As more than 50 fires burned across the state, tempers flared in the federal parliament, after the former Nationals leader intimated two of the fire victims voted for the Greens.

It followed an attack from senior Nationals party figures, claiming the bushfire threat had been heightened due to the environmental opposition to backburning.

"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. That's the last thing I want to do," Mr Joyce told Sky News on Tuesday.

Labor senator Kristina Keneally seized on the comments 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? Do you think it matters who they voted for?" Senator Keneally asked Coalition senator Simon Birmingham.

Greens senator Larissa Waters used question time to ask whether the Coalition would discipline Mr Joyce over the comments.

"It's not okay to talk about the climate crisis but it's okay to talk about people who burned alive," Senator Waters said.

Coalition senator Mathias Cormann said Mr Joyce's comments were not appropriate given the circumstances.

"We believe it's not an appropriate time to bring politics into the debate while these same fires continue to burn. The time for policy discussions is not in the middle of people literally fighting for their homes and survival," Senator Cormann said.

But Labor also rounded on the Greens after Senator Jordan Steele-John accused the Coalition of being "arsonists" during a debate on the big stick energy legislation.

"I cannot think of a more profound dereliction of duty in this moment of national crisis than seeking to actively make a problem worse," Senator Steele-John said.

"You are no better than a bunch of arsonists, borderline arsonists, and you should be ashamed."

Labor senator Murray Watt said the "highly offensive" comments were indicative of how far the Greens would go to to make their political point.