Boris Johnson urged lawmakers to "end this debilitating dispute" over Brexit and support its EU divorce settlement.
While Parliament was sitting for the first time on a Saturday in nearly four decades, the Prime Minister said there was "a burning desire to complete Brexit" and insisted that his agreement with Brussels was "the best possible solution".
British Prime Minister & # 39; cannot be trusted & # 39; with agreement on Brexit – Corbyn
However, he faces an additional hurdle, with opponents threatening to vote for an amendment that holds approval until legislation to implement the deal is in place.
Sir Oliver Letwin, a former cabinet minister who lost the Conservative whip after rebelling against Brexit, said it was an "insurance policy" to prevent Britain from "falling" without a deal on October 31.
But government sources signaled that if the so-called Letwin amendment were passed, it would make the significant vote a "meaningless vote."
If so, the source said conservative lawmakers would abstain from the final vote and EU withdrawal legislation would be introduced next week.
Opening the debate, the prime minister urged lawmakers to abandon the "illusion" that they could postpone Brexit again and said: "Now it is my judgment that we have come to the best possible solution.
"Now is the time to do that, and I tell all members to come together as Democrats to end this debilitating dispute."
But Labor leader Jeremy Corbyn said his lawmakers "would not be fooled" into backing the prime minister's Brexit deal and rejected Johnson's "empty promises" about workers' rights and the environment.
He continued: "This government cannot be trusted and these banks will not be fooled."
Commons' vote on the deal seems balanced, with Johnson's former DUP allies saying they will oppose it.
Westminster DUP leader Nigel Dodds argued that there must be "Brexit for the whole of the United Kingdom", leaving the single market and the customs union as one.
In a coup attempt at PM, Dodds said: "To avoid an overtime, he is too eager to get a deal at any cost."
DUP conflicts with PM over Brexit agreement
Ian Blackford, SNP leader in Westminster, said: "The prime minister has returned from Brussels to come up with a deal he knows, which we all know is actually worse than the Theresa May deal.
"An agreement that would see Scotland being shaped by this UK government, left at an economic disadvantage, with Scotland's views totally disregarded by this prime minister and his government."
Liberal Democratic Party leader Jo Swinson said: "The Prime Minister's agreement removes the protection of workers' rights, puts a border on the Irish Sea and, according to the government's own analysis, will hurt our economy on a larger scale. that the financial crisis ".
Plaid Cymru Westminster leader Liz Saville Roberts said: "How could Plaid Cymru support their billionaire Brexit?"
Letwin: Change is Insurance Policy
Meanwhile, a group of inter-party MPs sent a letter to Chancellor Sajid Javid asking him to release economic impact assessments for the proposed Brexit deal before Saturday's vote.
Thousands of protesters are also expected to converge on Westminster, demanding a new referendum on the prime minister's agreement.
The Popular Vote march will follow through central London to Parliament Square, where protesters will rally in support of a second public vote.
More follows …