By Zac de Silva

Petrol stations have been told not to rip off Australian motorists, amid warnings the war in the Middle East could drive up global oil prices.

The consumer watchdog has been tasked with monitoring fuel prices, while the nation’s biggest oil refining companies have promised not to hike prices unnecessarily.

Iran has shut the Strait of Hormuz – through which around one-fifth of the world’s oil supply passes – threatening to set on fire any ship which tries to use the route.

Energy Minister Chris Bowen met with the bosses of Australia’s refining companies on Tuesday, and says he was assured oil would continue being delivered until at least May.

“The refining companies told me they had absolutely no plans of increasing the price of petrol, until and unless the price of oil increase flows through to Australia,” Mr Bowen told reporters at Parliament House on Tuesday.

“There will be impacts from this crisis on petrol prices, but we don’t want to see anybody profiteering unnecessarily or unjustifiably from this very difficult circumstance. I have great confidence that the refineries won’t be doing that.”

Treasurer Jim Chalmers wrote to Australian Competition and Consumer Commission boss Mick Keogh on Tuesday, asking his agency to monitor petrol prices.

“Unfolding events should not be used as an excuse for retailers to gouge customers or to increase prices opportunistically above and beyond the impacts of events in the Middle East,” Dr Chalmers wrote.

Some retailers in Sydney, Melbourne and Brisbane are selling E10 petrol for well over $2 a litre, with diesel prices even higher in some areas.

But the high costs were driven by the regular price cycle, with further cost increases from the Middle East war yet to hit Australian commuters, NRMA spokesman Peter Khoury said.

“It takes seven to 10 days for prices overseas to flow on and impact prices at the bowser,” he told AAP on Tuesday.

Wholesale prices had gone up four cents a litre for petrol and three cents a litre for diesel, Mr Khoury said – an increase likely to be passed on to motorists.

“These are only small increases as of today. It’s such a volatile situation, things are going to change pretty quickly,” he said.

While the conflict has the potential to send oil prices skyrocketing, it hasn’t done so yet, AMP chief economist Shane Oliver said.

“So far we haven’t seen the horror scenarios where it surges through $100 (a barrel) yet, but that may still happen.

“I think there was general panic expected (on Monday) and overnight, and we didn’t see that so far in oil markets and share markets.”