Police say the force used towards the anti-mandate crowd at Parliament's grounds has been proportional to the circumstances as a video emerged of a protester's head being held down by an officer during arrest.
The video posted to Facebook also shows an officer kneeling on a protester's neck while two others handcuffed him.
Superintendent Corrie Parnell said police would not comment on individual cases of arrest and that images and videos did not provide the full context of what police officers were facing.
"This is an extremely difficult working environment for our frontline staff. However, police have been exercising their powers fairly and professionally, and have used force proportionate and relevant to the circumstances."