National Party leader Bill English says it would have been better if his Ministers had not been told of Winston Peters' super overpayment issue.
And Mr Peters is considering legal action after the bombshell revelations this morning, that government ministers and the Prime Minister's chief-of-staff had advanced knowledge of Mr Peters superannuation situation.
Three investigations are now underway into whether Mr Peters superannuation overpayment details were leaked.
"You've got a political party that's been deeply exposed now all the way to the prime minister," Mr Peters told media after a public meeting in Whangarei this morning.
"Don't tell me Paula Bennett knew when and the prime minister didn't know.
"Please don't tell me Wayne Eagleson's got a right to know (Prime Minister's chief of staff) when he's a political operative and not a civil servant in the context of your state services commission no surprises.
"This is humbug - it's tawdry, its dirty, it's filthy and they should not succeed on it."
The State Services Commission confirmed this morning that MSD, and the IRD are looking into the matter.
It follows confirmation this morning that the Minister of State Services Paula Bennett and Minister of Social Development Anne Tolley were briefed on the matter some weeks ago by the State Services Commission - in line with the government's "no surprises" policy.
It also been revealed that the Prime Minister's Chief of Staff was also informed of the matter by the Minister for Social Development Anne Tolley.
Mr English says his Chief of Staff made a judgement not to tell him about the matter.
In a statement Mr English said: "I believe that the leak did not come from within the Beehive or the National party. The two Ministers and my Chief of Staff have assured me of that. I would take any leak very seriously."
State Services Commissioner says: "It is entirely unacceptable for Public Servants to leak information.
"Leaking official information would undermine the trust New Zealanders have in the public service.
"Leaking is a political act which would compromise the political neutrality of the public service.
"There will be zero tolerance for any behaviour of this nature in the public service and both MSD and Inland Revenue have launched investigations to assess whether a leak took place."
1 News Political Editor Corin Dann says today's developments are potentially explosive for this campaign and could prove a major headache for National.
He says this is because even though there is no evidence to show that National Ministers leaked the information, Winston Peters and his supporters are unlikely to be convinced by National's denials and he is already claiming dirty politics are at play.
National may yet need to work with Winston Peters after the election and this could seriously damage relations.