Therapy is being offered to "cure" people who find themselves attracted to the same sex, where their attraction is contrary to their own religious beliefs.
Often called gay conversion therapy, it's illegal in some parts of the world, but not in New Zealand.
TVNZ’s Sunday programme spoke with three gay men about the conversion therapy they've been through.
Undercover footage of this therapy, or "spiritual healing", or "praying the gay away", shows the claims being made about its potential to cure same sex attraction.
One therapist says: "Your attraction can absolutely be changed. We need to rewire your brain, and it is completely doable."
Another therapist who Sunday spoke to undercover claims: "No one is born that way and so if that's the case, it must be possible to change. Alcoholics change, thieves change, all sorts of people change."
Aucklander Jim Marjoram was for 40 years a gay man hiding his true identity in the church.
"It's the underlying thing that anything's possible for God. So, if we're struggling with same sex attraction, then God can fix that," Mr Marjoram says.
"Most churches have someone there who will engage in some sort of pray away the gay."
He says the argument is that homosexuals are broken. "Broken in that something has caused us to be gay, like trauma, sexual abuse, bad parenting," Mr Marjoram says.
But Mr Marjoram believes that even if gay people are willingly putting their hands up asking for this therapy, it’s not right.
"The problem is nobody can change so, no matter how hard we try, we're fighting a losing battle," he says.
"It drives people into different forms of mental illness which include depression, anxiety and a host of other things."
Ryan Curran, 26, always believed the church was his calling, despite always knowing he was gay.
Mr Curran gives an insight into his experience of how pentecostal-type churches feel about homosexuality. "That it's a sin, and you are deemed to hell," he says.
Not wanting to be cut off from his church family, the teenage Mr Curran chose to suppress his sexuality while tolerating their attitude.
Mr Curran says if he found himself attracted to a man in a given moment, he would typically pray and ask God to "take those thoughts captive".
He said every single Sunday "without fail" he would pray in church asking God to heal him "from this disease".
But all the prayer in the world didn't work, and at 18 the church intern started seeing men.
At 19, Mr Curran confided to someone in his congregation, and was sent to a Christian counsellor.
"What I was told was that if I have a healthy lifestyle, if I read my Bible, if I eat right and have enough exercise that God would be able to heal me from this disease and I did think ‘is there some truth in this?’" Mr Curran says.
Mr Curran became a successful youth pastor, but his life was becoming a living hell.
"I would go to gay bars, hook up with whoever and just get really, really drunk," he says. "It got to the point, I must admit, where my life was out of control."
Torn between religion and his sexuality, Mr Curran made the toughest decision of his life, to walk away from his church career.
A few months later, alone, Mr Curran came out as a gay man online. That same night, he tried to kill himself.
"I woke up the next morning, I'm in, I'm in the psych unit, and all I did was cry and cry and cry for the next two weeks because, one, I didn't succeed, and two, because I just knew my life at that moment was the worst that it's ever, ever been," he said.
Sunday wanted to know how widespread gay conversion therapy is in New Zealand. It wasn't hard to find websites promoting the practice, so "Jay" went undercover as a young Christian struggling with same sex attraction.
It was surprisingly easy to find people willing to help.
Jay was referred to Natasha Ellis through Living Wisdom, a Nelson based religious counselling service led by David Riddell. Undercover footage shows her making numerous claims about Mr Riddell’s teaching.
"From his perspective your attraction can absolutely be changed," she says.
"He has never come across someone who has not been able to trace the cause of their same sex attraction and therefore undo it."
In their first session, Ms Ellis offers Jay cards with sayings on them, which she says can help rewire his brain.
"I want you to memorise them. If they stick with you, like, rewrite them, read them every morning, every night. Put them in your phone, text them to yourself twice a day," Ms Ellis says.
Leads to depression
Clinical psychologist and sexuality expert Rita Csako says no one should be practising conversion therapy.
"It leads to anxiety, depressive symptoms and in severe cases even suicide," Ms Csako says.
Asked if it is possible to change someone's sexual orientation, she said: "It's really difficult because people do say that they've changed sometimes.
"But it's quite often what's behind it, that they've tried to suppress their natural instincts and needs, and they pretend that they are someone who they are not."
Ms Csako wants conversion therapy banned in New Zealand.
"Because it's harmful, especially when it's happening to young people who are not in a position to make a decision," she says.
"But the problem is at the moment in New Zealand anybody can call themselves a therapist.
"My advice would be to join a religious group where they accept your sexual orientation, because there are religious groups that are OK that you're gay or lesbian or transexual or whatever you want to identify with."
When Sunday formally approached the conversion therapists Jay had met with to ask them about their practices, they weren’t too forthcoming. Trainee counsellor Natasha Ellis eventually hung up on the reporter.
"Anyone who comes to see me in any capacity regarding any issue I'm actually legally bound by confidentiality, so I won't be able to speak to you," she said over the phone.
"And also as a counsellor, I would never make any promise to be able to achieve any particular thing for any particular person."
Another conversion therapist Jay spoke to, Les Gale from Exodus Global Alliance, disagrees with the professionals, who he calls the pro-gay lobby.
"They've been talking this bull**** for generations just about, for decades anyway," Mr Gale said.
"While they're spouting on like this we are still having people experience change through Christ's help."
The three men the Sunday programme spoke to, whose full stories can be seen in the video above, have all put their conversion therapy behind them, and are living as openly gay men.
Ryan Curran now has a partner, Jerome, who he married just a couple of weeks ago.