The National Party has only dropped 2 per cent in the latest political poll, despite the tumultuous political events of last week.

The 1 NEWS Colmar Brunton poll, released tonight, had the National Party on 43 per cent support.

The Labour Party was ahead of National at 45 per cent support, up 3 per cent from the last poll.

The Green Party was up 1 per cent to 7 per cent support, while NZ First was steady on 5 per cent - right at the threshold for entering Parliament.

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The Act Party did not register in the poll.

Labour and the Greens could form a parliamentary majority on the basis of these numbers without the support of NZ First.

The poll was conducted from Monday to Friday last week.

Simon Bridges fell in the preferred PM stakes from 10 to 7 per cent, his lowest rating since becoming leader and only 2 per cent ahead of fellow MP Judith Collins on 5 per cent.

Jacinda Ardern was up 2 per cent to 42 per cent support, while New Zealand First leader Winston Peters had dropped 1 per cent to 4 per cent.

Asked how Bridges had handled the saga around the leak of his travel expenses, 51 per cent of those polled said it made no difference, 38 per cent felt less positively about him, and 2 per cent felt more positively about him.

1 NEWS reported that support for National dropped below 40 per cent on Wednesday, when a recording was released in which Bridges making disparaging comments about National MP Maureen Pugh, and Bridges and Ross compared Chinese and Indian candidates.

But support for National rose again on Thursday, after attention on allegations of Ross' inappropriate behaviour came to the fore.

The poll also asked people about the economy in the next 12 months; 41 per cent said it would get worse, while only 33 per cent said it would get better.

The latest poll follows a week of unprecedented political turmoil for the National Party, as Botany MP Jami-Lee Ross laid a police complaint about alleged electoral fraud and traded insults and accusations with Bridges and the party.

Ross quit the party just before the National caucus voted unanimously to expel him, and then released a recorded phone conversation that included embarrassing comments from Bridges, where he described National MP Maureen Pugh as "f***ing useless".

Bridges apologised to Pugh and welcomed the police probe, saying he had done nothing wrong.

He called Ross a liar and a leaker, while Bennett said Ross had acted in a way unbecoming for a married MP - a comment that Bridges has since reprimanded her for.

As the tension escalated, four women's stories were published in Newsroom accusing Ross of bullying and intimidating behaviour.

Ross disagreed with how he was portrayed, but apologised for any hurt he had inflicted on the women admitted to extra-marital affairs, including with a married MP. He publicly apologised to his wife.

The saga also opened up the National Party to accusations of a cash-for-candidates scheme, following the release of a recording where Ross and Bridges talked about taking Chinese donations and having an extra Chinese MP.

National Party president Peter Goodfellow said National seats were not for sale.

He also fended off accusations of a cover-up, after it was revealed he had brokered a confidentiality agreement between Ross and National candidate Katrina Bungard, who complained about Ross' harassing behaviour.

Goodfellow said both parties wanted confidentiality, and it was the only complaint against Ross that he was told about.

Bungard backed him up, saying she "always felt fully supported by the National Party and its leadership".