Brexit vote: Fate of May's deal on knife edge as DUP and Tory Brexiteers agonise over whether to support it

MPs wait for crucial legal verdicts before deciding whether to support prime minister's revised plan

The fate of Theresa May's Brexit deal hangs in the balance as Tory Eurosceptics and the DUP weigh up whether to support the plan.

The prime minister is waiting to hear whether some of the staunchest critics of her Brexit strategy have been won over by the new concessions announced in a dramatic late-night statement yesterday.

Ms May travelled to Strasbourg last night to sign off new guarantees from the EU that the controversial Irish backstop, which would keep the EU in a customs union with the bloc, will not be permanent.

After frantic last-minute talks, the government published three new documents: two new legally-binding agreements with the EU and a unilateral statement from the UK outlining how it would leave the backstop.

However, it is unclear whether the changes will be enough to overturn the historic 230-vote defeat Ms May's deal suffered when it was put to MPs in January.

The chances of the revised deal being passed when MPs vote on it tonight will be determined by the prime minister's Brexiteer backbenchers and her Commons partners in the DUP.

The sizeable European Research Group (ERG) of Tory Eurosceptics is yet to take a position on the new deal, saying it is awaiting the verdict of a committee of parliamentary lawyers that the group set up to scrutinise the government's plans. The decision of the panel, which is meeting this morning, is expected to be a highly significant in influencing other ERG members.

The attorney general, Geoffrey Cox, will also publish his legal opinion this morning on whether the changes secured by Ms May have altered his previous assessment that the backstop could "endure indefinitely".

Many Tory MPs who opposed the deal in January are waiting for those two rulings before announcing how they will vote tonight.

ERG chairman Jacob Rees-Mogg said he wanted to hear the opinion of the group's legal "star chamber" before coming to a decision, telling BBC Radio 4 Today: "The reason we haven't jumped to a conclusion is that there is a lot of detail in this. I'm not a lawyer, so that's why I'm waiting for lawyers to explain to me exactly what it means."

He added: "I'm not sure that the agreement with the EU are a major change - that they continue to be promises of goodwill.

"So my focus will be on whether the unilateral declaration is genuinely unilateral. That's the point that I want to be satisfied."

Mr Rees-Mogg said many Tory MPs would also be "heavily influenced" by the DUP.

DUP Westminster leader Nigel Dodds sits on the ERG's legal committee and will play a key role in determining whether or not Ms May's deal is passed.

Another DUP MP, Sammy Wilson, said Ms May's announcement last night "seems to fall short of what she herself has promised" but said the party would "give due diligence" to the new documents and would await Mr Cox's verdict.

As the prime minister hailed a last-gasp breakthrough in Strasbourg last night, all eyes turned to her backbenchers and the MPs who so comprehensively defeated her agreement two months ago.

Some senior figures who previously opposed Ms May's deal said they were now minded to support it.

David Davis, the former Brexit secretary, told talkRADIO that if Mr Cox confirms the new documents are legally binding, it would "make this just about acceptable to me".

He added: "This is a way to deliver a proper Brexit - it’s a lot worse than what I would have hoped for - it’s significantly better than what was presented in December."

The government is hoping that the new assurances on the backstop will be enough to get its exit deal over the line. Ms May has promised that, if her deal is rejected a second time, she will allow the Commons to vote on whether to pursue a no-deal Brexit or delay Britain's departure from the EU.

Urging MPs to back the plan, environment secretary Michael Gove told Today: "We have an improvement on the Withdrawal Agreement that was presented to the House of Commons in January. That improvement ensures that we have additional legal weight behind our position.

"It also ensures that, as in any agreement or any contract, if it is the case that one side - in this case the EU - seeks to act in a way that is not in accordance with their commitments then we can go to court and we can win.

"We have also made a declaration as a nation that, should the EU behave in that way, that is exactly what we will do."