The WTTC said more than 300,000 jobs were lost in the sector last year, with another 200,000-plus at risk if travel is not resumed.
The prediction comes as EU Ambassadors meet to agree on removing restrictions within the EU in June for those who have been fully vaccinated.
The WTTC warned the UK “could suffer a near repeat of last year”, when restrictions prevented any significant international travel.
It fears a “devastating” impact if only limited travel is permitted between now and the beginning of September “even if domestic travel boosts revenues”.
It said: “The impact of prolonged travel restrictions this year could wipe out a damaging £22.3 billion in the sector’s contribution to UK economic growth. However, if travel restrictions remain beyond the summer months, the impact on both jobs and GDP could be far worse.”
According to the WTTC’s recent Economic Impact Report, 307,000 jobs were lost in the sector last year, and a further 218,000 are now at serious risk, if international travel continues to be off limits for most of the summer.
Virginia Messina, WTTC senior vice president, said: “We fear the embattled UK travel and tourism sector simply cannot cope with another ‘lost summer’ if there is no significant international travel allowed, without damaging restrictions and unaffordable test requirements.
“WTTC’s latest research lays the consequences in the starkest way, with a further 218,000 jobs at risk of being lost if the government continues to throttle the resumption of meaningful international travel.
“While we understand protecting public health is the number one priority, if the government continues its overly cautious approach, hundreds of thousands more jobs could be lost and travel businesses up and down the country face going bust.
“The UK should be making the most of its successful vaccination roll-out to begin to restore international mobility safely.
“Staycations and domestic travel cannot fill the enormous financial hole left by the collapse of international travel and the trickle-down benefits it has across the supply chain.”
The WTTC estimates travel and tourism’s contributions to the UK’s GDP could reach as high as £153 billion if international travel resumes in time for the summer peak.
“However, should restrictions and changing rules continue, the UK could face a loss of at least £22 billion, significantly delaying the country’s economic recovery,” it warned.
