The defence against Winston Peters' superannuation privacy lawsuit has cost taxpayers more than half a million dollars so far, documents obtained by RNZ show, and that amount could rise further.
Mr Peters went to court this month - against the Ministry of Social Development (MSD), former National government ministers Paula Bennett and Anne Tolley, State Services Commissioner Peter Hughes and former MSD boss Brendan Boyle - arguing his privacy was breached in 2017 when officials informed Mrs Bennett and Ms Tolley that he had been overpaid superannuation.
Mr Peters paid back the full amount of almost $18,000 once he was notified of the error.
Information obtained by RNZ under the Official Information Act showed costs incurred by Crown Law amounted to $537,646. Of that, legal fees amounted to about $503,000 for the defendants involved.
About $19,000 was incurred in legal fees for work completed for the Department of Prime Minister and Cabinet, and another $4000 was in relation to work completed for the Department of Internal Affairs.
Disbursements amounted to almost $11,000 which included court filing fees, travel, courier, photocopying, printing, binding, and transcription fees.
In an OIA response, Crown Law said other costs would be known at the end of December, possibly January, due to the timeframes for invoices from external parties.
"We anticipate there may be other future costs incurred but are unable to provide an estimate at this stage," it said.
Mr Peters had been seeking $450,000 in damages from all five defendants, but Mrs Bennett and Ms Tolley have now been taken out of the damages part of the case.
Mr Peters is still seeking a court declaration that all defendants breached his privacy.
The judge had reserved his decision on the case.