Canberra, Jun 6 (IANS): Petrol prices were at their lowest in Australia since 1999, a report said on Monday.

The Australian Competition and Consumer Commission (ACCC) said prices across the nation were at 17-year lows, with the average cost of filling up the car coming at 81.4 US cents per litre throughout the March 2016 quarter -- almost 10 cents per litre cheaper than the previous quarter, Xinhua reported.

ACCC Chairman Rod Sims said a number of factors were influencing petrol prices in Australia, including a drop in crude oil prices and closer regulation by the retail watchdog.

"Motorists benefited from the lowest quarterly petrol prices in inflation adjusted terms since 1999," Sims said in a statement.

"The low petrol prices were due to two main influences: Firstly, crude oil prices and international refined petrol prices in inflation adjusted terms fell to lows not seen since 2002 and 2008, respectively."

"Secondly, gross retail margins decreased in the quarter. The ACCC believed that retail margins were unreasonably high in the second half of 2015 and wrote to the major petrol retailers in early February 2016 seeking an explanation for the high retail margins."

Sydney was the cheapest major city for motorists to fill up in, with an average March quarter price of 79.2 US cents, while Canberra and Tasmania's capital city Hobart were the most expensive -- with motorists paying up to 89.6 cents per litre throughout the first quarter of 2016.