The Ministry of Social Development (MSD) says there is no evidence that any of its employees leaked information about Winston Peters.
MSD launched an internal investigation after details about the New Zealand First leader being overpaid his superannuation were leaked to the media.
- Winston Peters admits taking extra pension payments
- Winston Peters says it's 'not clear' how superannuation overpayment happened
A statement released by MSD on Friday said "We can confirm that all staff that had access to the relevant information had a reasonable business purpose for accessing it, and there is no evidence that this information was passed to a third party.
"The Ministry holds a great deal of very personal information about people and their families that New Zealanders trust us to safeguard. Both data searches and staff interviews were employed in this investigation."
Earlier this week the Inland Revenue Department (IRD) said they were not responsible for the leak either.
Mr Peters has claimed that the National Party were responsible for the leak, after it was revealed that Social Development Minister Anne Tolley, State Services Commissioner Paula Bennett and Bill English's chief of staff Wayne Eagleson were among those who were informed of the incident.
Bill English has denied that the National Party are behind the leak and said he wasn't aware of the incident until it became public in media reports. He questioned why ministers were informed in the first place.
- Winston Peters accuses National of 'filth and dirt'
- Lloyd Burr: Why did so many people need to know about Peters' pension saga?