Donegal has probably the worst record for clerical child sex abuse in Ireland, Bishop Philip Boyce has admitted.
The Bishop of Raphoe also revealed that 20 people working for the Catholic Church in the diocese, which covers most of the county, had still not been vetted.
A report by the church's own watchdog warned that some priests had expressed reluctance to undergo Garda security clearance.
Bishop Boyce said he "didn't think" anyone had refused and that he did not know the breakdown of priests and lay people who had so far declined to return vetting papers.
The National Board for Safeguarding Children in the Catholic Church gave little detail on 52 known allegations against suspected abusers in Donegal since 1975.
More than 20 of the complaints were against notorious paedophile priest Eugene Greene, who abused dozens of youngsters while being moved from parish to parish. Greene was jailed for 12 years in 2000 after pleading guilty to 41 sample charges against 26 victims between 1962 and 1985. He was freed in 2008.
Asked about the prevalence of clerical child abuse cases in the diocese, Bishop Boyce accepted it was proportionately higher than many other dioceses and "probably" the worst in the country. "I haven't seen all the other dioceses to confirm that, but I would say it has one of the highest," he said.
Bishop Boyce, his predecessor Seamus Hegarty, who retired as Bishop of Derry earlier this month due to ill health, and his predecessor, Bishop Anthony McFeely, were all singled out for mishandling complaints against clergy since the 1970s.
The report found a priest put in charge of investigating sex abuse complaints as recently as January 2009 admitted he was "ill at ease" with the role, as alleged abusers were often life-long friends. The so-called "designated person" was emotionally challenged by the role and had taken no formal training beforehand, it was found.
Bishop Boyce, who took control of the diocese in 1995, said the priest was recently replaced by two lay people.