Eight ESB pensioners have accused the ESB and trustees of the ESB pension scheme of age discrimination for the way they have deducted the private sector pension levy from their pensions.
The pensioners have lodged a claim against the company and pension fund trustees at the Equality Tribunal.
ESB sources said they were aware of the case, but the company does not believe it has any case to answer.
In 2011, the Government introduced a 0.6% a year pension levy for four years from private and semi-state sector pension schemes to fund a job creation programme.
The scheme was intended to raise around €1.8 billion over four years.
The ESB scheme trustees are deducting 0.6% from the pensions of retirees, but are only deducting 0.3% from the benefits of current employees and former employees who have not yet begun claiming their deferred pension entitlements.
The eight pensioners have lodged a case at the Equality Tribunal arguing that this constitutes age discrimination, as retirees paying 0.6% are over 60 and are being treated differently from scheme members under 60, who are only paying 0.3%.
They also say that as the Government deduction is to continue at a lower rate indefinitely, the ESB, which is profitable, should increase its contributions to offset the levy.
The claimant pensioners calculate that the levy on the ESB scheme will cost the scheme €18m per year or €72 million over the four years in question.
The Equality Tribunal hearing is scheduled for 16 May.