A host of ex-Tory MPs whose support Boris Johnson needs to get his new Brexit deal through parliament are demanding a full analysis of the plans.
Senior MPs such as David Gauke and Oliver Letwin have signed a cross-party letter to the prime minister asking for impact assessments on the fresh agreement struck with Brussels.
It is a strong sign that Johnson’s deal will be voted down when it goes before the Commons on Saturday.
The prime minister may then be forced into a politically-damaging Brexit delay as a full economic analysis could take time.
The UK is currently on course to leave the EU on October 31 but Donald Tusk refused to rule out a further delay after the deal was published, telling reporters: “If there is a request for an extension, I will contact member states to see how to react.”
Pro-deal Labour MPs who fear Johnson is trying to “bounce” them into supporting a deal that could hit industry are sympathetic with the cross-party demand, HuffPost UK understands.
They also plan to press Johnson to enshrine in UK law EU-style workers rights and other protections as part of a bill published before Saturday, and could withhold support if the PM refuses.
It comes as pro-second referendum campaigners weigh up when to push a Commons vote on their plans.
Johnson faces an uphill struggle after the DUP, whose leader Arlene Foster once described a regulatory border as a “blood red line” for her party, refused to back the deal, saying it risked undermining the union.
Number 10′s snap decision to expel 21 Tory MPs from the party for defying him on Brexit also cut his chances of securing a majority.
It means Johnson must convince would-be rebel Labour MPs to get behind his deal. Downing Street will underline to them the ‘level playing field’ clause in his deal, which says UK regulations cannot dip below the EU’s, and claim that it does not compromise environmental protections and workers’ rights, but some are sceptical and cite a lack of detail.
But Jeremy Corbyn’s MPs are coming under pressure from unions, with the TUC’s Frances O’Grady and Unite deputy Steve Turner urging them not to cross the floor.
Some Tory Eurosceptics, who three times voted against Theresa May’s plans, are thought to be warming to the deal, however.
The legal text was published on Thursday, with the crunch vote due on Saturday afternoon, after UK negotiators re-entered negotiations with Brussels only last Friday.
The letter calling for a full economic analysis, penned by Plaid Cymru MP Liz Saville Roberts, says parliament has had too little time to scrutinise the plan.
Saville Roberts says it is “unfair” of ministers to vote on a deal which potentially has “serious ramifications for our country for decades to come, without allowing us the time to fully scrutinise the details.”.
She says: “MPs are being asked to vote on a generation-defining issue on Saturday, it is only right that we know its consequences.
“It would be incomprehensibly irresponsible of Boris Johnson not to undertake and release impact assessments, especially considering we had this information when voting on previous versions of Brexit.
“Parliament and the public deserve to know the truth about what faces them if this deal goes through. This is not about playing politics, but future of the four nations of the UK and communities we all represent.”
Speaking at a press conference in Brussels, Johnson repeated his mantra that MPs must “come together and get Brexit done”.
He said he was “very confident” MPs would vote for the deal once they “study” its detail.
He added: “This is our chance in the UK as democrats to get Brexit done, and come out on October 31.
“This is our chance to focus on our priorities, the people’s priorities, the NHS, putting 20,000 police on the streets, lifting up funding of education across the country, the biggest expansion of the living wage.”