SIPTU members at Iarnród Éireann are to ballot for strike action after they narrowly rejected a Labour Court recommendation on cost reduction plans at the State rail company.
The 1,700 members balloted voted by 51% to 49% to reject the recommendation.
The proposals included pay cuts ranging from 1.7% to 6.1%.
SIPTU organiser Paul Cullen said members had found the recommendation as it currently stands unacceptable.
He said that following the rejection, members will now be balloted on strike and industrial action, which will be undertaken if management attempts to implement changes to workers' terms and conditions of employment without agreement.
The TSSA, which represents clerical staff, has already accepted the Labour Court recommendation, while the result of the National Bus and Rail Union ballot is expected next week.
This is the second time that staff have balloted on a package of cost reductions, having rejected LRC proposals, which included more severe changes over a longer period of time.
Iarnród Éireann had previously warned staff that the company will face line closures and compulsory redundancies if the Labour Court recommendation was rejected.
Minister for Transport Leo Varadkar and Minister of State for Public and Commuter Transport Alan Kelly both expressed disappointment with the outcome of the ballot.