Nursing leaders have called for a halt to the loss of hospital beds after a study revealed that patients were being left on trolleys for hours on end and treated in corridors.
A survey of 1,200 nurses and healthcare assistants painted a "worrying picture", with patients regularly being kept in ambulances or held in a queue because of a lack of trolleys and beds, the Royal College of Nursing (RCN) said.
In some cases, patients were on hospital trolleys for more than 24 hours, while others were moved regularly for non-clinical reasons so targets could be met, the UK-wide research showed.
More than a fifth of nurses said patients were receiving care in corridors or other unsuitable areas every day. The situation was even worse in emergency departments.
Most nurses said patient safety was being compromised, according to the study, published before the RCN's annual conference in Harrogate.
The RCN said that in the last decade in England the average daily availability of general and acute hospital beds fell by 22%, with trusts often cutting back for financial reasons.
RCN general secretary Dr Peter Carter said: "This survey paints a worrying picture of what is happening in our hospitals. Two years ago we warned that the need to make £20 billion in efficiency savings in England alone would risk sending the NHS back to the days of treating patients in corridors or areas not designed for care. Sadly, it looks like those days have now returned.
"We know that there is huge demand in A&Es and that it is growing at a substantial rate. However, this sort of situation is not only unacceptable from a patient experience and safety point of view, but causes great distress to families, carers and nursing staff.
"Treating patients on corridors or areas not designed for care is a high-risk strategy which can have a serious impact on patient care.
Patients need to be able to interact with staff, to be able to reach call bells and to know they are visible.
"They also need regular monitoring and easy access to equipment if their condition deteriorates. Finally, patients need to have their privacy and dignity protected. It is extremely disappointing that in this day and age patients cannot rely on receiving this care."
A third of those polled said "intolerable pressure" was being placed on staff, highlighting the stress frontline workers were under, said the report.
One respondent who works on an emergency surgical admission unit, said: "My shifts have been so awful I seriously consider how I can carry on nursing. I'm 37 with 14 years' nursing experience and have never known things so bad.
"Two of the day staff who had been on duty since 7am stayed on the ward till 23.00 to help safely staff the ward as the normal night-shift staff is two staff nurses, one HCA (healthcare assistant) and this was not safe. No help was available from anywhere else to increase staffing.
"I feel so demoralised and stressed and exhausted."
Dean Royles, director of the NHS Employers organisation, said: "Hospitals and services will have varying demands from area to area and service to service, and NHS employers fully recognise the importance of having the right staffing levels to provide the safest care.
"Organisations need to plan care in a way that is best for the patient. We encourage NHS employers to put the ward sister or charge nurse in the driving seat to plan the right staffing levels and ensure patients get the safest care.
"Although there are thousands more staff working in the NHS than a decade ago, we know demands on staff are increasing. Work-related stress is something we can't ignore - it has a major impact on the well-being of staff, their productivity and patient care."
Health Minister Simon Burns said: "There is no excuse for patients to be left waiting on trolleys. The NHS has beds free and available, and hospitals should be supporting their nurses to ensure that patients are admitted to them quickly. We will not hesitate to take action where we find hospitals failing to do so.
"With an ageing population, we need to make sure we care for people better outside hospital so that they do not need to go in for treatment. This will help reduce pressure on beds and nurses working in hospitals.
"Over the last year, we have seen the number of emergency admissions to hospital go down for the first time in years, but we need to maintain this improvement so that people stay healthier for longer and that nurses have more time to care for patients in hospital."