Winston Peters has for the first time revealed it was someone "very high up" in the National Party who was first to alert him that information relating to his superannuation overpayments was going to be made public.
The comments from Mr Peters come as the Ministry of Social Development today released an official statement saying an internal investigation found no staff members of theirs were responsible for passing on Mr Peter's personal superannuation information to a third party.
The IRD has previously said the leak didn't come from them.
The New Zealand First leader had to pay back thousands of dollars after being paid the wrong rate of superannuation.
Mr Peters said the alert from an individual in the National Party came prior to another alert from an unnamed journalist, before it was widely reported in the media in late August.
"I am not ungrateful for that person inside another party who told me that, no, because I think there are admirable people of great character in every political party," Mr Peters told Sunday's Mark Crysell in an interview that will screen this weekend and was filmed before today's announcement.
"The trick is trying to find who they are.
"Some people have honesty and character and they know dirt when they see it."
Mr Peters said he believes the leak came from someone within the National Party, not a public servant.
"Well it came from the National Party, but then the National Party alerted me to it," Mr Peters said.
"One group said this is foul and dirty, I'll tell Winston before it comes, that's why I knew.
"That's why when the call came in from that first journalist, you can tell I'm on red alert, I now know exactly what I'm being warned about, but I knew beforehand."
National deputy leader Paula Bennett and Social Development Minister Anne Tolley were both privy to Mr Peter's superannuation overpayments prior to the media leak under the "no surprises" rule , but both have denied they were responsible for the leak.
The Sunday programme will have the indepth story with Mr Peters at 7.30pm this Sunday.