Theresa May warned MPs "there is not a better deal available" as she confirmed a crunch vote on her Brexit agreement will be held on 11 December.
Despite securing the backing of EU leaders for her divorce agreement, the prime minister now faces a battle to win parliamentary approval.
With it estimated Mrs May could be more than 60 votes short of the majority she needs to get her Brexit deal through the Commons, she has little more than a fortnight to convince enough MPs to support her.
The prime minister began that process on Monday, as she delivered a statement to parliament following Sunday's European Council summit.
She told MPs she had secured "the right deal for Britain" and repeated the message of EU leaders that they will not return to the negotiating table if parliament rejects the agreement.
Warning of the impact of the Commons voting down her deal, Mrs May said: "We can back this deal, deliver on the vote of the referendum and move on to building a brighter future of opportunity and prosperity for all our people.
"Or this House can choose to reject this deal and go back to square one. Because no-one knows what would happen if this deal doesn't pass.
"It would open the door to more division and more uncertainty, with all the risks that will entail."
In the face of widespread hostility to the terms of her agreement, both from her own MPs as well as opposition parties, Mrs May attempted to address the concerns about the agreement.
She admitted she would "not pretend that either we or the EU are entirely happy" with the provisions of a so-called backstop arrangement intended to avoid a hard border on the island of Ireland.
But, in a message aimed at both her Tory Brexiteer critics and Labour, Mrs May said: "There is no deal that comes without a backstop, and without a backstop there is no deal."
The prime minister hailed how the UK had fought off Spanish attempts to change the terms of the withdrawal agreement in relation to Gibraltar, telling MPs her government's position on The Rock's sovereignty "has not and will not change".
She also told the Commons how the UK has dismissed efforts by EU member states to tie continuing British access to markets to the rights of European countries to fish in UK waters.
In an apparent rebuke to French president Emmanuel Macron over the issue, Mrs May said: "It is no surprise some are already trying to lay down markers again for the future relationship, but they should be getting used to the answer by now: it is not going to happen."
However, despite her bullish assessment of her deal, the prime minister faced another barrage of criticism from MPs of all parties as she took questions in the Commons for more than two-and-a-half hours.
Labour leader Jeremy Corbyn told MPs the UK had "never got off square one" under Mrs May, with Sunday's EU summit merely signalling "the end of this government's failed and miserable negotiations".
Highlighting an analysis by the National Institute of Economic and Social Research that the prime minister's Brexit deal could leave the UK £100bn a year poorer, Mr Corbyn condemned the agreement as "the worst of all worlds".
3:34Amid the opposition to her deal, he told the prime minister "ploughing on is not stoic, it is an act of national self-harm".
"For the good of the nation this House has little choice but to reject this terrible deal," Mr Corbyn told the Commons.
Mrs May faced near constant criticism of her deal for the first hour in which she took MPs' questions from her agreement.
This included from her DUP allies, ex-foreign secretary Boris Johnson, former Brexit secretary David Davis and former defence secretary Sir Michael Fallon – normally a loyalist but who described the deal as a "huge gamble".
Following criticism from the SNP's Philipa Whitford, Mrs May also made an admission she should "not have used that language" when she recently claimed her post-Brexit immigration plans would stop EU workers being able to "jump the queue".
She faced a further blow when Andrew Lewer became the 26th Tory MP to publicly confirm he has submitted a letter of no confidence in Mrs May and wants a leadership contest.
1:07However, later during her long appearance in the Commons, there were signs of support for the prime minister from MPs on her own benches.
Ex-education secretary Nicky Morgan told MPs: "It's the easiest thing in the world for people to criticise any deal that they haven't spent time negotiating, and it's the easiest thing in the world for people to remain in their entrenched positions they've been in for the last two years."
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Former work and pensions secretary Stephen Crabb said the prime minister's deal has the "overwhelming advantage of it being the only one grounded in reality".
As the prime minister spoke in the Commons, Downing Street confirmed a five-day Commons debate on the Brexit deal will begin on 4 December, with a "meaningful vote" on the agreement to be held on 11 December.
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