Council cuts to care in England are so severe there is a real risk families may take legal action, experts say.
In a joint plea to ministers, the Nuffield Trust, King's Fund and Health Foundation said the sector was facing a major funding shortage.
The think tanks said cuts were so deep, councils may no longer be meeting their duties to the elderly and disabled.
The government says it is investing in the care system with £5bn set aside for the NHS to work with the care system.
An additional £1.5bn is being added to that by 2019, while councils have been allowed to increase council tax by 2% a year to invest in care services.
The latest warning about care services comes ahead of Chancellor Philip Hammond's Autumn Statement later this month on government spending.
Councils are complaining they have not been given enough cash. and last month, the regulator, the Care Quality Commission, said council care cuts were one of the major factors behind the growing demands on A&E units.
The three think tanks, which are making a joint submission to ministers ahead of that announcement, highlighted figures showing how councils had started reducing the amount of support they provided to older people.
The numbers getting help from their council with care had fallen by 26% to 850,000 in the four years to 2014
Spending on care by councils had fallen by 25% in real terms in the five years to 2015, to £5.1bn
Additional money from the NHS and increased contributions from individuals had topped this up to £7.2bn, but that still represented a cut of 9%
More than 40% of money paid to care homes came from people paying for themselves
One million people with care needs now receive no formal or informal help - a rise of 10% in a year
Once younger people with disabilities are included, the funding shortfall was likely to be in the region of £1.9bn next year
Richard Humphries, from the King's Fund, said it was clear councils were struggling to meet their statutory duties under the Care Act, including promoting well-being and providing high quality care to elderly and disabled people.
He said while he was not aware of any legal action yet, he pointed to rising numbers of complaints about care being made to the the Local Government Ombudsman and a rise in the number being upheld as a sign that could change.
"That shows that councils are struggling. It is a warning sign. We could start seeing people taking legal action," he added.