UK Prime Minister Rishi Sunak on Thursday insisted his government's latest immigration plan will work, as the issue threatened to tear apart his ruling Conservatives, putting his position in jeopardy.

Sunak's government unveiled its latest attempt to deport asylum seekers to Rwanda on Wednesday, which sparked the resignation of his immigration minister who said it did not go far enough.

At a hastily convened news conference in Downing Street, Sunak sought to allay right-wing Tories who want him to withdraw the UK from the European Court of Human Rights, to stop courts blocking removals.

"This bill blocks every single reason that has ever been used to prevent flights to Rwanda from taking off," he told reporters.

"The only extremely narrow exception will be if you can prove with credible and compelling evidence that you specifically have a real and imminent risk of serious and irreversible harm."

The bill -- drawn up after Supreme Court judges last month ruled the deportation plan was illegal as Rwanda was not a safe country -- is expected to be voted on by MPs for the first time next week.

It compels judges to treat Rwanda as a safe country and proposes giving UK ministers powers to disregard sections of human rights legislation.

A defiant Sunak asserted the primacy of parliament on the issue and also said he would not allow a "foreign court" to dictate what the UK could do.

"This bill will work... we will get flights off the ground, we will deter illegal migrants from coming here and we will finally stop the boats," he added.

"I want to finish the job. Finishing the job means getting this legislation on the statute book," he added.

The proposals have sparked fresh concerns from opposition parties and human rights groups while Rwanda warned it would withdraw from a bilateral treaty signed only on Tuesday if the UK does not respect international law.