A new report claims more than 35,000 pensioners are losing out because of changes to the state pension system.
Age Action says they are seeing a major impact from changes introduced in 2012 - with women worst affected.
Justin Moran is the head of advocacy for Age Action: "Well what we have discovered is that the changes the Government introduced, to the eligibility criteria of the state pension in 2012, has meant that over 35,000 pensioners, men and women, have had their pensions cut.
"Thousands of these retired workers are losing very substantial sums, in some cases more than €1,500 a year.
"Women pensioners are really taking the hardest hit."
The charity is now calling on the Government to reverse the cuts and restore the income of the affected pensioners.
Justin Moran, head of advocacy at Age Action, said: “We need to put to bed the myth that the state pension was protected by the last government.
“It was cut drastically for tens of thousands of older people who have lost subtantial sums of money as a result,” he said.
The changes affected the contributory state pension which is paid on a declining scale depending on how many PRSI contributions an individual makes and how those contributions average out over their working life.
Extra scales were introduced which made it harder for people to qualify for the full weekly payment, with a loss of more than €30 per week for many.
Mr Moran said Age Action’s research showed that women pensioners were hit hardest by the changes, widening an already unequal pension gap.
“Figures provided by the Department of Social Protection show that of the 36,000 people affected by these changes so far, more than 64% are women.
“Our research shows that this change, combined with the averaging rule used to calculate contributions, is punishing women who took time out of work to care for their children.”
The research, to be published today, also found the averaging rule meant two people could work the same length of time but one could be penalised financially for having a period out of the workplace.
“Someone who worked for a few months in the 1960s and then went back to work in 2000 gets a far smaller pension than someone of the same age who just started work in 2000. It’s an incredibly unfair system. They’re being punished for working.”
The Irish Human Rights and Equality Commission says women here have on average pensions that are 38% lower than men. That’s in addition to a gender pay gap of 14%.
Both issues are raised by the Commission in a report to the United Nations Committee on the Elimination of All Forms of Discrimination Against Women (CEDAW).
Next week this commission will hold hearings to review the State’s performance in combatting discrimination against women.
Other issues highlighted by the commission for the hearings include barriers hindering participation by women in politics and public life; the State’s failure to provide full redress for victims of historical abuses in Magdalene Laundries, mother and baby homes and as a result of symphysiotomy; and the failure to legislate for fuller access to abortion.
Additional reporting from the Irish Examiner.