British Immigration Minister Robert Jenrick resigned on Wednesday, saying that draft government legislation to implement a scheme to deport migrants in Rwanda did not go far enough.
Jenrick said in his resignation letter that the legislation was one of the last chances to fight the small boat crisis before next year's election.
The legislation should have gone further to limit the opportunities for domestic and international courts to challenge the policy, he said.
"The government has a responsibility to place national interests beyond contested interpretations of international law," he said in his resignation letter, which he posted on X - the platform formerly known as Twitter.
"I cannot work with the proposed legislation because I do not believe it offers the best opportunities for success." Jenrick has been a close political ally of the British Prime Minister, Rishi Sunak.
As a member of parliament since 2014, Jenrick has served in various ministerial positions over the years.
In recent days, Jenrick, who has been immigration minister since October last year, has been very vocal about the need to crack down on migrants coming to England on small boats.