Ministers were coming under intense pressure on Thursday to lift quarantine for holidaymakers returning from "safe" destinations including Malta and the Balearic Islands.
They were due to meet on Thursday afternoon to consider advice from scientific advisers that the two popular holiday destinations were safe enough to be added to the Government’s quarantine-free "green" list.
Travel industry chiefs and MPs believe the decision on the Balearic islands of Mallorca, Ibiza and Menorca will be a critical test of the Government’s appetite for opening up foreign travel this summer.
The current green list is limited to just 11 countries of which only Iceland, Gibraltar and Israel are viable holiday destinations after the sudden removal of Portugal.
By contrast, the Balearics are among the most popular Spanish destinations attracting five million British tourists a year before the Covid pandemic struck.
Henry Smith, Tory chair of the Future of Aviation all party parliamentary group, who is leading a Westminster Hall debate on Thursday on the issue, said: "Looking at the data, which is what ministers encourage us to do, I would expect the Balearics and Malta to be on an updated green list at the very least.
"I would hope it would be wider still, not just including popular holiday destinations to support the UK travel industry but also opening up the vital transatlantic route to the US.
"The efficacy of the vaccine against new variants does seem to have been confirmed and we now have 60 per cent of UK adults fully vaccinated.
"The safety of travel is something we can be much more confident in and it is about trying to salvage as much of this summer period as possible to save as many aviation and travel sector jobs as possible."
Tim Alderslade, chief executive of Airlines UK, said: "A limited green list will be another wasted opportunity, given where we are with the vaccination programme and its proven effectiveness against variants.
"The sector desperately needs a proper reopening – it’s now or never if we are to have any sort of summer season and the data shows this can be done safely and proportionately with many more countries being added to the list.
Travel countries on the red, green and amber list
"Data – not politics – must win out. The future of our aviation industry and the hundreds of thousands of jobs it supports depends on it."
The Balearics’ Covid infection rate is currently on a par with Portugal’s when it briefly went on the green list at 43 cases per 100,000 of the population, although the Balearics’ 29 per cent of adults fully vaccinated is half the UK’s rate.
Malta was recommended by scientists from the Government’s Joint Biosecurity Centre as safe three weeks ago for the green list but was rejected when Matt Hancock, the Health Secretary, led a lobby against its inclusion amid concerns over Covid variants entering the UK.
Malta’s double vaccination rate for adults is the same as the UK’s at 60 per cent, and its infection rate of eight cases per 100,000 of the population is well below the UK’s.
Speaking on Sky News on Thursday morning, George Eustice, the Environment Secretary, said the Government wanted to "get to a position to support people who want to travel".
The 43 hotel quarantine 'red list' countries
But he warned: "The biggest threat to our progress on the pandemic is that there will be another variant somewhere that may not have been detected properly in another country and that variant will be resistant to the vaccine."
The decision on whether to add countries to the green list is based on their Covid infection rates, the prevalence of variants, the countries’ vaccination rate and their capability to genome sequence the virus.
There has been speculation that the Portuguese island of Madeira with an infection rate of 35 cases per 100,000 and 34 per cent fully vaccinated could also be added to the green list, along with a number of Caribbean islands.
Turkey is expected to remain on the red list, and countries including The Dominican Republic, Haiti and Uganda could be added to it.
Ministers are also due to consider whether to go ahead with allowing fully-vaccinated Britons to travel to amber list countries without having to quarantine on their return.
On Wednesday, Angela Merkel, the German chancellor, demanded that EU countries impose quarantine on Britons travelling to them because of the surge in the Delta – or Indian – variant.