A Dáil committee is expected to seek legal advice to see if it can compel AIB officials to appear before it while the bank is conducting an internal investigation into overcharging.

AIB chief executive Mr Michael Buckley has written to the committee's chairman, Mr Seán Fleming TD, to reiterate that the bank would prefer to wait until its investigation is complete before attending.

The committee members will discuss the reply from AIB at their meeting today and are likely to consult the parliamentary legal adviser on whether the committee can insist that the bank comply with its request.

Mr Fleming said the committee had already asked the Central Bank governor, Mr John Hurley, to attend to discuss the role of the regulator and whether it is adequately empowered to deal with Irish and foreign financial institutions operating in the Republic.

"It would be better to hear from the Central Bank before we meet with any more financial institutions," Mr Fleming said. The governor has agreed to meet the committee next week.

The investigation at AIB is being carried out by former Auditor and Comptroller General Mr Lauri McDonnell and is expected to be completed by mid-June.

Its findings will then be considered by the bank's board of directors.

The Irish Financial Services Regulatory Authority is also separately investigating the bank's overcharging of some customers on foreign exchange transactions and the assignment of payment protection policies to some mortgage customers.

It has said that it will independently assess Mr McDonnell's findings. The regulator does not have the power to impose fines on the bank for its transgressions.

Proposed legislation that is still before the Dáil would allow it to impose a fine of up to €5 million on the bank. This cannot be applied retrospectively.