THE Clean Energy Regulator believes it's practical to abandon three planned auctions of carbon permits this year because a lack of buyers would make it costly and fruitless.

Environment Minister Greg Hunt on Monday announced he'd taken steps to stop these auctions, scheduled to occur before June 30, from going ahead.

But his declaration - which is to come into effect on Tuesday - can't go ahead without the support of the Senate, and the Australian Greens have already vowed to disallow it.

Clean Energy Regulator chair Chloe Munro said there was no evidence of market interest in carbon permits, and if the minister's declaration was barred they'd be forced to "go through the motions".

"To me this is a matter of practicality," Ms Munro told a Senate estimates committee in Canberra on Monday.

"I don't believe there is an impact (by not proceeding), principally for the reason that at present there doesn't appear to be any market for those units."

Pressing ahead would also incur "quite significant costs" for both the regulator and the external company they use to conduct the auction, she said.

Carbon permits are bought and surrendered by companies to pay their carbon tax bills, and the regulator is required by law to hold periodic auctions.

Mr Hunt said he intervened to stop the auctions because the carbon tax repeal was "imminent", and it was vital to give business certainty that they no longer needed to take part in the auctions.

Legislation to repeal the carbon tax has stalled in the upper house, and despite frustration within the federal government it's unlikely to pass before a less hostile Senate takes over in July.

Ms Munro said there was nothing preventing the regulator from recommencing auctions with a "short window of advance notice" if needed in the future.

Finance Minister Mathias Cormann said the government was simply trying to save money by not proceeding with the auction.

"Obviously, to go ahead with an auction at a time when there's no market ... would be quite wasteful," he said.

Greens leader Christine Milne accused the government of getting ahead of itself by trying to dismantle the functions of the carbon tax before it had actually been scrapped.

Originally published as Regulator backs abandoning carbon auctions