The Pensions Policy Institute said in 1981 people typically received the state pension for 25 per cent of their life.
But by 2000 increased longevity meant that the proportion of people's lives during which they were in receipt of the payment had jumped to 30 per cent, while it had increased further to 33 per cent by this year.
The group said if the Government wanted to maintain the amount of time people could claim the state pension constant at the 1981 level, it would need to increase the age at which they first received it to 72 by 2030.
It added that even if people were to receive it for around 30 per cent of their life, the state pension age would still need to rise to 68 within 20 years.
The group was responding to a Department for Work and Pensions consultation on the issue.