The retail price of petrol has risen 20 cents per litre in nine days and further increases are likely.
Oil companies say rises are inevitable while the New Zealand dollar remains weak and the cost of refined petrol continues to increase.
The New Zealand dollar is trading at about 53 US cents.
Mobil and BP announced another increase on 5 cents on Thursday, taking 91 octane to $1.52.9 per litre and 95 octane to $1.58.9 at most stations.
However, the retail price for diesel is still $1.03.9 per litre.
Energy Minister Gerry Brownlee says the increases appear to be justified because of international market trends.
He says it should be remembered that people were paying almost $2.20 per litre in July last year.