Price comparison websites are being probed by The Competition and Markets Authority to determine the degree to which consumers can trust them.
The study will look at whether people should be made aware of how sites comparing products like mortgages earn money, as firms often pay a fee for each new customer they gain.
The CMA will initially focus on home insurance, broadband, credit cards and flights and an interim report will be published next March.
Andrea Coscelli, acting chief executive of the CMA said: “Since emerging a decade or so ago, such tools have helped to inject significant competition into a number of markets, including private motor insurance.
“However, they have been more successful in some sectors than others. We want to understand why this is the case and whether more can be done to ensure consumers and businesses can benefit from them more widely.”
“Some people have also raised concerns about certain issues, including whether consumers can trust the information that’s available, and the study will look at these issues too.”