Tonight's One News Colmar Brunton Poll of a thou' />

Labour leader Phil Goff's ranking has improved in a new poll, despite not having the best month.

Tonight's One News Colmar Brunton Poll of a thousand voters confirmed incumbent John Key's popularity when he recorded 55 per cent as the preferred prime minister, up from 48 per cent in February.

But Mr Goff also increased - from 7 per cent in the past two polls to 11 per cent. That was despite a difficult time when MP Darren Hughes quit as police investigated a sexual complaint against him.

Former Labour prime minister Helen Clark was ranked 1 per cent, down a single percentage point, and New Zealand First leader Winston Peters got 3 per cent - steady on the past two polls.

National's overall support remained strong at 54 per cent, up 3 points on the last poll. Labour was up 1 point to 34 per cent, while the Greens dropped 2 to 6 per cent.

NZ First was down to 2.7 per cent (from 3.6 per cent) and the Maori Party fell to 1.4 per cent (from 2.3) the first time it has slipped below 2 per cent in at least the past four polls.

ACT remained low at 1.1 per cent.

On the economy, fewer people thought it was getting better - 38 per cent compared to 48 per cent in February --and more thought it was getting worse - 45 per cent compared to 32 per cent.

The poll was carried out from April 2-6 and had a margin of error of 3.1 per cent.