SNP MP Patricia Gibson challenged plans to bring forward the state pension age increase as life expectancy in Scotland has fallen for the past two years.
Mr Mills said: “If we accept that we should stick to the principle that we get roughly a third of our adult life in retirement, the reason why we would increase the State Pension age is that we have seen a three-year increase in life expectancy, and that should give us two more years on the State Pension age.
“So for every 12 months life expectancy goes up, people should effectively get four months of that in retirement and expect to work for eight months of it.”
The full basic state pension is currently £141.85 a week and £185.15 a week for the full new state pension. Some may get less than the full new state pension if they were contracted out before April 6, 2016.