Police have been called to Southern Work and Income offices more than 300 times since 2016.
The union representing Ministry of Social Development staff says they work with people when they are stressed and vulnerable, and that could get taken out on employees.
There were 305 police callouts to Otago and Southland offices, and 12 assaults, between 2016 and July 28 this year.
The Dunedin Central Community Link site had the most police calls at 68, followed by the Invercargill Community Link at 41 and the Mosgiel Service Centre at 37.
Nationally, there were 1047 callouts in 2020, up from 733 in 2006.
Public Service Association organiser Kathy Higgins said all working people should have a safe work environment, free from harassment and violence.
"Ministry of Social Development staff provide services for people with complex needs, at times in their lives where they are stressed and vulnerable.
"Staff are sometimes the focus of those frustrations."
The association had worked with the ministry at a strategic level of the organisation, and through member participation with workplace health and safety committees, to ensure the working environment was safe as it could possibly be, she said.
"We are always looking to see where improvements can be made.”
"Our members are passionate about the services they provide in their communities, and it always distressing when they are verbally or physically harmed at work."
In a statement the ministry said police were notified for a wide range of matters.
That could include, but was not limited to, the following: threats of self-harm, threats to staff members, notification of anticipated trespass, and clients seeking protection (such as in a domestic violence situation).
"The ministry has zero tolerance for people who demonstrate threatening and abusive behaviour towards its staff and clients, so all security events are interpreted in context of the potential worst-case outcome."
Threats of self-harm were also always taken seriously, the ministry said.
"The police are notified so that they can check in and ensure the safety of the client.
"These threats, dependent on severity, are recorded as ‘moderate’ at minimum."