Winston Peters has launched legal action over the leak of information about his superannuation overpayment.
Papers have been served to four former ministers and two journalists, among others.
In August the New Zealand First leader says it was unclear how the error in his superannuation overpayment had occurred and he had paid back the money.
He did not disclose the amount.
Mr Peters had confirmed the overpayment, in response to enquiries from the media.