New Zealand's consumer price index (CPI) increased 1.9 percent in the September 2018 year, driven by higher petrol prices, the statistics department Stats NZ said on Tuesday.

This follows a 1.5-percent annual inflation rate for the June 2018 year. For the September 2018 quarter, the inflation rate was 0.9 percent, Stats NZ said.

Petrol prices increased 19 percent in the September 2018 year, which is the highest annual increase since June 2011, prices senior manager Paul Pascoe said in a statement.

Petrol rose 5.5 percent in the September 2018 quarter. The price of petrol rose continually throughout the quarter, and by the last week of September was 3.2 percent above the September quarter average pump price, Pascoe said.

Multiple factors contributed to the petrol price increase this quarter. The exchange rate fell over the quarter, while crude oil prices rose. In addition, a regional fuel tax of 10 cents (6.6 U.S. cents) per liter plus Goods and Services Tax was introduced in Auckland on July 1, he said.

Petrol prices increased 8.8 percent in Auckland over the quarter, compared with 3 to 5 percent across the rest of the country, statistics show.

"While petrol only makes up about 4 percent of the CPI, it can have a large impact on overall inflation," Pascoe said, adding it contributed about 30 percent to the quarterly CPI movement for September, and about 40 percent to the annual movement.

This is the first time petrol prices have raised for four consecutive quarters since September 2008 during the global financial crisis, he said.

A national increase of 3.5 cents per liter in petrol tax was introduced on Sept. 30 with the effects to be seen in the December 2018 quarter, according to Stats NZ.