Boris Johnson has warned UK holidaymakers and businesspeople that going overseas will not return to normal until next year at the earliest, in a fresh blow to the travel sector.

The prime minister, speaking on a visit to a laboratory in Hertfordshire, said the government’s priority was keeping people safe in the UK.

“I want to stress that this is going to be — whatever happens — a difficult year for travel,” he said. “There will be hassle, there will be delays, I am afraid, because the priority has got to be to keep the country safe and stop the virus coming back in.”

Johnson’s comments come days after two of his cabinet ministers advised people to book summer holidays in the UK rather than abroad.

The government has introduced a traffic-light system for international travel with only people coming from “green list” countries allowed to skip a 10-day quarantine on arrival. At present there are 11 destinations on the green list although other countries could be added in the next update, on Thursday.

Johnson offered a glimmer of hope to the travel industry as he confirmed that ministers were examining plans to drop quarantine for those coming from countries on the “amber list” if they had received two doses of a coronavirus vaccine. “Almost 60 per cent of adults have had two jabs so there’s a great deal of potential there. When it comes to travel we will certainly be looking at that,” he said.

Airlines UK, the trade body for the industry, wrote to transport secretary Grant Shapps on Monday arguing that quarantine could be dropped for vaccinated travellers from amber list countries “given the incredible efficacy of vaccines”.

“If a meaningful reopening is not possible this summer . . . then targeted economic support including 100 per cent furlough extension will be essential to ensure UK airlines are able to reach the point when a restart is possible, in order to protect many tens of thousands of jobs,” the group warned.

Susan Hopkins, lead epidemiologist for Public Health England, told the BBC on Sunday that the new system could be modelled on an Israeli approach whereby citizens who have had two jabs can travel without quarantine by taking a test before and after their flight.

At the same time ministers are recruiting 40,000 people to take part in a pilot scheme aimed at scrapping the requirement for citizens to isolate for 10 days if they come into contact with an infected person so long as they have had two jabs.

Matt Hancock, health secretary, told the BBC that the government could remove the quarantine in favour of a system using lateral flow tests every day. “We’re not ready to be able to take that step yet, but it’s something that I want to see and we will introduce, subject to clinical advice, as soon as it’s reasonable to do so,” he told the BBC.

Johnson said the data were “looking good” for hitting his delayed target of lifting the last Covid-19 restrictions by July 19. “Looking at where we are, looking at the efficacy of the vaccines against all variants that we can currently see — so Alpha, Delta, the lot of them, Kappa — I think it’s looking good for July 19 to be that terminus point,” he said.

Some 10,633 new Covid-19 cases were reported across the UK on Monday, an increase of 2,891 on the same day last week. Five deaths were confirmed, up from three last Monday.

A further 273,158 vaccine doses were administered, of which three-fifths were first doses, as the rollout extended to all over-18s over the weekend. But Monday’s vaccination figures were down 17 per cent week on week.