Government plans to increase spending on state pensions have been criticised as "unaffordable and irresponsible" in a report by a free market think tank.
The Institute for Economic Affairs (IEA) said the government should speed up the introduction of a later retirement age, the BBC reports.
It also suggested a compulsory private pension scheme to replace the state pension.
In response, the government said it had already brought in automatic enrolment.
"While not compulsory, as people are free to opt out if they wish, it will mean millions more people will be saving for their retirement," a Department for Work and Pensions (DWP) spokesman told the BBC.
The DWP added that it was already reforming state pension age to ensure it reflected changes to life expectancy, and was also introducing "a simpler, flat rate state pension".
However, the IEA said its research showed that the current state pension system was incentivising early retirement.
Its report found that people retired earlier on average today than they did in the 1960s despite huge improvements in life expectancy.
As a result, it calculates state pension spending will surge by 42% as a proportion of national income between 2012 and 2062.
"Under current policies, state pension provision and other benefits paid to those who retire before state pension age represent a ticking time bomb for the public purse," the IEA said in the report.
The IEA's report makes a series of recommendations including increasing the state pension age to 68 by January 2023.
Under current government proposals, the state pension age will rise to 68 by the mid-2030s.
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