Two reports for the government have raised the possibility that millions of people may have to work for longer to qualify for a state pension.
The first report which was completed for the Department for Work and Pensions (DWP) has suggested that workers under the age of 30 may not get a pension until the age of 70.
The second report, by John Cridland, proposes that those under the age of 45 may have to work a year longer, to 68.
The government is due to make a decision on both reports by May.
Ministers are under pressure to address the expected rise in the cost of pensions, which stems from longer life expectancy and the increasing ratio of pensioners to workers.
But at least six million people face the prospect of having to work longer.
Experts from the Government Actuary's Department (GAD) said the state pension age could be raised as high as 70 as soon as 2054.
Under existing plans, the state pension age is due to rise to 68 for those born after 1978.
The scenario involves an assumption that people spend 32% of their adult life in retirement. The conventional assumption until now has been that people will spend 33.3% of their lives in retirement.
In the other report, by the former CBI chief John Cridland, foresees more modest changes.
He recommends bringing the change from 67 to 68 forward by seven years, from 2046 to 2039. That would mean anyone currently under the age of 45 having to work an extra year.
The changes are due to be phased in gradually, over a two-year period in each case.
Additionally, Cridland said there should be no up-rating from 68 to 69 before 2047 at the earliest, and that the pension age should never rise by more than one year in each ten-year period.
He also suggested that the so-called triple lock be ended in the next parliament.
Up to now the triple lock has guaranteed that the state pension rises each year by inflation, earnings or 2.5%, whichever is the highest.
However, by linking the rise in pension payouts to earnings alone, the bill for pensions would fall from 6.7% of GDP to 5.9% of GDP by 2066.