Ballymena bus manufacturer Wrightbus is cutting up to 125 jobs.
That includes up to 35 permanent employees and as many as 90 agency staff, trade union Unite said, over a phased period.
It follows an economic slowdown due to the coronavirus crisis.
Unite regional officer George Brash said: “Every job lost is a heavy blow for the individual concerned, their household, the wider community and economy – especially in the face of the current Covid-19 pandemic.”
Wrightbus was bought out of administration last year.
Mr Brash said the announcement was “profoundly regrettable”.
He urged the company to “ramp up” production of hydrogen buses to curb greenhouse gas emissions and transition to a more environmentally sustainable economy.
“The Wrightbus workforce is perfectly positioned to make a vital contribution to that; they have the skills to build the buses at the heart of any future green transport policy.
“The request for furlough will be top of Unite’s agenda in the consultation process.
“Having played a lead role in securing the transfer of Wrightbus, which faced liquidation, to the Bamford group we are determined to bring as many jobs as possible to Ballymena as a result.”