The EU has warned Theresa May she must offer 'acceptable' new ideas within 48 hours if she wants to salvage talks on the Brexit deal.
The Prime Minister is facing a defeat of up to 100 votes on her deal on Tuesday night after talks on the Irish border backstop collapsed in acrimony this week.
Mrs May is facing a last minute scramble to secure concessions and could travel to Brussels as late as Monday - despite Government sources admitting Sunday night is effectively the deadline to show a new deal to MPs.
The EU Commission has told the UK Government to come up with its new ideas by tomorrow night if they want officials to work on them through the weekend.
Chancellor Philip Hammond today warned Brexiteers to back the deal anyway insisting it is the 'last chance' to leave the EU on time today.
The Chancellor said a second loss for the Prime Minister would leave the fate of Brexit 'highly uncertain' as he predicted MPs would then vote to rule out no deal and delay Brexit.
If the PM's deal is defeated on Tuesday night, MPs will vote on whether to rule out no deal on Wednesday before deciding whether to delay Brexit on Thursday.
Mr Hammond told broadcasters: 'If we don't pass the meaningful vote on Tuesday we'll go into a parliamentary process that very likely will lead to an extension of time and an uncertain outcome, more uncertainty for the British economy, more uncertainty for people across the country.
'It's very important that my colleagues think about the consequences of not agreeing this deal.
'This is now the last chance to be confident that we can get this deal done and we can leave the EU on schedule.'
Mr Hammond refused to be drawn on how he would vote if Mrs May's deal is defeated and MPs are asked whether they want to delay Britain's exit from the EU.
'I'm not going to speculate about something that hasn't happened and I don't think will happen because I think the Government is very clear where the will of Parliament is on this,' he told Today.
'Parliament will vote not to leave the European Union without a deal next Wednesday, I have a high degree of confidence about that.
'But we do need to have clear confirmation. It's right that Parliament should make that decision and then we'll put the question about extending Article 50 and how we try to break this impasse by finding a consensus.'
Following Tuesday's meeting, Michel Barnier, the EU's chief negotiator, gave a gloomy assessment of the talks but said afterwards that he was 'still determined'.
EU officials are preparing to work round the clock this weekend, saying it is 'unlikely' an agreement will be reached before then and that talks will go down to the wire.
And in a warning there will be no significant concessions from the EU, French Europe minister Nathalie Loiseau today said the deal cannot be reopened.
She told BBC Radio 4's Today programme the deal was the 'best possible solution', and said: 'We cannot reopen this negotiation on the Withdrawal Agreement because it is balanced...
'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, and that it's a last resort solution.'
'There's no sign of a breakthrough and there will need to be some tough work in the days ahead if there's going to be deal,' one EU official said, adding that it was still possible negotiators could seal a deal by the end of the weekend.
But that would leave Mrs May just 24 hours to travel to Brussels to endorse the deal on Monday before taking it back to be voted on by MPs the next day.
Tory Brexiteers have already warned the Prime Minister they want at least two days to scrutinise any new offer and will not be 'bounced' into an early vote.
Mr Cox, who met Mr Barnier with Brexit Secretary Stephen Barclay, described Tuesday's late-night talks as 'robust' as he returned to London yesterday.
He said: 'We are into the meat of the matter now. We've put forward some proposals, very reasonable proposals, and we're now really into the detail of the discussions.
'Both sides have exchanged robust, strong views and we are now facing the real discussions. Talks will be resuming soon.'
Last night it emerged that Mr Cox is trying to secure an 'arbitration panel' that would determine if the two sides were acting in good faith in trying to find alternatives to the backstop.
But according to a report on the BuzzFeed website, the idea was rejected by Mr Barnier.
Sources say Mr Cox and Mr Barclay could be back in Brussels as early as tomorrow to help push a deal over the line in time for next week's vote.
Technical discussions, led by Mrs May's chief Brexit adviser Olly Robbins, will continue in Brussels. Neither side is said to have presented any new formal text.
The latest row over the backstop – designed to prevent a hard border emerging in Ireland – centres around disagreements over language which could either form a new document to be added to the Withdrawal Treaty or sit alongside it.
According to EU sources, 'inspiration' for the text has been drawn from a joint letter sent to Mrs May by EU Commission and Council chiefs Jean-Claude Juncker and Donald Tusk in January.
This included a pledge to reach a future trade agreement 'speedily' and talked of a 'firm determination' to have an alternative to the backstop ready so it would either never have to be used or only triggered 'temporarily'.
Negotiators are struggling with the 'semantic' challenge of agreeing a form of words which will please both sides.
Downing Street acknowledged the talks were deadlocked, but insisted they would continue.
A spokesman for the Prime Minister said: 'The EU continues to say they want this resolved and they want the UK to leave with a deal. Parliament has been clear we need legally-binding changes to ensure the UK cannot be stuck in the backstop indefinitely.'
An EU Commission spokesman said: 'While the talks were held under a constructive atmosphere, discussions have been difficult and we have not yet been able to identify any solution.'
Meanwhile, EU boats will be banned from fishing in UK waters if Britain leaves without a deal under a new law to be laid before Parliament today.
Environment Secretary Michael Gove will say boats which want to fish off the UK coast will need a licence from the Government.
MPs were warned last night they may lose their Easter holiday to push through Brexit legislation. It was the clearest hint yet that Brexit is set to be delayed.
Mr Gove warned MPs that votes on vital Brexit legislation could be held during Easter.
The prospect of a super-soft Brexit increased last night after Jeremy Corbyn held talks with Tory supporters of a Norway-style deal with the EU.
Norway's arrangement with the EU forces it to accept the free movement of people ruled out by Labour's 2017 manifesto.
But in a surprise move, the Labour leader discussed the idea with a cross-party group of MPs calling for the softest possible Brexit.
In a separate development last night, the House of Lords voted for plans that would force Theresa May to seek a permanent customs union with the EU after Brexit.
The moves underline fears at the top of Government that Parliament will seize control of the Brexit process if Mrs May's deal is rejected for a second time on March 12
Chief Whip Julian Smith warned the Cabinet on Tuesday that Parliament would 'try to force the Government into a customs union' if the deal is defeated next week. Mrs May is considering a public warning on the issue tomorrow in the hope of pressuring MPs into supporting her proposals.
A Whitehall source said the PM could make a major speech 'framing next week as the moment of decision for the country'.
Yesterday's talks involved Mr Corbyn, Tory ex-ministers Sir Oliver Letwin and Nick Boles and Labour backers of the Norway plan, Stephen Kinnock and Lucy Powell.
Mr Kinnock said the meeting involved talks about a Norway-style deal, adding: 'There is a strong cross-party consensus for a pragmatic, bridge-building Brexit.'
Sir Oliver, working with Labour's Yvette Cooper, is leading a push for Parliament to take control of the Brexit process.
Former Tory leader Iain Duncan Smith said last night it was 'astonishing' that senior Conservatives were willing to work with Labour's hard-Left leader on plans that would undermine Government policy.
Last night, peers backed an amendment to the Customs Bill by a majority of 66 that would require Mrs May to seek a permanent customs union with the EU after Brexit. An alliance of Labour, Lib Dem, cross bench and some Tory peers defeated the Government by 207 votes to 141.
Labour's trade spokesman in the Lords, Lord Stevenson of Balmacara, said: 'Ministers must drop their red lines on Brexit and embark on a fresh approach to the negotiations with the EU based around a Customs Union that protects jobs, secures opportunities for our industries, and removes the need for a hard border in Ireland.'
Ministers had been resigned to losing last night's vote, but No10 indicated it would seek to overturn the demand in the Commons, where MPs have already voted twice to reject a permanent customs union.
Mrs May's spokesman said: 'The PM has been clear about the importance of the UK being able to have its own trade policy.'
Norway is not in the customs union but is a member of the EU's single market, and has to accept free movement, pay into the EU budget and accept EU laws. Senior Tories warn that making the UK a rule-taker undermines the idea that the UK is taking back control from the EU.
This article has been adapted from its original source.
