It advises holidaymakers to avoid some big names in the industry such as Love Holidays, Last Minute and Teletext Holidays.

The consumer champion is warning holidaymakers against booking with more than 20 providers, based on shortcomings with their booking terms and commitments to refunding customers in the event of coronavirus-related disruption, or a lack of transparency about their policies.

Holidaymakers can search the findings for themselves using the Which? Holiday Checker. The tool compares the booking policies of more than 80 of the UK’s package holiday providers and rates each as red, amber, green or green+, depending on how they perform against criteria set by Which? experts.

Using the tool will help point customers in the direction of the companies with the best flexible booking options, so they can book with greater confidence that they won’t be left out of pocket should something go wrong.

The extensive research considered each company’s various policies on coronavirus-related disruption, including whether firms would refund customers in the event of a lockdown, if FCDO advice changes, if the customer was told to self-isolate before travelling, and if customers were forced to quarantine in a hotel on their return.

Which travel firms should you avoid?

The consumer champion says firms to avoid include Lastminute.com, Love Holidays, Teletext Holidays, Best At Travel, Holiday Gems, Mountain Kingdoms, and On The Beach.

Which? says holidaymakers booking with these firms risk being left out of pocket if they are unable to travel as planned. They are rated as ‘red’ on the Holiday Checker due to not providing clear information about their booking and refund policies.

While red companies’ policies were not necessarily in breach of consumer law, some have faced investigations from the Competition and Markets Authority (CMA) in the past year over failure to refund their customers, such as Love Holidays and Teletext.

Which? is advising anyone considering a holiday to avoid booking with a red company, and to check before they book to ensure their holiday provider offers a good flexible booking policy.

There were initially more companies rated as ‘red’ on Which?’s Holiday Checker as they failed to respond to Which?’s enquiries. But some companies, including Beachcomber Tours, Inspired by Travel and Travel Editions, came forward to clarify their refund policies at the last minute and are currently being investigated by Which?

Which are the best holiday companies to book with?

Companies that committed to offering refunds in most scenarios put to them by Which? included British Airways Holidays, First Choice, Hays Travel, Jet2 Holidays, Trailfinders and Tui. These firms were rated as green by Which?

Following a rise in concerns about people being contacted by NHS Test and Trace before they are due to travel, Which? also asked companies if they would provide full refunds in the event someone is told to self-isolate.

Only three companies – Exodus, Explore and Discover Egypt – guaranteed refunds in this situation, as well as every other situation put to them by Which?, and were rated green+ as a result.

Rory Boland, editor of Which? Travel, said: “Between changing travel restrictions, both in the UK and abroad, and the ongoing risk of being told to self-isolate, booking a foreign trip still comes with some uncertainty and things can go wrong if you’ve chosen the wrong provider. The best companies won’t leave you high and dry though, so it’s vital to do your research before booking.

“Anyone thinking about a holiday abroad can use the Which? Holiday Checker to check before they book, to make sure they don’t choose a company that could leave them out of pocket. The difference between choosing a red company over a green company could be losing the entire cost of your holiday if circumstances change and you have to amend or cancel your plans.”