Rishi Sunak will aim for a middle ground in the emergency legislation to get the Rwanda scheme off the ground as he remains under severe pressure to stop small boat crossings.

A senior government source has told Sky News that the prime minister is not planning to leave the European Convention on Human Rights (ECHR) as he seeks to prevent a split in his party.

It comes as more centrist Tory MPs are warning Mr Sunak publicly not to abandon international refugee and human rights treaties, while those on the right of the party want him to take a more hard-line approach.

Politics news – latest: Tory splits on migration spill into public view

The prime minister is trying to rescue the plan to deport migrants who arrive in the UK by irregular means to Rwanda and make it legally watertight following the Supreme Court’s ruling against the scheme.

In the wake of the judgement on 15 November, the government insisted it had been working on contingency measures and promised a treaty with Rwanda within days, along with emergency legislation in parliament.

The treaty was signed on Tuesday, and the government is expected to publish the emergency legislation to accompany it “soon”.

Read more: Rishi Sunak stuck between rock and hard place as Tories battle over migration policy

The legislation will be scrutinised on all sides of the debate, with members of the right-wing European Research Group (ERG) revealing to Sky News earlier that the group’s so-called “star chamber” of lawyers will examine it before MPs vote on it.

ERG chairman Mark Francois promised a conclusion within a matter of days, and added: “They will then examine the bill in detail to look at the question of whether it fully respects parliamentary sovereignty and whether it contains unambiguous wording that would facilitate planes taking off to Rwanda.”

He also warned that the prime minister would be “unwise” to “bounce” MPs into backing the legislation before it has been properly scrutinised.

The opposite wing of the party has warned that any attempt to override the ECHR or Refugee Convention would be a “red line”.

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Former cabinet minister Damian Green said earlier today: “What I am most encouraged by is what the home secretary said, which is the purpose of the treaty he signed is to directly address the problems the Supreme Court had with the system.”

He added that undermining international commitments would be the “wrong thing for this country to do, bad for our international reputation”, and it would also make it “pretty much impossible” for any bill to pass the House of Lords.

Stephen Hammond, a member of the One Nation grouping, said: “The prime minister has a tricky task on his hands to balance the economy, labour market, and stopping the boats.

“The package by the home secretary shows this is possible and, importantly, can be achieved by not leaving the ECHR, which would be a mistake and doesn’t have public support.

“Furthermore, moderates and mainstream Conservative MPs may struggle to support a so-called full-fat deal.”