Fake online reviews and paid-for endorsements of businesses may be misleading customers, the U.K.’s competition regulator said as it opened an investigation.

The Competition and Markets Authority said it’s also probing practices such as the failure to publish negative reviews, as part of a clampdown on unlawful practices. It didn’t identify any companies that would be involved in the investigation.

“Millions of people look at online reviews and endorsements before making decisions such as where to stay on holiday, or which plumber to use,” Nisha Arora, CMA senior director for consumer issues, said in an e-mailed statement. The agency “will take enforcement action where necessary.”

CMA research shows that more than half of U.K. adults use online reviews before buying a product or service. Websites run by TripAdvisor Inc. and Amazon.com Inc. allow users to post comments and ratings that are visible to potential customers.

This article was written by Kit Chellel from Bloomberg and was legally licensed through the NewsCred publisher network.