Tory Eurosceptic group says at least two days will be needed to scrutinise new compromise on Irish backstop

Tory Brexiters are to demand at least two days to scrutinise any new offer from Brussels on the Irish backstop mechanism, warning the prime minister not to “bounce” the group into an early vote on her Brexit deal.

May has pledged that a vote will take place on her proposal, including any changes agreed in Brussels, by 12 March, though it is possible that Downing Street will seek to bring the vote forward to this week if changes can be secured.

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The EU has suggested that progress has been minimal and a No 10 source said there was little optimism about putting any deal to a vote this week, despite rumours in Westminster that the prime minister could attempt two votes before the 12 March deadline, after which she has promised to hold a vote on a no-deal exit and on delaying article 50.

The attorney general, Geoffrey Cox, was reported to have abandoned plans to secure a unilateral exit mechanism or firm end date to the backstop and was reported to be now focusing efforts on securing an enhanced “arbitration mechanism” that allows the UK or the EU to give formal notice that the backstop arrangement should end.

The Telegraph reported that Brussels was resisting Cox’s demand that the mechanism should lie outside the jurisdiction of the European court of justice.

A No 10 spokesman declined to say whether an exit mechanism or date were still objectives for the negotiations. “The attorney general continues to pursue legally binding changes to the backstop that are necessary to ensure it cannot be indefinite,” the spokesman said. “We will not, however, comment on the specifics of the negotiations at this critical stage.”

The European Research Group, the group of Tory Eurosceptics led by Jacob Rees-Mogg, has agreed that a group of eight lawyers, seven of them MPs, will scrutinise and pass judgment on the final compromise offered by Cox. The group has made an exit date or a unilateral exit mechanism one of its three key demands for accepting any revised agreement.

One of the MPs on the panel, the former Department for Exiting the European Union minister Suella Braverman, said there was “every chance the deal will be passed” if the compromise was acceptable to the group.

“The prime minister has said she is seeking a legally binding, treaty-level clause that overrides the backstop, which provides a clear and unconditional route out of the backstop,” she said. “If she is able to achieve this, there’s every chance the deal will be passed.

Play Video 1:33 May: MPs will get vote in March on extending article 50 if no deal agreed - video

“Prejudging or speculating at this stage won’t help the renegotiating efforts. What colleagues do require is to be given enough time to digest the changes before being asked to vote on them.”

Another member of the ERG said there should be at least two days between the new offer being presented and the next meaningful vote. “Whatever they come back with, if they try and bounce parliament, then it will fail. For many, a quick vote would be a strong indication it won’t stand up to scrutiny.”

The so-called “star chamber” of Brexiters who will pass judgment on the compromise will be chaired by the veteran Eurosceptic Sir Bill Cash. It also includes the Democratic Unionist party’s Nigel Dodds, the former Brexit secretary Dominic Raab, former DExEU minister David Jones, the backbenchers Michael Tomlinson and Robert Courts, both former barristers, and Martin Howe QC, who chairs the pro-leave group Lawyers for Britain.

Tomlinson, seen as one of the hardcore Tory Brexiters, was one of 20 to vote against the prime minister’s offer of a vote on the article 50 extension. He told the Sunday Times that the committee would apply three tests to whatever Cox produced from the negotiations in Brussels. He said if the three were met, that would deliver the support of the group’s key backers, including Rees-Mogg and the former Brexit minister Steve Baker.

Tomlinson said the change “has got to be legally binding, so effectively treaty-level change” and that the attorney general must secure changes that altered his legal advice that the backstop could “endure indefinitely”. The third requirement is “a clear exit route”, such as an end date or a unilateral exit mechanism for the UK to leave the backstop.

Brussels is known to be unwilling to offer anything close to that demand. The EU’s deputy chief negotiator, Sabine Weyand, highlighted a tweet that said the demands “are way beyond what EU negotiators will countenance”.

A government source said it remained the intention to hold one vote close to or on 12 March, given the need to “focus minds” on the choices ahead. “We are not yet where we need to be,” the source said.

Play Video 1:08 Fox: article 50 delay may be only option for smooth Brexit – video

Speaking on Sunday, the international trade secretary, Liam Fox, said the panel of Eurosceptics seemed to be making a genuine attempt “to try to map out ground”. However, he said that should the deal be rejected, a delay to Brexit might now be the only way to ensure a smooth departure.

Fox said it would be “very unfortunate” if MPs were to reject May’s deal and then vote to extend article 50, in votes she has promised will take place by 14 March. “But, if we have no option, in order to deliver a smooth Brexit, then so be it,” Fox told BBC One’s Andrew Marr Show.

Meanwhile, the Danish prime minister, Lars Løkke Rasmussen, defended his own pledge to never put his country’s membership of the EU to a referendum by highlighting the damage to the British economy in which “one car factory after another stops or cancels planned production”.

Rasmussen said the British public had been taken in by “some rhetorically skilled politicians who turned out to be untrustworthy conmen who subsequently left the sinking ship”. He described Westminster as a circus and “a paralysed political system that is about to melt down”.

Over the weekend, Michel Barnier, the EU’s chief negotiator, suggested in an interview with European newspapers that May would need to delay Brexit even if she got her deal through parliament in mid-March. Asked if it was possible for the British parliament to pass the required legislation before 29 March, Barnier said: “No, no … there would have to be an extension that would be called motivated, technical.”

Barnier told ambassadors on Friday that he would be meeting the Brexit secretary, Stephen Barclay, and Cox on Tuesday to work on an “interpretative” document to reassure MPs on the temporary nature of the Irish backstop but without a time limit or unilateral exit mechanism.

But Wolfgang Schäuble, the president of Germany’s Bundestag, said this weekend that he was more convinced than ever that Britain would end up as a member of the European Union. “I believe Britain will either not leave the EU at all or come back at some point,” Schäuble told Funke Media Group.