Hospitals are having to redeploy nurses from wards to look after queues of patients in corridors, in a growing trend that has raised concerns about patient safety.

Many hospitals have become so overcrowded that they are being forced to tell nurses to spend part of their shift working as “corridor nurses” to look after patients who are waiting for a bed.

Nurses, doctors and hospital bosses have all voiced unease about the practice, which has risen sharply in recent weeks as the NHS has struggled to cope with the extra pressures of winter.

The disclosure of the rise in corridor nurses comes days after the NHS in England posted its worst-ever performance figures against the four-hour target for A&E care. They showed that last month almost 100,000 patients waited at least four hours and sometimes up to 12 or more on a trolley while hospital staff found them a bed on the ward appropriate for their condition.

“Corridor nursing is happening across the NHS in England and certainly in scores of hospitals. It’s very worrying to see this,” said Dave Smith, the chair of the Royal College of Nursing’s Emergency Care Association, which represents nurses in A&E units across the UK.

“Having to provide care to patients in corridors and on trolleys in overcrowded emergency departments is not just undignified for patients, it’s also often unsafe.”

A nurse in south-west England told the Guardian how nurses feared the redeployments were leaving specialist wards too short of staff, and patients without pain relief and other medication. Some wards were “dangerously understaffed” as a result, she claimed.

She said: “Many nurses, including myself, dread going into work in case we’re pulled from our own patients to then care for a number of people in the queue, which is clearly unsafe. We’re being asked to choose between the safety of our patients on the wards and those in the queue.

“When in the queue we are expected to cannulate and take bloods in corridors while patients are in chairs, on the floor or on trolleys.

“Some of our main concerns [include] ward patients [being] left in pain due to understaffed wards [and] late or missed administration of medication due to low staff numbers on the wards.”

At her own hospital some nurses who usually work on specialist wards now have to spend four hours of their shift in a corridor looking after often very sick patients.

“This is not only leaving the wards short but also putting huge amounts of stress on staff. It has hit staff morale as many staff don’t want to leave their own patients that may be acutely unwell or in pain.”

Dr Adrian Boyle, the vice-president of the Royal College of Emergency Medicine, which represents A&E doctors, said: “Looking after people in corridors is demoralising and shameful for staff. People do feel that it’s a failure when they have to look after people in corridors.

“If we had enough beds at the right time we wouldn’t have to do corridor care.”

Growing numbers of patients are being delayed either with ambulance crews outside an A&E unit because staff are too busy to allow a handover to take place or, once they have been dealt with in the emergency department, on a trolley while they wait for a bed.

Hospital bosses voiced their concern about the rise of corridor nursing.

“The fact that some trusts may have to redeploy nurses away from other wards to look after patients who are temporarily waiting in hospital corridors shows the level of strain the health service is now under,” said Saffron Cordery, the deputy chief executive of NHS Providers, which represents NHS trusts in England.

“Long waits or being treated in corridors or waiting rooms is not appropriate for patients, risking their dignity and safety. Although staff will do everything they can to provide the best possible care, these are extremely difficult working conditions. Corridor wards and other temporary arrangements add stress to an already pressurised working environment.

“We must not allow this to become the new normal.”

An NHS spokesperson said: “While the NHS has more beds open this winter than last, our A&Es have had to treat more than a million extra patients over the past year. So as well as 50,000 more nurses and extra hospital beds, over the next few years it’s also going to be necessary to rebuild and expand most A&E departments across England.”