The US move adds to the restrictions travellers face as new border rules come into force across France, Spain and Portugal this week amid concerns over the spread of the omicron variant.

From Thursday, Spain banned all non-vaccinated Britons from entering the country; previously they could visit by showing evidence of a negative PCR test. Interior minister Fernando Grande-Marlasca cited “the presence of new forms of the disease” for the move.

From Saturday, all UK holidaymakers arriving in France must show proof of a negative antigen (lateral flow) or PCR test, regardless of their vaccination status. Portugal requires a pre-travel PCR or antigen test for all UK arrivals, with a €300-800 fine for those who fail to comply.

Pre-departure testing not ruled out in UK 

Health Minister George Freeman told BBC’s Radio Four programme on Thursday morning that the Government had not ruled out reintroducing pre-departure testing.

“We are watching the data very closely and we will update the guidance as required,” he said. “Scientists advise. The Prime Minister, Cabinet and Health Secretary [Sajid Javid] have to take really difficult judgements balancing health and economics.”

Labour is pressing for the Government to reintroduce pre-departure testing as shadow home secretary Yvette Cooper warned the Government not to be too slow to take action to prevent cases of the omicron variant entering the UK.

“It is totally unacceptable that ministers are failing to take action at the border when even their own advisors are telling them to introduce pre-departure tests,” she said.

“It cannot be right that people can travel to an airport, board a busy flight, queue at busy departure gates, and travel on trains and buses in the UK, all without having taken a test.”