More than 20 countries including France, Italy and Austria are on track to join the UK’s green list and open to British holidaymakers this month, data has revealed.

The 22 nations – primarily in Europe – all meet the threshold for inclusion on the quarantine-free green list, according to the analysis.

All have infection rates below 20 cases per 100,000 of the population, fewer than 1.5 per cent of tests with a positive Covid result, high vaccination and testing rates and low prevalence of variants.

The analysis by Robert Boyle, the former BA strategy chief, claims to have cracked the algorithm used by the Government’s scientists to decide which countries are safe for travel.

At present there are 27 destinations – largely islands – on the green list of which Ibiza, Mallorca, Menorca, Malta and Madeira are the most popular holiday spots. Most of the rest are remote islands, many of which are closed to foreign travellers.

By analysing the data behind their inclusion, 22 more emerged as having better or similar figures in all the categories.

They are France, Italy, Austria, Bulgaria, Hungary, Romania, Poland, Norway, Vietnam, Denmark, Slovakia, North Macedonia, Czech Republic, Estonia, Finland, Lebanon, Liechtenstein, Lithuania, Luxembourg, Moldova, Taiwan and Azerbaijan.

Travel countries on the red, green and amber list

All are currently on the amber list which requires any holidaymaker returning to quarantine for 10 days and pay for at least two PCR tests on days two and eight.

But Mr Boyle said: “There seems to be nothing in the data the Government says it is using that explains why they are languishing on the amber list at this point.

“I’m sure the answer is politics somehow, but there doesn’t even seem to be any obvious political logic for why two apparently similar countries get classified differently.”

The analysis comes as the Government prepares to announce its latest update of the green list which will take effect on July 21.

Karen Dee, the Airport Operators Association chief executive, said: “In Parliament, the Transport Secretary repeatedly urged people to look at the data to understand why some countries get added to the green list and others not.  

“Yet when people do look at that data, it raises more questions than it answers. It is time that the Government explains transparently, and in full, how they decide on the green list and expand the green list to include countries that clearly meet the thresholds they appear to have applied.”

The Government will announce this month its plans for double-vaccinated Britons to travel to amber list countries without having to quarantine on their return, Boris Johnson said on Thursday.

Officials played down the prospect that it could be launched on July 26 in time for families to go abroad during the school holidays.

"I’m very confident that the double jabs will be a liberator and they will enable people to travel. We’ll be setting out a lot more about the details of that in the course of July, in the course of the next few days, about how we see it working,” he said.

“But I want to repeat a point that I’ve made before and I hope people will forgive me if I say this. Obviously I want travel to be possible, but I’ve got to stress that this year will not be like every other year because of the difficulties with Covid. People shouldn’t expect that to be completely hassle free."