Public support for John Key as Prime Minister has never been so high, according to the latest Herald-DigiPoll survey.

Mr Key registered 58 per cent backing in the preferred Prime Minister category, three points up from the last Herald poll in October.

It is the highest preferred Prime Minister rating since August 2005, when Helen Clark had 59 per cent support.

The latest poll showed public support for the Labour Party up just over 1 per cent to 34 per cent and National down slightly, but the Government on 56 per cent would still have enough support to govern alone.

No other parties reached the 5 per cent threshold, so returning to Parliament would depend on their winning electorate seats.

The poll was conducted from January 29 until February 10, starting the day after Labour leader Phil Goff's "the many, not the few" speech, but the results are unlikely to show any reaction to the Government's suggestion of raising GST, as it concluded one day after Mr Key's speech to Parliament.

Mr Goff also improved in the Prime Minister stakes, though at 6.8 per cent he still trails his predecessor as party leader, Helen Clark (7 per cent).

He said there had been some progress "but there is more work to do".

Three-fifths of the country said the Government was heading in the right direction, 28 per cent disagreed and 13 per cent were undecided.

The poll showed that Labour support was stronger among 18- to 24-year-olds, and those who had a household income of less than $60,000. National's stronghold were households earning more than $60,000.

Support for the Greens and the Maori Party held firm since the last poll, on 4.6 per cent and 2.8 per cent.

New Zealand First, which failed to return to Parliament at the last election, doubled its support to 1.7 per cent, ahead of Act, United Future and the Progressive Party, all polling at less than 1 per cent.

Returning to Parliament for the minor parties would depend on winning electorate seats, where Act leader Rodney Hide has a grip in Epsom, Progressive leader Jim Anderton in Wigram and United Future's Peter Dunne in Ohariu.

The Maori Party at present holds five Maori electorate seats.

A spokesman for Mr Key said the poll result reflected the Government's focus on delivering for New Zealanders.