They say the unit at Dewsbury and District Hospital has been chronically understaffed for at least six weeks.

In August, two beds were taken off the ward because staff were unable to cope.

However, it is said that staff are still struggling to deal with the remaining 10 beds and provide patients with the high standard of care they were receiving before the shortages.

A member of staff from the hospital, who did not want to be named, said: "At times, staff can't cope. You have to start prioritising certain patients. Staff can only do the things that are life and death. It's become a crisis."

Before the shortages, the standard number of staff on the ward for a weekday shift was five fully qualified nurses and one health care assistant.

The Mid Yorkshire Hospitals NHS Trust accepts that staff levels have fallen to as low as three registered nurses and two health care assistants – the minimum acceptable standard.

It is claimed by staff, however, that due to individual circumstances, the numbers have fallen below this minimum at times over the last six weeks.

"It has mainly been three nurses and one health care assistant, sometimes three and none, which is really pushing it as the unit is very often full," said the staff member.

"Four people really struggle. I know there have been shifts where there are only two nurses and one assistant. That is really dangerous. Something serious could happen to a patient.

"We are doing the best we can but you start thinking that if you spend less time washing a patient, or administering drugs, then you'll be able to spend more time with critically ill patients. Patients are getting care, just not as soon as they should.

"If two patients on the unit got acutely ill, it would be incredibly hard for the staff to manage. If three got ill, which is perfectly possible, it would be terrifying.

"So far, we've somehow managed to cope, but staff are pushing themselves further than they should have to. When people are under so much stress, and are so exhausted, that's when mistakes are made and accidents happen."

Michael Summers, vice chairman of the Patients' Association, said this was not an isolated incident and that many acute units were suffering shortages.

"We have heard about similar things in other hospitals. It's disgraceful and completely unacceptable. Patients are being let down.

"Patient care should be the primary concern," he said.

The trust says there have been staff shortages but says no patients have been put at risk.

Tracey McErlain-Burns, chief nurse and director of patient experience for the trust, said: "We have had staff vacancies and absences, but it is being managed on a day-to-day basis. Two beds were closed in August."

She said that they have hired two new fully qualified nurses and one extra health care assistant to deal with the present shortage.

However, she denied that the department has ever had below the minimum level of staff based on a full ward. She said: "The roster may have shown two registered nurses and one health care assistant, but we have people actively managing this who have been able to assess the critical care service and move staff into Dewsbury."

Mr Summers described this method as "borrowing staff" and said it was a "facade".

He said: "They are simply trying to meet targets and fill a few boxes. Borrowing from Peter to pay Paul is not how to keep a high standard of patient care."

Dr Ian Sutcliffe, respiratory consultant based at Dewsbury and District Hospital, said: "I provide medical care for a significant proportion of the patients on the HDU. I'm well aware and recognise the pressures on staffing levels as far as the nurses on HDU are concerned, and I know the trust is taking steps actively to address this.

"The nurses have demonstrably maintained a professional and caring approach to their work. There is in my own experience not a shred of evidence to suggest that patients' care has suffered in any way."