Energy Minister Megan Woods says she will push for new legislation after meeting leaders from oil giant BP at Parliament on Thursday.
A leaked email showed the executives bumping up prices in one area to stem losses. Ms Woods said the email was "alarming" - and called BP to her Parliament office for an urgent 'please explain' meeting.
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However she says she remains unconvinced, and will be taking further action against this "cynical behaviour".
"I didn't emerge convinced that people were necessarily paying a fair price at the pump," she told The AM Show on Friday morning.
"This might not be a market that's operating in the best interests of consumers."
Ms Woods says a fuel market report last year pointed to "hundreds of millions of dollars" being taken from Kiwi drivers by the fuel companies, but she needs more information.
There is legislation currently before Parliament seeking to give the Commerce Commission greater powers to obtain commercial information of petrol companies in order to regulate them. At the moment the Commission has no such power.
"We need to equip the Commerce Commission with market-study powers so we can have a proper look at this," she says.
This will "compel" fuel companies to provide data - and Ms Woods told host Duncan Garner she will be ready to take action as soon as she has it.
"What I've also asked officials to begin straight away is a piece of legislation... so once we get the market studies findings in that we have that information," she says.
"If there are regulatory changes that need to be made that we've basically got a piece of legislation that we can plug and play into."