A group of hardline Tory Brexiteers has criticised a key component of Rishi Sunak's Brexit deal, the Stormont brake, which was intended to offer a veto on the imposition of any new EU regulations in Northern Ireland.
The European Research Group labelled it "practically useless".
However, ERG Chairman, Mark Francois, has not committed to voting against the deal.
With Labor backing the agreement, the vote is expected to pass comfortably, in spite of opposition from hardline Tory Brexiteers.
The Democratic Unionist Party (DUP) has already announced that it will vote against the framework.
MPs are set to vote on the Windsor Framework, a part of the UK government's new Brexit deal for Northern Ireland.
However, in anticipation of Wednesday's parliamentary debate, the hardline Tory Brexiteers' group, the European Research Group, criticised the deal's "practically useless" Stormont brake.
They claim that it does not provide the veto that was promised over the imposition of new EU regulations across Northern Ireland, describing the agreement as only providing "limited legal changes".
The government may have the backing of the Labor Party, but the DUP has declared it will vote against the framework.
The ERG spokesman, Mark Francois, has declined to provide specific details on how the group will vote.
He plans to hold a meeting with the group on Wednesday to discuss the matter.
The group has published advice from a "Star Chamber" of lawyers, which provides a negative analysis of the Windsor Framework.
Its legal analysis has suggested that EU law will remain superior in Northern Ireland despite the framework.
A so-called green lane resulting from the deal does not function as it should, and the framework has no visible exit, other than a complicated legal process.
The government has refused to make any changes to the deal.
While the demand for legal changes has come from the ERG and the DUP, ultimately, the fate of the deal will be decided by the parliamentary vote.
The parliamentary vote will take place on Wednesday, and it is expected to be approved, despite criticism from some hardline Tory Brexiteers.