not.
Former trade minister Lord Digby Jones has called on Mrs May's successor to provide more "stability" for UK businesses over Brexit.
He told the BBC's Wake Up to Money programme that they should ensure the UK leaves the EU on 31 October, "preferably with a deal - but without a deal rather than not coming out".
Labour leader Jeremy Corbyn said: "I don't know who the new leader is going to be, but it seems to be a choice between no deal, no deal and no deal, as far as I can understand it."
On Tuesday 18 June BBC One will be hosting a live election debate between the Conservative MPs who are still in the race.
If you would like to ask the candidates a question live on air, use the form below. It should be open to all of them, not a specific politician.
If you are reading this page on the BBC News app, you will need to visit the mobile version of the BBC website to submit your question on this topic.

Theresa May has said she will quit as Conservative leader on 7 June, paving the way for a contest to decide a new prime minister.
In an emotional statement, she said she had done her best to deliver Brexit and it was a matter of "deep regret" that she had been unable to do so.
Mrs May said she would continue to serve as PM while a Conservative leadership contest took place.
The party said it hoped a new leader could be in place by the end of July.
It means Mrs May will still be prime minister when US President Donald Trump makes his state visit to the UK at the start of June.
Asked about the prime minister's announcement, Mr Trump said: "I feel badly for Theresa. I like her very much. She's a good woman. She worked very hard. She's very strong."
Mrs May said she would step down as Tory leader on 7 June and had agreed with the chairman of Tory backbenchers that the contest to replace her should begin the following week.
Foreign Secretary Jeremy Hunt has become the latest MP to say that he will run, joining Boris Johnson, Esther McVey and Rory Stewart.
More than a dozen other MPs are believed to be seriously considering entering the contest.
At the start she boasted about not being a creature of Westminster's bars and cliques.
But it meant this very private politician had few true friends to help when things turned sour, and neither the powers of patronage, nor the capability to schmooze or arm twist to get people around to her point of view.
Few of her cabinet colleagues, even now, know her well at all, one saying that "as things got harder the circle got smaller". Another revealed that "there was no trust, and no faith".
Settling the Tories' decades-long dispute over Europe was always perhaps beyond just one leader. But the wounds have got more painful under her leadership, rather than fading away.
Read Laura's blog
In her statement, delivered in Downing Street, Mrs May said she had done "everything I can" to convince MPs to support the withdrawal deal she had negotiated with the European Union but it was now in the "best interests of the country for a new prime minister to lead that effort".
She added that, in order to deliver Brexit, her successor would have to build agreement in Parliament.
"Such a consensus can only be reached if those on all sides of the debate are willing to compromise," she said.
Mrs May's voice shook as she ended her speech saying: "I will shortly leave the job that it has been the honour of my life to hold. The second female prime minister, but certainly not the last.
"I do so with no ill will, but with enormous and enduring gratitude to have had the opportunity to serve the country I love."
The prime minister had faced a backlash from her MPs after announcing her latest Brexit plan earlier this week, which included concessions aimed at attracting cross-party support.
The Conservative Party said the likely timetable for the leadership contest was that nominations would close during the week beginning 10 June, with candidates whittled down to the final two to by the end of the month.
Those names would then be put to a vote of party members before the end of July.
Former foreign secretary Boris Johnson, who is seen as the front-runner to succeed Mrs May, told an economic conference in Switzerland on Friday: "We will leave the EU on October 31, deal or no deal."
He said a new leader would have "the opportunity to do things differently".
Labour Leader Jeremy Corbyn said Mrs May had been "right to resign" and that the Conservative Party was now "disintegrating".
Foreign Secretary Jeremy Hunt called her a "true public servant" and Chancellor Philip Hammond said it had been a "privilege" to serve alongside her.
Mrs May's predecessor, David Cameron - who resigned as prime minister after campaigning for Remain and losing the referendum - said she should be thanked for her "tireless efforts".
He added: "I know how painful it is to accept that your time is up and a new leader is required. She has made the right decision - and I hope that the spirit of compromise is continued."
Scotland's First Minister Nicola Sturgeon wished Mrs May well despite "profound disagreements" but added: "The prospect of an even more hardline Brexiteer now becoming PM and threatening a no-deal exit is deeply concerning."
Democratic Unionist Party Leader Arlene Foster, whose party supported Mrs May's government in power after the Conservatives lost their majority in the 2017 election, praised Mrs May's "dutiful approach on national issues".
Lib Dem leader Sir Vince Cable said Mrs May's compromises with the right-wing of her party had been blame for her departure, adding: "The best and only option remains to take Brexit back to the people. I believe the public would now choose to stop Brexit."
But Brexit Party Leader Nigel Farage said two Conservative leaders whose "instincts were pro-EU" had now gone and the party either "learns that lesson, or it dies".

Theresa May has held meetings with leading Tory Remainers, amid speculation about further defections.
Justine Greening and Phillip Lee say Mrs May has ignored requests from pro-EU Tory MPs in favour of Brexiteers.
The pair had separate meetings with the PM in Downing Street.
Meanwhile, one ex-Labour member of the new Independent Group of MPs has said it could help keep Mrs May in power on condition that she agreed to another EU referendum with Remain as an option.
However, the PM was focused on her own party on Thursday, as she met cabinet ministers David Gauke and Greg Clark.
The pair have warned of the dangers to business of leaving the EU without a formal deal, an option which Brexiteers in the European Research Group of Conservative MPs insist must be preserved as negotiating leverage in Brussels.
The government said on Thursday that talks would continue "urgently" at a technical level, following "productive" meetings involving Brexit Secretary Stephen Barclay, Attorney General Geoffrey Cox and the EU's chief negotiator Michel Barnier.
In the UK, ex-Labour MP Gavin Shuker told The Huffington Post members of the new Independent Group had first made the offer of a potential confidence and supply agreement - like the one the DUP has with the government - last month in a meeting with the PM's second-in-command David Lidington.
Then-Labour MPs Chris Leslie, Luciana Berger and Chuka Umunna, along with then-Tory Anna Soubry, who have all joined the group this week, were also at the meeting.
Mr Shuker said he had told Mr Lidington he would support any type of deal provided there was a "confirmatory referendum" to get public backing but that the offer was rejected.
The leaders of both main parties are battling to prevent more defections after eight Labour MPs and three Tories broke away to form a new "centrist" group in Parliament.
Theresa May has written to the three Tory defectors - Anna Soubry, Heidi Allen and Sarah Wollaston - to reject what she describes as the "picture they paint of the party", saying its record on the NHS, employment and diversity proved it was "moderate" and "open-hearted".
The prime minister offered to "continue to work together on issues" where they agree - but told the three she rejected "the parallel you draw with the way Jeremy Corbyn and the hard left have warped a once-proud Labour Party".
In response to their claim that local Tory associations are being taken over by former UKIP members, Mrs May said: "An open, broad party should always welcome new members and supporters with a range of views, including those who have previously supported other parties."
But she said local party branches had been warned to ensure new members support the party's "values and objectives".
Ex-Tory MP Heidi Allen, one of the three defectors from the party, told ITV's Peston programme "a third" of Conservative MPs were fed up with the party's direction.
Ms Greening and Mr Lee, who quit as a justice minister over Brexit, have been named by Ms Allen as potential future defectors to the Independent Group.
The Right to Vote group, which is chaired by Mr Lee, said he had discussed the campaign's calls for a pause in the Brexit process and a possible second referendum with Mrs May.
"Talks were open and we are encouraged she listened to our case," the group said.
Mr Lee has said one of the reasons the Tory MPs decided to quit the party was the access the Brexiteer European Research Group got to the prime minister, who he said had refused to meet his wing of the party.
Justine Greening - a former education secretary - told the Today programme she had been tempted to break away from the Conservative Party and join the Independent Group.
"It is something that I have considered, but I have reached a different conclusion for the moment," Ms Greening told Today.
"I don't think I would be able to stay part of a party that was simply a Brexit party that had crashed us out of the European Union."
The Independent Group was set up by eight defecting Labour MPs unhappy with their party's handling of Brexit and anti-Semitism.
They were later joined by three pro-Remain Tories - who accuse the Conservative leadership of allowing right-wing hardliners to shape the party's approach to Brexit and other matters.
Labour's Ian Austin also expressed sympathy with the Independent Group's aims, saying he would think "long and hard" about his future in the Labour Party.
Shadow home Secretary Diane Abbott told BBC Radio 4's The World at One: "I am very sad that the Labour members of this new independent organisation have gone.
"Up until the last minute, people were talking to them, trying to persuade them not to take the step they have taken."
She said she hoped they would continue to work with Labour on issues like homelessness, the benefit system, the NHS and "most of all fighting this Tory Brexit".
Meanwhile, Labour have contacted the Information Commissioner over alleged attempts to access personal data held by the party.
It is understood there are concerns an MP accessed party systems to contact members after reports of their resignation on Tuesday night.
Enfield North MP Joan Ryan, who announced she was quitting Labour in an interview with the Times published on Tuesday evening, said: "Neither I nor my office have accessed or used any Labour Party data since I resigned the Labour Whip and my membership of the Labour Party."

Theresa May insisted "very good progress" was being made in Brexit negotiations - as the DUP said there was "more work to be done".
Mrs May appeared in Prime Minister's Questions after a phone call with DUP leader Arlene Foster, who has refused to support draft plans for the border.
One Tory MP said the PM's "red lines" on Brexit looked "a little bit pink".
Labour leader Jeremy Corbyn said the government should "get out of the way" if it couldn't negotiate a deal.
On Monday Northern Ireland's Democratic Unionist Party - whose support the PM needs to win key votes at Westminster - objected to draft plans drawn up by the UK and the EU.
The DUP said the proposals, which aimed to avoid a "hard border" by aligning regulations on both sides of the border between Northern Ireland and the Republic of Ireland, were not acceptable. Dublin says it wants firm guarantees that a hard border can be avoided.
This has left the UK government racing to find an agreement suiting all sides in time for next week's EU summit.
Following Mrs May's call with Ms Foster, a DUP spokesman said discussions were continuing and there was "more work to be done".
Mrs May also spoke on the phone with Ireland's Prime Minister Leo Varadkar, who "reiterated the firm Irish position", according to his spokesman.
Mr Varadkar also told parliamentarians in the Irish Dail that talks on the Irish border question could resume in the New Year if agreement could not be reached next week.
In response, Downing Street said it was focused on next week's summit, and the DUP's Nigel Dodds said the comments increased the likelihood of no trade deal being reached.
"Mr Varadkar may try to appear calm on the surface, but he is playing a dangerous game - not with us but with his own economy," he said.
In PMQs, Mrs May was asked by DUP MP Jim Shannon to ensure there would be no "constitutional, political or regulatory" barriers between Northern Ireland and the rest of the UK.
She said the short answer was yes, adding that the Brexit settlement would respect the UK's "constitutional integrity" and "internal market".
She said that finding a way to leave the customs union and single market while avoiding a hard border was the "whole point" of Brexit negotiations about future relations.
But the EU says talks about the future can only happen when enough progress has been made in agreeing what will happen at the Northern Ireland border.
The suggestion of "regulatory alignment" between Northern Ireland and the European Union - which emerged on Monday - has concerned some Eurosceptic Conservative MPs.
During PMQs backbencher Jacob Rees-Mogg proposed a new coat of red paint for Mrs May's negotiating "red lines".
She responded by referring to her previous speeches setting out her negotiating goals, adding: "Those principles remain."
Labour says the option of staying in the EU's customs union long-term should be kept "on the table" in negotiations and has criticised the government for ruling this out.
At the 14-15 December summit, European leaders will decide whether enough progress has been made in the negotiations on Ireland, the UK's "divorce bill" and citizens' rights so far to open trade talks.
Chancellor Philip Hammond has suggested the UK could pay the so-called Brexit bill, regardless of whether or not there is a subsequent trade agreement with the EU.
He told MPs on the Commons Treasury Committee that he found it "inconceivable" that the UK would "walk away from an obligation that we recognised as an obligation".
"That's just not a credible scenario," he added. "That's not the kind of country we are. And frankly it would not make us a credible partner for future international agreements."
A No 10 spokesman said the government's position remained that "nothing is agreed until everything is agreed and that applies to the financial settlement".
Reports have suggested the UK has raised its financial offer to a figure of up to 50bn euros (£44bn).

The European Union must "evolve" its position on Brexit and not fall back on unworkable proposals regarding the Irish border, Theresa May has said.
The prime minister made the remarks in Belfast on Friday, during a two-day visit to Northern Ireland.
The issue of the Irish border has been the key sticking point in Brexit talks so far.
The UK and EU have agreed that there should be no hard border in Ireland, but are at odds over how to achieve it.
The backstop solution is effectively an insurance policy -  to avoid a hard border between Northern Ireland and the Republic of Ireland if appropriate customs arrangements cannot be agreed by the EU and UK in time for the end of the transition period in December 2020.
The EU has proposed a backstop that would mean Northern Ireland staying in the EU customs union, large parts of the single market and the EU VAT system.
However, the UK said that would effectively create a border down the Irish Sea.
On Friday, Mrs May again repeated her opposition to that, saying: "The economic and constitutional dislocation of a formal 'third country' customs border within our own country is something I will never accept and believe no British prime minister could ever accept".
She also said both sides in the negotiation  "share a determination never to see a hard border in Northern Ireland".
"And no technology solution to address these issues has been designed yet, or implemented anywhere in the world, let alone in such a unique and highly sensitive context as the Northern Ireland border".
However, EU Brexit negotiator Michel Barnier has questioned Mrs May's plan for a future trade relationship with the EU, saying it could weaken the single market and create burdens for business.
He said the UK's Brexit White Paper, published on 12 July, opened "the way to a constructive discussion" but must be "workable".
Mr Barnier questioned whether plans for a common rulebook for goods and agri-foods were practical.
Earlier this week, the government backed an amendment to its Customs Bill that would make it illegal for Northern Ireland to be outside the UK's customs territory.
Mrs May said the EU's backstop proposal would be a breach of the Belfast Agreement - and that her plan, agreed by the Cabinet at Chequers earlier this month, was the best way forward.
"What I've said to the EU is that the legal text they've produced is not acceptable, that's why we proposed an alternative to that," she said.
She said there now needed to be a renewed focus on EU-UK negotiations with "increased pace and intensity".
The prime minister also met several of the political parties in Northern Ireland.
"In fact it's now clear the British prime minister has come here to pick a fight with Ireland and to pick a fight with the EU," Mrs McDonald said.
However, the DUP leader, Arlene Foster, defended the prime minister.
"What she has done is set out her agenda, that's very important. She talked about working together to find solutions, and the need to work collaboratively," she said.
Theresa May wants a backstop that would see the whole of the UK staying in the customs union for a limited period of time after the transition period - something the EU has said is unacceptable.
Northern Ireland Secretary Karen Bradley told BBC's Good Morning Ulster programme the government was committed to getting a legal text for a backstop.
Earlier, the Irish Tánaiste (deputy prime minister) Simon Coveney tweeted that if the UK did not accept the EU wording on a backstop in the draft withdrawal agreement, they would have to propose an  alternative that would deliver the same result.
Reacting to his comments, Mrs Bradley said while the EU had put forward a legal text, "we do not accept it".
"We've put forward a counter proposal and we're now working on how we get a backstop that we are committed to delivering but it has to be a backstop that respects the integrity of the whole UK and does not put a border in the Irish sea."
The Shadow Secretary of State, Tony Lloyd, told the BBC Labour had always been "very clear" that the UK should be part of the customs union.
EU and UK negotiators have been meeting in Brussels this week to discuss the border issue.
Friday's speech in Northern Ireland marks the prime minister's first major attempt to sell the Chequers agreement since it was reached by her cabinet earlier this month.
She is due to tour other parts of the UK over the summer in an attempt to persuade businesses and citizens of its benefits.
Both the UK and EU are stepping up preparations for a "no deal" Brexit.
The two sides insist it is not what they want - and that reaching a deal by the autumn is still very much on the cards.
But they have yet to agree how their final relationship will work, with key issues around cross-border trade unresolved, and the UK's official departure date of 29 March 2019 fast approaching.
The Republic of Ireland will remain within the EU and Taoiseach (Irish prime minister) Leo Varadkar has said his government is making contingency plans for "the unlikely event of a no-deal hard Brexit".
Mrs May also addressed the impasse at Stormont.
She added that until devolution is restored, the government would fulfil its responsibilities but warned interventions from Westminster were "no substitute" in the long-term.

Theresa May has said she wants EU citizens living in the UK to stay after Brexit as she announced plans designed to put their "anxiety to rest".
All EU nationals lawfully resident for at least five years will be able to apply for "settled status" and be able to bring over spouses and children.
Those who come after an as-yet-unagreed date will have two years to "regularise their status" but with no guarantees.
Jeremy Corbyn said the offer was "not generous" and "too little, too late".
Labour said the UK should have made a unilateral guarantee of security to EU citizens in the aftermath of last year's Brexit vote.
The EU's chief negotiator said the proposals did not go far enough.
A 15-page document outlining the detail of the UK's offer to EU citizens was published as Theresa May briefed MPs on the outcome of Friday's EU summit - at which she first set out her plans.
She told the Commons that she wanted to give reassurance and certainty to the 3.2 million EU citizens in the UK - as well as citizens of the three EEA countries and Switzerland - who she said were an "integral part of the economic and cultural fabric" of the UK.
But she said any deal on their future legal status and rights must be reciprocal and also give certainty to the 1.2 million British expats living on the continent after the UK leaves the EU - expected to be on 29 March 2019.
The key points of the UK's proposals are:
The prime minister told MPs that those granted settled status, equivalent to having indefinite leave to remain, would be "treated as if they were UK citizens for healthcare, benefits and pensions".
Mrs May said the process of application would be simplified and a "light touch" approach adopted. The existing application process for permanent residency, which involves filling out a 85-page form, has been widely criticised.
"Under these plans, no EU citizen currently in the UK lawfully will be asked to leave at the point the UK leaves the EU," Mrs May said.
By Danny Shaw, BBC home affairs correspondent
Officials anticipate that the process of administering "settled status" will be a huge challenge, with some 3.2 million potential applications.
Those EU nationals who've been assigned residency cards already will have to apply again under the new system, though the process for them is expected to be "streamlined".
It's thought applications for settled status will start to be processed from mid-2018.
Officials say they intend to put in place a new, online, simplified system - but say they are used to dealing with large volumes of applications - 2.5 million visas each year and seven million passports.

Read Danny's blog
Mrs May said spouses, children and other family members currently living overseas would be able to come to the UK and apply for settled status on the same basis as their partners and relatives.
Pressed by several Labour MPs, she suggested there would be no income barriers for anyone whose relatives have been in the UK for more than five years while, for others, existing rules applying to the foreign dependents of British citizens would be in force in future.
"There will be no extra requirements," she said. "We are not talking about splitting up families."
She also insisted the UK should police the new rules rather than the European Court of Justice.
But Mr Corbyn said the question of citizens' rights should have been dealt with in isolation rather than being dragged into the "delicate and complex" matrix of trade and other Brexit-related issues now being discussed.
"The truth is it is too little, too late. That could have been done and should have been done a year ago when Labour put that very proposal to the House of Commons. This isn't a generous offer. This is confirmation the government is prepared to use people as bargaining chips."
The SNP's Ian Blackford said there were still "more questions than answers" about how EU citizens living in Scotland would be affected.
And the Joint Council for the Welfare of Immigrants said it could not understand why those who already had permanent residence were being asked to re-apply to obtain the new status.
"These are people who have already proven their right to be here to the government's satisfaction under a very stringent process," said its chief executive Saira Grant.
"It is astonishing that the government wants to take on the expense and administrative hassle of reprocessing all of those applications under a new scheme."
Reacting on Twitter, Michel Barnier, who is leading the Brexit negotiations for the EU, said his goal was the same level of protection that citizens currently have under EU law.
He added: "More ambition, clarity and guarantees needed than in today's UK position."
Another key EU figure, Guy Verhofstadt, who is negotiating on behalf of the European Parliament, warned that any changes to free movement laws before the UK has left would break EU law.

Theresa May has suffered three Brexit defeats in the Commons as she set out to sell her EU deal to sceptical MPs.
Ministers have agreed to publish the government's full legal advice on the deal after MPs found them in contempt of Parliament for issuing a summary.
And MPs backed calls for the Commons to have a direct say in what happens if the PM's deal is rejected next Tuesday.
Mrs May said MPs had a duty to deliver on the 2016 Brexit vote and the deal on offer was an "honourable compromise".
She was addressing the Commons at the start of a five-day debate on her proposed agreement on the terms of the UK's withdrawal and future relations with the EU.
The agreement has been endorsed by EU leaders but must also be backed by the UK Parliament if it is to come into force. MPs will decide whether to reject or accept it on Tuesday 11 December.
Mrs May said Brexit divisions had become "corrosive" to UK politics and the public believed the issue had "gone on long enough" and must be resolved.
In other Brexit-related developments:
The BBC's political editor Laura Kuenssberg
The prime minister has had a terrible day today as the government made history in two excruciating ways.
Ministers were found to be in contempt of Parliament - a very serious telling off - and the government had a hat trick of defeats - the first time since the 1970s that's happened.
As you'd expect too, MP after MP after MP rose after Theresa May's remarks to slam her deal as Tory divisions were played out on the green benches, with harsh words exchanged.
But in this topsy-turvy world, the overall outcome of the day for Mrs May's big test a week tonight might have been not all bad...
By 311 votes to 293, the Commons supported a motion demanding full disclosure of the legal advice given to cabinet before the Brexit deal was agreed.
The move was backed by six opposition parties, including Northern Ireland's Democratic Unionist Party which has a parliamentary pact with the Conservatives.
It came after Attorney General Geoffrey Cox published a summary of the advice on Monday and answered MPs questions for three hours - but argued that full publication would not be in the national interest.
Labour had accused ministers of "wilfully refusing to comply" with a binding Commons vote last month demanding they provided the attorney general's full and final advice.
After Labour demanded the advice should be released ahead of next Tuesday's key vote on Mrs May's deal, Commons Speaker John Bercow said it was "unimaginable" this would not happen.
In response, Commons Leader Andrea Leadsom said she would "respond" on Wednesday, but would ask the Commons Privileges Committee to consider the constitutional repercussions.
An attempt by ministers to refer the whole issue, including the government's conduct, to the committee of MPs was earlier defeated by four votes.
The privileges committee will now decide which ministers should be held accountable and what sanction to apply, with options ranging from a reprimand to the more unlikely scenario of a minister being suspended from the Commons.
Lib Dem leader Sir Vince Cable said the result left the government "on the ropes", adding: "Theresa May's majority has evaporated, and the credibility of her deal is evaporating with it."
The prime minister suffered a further setback on Tuesday as MPs backed, by 321 votes to 299, changes to the parliamentary process should the Commons vote down her deal next week.
If that happens, the government has 21 days in which to return to the House and set out what it plans to do next.
But Tory Dominic Grieve's motion means that instead of MPs being confined to merely taking note of what the government tells them, the Commons would be able to exert more influence by voting on what they wanted the government to do as well.
Tuesday's vote, in which 26 Tory MPs rebelled, could potentially tilt the balance of power between government and Parliament if, as expected, MPs push for a "Plan B" alternative to Mrs May's deal and also seek to prevent any chance of a no-deal exit.
Mr Grieve, who has expressed support for another Brexit referendum, told Channel 4 News he was not seeking to "guarantee a particular outcome" if Mrs May's deal went down.
But he said it would "allow the UK time to consider its options", including potentially re-starting negotiations with the EU or giving the public the final say.
As she sought the backing of the Commons for her Brexit deal, the prime minister said she was confident the UK would enjoy a "better future" outside the European Union.
She said the "honourable compromise" on offer was "not the one-way street" many had portrayed it to be and that the EU had made it clear that the agreement would not be improved on.
"I never said this deal was perfect, it was never going to be. That is the nature of a negotiation," she said.
"We should not let the search for a perfect Brexit prevent a good Brexit... I promise you today that this is the very best deal for the British people and I ask you to back it in the best interest of our constituents and our country."
But Labour leader Jeremy Corbyn said it was a bad deal for the UK and Labour would seek a vote of no confidence in Mrs May if she could not get it through Parliament.
"This House will make its decision next Tuesday," he said. "I hope and expect this House will reject that deal.
"At that point, the government has lost the confidence of the House. Either they have to get a better deal from the EU or give way to those who will."
Nigel Dodds, the leader of the DUP in Westminster, said the agreement "falls short" of delivering Brexit "as one United Kingdom" and would mean entering "a twilight world where the EU is given unprecedented powers over the UK".
"We would have to rely on the goodwill of others to ever leave this arrangement," he said.
"So... the UK's future as a strong and independent global trading nation standing together is in real and imminent jeopardy - an outcome that doesn't honour the referendum or take back control of our laws, our money and our borders."
Ex-Foreign Secretary Boris Johnson dismissed the deal as a "paint and plaster pseudo-Brexit" and said its supporters would be "turning their backs" on the 17.4 million Leave voters.
"If we try to cheat them now, as I fear we are, they will spot it and will never forgive us," he said.
The leader of the SNP in Westminster, Ian Blackford, said beneath the "theatre" of the past few months was the "cold, hard truth" that this deal was "a moment of self-harm in our history".
He said it was "difficult" and "a real sorrow" to even respond to a motion that could see the UK leave the EU - an institution that he called the "greatest peace project in our lifetime".
"It is not too late to turn back. Fundamentally, there is no option that is going to be better for our economy, jobs, and for our communities than staying in the European Union.
"And it is the height of irresponsibility of any government to bring forward a proposition that is going to make its people poorer."
However, in closing the debate shortly after 01:00 GMT on Wednesday, Brexit Secretary Stephen Barclay argued the deal would bring "real changes which will improve the livelihoods of people up and down the country".
"This deal is a choice between the certainty of continued co-operation or the potentially damaging fracture of no deal, or indeed the instability of a second referendum vote," he said.
"Rejecting this deal would create even more uncertainty at a time when we owe it to our constituents to show clarity and conviction."

Theresa May is taking personal control of Brexit talks with the EU, with Dominic Raab deputising for her.
Mr Raab was drafted in as Brexit Secretary to replace David Davis, who quit in protest at the prime minister's proposals for post-Brexit trade.
A special unit in Mrs May's office has played an increasing role in Brexit talks during recent months.
Tuesday's announcement, in a written statement by Mrs May, formalises that shift in responsibility.
Labour's Shadow Brexit Minister Jenny Chapman said: "Dominic Raab has been sidelined by the prime minister before he has even had the chance to get his feet under the table."
Mr Raab, who was a leading figure in the Leave campaign in the 2016 EU referendum, insisted he had not been sidelined, telling MPs it had always been the case that Mrs May was in overall charge of the talks and the announcement amounted to some "shifting of the Whitehall deckchairs".
He said the prime minister had suggested the changes to him on the day he was offered David Davis's job and he had agreed to them.
He acknowledged there had previously been "tensions" between his department and the Cabinet Office and the changes would ensure there was "one chain of command" to "get the best possible deal".
Stewart Jackson, who was chief of staff for David Davis before he resigned two weeks ago, has previously accused Number 10 of running a "shadow, parallel operation" and keeping officials and ministers from the Brexit department "in the dark" about Brexit proposals.
The Europe Unit led by senior civil servant Olly Robbins in the Cabinet Office, which reports directly to the prime minister, will have "overall responsibility for the preparation and conduct of the negotiations", Mrs May said in her written statement.
"DExEU (the Department for Exiting the EU) will continue to lead on all of the government's preparations for Brexit: domestic preparations in both a deal and a no-deal scenario, all of the necessary legislation, and preparations for the negotiations to implement the detail of the Future Framework.
"I will lead the negotiations with the European Union, with the Secretary of State for Exiting the European Union deputising on my behalf."
Mrs May said that DExEU would recruit some new staff to work on preparations for Brexit, while a number of Cabinet Office officials would move over to the department.
There will be no net reduction to staff numbers in Mr Raab's department, she said.
Mr Raab told MPs on the Brexit committee, he would be going back out to Brussels shortly to continue talks with EU negotiator Michel Barnier, alongside Mr Robbins.
Conservative MP Craig Mackinlay suggested a "coup" had taken place to take control of the Brexit process away from David Davis.
Mr Robbins said: "I honestly don't recognise the picture you are painting."
It comes as the government published a White Paper saying how the UK's EU withdrawal agreement will be put into law.
Mr Raab said the proposed Withdrawal Agreement and Implementation Bill would deliver a "smooth and orderly" Brexit.
He said it would kick in only once MPs had given their backing to any deal struck with Brussels in the autumn. If there is no deal it will not be enacted.
The legislation would amend some parts of the EU Withdrawal Bill, passed last month after a series of knife-edge votes, to ensure the UK statute book continues to function during the 21 month transition period.
It would not end the supremacy of EU law altogether on 29 March next year, as promised in the EU Withdrawal Bill, with the continued jurisdiction of the European Court of Justice until December 2020, among other things.
Labour's Shadow Brexit secretary Sir Keir Starmer said it was now clear that the EU Withdrawal Act "will need major surgery," adding that the 29 March Brexit day was a "gimmick" which had come "unstuck".
"I can't remember legislation which has needed such great revision and amendment before the relevant parts have even come into force," he told MPs.
The new bill would create a financial authority to manage "divorce" payments, which will total between £35bn and £39bn, to the EU - and aim to protect citizens' rights.
Mr Raab told MPs: "It provides the clarity and certainty to EU citizens living here and UK nationals abroad that their rights will be properly protected.
"It will enact a time-limited implementation period, giving businesses greater certainty, giving the public finality with respect to our relationship with the EU and it provides for the appropriate means for paying the financial settlement.
"Above all, with 80% of the withdrawal agreement settled with our EU friends, the white paper is another key milestone on the UK's path to leaving the EU."
He said the publication of the white paper will allow "maximum scrutiny" of the government's plans by Parliament.
"It also sends a clear signal to the European Union that the United Kingdom is a reliable, dependable negotiating partner, delivering on the commitments it has made across the negotiation table," he told MPs.
In a separate development, the UK government guaranteed funding for EU programmes run by UK charities, businesses and universities up to the end of 2020, even if the UK left without a deal.

Prime Minister Theresa May is to face an unprecedented no-confidence challenge - from Conservative grassroots campaigners.
More than 70 local association chiefs - angry at her handling of Brexit - have called for an extraordinary general meeting to discuss her leadership.
A non-binding vote will be held at that National Conservative Convention EGM.
Dinah Glover, chairwoman of the London East Area Conservatives, said there was "despair in the party".
She told the BBC: "I'm afraid the prime minister is conducting negotiations in such a way that the party does not approve."
The Conservative Party's 800 highest-ranking officers, including those chairing the local associations, will take part in the vote.
Mrs May survived a vote of confidence of her MPs in December - although 117 Conservatives voted against her.
By Nick Eardley, BBC political correspondent
Did you enjoy the Easter Brexit truce? Don't expect it to last.
Westminster will return tomorrow with many familiar tensions.
Some Conservatives are angry at the prime minister's Brexit strategy and angry that she's holding talks with Labour.
Any vote of no-confidence by local party campaigners won't be binding. But if it did pass it would be another example of the pressure in the party.
In Parliament, there are continued calls from some for a rule change to allow another confidence vote by MPs (at the moment Mrs May is safe until December, one year on from the unsuccessful challenge at the end of 2018).
One well-placed Tory said many have had enough.
Mrs May does still have backers and seems determined to get on with the job.
But any Easter calm looks set to be short-lived.
Under party rules, MPs cannot call another no-confidence vote until December 2019.
However, an EGM has to convene if more than 65 local associations demand one via a petition.
The current petition, which has passed the signature threshold, states: "We no longer feel that Mrs May is the right person to continue as prime minister to lead us forward in the [Brexit] negotiations.
"We therefore, with great reluctance, ask that she considers her position and resigns, to allow the Conservative Party to choose another leader, and the country to move forward and negotiate our exit from the EU."
It is believed to be the first time the procedure has been used.

Donald Tusk has said Theresa May needs to come up with "a better idea" than the EU's controversial plan to prevent a hard border in Northern Ireland.
The PM has rejected keeping Northern Ireland in the EU's customs area saying this would split the UK in two.
But the European Council president said one of the "possible negative consequences" of the kind of Brexit Mrs May wants would be a hard border.
The two met in No 10 ahead of a big Brexit speech on Friday by Mrs May.
Mrs May, who chaired a meeting of the cabinet before her talks with Mr Tusk, has already pledged not to accept the draft withdrawal treaty published on Wednesday by the EU.
She reiterated this position to Mr Tusk during what Downing Street said was a "positive and constructive meeting".
The prime minister wants to resolve the Northern Ireland question "through the overall relationship between the UK and the EU", Downing Street said.
An EU source said the main focus had been the nature of the UK and EU's future relationship and that all the EU's remaining members supported its chief negotiator Michel Barnier.
The UK and the EU agree on wanting to avoid a return to a physical border - with border posts and checks - in Northern Ireland.
The UK has suggested new IT systems could be introduced to avoid the need for physical border checks but has yet to spell out how this would work in practice.
But the draft EU treaty also includes the option of a "common regulatory area" after Brexit on the island of Ireland - in effect keeping Northern Ireland in a customs union - if no other solution is found.
Both the EU and the Irish government say it is up to the UK to come up with concrete alternatives to what they describe as a "backstop" option.
Mrs May says the EU proposal would "threaten the constitutional integrity of the UK" by creating a border down the Irish Sea.
In a speech in Brussels before travelling to London Mr Tusk said he was "absolutely sure that all the essential elements of the draft" would be accepted by the 27 remaining EU members.
And he said Mrs May's decision to rule out membership of the single market and customs union had been acknowledged "without enthusiasm and without satisfaction".
The PM has said she wants a deal which will allow trade to be "as frictionless as possible".
But Mr Tusk warned: "There can be no frictionless trade outside of the customs union and the single market. Friction is an inevitable side-effect of Brexit by nature."
Mr Barnier has also been addressing the issue in a speech at the business conference in Brussels.
As a result of the UK's stated negotiation red lines, he said, the only option remaining was a free trade agreement in the vein of the deals the EU already has with other third countries.
He dismissed hopes of a "mutual recognition" arrangement on trade standards, saying this was impossible because of the UK's refusal to accept European Court of Justice oversight.
And in a message to other EU leaders, he said the "economic benefits of staying together" were "far bigger" than any negative knock-on impact from Brexit.
Mr Barnier also said Northern Ireland was a "sensitive" issue and that the problem was down to the UK's decision to leave the single market and customs union.
The EU will look at UK proposals "in a very constructive way", he said, adding: "Any vision of the future must take into account the fact that the EU cannot and will not compromise on its founding principles."
Irish senator Neale Richmond, European affairs spokesman for the Fine Gael party that leads the government, said Britain has provided "zero detail" on its proposed alternatives to keeping Northern Ireland in a customs area with the EU to avoid a hard border with the Republic of Ireland.
Veteran Eurosceptic Sir Bill Cash told the BBC's Newsnight there were "technical ways" of managing the Irish border and accused the EU of trying to create a "constitutional crisis" for the UK.
Cabinet ministers have suggested Friday's speech by Mrs May will give the EU the clarity that it has been seeking about what kind of trade relationship the UK wants after its departure on 29 March 2019.
In an apparent concession to the EU ahead of the speech, the government said EU nationals coming to the UK during a transition period after Brexit, expected to last two years, would be able to apply for indefinite leave to remain.
Mrs May has said her long-term goal is a "bespoke economic partnership", underpinned by a comprehensive free trade agreement guaranteeing tariff-free access to EU markets for British goods and services.
Earlier former prime minister Tony Blair urged the EU to put forward new ideas to address "genuine underlying grievances beneath the Brexit vote, especially around immigration" - saying this could lead voters to change their minds on leaving.
In a new report, the Commons Business Committee warned failure to reach any kind of deal would be damaging for the car industry and only close alignment with the EU would ensure its survival.
But on Tuesday the industry received a vote of confidence when Toyota said it would build the next generation of its Auris hatchback at its Burnaston plant in Derbyshire, safeguarding more than 3,000 jobs.

UK Prime Minister Theresa May has announced plans to call a snap general election on 8 June.
She said Britain needed certainty, stability and strong leadership following the EU referendum.
Explaining the decision, Mrs May said: "The country is coming together but Westminster is not."
Labour leader Jeremy Corbyn said his party wanted the election, calling it a chance to get a government that puts "the majority first".
The prime minister will refuse to take part in televised leader debates ahead of the vote, Number 10 sources said.
Mr Corbyn said Mrs May should not be "dodging" a head-to-head encounter, and the Lib Dems urged broadcasters to "empty-chair" the prime minister - hold a debate without her.
Live TV debates took place for the first time in a UK general election in 2010, and the experiment was repeated in 2015 using a range of different formats.
A BBC spokesman said that it was too early to say whether the broadcaster would put in a bid to stage a debate.
There will be a vote in the House of Commons on Wednesday to approve the election plan - the prime minister needs two thirds of MPs to vote in favour to bring forward the next scheduled election date of 2020.
Explaining her change of heart on an early election, Mrs May said: "I have concluded the only way to guarantee certainty and security for years ahead is to hold this election."
She accused Britain's other political parties of "game playing", adding that this risks "our ability to make a success of Brexit and it will cause damaging uncertainty and instability to the country".
"So we need a general election and we need one now. We have at this moment a one-off chance to get this done  while the European Union agrees its negotiating position and before the detailed talks begin.
"I have only recently and reluctantly come to this conclusion. Since I became prime minister I've said there should be no election until 2020, but now I have concluded that the only way to guarantee certainty and security for the years ahead is to hold this election and seek your support for the decisions we must take."
In a statement outside Number 10, Mrs May said Labour had threatened to vote against the final Brexit agreement and cited opposition to her plans from the Scottish National Party, the Lib Dems and "unelected" members of the House of Lords.
"If we don't hold a general election now, their political game-playing will continue and the negotiations with the European Union will reach their most difficult stage in the run-up to the next scheduled election," she said.
Senior government sources point to a specific factor that changed the prime minister's calculation on an early election.
The end of the likely tortuous Article 50 negotiations is a hard deadline set for March 2019.
Under the Fixed Term Parliaments Act, that's when the Tories would be starting to prepare for a general election the following year, with what one cabinet minister described as certain "political needs".
In other words, the government would be exposed to hardball from the EU because ministers would be desperate to avoid accepting anything that would be politically unpopular, or hold the Brexit process up, at the start of a crucial election cycle.
Ministers say that's the central reason for May's change of heart because "if there was an election in three years, we'd be up against the clock".
Read Laura's latest blog in full
The PM challenged the opposition parties: "Let us tomorrow vote for an election - let us put forward our plans for Brexit and our alternative programmes for government and then let the people decide.
"The decision facing the country will be all about leadership. It will be a choice between strong and stable leadership in the national interest, with me as your prime minister, or weak and unstable coalition government, led by Jeremy Corbyn, propped up by the Liberal Democrats - who want to reopen the divisions of the referendum - and Nicola Sturgeon and the SNP."
Mr Corbyn said he welcomed the prime minister's decision, saying it would "give the British people the chance to vote for a government that will put the interests of the majority first", saying that this would include dealing with "the crisis" in housing, education funding and the NHS and pushing for an "economy that works for all".
He told the BBC: "I'm starting straight away and I'm looking forward to it and we'll take our message to every single part of this country... We're campaigning to win this election - that's the only question now."
Asked if he will be the next prime minister, the Labour leader said: "If we win the election - yes - and I want to lead a government that will transform this country, give real hope to everybody and above all bring about a principle of justice for everybody and economic opportunities for everybody."
Scotland's First Minister Nicola Sturgeon said she would be fighting the election "to win".
"I think the prime minister has called this election for selfish, narrow, party political interests, but she has called it and therefore I relish the prospect of getting out to stand up for Scotland's interests and values, standing up for Scotland's voice being heard and standing against the ability of a right-wing Conservative Party to impose whatever policies it wants on Scotland."
In his response to Mrs May's announcement, Lib Dem leader Tim Farron tweeted: "This is your chance to change the direction of your country. If you want to avoid a disastrous hard Brexit. If you want to keep Britain in the single market. If you want a Britain that is open, tolerant and united, this is your chance."
He also accused the PM of "bottling" the TV debates and urged broadcasters to "empty chair" her if she refused to take part.
Mrs May spoke to the Queen on the phone on Easter Monday to let her know of the election plan, the prime minister's official spokesman said. She also got the full backing of the cabinet before calling the election.
Former prime minister David Cameron called Theresa May's decision to hold a snap general election "brave and right". In a tweet, he added: "My very best wishes to all Conservative candidates."
Another ex-PM, Tony Blair, said voters need to put election candidates under "sustained pressure" to say whether or not they would vote against a Brexit deal which does not deliver the same benefits as single market membership - or against a "damaging" decision to leave without a deal.
"This should cross party lines," he added.
British business groups gave a mixed response to the prime minister's sudden call for a general election, as the pound jumped on the news and shares fell.
European Council President Donald Tusk's spokesman said the 27 other EU states would forge ahead with Brexit, saying the UK election would not change their plans.
He added: "We expect to have the Brexit guidelines adopted by the European Council on 29 April and following that the Brexit negotiating directives ready on 22 May. This will allow the EU27 to start negotiations."

Ministers will be told by Theresa May they should be keeping cabinet discussions private, Number 10 says.
Following several leaks and briefings over the weekend, ministers will be "reminded" of their responsibilities when cabinet meets on Tuesday.
On Sunday Chancellor Philip Hammond suggested colleagues opposed to his approach to Brexit had been briefing against him.
It followed press reports of his cabinet remarks on public sector pay.
BBC political editor Laura Kuenssberg said several factors were at play, including some ministers' belief Mr Hammond was trying to slow down the Brexit process, and Mrs May's weakened position after the general election.
"With the PM's authority so reduced it's like the teacher has left the classroom and the teenagers have started a big rumble - and they are partly scrapping with each other because several of them fancy taking the controls themselves," she added.
Mrs May's spokesman declined to discuss the content of the leaks, but told reporters: "Of course, cabinet must be able to hold discussions of government policy in private and the prime minister will be reminding her colleagues of that at the cabinet meeting tomorrow."
Speaking on BBC Radio 4's Today programme, Transport Secretary Chris Grayling attempted to play down suggestions of cabinet splits over Brexit and criticised those who have been briefing about its meetings.
"I don't see these great divisions that are suggested to me in the Sunday newspapers and I have to say I think all of this is somewhat overplayed," he added.
One backbencher, Nadine Dorries, tweeted that she would rather see ministers sacked than another leadership contest.
Responding to the leaks on Sunday, Mr Hammond refused to comment on newspaper reports that he said public sector workers were "overpaid" and told his colleagues to "focus on the job at hand".
Another minister, International Trade Secretary Liam Fox, attacked the "self-indulgence" of those doing the leaking, adding that it had left Tory backbenchers "furious".

Leading Brexiteers in the cabinet have rallied behind Theresa May amid attempts to unseat her by Tory MPs.
Michael Gove said he "absolutely" had confidence in Mrs May as he confirmed he would not be following several other ministers out of the door.
And Liam Fox urged MPs to support the PM's draft Brexit agreement, saying a "deal was better than no deal".
The PM has named health minister Steve Barclay as her new Brexit Secretary following Dominic Raab's exit.
The 46-year old former banking executive backed Leave in the 2016 referendum and has never rebelled against the Tory whip during his eight years in the Parliament.
A mini-reshuffle has also seen Amber Rudd confirmed as the new work and pensions secretary after Esther McVey's resignation on Thursday.
The BBC understands Leader of the House Andrea Leadsom could oversee a meeting over the weekend of pro-Brexit cabinet members who have concerns about the deal.
Mr Gove and Mr Fox are expected be present, along with International Development Secretary Penny Mordaunt and Transport Secretary Chris Grayling.
The news came as more Conservatives expressed unhappiness with Mrs May's leadership and urged a confidence vote.
The BBC's political editor Laura Kuenssberg said about 20 Tories have, so far, publicly stated they have submitted letters of no confidence in the PM over her handling of Brexit.
This is some way short of the 48 needed to trigger a vote under Conservative Party rules.
One of those to do so, ex-minister Mark Francois, said the draft agreement negotiated by Mrs May with the EU was "truly awful" and the prime minister "just doesn't listen" to concerns within her party.
Ex-Brexit minister Steve Baker told the BBC's Politics Live that although he could not be sure of the number of letters submitted, he believed it was "close" to 48 and a contest was "imminent".
If this happened, he suggested the European Research Group of Brexiteer Tory MPs, headed by Jacob Rees-Mogg, would "collectively agree" which single candidate was best-placed to deliver the Brexit they wanted and back them.
But Cabinet Office minister David Lidington said Mrs May would win any contest "decisively" and "deserved to" since there was "no plausible alternative" to her approach.
Rumours had been rife that Mr Gove, a key figure in the 2016 Leave campaign, would follow fellow Brexiteers out of the cabinet in protest at the EU withdrawal agreement.
But the environment secretary, who reportedly rejected an offer to make him Brexit secretary after Dominic Raab's exit, told reporters on Friday he was focused on working in cabinet to get "the right deal in the future".
Asked if he had confidence in the PM, Mr Gove said: "I absolutely do."
He added: "I'm also looking forward to continuing to work with all my government colleagues and all my colleagues in parliament in order to make sure that we get the best future for Britain."
International Trade Secretary Liam Fox told an event in Bristol: "We are not elected to do what we want to do, but to do what is in the national interest."
Speaking in public for the first time since the withdrawal agreement was signed off by cabinet, Mr Fox said he hopes MPs "will take a rational and reasonable view" of the deal.
He added: "I hope across parliament we recognise that a deal is better than no deal, and businesses require certainty - it's in our national interest to provide certainty as soon as possible."
By BBC Assistant Political Editor Norman Smith
Michael Gove is not resigning because he thinks that even at this very late hour, he is the person who can make Theresa May change course with Brexit.
This is a huge relief for Theresa May, who meanwhile has been carrying on with business as usual by trying to sell her deal.
Theresa May has made it absolutely clear that she is going nowhere.
Senior placed Tory MPs are saying they have reached the magic 48 letters needed for a vote of confidence against Theresa May, but Sir Graham Brady - chairman of the 1922 committee - is giving precious little away.
A Conservative party leadership challenge is most definitely looming, if not this morning or this afternoon, by the weekend.
Michael Gove is a bit of a man of mystery, but if he doesn't take the Brexit Secretary role, it begs the question of who would take that job.
Mr Gove's decision to stay was a boost for Mrs May, who followed up a defiant Downing Street press conference on Thursday with a live phone-in on Friday morning on LBC radio, during which two callers said she should stand aside.
She compared herself to her cricketing hero Geoffrey Boycott who she said had "kept at the crease and carried on".
Ex-Culture Secretary John Whittingdale is among the latest Tory MP to demand a vote of confidence in the PM while a number of MPs, including Mr Francois and Adam Holloway, publicly tweeted copies of their letter.
But this prompted a blistering response from veteran Conservative MP Nicholas Soames.
I am truly dismayed at the dismal behaviour of some of my Colleagues parading their letters to Graham Brady on TV  in a vulgar and pathetic display of inferior virtue signalling #getagripwhatabouttheNationalInterest
Ambassadors from EU member states also met in Brussels on Friday morning to discuss the agreement.
The bloc's chief negotiator, Michel Barnier, paid tribute to Mrs May, but said that the EU had to protect its principles even if there were political problems in the UK.
BBC Brussels reporter Adam Fleming said the consensus from the meeting was that the EU should keep calm and not provoke the situation in the UK.
The government unveiled its long-awaited draft withdrawal agreement on Wednesday, which sets out the terms of the UK's departure from the EU, over 585 pages.
But Mrs May is facing opposition from across the political spectrum to the draft deal, which must be approved by Parliament, with critics saying it will leave the UK indefinitely tied to the EU.
It is also understood that a group of cabinet ministers are also considering whether to try to force Mrs May to make some changes to the withdrawal deal.
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Theresa May is coming under increasing pressure to set out where she stands on Britain's future trade agreements.
Speaking at the end of a trade visit to China, the PM said Britain would not face a choice between a free trade deal with the EU after Brexit and striking deals with the rest of the world.
It comes as she has faced criticism from Eurosceptic Tory MPs that she is heading for a "Brexit in name only".
Full negotiations on the UK's 2019 exit are to resume on Monday.
Brexit Secretary David Davis will meet his EU counterpart Michel Barnier in London on Monday for the first time this year, with officials from both sides continuing technical discussions during the week.
During the prime minister's three-day visit to China, Downing Street said more than £9bn of business deals were signed and it agreed to a joint investment and trade review as the "first step" to an "ambitious" post-Brexit deal with the world's second largest economy.
However, Mrs May has faced growing criticism from MPs, including many in her own party, who have called for her to be more specific about her priorities on UK's future trade arrangements with the EU.
In an interview with Bloomberg News, Liam Fox, who was with Mrs May in China, said the UK cannot be involved in any customs union with the EU following Brexit.
Number 10 said the international trade secretary was speaking for the government - but also said the details of future arrangements with Brussels were a matter for negotiation.
"It is fair to say the prime minister has an open mind when it comes to these negotiations," a Downing Street spokesman said.
By Iain Watson, BBC political correspondent
While Theresa May has been away - successfully signing trade deals -  I have been assessing the battles she faces on the home front, within her own party.
What is most striking is that some who supported her have, at the very least, become wobblier. One ex-minister said he felt "badly let down". She has been accused of blocking, not delivering, radical change.
A former supporter questioned her lack of decisiveness: "She has more reviews than a film critic would produce in a lifetime."
A Remainer who despises Boris Johnson wondered if - to coin a phrase - the foreign secretary's "bad leadership would be better than no leadership".
Council candidates fear poor results in London's May elections and think this could be a trigger for the PM to go.
And a Conservative-supporting business leader felt - though he didn't advocate it - that her opponents "will pull the pin from the grenade".
Downing Street believes the feeding frenzy of speculation will abate when more progress is made on EU withdrawal. But they are aware of the challenges at home as well as abroad.
Speaking to the BBC's political editor Laura Kuenssberg, the prime minister said she had already spelled out what she wants from the deal and did not believe the UK would have to choose between Europe and the rest of the world.
"I don't believe that those are the alternatives," she said.
"What the British people voted for is for us to take back control of our money, our borders and our laws and that's exactly what we are going to do.
"We also want to ensure that we can trade across borders."
By Kerry Allen, China Media Analyst, BBC Monitoring
Mainland Chinese media have praised Theresa May's 31 January-2 February visit from start to finish.
Official broadcaster CCTV says that the nickname media have given her - "Auntie May" - shows that she has become "one of the family" and newspapers have heralded her trip as showing that Sino-UK ties signal new heights for bilateral cultural exchanges, and post-Brexit trade deals.
They have also given a nod to Mrs May for, reportedly, not raising human rights issues in Hong Kong during her stay.
Nationalist newspaper Global Times commends the UK prime minister for "not making any comment contrary to the goals of her China trip", saying "the losses outweigh the gains if she appeases the British media at the cost of the visit's friendly atmosphere".
Independent Hong Kong and Taiwanese media have been critical of the Prime Minister for not raising the contentious issue of pro-democracy protests.
Publications including influential paper South China Morning Post quote former British governor Chris Patten, who said the Hong Kong dialogue was "critical" to granting assurances that developing ties with the mainland won't come at Hong Kong's expense.
The prime minister has come under pressure from Eurosceptics worried about potential concessions by the UK in the Brexit talks.
Last week, Chancellor Philip Hammond suggested Britain's relationship with the EU would change only "very modestly" after Brexit.
However, cabinet members - including Foreign Secretary Boris Johnson - have warned the UK will lose the main advantages of Brexit if it remains bound by trade rules of the single market and customs union.
They have called for the prime minister to be clearer about her own position.
She told the BBC her goal in upcoming talks with Europe was to strike a deal that "is going to be good for trade between the UK and EU and good for jobs in Britain".
She added: "It means a free trade agreement with the EU. We are now starting to negotiate that free trade agreement with the EU."
She has repeatedly said Brexit will mean leaving the single market and customs union.
Asked again about her own future as prime minister, Mrs May said: "I'm not a quitter. I'm in this because there is a job to be done here and that's delivering for the British people and doing that in a way that ensures the future prosperity of our country."

Theresa May has outlined plans to set the UK's departure date and time from the EU in law, warning she will not "tolerate" any attempt to block Brexit.
She said the EU Withdrawal Bill would be amended to formally commit to Brexit at 23:00 GMT on Friday 29 March 2019.
The bill will be scrutinised by MPs next week - but the PM warned against attempts to stop it or slow it down.
Mrs May was writing in the Daily Telegraph as a fresh round of Brexit negotiations are due to begin later.
The UK is due to leave the European Union after 2016's referendum in which 51.9% of voters backed Brexit.
The prime minister said the decision to put the specific time of Brexit "on the front page" of the Brexit bill showed the government was determined to see the process through.
"Let no-one doubt our determination or question our resolve, Brexit is happening," she wrote.
"It will be there in black and white on the front page of this historic piece of legislation: the United Kingdom will be leaving the EU on March 29, 2019 at 11pm GMT."
The draft legislation has already passed its second reading, and now faces several attempts to amend it at the next part of its parliamentary journey - the committee stage.
Mrs May said most people wanted politicians to "come together" to negotiate a good Brexit deal, adding that MPs "on all sides" should help scrutinise the bill.
She said the government would listen to MPs if they had ideas for improving the bill, but warned against attempts to halt the process.
"We will not tolerate attempts from any quarter to use the process of amendments to this Bill as a mechanism to try to block the democratic wishes of the British people by attempting to slow down or stop our departure from the European Union."
MPs have previously been told there have been 300 amendments and 54 new clauses proposed.
The PM said the "historic" bill was "fundamental to delivering a smooth and orderly Brexit" and would give "the greatest possible clarity and certainty for all businesses and families across the country".
Labour MP and remain campaigner, Chuka Umunna, said many experts believed the March 2019 leaving date did not give much time for negotiations.
He told BBC Radio 5 live: "Lord Bridges said he could not see the government being able to negotiate the transition arrangement, like the bridge to us leaving, and the divorce bill, by 2019.  So we may actually need more time."
Lord Kerr, the former diplomat who helped draft Article 50 of the Lisbon Treaty - the mechanism the UK has used to exit the EU - said putting the Brexit date on the bill did not mean the withdrawal process was irreversible.
The cross-bench peer told BBC Radio 4's Today programme that decisions such as these were being made in Westminster, and "had nothing to do with the treaty, and they have nothing to do with the views of our partners in Brussels".
But the Conservative MP and leave campaigner, Peter Bone, welcomed the decision to enshrine the leaving date in law, saying it was a "really big, important step".
It comes as a leaked account of a meeting of EU diplomats this week suggested that Northern Ireland may have to abide by the EU's rules on the customs union and single market after Brexit - in order to avoid the introduction of border checks.
Both Britain and the EU say they are committed to ensuring that Brexit does not undermine the 1998 Good Friday peace agreement or lead to the emergence of hard-border with the Republic of Ireland.
However, BBC correspondent Adam Fleming said the commission's suggestion appeared to be at odds with comments made by the Northern Ireland Secretary, James Brokenshire, this week.
Mr Brokenshire said it was "difficult to imagine" Northern Ireland remaining in either the customs union or the single market after Brexit.

Theresa May's Brexit deal is "doomed" and must be renegotiated, ex-defence secretary Sir Michael Fallon has said.
Sir Michael launched a scathing attack on the proposed EU agreement, saying it was the "worst of all worlds" and the PM's future was "up to colleagues".
The prime minister is visiting Wales and Northern Ireland to argue her deal will bring certainty to business.
DUP leader Arlene Foster told BBC News the trip was a "waste of time" as Parliament would not support her deal.
Mrs Foster, whose party has a parliamentary pact with the Conservatives to support the government, said Mrs May had "given up" on trying to secure a better deal for Northern Ireland.
While people were "fed up" with the Brexit process dragging on, that was not a good enough reason "to accept what's on the table", she told the BBC's political editor, Laura Kuenssberg.
Parliament will vote on whether to accept or reject the terms of the UK's withdrawal and future relations negotiated by Mrs May on 11 December.
Sir Michael's decision to come out against the deal is a blow to the prime minister, who is struggling to muster support in Parliament for it.
Labour, the Lib Dems, the SNP and the Democratic Unionists have said they will vote against the deal while many Tories have said publicly they are opposed.
Opponents of the deal say it will keep the UK too closely tied to EU rules and make it harder to strike future trade deals with other countries and minimise their value.
US President Donald Trump has suggested the withdrawal agreement "sounds like a great deal for the EU" and might hamper a future trade deal with the UK but Mrs May said this was not the case.
In other developments:
Sir Michael Fallon, who served as defence secretary under David Cameron and Theresa May before having to resign a year ago, told MPs on Monday the agreement was a "huge gamble" as it would see the UK give up its power to influence EU rules and regulations in return for vague assurances over future trade arrangements.
He told BBC Radio 4's Today that "this is not a good deal and we need a better deal", saying that Mr Trump's criticism of its repercussions for transatlantic relations "could not simply be brushed off".
"My fear is that this deal gives us the worst of all worlds," he said. "No guarantee of smooth trade in the future and no ability to reduce the tariffs that we need to conclude trade deals with the rest of the world.
"So, unless the House of Commons can be persuaded somehow that those are possible then I think, yes, the deal is doomed."
Asked if Mrs May was also doomed, he replied "that's up to my colleagues", while stressing that a change of leader would not necessarily address the difficulties the UK now found itself in.
When it was put to him that did not sound like an endorsement of Mrs May, he replied "take it any way you want".
The prominent Brexiteer Bernard Jenkin said there was a lot of "personal sympathy" for Mrs May but her authority when it came to the Brexit agreement was "collapsing".
Sir Michael said the 29 March 2019 date for Brexit, which is enshrined in UK law, may have to be pushed back to give negotiators the time to make major improvements to the agreement.
All 28 EU states would need to agree to extend the Article 50 process of negotiations to allow this to happen, something Theresa May has repeatedly ruled out.
Cabinet Office David Lidington said he did not think doing this "would get us anywhere" as the EU had made clear this was the only deal on the table.
He told Today there was no "Plan B" and the agreement was a "decent compromise" which would provide a springboard to the next stage of negotiations on the two sides' future relationship.
The prime minister is continuing to making the case for the agreement, which she says delivers on the 2016 referendum vote in key areas and is in the national interest.
Responding to Mr Trump's comments, Downing Street has insisted the UK will be able to pursue an independent trade policy under the terms of the political declaration on future relations.
During a visit to an agricultural show in Builth Wells, Powys, Mrs May said: "As regards the United States, we have already been talking to them about the sort of agreement that we could have in the future.
"We have a working group set up and that is working very well, has met several times and is continuing to work with the US on this."
Under the proposed agreement, the UK would not be able to complete any trade deal with a country outside the EU until the end of the proposed transition period - currently scheduled to last until 31 December 2020.
In reality, any bilateral agreement between the UK and the US is likely to take years to negotiate given its complexity, differing standards in areas such as agriculture, and the fact it would require ratification by the US Congress.

"The next General Election should be in 2020."
The words of Theresa May who has just executed an enormous political reversal.
For months she and her team have played down the prospect of an early poll.
The reasons were simple. They didn't want to cause instability during Brexit negotiations.
They didn't want to go through the technical process of getting round the Fixed Term Parliaments Act.
They didn't want the unpredictability of an election race.
And many in the Conservative Party believed there is so little chance of the Labour Party getting its act together before 2020 that they could carry on until then and still expect a sizeable majority.
There was also, for Theresa May, the desire to show that she will be a prime minister who sticks to her word.
But the relentless political logic proved too tempting to hold to all of that.
Dealing day-to-day with a small majority has given Conservative backbenchers significant power to force the government to back down on a variety of issues.
Election campaigns can be deeply unpredictable but opinion polls suggest a Tory majority that would make that problem disappear.
And while prime ministers are not directly elected, as she approaches the Brexit negotiations, the PM's hand in negotiations in Brussels - as well as in Westminster - would be fundamentally strengthened with an election mandate she believes she can win.
There are plenty of risks.
If the last few years have shown anything it's the politics of this era is extremely hard to predict.
With ministers in the dark until this morning, what is certain is that Theresa May is hard to read.

Prime Minister Theresa May has announced a plan to call a snap general election on 8 June. Here is the statement she made outside Number 10 in full:
"I have just chaired a meeting of the cabinet, where we agreed that the government should call a general election, to be held on 8 June.
"I want to explain the reasons for that decision, what will happen next and the choice facing the British people when you come to vote in this election.
"Last summer, after the country voted to leave the European Union, Britain needed certainty, stability and strong leadership, and since I became prime minister the government has delivered precisely that.
"Despite predictions of immediate financial and economic danger, since the referendum we have seen consumer confidence remain high, record numbers of jobs, and economic growth that has exceeded all expectations.
"We have also delivered on the mandate that we were handed by the referendum result. Britain is leaving the European Union and there can be no turning back.
"And as we look to the future, the Government has the right plan for negotiating our new relationship with Europe.
"We want a deep and special partnership between a strong and successful European Union and a United Kingdom that is free to chart its own way in the world.
"That means we will regain control of our own money, our own laws and our own borders and we will be free to strike trade deals with old friends and new partners all around the world.
"This is the right approach, and it is in the national interest. But the other political parties oppose it.
"At this moment of enormous national significance there should be unity here in Westminster, but instead there is division. The country is coming together, but Westminster is not.
"In recent weeks Labour has threatened to vote against the final agreement we reach with the European Union. The Liberal Democrats have said they want to grind the business of government to a standstill.
"The Scottish National Party say they will vote against the legislation that formally repeals Britain's membership of the European Union. And unelected members of the House of Lords have vowed to fight us every step of the way.
"Our opponents believe because the government's majority is so small, that our resolve will weaken and that they can force us to change course. They are wrong.
"They underestimate our determination to get the job done and I am not prepared to let them endanger the security of millions of working people across the country.
"Because what they are doing jeopardises the work we must do to prepare for Brexit at home and it weakens the government's negotiating position in Europe.
"If we do not hold a general election now their political game-playing will continue, and the negotiations with the European Union will reach their most difficult stage in the run-up to the next scheduled election.
"Division in Westminster will risk our ability to make a success of Brexit and it will cause damaging uncertainty and instability to the country.
"So we need a general election and we need one now, because we have at this moment a one-off chance to get this done while the European Union agrees its negotiating position and before the detailed talks begin.
"I have only recently and reluctantly come to this conclusion. Since I became prime minister I have said that there should be no election until 2020, but now I have concluded that the only way to guarantee certainty and stability for the years ahead is to hold this election and seek your support for the decisions I must take.
"And so tomorrow I will move a motion in the House of Commons calling for a general election to be held on 8 June. That motion, as set out by the Fixed-Term Parliaments Act, will require a two-thirds majority of the House of Commons.
"So I have a simple challenge to the opposition parties, you have criticised the government's vision for Brexit, you have challenged our objectives, you have threatened to block the legislation we put before Parliament.
"This is your moment to show you mean it, to show you are not opposing the government for the sake of it, to show that you do not treat politics as a game.
"Let us tomorrow vote for an election, let us put forward our plans for Brexit and our alternative programmes for government and then let the people decide.
"And the decision facing the country will be all about leadership. It will be a choice between strong and stable leadership in the national interest, with me as your prime minister, or weak and unstable coalition government, led by Jeremy Corbyn, propped up by the Liberal Democrats, who want to reopen the divisions of the referendum, and Nicola Sturgeon and the SNP.
"Every vote for the Conservatives will make it harder for opposition politicians who want to stop me from getting the job done.
"Every vote for the Conservatives will make me stronger when I negotiate for Britain with the prime ministers, presidents and chancellors of the European Union.
"Every vote for the Conservatives means we can stick to our plan for a stronger Britain and take the right long-term decisions for a more secure future.
"It was with reluctance that I decided the country needs this election, but it is with strong conviction that I say it is necessary to secure the strong and stable leadership the country needs to see us through Brexit and beyond.
"So, tomorrow, let the House of Commons vote for an election, let everybody put forward their proposals for Brexit and their programmes for government, and let us remove the risk of uncertainty and instability and continue to give the country the strong and stable leadership it demands."

For all the talk of the negotiations between Team May and Team Corbyn being "constructive and serious", Labour's leader always seemed somehow more likely to back away from a Brexit compromise with the prime minister than embrace one.
Some of his Labour critics still suspect - though he and his close aides deny it - that he's a lifelong Eurosceptic who would be content with a Brexit that also taints the Conservatives and takes him closer to power.
Mrs May's options are, of course, all but exhausted. Another, final, round of voting to see if any solution gains traction is one of them.
But will Tory rebels suddenly change their minds after three defeats?
Or will Labour MPs, feeling the pressure to deliver Brexit, break ranks and ride to Mrs May's rescue? Some maybe, but enough?
The prime minister has yet to name the date for her departure, but the Tory leadership contest is running at full tilt, as it has, in truth, for some time.
The next leader is more than likely to promise a harder Brexit - maybe with no deal at all. Parliament might oppose that but only the government could, at a single stroke, stop it happening.
So Mrs May's last remaining hope of achieving her "mission impossible" before leaving may just be that heightened fear of a no-deal Brexit changes Tory and Labour minds when the legislation to take the UK out is voted on in early June.
Stubbornness. Duty. A steady diet of faint hope. They'll all feature strongly in Theresa May's soon-to-be-written political epitaph. The chapter about the UK and its future place is the world is still being penned.

Theresa May called on politicians to be "careful about language" they use after words directed at her over Brexit.
In an article in the Sunday Times, a Tory backbencher was quoted as saying: "The moment is coming when the knife gets heated, stuck in her front and twisted. She'll be dead soon."
The PM was also told to "bring her own noose" to a meeting later this week.
Mrs May acknowledged "passionate beliefs" on Brexit, but said those in public life should watch their words.
MPs from all sides have condemned the quotes, with Conservative MP Sarah Wollaston calling those responsible "spineless cowards", adding: "Have they learned nothing following the assassination of Jo Cox?"
Labour MP Mrs Cox was murdered in her West Yorkshire constituency by right-wing extremist Thomas Mair, a week before the Brexit referendum in June 2016.
Fellow Conservative MP Heidi Allen told BBC 2's Politics Live that whoever said it is "worthy of having the whip removed and being thrown out the party".
In a debate in the House of Commons on Monday to update MPs on the latest progress on the Brexit negotiations, Labour leader Jeremy Corbyn said he hoped it would be conducted "without some of the language reported in the press over the weekend."
In response, Mrs May said: "I think it is incumbent on all of us in public life to be careful about the language we use.
"There are passionate beliefs and passionate views held on this subject [Brexit] and other subjects.
"But whatever the subject is, we should all be careful about our language."
SNP leader Ian Blackford also used some of his time in the debate to criticise the language, calling it "crass and violent", as well as "abhorrent and irresponsible".
He added: "Those responsible need to withdraw and apologise. Such language has no part to play in our public discourse."
Labour MP Yvette Cooper, chairwoman of the Commons Home Affairs committee, said the unnamed backbencher who made the comments should be publicly named to stop them from doing it again.
"This is vile and dehumanising language towards a woman MP, towards a prime minister who, no matter how much you might disagree with her, is someone who is doing a job in public life," she said.
"Nobody should be subject to that kind of violent language, which I think is normalising violence in public debate at a time when we lost Jo Cox, we have had threats against Rosie Cooper, we have had other violent death threats against women MPs."
Scotland's First Minister, Nicola Sturgeon, also condemned the use of language:
Asked on BBC Radio 4's Today programme about the language, Brexit-backing Conservative MP Mark Francois said it was "unacceptable", but that he would not tell Chief Whip Julian Smith how to do his job.
Instead, he criticised a "bunker mentality" in Downing Street, adding: "The problem is that there is a lot of frustration on the backbenches at the moment, both among Leavers and Remainers, at the general state of play.
"When you try to convey that to No 10, no-one is listening."
This led to a fresh wave of criticism from his colleagues, including Remain-backing Tory Anna Soubry.
Fellow Brexiteer Tory Andrew Bridgen said the language was "unhelpful" and warned his Leave-supporting colleagues that it risked increasing support for Mrs May.
He told ITV's Good Morning Britain: "At the moment that [language] is unhelpful. It won't persuade colleagues to back a change of leadership.
"It's actually going to be counterproductive at this point."
Asked how Theresa May viewed the use of such language, her official spokesman said: "I don't intend to dignify those specific anonymous comments with a response.
"The prime minister has always been very clear that we must set a tone in public discourse that is neither dehumanising nor derogatory.
"Personal vitriol has no place in our politics."

The prime minister has said voters want the Brexit issue resolved so the country can "move on".
Theresa May was speaking at the Scottish Conservative conference as she faced renewed calls to quit.
The deadlock over her Brexit deal has been blamed for the Conservatives losing more than 1,000 seats in English council elections.
But Mrs May insisted that she remains determined to deliver a deal that will ensure the UK has a "bright future".
The backlash against the two main Westminster parties over the Brexit deadlock has also seen Labour lose more 100 seats.
But the Liberal Democrats and Greens, who both back another referendum on Brexit, have made big gains.
Talks between the Conservatives and Labour aimed at finding a way forward on Brexit started a month ago and are ongoing - although it is not clear how much progress has been made, and both parties remain deeply divided over the best way forward.
Some Conservative councillors have openly blamed Mrs May for their election - with one council leader who lost his majority calling on her to "consider her position".
In her conference speech, Mrs May told delegates that all 13 Scottish Conservative MPs had backed her Brexit deal when parliament voted on it in March.
She added: "If others had followed-suit, we would be leaving the EU on 22 May. But they did not, and we have had to face up to that fact.
"We have had to reach out to the official opposition to secure cross-party support for a deal. That work continues with one clear aim - to get a deal over the line in parliament.
"Across the UK, people want to see the issue of Brexit resolved and for our country to move forward. That is our goal and it is one we are determined to deliver."
Mrs May also said politicians calling for "re-runs" of the Brexit or independence referendums should instead "accept the decision of the people".
She went on to claim that this "old fashioned belief" was a major difference between her and Scotland's first minister, Nicola Sturgeon, who wants to hold a second independence referendum in the next two years.
The UK government has already ruled out granting the consent that Ms Sturgeon says would be needed to ensure a referendum was legal.
Mrs May said Ms Sturgeon wants to "re-run the independence referendum because she did not like the decision of the people of Scotland" and to "re-run the EU referendum because she did not like the decision of the people of the UK".
The prime minister added: "She saw Brexit as an opportunity to further her party's obsession with one thing and one thing only - independence.
"Just imagine if Scotland had a government that put as much energy into improving Scotland's hospitals as the SNP put into chasing independence.
"A government as focused on boosting Scotland's economy as the SNP is on internal debates about the hypothetical currency of an independent Scotland.
"Or a first minister who actually lived up to her promises to restore Scotland's education system, instead of letting its standing slip in the international rankings."
Mrs May also used her speech to announce that the UK government was backing plans to create an underwater engineering base in Aberdeen to boost the oil and gas industries.
It is hoped the creation of the underwater hub will build on Scotland's expertise in subsea robotics, remotely-operated vessels and help the oil and gas sector diversify away from fossil fuels.
The two-day conference will hear from Scottish Conservative leader Ruth Davidson on Saturday in what will be her first speech since returning from maternity leave after the birth of her son in October.
Speaking ahead of the conference, Ms Davidson insisted that Mrs May was not to blame for the Brexit deadlock as she had done her job by negotiating a deal with the other 27 EU members.
She added: "I think even her harshest critics would have accepted that Prime Minister May has worked exceptionally hard with an almost impossible job.
"There is competing views on what Brexit means within all of the political parties out there, so it's not just a Tory issue, although I'm not covering over the cracks and there are definitely different views within the Conservatives.
"I think the frustration for voters is they've seen vote after vote after vote in the House of Commons, all of which showing what there isn't a majority for, but none of which is showing what there is a majority for.
"And the frustration is they see the voices that are getting louder are the ones at the edges."
Ms Davidson, who backed Remain ahead of the EU referendum, said she hoped the local government elections would "really focus minds" among the negotiating teams so they could reach an agreement that could get through the House of Commons.
But she said another referendum on Brexit would not be helpful to the current political situation - and could instead inflame it further.
Ms Davidson has been tipped as a future leader of the UK Conservative Party, but has previously ruled out ever taking on the job - saying that her ambition is instead to replace Nicola Sturgeon as first minister of Scotland.
And she said she would not be using her first day back from maternity leave to "lay down the law" on where Mrs May should give ground in the Brexit talks.

Theresa May has said that Brexit means there will be more money available to spend on the NHS and schools.
The prime minister told the BBC's Laura Kuenssberg Brexit "would deliver a country that will be different" but with the chance "of a bright future".
The PM visited England, Scotland, Wales and Northern Ireland, with one year to go to the UK leaving the EU.
Meanwhile ex-Prime Minister Tony Blair said Brexit could still be stopped, saying it was "not too late".
Mr Blair, a strong backer of UK membership of the EU, told BBC Radio 4's Today the "sensible" option was to "take a final decision" once the terms of the deal have been set out.
On 29 March 2019, the UK will formally leave the EU and is due to enter a 21-month transition period during which much of the current arrangements continue, before the final permanent post-membership relationship is due to kick-in.
Since formal negotiations began between the two sides last June, an agreement has been struck on a Brexit "divorce bill" - but the crucial issue of how they will trade together in the longer term has yet to be settled.
In her interview with the BBC's political editor, Mrs May was asked if there would be a "Brexit dividend".
She replied: "Of course when we leave the European Union, we'll no longer be spending vast sums of money, year in and year out, sending that money to the European Union, so there will be money available here in the UK to spend on our priorities like the NHS and schools."
Mrs May said she was confident of securing a deal which was good for all parts of the UK.
Asked if she thought Brexit was worth it, she added: "I think there are real opportunities for the UK, I think there's a bright future out there and, yes, I think Brexit is going to deliver a country that will be different, for us to be an independent nation for the future."
The issue of whether there would be a Brexit dividend was a contentious issue during the 2016 EU referendum. The Leave campaign said money sent to the EU should be spent on the NHS instead, while the Remain side said the economic impact of leaving would mean less money being available to spend on public services.
At some stage - most likely in October - the PM will have to put an outline of the Brexit deal to Parliament, with some opponents seeing that as a chance to force a rethink.
The government only has a majority in the Commons with the support of DUP MPs so Labour's position in that vote will be important.
Shadow chancellor John McDonnell told BBC Radio 4's Today programme Labour's "tests" on any proposed deal were "nowhere near being met" and insisted Labour would not vote for the deal unless "the government are sensible and they negotiate properly... [so we can] get a deal that meets the six tests".
Mrs May began her tour by visiting a textile factory in Ayrshire with other stops at a parent and toddler group in Newcastle, lunch with farmers near Belfast before meeting businesses in Barry, south Wales.
She vowed to regain control of "our laws, our borders and our money" and that the UK will "thrive as a strong and united country that works for everyone, no matter whether you voted Leave or Remain".
The prime minister has been accused of a power grab by the Scottish and Welsh governments over plans to repatriate some powers from Brussels to Westminster rather than to the devolved administrations.
She insisted each of the devolved administrations would see "an increase in their decision-making powers" and that her government remained "absolutely committed" to the devolution settlements.
But Wales' First Minister Carwyn Jones warned that Mrs May's Brexit plan would "do serious damage to our economy".
And Scotland's First Minister Nicola Sturgeon said she wanted to see progress in the talks over devolving powers to UK nations from Brussels.
"This is about powers over the environment, agriculture, fishing, justice - perhaps whether in future trade deals, our health service could be put up for grabs," she said.
"These things really matter and that's why this is such an issue of importance for us."
By BBC political editor Laura Kuenssberg
As was crystal clear with a focus group in Coventry last night, for many voters, Brexit was a demand for something else, a response to big promises made by politicians.
With only a year to go, and the government's main achievement so far being establishing a grace period that will pretty much keep us in the EU for another couple of years, I can't help using the phrase that haunted the prime minister in the election: "Nothing has changed."
And nothing will change any time soon either. But the argument over how to keep perhaps the biggest of those promises is alive and kicking.
Without mentioning the bus (yes, that bus), the boldest promise in the referendum that sticks in people's minds was to provide more money for the NHS.
The PM also promised to "protect the integrity of the United Kingdom as a whole", restating her opposition to a controversial EU "backstop" option which effectively keeps Northern Ireland inside its customs union.

Theresa May has told her critics that getting rid of her as PM would not make delivering Brexit any easier.
Mrs May defended last week's draft agreement for leaving the EU and said there was a "critical" week ahead.
She suggested agreeing more details of UK's future relationship with the EU, ahead of an expected summit next week, could satisfy the concerns of some of the Tory MPs opposed to her plans.
Ex-Brexit Secretary Dominic Raab said the UK was being "bullied" by the EU.
Labour leader Jeremy Corbyn said his party could get a better deal in time for Brexit, which is due to happen on 29 March.
There has been widespread criticism of the 585-page withdrawal agreement - published alongside a  shorter document setting out what the UK and EU's future relationship could look like - which is set be signed off at a summit next week.
There is also doubt over whether it can win the approval of the House of Commons.
Some cabinet ministers have resigned, including Mr Raab, and others are believed to be trying to change its wording.
In other developments:
Mrs May told Sky News's Ridge on Sunday it had been a "tough week" but that she would not be distracted. She added the next seven days "are going to be critical" for the UK's future.
Asked whether Sir Graham Brady - chairman of the backbench 1922 committee - had received the 48 letters needed to trigger a confidence vote in her leadership, she replied: "As far as I know, no - it has not."
And in a warning to those pushing for a change of leader, she said: "It is not going to make the negotiations any easier and it won't change the parliamentary arithmetic."
Mrs May said negotiations were still taking place to put more detail into the future deal proposals, saying it was this part that "delivers on the Brexit vote".
She also said she would be meeting European Commission chief Jean-Claude Juncker in Brussels ahead of the summit.
BBC Europe editor Katya Adler
The European Commission says Mrs May will only meet Mr Juncker when concrete progress has been made on the content of the political declaration document on the future relationship.
Those negotiations have been going on this weekend and had been expected to conclude on Tuesday - let's see.
EU sources are clearly spelling out that the PM's visit would be to finalise this political declaration - and not to re-open the withdrawal deal approved last week by the cabinet.
Despite the political turmoil in the UK, the EU intends the Brexit summit between EU leaders and the PM to go ahead next Sunday unless she is kicked out of her job, or she suddenly politically denounces the divorce deal she has been trying to sell.
Don't forget - the withdrawal agreement will be legally binding. The political declaration on the future will not. It can be altered after Brexit, because it is only then that the detailed EU-UK negotiations on a future trade deal begin in earnest.
EU chief negotiator Michel Barnier has been meeting diplomats from the 27 remaining EU member states.
The EU has now proposed 31 December 2022 as the ultimate end date for a possible extension to the transition period.
This period, during which the UK will have left but arrangements will largely continue as they are, is currently forecast to finish by the end of 2020.
The draft withdrawal agreement includes the option of extending it if more time is needed to reach a trade deal - but rather than specifying an end date, says a decision may be taken "extending the transition period up to [31 December 20XX]."
Also in the meeting there was a divide between states that want an ambitious trading relationship with the UK and those who want Britain's access to the single market to be more constrained, BBC Brussels correspondent Adam Fleming said.
The UK wants to maintain the status quo on internal security, which is also "a problem," ambassadors were told.
And Spain raised serious concerns about Gibraltar, which officials fear could grow in the coming days, he added.
A diplomat said the message from the EU's Brexit negotiators to the member states was: "Keep a lid on your concerns for now and we'll deal with them in the negotiations on the future relationship."
Sir Graham told BBC Radio 5 Live's Pienaar's Politics he would not reveal how many letters he had received - saying he had not even told his wife, who is his parliamentary assistant.
"I get asked in the supermarket, in the street," he said.
Sir Graham said he found the suggestion he had received 48 letters but not acted on it to be "slightly offensive".
"It's critical that people trust my integrity in this," he said.
Sir Graham also told the BBC's Sunday Politics North West it was "very likely" Mrs May would win a vote of no-confidence if there was one.
It is difficult to see how the 25 November EU summit could go ahead if Mrs May were to lose a confidence vote next week.
It is up to Sir Graham to decide when such a vote would be held, but he has said the process will move quickly.
The last time a Tory leader was ousted by their own MPs, in 2003, Iain Duncan Smith faced a confidence vote the next day.
If Mrs May were to lose that confidence vote it would spark a leadership election but she would not be allowed to run. She would remain prime minister until the contest was over unless she opted to resign and hand over to a caretaker prime minister.
In either circumstance, her version of Brexit would be in doubt.
European Council President Donald Tusk has said the summit will go ahead unless something "extraordinary" happens - he did not elaborate on what that might be.
Mr Raab, who negotiated with the EU's Michel Barnier, explained his decision to quit on the BBC's Andrew Marr show.
With "two or three points" being changed he could support the government's proposals, he said.
He said he did not know who had inserted a clause on customs relations into the future partnership document but said it was a "clear breach" of the Conservative manifesto.
"The difficulty for me is that I was being asked to go over to Brussels and sign on the bottom line... on a deal which I said in good conscience I did not feel was right for the country," he said.
"I do think we are being bullied, I do think we are being subjected to what is pretty close to blackmail frankly.
"I do think there is a point at which, we probably should have done it before, where we just say 'I'm sorry this is the United Kingdom of Great Britain and Northern Ireland, we cannot accept those dictated terms'."
The draft document sets out the terms of the UK's departure, including details such as how much money will be paid to the EU, details of the transition period and citizens' rights.
Both the UK and the EU want to avoid a hard Northern Ireland border so they agreed to include in the deal a "backstop" - or back-up plan - in case they cannot reach a long-term trade agreement which does this.
This would mean Northern Ireland would stay more closely aligned to some EU rules, which critics say is unacceptable.
And the UK would not be able to leave the backstop without the EU's consent.
Writing in the Sunday Telegraph, the Brexiteer MP Zac Goldsmith said under the PM's plan "in effect, Britain would remain in the EU, but without having any say".
He added: "Had that been the choice, I personally would have voted to remain."
Labour leader Mr Corbyn says his party, which has 257 MPs, will not support the deal.
He told Sky News the "one-way agreement" on Northern Ireland was "not acceptable", and there were no guarantees on workers' rights and environmental protections.
If it was voted down in the Commons, he said the government should go back to the EU and "renegotiate, rapidly".
Mr Corbyn insisted Labour would be able to negotiate a better deal, saying the proposed transition period - which will only happen if there is a withdrawal agreement - offered "some opportunities" for this.
He also said another referendum - as demanded by some of his MPs - was "an option for the future but not an option for today".
He said he voted Remain in the 2016 referendum but if there were to be another "I don't know how I would vote - what the options would be at that time".
He also revealed that he had not yet read all of the 585 page draft EU withdrawal agreement.

UK Prime Minister Theresa May has said the EU must treat the UK with more "respect" in Brexit negotiations.
In a statement at Downing Street she said for EU leaders to reject her plan with no alternative at this "late stage of negotiations" was "not acceptable".
She said talks had reached an "impasse" and could only be unblocked with "serious engagement" from the EU side.
European Council President Donald Tusk said a "compromise" was possible but the UK proposals had to be "reworked".
The pound's fall against the dollar and the euro deepened following Mrs May's statement.
The UK is due to leave the EU on 29 March 2019.
The two sides are trying to reach a deal by November so it can be ratified in time.
They want to avoid a hard border - physical infrastructure like cameras or guard posts - between Northern Ireland and the Irish Republic but cannot agree on how.
Mrs May says her plan for the UK and EU to share a "common rulebook" for goods, but not services, is the only credible way to avoid a hard border.
She tried to sell the plan directly to EU leaders at a summit in Salzburg, Austria, this week.
Speaking afterwards, Mr Tusk said that while there were some "positive elements" in Mrs May's proposals, EU leaders had agreed that "the suggested framework for economic co-operation will not work, not least because it is undermining the single market".
In response to Mrs May's latest statement, he said the UK's stance at the summit "was surprisingly tough and, in fact, uncompromising" but that he remained "convinced that a compromise, good for all, is still possible".
On Friday, the prime minister said: "Throughout this process, I have treated the EU with nothing but respect. The UK expects the same, a good relationship at the end of this process depends on it.
"At this late stage in the negotiations, it is not acceptable to simply reject the other side's proposals without a detailed explanation and counter proposals."
A stern tone, strong words.
But while there is no remote sign from the PM today that she is about to compromise, forces in the EU and in her own party are intent on forcing her to do so.
Her problem is that they want to push her in different directions.
Rhetoric doesn't change the fact that few of the players involved outside Number 10 believe that the suggestions the prime minister has put forward can be the ones that ultimately will win the day.
Read Laura's blog
She said the two sides were still "a long way apart" on two big issues: the post-Brexit economic relationship between the UK and EU, and the "backstop" for the Irish border, if there is a delay in implementing that relationship.
The two options being offered by the EU for the long-term relationship - for the UK to stay in the European Economic Area and customs union or a basic free trade agreement - were not acceptable, she added.
The first would "make a mockery of the referendum" she said, while the second would mean Northern Ireland would be "permanently separated economically from the rest of the UK by a border down the Irish Sea."
Mrs May said no UK prime minister would ever agree to that: "If the EU believe I will, they are making a fundamental mistake."
The prime minister attempted to reassure EU citizens living in the UK that, in the event no deal can be reached "your rights will be protected".
She said "no-one wants a good deal more than me", adding: "But the EU should be clear: I will not overturn the result of the referendum. Nor will I break up my country."
The BBC's Europe editor Katya Adler said EU diplomats did not consider that their officials working on Brexit negotiations had been disrespectful.
They said they had listened to the UK position and are offering a unique partnership post-Brexit, but will not agree to anything that would harm the EU.
She added that the prime minister's statement was being viewed in Brussels as a "tubthumper" designed to bolster her political position at home.
Mr Tusk followed up his remarks on Thursday by posting a photograph on Instagram of Mrs May and himself looking at cakes with the caption: "A piece of cake, perhaps? Sorry, no cherries."
The EU has argued that the UK cannot "cherry-pick" elements from its rulebook.
That was criticised by some Conservatives, including Brexiteer Iain Duncan Smith who described it as "quite insulting".
Mr Tusk's team says the Instagram presence is aimed at reaching out to a younger audience.
Labour leader Jeremy Corbyn said the prime minister's negotiating strategy "has been a disaster" and said "political games from both the EU and our government need to end" to avoid a no-deal scenario.
"The Tories have spent more time arguing among themselves than negotiating with the EU. From day one, the prime minister has looked incapable of delivering a good Brexit deal for Britain," he said.
Labour wants to see the UK join a customs union with the EU after Brexit, but remain outside of the single market.
Arlene Foster, leader of Northern Ireland's DUP, who Mrs May relies on for a Commons majority in key votes, said the prime minister was "right to stand firm in the face of disrespectful, intransigent and disgraceful behaviour by the European Union".
She added that the UK would "not countenance any new regulatory or customs barriers" between Northern Ireland and the rest of the UK.
Leading Conservative Brexiteer Jacob Rees-Mogg welcomed the "strong and forthright" speech from the prime minister but said she should abandon her Chequers plan and come forward with a Canada-style free trade agreement.
"This is the most realistic approach and similar to the EU's proposal."
Scotland's First Minister Nicola Sturgeon said that while the EU position had been "bluntly expressed" it was not new - it was just that the prime minister "hasn't been listening".
She tweeted:
The Lib Dems said Parliament should be recalled to sort out the "mess," with leader Sir Vince Cable describing the Chequers plan as "dead as a Dodo":

Theresa May has said she has the "full support of her cabinet" after a former party chairman said there should be a Conservative leadership contest.
The PM insisted she was providing the "calm leadership" the country needed.
Grant Shapps says about 30 Tory MPs back his call for a leadership contest in the wake of the general election results and conference mishaps.
But his claims prompted a backlash from loyal backbenchers, several of whom called on him to "shut up".
There has been leadership speculation since Mrs May's decision to call a snap general election backfired and the Conservatives lost their majority.
The Conservative conference this week was meant to be a chance to assert her authority over the party, but her big speech was plagued by a series of mishaps, as she struggled with a persistent cough, was interrupted by a prankster and some of the letters fell off the conference stage backdrop behind her.
Asked about leadership speculation as she attended a charity event in her constituency, Mrs May said: "What the country needs is calm leadership and that's what I am providing with the full support of my cabinet."
She said her recent speech in Florence had given "real momentum" to Brexit negotiations and she was intending to update MPs next week on her plans to help "ordinary working families" with a cap on energy bills.
Environment Secretary Michael Gove was among cabinet ministers and MPs publicly defending Mrs May on Friday morning, as the story broke that Mr Shapps was the senior Tory behind a bid to persuade her to go.
Mr Gove told BBC Radio 4 the prime minister was a "fantastic" leader, had widespread support, and should stay "as long as she wants".
He said that the "overwhelming majority of MPs and the entirety of the cabinet" backed the prime minister.
Home Secretary Amber Rudd wrote an article in the Telegraph urging the prime minister to stay, while First Secretary of State Damian Green said on the BBC's Question Time the prime minister "was determined as ever to get on with her job - she sees it as her duty to do so".
Ruth Davidson, the leader of the Scottish Conservatives, hit out at those plotting to oust Mrs May as prime minister.
Speaking to the BBC's Political Thinking podcast, she said: "I have to say, I've not got much time for them...
"I really don't think that having a bit of a cold... when you are trying to make a speech changes the fundamentals of whether Theresa May is the right person to lead the country."
There is, this morning, an operation being mounted by the government to try to show that nothing has changed in the Conservative Party in the last few days.
That Theresa May's leadership remains on track and she is, to use another of her famous phrases, just, "getting on with the job".
Except, as happened the last time she proclaimed "nothing has changed", something rather fundamental has, after all.
For the doubts that have been building about her in the party for months are now out there in the wide open.
To trigger a vote of confidence in the party leader, 48 of the 316 Conservative MPs would need to write to the chairman of the backbench 1922 committee.
A leadership contest would only be triggered if Mrs May lost that vote, or chose to quit.
Mr Shapps, who was co-chair of the party between 2012 and 2015, said no letter had been sent and said his intention had been to gather signatures privately and persuade Mrs May to stand down.
But he claimed party whips had taken the "extraordinary" step of making it public by naming him as the ringleader of a plot to oust the PM in a story in the Times.
He told the BBC: "I think it's time we actually tackle this issue of leadership and so do many colleagues.
"We wanted to present that to Theresa May privately. Now I'm afraid it's being done a bit more publicly."
He added: "The country needs leadership. It needs leadership at this time in particular. I think the conference and the lead-up through the summer has shown that that's not going to happen. I think it's time that we have a leadership election now, or at least let's set out that timetable."
But Conservative MP Nigel Evans told the BBC's Daily Politics that if Grant Shapps "can't get 48 signatures, he should just shut up: "In my chats to MPs at Westminster nobody wants an early leadership election. We just simply don't want that."
Fellow MP James Cleverly tweeted: "I've always liked Grant Shapps but he really is doing himself, the party and (most importantly) the country no favours at all. Just stop."
Among other MPs criticising Mr Shapps was Charles Walker, vice chairman of the Tory backbench 1922 committee, who suggested the plot was going to "fizzle out".
"No 10 must be delighted to learn that it's Grant Shapps leading this alleged coup," he said. "Grant has many talents but one thing he doesn't have is a following in the party."
Former minister Ed Vaizey was the first MP to publicly suggest Mrs May should quit on Thursday, telling the BBC: "I think there will be quite a few people who will now be pretty firmly of the view that she should resign."

Senior Tories have ruled out changing their rules to allow an early challenge to Theresa May's leadership, but have asked for more clarity about how long she will remain in office.
Under current rules, MPs cannot hold a new confidence vote in her leadership until December - 12 months on from last year's vote which she won.
The 1922 Committee rejected bringing forward this deadline at a meeting.
But chair Graham Brady said MPs asked for a "clear roadmap" about her future.
And amid signs of a growing grassroots revolt against Mrs May, the Clwyd South Conservative Association has passed a motion of no confidence in the prime minister.
In a ballot of its members, only 3.7% supported Mrs May, while 88.8% said they had no confidence in her.
Last month, Mrs May pledged to stand down if and when Parliament ratified her Brexit withdrawal agreement with the EU.
Some long-standing Leave campaigners want her to announce a date now, irrespective of whether a Brexit deal is completed.
Joint executive secretary of the 1922 Nigel Evans was among them, insisting on Tuesday that the calls for her to quit had become "a clamour".
Following a meeting of all Tory MPs, Sir Graham said colleagues concerned about Mrs May's leadership were free to express their concerns to him, which would be "communicated" to Downing Street.
In light of the PM's commitment to stand down if Parliament approved a Brexit deal, he said MPs were seeking "similar clarity from her" about what would happen "in other circumstances".
"I think the 1922 executive is asking on behalf of the Conservative Party in Parliament that we should have a clear road map forward," he told the BBC.
"We haven't set out a timetable, we asked her to set out a clear timetable, just to give some certainty and clarity to colleagues in Parliament and the wider Conservative Party and to the country most importantly."
Former minister Robert Halfon said it would have been "entirely wrong" to have staged another vote right now given the uncertainty surrounding Brexit.
"The rules are the rules," he told BBC News. "We are the Conservative Party, not a Stalinist Party, where you suddenly rip up the rule book and change them if you don't like them."
"It would have been behaving like a dictatorship, not the Conservative Party."
Speaking before Wednesday's meeting, a Downing Street spokesman said the prime minister had given a commitment to stand down "earlier than she would have liked" and would not lead negotiations on the UK's future relations with the EU.
But he said this did "not necessarily mean" she would quit straight away if Brexit happened on 31 October, the new deadline set by the EU for the UK's exit.
The party's most senior backbenchers met twice behind closed doors but were split on whether to change its leadership rules.
Sources suggest there was a slim majority in favour of the status quo.
But while Conservative MPs decided not to change the rules, grandee Sir Graham Brady said they wanted more clarity from the PM on when she would stand down.
Some MPs are keen that the PM signals a willingness to go soon after next month's unwanted European elections. So this could be a coup postponed - not a coup averted.
Mrs May survived a vote of no confidence in her on 12 December 2018 by 200 to 117 votes.
The ballot was triggered after 48 Tory MPs wrote to the 1922 committee's chair Sir Graham Brady to say they had lost faith in her, exceeding the threshold required.
Some of those who wanted to change the Conservative rules argued another vote of confidence should be permitted after six months, rather than a year, if a relatively high number of MPs - 30% or 40% - call for it.
But other members of 1922 Committee, who started discussing the issue on Tuesday, were sceptical of long-term rule changes to address a very specific circumstance.
They were also worried about showing further party divisions ahead of local elections next week and the potential European elections on 23 May.

Theresa May has told the Conservatives they must be the "party for everyone" and said austerity was ending in her party conference speech in Birmingham.
The prime minister said that a decade on from the financial crash, "there are better days ahead", signalling an increase in public spending.
She also defended her under-fire Brexit strategy, saying she was "standing up for Britain".
And she announced new borrowing powers for councils to build more homes.
A cap on the amount councils can borrow to fund new developments "doesn't make sense" and would be scrapped, she said.
Other promises included a "step change" in how cancer is diagnosed with a strategy aimed at increasing early detection rates, plus another freeze in fuel duty.
The prime minister - whose dancing in Kenya made headlines in August - danced on to the stage to the sounds of Abba, and immediately sought to make light of last year's difficult speech.
She joked that if she had a cough this time, it was only because she had been up all night gluing the letters on to the backdrop.
The Tory conference has been dominated by Brexit, with former foreign secretary Boris Johnson launching a fresh broadside against her Chequers plan - it is known by the country residence where it was agreed in July - for trade with the EU.
And as she prepared to deliver the speech, Conservative MP James Duddridge announced he had submitted a letter to the backbench 1922 Committee calling for a leadership contest.
In her speech there was no mention of "Chequers" specifically - with Mrs May describing her plan as a "free trade deal that provides for frictionless trade in goods".
Defending it, she warned delegates that pursuing "our own visions of the perfect Brexit" could lead to "no Brexit at all".
On austerity, Mrs May said people needed to know "that the end is in sight".
The Tories could not just "clean up a mess" they should "steer a course to a better future", she said.
"Sound finances are essential, but they are not the limit of our ambition. Because you made sacrifices, there are better days ahead."
At next year's Spending Review she said "debt as a share of the economy will continue to go down, support for public services will go up".
"Because, a decade after the financial crash, people need to know that the austerity it led to is over and that their hard work has paid off."
In her speech, Mrs May said the Tories must be "a party not for the few, not even for the many but for everyone who is willing to work hard and do their best".
"Our best days lie ahead of us", she said, adding: "Don't let anyone tell you we don't have what it takes."
She also condemned the personal abuse of politicians, speaking up for Labour's Diane Abbott and calling for an end to "the bitterness and bile which is poisoning our politics".
Mrs May made repeated attacks on Labour leader Jeremy Corbyn's politics, criticising his opposition to military action and claiming he would raise taxes "higher and higher".
But the Tories needed to "do more than criticise" Labour, she said, vowing to "make markets work in the interests of ordinary people again".
She said she wanted to help people on low incomes, ruling out any increase in fuel duty in the Budget on 29 October.
Theresa May's performance
With the complexities of Brexit, the divisions in her party, the calamity of last year's conference speech, the antics of the former foreign secretary, and of course, her own fragilities, Theresa May has struggled to find her voice - and that's got nothing to do with running out of Strepsils.
Well today she found it, and in the words of one of her cabinet colleagues, not a particularly close ally, said "she found her mojo". From the moment she danced on to the stage (who would have thought we'd ever see that), she looked comfortable in her own skin, actually happy to be there.
It sounds strange, but it is so rare to see her overtly enjoying her job. On so many occasions the public has seen a politician who seems constricted, conflicted, and ill-at-ease. For voters, frankly, if she doesn't look like she is enjoying being prime minister, why should any of us be happy about the fact she's doing it. Read Laura's full blog.
The 'end of austerity'
Philip Hammond is always wary of announcing the "end of austerity", given the fragility of economic growth and the fact that many cuts, such as to benefits, have yet to work through the system.
People are still feeling the pain. He is keener to emphasise that the effort expended bringing the public finances back towards balance - where the government raises in revenues the same at it spends on services - will not be put at risk with some form of "spending splurge".
The PM just made that task harder. Read Kamal's full blog.
The housing proposal
Lifting the cap on how much English local authorities can borrow to build traditional council houses could have a significant impact on the supply of homes for social rent.
Currently, town halls have a housing debt of about £26bn, the value of their existing stock acting as collateral.  Doing away with the cap would conservatively allow an extra £10-15bn of borrowing.  This money could be used to build an extra 15-20,000 new council homes a year over ten years.
Given that the latest annual figure for completed social rent homes is less than 6,000, this might well quadruple supply in the medium term. Even that increase would not get close to meeting demand for social housing, however.
The extra borrowing will count against the government's balance sheet and may well mean some tough decisions on cuts to budgets elsewhere, although there are arguments that the money could be seen as an investment rather than a subsidy because the new housing would provide a reliable income stream. Since 2012, council housing in England has realised a net rental surplus.
The extra borrowing would be ring-fenced for housing but it is unclear whether all of the new stock would be for social rent.  Some shared-ownership homes might be included, for example.
Although the extra borrowing freedom could come into force after early as next year, with planning and land acquisition to be sorted out, it is unlikely the boost to social housing supply will come to pass for some years.
The NHS plan
The pledge to create a new cancer strategy is not surprising - it was already one of the priority areas for the 10-year plan NHS England boss Simon Stevens has been asked to draw up in return for the £20bn funding rise the health service has been promised by 2023.
Her high profile promise was to increase early detection - defined as at stages one and two - from 50% to 75% by 2028.
Progress is already being made towards this. The existing cancer strategy has already made that a priority and in the last four years there has been an 11% improvement, meaning the NHS is already well on course to achieve this target.
Beyond that, there were few details on what it would mean for services so it looks like we will have to wait until the 10-year NHS plan is published, expected to be November, before we know more.
In response, Labour's shadow chancellor John McDonnell said Mrs May's claim on austerity was a "con" unless the chancellor takes immediate action.
He said: "If the prime minister wants to back up her words with action, Philip Hammond should announce immediately that the cuts scheduled for the next four years will be cancelled."
The SNP's Ian Blackford said Mrs May had "danced around the key issues - the disastrous impact of Tory austerity and a Tory hard Brexit".
"There is a massive gulf between her rhetoric and the reality of what is now facing the UK," he added.
Lib Dem leader Sir Vince Cable said: "As somebody who takes dancing seriously, I was delighted to see Theresa May show that she is developing her new hobby. But she was dancing on the head of a pin, confronted by an audience full of people plotting to oust her."
The Local Government Association, which has been calling for an end to the cap on borrowing for house-building, welcomed the council spending announcement.
"Many of the projects that are already under way could quickly be scaled up," Conservative councillor David Simmonds, the body's deputy chairman, said.
"Councils have been asking for this for a long time and clearly the announcement today is something that means we can get on with the job."
The CBI - which criticised Mrs May's immigration plans on Tuesday - welcomed her call to "back business" and urged MPs to support her Brexit plan to get a deal "over the line".

Donald Trump told Theresa May she should sue the EU rather than negotiate over Brexit, she has told the BBC.
The US president said on Friday at a joint news conference he had given Mrs May a suggestion - but she had found it too "brutal".
Asked by the BBC's Andrew Marr what he had said, she replied: "He told me I should sue the EU - not go into negotiations."
It came as another government member resigned over her Brexit plans.
Robert Courts said he quit as a parliamentary private secretary - an unpaid ministerial aide - at the Foreign Office to "express discontent" with Mrs May's policy before key Brexit votes on Monday.
"I had to think who I wanted to see in the mirror for the rest of my life," he said in tweet.
He could not tell his constituents he supported Mrs May's proposals "in their current form," he added.
Mr Courts replaced David Cameron as the Conservative MP for Witney, Oxfordshire in 2016.
Defending her Brexit blueprint on the Andrew Marr show, the prime minister said it would allow the UK to strike trade deals with other nations, end free movement of people, and end the jurisdiction of the European Court of Justice.
A White Paper published on Thursday fleshed out details of her plan, which advocates close links with the EU on trade in goods, but not services.
Before the paper was published, Brexit Secretary David Davis and Foreign Secretary Boris Johnson resigned, along with several junior government figures, saying it would not deliver the Brexit people voted for in the 2016 referendum.
Mrs May laughed off the president's legal action suggestion, but added: "Interestingly, what the president also said at that press conference was 'don't walk away'.
"Don't walk away from those negotiations because then you'll be stuck. So I want us to be able to sit down to negotiate the best deal for Britain."
Donald Trump declined to spell out what his advice to Mrs May had been, in an interview with US TV network CBS, but added: "Maybe she'll take it, it's something she could do if she wanted to.
"But it was strong advice. And I think it probably would have worked."
Ahead of his meeting with Mrs May, Mr Trump told the Sun newspaper her Brexit proposals would "probably kill" a trade deal with his country.
But hours later he said a US-UK trade deal would "absolutely be possible".
Leading Tory Brexiteer Jacob Rees-Mogg has called the White Paper a "bad deal for Britain".
He told the BBC's Sunday Politics: "The government unfortunately believes that Brexit is not a good thing in itself, it seems to think it has to be tempered by non-Brexit."
He said Mrs May, who campaigned to keep Britain in the EU in the 2016 referendum, had failed to grasp the "enormously positive" opportunities offered.
He described her as a "Remainer who has remained a Remainer".
He also said she would have to change her policy in order to get it through Parliament, without having to rely on Labour votes.
Mrs May urged Brexiteers in her own party to "keep their eye on the prize" of Brexit - and said her plan was the only workable way to deliver it.
Analysis by BBC legal correspondent Clive Coleman
Frankly, it is difficult to see any grounds for the UK suing the EU.
Like any other member state, the UK can sue the EU in relation to any specific measure it has taken which breaches EU law.
Such action would be heard at the European Court of Justice, the ultimate arbiter of EU law.
An example would be if the UK was denied agricultural subsidies, or structural funds to which it was entitled under EU law.
The Conservative government of David Cameron successfully sued when the European Central Bank said it would only license financial institutions within the Eurozone as clearing houses for transactions in euros.
The UK and the EU have not reached a Brexit agreement yet, so there can be no action for breach of that agreement.
Parties to a negotiation are under what are known as "procedural duties" - for instance, to act in good faith.
But it is very difficult to bring an action, within a negotiation, on that basis. Some would say that even attempting to do so would seriously harm the negotiation.
Mrs May's message comes ahead of crucial Commons votes on trade and customs policy in the coming week, with Tory Brexiteers tabling a series of amendments to the legislation.
Mr Rees-Mogg said he was not expecting either the Customs Bill or the Trade Bill to be voted down at this stage. There are also likely to be amendments tabled by Remain supporting MPs.
Mrs May told Andrew Marr: "Some people are saying they want to vote in the Trade Bill to keep us in the customs union. I say that's not acceptable, that's not what the British people voted for.
"Others are saying that perhaps we cannot have the bill at all. That would be damaging to our 'no deal' preparations.
"So let's just keep our eyes on the prize here. The prize is delivering leaving the European Union in a way that's in our national interest."
Mrs May insists her plans would allow the UK to strike its own trade deals, despite agreeing a "common rulebook" with the EU on cross-border trade.
She said such rules were needed to protect jobs in firms with supply chains that crossed borders and deal with the Irish border issue.
Labour Party chairman Ian Lavery said Mrs May's "so-called plan" did not "stand up to scrutiny".
"No-one - not the public, Parliament or the Conservative party - is happy with Theresa May's offer. This has descended into a shambles," he said.
Labour MP Ian Murray, a member of the People's Vote campaign, said the British people needed a vote on the final deal.
Labour Deputy Leader Tom Watson said it was not the party's policy to back another referendum - but said it should not be ruled out.

The UK cannot expect to hold on to "bits" of its membership after leaving the EU, Theresa May has said.
The prime minister's comment came after she was asked whether she would "prioritise" controlling immigration over staying in the single market.
She told Sky News her approach was not "muddled", following criticism by the UK's former EU ambassador.
Mrs May, whose critics have demanded more detail of her aims, promised to provide this in "the coming weeks".
But Labour urged the prime minister to give "more clarity" ahead of the "most important negotiations for a generation".
Brexit talks with the EU are expected to begin as early as April.
There has been much debate in recent weeks about the nature of the deal the government is aiming for, in particular whether controls on the movement of EU citizens will mean the UK leaves the European single market and customs union.
By Susana Mendonca, BBC political correspondent
Theresa May doesn't like to give a running commentary on Brexit, so you have to read between the lines on this one.
While she didn't go as far as to say she would ditch single market access in favour of being free to control EU immigration, she certainly appeared to hint at it.
Mrs May said the UK would have control of its borders and the best possible trade deal with the EU. She didn't commit to maintaining "single market access", and she suggested that people who thought the country could keep "bits of EU membership" were missing the point that it "would be leaving".
This failure to commit to the single market will be music to the ears of Brexiteers. To Remainers it will raise concerns that a "hard Brexit" could be on the offing.
But, as with so much in the Brexit debate, clarity over the UK's position in the negotiations, due to start very soon, remains lacking.
Sir Ivan Rogers, who resigned as the UK's ambassador to the EU last week, criticised "muddled thinking" among ministers.
But Mrs May told Sky News's Sophy Ridge on Sunday: "Anybody who looks at this question of free movement and trade as a sort of zero-sum game is approaching it in the wrong way.
"I'm ambitious for what we can get for the UK in terms of our relationship with the European Union because I also think that's going to be good for the European Union. Our thinking on this isn't muddled at all."
However, it was "important to take some time" to look at the "complexity of the issues", she added.
The prime minister has promised to invoke Article 50 of the Lisbon Treaty - getting formal Brexit negotiations with the EU under way - by the end of March.
Asked whether she was "prepared to prioritise full control over immigration above membership of the single market", Mrs May said: "Often people talk in terms as if somehow we are leaving the EU, but we still want to kind of keep bits of membership of the EU.
"We are leaving. We are coming out. We are not going to be a member of the EU any longer.
"So the question is what is the right relationship for the UK to have with the European Union when we are outside. We will be able to have control of our borders, control of our laws.
"This is what people were voting for on 23 June.
"But of course we still want the best possible deal for us, companies to be able to trade, UK companies to be able to trade in and operate within the European Union and also European companies to be able to trade with the UK and operate within the UK."
In the referendum last summer, voters opted by 51.9% to 48.1% in favour of Brexit.
Mrs May told Sky: "Over the coming weeks, I'll be setting out more details of my plan for Britain. Yes, that's about getting the right deal for Brexit, but it is also about economic reform...
"It's about getting the right deal internationally, but it's also about a fair deal at home."
Following Mrs May's interview, shadow Brexit secretary Sir Keir Starmer told the BBC: "She had one question put to her three times and still didn't answer it, which is, 'Are you prioritising immigration over access to the single market?'
"That was the question she didn't want to answer. And I think now, 10 to 11 weeks from the triggering of Article 50, and the most important negotiations for a generation, we need more clarity than that, and we haven't got it."
Liberal Democrat leader Tim Farron said Mrs May's comments "confirmed she is taking us towards a disastrous hard Brexit that will leave our country poorer and more divided".
But Richard Tice, co-chairman of the Leave Means Leave campaign, said: "We welcome the prime minister's commitment to taking back control of Britain's borders, therefore ending preferential treatment for EU citizens.
"She is right that issues of trade and immigration are not binary because when Britain leaves the single market and the customs union, though freedom of movement will cease, Britain's ability to trade with the EU and access the single market will continue."
Labour MP and leading supporter of pro-EU Open Britain group, Chuka Umunna, said:"Any trading arrangement outside the single market would erect barriers with our largest trading partner and would be disastrous for the UK economy, jobs and businesses."
Europhile former Conservative chancellor Ken Clarke told BBC One's Andrew Marr Show: "Theresa needs to address the more serious question of the muddle [Sir Ivan is] complaining about, see whether she agrees with him and decide whether she can improve the way in which she organises the government to get to a proper conclusion."

Conservative MPs Boris Johnson and Jeremy Hunt are going head-to-head to become the next Tory leader and prime minister.
After getting the backing of Tory MPs, they are now waiting to hear whether they have won the support of around 160,000 Conservative Party members in the ballot for the top job.
Voting closes at 17:00 BST with the winner to be announced on Tuesday morning.
But where do the potential new prime ministers stand on key issues?
Here's a quick guide to their positions on Brexit, immigration, tax, spending, health and social care and education.
More than half the ballot papers sent to the homes of party members are thought to have been returned so far, and the winner will be announced on 23 July.
In a recent Conservative Home poll of 1,300 party members, Mr Johnson came out on top.
The bookmakers are offering odds on who the next leader will be and Mr Johnson is the clear favourite.
The two candidates have been taking part in a series of hustings or debates to try to win over party members. The last one was on Wednesday, 17 July.
Out of the two, Jeremy Hunt, who replaced Mr Johnson as foreign secretary last year, has more experience in government and has held more cabinet posts.
He was made culture secretary under the coalition government in 2010 and oversaw the 2012 London Olympics before becoming health secretary.
In 2018, Mr Hunt became the longest-serving health secretary, and arguably one of the most controversial, since the NHS was created, completing six years in the role.
During his tenure, Mr Hunt clashed with unions over contracts for junior doctors, who took part in a series of walkouts in 2015.
Mr Johnson was the MP for Henley for seven years before being elected Mayor of London in 2008. He returned to Parliament as MP for Uxbridge and South Ruislip in 2015.
On a personal level, the two candidates have similar backgrounds - being educated at private schools and both attending Oxford University.
Mr Johnson was born in New York to English parents, giving him dual nationality. But he later renounced his US citizenship.
Tory MPs voted five times to choose their preferred candidates.
In the fifth and final round of voting, Boris Johnson came out on top with 160 out of the 313 votes cast. One ballot paper was spoiled.
Jeremy Hunt was second with 77 votes and Michael Gove was eliminated after securing the support of 75 fellow MPs.
But 10 candidates started the race on 10 June.
Mark Harper, Andrea Leadsom and Esther McVey were eliminated in the first round after failing to get the necessary 17 votes.
Matt Hancock, who won 20 votes, later withdrew from the contest, pledging his support for Boris Johnson.
Dominic Raab was eliminated in round two, after falling three votes short of the required 33.
Rory Stewart's campaign came to an end after he finished last in the third ballot.
Sajid Javid and Michael Gove were knocked out after they finished last in last two successive ballots.
Speaker John Bercow has thrown the UK's Brexit plans into further confusion by ruling out another vote on the PM's deal unless MPs are given a new motion.
In a surprise ruling, he said he would not allow a third "meaningful vote" in the coming days on "substantially the same" motion as MPs rejected last week.
With 11 days to go before the UK is due to leave the EU, ministers have warned of a looming "constitutional crisis".
The UK is currently due to leave the EU on 29 March.
Theresa May has negotiated the withdrawal deal with the EU but it must also be agreed by MPs.
They have voted against it twice, and the government has been considering a third attempt to get it through Parliament.
Mr Bercow cited a convention dating back to 1604 that a defeated motion could not be brought back in the same form during the course of a parliamentary session.
He said the second vote on the prime minister's deal last week was "in order" as it was substantially different to the first, but any further votes must pass the "test" he set out to be allowed.
The BBC's political editor Laura Kuenssberg said the speaker's intervention does not stop Brexit from happening, but it makes it "extremely unlikely" that the government will put another vote on the deal to Parliament this week.
She said this makes it less likely the prime minister will ask EU leaders at a summit this week for a short extension - which Mrs May had said she would do if her deal got through Parliament.
This in turn makes it more likely there will be a longer delay to Brexit, she added.
She said: "The conclusion that most people in Westminster would reach from that means that we're heading - it's likely - towards a closer relationship with the European Union, a softer Brexit than the one Theresa May has set out."
However, she added: "That said, the government does believe that, although they're not clear about what it might be yet,  there is a way round this complication - but it is another significant obstacle for Number 10 tonight and it has, in the words of one senior official, made things significantly more complicated."
Mr Bercow's statement appeared to take Downing Street by surprise, with the prime minister's official spokesman saying it had not been warned of its contents "or indeed the fact that he was making one".
Later, a Number 10 spokesman said the statement had been noted and required "proper consideration".
The role of the speaker, who is the highest authority of the House of Commons, includes controlling debates, calling MPs to speak and choosing which amendments can be debated.
Analysis by BBC political correspondent Iain Watson
How can the government get another vote on Theresa May's deal?
Well, first of all, rules are there to be changed.
If MPs suspend or change the "standing orders" of Parliament, they could get the Brexit deal back on the agenda.
Secondly, the government could change the proposition on offer.
The former Attorney General Dominic Grieve has suggested that something "substantially" different would be to ask Parliament to vote for the deal subject to a referendum.
Or change the Parliament?
If MPs can't discuss the same thing in the same session of Parliament, why not simply start a new one?
Read Iain's complete analysis here.
The prime minister had been expected to submit her Brexit deal for MPs to vote on for a third time this week - a week after they rejected it by 149 votes - and ahead of the EU summit on Thursday.
Last week MPs also voted in favour of ruling out leaving the EU without a deal, and in favour of extending the Brexit process - though an extension would have to be agreed by all 27 EU member states.
Brexit minister Kwasi Kwarteng has confirmed Mrs May will be writing to European Council President Donald Tusk to ask to postpone the UK's exit date.
If the EU agreed, the government would ask both Houses of Parliament to approve the change, he said.
Mr Kwarteng said the length of the extension would depend on "whether the meaningful vote goes through or not".
"If we have a deal... we will ask for a short extension," he said.
"Now if for whatever reason that vote doesn't happen, or is frustrated or is voted down, we will probably ask for a long extension of the period - and that would be a matter for the EU and for our government to decide."
European leaders are expected to discuss the UK request to extend the Brexit process and delay the UK's departure at the summit on Thursday.
Shadow Brexit minister Matthew Pennycook said the fact that Article 50 needed to be extended was "a mark of this government's failure".
Meanwhile, the government has been trying to convince the DUP and Tory Brexiteers, who have both voiced concerns about the backstop - the controversial arrangement to prevent physical checks on the border between Northern Ireland and the Republic of Ireland - to vote in favour of the deal.
The DUP has opposed the deal up to now and are seeking further "clarifications" on the government's legal advice about the backstop, and how the UK could exit it.
Ministers and MPs supportive of Mrs May's deal expressed anger at the timing of Mr Bercow's intervention.
Conservative MP James Gray, who plans to vote for the deal after rejecting it twice, said he was "absolutely furious"; while fellow Tory Greg Hands suggested Mr Bercow was the only person in the country who was "accountable to nobody".
Solicitor General Robert Buckland warned there was now a "constitutional crisis" and suggested the onus was on the EU to come up with "new solutions" to enable MPs to vote on the deal again.
"Frankly we could have done without this, but it is something we are going to have to deal with," he said.
He suggested "there were ways around this" - including potentially cutting short the current session of Parliament, a move which would lead to calls for a general election.
Some opponents of the PM's Brexit deal welcomed the Speaker's ruling.
Conservative former cabinet minister Owen Paterson said it was a "game-changer" and would "concentrate minds" ahead of Thursday's EU summit.
Sir Bill Cash, chairman of the European Scrutiny Committee, said it seemed to make an "enormous amount of sense" given that the Brexit deal has been defeated twice and there would need to be a "substantial difference" to allow a third vote.
But the SNP's Westminster leader Ian Blackford suggested there was now a "constitutional crisis" and he suggested the prime minister should "immediately" call a meeting of opposition leaders.
And Brexiteer Nadhim Zahawi, Tory minister for children and families, told BBC Newsnight that the Speaker had "made it now much more difficult to have the short extension" and a meaningful vote, "therefore the longer extension is now clearly on the table. I don't believe that's a good thing".
By BBC Brussels reporter Adam Fleming
The EU's official position is that they are waiting for Theresa May to come to a summit in Brussels on Thursday with a clear statement about how she plans to proceed, and there definitely won't be any more negotiations when she gets here.
Unofficially, EU officials wonder if the government can get itself out of this situation, either with Parliamentary wizardry or by coming up with UK-only additions to the package, such as new guarantees about the role of Northern Ireland's Stormont Assembly in the future.
And could the joint UK/EU decision about an extension to the Brexit process, due to be taken on Thursday, be appended to the deal and then count as something new enough to justify another vote in the Commons?
But explain to diplomats that the solution might be the Queen closing Parliament and re-opening a new session with a speech and their reactions are priceless.

The UK will have to "face the consequences" if it opts to leave without a deal, the EU's chief Brexit negotiator has said.
Michel Barnier told BBC Panorama the thrice-rejected agreement negotiated by Theresa May was the "only way to leave the EU in an orderly manner".
He also insisted Mrs May and her ministers "never" told him during Brexit talks she might opt for no deal.
Publicly, Mrs May has always insisted no deal is better than a bad deal.
Meanwhile, the Office for Budget Responsibility has said the UK will fall into recession next year if there is a no-deal Brexit.
The fiscal watchdog said economic growth would fall by 2% by the end of 2020 if it left the bloc without an agreement.
In his first UK broadcast interview - conducted in May before the start of the Conservative leadership contest - Mr Barnier was asked what would happen if the UK "just tore up the membership card" for the EU.
"The UK will have to face the consequences," he replied.
Asked whether the UK had ever genuinely threatened to leave in such a way with no deal, Mr Barnier said: "I think that the UK side, which is well informed and competent and knows the way we work on the EU side, knew from the very beginning that we've never been impressed by such a threat.
"It's not useful to use it."
Panorama: Britain's Brexit Crisis will be broadcast on Thursday at 21:00 BST.
Conservative Party leadership contender Jeremy Hunt told BBC Radio 4's Today programme that the fact the EU "never believed that no deal was a credible threat" was "one of our mistakes in the last two years".
He said while there will be economic consequences to no deal, "we are much better prepared for no deal than we were before".
He said the issue of the Northern Ireland border could be solved with "existing technology" and the controversial Irish backstop, which aims to prevent a hard border on the island of Ireland, "isn't going to happen".
Former Tory leader Iain Duncan Smith, a key figure in Boris Johnson's leadership campaign, accused Mr Barnier of trying to "threaten" the UK.
He said Mr Barnier's remarks were an indictment of Britain's negotiating strategy and showed "how useless" Mrs May's approach had been.
Leadership frontrunner Mr Johnson was asked for an interview by Panorama, but he declined.
Elsewhere in the programme, Mrs May's de facto deputy David Lidington revealed that a senior EU official made a secret offer to the UK to put Brexit on hold for five years and negotiate a "new deal for Europe".
Mr Lidington said the offer was passed on in 2018 by Martin Selmayr, a senior aide to EU Commission President Jean-Claude Juncker.
"Martin sort of said, 'Look, why don't we have a deal whereby we just put all this on ice for five years?'
"Let's see how things go, let's get the UK involved with France and Germany, let's see how the dust settles and let's talk about whether we can come to a new deal for Europe.'"
In his own interview for the programme - also recorded in May - Mr Selmayr said he was "very certain" the UK was not ready to leave without a deal before the original Brexit deadline in March this year.
"We have seen what has been prepared on our side of the border for a hard Brexit. We don't see the same level of preparation on the other side of the border," he added.
In another interview for the programme, the EU Commission's First Vice-President, Frans Timmermans, said UK ministers were "running around like idiots" when they arrived to negotiate Brexit in 2017.
Mr Timmermans said while he expected a "Harry Potter-like book of tricks" from ministers, instead they were like a character from from Dad's Army.
In an interview in March 2019 with the BBC's Nick Robinson, Mr Timmermans said he found it "shocking" how unprepared the UK team was when it began negotiations.
"We thought they are so brilliant," he said. "That in some vault somewhere in Westminster there will be a Harry Potter-like book with all the tricks and all the things in it to do."
But after seeing the then-Brexit Secretary David Davis - who resigned over his disagreements with the deal - speaking in public, his mind changed.
"I saw him not coming, not negotiating, grandstanding elsewhere [and] I thought, 'Oh my God, they haven't got a plan, they haven't got a plan.'
"That was really shocking, frankly, because the damage if you don't have a plan...
"Time's running out and you don't have a plan. It's like Lance Corporal Jones, you know, 'Don't panic, don't panic!' Running around like idiots."
Mr Timmermans - interviewed two months before Mrs May announced her resignation - also criticised Boris Johnson's approach to Brexit negotiations from when they began.
"Perhaps I am being a bit harsh, but it is about time we became a bit harsh. I am not sure he was being genuine," he said.
"I have always had the impression he is playing games."
Negotiations between the UK and EU began in 2017 after Prime Minister Theresa May triggered the Article 50 process to leave the bloc.
At the end of 2018, a withdrawal agreement was settled between the two sides and EU officials said the matter was closed.
But MPs voted against the plan three times, which led to a number of delays to the exit date - now set for 31 October.

Tony Blair has said it is his "mission" to persuade Britons to "rise up" and change their minds on Brexit.
Speaking in the City of London, the former prime minister claimed that people voted in the referendum "without knowledge of the true terms of Brexit".
He urged "a way out from the present rush over the cliff's edge".
Former Tory leader Iain Duncan Smith said the comments were arrogant and undemocratic but Lib Dem Nick Clegg said he "agreed with every word".
Former UKIP leader Nigel Farage said Mr Blair was "yesterday's man" while Downing Street said it was "absolutely committed" to seeing Brexit through.
Foreign Secretary Boris Johnson added: "I urge the British people to rise up and turn off the TV next time Blair comes on with his condescending campaign."
Prime Minister Theresa May wants to trigger formal Brexit talks by the end of March - a move which was backed in the House of Commons by MPs last week.
Mr Blair, who was UK prime minister between 1997 and 2007, used the speech to the pro-European campaign group Open Britain to argue that leaving the EU would be "painful" for Britain and Europe and the benefits would be "largely illusory".
Mr Blair, who campaigned to remain in the EU, said that while he accepted that people voted to leave by 52% to 48%, he would recommend looking again at Brexit when "we have a clear sense of where we're going".
Pressed on whether he thought there should be a second referendum, he said: "All I'm saying is a very, very simple thing, that this is the beginning of the debate - that if a significant part of that 52% show real change of mind, however you measure it, we should have the opportunity to reconsider this decision.
"Whether you do it through another referendum or another method, that's a second order question.
"But this issue is the single most important decision this country has taken since the Second World War and debate can't now be shut down about it."
Analysis by political correspondent Tom Bateman
Tony Blair's warnings about the risks of Brexit might have made some viewers believe the referendum campaign was still being fought.
But his central political point takes us onto new ground - that the voters could still change their minds about leaving the EU and Remainers should persuade them to do so.
It will be seen by some as a call to arms - Tony Blair's Brexit insurrection.
Brexiteer MPs were unsurprisingly excoriating, with the foreign secretary hinting at what Mr Blair's opponents see as his toxicity after the Iraq war.
But importantly the former PM's speech raises a tactical question for Remainer MPs wondering what to do next: fight for Brexit on their terms or fight Brexit itself.
In the absence of an effective opposition, he said pro-Europeans needed to build a "movement " reaching across party lines, he said, adding the institute he is launching would play its part in developing the arguments to rethink the country's position.
"The debilitation of the Labour Party is the facilitator of Brexit. I hate to say that, but it is true."
While he fully accepted immigration was "a substantial issue", he said it had become the "primary consideration" for the government and suggested the public were more concerned about arrivals from outside the EU.
Mr Blair has faced criticism in the past for his government's decision to allow people from Poland, Hungary and the Czech Republic to work in Britain without restrictions, while most EU states imposed transitional controls to slow the rate of migration.
Mr Blair stressed that the Conservative government only "has bandwidth for only one thing - Brexit", at the cost of the NHS, education, investment in communities, the rise in serious crime, the increased burden of social care and control of immigration.
"This is a government for Brexit, of Brexit and dominated by Brexit, he said, adding that the issue was the government's "waking thought, the daily grind, the meditation before sleep and the stuff of its dreams or nightmares".
Iain Duncan Smith, who was a prominent Leave campaigner, said Mr Blair had shown the political elite was completely out of touch with the British people.
He compared Mr Blair returning to the political scene to the British horror comedy "Shaun of the Dead", with "his hands outstretched to tell the British people they were too stupid to be able to understand what they were voting on", adding that this "is both arrogant and a form of bullying".
And Mr Farage described Mr Blair as a "former heavyweight champion coming out of retirement" who would "end up on the canvas".
Kate Hoey, a prominent Leave campaigner and Labour former minister, told the BBC she did not think anyone would take Mr Blair's "patronising" opinion seriously.
"I'm really quite sad that he doesn't feel that as a former prime minister - he's travelled all round the world, he's made himself lots of money - he's come back. Why doesn't he just now go and find himself a job?"
But Alan Johnson, who led Labour's campaign to keep Britain in the EU - urged people to listen to the message, not the messenger.
Stressing he would not rule out a second referendum, Mr Johnson said people are concerned that Britain could end up as a "low tax, anything goes, race-to-the-bottom kind of country" post Brexit.
Supporters of leaving the EU argue it will free up the UK to trade better globally and give the government better control of immigration.
Earlier this month, MPs overwhelmingly agreed, by 494 votes to 122, to let the government begin the UK's departure from the EU by voting for the Brexit bill.
The Commons vote prompted splits in the Labour party. Despite calls by leader Jeremy Corbyn for his party to back the government, 52 MPs rebelled.
Lib Dem attempts to amend the bill to include a provision for another referendum were defeated by 340 votes to 33.

Some EU leaders may be prepared to compromise on the free movement of people to help Britain stay in the single market, Tony Blair has said.
He told the Today programme one option was for Britain "staying within a reformed EU".
The ex-PM said he would not disclose conversations he had had in Europe - but insisted he was not speaking "on a whim".
The government insists Brexit will give the UK greater control of its borders.
Labour's shadow chancellor, John McDonnell, said Mr Blair "hadn't really listened to the nature of the debate going on in the pubs, the clubs and school gates".
"We have to respect the referendum result," Mr McDonnell said, adding that Labour could "negotiate access to the single market".
Mr Blair spoke to the BBC after he argued in an article for his own institute that there was room for compromise on free movement of people.
He told Today the situation in Europe was different to when Britain voted to leave the EU - a move Mr Blair described as "the most serious it's taken since the Second World War".
He said France's new president, Emmanuel Macron - whose political party was formed last year - was proposing "far-reaching reforms" for the EU.
"Europe itself is now looking at its own reform programme," Mr Blair said.
"They will have an inner circle in the EU that will be part of the eurozone and an outer circle."
When pressed on what evidence there was to suggest European nations would compromise, Mr Blair said: "I'm not going to disclose conversations I've had within Europe, but I'm not saying this literally on the basis of a whim.
"They will make reforms that I think will make it much more comfortable for Britain to fit itself in that outer circle."
He said "majorities" of people in France, Germany and the UK supported changes around benefits and with regards to those who come to Europe without a job.
"I'm not saying these could be negotiated," Mr Blair said.
"I'm simply saying if we were looking at this from the point of view of the interests of the country, one option within this negotiation would be Britain staying within a reformed European Union."
He said the majority of EU migrants in the UK are "people we want in this country".
EU leaders have previously said the UK must accept free movement of people if it wants to stay inside the single market.
But in his article for the Institute for Global Change, Mr Blair said senior figures had told him they were willing to consider changes to one of the key principles of the single market.
"The French and Germans share some of the British worries, notably around immigration, and would compromise on freedom of movement," he wrote.
But last week the EU's chief negotiator, Michel Barnier, said the freedom of movement of people, goods, services and capital - the key principles of the single market - were "indivisible".
Prime Minister Theresa May has pledged to control EU migration and has reiterated her commitment to reducing net migration to the tens of thousands.
She has said that outside the single market, and without rules on freedom of movement, the UK will be able to make its own decisions on immigration.
Mr Blair also said more was known now about the effects of the Brexit process on the UK.
"We know our currency is down significantly, that's a prediction by the international markets as to our future prosperity. We know businesses are already moving jobs out of the country.
"We know last year we were the fastest-growing economy in the G7. We're now the slowest."
Mr Blair accepted Labour was behind its leader Jeremy Corbyn "for now".
But he warned if Brexit was combined with leaving the single market, and "the largest spending programme Labour had ever proposed" the country "would be in a very serious situation."
Mr Blair said leaving the single market was a "damaging position" shared by Labour and he urged the party's leadership to champion a "radically distinct" position on Europe.
But Jeremy Corbyn said Labour's position on free movement was "very clear", adding: "We would protect EU nationals' rights to remain here, including the rights of family reunion."
Responding to Mr Blair's comments, the party leader said: "I think our economy will do very well under a Labour government.
"It will be an investment-led economy that works for all - so we won't have zero-hour contracts, insecure employment.
"We won't have communities being left behind."
Mr Blair has previously said Brexit was an issue he felt so strongly about, that it tempted him to return to politics.
But Labour MP Frank Field, who backed Brexit, said he did not think Mr Blair was "a person to influence public opinion now".
"We're now set on the course of leaving [the EU]. We actually need a safe harbour to continue those negotiations when we're out.
"And I wouldn't actually be believing those people who are set on destroying our attempts to leave, who are now appearing as wolves in sheep's clothing."
Richard Tice, of pro-Brexit group Leave Means Leave, said Mr Blair's comments "demonstrate how out of touch he is with British voters".
"The former prime minister believes that freedom of movement is the only issue with the EU, when in reality the British people also voted to leave in order to take back control of our laws and money and no longer be dictated to by the European Court of Justice," he added.
Conservative MEP David Campbell Bannerman said Mr Blair's assertion that Britain could find a way to remain within a reformed EU was a "dodgy claim, as opposed to a dodgy dossier".
"We've heard this all before. David Cameron was given such assurances and in the end the EU did nothing for him.
"If they do nothing for Cameron, they're not going to do anything for Blair, I'm afraid."

Tony Blair has urged European leaders to reform the EU so British people "change their mind" about Brexit.
The former prime minister argued that if "comprehensive" immigration reforms are offered, voters will realise their "genuine underlying grievances" can be addressed.
He thinks Brexit can then be "averted" via another referendum, this time on the final deal reached with the EU.
Mr Blair, who opposed Brexit, also said Northern Ireland could be at risk.
Speaking to BBC Radio 4's Today programme, he said: "I find it not just disappointing but sickening that people should really be prepared to sacrifice peace in Northern Ireland on the altar of Brexit."
Brexit campaigners dismissed his remarks.
"Former prime ministers who no longer believe in our great nation are engaged in a desperate last ditch attempt to defy the largest democratic mandate ever in the UK," said Leave Means Leave's Richard Tice.
"Disgracefully, they are using the Irish border as their proxy, ignoring the technological solutions that solve the issue."
Mr Blair's speech, in Brussels, was the second warning about leaving the EU by a former prime minister in two days, following Sir John Major's intervention on Wednesday.
He said that Labour should "say what it really believes" on Brexit - which was that leaving the EU will "make problems worse".
If he was still in charge, he said, "I would be hammering the Tories all the time" on the "destructive impact" of Brexit.
"We could be making that case so forcefully," he added.
Mr Blair earlier set out the three steps he said could lead to a "reconsideration of Brexit".
These are firstly showing voters that Brexit "has turned out much more complex and costly than they had thought", secondly, responding to their grievances, especially around immigration, and thirdly the EU accepting the vote as a "wake-up call" to change.
"Reform in Europe is key to getting Britain to change its mind," he told the European Policy Centre think tank, calling for "a comprehensive plan on immigration control, which preserves Europe's values but is consistent with the concerns of its people and includes sensitivity to the challenges of the freedom of movement principle".
He also wants a "roadmap for future European reform".
Conservative MP Nigel Huddleston hit back, tweeting: "As Tony Blair lectures today's politicians on what we should be doing on Brexit one wonders if he has the self-awareness to realise one of the key reasons we are leaving the EU is because of his inability to control immigration when he was PM for a decade."
Mr Blair's views on Brexit are not shared by the present-day leadership of the Labour Party - Jeremy Corbyn says the result should be respected and is not calling for a second referendum.
Speaking on the Today programme, Mr Blair said Mr Corbyn's recent commitment to a customs union with the EU was "sensible", but warned Labour will "very soon find that we've got to move further in order to escape the dilemma ourselves".
On Friday Prime Minister Theresa May will deliver a major speech setting out the UK's strategy for the next phase of the negotiations, including striking a new free trade deal with Brussels.
On Wednesday she attacked EU proposals for Northern Ireland to stay in the customs union, saying they undermined the UK's constitutional integrity.
Foreign Secretary Boris Johnson has suggested the row about Northern Ireland is being stoked by people who want to "frustrate" Brexit.

Tory ministers have rallied round Theresa May after her conference speech on Wednesday was marred by mishaps.
First Secretary of State Damian Green said it was "nonsense" to suggest she should quit because her speech was interrupted by a cough and a prankster.
He said the prime minister was "as determined as ever" to get on with the job. Home Secretary Amber Rudd said Mrs May was doing an "excellent job".
But ex-minister Ed Vaizey said "quite a few people" wanted her to quit.
The BBC's Laura Kuenssberg said that while many MPs wanted her to stay as leader, there were "emerging plots".
These involved Tory MPs trying to gather support to approach Mrs May privately and persuade her to stand aside.
This group will only act if they feel they have the numbers to do so "quickly and cleanly", the BBC political editor added, saying: "It is just not clear at the moment where the numbers really lie."
Speaking on BBC Radio Oxford, Mr Vaizey, who was sacked as a culture minister when Mrs May became leader in 2016, said most people were being "pretty loyal" in public but were "very concerned" in private. He added: "I think there will be quite a few people who will now be pretty firmly of the view that she should resign."
Politics is certainly cruel, and clearly the prime minister was the victim of some appallingly bad luck.
A former minister told me that after the election and Grenfell it would only have taken one more event to trigger her exit and this "was the event".
In normal political times, it is probably the case that what one minister described as a "tragedy" would have led to a prime minister being forced out or quitting.
But these aren't normal times. Allies of Theresa May say Wednesday's events have shown her resilience and determination in spades, demonstrating exactly why she deserves to stay in the job.
But speaking on BBC One's Question Time Mr Green said: "I know that she is as determined as ever to get on with her job - she sees it as her duty to do so. She will carry on and she will make a success of this government".
He said it was "complete nonsense" to suggest that having a cold or having an "unfunny pillock" interrupt her speech meant she was the wrong person for the job.
The PM's speech was seen as her opportunity to assert her authority, after her decision to call a snap election backfired.
She apologised to activists and put forward new policies, including an extra £2bn to build 25,000 new council houses and social homes for rent by 2021 and draft legislation for a cap on standard tariff energy bills, which she said were part of her mission to improve people's lives and promote a "British dream".
But a nagging cough and croaky voice forced the PM to stop on more than one occasion. Prankster Simon Brodkin - also known as his TV persona Lee Nelson - was arrested by Greater Manchester Police after briefly interrupting the PM and giving her and a mock P45 redundancy notice he claimed was from Boris Johnson.
To add to Mrs May's woes, some of the letters fell off the conference stage backdrop behind her. By the end it read: "Building a country that works or everyon."
Cabinet ministers including Mr Johnson, Michael Gove and Jeremy Hunt have praised the speech and a No 10 source said colleagues had been "offering support" and declared "resignation is not an issue" for Mrs May.
But backbench Tory MP Mark Pritchard said on Twitter that a "small number" of colleagues were raising questions over her leadership in text messages.
Mr Pritchard, one of Mrs May's trade envoys, warned those "circling above" that there was only one message: "There is no vacancy at No 10."
And his colleague Charles Walker, vice chairman of the 1922 committee of backbench Tory MPs, praised Mrs May's "heroic" efforts on stage, telling the BBC: "You are actually allowed to be ill occasionally and that's what she was, ill - and she was ill because she's been working so damn hard on behalf of this country."
Ex-chancellor Lord Lamont warned against "political instability" during the "massively important" Brexit negotiations.
"I think what people ought to remember before they pitch in is that we are facing a very serious situation at the moment," he said.
Speaking on BBC Radio 4's Today programme, Business Secretary Greg Clark said people admired the "poise" and "guts" the PM showed to get through her speech.
He also said the fact that a comedian was able to get within yards of the prime minister showed a "weakness in the system".
Security at future Conservative events is to be reviewed. The prankster, Mr Brodkin, was later released by police who said he had "legitimate accreditation" to attend the event.
Former Conservative deputy chairman Lord Ashcroft said there was an air of a party that did not "know what it is doing".
But Business Minister Margot James told the BBC's Daily Politics she believed the coverage of the speech had been "pretty vicious" and Theresa May was "a very good prime minister".
Asked about reports of MPs plotting against her, Ms James said: "I think there will be a small minority of disaffected colleagues who are angry, bitter for whatever personal reasons they've got, and I do hope my other colleagues will have the sense to disown them."

Conservative MP Stephen Phillips has quit over "irreconcilable policy differences" with the government.
The MP, who has held the Lincolnshire seat of Sleaford and North Hykeham since 2010, backed leaving the EU but has accused ministers of ignoring Parliament since the Brexit vote.
He said he was "unable properly to represent the people who elected me".
It comes as Theresa May said she was confident she would win a legal battle over her approach to Brexit talks.
On Thursday, three High Court judges ruled the government cannot officially notify the EU of its intention to leave, thus beginning formal talks, without Parliament's support.
In a series of phone calls, the prime minister told European Commission president Jean-Claude Juncker and Germany's Angela Merkel that the government believed it would win its Supreme Court appeal against the ruling and she was committed to triggering Article 50 by March 2017.
Although Mr Phillips represents a safe Conservative seat, his surprise departure increases the pressure on Mrs May's government - which has a working majority of 17.
It is not yet clear whether Mr Phillips, who won the seat last year with a majority of more than 24,000, will stand as an independent in a future by-election although this is thought to be unlikely.
by Ross Hawkins, BBC political correspondent
The government's values were no longer his values. On child refugees, on the use of aid money, on the handling of Brexit, he dissented from a party he thought was heading inexorably to the right.
That is the view from sources close to Stephen Phillips. One said he twice rejected a meeting with the prime minister.
Will other Tories follow? Some on the party's left tell me they'd rather stay and fight. Others reflect ruefully that unlike him they have no well-paid alternative career as a barrister.
A by-election in a safe seat won't much trouble party bosses. But while Downing Street doesn't want one, the departure of - yet another - Tory MP means the voices calling for a swift general election will grow a little louder.
The politician, who is a barrister and part-time Crown Court judge, is the second Conservative MP to stand down in as many weeks - Zac Goldsmith last week forced a by-election over his opposition to expanding Heathrow airport.
Sources say Mr Phillips informed party whips earlier this week that he would resign as an MP because he felt his values were not the values of the government.
He has been critical of the government's approach to Brexit since June's Leave vote, accusing Theresa May of trying to "ignore the views" of Parliament and avoiding scrutiny of the government's negotiating position.
In a recent newspaper article, he suggested the government was "lurching to the right" and that its attempt to start negotiations with the EU without the explicit approval of Parliament was "divisive and plain wrong".
In a statement, he did not spell out the specific reasons for his resignation but said: "It has become clear to me over the last few months that my growing and very significant policy differences with the current government mean that I am unable properly to represent the people who elected me".
However, in a letter to his constituency chairman, Mr Phillips attacked the government for "shirking" responsibility for unaccompanied child refugees and changes in the way international aid is spent.
Mr Phillips said: "Some will label me a quitter or, no doubt, worse. Those are labels with which I can live. The label Conservative no longer is."
In last year's election, Mr Phillips won a majority of 24,115, with 56% of the vote. Labour finished second, closely followed by UKIP.
Labour said the impending by-election would be "more about Tory failure and in-fighting than what is in the best interests of the country".
"It's clear that even Theresa May's own MPs realise that she has failed to lay out a convincing plan to deliver for Britain," said national campaign co-ordinator Jon Trickett.
UKIP leadership contender Suzanne Evans has said she would like to be considered to be the party's candidate in the by-election.
Asked about the resignation during a visit to Berlin, Foreign Secretary Boris Johnson suggested it was part of the prevailing "sturm und drang" (storm and stress) over Brexit - a reference to the movement of 18th Century German writers who gave free expression to emotions and ideas which sought to break with tradition.
He told reporters he did not believe that the legal battle over Parliament's role would "interfere" with the UK's Brexit timetable - insisting that the High Court ruling was "one stage" in the legal process and the British people had made their views clear.
Mrs May has also been seeking to reassure EU leaders about the UK's commitment to Brexit following Thursday's legal setback.
No 10 said she had explained the government was "disappointed" by the ruling but felt it "had strong legal arguments ahead of the case moving to the Supreme Court".
The European Commission said the timetable for beginning talks was in the UK's hands.
"The president explicitly said the legal order and the constitutional order of the UK will be respected and we won't speculate on a possible delay," a spokeswoman said.
The UK voted by 52% to 48% to leave the European Union in a referendum on 23 June.
The EU's other 27 member states have said negotiations about the terms of the UK's exit - due to last two years - cannot begin until Article 50 has been invoked.

A Eurosceptic Tory MP has been accused of compiling a "hit list" of university professors who teach Brexit courses.
Downing Street has distanced itself from government whip Chris Heaton-Harris, who wrote to universities asking for the names of professors.
Lecturers reacted with fury to the letter, calling it a "sinister" attempt to censor them and accusing him of conducting a "McCarthyite" witch hunt.
Mr Heaton-Harris said he believed in "open" debate on Brexit.
The government whip tweeted: "To be absolutely clear, I believe in free speech in our universities and in having an open and vigorous debate on Brexit."
Mr Heaton-Harris is a member of the pro-Brexit European Research Group of Conservative MPs.
Labour accused the MP of seeking to draw up "what looks like a register of Brexit heretics" and branded the government response to it a "shambles".
The Liberal Democrats said the letter was "chilling" and that Mr Heaton-Harris should stand down from the government, adding that ministers should reassure universities that they were not expected to comply with his demands.
Downing Street said Mr Heaton-Harris had written to universities in his capacity as an MP and not as a representative of government.
The prime minister's official spokesman said Theresa May respected the freedom and independence of universities and the role they played in providing open and stimulating debate.
Commons leader Andrea Leadsom insisted Mr Heaton-Harris had not sent a "threatening letter" to universities, although she could not say why he had sought the information.
She told BBC Radio 4's The World at One: "It does seem to me to be a bit odd that universities should react in such a negative way to a fairly courteous request."
Sally Hunt, chairwoman of lecturers' union the University and College Union, said: "Our society will suffer if politicians seek to police what universities can and cannot teach.
"This attempt by Chris Heaton-Harris to compile a hit list of professors has the acrid whiff of McCarthyism about it and (universities minister) Jo Johnson must disown it in the strongest terms."
University lecturers took to twitter to mock Mr Heaton-Harris and the government over the letter.
Professor David Green, vice-chancellor at the University of Worcester, said: "When I read this extraordinary letter on Parliamentary paper from a serving MP, I felt a chill down my spine. Was this the beginnings of a very British McCarthyism?"
He said he feared he would be denounced in Parliament by Mr Heaton-Harris as an "enemy of the people" if he did not supply the list - something he said he had no intention of doing.
He added: "I realised that his letter just asking for information appears so innocent but is really so, so dangerous.
"Here is the first step to the thought police, the political censor and Newspeak, naturally justified as 'the will of the British people'."
The Guardian revealed that Mr Heaton-Harris wrote to university vice-chancellors at the start of this month asking for the names of professors "involved in the teaching of European affairs, with particular reference to Brexit".
The MP's letter also asks for a "copy of the syllabus" and online links to lectures on Brexit.
Lord Patten, the chancellor of Oxford University, and former chairman of the BBC Trust, described Mr Heaton-Harris's letter as an "extraordinary example of outrageous and foolish behaviour - offensive and idiotic Leninism".
The peer, a longstanding supporter of Britain's membership of the EU, told BBC Radio 4's The World At One: "I couldn't believe that it had come from a Conservative MP.
"I think he must be an agent of Mr Corbyn intent on further increasing the number of young people who want to vote Labour."
He said he was sure most university vice-chancellors would drop the letter "in the waste-paper basket" and he accused Mr Heaton-Harris of an affront to free speech and of treating UK universities like "Chinese re-education camps".
McCarthyism refers to US Senator Joseph McCarthy who led attempts to purge alleged Communists in public life the 1950s.

Dozens of Eurosceptic Tory MPs are warning ministers not to use a post-Brexit transitional period to stay in the EU "by stealth".
They say to remain in the single market for a period would be a "historic mistake", in a letter seen by the BBC.
MP Suella Fernandes, who circulated the letter, said its demands were all "consistent with government policy".
Downing Street said an "implementation period" was government policy but had not yet been agreed or negotiated.
Chancellor Philip Hammond has already said the UK will quit the EU's single market and customs union when it leaves in March 2019.
A so-called transitional period, after the UK leaves the EU but before new arrangements come into force, is intended to avoid a "cliff-edge" scenario for businesses and citizens.
The government has said this must come to an end by June 2022, when the next general election is due, and is hoping for a new free trade deal to replace the UK's single market membership.
After a summer where Tory supporters of a more gradual Brexit were heartened by statements from ministers, now comes the, probably inevitable, pushback.
A letter leaked to the BBC, signed by dozens of Tory MPs, was scheduled for the pages of a Sunday newspaper, demanding that Theresa May stand firm, and stick to her original plan for Brexit.
The letter will be seen as a warning to ministers too, particularly Chancellor Philip Hammond who Eurosceptics see as trying to water down Mrs May's original Brexit plan to leave the single market and customs union.
The MPs' letter has been obtained by BBC political editor Laura Kuenssberg, who says it is designed to send a message to ministers "not to soften the government's plans".
One source told her it was a warning to "people like Hammond who think the election result means a softer Brexit".
But a Remain-supporting MP said the signatories were trying to "tie the government's hands on any transitional deal, destroying any chance of continuing the benefits of the customs union and the single market".
Already signed by nearly 40 Conservatives, it was drawn up for publication in a Sunday newspaper.
It says: "Continued membership of the single market, even as part of a transitional arrangement, would quite simply mean EU membership by another name - and we cannot allow our country to be kept in the EU by stealth.
"The government must respect the will of the British people, and that means leaving the Single Market at the same time as we leave the EU."
The letter also demands that the government adds clauses to any transition deal to establish a "clearly-defined timetable" for leaving the single market and customs union.
It also calls for the UK to be able to "unilaterally withdraw" from the transitional deal.
Suella Fernandes, who is a junior government aide, told the BBC that the letter stated that "we are in favour of" leaving the single market, the customs union, taking back control of laws and a time-limited transition period: "All of that is consistent with government policy."
A Downing Street spokeswoman said the implementation period had not yet been agreed, announced or negotiated. "We have been perfectly clear that we want an implementation period. That's government policy," she said.
"People have their opinions, but we have set out what our intentions are."
Unlike the government, Labour has said it would keep the UK in the single market and customs union for a transitional period which would be "as short as possible but as long as necessary".
Speaking in the Commons on Thursday morning, Brexit Secretary David Davis said Labour's proposals would be "the worst of all outcomes".

The headline act - Boris Johnson's speech - may be three days away, but what better opener for a Tory Party conference tag-lined "Get Brexit Done" than three of its biggest cheerleaders.
Such a trio was presented to members on Sunday afternoon in the form of Michael Gove, Jacob Rees-Mogg and Steve Barclay.
Mr Gove - no-deal planner in-chief and Chancellor of the Duchy of Lancaster - kicked off the session with a little doom and gloom.
He said the government was facing "a paralysed Parliament" - echoing the words of the attorney general earlier this week - and "polarised politics", all because the referendum result had not been delivered after more than three years.
Mr Gove said the only party to lift this fog was his very own.
"I've known Boris for more than 30 years, and while we haven't always agreed on everything, let me tell you this," he told the audience.
"Boris is brave, he is determined, he loves this country, and he delivers."
Sniggers rose from a crowd familiar with his sometimes frayed relationship with the prime minister.
But after ensuring he was on his boss's Christmas card list, Mr Gove went on to describe how the pair were definitely on the same page when it came to leaving the EU on 31 October - no ifs, no buts.
He did admit, however, that it may not all be smooth sailing, and leaving without a deal, as the government - at least - is prepared to do, would present "some challenges".
But, despite "new tariffs", "new checks on trade" and potential issues for UK citizens abroad, he said the UK had ramped up its preparations, adding: "While the difficulties caused by leaving without a deal will pass, the damage to our democracy in not getting Brexit done would endure, and resound, for much longer."
His speech brought waves of applause from those in the hall - the assembled members undoubtedly want to get Brexit done.
But the mention of no deal did prompt a few bristles and there were some hands thrust grumpily into pockets.
There are certainly members, even if they appear as a minority, who want out but not at any cost.
The Leader of the House, Mr Rees-Mogg, was next to take the podium and got a standing ovation before uttering a word.
The speech was "classic Mogg", as one party member put it, offering history lessons, literary refreshers and high-brow jokes to please the crowd.
Reports earlier this week that the bespectacled MP had called the Supreme Court decision to rule the suspension of Parliament unlawful a "constitutional coup" caused controversy.
But he decided to invoke a similar sentiment all over again, describing attempts by opposition parties to form a government of national unity as a "Remoaner coup".
Mr Rees-Mogg said they left the government feeling like "Gulliver tied down in Lilliput", fighting against "fumbling, fettling, flitting politicians" who have the "unworthy aim" of stopping Brexit.
He then turned his sharp tongue to the Speaker of the House of Commons, John Bercow.
"As a parliamentarian I have been, and in some ways remain, an admirer of the Speaker," said Mr Rees-Mogg. "But now he has flown too close to the sun.
"His recent mistakes have damaged the standing of the House in the eyes of the public to its lowest point in modern history."
But despite all of dramatic rhetoric, Mr Rees-Mogg sought to reassure delegates.
"Fear nothing that they try to do, fear nothing of their schemes and their stratagems," he said.
"Because ultimately we will have a general election and parties that deny democracy get into great trouble when people have the chance to vote."
Last up was the Brexit secretary himself, Mr Barclay.
It was not an enviable task to follow two stalwarts of the Leave campaign, but he had the experience of the Brussels negotiations (and the ticket stubs to prove it) to see him through.
Like an underdog edging towards the front of the race, he was optimistic - even if the noises from the EU haven't been especially positive.
"The Irish deputy prime minister said on Wednesday that 'there are solutions to this but it is a matter of political will' - I agree," he said.
"The Commission has said that it is open to 'creative and flexible solutions on the border in Northern Ireland' - I am too.
"And President Juncker said he is 'not wedded to the backstop' - Nor are we. So let's abolish it."
The crux of his message - we want a deal, we're working hard to get it, but in the end, no deal? No matter.
Outside the conference confines, though, it matters very much. And while everyone stayed on message (and warm and dry) indoors, on the streets of Manchester it was a decidedly less pro-Tory affair.
The grey skies and drizzle didn't stop thousands of protesters telling Mr Johnson exactly what they thought of him and his Brexit plan.
A giant inflatable modelled on the prime minister was even on show to poke fun - dressed in blue shorts with the word "Nigel" on it and a t-shirt emblazoned with a certain Brexit bus.
Shadow education secretary Angela Rayner was one of the better-known faces at the rally, carrying her banner saying: "No More Austerity".
Others proclaimed "Tories Out" and "Defy Tory Rule", while draped in EU flags.
Human rights campaigner Peter Tatchell told the crowd: "The time for party self-interest is over. Everybody from every party must unite to stop a no-deal Brexit."

Two Tory leadership candidates have clashed over whether they would shut down Parliament early to force through a no-deal Brexit.
Esther McVey said the measure was part of a "toolkit" that could be used to ensure Brexit is delivered on time.
But Michael Gove said such a move would be "wrong" and contradict "the best traditions of British democracy".
Eleven Conservative MPs are vying to replace Theresa May as party leader and, ultimately, prime minister.
The candidates have been laying out their policies on Brexit and other issues before nominations close at 17:00 BST on Monday. They need eight MPs to back them or they are eliminated from the contest.
Jeremy Hunt, another leadership contender, said the EU would be "willing to negotiate" on the Brexit deal if the UK takes the "right approach".
Speaking on Sky News on Sunday, the foreign secretary said he had spoken with German Chancellor Angela Merkel and suggested she was open to looking at new solutions for the Irish border issue in talks.
"She said that [...] with a new British prime minister, we would want to look at any solutions you have," he added.
Asked whether she would consider using ending the current session of Parliament - a process known as prorogation - to force through a no-deal Brexit, Ms McVey said it would not be her "priority" and she would "not be looking to do that" as prime minister.
But the former work and pensions secretary told the BBC's Andrew Marr Show: "I've said I'd use every tool at my disposal, so that would include that."
She also said MPs who wanted to "frustrate" the Brexit process had "ripped up the rule book" and were guilty of "tearing up 400 years of history".
Environment Secretary Michael Gove said MPs who had voted to start Brexit talks by triggering Article 50 should respect the result of the vote to leave the EU, but halting Parliament would "not be true to the best traditions of British democracy".
Earlier, he said that he would replace VAT with a "lower, simpler, sales tax" in an interview in the Sunday Telegraph.
Could prorogation be used to push through no deal?
If a new prime minister is concerned about MPs blocking the UK's exit from the EU, they could advise the Queen to prorogue Parliament.
This would send MPs away so that they cannot do anything in the Commons to hold up Brexit.
However, it would be an unprecedented move in modern times to use this power for political reasons, rather than to end a session in preparation for a new Queen's Speech.
Fellow Tory leadership candidate Dominic Raab has also suggested he would be prepared to shut down Parliament to ensure the UK leaves the EU on 31 October.
The suggestion has led to criticism from a number of MPs, with Commons Speaker John Bercow saying prorogation to enforce a no-deal exit is "simply not going to happen".
Meanwhile, Boris Johnson - in his first major interview of the campaign - compared the Labour and Brexit Party leaders to sea monsters from Greek mythology.
"I truly believe only I can steer the country between the Scylla and Charybdis of Corbyn and Farage and on to calmer water," he told the Sunday Times.
Mr Johnson said as prime minister, he would refuse to pay the EU a £39bn settlement until there was "greater clarity" about a future relationship.
He also said he would scrap the Irish backstop and would only settle the border issue when Brussels was ready to agree to a deal.
Welsh Secretary Alun Cairns, Transport Secretary Chris Grayling and Housing Secretary James Brokenshire have all declared their support for Mr Johnson's leadership bid.
The former foreign secretary has also won the backing of Brexit Minister James Cleverly, who became the first Tory MP to pull out of the leadership race on Tuesday.
The winner of the contest to lead the Conservative Party will become the next prime minister.
Home Secretary Sajid Javid, another MP hoping to become Tory leader, told Sky News his offer to pay Ireland for new technology to ensure a frictionless Irish border would "change the dynamic" in Brexit talks.
Mr Javid also said he would pay for a "multi-billion pound" spending increase in education by slowing down government debt repayment.
He said that could free between £15bn and £25bn a year, some of which would go to the education system.
Mr Javid has won the backing of Scottish Conservative leader Ruth Davidson, who wrote in the Scottish Mail on Sunday that he had a vision to unite a "divided Britain".
In his Sky interview, Jeremy Hunt also repeated his support for lowering the standard legal time limit for abortion from the current 24 to 12 weeks, but added that it would not be government policy to change the law if he became PM.
After nominations close on Monday, MPs will then vote for their preferred candidates in a series of secret ballots held on 13, 18, 19 and 20 June.
The final two will be put to a vote of members of the wider Conservative Party from 22 June, with the winner expected to be announced about four weeks later.

Not delivering Brexit at all would be "significantly more damaging" than no deal, Conservative leadership candidate James Cleverly has said.
However, the Brexit minister added that leaving the EU without a deal was "not my preferred outcome".
"I am Brexit tooth and claw, but we need to be pragmatic and sensible and leave with a deal," he told the BBC.
Meanwhile another leadership hopeful, Home Secretary Sajid Javid, has vowed to recruit 20,000 new police officers.
Writing in the Sun, Mr Javid says: "More police on the beat means less crime on our streets. Not exactly rocket science is it?"
BBC Reality Check says, under the Conservative and coalition governments, the number of police offices has fallen by somewhere between 19,000 and 22,000.
The contest to replace Theresa May has not officially begun, but the list of hopefuls already setting out their stalls is growing by the day.
A key dividing line appears to be between those who have indicated they would consider leaving the EU on 31 October - the current deadline - without a deal, and those who feel that would be unacceptable.
Speaking to BBC Radio 4's Today programme, Mr Cleverly - the latest to enter the race - said his party's "political reputation would be damaged" if Brexit was not delivered.
"The idea that we revert to a pre-referendum reality [if it does not happen] is for the birds."
On the possibility of no deal, he insisted it would bring "uncertainty" and difficulty", but would not be the disaster many fear.
When asked about his lack of experience - Mr Cleverly became an MP in 2015 and has only been a minister for a few months - he said "two of our most successful prime ministers" out of the last four had been those with "zero government experience", referring to Tony Blair and David Cameron.
He also welcomed the large number of MPs vying to become leader, arguing that when Mrs May was elected she had been "uncontested and untested" because rivals dropped out - and later turned out not to "fit well with the role of prime minister".
Analysis by BBC political correspondent Norman Smith
The more the merrier? Or is this Tory leadership race descending into farce?
Already there are 11 candidates. But there are more who look like they are waiting in the wings. Priti Patel, Sir Graham Brady, Jesse Norman. Steve Baker. And maybe more.
Now at one level you can say this is all well and good. Outsiders. No hopers. They often end up winning political contests nowadays. Think Jeremy Corbyn, Emmanuel Macron, Donald Trump. So why shouldn't these little-known Tories have a go?
It also reflects a real impatience among a new generation of Tories, fed up with an old guard, still clogging up all the top jobs in government. But there is a risk with this huge cast list of candidates.
First, that it turns this saga into a rambling, shambling bore and that voters simply turn off, bored by the cacophony of competing voices.
Secondly, that there is no clarity or real focus on the key issues and potential prime ministers.
And lastly that it devalues the importance of this contest if it becomes an exercise in career promotion for lesser-known Tory MPs.
As Jacob Rees-Mogg observed, perhaps its time for some self restraint.
Mr Cleverly was also asked about the possibility of becoming the UK's first black prime minister.
He said it was not something he thought much about, but was "very proud that the Conservative Party looks like it might have the first prime minister from a BME background".
In an open letter earlier, the MP for Braintree in Essex spoke about the need to unite the party, arguing: "We cannot bring the country back together unless the party of government is united, and the party cannot unite if it is led from its fringes."
He added: "To inspire the British people we need to look different, sound different, and offer something new. I believe I can do that."
As the campaign progresses, leadership candidates are signing a "clean campaign" pledge.
Health Secretary Matt Hancock, former Brexit Secretary Dominic Raab and Mr Javid have promised not to "speak ill of fellow Conservatives".
Mr Raab said the campaign should be a "battle of ideas not of personalities".
International Development Secretary Rory Stewart and Housing Minister Kit Malthouse have also committed to the pledge.
On Tuesday, Mrs May urged her successor to seek a consensus on Brexit in Parliament, while senior EU figures reiterated that the UK-EU withdrawal agreement could not be re-opened - despite promises by leadership hopefuls to do so.
Along with Mr Cleverly, the confirmed candidates to replace Mrs May are:
The winner, expected to be named by late July, will also become prime minister.
Other MPs are considering running, including Treasury Minister Jesse Norman.
The deadline to put their names forward is the week commencing 10 June, and they must have at least two of their colleagues supporting them.
In June, the BBC will hold a series of special programmes on the race.
All candidates still standing by mid-June will be invited to a hustings event on BBC One and the final two will go head-to-head in a Question Time Special.
The winner of the contest to lead the Conservative Party will become the next prime minister.

Tory leadership candidate Jeremy Hunt has warned that his party will be committing "political suicide" if it tries to push through a no-deal Brexit.
He told BBC Radio 4's Today programme the move to no deal would result in a general election, which could see Labour take power.
The foreign secretary is one of 10 people seeking to replace Theresa May.
Another contender, Esther McVey, said "political suicide" would be not leaving the EU on 31 October.
The UK's departure was pushed back to that date after the country missed the previous deadline of 29 March.
The official race to be Conservative Party leader gets under way in early June, after Theresa May stands down - but jostling between candidates has already begun.
The winner, expected to be named by late July, will also become prime minister.
Speaking to BBC Radio 4's Today programme, Mr Hunt said he wanted to change the withdrawal agreement that Mrs May negotiated with the EU - despite the bloc repeatedly refusing to re-open talks on the document.
He also pledged to create a new UK negotiating team - drawn from all sides of the Tory Party, plus members of Northern Ireland's DUP - to "give the EU the confidence that any offer can be delivered through Parliament".
Several leadership contenders, including Boris Johnson, have said they would be prepared to leave on 31 October without a deal with Brussels.
But, writing in the Daily Telegraph, Mr Hunt warned that a prime minister advocating that option would risk losing a confidence vote in Parliament - thereby effectively committing to a general election in which the Tories would mostly likely be "annihilated".
It would "probably put Jeremy Corbyn in No 10 by Christmas", he added.
Tory backbencher and leading Brexiteer Jacob Rees-Mogg said Mr Hunt's proposal for a new negotiating team was a "very well intentioned offer", but there may not be time to put together such a group before 31 October.
Mr Rees-Mogg also said any Tories prepared to vote against their own government for pursuing a no-deal exit must understand they would be "putting Jeremy Corbyn into office".
The latest candidate to announce his leadership bid, Housing Minister Kit Malthouse, told the BBC's Victoria Derbyshire programme he would like to "get some movement on the withdrawal agreement or a new withdrawal agreement" - and if a new PM approached Brussels "with the right tone" and negotiating team, there was "the prospect of getting a deal".
But he said the EU could refuse to play ball, thereby "effectively choosing no deal on our behalf".
And Mr Malthouse added: "Those people who say no deal would be a catastrophe and those people who say it would be a walk in the park are both wrong - it is somewhere in the middle."
Former Brexit Secretary Dominic Raab has also released a video, saying as leader he would focus on "fairness" - from cutting taxes for the lowest paid and lowering the cost of living, to increasing opportunities for young people.
"We live in an age when the actions of competent leaders and good government can and should go a long way to making the world a fairer place," he said.
"And that driving conviction, that things can and will be fairer, should be at the heart of what the future of the Conservative Party is all about."
Fellow hopeful Michael Gove has pledged to allow up to three million EU nationals in the UK at the time of the referendum an easier path to citizenship after Brexit.
As part of the plan, he would remove the requirement for them to provide proof of their right to be here - getting rid of the so-called "settled status" scheme.
A source close to the environment secretary said: "This is simply the right thing to do - honouring the promise of Vote Leave that EU nationals studying, working and living in the UK were welcome to stay."
Meanwhile, International Development Secretary Rory Stewart, is promising a "listening exercise" on Brexit if he wins the leadership race.
And the Sun reports that rival contender Health Secretary Matt Hancock has written to ITV, BBC, Sky and Channel 4 to ask them to broadcast a live debate between those vying for the job.
The declared candidates to replace Mrs May are:

Michael Gove will allow EU nationals living in the UK at the time of the referendum to apply free of charge for citizenship if he becomes PM.
The Brexit-supporting environment secretary, who is running to replace Theresa May, will make an "open and generous" offer, sources said.
A Tory rival, International Development Secretary Rory Stewart, promised a "listening exercise" on Brexit.
So far, 10 Conservative MPs have said they will contest the party leadership.
The official race gets under way in early June, after Theresa May stands down - but jostling between candidates has begun. The winner, expected to be named by late July, will also become prime minister.
Sources close to Mr Gove, one of the leaders of the Leave campaign during the 2016 Brexit referendum, have told the BBC he is ready to accept proposals put forward by the Conservative MP Alberto Costa, who quit his government post over ministers' attitude to EU nationals living in the UK.
If chosen as the next Tory leader, it is said he would remove the requirement of EU citizens to provide proof of their right to be in the UK, getting rid of the "settled status" scheme.
Those living in the country would require documentation only for specific purposes, rather than being required to register.
Mr Costa welcomed Mr Gove's proposal, calling it "the morally right thing to do"
A source close to the environment secretary said: "This is simply the right thing to do - honouring the promise of Vote Leave that EU nationals studying, working and living in the UK were welcome to stay."
The leadership contest comes after Mrs May tried and failed three times to get her Brexit withdrawal agreement through the House of Commons.
She announced her resignation last week following an outcry within her party when she proposed a fourth vote by MPs.
The Conservatives suffered heavy losses in Thursday's European elections.
Mr Stewart said: "I would like thousands of conversations up and down the country, co-ordinated on social media with all the results being brought together digitally.
"And then we come back into Parliament and we move very quickly to ban conversation about no deal, ban conversation about second referendum and focus on getting a deal done."
Meanwhile, housing minister Kit Malthouse has become the latest Conservative MP to join the race to become party leader.
Writing in the Sun newspaper on Tuesday, Mr Malthouse said the campaign "cannot be about the same old faces" and described himself as "the new face, with fresh new ideas".
The other declared candidates to replace Mrs May are:

Four men are left in the race to be next prime minister after Rory Stewart was knocked out.
The international development secretary was eliminated after coming last with 27 votes, 10 fewer than last time.
He said his warnings about a no-deal Brexit "probably proved to be truths people weren't quite ready to hear".
Boris Johnson topped the vote again with 143 votes, 17 more than last time. Jeremy Hunt came second with 54, Michael Gove got 51 and Sajid Javid 38.
A fourth round of voting will take place on Thursday.
Mr Stewart started as a rank outsider in the race but gained support on the back of an unusual campaign strategy.
Touring the country for pop-up meetings, which were promoted and recorded on social media, he drew large crowds and won the backing of several senior cabinet ministers.
He had accused other candidates, including Mr Johnson, of lacking realism over Brexit and making undeliverable promises.
After his elimination, he tweeted that he had been "inspired" by the support he received which had rekindled his faith and belief in politics.
Mr Stewart's vote tally fell from Tuesday - following a live BBC TV debate in which he summed up his own performance as "lacklustre".
There have also been suggestions of tactical voting - "dark arts" as he called them - with candidates lending votes to others in order to help eliminate certain rivals.
One MP supporting Mr Stewart claimed he had been "let down" by "thieving, mendacious, lying" colleagues who had switched.
Following his exit, Mr Stewart - MP for Penrith and The Border - told the BBC he was "disappointed" and believed his party "didn't seem ready to hear his message" about Brexit and the need to seek out the centre ground.
He said his arguments during the campaign that an alternative Brexit deal was not on offer from the EU, and a no deal would be catastrophic, were "probably truths people were not quite ready to hear, but I still think they are truths".
He defended his attacks on Mr Johnson, saying the gravity of the situation meant it was right to warn that the frontrunner risked "letting down" his supporters over Brexit.
"These are the times to ask these questions, but I agree they are uncomfortable questions," he said.
"People felt they were exposing divisions in the party they were not comfortable with.
"My conclusion is that you don't unify a family or a party by pretending to agree when you disagree. You unify through honesty and trust."
Mr Stewart, who has ruled out serving under Mr Johnson because of their differences over Brexit, added "I appear to have written my cabinet resignation letter."
He said he had not decided who to now support.
Home Secretary Mr Javid, who leapfrogged Mr Stewart in Wednesday's poll after gaining five votes on his second round tally, thanked Mr Stewart for his contribution to the campaign.
Mr Javid said he was pleased to make it through into the next round, adding that he could provide "constructive competition" to frontrunner Boris Johnson if he made it into the final two.
"People are crying out for change, if we don't offer change ourselves, they'll vote for change in the form of Corbyn - and I can be that agent of change", he said.
Reacting to his third consecutive second place, Mr Hunt said the "stakes were too high to allow someone to sail through untested".
Liam Fox, who is backing Foreign Secretary Mr Hunt, said the surviving candidates were the four most experienced men in the field and this is what people expected all along.
Tory MP Johnny Mercer, who is backing Mr Johnson, insisted there was "no complacency" despite his large lead, telling BBC News "there is still work to do".
Education Secretary Damian Hinds said Mr Gove had "closed the gap" on Mr Hunt in second place and was gaining momentum.
He said the environment secretary had the experience, the vision and the plan to deliver Brexit that could unite the country.
Unless another candidate drops out, there will be a fifth ballot on Thursday evening to determine the final two candidates who will go forward into a run-off of the party's 160,000 or so members.
The winner will be announced in the week of 22 July.

Contenders to replace Theresa May as Conservative leader have clashed over delivering Brexit during a TV debate.
The MPs argued over whether a new deal could be renegotiated with the EU, and the prospect of a no-deal Brexit.
Boris Johnson came under fire for not taking part in the Channel 4 debate but defended his stance, suggesting it would "be slightly cacophonous".
His leadership bid has been backed by Health Secretary Matt Hancock, who dropped out of the race on Friday.
Some of the sharpest exchanges came over whether Parliament should be shut down - prorogued - in order to push through a no-deal Brexit by 31 October - something four of the five candidates argued against.
The UK had been due to leave the EU on 29 March, but EU leaders agreed to delay the date to October after MPs repeatedly rejected Theresa May's Brexit deal.
International Development Secretary Rory Stewart said proroguing Parliament was a "deeply disturbing" option and Home Secretary Sajid Javid warned "you don't deliver democracy by trashing our democracy".
However ex-Brexit Secretary Dominic Raab refused to rule it out, saying "every time one of these candidates take an option away… we weaken our chances of getting the best deal."
Channel 4's debate attracted an audience of 1.3 million and 7.8% of the audience share. The programme was up against Soccer Aid on ITV, Countryfile on BBC One and Top Gear on BBC Two.
Analysis by BBC political correspondent Ben Wright
No stand-out winner and a debate that won't trouble the absent front-runner Boris Johnson.
His team thought there was nothing to be gained from pitching up for this blue-on-blue skirmish which was mostly good natured but repeatedly raised questions the candidates struggled to answer.
How can the next prime minister renegotiate a deal with the EU? How can it be done by October? How could the UK leave without a deal if MPs refuse?
At one end of the debate, Dominic Raab was rounded on for saying he would be prepared to try and suspend parliament if it was the only way to get the UK out without a deal at the end of October.
In the opposite corner, Rory Stewart was the only one who said a renegotiation with the EU in the next four months was a fantasy promise.
At some point this week one of the five will break out and become the challenger to Boris Johnson for the ballot of Tory members.
The candidates at the debate before a studio audience in east London also argued over whether a no-deal Brexit should be considered.
Mr Javid said no deal was the "last thing" he wanted, but added: "You do plan for no deal precisely because you want a deal."
Mr Raab said Britain would be able to "manage those risks" associated with leaving the EU without a deal.
However, Mr Stewart said "I think a no-deal Brexit is a complete nonsense," adding "it would be deeply damaging for our economy."
The candidates were united in condemnation of the Labour leader with Foreign Secretary Jeremy Hunt accusing Jeremy Corbyn of being "against aspiration".
Environment Secretary Michael Gove argued that he was the candidate Mr Corbyn would be most scared of facing at Prime Minister's Questions.
Mr Johnson, the front-runner in the leadership race, was represented at the debate by an empty lectern.
And Mr Hunt attacked his failure to appear.
"Where's Boris?" he asked, adding "if his team won't allow him out with five fairly friendly colleagues, how is he going to deal with 27 European countries?"
Mr Stewart also made a pointed dig at his absent colleague, saying he hoped "one of us" - referring to the MPs who had attended the debate - becomes prime minister.
Speaking to Radio 4's World at One on Friday, Mr Johnson said he was "pretty bewildered" by claims he was dodging scrutiny and said the public had had "quite a lot of blue-on-blue action, frankly, over the last three years".
He said the best time to take part was on Tuesday after the second ballot and would be at the BBC debate on Tuesday, hosted by Emily Maitlis.
Health Secretary Matt Hancock - who withdrew from the leadership race after the first ballot - has backed Mr Johnson "as the best candidate to unite the Conservative Party" as has Esther McVey, who was eliminated in the first round.
Writing in the Times, Mr Hancock said Mr Johnson had a "unique personality", adding: "I have confidence Boris will be a One Nation prime minister because that's how he ran London - consistently - for eight years."
Mr Gove told BBC Radio 4's Today he was "naturally disappointed" that Mr Hancock had chosen to endorse his rival rather than himself.
While Mr Johnson remained the frontrunner, Mr Gove said "we need to make sure he is tested" and he believed he could make it to the final two as a "strong alternative" who was equipped to "be prime minister from day one".
The TV debate also saw politicians being asked about their priorities apart from Brexit.
Mr Javid chose funding education and further education colleges, saying: "We have cut back too much in that space."
Mr Raab said he wanted to improve state schools and offer more choices for young apprenticeships, while Mr Gove said children would be his top priority and emphasised the importance of protecting the environment for the future.
Mr Hunt told the audience "every Conservative has two desires: cut taxes and spend more on public services." He also said he would focus on literacy and the social care system.
Mr Stewart said his central priority would be fixing adult social care, describing the issue as "the great unfinished revolution".
Asked about their weaknesses, Mr Gove said he was impatient, while Mr Raab said he was "a restless soul" who "always wanted to make things better".
Mr Javid admitted to being stubborn while Mr Stewart said there were "many things he didn't know about the world". However, he added that "we need leaders who listen" and criticised "macho posturing".
Mr Hunt joked that his biggest weakness was "getting my wife's nationality wrong" - but on a more serious note, said in his battle with junior doctors as health secretary, he could have been "better at communicating" what he was trying to do.
The candidates will now go on to take part in further ballots until only two remain.
The final pair will be put to a vote of the 160,000 members of the Conservative Party from 22 June. The winner is expected to be announced about four weeks later.

The EU "would be willing to renegotiate" a Brexit deal, says Tory leadership hopeful Jeremy Hunt, adding "they want to solve the problem".
The EU has previously said the withdrawal agreement reached with the UK cannot be reopened.
Unlike the race frontrunner, Boris Johnson, Mr Hunt did not commit to leaving the EU on 31 October.
Meanwhile, fellow leadership contender Rory Stewart insisted "there is no new negotiation with Europe".
He said the EU had made it clear they would not revisit the withdrawal agreement. Instead he proposed setting up a citizens' jury to break the Brexit impasse.
Under his plan, a group of 50,000 people would be selected randomly from the electoral register. Those people would get a phone call in late July to check they were available to participate.
A polling company would then whittle the number down, making sure the final group was representative of the country. That group would be given three weeks to make recommendations which Parliament would then be able to approve or reject.
Dominic Raab - also running to replace Theresa May and become the next prime minister - told Sky News' Ridge on Sunday programme the Conservative Party "will be toast unless we are out by October".
The UK had been due to leave the EU on 29 March, but EU leaders agreed to delay the date, after MPs repeatedly rejected Theresa May's Brexit deal.
The current date for leaving the EU is 31 October.
Brexit: Where do Conservative leadership candidates stand?
Mr Hunt told the BBC's Andrew Marr Show the EU is open to solutions surrounding the Northern Ireland backstop.
"They say if they were approached by a British prime minister who had ideas on how to solve the Northern Ireland backstop, they would be willing to renegotiate the package."
He also said it would be wrong to commit to leaving the EU by 31 October, but added "if there was no prospect of a deal," he would be prepared to leave the EU without a deal.
Analysis by BBC political correspondent Nick Eardley
With Boris Johnson so far ahead when it comes to support from Tory MPs, the other candidates are increasingly pitching to be the other person on the ballot of Tory members.
Jeremy Hunt's claim he can renegotiate the deal will seem overly optimistic to many, and completely impossible to some.
His refusal to guarantee the UK will leave this year will also concern many Tories - who worry about the process going on and on and on.
Hence Dominic Raab's warning his party will be toast unless it delivers in October.
But listen carefully and he's also turning his fire on Mr Johnson - questioning whether the frontrunner has a proper plan on Brexit.
That point is made much more directly by Rory Stewart who says simply that he doesn't think Mr Johnson can deliver.
In this race, it's fast becoming about how to stay in the race with Mr Johnson - even if that involves trying to trip him up.
Mr Hunt said Boris Johnson was "effectively committing the country to no-deal or an election" by saying he would definitely leave the EU on 31 October,
The foreign secretary also said he had "profound issues" with Theresa May's approach to getting a deal through Parliament.
"I did not think we should be trying to persuade Parliament to accept the backstop," he said.
Dismissing the idea of getting new deal from the EU, Mr Stewart said other candidates "who are promising what they can't deliver are going to let people down terribly".
He said the tactic of threatening no deal in order to secure a better deal with the EU was unrealistic.
"The EU is not scared of it because it is not a credible threat," he said.
He challenged Mr Johnson - who won support from 114 MPs in the first leadership ballot - to reveal his Brexit tactics in the BBC debate on Tuesday.
"As soon as I sit down with him and ask how are you going to deliver Brexit, then it begins to come off the rails," he told Marr.
Mr Stewart has ruled out serving in Boris Johnson's cabinet, if the ex-London Mayor becomes prime minister.
On Tuesday 18 June BBC One will host a live election debate between the Conservative MPs who remain in the race.
If you would like to ask the candidates a question live on-air, use the form below. It should be addressed to all of them, not a specific politician.
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Tory leadership rivals have clashed in a live BBC TV debate on whether the UK can leave the EU, no matter what, by the 31 October deadline.
Asked for a guarantee he would do this, Boris Johnson described the deadline as "eminently feasible".
Sajid Javid said it "focused minds", but Michael Gove and Jeremy Hunt said extra time might be needed.
Rory Stewart accused his colleagues of lacking realism - of "staring at the wall and saying 'believe in Britain'".
The five men vying to be Conservative Party leader - and the UK's next prime minister - were taking part in a live debate on BBC One on Tuesday night.
Former Brexit Secretary Dominic Raab was earlier eliminated in the second round of voting, when Conservative MPs held a secret ballot.
The third round of voting will take place later, between 15:00 and 17:00 BST. The result is expected at 18:00 BST and the MP with the lowest number of votes will be out of the race.
During Tuesday's hour-long debate, all five men ruled out calling a general election until Brexit was resolved.
But the encounter exposed divisions in their approaches to Brexit and whether they could accept the UK leaving the EU without an agreement.
The candidates, who faced questions from members of the public on issues ranging from climate change to Islamophobia, also disagreed over whether to prioritise tax cuts or increased spending on public services after the UK leaves the EU.
Mr Johnson, the frontrunner in the contest, was taking part in his first debate of the campaign after he skipped Sunday's Channel 4 encounter.
Rory Stewart, reflecting on the debate on BBC Radio 4's Today programme, said he had found it a "frustrating" format and wished he had pressed Mr Johnson further to explain how he would get a no-deal Brexit through without the consent of Parliament.
Looking ahead to the vote later, he said he had received a "couple of positive responses" to appeals for support from MPs who had previously given their backing to Dominic Raab.
Conservative MP Nadhim Zahawi, who has switched his support from Mr Raab to Mr Johnson, said he "certainly believed" the UK would leave the EU by 31 October under Mr Johnson.
Pressed on why Mr Johnson did not "guarantee" that on live TV, Mr Zahawi said: "If the other side don't believe you will leave on 31 October on WTO terms then they will not come forward with a deal."
He added that EU negotiators would take Mr Johnson "very seriously because they know he will prepare the country".
Jeremy Hunt said the EU needed to be able to trust the person they negotiate with. "I believe they would trust Jeremy Hunt, they would sit around the table, they would listen," he told the Today programme.
Asked if he was missing the charisma needed to win the leadership race, he said he had been underestimated all his life - in politics and in setting up his own successful business - and planned to surprise people.
The former foreign secretary said the British people were "fed up" with the current deadlock over Brexit and the Tories would pay a "really serious price" if this continued.
He warned of a "catastrophic loss of confidence in politics" if the latest Brexit deadline was not met. Asked if he could guarantee this, he replied that "October 31 is eminently feasible".
"If we allow 31 October to come and go as we let March come and go, I think the public would look on us with increasing mystification," Mr Johnson said.
He also suggested there was no issue with continuing free trade after Brexit - citing something called Article 24 of GATT - but as BBC Reality Check points out, that relies on the UK and EU both signing up and in the event of no deal, that will not happen.
Mr Javid, who came fifth in Tuesday's second round of voting, said a deadline was needed to "focus minds" in both the EU and the UK.
"We have to learn from our mistakes," he said. "One of the mistakes we have made is having a flexible deadline."
He suggested the route to getting a Brexit deal through Parliament was by re-presenting Theresa May's Withdrawal Agreement but without the controversial Irish backstop.
Mr Gove said an "arbitrary" deadline was counter-productive and if he was prime minister he would be prepared to delay Brexit by a matter of days to finalise a deal.
"You sometimes have extra time in football matches in order to slot home the winner."
Mr Hunt said he would back a no-deal exit as a "last resort" but if the UK was close to finalising a deal with the EU he would extend the talks to prevent the disruption a no-deal exit would cause to business.
Both Mr Hunt and Mr Javid suggested new technology could potentially solve the intractable Irish border issue, but the EU has said there is currently none in use anywhere in the world that can keep it as open after Brexit as it is now.
Mr Stewart said he would not allow a "damaging and unnecessary" no-deal exit and his rivals could not explain how they could possibly do this "against the consent of Parliament".
He suggested he was seeking the most realistic "door" out of the EU while "everyone else was staring at the wall and saying believe in Britain".
EU politicians across the continent were dipping in and out of the debate. The comments I've heard so far off-the-record have not been particularly complimentary.
The EU simply thinks that most of those leadership candidates are not being realistic.
EU leaders are preparing a united, determined front when it comes to the idea of renegotiating the Brexit deal, and the answer is no.
Even if, come the autumn, the EU were to be tempted to reopen some of those questions such as the Irish backstop, those conversations could never be finished by 31 October - the date by which most of those leadership candidates want to leave the EU.
That's why this evening the EU thinks the idea of a no-deal Brexit is becoming increasingly likely.
Moving beyond Brexit, the candidates clashed over their economic plans and whether to prioritise higher spending on public services or tax cuts.
There were sharp exchanges between Mr Stewart and other contenders, Michael Gove accusing him of having "no plan" for how to run the economy or public services.
"Bringing people together is not enough," he told Mr Stewart, who has emerged as the surprise contender in the race.
However, after the debate Mr Stewart admitted his performance had been lacklustre, adding he did not think the "strange" format worked for him.
Mr Gove also took aim at Mr Johnson's plans to give a tax cut to those earning more than £50,000 a year, saying the focus should be on "helping the poorest in society".
Helping middle-earners was "sensible", Mr Johnson responded.
Mr Stewart said promising tax cuts was "wrong" given the uncertainty around Brexit.
He called for a "revolution" in care for the elderly, calling current provision a "disgrace".
Mr Hunt, who was health secretary for six years, also called for increased investment, suggesting cuts to care budgets under the current government had gone "too far".
Mr Johnson reiterated that it was his "ambition" to cut taxes for higher earners, but as political correspondent Chris Mason pointed out, that seemed less committal than a "promise" to do it.
Plenty expected lots of ganging up on Boris Johnson tonight from his rivals.
But what was striking - after the Stewart surge in votes between rounds one and two in Parliament - is there was at least as much, if not more, ganging up on Rory Stewart.
Why?
Look at the numbers.
There were just 13 votes separating Jeremy Hunt, who finished second, and Sajid Javid, who finished fifth in the leadership ballot.
In other words, all of them, other than Boris Johnson, are potentially vulnerable to relatively small shifts in votes.
And Mr Stewart, in the build up to tonight, had the momentum.
Meanwhile, speaking to Newsnight after the debate, Mr Gove said he believed he had won the debate because of what he said were his "detailed answers" and "clear plan" on Brexit.
Of his rivals, he said there were "some other great people" but added: "They will all be fantastic members of my team."
Amid claims that the Conservatives have failed to tackle Islamophobia in the party, the candidates were pressed by an imam to accept that "words have consequences".
Mr Johnson said he apologised if anything he had written, during 20 to 30 years as a journalist, or had said during his political career had caused offence.
But he defended his conduct as foreign secretary in relation to the case of Nazanin Zaghari-Ratcliffe, who remains in jail in Iran on spying charges.
He suggested his claim in 2017 that the dual British-Iranian national was actually working as a journalist in the country - which the Iranian authorities cited as a reason to increase her sentence - "did not make any difference".
"If you point the finger at the UK, all you are doing is exculpating those who are truly responsible," he said.
Mr Javid challenged the other candidates to agree to an external inquiry into Islamophobia in the Tory Party - which they all appeared to do.
Referring to Donald Trump's string of attacks on London's Muslim mayor Sadiq Khan, he said politicians should be "brave enough" to call out Islamophobia wherever it came from.

"Nothing has changed." Remember that?
There is, this morning, an operation being mounted by the government to try to show that nothing has changed in the Conservative Party in the last few days, that Theresa May's leadership remains on track and she is, to use another of her famous phrases, just, "getting on with the job".
Except, as happened the last time she proclaimed "nothing has changed", something rather fundamental has, after all.
For the doubts that have been building about her in the party for months are now out there in the wide open.
Yes, they have only been articulated by two former ministers, Grant Shapps and Ed Vaizey. Yes they were both close to David Cameron. Yes they were both Remainers too, which allows a conspiracy theory to take hold that the efforts to get rid of Theresa May are really a guise for stopping Brexit.
(Having talked to those involved for some time, the doubts are about competence and authority, not Brexit and there is at least one senior Brexiteer among their number).
And yes, most importantly of all, just as it was on the morning after the election, there is still no obvious successor to Theresa May, who commands broad support right across the Tory Party.
If there had been, it's likely that she would have gone then. That is really why those around Theresa May believe they have got the plot under control.
But the public, and now the prime minister's opponents across the table in the Brexit talks are aware that some of her colleagues simply don't think that she is up to the job.
Remarks by Mr Vaizey and Mr Shapps can't be unsaid. The private questions are now out there in the ether and can't be taken back.
Even if the plot has been killed off at birth, it's another crack in her authority, already so fractured after the election.
It doesn't mean she'll have to go now, or indeed anytime soon. Other leaders have survived countless attempts to shove them out.
But even many of Theresa May's supporters know that something is deeply wrong, however many times they tell themselves, "nothing has changed".

Foreign Secretary Jeremy Hunt has told a Conservative Party leadership hustings that as Brexit approaches, the Northern Irish backstop "has to change or has to go".
He and Boris Johnson made their pitch to be the next PM to Conservative Party members in Northern Ireland.
The two candidates for the Tory leadership have been taking part in a series of party events across the UK.
The current EU withdrawal agreement was "a dead letter", said Mr Johnson.
He said the backstop presented the UK with the "unacceptable choice" between "abandoning the ability to govern ourselves" or to "give up control of the government of Northern Ireland".
The backstop - the most controversial part of the deal Theresa May negotiated with the EU - is a position of last resort to prevent any new checks or controls on the Irish border after Brexit.
The UK and EU would prefer to maintain the border status quo through a comprehensive trade deal.
Mr Johnson met with DUP leader Arlene Foster at Stormont after the hustings.
He reaffirmed his promise of there being no hard border between Northern Ireland and the Republic of Ireland.
Mrs Foster said they had a "useful discussion about restoring devolution and delivering on the EU referendum result".
By Jayne McCormack, BBC News NI political reporter
It was described as the Northern Ireland version of "Tories got talent" by host, broadcaster Iain Dale.
But Jeremy Hunt and Boris Johnson stuck to their scripts on Brexit and the backstop - which seemed to go down well with the Northern Ireland Conservatives in the room.
However, they diverged on restoring the Northern Ireland Assembly.
Mr Hunt said he would be "personally" involved, while Mr Johnson told the parties just to "get on with it".
The 500 NI Conservative members will all get their say on who becomes the next PM -  but it's the DUP vote that the two men are really courting.
They both agreed that winning over their unionist allies is vital for a Tory majority in Parliament.
That's something the new prime minister will have to address quickly, by renewing the £1bn confidence and supply pact when he enters No 10 later this month.
The Conservative Party's 160,000 members will begin voting next week and Mrs May's successor is expected to be announced on 23 July.
Mr Hunt was first to take to the stage at the event.
"We are never going to have a deal to leave the EU with the backstop," he said.
Mr Hunt has said he would decide by the end of September whether there was a "realistic chance" of reaching a new Brexit deal with the EU.
He said he would deliver a provisional "no-deal Brexit budget" in early September and then give the EU three weeks.
"The fundamental issue with the backstop is not the principle that we shouldn't have border infrastructure on the island of Ireland - that's accepted by all sides," he said.
"The principle is the backstop which traps us into following EU customs tariffs until the EU gives us permission to leave the customs union... we have to find a different solution."
He said he believed the answer was a technology-led solution, as modelled in Germany.
He told Sky News earlier that German Chancellor Angela Merkel was willing to look at any new proposals put forward by the next prime minister.
For his part, Mr Johnson said the backstop presented the UK with an unacceptable choice and that "the UK as a whole should come out of the EU".
Mr Johnson has vowed to leave the EU "come what may" by 31 October.
Speaking to reporters on Monday, he said it was important to have a "hard deadline" for leaving, adding that previous no-deal preparations had "sagged back down" after exit dates were not met.
Mr Hunt said his campaign was based on trying to fire up the economy, increasing defence spending, abolishing illiteracy and supporting young people.
Were he from Northern Ireland, he would want the law changed on both abortion and same-sex marriage, he said, but added that both matters were issues for a devolved government.
Unlike other parts of the UK, the 1967 Abortion Act does not extend to Northern Ireland.
Currently, a termination is only permitted in Northern Ireland if a woman's life is at risk or if there is a risk of permanent and serious damage to her mental or physical health.
Northern Ireland is also the only part of the UK where same-sex marriage is illegal.
Mr Johnson also said the NI abortion issue should be debated at Stormont.
"I don't think that the UK should be imposing something that should be decided here."
During a vote in November 2015, Northern Ireland assembly members supported same-sex marriage by a slim majority of 53 votes to 52.
Both would-be prime ministers pledged to put renewed efforts to get Stormont up and running.
"It is totally unacceptable that politicians that are paid to run the NHS and schools, and promote inward investment are not turning up to work and doing their job," said Mr Hunt.
Mr Johnson said if he was leader, he "would do whatever I can personally to energise" power-sharing talks which are currently stalled.
"Everyone needs to recognise that it is the citizens and voters of Northern Ireland that are losing out."
Following the hustings event, Mr Johnson tweeted that it was a "pleasure to meet" DUP leader Arlene Foster "to discuss restoring and protecting the governance of Northern Ireland".
In 2017, the Conservative Party entered into a confidence-and-supply pact with the DUP.
The Conservatives needed the votes of the DUP's 10 MPs in order to have a working Commons majority after the 2017 Westminster election, but had to agree to an extra £1bn in spending for Northern Ireland.
At the hustings event, Mr Johnson was asked about his attendance at a DUP conference last year.
Mr Hunt said he would "infinitely prefer if we had Conservative MPs in Northern Ireland so we didn't have to rely on other parties for that majority but to govern is to accept the world as it is".
The candidates are set to face each other in an ITV debate on 9 July and at an event hosted by the Sun newspaper and talkRADIO on 15 July.
Mr Hunt tweeted on Tuesday that he had been invited to a live BBC TV debate against Mr Johnson on 16 July.
He argued that about 90% of Conservative members would have already voted in the leadership race by then.
Meanwhile, former party leader William Hague, who served as leader of the opposition between 1997 and 2001, wrote in the Daily Telegraph that both candidates had "great merits" but added that he believed Mr Hunt would make the better prime minister.

Jeremy Hunt has promised Boris Johnson "the fight of his life" as the two compete to become the next Conservative leader and PM.
Mr Johnson said he was "honoured" to get the backing of 160 MPs in the final ballot of the party's MPs - more than half of the total.
Mr Hunt got 77 votes - two more votes than the next candidate Michael Gove.
Mr Johnson and Mr Hunt now face a vote involving up to 160,000 Tory members, with a result due by late July.
All 313 Conservative MPs took part in the final ballot in the House of Commons, with one paper spoilt.
Mr Johnson's victory in the latest round of the contest had been widely expected, but Environment Secretary Mr Gove and Foreign Secretary Mr Hunt had been engaged for several days in a fight for second place.
In the penultimate MPs' ballot, earlier on Thursday, Mr Gove overtook his rival, only to see his lead reversed in the final vote.
Before the final vote, a source close to Mr Hunt warned against reigniting the "personal psychodrama" between Mr Gove and Mr Johnson - who spearheaded the Vote Leave campaign together in 2016, but fell out after Mr Gove abandoned Mr Johnson's previous leadership bid to launch his own.
Following the result of the final ballot, Mr Johnson tweeted that he was "deeply honoured" by his level of support.
Meanwhile, Mr Hunt, acknowledged Mr Johnson as frontrunner to become party leader and prime minister, tweeting that he was the "underdog" but in politics "surprises happen".
He went on to praise Mr Gove as one of the "brightest stars in the Conservative team" and pledged to "give Boris the fight of his life."
Mr Gove congratulated his rivals and said he was "naturally disappointed but so proud of the campaign we ran".
His campaign manager, Mel Stride, said he believed that Mr Gove's admission that he had taken cocaine during the 1990s had damaged his bid, adding: "It stalled us and meant momentum was lost at that time."
There's no doubt that Mr Johnson is, at this stage (and there's a long way to go), widely expected to end up in Number 10.
But this result is an enormous relief to his camp, for the simple reason that they think Mr Hunt is easier to beat.
Forget any differences in style between the two challengers and their comparative talents - Jeremy Hunt voted Remain in the EU referendum.
And for many Tory members it is a priority for the next leader to have been committed to that cause, rather than a recent convert, however zealous.
Read Laura's blog in full
Mr Johnson and Mr Hunt will now take part in hustings in front of Conservative Party members around the country, before the votes are counted, with the final result to be announced during the week of 22 July.
They will also take part in a head-to-head debate on ITV on 9 July, following previous leadership debates hosted by Channel 4 and the BBC.
Mr Hunt has been in the cabinet since 2010. Before he became Foreign Secretary, he was the UK's longest-serving Health Secretary. Former Foreign Secretary Mr Johnson, who quit the cabinet last year over Theresa May's Brexit strategy is one of the UK's most recognisable politicians and was Mayor of London from 2008 to 2016.
The Conservatives said there had been 20,000 applications for places at the 16 leadership hustings around the UK. Party chairman Brandon Lewis congratulated the final two contenders.
He said: "We are conscious that the Conservatives are not just selecting a new leader but also the next prime minister, and we take that responsibility extremely seriously at such an important time for our nation."
Labour's national campaigns co-ordinator Andrew Gwynne said: "What a choice: the man who broke the NHS or the man who wants to sell it to Donald Trump.
"A handful of unrepresentative Conservative members should not be choosing our next prime minister. People should decide through a general election."
The ballot of MPs earlier on Thursday saw Home Secretary Sajid Javid eliminated from the contest.

Boris Johnson has said he is "not aiming for a no-deal outcome" for Brexit at the launch of his campaign for the Tory leadership.
But he said the threat of no deal was a "vital" negotiation tool and the UK "must do better" than the current deal.
At his campaign launch, Home Secretary Sajid Javid said Mr Johnson was "yesterday's news".
He argued the party should not vote for "the same old insiders" and a leader from a "new generation" was needed.
Meanwhile, Labour's cross-party motion aimed at stopping a no-deal Brexit being pushed through by a future prime minister was rejected by MPs.
The Commons opposed the move by 309 votes to 298.
Mr Johnson and Mr Javid are the last of the 10 candidates in the contest to officially launch their campaigns for the job of Conservative Party leader - and prime minister - ahead of Thursday's first ballot of Tory MPs.
Mr Javid focused much of his speech on his personal back story and own experience of exclusion, insisting it gave him an understanding of how to make people feel "included and welcome" in the Tory Party.
"I have the background, ideas and positive vision for the future [to] keep Jeremy Corbyn far away from 10 Downing Street," he said.
In a swipe at his rivals, he argued: "We can't risk going with [the] short-term comfort zone choice."
On Brexit, he said he could "make post-Brexit Britain what many naysayers say it can't be", and had a "credible plan to leave by the end of October".
Scottish Conservative leader Ruth Davidson, who introduced him at Wednesday's event, said Mr Javid would give voters a "greater reason to feel pride" in the UK.
Earlier, she told the BBC she would not support leaving the EU without a deal, but Mr Javid had the most credible plan to get a deal through Parliament.
Mr Javid has said he would be prepared to leave without a deal if the alternative was no Brexit at all.
The winner of the contest to lead the Conservative Party will become the next prime minister.
Mr Johnson is regarded as the frontrunner in the contest, with many more endorsements from Tory MPs than any other candidate.
He has kept a low profile in the race to succeed Theresa May so far, his only significant intervention being a pledge - immediately criticised by his rivals - to cut income tax bills for people earning more than £50,000 a year.
At Wednesday's launch, the former foreign secretary - who quit cabinet over Mrs May's Brexit policy - said it was "right for our great country to prepare" for a no-deal outcome.
He said any delay to Brexit would "further alienate not just our natural supporters but anyone who believes that politicians should deliver on their promises".
And he warned his party it would "kick the bucket" if it went into the next election having failed to carry out the mandate given to it by the British people.
"Delay means defeat, delay means Corbyn," he said, saying the UK must leave the EU on 31 October.
By Norman Smith, BBC assistant political editor
The speech was classic Boris Johnson - a real pick-me-up performance calling for courage and conviction.
But there was no clarity on what his Brexit plan might be or how he might go about putting together a new deal that the EU would be prepared to negotiate on.
He did say he would keep no deal on the table though, and said it was "astonishing" Theresa May had taken it off.
We did get the character question too - a blunt one about the remark he had made about Muslim women wearing the burka looking like letter boxes.
He knew those questions were coming, and his answer was to say that he was plain speaking, and that people like it when you don't shield everything in carefully calibrated phrases.
It seemed to me that this was a man absolutely not apologising for how he does politics.
Several of Mr Johnson's rivals, including Rory Stewart and Matt Hancock, have said they would not countenance leaving the EU at all without some form of legally-binding agreement on the shape of the future relationship because of the economic disruption it would cause.
Others, including Michael Gove and Mark Harper, have indicated they would be prepared to seek a further extension from the EU to finalise a better deal.
Brexiteers such as Dominic Raab and Esther McVey have said the priority must be honouring the 2016 referendum result and the UK should be prepared to accept no deal.
Chancellor Philip Hammond - who is not running for leader - said it was "impossible" to leave the EU by 31 October and it was "not sensible" for leadership hopefuls to "box themselves into a corner on this" as Parliament "will not allow a no-deal exit".
Labour leader Jeremy Corbyn has said a no-deal Brexit would be "disastrous", telling MPs: "I think some of [the PM's] colleagues need reminding of that."
At his launch Mr Johnson was also pressed by journalists on his use of language - including when he wrote in his Daily Telegraph column that Muslim women wearing the burka looked like "letterboxes".
Mr Johnson apologised for "the offence I have caused", but said: "I will continue to speak as directly as I can."
One of the reasons the public "feels alienated" from politicians is because "we are muffling and veiling our language", he added.
He also appeared to dodge a question asking him about a previous confession he had taken cocaine while at university.
Mr Johnson said: "I think what most people in this country want us to really focus on in this campaign, if I may say so, is what we can do for them and what our plans are for this great country of ours."
On Tuesday 18 June BBC One will host a live election debate between the Conservative MPs still in the race.
If you would like to ask the candidates a question live on air, use the form below. It should be open to all of them, not a specific politician.
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Former Conservative leadership contender Esther McVey has thrown her support behind Boris Johnson's bid.
Ms McVey - eliminated in the first ballot - told the Sunday Telegraph she was backing him because he had promised to deliver Brexit by 31 October.
Mr Johnson is the clear frontrunner to replace Theresa May but his rivals have insisted they will not drop out.
He is the only one of the six remaining candidates who will not take part in the first TV debate on Channel 4 later.
His team reportedly have reservations about its proposed format, but Mr Johnson has agreed to take part in the BBC's debate on Tuesday.
BBC political correspondent Ben Wright said there was "intense arm-twisting and lobbying under way" ahead of the second ballot of Tory MPs on Tuesday.
He said Health Secretary Matt Hancock, who pulled out of the leadership race on Friday, was understood to be considering whether to back Mr Johnson or Michael Gove.
Mr Gove finished third in round one behind Foreign Secretary Jeremy Hunt, but has told the Sunday Times he is the "comeback kid".
The environment secretary also said he would be happy to serve under Mr Johnson, whose leadership bid he scuppered in 2016.
"I would absolutely work with Boris in any way that he wanted to work with me," he said. "No question. It is a different time requiring a different approach."
Mr Hunt insisted he had still not given up hope of winning in the final postal ballot of party members, despite being a distant second to Mr Johnson in the first round.
"I am the insurgent in this race," he told The Mail on Sunday.
"I am in it to win it because we have to give the country better choices given the crisis that we're in now."
Home Secretary Sajid Javid said voters were looking for a "change" - something only he and Mr Johnson offered.
He told the Sunday Times: "We need change. And Boris is change. But I'm change too. And there are only two change candidates in the remaining six - and that's Boris and me."
He also took a swipe at Mr Hunt, who he said was "an asset to the party" but didn't represent change.
Meanwhile fellow contender, Rory Stewart, responded to a Sunday Times headline saying that the leadership rivals were eyeing cabinet roles under Mr Johnson by tweeting: "This may be true of some contenders but it isn't true of me."
The international development secretary added: "I want to give members and the public a real choice of two quite different futures for the Conservative party. I don't want to be in a Boris cabinet."
Mr Johnson gained 114 votes in the first ballot - more than double his nearest rival, Mr Hunt.
Writing in the Sunday Telegraph, Ms McVey said she would "wholeheartedly support" Mr Johnson after he agreed to incorporate aspects of her "blue-collar conservatism" ideas - such as investing money into public services - into his plans for government.
She added: "He has promised to deliver Brexit on 31 October, deal or no deal, and has shown time and time again that he is a dynamic leader, capable of building a strong team around him that will deliver on his promises.
"Our country is crying out for strong, optimistic leadership and Boris is the man best equipped to take us out of the EU."
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The leadership candidates' hardening of position on the controversial Irish backstop is "significant", ex-attorney general Dominic Grieve says.
The views of Jeremy Hunt and Boris Johnson expressed at a debate seem to rule out any compromise, the MP added.
They both declared the backstop "dead" and rejected the idea of a time limit, which the BBC's Norman Smith said was a "huge heave" towards no deal.
But Mr Grieve warned that a government seeking no deal would collapse.
The Remain-supporting MP said he believed more Conservative colleagues, including current front benchers, would join him in attempts to prevent the UK leaving on 31 October without a deal.
Work and Pensions Secretary Amber Rudd said she was "surprised" by the contenders' comments on the backstop, but believed they would "find they have to compromise".
The cabinet minister, who has been convinced by her preferred candidate Mr Hunt that no-deal should remain on the table, told Politico: "I think their views will collide with the reality when, whichever one wins, starts negotiating and starts dealing with a Parliament which may be more difficult than they think to engage with."
The backstop, included in the withdrawal agreement negotiated by Prime Minister Theresa May and the EU, is designed as an insurance policy to prevent a hard border on the island of Ireland after Brexit.
But this deal was rejected three times by MPs in the Commons, with the backstop a key sticking point.
Critics fear it would be used to permanently trap the UK in the EU customs union, preventing the country from striking its own trade deals.
Other MPs have said the backstop would only be acceptable if it had a strict time limit, or if the UK had a unilateral right to end the arrangement.
The EU has repeatedly said it will not renegotiate the withdrawal agreement and insisted the backstop must be part of any deal agreed.
Ursula Von der Leyen - who MEPs have elected to be the next European Commission president - told MEPs on Tuesday: "The Withdrawal Agreement provides certainty where Brexit created uncertainty, preserving the rights of citizens and in preserving peace and stability on the island of Ireland."
To groans from Brexit Party MEPs in the chamber, she added, "However, I stand ready for further extension of the withdrawal date should more time be required for a good reason."
At a head-to-head leadership debate run by the Sun on Monday, Mr Johnson said he would not be seeking a time limit to the backstop, insisting: "It needs to come out."
He said the UK must say "no to time limits or unilateral escape hatches or all those kind of elaborate devices, glosses, codicils and so on that you could apply to the backstop".
Mr Hunt also said the backstop was "dead" and rejected the idea of a time limit.
"The backstop, as it is, is dead, so I agree with Boris - I don't think tweaking it with a time limit will do the trick, we've got to find a new way," he said.
"But the thing that mustn't die... is a cast-iron commitment to the Republic of Ireland that we will not have border infrastructure."
By Norman Smith, BBC assistant political editor
Boris Johnson and Jeremy Hunt have given the UK another almighty heave in the direction of no deal. By ruling out any reworking of the backstop, they have closed off what some regarded as the best route to securing a Brexit deal.
Even some leading Brexiteers had mooted the idea of trying to secure an end date for the backstop. A compromise, they argued, which it might have been possible to sell to Parliament. And which the EU - having already said the backstop would be temporary - might have been prepared to concede.
Now, however, Mr Hunt and Mr Johnson have declared the backstop "dead". It means that whoever becomes PM will have to try and construct an entirely new Brexit deal in just three months. It also pre-supposes the EU will be willing to negotiate a fresh deal.
Of course, it's possible this is all bluff, designed to force the EU to blink. If they don't, however, then it's hard to see a likely alternative to no deal.
Speaking to BBC Radio 4's Today programme, pro-EU Tory MP and People's Vote campaign co-chairman Mr Grieve said: "I think it is significant because I have in the past heard it suggested… that there might be some possibility of compromise by the backstop being tweaked and on the face of it, it entirely rules it out."
He said blocking no deal "might be quite difficult" on a technical level - meaning that bringing down the government could be the only option in a confidence vote.
"If a government persists in trying to carry out a no-deal Brexit, I think that administration is going to fall," he said.
"By the end of next week there are going to be more Conservatives who have indicated very clearly that no-deal is unacceptable and I notice that many of them will no longer be on the front bench."
Meanwhile, Mr Grieve and Labour former foreign secretary Dame Margaret Beckett have launched a report that argues a series of possible Brexit outcomes will probably lead to further political deadlock, including renegotiating the backstop.
The report from the People's Vote campaign says that another referendum is the "most popular way of resolving the Brexit crisis" and the "only legitimate and democratic solution available".
The result of the contest to succeed Theresa May as prime minister will be announced on 23 July, with the winner taking office a day later.
Some 160,000 Conservative Party members are voting in a postal ballot to elect the next leader.

Boris Johnson and Jeremy Hunt have made their pitch to be the next prime minister at the first of 16 Conservative Party hustings.
The two contenders for Number 10 laid out their vision for the country at a conference in Birmingham.
Mr Johnson said these were "dark days" for his party, but insisted he could turn things around.
But his rival warned members not to elect the "wrong person" and risk "catastrophe".
Mr Johnson said the most important thing was to "get Brexit done".
He said: "My ambition is to unite this country and our society... let's take Britain forward.
"We need to discover a new confidence in our country."
The former mayor of London featured on most of Saturday's newspaper front pages following reports by the Guardian that police were called to his London home after neighbours reported "slamming and banging" in the early hours of Friday morning.
The Metropolitan Police Service have said they will not be taking any further action following the episode.
Asked by the hustings moderator, LBC presenter Iain Dale, whether character mattered when choosing a prime minister, Mr Johnson said: "I don't think people want to hear about that."
Accused of ducking questions, Mr Johnson said: "People are entitled to ask me what I want to do for the country."
His rival, Mr Hunt, said the UK was in a "very serious situation".
He continued: "Get things wrong and and there will be no Conservative government, and maybe even no Conservative Party.
"Get things right and we can deliver Brexit, unite the party and send [Labour leader Jeremy] Corbyn packing."
But he warned that if Tory party members elected the "wrong person" as leader then "catastrophe awaits".
Mr Johnson, meanwhile, said he would prepare for a no-deal Brexit if he became PM.
He said: "We must be able to come out on WTO terms, so that for the first time in these negotiations we carry conviction.
"And it is precisely because we will be preparing between now and 31 October for a no-deal Brexit that we will get the deal we need."
He repeated his previous claim that it was "eminently feasible" for the UK to leave the EU by 31 October, saying he intended to make it happen.
That is the date that the EU's membership extension runs out, and if nothing has changed, the UK leaves without a deal.
Theresa May officially stood down as Tory leader on 7 June and will cease to be prime minister in the week commencing 22 July.
An initial list of 10 candidates to replace her was whittled down to Mr Hunt and Mr Johnson in a vote by Tory MPs.
In the fifth and final round on Thursday, Boris Johnson came out on top with 160 out of the 313 votes cast. Mr Hunt received 77 votes and Michael Gove was knocked out with 75.
One questioner at the hustings wanted to know whether Mr Johnson's approach to British business in the context of Brexit was as "cavalier and careless" as previously, when he used an expletive.
He replied: "I believe passionately in UK businesses, and as foreign secretary I spent a lot of my time promoting UK businesses at home abroad."
Jeremy Hunt insisted he would leave the EU with no deal if necessary.
He said: "I would do so with a heavy heart. But if we have to in the end I would do that."
Of a mooted renegotiation with Brussels, he said: "If we send the wrong person there's going to be no negotiation, no trust, no deal, and if Parliament stops that, maybe no Brexit.
"Send the right person and there's a deal to be done."
And challenged over the fact he campaigned for Remain in 2016, the would-be premier said: "Look at my record since that referendum.
"I have been very clear on every occasion... I have voted for Brexit."
In another jibe at his rival, Mr Hunt warned members not to elect a Conservative "populist" to oppose "hard-left populist" Jeremy Corbyn.
Referring to himself, he said: "Or we could do better and choose our own Jeremy."
He continued: "If Corbyn gets into Downing Street there will never be Brexit.
"That's why it's so important that we hold together our Conservative and DUP family and deliver Brexit."
Mr Hunt said he would increase defence spending and called for Conservatives to have a "social mission", focusing on social care for older people.
He also vowed to get more young people voting Tory.
And he promised: "I will never provoke a general election before we have left the EU."
Members will receive their ballots between 6 and 8 July, with the new leader expected to be announced in the week beginning 22 July.

Boris Johnson and Jeremy Hunt have clashed on Brexit and UK relations with Donald Trump in a lively and occasionally bad-tempered TV debate.
Mr Hunt accused his rival of not being willing to "put his neck on the line" by saying he would quit as PM if he did not hit the 31 October deadline.
Mr Johnson said he admired his rival's ability "to change his mind" so often - a dig at the fact Mr Hunt voted Remain.
Mr Johnson declined to condemn Mr Trump for his response to the emails row.
He refused to confirm whether he would keep the UK's top diplomat in the US, Sir Kim Darroch, in his post until his scheduled retirement in December, after Mr Trump said he was no longer prepared to deal with him.
The US president has lambasted Sir Kim, and criticised Theresa May, after the diplomat described the White House as "inept and dysfunctional" in leaked cables.
While stressing the value of the "special relationship" with the US, Mr Johnson insisted that only he, as prime minister, would take "important and politically sensitive" decisions such as who should represent the UK in the US.
During the first head-to-head debate of the leadership campaign, the two clashed over their different Brexit strategies, political styles and why they were best equipped to be prime minister.
The exchanges were pointed and personal in nature at times, with former Mayor of London Mr Johnson dismissing his opponent's "managerial" style of politics and accusing him of flip-flopping on certain issues.
Foreign Secretary Mr Hunt said the UK needed a leader not a "newspaper columnist" - a reference to his rival's work for the Daily Telegraph.
He joked that he admired Mr Johnson's "ability to answer the question", adding: "He puts a smile on your face and you forget what the question was, a great quality for a politician but not necessarily a prime minister."
After an opening speech from each contender, the foreign secretary immediately went on the attack over Brexit, pressing his rival on whether he would quit Downing Street if he failed to take the UK out of the EU by 31 October.
He said by failing to answer the question, Mr Johnson - who previously said the deadline was a "do or die" issue for him - showed he was motivated by personal ambition not leadership.
"It is not do or die," Mr Hunt said. "It is Boris in Number 10 that matters."
Accusing his rival of not being straight with the electorate, he said: "Being prime minister is about telling people what they need to hear, not just what they want to hear."
Mr Johnson, in turn, said it was clear his rival was "not absolutely committed" to the deadline himself, branding him "defeatist".
He urged Mr Hunt to guarantee that Brexit would happen by Christmas, adding that the EU would not take a "papier mache deadline" seriously.
"If we are going to have a 31 October deadline, we must stick to it," he said. "The EU will understand we are ready and will give us the deal we need.
"I don't want to hold out to the EU the prospect that they might encourage my resignation by refusing to agree a deal.
"I think it is extraordinary we should be telling the British electorate we are willing to kick the can down the road.
"I would like to know how many more days my opponent would be willing to delay."
Both men have said they would be prepared to leave the EU without a deal, but Mr Johnson has been far more relaxed about the impact that could have.
Mr Hunt suggested his rival was "minimising the risk of a no-deal Brexit" and "peddling optimism", but Mr Johnson said the UK had had a "bellyful of defeatism" and the UK could look forward to a bright future outside the EU.
The pair also disagreed over whether they might be prepared to suspend Parliament to force through a no-deal exit - so-called prorogation.
While Mr Hunt categorically ruled this out, Mr Johnson said he would "not take anything off the table".
Both teams will leave Salford content with their candidates' performance.
The gaffe prone former foreign secretary avoided slipping on any banana skins, and managing not to commit on some of the more controversial issues before him.
And the current foreign secretary managed to land his blows on his opponent.
There was perhaps though no jaw dropper, no moment that turned this race upside down.
Mr Johnson arrived the favourite and leaves in the same position. Mr Hunt turned up keen to show that he is ready to use sharp elbows to scrap and to make himself heard with attacks on his rival that are a contrast to his normal careful style.
Their respective status as the front runner and challenger may not have changed.
Yet while Jeremy Hunt may not, from this performance alone, manage to stop Boris Johnson's journey to No 10, he has at least shown that if he gets there, he is likely to face a very tricky time.
On the escalating diplomatic row with the US, Mr Hunt said the president's criticism of Sir Kim Darroch had been ill-judged and he would, if he became PM, not be forced into recalling the diplomat early.
He also took issue with Mr Trump for saying the prime minister had failed to listen to his advice and been made to look "foolish" over Brexit.
"His comments about Theresa May were unacceptable and I don't think he should have made them," he said, remarks which prompted audience applause.
Mr Johnson said the US president had been "dragged into a British political debate" not of his making, but did suggest his outburst on Twitter - in which he called Sir Kim a "pompous fool" - had "not necessarily been the right thing to do".
While civil servants must be able to give confidential advice, he declined to comment on Sir Kim's future, only asking Mr Hunt to rule out "extending his term out of sympathy".
Both men have been criticised for making uncosted spending promises and offers of tax cuts during the campaign.
Mr Hunt sought to make capital out of Mr Johnson's pledge to give a tax cut to higher earners by raising the threshold at which people pay 40% tax from £50,000 to £80,000.
"It was a mistake, tax cuts for the rich," he said. "I have spent my life trying to persuade people that we are not the party of the rich."
Mr Johnson defended what he said was a "package" of measures to reduce the tax burden for both low and middle earners and which he said would boost the economy.
The show, entitled Britain's Next Prime Minister: The ITV Debate, was hosted by journalist Julie Etchingham in front of a studio audience of 200 people at MediaCityUK in Salford.
It took place as 160,000 or so party members get the chance to vote by post on who should succeed Theresa May.
The winner and next PM will be revealed on 23 July - it will be the first time a sitting prime minister has been chosen by party members.

Blimey.
If you are looking for drama, the Conservative Party rarely disappoints.
If you are looking for stability these days, that's a different matter.
To absolutely no one's surprise, Boris Johnson's march to Number 10 has taken a giant stride.
Love him or loathe him, he is the biggest political star in this contest, and he persuaded his colleagues by a handsome margin that he's meant for the highest office in the land.
The number of votes he received increased again, up to 160 this time, more than half of the parliamentary party.
The gasps in central lobby when the result emerged though were not because of his stellar lead, but down to the wafer-thin margin in the race to be his challenger.
Environment Secretary Michael Gove, Mr Johnson's companion on the referendum campaign trail before he sabotaged his leadership bid, received 75 votes.
That's quite something when you consider just 10 days ago he was under the cosh over revelations of taking cocaine when he was working as a journalist.
But Jeremy Hunt, the former Remainer and current Foreign Secretary, won 77 votes - so close you can almost hear the squeak.
Now, there's no doubt that Mr Johnson is, at this stage (and there's a long way to go), widely expected to end up in Number 10.
But this result is an enormous relief to his camp, for the simple reason that they think Mr Hunt is easier to beat.
Forget any differences in style between the two challengers and their comparative talents - Jeremy Hunt voted Remain in the EU referendum.
And for many Tory members it is a priority for the next leader to have been committed to that cause, rather than a recent convert, however zealous.
Of course, pay attention to recent political history. Upsets are the norm. Outsiders become insiders. Strange things happen, and that's before you price in Mr Johnson's ability to cause havoc for himself.
But this result has left Mr Johnson's camp hugely relieved.
One of his most committed backers was laughing with joy and savouring not a little bit of revenge when I talked to them.
Memories and suspicion linger long around here. And the narrow margin between Mr Gove and Mr Hunt has created doubts of its own.
Rumours are swirling that Mr Johnson's camp were engaged in skulduggery all day, that they would have pushed some of their own supporters to back Mr Hunt, to try to stop Mr Gove from coming second.
The message from on high in Mr Johnson's campaign is that the candidate himself was clear that absolutely must not happen, that he'd frown on any attempt to engineer the result.
Eyebrows have been raised, though. At least four of Sajid Javid's supporters declared online they would switch their support to Mr Johnson. But his actual tally only went up by three in the final ballot.
Were their arms twisted to "lend" their actual votes to Mr Hunt to keep Mr Gove off the ballot?
One member of the cabinet said there had been "more churn than a washing machine". It was a secret ballot, so we will never know exactly what happened. But corralling votes is the fundamental art of getting politics done.
But now this episode is over, we know which pair of politicians will vie to run the country.
The favourite, a public school and Oxford-educated former cabinet minister, who has survived more serious scrapes than Theresa May's had hot dinners.
The other, a millionaire public school-educated Oxford graduate, who's been in the cabinet for nearly a decade who tonight, has branded himself "the underdog".
And remember it's Tory members, not the rest of us, who'll make the final call.

Boris Johnson, the front-runner in the Tory leadership race, has said the party could be "fired from running the country" if it does not deliver Brexit.
Writing in the Daily Telegraph, he said voters in the EU election issued a "crushing rebuke" to the Conservatives.
Fellow candidate, Foreign Secretary Jeremy Hunt, said the party faces an "existential risk" over Brexit.
Eight candidates have declared they are standing for leader, after Theresa May said she would resign.
Mr Johnson said voters had issued the party with a "final warning" as the Tories came fourth in Hillingdon, where he is an MP, and the Brexit Party emerged with the largest number of MEPs overall.
He said: "If we go on like this, we will be fired: dismissed from the job of running the country."
Mr Hunt said on Twitter that the "painful result" meant there was an "existential risk to our party unless we now come together and get Brexit done".
With some results still to declare, the overnight count has seen Conservative voters deserting the party, with the party scoring less than 10% of the total vote - compared to nearly 25% in the last EU election.
BBC political