Winston Peters is appealing a High Court decision over the leak of his pension details.
A judgment released last month found Peters' privacy was deliberately breached before the 2017 general election to embarrass him and cause harm.
But Peters' claim against former Government ministers Paula Bennett, Anne Tolley and others failed - because he couldn't establish who was responsible.
Now, the New Zealand First leader claims he knows who leaked the story.
Newstalk ZB can exclusively reveal Peters wants the decision reversed - saying the judgment is wrong, and the High Court didn't draw the right inferences from the facts it found.
ZB political editor Barry Soper says Peters' has stated he is not pursuing the case just for himself.
"That anyone that's had their privacy breached do deserve a day in court, he wants another day in court."
In a statement, Peters said he is persisting with the case not just for himself but for all people who've had their privacy breached.
He said it's always been known this case was leaked, with intent to do harm and for a purpose, and he knows who the leak is.
Around 51,000 people had made a mistake on their pension application, but Peters was the only one to be made a public example of this, he said.
The original case was against the two ministers and their respective chief executives, State Services Commissioner Peters Hughes, and former Ministry of Soc ail Development chief executive Brendan Boyle.
The appeal cites only the chief executives as respondents, not Bennett or Tolley, because Peters withdrew allegations of leaking against the ministers during the case.
The Crown has not yet decided whether to pursue costs against Peters for the defence of the ministers and senior public servants which would likely to to over $1 million.
Bennett was not impressed by Peters' decision to appeal.
"I think Winston Peters has wasted enough of taxpayers' money on court cases where he has no proven evidence and he should move one."
She believes the Crown should pursue costs against Peters. "They need to otherwise anyone could take a case against public servants and their ministers and even though they have got no proven evidence, there is no repercussions for them spending well over $1 million of taxpayers' money."