The Greens have warmed relations with Mr Peters and New Zealand First in the past three years in Opposition but clearly not enough for his liking.
"New Zealand First is saying that some of the alternatives being offered New Zealand voters in the election are a serious cause for concern."
He criticised the Greens for what he described as twice making "an assault on the Labour Party" in this election campaign.
The first time was when Greens co-leader Russel Norman had suggested that Labour's alternative Budget, prepared by finance spokesman David Parker, should be audited.
The other was last week when Dr Norman raised the prospect of entering another co-operation agreement with a National Government as it had in 2008 to 2011.
Reading out a formally prepared statement to reporter in Wairarapa, Mr Peters said: "This statement in no way challenges the Labour Party's belief that in the right circumstances they could form an alternative Government."
But he added: "Voters need to be disabused of the view promoted by the Greens that we in New Zealand First would stand by whilst they promote extremist policies in Government."
With the ruling National Party so far ahead in the polls, but probably still requiring support partners, much of the speculation about future Governments has centred on a National-New Zealand First Government.
Mr Peters' speech is sending National a message that there may well be alternatives. The Greens' strong preference as determined by its AGM is to work with Labour in Government and it has said it is strongly unlikely it would ever support a National-led Government.
Mr Peters said he was the first MP to back Mr Parker in 2006 when he resigned as Attorney-General following an allegation he had filed an incorrect return to the Companies Office.
Mr Peters said he stood by Mr Parker because he was a "man of honour" and was being "unfairly vilified".
He also said he admired Finance Minister Bill English's integrity on the issues of dirty politics and the affordability of tax cuts.
"Like Mr Parker, he has a certain integrity and honour. Consequently I see both of them as capable of being Ministers of Finance."
He said Greens have discussed having joint Finance Ministers, and he did not think this could work.
"We all want a clean environment ... If the Greens think they are going to take over the leadership of economic management, they are assuming that other parties are not watching their record."