Irish Congress of Trade Unions General Secretary David Begg has said plans to change the State pension age should be postponed.
Mr Begg was speaking ahead of a conference on the issue in Dublin today organised by ICTU.
The Government plans to increase the pension age to 68 by 2028.
But speaking on RTÉ’s Morning Ireland, Mr Begg said he has concerns about how it would work in practice.
"The practical problems of the labour market effects on it - we have to sort them out," he said.
"What do you answer to somebody who's left out of their job at age 65, and has a year or more to wait until they receive their pension? What do they do? What do they actually live on? So you have to sort that problem out.”
Mr Begg said a recent survey of employers showed the majority had no intention of changing the age of retirement for their workers.
He said there was also no answer for people working in trades such as scaffolders or nurses, where there was a physical issue of working until a later age.
Mr Begg claimed there was also an issue for people who had been in and out of the workforce at different stages of their careers.
"It seems from reports that there is a significant change in the eligibility criteria in prospect,” he said.
“If it happens, it can have a huge affect on the amount of pension people will actually receive when they retire.
“And that is particularly important for women because many women have left the workforce during their careers, often during the child rearing years, and they come back in again."
Mr Begg said the proposed pension changes in Ireland were "deeper and faster" than in any other European country.
The Government plans to increase the qualifying age to 66 in 2014, 67 in 2021 and 68 in 2028.
Mr Begg called for unions and employers to now meet to discuss any changes that he said should be planned, well thought out and gradual.
Minister for Social Protection Joan Burton said that once the State pension age rises - beginning in 2014 - anyone still obliged to retire from their jobs at age 65 will be entitled to Jobseeker's Benefit and every other social welfare support available to people without work until they qualify for the State pension.
Ms Burton said there is legislation promised from Minister for Public Reform Brendan Howlin to deal with the retirement age change in the public service, but otherwise it is a matter for unions and employers to discuss opportunities for people to stay on working longer.