Former prime minister Tony Abbott says he was "headbutted" by a same-sex marriage campaigner on a Hobart street.
Mr Abbott said he was walking back to his hotel when he was confronted by a man.
"A fellow sung out at me, 'Hey Tony'. I turned around and there was a chap wearing a vote 'yes' badge," the former leader told 2GB.
"He says, 'I want to shake your hand.' I went over to shake his hand and then he headbutted me."
Police made contact with Mr Abbott and are investigating the alleged assault.
"Tasmania Police is investigating an alleged assault on Hobart’s waterfront about 4.35pm today involving a 59 year old man from NSW," the statement read.
"Tasmania Police contacted the alleged victim after becoming aware of the claims and the man has tonight made a formal complaint."
Mr Abbott said the man did not deliver a very good headbutt but he did make contact.
"The only damage was a very, very slightly swollen lip," he said.
Mr Abbott said a member of his staff who was with him then briefly grappled with the man.
"He ran off swearing his head off," he said.
"It was just very disconcerting to find that the 'love is love brigade'… should under the guise of wanting to shake your hand in fact tried to give [me] a so-called Liverpool kiss.
"As he was scarpering away, amidst the 'effing this and effing that', it was a 'you deserve it because of all the things you’ve said'.
"It was pretty clear this was politicially motivated violence."
Liberal Senator Eric Abetz told the ABC the incident was a reminder of the "ugliness" of the "Yes" campaign.
"Yes, I have seen the former prime minister since that very ugly and unfortunate incident. But can I say, this is not about the former prime minister," he said on Friday morning.
"This is about highlighting, yet again, another example of the ugliness of the "yes" campaign, the slogan of "Love is love" is unfortunately shown in practice to be intolerance, not wanting people to be able to have their point of view, hold their point of view."
Cabinet minister Christopher Pyne said no one should be attacked for having a different view on marriage and it must have come as a nasty shock for Mr Abbott.
"It is an un-Australian thing to do and I hope that Tony is okay," he told the Nine Network.
Deputy Liberal leader Julie Bishop echoed that sentiment. "Violence of any form is never acceptable," she told reporters in New York.
Opposition Leader Bill Shorten described the attack as unacceptable.
"I'm glad Mr Abbott isn't seriously injured and I've rung him to say so," he said on Twitter.
Labor frontbencher Penny Wong said the yes campaign was about hope, respect and unity and the debate should reflect those values.
After the incident, Australian Marriage Equality co-chair Alex Greenwich condemned the attack.
"There is absolutely no place for violence in the marriage equality debate. This is about treating people fairly and with respect & dignity," he tweeted.
Meanwhile The Equality Campaign said they sought the "dignity and fairness of equal status before the law for all Australians".
"We are a campaign of respectful conversations, not angry debates, and never confrontations," a statement said.
Mr Abbott had been in Tasmania lunching with campaigners opposed to gay marriage, including Liberal Party Senator Eric Abetz.
Mr Abbott and Senator Abetz also visited Hobart Airport to inspect the runway, which was extended as a result of funding from the Abbott government.
- with AAP
