TripAdvisor is failing to stop a “flood” of fake and suspicious five-star reviews from artificially boosting the ratings of some of its highest-ranked hotels, a Which? Travel investigation has revealed.

The consumer champion analysed almost 250,000 reviews for the top ten ranked hotels in ten popular tourist destinations around the world – and flagged one in seven of these 100 hotels as having blatant hallmarks of fake reviews, while others raised serious concerns.

Which? Travel reported 15 of the worst cases to TripAdvisor and it admitted that 14 of these had already been caught with fake positive reviews in the last year.

The world’s biggest travel website revealed six of these hotels had been penalised for breaking guidelines and two had previously been given a “red badge” warning for suspicious activity, yet this was not made clear to travellers and a highly suspicious pattern of reviews had continued to appear – suggesting a lack of serious ongoing oversight and action to address repeated abuse of the system.

Following Which? Travel’s investigation, TripAdvisor has taken down hundreds of reviews, while Travelodge admitted having previously been hit with the website’s most severe red badge warning for suspicious reviews after two of its hotels in London were flagged in the research.

There were striking results in the Middle East, with a hugely suspicious pattern of reviews at the ‘best hotel’ in the whole of Jordan.

The hotel denies doing anything wrong but shortly afterwards TripAdvisor removed 730 of its five-star reviews.

Despite this it is still listed as one of the ten best-ranked hotels in the increasingly popular holiday destination, with holidaymakers none the wiser.

Some of the best-rated hotels in London, Paris, Barcelona and Cape Town gave some reason for suspicion but had none of the similar extreme patterns.

The findings come as the Competition & Markets Authority is carrying out a programme of work aimed at tackling the increasing problem of fake and misleading reviews.

Which? believes the regulator should ensure the scope of its investigation includes online sites that host reviews, and that platforms like TripAdvisor should be more responsible for the information presented to consumers.

Naomi Leach from Which? Travel said: “TripAdvisor’s failure to stop fake reviews and take strong action against hotels that abuse the system risks misleading millions of travellers and potentially ruining their holidays.

“Sites like TripAdvisor must do more to ensure the information on their platforms is reliable and if they continue to fall short, they should be compelled to make changes so holidaymakers are no longer at risk of being duped by a flood of fake reviews.”