The paramedics union has accused the Victorian ambulance service of gagging its members during enterprise bargaining negotiations.
Ambulance Victoria guidelines prohibit workers from posting photos of ambulances, or of themselves in uniform, online.
Paramedics are also required to gain the approval of superiors before they comment on work issues on social media websites.
Ambulance Employees Association secretary Steve McGhie says the policy is heavy-handed and silences paramedics.
"We're in the middle of enterprise bargaining negotiations and I think it's in response to that," he said.
Ambulance Victoria says the policy is not a gag, but in place to uphold professionalism.
It says the rules are similar in other government departments.