Tony Abbott has been left with a "slightly swollen lip" on Thursday, after being headbutted by a campaigner for same-sex marriage in Hobart.
The former Prime Minister of Australia was understood to be attending a Young Liberal cocktail party when the incident occurred.
Mr Abbott said he was the victim of a "politically motivated violence", after strongly advocating for the "no" vote in the same-sex marriage postal survey.
"A fellow sung out to me, 'Hey, Tony'," Mr Abbott said.
"I turned around, there was a chap wearing a 'vote yes' badge, he says, 'I want to shake your hand', I went over to shake his hand - and he headbutted me."
While Mr Abbott insisted he wasn't badly hurt, he said the incident was "a reminder of how ugly this [same-sex marriage] debate is getting".
Tasmania Police is currently investigating the alleged assault.