Former Australian prime minister Tony Abbott says he was 'headbutted' by same-sex marriage campaigner

Former Australian prime minister Tony Abbott claims that he was "headbutted" in an assault by a campaigner in Hobart, as tensions grow over a vote on same-sex marriage.

Mr Abbott was in the Tasmanian capital on Thursday meeting with campaigners opposed to gay marriage, and was walking in the street when he was allegedly attacked.

The former Liberal Party leader told Sky News he was "headbutted" and later described the incident to 2GB radio: "A fellow sung out to me, ‘Hey, Tony’, I turned around, there was a chap wearing a ‘vote Yes’ badge, he says ‘I wanna shake your hand’,” Mr Abbott said. “I went over to shake his hand and he headbutted me.”

Mr Abbott said he suffered a "swollen lip" but his spokesman told AAP he did not sustain any serious injuries.

Mr Abbott, a former amateur boxer, apparently opted not to defend himself, but said one of his minders "grappled" with the alleged attacker, who "scarpered off, swearing". 

“It was very disconcerting to find ... someone who under the guise of wanting to shake your hand gives you a so-called Liverpool kiss," he added.

Video footage or pictures of the incident have not yet emerged.

Alex Greenwich, head of the Marriage Equality campaign condemned the alleged assault on Twitter saying "there is no place for violence" in the campaign.

"This is about treating people fairly, with respect and dignity."

Hobart police told the ABC they were aware of reports Mr Abbott was assaulted. Police said they were making enquiries, but "there is a lot of rumour and speculation" and they would not comment further until they had more details.

A controversial non-binding postal vote asking Australians whether they believe the country should allow same-sex marriage is underway, with a result expected on November 15. 

The campaign has been increasingly fractious, with claims of unethical behaviour on both sides. 

Mr Abbott claimed "yes" campaigners have been responsible for multiple acts of "bullying and hate speech".

Last week former Labor Party prime minister Kevin Rudd's godson was punched in the face during a confrontation with a man who was tearing down rainbow flags at a bus stop in Brisbane.

Mr Rudd uploaded a photograph of 19-year-old musician Sean Foster’s bloodied face to Twitter and lashed out at conservative prime minister Malcolm Turnbull for allowing the postal survey to go ahead.

Mr Turnbull told 4BC radio his actions would be guided by the results of the survey.

"If there is a Yes vote then we’ll facilitate a private member’s bill to legalise same-sex marriage. "If there’s a no vote, we won’t. That’s it, very straight forward.”

Australia is one of the last major western economies in which where same sex marriage is not yet legal. 

Research released on Thursday estimated that allowing same-sex marriage could prevent up to 3000 suicide attempts a year. 

At a glance | Where gay marriage has been legalised