Key: Peters will be responsible with balance of power

Winston Peters spoke outside the Hamilton City Council building in Garden Place. Photo / Christine Cornege

Prime Minister John Key says if Winston Peters holds the balance of power after the election, he believes the NZ First leader will exercise it responsibly and not force New Zealand back into an election.

In today's Herald DigiPoll NZ First has just squeaked over the 5 per cent threshold and it could be critical if National's support falls.

TV3's Reid Research poll last night had Peters as the kingmaker - but if he had sided with Labour it would have resulted in a hung Parliament.

Mr Peters' stance is that he will talk to the largest polling party first after election day if needed, but has not ruled out going on the cross benches.

Mr Key said he believed Mr Peters would not make any move that would force New Zealand into a new election based on his track record.

Mr Key ruled out working with Mr Peters in 2008 and 2011, saying he could not trust him. However, he has said he is willing to work with him if required this time. Asked if he trusted Mr Peters now, Mr Key said if it came to a choice between calling a new election or recognising he needed to work with National to provide a government "I trust him to do that."

"I find myself in the highly unusual position of slightly having to defend Mr Peters. If you're asking me would he drive the country back to another election, I think it's no. Will he have a big shopping list? I think the answer's probably yes."

He said even if Mr Peters did opt for the cross benches in such a scenario it did not necessarily rule out some arrangement, such as abstaining on confidence and supply.

"I'd be more than happy running a minority government with confidence and supply for the core issues. In the perfect world you'd have to know that when you pass your Budget that he would vote for that."

He said Canada's Prime Minister Stephen Harper had run a minority government which worked because Opposition parties would have brought down the Government if they did not vote for critical legislation. That raised the prospect of voters punishing them for doing so.

He said Mr Peters had been criticised for entering a support arrangement with Labour in 2005 after infamously saying he would eschew the baubles of office. However, Mr Key said he believed Mr Peters had genuinely intended to go on the cross benches in that election, but the election day results made that difficult because he was needed to form a Government.

He said his lack of trust for Mr Peters in the past was over a different issue - undeclared donations - and it was six years ago.

He would not say whether he would prefer to work with the Conservatives or NZ First, saying he would prefer to work with "61 other National MPs."