A week after the United Firefighters Union's state leaders called for a royal commission, its national body has written to the prime minister, saying there's already been scores of bushfire-related inquiries over the past two decades.

Instead of a royal commission the prime minister should set up a Council of Australian Governments audit of all of the existing recommendations that haven't been implemented, UFU Australia believes.

UFUA's national secretary Peter Marshall said previous inquiries had already considered issues such as the deployment of defence personnel, the role of the commonwealth, climate change and prescribed burning.

Victoria and NSW are conducting their own inquiries into the fires, making a federal probe unworkable, Mr Marshall believes.

"Especially if there is a contradiction between a recommendation out of a federal royal commission to a state based inquiry or coronial inquest," he told reporters in Melbourne.

"It is not the magic bullet to address these issues."

But the union's representatives in NSW, Queensland, Western Australia and South Australia last week called for a royal commission.

UFU Queensland state secretary John Oliver said there needed to be a proper examination of the fire season.

"We need to have confidence in a body that could be set up to do such work - only a royal commission will give us that," Mr Oliver said at the time.

He called for a royal commission "or more lives will be lost".

Mr Marshall says he's not sure why the state branches backed a royal commission.

"As well-meaning as that call might have been, it was ill-conceived and not well thought out," he said on Wednesday.

Mr Marshall says a federal probe wouldn't have the powers to compel the state-based agencies.

"It would be ill-conceived to think that if there are problems in NSW between the fire service and the government up there, that a federal government royal commission will be able to rectify that, it won't."

Mr Morrison is preparing to take a proposal for a bushfire royal commission to cabinet.

He wants it to consider when the federal government should step in to help with state issues, as well as agency responses, future resilience to bushfires, and what a national state of emergency would entail.

The state response to Mr Morrison's idea has been lukewarm, with Victoria's Labor premier Daniel Andrews questioning what a federal inquiry would achieve.

But federal Labor leader Anthony Albanese has said the party is not opposed to a royal commission.

Australian Associated Press