Millionaire businessman Mr Denis O'Brien today tried to block the Moriarty tribunal investigating into his business affairs as vital witnesses are not available to give evidence in public.
Lawyers for Mr O'Brien sought a High Court injunction to stop the inquiry from investigating the purchase of Doncaster Rovers football ground in 1998.
The tribunal wants to know if former communications minister Mr Michael Lowry was involved in the deal.
But Mr Eoin McGonigal SC, for Mr O'Brien, accused the tribunal of a "gross abuse of fair procedure" against Mr O'Brien (44), because two key figures linked to the Doncaster deal won't be giving evidence in Dublin.
Mr McGonigal called for Northampton solicitor Mr Christopher Vaughan and Northern Ireland businessman Mr Ken Phelan to appear as witnesses so that they can be cross-examined by Mr O'Brien.
However, both have indicated that they are not willing to travel to Dublin to give evidence.
A letter written by Mr Vaughan in September 1998 alleged that Mr Lowry had "total involvement" in the deal. But Mr Lowry denied any such links and Mr Vaughan has since told the tribunal he made a mistake in assuming Mr Lowry was involved.
Mr Justice Dan Herbert also heard today that counsel for the tribunal had travelled to London two weeks ago and held a meeting with Mr Vaughan because they knew he would not be attending public sittings.
A transcript of that meeting was made available to the chairman of the tribunal, Judge Michael Moriarty.
Mr McGonigal said the tribunal had powers to conduct investigations in private only to determine if evidence existed to warrant it proceeding to a full public inquiry.
Earlier, Mr Justice Herbert admitted to both parties that he had been involved as a barrister in the Moriarty tribunal during modules relating to Mr Charles Haughey but "it's so many years now that it's been buried in my mind."
But counsel for Mr O'Brien and Mr Bryan Murray SC, for the tribunal, both said they had no difficulty with this fact.