Comparison sites are facing an investigation by the Financial Conduct Authority (FCA) to ensure consumers are not "being misled".
The watchdog announced the thematic review, which will focus on 14 websites covering 90% of the market, on Sunday.
The FCA said while comparison sites had made it easier for consumers it would investigate potential risks, including that consumers may not fully understand the services provided by the websites and may be misled into buying products or add-ons that do not meet their needs.
It also highlighted that consumers could be treated unfairly if sites focus on generating profits, do not enough oversight of the firms/products they display or are not aware of any possible conflicts of interest.
The results will be published next year.
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