The restart of international travel this summer will be “gradual” and not an “open sesame” process from May 17, Abta chief executive Mark Tanzer has warned.

Tanzer described it as “explicit and implicit in the government’s taskforce statement that the restart of international travel is going to be a gradual process”.

He told Travel Weekly: “We want it to be as quick as possible, and we want there to be a proper summer season, but it’s not going to be a May 17 ‘open sesame’ [and] everyone can travel.”

His comments came amid reports that only eight countries would make the government’s ‘green list’ for safe travel next month.

They are expected to be the US, Gibraltar, Israel, Iceland, Ireland, Malta, and Australia and New Zealand – both currently closed to travellers from overseas, the Sunday Telegraph reported.

However, the entire US may struggle to qualify unless its Covid rates drop.

Analysis by former British Airways strategy chief Robert Boyle reportedly suggests almost all of Europe is likely to be either on the amber list, requiring home quarantine of 10 days, or even the red list, where arrivals have to hotel quarantine at a cost of £1,750 per person.

The research places mainstream holiday destinations of Spain, Greece, Italy and Cyprus on amber due to their high Covid rates but it says they could still turn green by the government’s next review date of June 28 – still in time for the summer peak.

“Last year, the Spanish and Greek islands were given a lower-risk rating than the mainland and that could happen again this year,” according to the report, which is said to be “circulating within industry circles”.

Meanwhile, the Foreign Office relaxed its travel advice for Portugal on Friday, saying it “no longer advises against all but essential travel to Portugal and the autonomous region of Madeira” but it is still illegal to travel abroad from the UK for holidays.

Tanzer welcomed the government dropping its insistence that now is not the time to book a summer holiday abroad.

Speaking on a Travel Weekly webcast, he said: “Every time a minister was interviewed on TV saying ‘People shouldn’t book’ members’ bookings dried up. The effect was dramatic on people’s confidence to book.

“That message that ‘You can book’ and you’ll be able to travel or, if that’s not the case, members’ booking conditions are very flexible now, is critical.”

He added: “We need to let people start booking and anticipating going on holiday. But because there is no certainty about which countries are on the green list and which amber, people will be leaning towards booking later.”

Tanzer declined to speculate on which countries might make the ‘green’ category, saying: “I can’t predict. I would like the biggest-possible green list because amber is a pretty big barrier. But I don’t know which countries will be on it. If the biggest destinations were there, that would be great.”

However, he insisted: “I do think travel will start after May 17. I don’t see anything at the moment that means the government would need to deviate from its roadmap.

“There is evidence of Covid variants overseas and other European countries are having lockdowns which is an obstacle. But there is enough hope and enough places people can travel to.”

He described expectations that the green list would be limited at the outset but give way to a more expansive opening as “realistic”.

The Abta chief said: “There is clearly going to be a sense of learning as we go along with this traffic light system – how countries get on the green list, how quickly they come off, how they move up – and that will be refined as we get into the summer.

“I hope by the time we get to July or August there is a solid system that people understand and can travel with.

“[But] on May 18 we’ll still be learning how all this is going to come together. There will probably be fewer countries accessible immediately.”

However, he described fears that travel might only resume from September or October as pessimistic.

Tanzer said: “The government is opening the door. There are lots of constraints and precautions, but that is because they anticipate people traveling.”