The Government is concerned at the rise in petrol prices hitting Wellington and South Island users.
Energy Minister Megan Woods said today the recent petrol price hikes are "exactly why we're pushing ahead to get the market study powers" - meaning companies would be made to provide information to enable the regulator to have a greater understanding of the fuel market.
It comes after Wellington and South Island 91 octane rose to $2.30 a litre last week.
A Z Energy spokesperson told Newstalk ZB the price hike was mainly driven by international market increases that were passed along to customers.
The depreciating Kiwi dollar is another factor which have risen the price of petrol to it's current level above $2.10 per litre, Road Transport Forum NZ chief executive Ken Shirely said.
Geo-political trends, and the instability of the Iran nuclear deal with US sanctions on the middle eastern country, are also influences.
National's Sarah Dowie told Stuff last week the rise in petrol prices in the South Island is "going to get worse".
"Part of the reason prices are climbing is due to price spreading as fuel companies try to hide the effects of the Government's new 11.5 cents per litre Auckland Regional Fuel tax in other parts of the country," Ms Dowie told Stuff.
She said the nationwide fuel excise increases over the next three years also mean "hardworking Southlanders, who already face high fuel prices, are going to be paying even more".
Ms Woods said the Government is "really concerned" about the issue.
"We want reassurance people are paying a fair price when they fill up their cars and that we're doing the work to make sure that we have all the information we need."
"I think every New Zealander feels concerned when they're seeing price rises like that, particularly in the Wellington region and the South Island," Ms Woods said.
Finance Minister Grant Robertson says the rise in petrol "was exactly why we're beefing up the powers of the Commerce Commission... so they can actually identify what is going on here".
"We've had a problem that we haven't been able to get to the bottom of this, haven't been able to get the information we need."
Ms Woods said the legislation for market powers have been through the first reading in Parliament.
"We've moved really fast on that piece of legislation, but I am discussing with officials if there is anything we can do in the interim," Ms Woods said.
"Unfortunately most of the solutions do actually require us to have the information that we'll get through the market studies powers."
Mr Robertson said if there was anti-competitive behaviour happening, "we'd stamp down on that".