The Prime Minister has been dealt a humiliating defeat in the "meaningful vote" on Brexit tonight.
MPs have voted 432 to 202 to vote down Theresa May's deal 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.
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 Prime Minister from office.
READ MORE: Here's how your MP voted
Earlier Mrs May 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".
Mrs May said: "Tonight's vote tells us nothing about what it does support, nothing about how it intends to uphold people's decision. People living here and UK citizens in the EU deserve clarity.
"We need to confirm whether this government enjoys the confidence of this house. If the opposition tables a confidence motion, we will make time tomorrow to consider it."
Labour leader Jeremy Corbyn told the House of Commons that Mrs May's "catastrophic" defeat represented an "absolutely decisive" verdict on her Brexit negotiations and said he has tabled a vote of confidence.
Mr Corbyn said the confidence vote would allow the Commons to "give its verdict on the sheer incompetence of this Government".
The European Parliament's Brexit Co-ordinator Guy Verhofstadt tweeted: "The UK Parliament has said what it doesn't want. Now is the time to find out what UK parliamentarians want. In the meantime, the rights of citizens must be safeguarded."
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."
Responding to the Government defeat, Liberal Democrat leader Sir Vince Cable said: "Brexit is becoming a national humiliation.
"Liberal Democrats have campaigned since the referendum to give people the final say on Brexit. Theresa May has failed to persuade her party, failed to persuade Parliament and failed in her attempts to scaremonger MPs to back her.
"The Prime Minister now needs to pull her head out of the sand and start acting responsibly by taking the ludicrous threat of a no-deal Brexit off the table. The only way forward for the country is through a People's Vote where people have the right to choose to stay in the EU.
"It is also time for Jeremy Corbyn to find his backbone, drop his plans for a Labour-led Brexit, and back our calls for a People's Vote."
Moments before the crunch 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.
"The responsibility of each and every one of us at this moment is profound, for this is a historic decision that will set the future of our country for generations."
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."
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 which culminated in a final result around 7.30pm.
Heavily pregnant Labour MP Tulip Siddiq, who postponed her planned Caesarean in order to vote, attended the Commons in a wheelchair.
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 "backstop" received from the EU on Monday failed to win over significant numbers of the deal's critics among the Tories and their DUP allies.
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."