(Bloomberg) -- The Conservative Party’s euro-skeptic caucus will huddle to weigh up how to handle Rishi Sunak’s Rwanda deportation legislation, as the British prime minister girds for a critical test of his authority over his own party this week. 

The European Research Group, a bloc of pro-Brexit Members of Parliament, was scheduled to discuss the bill Monday ahead of a preliminary vote slated for the following day, said the group’s head, Mark Francois. The vote represents the first time the House of Commons will take a position on the legislation, which Sunak argues would lift most of the legal barriers that have blocked the government’s plan to deport asylum-seekers to Rwanda. 

The One Nation conference of moderate Tories were also slated to hold their own meeting on the legislation Monday, according to a person familiar with the group’s plans. The bloc has so far appeared accepting of the bill in its current form, and the person said members would likely support the government Tuesday.  

It’s unclear whether the ERG group can muster the 29 votes that would be needed to sink Sunak’s legislation. The group is less unified than it once was and former leader Jacob Rees-Mogg initially said that he was happy with the bill. 

About a quarter of One Nation’s 106 MPs are in government and obligated to vote with Sunak. Labour and other opposition parties are expected to vote against it. 

Speaking for the government Sunday on the BBC, Cabinet minister Michael Gove said the bill was “legally sound” and “tough and robust,” although he left the door open to possible changes.

The episode invoked memories of similar disputes of over Brexit, in which the ERG stymied then-Prime Minister Theresa May’s effort to reach a deal with Brussels, ultimately undoing her premiership. In a parallel to those fights, some harder-line Tories are demanding stronger language blocking the European Court of Human Rights from intervening to stop the deportation of those who arrived on British shores to seek asylum. 

The deportation deal with Rwanda is the centerpiece of Sunak’s effort to curb a surge in migrants crossing the English Channel in small boats and claiming asylum. Last month, the UK Supreme Court deemed the plan was unlawful, prompting Sunak to pledge to pass a law bypassing the legal barriers. 

While Sunak needs to get the legislation through the Commons to show he still controls a governing majority, he has stopped short of making its passage a test of confidence in his leadership. The preliminary vote planned for Tuesday comes a day after Sunak is scheduled for an hours-long appearance before a committee investigating the government’s handling of the Covid-19 pandemic, a period when he was Chancellor of the Exchequer. 

Government officials acknowledged Sunday that the legislation might not reach a final vote before a planned Christmas recess on Dec. 19 and debate could spill into the new year. MPs opposed to the bill could abstain during Tuesday’s vote and offer amendments before a final vote later. 

Former Immigration Minister Robert Jenrick, who resigned in protest over the legislation last week, reaffirmed his opposition to it on Sunday, telling the BBC that the measure wouldn’t represent a “serious deterrent” to dissuade people from entering the country illegally and would not prevent deportations from being tied up in the courts. He did, however, indicate he would seek to amend the bill to make it stronger.

“I won’t support this bill, but I do feel like we can fix this,” Jenrick said. 

--With assistance from Andrew Davis.

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