CommSec economist Savanth Sebastian said although national prices were at a three-month high, he warned they were going to keep rising to above 150c a litre.

"Higher crude prices and a substantially weaker Aussie dollar - pushing up the cost of imported fuel - are likely to see domestic pump prices rise considerably over the next few weeks," he said.

"And indirectly that means that retailers also need to brace for more conservative and price-conscious consumers. A petrol price above $1.50 a litre will become more common-place across Australia in coming weeks.

"Had the Aussie dollar remained at levels it was two months ago (US103c) motorists would be saving around 9 cents a litre. CommSec expects the national average price to rise by a further 3 cents a litre over the next fortnight."

The latest figures from the Australian Institute of Petroleum found unleaded prices rose 3.4c to an average 148.6c a litre nationally last week, while Canberra prices were effectively unchanged at 1.47c a litre.

The average unleaded price has been steadily decreasing in Canberra since April, when it hit highs close to 156c a litre.

Around the region, petrol was cheaper still in Queanbeyan, at 144.2c a litre, and Goulburn, at 145.9c, but more expensive in Yass where unleaded was costing an average of 153.1c.