A prominent gay rights campaigner has written to the Anti-Discrimination Board of NSW to accuse ex-Wallaby Israel Folau of homosexuality vilification.

Israel Folau is set to enter mediation with Rugby Australia over his dismissal. Credit:Janie Barrett

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."

Burns has demanded Folau apologise and make a $100,000 donation to a charity.

Burns also complained about the rugby player's more recent comments in a video sermon linking severe droughts and bushfires to same-sex marriage legislation.