The SIPTU trade union has joined the National Bus and Rail Union in threatening industrial action at Irish Rail.
Both unions say there's growing frustration among train drivers over carrying out additional duties, without extra pay.
The company says the move is unecessary and is urging unions to stick with ongoing talks at the Labour Relations Commission.
Union figures are not ruling out more industrial action at Irish Rail, as driver frustration reaches 'fever pitch'.
It is almost a year since a nationwide strike caused disruption for commuters, but now a row over pay and conditions is among the factors leaving drivers unhappy.
The National Bus and Rail Union (NBRU) has told the Irish Independent that while industrial action would be a "last resort", it is an approach being considered.
Irish Rail says it has not been notified of any strike, or balloting of union members.
Paul Cullen of SIPTU told Newstalk Breakfast drivers feel they are not being listened to.
While Irish Rail spokesman Barry Kenny says improvements are being made in the company, and they need to continue.
