St John Ambulance is looking into cutting more than 30 management and support jobs.
A proposal out for consultation suggests 33 jobs would be cut.
First Union ambulance organiser Neil Chapman said no one should be losing their job when more ambulance crews were needed.
"You know, it's not long since those positions have been created," he said.
"It just seems there's no sort of logic to disbanding those positions without some consideration of redeployment to the front-line environments."
St John Ambulance chief executive Peter Bradley said the proposal would not directly affect front-line ambulance services and so would not impact on the quality of patient care.