Travel insurers who “cherry-pick” customers by refusing to cover people with medical conditions could be breaking the law, according to the Association of British Insurers (ABI).

Some would-be holidaymakers are being left dangerously uninsured, even after being given the all-clear to travel by their doctor.

Under the 1995 Disability Discrimination Act (DDA), insurance companies are barred from refusing cover for “pre-existing conditions” such as angina and diabetes, unless they have evidence that the level of risk is unacceptable.

However, insurers can turn people away if they state categorically that they will not insure for any pre-existing condition.

ABI spokesman Malcolm Tarling said: “Insurers who load premiums or exclude certain risks must be able to back this up with evidence to justify the decision.”

According to British Insurance Brokers Association (Biba), there has been an increase in complaints from would-be holidaymakers who cannot obtain cover at all.

Mike Williams of Biba claims the worst offenders for turning people away are low cost direct writers, tour operators and travel agents.

Among those who refuse to cover certain illnesses are Europ Assistance, Thomas Cook and Boots, which will not automatically give cover to anyone who has been on medication for the past 12 months.

Travel insurer Club Direct's managing director Brent Escott said the company's research had shown that 60% of the industry failed to comply with the DDA.

“Many companies employ medical screening firms, but these do not always stick to the rules of the DDA. They are supposed to use medically qualified people to quantify risk and use accurate data but most do not do this.”

But he believes that, while some medical screening companies leave much room for improvement, they are still a benefit to the industry, as they reduce fatalities and cut claims.

Phone-based insurer Columbus Direct has opted out of covering medical conditions at all.

Marketing manager Paul Dittner explained: “It is sensible business practice to write standard risks.

“We had the world record for a medical claim of £1.2m, so obviously we have to be careful on the medical side.”

Bishopscourt Group Insurance Services specialises in covering travellers with medical conditions.

General manager Laurence Law said Bishopscourt would cover any condition, but premium costs could run into four figures.

The term ‘pre-existing medical conditions' is interpreted differently throughout the insurance industry and can apply to pregnant women, anyone awaiting an operation or anyone who has had medical treatment in the past two years.