Update 9pm: MPs have rejected Theresa May’s Brexit plans by an emphatic 432 votes to 202 in a historic vote which has thrown the future of her administration and the nature of the UK’s EU withdrawal into doubt.
The humiliating rebuff was delivered in the House of Commons just moments after the British Prime Minister made a last-ditch appeal for MPs to back the Withdrawal Agreement which she sealed with Brussels in November after almost two years of negotiation.
The 118 Conservative rebels included fervent Brexiteers like Boris Johnson and Jacob Rees-Mogg and former Brexit secretaries David Davis and Dominic Raab, as well as Remainers Anna Soubry and Dominic Grieve.
The 230-vote margin of defeat was by far the worst suffered by any Government in a meaningful division since at least the First World War and in normal circumstances would be enough to force a UK Prime Minister from office.
But Mrs May made clear she intends to stay on, setting out plans for talks with senior parliamentarians from parties across the Commons in the hope of finding “genuinely negotiable” solutions which she can take to Brussels.
Jeremy Corbyn said the “catastrophic” defeat represented an “absolutely decisive” verdict by MPs on Mrs May’s handling of Brexit.
He announced he has tabled a motion of no confidence in the Government, which will go to a Commons vote on Wednesday which could force an early general election if it wins the support of more than 50% of MPs.
But his hopes of ousting the PM were undermined when the DUP’s Sammy Wilson said that the Unionist party will back Mrs May in her fight for survival, saying: “We never wanted a change of government, we want a change of policy.”
And a spokesman for the European Research Group of eurosceptic Tories, chaired by Mr Rees-Mogg, confirmed that they too would back the Government.
Mrs May – who said she expected to survive Wednesday’s vote – has until January 21 to set out a Plan B, with the clock ticking on the scheduled date of Brexit in just 73 days’ time on March 29.
In a statement to the Commons immediately after her drubbing, the Prime Minister told MPs: “The House has spoken and this Government will listen. It is clear that this House does not support this deal, but tonight’s vote tells us nothing about what it does support.”
She said she would consult with Conservative colleagues, her Democratic Unionist Party allies and senior parliamentarians from across the Commons to identify “what now is required to secure the backing of the House”.
The PM promised to approach the talks “in a constructive spirit”, but cautioned that proposals would have to be “genuinely negotiable and have sufficient support in this House” if she was to take them back to Brussels to “explore” with the EU.
Mrs May assured MPs that she was not seeking to run the clock down to a no-deal Brexit in March, insisting that she still hoped to take the UK out of the EU “in an orderly way, with a good deal”.
Meanwhile Scottish First Minister Nicola Sturgeon has insisted a second European referendum is now the “only credible option”.
Update 7.40pm: MPs have rejected Theresa May’s Brexit deal by 432 votes to 202 (ie by a majority of 230).
The humiliating rebuff was delivered in the House of Commons just moments after Mrs May made a last-ditch appeal for MPs to back the Withdrawal Agreement which she sealed with Brussels in November after almost two years of negotiation.
Responding to the defeat, Ms May said: “The House has spoken and the Government will listen. It is clear that the House does not support this deal but tonight’s vote tells us what it does support.
“Nothing about how or even if it intends to honour the decision in a referendum Parliament decided to hold.”
She told MPs that the Government would “make a statement about the way forward and table an amendable motion” by Monday January 21.
She also offered assurances to the Commons that Government was not seeking to “run down the clock”.
She said: “I’ve always believed that the best way forward is to leave in an orderly way with a good deal and have devoted much of the last two years negotiating such a deal.”
Ms May added that the Government will make time for a confidence vote tomorrow if one was tabled.
Labour leader Jeremy Corbyn told the House of Commons that Ms May’s “catastrophic” defeat represented an “absolutely decisive” verdict on her Brexit negotiations and said he has tabled a vote of confidence.
He said: "The result of tonight’s vote is the greatest defeat for a Government since the 1920s in this House. This is a catastrophic defeat for this Government.
“After two years of failed negotiations the House of Commons has delivered its verdict on her Brexit deal and that verdict is absolutely decisive.
“I hear the words of the Prime Minister but the actions of the past two years speak equally clearly.”
He added: “The most important issue facing us is that the Government has lost the confidence of this House and this country.
“I therefore inform you I have now tabled a motion of no confidence in this Government.”
Labour deputy leader Tom Watson posted on Twitter: “Tonight by 432 votes to 202, the PM has suffered the biggest defeat in the House of Commons in over 100 years.
“She is devoid of authority in the Commons, in the country, and even within her own party.
“She should call an immediate General Election.”
After the vote, former Ukip leader Nigel Farage said it was “a catastrophic failure of leadership" by Mrs May.
A catastrophic failure of leadership by @Theresa_May. If she has any sense of honour then she will resign.— Nigel Farage (@Nigel_Farage) January 15, 2019
Speaking after the vote, Mayor of London Sadiq Khan said: “MPs have done the right thing tonight by rejecting the Government’s bad Brexit deal.”
He added: “What happens next will define our future for decades to come.
“It is absolutely vital that the Prime Minister acts immediately to take any prospect of a no-deal Brexit off the table for good. That means withdrawing Article 50.
BREAKING: MPs from all sides have rejected this bad Brexit deal.
What happens next will define our future for decades to come.January 15, 2019
“We then need a fundamental rethink about how we take this crucial decision. The politicians have failed and in the absence of a general election, the British public must be allowed to decide what happens next.”
Tom Pursglove told the Press Association that he resigned as a Conservative Party vice-chair in order to vote against the Brexit deal.
The MP for Corby was appointed to the role by Mrs May in July last year.
As MPs voted, noisy crowds of pro- and anti-Brexit protesters in Parliament Square could be heard inside the Palace of Westminster.
MPs had been due to vote first on a series of four amendments chosen by Speaker John Bercow.
But Mr Corbyn, Scottish National Party leader Ian Blackford and Tory backbencher Sir Edward Leigh opted not to move their amendments, leaving only one division.
In that vote, a proposal from Conservative MP John Baron for the UK to take unilateral powers to end controversial “backstop” arrangements was rejected by 600 votes to 24.
Donald Tusk, President of the European Council, commented after the vote saying: "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?"
European Commission president Jean-Claude Juncker, who had pulled out of an event in Strasbourg on Wednesday because of the vote, said in a statement: “I take note with regret of the outcome of the vote in the House of Commons this evening.
“On the EU side, the process of ratification of the Withdrawal Agreement continues.
“The Withdrawal Agreement is a fair compromise and the best possible deal. It reduces the damage caused by Brexit for citizens and businesses across Europe. It is the only way to ensure an orderly withdrawal of the United Kingdom from the European Union.
“The European Commission, and notably our Chief Negotiator Michel Barnier, has invested enormous time and effort to negotiate the Withdrawal Agreement. We have shown creativity and flexibility throughout. I, together with President Tusk, have demonstrated goodwill again by offering additional clarifications and reassurances in an exchange of letters with Prime Minister May earlier this week.
“The risk of a disorderly withdrawal of the United Kingdom has increased with this evening’s vote. While we do not want this to happen, the European Commission will continue its contingency work to help ensure the EU is fully prepared.
“I urge the United Kingdom to clarify its intentions as soon as possible.
“Time is almost up.”
In other international reaction, Spanish Prime Minister Pedro Sanchez said on Twitter that his Government regretted the “negative result” in the House of Commons.
He added that Theresa May’s Withdrawal Agreement was the “best possible” and said a disorderly exit would be “negative for the EU and catastrophic for the United Kingdom”.
Spain would work on contingency measures and “would prioritise the rights of citizens and residents”, he said.
Update 7.30pm: MPs defeated John Baron’s amendment, which sought to give the UK the right to terminate the Irish border backstop without the agreement of the EU, by 600 votes to 24 – majority 576.
As MPs voted in the Commons, Labour leader Jeremy Corbyn tweeted: "Theresa May's deal is bad for our economy, for our democracy and for the country. Labour will vote against it tonight."
Earlier: Theresa May calls on MPs to 'do their duty' and back her Brexit deal
Theresa May has made a last-ditch plea to MPs to back her EU withdrawal plan, telling them: "I believe we have a duty to deliver on the democratic decision of the British people, and to do so in a way that brings our country together".
The British Prime Minister looks set for humiliating defeat in the "meaningful vote" taking place in the House of Commons at the end of eight days of debate and two years of negotiation following the EU referendum of June 2016.
Rejection of Mrs May's Withdrawal Agreement by MPs would give her until January 21 to set out her Plan B - expected to involve going back to Brussels to seek further concessions.
And it is also likely to trigger a bid to force a general election by Jeremy Corbyn, who has said he will table a motion of no-confidence in the Government "soon" after it is defeated on its central policy platform.
Moments before the historic vote, Mrs May told MPs: "Parliament gave the people a choice, we set the clock ticking on our departure and tonight we will determine whether we move forward with a Withdrawal Agreement that honours the vote and sets us on course for a better future.
But the Labour leader called on MPs to vote down the agreement, saying: "This deal is bad for our economy, a bad deal for our democracy, and a bad deal for this country."
Mr Corbyn could use a point of order in the immediate wake of Tuesday's vote to trigger a no-confidence debate as early as Wednesday.
And Mrs May is expected to deliver her immediate response to the historic reverse in a statement to the Commons moments after her anticipated drubbing.
Attorney General Geoffrey Cox appeared to indicate that the PM will resist pressure to tear up her plan or to seek cross-party consensus on a new approach.
He told MPs that in the event of a Government defeat the Agreement would have to return to the Commons later "in much the same form with much the same content".
Noisy crowds of pro- and anti-Brexit protesters in Parliament Square could be heard inside the Palace of Westminster as MPs prepared to vote at 7pm, in a process expected to culminate in a final result around 8.15.
MPs were first voting on a series of four amendments chosen by Speaker John Bercow, including a call from Mr Corbyn for the Government to pursue all options to avoid a no-deal Brexit.
A Scottish National Party amendment rejected Mrs May's Brexit deal, while Tory backbenchers Edward Leigh and John Baron proposed means for the UK to take unilateral powers to end controversial "backstop" arrangements.
By the time Mrs May concluded the debate with a passionate plea to MPs to deliver the Brexit demanded by voters, her hopes of victory appeared vanishingly small.
Assurances over the controversial "backstop" received from the EU on Monday appear to have failed to win over significant numbers of the deal's critics among the Tories and their DUP allies.
While some MPs - including former Labour minister Frank Field - declared their intention to back the PM's deal, normally loyal Tories like Hugo Swire said they would not do so.
Confirming that the 10 DUP MPs will not back the PM's deal, party leader Arlene Foster told a press conference in London: "We said to the Prime Minister she had to get rid of the backstop and get a Withdrawal Agreement that can be lived with. I don't think she even asked to get rid of the backstop."
In the final day of debate on Mrs May's deal, Mr Cox acknowledged that the agreement reached with the EU in November was not perfect, but said he was supporting it "for wholly pragmatic reasons".
"It is the necessary means to secure our orderly departure and unlock our future outside the European Union," he told MPs.
Thousands of businesses with contracts based on EU law would find "the rug pulled from under (them)" if the UK left with a deal, he said.
They would ask MPs: "What are you playing at? What are you doing? You are not children in the playground, you are legislators'," Mr Cox said, adding: "We are playing with people's lives."
Mr Cox compared the Withdrawal Agreement to an "airlock" providing a route towards a future trade and security relationship with the remaining 27 EU states.
But the Labour chair of the Brexit Select Committee Hilary Benn retorted: "The reason why many of us will vote against the deal tonight is because on the other side of the second airlock is a complete vacuum about our future relationship with our biggest, nearest and most important trading partners."
Mrs May's deal came under assault from a series of MPs on both sides of the Brexit debate, with eurosceptics warning that it failed to resolve their concerns that the backstop arrangements designed to avoid a hard border in Ireland could become permanent.
The Tory chairman of the European Scrutiny Committee Bill Cash called on Mrs May to "consider her position", comparing it to Neville Chamberlain's resignation in 1940 which cleared the way for Winston Churchill to take over.
"Now is the time to walk away from the intransigence of the EU and our failed policy of seeking to supplicate their guidelines, their terms and their paymasters," he said.
In the final Cabinet meeting before the crucial vote, Mrs May told senior ministers that the Government was "the servant of the people" and she believed "passionately" that it must deliver on the result of the referendum, in which voters opted to Leave by a margin of 52%-48%.
She spent much of the day meeting Tory MPs in her Commons office in an eleventh-hour bid to bolster support.
But analysis of polling released by the Best for Britain campaign for a second referendum suggested that around 60% of voters - including majorities in every region of the country - want a public vote if Parliament proves unable to decide on a Brexit deal.
German foreign minister Heiko Maas said Brexit talks would continue if Mrs May's deal was rejected by MPs, but there was unlikely to be "substantial" change to the agreement.
Mr Maas said: "If there were still a solution that could be presented under even greater pressure, I would ask myself why it has not been put on the table before in order to ensure that this evening's vote takes place under better circumstances.
"That is why I believe that the agreement is as it stands and will not be substantially changed, but that, if things go wrong tonight, there will certainly be talks again."
- Press Association