The number of homeowners using equity release to pay off interest-only loans has tripled since the introduction of tougher mortgage rules last year. Tougher affordability criteria, introduced as part of the Mortgage Market Review, has meant older homeowners are finding it harder to remortgage their loans as a result of their age. The findings come from retirement income specialist Age Partnership, which said lifetime mortgages are often the only option open to borrowers. This form of equity release enables older homeowners to unlock some of the equity that has built up in their home. Unlike conventional mortgages, no monthly repayments are required and instead the loan, plus interest that has rolled up during the life the loan, is repaid when the property is eventually sold – usually when the homeowner dies or moves into long-term care. According to the Financial Conduct Authority, some 600,000 interest-only loans will reach the end of their term by 2020 and it estimates that half of those borrowers have no means of paying those loans off, creating some 300,000 so-called mortgage prisoners.Get help finding the best mortgage for you Interest-only time bombSimon Chalk, equity release expert at Age Partnership, said: "The interest-only time-bomb has been made all the more devastating by the affordability criteria introduced by lenders as a consequence of the Mortgage Market Review."Fewer older homeowners have the opportunity to remortgage to set up a new strategy to clear their debt. That leaves swathes of homeowners with no obvious way to clear their interest-only debt whilst still remaining in their home. In the worst cases, retirees are being forced to sell-up and move to a smaller home to pay down their debt - a stressful and emotionally turbulent outcome which often causes unnecessary upset in later life." But equity release is not a perfect solution. As interest rolls up, the remaining equity in the property is gradually eroded and while no-negative equity guarantees mean you'll never owe more than the value of your home, there may be little money left to pass on as an inheritance. According to LV= a £50,000 loan with an interest rate of 6.19% would create a total debt of £53,095 after a year, after 10 years the debt would have racked up to £91,160 reaching a staggering £166,204 after 20 years.