Her intervention will be seen as an appeal to MPs to support amendments likely to be laid when the Government introduces its emergency legislation later this month.
On Thursday, Jeremy Hunt, the Chancellor, admitted that the Government could not guarantee migrant flights would take off next year, while James Cleverly, the new Home Secretary, said “the timescales that we are looking at can vary depending on circumstances” although he was “absolutely determined” to make it happen before the election.
Mr Sunak faces the legislation being thwarted by the Lords with peers branding it a “constitutional outrage” and “profoundly discreditable” on Thursday and warning it would be “completely bogged down” by “constructive obstruction” and “eternal ping pong”.
The Prime Minister’s treaty is expected to be published on Monday and the emergency law will be introduced a week later.
The legislation will declare Rwanda safe and bar anyone from lodging a legal challenge against the policy as a whole. Individual migrants will, however, still be able to appeal against deportation by using human rights law and other domestic and international legislation.
Under the legally binding treaty, to be approved by Parliament, Rwanda will commit not to deport anyone sent to them by the UK. This aims to prevent any deported migrants from being sent to their home country where they could face persecution, the reason why the Supreme Court ruled the original plan unsafe.
However, Mrs Braverman says the treaty and new law would not answer a “fundamental” problem identified by the Supreme Court that Rwanda could not be trusted to fulfil its commitments not to remove anyone.
“To try and deliver flights to Rwanda under any new treaty would still require going back through the courts, a process that would likely take at least another year,” she says.
“That process could culminate in yet another defeat, on new grounds, or on similar grounds to Wednesday, principally, that judges can’t be certain Rwanda will abide by the terms of any new treaty.
“Even if we won in the domestic court, the saga would simply relocate to Strasbourg where the European court would take its time deciding if it liked our laws.”