Police budget cuts will mean 1,500 staff will be lost over the next four years, the chief constable of West Yorkshire Police has said.
Sir Norman Bettison said there were 13 reviews going on within the force to consider ways of saving cash.
But he insisted that front line services would not be cut and local policing and emergency responses were a priority.
West Yorkshire Police Federation said the cuts would have a knock-on effect.
The force has an annual budget of £450m, but must cut £90m from that over four years.
Sir Norman said that 85% of the total budget was spent on staff.
He said: "The aggregate figure over the next four years is, I predict, this organisation of 10,500 people will have 1,500 fewer than it has now."
He said that natural wastage over that period would account for some of the jobs.
Sir Norman said: "There are two central drivers, two real things I'm prepared to die in a ditch over.
"The first one is local policing will not suffer, the sort of policing you see when you open your curtains.
"And the emergency response of the police at the times when people are feeling vulnerable, under threat or have suffered some criminal act or tragedy."
"The second thing to remember throughout this organisational change period is the human cost that goes with organisational change."
In looking for efficiencies the chief constable said that crime prevention initiatives, IT and roads policing were some of areas being considered.
He said that crime prevention initiatives could be managed from a headquarters level, IT may not develop as quickly as he hoped and the focus on roads policing could change.
Sir Norman said workers dealing with abusive images, combating organised crime and the Homicide and Major Enquires Team accounted for about 55% of the day-to-day staff.
"We have 13 consecutive reviews in place looking at all that support function," he said.
He said that the number of occasions when crime scene investigators, such as fingerprint teams, were deployed would be cut back.
"All of the things that sit behind the front line are going to have to be reviewed and revised," he added.
Michael Downes of the West Yorkshire Police Federation said taking staff away from so-called "back offices" "at some point they will drain on front-end services".
Mr Downes said the cuts would impact on a major way "on policing not just in West Yorkshire but across England and Wales".