County councils might need to make almost £1bn worth of savings next year.
Research by the County Councils Network says its members will set out £685m in savings and cuts next February to balance their 2019-20 budgets.
An extra £233m of ‘unplanned’ frontline service cuts, which have not yet been identified, will also be needed.
This comes after CCN members overspent by £264m on children’s services in 2017-18.
As 13 county councils have already levied the maximum adult social care precept in the last two years, they will be unable to add anything extra to council tax bills next year.
Reductions are likely to result in cuts to care and public health services, the introduction of extra charges, the closure of recycling centres and bus routes, and fewer potholes being filled.
With counties using at least £185m of reserves this year, their ability to draw down the same levels next year to offset cuts is becoming increasingly limited. CCN said rural councils are likely to draw down £65m less in 2019-20 compared to this year.
In the last three years, ministers have stumped up extra cash for councils at the last minute following intense lobbying.
In its response to the local government finance settlement technical consultation, CCN has once again called on the government to provide its members with extra funding to help tackle budget pressures.
Nick Rushton (Con), CCN finance spokesman, said: “County authorities are in a serious and extremely challenging financial position. The further planned funding cuts and continued escalation of costs outside of our control will make this bad situation even worse.”
He said “there is not enough money today to run vital services” and added there will be even less next year.
Cllr Rushton, who is also Leicestershire CC leader, said his own authority is facing £40m cost pressures in 2019-20. Some of that can be offset by increasing council tax “but further savings will be necessary”, he warned.
Cllr Rushton urged the government to “intervene if we are going to avoid unpalatable cutbacks”.
“It is only with extra resource delivered on a sustained basis that will allow delivery of services that the public deserve, growth of our economies, and protection of the vulnerable and elderly,” he said.
The government “must act” to create a fairer funding system as well, said Cllr Rushton.