A British-based journalist, who is at the centre of a controversy about businessman Denis O'Brien, had asked RTÉ News for documents in its possession about the billionaire's finances.
He requested the material seen by RTÉ News, which contained details of Mr O'Brien's banking arrangements with IBRC, formerly Anglo Irish Bank.
The documents formed the basis of an RTÉ story, which was the subject of a High Court injunction by Mr O'Brien earlier this year.
The journalist, Mark Hollingsworth, claimed he was writing a story for the Sunday Times Magazine.
He was told by RTÉ News that the broadcaster would not reveal the documentation or arrange for the journalist to speak to the source of the material.
Although a contributor to the Sunday Times, the newspaper told RTÉ Mr Hollingsworth was not commissioned to write a piece about Mr O'Brien.
Yesterday it was reported that Mr Hollingsworth also received a dossier about Mr O'Brien from a public relations company, Red Flag.
Last week the businessman took a High Court action against Red Flag's CEO Karl Brophy and Chairman Gavin O'Reilly claiming the company had spread defamatory material about Mr O'Brien and his business.
In the High Court counsel for Mr O'Brien said he was anonymously given a USB stick containing files about the businessman, which they claim had been assembled by Red Flag.
Mr O'Brien had hired private investigators, who made inquiries about an alleged conspiracy against the businessman.
Mr Hollingsworth told the Sunday Times he was given the dossier, which contained a file of media articles about Mr O'Brien, via file-sharing website Dropbox.
The journalist told the Sunday Times that his computer had been hacked two weeks ago.
There is no suggestion of a link between the USB stick being given to Mr O'Brien and the hacking of Mr Hollingsworth's computer.
Mr Hollingsworth first contacted RTÉ News in July. He also spoke to a number of politicians as part of his research.
He is the author of seven books and contributor to a number of British newspapers.
