NOT SURPRISED: Winston Peters says his rise in the polls is not unexpected. 'We know our hard slog has worked.'

Forget Phil Goff, John Key, and the "teapot" tapes – the minor parties could yet decide who governs New Zealand.

A Horizon poll of 2874 people is projecting National on 46 seats in a 122-seat parliament, and Labour and the Greens on 50.

That leaves 26 seats to decide the government and, according to Horizon, Winston Peters' New Zealand First is on track to take up to 13 of them.

The teapot tapes, in which Key and Act's John Banks were secretly recorded during a meeting, has seen the prime minister suffer a 5 per cent drop in credibility, even among his own supporters.

National leads Act in Epsom, which would hurt National in terms of a coalition because the Horizon poll shows Act must win the seat to get into parliament, with its current 3.4% party rating below the 5% threshold to earn list seats. If it wins Epsom it will take four seats, if it loses it gets none.

Horizon has consistently returned higher figures for smaller parties such as NZ First and the Greens but Peters said his rise in the polls was not unexpected.

"There are polls and there are polls, but there are unseen indicators that tell you whether the party is on the rise. That's what we're feeling around the country, and it's what candidates are reporting," he said. "We know our hard slog has worked."

And Peters said Key talking about National getting half the vote would backfire because the electorate would rebel against one party having unbridled power.

"New Zealanders know what that has meant. That's why we went to MMP. With unfettered power, with nobody acting as a watchdog, they just did what they liked between 1984 and 1990, and National went down the same path.

"There are a number of people who are concerned about that happening, and that's being reflected in the polls."

He described the teapot coverage as a "circus" but despite saying the conversation should not be released, he then gave details of what was discussed at a meeting in Invercargill.

"Political stunts can go horribly wrong, and this one did."

But he reiterated his party's pledge to sit on the cross-benches if it was returned to parliament, a strategy he first aired in the Sunday Star-Times a year ago.

"We can stop asset sales from the cross-benches. We can do all those things, because those who want to sell their country out won't have the votes."

NZ First's poll surge is in line with the Star-Times' front page of a year ago. The headline, "Peters the kingmaker again", reflected a Horizon poll that put the party's support at 6 per cent.

New Zealand Herald assistant editor John Roughan wrote a column slating the story but on Friday the Herald front page headline read: "Winston within a whisker: Poll jump puts NZ First close to dramatic comeback and maybe balance of power" over a story that its own polling had support at 4.9 per cent.

Representation for other minor parties will depend on who takes which electorates. The Maori Party vote has slumped and it will probably take only the three or four electorate seats it wins, Horizon says.

Hone Harawira's Mana Party will probably win only one electorate, but its wider support could bring it three seats.

The other dark horse is the right-wing Conservative Party, which Horizon has hovering around the 5 per cent threshold.