The Independent Māori Statutory Board says it had "supposed commitment" from Auckland Council to do a study examining how the fuel tax would hit Auckland's poorest.

Auckland Council is being accused of delaying work looking at how low-income households, including Māori living in south and west Auckland, would be impacted by the new regional fuel tax.

David Taipari, chairman of the Independent Māori Statutory Board (IMSB), said the council was asked to do the research before the fuel tax was introduced. He believed the work was held up.

Email correspondence obtained by Stuff also shows IMSB chief executive Brandi​ Hudson recommended Mayor Phil Goff's office consider a study of the tax's impact. However, it appears the work was never done.

IMSB eventually did the research itself.

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The findings have just been released – more than a month after the fuel tax was approved – and suggest the controversial levy could cost low-earning Aucklanders with inefficient vehicles up to $452 more per year.

But Goff, who campaigned for the fuel tax, has spoken out against the research, while Transport Minister Phil Twyford has rubbished it as out of date.

Taipari told Stuff the IMSB had a "supposed commitment" from Auckland Council to provide the report before introducing the regional fuel tax.

"In my view it was being delayed, and I'm not sure why," he said.

"But the board chose the position to undertake the report itself with Sapere [Research Group]."

Taipari said he asked for the report to be done in his capacity as a member of the council Finance and Performance Committee

There had been a commitment, he said, that the work was being rolled out in stages and that a report would be provided on "low socio-economic families and demographics".

"All of a sudden, we've got the regional fuel tax ... and we're still doing it without information," Taipari said.

"So, yes, the board has a function and a responsibility to provide direction to council and we did that by commissioning this report."

JASON DORDAY/STUFF After earlier rubbishing the report's findings, a spokesman for Phil Goff says the mayor will consider the report.

Hudson first suggested a research paper to the mayor's office in January.

Twice her correspondence went unanswered until she followed up with mayoral staffers, she said.

Correspondence between mayoral staff members suggests research had not gone anywhere by May – the fuel tax was approved later that month.

A spokesman for the mayor said the council consulted ratepayers in different wards and socio-economic groups on the council's latest budget, which included the fuel tax.

"Following points raised by the IMSB in a December Finance and Performance Committee on the impact of the fuel tax on lower-socio economic groups, David Taipari was invited to be a member of the political advisory group overseeing the development of the regional fuel tax policy," he said.

"He was unable to attend and IMSB's Deputy Chairman Glen Wilcox attended several meetings in his stead.

"The Mayor and council will now consider the report and respond in due course."

WHAT THE RESEARCH SHOWS

The IMSB's research showed increased costs due to the fuel tax were "more likely to be a foregone school lunch than a cup of coffee" in the hardest hit areas.

The lowest income households could face additional annual fuel costs of between $244 and $366. Additional weekly fuel costs for the lowest income households were pegged between $4.88 and $7.32.

The research found development of the fuel tax policy "neglected equity impacts, but the impacts are material for lowest income households".

But Twyford labelled the report "out of date".

"It fails to take into account the Families Package introduced by the Government in July," he said.

"The Families Package is putting an average of $75 extra in the pockets of 384,000 low-income families with children. This will help offset the 11.5c a litre increase in fuel for drivers in the Auckland region."

Taipari said it was "very unfortunate" people were "dismissive of the report".

"And it's not just fuel tax that's going up, there's a range of costs," he said.

"The cost of living is outrageous and these families are struggling, and we see that on a range of fronts."

Government benefits were not only offsetting the fuel tax, but a number of increased costs, he said.

ABIGAIL DOUGHERTY/STUFF Transport Minister Phil Twyford dismissed the IMSB-commissioned research as dated.

"There's a range of mitigation or remedies we think that can happen," Taipari said.

"Increases to Working for Families was one of those, there's also tax relief, discount cards [and], from the council's point of view, rates relief.

"More importantly, where we're focussing strongly is the targeted transport services, particularly out south and out west."

A "constructive way forward" was for the IMSB and others to work together on solutions.

Goff said 2.4 per cent of household income was spent on petrol in high spending households and 2.6 per cent in low spending households, according to Stats NZ.

"In proportional terms the difference is very small. In absolute terms the 20 per cent of households who earn the most spend three times as much on petrol as the 20 per cent of households who earn the least," he said.

"Offsetting the around $2.40 a week that the AA says represents the average cost of the RFT to Auckland motorists is the $75 on average that low income families will receive from the government's families package.

"This will benefit approximately 115,000 low income families who live in Auckland."