The High Court unanimously upheld the validity of former prime minister Julia Gillard's carbon tax, which Queensland Nickel attempted to argue discriminated between Western Australian nickel producers and Queensland refineries.

Queensland Nickel's refinery is wholly owned by Clive Palmer and in 2012, Mr Palmer, who had not entered the Parliament at the time, claimed to have received legal advice that the carbon tax was unconstitutional.

Queensland Nickel argued the producers in WA processed a different kind of ore with a smaller greenhouse gas footprint, meaning it paid a higher carbon tax bill than its competitors.

Queensland Nickel claimed that the carbon discriminated against Queensland producers compared to West Australian ones. But the High Court rejected this argument and said the carbon tax applied equally to nickel miners across the country.

When contacted for comment Mr Palmer claimed to know nothing about the High Court judgment.

"I know nothing about it," he said.

"I'm not a director [of Queensland Nickel], I'm retired, I'm a parliamentarian now," he said.

"It's none of my concern really," he said before hanging up.

Clive Palmer's register of interests says he gave up his directorship of Queensland Nickel in April 2014 but a recent update says he took a directorship back on in January 2015.

Constitutional law professor George Williams said the High Court's judgment was "no surprise".

"The expected result occurred," he said.

"It just doesn't appear on the facts of the matter that there was any preference because the tax operated Australia wide," he said.

Clive Palmer and his Palmer United senators helped the Coalition repeal the carbon tax in 2014. But since then, Mr Palmer's political clout has diminished with two of his senators, Jacqui Lambie and Glenn Lazarus defecting to become independents.

Mr Palmer has threatened legal action against the senators, claiming they broke their promise to represent his Palmer United Party.

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