Sir Keir Starmer has vowed to scrap plans to forcibly remove asylum seekers to Rwanda even if the policy is deemed legal by the courts and such action reduces the number of unauthorised Channel crossings.

The Labour leader was clear he would reverse the “hugely expensive” and “wrong” scheme which he said would only ever impact a very small proportion of migrants crossing the Channel.

The Supreme Court will on Monday begin hearing the Government’s appeal against the ruling that the policy is unlawful as ministers struggle to achieve Rishi Sunak’s pledge to “stop the boats”.

In a BBC interview in Liverpool ahead of the Labour conference, Sir Keir was asked if he would terminate the plans even if the judges approve it and small boat crossings then decline.

“Yes. I think it’s the wrong policy, it’s hugely expensive,” he told the Sunday With Laura Kuenssberg programme.

“It’s a tiny number of individuals who would go to Rwanda and the real problem is at source.

“You’re putting this to me on the basis that it’s working, we’ve been told by the Government time and again that even saying they’ve got a Rwanda scheme will reduce the numbers – that hasn’t happened.”

Instead Sir Keir said he would work with other countries to “smash the criminal gangs who are running this vile trade” of people smuggling.

“As a pragmatist I want a pragmatic plan that is actually going to fix this problem, not rhetoric which has got this Government absolutely nowhere,” he added.

Senior Conservatives seized on the comments, with party chairman Greg Hands arguing Sir Keir “failed to give another option” to the Rwanda policy.

Immigration minister Robert Jenrick said: “Proof, if it were needed, that Labour don’t even want to stop the boats.

“They are ideologically opposed to border controls. Their solution is to force British communities to tolerate this flagrant criminality.”

A government source said: “(Sir Keir’s) just another human rights lawyer from north London who puts party interests before the British people.”

The UK has already paid Rwanda £140 million under its asylum partnership announced in April last year – but not a single removal flight has taken off for the capital of Kigali yet.

In June, Court of Appeal judges overturned an earlier High Court ruling which found Rwanda could be considered a “safe third country”, disrupting the key plan in the Prime Minister’s boats strategy.

Home Office figures have suggested the Government could spend £169,000 on every asylum seeker forcibly removed to third countries, such as Rwanda.

And they indicated that nearly two in five people would need to be deterred from crossing the Channel in small boats for the policies set out in the Illegal Migration Bill to break even.

Research from the Refugee Council, which opposes the policy, has suggested that three-quarters of people who crossed the Channel in small boats this year would be recognised as refugees if their application had been processed.