Costings unit a good idea, big parties agree - but how could it work?

National and Labour agree there should be some form of costings unit to consider election year policies independently, but disagree on how it should be implemented.

National's finance spokesperson said she supported a "light touch" costings unit that would "run the ruler over" costings for political parties.

Labour's deputy leader said her party supported the idea, and had a member's bill in place that would be sent to select committee if National backed it.

It comes after the Green Party wrote to both National and Labour's finance spokespeople urging support for an independent Parliamentary Budget Office to cost political commitments and "lift the standard of public debate".

Green Party co-leader Chlöe Swarbrick said independent analysis of costs would give people the information they need to engage with the choices in front of them.

She said the votes exist in Parliament to make it a reality before the election, "even if only National and the Greens agree" but there's an opportunity to get Labour around the table for "sustainable, long-term, cross-partisan support."

Speaking on Morning Report's political panel on Wednesday, Nicola Willis said Treasury did independent forecasting, but a costings unit "would be helpful in election year and would support transparency in our democracy".

Labour's Carmel Sepuloni said New Zealand First and ACT had blocked an earlier proposal by Willis herself, and pointed to Labour's Barbara Edmonds' members bill that would a the unit up. Sepuloni said National and Labour could progress that without needing New Zealand First or ACT.

Willis did not support Edmonds' proposal, saying it would create an entirely new institution employing more public servants: "A parallel bureaucracy to the one that we already have."

"Unfortunately," she said, "the bill that Carmel is reporting to proposes a 'bigger than Ben-Hur' solution."

She said the proposal she had taken to Cabinet was a "much more light-touch approach, using existing resources within the public service in election year".

Willis confirmed the proposal did not earn the support of National's coalition colleagues, but said Labour and the Greens' proposal "goes too far, would be very costly to the taxpayer, and it's not necessary".

"We already have in the Treasury an independent forecasting institution that, by and large, does a pretty good job."

Sepuloni pointed out Labour's member's bill could go to select committee and get a "pretty speedy process", as well as be reviewed.

"If there isn't support for what is currently in the bill, then that could be scaled back. That's always a possibility.

"It's about getting something over the line and getting it to select committee. So, if there was the will from the National Party, then it would be possible."

Asked if Labour would support a light-touch version, Sepuloni suggested letting the bill go to select committee and having the conversation there.

"Obviously, Greens and Labour would not have the numbers by themselves, and so there would need to be a level of compromise and negotiation," said Sepuloni.

She added Labour was "willing to do that" because it was the right thing to do.

"It's just a pity that National again have been blocked by their coalition partners on something that is the right thing to do."

The ACT Party said the country already had organisations that scrutinised election promises, from independent consultancies to political parties and the media. Taxpayers did not need to fund another one.

In a statement, leader David Seymour said: "It's bad enough fighting the bureaucracy after you win the election, we don't want them refereeing it as well.

"There is something fundamentally undemocratic about the underlying belief here: that ordinary people can't be trusted, only those with official titles and state resources."

New Zealand First has also been approached for comment.

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