Thousands of older patients are being forced to stay in hospital long after they are fit enough to leave, doctors are warning – and the problem is being exacerbated by the coalition's cuts to council budgets.

In a survey of 502 doctors working in UK hospitals, 251 (50%) said the problem known as "bed blocking" – which costs the NHS tens of millions of pounds a year and forces needier patients to wait on trolleys – was worse now than a year ago, while 200 (40%) said it had not improved.

The poll was conducted for the Guardian by Doctors.net.uk, an online professional network to which 90% of UK medics belong.

Senior doctors and hospital bosses confirmed that the gloomy picture emerging from the poll reflected reality. They blamed local councils for making it harder for older people to access home help for vital tasks, such as eating and washing, and so forcing them to stay in hospital unnecessarily. Some questioned whether the NHS's ongoing reduction in its bed capacity had gone too far.

They also said that recent cuts to local council social services budgets were exacerbating the problem. Councils' recent restriction of access to social care by redefining the eligibility criteria has left older people who have been unwell trapped in hospital because they cannot afford to return to living independently at home.

Some patients with pressing medical conditions cannot be admitted immediately because healthy patients are occupying beds, said Dr Mark Porter, chairman of the British Medical Association's hospital consultants committee.

"I would estimate that several thousand such patients are in the NHS at any one time – that's a fairly significant problem," said Porter. "It's very distressing for individual patients, of great concern to the medical profession and an organisational problem for the NHS.

"If you have a core of people who should be moving on but aren't, your capacity to respond to new admissions is diminished and that leads to inefficiency and increased cost. There's definitely a feeling [among doctors] that it's difficult to move patients out of hospital who are medically fit but can't be discharged because there's nowhere else to go where they'll be adequately supported."

One respondent to the survey said patients with severe dementia were spending months in beds intended for those with acute medical problems because the NHS does not have enough places in wards specialising in dementia care. Another said that as many as 80% of the patients they see on an elderly ward "are fit to leave an acute bed but there is nowhere else to go".

Nigel Edwards of the NHS Confederation, which represents hospitals, said: "This is something we've been worrying about. There was a big improvement in this four or five years ago. But over the last few years there's been a feeling that in some places the situation has deteriorated again. People [hospital managers] who haven't had this problem before are starting to find quite large numbers of people that they are having trouble discharging because it's hard to arrange to get them back home or into a residential home."

Dr Tim Ringrose, medical director of Doctors.net.uk, said: "This research shows that hospital doctors throughout the UK are still struggling with the phenomenon of bed blocking. It's not good for patients and it's wasting valuable resources."

The Commons Public Accounts Committee has previously estimated that bed blocking costs the NHS £170m a year and has complained that an "intolerable" number of elderly patients wait too long after treatment before they are discharged.

Patients who have a prolonged spell in hospital face an increased risk of suffering complications associated with healthcare, such as infections, blood clots, and social isolation, added Porter.

Jennifer Dixon, director of the Nuffield Trust health thinktank, said bed blocking was caused by social services delaying their assessment of patients' needs or not providing the support they need; hospitals having inefficient discharge systems; and inadequate post-discharge community support services.

The problem should be seen in the context of growing numbers of A&E admissions, many of which could be prevented if health and social care outside hospital were improved, she said. "The NHS is not well integrated and people fall through the cracks leading to services that are not joined up, sub-optimal care and avoidable admission to hospital," Dixon added.

The Department of Health said it was making an extra £162m available between now and the start of April to help patients leave hospital sooner and live independently at home. "It's really important, particularly at this time of year, that we help people to leave hospital as quickly as they can, when they are ready. The latest figures show that 2,575 beds are unavailable due to delayed transfers of care," said Andrew Lansley, the health secretary.The money is intended to free up hospital beds by helping older people get more support before and after they leave and to reduce the high number who return to hospital soon after discharge.