Theresa May has set out plans to bypass Commons rules in order to get a Brexit deal ratified in time for the UK to leave the EU on 29 March.
The prime minister told MPs she would lift a requirement for a 21-day delay before any vote to approve an international treaty.
It opens up the possibility she could delay the final Brexit vote until days before the UK is due to leave the EU.
No 10 insists Mrs May will hold a vote on her deal as soon as possible.
But Jeremy Corbyn accused her of “running down the clock” in an effort to “blackmail” MPs into backing her deal.
Britain is currently leaving the EU on 29 March, with or without a deal.
The government has tabled an amendable motion for debate on Thursday, seeking the House’s continued support for the prime minister to demand “alternative arrangements” on the controversial Irish backstop.
The backstop is an insurance policy to prevent checks on goods and people returning to the Northern Ireland border.
And Mrs May promised to return to the Commons on 26 February with a further statement – triggering another debate and votes the following day – if a deal has not been secured by that date.
If a deal is agreed, MPs will have a second “meaningful vote”, more than a month after Mrs May’s deal was rejected in the first one.
The PM said she was discussing a number of options with the EU to secure legally-binding changes to the backstop: Replacing it with “alternative arrangements”, putting a time limit on how long it can stay in place or a unilateral exit clause so the UK can leave it at a time of its choosing.
The 27 February votes are expected to come soon after Mrs May’s planned meeting with European Commission President Jean-Claude Juncker.
Former attorney general Dominic Grieve warned that time was running short for the ratification of a deal under the Constitutional Reform and Governance Act.
But Mrs May responded: “In most circumstances, that period may be important in order for this House to have an opportunity to study that agreement.
“But of course, in this instance MPs will already have debated and approved the agreement as part of the meaningful vote.
“So while we will follow normal procedure if we can, where there is insufficient time remaining following a successful meaningful vote, we will make provision in the Withdrawal Agreement Bill – with Parliament’s consent – to ensure that we are able to ratify on time to guarantee our exit in an orderly way.”
But Labour claims Mrs May is planning to delay the final, binding vote on the withdrawal deal she has agreed with the EU until the last possible moment, so that MPs will be faced with a stark choice between her deal and no deal.
The party has tabled an amendment for Thursday that would force the government to come back to Parliament by the end of the month to hold a substantive vote in the Commons on its plan for Brexit.
Mr Corbyn said: “The prime minister is playing for time and playing with people’s jobs, our economic security and the future of our industry.
“This week Parliament should set a clear deadline for the government to come forward with its revised deal or give MPs the chance to decide what happens next.”
Will May delay Brexit vote to last minute?
As we talked about late on Monday, there has been a sense building in Westminster that the prime minister is, maybe by accident, maybe increasingly by design, looking to almost the last possible minute for the definitive Brexit vote.
While ministers speak publicly of “talks” that must be given time to be completed with the EU, and officials continue to chew over the possibility of the “Malthouse compromise” (remember that? It already seems like months ago that it emerged, blinking, into the Brexit saga) more and more MPs believe it is displacement activity – ministers keeping outwardly busy while they run down the clock.
Early on Tuesday morning, Commons leader Andrea Leadsom did not exactly quash that notion in an interview with the Today programme.
She appeared to open up the possibility that MPs might in the end be asked to vote at a moment of peak jeopardy, and that ministers might be willing to let the matter run that long.
Then, on Tuesday afternoon, the prime minister herself hinted that the government was prepared to do that.
A cross-party group of MPs has said that if there is no deal by 26 February, they will attempt to force the government to reach a decision on Brexit, and whether the UK is leaving without a deal, by mid-March.
The group – including Labour MP Yvette Cooper and Conservative former ministers Sir Oliver Letwin and Nicholas Boles – say they will put down an amendment creating parliamentary time for a bill enforcing a deadline for the prime minister and Parliament.
“This bill creates a parliamentary safeguard to prevent us drifting into no-deal by accident, and to prevent those crucial decisions being left until the final fortnight,” Ms Cooper said.
Sir Oliver said: “Any MP who genuinely wants to prevent an under-prepared no-deal Brexit will need to vote for this bill at the end of February.
“It is the only way of giving the House of Commons the time to produce a consensus about a positive way forward if the PM cannot get her deal through by mid-March.”
A similar amendment that set a deal deadline of 26 February and suggested the possibility of extending Article 50 was tabled by Ms Cooper and narrowly defeated in the Commons in January.