The world's biggest trade union says US energy giant Chevron has been profit-shifting to drive down the tax it pays in Australia.

The International Transport Workers Federation has issued a report claiming Chevron has hidden over $US35 billion in untaxed revenue offshore.

The federation says Chevron has around 600 shell companies in tax haven locations like Bermuda and Delaware.

The company’s tax returns have been challenged in the US and other countries.

In fact, the US government has reportedly not approved Chevron's tax filings for over seven years.

But Chevron denies breaching any tax laws in the countries that it operates in.

The energy giant is heavily involved in Australian projects, including its Gorgon and Wheatstone gas projects off the northern coast of Western Australia, which are together worth $84 billion.

There are about 17,000 jobs connected with the Gorgon and Wheatstone projects.

But the union says Chevron will pay no royalty (PRRT) payments on Gorgon for the first 8 years or longer.

The company is also part way through a Federal Court dispute with the Australian Taxation Office (ATO) over a recent tax bill.

The Transport Workers Federation claims Chevron’s latest tax schemes could reduce Chevron’s tax bill by $35 billion or more, and that the company has set aside $350 million to settle a previous Chevron tax scheme being litigated by the ATO.

The ATO alleges Chevron has used a complex scheme of related-company loans to cut its Australian tax bill by at least $250 million.

“If Chevron and its partners can be forced to pay their fair share of tax revenues on these massive LNG projects it has the potential to increase funding for schools, hospitals and other essential public services,” said Paddy Crumlin, the president of the International Transport Workers’ Federation.

A Chevron spokesperson has defended the company’s tax arrangements.

“Chevron abides by a stringent code of business ethics, under which we comply with all applicable laws and regulations in the countries in which we operate, including Australia,” the spokesperson said.

“As one of the Australia's largest investors, Chevron will pay its fair share of tax and, through the Chevron-led Gorgon and Wheatstone Projects, Australia will continue to enjoy the associated economic benefits over the life of the projects.”

Sharan Burrow, the General Secretary of the International Trade Union Confederation (ITUC), said such large scale tax-dodging can have impacts on all parts of society.

“Aggressive tax avoidance hurts schools and hospitals, undermines governments, and expands inequality. If Chevron avoids so much tax in Australia, imagine what they might do elsewhere. Australia needs to ensure Chevron pays its fair share and we need a global examination of Chevron’s tax schemes,” she said.