About 240 miners at the Tara mine in Navan, Co Meath, last night placed pickets on all entrances to the site as attempts failed to prevent a strike in a nine-month dispute about working conditions underground.
The Minister for Education and Science, Mr Dempsey, a Fianna Fáil TD for Meath, offered his services as a facilitator to try to bring the parties back to the negotiating table.
The miners, represented by SIPTU and management, last held talks in mid-May, producing an agreed package of proposals, but these were turned down by the underground miners.
The company confirmed that it would be left with no choice but to suspend operations as its smelter companies would be receiving no concentrate from the plant this week due to the strike.
The company announced that it will start laying off most of the 450 other workers at Tara, ranging from fitters to administrative and professional staff, from Thursday.