Israel Folau faces a showdown with Australian rugby chiefs after posting anti-gay views on social media.

In a statement, Rugby Australia described content within the post as "unacceptable" and said its integrity unit was looking into Folau's conduct.

The Wallabies star was warned last year, but avoided any disciplinary action, for making homophobic comments on his social media channels.

A message published on his Instagram account on Wednesday read that "hell awaits" for "drunks, homosexuals, adulterers, liars, fornicators, thieves, atheists, idolators."

Folau said on Instagram: "Those that are living in Sin will end up in Hell unless you repent. Jesus Christ loves you and is giving you time to turn away from your sin and come to him."

Rugby Australia responded in a statement, which read: "Rugby Australia is aware of a post made by Israel Folau on his Instagram account this afternoon.

"The content within the post is unacceptable. It does not represent the values of the sport and is disrespectful to members of the Rugby community.

"The Rugby Australia Integrity Unit has been engaged on the matter tonight."

Folau, 30, was reminded of his social media obligations by RA chief executive Raelene Castle last year.

There were also threats from sponsors of the Australian national team that they would withdraw support following his social media posts.

Folau has won 73 caps and is a key part of Australia head coach Michael Cheika's World Cup plans this year. Last weekend, he broke the Super Rugby try-scoring record.

He currently has a contract with the Wallabies and Sydney-based Waratahs that does not expire until 2022.

In a Twitter post on Wednesday, meanwhile, Folau became involved in Tasmania's gender birth certificate debate.

Tasmanian authorities have decided, in a ground-breaking move for an Australian state or territory, to make genders optional on birth certificates.

But in response to that, above a screenshot of a report on the subject, Folau tweeted: "The devil has blinded so many people in this world, REPENT and turn away from your evil ways. Turn to Jesus Christ who will set you free."