Workers at Eircom are to vote on industrial action in a dispute over a 2% pay increase.
The unions claim that Eircom's owners, Babcock & Brown, are refusing to pay the increase due under the Towards 2016 national wage deal until workers agree new terms and conditions.
Workers at Eircom have not gone on strike since 1978. The company was then owned by the State.
This row threatens disruption of services to business and household customers of the biggest telecoms provider in the country.
The Communications Workers Union, which represents 5,000 Eircom staff along with other unions, has said it is to ballot workers over the next two weeks on industrial action.
The unions say they are entitled to the 2% increase without pre-conditions.
Eircom has said it expects to reach a resolution with workers who are to be balloted on industrial action. The company said it fully supports the agreement outlined in Towards 2016 and had paid the first phase of increases last November.
