Lawyers for RTÉ have told the High Court it should ignore a threat from businessman Denis O'Brien to review all his arrangements with Irish banks if information about his private banking affairs is disclosed.

Senior Counsel David Holland said Mr O'Brien had said in a sworn statement that if the pretext for disclosing the information was that he was a businessman dealing with Irish banks, then that would have profound implications.

Mr O'Brien said that would cause him and others to review all their arrangements with Irish banks.

Mr Holland said Mr O'Brien should find some other horses to frighten.

He said no sovereign state and no court should put up with that kind of threat.

He said what Mr O'Brien decided to do with his financial affairs and where he decided to locate them was a matter for him. He said that kind of threat should be ignored.

Mr O'Brien is asking the court for an injunction to stop RTÉ broadcasting a report about his banking affairs with the Irish Bank Resolution Corporation.

Earlier, lawyers for RTÉ told the court that publishing businessman Mr O'Brien's name in the context of a story about a major debtor seeking to extend his loans with the IBRC, was an entirely legitimate journalistic judgement.

Mr Holland said anonymous news was no news and Mr O'Brien wanted RTÉ to broadcast the story in a "boring, dry and sterile way".

He said the courts should not readily interfere in journalistic decisions. He said what Mr O'Brien would like to be done in this case is to suck the lifeblood out of the story by anonymising it.

Mr Holland said Mr O'Brien was a public figure who created and managed his public profile and was not entitled to set the boundaries of how much the public should know about him.

By dint of his public profile and his control of significant elements of the media, he was a person who should be exposed to close scrutiny by the press, Mr Holland said.

He said the publishing of confidential information would not always be an aspect of close scrutiny, but there was no reason to suggest that it could not be on the facts of a particular case.

He said close scrutiny was the first necessary step in the media's performance of its role as a vital public watchdog.

He said there was no point in the press scrutinising matters if it could not publish information. He said a watchdog must not merely watch, he must bark.

Mr Holland urged the court to reject a suggestion by lawyers for Mr O'Brien that publishing this information could lead to the floodgates being opened.

He rejected a suggestion by Mr O'Brien that commercial banks would be unwilling to deal with him if this information was published.

Mr Holland said Mr O'Brien's dealings with IBRC were dealings with a very particular, unusual type of bank in which very particular public interests arose.

Commercial banks would never believe they faced the same kind of disclosure of private information.

Mr Holland said it was a fair question to ask in the public interest if it was commensurate with the recovery of money owed to the IBRC to grant an extension to Mr O'Brien's loans for the period of time in question in the proposed story.

He said the public were entitled to know about it, so it could take a view.

It was not a question for the court or RTÉ to take a view on but for the public.

He said what was at issue here was the publication of matters which were of grave concern to the political system and the state.

Mr Holland said in the context of the political controversies which were raging as he spoke, the affairs of IBRC and its dealings since 2009 with major debtors were of public interest and should be published so people would know about them.

He said the courts should be very slow to impose its fine judgments as to whether or not a matter was in the public interest.

He said the leader of the Opposition and the Minister for Finance agreed that the affairs of IBRC were matters of public interest, of very significant weight, meriting an inquiry.

Mr Holland said information had come out in the past two weeks and one would want to be "deprived of all senses and locked in a dark room to think this was not a matter of public and political importance in this state."

He said there may also be a public interest in knowing what the outcome of Mr O'Brien's dealings with the Special Liquidator of the IBRC over his loans was.

"We don't know what happened, others might find out, others might tell us and he might even be back in here trying to prevent publication."

He said to suggest that because RTÉ did not know those things, the public interest was not engaged was an untenable position.

He said news stories "do not emerge from the womb fully formed." He said it was a process. One publishes information and one does not have all the information and over time more facts emerge.

The story may grow, the story may die but to suggest that if you do not know everything you can publish nothing would be to undermine the role of a free press in a free society, he said.

Mr Holland said he agreed with lawyers for IBRC that it was not uncommon for debtors to seek extensions on their loans. But he said it was uncommon for it to arise between Mr O'Brien and the IBRC.