The Illegal Migration Bill is back this afternoon for ‘ping pong’ – the final stage of its legislative passage where MPs and peers bat amendments between their respective chambers until a compromise is found. There were 20 such amendments for the government to deal with and there is still a chance that some key Conservatives might rebel tonight. Ministers want to overturn 15 changes.

Two of the loudest critics are, inconveniently, former home secretaries

Two of the loudest critics are, inconveniently, former home secretaries. Theresa May has criticised the Bill throughout its passage and it is still not clear whether she will vote with the government or rebel tonight. She never indicates how she will vote before she stands up in the Commons, which means there will be a moment of drama when she stands up to speak. Her main beef – and that of former Tory party leader and work and pensions secretary Iain Duncan Smith – is that the legislation waters down protections for victims of modern slavery. So far there has been no concession offered ahead of tonight’s ping pong. Duncan Smith says that he is likely to vote against the government on this: ‘I’m quite in favour of the Bill going through, but we are still in discussion with the government on the modern slavery amendment. They’ve got to rethink this as it weakens the chance of getting prosecutions and to go after the very people who are getting them on the boats in the first place.’ He has been told that ministers will put protections into guidance – but is unhappy with that because guidance is not produced until after the legislation is on the statute books and is of course only guidance rather than something that is enforceable.

Another former home secretary, Priti Patel, this morning tweeted that ‘we were told that the Illegal Migration Bill would ‘stop the boats’. Key pillars of that Bill have now been abandoned.’ When I spoke to Patel today, she added that one of the big failures of this government was not having a proper plan for its delivery: ‘Resolving the issue of illegal migration has never been simple. There is no one single solution to stopping the small boats which is why a package of end-to-end policy and operational measures to bring lasting change to the system is vital. This should also cover asylum accommodation as outlined in the previous policy statement the New Plan for Immigration.’

Her tweet has not gone down well with government sources, who have hit back and told Coffee House: ‘Clueless. And not like her record of three years in office is much of a defence on this topic?’ Patel hasn’t actually voted on any stage of this legislation, which at least means that she isn’t a threat in a parliamentary sense: but of course if this legislation does make it onto the statute book within the next week, as the Home Office hopes, then what follows will merely be a public debate – but it could become a blame game if the battles in the courts and over the wider implementation don’t go to plan.

Other Tory MPs are a little more relaxed. Danny Kruger, now chair of the New Conservatives, had been calling for ministers to use the Parliament Act to ram through the Bill in the form it left the Commons rather than the much-amended version the Lords are sending back. He says he is now largely content with the legislation and that the government is defending the principle of the Bill. ‘I think our robust defence of the Bill has ensured the government is not caving in on the main provisions – because there would be a big rebellion then.’ The bigger problem, of course, is if the Bill doesn’t actually stop the boats – even if the Supreme Court does rule in favour of the Rwanda policy.