Caving to pressure from Labour and Tory Remainers, the Prime Minister confirmed plans to let MPs decide whether to hold a second referendum - but only on the condition they vote for her Withdrawal Agreement Bill.
She said MPs will vote in parliament on whether to hold a second referendum, despite her belief that the 2016 vote should continue to be honoured.
She said: "The Government will include in the Withdrawal Agreement Bill at introduction a requirement to vote on whether to hold a second referendum and this must take place before the Withdrawal Agreement can be ratified.
“If MPs vote against the second reading of this bill they are voting to stop Brexit.”
In a speech which signalled just how desperate she has become, Mrs May pleaded for political collaboration, noting that 30 MPs voted differently her previous deal would have been successful.
She said: “This is a huge opportunity for the United Kingdom. Out of the EU. Out of ever-closer union. Free to do things differently.
"And right now, it is slipping away from us. We risk losing a great opportunity."
Despite her appeal, some Conservative MPs took to Twitter to voice their disgust - one doing so before the speech was even over.
MP Simon Clarke tweeted: "So if we pass the Withdrawal Agreement Bill at 2nd reading, we allow a Remain Parliament to insist upon a 2nd referendum and a Customs Union? This is *outrageous*.”
And Conservative MEP David Bannerman tweeted: "On PM speech this illusory attempt to keep as close as possible to 'frictionless trade' - now by law - has been the problem all along.
"Led to Chequers to Customs FA. Just go to SuperCanada FTA! Now a vote on 2nd Ref! This is a total sellout by May & she must go immediately."
And former Tory leader Iain Duncan Smith MP said there was nothing new in Mrs May's latest deal.
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He said: "I can't see that we've taken back control over anything.
"The backstop is still there, it's a customs union in all but name and it puts Brussels firmly in control of our destiny.
"There's nothing new or bold about this bad buffet of non-Brexit options.
"At a time when people are deserting the main parties this is the PM's response, to do all she can to defy the result of the referendum.
"Today the Government has moved from take back control to give back control."
Conservative MP and Brexiteer Charlie Elphicke condemned the deal as a "dog's breakfast" that he could not support, despite voting for Mrs May's deal last time.
He said: "This is even more of a dog's breakfast than the last deal, it is not Brexit and I won't be supporting it.”
And Jacob Rees-Mogg described the new bill as “worse than before”
The Prime Minister’s latest proposals are worse than before and would leave us bound deeply in to the EU. It is time to leave on WTO terms.— Jacob Rees-Mogg (@Jacob_Rees_Mogg) May 21, 2019
The criticism wasn’t limited to her own party.
Scotland First Minister Nicola Sturgeon tweeted: "The PM is asking MPs to vote for a Bill that takes us out of the EU - in Scotland's case against our will - out of the single market and possibly out of the Customs Union. And with no actual commitment to putting the deal to a second referendum. @theSNP will not do that.
1/ The PM is asking MPs to vote for a Bill that takes us out of the EU - in Scotland’s case against our will - out of the single market and possibly out of the Customs Union. And with no actual commitment to put the deal to a second referendum. @theSNP will not do that.— Nicola Sturgeon (@NicolaSturgeon) May 21, 2019
She continued: "In PM's own words, 'if MPs vote against the Bill, they will be voting to stop Brexit.' That is what @theSNP will do because Scotland did not vote for Brexit. #StopBrexit."
Mrs May said her new Brexit deal had "listened to Unionist concerns" about the backstop.
"So the new Brexit deal goes further," she said. "It will commit that should the backstop come into force the Government will commit to ensure that Great Britain will stay aligned with Northern Ireland.
"We will prohibit the proposal that a future government could split Northern Ireland off from the UK's customs territory."
Labour leader Jeremy Corbyn said his party would not support a "repackaged version of the same old deal".
He said: "The Prime Minister's proposal tonight seems to be largely a rehash of the Government's position in the cross-party talks that failed to reach a compromise last week.”
PM’s “new” deal is putting lipstick on a pig - rehash of old deal with a few concessions attached.— Caroline Lucas (@CarolineLucas) May 21, 2019
Using bait of possible #PeoplesVote to get flawed deal over line won’t work. Democracy shouldn’t come with strings attached. PV needs to be guaranteed now, not left to chance
While Green Party leader Caroline Lucas said it was like “putting lipstick on a pig”.
Lots of us have been very clear that the PM’s deal can pass on the condition that the people get to decide through a referendum. That’s not what the PM is promising I’m afraid. Will look at the detail first, but on that basis it’s unlikely I’ll vote for the Bill at Second Reading— Wes Streeting MP (@wesstreeting) May 21, 2019
May’s last stand?
Asked if she would resign if the Withdrawal Agreement Bill was defeated, Mrs May said: "That was last week's news.
"And I set out with the chairman of the 22 (1922 Committee of Tory backbenchers) what would be happening."