Australia's trade unions said they would call on the government to introduce a millionaires' tax similar to US President Barack Obama's so-called "Buffett Rule".
The Australian Council of Trade Unions said it wanted to ensure mining billionaires such as Clive Palmer, Andrew Forrest and Gina Rinehart paid a minimum tax on their incomes regardless of how they were derived.
"The income tax system is absurdly inequitable when it comes to taxing the mega-rich," said ACTU assistant secretary Tim Lyons.
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"Because most of their income comes from investment, billionaires... pay a much lower proportional rate than the average Australian family."
Lyons said the ACTU policy would be similar to top-end tax changes debated recently in the United States requiring those earning more than US$1 million per year to pay at least 30 percent in taxes.
The "Buffett Rule", which failed in the US Senate last month, was proposed by Obama's Democrats in a bid to improve tax code fairness as working-class Americans struggle with economic hardships.
It was named after billionaire investor Warren Buffett, who has publicly spoken out against being taxed at a lower rate than his secretary due to tax loopholes imposed by former president George W. Bush.
The ACTU proposal would be aimed at millionaires whose main income was from capital gains and would require them to pay at least as much tax, proportional to income, as ordinary working Australians, Lyons said.
Unions would vote on the "Down Under version of the Buffett rule" at the ACTU's national policy congress in the coming week, he added.
Australia's centre-left Labor government passed tough new taxes on mining profits and corporate pollution this year, and the party has strong links to the union movement, with a number of former union chiefs now cabinet ministers.
