Only about 1 per cent of the land burnt in NSW this bushfire season can be officially attributed to arson, and it is even less in Victoria, the ABC can reveal.

The world has been shocked by the scenes of devastation as the unprecedented destruction of Australia's horror bushfire season rages on.

The disaster has sparked significant media speculation that many of the blazes were deliberately lit.

While it is true firebugs remain a legitimate and serious threat, we crunched the numbers provided by police and fire authorities around the country.

The results might surprise you.

NSW Rural Fire Service (RFS) Inspector Ben Shepherd said earlier this week lightning was predominantly responsible for the bushfire crisis.

"I can confidently say the majority of the larger fires that we have been dealing with have been a result of fires coming out of remote areas as a result of dry lightning storms," he said.

In Victoria, where about 1.2 million hectares has burned, only 385 hectares — or 0.03 per cent — have been attributed to suspicious circumstances.

This state-by-state breakdown reveals the true impact of arson this bushfire season.

New South Wales

Firefighters tackling the massive Gospers Mountain blaze in December. ( Supplied: Gena Dray )

The Busbys Flat fire, which burned through some 51,000 hectares of land and destroyed 44 homes in the village of Rappville in northern NSW, may have been deliberately lit.

Police Minister David Elliott said whoever started that blaze in October was responsible for a "bastard act".

A fire at Turramurra which briefly threatened homes on Sydney's north shore is also suspected of being deliberately lit, as are a series of small fires in the Royal National Park.

Houses in Turramurra were doused with fire retardant when the fires took hold. ( AAP: Dan Himbrechts )

NSW has been the epicentre of Australia's bushfire crisis, but the facts show arson has little to do with it.

This week, a NSW Police media release revealed 24 people had been charged over deliberately-lit bushfires this season.

However, the majority of suspected arson relates to small grass fires and rubbish bins set alight, which have inflicted negligible damage and burnt a tiny area compared with fires sparked by lightning.

The Gospers Mountain "mega-blaze" and the Green Wattle Creek fire, which are both near Sydney, were ignited by lightning.

All the major blazes in the Snowy Mountains and South Coast which have taken hold since New Year's Eve were also started by lightning.

This includes the Dunns Road and Green Valley fires burning near the state's south border, which on Friday formed a new "mega-blaze".

Victoria

The blaze at Corryong in Victoria, close to the NSW border. ( Supplied: Amber Rendell )

Despite massive fires causing chaos in Victoria this season, authorities are treating only one blaze as suspicious.

The Euroa blaze on January 4 closed a section of the Hume Highway, burnt about 385 hectares, and destroyed no properties.

More than 1.3 million hectares has been burnt in Victoria so far this season.

The Country Fire Authority (CFA) said the majority of fires were not arson-related.

"Most of the fires have been caused by lightning," said Brett Mitchell, the CFA incident controller in Bairnsdale, in East Gippsland.

"Our intelligence suggests there are no deliberate lightings that we are aware of."

Victoria Police had no arson figures available for this bushfire season, but said in the 12 months to September 2019, a dozen people had been arrested for causing bushfires.

South Australia

Koalas rescued from the bushfire at Cudlee Creek. ( Supplied )

None of SA's deadliest or most destructive fires are being treated as suspicious.

Two fires which have blackened more than a third of Kangaroo Island and killed two people, are believed to have been sparked by lightning strikes, according to the state's Country Fire Service (CFS).

The Cudlee Creek blaze in the Adelaide Hills, which started in catastrophic conditions and killed one person and destroyed more than 80 homes, was caused by a tree falling on power lines.

The CFS said a fire on Yorke Peninsula which destroyed homes and burnt 5,000 hectares in November was sparked by power lines falling on grass during catastrophic fire conditions and extreme winds.

A fire at Keilira in SA's south-east, which destroyed homes and killed thousands of livestock, has been officially attributed to lightning strikes, after an investigation by the CFS and South Australian Police.

Police said 10 people in SA had been reported or arrested for intentionally or recklessly causing a bushfire since September.

Queensland

Firefighters discuss their next move at the Peregian Springs blaze. ( ABC News: Tara Cassidy )

The Queensland Fire and Emergency Services (QFES) said 3 per cent of the bushfires in the state this season were deliberately lit.

Over 2.5 million hectares of the sunshine state has been engulfed by blazes since August 1.

The QFES also said about 6 per cent of the ignition causes were being treated as suspicious but 19 per cent was being categorised as "accidental or natural".

This category includes lightning strikes.

The remaining 72 per cent has been categorised as "undetermined".

The Sunshine Coast town of Peregian has been threatened by several blazes this season.

In September, two teenagers were charged with lighting a blaze there, while authorities are investigating "suspicious" fires that also took hold there in October and December.

Queensland Police said there had been 1,068 reported bushfires between September and January 8, 114 of which had been deliberately lit.

Western Australia

The Eyre Highway was closed by bushfires burning near Balladonia earlier this month. ( Supplied: DFES )

The Department of Fire and Emergency Service (DFES) said about 2.2 million hectares of land had been burned since the start of November.

The DFES said 449 of the 1,537 bushfires across the state between November 1 and January 14 were considered suspicious or were deliberately lit.

In metropolitan areas, it was higher with 43.6 per cent of the 679 fires being considered suspicious or deliberately lit.

A DFES spokesperson said the percentage of fires categorised as suspicious or deliberate was not an unusual number compared to other years.

The other major causes of ignitions in WA were cigarettes, weather conditions and vehicles, which combined made up about 24 per cent of the ignition causes.

Tasmania, ACT

Tasmania is the only state where arson has allegedly been the overwhelming cause of fires.

Authorities attributed almost two-thirds of the blazes burning on the state's east coast and in the south since late December to arson.

"Approximately 21,000 of the 35,000 hectares burnt is a result of deliberately lit fires," a Tasmanian Fire Service spokesperson said.

Meanwhile, in the ACT, one person has been charged for deliberately lighting a fire, according to the Australian Federal Police (AFP).

The 20-year-old Mawson man allegedly lit several small grass fires, although no property was damaged, and was charged with breaching a total fire ban.

Police are treating as suspicious another grass fire which started on Friday in Canberra's south.