The ESB has claimed that it has done all it can to ensure equal pay for Serbs working on its €3bn networks programme.
Trade unions are claiming that up to 200 men are owed up to €40,000 each in arrears from the Serbian firm Energo, who were hired by Irish contractors Laing O'Rourke.
They said the men were paid less than half the minimum wage while working on the north midlands programme.
A spokesman for the ESB said today that they arranged talks last October between the sub-contractor and union representatives.