National Irish Bank's top management is expected at Garda Headquarters in the Phoenix Park today to meet Garda fraud officers investigating the imposition of illicit charges on customers.

Officers from the Garda Bureau of Fraud Investigation yesterday met top officials from the Bank of Ireland and Allied Irish Banks at venues in Dublin.

According to Garda sources close to the investigation, the senior B of I and AIB officials indicated they would co-operate in every way with their work. A senior Garda source said they were "very happy" with the responses from the AIB and B of I senior management.

It was not clear yesterday who would represent NIB during today's visit to the Garda Depot today but it is expected that the bank delegation will include officials to at least deputy chief executive and director level.

The Garda investigators had, by yesterday evening, received some 260 complaints from the public and, of these, around 70 per cent concern accounts in the NIB. There is a wide geographical spread of complainants and some are being investigated by local detectives with training in fraud investigation. The fraud bureau has a unit in Cork and this is investigating complaints about the NIB branch in the city. Officers from the bureau's headquarters travelled to Donegal and Leitrim in the last two days, it is understood, to look into the complaints about NIB branches in Carndonagh and Carrick-on-Shannon.

At least 12 headquarters fraud investigators are expected to remain on the case for the next few weeks.

The investigation is the largest in terms of the number of complainants yet carried out by the bureau but it is not said to be large in terms of the total amount of money involved.

About three-quarters of the complaints against NIB concern suspicious additional fees and interest charges. However, the bureau has received a wide variety of complaints.

According to Garda sources, there are clear grounds for suspecting unusual banking activity in relation to many of the complaints but several are unlikely to lead to Garda action against a financial institution. One source said many of the complaints coming into the investigation are more likely to fall into the category of "sharp practice" rather than fraud.

The Garda Bureau of Fraud Investigation is contactable through the main Garda HQ switchboard, at Dublin 6771156.