In a statement to MPs, Mrs May today said the Government was stepping up preparations for a possible no-deal Brexit.
And she said that MPs who were threatening to vote against the deal she secured with Brussels must ask themselves the fundamental question: "Does this House want to deliver Brexit?"
If the answer was yes, she said that they needed to consider whether they were prepared to make "compromises" in order to make good on the 2016 referendum vote to leave the EU.
Mrs May's statement came amid dramatic scenes at Westminster, as news of her plan to postpone Tuesday's "meaningful vote" broke just minutes after Downing Street had insisted it was going ahead.
It is understood that the PM had been warned that she faced a large-scale defeat when MPs voted at the end of five days of debate in the Commons on her plans. She spoke with her Cabinet colleagues by a telephone conference call before addressing the Commons.
Responding to the decision, Leeds East MP and Shadow Justice Secretary Richard Burgon wrote on Twitter: “May’s 11th hour decision to cancel the vote on her deal further undermines the Government’s credibility.”
As Theresa May sat down to shouts of "resign" from the opposition benches, Labour leader Jeremy Corbyn said she was "trying to buy herself one last chance".
He said: "If the Prime Minister cannot be clear that she can and will renegotiate a deal then she must make way.
"The Prime Minister is trying to buy herself one last chance to save this deal. If she doesn't take on board the fundamental changes required then she must make way for those who can."