Activist Garry Burns on Sunday wrote to the board's president complaining about Folau's infamous April Instagram post in which he warned hell awaits homosexuals.

Mr Burns also complained about the rugby player's more recent comments in a video sermon linking severe droughts and unprecedented bushfires to the legalisation of same-sex marriage in late 2017.

He wrote that Folau's statements were "objectively capable of incitement of contempt and or hatred of homosexual persons on the ground of their homosexuality".

"To suggest or imply that same-sex couples are causing these dreadful (natural disaster) events to occur, that - I would allege - is vilification because it's singling out a particular group within the community," Mr Burns told AAP.

"I'm confident that if this goes to a hearing, the complaint will be substantiated."

If the president of the anti-discrimination board accepts the complaint under the state's Anti-Discrimination Act, the matter would normally go to conciliation.

If that fails to resolve the matter, it can be referred to the NSW Civil and Administrative Tribunal for a legal decision.

Mr Burns in his complaint argues Folau's statements in relation to transgender and homosexual Australians could have a dire effect on teenagers suffering from low self-esteem.

"The continual targeting of them by Mr Folau in the media ... could lead those teens to suicide," he states.

Mr Burns in 2013 and 2014 had success at NCAT when the tribunal found a former Katter Party candidate had vilified homosexuals and ordered she publicly apologise.

But when Tess Corbett, a Victorian, didn't retract her comments, he couldn't enforce the ruling because she wasn't a NSW resident.

Mr Burns subsequently lost cases in the NSW Supreme Court and the High Court in pursuit of the matter.

Folau, a hardline Christian, claims he was wrongfully dismissed by Rugby Australia and Rugby NSW after his controversial Instagram post. He's claiming $14 million in damages.

Australian Associated Press