Rishi Sunak is facing the biggest week of his premiership, with his authority in the hands of two warring Tory tribes vying to set out their battle lines on his flagship Rwanda bill. The prime minister is beset by rebellion on the right and left of the party, with up to 100 MPs on each side due to meet on Monday afternoon to debate how to vote on the legislation. To avoid defeat at Tuesday’s parliamentary vote, Sunak will need to keep the rebellion below 56 abstentions or 28 votes against. The prime minister’s allies have spent the weekend pleading with key groups on the left and right of the party, hoping to stave off a rebellion that could sink a bill he claims will stop most court challenges to deporting migrants to east Africa. David Cameron, the foreign secretary, has been among those spending the past few days trying urgently to persuade Tory MPs to back the plan at the second reading. In a hint Sunak could be open to further compromise, a government source said: “We are talking to colleagues, but we are confident this bill is extremely robust and makes the routes for any individual challenge vanishing small. This is the strongest possible piece of legislation to get Rwanda operational.” Monday’s drama will unfold as Sunak faces a gruelling day giving evidence to the Covid inquiry on issues such as the controversial “eat out to help out” scheme which has been blamed for spreading the virus in 2020. While Sunak speaks, up to 100 backbench MPs on the right of the party are expected to gather from noon to discuss the Rwanda bill. Robert Jenrick, a former close ally who resigned as immigration minister on Wednesday, is among those who say they cannot support the legislation in its current form. “I won’t be supporting this bill, but I do think we can fix this, and that’s what I want to do now,” he told the BBC on Sunday. “I care about this policy because I care about border security and I’m determined that we can persuade the government and colleagues in parliament that there is a better way.” A number of MPs from overlapping groups on the Tory right, are expected to join Jenrick in abstaining or even voting against the legislation at second reading – saying that they will only be able to support it with changes to harden it. They will meet in parliament’s Thatcher Room to hear from the veteran Tory Eurosceptic MP Sir Bill Cash’s “star chamber” of lawyers, who will warn the bill does not go far enough to set aside human rights law in order to deport migrants to Rwanda. There was, however, evidence that some MPs were open to making the legislation work, with the New Conservative leaders Danny Kruger and Miriam Cates suggesting this was their approach over the weekend. Later, the One Nation group of Conservative of MPs, which also has about 100 members, will meet at 6pm and release its verdict an hour later. Tory sources said its “centre of gravity” was moving towards backing the bill at second reading, but that they would not be able to stomach changes demanded by the right of the party that involved circumventing international human rights law. A handful of MPs on this side may vote against or abstain. They are expected to say the bill comes very close to what they can accept. One member suggested that leading cabinet members such as Alex Chalk, the justice secretary, and Victoria Prentis, the attorney general, could find it difficult to accept a hardening of the bill. A leading One Nation MP said: “Success looks like the ‘left’ of the party saying ‘this is as far as we can reasonably go’, and there’s quite a lot of us, and the right of the party saying ‘how about this’ – and hopefully coming up with something with that doesn’t trash all of international law. Then maybe we would be fine. “But the difficulty is no one thinks this legislation is perfect. There will be people on my side who say it disapplies bits of the HRA [Human Rights Act] and I’m not going to vote for it. My gut, which sounds like wishful thinking, is that we will find a way through it … But the thing that blows it all up is Jenrick and Suella [Braverman] saying it won’t work. The thing we all care about is finding a way that it can work.” With his flagship legislation in trouble and little sign of the polls narrowing, there is growing talk of ousting the prime minister before the election by plotters within his own party. Some backbenchers are keen to reinstall either Boris Johnson or an ally of Liz Truss. Johnson is no longer in parliament but some MPs think he could return in a byelection if Sunak were removed, with others pushing for him to team up with the Reform politician and former Ukip leader Nigel Farage. The Mail on Sunday reported that his critics within the Tories were planning “an Advent calendar of shit” to destabilise his leadership in the run-up to Christmas. But many Conservative MPs on the left of the party are anxious about the idea of a plot against Sunak before going to the polls, as getting rid of him would bring in a third unelected prime minister since the last election. Damian Green, the leader of the One Nation group of MPs and a former deputy prime minister, said those wanting to remove Sunak were “mad or malicious, or both”. Sunak’s position was defended on Sunday by Michael Gove, the communities secretary, who insisted top lawyers had said the government’s new legislation aimed at sending asylum seekers to Rwanda was “sound”. Speaking to Sunday Morning with Trevor Phillips on Sky News, Gove suggested his party had had a “relative success” already in responding to irregular migration, which reached a record high this summer. “It’s pretty tough, actually, if you look at what we’re saying,” he said. “Of course we will look at what any colleague and, indeed, any eminent lawyer says, but whether it’s Jonathan Sumption or David Wolfson, they are pretty clear, this law is sound.” He also insisted the government was “not contemplating” holding a general election if the legislation were voted down.