Fruit distribution company Keeling's is to axe 130 jobs.
Union officials say the redundancies were brought about by the loss of a transport contract with Tesco.
Most of the workers affected are drivers but some management and support staff also face layoffs.
SIPTU says the Keeling's employees are being offered a transfer to the company which has won the Tesco contract.
However, there is no guarantee on employment terms and conditions with the firm, which has no union representation.