The Association of Professional Ambulance Personnel (APAP) is to highlight the issue at its conference on Friday.

The association has lobbied the government since 1997 to make anti-stab vests available for front-line staff.

However, despite the much-touted policy of zero tolerance of violence against medical staff, the government has failed to respond positively.

Jonathan Fox, APAP press officer and a para-medic, is among those who has been threatened while on duty.

'Angry and scared'

He said: "People have been stabbed. Thankfully nobody has been killed in the line of duty, but that is more by luck than judgement.

"People are often angry, scared and looking for somebody on who to vent their frustration. Invariably the first point of contact is ambulance personnel.

"While individuals face up to the personal cost of exposure to these incidents, our predominantly desk-bound administrators continue to dismiss the concept of personal protective equipment as a safety option for ambulance crews."

Mr Fox said a study by the London Ambulance Service had found that some managers were reluctant to issue body armour as they thought it provocative and inflammatory, and might lull ambulance workers into a false sense of security.

He said: "One manager said it would make us look like para-military paramedics, but they are just standard padded motorway jackets. It looks like you have got a couple of wallets in your pocket - that's all."