Spain-based OTA eDreams could only answer a third of the questions correctly. It told a researcher a holiday bought would be Atol-protected despite the company’s Atol having expired three months before the call. EDreams now offers financial protection from a Spanish scheme.

Ryanair answered two-thirds of the questions wrongly. One staff member was unable to tell Which? what a package was, claiming “because the hotel was provided by a third party, it doesn’t count as a package”. However, the “third party” the hotel was booked through was Ryanair Rooms, and the flight and hotel were part of the same transaction.

Which? surveyed seven companies, with Trailfinders coming top of the list, answering 12 of 15 questions correctly. Below it, Expedia scored 11 correct answers, with British Airways Holidays, Lastminute.com and Travel Republic all managing eight correct answers.

Only Expedia agents were able to correctly define a Linked Travel Arrangement, but they failed to mention its limitations, with Which? warning: “There’s no cover if something goes wrong or your holiday is not as it was described in the brochure.”

Which? said ignorance of the rules meant firms “are putting travellers at risk of missing out on crucial holiday protections”.

EDreams told the magazine it would review its training materials and internal processes. Ryanair did not respond to requests for comment from Which? or TTG.

The magazine said: “The new Package Travel Regulations may be complicated, but the fact Trailfinders managed to get most of the answers right is proof that the advice given can be correct, and that other companies need to carry out urgent training.

"We’ve presented our findings to the Department for Business, Energy & Industrial Strategy, which is reviewing the regulations."

Which? has also shared the results with the CAA, urging it to take action against companies “that are regularly misleading people about how well their holiday is protected, including those claiming to have an Atol licence when they don’t”.