Police forces in England and Wales could save £1bn a year by outsourcing backroom services to private companies, private security firm G4S has said.
The firm signed a £200m contract with Lincolnshire Police in 2012, with G4S staff now employed in backroom roles.
John Shaw, from G4S, said it has saved the force £6m a year - and other forces could "easily" make similar savings.
The Police Federation of England and Wales said any changes should "not compromise public safety".
Its chairman Steve White also said any savings would have to be reinvested into policing.
G4S, which faced heavy criticism when soldiers had to be deployed at the London Olympics after the firm admitted it could not fulfil its security contract, signed a 10-year deal with Lincolnshire Police in 2012.
Its staff are employed in police control rooms, custody suites, in areas of firearms licensing, as well as in financial, HR and technology roles.
Mr Shaw, the firm's managing director for public services, said the model in Lincolnshire could be replicated elsewhere, potentially saving £1bn a year across all 43 forces.
By Danny Shaw, BBC home affairs correspondent
Even if John Shaw is only half right the savings police could make from running their back and middle offices more efficiently would still amount to £500m - a colossal sum.
So why haven't more forces explored the approach he suggests?
Partly it's because some constabularies have an institutional distrust of the private sector, made more acute by G4S's security failings during the Olympics.
It's also perhaps due to the risk-averse nature of some forces: radical change is not in their DNA.
And it's down to this stark truth: changing the way police support services are managed means changing the managers. And, as one wise old policing hand put it, turkeys don't vote for Christmas.
Mr Shaw said: "We save about 22% per year here in Lincolnshire and on an individual force basis we think that similar levels of savings are easily achievable.
"But actually if you combine together you can then make greater savings."
He said there was no "one size fits all" solution, but added that there were "a range of things" you could do with other forces to make savings.
It comes as three police forces in the East Midlands - Leicestershire, Nottinghamshire and Northamptonshire - have asked G4S to carry out a feasibility study about the outsourcing of their control rooms.
'Drag and drop'
Sara Thornton, the National Police Chiefs' Council chairman, said police budget cuts meant forces were having to make "fundamental changes".
Some forces are already using private sector support while others "are considering it", she added.
But she said decisions about how to meet those targets would be taken "at local level" by chief constables and police and crime commissioners.
Police Federation chairman Mr White said: "Privatisation may be working well in some force areas but there is not a one size fits all solution.
"There is much to consider, not least varying force structures and accountability, but there needs to be a balance when considering private sector involvement.
"We are not averse to exploring greater efficiencies, as long as it does not compromise public safety and if any savings made are retained by the service to invest back into policing."
Former chief constable Peter Neyroud said you could not just "drag and drop" such a model on all police forces.
The former head of the National Policing Improvement Agency said he was cautious about "extrapolating too much from Lincolnshire example".