Research from the Australian Competition and Consumer Commission (ACCC) released on Friday showed that through the past year, unleaded petrol averaged 141.2 a litre across Sydney, Melbourne, Brisbane, Perth and Adelaide.

The 6.7 increase on the previous year took nominal prices to their highest point since 2013-14. After inflation, prices are at their highest level in four years.

Sydney prices reached 138 a litre after averaging 131.9 a litre the previous year, while in Melbourne they hit 141.8 after averaging 135.6 through 2017-18.

The average household spends more than $44 a week on petrol, making it the single most expensive regular purchase. The 5 per cent jump in average prices since 2017-18 compares with a 1.6 per cent rise in general inflation over the same period.

It comes as households are already grappling with price hikes in essential goods and services in government-dominated sectors such as healthcare, education and energy, while wages stagnate.

ACCC chairman Rod Sims said the main factor in the lift in petrol prices was the Australian dollar, which had fallen by US6 against its American counterpart.

"The Australian dollar-US dollar exchange rate is a significant determinant of Australia's retail petrol prices because international refined petrol is bought and sold in US dollars in global markets," he said.

The ACCC noted that gross retail margins fell marginally, down 0.6 a litre. But at 12 a litre, the retail margin was the second highest on record.

Retailers have told the commission that the lift in gross margins in recent years was due to higher regulatory and compliance costs, especially in NSW. The ACCC is working on an industry report, due later this year, into the lift in margins.

Regional motorists did it tougher than those in capital cities, with the average price difference growing by 2.1 to 6.5 a litre through 2018-19.

Higher petrol prices feed into stronger tax collections, particularly via the GST.

But research from the Commonwealth Bank shows that the fiscal benefits from higher global prices for commodities such as oil and iron ore are not being shared with households, which continue to face slow wages growth.

CBA senior economist Gareth Aird said the federal government's budget bottom line was improving due to the lift in commodity prices but, even with recent tax cuts, money was being pulled out of the economy.

"The government is pursuing a balanced budget. This means that it is holding on to some of the revenue windfall courtesy of our external sector rather than circulating it back through the economy through tax cuts," he said.

"Shrinking the deficit in this manner effectively sucks money out of the economy. Putting the money back into the pockets of households via tax cuts would share the gains of decent national income growth."

Treasurer Josh Frydenberg has argued the government is supporting households through this year's tax cuts, with more than $11 billion of refunds returned to 4.4 million individuals since June.

But research by National Australia Bank this week, which has tracked spending patterns through its customers' use of their debit and credit cards, suggests the tax cuts have yet to find their way back into the economy.