Police responded to a verbal altercation between Liberal candidate for Canberra Mina Zaki and a Labor volunteer at the Exhibition Park pre-polling station about 2pm on Thursday.
Witnesses told The Canberra Times comments had been made between the Labor volunteer and Ms Zaki over the course of the day before Ms Zaki told Labor ACT Senate candidate Katy Gallagher to "put a leash on your dog".
ABC video footage shows Ms Zaki yelling at Ms Gallagher, before a bystander said "leave Katy alone".
There are disputed claims the volunteer made barking noises at Ms Zaki. Witnesses said tension had been increasing between volunteers from the two parties at the pre-poll site throughout the day.
ACT Labor secretary Matt Byrne has written to the president of the Canberra Liberals, calling on Ms Zaki to be disendorsed and saying the behaviour of one Liberal volunteer had been inappropriate.
"This volunteer has been making inappropriate comments that have left other volunteers, not just from the Labor Party, feeling uncomfortable and in some cases mildly harassed," Mr Byrne wrote.
Australian Electoral Commission staff called the police after the incident became heated. A witness said between four and six officers attended.
Ms Zaki left the polling place before the police arrived.
Ms Gallagher said it was unacceptable for such an incident to happen at a polling place.
"We deal with tension at pre-poll all the time, there's no reason and no excuse for that kind of language and that kind of behaviour," she told The Canberra Times.
"I've never seen it before and I've never seen it from a candidate for public office."
"The public should be able to vote freely and without any confrontation and that's not what happened at Mitchell today," Ms Gallagher said.
An ACT Policing spokesman said no offences had been identified and no further police action was expected.
A spokeswoman for the Canberra Liberals said in a statement "we are disappointed that other parties have sought to denigrate and provoke our volunteers at prepoll over a period of weeks. All we seek is that all volunteers treat each other with respect and courtesy."
Ms Zaki has been contacted for comment.
with Jasper Lindell