The BBC's Kate Bouwerman reports on the biggest ever survey on violence in the health service

And in one in three cases the incident involved a weapon.

More than 4,000 health workers, including nurses, porters, cleaners and ambulance crews, took part in the biggest ever survey of violence in the NHS.

Unison said that one 999 ambulance worker has not worked since a night in May when a man held a gun to her head and pulled the trigger.

The gun turned out to be a replica but the worker, who has been in the service for 14 years, has been shattered by the experience, the trade union said.

Nurses also at risk

Nurses came second in the survey, with 46% reporting a violent crime in the past year.

The findings came as another survey, carried out by the Royal College of Nursing, revealed that more than seven out of 10 nurses felt safer out in the streets than in the hospitals where they work.

Dennis Killelay, who works for West Country Ambulance service, was the victim of two violent assaults in the space of 12 months.

He said: "The first incident will always stay with me. It was a routine call to a patient who had taken an overdose. When we arrived he was curled up in a corner beside a block of wood which I soon realised contained a knife.

"He lashed out with the carving knife and I was caught between him, my partner and the door.

"He chased after me and I will never forget the knife coming at me between the door and the frame. It seemed like an eternity before the police came."

Call for special help for ambulance crews

Bob Abberley, head of health for Unison, which represents many health service workers, said that although the government takes the issue of violence seriously, the Department of Health seemed to focus solely on nurses.

He called for special efforts to counter the risks run by ambulance crews.

At the Labour Party conference last month, Health Secretary Frank Dobson said the NHS had to better look after its staff.