Ryanair and Manchester Airport Group are to launch a legal challenge against the government over the travel traffic light system.

The BBC understands it has the backing of other major UK airlines.

There is anger across the travel industry that the government has not been transparent in the way it makes decisions about the travel green list.

They believe the Balearic and Greek Islands should have been included last month when health data is analysed.

The challenge has been put together after huge frustration within the travel industry at the inclusion of Portugal on the green list in mid-May and then its sudden removal a few weeks later.

The decision to move Portugal to the amber list caused huge disruption for businesses and travellers.

But the government said it was necessary because of an increase in infection rates in the country and the emergence of the "Nepal variant", a mutation of the Indian/Delta version of the virus. There were concerns that vaccines would not work as well on this particular mutation.

The move meant that some British holidaymakers had to cut short their holidays and dash back from Portugal on extra flights put on by airlines before the country came off the green travel list in early June.

Travellers the BBC spoke to said it cost them hundreds of pounds to book new flights to get home before the deadline.

Anger from the travel industry

Travel bosses are concerned the damage of these sudden reversals will continue to erode the confidence of the British travelling public.

They maintain there is huge pent-up demand to travel abroad this summer, following three coronavirus lockdowns and huge numbers of cancelled or postponed holidays.

The travel industry has stipulated that the legal challenge is about getting the government to commit to transparency about the ways in which it analyses data when making decisions about which countries to include on the travel green list, and which to leave out.

Further signatories to the challenge will be revealed tomorrow, it is understood.

Those included will ask for the government's response to be expedited, due to the severe situation the travel industry is in, with planes and holidays effectively grounded.

But epidemiologists worry that mass travel before more people are fully vaccinated, both in the UK and at holiday destinations, will allow the virus to spread more rapidly.

And if Covid cases spiral suddenly on holiday islands, it is not clear if healthcare systems there are in a position to manage their care.