Tony Abbott has criticised the "disgraceful behaviour" of protesters after violent scenes erupted at his Sydney fundraising event.
On Friday, several hundred protesters outside the event in Redfern confronted invited guests, including Mr Abbott's sister Christine Forster and her partner Virginia.
Ms Forster's jacket was ripped as she struggled through the crowd and she said it was like "being in the middle of a riot."
She told Weekend Sunrise "it was an ugly, ugly scene" and "just wanted to protect Virginia", her long time partner.
Mr Abbott acknowledged the attack, tweeting "it shouldn't have happened".
"Disgraceful behaviour by protestors last night. Denying Australians' real rights to uphold the supposed rights of boat people," he wrote.
"My sister is herself a brave campaigner for rights and should never have been assaulted."
Ms Forster was forced back from the entrance until police formed a ring around her and pushed their way through the crowd.
She described the attack as "scary, dangerous and unpleasant".
"People have absolutely the right to protest but you don't have the right to assault people, and you don't have the right to abuse them," she said.
"That is not right. That is not how you make a political statement in Australia.
"Make your statements, make your protest, state your case, but don't physically assault people and don't shred the jacket off their back."
The protest is being held to oppose Australia's offshore detention system and will be attended by Immigration Minister Peter Dutton.Both Mr Dutton or Mr Abbott eluded the protesters and were not seen entering the event.
One protester was pushed over by a man arriving at the event, before police were able to intervene.
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Another guest, who did not want to be named, told AAP he believed the protesters were "doing more harm than good for their cause".
NSW police confirmed at least one person had been arrested during the protest.
Ms Forster said people should able to walk into an event "unmolested, unassaulted and unattacked".
"It felt like being in the middle of a riot - thank god for police being there," she said.
"People were trying to physically assault us, spit at us and abuse us."
Greens Senator Lee Rhiannon, who was at the protest, defended the protesters and said the refugees on Manus Island needed to be evacuated."What was full-on was the police, the police have mishandled tonight," Ms Rhiannon told AAP.
"We're here standing with the 600 men on Manus Island, I'm angry, so many people are angry."Hundreds of men have been holed up in the Manus Island detention facility for more than a week after it was shut down.