BP cut the price of petrol by 3 cents a litre and diesel by 2 cents a litre on Monday.
The fuel retailer is charging 214.9 cents a litre for 91 unleaded, while diesel is 155.9 cents a litre.
Managing director Matt Elliott says a fall in prices for refined oils, coupled with the continuing strength of the New Zealand dollar, has allowed the move.
Mr Elliott says, however, the market remains unpredictable.
Petrol companies also cut prices last week.