Four out of ten former Exclusive Brethrens who responded to a study looking at traumatic experiences growing up in the sect say they were sexually abused as children in New Zealand.
The study, carried out by a former Brethren, found 18 of 44 participants claimed they had been sexually abused as children.
The figure was significantly higher than the worldwide average, which found around 27 per cent claimed they had suffered child sex abuse.
It's the first piece of academic research into allegations of abuse suffered by members of the church.
Researcher Jill Mytton, from the United Kingdom, believes levels of child sexual abuse in the former member population are much higher than in the general population.
"That appears to be particularly high in New Zealand though, and this warrants further investigation."
Mytton said she could not be sure who the abusers were in every case, but those who had spoken to her said that their abusers were members of the Brethren.
Mytton said said she came under attack by the Brethren and her study was suddenly cancelled by her UK-based university after the Brethren made legal threats.
"I was in the process of finding out about that when legal action by the Brethren halted the research. The university who were hosting the research pulled the plug I assume because they feared a lawsuit."
The Brethren commissioned three academics, professors from the University College London and Warwick University, who severely criticised Mytton's research.
In a statement, church spokesman Doug Watt said: "Jill Mytton's research has been widely discredited and she has a personal vendetta against the Plymouth Brethren Christian Church.
"The church, like all other decent individuals and organisations, is appalled with sexual assault of any sort. Where we discover such incidents we have and will continue to take appropriate action."
Fairfax has spoken to three former Exclusive Brethrens members who say they experienced child sexual abuse. None had taken their cases to the police, and each said they had felt powerless to confront their abusers, who they claim were family members or elders within the church.
One woman, who now helps other Brethren who are trying to leave the church, said she was "dreadfully abused" as a child.
"I ran away from home and I tried to kill myself and I still see people coming out who have suffered years and years of abuse. Every other church has safeguarding. I have had young girls in my home who have been dreadfully abused and have been alcoholics in their early 20s."
After high profile sex abuse cases against senior Brethren members in 2009, the church promised to introduce a new code of care for complainants.
Requests this month for a copy of the code of care or any information about how the Brethren treats alleged victims of sexual abuse were refused.
Jill Mytton said her research had found Brethren who left the sect showed higher levels of psychological distress that the general population including depression, anxiety, post traumatic stress symptoms, and interpersonal problems.
'SPIRITUAL ABUSE'
A former Exclusive Brethren member has described feeling 'violated' by two sect leaders who were investigating allegations of sexual impropriety by an older Brethren member.
The woman said as a 16-year-old girl she was taken to a room and questioned by two sect leaders, or 'priestlies' as they were known.
She says the treatment by church elders was worse than the experience itself.
"I look back and I go that is an incredible violation. If you're vulnerable, it's an incredibly vulnerable position to be put into."
The woman said she had already begun to question Brethren teachings, for which she was subjected to extreme psychological abuse by church elders.
She says she was told: "you're mental, you're evil, you're possessed."
"It's spiritual abuse. It's appealing to the highest power that people can believe in. Twisting of scripture to force submission of women."
The woman said she met the Exclusive Brethren world leader Bruce Hales as a teenager, at a time when she was already doubting it's teachings.
She was particularly nervous, as she'd been taught in Brethren folklore that Hales could read minds.
"I was looking at him thinking he's a lying, conniving emperor with no clothes on. He just looked at me with the same greasy smile that he looked at everyone. Clearly he didn't have a clue what was going on in my mind."
She was excommunicated at age 21.
"It was a bit like jumping out of a plane into a big black hole."
Still in her 20s, she's now managed to establish a career and found a partner, and says she has says has been able to fulfil many of her life wishes since leaving the sect.
"It's wonderful to be free of that control and to be able to grow as a person the way that I believe I was meant to be."
But she is torn by never being able to see her family again.
"I'd love to see them free, there are amazing men and women in there -full of talent and potential. One of the most horrible things they're doing is to restrict people from being all that they can be. In all seriousness there are so many amazing men and women.
"They're not enjoying it and yet they can't conceive of another way of life. They don't know how to break down the fear."
SEX ABUSE CASES
* Clive Allen Petrie, 74, of Nelson, was found guilty in 2009 of nine charges of indecent assault, as well as inducing a girl under 12 to perform an indecent act.
* William David McLean, 44, of Levin, was jailed for three years in 2012 for raping a woman over an 11-year period.
* Fairfax is aware of three other recent or pending criminal sex abuse cases against former or current Brethren members.