A budget shortfall could force a cut in the number of police officers on the beat in England and Wales, senior police have warned.
Police numbers are now at an all-time high
Chief constables and local authorities say government caps on council tax rises will leave a shortfall in the police budget.
They say £350m is needed to maintain current police numbers, now at a record high of nearly 140,000.
The Home Office says the budget for next year is still being considered.
The Association of Chief Police Officers (Acpo) and the Association of Police Authorities claim a funding increase of nearly 6% is needed, but that police forces may only receive a rise of 3%.
The groups will lobby more than 100 MPs at Westminster on Wednesday, warning that frontline officers could be forced into back office jobs to save money.
Acpo president Chris Fox said: "The last thing we want is a reduction in frontline policing but it is a very real possibility."
Baroness Ruth Henig, chairman of the Association of Police Authorities, said: "Central funding has fallen short of what we need in previous years but we have been able to make up the difference from the resources we get from council tax.
"We can't continue to do this because the public are getting fed up of rising council tax and the government are threatening to cap increases."
Speaking on the BBC Radio 4's Today programme Home Office Minister Hazel Blears said she would be making a statement in November, but insisted the government intended to see low council tax rises in the coming year.
"At the moment we are looking at how we can maximise the grant for policing, " she said.
"But this is in the context of the best policing we have ever had in this country.
"Over the last three years, we have seen 21% real-terms [funding] increases for police over and above inflation."
Ms Blears accepted many police authorities were facing rocketing pension costs as more and more officers retire.
But she added: "People knew when they were going to retire and the police authorities have known that they have got a spike in retirement.
"I have committed to reviewing the whole pension system, so we can take back some of the pensions responsibility into the centre."