After late-night talks in Strasbourg with EU chief Jean-Claude Juncker, the Primer Minister said she had secured an agreement with the EU that there will be “no indefinite backstop” – the key sticking point for many hard-line Brexiteers who Mrs May must win over.
She said the new agreement – or “instrument” – could be used to start a formal dispute against the EU if it tries to keep the UK tied to the backstop. The “Irish backstop” is an insurance policy that will ensure there is no hard border in Ireland.
Mr Juncker said: “It’s this deal or Brexit might not happen at all.”
Not a single word of the Withdrawal Agreement so roundly rejected by MPs has changed. Instead, the UK and EU say they have produced a legally-binding, parallel agreement in an attempt to pacify MPs unhappy at the current deal.
Critics have, however, already pointed to potential holes with the wording, pointing out that the new agreement only says it “reduces the risk” that the UK could be deliberately held in the backstop indefinitely. It is this phrase that could prove a sticking point for many MPs.
Labour immediately dismissed the new deal. Steve Baker, a senior voice in the hard-line Tory Brexiteer group the ERG, said it was nowhere near enough what he wanted. The DUP has said it will study the deal carefully.
This is Mrs May’s last throw of the dice and she urged MPs to back her “improved” deal in the meaningful vote tonight. She said: “I will speak in more detail about them when I open that debate.
“MPs were clear that legal changes were needed to the backstop. Today we have secured legal changes. Now is the time to come together to back this improved Brexit deal and deliver on the instruction of the British people.”
She must now hope she can avoid a second humiliating defeat on her Withdrawal Agreement, which takes place on Tuesday evening. If Mrs May can win the vote, Brexit will almost certainly take place as planned on 29 March.
The pound spiked sharply as details as of the deal emerged, at one point hitting a 22-month high against the euro.
What the EU said
Mr Juncker said this was absolutely the final offer on the table, insisting there would be “no third chances”.
He added: “The Prime Minister and I have agreed on a joint legally-binding instrument relating to the Withdrawal Agreement. This instrument provides meaningful clarifications and legal guarantees on the nature of the backstop.
“The backstop is an insurance policy, nothing more, nothing less. The intention is for it not to be used, like in every insurance policy.”
Mr Juncker said he had spoken to Irish Taoiseach Leo Varadkar, who he said had indicated he was “prepared to back this approach in the interests of an overall deal”.
Reaction from MPs has been mixed ahead of a week that could plunge the UK into a full-blown political crisis.
Steve Baker suggested Mrs May has not done enough to sway his vote. He told the BBC: “The Government has had to put a very good gloss on something that falls short of what was expected”.
But another Tory MP, Mike Penning, said that he would now back the deal having voted against it last time.
Elsewhere, the DUP – whose votes will be crucial – has said their MPs will study the changes ahead of Tuesday’s vote.
Labour leader Jeremy Corbyn said the changes were meaningless: “The Prime Minister’s negotiations have failed. This evening’s agreement with the European Commission does not contain anything approaching the changes Theresa May promised Parliament.
“MPs must reject this deal tomorrow (Tuesday).”
Three days, three votes
If Mrs May’s deal is defeated for a second time on Tuesday, she has promised to give MPs a vote on whether to accept a no-deal Brexit on March 29 or to extend Article 50 in order to delay the UK’s departure beyond the current deadline.
Tory former minister Nick Boles said: “I am sure that the Prime Minister will honour these three commitments. If she doesn’t she will forfeit the confidence of the House of Commons.”
Senior Labour backbencher Yvette Cooper said the PM would be guilty of a “straight-up lie” if she failed to go through with votes allowing MPs to delay Brexit.