Dorset and Devon & Cornwall Police to merge services
Dorset Police is to share some services with Devon & Cornwall's force following an agreement to form a cost-cutting "strategic alliance".
Initial plans have already identified at least £12m of cuts across both forces.
Decisions about which functions will be merged or handed to external organisations will be made over the next 12 months, a statement said.
No announcement has been made about how many jobs could be lost.
A Dorset Police spokesman said both forces would remain as separate organisations with their own commissioners and chief constables but more policing would be delivered jointly by the two forces, resulting in shared leadership for some functions.
In a statement, Devon and Cornwall Police said: "Working together more closely and sharing many services is a significant move that will allow the forces to continue to provide efficient and effective policing."
Most changes will be to internal structures so "will not be noticeable to local people", the statement said.
Devon & Cornwall Police Chief Constable Shaun Sawyer said: "We have lost 450 police officers from Devon and Cornwall with up to 500 police staff as well.
"If we don't make these kind of savings and work this way it'll be another 800 people."
Nigel Rabbitts, chairman of the Devon & Cornwall Police Federation, said: "We welcome anything which is going to help with the budget but it is a consequence of the budgetary disaster which both forces are in.
"Will this actually put resources thinner over the three counties and islands rather than making us more efficient?
"If it does make the savings, we will welcome this but our concern is it will lead to further job reductions."
Dorset Police and Crime Commissioner (PCC) Martyn Underhill said: "We are facing unprecedented times in policing. We need to deliver more for less and this alliance will help us achieve that."