The Institute for Fiscal Studies has warned that the government could increase the state pension age to 70 by 2050.
In their report, experts warned millions of people are set to face a delayed retirement.
They said the UK's ageing population could mean a rise in pension age in order to maintain the proportion of people in work.
They also warned that workers in their 30s and 40s in particular were not saving enough for retirement.
Deputy director for the Institute for Fiscal Studies, Carl Emmerson, told our business correspondent Ian King today: "One option to help people with their retirement saving is to make the state pension more generous.
"But that does look difficult in a world where on the government's projections over the next 50 years we will be spending the equivalent of £100bn more on the state pension because of the triple lock, an ageing population and because of people living longer at older ages.
"And that comes on top of an increasing bill for the NHS.
"The state could do more but that already is looking difficult looking at those projections."
