Unions at the Electricity Supply Board are to conduct a ballot for industrial action, including strike, in a dispute over pension arrangements.
A meeting of shop stewards in Dublin this afternoon voted for the ballot, which will be conducted in the coming weeks.
The unions say the ESB has changed the company's pension scheme from a defined benefit system to a defined contribution scheme.
The ESB Defined Benefit pension scheme is a statutory scheme that has existed since 1942 to which employees pay 8.5% of pensionable income.
Its group of unions has said that it currently has a Minimum Funding Standard deficit of €1.6bn, an accounting standard deficit of at least €2.07bn and has to make returns of 6.25% ongoing just to remain solvent.
The unions say that ESB shifting all of this risk on to serving staff is an attack on their pension rights and constitutes a trade dispute.