The war in the Middle East has sent petrol, diesel and jet fuel prices skyrocketing, causing chaos for travellers as the cost of flying soars and some services are cancelled.
A surge in motorists stocking up has led to hundreds of service stations running dry.
A national fuel emergency response manual suggests a daily transaction limit, which could be set by the federal energy minister.
At current prices, the $40 cap equates to around 16 litres.
The document was developed in 2019 and such a limit was not being considered, ministers said on Wednesday.
"The government has no intention of applying caps to the consumption of petrol," Trade Minister Don Farrell told reporters in Canberra.
The manual was obtained by former independent senator Rex Patrick under freedom of information laws.
"The government is already using a number of approaches suggested in the manual," he told AAP.
"I don't think they are necessarily prescriptive ... for example the $40 purchase cap may well be adjusted to some other number," Mr Patrick said.
Any rationing of petrol must be fair and transparent, while helping constrain demand, the document said.
"Whilst the 'total transaction value' would be fixed, the price per litre would be able to fluctuate according to the normal operation of the market," it said.
"This would have the effect of reducing or increasing the volume of fuel sold if prices rise or fall respectively."
It also outlines other measures the government could take, including directing fuel to be delivered to areas of shortage or essential users, ordering petrol companies to maintain minimum stocks, transferring fuel between states and territories and directing refineries to produce quantities of petrol or diesel.
Some of those steps have already been taken in the wake of the Middle East war.
Soaring oil prices are also throwing travel plans into disarray, with Jetstar confirming it has cut back on flights due to rising jet fuel prices and other costs.
One in 10 of the budget carrier's May services have been impacted, including domestic New Zealand services and flights between Auckland and Sydney and Brisbane, a spokeswoman said.
Most affected passengers have been offered seats on same-day Jetstar flights.
The government needed to be more transparent about its response to soaring fuel prices, shadow attorney-general Michaelia Cash told Seven's Sunrise program.
"Apparently they understand that people are doing it tough, but they are doing nothing to alleviate that pain," she said.
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