Mr Joyce made the provocative comment while blaming the minor party for increasing the threat of bushfires.

"I acknowledge that the two people who died were most likely people who voted for the Green party, so I am not going to start attacking them," he told Sky News on Tuesday.

"That's the last thing I want to do. What I wanted to concentrate on is the policies that we can mitigate these tragedies happening again in the future."

Mr Joyce doubled down on disputed claims the fire service had conducted insufficient hazard reduction burns this year as a result of opposition from Greens councils.

He also criticised Greens MP Adam Bandt for demanding an end to coal production.

"To make these spurious links - that a policy change would have stopped the fire - is so insulting and just completely beyond the pale," Mr Joyce said.

Labor frontbencher Kristina Keneally slammed his remarks during a Senate estimates hearing.

"How does he know who they voted for and why does it matter? They're dead; they died in a bushfire. Isn't that enough?" Senator Keneally said.

The Greens Larissa Waters asked Finance Minister Mathias Cormann about Mr Joyce's "vile" comments during Senate question time.

Senator Cormann, responding on behalf of the prime minister, said the comments were not appropriate.

"We believe that it is not an appropriate time to bring politics into this debate when people have lost their lives and while these same fires continue to burn," he told parliament.

"Equally, the time to have policy discussions is not in the middle of an operational response."

Mr Joyce's remarks are the latest in an increasingly bitter stoush between the Nationals and Greens over the cause of the bushfires.

On Monday, Nationals leader Michael McCormack attacked "raving inner-city lunatics" for linking climate change to the fires.

In return, the Greens labelled the deputy prime minister a "dangerous fool" who was putting lives at risk.

Greens senator Jordon Steele-John branded major party politicians "arsonists" for supporting the coal industry.

His incendiary spray on climate policy came as catastrophic fire conditions gripped NSW.

"You are no better than a bunch of arsonists - borderline arsonists - and you should be ashamed," Senator Steele-John told the chamber.

Australian Associated Press