Special 'over-fifties' life assurance policies that guarantee acceptance, no medical questions asked, are becoming increasingly popular. Ads for such plans often feature 'mature' celebrities such as Sir Michael Parkinson and Cilla Black. Yet many people who take out these plans get trapped into paying much more than their families will ever get out.

These plans are sold to people aged between 50 and 80 and, in return for monthly premiums ranging from around £6 to £60, the insurance company guarantees it will pay out a fixed sum on the policyholder's death to their beneficiaries. The amount will depend on the premium paid, gender and age when the policy is started.

Crucially, unlike ordinary life insurance policies, policyholders will not be asked any questions about their health that might otherwise influence the amount of the premium they pay. The monthly premiums are payable in some cases until the policyholder dies; other plans' payments may stop after a certain time, but the policy will remain valid until the holder dies.

So, depending on when they die, the policyholder may have paid more or less in premiums than the policy will pay out. For example, if a 60-year-old man pays £10 per month for a policy that will pay out £2,000 and he dies after five years, he will have paid £600 so his beneficiaries will get back more than the policy cost him. But if he lives for 20 years he will have paid £2,400, £400 more than the payout.

'I can't understand Michael Parkinson endorsing this type of product. He is a quality act, but the same cannot be said for this policy,' says Peter Chadborn of independent financial adviser CBK Colchester, referring to adverts for Axa Sun Life's plan.

Mark Howes, managing director at Axa Sun Life Direct, defends Parkinson's role, saying he is merely highlighting the existence of the plans, for which there is a considerable demand. 'The attraction is their affordability because of their low premiums and the guaranteed acceptance process,' he says.

Heidi Welch, director of direct distribution at LV, which says it uses Cilla Black to 'create awareness' of its over-fifties policy, adds: 'The other reasons people like the policies are because they know exactly what they will pay.'

But many people could get a better deal elsewhere on the same terms if they bought an ordinary policy. Alan Lakey, an independent protection specialist at Highclere Financial Services, says: 'People could get twice or three times as much for their money from an ordinary life policy, in return for answering a few questions.'

He says that for £10 per month, a 60-year-old man could get an assured £3,359 with an ordinary Legal & General life policy, against just £1,520 from Axa's over-fifties plan.

Higher premiums have to be charged for over-fifties plans because by not asking about health, insurers risk attracting more people with pre-existing conditions who will die before the company has covered its costs. Insurers also protect themselves is by imposing a moratorium on payouts for the first one or two years. If the policyholder dies of natural causes during this period, a refund of premiums is normally given instead.

Gev Lynott, director of financial services at Asda, which also offers an over-fifties plan, admits that people may pay less for ordinary life cover but says by the time they get into their fifties or older, many have suffered some sort of medical condition, which is what attracts them to the over-fifties plans. However, one aspect of competitors' plans he disagrees with, he says, is policyholders paying more in than they can ever get out. 'When we put together our plan we decided to put a cap on the premiums,' he explains, so when customers have paid in the equivalent of the sum assured, their premiums stop.

Howes at Axa Sun Life argues: 'It is about pooling risk. Those who die earlier than average will get back more than they have paid in, and we make it clear in our promotional material that policyholders could pay more. But we will be reviewing all our policies in the new year.'

Other leading over-fifties policies do have eventual cut-off points, but not before some policyholders have paid over the odds. With LV's policy, premiums stop at age 90: with the Post Office they run for a set term.

Another potential problem is whether the plans will actually achieve what policyholders want from them. Insurers say the main reason people take them out is to cover funeral expenses, but the eventual payout may not be enough. People would be better off opting for a pre-payment plan: Co-operative Funeralcare, the UK's largest undertaker, offers three guaranteed funeral 'packages' for between £2,535 and £3,095, which can be paid for over a period of three years.