Travel agents were accused last week of selling insurance policies without explaining the small print. As a result, holidaymakers with pre-existing conditions such as asthma could be forced to pay high medical bills if they fell ill abroad.

Undercover research by the Consumers' Association found evidence of mis-selling of insurance policies. Only one of 28 travel agents visited by Which? inspectors explained the content of the policy and asked if there was a pre-existing medical condition that could invalidate the cover. Six agents asked about pre-existing conditions without explaining what the policy covered, and four explained the details without asking about conditions.

Which? warned consumers to check their policies to ensure full coverage; in most cases they can be cancelled within 14 days of purchase. A previous survey found that 85% of travel insurance policies were bought through agents.