Theresa May has made a final plea to MPs to back her Brexit plan as she closed the Commons debate on Britain's withdrawal agreement with the EU.
The Prime Minister told Parliament it faced a "historic" decision in the so-called meaningful vote later on Tuesday evening, expected between 8pm and 9pm.
Her deal is expected to be resoundingly rejected by MPs, with many in her own party opposed along with most of Labour, the SNP, the Liberal Democrats and the DUP.
May told parliamentarians they faced "the most significant vote that any of us will be part of in our political careers".
She said the eight days of Commons debate on the deal, including days of debate in December before the first scheduled vote was postponed by the Prime Minister, had seen Parliament at its "most passionate and vigorous".
May continued: "This is a debate about our economy and security, the livelihoods of our constituents and the future for our children and for generations to come.
"It goes to the heart of our constitution and no one should forget that it is a democratic process that has got us to where we are."
The Prime Minister said the result of the 2016 referendum was "clear and decisive" but pointed out the risks of leaving the EU without a deal.
She 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 an historic decision that will set the future of our country for generations."
May added: "Our deal delivers certainty for businesses with a time-limited implementation period to prepare for the new arrangements of the future relationship. No deal means no implementation period.
"Our deal protects the rights of EU citizens living in the UK and UK citizens living in the EU so they can carry on their lives as before. No deal means no reciprocal agreement to protects those citizens' rights.
"Our deal delivers the deepest security partnership in the EU's history so our police and security services can continue to work together with their European partners to keep all our people safe."
"No deal means no such security partnership, and our deal delivers the foundations for an unprecedented economic relationship with the EU that is more ambitious than anything they have ever entered into with a third country."
"It will give us the benefits of trading with the EU and the ability to forge new trade deals in our own right."
Speaking before the Prime Minister, Labour leader Jeremy Corbyn urged MPs not to back the deal, saying it would leave Britain "over a barrel.".
He said: "The withdrawal agreement is a reckless leap in the dark.
"Under this deal in December 2020 we will be faced with a choice - either pay more and extend the transition period or lock us into the backstop.
"At that point the UK would be over a barrel.
"We would have left the EU have lost the UK rebate and be forced to pay whatever was demanded."
Confirming Labour would reject the deal, Corbyn said: "Labour will vote against it because it is a bad deal for this country.
"But it's not enough for the House to vote against the deal before us and against no deal - we also have to be for something."
Corbyn said re-opening negotiations with the EU "should not and cannot be ruled out" and called for a general election to allow Labour to take over.
May blasted Labour's calls for a fresh election and said if it did not shift the parliamentary arithmetic, the outcome of another election would merely amount to "two more months of uncertainty and division".
The Prime Minister added: "Today's vote is not about what is best for the leader of the opposition, it is about what is best for the country."
During May's speech, she took an intervention from the SNP's Westminster leader Ian Blackford, who urged her to back a second Brexit referendum in light of economic analysis suggesting all forms of Brexit will make the UK poorer.
Blackford asked: "Will the Prime Minister not realise, on the basis of this knowledge and on the fact that people are going to lose opportunities as a consequence of Brexit, the alternative is to extend Article 50?"
"Go back and give the people the say - let's act in all our interests on the basis of the information we now have."
Such a course of action would not respect the result of the 2016 referendum, the Prime Minister answered.
She added: "A vote against this deal is a vote for nothing more than uncertainty, division and the very real risk of no deal or no Brexit at all."
If May loses the vote as anticipated, Labour has indicated it will quickly move to force a confidence vote in her government.
If it falls, Jeremy Corbyn's party wants to hold and win a general election and renegotiate the Brexit deal.
He has also indicated his party could choose to extend Article 50 if it entered government, giving Britain more time before leaving the EU than its current deadline of March 29.
Remain-supporting parties such as the SNP and Lib Dems are calling for a second EU referendum, or so-called People's Vote, if May's deal is defeated.
Three Scottish Conservative MPs have said they will join the party rebels in voting against the Prime Minister's deal.
Berwickshire, Roxburgh and Selkirk MP John Lamont said he would be rejecting it with a "heavy heart" because it risks "undermining the integrity of the UK".
He is joined by Aberdeen South MP Ross Thomson, who says the deal is the "biggest threat to the Union" since the independence referendum.
Moray MP Douglas Ross also announced he could not back May's Brexit agreement in a speech to the Commons last week, citing concerns over fishing.