Staff in Dublin Bus, who are members of Siptu, are to ballot for industrial action over pension issues.
The union said the company had breached the terms of a settlement that ended a strike by Dublin Bus workers last autumn.
That settlement was brokered at the Workplace Relations Commission.
Siptu said the settlement terms included a proposal that any increase in basic pay must be recognised for pension purposes from 1st February last.
The union said that Dublin Bus management refused to honour this element of the settlement .
"This is a fundamental issue as our members are facing a drastic cut to their pension entitlements and it is particularly unacceptable that this is being imposed by a semi-state body which is ignoring the State's dispute resolution mechanisms," Siptu sector organiser, Willie Noone said on Monday.
“While Dublin Bus management has been in contact with this union today to discuss a meeting on the pensions issue, it appears that the company has only now realised the anger its action has provoked among our members and the potential it has to spark a serious industrial relations dispute.”
Members of the National Bus and Rail Union at Dublin Bus are also to ballot for industrial action over the issue of pensions.
Dublin Bus has said that talks are underway at the level of the broader CIE group of companies regarding pensions for staff.
