Britain's ruling Conservative party was in disarray Wednesday after its immigration minister quit over legislation regarding sending migrants to Rwanda as hardliners turned the screw on Prime Minister Rishi Sunak.

The UK leader's position looked increasingly vulnerable after Robert Jenrick said he had resigned due to "strong disagreements with the direction" of the government's policy on immigration.

The bombshell resignation came after Rwanda warned that it would pull out of a treaty to accept migrants if Britain did not respect international law.

Former hardline interior minister Suella Braverman also issued Sunak an ultimatum to get tougher on immigration or face certain wipeout in the next general election, in a torrid day for the British prime minister.

Jenrick resigned after Sunak's administration published emergency legislation designed to ensure Rwanda is considered a safe country after UK Supreme Court judges last month deemed that it was not.

In his resignation letter to the prime minister, Jenrick wrote that the proposed laws were "a triumph of hope over experience".

"The stakes for the country are too high for us not to pursue the stronger protections required to end the merry-go-round of legal challenges which risk paralyzing the scheme and negating its intended deterrent," he wrote.

That was seen as a reference to Sunak's refusal to take Britain out of the European Convention on Human Rights (ECHR).

The bill proposes giving ministers powers to disregard sections of the UK Human Rights Act and ECHR when considering deportation cases.

In his reply, Sunak said Jenrick's resignation was "disappointing" and "based on a fundamental misunderstanding of the situation".

But some right-wing Tories, including Braverman, want Sunak to leave the ECHR altogether.

Braverman, sacked last month after a series of outspoken comments, told parliament earlier that the government needed to go further to tackle "mass, uncontrolled, illegal immigration".

Among her demands was to block "all routes" of legal challenges to deportations to get deportation flights to Rwanda by the time of the poll, which is expected next year.

She has become the cheerleader of the vocal Tory right wing and is thought to be positioning herself as a future leader if Sunak is forced to quit after the nationwide vote.

The Tories lag well behind the main opposition Labour Party in opinion polls ahead of an election that must be held by January 2025.

Braverman, a former attorney general, has called for tougher measures before and criticized the UN convention on refugees and European human rights legislation for blocking the government's plans.

Her latest comments are red meat to fellow firebrands who see having total control over Britain's borders as the final piece in the Brexit jigsaw.

"The Conservative party faces electoral oblivion in a matter of months if it introduces yet another bill destined to fail," she told MPs.

The Tories face a stark choice to "fight for sovereignty or let our party die", she said, adding ominously: "I refuse to sit by and allow us to fail."

In Kigali, Foreign Minister Vincent Biruta, who signed a new bilateral treaty on migrants with Braverman's successor James Cleverly on Tuesday, said any breach of global conventions could see Rwanda withdraw from the deal.

"Without lawful behavior by the UK, Rwanda would not be able to continue with the Migration and Economic Development Partnership," he added, referring to the controversial deal.

Cleverly insisted in parliament that the UK and Rwanda were "both completely committed" to the partnership, adding that London's proposed law put "beyond legal doubt the safety of Rwanda".

The first deportees were due to be sent to Rwanda in June last year but were pulled off a flight at the last minute after a judge at the European Court of Human Rights issued an injunction.

Since then, their cases — and the wider legality of the policy — have been stuck in the courts, hampering Sunak's pledge to "stop the boats".

Almost 30,000 irregular migrants have crossed the Channel from northern France in rudimentary vessels this year.

Labour's home affairs spokeswoman Yvette Cooper said the UK government was in "total chaos".

"This is the desperate dying days of a party ripping itself apart, clearly totally out of ideas, lost any sense of leadership or direction," she told parliament.