THE Coalition for Marriage is facing a potential defamation lawsuit, accused of unfairly labelling a Canberra public servant and same-sex marriage supporter as an “extremist” on its website.

A photograph of Jill Moran at what she claims was a peaceful rally appeared on the same-sex marriage opponents’ website last month.

The accompanying media release hit out at the “extremists” of the Yes campaign. Ms Moran’s lawyers say it also contained allegations of violent protesting, bullying and intimidation.

Ms Moran, 26, said she felt “sick to her stomach” when a friend pointed out how the image had been used.

“I am a passionate supporter of marriage equality and I am proud to campaign publicly, but it is completely untrue and hurtful to paint me as violent or a political extremist,” she said in a statement.

“I am embarrassed and angry to be associated with anything other than peaceful campaigning.” But the Coalition for Marriage denies it has defamed anyone and says it was fighting for freedom of speech.

“That includes freedom of political communication,” a spokeswoman told AAP in a statement.

The image showed Yes campaigners “brazenly disrupting a peaceful anti-Safe Schools event in Canberra,” she said.

media_camera Anti same-sex marriage supporters are seen at "Straight Lives Matter" rally held in Darlinghurst, Sydney. Picture: AAP / Danny Casey

The media release quoted Coalition for Marriage spokeswoman Sophie York, who referred to the “bullying and intimidation tactics” at the base of the Yes campaign, along with its “loud, violent protests”.

Slater and Gordon defamation lawyer Phil Johnston said the photograph remained online despite requests for it to be taken down and an apology issued. Mr Johnston warned other people depicted in material issued by the group could also have been defamed.

The Coalition for Marriage said it had not referred to anyone by name, however defamation legislation also includes “indirect identification”.

The group alleged Ms Moran was a “seasoned political activist” and former Greens candidate who used the image as her Facebook profile picture. It also claimed she had tweeted the image with a statement that she was “smashing the heteropatriarchy”.

Under defamation law, the Coalition for Marriage has 28 days to adhere to Slater and Gordon’s requests, which were issued on September 25.

Originally published as ‘No’ campaign defamation charge