The prime minister has joined criticism of fuel giant BP's pricing tactics, saying its behaviour is unfair and the government wants answers.
An internal email, leaked to Stuff, has revealed the fuel company's tactics to reduce sales losses at its Otaki petrol station, just south of Levin.
The email revealed BP was going to raise prices in Paraparaumu, Kapiti and Levin to reduce the pricing gap with Otaki and hoped its competitors followed suit.
"What's been revealed today probably wouldn't surprise some motorists, but to hear so blatantly that pricing decisions have been made that sit outside of the price of crude oil, that sit outside the exchange rate, or that sit outside for instance operating costs will no doubt be raising the eyebrows with consumers," Ms Ardern said.
"It certainly raised eyebrows with our [energy] minister [Megan Woods], which is why she has called them in for a meeting."
It was not clear yet whether BP's actions were legal, Ms Ardern said.
"There is a question here over whether or not they have in fact breached any of our legislation or not, but regardless of whether they have or not certainly motorists won't look upon it as fair."
BP's bosses will meet with Ms Woods later this week.
The government wanted answers, Ms Ardern said.
"First we need to hear the explanation from BP - as I say, 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 beyond that."
The government was still considering recommendations that arose from last year's petrol price inquiry.
In the meantime, there is legislation before parliament giving the Commerce Commission more power to compel fuel companies to hand over commercial information.