Fear of war in the Middle East, a political crisis in Venezuela and a crude oil cartel agreement means Australians are paying more for petrol, the consumer watchdog says.

Unleaded petrol has reached its highest price in almost four years across Australia’s capital cities, according to the Australian Competition and Consumer Commission.

The average price in Sydney, Melbourne, Brisbane, Adelaide and Perth was $1.452 per litre in the June quarter.

The price of unleaded petrol is up almost 12 per cent from a year earlier.

The annual average retail price was also up by 11.09 cents for the year to $1.345 in 2017-18.

“After adjusting for inflation over time, this was the highest annual average price since 2014-15,” the ACCC said in its report released on Tuesday.

The watchdog blamed a jump in international crude oil and refined petrol prices, noting the Organisation of Petroleum Exporting Countries (OPEC cartel) also significantly bumped up prices.

The ripples of the cartel’s 2016 agreement to cut crude production is now being felt across the world, compounded by concerns of risks to international oil supplies.

The supply concerns are born out of renewed US sanctions against Iran and fears of spreading conflict in the Middle East, the ACCC said.

The political and economic crisis in Venezuela has also resulted in falling crude oil production.

The weakened Australian dollar also contributed to the price hike, with the AUD-USD exchange rate hitting local petrol prices because it is bought and sold in US dollars in global markets.

The AUD decreased about $0.03 to the US dollar in the June quarter.

“The lower AUD-USD exchange rate in the June quarter 2018 compounded the influence of the increase in international refined petrol prices on Australian retail petrol prices,” the report said.

Brisbane continued to have the highest retail petrol prices, averaging $1.484, up from $1.382 in the quarter to March.

Sydney prices increased most in real terms between the March and June quarters, up from $1.32 to $1.433.

Melbourne prices went from $1.371 to $1.46, while prices in Adelaide went from $1.327 to $1.427.

Prices in Perth reached $1.453, up from $1.374.

The ACCC recommended motorists use live fuel price monitoring apps and websites to find the best price and encourage competitiveness.

“If retailers know that price is the No.1 consideration for consumers when choosing where to buy their petrol, it gives them a very clear incentive to be as competitive as possible with their pricing,” ACCC chair Rod Sims said.

He also recommended motorists avoid buying at the peak of the price cycle, saving an average of around 0.27 cents per litre over six months, or up to 0.47 cents in Adelaide.

“For an individual tank of petrol, this saving represents just a few dollars, but over the course of a year, the savings stack up,” Mr Sims said.

The Queensland government recently committed to a two-year trial of live fuel price monitoring to start in December.

Motorists will be able to search for the best price on a smartphone app and websites like MotorMouth, GasBuddy, Petrol Spy, RACQ and Compare the Market.

The NSW government in June said 220,000 drivers had downloaded its FuelCheck app.

-with AAP