Investigations by the Department of Enterprise, Trade and Employment into six companies, are taking a long time because of the number of documents involved and the need to obtain legal advice, according to the Tanaiste.

Ms Harney said: "The volume of documentation and the number of people involved in these investigations is as great and greater, in some cases, than the number being investigated by the two tribunals of inquiry. We know how long it has taken those tribunals to reach their current position."

She expected to receive final reports over the summer on most of these investigations and had appointed an authorised officer to a further three companies. She had already referred four completed reports to the Director of Public Prosecutions.

The Minister was responding at Question Time in the Dail to Fine Gael's deputy leader, Ms Nora Owen, who said many people were frustrated by the delay in concluding the inquiries.