SIPTU has warned of further industrial action at the Tyndall National Institute in Cork if progress is not made on pay rates for staff.
SIPTU organiser Bill Mulcahy said the staff are University College Cork staff, and should be on UCC rates.
But he said currently there is a gap of 10% to 20% between their pay and that of their colleagues in UCC.
Talks last week at the Labour Relations Commission with officials from the Department of Education and from the Department of Public Expenditure and Reform failed to resolve the four-year dispute.
The institute is Ireland's largest research centre and around 460 researchers and support staff work there.
In a statement issued yesterday, UCC said it greatly values its staff and acknowledged there should be no disparity of treatment between colleagues.
However, it said any resolution had to be in accordance with current public pay policy and the Haddington Road Agreement.
The university also acknowledged that any industrial action poses significant financial and reputational risk to the institute.
In a statement today, the Department of Education and Skills said it regrets the industrial action being taken and any consequential disruption to Tyndall and UCC, considering the efforts to resolve the dispute.
Mr Mulcahy said his members do not want to damage the reputation of the institute, but the issue has nothing to do with the Haddington Road Agreement.
It is a claim, he said, for the current pay for the job, not about a pay increase.
Staff have withdrawn from certain duties, and further one day stoppages are likely in the coming weeks.
The union said it has not ruled out a ballot of its 800 members at UCC for supportive industrial action, if the situation is not addressed.