Arsonists could face life imprisonment under proposed new laws in Western Australia.

The Liberal-National government said the legislation, to be introduced on Tuesday, would ensure arson was treated as one of the most serious criminal offences in the state.

The legislation would increase the maximum jail term from 14 years to 20 years for lighting a fire where it is likely damage would be done to people or property.

Where the offender wilfully destroys or damages property by fire the maximum penalty will increase from 14 years to life imprisonment.

WA Attorney-General Christian Porter said Victoria's Black Saturday bushfires showed the widespread devastation that arsonists could cause.

"The state government has worked hard to develop laws that target and appropriately penalise all possible arson-related offences," Mr Porter said.

"Our legislation will significantly increase penalties and ensure the laws of this state recognise the inherent danger arsonists cause."

WA Police Minister Rob Johnson said that under the new legislation, vegetation would be clearly defined as property.

"This means that if a person wilfully lights a fire that damages any sort of property or bushland, they will be sentenced under the new laws," Mr Johnson said.

"The new legislation will also create an entirely new offence which makes it clear that if a person does not take reasonable care when in control of a fire or ignition source and someone is injured or killed as a result, the offender will be held to account."

The Liberal-National government is aiming to have the legislation passed before summer, Mr Johnson said.