Money is being diverted away from road repairs, leisure centres and local bus routes in order to maintain the struggling social care sector, council leaders have warned.
The Local Government Association (LGA) said councils are increasingly having to redirect cash from other local services to prop up the funding gaps in the sector.
The nation's care and support system is "in crisis", the LGA said as it called on the Government to invest in social care in the Autumn Statement.
It said that the current funding gap in the social care system is hampering councils' ability to support the nation's most vulnerable adults.
The LGA said that councils spend around 35% of their budgets on adult social care and are increasingly having to divert money away from other services to plug gaps.
Adult social care services face a potential funding gap of at least £2.6 billion, according to a new report from the LGA.
Meanwhile disability charity Leonard Cheshire warned that as a result to cuts in care, many people are left without the help they need or are being left trapped in their homes for "days on end without vital support and human contact".
A poll of 1,000 working-age disabled Britons conducted by the charity found that 48% who say they need social care are not currently receiving any support.
In the foreword to the new LGA report, Councillor Izzi Seccombe, chairwoman of the LGA's community wellbeing board, said: "For too long the service has too often been seen by decision-makers as an adjunct to the NHS, rather than a service of equal importance.
"A lack of recognition in terms of profile has combined with a lack of recognition in terms of funding to place our care and support system under enormous pressure.
"The situation now is critical and it is no exaggeration to say that our care and support system is in crisis."
Senior vice chairman of the LGA, councillor Nick Forbes, added: "Councils have long argued that it is a false economy to pump money into the NHS but leave social care so chronically underfunded.
"The Government must use the Autumn Statement to provide councils with the funding to ensure we have a fair care system where everybody can receive safe, high-quality care and support."
The King's Fund said that spending cuts have left social care in a "perilous state".
Richard Humphries, assistant director of policy at The King's Fund, added: "The top priority for the Autumn Statement later this month must be to increase funding for social care.
"This is a key test of the Prime Minister's promise of a more equal country that works for everyone - there is no more burning injustice in Britain today than older and disabled people being denied the care they need to live with independence and dignity."
Leonard Cheshire's chief executive Neil Heslop said: "It is a national scandal that thousands of disabled and older people do not have the support to do everyday tasks such as washing and dressing, and even more shockingly, no support to eat.
"A lack of social care creates a perfect storm of problems that significantly reduces the life chances of disabled people.
"The right social care allows people to stay well, be independent, get jobs, volunteer, have relationships and contribute fully to society. But as our research shows, dignified everyday care is simply not available to many people, and that is unacceptable."
On Monday Dr Sarah Wollaston, chairwoman of the Commons Health Committee, called for an urgent cash injection to head off a looming "crisis" in social care.
She said that Chancellor Philip Hammond should allocate more money to the sector when he delivers his first Autumn Statement next month.
Last month the Care Quality Commission warned that the social care sector was approaching "tipping point" as it called on the Government to inject more cash into the system.
A Department of Health spokeswoman said: "This Government is committed to ensuring older people throughout the country get affordable and dignified care.
"That is why we are significantly increasing the amount of money local authorities have access to for social care, by up to £3.5 billion by 2020.
"We recognise the challenges faced by the sector and are working with the Local Government Association and the Association of Directors of Adult Social Services to support councils to make efficiencies, whilst meeting their legal duty to ensure a sustainable provider market for their populations."
Mr Forbes, who will be addressing the National Children and Adult Services Conference tomorrow, added: "Councils have had their budgets significantly reduced by central government and are increasingly having to manage greater demand with less money and are working hard to try and find ways to protect services, such as caring for the elderly and disabled.
"This means having less to spend on many of the other services people value, such as filling potholes and funding leisure facilities like pools, gyms and parks, libraries and museums."