Former CEO of the Rehab group Angela Kerins has asked the High Court not to award costs against her for her failed legal challenge to the Dáil's Public Accounts Committee.
Lawyers for Ms Kerins told the three-judge divisional High Court the case was an "exceptional one".
Senior Counsel John Rogers asked the court to depart from the norm where the losing party has to pay the costs of the case.
In a case which she lost last month, Ms Kerins had claimed two hearings by the Public Accounts Committee into money paid to the Rehab group amounted to a witch-hunt against her.
She said she was so overwhelmed by what happened at the first hearing in February 2014, she tried to take her own life two weeks later.
She wanted damages for personal injury, loss of reputation and loss of career.
The court ruled that Ms Kerins was inviting the court to analyse utterances made by Oireachtas members in a Dáil committee and this could not be done.
The court said they could not analyse, examine, discuss and adjudge utterances made in the Oireachtas.
In a costs application this morning, Mr Rogers said there was no precedent of the Irish courts which determine the extent of the immunities enjoyed by Oireachtas Committees.
He said Ms Kerins had engaged with the institutions of parliament for the purpose of assisting parliament in its endeavours.
He said by reason of her position she believed it was her obligation to appear before the PAC.
She also believed she understood what faced her but was not on notice of the matters that were put to her.
Mr Rogers said the court had found there were proven "wrongs" to his client notwithstanding that there were no remedies in court.
He said the committee on privileges and procedures had found the PAC acted beyond its powers.
Mr Rogers said her claims were neither unreasonable nor unstatable. He said it was a case where a citizen was assailed in her absence and she was entitled to bring her complaint to the court.
"This was a case where the merits and bona fides of the claim are transparent and a case where she should be awarded costs because of the boundaries of the Constitution."
Mr Rogers said Ms Kerins' rights under Article 40 were "trumped by article 15 of the Constitution”.
He asked that no order for costs be made against his client and the PAC should cover her costs.
Lawyers for the PAC opposed the application by Ms Kerins. After handing in written submissions, Senior Counsel Brian Kennedy said the onus was on the unsuccessful party to pay the costs of the case.
He said in certain circumstances the court may award costs to the losing party if the interests of justice required it but this was not one such case.
Mr Kennedy said the bar was set very high in terms of a case demonstrating exceptional public importance and this case did not meet that threshold.
He said Ms Kerins had a private interest in the case and had not pursued the case solely in the public interest.
He said they were not dealing with uncharted territory and he did not understand the judgment in the case to have accepted there were "wrongs" against Ms Kerins.
Lawyers for the Attorney General said they also opposed the application and said they had been "forced" to attend the case.
They said the Attorney General had been joined to the case by Ms Kerins who had refused to let them out of the proceedings despite their request to be allowed out.
President of the High Court Mr Justice Peter Kelly said the court would give its decision at a later date.