"I can understand that people have noticed the disparity."
The price of petrol has increased across the country twice in February.
In a statement from Automobile Association New Zealand, Mark Stockdale said the three cents per litre rise in fuel prices was apparently led by BP.
"Commodity prices are only up just over a cent since the last increase, so a 3c retail price is difficult to justify," the statement said.
Fuel prices are at their highest since April 2012.
Mr Mills said the competitive market in Whangarei is not going to change.
"We will continue to compete strongly in price wherever and whenever we can."