An emphatic Commons rejection for Jeremy Corbyn's Brexit vision has paved the way for Labour to back a People's Vote.
Defeat of the party's amendment, which was voted down by 323 votes to 240, will put immense pressure on Corbyn to throw his party's full weight behind demands for a second EU referendum.
Mr Corbyn told Labour MPs on Monday that he was ready to support moves to demand a public vote "to prevent a damaging Tory Brexit being forced on the country".
Theresa May's dramatic announcement on Tuesday that she would allow MPs to vote on delaying the UK's EU withdrawal beyond March 29 took the sting out of an evening of Brext votes which had been expected to feature a number of ministerial resignations.
Any Conservative bust-ups have now been delayed for up to two weeks, as Mrs May prepares to bring her Withdrawal Agreement back to the Commons for a "meaningful vote" by March 12.
If she fails to overturn the 230-vote mauling the Agreement received in January, votes will be held on the following days on blocking a no-deal Brexit on March 29 and extending the two-year Article 50 negotiation process.
Mrs May's U-turn threw a spotlight on the Labour leader, whose "constructive ambiguity" on Brexit has long frustrated those in his party who back a so-called People's Vote and played a part in the defection of eight MPs to the new Independent Group last week.
Labour's annual conference voted to keep a second referendum on the table, but made clear that the party's priority was an early election to allow it to implement its Brexit plan for a customs union with a UK say, close ties with the single market and dynamic alignment with EU workplace and environmental regulations.
Read more: Brexit vote explained: What MPs are voting on and what amendments mean
Speaking to MPs on Monday, Mr Corbyn said that Labour would put forward its plans in an amendment to the Government's Brexit motion, but was also committed to "putting forward or supporting an amendment in favour of a public vote to prevent a damaging Tory Brexit being forced on the country".
A briefing note to Labour MPs made clear the party would back the inclusion of Remaining in the EU on the ballot paper, as an alternative to a "credible Leave option", but would not back no-deal being a choice on offer.
Mr Corbyn failed to back a referendum amendment tabled by Independent Group MP Anna Soubry, which was not selected for debate on Wednesday by Speaker John Bercow.
But anti-Brexit campaigners will hope that he will now give his full support to the People's Vote cause.
Speaking ahead of the vote, a Labour spokesman sidestepped questions on when the party would back a second referendum if their amendment was amended.
The spokesman said: "We support a public vote in order to prevent no-deal or a damaging Tory Brexit. Our focus is on our credible alternative plan."
Mr Corbyn's plan was supported in Wednesday night's vote by Conservative former chancellor Kenneth Clarke and Liberal Democrat deputy leader Jo Swinson. All other Liberal Democrat MPs abstained.
MPs later rejected a Scottish National Party amendment to rule out a no-deal Brexit in any circumstances and at any time by a margin of 288-324.
And a proposal from Conservative backbencher Alberto Costa for a UK/EU treaty to protect expat citizens' rights in the event of a no-deal was passed without a vote.
Mr Costa quit his position as an unpaid parliamentary aide in the Scotland Office, despite Home Secretary Sajid Javid saying he supported his proposal and Downing Street making clear that Mrs May does not oppose it.
A Number 10 source said the South Leicestershire MP had breached a long-standing convention that members of the administration - including parliamentary private secretaries (PPSs) - cannot table amendments to Government motions.
But Labour said he had effectively been sacked. Shadow home secretary Diane Abbott said his removal "prolongs the anxiety and uncertainty that over five million people have faced for two and a half years".
A cross-party amendment designed to give Parliament the power to force a vote on extending Article 50 was pulled, after its tablers - Conservative Dame Caroline Spelman and Labour's Jack Dromey - received assurances that Mrs May's plan would have the same effect.
In a joint statement, they said: "The Government has just confirmed acceptance of all the proposals in our amendments. There will not now be a no-deal Brexit In 30 days' time because there is not a majority in the House for crashing out without a deal.
"We will not plunge over the cliff on March 29 into an abyss, making the country poorer in every sense of the word. There will now be an extension of the Brexit deadline to allow for serious cross-party dialogue on a better deal to protect the British national interest."
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