The co-founder of the Safe Schools program claimed "40 to 50 per cent" of all young people are attracted to members of the same sex, at a speaking engagement at Victoria University.
Roz Ward, who no longer represents the controversial anti-homophobia education program, made the comments at a Pride Week event at the university last week, The Australian reports.
Ms Ward rejected figures that 10 per cent of young people were same-sex attracted, scoffing they were "a bit of a joke" at the unofficial Safe Schools event.
"It's more like 40-50 per cent of young people who are not exclusively attracted to the opposite sex," the academic said.
"That's how fluid sexuality is headed.
"The stats coming out of studies that look at young people in the UK, in the US is more like 40 to 50 per cent."
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Sexual health expert Prof Juliet Richters from the University of NSW told the News Corp Ms Ward's comments were a "gross over-estimate".
"The only studies that would produce that are voluntary online studies which always get much higher response rates from gay and bisexual people," said Prof Richters.
The expert with three decades experience in the field said, "40 to 50 per cent, that is a gross over-estimate".
Ms Ward resigned from the Safe Schools' government advisory body in May last year after she declared the Australian flag racist in a Facebook post.
Her resignation prompted the Victorian government to take over the Safe Schools program while NSW, South Australia and Tasmania said they intended to ditch the initiative entirely and develop their own anti-homophobia education strategies.
Safe Schools has been marred in controversy since its inception and has been likened to a "pedophile grooming a victim" by conservative MP George Christensen and labelled a platform to promote "cross-dressing" by the Australian Christian Lobby's Queensland director Wendy Francis.