The scheme will be trialled for six months

Last year, 40 staff were assaulted, and another 40 were verbally abused by patients and their relatives.

Now the hospital may take out anti- social behaviour orders (Asbos) to keep staff safe and ban violent patients.

It comes as new research calls for the UK government to tackle the underlying causes of anti-social behaviour.

The study by the Joseph Rowntree Foundation said the scope of Asbos should be better defined and they should only be used within "agreed limits".

The research shows that two thirds of adults believe preventative action is the most effective way to tackle problem behaviour.

Incident form

In Merthyr Tydfil, the Prince Charles hospital is introducing a scheme called "Your Card is Marked".

Anyone acting in an aggressive or violent way in the accident and emergency department will have an incident form attached to their medical notes.

That will automatically trigger an alert on later visits and security staff will be warned that they are in the building.

Nurse Andrew Evans says he has been threatend with violence

In serious or repeated cases, the hospital would consider applying to local magistrates for an anti-social behaviour order (Asbo), which would ban offenders from the department for two years.

Russell Hoare, of the North Glamorgan NHS Trust, said: "If it was to go to an Asbo, then no doubt a magistrate would look very closely at what sort of restrictions would be placed on an individual.

"But if they were coming to the hospital, they would still get treated."

Andrew Evans, a nurse with 35 years' experience, has been a victim of abuse himself.

"I've been threatened verbally of physical abuse," he said.

"Patients have actually said to me, if you don't go away they will lay you out, at which point you phone the police."