The Supreme Court has ruled that the Rwanda asylum policy is unlawful, in a major blow for Rishi Sunak’s promise to “stop the boats”.

Five justices at the UK’s highest court unanimously rejected the Government’s appeal over its policy of removing asylum seekers to the east African nation if they arrive by unauthorised means.

Flights forcibly removing migrants to Kigali will continue to be grounded after the ruling on the flagship policy that has been stalled by more than a year of legal challenges.

In a summary of the judgment read out by Supreme Court President Lord Reed on Wednesday, the justices found there would be a risk of genuine asylum seekers being returned by Rwanda to the home country from where they fled.

The flagship asylum policy was first announced by Boris Johnson back in April 2020, but not a single migrant has been removed to Kigali after a series of legal challenges – despite Kigali being paid £140 million by the UK.

Mr Sunak will deliver his verdict on the ruling at Prime Minister’s Questions before new Home Secretary James Cleverly gives further details.

Suella Braverman warned after her sacking as home secretary that there is no “credible Plan B” if the Supreme Court rejects the Government appeal.

Lord Reed agreed the Court of Appeal was entitled to rule that there is “substantial” grounds to believe there is a “real risk” of refugees being returned to countries where they could face “ill treatment”.

But he made clear the judgment was only based on the current failure to “eliminate the risk” in Rwanda and said that the changes needed to reduce this “may be delivered in the future”.

This grubby, cash-for-people deal was always cruel and immoral, but, most importantly, it is unlawful. Today’s judgment should bring this shameful mark on the UK’s history to a close

Campaigners welcomed the verdict with the Freedom from Torture charity hailing it as a “victory for reason and compassion”.

Steve Smith, the chief executive of the Care4Calais refugee charity, said: “The Supreme Court’s judgment is a victory for humanity.

“This grubby, cash-for-people deal was always cruel and immoral, but, most importantly, it is unlawful.

“Today’s judgment should bring this shameful mark on the UK’s history to a close.”

Mr Sunak will now come under pressure from Mrs Braverman and the Tory right to haul Britain out of the European Convention on Human Rights.

But Lord Reed made clear that it is not the only international treaty relevant to the court’s decision, which also took into account domestic law.

The rulings were based on evidence that Kigali has a “poor human rights record”, including British police warning Rwandans in the UK of credible plans by the nation’s government to kill them.

Concerns of political and media freedom were also raised, and an inability of the Rwandan courts to act independently of the government.

Evidence from the UNHCR, the United Nations’ refugee agency, cited Rwanda’s 100% rate of rejection of claims from countries in conflict zones such as Syria, Yemen and Afghanistan.

This is despite the UK authorities often finding the claims are “well-founded”.

The body also presented evidence of more than 100 cases of “refoulement” – the process of returning refugees to their origin countries – that have taken place after the UK agreed its deal with Rwanda.

Dover’s Tory MP Natalie Elphicke said a deal with France was now the best way to stop small boats crossing the English Channel.

She said the Supreme Court’s ruling on Rwanda “means the policy is effectively at an end”.