The way the social care system is funded needs urgent reform to meet the needs of an ageing population, health experts said on Tuesday.
More public funds will have to be found to stop vulnerable older people from falling through the net and to support those who face high, unpredictable care costs.
A report from the Nuffield Trust said that without reform, spending on social care will rise by almost £10 bn over the next 15 years, from £14.6 billion in 2010/11 to £23 billion in 2025/26.
The health care think-tank says much of that money can be found from the £140 billion of state funding already spent on older people.
But if it cannot, higher taxation of more wealthy older people could be needed.
It suggested the shortfall could be plugged by restricting some of the universal benefits, such as the winter fuel allowance, and free TV licences and bus passes.
The Nuffield Trust said a £1.5 billion NHS under-spend could be used to protect and extend people's eligibility for care, and also support more preventative work.
There should be a review of the balance of spending across health, social care and welfare payments, the report said.
The government should shift some of the health budget towards social care, which together would create a larger pool of shared public money to pay for care services.
A cap on the cost of lifetime care to individuals is also being considered, which would be between £35,000 and £50,000.
Recent cuts to social care budgets have highlighted a mismatch between funding and demand, so a growing number of people on low incomes are no longer eligible for state support.
In addition, many people are forced to sell their homes to meet the costs of residential care.
Estimates suggest an additional £3.6 billion of public spending on social care will be needed each year by 2025/26.
The government is finalising plans on social care reform and is due to publish a White Paper and draft Bill next month.
Anita Charlesworth, chief economist of the Nuffield Trust, said: "The social care system is looking increasingly unsustainable. There is growing support for the principle of sharing costs between individuals and the state.
"But it is clear that to meet the needs of an ageing population and tackle the perceived unfairness in the current system, both individuals and the government will need to spend more on social care.
"The government spends some £140 billion a year on older people through the health, social care and welfare budgets.
"If you were starting with a blank sheet of paper, is this the best balance of spending to ensure quality of life, dignity and respect in older age?
"For instance, would people support shifting some of the money that goes on health and on benefits for better-off older people to fund a fairer, higher quality social care system?
"Or should older people with wealth be asked to contribute more to the social care budget from higher taxes?
"All of these are key questions that need to be addressed by the government ahead of the publication of the draft Bill."