Iarnrod Eireann is threatening legal action if train drivers who are members the former Irish Locomotive Drivers Association (ILDA) go on strike next month.
The drivers will be balloted tomorrow on a proposal to engage in a series of one-day stoppages beginning in two weeks' time.
In a statement issued this evening, the company said it regretted the "apparent re-emergence of a threat to services from locomotive drivers led by Brendan Ogle".
The threat is a result of the planned introduction of a new a timetable due for implementation on December 14th.
"In the face of the renewed threat to those services, [the company] will explore every avenue to deal effectively with it, including litigation and steps to deal with one-day stoppages that are clearly unjustified and unsustainable," the statement said.
Mr Ogle led a group of over 100 drivers who broke ranks with their union to form ILDA. They held a series of strikes in 200 and 2001 before being assimilated into the ATGWU.
Iarnrod Éireann said the train drivers' issue was essentially an inter-union matter and that ILDA does not have negotiation rights through its assimilation into the ATGWU.
The new timetable had been agreed with recognised unions, it pointed out, adding that ILDA/ATGWU wanted to be recognised it should pursue the matter through ICTU.
The company appealed to the drivers "to give full consideration to the implications of a strike" especially in light of the improvements to the service created by the new timetable.