The deadline for the publication of AIB's investigation into overcharging for foreign exchange has been extended due to the volume of work required as the probe has now been extended.
The report into overcharging was expected to be completed by mid-June but the investigation will now cover all charges from 1996 which were notifiable to the financial regulator.
This will be followed by a report which will determine why the overcharging occurred and why it was allowed to persist for such a long period. An additional report covering systems and control issues will be submitted to AIB and IFSRA as soon as possible after this.
Mr Lauri McDonnell of accountants, Deloitte, was appointed in May to act as independent assurer of the investigation.
The AIB board will consider the reports and will determine "appropriate actions" in light of its conclusions and findings as well as any regulatory findings and requirements made by IFSRA.
AIB has already lodged €25 million with the Central Bank to cover the expected cost of reimbursing customers.
The Labour Party's spokeswoman on finance Ms Joan Burton said she was concerned about the implications of the announcement for the promised appearance by AIB officials before the Dáil Committee on Finance and the Public Service.
AIB has said its officials could not appear before the committee until the bank's own internal investigation had been completed.
"But if the investigation goes on until the end of July, it may not be possible to have the matter considered by the committee until the autumn," Ms Burton said.
"This is not a satisfactory situation. AIB has been less than honest with the public and its customers and information has been emerging in dribs and drabs. I am now calling on the bank to ensure the earliest possible completion of the investigation and to give an unequivocal commitment to cooperate
fully with the Dáil committee."