Riot police formed a human chain to shield guests arriving for a Liberal Party fundraiser from several hundred Manus Island protesters who had formed outside the Friday night event which was also attended by Tony Abbott and Immigration Minister Peter Dutton.
Cr Forster had to be helped through the crowds by police and had her jacket torn in the crossfire.
“Basically a melee broke out, it was a riot,” she said.
“It was an extraordinary situation, it was very unpleasant, it was dangerous for everybody, it was an aggressive, awful, scary situation.
“I’m a local City of Sydney councillor and I don’t want to ever have this kind of stuff happening in my electorate.”
Cr Forster said people should able to walk into an event “unmolested, unassaulted and unattacked”.
“It was shocking to me and it was dangerous. People were trying to punch us, people ripped the jacket off my back … If you want to make your political protest, anyone can make a political protest anywhere in Australia, but you don’t do it like that.”
“It was a very unpleasant, unnecessary, dangerous situation that those people put everybody in,” she said.
“It was a situation that I have never been in and I would never choose to be in ever again. It’s my favourite jacket and it’s shredded sadly and it was shredded off me from behind.
“It was a very volatile and extraordinarily surprising situation to me.”
The protesters were calling for the Immigration Minster to restore services to the now-closed Manus Island detention centre and bring the remaining asylum seekers to Australia.
The Australian Government had officially closed the detention centre on the Papua New Guinea Island on October 31.
On Friday, refugees and asylum seekers on Manus island told the ABC they were “extremely scared” as workers tore down fences around the compound.
The Papua New Guinea Government also put up a notice warning “force may be used to relocate those who refuse to move voluntarily”.
Protesters outside the Liberal Party event at Australian Technology Park in Eveleigh spoke on loudspeakers and harassed and berated guests, with police forced to intervene several times.
Hundreds of protesters came with whistles, pots and pans, shouting “Abbott, Dutton, blood on your hands” and “Shame on you” to the guests who made their way through through the crowd.
Activist Lily Campbell said she was protesting because Mr Dutton and Mr Abbott were “responsible for the siege on Manus Island right now”.
“I think every refugee should be brought here and should be granted asylum in Australia,” she said.
“I can’t believe the state it’s got to on Manus Island,” another protester, Margaret Walters, said.
“It’s just atrocious … they should never have been put in an offshore detention camp.”
Hundreds of people also marched through central Melbourne calling on the Federal Government to assist refugees at the Manus Island detention centre.
The rally began at the State Library before demonstrators marched along Swanston Street.
There were no arrests.