The House of Commons has emphatically rejected Jeremy Corbyn’s Brexit vision by a margin of 240 votes to 323.
The 83-vote defeat will place immense pressure on the Labour leader to throw his party’s full weight behind demands for a second referendum on EU withdrawal.
Brexit spokesman Matthew Pennycook appeared to suggest the party is ready to act, tweeting it is “now time to wholeheartedly get behind efforts to facilitate a new public vote that includes the option of staying in the EU”.
Shadow Brexit secretary Sir Keir Starmer said he was “disappointed” at the defeat of Labour’s amendment, adding: “We must do all we can to protect jobs and the economy. That’s why Labour will put forward or support an amendment in favour of a public vote to prevent a damaging Tory Brexit.”
Mr Corbyn told Labour MPs on Monday that he was ready to support moves to demand a second public vote “to prevent a damaging Tory Brexit being forced on the country”.
An amendment tabled by Labour’s Yvette Cooper, designed to pin the PM down by placing her promise in a motion approved by Parliament, was passed by an overwhelming 502 votes to 20.
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.
Labour’s annual conference voted to keep a second referendum on the table, but made clear 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.
Speaking to MPs on Monday, Mr Corbyn said 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 he will now give his full support to the People’s Vote cause.
Labour MP Alison McGovern, a leading supporter of the People’s Vote campaign, said: “Labour policy was adopted unanimously at the party conference to campaign to give the people the choice of staying in the EU on the same terms as now or opting for a negotiated form of Brexit. The crisis is now so great the public must be heard.”
Following the vote, frontbencher Richard Burgon appeared to cast doubt on how quickly Labour would move to a second referendum position by tweeting that there would be “further opportunities to secure support for Labour’s alternative Brexit deal”.
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.
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.
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.”