Sacked Australia full-back Israel Folau says "the devil" is trying to influence the debate over transgender rights.
Folau, 30, is taking legal action after having his Rugby Australia contract terminated over a social media post saying "hell awaits" gay people.
In a church sermon on Sunday, he again criticised homosexuality.
Folau also said "kids in primary school" were being allowed to "change their gender" because the government was taking away input from parents.
In April, Tasmania became the first state in Australia to make it legally optional to list gender on birth certificates.
The legislation allows people aged 16 or older to apply to change their listed gender without the approval of their parents.
Legislation changes have also been discussed in the state of Western Australia.
In his sermon on Sunday, which was broadcast on Facebook, Folau - a devout Christian - said: "They are allowing young kids in primary school to be able to have the permission to change their gender if they want by taking away the permission of the parents.
"They are trying to take control, as a government, to make those decisions for young kids who are basically 16 years old, or young.
"They don't even know what they are doing.
"This is what the devil is trying to do. To instil into this government, into this world, into society. And it is slowly happening."
He added: "They say that a man and a man should be able to be married and there is nothing wrong with it.
"This buys into the theme of pleasing man rather than pleasing God and standing up for the truth."
Folau earned 73 rugby union caps for his country, and also represented Australia at rugby league and Australian rules football.
He had a contract with Rugby Australia until 2022 and had been expected to play at this year's World Cup. As well as being sacked, he lost sponsorship deals, including with car manufacturer Land Rover and sportswear brand Asics.
When it was announced earlier in June that he is claiming his employment was unlawfully terminated, Folau said: "No Australian of any faith should be fired for practising their religion."