Up to 100 jobs are at risk at a perfume factory in Co Louth.
Management at Irish Flavours and Fragrances (IFF) in Drogheda is seeking to make the staff redundant and close the plant.
The US-based company blends aromas for major fashion houses.
Trade union Unite said the workers were devastated and angered by the possible lay-offs.
Richie Browne, regional officer, said: "Our members have recently been working a three-day week in order to secure the future of IFF in Drogheda.
"They are in shock and are angry that this decision has been made despite their willingness to do whatever was asked of them to maintain a presence in the area."
The union said the company sent its officials a letter outlining their plans to close on a phased basis between January and September of next year. Union chiefs will meet management tomorrow to try and save as many jobs as possible.
IFF operates in 30 countries across the world and has been in Ireland for around three decades.
In a statement the company said the decision was not taken lightly as it deeply values its employees.
"Should the redundancies go ahead; a comprehensive programme will be put in place for all affected staff," it said.
Louth Fine Gael TD Fergus O'Dowd said the job losses would devastate the town and region.
"Louth has been hammered by job losses in recent years, with the closure of Coca-Cola and other operations," he said.
"Now the closure of the IFF facility seems to be a distinct possibility, inflicting further damage on Drogheda's economy and community."
Labour Party Meath East Senator Dominic Hannigan branded the proposed losses profoundly disappointing.
"IFF has been in operation in Drogheda for about 30 years, and my thoughts today first and foremost are with those people who have learned that they are to lose their jobs," he said.
"In a period when unemployment is still spiralling upwards, it is likely to be very challenging for people to get back on their feet in the short term."
Senator Hannigan said it was time for the Government to step in and tackle the rising job losses in the north-east.