Seven per cent of Australia’s Catholic priests were accused of abusing children in the six decades since 1950, according to new data from the royal commission.

On Monday the royal commission into institutional responses to child sexual abuse released damning statistics on the scale of the crisis within the Catholic Church. The numbers confirm the extent of sexual predation already suggested by four years of royal commission hearings involving the church, which are now entering their final weeks.

Up to 15% of priests in some dioceses were alleged perpetrators between 1950 and 2015, with abusers most prevalent in the dioceses of Sale and Sandhurst in Victoria, Port Pirie in South Australia, and Lismore and Wollongong in New South Wales. The numbers were even worse in some national Catholic orders. By far the worst was the order of the St John of God Brothers, where a staggering 40% of religious brothers are believed to have abused children.

As Catholics, we hang our heads in shame Truth, Justice and Healing council chief executive Francis Sullivan

Twenty-two per cent of Christian Brothers and 20% of Marist Brothers, both orders that run schools, were alleged perpetrators. More than one in five priests in the Benedictine community of New Norcia were alleged perpetrators, while 17.2% of clergy were accused of crimes against children in the Salesians of Don Bosco order.

In total, between 1980 and 2015, 4,444 people alleged incidents of child sexual abuse relating to 93 Catholic Church authorities. The abuse allegedly took place in more than 1,000 institutions. The average age of victims was 10.5 for girls and 11.6 for boys. The overwhelming majority of survivors were male. Almost 1,900 perpetrators were identified and another 500 remained unidentified. Thirty-two per cent were religious brothers, 30% were priests, 29% were lay people and 5% were religious sisters.

The royal commission said 37% of all private sessions it held with survivors from all institutions related to abuse in the Catholic Church.

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The disturbing figures were revealed by senior counsel assisting, Gail Furness, SC. She also revealed that the Holy See had refused to hand over documents involving Australian priests accused of abuse.

“The royal commission hoped to gain an understanding of the action taken in each case,” Furness said. “The Holy See responded, on 1 July 2014, that it was ‘neither possible nor appropriate to provide the information requested’,” she said.

Furness said the responses of Catholic diocese and orders across the country were “depressingly similar”.

“Children were ignored or worse, punished. Allegations were not investigated. Priests and religious [brothers] were moved. The parishes or communities to which they were moved knew nothing of their past,” she said. “Documents were not kept or they were destroyed. Secrecy prevailed as did cover-ups.”

The church’s Truth, Justice and Healing council, set up to coordinate the church’s response to the crisis, made an opening statement following the release of the data. Chief executive Francis Sullivan struggled with emotion as he spoke, saying the data without doubt “undermines the image and credibility of the priesthood”.

“These numbers are shocking, they are tragic, they are indefensible,” Sullivan said. “And 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.

“The data is an indictment on the priests and religious who abused these children. It also reflects on the church leaders who at times failed to take steps to deal with the abusers, failed to call them to order and failed to deal with them in accordance with the law.”

Sullivan described the abuse as a “massive failure” of the church and as a corruption of the gospel.

“As Catholics, we hang our heads in shame,” he said.

Sullivan outlined the key programs of change undertaken by the church. That included the establishment of the professional standards body responsible for auditing and reporting on the compliance of bishops and church leaders with child protection standards. It also includes revisiting abuse claims, the push for a national redress scheme, the recruitment of new professional standards officers and the creation of stronger child protection policies and procedures.

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The royal commission is now in its final stage of examining abuse by Catholic clergy and the responses of various Catholic authorities. The final three weeks are expected to focus on cultural causes of the offending, the current child protection policies of the church, and the way it has responded to the royal commission case studies so far. The archbishops of Sydney, Adelaide, Melbourne Canberra-Goulburn, Perth and Brisbane are due to give evidence.

The hearing aims to answer the questions that linger in many survivors’ minds: why did the abuse happen at such a scale? And why was it covered-up for so long?

Church leaders last week began warning churchgoers and schools about the final weeks of the royal commission. The archbishop of Brisbane, Mark Coleridge, released a video to Catholic school parents and churches warning them to expect some “grim moments”. He said the final hearing would allow the church to tell a “better story” about how it has changed.

“Through these three weeks there will be some grim moments and there will be some shocks, inevitably,” he said. “But there will also be a chance to tell a better story of what has been done and what is being done now.”

He said the church would need to show how it had changed culturally, as well as through amendments to flawed child protection policies and procedures.

“It’s not enough to change procedures and protocols, that has to happen. But we have to shift the culture and that’s a much more difficult thing to do,” he said.