Chivers' jam is to close its production plant on Dublin's northside with the loss of 100 jobs.
Owners Premier Foods are to close the Coolock plant and move its manufacturing base to England.
The distribution process is also being outsourced.
SIPTU has opposed the plans saying the losses are unnecessary and is rejecting an offer to discuss redundancy terms.
The union said it will fight to save the jobs and is seeking an urgent meeting with Premier Foods.