Theresa May has been appealing for help from union chiefs amid signs she faces the biggest Commons defeat ever over her Brexit deal.
The PM is on track to lose by a massive 228 vote margin next Tuesday as Tory Brexiteers and Remainers rebel to join Labour in the division lobbies, according to a BBC analysis.
The biggest previous setback for a government is believed to be by 166 in 1924, when Labour's Ramsay MacDonald was leading a minority administration.
However, in a chink of light for Mrs May two Tory MPs, George Freeman and Trudy Harrison, revealed they are switching sides to support her deal.
At a Downing Street press conference, the Prime Minister insisted 'for those who want to avoid no deal, backing the deal is the right thing to do'.
Speaking alongside her, Japan's PM Shinzo Abe warned Britain against no deal and said the 'world is watching' as MPs wrestle with how to deliver Brexit.
The intervention was slammed by Brexiteers who warned it would prove as damaging to the PM as Barack Obama's endorsement of Remain in 2016.
As efforts step up to turn the tide, No10 also confirmed spoken to Unite chief Len McCluskey - a close ally of Jeremy Corbyn - about how to find a way forward on Brexit.
The move comes after senior Tories opened discussions with Labour amid fears that Parliament has descended into a 'Mexican stand-off' - with all sides vowing to block the others' plans.
Meanwhile as the Brexit debate continued in the Commons ahead of Tuesday's showdown vote, Environment Secretary Michael Gove lambasted Labour's position as 'b*******'.
Desperate cross-party talks are under way today as the political crisis over Brexit mounts dramatically as Theresa May (pictured today at a welcome ceremony for Japan's PM Shinzo Abe) faces defeat
At a Downing Street press conference, the Prime Minister insisted 'for those who want to avoid no deal, backing the deal is the right thing to do'
The depth of the deadlock was underlined over the past two days with Mrs May suffering two humiliating defeats in the Commons, stepping up the timetable for her to spell out a 'Plan B' and restricting the Treasury's tax-raising powers if there is no-deal Brexit.
May backs Labour plan to protect worker rights and the environment after Brexit
The Government confirmed today it will back moves by Labour MPs to safeguard workers' rights after Brexit in an attempt to win support for the deal.
The backbench amendment would require Britain to at least match EU rules on pay and conditions, health and safety issues, plus environmental standards.
The Government would be obliged to 'consider' any new laws on these standards passed by the EU after Brexit.
John Mann, one of the Labour MPs behind the amendment, said Government backing for the proposal could make the Prime Minister's plan 'more attractive'.
'If we have a guarantee that works on workers' rights and conditions, that's significant,' he told the Daily Mirror.
As the vote nears, Mrs May used a press conference with Mr Abe to warn against No Deal.
She said: '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 deal that is the deal that the EU has made clear is the only deal.
'There's an issue that's been raised about the backstop, and we are continuing to work with the EU on that particular issue, but there is a good deal on the table and for those who want to avoid no deal then backing the deal is the thing to do.'
Mr Abe said: '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 transition to ensure legal stability for businesses that have invested into this country.'
Brexiteer Simon Clarke said: 'Today's stunt brings back memories of President Obama being wheeled out by David Cameron before the referendum.
'This is about how we implement a decision made by the British people and one which British MPs need to get right for the future of our country.
'That does not involve being stuck as a rule-taking hostage of the EU, no matter how convenient that might be for others.'
Speaker John Bercow also caused fury yesterday when he demonstrated he is willing to tear up the Parliamentary rulebook in order to bring the government to heel.
Mrs May has been privately meeting Leave-leaning Labour MPs in an attempt to boost support for her deal ahead of a crunch vote on Tuesday.
But estimates from the BBC suggest just 206 are going to back her plan - with 433 against.
The PM's spokeswoman confirmed Mrs May has spoken to Mr McCluskey and Tim Roach for the first time since becoming Prime Minister.
She said: 'She has had some phone calls today.
'Obviously the PM is seeking the widest possible support for her deal, and it is a dal that protects jobs and the economy and it's a good deal for workers. Union leaders obviously represent workers across the country and as part of her widespread engagement she has spoken to some of those leaders today.'
Characterising the calls, she said: 'They were constructive calls.'
She was asked if Mrs May was doing too little too late' and if it was 'desperate' for the PM to turn to 'Red Len' as she tries to drum up support for her deal.
The spokeswoman said: 'The PM speaks to leaders across a range of industries, business groups etc and has done that consistently throughout this process and today she spoke to a couple of union leaders and there will be further engagement in the days ahead.'
Jeremy Corbyn used a speech in Yorkshire today to repeat that Labour will vote down the PM's Brexit deal
Gove shocks MPs by repeatedly branding Labour's Brexit policy 'boll***s'
Michael Gove shocked MPs today as he repeatedly branded Labour's Brexit policy 'boll***s'.
The Environment Secretary deployed the swear word twice as he spoke during the debate on Theresa May's deal.
But Speaker John Bercow dismissed complaints that the term breached conduct rules, saying it was a matter of 'taste'.
The spat came as MPs resumed discussion on the PM's deal in the chamber today - amid fears that Parliament is locked in a 'Mexican stand-off' where every possible option for resolving the crisis is blocked.
Opening the debate in the House, Mr Gove highlighted that shadow international trade secretary Barry Gardiner had once been caught out privately using the swear word to refer to Labour's six tests for a Brexit deal.
And he then pointed out that Mr Bercow's wife Sally had a sticker saying 'Boll***s to Brexit' in her Land Rover.
'I know, Mr Speaker, there are some distinguished citizens in this country who have put on their cars a poster or sticker saying boll***s to Brexit,' Mr Gove said.
'But we now know from Labour's own frontbench that their official Brexit position is boll***s.'
In the Commons debate today, Tory MP Mr Freeman confirmed he will be voting for the deal.
He tweeted afterwards that 'we urgently need an orderly Brexit'. 'So, with a very heavy heart, I will vote for the Withdrawal Agreement,' he said.
However, Mr Freeman added that if the package falls he will push for a Norway-style deal.
The focus of ministers and MPs is already turning to what happens after the PM's plan has been defeated.
Tory and Labour MPs have been mobilising against no-deal Brexit. More than a dozen Conservatives have indicated they could vote no-confidence in the government to avoid the UK crashing out in March.
Sarah Wollaston this morning told the BBC she 'will resign the Conservative whip' if policy becomes to go for no deal.
Business Secretary Greg Clark dodged around when asked whether he would stay in government if the PM decided to take the country out without an agreement.
He told Politico: 'This is a time for parliament to come together and work intensively to establish an agreement that can command majority support.'
Senior Conservative Sir Oliver Letwin effectively opened negotiations with shadow Brexit secretary Sir Keir Starmer in the Commons yesterday, raising the prospect of a joint approach on a customs union and single market deal.
Sir Keir replied: 'Obviously, at some stage, if we are to leave other than without a deal there has to be a consensus in this House for something.'
Speaker John Bercow was berated by ministers and Tory Eurosceptic MPs after he made the extraordinary ruling yesterday
Mrs May (pictured at PMQs yesterday) has been privately meeting Leave-leaning Labour MPs in an increasingly vain attempt to boost support for her deal ahead of a crunch vote on Tuesday
But the focus of ministers and MPs is already turning to what happens after the package has been defeated next week
Speaker John Bercow also caused fury yesterday when he demonstrated he is willing to tear up the Parliamentary rulebook in order to bring the government to heel
Pressed by former chancellor Ken Clarke, Sir Keir said: We are going to have to sit down and consider credibly what are the options and how parliament takes control of what happens next.'
How could MPs try to block a no-deal Brexit?
To prepare for Brexit, several major laws must be passed between now and March 29 and any or all could be amended by MPs in a bid to stop no deal.
If ministers ignored motions for a second referendum or an extension of Article 50 they could, with the likely connivance of Speaker Bercow, be held in contempt of Parliament. Repeated contempt motions would be difficult, if not impossible, for ministers to ignore.
If the Government repeatedly ignored parliamentary votes and a no deal Brexit appeared close, Labour could table a no-confidence motion, potentially triggering an election.
Both Mr Clarke and Sir Keir raised the prospect of delaying Brexit by extending Article 50 - something that would be anathema to many Tory Eurosceptics.
Mrs May is said to have met Gareth Snell, Lisa Nandy, Jon Cruddas, Caroline Flint and John Mann last night.
Concessions being mooted include giving a commitment to stick to EU standards on workers' rights. Mr Mann suggested that could make a difference.
However, shadow justice secretary Richard Burgon made clear there was little enthusiasm for the idea among the Labour leadership.
'When it comes to the crunch I don't trust the Conservatives on workers' rights,' he told the BBC Radio 4 Today programme.
'Even the noises that are being made in the press by the Conservatives don't mean any such agreement would be legally binding when it comes to protecting workers' rights.'
Mrs May's former chief of staff, Nick Timothy, used his column in the Telegraph today to liken the situation in Parliament to a 'Mexican stand-off'.
'Theresa May's metaphorical gun is aimed at the MPs who back a second referendum. Whose guns are pointed at the no-dealers. Whose guns are trained on supporters of Norway-plus. Whose guns are aimed at Jeremy Corbyn. Whose gun is pointed at Theresa May,' he said.
'Like in the movies, nobody wants to drop their weapon, yet nobody is prepared to pull the trigger. Everybody says they're ready to shoot. And everybody is starting to get twitchy.'
Former chancellor Ken Clarke (left) and Oliver Letwin (right) raised the prospect of a cross-party approach to end the deadlock in Parliament
Labour leader Jeremy Corbyn today repeated his demand for a general election, saying it is the most 'practical and democratic' way to 'break the deadlock' in the Commons over Brexit.
Mr Corbyn used a speech in Yorkshire today to repeat that Labour will vote down the PM's Brexit deal.
He said: 'If the Government cannot pass its most important legislation, then there must be a general election at the earliest opportunity.
'To break the deadlock, an election is not only the most practical option, it is also the most democratic option.
'It would give the winning party a renewed mandate to negotiate a better deal for Britain and secure support for it in Parliament and across the country.'
However, Sir Keir and scores of Labour MPs are believed to favour pushing for a second referendum.