Earlier this year, several major hotel booking sites pledged to make some major changes to their practices after a Competition and Markets Authority (CMA) investigation.

Expedia, Booking.com, Agoda, Hotels.com, ebookers and trivago had been subject to CMA enforcement action due to concerns around tactics such as pressure selling, misleading discount claims, the impact commission has on how hotels are ordered on sites, and hidden charges.

The companies have agreed to make changes to the way they operate to address the CMA’s concerns, with a deadline to comply of 1 September.

But Which? said research showed these sites were continuing to use “dubious tactics” to pressurise holidaymakers, such as “skewing search results, using pressure tactics and claiming false discounts”.

Rory Boland, editor of Which? Travel, said: “These sites have been getting away with dodgy sales practices for years and, while the regulator’s intervention is a positive step, millions of holidaymakers still going to be duped this summer before any changes are made.”