Petrol prices have risen for the second time in two weeks, with the AA labelling today's increase to diesel prices "completely unjustified".
Z Energy raised petrol and diesel by 2 cents a litre today, having done the same less than two weeks ago.
A litre of 91-octane rose to 218.9c, while diesel was up to 151.9c.
AA PetrolWatch spokesman Mark Stockdale said the imported cost of petrol had risen, but importer margins had fallen, while the New Zealand dollar had dropped 1c.
Despite this the cost rise was not high enough to justify a price rise at the pump, though companies had been raising prices at these margins recently.
For diesel, however, the commodity price had not risen, meaning diesel margins were above average.
"Therefore, the 2c price in diesel pump prices is completely unjustified," Stockdale said.
"If anything diesel prices should be falling."
The last time commodity prices were this high consumers were paying 1c less for petrol and 2c less for diesel, while the exchange rate was the same as today, he said.
Little Shop: Harmful or harmless?Related story: Shopping giveaway 'harming children'