The signing of the Trans-Pacific Partnership prompted large protests but has had no dent in the National Party's ratings in the latest opinion poll.

National remains steady at 47 per cent support in the One News-Colmar Brunton poll taken in the aftermath of the signing of the controversial 12-nation trade pact in Auckland on February 5.

The worst news from the poll was for the Green Party, which dropped four points to 8 per cent. Its misfortune was New Zealand First's win -- Winston Peters' party went up one point to 10 per cent, propelling it ahead of the Green Party.

If that continues, NZ First would be the third-largest party in Parliament -- a long-held goal of Mr Peters, which raises the stakes for both National and Labour should his support be required for a future government.

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NZ First would have the balance of power if the poll results were repeated in an election.

Mr Peters would not say whether his party would prefer to go with Labour or National, saying it was too far out from the election to answer such questions.

"We are sticking to our knitting and that's why we're rising."

John Key's decision to give Waitangi a miss over Waitangi Day also did little harm -- he was at 40 per cent as preferred prime minister, the same as the last poll in October.

That level if support is well ahead of Labour leader Andrew Little and Mr Peters, who were both on 9 per cent.

Labour got a small lift after a fortnight that included a major policy announcement of three years of fees-free tertiary education -- its party support went up one point to 32 per cent.

Of the other parties, the Maori Party was on 1 per cent, Act on 0.3 per cent, the Conservatives on 0.6 per cent, and the Mana Party at 0.3 per cent.

The poll was taken from February 13-17 and has a margin of error of 3.1 per cent.