Green Party co-leader Russel Norman says his party won't work with Winston Peters in Government until the latest allegations surrounding him are resolved.
The party has called for a commission of inquiry into allegations of donations being used to get policy gains.
Over the weekend, The Dominion Post published material that appeared to show that one of Mr Peters' advisers - former National MP Ross Meurant -claimed he could get policy deals in exchange for donations.
Dr Norman said he did not know enough about the Dunne case but said allegations swirling around Mr Peters meant the Greens could not sit around a Cabinet table with him should Labour win the election on Saturday.
"If we get to the position post election where Winston Peters is being proposed as a minister if he gets back in I think he can't sit around the Cabinet table until we clear this issue up," he told reporters.
"I think the latest allegations are the most serious yet, because they are allegations of money for policy and you can't have a Cabinet minister with those allegations over him.
"The public's got a right to know and Winston's got a right to clear his name."
He said the Greens would accept NZ First in an arrangement where Mr Peters was not a Minister.
According to the Dominion Post, Mr Meurant brokered donations from Philip Vela, a senior member of the wealthy fishing and horse racing Vela family, before the 1999 election.
Mr Vela was told by Mr Meurant that he would have an opportunity to frame friendly policy in business areas to which Mr Vela was connected.
Mr Peters said the money had no bearing on his party's racing policy, which he said was written in 1993.
The Dominion Post said it had been sent a box of documents relating to Mr Meurant, the Vela family and Mr Peters.
One document showed Mr Meurant sought help from Mr Vela "when required to show my face in Parliament to thrash out policy positions which I will have already developed with your people on taxation, fishing, thoroughbred with Winston's bunch".
Today, United Future leader Peter Dunne was drawn into the controversy over a donation his party received from Mr Vela.
The Greens want donation laws revamped and said the latest allegations showed it was vital.
"For me what it shows is we just need to tidy the whole thing up."
Yesterday Mr Peters was challenged about demanding a helicopter from the Velas - and initially denied ever using one despite being caught on camera walking out to one during the 1999 campaign.
The Dominion Post said that aircraft - which the newspaper ran a photograph of - was listed as being registered to a P M Vela.
One transcript of an alleged conversation between Mr Peters and Mr Meurant said Mr Peters wanted the family to provide him with a helicopter so he could paint it in his party's colours and use it during the 1999 election campaign.
When Mr Peters appeared on TVNZ's Agenda programme yesterday he said the suggestion was stupid.
This morning Mr Peters issued a statement confirming he used choppers for travel in 1999 and 2005 but said that was not the same as campaigning.
The Serious Fraud Office looked into donations to NZ First but found nothing untoward. Police are yet to announce the outcome of their inquiries.