Prime Minister Scott Morrison says he won't become involved in a debate about gay "conversion" therapy, which has been discredited by psychiatrists across the world.

However, Labor has reiterated a pledge to outlaw the controversial practice if the party wins the next election.

A coalition of those who have endured the practice, churches and community advocates is urging Australia's major parties to address the issue before the next federal poll. Some 43,000 signatories to a petition are calling for a crackdown on the practice, including greater powers for health and consumer watchdogs and tougher regulations.

The prime minister said people should make their own choices about their lives. "I respect people of all sexualities, I respect people of all religions, all faiths. I love all Australians," Mr Morrison told Melbourne radio station 3AW when asked about the petition.

"I've never been involved in anything like that, I've never supported anything like that, it's just not an issue for me and I'm not planning to get engaged in the issue."

However, Labor is demanding the prime minister unequivocally condemn the practice and work with the states to ban it.

Mr Shorten said being gay was not a sin, describing the therapy as harmful and not evidence-based.

"I don't think the way that we help this community grow together is by stigmatising gay people," he told reporters in Brisbane. Greens senator Janet Rice said conversion therapies and sexual orientation change efforts can have fatal consequences and must be stamped out. Read more via news.com.au