More than 20 per cent of the members of some Catholic religious orders — including Marist Brothers and Christian Brothers — were allegedly involved in child sexual abuse, a royal commission hearing in Sydney has been told.

Nearly 2,000 Catholic Church figures, including priests, religious brothers and sisters, and employees, were identified as alleged perpetrators in a report released by the Royal Commission into Institutional Responses to Child Sexual Abuse.

The hearing is examining the current policies and procedures of the church's authorities in Australia relating to child protection and child safety standards, as well as their response to allegations of abuse.

In her opening address, Gail Furness SC said a survey revealed 4,444 allegations of incidents of abuse between January 1980 and February 2015 were made to Catholic Church authorities.

Ms Furness said 60 per cent of all abuse survivors attending private royal commission sessions reported sexual abuse at faith-based institutions.

Proportion of non-ordained religious order members who were alleged perpetrators Religious institute Percentage Brothers of St John of God 40.4 Christian Brothers 22.0 Salesians of Don Bosco 21.9 Marist Brothers 20.4 De La Salle Brothers 13.8 Patrician Brothers 12.4 Society of Jesus 4.8 Missionaries of the Sacred Heart 3.3 Sisters of St Joseph of the Sacred Heart 0.6 Sisters of Mercy (Brisbane) 0.3 *Weighted figures for 1950 - 2010. Source: Royal Commission into Institutional Responses to Child Sexual Abuse

Of those, almost two-thirds reported abuse in Catholic institutions.

The royal commission's report found of the 1,880 alleged perpetrators from within the Catholic Church, 572 were priests.

Ms Furness described the victims' accounts as "depressingly similar".

"Children were ignored or worse, punished," she said.

"Allegations were not investigated. Priests and religious [figures] were moved. The parishes or communities to which they were moved knew nothing of their past.

"Documents were not kept, or they were destroyed. Secrecy prevailed as did cover-ups."

The average age of the victims at the time they were allegedly abused was 10 for girls and 11 for boys.

Religious orders were in the firing line with the data suggesting that between 1950 and 2010, more than 20 per cent of Marist Brothers, Salesians of the Don Bosco and Christian Brothers had allegations of child sexual abuse against them.

For the Brothers of St John of God, that number was 40.4 per cent.

It is the first time the data has been released.

'They give God a bad name'

Two daughters of Anthony and Chrissie Foster were abused. One has since died.

Anthony and Chrissie Foster gave a scathing assessment of the church. ( ABC News: Philippa McDonald )

Outside the hearing, Ms Foster gave a scathing account of their treatment by the Catholic Church.

"The Catholic priesthood give God a bad name. They're a disgrace. They are unremorseful," she said.

"For so long this has been the way they acted to hide perpetrators, to move them on, with no regard for children whatsoever, that other children have become victims, and suffered this terrible fate.

"They have shown no mercy, no remorse. Nothing."

Figures 'tragic and indefensible'

One of the Catholic Church's most senior figures choked up as he acknowledged the abuse during the hearing.

Francis Sullivan broke down while speaking at the royal commission. ( AAP Image: Paul Miller )

Francis Sullivan from the church's Truth, Justice and Healing Council described the number as "shocking".

"They are tragic and they are indefensible," he said.

"Each entry in this data, for the most part represents a child who suffered at the hands of someone who should have cared for, and protected them."

Gail Furness SC delivered the opening address at this morning's hearing in Sydney. ( Supplied )

The Archbishops of Sydney, Perth, Brisbane, Adelaide, Melbourne and Canberra-Goulburn have congregated in Sydney to give evidence as part of the three-week public hearing.

Questions are expected to focus on the extent of child abuse over almost seven decades and what church leaders are doing to protect children.

This is the 50th public hearing of the four-year-long royal commission and it is the 16th dealing with abuse in the Catholic Church.

The royal commission has investigated how institutions across the country, including schools, churches, sports clubs and government organisations, have responded to allegations and instances of abuse.