The ESB Group of Unions is to convene a delegate conference of workplace representatives to discuss taking industrial action over the company's €1.7 billion pension deficit.
The unions also voted unanimously to withdraw from cooperating with further cost-cutting or productivity measures unless the ESB accepts liability for the current and future pension scheme deficits.
The ESB insists that following a restructuring deal in 2010, the company no longer carries responsibility for any deficit arising.
Under the 2010 arrangement, the company agreed to pay an additional sum of €591 million, while contribution rates and benefits were also altered in a bid to address the deficit which then stood at €1.9 billion.
The date for that delegate conference to discuss strike action has not yet been fixed - but it is expected to take place in September.
The four unions involved are SIPTU, Unite, the Technical Engineering and Electrical Union and the Electrical Services Union.
Meanwhile, four staff members are expected to issue legal proceedings against the company early next week.
The four will be challenging the company's payment of a dividend to the state of €74.4m two weeks ago, as well as the proposed payment of a special dividend of €400 million next year from the sale of overseas assets.
In addition, the government is seeking a further €65 million in dividend payments from the ESB by the end of this year.
Unions argue that the dividend payments are inappropriate and unlawful at a time when the pension fund deficit remains so high.
They have already issued a letter to the company warning of their intention to take legal action.
The ESB unions will also be organising a political campaign whereby staff will write letters outlining their position to politicians across all parties.