Prime Minister Tony Blair pledged yesterday that the Government would do all it could to "turn back the tide" of violence against NHS staff, as he visited a scheme aimed at deterring attacks in hospitals.

At a nurses' seminar at the Royal London Hospital, Mr Blair said he had been shocked by the level of violence and abuse suffered by frontline NHS staff - a total of 65,000 incidents were reported last year.

"It is a minority of people who are doing it. It is something that has been growing over the years, and the principle of what we are trying to do is one of turning the tide back the other way," he told nurses.

He said he found the level of abuse against staff incredible.

"You always think that people treat nurses well. It is just amazing, isn't it, when you are looking after people and caring for them?"

Mr Blair was visiting a "red card" scheme aimed at deterring violence against staff working at Bart's and the London NHS Trust, which covers Bart's, the Royal London and the London Chest Hospital.

Under the scheme, outlined yesterday by Health Secretary Alan Milburn as part of a new "zero tolerance'' policy against violence, persistent offenders can face a year-long ban from a trust.

They are warned verbally that if they persist they will be given a written warning known as a yellow card. If the abuse persists, a senior manager or member of clinical care can issue a "red card" and exclude the patient from the hospital.

Emergency treatment is given to patients who have been excluded, but staff will seek to transfer the patient as soon as possible.

In the seminar, Mr Blair was told by Jonathan Asbridge, acting chief executive for the trust that since the scheme was set up, four patients had been given yellow cards, with three others given verbal warnings.

"We have only been on the brink of issuing one red card so far," he told Mr Blair.

Trust figures show that last year there were 74 reported incidents of assault, 55 of which resulted in injury to staff.

There were 85 reported incidents of verbal abuse and 53 reported incidents of threatening behaviour in trust hospitals.

So far this year there have been 29 reported incidents of assault, 23 of which resulted in injury, 49 reported incidents of verbal abuse and 65 of threatening behaviour.

Managers have said that patient behaviour has "vastly improved" under the system.

Mr Blair heard from Gerry Gallagher, 33, a staff nurse in the accident and emergency department of the Royal London Hospital, how he and another male nurse were punched in the face and a porter was punched in the head and bitten. Two men were prosecuted.

Mr Gallagher said the red card system made staff feel safer.

Under the system patients with mental illness, life threatening conditions and substance abuse problems are exempted.