They are designed to clarify what can often be a confusing chore but the City watchdog yesterday warned that some insurance comparison websites could be misleading consumers because of the way they presented information.

The Financial Services Authority (FSA) reviewed 17 comparison websites and found that while they were all appropriately authorised, the clarity, fairness and accuracy of information could be improved in some cases.

The FSA declined to name the 17 websites it checked as part of its review but a spokesman said those involved covered 95% of the market.

The review found a number of problems with the sites, such as some of them using assumptions to generate quotes, but not allowing consumers to review these assumptions.

Other issues included sites giving details on policies that were inaccurate and out of date, sites failing to list all of the features of a policy, and information on the excess consumers would have to pay being wrong or misleading.

In one case, consumers were given full information on a policy only once they had committed to taking it out.

The FSA also expressed concern that the sites encouraged consumers to focus too much on price and not enough on the different features of policies. It wants sites to warn consumers that the policies have different features and that these should be taken into account.

Ed Harley, the FSA's head of financial promotions, said: "We welcome innovation and competition in the rapidly expanding insurance comparison website market.

"However, we are keen that the market develops in a way that ensures customers are treated fairly, and expect comparison sites to provide information that is clear, fair and not misleading.

"We recognise that many consumers use these websites to search for insurance products. Consumers should shop around for the best deal, but it is important they compare what's covered by a policy, and not just focus on the price."