Speaking at First Minister's Questions, Alex Salmond quoted a letter his constituent received from the Department for Work and Pensions (DWP) which stated that independence "will have no effect on your state pension".
He accused the Conservative Party of persistent "scaremongering" over pensions after Tory leader Ruth Davidson challenged him over apparently contradictory statements from the Deputy First Minister and the National Records of Scotland (NRS).
Yesterday, Nicola Sturgeon told MSPs: "Those who try to perpetuate the myth that Scotland's population is somehow uniquely ageing or ageing faster than that of the rest of the UK are simply wrong."
In a submission to Holyrood's Finance Committee, NRS said: "The age structure of Scotland's population means that it is projected to age more rapidly compared to the UK."
In response, Mr Salmond said: "Given the Tory track record of fairly blatant scaremongering over pensions, I was interested in a letter that one of my constituents in Aberdeen sent to the Department of Work and Pensions, who replied: 'If Scotland does become independent this will have no effect on your state pension, you will continue to receive it just as you do at present.'
"Given that the pensions service, the agency of the UK Government, is sending to my constituents in Aberdeenshire such definitive information, it ill-behoves Labour and Tory scaremongerers who come to this chamber with a scaremongering agenda."
Mr Salmond said his Government's pensions review, which was released on Monday and suggested Scots pensioners might be able to retire earlier than UK pensioners, was based on "another matter" other than demographics as it is designed to account for Scotland's lower life expectancy.
But Miss Davidson accused him of diverting attention from the looming "demographic timebomb".
Mr Salmond said: "The dependency ratio of Scotland is currently below that of the UK, an estimated 589 dependents per 1,000 people of working age in 2013 compared to 615 dependents in the UK as a whole. From around 2026 the gap between the Scottish and UK dependency ratios is projected to decrease."
Miss Davidson said: "The Scottish Government used some of the projections of NRS, which showed that the number of pensioners between 2010-2035 in Scotland would increase by 26% while in the UK it would increase by 28%.
"They didn't include that the number of working age people in the rest of the UK would increase by 16%, and the Scottish working age population would increase by just 7% over the same period.
"Monday's paper said under independence, Scots could retire earlier and on more money because Scotland's population is ageing at a different rate to the rest of the UK.
"NRS shows that 7% to 26% is 3.71 pensioners for every worker, more than twice the rate of the rest of the UK.
"The figures that they used compared the ratio of workers to the ratio of pensioners and children, but as everyone knows when you're dealing with pensions, it's the ratio of workers to pensioners that counts.
"So all of Monday's promises are based on the SNP convincing people that Scotland's demographic timebomb isn't the same as other countries."
Mr Salmond said: "The dependency ratio is the number of under-16s and people over pensionable age per 1,000.
"The review of the increase in terms of when the pension is paid is based on another matter, which is that life-expectancy aged 65 is 1.3 years higher in the UK than in Scotland for women and 1.3 years higher for men.
"We obviously want to do something about life expectancy, but it's not fair to ignore that reality in terms of deciding what the appropriate pension age is, and we doubt very much if the UK Government, in increasing the pension age, took into account these life expectancy figures in Scotland."