Former Government press secretary PJ Mara has applied at the Mahon Tribunal to have his legal bills paid by the State.
The second interim report of the tribunal found that Mr Mara had failed to co-operate with the inquiry by not disclosing the existence of an off shore account. However, no finding of corruption was made against him.
Lawyers for PJ Mara have said that in the tribunal's report no link was found between any of his financial records and any matter being investigated.
None of the allegations made against him were substantiated and that, apart from the isolated incidents of the omission of an Isle of Man account, Mr Mara had co-operated.
The lawyers also said that he had already apologised for the omission and that in total less than ten transactions were not disclosed.
They have said a full award of costs would be just, fair and proportionate.
They have claimed that the tribunal's investigation has had a profound effect on his life and it is difficult to overestimate the stress involved in being a witness.
PJ Mara’s costs are understood to have run into six figures.
Judge Mahon will deliver a ruling on the matter at a later date.