The UK Competition and Markets Authority (CMA) has launched an investigation into hotel-booking sites including Expedia and following a series of complaints.

The CMA said it is “concerned about the clarity, accuracy and presentation of information on sites” and will look into their search results, discount claims and hidden charges.

The authority is requesting information from across the sector, including from hotels and consumers.

CMA chief executive Andrea Coscelli said: “Around 70% of people who shopped around for hotels last year used these sites and they should be confident they have chosen the best accommodation for their needs and are getting a good deal.”

He said information on the sites “must be clear and accurate” and said: “We are concerned that this is not happening and that the information on sites may be making it difficult for people to make the right choice.

“That is why we have started our investigation – to get to the bottom of these issues, to see whether sites are breaking consumer law and make sure they help, not hinder, people searching for their next hotel room.”

The regulator will explore whether the ranking of hotels in search results is linked to the commission hotels pay to sites.

CMA senior director Nisha Arora told the BBC: “When you put in your criteria – which room you want, when you want to stay – they [hotel search results] are listed in a certain order.

“This is not just influenced by consumer preference, but by commission – by commercial considerations – and consumers might not be aware of this.”

The CMA will also decide whether charges are displayed clearly and examine how sites display how many rooms are available at properties.

The investigation follows a series of complaints to the CMA by the UK Bed and Breakfast Association which has filed five complaints against and one each against Expedia and

The association alleges ‘rate parity’ clauses imposed on accommodation providers are driving up prices to consumers and that OTAs mislead consumers with “false discounts” and “false availability claims”.

It has also complained about “misleading and manipulated default search rankings” and of “forced bidding” by OTAs on hotel and B&B names.

Alex Neill, Which? managing director of home products and services, said: “We have found evidence of booking sites using pressure selling tactics and making claims about discount deals that don’t add up. If the CMA finds breaches of consumer law, they should take enforcement action against those sites.”