Winston Peters: Going with the largest party 'only a convention'

New Zealand First leader Winston Peters, who could be kingmaker on Election Day, won't necessarily negotiate with the largest party first to try to form a government.

"There's been in the last twenty years an emerging convention that you start with the party that has the most votes but that's only a convention," he told reporters in Northland on Friday.

Mr Peters said he wouldn't be rushed into making a decision about which party he would form a Government with, if he's in a position to do so.

Earlier on Friday Jacinda Ardern said Labour's internal polling had them "neck and neck" with the National party, and the latest Newshub Reid Research poll showed a Labour-Green combination was almost equal to National.

The most recent 1News Colmar Brunton poll had NZ First on 5 percent, while Newshub's poll had the party on 7.1 percent.

If there's no clear winner on election night on September 23, Mr Peters wouldn't comment on what his preference would be or what the process would be.

"The problem with trying to answer your questions is they're all hypothetical and so are the answers," he said.

"I'd rather wait until I've seen the cards. It's one hell of a job trying to play card when you've never seen them."

Mr Peters said the emerging convention has been that a government should be formed "quicker than ever before", but he doesn't want to be rushed.

"You can't be too fast because the reality is the writs don't get in until a certain date… It's very seriously overemphasised this importance of speed. You're better to get it right than do it in haste like any good sound job."