New research from Sainsbury's Finance has indicated that 1.2 million travel insurance policies taken out in the UK may be invalid as holidaymakers fail to inform insurers of pre existing medical conditions.

In addition to the 1.2 million travellers lying about pre existing conditions to their insurer, they found that a further 500,000 with pre existing conditions had travelled abroad with no travel insurance whatsoever.

Apparently those with pre existing conditions feared that they would be either refused insurance or forced to pay extortionate premiums, so decided that it would be better to lie about their condition.

15 per cent admitted that they had kept quiet about a medical condition as they believed that they would be turned down by the insurance provider, while 19 per cent said that the reason they failed to mention their condition was because they wanted a cheaper premium.

In actual fact, rather than lying, they would have been better off not taking insurance at all, as by lying to the insurer, the policy is made completely void and they are not covered for anything, despite the fact that they will have paid their insurer.

The most common condition which people lied about was back problems, with an estimated 474,000 people travelling abroad with back problems not informing their insurance provider of their condition.

Osteoarthritis, a common degenerative joint disease, and heart disease were jostling for second place as Sainsbury's Finance estimated that 267,000 people lied about having heart disease and 262,000 lied about osteoarthritis when taking out their travel insurance.

Sam Marrs, who is head of travel insurance at Sainsbury's finance, warned that lying when taking out any kind of insurance is a huge risk and could leave you seriously out of pocket.

"The purpose of travel insurance is to ensure that if a disaster does strike, you will get the necessary care and support. Withholding key information such as any medical conditions could mean your cover may be invalidated and in the worst of cases, this could mean facing large hospital bills or arranging your own repatriation,” he said.

The Association of British Insurers agreed, with a spokesman saying: “If you withhold important medical information and make a claim the chances are your insurance company will find out and may not pay out.”

Natasha Virtue, communications manger at Sainsbury's Finance also voiced similar sentiments, saying: "Withholding key information such as any medical conditions could result in your cover not being valid, meaning that you're not insured and may well have to finance treatment or even arrange for your own repatriation back to the UK."

Mr Marrs of Sainsbury's finance added that holidaymakers with pre existing conditions should not be afraid of high premiums as there are insurance options out there for everyone.

“It is important to be honest with your insurer and provide all the information they ask for. It is a fiercely competitive market so if you have a common medical condition there is a good chance you will find an insurer to cover you for a fair and competitive premium. For those with more serious medical conditions, there are specialist insurers available. It is not worth taking the risk and travelling with potentially invalid cover or no cover at all,” he advised