Gay teens are being sent to counselling to turn them "straight" through controversial therapies that are facing a ban overseas.
Experts warn that the practice is rife in Queensland as desperate parents and some Christian leaders try to get children to change their sexuality.
California is looking at banning "ex-gay" - or reparative - therapies for minors due to concerns about the potential long-term harm to young people.
Brisbane psychologist Paul Martin has helped children as young as 14 who have been severely affected by the therapies and is contacted by a new patient every few weeks.
"The psychological damage being done to Queenslanders under our noses as we speak is just horrendous," he warned.
Mr Martin underwent - and then carried out "gay recovery" programs - with Exodus ministries in Melbourne 25 years ago but quit and now supports "survivors".
The therapies treat homosexuality as a psychological disorder that can develop from factors such as sexual abuse as a child or a lack of strong parental figures. In some cases, therapies involve banning males from kitchens or instructing people to wear more masculine or feminine clothes.
"With Christian reparative therapy, being gay is not only a psychological disorder but it is inherently sinful, which means every time they have a thought about a boy or girl they believe there are going to hell," Mr Martin said.
"If you start saying that to a kid at that age during puberty, it instils a belief that they are defective and that can cause depression and turn the volume up much higher in suicide and mental illness."
Exodus Asia Pacific's website lists five ministries in Queensland, two in NSW and one in Victoria that claim they can help people overcome homosexuality. The ministries did not return calls last week.
The Australian Psychological Society recommended in 2000 that practitioners refrain from therapies that attempted to change a person's sexuality.
But a research project set to be released within months has found Australian psychologists and psychiatrists are covertly using or recommending the therapies.
Bond University masters student Heidi Jansen said a sample of 268 lesbian and bisexual women from across the country revealed that some were encouraged to complete conversion therapy to "cure" them of their sexuality.
The British Association of Counselling last year found UK Christian therapist Lesley Pilkington guilty of professional malpractice after telling a gay undercover journalist homosexuality was a "mental illness" that could be overcome.
Sydney-based Anthony Venn-Brown - who also went through the therapy and now warns of its dangers - said online courses were "the most dangerous of all".
"People don't know who they are contacting," Mr Venn-Brown said.
"These people are not professionally trained - not psychologists. I know of people who have attempted suicide after trying it."
Brisbane filmmaker Heather Corkhill, who investigated "ex-gay" therapy in Australia for her documentary The Cure, said children as young as 12 were believed to have gone through the programs.
What they believe
* Ex-gay ministries treat homosexuality as a failing that can be overcome like an alcohol, drug or gambling addiction
* They link homosexuality to sexual abuse as a child or the search for a father figure
* Along with worship and prayer, gay Christians are encouraged to go to regular meetings on topics such as the true feminine and the true masculine
* Often, participants are bombarded with testimonials from former gay leaders who claim they have transformed their sexual orientation
* Participants also can enter 12-week courses or go away on weekend retreats. Groups are aware of the scrutiny and some offer participants the option to pay in cash or via PayPal to avoid linking the person back to the organisation