The head of the Office of the Director of Corporate Enforcement (ODCE) has admitted its investigation into Anglo Irish Bank "went wrong in a pretty catastrophic way".
Ian Drennan has told an Oireachtas committee that valuable lessons were learned from the investigation.
He appeared before the Joint Committee on Business, Enterprise and Innovation to discuss the collapse of the trial involving the bank's former chairman, Sean Fitzpatrick.
Mr FitzPatrick was acquitted of all charges against him in May 2017.
But the judge was highly critical of how the ODCE handled its investigation, saying fundamental errors were made.
However Mr Drennan also defended the group's role in the Anglo Irish Bank trials.
He told the committee that this was never suggested in any of its other Anglo-related investigations.
"It is important to place on record that the ODCE's Anglo-related investigation - which actually comprised of five separate investigations - resulted in four trials, all of which resulted in persons being convicted on indictment of criminal offences.
"In the narrative that has followed DPP versus FitzPatrick, sight is sometimes lost of that fact.
"It is also important to note that it has never been suggested, in any court, that any of these investigations were in any way deficient or below the requisite standard."
"It was completely unprecedented in terms of the sheer scale of five separate strands of investigation, each of which on their own merits were enormous.
"The reality (is) any organisation irrespective of how big or small it is, if you're trying to carry that kind of a load across a relatively small number of people that level of complexity and volume things go wrong, and unfortunately in this case they went wrong in a pretty catastrophic way and the wheels came off".