Four Corners spoke to more than a dozen men who say Williams compelled them to perform sex acts.

Former member Gunther Frantz says he was 12 year-old when he first started to be indoctrinated in Williams' organisation, the Christian Assemblies International.

He told the ABC how Williams would be in the centre of a group being touched by a male member of the cult.

"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."

Mr Frantz said Williams had brainwashed him, telling them that "anyone who is not within the church is a heathen who is going to burn in hell, and they either convert or die, and you have nothing to do with them".

He and other former members say the group is not a religion, but a shocking cult that abuses its followers and that does not deserve its charitable status in Australia.

Members were also told to donate 10 per cent of their income to the Assemblies as part of their membership in the group.

The group is a registered charity in Australia.

It started in the German town of Feldafin in the 1970s, its headquarters are now in Coffs Harbour.

Williams and other senior members of the group declined the ABC's requests for interviews.

The Australian Charities and Not-for-profits Commission, the national charity regulator, has pledged to investigate the allegations.

Cult of Horrors aired on Monday night on ABC.