A watchdog review of the Diocese of Clogher found opportunities to prevent attacks in the past were consistently missed when concerns were raised.
Clogher diocese has 37 parishes and 73 priests across counties Fermanagh, Tyrone, Donegal, Monaghan, Louth, Cavan and the renowned Lough Derg pilgrimage site.
The report is the latest in a series carried out by the National Board for Safeguarding Children (NBSC) into historic abuse at institutions across Ireland.
The Board said that a line should be drawn in how the diocese dealt with allegations and the procedures it has in place today.
Bishop Joseph Duffy led the diocese for about 30 years until his retirement in 2010, when Bishop Liam McDaid took over the role.
The review said that 13 priests in the diocese faced allegations, one of whom is classified as either "in ministry or retired" and two have been convicted.
Ian Elliot, head of the Catholic church watchdog, noted an "unacceptable delay" in removing a priest from ministry after a credible child abuse allegation.
He also highlighted that there was another case where a priest suspected of multiple abuse was not removed from ministry, but transferred to another parish and eventually sent overseas for therapy.
Ultimately he was extradited back to Ireland, but died before he could face trial.
In a number of cases, allegations emerged against priests following their death making it impossible for any investigation to take place.
Watchdog review of the Diocese of Clogher
"The impression formed by the reviewers of past practice was that the response to abuse concerns was often unsatisfactory and that risky behaviour was not addressed as strongly as it should have been," the report found.
Between 1975 and November 2012 in Clogher, 23 allegations of abuse were reported to gardaí and 22 to the health service.
Seven of the priests facing allegations were dead.
One priest in the diocese was known to have faced abuse allegations from a previous ministry, the report also found.
Amnesty International has reiterated its demand for a state-instituted inquiry into clerical child abuse allegations in Northern Ireland.
Patrick Corrigan, Northern Ireland programme director, said: "Church-approved reviews are no substitute for a proper, independent investigation into clerical child sex abuse throughout Northern Ireland.
"The abuse knew no borders and, indeed as we know, in some instances, the abusers were moved across parish and national borders, abusing children as they went."
Other audits looked at the dioceses of Galway, Kilmacduagh and Kilfenora, Ferns, Killala, Elphin, Waterford and one religious order, the Society of African Missions (SMA).
The report found allegations against 21 SMA Irish Province priests from January 1975 until last January's review, with one convicted.
Two others have been laicised and an application is being processed in Rome for the laicisation of a third, the audit reported.
Three others, about whom concerns were raised, remain in some form of ministry in mission countries.
"All of these cases were fully examined and assessed and the outcome in all three cases was that there were no safeguarding children issues to be addressed," the audit found.