Ministers are using an “outdated and flawed” Home Office analysis to persuade Conservative MPs to vote for Rishi Sunak’s Rwanda bill, informed party sources have said. Modelling distributed to MPs claims that 99.5% of individual legal challenges submitted by asylum seekers will fail to block their deportation to Rwanda. The document, entitled High Level Process for the New Bill and first disclosed in the Times, is being circulated by whips before the first vote on the bill in the Commons, due on Tuesday. The government is conducting a major lobbying operation as it attempts to heal deepening party rifts that threaten to overturn Sunak’s keynote policy. The Home Office also released a legal assessment of the bill that claimed that blocking all individual claims against deportation to Rwanda would “breach international law” and ran against UK’s tradition of “liberty and justice”. A Conservative source said the modelling was based on data from March, and did not take into account subsequent rulings by the appeal court and supreme court that had lowered the threshold of asylum claims. The source said: “This is an outdated and analytically flawed model from March which came before defeats in the court of appeal and supreme court. No 10 don’t realise the world has changed and that’s their fundamental problem. There was never any modelling done for the new Rwanda bill because they failed to plan. Even this old, optimistic model says it could take more than two months to remove a migrant. It would be laughable if it wasn’t so serious.” The disclosure comes after it emerged that the Home Office had earmarked at least £700m to manage the arrival of refugees and migrants on small boats until 2030, with the option of extending the contracts until 2034. The money would be spent running the Western Jet Foil facility in Dover and the reception centre at the former Manston airfield in Kent, documents discovered by the BBC said. The modelling being sent to MPs claims that nine out of 10 individual legal challenges against Sunak’s emergency bill would be rejected with no right of appeal within 10 days of the claimant’s arrival in the UK. This was because they would have to provide evidence that they would face “serious and irreversible harm” if removed to Rwanda, Home Office officials claimed. They would then be removed to Rwanda seven days later, having spent less than three weeks in the UK, the document continues. MPs on the right of the Conservative party have urged the government to “pull” the bill after their legal advisers said it could face numerous legal challenges. Mark Francois, the chair of the European Research Group, said: “The bill, because of the shape of it, because of its style, its legal structure would be quite difficult to amend. “I very much hope that, rather than plough on and damn the torpedoes, the government will listen, exercise common sense, pull the legislation and come back with something that is fit for purpose.” Several MPs in the One Nation centre-right grouping had told whips they intended to vote against the bill on Tuesday, sources said. A report from the rightwing thinktank Policy Exchange claims that the bill as it stands does not adequately anticipate and address the risk of other types of litigation, which may challenge the premises of the bill or frustrate its implementation in practice. Policy Exchange suggests ways that the bill can and should be amended to address the relevant risks. Asked about the analysis, the prime minister’s official spokesperson said: “It’s right to say that we remain firmly of the view that the vast majority of cases would be rejected. This tough bill will remove the ability for the vast majority of cases. That’s not just our view, it’s the view expressed by a number of legal experts including, over the weekend, Lord Wilson.”