Police Commissioner Peter Marshall says the force will be cutting staff numbers in an effort to save money but there will be no reduction in frontline staff.
Staff have been told to find savings of 3% from operating costs and 4% from non-sworn police staff cuts.
This means about 125 jobs will be lost, 75 of them from existing vacancies that won't be filled.
There will be job losses for non-sworn support staff and police will centralise administration, HR and finance roles.
Police Minister Anne Tolley says there will be an increase in frontline police hours and a greater emphasis on preventing crime.
A decision will be made in the next couple of months on the number of non-sworn police staff who will be made redundant.
Police Association president Greg O'Connor says if backroom staff are taken away then front line staff are the ones who have to spend time doing their work.
Mr O'Connor says while there will be more than 100 fewer staff there won't be any reduction in demand for services, which means the level of service will drop.
Labour Party MPs say the cuts in police support staff will result in police officers spending more time off the frontline.
Labour's police spokespeson Kris Faafoi says the move will mean police are spending more time on administrative work and that will have an impact on the frontline service.
But Ms Tolley says police are making changes which will increase frontline police hours, with more of a focus on crime prevention.