Jeremy Corbyn has said he will continue to push for a version of his Brexit plan despite its overwhelming rejection by the House of Commons as pressure mounted on Labour to commit to a second referendum.
Labour's Brexit vision was defeated by 240 votes to 323 in the Commons and Mr Corbyn confirmed Labour would now back a referendum if faced with a "damaging Tory Brexit" or a no-deal departure from the European Union.
But he insisted that Labour would also continue to push for "other available options" to prevent either Prime Minister Theresa May's deal or the UK crashing out without an agreement.
After the result in the Commons, shadow 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".
Owen Smith, who was sacked from the shadow cabinet for calling for a second referendum, told the Press Association: "Now that Labour's version of Brexit has been rejected by Parliament, I expect Jeremy Corbyn to throw his full weight behind campaigning for a public vote."
That would mean "speaking out and campaigning, in accordance with our conference motion, in favour of such a vote and of the option to remain in the EU at the end of it".
However shadow justice secretary Richard Burgon indicated Labour would not be throwing its weight behind a second referendum just yet.
"Given parliament looks set to extend Article 50, there'll be further opportunities to secure support for Labour's alternative Brexit deal," he said.
Mr Corbyn confirmed he was not yet ready to fully abandon Labour's Brexit plan in favour of a second referendum.
"We will back a public vote in order to prevent a damaging Tory Brexit or a disastrous no-deal outcome," he said.
"We will also continue to push for the other available options to prevent those outcomes, including a close economic relationship based on our credible alternative plan or a general election."
Former shadow cabinet minister Caroline Flint warned that a second referendum would be opposed by a number of Labour MPs, as well as members and voters.
"I don't support a second referendum, many of my Labour colleagues in the Parliamentary Labour Party - but also members as well as Labour leave voters - want the Labour Party to stand by its promise, and the promise was to respect the referendum," she said.
The Prime Minster's dramatic announcement yesterday that she would allow MPs to vote on delaying the UK's EU withdrawal beyond 29 March took the sting out of an evening of Brexit votes which had been expected to feature a number of ministerial resignations.
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 a majority of 482 - with 20 Tory hardliners opposing it.
Any more significant 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 12 March, although there have been hints the showdown could be as soon as next week.
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 29 March 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 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's plan was supported in tonight's vote by Conservative former chancellor Kenneth Clarke and Liberal Democrat deputy leader Jo Swinson - who backed the plan accidentally. 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.
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".