People Before Profit have dismissed as "not accurate" an actuarial review, which predicts a pensions timebomb in Ireland with a potential deficit of over €400bn.
The review of Social Insurance Fund by accountants KPMG in 2015, said the number of over-66s will rise from 12pc of the population in 2015 to 17pc in 2035 and 23pc in 2055.
It found there were 4.9 workers for every pensioner but this will fall to 2.9 workers per pensioner in 2035 and two workers per pensioner by 2055.
The report said the social insurance fund could accumulate a potential deficit of up to €404bn by 2071.
The last government's Pensions Roadmap draws heavily on this report. It said pensioner numbers would more than double over the next 40 years.
The Central Statistics Office predicted that the number of people aged 65 or over will have risen from 629,800 four years ago to between 1.5 and 1.6 million by 2051.
Despite this, People Before Profit TD, Bríd Smith, said that the report doesn't take into account certain factors which could alleviate the financial burden attached to a pension age of 65.
Ms Smith said that part of affording a growing number of pensions is employers paying appropriate PRSI.
"Economists in SIPTU have done studies that disagree with that actuarial review," she said.
"You can't just project ahead 20 or 30 or even 50 years to say that there will be this void in the ability to be able to pay the proper pensions without measuring the productivity of workers and the potential for more workers to come into the country or more economic growth, and that's exactly what the actuarial review does, it doesn't allow for those things.
"There's an argument about that and it shouldn't be accepted automatically that there's a pension time bomb about to blow. There are arguments about this and the key thing is to get employers paying their fair share of PRSI so that there are funds there and very clearly the pension fund was raided to the tune of €17bn during the austerity years and that has caused what they see as a pension timebomb."
"We see it as pure daylight robbery on workersm," she continued.
"It's not accurate to say there's a pension time bomb. There's obviously a challenge as people live longer, but it is not a time bomb and they cannot predict that without looking at a huge number of other factors."
Ms Smith went on to belt out a verse of 'Where is our James Connolly' in front of his statue at her party's launch of their Workers' Rights Charter.
"Connolly, who was a champion of workers' rights, equality and the fight for socialism and peace across his history," Ms Smith said, would be in agreement with their charter, which includes calls for a €15-an-hour living wage, equal pay for equal work, the right to retire at 65 and a 35-hour working week.
Around the corner, a poster spanning the length of the SIPTU building in Dublin's city center showed a woman in a work uniform quoted saying, "I expected to retire and get my pension at 65. Instead the Government is forcing me on the Dole."
Solidarity-People Before Profit leader Richard Boyd Barrett, was also at the launch. He echoed Ms Smith's rejection of the actuarial review.
The Central Statistics Office has predicted life expectancy in Ireland will rise from 79 to almost 86 for men by 2051. It forecasts it will increase from 83 to 88 for women.
Despite this, Mr Boyd Barrett said that Ireland has one of the youngest populations in Europe, and criticised Fianna Fáil and Fine Gael for "having us working longer than any other worker in Europe."
"We have one of the youngest populations anywhere in Europe and yet the plan of both Fianna Fáil and Fine Gael is to have us working longer than any other worker in Europe before they are entitled to their pension," the Dún Laoghaire TD said.
"That doesn't add up. Why given that we have a younger demographic than the rest of Europe are we going to have the highest pension entitlement age in Europe?
"If there is a challenge in terms of pensions, surely that challenge is greater in the rest of Europe. Why is it that in Ireland it's being used as an excuse to have the highest pension entitlement age?
"Really it's just a ruse and excuse to attack those workers' pension entitlement - pension entitlements, by the way, they paid for."
The age at which the State pension is paid has become a major issue in the General Election. Following the effective raising of this age from 65 to 66 in 2014, legislation is in place to raise the age to 67 in 2021 and to 68 in 2028.