Only one school has withdrawn from Safe Schools since a review into the anti-bullying initiative thrust the program into the spotlight, and 32 more schools have signed up.

The review, ordered by Malcolm Turnbull, is on course to report to the federal education minister, Simon Birmingham, on Friday. When the review was announced in late February the program, which aims to stamp out homophobia and transphobia among students, had 495 participating schools. On Friday, it had 526.

“Since the announcement of the review there has been a spike in school membership nationally, with an additional 32 schools becoming registered and only one school deciding to withdraw from the program,” a spokeswoman for the Safe Schools program told Guardian Australia.

Only one other school has pulled out of the voluntary Safe Schools initiative in the two and a half years since its inception.

One of the program’s staunchest critics, Lyle Shelton from the Australian Christian Lobby, told Guardian Australia he was not surprised by the statistics.

“Parents aren’t appraised of the full content of the program,” he said. “Once the public has fully grasped the extent of the program, I don’t see how it could continue.”

He has accused the Safe Schools Coalition, which runs the program, and the state and territory departments of education, which administer it, of not telling the full truth about its content.

The Labor MP Terri Butler told Guardian Australia she was pleased the review “had opposite of the desired effect” of conservatives who were seeking to shut Safe Schools down.

“I think the amount of homophobia exposed in the last weeks has emphasised the importance of these programs,” she said, adding that the review was an “obvious cave-in” by the prime minister, Malcolm Turnbull, to appease his party’s right wing.

The Greens senator Janet Rice said: “Safe Schools saves lives. The number of schools opting in to the program shows that people on the ground are seeing its true value. The only voices against Safe Schools are coming from the dark recesses of the Coalition backbench.”

Last month concern from conservative members of the government over the appropriateness of the material in Safe Schools led Turnbull to initiate the review.

The findings of the review, led by two prominent academics, will be released within weeks.

It has investigated whether the program is age-appropriate and educationally sound, whether it aligns with the Australian curriculum and whether it suitably achieves its objective to reduce harm and stigmatisation of same-sex attracted and gender diverse young people.

It will also investigate the extent to which parents and the school community are consulted about the program.

Shelton said many people had concerns about the content of the Minus 18 website, which is linked to the Safe Schools program.

The site contained information on subjects such as penis tucking, chest-binding and unisex school toilets, Shelton said, and until those references were removed parents would continue to be “misinformed” about Safe Schools by thinking it was purely about anti-bullying.

“If it continues with its ideological side, then we’ll continue to oppose it,” he said.