Research published in the Lancet Public Health journal predicted the number of adults over 85 needing round-the-clock care will almost double to 446,000 in the next 20 years.
The number of over-65s with the same high dependency levels will also increase by a third, to more than 1 million people, over the same period.
The research, conducted by academics from Newcastle University and the London School of Economics and Political Science projected that the number of adults aged 65 and older living without care needs is set to rise from 5.5 million in 2015 to 8.9 million by 2035.
The authors warned this will increase reliance on informal carers, such as family members, who already provide around £57bn worth of care annually in the UK, and said this is not a “sustainable solution”.
Carol Jagger, co-author of the research paper and professor at the Newcastle University Institute for Ageing, said: “Our study suggests that older spouse carers are increasingly likely to be living with disabilities themselves, resulting in mutual care relationships.
“On top of that, extending the retirement age of the UK population is likely to further reduce the informal and unpaid carer pool, who have traditionally provided for older family members.
“These constraints will exacerbate pressures on already stretched social care budgets.”
Nick Forbes, senior vice chair of the Local Government Association, said: “This report is a further warning of the crisis in adult social care and the urgent need to plug the immediate funding gap and find a long-term solution on how we pay for it and improve people’s independence and wellbeing.
“With people living longer, increases in costs, decreases in funding, care providers closing and contracts being returned to councils, the system is at breaking point, ramping up pressures on unpaid carers who are the backbone of the care system.
In June, the government announced it would delay its green paper on social care, a move that was criticised by social care leaders.
The LGA recently published its own social care green paper in which it suggest over 40s should pay extra tax to fund social care.
The Department of Health and Social Care has been contacted for comment.
