Almost one in three families do not have the right support in place to care for elderly relatives leaving hospital, according to a new report.
Many families believe discharging the elderly from hospital too early is a far bigger problem than them being delayed, it said.
Figures released by the Royal College of Emergency Medicine (RCEM) last week showed hospitals are experiencing major problems discharging patients who are medically fit to go home.
In some places, around a fifth of hospital beds are occupied by patients who cannot leave - so-called "bed blockers" - because there is not the right support in the community for them.
Experts say the increasing problems in social care are having a major impact on the NHS.
The new report, from the charity the Royal Voluntary Service, found almost one in three families would not be able to care for an older relative after they leave hospital without extra support.
The study of 1,000 people with parents over 75, compiled with help from the King's Fund think tank, found 30% believing their support network is not strong enough to cope without external help. Many said this was due to their own work and family commitments.
A third of families (33%) said they live too far away to keep up with the daily care needs of relatives, such as dressing, cooking or shopping.
Juggling work (28%) and childcare (9%) adds pressure, while one in five (21%) people surveyed said they felt guilty about not being able to do more to help older relatives.
Nearly a fifth (19%) had found premature discharge from hospital a problem, compared with 3% who said delayed discharges were an issue.
And almost a third (30%) of people had not had their relative's needs properly discussed before they left hospital.
The report calls for better care for vulnerable older people in their own homes following discharge from hospital, and a greater role for volunteers.
Chancellor George Osborne announced last week in his spending review that councils would be able to add up to 2% to council tax bills to provide an extra £2 billion for social care.
David McCullough, chief executive, Royal Voluntary Service said: "The funding top up announced for our struggling care sector is very welcome.
"However, the obvious fact remains that many, many older people won't qualify for formal care, but will still need support if they are to recover well after a hospital stay.
"Often at discharge, there is an expectation that family and friends will step in, but in modern-day Britain not everyone has this supportive circle close by.
"There is a need to make a good assessment of the strength of an individual's available network and imaginative solutions are needed where formal care is in shorter supply.
"This is where the voluntary sector can step in to bolster support; families would give if they could."
David Buck, senior fellow at the King's Fund, said: "Delayed discharges are a key problem for the health and care system.
"But families and patients say premature discharge is a greater concern. We know that older patients who felt they left hospital too early are much more likely to be readmitted and this new report shows that families are very concerned about this too."
A Department of Health spokesman said: "It's vital that older people get the support they need to leave hospital, so they can recover in the comfort of their own home or care home and our hospitals are free to care for other patients.
"We are committed to the NHS and its values, which is why we have invested £10 billion to fund the NHS's own plan for the future, including joining up health and social care services to help people stay well and avoid unnecessary stays in hospital.
"Alongside this, the Spending Review gave local authorities access to up to £3.5 billion extra a year by the end of this Parliament, helping give greater certainty on adult social care funding."