An Bord Pleanála spent €10 million on legal fees last year.
Chair Oonagh Buckley told the Public Accounts Committee that in 2022 it won nine judicial review cases, lost nine cases, conceded 35 and 12 were withdrawn.
She admitted that conceding cases is "problematic and raises the question of why the board is taking decisions it can't stand over".
Ms Buckley said it is expanding the in-house legal department and has hired a head of legal services as she expects the body will continue to deal with high levels of litigation.
"I don’t believe there will be a reduction in Judicial Reviews going forward, the only way we can achieve that is by making it more difficult to win against An Bord Pleanála," she said.
She described 2022 as a "particularly difficult" year for the organisation.
"The board attracted major regulatory and public attention, in particular in relation to conflicts of interest that may arise in the course of the decision making process," she said.
Ms Buckley went on to outline that a number of departures from the board occurred "including that of the deputy chairperson in July and the chairperson in November and others as their term of office expired."
"I cannot discuss those matters given pending matters before the courts but suffice to say that these events have had a serious detrimental impact on the board's reputation," she said.
Former An Bord Pleanála deputy chairman Paul Hyde has appeared in court on nine counts of failing to comply with planning laws.
Read more: An Bord Pleanála to be renamed as part of changes under draft bill
Ms Buckley has not appointed an external senior counsel to undertake a scoping investigation.
Senior Counsel Lorna Lynch has begun her investigation into a substantial number of files and is to make recommendations to the chair on any next steps.
"Ms Lynch and a colleague have recently begun interviewing members of the board I have asked that her report be capable of being published although that event may have to be deferred if any disciplinary or other action is indicated appropriate following the scoping investigation," Ms Buckley said.
Last year 180 applications for Strategic Housing Developments (SHD) were received and there were "insufficient decision makers available".
"This resulted in the board incurring fines in 134 cases for running over time," she said.
The fine as laid down by law is €10,000 per application so An Bord Pleanála incurred a fine of €1.34 million.
There are around 2,700 cases before the board at various stages. This means it is overtime in 65% of cases.
But she added that with the recent appointment of board members "the engine is moving again".
Ms Buckley said in order to deal with the backlog of cases it needs to make around 300 decisions every month - 50 decisions were taken in February and 90 in March.
One of the longest running cases has been before An Bord Pleanála for around four or five years.
But Ms Buckley said it is likely that this is a file where more information is required before a decision can be made.
She said she was very sorry that she became the story following her appearance at a planning conference last month.
"I am very sorry I name-checked someone who was not in the room," Ms Buckley said. "I have to learn a lesson from that."
She did consider making a corporate apology when she took over as interim chair last year and quickly moved to apologise to all of the people whose applications have been held up.
Ms Buckley said she is happy to repeat the apology to the people and to the staff "who through no fault of their own had to deal with very difficult discussions with members of the public about what was going on in An Bord Pleanála".
