The NHS will waste £3.3 billion over the next five years on "bed blocking" as the number stuck in hospitals continues to rise, a new report predicts.
The study from the think tank ResPublica said delayed transfers in England was a growing problem, and Government efforts have so far failed to tackle it.
It called for greater investment in social care to drive down the numbers of people relying on the NHS despite being medically fit to be discharged.
In February, a separate study of NHS finances commissioned by the Government found about 8,500 bed-blocking patients are trapped in NHS hospitals every day - potentially costing the health service £900 million a year.
It said bed blocking - which occurs when patients are medically fit to leave but care has not yet been organised in the community - is a bigger problem for NHS hospitals than previously thought.
In the new ResPublica study, experts predicted that the NHS bill for bed blocking will reach £3.3 billion by 2020/21.
Experts behind the study forecast a 24% rise in the number of delayed transfer of care beds between 2015/16 and 2020/21. The associated cost to hospitals in 2020/21 will be £763 million - 51% higher than in 2015/16.
Caring for bed blocking patients in care homes, rather than in high-cost beds, would cost just £835 million across the entire five-year period, it said.
"This would generate a surplus of £2.4 billion currently due to be spent on inappropriate in-hospital care for patients," the study said.
Experts also pointed to the non-financial risks of bed blocking, including increasing risk of infection for patients, emotional poor health and a loss of independence and confidence.
"For older people, a hospital stay is often associated with marked functional decline - an inability to carry out tasks, including self-care, which were previously non-problematic," it said.
"Lying in a hospital bed typically means a lack of independence, decreased mobility and increased isolation.
"The longer an older person stays in hospital, the higher the risk of functional decline becomes. A delayed discharge can therefore take away day-to-day life as an older person has known it - irreversibly."
The report said the Better Care Fund set up by the Government to better integrate health and social care had so far failed to stem the rising number of bed blockers.
Backing the report, Conservative MP Dr Sarah Wollaston, chairwoman of the Commons health committee, said: "This report from ResPublica provides compelling evidence that social care cannot be seen in isolation from the NHS.
"There is an urgent need to improve access to social care and to address the delayed transfers of care and this can no longer be sidelined by policy makers."
Baroness Joan Bakewell, a champion for older people, said: "Care homes are vital to our community and most importantly to the people who live in them. I welcome ResPublica's report that acknowledges the important role that care homes play in our society and proposes important mechanisms for ensuring their sustainable future."
Phillip Blond, director of ResPublica, said: "The way health and social care work together needs to improve dramatically.
"The bed blocking crisis in the NHS is only getting worse - clogging up wards and leaving newly arrived patients on trolleys in hospital corridors.
"Meanwhile, as ResPublica showed last year, a staggering 37,000 beds could be lost in residential care homes over the next five years because the sector is losing money for every publicly-funded resident.
"To redress both of these awful situations, care homes should be given the necessary financial resources as an appropriate alternate care setting to alleviate the problem of bed blocking."
In February, the Government review led by Lord Carter of Coles found an increase in delayed transfers of care to around 5,500 patients per day.
But it estimated the problem was actually much bigger, with as many as 8,500 beds every day blocked with patients who are medically fit to be transferred.