British Prime Minister Boris Johnson said on Monday that he wanted to get the travel industry moving again with a simple user-friendly system of rules to allow for trips abroad."We need to get people, get the travel industry moving again," Mr Johnson told reporters. "We want an approach that is as simple as we can possibly make it."

Britain reopened its borders to large parts of the world on Monday, scrapping quarantine for fully vaccinated arrivals from the European Union, excluding France, and the United States. But the boost for the travel industry was dimmed by speculation that the government could also soon slap new rules on holidays.

The Times newspaper reported a COVID-19 warning against trips to Spain, the UK's most popular destination, was likely. Spain could go on a new category of risk - the "amber watchlist" - meaning it could be upgraded to "red" at short notice, with arrivals having to quarantine in hotels, the Times said.

Asked about the possibility of an "amber watchlist", Mr Johnson said that people had to remember that COVID-19 remained dangerous.

"We must try and stop variants coming in, must stop importing variants from abroad, so we have to have a balanced approach," he said. "What I want to see is something that is as simple and as user friendly for people as possible."