Theresa May is holding crisis talks with the Cabinet amid signs she is preparing a humiliating retreat over her Brexit deal.
Ministers are on an emergency conference call as the PM desperately tries to pick a way through the mounting chaos.
Mrs May has been locked in intense talks with allies and aides as they try to find a way through the dire situation.
Some 110 Tory MPs are pledged to oppose the plan, making victory all-but impossible as they line up with Labour, the SNP, and the Lib Dems.
A spokeswoman for the PM said this morning that vote was 'going ahead as planned'.
But senior sources are increasingly certain that the Commons showdown will be put off.
A decision is expected to be confirmed at the end of the call.
A climbdown would allow Mrs May to avoid catastrophic defeat, but would demonstrate how low her authority has sunk.
The dramatic developments come as Tory infighting escalates dramatically, with leadership rivals getting ready to pounce.
Foreign minister Alan Duncan warned that those who kill off Mrs May deal 'will forever be known as the wreckers'.
He also said if Boris Johnson took over at No10 he will be met with 'loud raspberries in many many different languages'.
A growing number of ministers are believed to be urging Mrs May to shelve the clash tomorrow to avoid disaster.
But others insist that will look like cowardice, and she needs a demonstration of Parliament's view to strengthen her hand with Brussels.
Environment Secretary Michael Gove today tried to quell mounting speculation about a retreat by the PM before the crunch showdown on her deal tomorrow night.
He also gave a clear indication that the government is seeking from concessions from the EU, saying there was 'no-one better placed' than Mrs May to get more concessions.
But he warned there were significant 'risks' in reopening the Withdrawal Agreement thrashed out with Brussels.
Mr Gove dismissed suggestions that Mrs May could be helped in her efforts by a heavy defeat in Parliament.
In a reference to the famous resignation speech by Geoffrey Howe that sunk Margaret Thatcher, he warned that would be the 'equivalent of breaking the cricket bat in half before the leader went to the crease'.
'If colleagues really want to help the PM I'm sure the PM would urge them gently but firmly to support her tomorrow,' Mr Gove told BBC Radio 4's Today programme.
There are doubts over whether Mrs May would be able to abandon the vote, with speculation that Speaker John Bercow could force one even if she tries.
Mrs May spoke with EU council president Mr Tusk last night as she considers a bid to squeeze more concessions out of the EU.
Number Ten remained tight-lipped, but Mr Tusk tweeted that it 'will be an important week for the fate of Brexit'.
An EU summit is scheduled for the end of the week, which could provide a stage for Mrs May to emulate Margaret Thatcher and have a 'handbag moment' to demand more concessions on the Irish border 'backstop'.
But Ireland's deputy PM Simon Coveney today delivered a savage blow by dismissing her chances of getting fresh concessions on Brexit.
He insisted the deal is 'not going to change'.
In a clear leadership pitch yesterday, Mr Johnson also predicted that Mrs May will lose her crunch vote on the deal by a huge margin this week, as he told of the deep 'personal responsibility' he feels towards Brexit.
Looking visibly emotional as he appeared on the BBC's Andrew Marr show, he said the UK can do 'much much better' than the PM's deal.
There are claims that Home Secretary Sajid Javid is also brazenly canvassing Cabinet colleagues for a tilt at the top job if Mrs May is ousted. Aides insisted he is focused on helping the PM get her deal through.
In a sign of what could be a torrent of resignations if she goes ahead with the vote, Tory MP Will Quince yesterday quit as a parliamentary aide to Defence Secretary Gavin Williamson.
At least two government whips are understood to be considering falling on their swords in order to vote against the Brexit package.
Mrs May's position was further undermined today when the European Court of Justice ruled that the UK can unilaterally halt the Brexit process by withdrawing Article 50.
The judgement that permission is not needed was hailed by Remainers as opening the door to holding a second referendum.
Foreign Secretary Jeremy Hunt, in Brussels for regular talks with counterparts this morning, said the government has no intention of reversing Article 50 and voters would be 'shocked' if it did.
Staring down the barrel of defeat, Mrs May is under mounting pressure to delay the vote and use an EU summit in Brussels next Thursday to hammer the bloc for more concessions.
And with the Government in chaos over Brexit, several senior ministers are in talks with Labour over whether a second referendum or a Norway-style deal would break the deadlock.
The PM's de facto deputy David Lidington, and Justice Secretary, David Gauke, have been in talks with Labour MPs over the two possibilities.
Sir Alan claimed his Tory colleagues lining up to oppose Mrs May's Brexit deal had not 'thought strategically enough about what the consequences of that would be'.
'The first is that even if they overturn it they are not necessarily going to get an alternative which they are campaigning for, and instead what they will probably do is set in train a course of events which could lead to chaos in many, many areas,' he told BBC Radio 4's Today programme.
He warned there could be a leadership contest, or a general election, and said the UK could be 'top dog in Europe at the moment when France is burning and Germany is in transition' but instead 'we're just beating ourselves up'.
Sir Alan also said Tory former foreign secretary Boris Johnson would be 'met with a very, very loud raspberry in many, many different languages' if he walked into a negotiating room in Brussels.
And he warned: 'What I really resent is the glee some people have in wanting to oppose this, and then in jostling for their own personal gain. This is contemptible.
'Let's be absolutely clear that if this goes pear-shaped in the way that it really could, on the back of people opposing the deal that is on offer tomorrow night, the wreckers in history will forever be known as the wreckers.'
Under a barrage of attacks from all sides, the PM mounted a fresh fightback today by warning Eurosceptics that risk losing Brexit altogether unless they back her.
She used a powerful interview in the Mail on Sunday yesterday to try to avert the rebellion by 'weaponising' the prospect of Mr Corbyn becoming Prime Minister.
Mrs May said Britain 'would truly be in uncharted waters' if the deal is voted down.
She said: 'It would mean grave uncertainty for the nation with a very real risk of no Brexit.
'We have a leader of the Opposition who thinks of nothing but attempting to bring about a General Election, no matter what the cost to the country… I believe Jeremy Corbyn getting his hands on power is a risk we cannot afford to take.'
Mutinous Tories are furious at her deal's Irish backstop plan, which would see the UK tied to the customs union and more single market checks have to be carried out in Northern Ireland.
They warn the UK cannot pull out of the backstop without the EU's permission - potentially keeping the UK 'locked' to Brussels against its will.
Mr Johnson launched a fresh broadside against the deal as he laid out his pitch for the Brexit negotiations in what will be seen as a thinly veiled leadership pitch.
Writing in The Sun, he said the UK should refuse to hand over half of the £39billion divorce bill until a free trade is done.
Mr Johnson has become the PM's fiercest critic since quitting as Foreign Secretary in fury at her Brexit plan.
He wrote: 'It is time now to show our EU friends that we mean business. This should be a take-it-or-leave-it offer.
'And, to show that we mean business, we must be able to walk away.
'This is a great country, capable of rising to immense challenges — and I believe the people of this country are fed up to the back teeth of being told by their Government that they are simply incapable of managing the logistical problems of Brexit.'
Amid mounting opposition to the deal, civil servants have war-gamed two versions of the UK holding another referendum.
The first is a straight choice between the PM's deal and remaining in the EU, and the second would be a leave, remain contest with a second question asking them if they prefer the existing deal or a no-deal departure on World Trade Organisation terms, The Sunday Times reported.
If Mrs May loses an immediate no-confidence vote tomorrow, Parliament could have to sit on Christmas Day because the Fixed Term Parliament Act sets a deadline of 14 calendar days for a new Government to be formed, meaning December 25 would be the last chance for any coalition to try to win a Commons majority.
It's believed that the last time the Commons sat on Christmas Day was in 1656.
This article has been adapted from its original source.
