A four-year investigation by the ABC has uncovered shocking claims of abuse and torment in relation to NSW-based registered charity and religious group Christian Assemblies International (CAI).

Four Corners has revealed that self-styled religious guru Pastor Scott Williams was using his warped brand of evangelical Pentecostalism to run a clandestine homosexual sex ring while allegedly misusing vast amounts of member donations for personal use.

Courageous former members broke their silence and told of their torment living inside the group, which they said is not a Christian church but a horrendous cult run by one man.

The ex-members have remained in the shadows until now out of fear and shame. They detailed shocking acts of abuse ranging from spiritual abuse, financial abuse, verbal and physical abuse, and the sexual abuse of adult men.

They said bizarre sexual rituals were carried out in secret by Williams, who described himself as "The Anointed One" with the Lord's authorisation to sidestep biblical commands against homosexuality and sexually train his male members into submission and obedience.

Four Corners approached Williams, whose full name is Anthony Scott Williams, and senior people in the church. All declined requests for interviews and refused to answer the program's questions.

The CAI is one of more than 60,000 registered charities in Australia and Four Corners can reveal it has been investigated by multiple authorities around the world.

But until now, the Australian Charities and Not for Profits Commission (ACNC) had no idea of the systemic abuse and allegations of corruption regarding the CAI, despite other authorities in Australia being alerted and informed of possibly illegal acts several years ago.

ACNC head Susan Pascoe has pledged to take immediate action.

"This is clearly one that we've been alerted to by the media, and in that instance we would certainly be investigating," she said.

"If there was evidence that this was not acting in a charitable way or causing serious harm, then the charity can be deregistered."

It is a pledge that should strike fear into the current leadership of the CAI, of which Williams is still a director.

Origins of Christian Assemblies International

The CAI headquarters may be in Coffs Harbour, New South Wales, but the organisation began in the small German town of Feldafing in the late 1970s.

Former members say they were recruited by Williams as teenagers and young adults, with many still at school. They say they were brainwashed into believing Williams was The Anointed One, filled with the Holy Spirit and gifted with the divine power of healing.

Williams was working in Feldafing as a pool attendant at a military school for young men.

The headquarters of Christian Assemblies International is in Coffs Harbour, New South Wales. ( ABC News )

Steve Forkin was converted when he was 17. He told Four Corners Williams paid special attention to young males.

"He was an Australian obviously and I'd never met anyone from Australia at that point in my life," Mr Forkin said.

"He was very charismatic. He was very friendly. He was very outgoing, quite fun-loving, to be honest. Initially he presented himself as a missionary who'd come to Germany with a calling from God to start a church there.

"He's very, very eloquent when it comes to knowledge of the Bible as such, and of course the flipside of that coin is that in Bavaria kids have no concept of the Bible and very little concept of religion per se, so really he could have told us anything and we would have believed it."

Once introduced to Williams, usually through a church meeting or a weekend barbecue, Mr Forkin says Williams began to brainwash people.

"At that stage his message was that the world was going to come to an end very soon and that we didn't have much time and we needed to convert as many people as possible before the return of Jesus," he said.

"Also his message was very much predominating around that Russia would invade Germany, a third world war would break out, and he brought up all sorts of scriptures from the Old Testament to prove his prophetic statements."

Gunther Frantz, Williams's first convert in Germany, says he was 12 when he began to be indoctrinated. He says Williams brainwashed him into doing almost anything.

"He had such power over people," Mr Frantz said.

"His beautiful saying was always, 'I'm gonna convert the German nation, this time to do a better deed instead of what Hitler did - a bad deed'."

Williams's core beliefs included a strict literal adherence to the Bible and a highly conservative lifestyle.

Upon baptism, members would often speak in tongues. As part of their membership, they were expected to donate 10 per cent of their gross income to the CAI in addition to many different offerings every year.

Members recall bizarre homosexual rituals

Four Corners spoke to more than a dozen men around the world who all claim they were pressured and led to perform sex acts against their will by Williams.

Warping biblical scripture to carry out perverse sexual acts, Williams began to hold regular men's nights. During these nights, the males attending would be asked to undress and participate in mass massage sessions.

Former members told Four Corners that Williams would often be in the centre of the group receiving massages and caresses from a male member of the church.

Mr Frantz says he was often present and forced to take part by Williams.

"I think the biggest one I ever remember was 80 males in rooms covered only in naked bodies, and everybody giving massages," he said.

"And Scott always had his personal private room with one or two at the end of any of those sessions. And then at two o'clock he sends everybody out of the room and out of everywhere else and he usually picks somebody to stay with him, to get more training."

Four Corners has been told that Williams would choose a man to stay back with him and spend the night with him, ordering them to surrender and submit to him for the Lord's training.

He would then order them to perform sex acts on him during a personal naked massage and during naked showers.

The shocking ritual played out for more than two decades, with victims believing they were the only ones suffering at the hands of Williams.

Mr Frantz says he, like other men, never consented to the sexual acts and that it could happen to anyone.

"It's possible. It happened to me. And I'm not the only one," he said.

Mr Frantz says the number of possible victims is staggering.

"Firstly, he made himself rich, and secondly, he has groomed people, particularly men and boys, boys to start off and kids, for his own pleasure," he said.

"The Pentecostal church which he represents is just ... a facade which he has built to build his own kingdom."

Underlying it all was the peculiar policy created and described by Williams as a "bundschaft", a special relationship between two men.

Mr Forkin said the policy of the bundschaft was mandatory for all senior men in the CAI. Men had to have a male partner if they were to be trusted, and their bond was above that of husband and wife.

"Well, it's basically a German word for the English word covenant," Mr Forkin said.

"So in his, in CAI terminology, it's a very special connection between two men, a very close friendship really, but it's more than that. It's like a lifelong commitment.

"So Scott would probably view that as a marriage without a marriage certificate, but in his eyes even if a man was married to another woman, the bundschaft friend was more appropriate and more valid to him than his own marriage."

Williams amasses impressive property portfolio

Williams, now 70, is living with his wife Ree in a luxury apartment in the beachfront Pacific Towers complex in Coffs Harbour. It is one of many properties Williams purchased using money donated by church members who believed much of it was being used for charitable purposes.

Today, the CAI boasts an impressive multi-million-dollar property portfolio including Pitversie House and Douglas House, a hotel in Abernethy, Scotland.

All were renovated to luxurious standards by church members, who have told Four Corners they worked hundreds of hours updating the properties while Williams monitored their work and punished them for any mistakes or minor misdemeanours.

Former member Gunther Frantz says he was 12 when he began to be indoctrinated. ( ABC: Four Corners )

Katja Forkin was recruited into the Assembly as a teenager living in Germany. She says women and men were expected to work on the properties night and day, and if they did not they would be severely punished or excommunicated.

She says life in the Assembly got worse once Williams began to purchase more and more properties.

"It started to change once the Assembly owned properties in Scotland, because basically all we did from then is just work on the properties, renovating, looking after Scott and Ree more or less, and everything evolved around their lives," she said.

"So the little spare time that we had sort of dwindled away more and more to the point that we started to have less and less connections to the outside."

As members disconnected from the outside world, following Williams around the world and moving away from family and friends, they say their leader's language and demeanour began to change.

Former members told Four Corners they were regularly denigrated and humiliated, losing their self-identity, confidence and sense of self.

Klaus Tishcer says it happened gradually.

"As the years went on and he was sort of more sure that things were going his way or going the Lord's way, then he was more confident to express that we were a waste of space, useless heathen and would burn in hell and "the devil would rip our balls off" in a man's case, or in females other words were used," he said.

Widows, pensioners pressured to make donations

Mr Frantz says there was extreme pressure applied to members to donate regularly to the church, in addition to 10 per cent of their gross income.

Over the years, an estimated $20 million to $25 million flowed into the Assembly by way of donations or tithes. If you did not give enough you would be punished.

"You would be spoken to. There would be an investigation to find out why," Mr Frantz said.

"And if you don't have good enough reasons, then there could be hell, blood and fire, because you might not make it into heavenly places."

Former members say they were brainwashed into believing Scott Williams was gifted with the divine power of healing. ( ABC News )

Four Corners has counted that at one point there were up to 20 mandated donations per year and all sources of income were targeted. Senior officers were sent out to widows and pensioners to pressure them to hand over inheritances.

Church documents detail how members were to be targeted for financial contributions, with those on low incomes told to sell their property and belongings in order to give to Williams's Assembly and to ensure he grants them salvation on judgment day.

But Assembly documents reveal something even more sinister. Four Corners has discovered members were also being fined by Williams for minor misdemeanours.

Mr Tischer worked in the finance department and was assigned to be a fine collector.

"Anybody who forgot to do their normal duties and their normal scripts and was found to be wanting that they had forgotten to do their tasks, could be fined," he said.

"If somebody, say, did a tithe report and they didn't send a report on time, they were fined, and I had to go and pick the tab up from all the people that were sent to me via email, 'he is to be fined' and so on and so forth."

Mr Frantz says Williams introduced a disturbing culture of spying and monitoring in order to maintain control over members and their everyday lives.

Four Corners obtained church documentation listing what members were allowed to read, what movies they were allowed to watch and what music they were allowed to listen to.

"We had a black book where people were on the black list. If they don't perform, then they have to be excommunicated or cut off," Mr Frantz said.

"People who didn't, for example, abide within the certain rules, for example, people came to our house and checked the fridge, checked the house, the clothes, it was clean; if not, my ex-wife would be severely punished."

Women were 'satanic beings not to be trusted'

Church documents show that Williams preached that women were Jezebels, swines, dogs and satanic beings, not to be trusted. Instead, they were to be punished.

In an extreme escalation, male members have told Four Corners that if they did not comply with Williams's demands regarding how women were to be controlled and treated, he would order women be beaten.

Women were also routinely excommunicated and their children given to other church members to be raised temporarily.

Four Corners also obtained church documents written by Williams detailing how women and children were to be beaten with a rod if they misbehaved.

Mr Frantz says Williams directed him to beat his then wife for not being obedient enough, something he is deeply ashamed of today. Mr Frantz says his brainwashing, like many others, was so acute that he believed Williams had ultimate power and authority on Earth.

"Otherwise we would've been chucked out of the church," he said. "Otherwise we wouldn't have been together.

"Otherwise he would've had the power to separate us, he would've had the power to eliminate our marriage, he would have had the power to excommunicate us and burn in hell."

Sylvia Wagner, another convert originally from Germany, says she was terrified inside the Assembly.

"We were told he's the overseer and that's the highest instance before [God]," she said.

"He told us he will give account on judgment day on how well we have been doing and we ought not to offend him in any way because ... he will give account on all his sheep.

"[If his account wasn't positive] I lived under the impression that I will burn in hell. I was often told I would burn in hell. My impression was, if I had left the church and joined another church I would possibly burn in hell because it's not allowed to leave this church.

"I was scared."

Ms Forkin says women were treated and used as servants inside Williams's organisation. Their role was to cook, clean, and produce children for the Assembly. Women were told what to wear, what to cook and how to behave.

"We were supposed to be at all times what they called humble and subdued and obey our husbands," she said.

"So they were the ones that made the decisions over us, whether they were good at what they were doing or not; that didn't come into it. And I suppose that was the same on them, was the pressure that they were to be seen as being in charge of us."

Katja's husband, Steve, says women were treated as less than men.

"Women were second-rate citizens," he said. "They were there to have children and stand in the kitchen and make food."

Using biblical scripture, Williams also preached that children were born evil and that the evil had to beaten out of them with an iron rod.

Four Corners spoke to many children who were born into the cult who are now adults. They detailed disturbing policies of punishment, including children being publically beaten for making any noise during a Sunday sermon or for moving off a mat laid out at the front of the Assembly.

'We won't stop until justice is done'

For all of the former members of the CAI who have broken their silence, they hope by going public and exposing their former leader that justice will finally be served.

Mr Frantz says CAI is not a Christian organisation, nor is it charitable, and it should not enjoy the tax-free status it currently does in Australia.

"It's a cult," he said. "I was abused and I didn't understand it. For me I just thought maybe it's me, it's me? I just don't understand why is this happening?

"I said to him, 'I don't understand why are you doing this', and he says, 'Well, the Bible says you've got to surrender, you're my bundtling', and all the rest of it.

"I remember the times where I begged, 'Give me time'. He says, 'You're still not surrendering fully and I can't use you and God is not gonna use you'."

Mr Frantz now realises what happened to him was wrong. He is calling for more members of the CAI to come forward and expose the truth about the tormented regime run by Williams.

"I hope that many more people out there hear the message and have the guts to come out, because more and more people are coming out," he said.

"Whatever happened to you, come out and tell them about it. Go to the police. Go public. I hope people have the guts."