Conservative MPs are split in their views on the government’s safety of Rwanda bill, which is aimed at overcoming the legal issues that have delayed the deportation plans. Pressure is being brought to bear on Rishi Sunak by moderate MPs, coalescing under the banner of the One Nation caucus, while rightwingers associated with a number of groups known as the “five families” have already received advice from a group of lawyers to the effect that the bill does not go far enough to ensure that the Rwanda deportation plan is not be frustrated by court challenges. To avoid defeat in Tuesday’s parliamentary vote, Sunak will need to keep the rebellion below 56 abstentions or 29 votes against. The five families Believed to be a reference to the five families who are alleged to control the mafia in the US, these MPs come from among the members of the European Research Group (ERG), the Northern Research Group (NRG), the New Conservatives, the Common Sense Group and the Conservative Growth Group. The groups, who favour a hard line on immigration but have expressed differing shades of scepticism about the bill, met at Westminster on Monday. A “star chamber” of lawyers convened by the ERG has already told them that the bill does not go far enough to deliver the policy as intended. The findings, by the veteran backbencher Sir Bill Cash and four others, said that “significant amendments” would be needed to stop the removal of people to Rwanda being frustrated through legal challenges. While the bill seeks to allow parliament to deem Rwanda a “safe” country and block courts from considering claims that it will not act in accordance with international obligations, some on the right believe more radical measures are needed, such as moves to set aside international law. The severity of the star chamber’s criticism took some by surprise and clashed with the government’s own legal advice, which was published on Monday. Rightwing MPs are urging the government to make concessions, although there is varying degrees of opposition among their ranks. In a statement on Monday night, the New Conservative caucus said that the bill needed “major surgery or replacement”. Briefing of Tory MPs was under way by government whips on Monday, who were expected to argue that key elements of the star chamber’s advice was simply wrong. Sunak will also seek to win over a group of influential rightwingers over a breakfast at Downing Street on Tuesday morning. The most likely scenario is that rightwingers support the bill at its second reading, with a view to seeking to amend it at a later date, abstain or vote the legislation down. One Nation caucus Conservative MPs from the largest single group in the parliamentary party – counting more than 100 members, almost a third of the total – have the numbers to bring down the bill. But as a wing, they have a vested interest in keeping Sunak in power, as the failure of the bill would imperil his position and open the door for a challenge from the right. Nevertheless, many are concerned that the bill sets aside some of the UK’s obligations in international law and have been taking legal advice from the former solicitor general Lord Garnier, who has told the BBC that the legislation is “political nonsense and legal nonsense”. Matt Warman, a former minister who is a leading member in the caucus, wrote on the Conservative Home website on Monday that many of its members worried that declaring Rwanda a safe country in law was a push too far. But he expressed caution about whether now was the time for the parliamentary party to “push the prime minister off a tightrope”. This week’s vote was not procedurally the moment where amendments would be laid, he added, but it was where all sides had a chance to set out their stalls and for the government to provide vital reassurances. Any big group of MPs was likely to hold a range of views, and the next steps “shouldn’t be to push for a further compromise that might break a delicate balance”. On Monday evening, after a meeting in Westminster, the group announced that it will vote for the legislation.