Lawyers for the Moriarty Tribunal have told the High Court that a case being taken by businessmen Denis O'Brien and Dermot Desmond against it 'simply does not get off the ground'.

Mr O'Brien and Mr Desmond have asked the court to stop former Tánaiste Michael McDowell from acting as a barrister for the tribunal.

They say Mr McDowell's retention as a senior counsel gives the appearance that the tribunal is biased.

But Senior Counsel Brian Murray, for the tribunal, said allegations of bias could only be directed against a decision maker.

He said Mr McDowell was acting as a barrister in a very limited capacity for the tribunal and had no role of any kind in the decision making process of the inquiry.

Mr Murray agreed with Mr Justice John Hedigan that the case came down to the nature of Mr McDowell's role.

He said this was a most unusual application and it did not meet the criteria to be allowed to proceed.

Mr Murray also told the court that if an injunction stopping Mr McDowell from examining telecommunications expert Michael Andersen was granted, it would delay the work of the tribunal and cause it critical problems.

Mr Andersen has indicated he is only available to give evidence until 5 November and will not be available again until the second half of next year.

Mr Justice John Hedigan will decide tomorrow morning whether to give permission for the two men to continue with their challenge to Mr McDowell's retention.