AIB set up six major lending groups within its Republic of Ireland operations that for years operated as special units in advancing major loans to property developers, independently of the retail branch network, the Sunday Tribune has learned.

The number of special lending groups is much higher, their involvement in lending to major property figures was much more extensive, and they operated over many more years than has ever been known.

AIB insiders said the operations of the six groups explain why Ireland's largest bank perilously ramped up lending to developers, which has led to the bank to the brink of transferring over €19bn in property loans, or a seventh of its loan book, into the taxpayer-backed National Asset Management Agency.

The Financial Regulator, responding to a list of detailed questions on the controls AIB exercised over the six lending groups and potential conflicts of interest, their location and the regulator's knowledge of the lending groups, said it could not comment "in relation to ongoing supervisory issues".

In a so-called 20-F report filed in the United States last week, AIB executive chairman Dan O'Connor alluded briefly to the lending groups, which the bank calls "teams", but did not refer to the scope of their lending activities. He said that "within the control of the bank, but separate from the day-to-day activities of the branch network, we set up teams to lend money to developers in the property and construction sector."

O'Connor did not indicate how many groups operated within the bank or whether any of the "teams" were involved in lending outside Ireland.

In a statement, AIB said the lending groups were not part of the branch network but were part of its Republic of Ireland division "and therefore subject to the same reporting structure". It would not confirm whether the bank was in discussions with the regulator about the lending groups.

Separately, AIB's annual statements reveal that former chief executive Eugene Sheehy, who bought €2.8m worth of AIB shares in late 2007 which have since collapsed in value, repaid in recent months a loan or loans worth €2.3m he had borrowed from the bank as a director.

The filings also show that the bank's new managing director, Colm Doherty, six years after the sale of AIB investment arm Govett, is still personally indemnified by AIB for potential losses that could arise from any lawsuits by investors who held Govett split-capital funds.

An AIB spokeswoman said the insurance issue was not specific to Colm Doherty or to AIB and arose because of the general changes introduced by the insurance industry. The regulator has not raised any issue on the insurance in recent times, the bank said.

For the first time this year, AIB and other Irish lenders have had to disclose the amount of loans borrowed by individual directors.

AIB's latest filings showed that Sheehy, who left the bank in November, repaid a loan or loans of €2.3m in recent months. But despite the changes imposed in February last year, the new regulations on disclosures still make it impossible to detect with any precision when banks advanced the loans to its directors in previous years.

Regulatory stock market filings show that, in early August 2007, Sheehy bought 150,000 AIB shares worth €2.8m in four blocks at an average price of €18.72 a share.

AIB said on Friday that its loans to directors were advanced "on normal commercial terms".

In previous years, lenders were obliged to disclose only the aggregate amounts of loans borrowed by directors and the new regulations still do not oblige lenders to disclose the amounts lent in previous years.