Another hit to National's support, but Labour's dropped back to a 17-year low, in a One News-Colmar Brunton poll.

It sees National drop four points to 46 per cent support, while Labour sheds one point to 25 per cent.

Meanwhile, the Greens are up three, to 14 per cent.

The Conservatives are creeping towards the five per cent threshold, on four per cent support, while New Zealand First is steady on seven per cent.