AIB has sent confidential letters relating to 12 customers' overdrawn accounts to a third party who had no right to the correspondence.
The Republic's biggest bank admitted yesterday that it had been forced to apologise to 12 customers after mistakenly sending letters relating to their accounts to the wrong person.
The letters, some of which where seen by The Irish Times, were issued by the bank's insolvency and debt unit in Dublin.
All of them deal with overdue debts owed by the individuals to the bank.
The sums involved range from just over €600 to close to €9,000 and the letters are dated between July 19th and 24th.
Along with the amounts owed to the bank, the letters include the individuals' names, addresses and the numbers of the deposit, current and loan accounts that they hold with the bank.
Each of the letters states that, as the customers have "failed to meet their obligations to the bank" as outlined in earlier correspondence, the institution intends to end its relationship with them.
They then go on to point out that the bank reserves the right to offset any sums credited to them in any of their accounts against the full amounts that they owe. The letters also make it clear that the bank intends pursuing them for their debts.
While the letters originate in the insolvency and debt unit based in Dublin's Adelaide Road, the accounts to which they refer are located in various centres around the Republic, including Dublin, Roscommon, Limerick and Mayo, as well as in the UK.
All banks and financial institutions are obliged to treat customers' affairs with absolute confidentiality and are not in any circumstances supposed to allow any unauthorised information to fall into a third party's hands.
In a statement issued to The Irish Times yesterday, the bank said that documents sent to one customer were photocopied at the same time as letters due to be sent to other clients.
"Some of these letters were then mistakenly included in the batch of documents sent to the first customer," it said.
"This was a very regrettable case of human error. We are in the process of contacting the customers involved to inform them about what happened and to apologise to them."
The bank added that it was taking whatever action was necessary to prevent anything like this happening again.
One individual involved complained that, not only had the bank sent confidential and embarrassing information to the wrong person, it had exposed people to a number of risks, including the possibility of identity theft.
AIB has been embroiled in various scandals over the last seven years.
It was one of the main focuses of the investigation into the use by Irish banks' customers of bogus non-resident accounts to evade retention tax (DIRT) obligations.
Two years ago, the financial regulator carried out another investigation into AIB after it emerged that it had been overcharging customers on non-cash foreign exchange transactions.