Families hoping to get away over Easter are unlikely to get cheaper petrol before the long weekend, while regional people could wait weeks for relief.

The federal government has cut wholesale fuel prices by 26 cents a litre from Wednesday to try to head off the worst economic effects of the Middle East war.

But the change would not be felt straight away because service stations needed to sell all their older, higher-taxed stock before bringing in the cheaper fuel, NRMA spokesman Peter Khoury said.

That process would likely take anything from a day or two for high-turnover metro stations to two or more weeks for some regional sites, he said.

“Once they buy new fuel, they will pass the discount on at that point,” Khoury said.

Treasurer Jim Chalmers said the consumer watchdog would watch closely to ensure service stations passed price cuts on to consumers. But he reiterated the change would not kick in straight away.

“I want to manage expectations on that front because people shouldn’t rock up at five past midnight … and expect to see the full benefit passed on,” he said on Tuesday.

Former Australian Competition and Consumer Commission boss Allan Fels said while there was no law against price-gouging, public shaming would be a powerful tool to force fuel companies to do the right thing.

“The ACCC has no direct powers either to set maximum prices or to fine companies for excessive pricing or price-gouging,” he said.

“But the ACCC can publicly criticise someone that’s not passing on the benefit.”

The watchdog would also need to keep a close eye on the “rocket and feather” effect on fuel prices, Fels said.

“When costs go up, prices go up like a rocket. When costs go down, prices fall slowly like a feather to the ground,” he said.

States and territories are considering forgoing some GST revenue on the higher fuel prices, but the reforms appear to be bogged down because jurisdictions cannot agree on the best way forward.

Some states want to reduce the 10 per cent GST on petrol and diesel, giving motorists a direct benefit. Others are keen to keep the rate as is but use increased revenue to fund broad cost-of-living payments.

-AAP