Motorists are right to feel they are being unfairly treated after revelations about how BP sets its petrol prices, Prime Minister Jacinda Ardern says.

"Certainly what's been revealed today probably wouldn't surprise some motorists," Ardern said at her weekly press conference on Monday.

"But to hear so blatantly that pricing decisions are being made that sit outside of the price of crude oil, that sit outside the exchange rate, or that sit outside operating costs will no doubt be raising eyebrows with consumers.

"It certainly raised eyebrows with our minister, which is why she called them in for a meeting."

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Energy Minister Megan Woods called BP executives into Parliament today to explain how they set their prices at the pump.

The meeting came after an internal BP email leaked to Stuff showed a pricing manager outlining a plan to counter dwindling sales in Ōtaki, where the price of fuel was 20 cents more expensive than in the nearby town Levin.

Instead of reducing the price in Ōtaki to make the station more competitive, the manager proposed an increase of the fuel price across the entire region, with the expectation that competitors would match the new price.

Ardern said it raised questions about whether BP had broken any laws.

"Regardless of whether they have or not, certainly motorists won't look upon it as fair."

The Labour-led Government plans to change the law to allow the Commerce Commission to compel petrol companies to provide information on its pricing.

That is because not all companies disclosed their information to a fuel price inquiry launched by the previous National Government.

The latest revelations about BP added impetus to the Government's proposed law change, Ardern said.

"First we need to hear the explanation from BP. The usual explanations in this case just don't exist.

"There is a pretty high test that has to be met in our law for them to have fallen foul of around particular behaviours. So first we'll seek an explanation and then we'll consider what our options are."

Ardern compared BP's price hikes revealed in the leaked email to Labour's plan to charge a regional fuel tax of between 3c and 4c a year.

"We are having a debate right now about the application of an additional 3c over a year. They are putting up 3c in a day.

"This demonstrates the kind of impact those decisions have on motorists and the scale of them."