The Rwanda plan is a cruel policy pursued by a prime minister who knows it will not work

Editorial: As was long suspected, Rishi Sunak never thought the plan would succeed in deterring asylum seekers

Sunak persists with a policy in which he does not believe, presumably because he has made such a totem of it (PA)

It is hard to avoid the conclusion reached by Yvette Cooper, the shadow home secretary, that the documents leaked from Rishi Sunak’s time as chancellor show how “incredibly weak” he is.

Here was a minister who said he believed the Rwanda scheme “deterrent won’t work”, who tried to limit the amount of public money wasted on it and who, when he succeeded to the top job, carried on with the policy. The only plausible explanation is that he was trying to appease the unreasonable wing of his own party, having bought their support in the leadership struggle by putting Suella Braverman in the Home Office.

The result has been predictable. The unappeasable element of the anti-immigration wing of the Conservative Party remains unappeased. The policy itself remains stranded in legislative limbo after the Supreme Court said it was unlawful. And the only progress that has been made in reducing the number of people crossing the Channel in small boats has been achieved by better cooperation with the French authorities, which was the only workable basis for policy in the first place.

Yet Mr Sunak persists with a policy in which he does not believe, presumably because he has made such a totem of it, which means that retreat will induce another episode of Conservative infighting reminiscent of the Lord of the Flies. Not only does he not believe in it, but James Cleverly, the new home secretary, does not appear to believe in it, and neither does Lord Cameron, the new foreign secretary.

We can see only trouble ahead, as Robert Jenrick, the former immigration minister, tries to “strengthen” an unworkable bill – which will not only remain unworkable but will then lose the support of the 100 or so One Nation Tory MPs who believe in the rule of international law.

Such antics seem almost designed to make the opposition look credible. Ms Cooper’s alternative to the Rwanda scheme has always been paper-thin, at times wilfully overlooking the legal difficulties posed to any government by undocumented arrivals. The recent publication of cabinet papers from the Labour government 20 years ago, with its “brainstorming” ideas such as detaining people in a camp on the island of Mull, processing asylum seekers in African countries and repudiating the European Court of Human Rights, ought to remind her that governments of both parties have struggled with this issue.

Nevertheless, Ms Cooper and Sir Keir Starmer have two things in their favour. One is that they recognise, as does the prime minister in private, that a deportation scheme will not work. The other is that they suggest negotiations with “France and other countries” to secure a “new agreement on returns and family union”.

This is frustratingly vague, but it is impossible for Labour to say what kind of agreements they might succeed in negotiating if they were in government. The opposition remains allergic to any suggestion that managing asylum and migration will require EU-wide agreement that could include the UK. Yet it should be obvious, looking at the situation in the Mediterranean and across the Rio Grande, that this is a problem affecting much of the world.

It may be, of course, that a great deal more could be achieved by greater cooperation just between Britain and France. It may be, too, that Sir Keir would do better with Emmanuel Macron, the French president, than Mr Sunak did. Mr Sunak did achieve something, and it is at least conceivable that a Labour prime minister, not beholden to an anti-EU and sometimes anti-French party, might be able to achieve more.

The longer that Mr Sunak persists in a cruel and unworkable policy in which he does not believe, the stronger the case is made that Sir Keir and Ms Cooper should be given the chance to try to do better.