The Clean Energy Regulator (CER) has vowed to pursue federal MP and mining magnate Clive Palmer over his outstanding carbon tax debt - plus interest.

Mr Palmer’s company Queensland Nickel is refusing to pay a $6.2 million carbon tax bill and is challenging the tax in the courts.

His Palmer United Party (PUP) has campaigned to remove the carbon tax and compensate big polluting companies for their first year of liabilities.

The Queensland MP will abstain from voting on the federal government’s carbon tax repeal legislation currently before the parliament to avoid a conflict of interest.

The CER, the entity tasked with enforcing payment of the carbon price, has told a Senate estimates committee it’s in talks with Queensland Nickel and can’t comment about specifics.

“What I can say is we’re in discussions with Queensland Nickel about how they might pay their outstanding debt,” CER general counsel Geoff Purvis-Smith said on Monday.

“We will pursue these debts in accordance with the Financial Management and Accountability Act.”

The last time the regulator communicated with Queensland Nickel was at the end of October, he added.  Queensland Nickel is one of just three companies that hasn’t paid its carbon liability.

Mr Purvis-Smith wouldn’t comment on when the CER expected to collect its debt, but agreed Queensland Nickel couldn’t continue to evade its payments forever.

He said the regulator would be pursuing the best possible return for the Commonwealth.

“Our preference for this stage is that they pay the full amount that’s outstanding, including the interest,” he said.