The country's prime minister Scott Morrison opposed gay marriage while opposition leader Bill Shorten argued for marriage equality ahead of a national vote in 2017 that led to Australia legally recognising same-sex unions.
Mr Morrison, a Pentecostal Christian, accused Mr Shorten, a Catholic before converting to his second wife's Anglican faith, of a "desperate, cheap shot" ahead of elections on Saturday by challenging the prime minister to say whether he believed gays went to hell.
Mr Morrison said he did not believe gays went to hell, after failing to directly answer the same question from a journalist a day earlier.
"I'm not running for pope, I'm running for prime minister," Mr Morrison told reporters.
"So ... theological questions, you can leave at the door."
Australian political leaders' religious views are rarely raised in election campaigns, which have long been regarded as a strictly secular argument over who should govern.
But nine prominent Christian church leaders wrote to both leaders this week demanding protections for religious beliefs and freedom of speech after Australian rugby union team star Israel Folau, the son of a Pentecostal preacher, was found guilty by the sport's administration last week of breaching the sport's code of conduct when he using social media to say gays were doomed to hell.
While Mr Morrison is a centrist, his opposition to gay marriage was out of step with the 62% of voters who supported gay marriage.
Mr Shorten attacked Mr Morrison for failing to address the theological fate of homosexuals when questioned on Monday.
"I cannot believe that the prime minister has not immediately said that gay people will not go to hell," he told reporters.
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