The Unite trade union has said that even limited industrial action by ESB workers will result in power outages.
Management and unions are due to meet tomorrow to discuss a dispute over a deficit in the company's pension scheme.
Speaking on RTÉ's Morning Ireland, Unite spokesperson Richie Browne said that given the depth of feeling on the issue among workers it is likely that some sort of action will be taken.
"Even limited industrial action, given as I said the number of staff involved and the depth of feeling of our members, that even if there is action taken short of an all-out strike that will invariably end up in widespread disruption to the service," he said.
The Minister for Communications, Energy and Natural Resources said any decision by management in relation to the pension dispute is in accordance to professional and accountancy practice and was referred by the union through some of its members to the Commercial Court.
Speaking on RTÉ's Today with Sean O’Rourke, Pat Rabbitte said he spoke directly to ESB workers and reiterated that there was no threat to the company's pension fund.
He said the scheme will be back in surplus by 2018 and anyone who workers who are due to or want to retire between now and then are assured of their full pension benefits.
"Let me say again to ESB workers and their families, there is no risk to the ESB pension scheme," he said.
"It is one of the most robust and safe pension schemes in the country.
"There is no intention on the path of Government or the company to wind up the pension scheme. There is no intention to close down the ESB."