Thousands of women are getting smaller pensions because they left the workforce before 1994 to care for children.
Others are taking a pensions hit because they once had a summer job or worked part time for a while.
It is estimated that 23,000 females have been hit with lower payments due to changes to State pension eligibility rules in 2012.
Changes made by then social protection minister Joan Burton in the previous government make it more difficult to qualify for a full pension.
Retired women are losing more than €1,500 a year on average, according to calculations by advocacy group Age Action.
The rule change also means that the women affected will not get the full €5 increase in the State pension announced in the Budget and due from the end of March.
He was reacting to a caller to the 'Today with Sean O'Rourke' show, whose wife is losing money due to the change.
Eamon Tynan, a pensioner from Co Longford, said the situation was costing her €35 a week in her pension payments.
His wife had a summer job in the 1960s when she was a secondary school student before joining the civil service.
The minister responded that it was "bonkers and unbelievable" that women who worked and obeyed the law by paying pension contributions were now getting lower pensions.