Delayed discharges from hospitals - so-called "bed-blocking" - rose sharply last year, according to figures released in Parliament.
Lack of community options can keep patients in hospital
In total, more than a million "bed days" were lost, with an increase of almost 30% in acute hospitals.
In previous years, incentives for the best-performing hospitals had led to substantial drops across the NHS.
The Patients Association described the figures as avoidable, unacceptable and extremely worrying.
Delayed discharges do not mean that hospitals are taking too long to get patients ready to leave, but are often due to delays in arranging the necessary level of care for patients who are often still heavily dependent following serious illness or major surgery.
In 2005/06, a total of 756,581 "bed-days" were lost due to delayed discharge in acute hospitals - each "bed day" meaning a single day in which a bed was unavailable for a new patient because its previous occupant was staying too long.
Last year, this rose to 963,776, an increase of almost 30%.
When delayed discharges from community hospitals - which submitted figures for the first full year in 2006/07 - are added to the total, there were more than a million.
The statistics were released in response to a Parliamentary question by the Liberal Democrats.
They said that the problem was costing the NHS £100 million a year.
Health spokesman Norman Lamb MP said: "It's a crazy situation. It's down to a failure to integrate effectively health and social care."
However, the NHS Confederation said it was hard to pin down a single reason for the sharp rises.
Jo Webber, its Deputy Policy Director, said: "No one should have to stay in hospital any longer than is necessary.
"There may be many different reasons for the increase in the figures; for example, local circumstances such as the supply of care home beds.
"Such difficulties will be of concern to both health and social care partners in an area."
She said that the joint working needed between local authorities and hospitals to ensure smooth discharges was "a difficult balancing act".
Back to hospital
The vice-chairman of the Patients Association, Michael Summers, said the figures were alarming.
"These delays are really avoidable, they're really unacceptable and unfortunately it's happening to a lot of people," he said.
"Last year there was an increase in bed blocking by something like 30% and involving almost 50% of NHS trusts, so it's not isolated by any means. It's extremely worrying."
Gordon Lishman, the Director General of Age Concern, said that the figures suggested delayed discharge remained a "major problem".
"No one wants to stay in hospital longer than they have to but it is sadly the case that older patients often have nowhere else to go," he said.
"The NHS and social services have failed to invest adequately in appropriate community services and support, which is leaving it unsafe to discharge some older people from hospital."
He said that the same deficiencies were leading to large numbers of patients having to be re-admitted to hospital because the right support was not in place to help them cope at home.
The Local Government Association said it was unfair to blame local authorities for any increase in delayed discharges.
A spokesman said: "These figures clearly demonstrate that health and social care are two sides of the same coin; where you underfund one, you overstretch the other.
"Support for services such as social care through the government grant has increased by just 14% in real terms since 1997.
"This is in stark contrast to the NHS, which has seen a 90% rise over the same period."
Care Services Minister Ivan Lewis said that over the past six years, there had been a 71% drop in the number of patients having their discharge delayed.
"By March 2007, on an average day, just over 2,000 patients had their discharge delayed compared to over 7,000 in September 2001.
"In areas where this remains a problem we expect NHS Trusts working with local authorities to address this issue as a matter of priority."