Tory ministers are considering raising the UK state pension age to 68 by the end of the next decade.
Scots born in the 1970s and after could be told as soon as the next UK Budget in March that they will be expected to work even longer before they receive the benefit.
The state pension age is already due to rise from 66 to 67 by 2028. The next increase - to 68 - was not due to happen until 2046, but an upcoming review is set to say it should be brought forward.
Chancellor Jeremy Hunt is reportedly backing the hike.
David Linden, the SNP social justice spokesman at Westminster, described the reports as "the latest in a long line of attacks from the Tories on the UK's state pension".
The Department for Work and Pensions (DWP) said no final decision had been taken.
Linden said: "This is just the latest in a long line of attacks from the Tories on the UK's state pension. In 2014, the people of Scotland were warned that the only way to protect their pensions was by voting No.
"Fast forward nine years and the current state pension doesn't support the minimum standard of living, with the state age now set to rise to a staggering 68.
"This is scandalous, and must be condemned in the strongest possible way. Be in no doubt, for as long as Scotland remains under Westminster control, our pensions will continue to be under threat."
A spokesman for the DWP said: "No decision has been taken on changes to the State Pension age.
"The UK Government is required by law to regularly review the state pension age and the second State Pension Age Review is currently considering, based on a wide range of evidence including latest life expectancy data and two independent reports, whether the rules around state pension age remain appropriate."
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