What scale of rebellion will Rishi Sunak face on his Brexit deal? There had been hopes in Downing Street and the Whips’ Office that this could be in single figures when the deal is put to a vote on Wednesday.

However, the DUP leader Jeffrey Donaldson has said his party – all eight MPs – will vote against (notably the Ulster Unionist party today described it as ‘an important stepping stone’), leading to concerns that Tory Brexiteers could follow suit. Today, the European Research Group (ERG) met to discuss its ‘Star Chamber’s’ legal findings – and it doesn’t make for pretty reading for the Prime Minister.

While Sunak would like the group to back the deal, their opinion does not carry the same weight as it did

The group – led by chairman Mark Francois – accused Sunak of promising more than the Windsor Framework really offers. Speaking after the meeting, Francois spoke of the 30-strong group’s key criticisms which include a fear that the Stormont brake (the aspect MPs are being asked to vote on), meant to provide a mechanism for Stormont and the UK government to say no to new EU single market rules, is ‘practically useless’. This is on the grounds that it would have a ‘very narrow application in theory’ and ‘allows the EU to take “remedial” countermeasures’. The ‘Star Chamber’ report also criticises Sunak’s claims over the ‘green lane’ on the grounds it won’t apply to all ‘at risk’ goods and also raises concerns that EU law will still be supreme in Northern Ireland.

The document is long in its criticisms, which is why it’s rather curious that Francois’s announcement was not accompanied with a pledge that the ERG will vote against the deal. Instead, he suggested that the group may not vote unanimously – with a further update to follow on Wednesday. This points to how opinion is divided among Tory Brexiteers. As I reported when the agreement was first unveiled, in an initial meeting over the framework, figures such as Bernard Jenkin were downbeat, questioning the differences between UK and EU versions of the text and asking whether Sunak has oversold it. Yet others argued that, given the deal was undeniably an improvement on the status quo, it was hard to make a case against it.

It’s also the case that while Sunak would like the group to back the deal, their opinion does not carry the same weight as it did back in the Theresa May years. Not only has the parliamentary arithmetic moved in the Prime Minister’s favour, many Leave-voting MPs – such as former ERG chair and current Northern Ireland minister Steve Baker – see the framework as a palatable way to close a bruising chapter between the UK and Brussels.