Budget cuts to the Fire Service in Londonderry could put the public at risk, the Fire Brigades Union (FBU) has said.
Changes to staffing levels at the city's stations could result in call-out delays, said the FBU's James Quinn.
The cuts mean the only appliance in Derry used to tackle tall building fires no longer has a specialist crew, he added.
The Fire and Rescue Service described the changes as a "low-risk option."
But Mr Quinn said he felt "terrified".
"We are there as a lifesaving service and our job is to get there as fast, as promptly as possible and do the most professional job we can," he added.
"If we are being hampered by the decisions taken by bean counters effectively, then I fear for the lives of the public and firefighters in Derry."
Mr Quinn said Crescent Link station now has seven fire fighters on shift, instead of the recommended nine personnel.
At Northland Road station the current staffing level is nine instead of the recommended 11, he added.
FBU members were both "disgusted and afraid" by the measures that came into effect on Tuesday, he added.
"They are afraid that they are going to end up attending a fire or an incident not having enough personnel to deal with it and letting down the public through no fault of their own."
The FBU said the impact of the £2m funding shortfall will be felt right across Northern Ireland in the long term.
A spokesman for the Department of Health, which funds the Fire Service, said the service was asked to find savings for this year's budget "that minimised the impact on frontline service delivery".
"The safety of the public and firefighters remains the priority," he added.
The Northern Ireland Fire and Rescue Service confirmed the changes to the staffing of the Aerial Ladder Platform (ALP) at Northland Station.
"This change brings it in line with the current crewing arrangements for the other ALPs at Springfield and Knock Stations," it said.