It comes as the PM comes under growing pressure from Suella Braverman and the Tory right to flout international law by “disapplying” the European Convention on Human Rights (ECHR).
Mr Sunak is reportedly weighing up some elements of the hardline plan proposed by Ms Braverman – whom he sacked earlier this week – to thwart fresh legal challenges to Rwanda flights.
The Tory leader is considering an emergency bill that would deem Rwanda a “safe country” and attempt to make clear that this designation overrides the Human Rights Act, according to The Times.
A less contentious option is to try to designate Rwanda a “safe” country without any attempt to override human rights law, with the two possibilities said to be part of “live” discussions.
Mr Sunak’s two-pronged strategy for dealing with the Supreme Court ruling against the government is to announce an emergency law that he says will enable parliament to “unequivocally” declare Rwanda a safe destination for asylum seekers.
The PM will also publish an upgraded agreement with the country which is expected to attempt to address the court’s concerns around “refoulement” – the potential for refugees rejected by Rwanda to be sent back to the country they are fleeing.
But Ms Braverman has insisted that Mr Sunak goes further – saying she “demands of the government an end to self-deception and spin”. She wrote: “Tinkering with a failed plan will not stop the boats.”
The ex-home secretary also said the UK’s domestic or international obligations – the Human Rights Act and ECHR – need to be made invalid using “notwithstanding clauses”.
Senior Tory MP Danny Kruger, co-founder of the increasingly influential New Conservatives group, backed Ms Braverman and demanded that Mr Sunak “change course or we will lose the general election”.
Writing in The Telegraph, the leading right-winger warned No 10 that failure to get the Rwanda flights going could lead to a “formal split” in the Conservatives and “splinter” the party forever.
“We need the Emergency Rwanda Bill to assert supremacy over all the laws and international treaties invoked by the Supreme Court,” Mr Kruger wrote. “This is existential. If we get this wrong, our party won’t just face rejection at the ballot box, but we risk splintering our coalition forever.”
He said Mr Sunak’s response to the Supreme Court ruling “makes me worry that they are not prepared to cut through the thicket of international and domestic laws and protocols that undermine parliament’s sovereignty”.
Some Conservative MPs are pushing Mr Sunak to consider going further than disapplying parts of the Human Rights Act by coming up with a “derogation” of the ECHR in a bid to set aside some of the international convention’s protections.
Tory MP Martin Vickers, a member of the Common Sense Group of right-wingers, told The Independent: “I would support any legislation necessary to deliver the policy.”
“I would be quite comfortable to override parts of the Human Rights Act, even though they [the government] will be looking at complications,” Mr Vickers said. “Another possibility is looking at the [ECHR] treaty option. I would be happy to go as far as possible.”
But Mr Sunak is facing concerns over the dilemma from both sides of his party, with the leading One Nation Tory moderate Damian Green stressing the importance of observing the rule of law.
“It’s not just all our own laws passed by parliament, and all international treaties that we have signed, that Suella wants to sweep away,” Mr Green told BBC Radio 4’s Today programme on Friday – before comparing Ms Braverman to dictators.
“Conservatives believe in a democratic country run by the rule of law. And dictators, Xi and Putin, would prefer to have the state completely untrammelled by any law. And so, as a democrat, I oppose it.”
Immigration minister Robert Jenrick reportedly backs elements of Ms Braverman’s Rwanda plan in a “belt and braces” push to get the flights to take off.
The Home Office minister had joined Ms Braverman in previously submitting proposals to No 10 which included four of the five points she outlined this week, according to The Telegraph.
Mr Sunak has denied “tinkering” with the Rwanda policy after Ms Braverman suggested his plan to save the scheme would fail without more radical measures.
Speaking to broadcasters on Friday, the PM insisted he would “work night and day” to ensure domestic courts cannot “systemically” block flights to the east African nation. Mr Sunak declined to say whether he would call a general election if the new law was blocked.
Meanwhile, Lord Sumption, a former Supreme Court judge, told the BBC the plan to use a law to declare Rwanda as safe was “profoundly discreditable”, “constitutionally really quite extraordinary”, and would “effectively overrule” a decision by the UK’s highest court.
A government source said the treaty with Rwanda would be published “shortly”, but perhaps not as soon as Monday, as reports earlier suggested.
The Independent has approached No 10 and Mr Jenrick for comment.