When Sir Graham Brady tabled his Brexit amendment asserting that Theresa May's deal would be palatable if the backstop is replaced with an alternative arrangement, the hope was that enough Conservative MPs would align behind it to show Brussels that – so long as they were prepared to compromise – a deal could pass the Commons. That plan has hit a fairly large stumbling block this evening. Members of the European Research Group – made up of backbench Tory Eurosceptics – gathered in Portcullis House to come up with a formal position ahead of tomorrow night's vote.

The consensus was that they would not back the Brady amendment – nor any other, including the Murrison amendment which attempts to put a time limit on the backstop. As one MP put it when they exited the room early; 'We've decided that no deal is better than a bad deal'. Speaking after the meeting, Jacob Rees-Mogg told assembled hacks that the Brady amendment was too vague on what would replace the backstop and things had been made worse by the fact Brady had said he could live with a codicil setting out additional changes rather than the withdrawal agreement being reopened. As for the Murrison amendment which attempts to put a time limit on the backstop, Ress-Mogg said this wasn't a goer either.

That's not to say that there is no chance of the ERG coming around before tomorrow night's vote. Rees-Mogg said the group could potentially back an amendment on the backstop so long as it was specific about how to solve the backstop – and it came directly from the government; 'The expectation is that the government will come forward with an amendment that it supports and make it clear what its position is.' The Leave MP did add, however, that he was leaning on 'triumph and hope over experience' in his hope for a better amendment than the ones currently on offer. The group will meet again tomorrow evening to make a final decision.

The problem is that the ERG's decision is a gamble and if it backfires it's not just May who suffers. If the Prime Minister is unable to turn up to Brussels and say she has proof a version of her deal can get through the Commons, EU leaders will try and insist the way to find the numbers is to go softer still. What's more, a number of Conservative MPs believe their Remain-leaning colleagues are more likely to back the Yvette Cooper no deal amendment tomorrow if it looks as though there is no alternative compromise on the backstop. As one put it earlier: 'If it looks like the Brexiteers will only accept no deal, that option will be removed for them.' That would weaken May and the Brexiteer MPs' hands further still. With the Brady amendment lacking sufficient support, No. 10 must decide whether to table their own amendment or to sit still and see who cracks first.