Motorists are missing out on cheaper fuel prices and could save up to 10 cents a litre if they make more of an effort to shop around, according to the consumer watchdog.

The Australian Competition and Consumer Commission has released its first report on the fuel industry after the Federal Government last year directed it to monitor prices and profits.

An analysis of 2017 figures revealed a large discrepancy between the amount retailers were charging in capital cities.

The ACCC looked at prices at major retailers in Brisbane, Sydney, Melbourne, Adelaide and Perth, finding that in Sydney there was a difference of up to 10c per litre between different service stations.

Other cities had price differences of up to 7c per litre.

The report also found the gap between the highest price and the lowest price had grown significantly in the last decade.

The Federal Government asked the ACCC to start monitoring fuel prices more closely. ( ABC News )

The ACCC found people were missing out on savings because they tend to go to the same service station every time they fill up.

"As in any market there's always someone trying to rip you off, whether it's electricity, groceries or petrol," chairman Rod Simms said.

"Drivers can save a lot of money by shopping around."

Nationally, Coles and BP retailers were charging the most on average, while the independents were often the cheapest, Mr Simms said.

The ACCC said drivers needed to weigh up offers like shopping vouchers or other discounts with the price they paid at the pump.

It said by making the effort to shop around, motorists would save money but also encourage a more competitive market.

"Companies can set prices as they want. We've (the ACCC) got no role in regulating the price of petrol, our job is to help you find the cheapest petrol," Mr Simms said.

In a statement, BP said: "Our aim is to always be competitive with our fuel pricing as we value our customers' patronage and we know they have a choice."

