New Zealand First leader Winston Peters has ruled out going into coalition with another party - but Labour leader Phil Goff won't rule out still trying to woo NZ First if the numbers allow it after election day.

Mr Peters outlined his new stance yesterday, saying it was more important for NZ First - "the political street fighters" - to be in Opposition.

"You need more than an Opposition in Parliament - you need an effective Opposition in Parliament. Our CV is second to none when it comes to holding the Government of the day to account."

Asked if NZ First was still an option for Labour, Mr Goff said Mr Peters had to be elected first.

Advertisement

"We'll see what happens when the people speak and then we'll have discussions with people who might be compatible."

Mr Goff has consistently refused to rule out working with Mr Peters, although he had ruled out Hone Harawira.

Asked if it was a good look to go into business with Mr Peters, he said National leader John Key was "in bed" with both Hone Harawira and Rodney Hide at one point. "I didn't think that was a particularly good look."

Mr Key said Mr Peters' decision was of little interest to him given that he had already ruled him out and had not changed his mind. He said it was up to the voters to decide if Mr Peters returned to Parliament "but I don't want to deal with him".

"The next three years will be critical for New Zealand. We need stable government and one thing Winston Peters and Hone Harawira aren't is stable."

It is the first time Mr Peters has given such a clear position before an election - his usual line is that coalition agreements cannot be decided on until after the voters have voted.

NZ First needs at least 5 per cent to make it back into Parliament, and is polling at about 2 per cent.

Mr Peters said the three critical issues NZ First would hold the Government to account on included the Treaty of Waitangi and the foreshore and seabed, which he said were building an increasingly separatist society.

It would also rail against state asset sales.