By VERNON SMALL deputy political editor

The National Party's change of leaders has won voters' approval but is yet to have any impact on Labour's big lead over its main rival.

That is the message from the latest One News/Colmar Brunton poll released yesterday which showed Labour opening up a seven-point gap over National, underscoring the hard work ahead for Bill English.

The survey, taken in the days after Jenny Shipley resigned under pressure from her caucus, had Labour at 46 per cent, up two points on a similar poll a month ago. National was down one at 39 per cent.

The Greens, down one on 5 per cent, were the only other party to make the threshold needed to ensure seats under the MMP system.

Bill English made a strong showing in his first poll as National leader, with 21 per cent picking the Southland man as their preferred prime minister. He had scored just 5 per cent in the previous poll.

But Prime Minister Helen Clark continued to dominate, with her rating as preferred leader of the country rising three points to 41 per cent.

Mrs Shipley's backing dived nine points to 5 per cent.

Support for minor parties was little changed. New Zealand First's backing was up 0.8 of a percentage point to 3.5 per cent, Act languished at 3.1 per cent, down 0.3, and the Alliance still struggled to make any impression at 2 per cent, down 0.2 points.

Optimism about the economic outlook has deteriorated from 39 per cent to 33 per cent in the month since the terrorist attacks on the United States.

Those who thought economic conditions would worsen rose from 40 per cent to 43 per cent.

However, despite controversy surrounding the problems of national flag carrier Air New Zealand, approval of the Government's performance improved to 51 per cent from 46 per cent a month ago.

Those disapproving of the Government's effort fell to 33 per cent from 36 per cent.

On the issue of the Air NZ crisis, the poll showed 49 per cent approved of the Government's actions, compared with 44 per cent who disapproved.

Opinions have firmed up since Finance Minister Michael Cullen said the Government planned to own up to 83 per cent of the struggling airline at a cost of $885 million.

A month ago, 38 per cent approved but 41 per cent disapproved of the Government's action.

"Don't knows" have fallen from 20 per cent to just 7 per cent in the latest poll.

The survey of 1000 people was taken over three days from October 9. It has a margin of error of 3.2 per cent.