Peterson Toscano, a 47-year-old American, underwent gay 'conversion' therapies for 20 years as he struggled to reconcile his Pentecostal Christianity with homosexual attraction. It devastated his life, cost him tens of thousands of dollars and left him needing a decade of counselling and therapy, he said.

He now lives happily as a Quaker and is in a gay relationship but in 1996 he was in crisis. He had been married for five years and was working with his wife as a missionary in Zambia, when he was forced to leave the project and his wife because of his struggles with same-sex attractions. He found himself in the Worcestershire town of Kidderminster and attended a community church where another experience of an attempted gay conversion began.

"This is how it always works out," he recalled. "Someone in the church knows you are struggling through people sharing prayer requests about you or talking behind your back. One way or another some church authority finds out about it and they say: 'listen, let's help you brother'. The treatments are varied.

"One person will try and cast out demons, the other will take you through a 12-step programme. In essence they are saying it is wrong to be gay, it is not natural and you have to change. If you don't there are direct consequences in this life and the next.

"The mission I worked with connected me with a counsellor at True Freedom Trust [a charity that offers gay Christians counselling to overcome their homosexual feelings]. We went for walks two to three times a week to chat about the issues and we would meet in his office. It was very grandfatherly and in many ways very sweet. But on the other hand he reinforced the idea that I needed to change and while I still may have the same desires, I was making the right choice in denying them.

"We talked about my desires. Masturbation is a big thing that comes up in that world a lot. Even if you are not doing something with someone else you are doing it with yourself. He looked at the roots of it and he leaned on the addictive model – suggesting I was lonely, angry and my homosexual urges were a way of comforting myself.

"It was not seen as a natural orientation, but rather a twisted addiction to help you cope with a hard life. It was kinder and gentler than what I had been getting in my church up to that point with people telling me it was an evil spirit and I was an unrepentant sinner. But they are savvy at being gentle. Even though you are feeling miserable as you go through it, they are giving you all this positive attention. But when it stops working, you get blamed."

The counsellor also ran a support group, but half of its members were sex offenders, including paedophiles.

"We would go on long walks," Toscano said. "The counsellor was gay, had repented, married and had children, so for him it was a chance to hang out with a gay guy. Nothing happened sexually between us, but it was a way of having companionship, of being gay without having sex."

Then a fellow churchgoer tried to help too.

"She ran what she called a 'deliverance ministry', delivering people from evil spirits. In her little home in Kidderminster, right up against the animal park so I could hear lions and baboons in the background, she had me lie down. It was like a reiki session where she hovered over me and identified the evil spirit in my body and together we willed them to be gone.

"At one point she said to me: 'If you don't want these evil spirits, take a deep breath and let it out and, pfff, there they go'. It was crazy, because it was sweet in some ways. She believed it and I was desperate for a cure, a gift from God to drive out this evil. That was the idea: cut it out like some cancer and you won't be gay any more."

It didn't work.

"I saw a cute guy on the street and knew I was still gay," he said. "I didn't say anything because if I did it would have been a case of me not wanting it enough or letting it [the demon] back in.

"It always falls back on the patient if the cure doesn't work and that is where these therapies get cruel. They are trying to do something that is impossible and when it doesn't work you get blamed for it.

"The consequences are being separated from God, being shunned by your church and going to hell."

Toscano went on to spend two years in a residential treatment facility in Memphis, where he tried again to turn away from his sexuality. He estimates he spent $30,000 (£23,000) pursuing treatments around the world.

"It has been devastating," he said. "It took me 10 years of very intensive therapy and treatments to begin to overcome the damaging effects, the depression, confusion and shame that gets imprinted on you. It screws up your career, because so many of us put our lives on hold to pursue this.

"You get involved in relationships that are unworkable, marrying women, and everyone gets hurt. I still struggle when this issue come up because it has eaten so much of my life.

"I get so angry that these folks are consistently lying about a change that is possible when that has clearly been debunked. They are unhappy with being gay and that is their own personal issue, if you don't want to be gay, fine but please, please don't put this on all the rest of us. Since they do it in the name of religion they give moral authority to bullies."