The Accident Compensation Corporation averaged 75 privacy breaches a month in the last financial year.
ACC appeared before Parliament's Transport and Industrial Relations Committee for its annual review on Thursday.
In 2012, the Privacy Commissioner said a culture change was needed at the corporation after an investigation into how details of thousands of clients were sent to ACC claimant Bronwyn Pullar.
ACC chairperson Paula Rebstock admits the breaches are still unacceptably high, but told the committee with 80 million documents in ACC's file and nearly 50,000 client interactions a day, it was not surprising there were breaches.
"When you look at where the opportunities for breaches to occur are, it's vast in the corporation. Not just on any one day, but because of the length of the files and the life cycle over which many of our clients are with the scheme."
She said ACC wants to re-engineer its processes to put clients first.
Paula Rebstock told the committee she has been given assurances that the role of deputy chairperson Trevor Janes with ACC is appropriate.
Mr Janes is a former director of failed finance company Capital + Merchant Finance and is being investigated by the Financial Markets Authority.
Ms Rebstock said before Mr Janes was appointed to ACC's board in 2012, those matters were disclosed and officials did due diligence on Mr Janes and talked to the FMA.
Mr Janes is chair of ACC's investment committee which has $20.4 billion invested.