British Prime Minister Boris Johnson said on Saturday he was confident of the legality of his government's plan to send some asylum seekers to Rwanda after the first flight was blocked at the last minute by the European human rights court.

The court issued an injunction on Tuesday to stop the scheduled deportation of a handful of migrants on board, a decision Johnson described as a “weird last minute hiccup”.

“Every single court in this country said there was no obstacle that they could see, no court in this country ruled the policy unlawful which was very, very encouraging,” Johnson told reporters.

“We are very confident in the legality, the lawfulness of what we are doing and we are going to pursue the policy.”

The British government's plan to send some migrants to the East African country has been criticised by opponents, charities, and religious leaders who say it is inhumane. It has been forced to fight a series of legal challenges in London courts aiming to stop it going ahead.

Britain says the 120-million-pound ($147 million) deal struck with Rwanda will stem the flow of dangerous cross-Channel trips and smash the business model of people-smuggling networks.

Earlier this week, Britain's Home Office published guidance on a 12-month pilot using electronic tagging to monitor individuals who arrive in the country illegally.

On Saturday, the Home Office said some of those who had been due to be on Tuesday's flight to Rwanda could be tagged.

“We will keep as many people in detention as the law allows but where a court orders that an individual due to be on Tuesday’s flight should be released, we will tag them where appropriate,” a spokesperson said.