Winston Peters has launched a stinging attack on the head of the Ministry of Social Development, Brendan Boyle, accusing him being in a politically motivated conspiracy to leak details of his superannuation overpayment.
The New Zealand First leader made the claim in Wellington today to reporters after giving a speech to an infrastructure conference.
"It is a breach of privacy and that is serious and if you are responsible for it, it's $15,000 and six months in prison.
"What you've got here is a disgusting little cartel playing filthy politics and at the highest level of our civil service."
He said it was "the politicisation of the public service".
Peters, aged 72, revealed on Sunday after media inquiries that he had been overpaid superannuation for seven years, which he repaid immediately.
On Tuesday the Herald revealed that Social Development Minister Anne Tolley has been informed about the matter under the "no surprises" policy by MSD and she had told the Prime Minister's chief of staff, Wayne Eagleson.
It then emerged that before telling Tolley, Boyle had consulted State Services Commissioner Peter Hughes, who in turn consulted Solicitor General Una Jagose, before Tolley and State Services Minister Paula Bennett were told.
"I do not think these people should be allowed to get away with it and I do not intend to stop until I get justice on this matter.
"My lawyer is looking at the whole ambit of the thing and he'll be starting off very shortly," Peters said.
Peters singled out Boyle, saying he was politically motivated and had "form".
Peters said that was a reference to him having released official documents during the 2008 campaign on the matter of Bill Liu's controversial citizenship approval by former Associate Immigration Minister Shane Jones, who is now a New Zealand First candidate.
"This guy has got form for being politically involved and I want to know what he thought he was doing being briefed in the first place," said Peters.
"He might be head of the department, but nothing about this required his intervention.
"It is very clear to me that senior civil servants are operating right outside the law and that they are, in fact, straight into a conspiracy.
"A conspiracy is when two or more decided they would break the law and that's what they did in tandem with these ministers".
Boyle declined to comment.
Prime Minister Bill English has said Peters' superannuation overpayment was not the sort of information that officials should have passed on to a minister.
Peters said he had not received any apology from anyone in National but he said he had received "coded messages around the back door that have been of a very helpful nature".
"I think a small cabal had a strategy in their mind and they decided to pursue that strategy. It wasn't approved but they went ahead regardless."
Some people have claimed that Peters would have received a letter every year for the past seven years asking him to confirm his relationship status.
But that in fact is not the case. The Ministry of Social development says that "annual circumstances letters" were sent to NZ superannuation clients: who do not have personal earnings and who receive the accommodation supplement, or the single living alone rate of NZ Super, or a disability allowance with a permanent medical condition.
"Any other NZ superannuitant is not routinely contacted to reconfirm their circumstances".