Opponents vow they'll fight plans to increase the pension age to 70
Advocacy groups for older people have said they will oppose any efforts to extend the pension age beyond 68.
Age Action said any move to delay pension entitlements could have "serious health implications" for people who work in physically demanding jobs such as construction, agriculture or healthcare.
It comes after a study by the Economic and Social Research Institute (ESRI) warned that the ageing population would put pressure on public expenditure in the years ahead.
It has compiled a report which shows the cost of population ageing could be offset fully by extending the pension age to 70.
The pension age is already set to rise from 66 to 68 over the next decade.
Justin Moran, of Age Action, said the organisation would "be absolutely opposed to any suggestion to increase it again".
"The overwhelming majority of us are going to rely on the State pension in retirement. We need to ensure it is fair and sustainable. But the solution is not simply to keep increasing the pension age," he said.
Addressing the Oireachtas committee on Budget Oversight yesterday, ERSI director Alan Barrett said provision would have to be made for the changing demographic.
He cited research which said one route to achieving this would be simply to raise the pension age.
"Whether or not it's a good idea, I think the crucial point here people talk about is that it's really all about offering people choice.
"When 65 became engrained as the retirement age, that was quite a long time ago now. Health status of 65-year-olds has changed enormously."
Mr Barrett said the "simple truth" is that many 65-year-olds are "perfectly capable" of continuing to work but others are not.
"The trick here and the policy prescription has to be about facilitating people if they want to work longer."
Former social protection minister Joan Burton said raising the pension age to 70 would be "little short of a catastrophe".
"I don't think societally and economically a lot of people who would really be on the pension would be able to sustain work until the age of 70," she said.
The latest census figures show that the over-65 age group saw the largest increase in population since 2011, rising by more than 100,000 to close to 640,000.
Mr Barrett said it was "absolutely critical" that the existing State pension system is protected.
"The public social welfare pension system is one of the great success stories of Irish social policy," he said.