Dave Galligan, health spokesman for the public services union Unison, said hospitals' promises of 'zero tolerance' against those who attack doctors and nurses are not reducing the number of attacks.

There is no evidence to suggest there's any substantial progress by trusts towards pursuing private prosecutions

Dave Galligan of NHS union, Unison

Figures compiled by BBC Wales' Week In Week Out programme reveal that nearly 2,000 incidents of abuse were recorded in Welsh hospitals this year.

But the number of violent incidents may be set to soar as many health service bosses said they noticed the overall trend was upward.

The programme shows how nurses, doctors and paramedics working round-the-clock are bearing the brunt of violence against NHS staff.

They have to deal with people out of control through drug and alcohol abuse, as well as the public's anger over bed shortages and long waits for treatment.

Unions believe that many more incidents of violence against staff are not being recorded.

Figures

Three NHS trusts - including one covering Prince Charles Hospital in Merthyr Tydfil and another Ysbyty Gwynedd in Bangor - did not offer figures.

Mr Galligan said: "What I would like to see is a whole sea-change of culture - a message has to be sent and the people that can send that message is the employer, the trust - prosecuting people as a matter of course who offend, who are violent.

"It's all well and good having a notice on the wall, but people don't always take much notice of pieces of paper.

"There is no evidence to suggest there's any substantial progress by trusts towards pursuing private prosecutions, on behalf of the trust, on behalf of the staff who are the victims of assault."

The programme interviewed a number of NHS staff who had been attacked.

Frightened: Sue Simms was attacked on the ward

Sue Simms, a nurse at the casualty unit of the University Hospital of Wales in Cardiff, suffered a sexual assault while on duty.

The incident has left her angry and upset.

She said: "I thought I could handle myself, I'm trained to, but I just froze, absolutely terrified - it really did frighten me, it's something that happens to other people on television, not here."

On the same shift, nurse Emily Miles was attacked while trying to help a young woman.

She said, "I asked one of the doctors to take a look at her and he asked her had she taken any medication, and she didn't answer.

Paramedics

"I leant forward and said, 'have you taken any medication?', and with that she just punched me in the eye and I was thrown across the room.

"As a result I developed a cataract in that eye and I needed surgery."

But it is not just nurses who are in the firing line of abuse.

Paramedics who are first on the scene of an emergency are often greeted with obscene language and even physical attacks that have included bites, kicks, death threats and threats of HIV contamination.

Week In Week Out is screened on BBC One Wales at 2235 GMT on 5 November 2002