Rishi Sunak is considering blocking a key human rights law to help force through plans to send asylum seekers to Rwanda amid growing pressure from rightwing Conservative MPs. No 10 has discussed the possibility of “disapplying” the Human Rights Act to an emergency bill in an effort to minimise legal challenges against the prime minister’s key immigration policy. Ministers are aware such a proposal could face rebellions in the Commons and the Lords, which could vote down the proposals. A Conservative party source said: “This would tear the party apart. Several cabinet ministers and the one nationers would not stand for it – the prime minister wouldn’t even get it through the Commons. Never mind that this wouldn’t placate the head-bangers on the right either.” The government’s quandary has emerged as a former supreme court judge said the proposals to send people seeking asylum to the east African country with no possibility of a return to the UK were “probably dead”. The prime minister is under intense pressure from the Conservative right to get the scheme working as part of his pledge to “stop the boats” amid the Channel refugee crisis. Right-leaning MPs are demanding that a flight takes off for Kigali before the next general election, which is expected to take place before the end of 2024. It follows a ruling by the UK’s highest court on Wednesday that Sunak’s flagship policy is unlawful because of the possibility of “refoulement” – that refugees are at risk of being sent back to their country of origin by the Rwandan government. Refoulement is prohibited by international laws, including the European convention on human rights (ECHR), the UN refugee convention and the UN convention against torture, which have been given effect in domestic law by the Human Rights Act. Discussions about blocking the Human Rights Act had taken place in Downing Street since the ruling, sources said. Hours after the court ruling, Sunak said he would upgrade the agreement with the Rwandan government to a treaty and launch an emergency bill within weeks to prevent court challenges. Ministers are looking at requiring MPs to sit on Fridays and reordering the parliamentary timetable to accelerate a new bill. Party sources said they were aware that dozens of Tory MPs could vote with Labour to block any such change. Any block on human rights laws could also face objections in the House of Lords because of mounting concern it would breach the UK’s international law obligations under the ECHR. The hard-right New Conservatives grouping demanded that Sunak’s new legislation “must disapply the Human Rights Act”, while the former home secretary Suella Braverman, who was sacked by Sunak last week, said the new bill must exclude all avenues of legal challenge. When approached by the Guardian, No 10 declined to comment. The former supreme court judge Lord Sumption said of the Rwanda plan: “I think the current Rwanda scheme is probably dead, but we obviously have to suspend judgment until we see what this legislation or this new treaty looks like.” He also suggested judges in Strasbourg would come to a similar view of the scheme’s legality as UK supreme court justices. He told Sky News: “The government have made clear … that they don’t intend to do that [withdraw from the ECHR]. Although the government may well ignore interim orders from Strasbourg, they presumably intend to comply with final orders from Strasbourg. It [the Strasbourg court] will investigate safety for itself and probably arrive at a conclusion very similar to that of the supreme court.” He said he was “sceptical” of reported plans to send British civil servants to work in the east African country, adding: “The main problem [with the] scheme is that it outsources to Rwanda the decision about whether people have refugee status.” Speaking on Sunday, Jeremy Hunt, the chancellor, defended the government’s plans for emergency legislation and added that the government did not want to leave the ECHR despite calls from the right of the Conservative party. “I think we will see that, because I do think, when you interview me next year, we will be having a discussion about how we have succeeded in this plan, and I will be saying: look, it wasn’t easy, we kept at it, but that is what we promise to do,” he told the BBC’s Laura Kuenssberg. Ministers are under pressure to process the asylum claims of tens of thousands of people who arrived in the UK after the illegal migration act was passed in July. Immigration experts said ministers could be in breach of the UN refugee convention because asylum seekers were being held – in some cases in detention centres – indefinitely. They have no prospect of being removed to a third safe country or being granted access to the asylum system in the UK under the act. Enver Solomon, the chief executive of the Refugee Council, said: “The Illegal Migration Act is unfair, unworkable, and expensive. It’s causing huge distress and anxiety for those we support with rising levels of acute mental health problems for already traumatised men, women and children. There are serious questions about the legality of leaving people in this situation indefinitely and the government should swiftly take action by allowing them all to be given a fair hearing in the asylum system and treated with compassion and dignity.”