Sacked Australian rugby player Israel Folau has sparked outrage by suggesting destructive bushfires and drought ravaging Australia were "God's judgement" for the legalisation of same-sex marriage and abortion.

The devout Christian is pursuing legal action against Rugby Australia after being fired in May for posting on Instagram that "hell awaits" gay people and others he considers sinners.

He made his latest outburst in a Sydney church sermon over the weekend.

The comments were slammed as "appallingly insensitive" by Australian Prime Minister Scott Morrison, himself an evangelical Christian.

Mr Folau said the devastating drought and timing of fires across swathes of New South Wales and Queensland, which have left six people dead and destroyed hundreds of homes, were no coincidence.

"I've been looking around at the events that's been happening in Australia, this past couple of weeks, with all the natural disasters, the bushfires and the droughts," he said.

Mr Folau, Super Rugby's record try-scorer who has played for Australia 73 times, then talked to the congregation about same-sex marriage and abortion.

"God's word says for a man and a woman to be together, one man and one woman in the covenant of marriage," he said, while adding: "Abortion, it's okay now to murder, kill infants, unborn children."

Mr Folau continued: "Look how rapid these bushfires, these droughts, all these things have come in a short period of time. Do you think it's a coincidence or not?

"God is speaking to you guys. Australia you need to repent and take these laws and turn it back to what is right by God."

Same-sex marriage became law in Australia following a referendum in 2017, while New South Wales became the last state to decriminalise abortion in September this year.

Six people have been killed in the bushfires

In the sermon posted on The Truth of Jesus Christ Church's Facebook page, Mr Folau said he was sharing his message "out of love" and warned the fires were "only a little taste of God's judgement coming".

While Mr Folau has gained the support of prominent conservatives in the past, Mr Morrison was quick to criticise.

"They were appalling comments and he is a free citizen, he can say whatever he likes. But that doesn't mean he can't have regard to the grievous offence this would have caused to people whose homes have been burnt down," said the prime minister. 

Even one of his most staunch allies, former Wallabies coach and conservative radio host Alan Jones, was unimpressed.

"Israel is a lovely human being, I know him well. But, Israel, button up," Mr Jones said on his 2GB radio programme. "These comments don't help."

Mr Folau is reportedly seeking Aus$10m (€6.1m) in compensation from Rugby Australia, challenging his dismissal under laws that disallow sackings because of a person's religion.

The governing body insists his firing was purely contractual. A trial has been set for February unless a court-ordered mediation in December is successful.

Mr Folau is well funded after the Australian Christian Lobby raised more than Aus$2m in just two days to help pay his legal fees.