NHS funding should be diverted to fund social service care if needed, says the Local Government Association chairman.
Access to care varies widely around the country
Sir Simon Milton said the rationing of social care would get worse if councils did not get adequate funds in the next government spending settlement.
He said such care had a key role in preventing people ending up in hospital, which was more costly.
Local Government Minister John Healey said councils should wait for the settlement, not try to second guess it.
NHS deficits have been in the headlines in recent years, but social services have also felt the pinch.
Sir Simon said the NHS had received a 90% increase in its budget since 1997, compared with 14% for social services.
He argued council social care staff play a key role in supporting elderly people and those with long-term conditions within the community.
Such care is seen as vital in preventing people developing serious problems and ending up in hospital - one of the major planks of NHS policy.
Sir Simon said councils were hoping for an annual 2% increase in real terms - that is above the rate of inflation - and if it dropped much lower they would struggle to provide services without huge hikes in council taxes.
The LGA said, if necessary, 0.5% of the NHS budget should be diverted into preventative care services.
Sir Simon said without adequate funding lower level care, which includes basic home care help, would be the first to be hit.
"Without additional funding, local government may potentially face a situation, by as early as 2009, where it cannot afford to provide support to 370,000 people with lower levels of need.
"This is not a situation older people and their families expect or deserve.
"There is a strong and compelling argument for ministers to invest in preventative services, provided by councils.
"This would save the NHS money and consequently provide better value for the taxpayer."
Professor John Appleby, chief economist at the King's Fund think tank, said he had some sympathy for the LGA call.
"They have a real need for more funding and the preventative work social care does is so important with the direction the NHS is heading.
"But money is tighter this time round so it is going to be challenging for both local government and the NHS."
Bryan Stoten, chairman of the NHS Confederation which represents over 95% of NHS organisations, said it was key that both the NHS and local government were given adequate funds.
He said: "It is simplistic to suggest that taking money away from one public organisation - the NHS - and giving it to another - local government - is the solution.
"The NHS not only deals with the longer term problems of preventative care, they also deal with the immediate healthcare needs of their local population. Partisan solutions will not work."
The Treasury said there would be no announcement on funding until the comprehensive spending review was announced later in the year.