(Bloomberg) -- Rishi Sunak’s top political strategist warned Conservative MPs that divisions would mean certain defeat in this year’s UK general election, as party rebels threatened to derail the prime minister’s flagship migration bill unless he makes it tougher.

The plea for unity from Tory campaign chief Isaac Levido came at a closed-door meeting of backbench Conservatives on Monday in Westminster. The Australian election strategist was seeking to quell a rebellion in which some Conservative members of Parliament have pushed for changes that could fracture moderate support for Sunak’s legislation, which would allow the government to deport asylum-seekers to Rwanda. 

“Let me be clear. ⁠Divided parties fail,” Levido said, according to a transcript provided by a Conservative official. “It’s time to get serious.” 

The remarks by Levido show that Sunak remains concerned about fissures in the ruling party over the bill, despite fending off a rebellion during a test vote last month. The legislation, which would seek to overcome a November UK Supreme Court decision deeming the plan to be unlawful, is returning to the House of Commons this week, with a key vote due as soon as Wednesday. 

Sunak has made passing the legislation central to his efforts to whittle down a roughly 20-point lead in public opinion polls by the opposition Labour Party. Still, some Conservatives, including Sunak’s own former home secretary, Suella Braverman, argue it doesn’t go far enough to block European judges from stopping deportation flights.

Lee Anderson, the Tories’ deputy party chairman, said on Monday evening that he would support rebel amendments to toughen Sunak’s legislation.  

Adding to the heat on Sunak, the right-leaning Telegraph newspaper published a YouGov poll on Monday suggested that Labour leader Keir Starmer was on course for a majority of more than 100 seats. The report was accompanied by commentary by potential Sunak rival David Frost, a member of the House of Lords, who argued that a tougher immigration policy was key to preventing defeat. 

In an interview with GB News on Monday, Sunak indicated that he would ignore rulings by the European Court of Justice if it sought to stop deportation flights from taking place. However, he declined to offer any assurances he would strengthen the legislation to block legal challenges.

Downing Street officials say they’re confident Sunak will win Wednesday’s vote without making significant concessions to rebels that might put the UK in beach of international law. However, in a sign of nervousness among Sunak’s aides, government whips have warned MPs that if they voted down the bill they risked killing off the beleaguered Rwanda policy entirely and rekindling the turmoil that has led the Conservative Party to cycle through five prime ministers over the past eight years. 

Addressing the YouGov poll at the evening gathering of Tory MPs, Levido said it was intended to damage Sunak.   

“The people who organized this poll and analyzed and timed the release of it seem to be intent on undermining this government and our party, and therefore the re-election prospects of every single one of you in this room,” Levido said, according to the transcript. “They seem to be throwing in the towel.”

--With assistance from Kitty Donaldson.

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