The number of older people in England needing care will "outstrip" the number of family members able to provide it by 2017, a think tank has warned.
An Institute for Public Policy Research (IPPR) report estimates that by 2030 there will be more than two million people aged 65 and over with no child living nearby to give care if needed.
The IPPR said the country must "build new community institutions" to cope.
The government said it was working to make sure more people got care at home.
The IPPR report estimates that, of the two million people it says will have no child living nearby to care for them in England in 2030, 230,000 will need more than 20 hours of care per week.
'Left to cope'
Clare McNeil, senior research fellow at the centre-left think tank, told the BBC: "There won't be the family members needed to provide the types care that people see at the moment. That will mean there is more pressure on social services, and stretched services like the NHS.
"We need to have a fundamental rethink about the way that we how we look after each other later in life."
She said the government needed to invest in community networks and make it easier for people to combine care and work.
To fill the care "gap", the report suggested the UK should:
- widen the use of "neighbourhood networks", highlighting those run in Leeds by older people and offering activities to reduce social isolation as well as providing care and support
- invest in strengthening community groups in areas with the "weakest record for community-based care"
- follow international examples, highlighting initiatives in Germany, Australia and Japan's 10-year nationwide campaign "to train one million dementia supporters"
- house public services for different age groups, such as childcare and care for the elderly, together in the same buildings as is done in Germany
- strengthen employment rights for carers
The report also highlights the number of older people providing care, and estimates that the amount of "intensive" care provided by spouses and partners will rise by 90% over the next 15 years.
It says the average annual cost for those who pay for care is currently £25,000 for home care and £36,000 for a nursing home.
The government said it was working to integrate health and council care services to ensure more older people received care at home.
Helena Herklots, chief executive of Carers UK said it was " absolutely critical" that the government took action to fill the "policy void" around elderly care.
She added: "Our families, society and economy need reliable, affordable, quality care and support services and solid support and rights for those caring to ensure such breakdowns are prevented.
"Support for working parents has transformed in the last decade; the same shift in attitude must now be adopted to dealing with the care of older, seriously ill and disabled loved ones."