Australia is set to blow another resources boom, forgoing billions of dollars in potential tax revenue, because its tax regime is failing to collect adequate revenue from the explosion in liquefied natural gas exports, according to a new analysis.

The Turnbull government and Labor are now being lobbied to set up a parliamentary inquiry to investigate why the petroleum resource rent tax (PRRT) is collecting so little revenue.

The Greens senator Larissa Waters has told Guardian Australia the Greens would support such an inquiry.

Researcher Jason Ward, from the Tax Justice Network, has warned that Australia’s PRRT is failing to ensure the federal government gets a fair share of revenue from the exploitation of the country’s natural resources.

He says Australia is set to become the world’s largest exporter of LNG by 2021, overtaking Qatar in the Persian Gulf.

But that year, when both countries are each forecast to export roughly 100bn cubic metres of LNG, Australia’s government is expected to receive just $800m in PRRT revenues, while Qatar’s government is expected to receive $26.6bn in royalties.

The problem becomes starker when looking at the trend in PRRT revenue, Ward says.

According to the Treasury, in 2005 the government collected $1.9bn in PRRT and last year that figure fell to $1.4bn. But it is estimated to fall again – to just $800m – when Australia becomes the world’s dominant LNG exporter by 2021.

Ward says this shows the PRRT – which is a profits-based tax – is ill-suited for modern tax purposes.

“I genuinely hope that we can get this parliamentary inquiry up because it’s an issue of huge national significance,” he said.

Ward compared the revenues of Australia’s PRRT with Qatar’s LNG royalties for the International Transport Workers’ Federation. He used forecasts by the International Monetary Fund and Qatar government data.

He says Qatar either takes a stake in an LNG project or it charges a flat royalty rate on production.

A letter cosigned by 21 union and left-leaning organisations, including the Australian Council of Social Service, the ACTU, Greenpeace, the Australia Institute, ActionAid, GetUp and the Uniting church has been sent to Malcolm Turnbull and Scott Morrison calling for a parliamentary inquiry into the PRRT.

“The undersigned organisations have major concerns about forecasts of declining or stagnant government revenue from the PRRT coinciding with Australia becoming the world’s largest exporter of LNG,” the letter says.

“LNG will soon compete with iron ore to become Australia’s largest export. However, various analyses show that the primary resource tax on this export, the PRRT, will not collect any new revenue for decades to come.

“The PRRT system, based on voluntary compliance and self-reporting [by gas companies], operates with limited transparency and inadequate oversight. Australians need greater public confidence that they will benefit fairly from the exploitation of our natural resources.”

In 2010 the Henry tax review warned the PRRT “fails to collect an appropriate and constant share of resource rents from successful projects due to uplift rates that overcompensate successful investors for the deferral of PRRT deductions”.