Brisbane motorists could be among the first to pay the higher price, with petrol prices already reaching $1.44 at some outlets - 9c a litre more than the national average.

Commsec has warned consumers to expect average prices to continue climbing by about 3c a litre each fortnight - more if tensions in Egypt escalate and supplies from the Suez Canal are interrupted.

"At the peak end of the cycle, $1.50 (a litre) is not too far off," Commsec economist Savanth Sebastian said.

"Even if you put aside the Middle East story, petrol prices will continue to track higher."

He said the longer term outlook was just as grim, with the Aussie dollar predicted to come off the boil and demand for oil increasing in Asia as a result of "phenomenal growth".

A spokeswoman for Australia's petrol commissioner, Joe Dimasi, said the 26-month highs at petrol bowsers in recent days were the result of sharp rises in the Singapore benchmark price.

Since last September, the Mogas 95 price has risen $US25 to $US105.

But FUELtrac's Geoff Trotter said Coles and Woolworths were inflating petrol prices to counter losses from a bread and milk price war.

"If they (Coles and Woolworths) are giving away margin on bread and milk, fuel is a wonderful way to recover that margin," Mr Trotter said.

A Coles spokesman said Mr Trotter's claims were "ludicrous".

"We do not, and never have, cross-subsidised prices between our supermarkets and fuel sites," he said.

"Our milk price cut is a genuine reduction and our fuel prices simply reflect the recent price cycle move by all major fuel retailers."