Theresa May's government faces a vote of no confidence later after MPs rejected the PM's Brexit deal.
Labour launched the bid to trigger a general election after the deal setting out the terms of Britain's exit from the EU was rejected by 230 votes.
However, one senior party figure has suggested it is unlikely to succeed, with Northern Ireland's DUP and Tory rebels saying they will back the PM.
The confidence vote is expected to be held at about 19:00 GMT.
Mrs May has told MPs she will return to the Commons with an alternative plan next week, provided she survives the confidence vote.
"The House has spoken and this government will listen," she said on Tuesday night, offering cross-party talks to determine a way forward.
What happens next?
MPs are set to debate the confidence motion for about six hours following Prime Minister's Questions at 12:00 GMT, with Labour leader Jeremy Corbyn saying it would allow them to give their verdict on "the sheer incompetence of this government".
BBC political correspondent Iain Watson says that if the prime minister sees off the challenge, she will begin a series of meetings with "senior Parliamentarians" on Thursday.
He said Mrs May intended to retain her "red lines" – ruling out Labour's demand for a customs union with the EU – with sources suggesting compromising on this would risk cabinet resignations.
But first the prime minister must survive the confidence vote tabled by Mr Corbyn and backed by MPs from the SNP, Lib Dems, Plaid Cymru and Green Party.
Shadow chancellor John McDonnell told the BBC that they were expected to lose the vote.
"But who can tell anymore because after yesterday's vote anything can happen in Parliament," he said.
"What we expect to happen then is proper negotiation and discussions to see if there's a compromise that can be reached."
But he said Jeremy Corbyn had not been contacted for discussions with Mrs May.
Despite the government's heavy loss in the Brexit vote, Conservative rebels are likely to come back on-side in the confidence vote.
Leading Brexiteer Boris Johnson said the huge defeat gave the PM a "massive mandate to go back to Brussels" to negotiate a better deal.
And DUP Westminster leader Nigel Dodds told the BBC his party would be backing the government in the confidence vote.
"I think that this government still has the opportunity to deliver on the referendum result," he said.
He said the backstop "was clearly the problem" and if that "can be sorted out" then his party and others against Mrs May's deal "can be brought back on board"./BBC