Businessman Denis O'Brien is taking a legal action against a public relations and consulting firm, alleging members of the firm are involved in a conspiracy against him.

Mr O'Brien has been granted an order against Red Flag Consulting, its Chief Executive Officer Karl Brophy - who is a former director of corporate affairs and content development at Independent News and Media, its Chairman Gavin O'Reilly - the former Chief Executive Officer of Independent News and Media, Director Seamus Conboy, Account Manager Brid Murphy, and Account Executive Kevin Hiney.

The order prevents them from interfering with a list of more than 80 media articles and several other documents, which Mr O'Brien says are contained in a dossier about him.

The court has also granted an order preventing any interference with any computer equipment, which could identify who commissioned, contributed to or received the dossier.

Mr O'Brien's lawyers went to the High Court yesterday seeking orders to allow them to search Red Flag's premises.

But the Court ordered them to notify Red Flag and the other defendants and come back to court today.

Mr O'Brien is now seeking an order allowing him to inspect documents and equipment belonging to Red Flag.

Senior Counsel Michael Cush said Mr O'Brien was seeking damages for a conspiracy. The court heard he is claiming he has been defamed as part of that conspiracy against him.

He claims the defendants are involved in authoring and changing documents that make up the dossier.   

Mr Cush said Mr O'Brien wants to know who commissioned them to put together and disseminate the material, who else is involved in authorship of the dossier, and to whom it has already been disseminated.

Mr Cush said experts engaged by Mr O'Brien had been able to identify who was responsible for authoring some of the documents.

He said Mr O'Brien wanted an early hearing of the matter and was concerned, as the orders preventing the defendants from interfering with the documents or computer equipment relied on the good faith of the defendants.

Lawyers for Red Flag said the action would be fully defended. Senior Counsel Michael Collins said Mr O'Brien seemed to be concerned about what he alleged was a campaign against him in the media.

He had commissioned a private investigator and had received a dossier anonymously on a USB stick last Friday.

He then engaged IT consultants to prepare a report. Mr Collins said they would need to engage their own consultants, possibly consult gardaí and other people.

Mr Justice Colm MacEochaidh asked if Mr O'Brien's experts would be able to tell if anyone interfered with the documents or the equipment.

He adjourned the case until 2pm on Friday to allow time for evidence from technical experts.

The dossier contains two PDF documents titled "Denis O'Brien IPO Experience" and "The Moriarty Tribunal Explainer", as well as more than 80 articles from national and international media and transcripts of Dáil debates.

A statement released on behalf of Mr O'Brien in relation to the High Court proceedings said the businessman "became aware of a concerted campaign which involved the circulation of very serious and incorrect information about him and his business interests.

"This included very serious false allegations contained on a USB memory stick delivered anonymously to Mr O'Brien."