"Serious" incidents included physical harm that required medical treatment, threats made with an intention to harm, stalking or intimidation of staff.
"Moderate" incidents included assaults where there was no injury, aggression or abuse.
Bay of Plenty regional commissioner for social development Mike Bryant said a hike in security incidents was largely because staff were reporting more.
"Post-Ashburton our staff are escalating incidents, as we can no longer consider many day-to-day incidents as simple idle threats.
"We need to make it clear that threatening behaviour is not okay," he said.
He said Work and Income staff did more than 1000 face-to-face interviews per week in the Western Bay. Staff were trained to treat people with respect and expected the same from clients.
The impact on staff was way beyond just numbers on paper, Mr Bryant said.
Security measures were in place, such as open plan offices, controlled access and security guards on site.
Spokesman for NZ Beneficiaries and Unemployed Workers Union Miles Lacey said most of the people who lashed out at staff were not thugs or bullies but people who cracked under strain.
He said it was hard to pin down a specific reason for abusive behaviour but it could be related to "endless bureaucratic hurdles", communication failure or mental health issues.
He said the benefit system was increasingly punitive and people had to "jump through endless bureaucratic hurdles just to keep their benefit".
Tommy Wilson, of Te Tuinga Whanau Support Services, said people wanted to know they were cared about before anything else.
"All violence comes from anger, all anger comes from fear and all fear comes from not knowing or understanding. This is the cycle of what you see manifest itself at Winz offices."
Winz staff did not have the luxury of time and it was a daunting environment for clients to go into when they knew it was their last chance - "if they walk out with nothing, they've got nothing to go home to".
Mr Wilson said Winz needed to work out "why these people react the way they do and not work out how you punish them for acting that way".
NZ Beneficiaries and Unemployed Workers Union tips for frustrated clients
- Always go to interviews with the information requested by Work and Income. It will avoid delays and lost paperwork.
- Be prepared to negotiate or compromise.
- If you are angry because your benefit has been stopped or because you have been declined assistance ask the case manager to explain why in plain terms.
