The family of Seán Quinn has there was "no impropriety" in its dealings with Anglo Irish Bank, which was nationalised by the Government in January.
The comments were issued in a statement published on the Quinn Group's website today in response to a report by RTÉ that the financing of Mr Quinn's 25 per cent stake in the bank was under investigation.
It said the Quinn family assets, "which are held outside of the group, have over the years been financed from a number of sources including related party loans from the group, internally generated cash, and finance from both Irish and international financial institutions, including Anglo Irish Bank".
The statement said it would not comment on private family financial matters, "except to say that over 36 years we have never had a problem repaying our borrowings and this will not change in the future".
It said Mr Quinn's 25 per cent stake in the bank was acquired initially through contracts for difference (CFDs), "which are a legitimate and widely-used investment vehicle".
Mr Quinn and his family acquired 15 per cent of the ordinary shares in the bank in July 2008, leaving an "overhang" of 10 per cent, which was acquired by 10 investors assembled by the bank.
"As previously stated, there has been absolutely no impropriety regarding the family's dealings in any transactions relating to any of its investments including Anglo Irish Bank, and we have no doubt that the current investigations will prove this," the statement said.
It described the media attention as "disappointing".
The Quinn Group employs some 5,500 people in Ireland.