It interviewed 1,703 Which? Connect online community members in August 2010 about their usage and attitudes towards comparison sites.
It asked them whether they purchased a product via the site or bought directly from the provider.
It says consumers believed that they only include products that will make the comparison site the most commission rather than delivering the best price for the customer.
Only 21% trust the sites to find the best price available. Despite this, almost four fifths said they wouldn’t be put off using a comparison website – even if they have had a bad experience.
Almost three quarters of under 45s stated that price was their main reason for making their selection when on a comparison site.
Peter Vicary Smith, chief executive of Which?, says: “Comparison websites are part and parcel of renewing insurance or finding new financial products so they really need to do a better job at keeping their customers happy.”