Attacks on ambulance staff could see them wearing stab-proof vests.

Assaults have tripled in the past six years, sparking an investigation into the feasibility of stab-proof vests.

St John medical director Dr Tony Smith said call-outs to parties and bars often turn dangerous.

"Any situation where people are intoxicated can become unpredictable and violent," he said.

Last year there were 43 reported assaults on St John officers, up from 16 in 2003-2004.

Smith said safety was compounded in smaller cities where ambulances are usually staffed by a lone crew member. Stab-proof vests have been on the cards for over a year, he said.