And he said the legislation, designed to salvage the government’s Rwanda deportation plan, will not work.
Mr Sunak branded the departure “disappointing”, but told Mr Jenrick in a letter he fears it was “based on a fundamental misunderstanding of the situation”.
But former minister Sir Simon Clarke said Mr Jenrick’s departure was “very concerning”.
The senior MP said: “Very sorry - and concerned - to see Rob Jenrick leave government this evening.
“He understands totally the strength of public feeling on this issue.”
Sir Simon said the question now is “simply will this legislation work”.
On Wednesday, chairman of the right-wing European Research Group (ERG) of Tory MPs, said: “If the immigration minister, who is a good man, has resigned over this bill that is deeply worrying.”
And former minister Andrea Jenkyns, an ardent Boris Johnson loyalist, said Mr Jenrick’s resignation “may be the death knell for Sunak’s leadership”.
Tory former attorney general Dominic Grieve said the party is now “seriously split ideologically in a way that I have never seen before”.
“What we’re now watching is a split between people who believe in the rule of law, and people who don’t actually believe in the rule of law at all,” he told the BBC.
Cabinet minister Chris Heaton-Harris said it was a "great shame" that Mr Jenrick had quit as immigration minister over the Rwanda policy.
But he insisted the legislation will work at getting flights off the ground to the east African nation, telling Sky News: “I think it will work.”
Labour’s Yvette Cooper said Mr Jenrick’s resignation showed the “starting gun has been fired” on the next Tory leadership election.
The shadow home secretary added: “This is the desperate dying days of a party ripping itself apart, clearly totally out of ideas, lost any sense of leadership or direction.”
Mr Jenrick’s resignation letter made clear he wanted to bypass the ECHR – revealing that he had been “pushing for the strongest possible” bill that would put “national interests above highly contested interpretations of international law”.
It leaves Mr Sunak facing the near-impossible task of winning votes from both the Tory right, who wanted a “full fat” crackdown on the ECHR, and moderate MPs in the “One Nation” group who warn they cannot back legislation that flouts human rights law.
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