The head of the International Energy Agency has warned the Albanese government against sudden changes to corporate taxes, suggesting a proposed 25% export levy on windfall gas profits would spook investors.

It was revealed last week that Anthony Albanese’s department has asked Treasury to model the effects of placing a flat 25% tax on gas exports, and to model possible changes to the petroleum resource rent tax (PRRT) and corporate income tax.

The move comes as gas profits soar amid the global energy crisis sparked by the war in Iran, and could lead to changes as soon as the May federal budget.

But, ahead of his meeting with Albanese in Canberra on Monday, the IEA’s executive director, Fatih Birol, said energy companies wanted a predictable set of rules and tax to spend their money within.

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“Energy investors are like butterflies. When they are scared, they fly away,” he said at the National Press Club.

“So you should be careful … that those companies feel that the investment framework is predictable for them.

“At the same time, it is important that the consumers, the citizens of the country, which are the real owners of the resource endowment, get their fair share from the profits that those companies are making.”

Albanese told a Minerals Council of Australia event on Monday night the government would “continue to look at every practical option to protect Australia from the worst of this international crisis”.

He said even an immediate end to the war would leave “a long economic tail” for governments and business to reckon with.

“The stable, predictable world of ever-expanding free trade is gone – and it will not be returning any time soon,” Albanese said.

The Greens, crossbenchers and the ACT senator David Pocock have urged the government to do more to capture billions of dollars in potential revenue as prices soar.

But the gas industry’s peak representative body, Australian Energy Producers, said a 25% levy would come at the “worst possible time for Australia’s economy and energy security”.

In question time on Monday, the treasurer, Jim Chalmers, told parliament the government had not changed its tax policy. Similar language has been used by Labor ahead of changes to personal income tax rates and superannuation concessions.

“[We] more than believe it is necessary that Australians receive a fair return from the natural resources that they own,” Chalmers said.

“We have taken some steps in the course of the life of this government to make sure that offshore gas companies, for example, pay more tax sooner.”

Labor senator Michelle Ananda-Rajah became the first government member to publicly back the proposed gas tax changes, saying the industry was a “highly lucrative” for producers.

She said Labor’s updates to the PRRT had pulled in extra takings from resources companies, but that the Middle East conflict had seen gas prices spike.

“The gas companies are raking it in as a result of this conflict,” Ananda-Rajah told the Senate.

“I do agree with the Greens … that we need to go further, and I think that Australian gas producers have been operating in fairly generous circumstances for some time, and yes, they do create jobs, yes they do create revenue, yes they do create value.”

Ananda-Rajah rebuffed suggestions that such a change would disincentivise investment in Australia.

The Greens leader, Larissa Waters, said her party would support legislation for a 25% export tax immediately. She accused “greedy gas corporations” of “taking the piss.”

“They’ve been price-gouging Australians for far too long, and it’s time our government placed a minimum 25% gas export levy to use that revenue to help people who are in a cost of living crisis,” Waters said.