Staff at the Fás training centre in Tallaght, Dublin, yesterday held a 24-hour work stoppage in a row about overtime.
Siptu, which represents six general assistants at the Tallaght centre, said its members had collectively lost out on €13,000 in overtime as a result of curbs put in place by Fás management.
About 350 trainees at the centre were sent home yesterday as a result of the dispute.
Siptu said the staff had taken industrial action because Fás management had breached an agreement which stated that "no general assistant will lose the financial benefits of established local agreements without agreement".
Siptu branch organiser Brendan O'Brien said that, in the current dispute, management had withheld payments due to members "to try to force discussions on a new local agreement for general assistants in Tallaght".
"We have indicated our willingness to enter discussions on a new local agreement as soon as the outstanding payments are made to our members," he said.
Mr O'Brien said Siptu had made a compromise proposal based on a recommendation drawn up by the Labour Relations Commission (LRC) but that this had been rejected by management.
"This dispute could and should have been avoided if management was prepared to honour an established agreement," he said.
A spokesman for Fás said that historically it had had an agreement governing overtime with staff in Tallaght. He said this agreement had been drawn up when the centre was based in its former premises, which required more maintenance. Under the deal, general assistants accompanied maintenance staff on overtime.
The spokesman said Fás had since moved into a €35 million state-of-the-art centre which did not require the same level of maintenance.
Fás said both management and the union had accepted an LRC recommendation on this issue but it had been rejected by the staff concerned.
The spokesman said Fás was prepared to return to the LRC for a clarification of the recommendation.
However, Fás said it was not prepared to prejudge such talks and to agree in advance to pay amounts put forward unilaterally by the union.