New South Wales, the Australian state worst hit by this season's enormous bushfires, has announced an independent inquiry into the continuing blazes, including the reasons why they started and the role that climate change may have played.

The six-month inquiry that will begin this week will examine how state authorities prepared and responded to the "unprecedented" 2019-20 bushfire crisis, state Premier Gladys Berejiklian said on Thursday.

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It would be crucial to "leave no stone unturned," Berejiklian said.

She said the inquiry will be led by two experts - former state police Deputy Commissioner Dave Owens and former state chief scientist Mary O'Kane, who will travel to affected communities and take submissions from the public.

They will not hold public hearings.

"We've asked them to start during the [bush fire] season to ensure that they can do all the work they need to do for now because we want to report in a timely fashion, we want it ahead of the next season," Berejiklian told reporters in Sydney.

The inquiry will look into how climate change, drought, hazard-reduction burns - which are conducted to reduce fuel load before the bushfire season - and human activity contributed to the fires.

The relationship between state authorities and federal authorities during the crisis will also be examined.

Billions of dollars in damage

Australia's conservative federal government led by coal industry-promoting Prime Minister Scott Morrison has been heavily criticised for climate inaction and over its handling of the crisis.

SBS online reported Morrison had also been at odds with New South Wales Environment Minister Matt Kean over the fires and climate change.

Morrison had dismissed Kean's proposal for the federal government to take on a bigger role in dealing with climate change in the wake of the fires, it reported.

The prime minister has also defended the country's coal industry, saying he is protecting jobs.

But critics say coal and climate change have contributed to the unprecedented bushfires continuing to burn.

New South Wales Premier Gladys Berejiklian (left) looks at a map of fire-affected areas of the state before the news conference on Thursday [Paul Braven/EPA]

Since September, more than six million hectares of land (14.8 million acres) has already burned in New South Wales, with dozens of fires still not under control.

A total of 2,400 homes have been destroyed and 25 people have died, while an estimated one billion animals have also perished.

The bushfires damage is estimated at 2 billion Australian dollars ($1.3bn.

Although heavy rain and lower temperatures this month have helped put out some fires, the threat has not diminished.

During the news conference on Thursday, Berejiklian said the bushfire season was still not over.

"While we are focused on the rebuilding process we are mindful of the remaining fire threats," she said.