Federal Attorney-General George Brandis says people who say the science is settled on climate change are "ignorant and medieval".

In an article published in the online political magazine Spiked, Senator Brandis spoke to a journalist about his fight against "the cultural tyranny of political correctness".

Senator Brandis said he was on the side of free speech and the two main debates that sparked his push to propose changes to the Racial Vilification Act were the Andrew Bolt case and the climate change debate.

In the article he said he believed humans were causing global warming, but he was "really shocked by the sheer authoritarianism of those who would have excluded from the debate the point of view of people who were climate-change deniers".

He said people who believed in climate change would accept the science without "intellectually" engaging with deniers.

Senator Brandis also criticised former Gillard government climate change minister Penny Wong, who he said would stand up in the Senate and say the science was settled on climate change.

"It was ignorant, it was medieval, the approach of these true believers in climate change," he said.

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Senator Wong was the "high priestess of political correctness", Senator Brandis was quoted in the article as having said.

Greens say Brandis' argument 'worrying'

But acting Greens leader Adam Bandt has hit back, saying it is a feudal way of thinking to say that everyone's view of climate change is equally valid.

"If someone said 'two plus two equals five', would you insist on giving them as much airtime in the media as someone who said 'two plus two equals four'?" he told the ABC's AM program.

"That's in effect what the country's highest law officer is arguing, and it's very worrying.

"This Abbott Government is using every trick in the book to hide the fact that they're not taking the action that the science calls for on climate change.

"And to suggest that somehow people in this country are being restricted from airing albeit very wrong views on climate change is completely misleading."

Mr Bandt says people are free to say that climate change is wrong.

"People are saying that, and they're saying it at the moment and they're wrong," he said.

"The science community is now essentially speaking with one voice.

"To say someone without science training can somehow simply on a free speech basis say that they're all wrong is a very feudal way of thinking."

The ABC has requested comment from Senator Brandis.