English councils face a funding "black hole" of more than £50bn over the next six years unless extra cash is made available, a lobby group has said.
The County Councils Network said rising costs and demand for services, like social care, could mean councils resort to providing the "bare minimum".
It said yearly council tax rises and making services more efficient will "not be enough" to plug the gap.
The government said councils will have access to £46.4bn this year.
The County Councils Network, which represents large, often rural authorities, commissioned PricewaterhouseCoopers to analyse the future financial stability of councils in England.
In its research, to be published on Wednesday, it found that even if council tax is increased as much as possible, and all money held in reserves is used, there will still be a funding shortfall.
Paul Carter, County Councils Network chairman, said: "If government does not provide additional funding for councils over the medium term, many local authorities will resort to providing the bare minimum, with many vital services all but disappearing."
He said even "draconian cuts won't be enough for many well-run councils to balance the books" and council finances will be left in "disarray with many of us struggling to deliver even the basic level of local services".
The organisation has called for clarity from the government about spending plans.
Councils receive their money from a mix of central government grants and money raised locally through taxes and charges.
Since 2010, council spending power, including funding from central government and local taxes, has fallen by almost 30%.
'Funding debate needed'
Staffordshire County Council leader Philip Atkins said he has had to cut spending while facing growing demand and costs for care services.
"We really need a proper adult, cross-party debate on the future funding of adult social care," he said.
"We need to know how we are going to fund this in the future.
"It can't fall just on the council tax and the business-rate payer."
A government spokesperson said this year's local government finance settlement included extra funding for local services.
"Local authorities will have access to £46.4bn this year, a real-terms increase that will strengthen services, support local communities and help councils meet the needs of their residents."
The government will be looking at funding for services as part of a spending review, the spokesperson added.