When a teenager confided to her pastor that she had been having sex with a church youth worker and that she'd also seen the man kissing another girl, she was told the story couldn't be believed.

That wasn't the view of a court, which years later jailed the worker, Wayne Paul Mason, for more than seven years for indecently and sexually assaulting four underage girls, including the whistleblowing teen.

As Australia steels itself for a national inquiry into institutional responses to child sex abuse, the case highlighted just how hard it can be to bring perpetrators to justice when those around them remain silent.

This month Mason, a former cop now aged 42, was jailed for more than seven years for almost 30 counts of indecently and sexually assaulting the girls between 1996 and 2005.

Described by the District Court as a "serial seducer" who used his power and influence over his victims for his own sexual gratification, Mason was also jailed for numerous child pornography offences.

But years before the charges were ever laid against him, Mason's church had heard allegations of his predatory behaviour.

In December 2002 the then 16-year-old girl - who cannot be named - went to the Senior Pastor of the Greenacre Baptist Church Steven Chard and his teacher wife Jill.

She told them she had been having sex with Mason since she was 15 - once against her will - and that she had just witnessed the then 32-year-old passionately kissing another 15-year-old girl.

"What I told her was the way she presented the story to us the story couldn't be believed," Mr Chard told AAP.

In evidence given to the court, Mr Chard said he told the girl that if she did not change her mind about the allegation he would ring the Department of Community Services (DoCS) immediately.

"She needed to think about the consequences to Wayne and his family," Mr Chard told the court.

Rather than going to police, DoCS or her parents, the next day Mr Chard wrote Mason a letter designed to protect the church while allowing Mason to pursue a relationship with the 15-year-old girl he had been seen kissing.

"This ministry is full of dangers which can be as damaging to yourself and for the youth work of this church," it states.

In order to, "protect you and to protect ourselves in times of accusation", the letter directed Mason to, "not allow (the girl) to express her affection to you physically on church grounds".

Mason was also removed from his involvement in a Friday night youth group.

At the time the Chards, who counted among their friends Mason's parents, had known for more than two months that Mason was seeing the 15-year-old.

They considered the relationship to be legitimate.

Police became involved following an alert from a friend of the 16-year-old girl. Mason was immediately removed from the church and by April, the Chards had also left.

Meanwhile the girl who had originally confided to Mr Chard said his "scare tactics" and bullying from Mason led her to withdraw her police complaint.

She told AAP that she felt isolated, alone and without support.

"He was the minister of the church and I told him and it just got disregarded," she said.

"He (Mason) isolated me from my parents and made me think they were against me.

"People from the church that I was friends with, he (Mason) told them to stay away from me, that I was a big liar.

"I just wanted things to go back to the life I had."

Her father, who also raised concerns about allegations long before the police first became aware of the situation in 2002, says he can't forgive the Chards.

"I trusted him because he was a minister," he said.

"I should have taken it further. For that I feel guilty."

Mr Chard told AAP that he doesn't remember discussing the matter with the girl's father.

Allegations against Mason didn't surface again until 2010 when one of his victims discovered sexually explicit photoshopped photographs of herself and other teenage girls.

Asked why he failed to act despite the warning signs, Mr Chard has many reasons.

"I am guessing my conflict was knowing the good (Mason) had done I couldn't reconcile that he had done something so evil," he told AAP.

Mr Chard also says he also wasn't aware of his legal responsibilities as a mandatory reporter and had received no training in the matter.

"(I) didn't know that a 14-year-old, even though that's underage, I didn't know that was a child," he adds.

Following the Wood Royal Commission which delved into organised pedophile networks in NSW, Dr Alan Rice from the Baptist Union said mandatory reporting responsibilities were well covered in the press and several letters were sent to the church about pastors' obligations between 1998 and 2003.

He conceded that at the time, however, the union did not have mandatory training regarding reporting which they have now.

"This case certainly contributed to the change," Dr Rice said.

"Our prayers are with Mr Chard as he continues to deal with the consequences of his decisions."

Mr Chard continues to grapple with his decisions, though he admits he wished he could have been "more supportive" of the girl.

"I made decisions that perhaps were wrong," he says.

"Even now I still don't know how I could have known to do more than I did."