Power supplies could be disrupted from next weekend as a result of unofficial industrial action by ESB workers.
Shop stewards representing network technicians and power station staff have called the strike in an escalating row over the position of the company's deputy chairman, Mr Joe LaCumbre.
The ESB condemned the threat last night as "totally unwarranted".
Mr LaCumbre, a worker director, claims he was in effect removed from his position following a row with the ESB chairman, Mr Tadgh O'Donoghue, over the company's €511 million pension deficit.
Shop stewards representing 1,800 members of his union, the TEEU, claimed yesterday he had been removed for raising "legitimate concerns" about the company's pension fund.
In a statement, they said a process of industrial action would commence and escalate on subsequent dates "in demand of [ Mr LaCumbre's] reappointment".
The statement did not specify the timing or nature of industrial action planned.
It is understood, however, that it would begin this Friday at 8 a.m. with network technicians leaving their posts and not reporting for duty again until Monday morning.
That would make localised power cuts a strong possibility over the weekend, as repairs would not be carried out in the event of breakdowns.
Network technicians are responsible for operating and maintaining the ESB's distribution network.
It is understood that in the absence of a resolution, the action would be escalated by the middle of next week, with power station staff becoming involved.
The extent of consequent power cuts would depend on the particular stations affected, but any action by power station staff has the potential to cause serious disruption.
A strike could be averted if Mr LaCumbre's situation is resolved at the next ESB board meeting on Tuesday of next week.
An ESB spokesman, however, said a resolution would be difficult given that Mr LaCumbre was still the company's deputy chairman, so he could not be "reappointed".
Mr LaCumbre's contention that he was removed arises from a vote by the board that, in the absence of Mr O'Donoghue, another board member, Mr Eoin Fahy, would act as chairman.
The ESB spokesman said this was in accordance with board procedures in place since 2001, and that Mr Fahy had been appointed stand-in on a one-off basis. Other decisions could be taken at other times in the future.
In a statement last night, the ESB said it had not been made aware of any threat of industrial action. It said there were agreed industrial relations procedures for resolving disputes and appealed to union members to refrain from unofficial action.
