Summer holidays overseas are “extremely unlikely” because of the risk of travellers bringing coronavirus variants back to the UK, a scientist on a government advisory body has said.

The UK faces a “real risk” if people travel abroad, Dr Mike Tildesley said.

Foreign holidays are currently not allowed and returning travellers have to quarantine.

Transport Secretary Grant Shapps said it was “too early to tell” when holidays abroad would be allowed.

Under the current roadmap for easing restrictions, the earliest date people in England could holiday abroad would be 17 May.

People can currently travel abroad for a limited number of reasons, such as education or work, with anyone who does having to fill in a “Declaration to Travel” form stating a valid reason for leaving the country.

A government taskforce will report to the prime minister on 12 April detailing when and how international travel can resume.

In Scotland, national clinical director Jason Leitch also said foreign summer holidays in Europe were looking “less likely” as Covid numbers in some countries were a “cause for concern”.

Health Secretary Matt Hancock said on Saturday morning half of all adults in the UK have now received a coronavirus vaccine.

Friday was also a record-breaking day for jabs, Mr Hancock added.

Dr Tildesley, a member of the government’s Scientific Pandemic Influenza Group on Modelling, which feeds into Sage, said there was a danger holidaymakers could bring back variants, like the one that emerged in South Africa – which were less susceptible to vaccines.

Dr Tildesley told BBC Radio 4’s Today programme: “I think that international travel this summer is, for the average holidaymaker, sadly I think, extremely unlikely.

“I think we are running a real risk if we do start to have lots of people going overseas in July, for instance, and August because of the potential for bringing more of these new variants back into the country.

“What is really dangerous is if we jeopardise our vaccination campaign by having these variants, where the vaccines don’t work as effectively, spreading more rapidly.”

Future vaccination campaigns might need to be considered to tackle future variants, but “the longer that we can push that down the road… the better”, Dr Tildesley added.

Prof Andrew Hayward, from Sage, said it was “unlikely” the government would want to encourage travel to European countries currently experiencing high levels of coronavirus infections.

“I suppose one of the more worrying things about this resurgence is that in some parts of Europe the South African variant is beginning to creep up to higher levels,” he told Times Radio.

He said this variant was of “particular concern” because vaccine effectiveness against it was “quite low”.

Airlines UK, which represents UK-registered carriers, said it was “too early to say” what the state of Covid will be in Europe and the rest of the world in 10 weeks’ time.

“We have always said any reopening must be risk-based, but also led by the overriding assumption that as the vaccine rollout accelerates both here and abroad, a phased easing of restrictions is achievable,” Airlines UK said.

“We know that universal, restriction-free travel is unlikely from 17 May but under a tiered system, based on risk, international travel can meaningfully restart and build up, with minimal restrictions in time.”