Thousands of holidaymakers are preparing to head overseas when the ban on foreign leisure travel is lifted in England and Wales on Monday.

Travel firms have reported a surge in demand for trips to Portugal, after the Government put the country on its green list for travel.

That means returning travellers will not need to self-isolate on their return, and are only required to take one post-arrival test.

EasyJet has added 105,000 extra seats to its flights serving green-tier destinations, while Tui will use aircraft which normally operate long-haul routes to accommodate the surge of people booked to fly to Portugal.

Only a dozen countries and territories are on the green list but most are either remote islands or do not currently allow UK tourists to enter.

The Government is advising people not to make non-essential trips to locations on its amber list, which covers popular destinations such as Spain, France, Italy and Greece.

But this guidance is expected to be ignored by some holidaymakers.

Health Secretary Matt Hancock said people should not travel to amber or red list countries “unless it’s absolutely necessary, and certainly not for holiday purposes”.

He told Times Radio: “The red and amber list countries are places that you shouldn’t go to unless you have an absolutely compelling reason.”

Those who do travel will be required to self-isolate at home for 10 days on their return, and take two post-arrival tests.

They can end their quarantine early if they receive a negative result from an additional test taken after five days.

I think people just have to get used to the fact that Cornwall or Bournemouth or wherever is not so bad. And they should just enjoy the summer and then we can get back to this properly when things settle down

Travel firms such as airlines and tour operators have called for quarantine and testing requirements to be relaxed, and for more destinations to be added to the green list.

But Sir John Bell, regius professor of medicine at Oxford University, cautioned that there are “broad swathes of Europe that are largely unvaccinated” and are therefore “pretty vulnerable to new variants, be it Indian or otherwise, sweeping across the continent”.

He advised that travel abroad is therefore “not a good idea” at the minute.

He told Times Radio: “We aren’t at the peak of this thing globally at all yet, we’re still going up the mountain. So having people flying around and coming back with whatever local variant they run into, that is not a good idea in my view.

“I think people just have to get used to the fact that Cornwall or Bournemouth or wherever is not so bad. And they should just enjoy the summer and then we can get back to this properly when things settle down.”

The Government has pledged to update its lists on June 7, and will review its overall policy in relation to arriving travellers on June 28.

Scotland will permit foreign holidays from May 24.

Non-essential travel from Northern Ireland to the Common Travel Area – which consists of the UK, Republic of Ireland, Channel Islands and Isle of Man, will be allowed from the same date.