Fourteen Labour MPs from leave-backing constituencies rebelled against Jeremy Corbyn last night to sink the party's plan to delay Brexit and send Theresa May back to Brussels with a stronger hand.
Backbench rebels including veteran left-winger Dennis Skinner joined the Conservatives in the division lobbies to vote down Yvette Cooper's amendment but were accused of 'letting the party down'.
Seven of the Labour rebels also joined the Government in backing the Graham Brady amendment, supported by Theresa May, which gives the PM a mandate to renegotiate her Brexit deal.
The defections helped Mrs May to triumph in the Commons and win backing for her plans to seek an alternative to the Irish backstop.
But there are growing calls from members of Jeremy Corbyn's Momentum group to deselect them with critics calling them 'traitors'.
Veteran left-winger Dennis Skinner (left) and Don Valley MP Caroline Flint (right) were among the Labour MPs who rebelled against Jeremy Corbyn in the House of Commons last night
Jeremy Corbyn (pictured) finally agreed to Brexit talks with Theresa May tonight after the Prime Minister navigated a minefield of seven votes on Plan B
The Cooper plan, which was backed by Mr Corbyn, called for an extension of Article 50 to keep the UK in the EU until the end of the year in order to reach a deal.
It was supported by the Labour frontbench as well as Tories including Nick Boles, but was defeated by 321 votes to 298 last night.
The Labour MPs who voted against it were Ian Austin, Kevin Barron, Ronnie Campbell, Rosie Cooper, Jim Fitzpatrick, Caroline Flint, Roger Godsiff, Stephen Hepburn, Kate Hoey, John Mann, Dennis Skinner, Laura Smith, Gareth Snell and Graham Stringer.
Mr Austin and Mr Mann are vocal opponents of Mr Corbyn's leadership while Ms Hoey has been one of the most prominent Labour Brexiteers.
Of the rebels, Ronnie Campbell, Roger Godsiff, John Mann, Graham Stringer and Dennis Skinner were also Leave supporters in the 2016 referendum.
Others including Caroline Flint in Don Valley and Kevin Barron in Rother Valley were pro-Remain in 2016 but represent very Leave-supporting constituencies.
Some Labour members have voiced fears of a backlash from voters if MPs were seen to be delaying or frustrating Brexit.
It is not yet clear whether there will be any punishment for the Labour rebels who defied the whip.
Labour MP Ben Bradshaw said it was 'disappointing' that Labour defectors had voted with the Tories.
He said: 'Labour whipped the right way. A handful of colleagues let us down.'
But his colleague Lucy Powell said: 'All this talk of 'recriminations' and being 'cross' with colleagues who voted differently tonight is deeply unhelpful.'
This chart shows how MPs voted on the Cooper amendment to delay Article 50, with 14 Labour rebels defying their party's whip to reject the plan
Labour Brexiteer Kate Hoey (left) and Birmingham Hall Green MP Roger Godsiff (right) voted in favour of the Graham Brady amendment backed by Theresa May's Government
Kevin Barron (left), John Mann (centre) and Ian Austin (right) were among the Labour MPs who voted for the Graham Brady amendment in the House of Commons last night
Labour MPs Graham Stringer (left) and Gareth Snell (right) were among 14 backbenchers to rebel against Yvette Cooper's amendment to delay Brexit
Laura Smith (left), Ronnie Campbell (centre) and Stephen Hepburn (right) voted with the Government to reject Yvette Cooper's amendment
Labour MPs Jim Fitzpatrick (left) and Rosie Cooper (right) opposed Cooper's amendment
The rebellion against Mr Corbyn's whips helped to cancel out 17 Conservative defections, as Tories including Anna Soubry and Ken Clarke backed the proposed delay.
Ms Cooper and Mr Boles had sought to postpone Brexit to prevent a no-deal departure on March 29.
The two members said they were 'deeply concerned that there is no safeguard in place to prevent a cliff edge in March 2019'.
In a statement the pair said Britain was 'running out of time' to prevent a no-deal Brexit.
The Brady amendment, which was backed by the Government, called for 'alternative arrangements' to the much-maligned Irish backstop.
The Commons voted by 317 to 301 in favour of the backstop changes - which Mrs May said showed there was a means of securing a 'substantial and sustainable majority in this House for leaving the EU with a deal'.
Seven Labour MPs backed the amendment: Ian Austin, Kevin Barron, Jim Fitzpatrick, Roger Godsiff, Kate Hoey, John Mann and Graham Stringer.
Theresa May (pictured in the Commons ) told MPs the Withdrawal Agreement will be reopened, as MPs backed her plan to go to Brussels and demand changes to the backstop
A diagram showing how Graham Brady's amendment - calling on Theresa May to renegotiate the Irish backstop - won the support of the House of Commons
Several other Labour MPs including Ms Cooper and Ms Flint did not vote on the Brady amendment.
The backstop seeks to prevent a return to border checks between Northern Ireland and the Republic of Ireland.
But it is widely disliked by Tory MPs, who helped inflict a record defeat on Mrs May - 432 votes to 202 - when her deal was first voted on earlier this month.
The Commons also approved a cross-party amendment, tabled by Midlands MPs Caroline Spelman and Jack Dromey, rejecting a no-deal Brexit by 318 to 310.
The vote is not legally binding on the Government but will impose further pressure on Mrs May as she tries to secure a new deal.
Mrs May said she would seek 'legally binding changes to the Withdrawal Agreement that deal with concerns on the backstop while guaranteeing no return to a hard border'.
But she earned an immediate rebuff from Brussels, where European Council president Donald Tusk insisted that the Withdrawal Agreement struck last November was not open for renegotiation.
Yvette Cooper, left, and Conservative MP Nick Boles, right, backed an amendment to delay Brexit but the plan was voted down by the House of Commons
In a statement, Mr Tusk's spokesman said: 'The Withdrawal Agreement is and remains the best and only way to ensure an orderly withdrawal of the UK from the European Union.
'The backstop is part of the Withdrawal Agreement, and the Withdrawal Agreement is not open for re-negotiation.'
Another cross-party amendment, tabled by Labour's Rachel Reeves, which would have required the Prime Minister to seek an extension of Article 50 if no deal had been reached by February 26, was also defeated.
However MPs issued an order to Theresa May to prevent a no-deal Brexit as they passed an amendment which rejects the UK leaving the EU without a Withdrawal Agreement.
The cross-party plan, headed by Tory Dame Caroline Spelman and Labour's Jack Dromey, won by 318 votes to 310, majority eight.
Earlier, MPs rejected a bid by Jeremy Corbyn to force a debate on Labour's Brexit plans.
Mr Corbyn, who had earlier boycotted cross-party talks, said he was now ready to meet the Prime Minister to discuss a 'sensible Brexit solution that works for the whole country'.
How May snatched a surprise victory from jaws of defeat as Commons BACKS her to return to Brussels for new talks on the Irish border backstop
By Tim Sculthorpe, Deputy Political Editor for MailOnline
Theresa May claimed there was a 'way forward' on Brexit last night after snatching a surprise victory from a minefield in the Commons.
The latest showdown over Brexit dawned with the Prime Minister facing the prospect of humiliation at the hands of MPs for the second time in a fortnight.
Mrs May pleaded with her party for support and ordered them to rally round a plan by Sir Graham Brady, the influential chairman of the 1922 Committee of Tory MPs.
But she had issued her orders just minutes after Jacob Rees-Mogg, the shop steward of Tory Brexiteers, had told MPs to do the opposite.
The Prime Minister made her first move as she gathered her Cabinet in Downing Street on Tuesday morning.
She told ministers she was ready to demand Brussels reopens the Withdrawal Agreement to seek legally-binding changes to the backstop.
Theresa May claimed there was a 'way forward' on Brexit last night after snatching a surprise victory from a minefield in the House of Commons
The U-turn - which Mrs May has repeatedly warned against for fears it would risk British success in the negotiations on Gibraltar and fishing - was a key demand of Brexiteers.
Mrs May also set a new deadline of February 13, telling her Cabinet that there would either be a new vote to approve her deal or another round of votes on what to do instead.
It was a crucial concession to Remain ministers such as Work and Pensions Secretary Amber Rudd who had threatened to resign to vote in favour of blocking no deal.
The moves combined with the surprise emergence over night of a new Brexit compromise between Mr Rees-Mogg and Remainer Nicky Morgan built a basis for last night's success.
It was not all one way traffic: shortly after Cabinet broke up, Labour leader Jeremy Corbyn finally clambered off the fence and announced he would back the amendments against no deal.
The move was a huge boost to the plan tabled by Labour MP Yvette Cooper to tear up the Commons rules and try to change the law next week.
Her amendment would have scrapped the decades-old rule that only ministers set the timetable of the Commons and given MPs the chance to pass a law saying if there was no deal by February 26, the PM must delay Brexit.
If the Cooper amendment carried, Mrs May's hopes of getting a renegotiation in Brussels would have been bleak.
With Labour votes, Tory Remain rebels were confident they could use Parliament to seize control of the Brexit process to prevent no deal and significantly soften Brexit.
A crucial moment came when Speaker John Bercow selected all of the main plans at the start of the debate - ending fears he would ignore the Brady plan favoured by No 10.
It meant when Mrs May arrived at the Despatch Box at 1.51pm this afternoon both main amendments - Brady and Cooper - were in with a fighting chance when the votes came at 7pm.
In her speech, Mrs May repeated her promises to Cabinet about demanding the Brexit deal was reopened and told MPs: 'I will never stop battling for Britain, but the odds of success become much longer if this House ties one hand behind my back.'
She tells Parliament the Brady amendment 'will give the mandate I need to negotiate with Brussels'.
The PM used her appearance to support the apparent 'Plan C' from Mr Rees-Mogg and Ms Morgan - saying it was a 'serious proposal'.
The efforts of Tory whips appeared to be working - even Boris Johnson said he would vote for the Brady plan if Mrs May was sincere about reopening talks on the divorce deal
Behind the scenes, Tory whips pressed MPs hard to vote down the no deal plans and instead endorse Mrs May's hopes of renegotiating.
The effort appeared to be working - even Boris Johnson said he would vote for the Brady plan if Mrs May was sincere about reopening talks on the divorce deal.
DUP deputy leader Nigel Dodds also spoke up in favour of the PM's new position, while Mr Rees-Mogg thanked Mrs May for her shift.
Again there were blows against Mrs May - with Tory Remain supporters Sarah Wollaston and Ed Vaizey insisting they could not vote for renewed talks on the backstop.
After more than five hours of debate, Mr Bercow finally called the Commons to order at 7pm.
Amendments from Mr Corbyn and SNP leader Ian Blackford were both dispatched with ease - 327 MPs filed into the Government lobby both times, enough to win any vote.
The third vote was crucial as a plan from Tory MP Dominic Grieve - to hand MPs the power to debate and vote on Brexit every Tuesday until there is a deal - was tested.
Fifteen Conservative MPs rebelled - the usual Remain rebels including Ken Clarke and Anna Soubry - but they were cancelled out by 14 Labour MPs.
The Labour group included Brexit supporters like Kate Hoey and Dennis Skinner, and those from Leave-voting areas like Caroline Flint.
It meant the Government won again - 321 to 301 - and by a bigger margin than many had expected.
It set the stage for the Cooper amendment to fail in the fourth vote of the night. This time 17 Tories rebelled but again they were cancelled out by the same bloc of 14 Labour MPs.
Ms Cooper's plan lost by a slightly larger margin of 321 to 298 - a majority of 23 and a clear signal the Commons would back Mrs May to renegotiate the deal.
A fifth vote on an amendment from Rachel Reeves - to make a political statement saying the same as Ms Cooper's proposed law - was seen off 322-290.
The sixth vote on Dame Caroline Spelman's amendment tarnished the night for Mrs May.
The amendment set out a statement that a no deal Brexit would be unacceptable - but made no effort to change the law or force the Government to do anything.
The same 17 Conservative MPs rebelled to support the motion but this time only three Labour MPs went the other way.
It meant the rebels won 318 to 310 - a symbolic blow to Mrs May that could encourage the EU not to give ground in any new negotiations.
But it did not stop Mrs May securing the most important victory of the night when the Brady amendment was finally called to a vote at 8.26pm.
The motion carried 317 to 301, with just eight Tory rebels voting against sending Mrs May back for a final push on the border backstop.
Seven Labour MPs voted the other way, joining forces with all 10 DUP MPs and three Independents to get Mrs May over the line.
She told the Commons: 'A fortnight ago, this House clearly rejected the proposed Withdrawal Agreement and Political Declaration with just 202 members voting in favour.
'Tonight a majority of Honourable Members have said they would support a deal with changes to the backstop.
'Combined with measures to address concerns over Parliament's role in the negotiation of the future relationship and commitments on workers' rights, in law where need be, it is now clear that there is a route that can secure a substantial and sustainable majority in this House for leaving the EU with a deal.
'We will now take this mandate forward and seek to obtain legally binding changes to the Withdrawal Agreement that deal with concerns on the backstop while guaranteeing no return to a hard border between Northern Ireland and Ireland.'