National has overtaken Labour for the first time since the election, a new poll says.

The National Business Review-Compaq poll gives National 41 per cent and Labour 36.

Labour's support is well down from a post-election high of 48 per cent recorded by the same poll in March, when National was polling at its lowest level ever - 27 per cent.

National would still not have the numbers to govern without Act, however.

Act's support dropped below the 5 per cent threshold to 4 per cent, while the Green Party and the Alliance polled 7 per cent and 6 per cent respectively.

The poll results follow a string of problems for the Government, including controversy over the response by Maori ministers to comments about child abuse; Associate Maori Affairs Minister Tariana Turia's reference to the Holocaust in relation to Maori; bad economic news including the plummeting dollar; and fallout from the sacking of Maori Affairs Minister Dover Samuels.

The poll surveyed 750 people between September 7 and 10 and has a margin of error of 3.5 per cent.

After the election, Labour surged to record levels, at one stage reaching 50 per cent.

Even a month ago, its support was largely holding up - a TV3-CM Research poll put its support at 47 per cent, compared with National on 36 per cent.

A One News/Colmar Brunton poll recorded a poorer result for Labour last month, however, ranking its support at 42 per cent, compared with National's 41.

On yesterday's polling, Labour is still not far short of what it achieved on election night, when 38.7 per cent of people voted the party into power.