Fresh allegations that big-money donors may have influenced political policy have led the Greens to rule out sitting alongside Winston Peters in Cabinet - and to call for a big clean-up of the way government works.
The latest allegations have linked both New Zealand First and United Future to the wealthy Vela family, who made donations to the two parties either directly or through a trust.
The allegations date back to 1999 and stem from documents cited in the Dominion Post newspaper which indicate that former National MP Ross Meurant brokered donations from the Velas while working as an adviser to Mr Peters.
United Future leader Peter Dunne has become embroiled in the mess after it was revealed that he too had received money from the Velas after meeting Mr Meurant to be lobbied about fishing legislation.
Both Mr Peters and Mr Dunne deny their policy was influenced by the money.
But Greens co-leader Russel Norman said yesterday that the latest allegations were the most serious yet against Mr Peters and it was time to clean up the system.
"I know everyone's really bored with the whole Winston Peters/New Zealand First affair, but actually I think the most recent stuff is quite serious," Dr Norman said.
"Because they are allegations of money for policy."
Asked if the Greens would be prepared to work in Cabinet with Mr Peters post-election if the opportunity arose, Dr Norman said they would not do so until the issue was adequately cleared up.
That would best be done through a commission of inquiry, he said.
"We can't have a Cabinet minister sitting at the table with those allegations hanging over him - the public have got a right to know, and also Winston's got a right to clear his name."
Mr Peters has rubbished the latest allegations, which centre around Mr Meurant telling the Velas he had direct access to the NZ First leader at all times.
Documents cited in the Dominion Post suggest Mr Meurant was paid by the taxpayer and was also seeking top-ups from the corporate sector as he carried out his role as an insider.
Mr Dunne vigorously defended himself yesterday, saying he had actually ended up voting for the legislation he had been lobbied to vote against.
Parliament's Hansard records of the time back his claim.
"I have never discussed policy with any lobbyist on a 'cash for votes' basis, nor will I," Mr Dunne said.
"I have never met the Vela brothers, nor have my party or I ever received any donation from them, other than this one."
But returns show United Future has had two anonymous donations - one of $22,500 in 2002 and another of $15,000 in 2005 - so it is difficult to entirely rule out anyone as a donor.
Mr Dunne has sided with National before the election and yesterday John Key said he accepted his ally's word about the issue.
The Greens said they would need to know more about the allegations around Mr Dunne before making a call on whether they could work with him.
The Greens' wish list for greater transparency
* Fixed election date.
* Cabinet minutes and decisions made public within one month (with exceptions for security).
* Tighter rules on Official Information Act to stop it being used to avoid giving out information.
* All archives opened within 30 years.
* Annual limit of $35,000 on donations to parties from any one person or entity.
* Identity of source of any party donation above $1000 must be disclosed.
* Lobbyist register with disclosure of clients, target, methods and subject.
* Bring Parliament within Official Information Act.
* Treaties such as China free-trade agreement subject to vote of Parliament.