The Number 10 papers, prepared in March 2022 shortly before the Rwanda plan was first announced, also suggest the prime minister wanted to scale back the plans.

In a further sign of discontent among Tory ranks, former immigration minister Robert Jenrick told Sky News on Saturday he will "lay amendments" to the bill if Mr Sunak doesn't make them "sufficiently robust".

A government source said Mr Sunak has put the Rwanda policy at the heart of his plan for government, and as chancellor, funded the scheme.

The documents state the "chancellor wants to pursue smaller volumes initially" of people being sent to Rwanda with "500 instead of 1.5k this year, and 3k instead of 5k, in years two or three".

Briefing papers prepared for a meeting involving then prime minister Boris Johnson and Mr Sunak also suggest the then chancellor thought the "deterrent won't work" and there would be more boat crossings in the summer.

A separate document from Downing Street summarising Mr Sunak's position stated he was "refusing to fund any non-detained accommodation (eg Greek-style reception centres) because hotels are cheaper".

The papers suggest Mr Sunak was instead in favour of increasing the "dispersal of people out of hotels into private sector accommodation" around the country.

One e-mail also shows Number 10 suggesting "Rishi may want to consider how his popularity might fare with the base" if he did not agree to the Rwanda plan and other policy changes.

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A government source said: "As chancellor, Rishi funded the Rwanda scheme and put it at the heart of his 10-point plan the month after becoming PM.

"Now he is passing the Rwanda Bill following the Supreme Court judgment to get flights off the ground.

"He is the first prime minister ever to oversee a reduction in small boat crossings, which were down by 36% last year."

Sunak prepares to bring back legislation to allow Rwanda scheme to function

The revelations come as Mr Sunak prepares to bring back legislation to the Commons that Downing Street says will allow the Rwanda scheme to function.

Tory backbenchers have called for the prime minister to go further in the bill and disregard more sections of international law.

Read more:
What is the new Rwanda plan and why is it controversial?
Govt reveals cost of Rwanda asylum policy

The leaked documents are likely to add to the concerns of these MPs that Mr Sunak is not willing to do what it takes to put the policy into action.

Mr Jenrick, who resigned from his post citing "strong disagreements" with the government over the Rwanda policy, appeared optimistic about the prime minister's ability to pull off the Rwanda plan - but said it must "actually work".

"I know the prime minister very well and I believe that he does see the urgent need to control our borders to get the Rwanda plan up and running - because that's such a critical element to stopping the small boat crossings," he told Sky News.

"I hope that he will strengthen the bill that's coming through parliament, and I've been very clear that if he doesn't do that then I will lay amendments to the bill next week to make sure that it is sufficiently robust to do the job that the British public expect."

He added he "doesn't care if it's not the strongest piece of legislation that we've ever done" as long as it "does the job".

"We've done three pieces of legislation in as many years, I've said it before - it's three strikes or you're out, we've got to make sure that this one works," he said.

Meanwhile, Labour Party chair Anneliese Dodds told Sky News the documents showed Mr Sunak was "aware of some of [the] problems" with the Rwanda policy but had done "nothing about them because of his focus on internal Conservative Party management".