MPs have begun to debate a motion of no confidence in Theresa May’s government, after her Brexit deal was rejected.
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 told MPs she will return to the Commons with an alternative plan next week, provided she survives the confidence vote.
At Wednesday’s Prime Minister’s Questions she said she would listen to “the views of the House” in order to “identify what could command the support of this House”.
“There are actually two ways of avoiding no deal,” Mrs May told MPs.
“The first is to agree a deal. The second to revoke Article 50 – that would mean staying in the European Union, failing to respect the result of the referendum, and that is something that this government would not do.”
But Labour Leader Jeremy Corbyn said the prime minister was “in denial” over Tuesday night’s vote and she “needs to come up with something different”.
Opening the confidence debate he said that “if a government cannot get its legislation through Parliament, it must go to the country”, adding that the Fixed-term Parliaments Act “was never intended to prop up a zombie government”.
And SNP Westminster leader Ian Blackford said the rejection of Mrs May’s deal had been the “last straw” and the “only way forward” was to extend Article 50 and legislate for a “people’s vote” – which the prime minister has said will not happen.
Former Prime Minister gives backing
David Cameron, who resigned the day after the UK voted in 2016 to leave the EU, said he hoped, and thought, Mrs May would win Wednesday’s vote.
Speaking to the BBC he also insisted he did not regret calling the referendum.
What happens next?
MPs have begun to debate the confidence motion, which is expected to last about six hours, with Mr 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.
Leader of the House Andrea Leadsom told the BBC the government was clear that it will not delay or revoke Article 50, although Chancellor Philip Hammond reportedly suggested delaying Brexit in a conference call on Tuesday evening.
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 and he hoped “proper negotiation and discussions” about Brexit would follow.
But he said Mr Corbyn had yet 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 as it still had the opportunity to deliver on the referendum result.
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”.
How does a no confidence motion work?
By the BBC’s head of political research Peter Barnes
Under the Fixed Term Parliaments Act 2011, UK general elections are only supposed to happen every five years. The next one is due in 2022.
But a vote of no confidence lets MPs decide on whether they want the government to continue. The motion must be worded: “That this House has no confidence in Her Majesty’s Government.”
If a majority of MPs vote for the motion then it starts a 14-day countdown.
If during that time the current government, or any other alternative government cannot win a new vote of confidence, then an early general election would be called.
That election cannot happen for at least 25 working days.
How has the EU reacted?
European leaders reacted to Tuesday’s vote with dismay but gave no indication they were willing to make concessions.
Several have warned of increased chances of a no-deal Brexit, which many MPs fear will cause chaos at ports and damage industry.
Michel Barnier, the EU’s chief Brexit negotiator, said Brussels “profoundly regrets” how the UK’s MPs voted, after two years of negotiation “based on the red lines of the British government”.
He said it was “up to the British authorities” to indicate how it would move forward.
European Commission President Jean-Claude Juncker urged the UK to clarify its intentions, saying: “Time is almost up.”
And European Council President Donald Tusk has appeared to suggest that the UK should stay in the EU.
“If a deal is impossible, and no one wants no deal, then who will finally have the courage to say what the only positive solution is?”, he tweeted.
Why did MPs reject Theresa May’s deal?
The Commons defeat – the largest in history, by 432 votes to 202 – came as a huge blow for Mrs May.
She had spent two years negotiating the plan aimed at bringing about an orderly Brexit on 29 March, 2019, and setting up a 21-month transition period to negotiate a free-trade deal with Brussels.
Her deal included both the withdrawal agreement on the terms on which the UK leaves the EU and a political declaration for the future relationship.
But it faced opposition across Parliament, which has never had a majority in favour of Brexit. Brexit is happening because people voted by 52% to 48% to leave the EU in the 2016 referendum.
Some Remain MPs oppose the deal because they want a further referendum with the option to scrap Brexit, while others accept Brexit will happen but want the UK to have a closer relationship with the EU than currently proposed.
On the other side are MPs who think Mrs May’s deal leaves the UK tied too closely to EU rules, while some want to see a no-deal Brexit, which is where the UK leaves the EU without any special arrangements in place.
A key sticking point on the plan remains the Northern Irish backstop – the fallback plan to avoid any return to physical border checks between the country and Ireland. Many MPs argue it could keep the UK tied to EU customs rules indefinitely.
Click here if you cannot see the look-up. Data from Commons Votes Services.
In the run up to the vote, the prime minister tried to reassure MPs from all sides of the House over the controversial backstop – having received new written assurances from the EU that it would be temporary and, if triggered, would last for “the shortest possible period”.
But some 118 Conservative MPs – from both the Leave and Remain wings of Mrs May’s party – voted with the opposition parties against her deal, while three Labour MPs supported the deal.
Former Conservative education secretary Justine Greening told the BBC the prime minister needed to find a compromise quickly.
Meanwhile, Labour MP Chuka Umunna said that if his leader did not secure a general election, Mr Corbyn should do what the “overwhelming majority” of Labour members want and get behind a further EU referendum.
Lib Dem leader Sir Vince Cable, who also wants a second referendum, said Mrs May’s defeat was “the beginning of the end of Brexit”.
What does this mean for Northern Ireland and the Irish border?
Dublin is playing this carefully, writes BBC political reporter Jayne McCormick.
The Irish government is reluctant to say anything that could further stoke tensions, but all the while acutely aware that time is running out.
It continues to ramp up no-deal preparations, including on key issues like transport and the supply of medicines.
The DUP says the scale of the defeat last night means the backstop cannot remain in the deal, but Irish thinking is unlikely to budge.
It is mindful of its often-repeated commitment to avoid the return of a hard Irish border, and has banked on the backstop being its insurance policy to ensure that.
It will now be looking to its support network in Brussels to stand firm in the face of any political pressure from Westminster.
The taoiseach (Irish prime minister), Leo Varadkar, said he would do everything he could to avoid no deal, but had to ensure the Republic of Ireland is fully prepared.
It doesn’t sound like Theresa May has any enthusiasm for junking her deal.
Indeed, a source that was on a conference call with business leaders – hosted by the chancellor and other cabinet ministers – was told they could not renegotiate the Withdrawal Agreement.
The plan instead was for a “shake down” of MPs in the next few days to find out what they would tolerate in terms of promises for the longer term future relationship.
As we’ve discussed here before, the cabinet doesn’t even have a clear view itself on how she should proceed.[On Tuesday], the leader of the House of Commons told me it would be Brussels that has to move. But some others are crystal clear that the PM will have to soften her offer, because that’s what Parliament will tolerate.