More than 30 Humberside Police staff are at risk of losing their jobs, according to Unison.
The union is calling on the force to reconsider plans which it said could affect 32 staff, including investigators and domestic abuse teams.
Humberside Police said the changes were part of Operation Balance, which aimed to save £5m to make the force financially stable.
Chief Constable Chris Todd said the force had been consulting staff and Unison, and added: “These are very difficult decisions for us to make.”
Unison said staff who could lose their jobs included 12 investigating officers and three licensing officers.
CCTV specialists, warrant officers and a missing-persons officer could also go, according to the union.
As well as the job losses, the force intended having no police community support officers working beyond 20:00 BST, it added.
Unison has been told the work currently undertaken by the staff at risk would be transferred to police officers.
It also understands that Humberside Police intends to recruit more officers.