Suella Braverman is said to be making a statement in the Commons this afternoon, in what is expected to be an explosive intervention on the increasingly heated issue of migration.
Giving a statement in the Commons, she is expected to call into question Rishi Sunak's leadership and put pressure on the Prime Minister to withdraw from the European Court of Human Rights, GB News understands.
This comes amid mounting fury from MPs over migration, with Braverman having repeatedly criticised the Government's approach to the issue.
Earlier this week, she launched a scathing attack on the Government's new plans to cut legal migration, pointing out that the impacts of the changes are unlikely to be felt before the next election.
WATCH: Cleverly unveils new treaty with Rwanda
This came after James Cleverly unveiled a five-point plan, in a move which he said would cut net migration by up to 300,000.
But Braverman said the package of measures came "too late", claiming the Government "can go further".
The former home secretary attended a meeting of Tory rebels last night, which saw multiple right-wing factions come together to discuss James Cleverly's new Rwanda migration bill, GB News understands.
This came after Cleverly announced a new treaty with Rwanda yesterday, which Rwanda’s foreign affairs minister Vincent Biruta said would “strengthen” the asylum processing system.
MPs from the European Research Group (ERG), New Conservatives and the Common Sense Group came together last night in a meeting which one former minister described as "very bracing".
Around 30 MPs - including the two former Home Secretaries Braverman and Priti Patel - attended the meeting, hosted by the ERG.
The so-called 'Star Chamber' of lawyers, which scrutinised many of the Brexit deals, is set to look at Cleverly's new plan to send flights to Rwanda and provide an answer on whether it will successfully facilitate the scheme in the coming days.
A source inside the meeting told GB News: "We’ve only seen a treaty. The important bit will be the Bill.
"The Bill will have to meet the obstacles identified in the Supreme Court judgment.
"Anything less won’t work and frankly it would be pointless to introduce a Bill that doesn’t achieve that."
Another ERG source told GB News that MPs in attendance at the meeting were "united and focussed" on the issue at hand.
In a statement after the meeting, ERG Chairman Mark Francois said: "Our ERG Meeting this evening, which also included members of the New Conservatives and the Common Sense Group, resolved to refer the Rwanda Bill, as soon as it is published, to the 'Star Chamber' of legal experts, chaired by Sir Bill Cash.
"The Star Chamber will be asked to decide on the following question: 'Whether the Bill fully respects Parliamentary Sovereignty, with unambiguous wording, which would facilitate flights to Rwanda.'
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Cleverly announced a new treaty with Rwanda yesterday
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"The Star Chamber will complete this task in days, not weeks."
If the Star Chamber finds that the new Bill does not go far enough to be approved by the Supreme Court, the joined-up group of rebels would constitute a major rebellion for the Prime Minister.
But today's statement from Braverman, given weeks after she was sacked as home secretary, is likely to come ahead of the Star Chamber's verdict.
ADDITIONAL REPORTING BY CHRISTOPHER HOPE