Former NSW Fire and Rescue commissioner Greg Mullins says Australia must have more resources to fight bushfires after a Boeing 737 air tanker was sent from the effort in NSW to blazes in Western Australia.

Mr Mullins said the current arrangements which outline how resources, including aircraft, are shared interstate were established when the "fire seasons were progressive".

Former NSW Fire and Rescue commissioner Greg Mullins says more needs to be done to ensure states and territories have enough resources as bushfire seasons get longer and more severe. Credit:AAP

"As one state ended its fire season, fires further south started," he said. "Climate change has made the season longer, they now overlap and the fires are more intense and widespread.

"It's one facet that illustrates to people it is getting worse, the old ways might not be enough any more."