More than two-thirds of workers at one of the country's main cement plants are to lose their jobs.
Fifty-five out of 75 staff at Irish Cement's Limerick plant are to be made redundant.
Last night, Irish Cement blamed the job losses on a massive downturn in the construction sector where activity has dropped 80pc from its 2007 peak.
Management at the Limerick plant met their employees last Friday where the news was broken to them.
The company is keen to emphasise that the Castlemungret plant is not closing.
SIPTU organiser David Lane described the announcement as "shocking".
The company also has a second plant at Platin, Co Meath, and employees there will not be affected.
An Irish Cement spokesman said the redundancies would be the subject of dialogue between management, unions and employees.