A protester claims police broke her arm as she was being moved out of the way of a bus carrying weapons expo delegates.
The delegates spent two days attending the New Zealand Defence Industry Association conference in Palmerston North on Wednesday and Thursday last week.
But Hamilton woman Kerry Tankard, a member of Auckland Peace Action, says she now has a broken arm after an "aggressive" officer pushed her to the ground.
"The cops were not all in weather gear so they were getting rained on hard and getting grumpy. They were moving us away from the driveway of the Copthorne Hotel ... there was a small group of us left and as they were moving us along this guy was being quite aggressive.
"He just thumped me and I went down like a sack of potatoes. I went flying through the air and came down on one arm. He didn't hit me straight on, he hit me on my right shoulder.
"That was a serious two-handed shove."
She says she is now struggling to perform basic activities, including tying her shoelaces and zipping up her coat.
Auckland Peace Action member Valerie Morse said police violated their "basic fundamental rights" to be able to protest on a public footpath.
"They violently pushed people in an effort to escort these warmongers to their weapons expo."
Inspector Peter Thurston confirmed police had received a complaint from a woman following the conference.
"We take any complaint seriously and this will be thoroughly investigated."
He said their role was to ensure the "lawful right to protest while allowing members of the public to go about their daily business safely".
"On the day we were dealing with a number of protesters who acted in a way that created safety issues, disrupted traffic, inconvenienced the wider public and in one instance an officer was spat at."
Although 12 were arrested, 10 were let off with pre-charge warnings and the other two are facing a court hearing.
"Two people, a 26-year-old man and 31-year-old woman are due to appear in the Palmerston North District Court tomorrow, charged with assaulting police."