The women were high school students at Trinity Christian School between 2003 and 2005.

The Tuggeranong school came under fire last month after urging parents to lobby against the ACT government's marriage equality bill, which is due to be debated in the Legislative Assembly on Tuesday.

The former Trinity students say the counselling sessions were not to support them with coming to terms with their sexuality, but to convince them that being gay was wrong, that they were not actually gay, or that their sexuality could be changed.

The women, now in their 20s, but aged between 14 and 15 at the time, say the sessions with teaching staff began after they came out to their classmates.

Trinity Christian School, asked if it knew of the claims and if it was a current practice of the school to counsel gay students, responded in an email that its current principal was not at the school at the time the events are said to have occurred and he "knows nothing of the matter".

"There will be no further comment," the email said.

The school's former principal, Carl Palmer, said he had no knowledge of the sessions.

"Discussions of the nature you describe would not have been consistent with the school's approach to student pastoral care," Mr Palmer said.

But the women, whose names Fairfax Media has chosen not to

reveal, said they had to meet individually with Trinity teaching staff after it became known within the school that they were gay.

The students were in a brief relationship with each other and said staff ''quickly caught on'' that they were dating.

In the case of the first woman, she said the meetings occurred after the school called her parents, outed her and suggested counselling.

After two sessions with teachers, ''I realised that I wasn't actually being properly counselled in regards to helping me come out,'' she said. ''It was to convince me that I wasn't actually gay, just young and confused.''

The second woman said her parents did not remember being asked for consent for counselling sessions, which were held a few times a week through years 8 and 9.

The sessions focused on her sexuality, the fact she was a non-Christian and sometimes involved prayer.

''They never were blatantly saying 'you're wrong', it was an undercurrent,'' the former student said.

''It was the whole understanding … you need to understand you can fix this by accepting something that's missing from your life, which is our religion.''

Psychologist Paul Martin, who treats people who have experienced reparative therapy for their sexuality, said counselling that tried to influence or make a young person feel ashamed of their sexuality could cause ''tremendous psychological damage'', and could lead to mental illness and suicidal thoughts.

He said the circumstances described by the second woman were ''in the ballpark'' of reparative therapy, which has been outlawed for children by some overseas jurisdictions, but is not regulated in Australia.

Mr Martin said a lack of regulation made it possible for some Christian schools to ''fly under the radar'' with the counselling of students.

''A number of my clients over the last 25 years who have been to Christian schools have experienced counselling about their sexual orientation in terms of 'it's a bad thing, it's against God, you really can change','' he said.

Head of the ACT branch of Parents, Families and Friends of Lesbians and Gays, Dianne Hinton, called on the ACT government to create protections for young people coming out.

The ACT's Discrimination Act, which is under review, allows discrimination by religious education institutions, so long as it is done ''in good faith'' and to ''avoid injury to the religious susceptibilities of adherents of the religion''.

''While not prejudging a potential complaint, I am concerned if young people who are same-sex attracted are being treated unfavourably, implying that their [sexuality] is a disability that needs to be cured,'' the ACT Human Rights Commissioner, Dr Helen Watchirs, said.

NSW independent MP Alex Greenwich, who is pursuing legislation to prevent discrimination against gay students in schools, said federal, state and territory leaders had to act together to protect vulnerable young people.

The Canberra Times sought comment from the ACT Attorney-General Simon Corbell and Education Minister Joy Burch.