The cover-up involving former Victorian Father Gerald Ridsdale and his crimes in NSW in the 1980s has been detailed for the first time in the Royal Commission into Institutional Responses to Child Sexual Abuse.

Now defrocked and considered to be Australia's worst paedophile priest, Ridsdale has been convicted of abusing dozens of children in Victoria and faces further investigation relating to untold other assaults.

Statements, correspondence and interviews submitted to the commission, detail how the paedophile was able to maintain his criminal behaviour in New South Wales before being returned to Victoria and then quietly shipped off to a special clinic for sex-abusing priests in New Mexico in 1989.

They reveal Ridsdale had been transferred to the Catholic Enquiry Centre CEC then at Maroubra in 1982 despite his superior, Ballarat Bishop Ronald Mulkearns, being aware of Ridsdale admitting to sexually assaulting a child in 1975. Other allegations had also surfaced in 1981.

Correspondence to Church figures reveal that several years after his Sydney appointment at least two confirmed allegations against Ridsdale abusing children in Sydney surfaced including one at Maroubra and another involving a boy from Yarra Bay, who attempted suicide because of the abuse.

Before his appointment to the CEC in 1982, an issue relating to a boy and Ridsdale was known to its  then head Father James Fitzpatrick, according to an interview conducted with CEC secretary Val Leal.

Ms Leal said that Fitzpatrick had told there was a "problem" with Ridsdale and a young boy near Ballarat.

She said Ridsdale had told CEC staff only that he had been released from his diocese to go to the centre after having a "personal breakdown" following the untimely death of his brother.

Ridsdale was supposed to answer correspondence for the centre but soon after arriving, he became involved in local prayer groups, had local children visit him at the centre and took  them on unsupervised extended trips away.

"They were just children who had befriended him since he arrived at the centre. One was the child of (name redacted) at Maroubra Beach at the time," said Ms Leal.

Ms Leal said the child, a girl, used to visit on a regular basis, as did  quite a few young boys.

"He used to bring them in for the day or on the weekend, something like that."

One destination for Ridsdale and the children was a visit to his remote "dug-out" a opal digging plot he had at White Cliffs, nearly 1000 kilometres north-west of Sydney.

Another statement about Ridsdale submitted to the inquiry was from Yarra Bay Eucharistic Prayer Community member Marika Gubacsi, who revealed a 15 year-old-boy had come forward in 1988 to confirm Ridsdale had abused him for years after Ridsdale began conducting mass at Yarra Bay.

She said the boy had tried to commit suicide in 1989.

Ms Gubacsi said in 1993 when she heard Ridsdale was charged over Victoria offences she contacted the then Dean of St Mary's Cathedral Father Vince Redden, who said: "We sent him [Ridsdale] to America for medical treatment for two years, I assure you he is healed."

Redden appeared to referring to a course of action taken in 1989 by Bishop Mulkearns, who sent Ridsdale off to a special clinic for paedophile priests in New Mexico.

In a letter written by Ridsdale to Mulkearns about the clinic and tendered in the inquiry, Ridsdale whined that the trip had been "hell" because he had to wait an hour an a half at the airport for pickup and then the car had broken down.

Ridsdale is serving an eight-year prison sentence after pleading guilty to 30 child sex offences in 2014.

A spokesman for the Church's Truth Justice and Healing Council which represents the Ballarat Diocese said he could not comment on the allegations as the issues are being dealt with by the royal commission.

A spokeswoman for the Catholic Archdiocese of Sydney declined to comment while the Royal Commission's hearings were ongoing about Ridsdale.

"We understand Gerald Ridsdale will be giving evidence to the Royal Commission via video link this week – possibly as early as tomorrow," she said.

"However we are not aware what other witnesses may or may not be questioned about and it would be inappropriate to pre-empt the hearing at this time."

Efforts to contact former Bishop Mulkearns and Monsignor Redden  and Father Fitzpatrick were unsuccessful.