An investigation of insurance comparison websites by consumer champion Which? has revealed “staggering” numbers of errors and inconsistencies.

Policies did not match details listed on the sites in six out of 10 cases, leaving consumers at risk of buying insurance that does not match their needs.

Which? cross-checked policy descriptions for 21 brands – across four popular price comparison websites – against policy information on insurers’ own websites and in policy documents.

It says that for six in 10 policies, at least one detail published on the comparison site was different to that posted in policy documents.

Which? also says many of the results from price comparison searches came from the same few parent companies, and some identical policies appeared more than once with large price differences depending on the broker involved.

“We were staggered to see such a high number of errors across the policies listed on price comparison sites,” Which? Money Editor Harry Rose said. “Millions of consumers visit these websites hoping to find all the information they need to make an informed decision in one place – yet our findings cast real doubt on their ability to do so.

“These sites should up their game to ensure customers know exactly what they’re purchasing and from whom, otherwise they might well end up with policies and contracts that simply don’t meet their needs.”

Which? advises consumers to check policy documents on the provider’s website before purchase.