The Office of the Director of Corporate Enforcement (ODCE) has said it fully accepts a judge's criticism of its investigation into the former chairman of Anglo Irish Bank after he was acquitted of misleading auditors.
Sean FitzPatrick was on trial for the last 126 days accused of "artificially reducing" personal loans for a few weeks around the end of the defunct bank's financial year to avoid their full value being shown in accounts.
After the longest criminal trial in Irish history, the former bank boss was told the jury will be given a direction to find him not guilty at a hearing in the Circuit Criminal Court in Dublin on Wednesday morning.
The Office of the Director of Corporate Enforcement (ODCE) said it accepted witnesses were coached when giving statements during the investigation and that their evidence was contaminated.
It also admitted that other documents held by the watchdog were shredded by one its own officials. He was said to be under enormous stress at the time.
"Those actions clearly should not have occurred," the ODCE said.
Mr FitzPatrick, who has always denied wrongdoing and pleaded not guilty, walked from the Criminal Courts of Justice complex in Dublin holding his daughter Sarah's hand after being told that he was being acquitted.
"I want to say it was a very long and tiring and difficult time for my family and myself and thankfully today the trial is over," he said.
Mr FitzPatrick thanked his legal team by name and added: "As you can appreciate it's a wonderful day for me and my family. I appreciated the media's restraint in this current trial and I would hope that my privacy and that of my family is respected over the coming days."
The ODCE said it accepted that witnesses from auditors Ernst and Young were coached while making statements and that their evidence was contaminated.
In a lengthy statement following Mr FitzPatrick's acquittal, the ODCE also said there were "serious failures" in its investigations into the former banker's personal loans.
"It is clear at this remove that, at that time, the ODCE was simply not equipped to undertake parallel investigations on the scale involved," the watchdog said.
It said the witness statements were taken by "civilian staff".
"Regrettably however, none of those individuals had any training or experience of taking witness statements," the ODCE said.
"Moreover, the inappropriateness of the approach that was subsequently adopted in obtaining those statements was not sufficiently appreciated nor were the attendant risks responded to appropriately."
The ODCE said it has undergone "substantial organisational change" over the last eight years.
It said: "It is a very different organisation to what it was."
Mr FitzPatrick of Whitshed Road, Greystones, Co Wicklow had pleaded not guilty to more than two dozen offences under company law, including making a misleading, false or deceptive statement to auditors and furnishing false information between 2002 to 2007.
The former banker's acquittal sparked criticism from opposition politicians over the handling of the investigation.
Pearse Doherty, Sinn Féin's finance spokesman, claimed fraud investigators in Ireland were under-resourced.
Alan Kelly, Labour Party deputy leader, called for an independent inquiry into the ODCE's handling of the case.
The Director of Public Prosecutions declined to comment on the outcome of the case.
Mr FitzPatrick went on trial last September. Proceedings were scheduled to end by Christmas but it was delayed by weeks of legal argument in the absence of the jury and only began hearing evidence in December.