Price-comparison websites should sign up to a code of practice guaranteeing the accuracy and impartiality of the information they display, according to the Resolution Foundation, an independent research firm.
As part of the code, sites would have to disclose how much of the market they cover, and let users know upfront of any commercial relationships with product providers.
The number of comparison sites has risen dramatically in recent years. Some, such as uSwitch, Moneysupermarket and MoneyExpert, have become big brands, channelling millions of pounds worth of business to utility companies and insurers.
The Resolution Foundation said almost half of a YouGov poll of 2,010 British adults had used a comparison site in the past year.