Major OTAs including Trivago, Expedia, Agoda and Booking.com have agreed to change the way they do business after a UK investigation found some of them were deceiving users about hotel room prices and search results.

The UK Competition and Markets Authority on Wednesday announced the results of its probe, which focused on issues such as pressure selling, misleading discount claims and hidden charges.

The regulator said that some buyers were warned that other users were looking at the same hotel, giving them a "false impression" of a room's popularity. In other cases, the full cost of the room was not displayed.

The problem: The new standards will only apply to OTAs registered in the United Kingdom.