The Christian Brothers have said that "they deeply regret" the hurt caused by their response to abuse allegations which resulted in only 12 brothers being convicted of crimes in the past 38 years.
The Catholic Church's child protection watchdog has published eight reviews of the practices and procedures in place to address sex abuse cases.
The audit, which covers the period between January 1975 and May 2013, examines six separate dioceses and two religious congregations.
The work was carried out by the National Board for Safeguarding Children in the Catholic Church.
The congregation in a statement said they accept that a "safeguarding deficit" existed in the past and they "deeply regret" the hurt that this causes.
Their statement said: "We want to learn from the mistakes of the past and to create a safe environment for all children and young adults. By developing robust child protection measures and inviting the National Board to independently assess these, we aim to continuously enhance child protection safeguards so that the mistakes of the past may never be repeated.
"The congregation accepts in full the National Board’s recommendations on how to further enhance safeguarding measures for the future. Half of the Board’s recommendations have already been implemented or are nearing completion and work on the remaining elements is underway."
This latest tranche of reports from the Catholic Church's child protection watchdog shows that during a period of almost three decades, 870 allegations of child sex abuse were made against 325 members of the Christian Brothers order.
The audit, which shows that 12 have been convicted, describes the number of allegations as substantial and says the reviewers were in no doubt that a great number of children were seriously abused by the Brothers.
The review of the St Patrick's Missionary Society, known as the Kiltegan Fathers, says 50 allegations were made against 15 members of the order - with one conviction since 1975.
In the Armagh Archdiocese, run by Cardinal Sean Brady, the audit warned that it found little information on the receipt and management of allegations before 1995.
It said there was “inconsistent filing leading to a lack of clarity about how decisions were made”.
The report found Cardinal Brady, on taking up his role as Primate of All-Ireland in 1996, made a “commendable decision to gather and document whatever information was available,” the review board found.
“However the reviewers cannot be confident that the records of allegations made prior to 1995 are complete. The reviewers looked at a small sample of documentation from this period.”
Sixteen priests in the archdiocese have faced 36 allegations and four of them are still in ministry, the audit found.
Only one priest has been convicted and the audit said no allegations have been made since 2000.
In Armagh the audit team found some case files with significant gaps but it also praised the Cardinal for adopting a more focused and committed approach to the safeguarding of children since he took over.
Cardinal Brady, who has been heavily criticised for swearing two victims of paedophile priest Brendan Smyth to secrecy during an internal church inquiry in 1975, said his first thoughts today are with abuse survivors.
“I know that for you, survivors of abuse and your families, days such as today are especially difficult. You have suffered terribly and I am truly sorry. I pray for you and will work to ensure that you are supported on your journey towards healing and peace,” he said.
He added: “I am reassured that safeguarding practice in the Archdiocese conforms to the highest national standards.
“While we acknowledge the report’s findings that in the past the response was not as prompt, robust and coordinated as in the present, we will continue to do all we can to ensure that current high standards of safeguarding practice are maintained.”
Elsewhere, in the Diocese of Achonry, Bishop Brendan Kelly informed reviewers that the diocese did not have a safeguarding policy and procedures document in place before 2008.
There had also been little evidence of a systematic process for filing or managing information about abuse allegations before then.
The watchdog, however, commended the diocese for its work over the last five years to put a safeguarding system in place.
There have been no fresh allegations against the diocese since Bishop Kelly was appointed in 2007.
Before that, a total 15 allegations had been made against it, relating to 11 priests.
Thirteen of those charges were reported to gardai, and 12 of them to the HSE. No priest was convicted of any offence.
Only two of the 11 priests accused are still living.
Bishop Kelly said: “Vigilance will be maintained as an absolute priority in this critical area. That is our assurance to all parents and children.”
The bishop also apologised to anyone who has suffered clerical abuse, which he said causes “incalculable damage”.
“It is entirely reprehensible, a serious crime and a grave sin,” he said.
“It is all the more grievous when the perpetrator is a person in a position of trust, such as a priest, who is called to be a minister of the good news of love, compassion and justice.”