Rebel MPs will today launch a fresh attempt to force Theresa May into a soft Brexit tonight by holding votes on alternatives to her deal including a customs union or a second referendum.
Ministers believe as many as 70 Tory MPs could back a proposal to remain in the EU, which could lead to it winning over a majority of MPs and killing off the Prime Minister's deal.
The Commons is then expected to demand Mrs May adopts a softer Brexit as part of her plan and present it to Brussels, with MPs willing to change the law to force her hand.
But the PM would also face a slew of resignations by Brexiteers, forcing her to consider a snap general election to break the deadlock.
Ministers are considering an unprecedented parliamentary 'run off' pitting Mrs May's deal against the soft Brexit option chosen by MPs in the hope of focusing the minds of Tory eurosceptics.
A first round of indicative votes was held last Wednesday but MPs were unable to agree on how to proceed. Eight different scenarios were put to a vote and all were defeated.
This afternoon Speaker John Bercow is expected to select three or four alternatives to go on a ballot paper, with the votes scheduled to take place at 8pm and results due around 10pm.
Such is the power of the Speaker he does not have to justify his choices or explain how they were made.
But he has previously looked more favorably on motions and amendments that have cross-party backing rather than being partisan in nature.
This means he is likely to go for the motions MPs came closest to backing with a majority last Wednesday: remaining in a customs union, a second referendum and revoking Article 50.
This afternoon Speaker John Bercow is expected to select three or four of the eight Brexit alternatives to go on a ballot paper, with the votes scheduled to take place at 8pm and results due in around 10pm
These are the results of last week's indicative votes on Brexit, in order of preference. It shows that while MPs can't find a consensus they lean heavily towards a softer Brexit or second referendum
These have backing from both the two main parties and in many cases support from the smaller parties.
But under this precedent it would suggest that the motions supporting a no-deal Brexit will not be called for a vote - and in any case they were the least popular last week and seem doomed to fail.
Backbenchers led by Sir Oliver Letwin have taken control of the Commons timetable to stage a second round of indicative votes after none of the eight options put to MPs last week won enough support.
If a majority emerges for one of the alternatives tonight, the rebels plan to put down legislation on Wednesday that would force ministers to act.
Former Cabinet minister Ken Clarke, who drew up the customs union plan defeated by just six votes last week, has said he is 'reasonably confident' it will get over the line this time.
Meanwhile, supporters of a so-called 'Common Market 2.0' proposal that would keep Britain in the customs union and the single market have been seeking to win over DUP and SNP MPs who all abstained when it was voted on last week.
Staying in the single market would involve continued freedom of movement and making contributions to the EU budget, while being in a customs union would prevent Britain from striking its own trade deals.
The Brexit options that MPs are poised to vote on tonight:
Theresa May faces a battle to keep control of Brexit as MPs vote on alternatives to her deal tonigh
Motion A: Unilateral right of exit from the backstop
Brexiteer Tory backbenchers led by Basildon and Billericay's John Baron, want the UK to leave the EU on May 22 2019 with the Withdrawal Agreement amended to allow the UK unilaterally to exit the controversial Northern Ireland backstop.
The EU has consistently refused to reopen the Withdrawal Agreement that was agreed last year and even Downing Street now accept that this idea is a non-starter.
And if this amendment was passed it would run contrary to the extension agreed with EU leaders two weeks ago in order the get the extension to may 22 - which was dependent on the current WA being passed by last Friday.
In addition, Speaker John Bercow is not likely to allow it to proceed as it is only backed by a small group of Tory Brexiteers.
Motion B: No deal in the absence of a Withdrawal Agreement
This is an even more extreme motion by Mr Baron and a hardcore group of European Research Group holdouts including Andrew Bridgen and John Redwood.
It Baron, which calls for a no-deal Brexit on April 12 if no Withdrawal Agreement can be agreed by the Commons.
While a no-deal Brexit remains the default option if no deal or alternative is passed by MPs, parliamentarians have already voted against it.
A very similar motion last week lost by 400 votes to 160, the widest margin of any of the eight that were put to the vote.
Motion C: Customs union with the EU
Tory former chancellor Ken Clarke's customs union plan requires any Brexit deal to include, as a minimum, a commitment to negotiate a 'permanent and comprehensive UK-wide customs union with the EU'.
This is where tonight's vote could get interesting. This amendment last week lost by the tightest margin of them all.
It went down by eight votes, losing by 272 to 264. It means that a handful of MPs changing their mind could see it across the line.
But the SNP and Lib Dems abstained last time so those votes may not be easy to find on the polarised Tory and Labour benches.
And it if did win it would cause havoc in the Government with Brexiteers going on the warpath.
Motion D: Common market 2.0
A cross-party motion tabled by Conservatives Nick Boles, Robert Halfon and Dame Caroline Spelman and Labour's Stephen Kinnock, Lucy Powell plus the SNP's Stewart Hosie.
The motion proposes UK membership of the European Free Trade Association and European Economic Area. It allows continued participation in the single market and a 'comprehensive customs arrangement' with the EU after Brexit - including a 'UK say' on future EU trade deals - would remain in place until the agreement of a wider trade deal which guarantees frictionless movement of goods and an open border in Ireland.
Despite Labour backing last week this lost by almost 100 votes, 283 to 188. But 167 MPs abstained on it, including the DUP. If the Northern Irish party could be talked in to backing it there could be some movement.
Motion E: Second referendum to approve any Brexit deal
Drawn up by Labour MPs Peter Kyle and Phil Wilson, this motion would require a public vote to confirm any Brexit deal passed by Parliament before its ratification.
This option, tabled last time by Labour former minister Dame Margaret Beckett, polled the highest number of votes, although was defeated by 295 votes to 268.
Labour MPs were whipped to support it but 27 mainly from northern Leave-voting areas voted against it and a further 18 - including several frontbenchers - abstained.
Their support would have been enough to pass it but it seems unlikely they will change their minds, given that their concerns remain the same.
Motion F: Public vote to prevent no deal
Moved by Labour's Graham Jones and Tory former minister Dominic Grieve, this proposal would require a referendum, if necessary, to prevent the UK leaving the EU without a deal.
Grieve is a hardcore Remainer who lost a confidence vote in his local Beaconsfield party at the weekend and he has long been a thorn in the side of the Prime Minister.
It seeks to build on a motion tabled last week to revoke article 50 altogether to avoid leaving with no deal, which was defeated by more than 100 votes.
But they are the only signatories to this motion so it is unlikely to be called by the Speaker.
Motion G: Parliamentary supremacy
SNP MP Joanna Cherry joins with Mr Grieve and MPs from other parties with this plan to seek an extension to the Brexit process to allow Parliament and the Government to achieve a Brexit deal.
If if this is not possible then Parliament will choose between either no-deal or revoking Article 50.
An inquiry would follow to assess the future relationship likely to be acceptable to Brussels and have majority support in the UK.
This has wide cross-party support so could still be called by the Speaker.
Motion H: European Free Trade Association and European Economic Area
A motion tabled by Conservative MP George Eustice - who quit as agriculture minister to fight for Brexit - proposes rejoining Efta at the 'earliest opportunity'.
It also calls for a short extension to the UK's membership of the EU to conclude accession to Efta and negotiate with the EU additional protocols relating to the Northern Ireland border and agri-food trade.
This is unlikely to be put to a vote as an almost identical motion attracted the backing of just 65 MPs last week so would be almost certain to fail this time as well.
What are MPs voting on this week?
Today: MPs led by Tory Sir Oliver Letwin and Labour's Yvette Cooper will vote tonight on whether to adopt a soft Brexit option, such as a customs union or membership of the single market, possibly accompanied by a second referendum. Last week, MPs rejected all eight Brexit options put to them in a series of 'indicative votes', but supporters of a soft Brexit from both the Tory and Labour benches believe they have a better chance tonight following the third defeat for Theresa May's deal.
Tomorrow: The Cabinet will meet to discuss a response to the votes. If MPs have backed a customs union, Mrs