LONDON: The UK Supreme Court ruled on Wednesday that the government's scheme to send asylum seekers to Rwanda was unlawful, dealing a massive blow to Prime Minister Rishi Sunak's immigration policy and major election pledge before a vote expected next year.

The court unanimously rejected the government's appeal against an earlier ruling that migrants could not be sent to Rwanda because it could not be considered a safe third country.

The Rwanda scheme is the central plank of Sunak's immigration policy as he prepares to face an election next year, amid concern among some voters about the numbers of asylum seekers arriving in small boats on Britain's shores.

The ruling is a major setback to Sunak's promise to stop migrants arriving without permission on the south coast of Britain in small boats from Europe.