WTTC issued the warning as the EU launched its own digital Covid-19 certificate which is designed to reopen travel across the continent.

The organisation blamed the UK’s “controversial” traffic light system, use of quarantines, high cost of Covid tests and “confusing” travel rules and regulations for bringing the travel sector “almost to its knees”.

WTTC has already forecast that the country will lose £19.8 billion if international travel does not open up in July, with similar losses in August if there is no lifting of restrictions.

Virginia Messina, WTTC’s senior vice president, said: “It’s hard to believe that the UK travel and tourism sector and holidaymakers are facing yet another ‘lost summer’ with no significant travel in sight - despite the hugely successful vaccine rollout. 

“The vaccination programme should have unlocked the door to international travel. Instead, we are seeing the second summer with only limited travel in prospect while Europe is reopening, enjoying a summer break and kickstarting their economies.” 

Messina argued international travel could be safely reopened with health and safety “still the priority”.

“We should take advantage of the opportunity created by the high percentage of the population which has been fully inoculated to allow them to travel safely abroad again, and get back to their lives, colleagues, families, and friends,” she said.

“We must also be very careful not to discriminate against entire nationalities due to the appearance of variants. A combination of vaccines and testing will provide the protection needed to minimise the risk of transmission.”

WTTC said the traffic light system should be abandoned by the UK government, as part of a move to immediately “unlock the doors” to international travel.