The Public Accounts Committee will have to pay two thirds of Angela Kerins' legal costs after her failed High Court action against it.

In a ruling which departed from the norm where the losing side usually pays the costs, the High Court said the former Rehab CEO was entitled to take the case which raised issues of "special and general public importance".

The decision may also have implications for how the PAC operates in future.

Ms Kerins had claimed two hearings by the PAC 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.

She lost the case in January after the court ruled it could not analyse, examine, discuss and adjudge utterances made in the Oireachtas.

In her costs application in February lawyers for Ms Kerins told the three-judge divisional High Court the case was an "exceptional one".

This morning the High Court ruled that Ms Kerins should be awarded two thirds of her costs against the PAC.

It made no order for costs against Ireland and the Attorney General who were also respondents in the case. This means Ms Kerins will not have to pay the costs for these respondents.

In its costs ruling the court noted Ms Kerins had attended the PAC in a voluntary capacity and was dealt with on 27 February 2014 and was not in attendance for medical reasons on 10 April that year.

The judges said they had "already pointed out that the court is limited by the Constitution from making any comment which would touch directly on the utterances of any member of the PAC but nonetheless it cannot be gainsaid that much of what was put to the applicant and said about her in the course of the two meetings in question was damaging to her reputation both personally and professionally."

The ruling continued: "The court is satisfied that the institution of these proceedings was proportionate reaction on the part of the applicant to the situation arising from what took place before the PAC."

The court was also satisfied that in her action she raised issues of special and general public importance and some novelty.

She raised issues concerning the legal safeguards (if any) available to witnesses who appear before the PAC in a voluntary capacity. "The PAC has an important function, questions concerning the proper discharge of its function and the conduct of it members are matters of public importance," the ruling said.

The court found the case also raised "important questions of freedom of speech in parliament, the separation of powers and the extent to which the court may interfere in the affairs of the legislature".

The court was also satisfied that the case raised issues of importance for the respondents.

"It determined that Article 15(13) extends to utterances in committee as well as utterances in the parliamentary chambers. The case also cast a light on the position of persons who volunteer to appear before the PAC. This may well have implications for the PAC in future since the court was told that it operates to a significant extent on voluntary participation of witnesses."

The court accepted that there was a personal interest on the part of Ms Kerins in taking the case but that was "not fatal" to her costs application.

"The court is of the opinion that justice of the case will be met if the applicant is awarded two thirds of her costs" against the members of the PAC of 2014.

The State - Ireland and the Attorney General - will have to pay their own costs.