The WA Electoral Commission (WAEC) has renewed calls for voting reform, warning participation in Australian democracy is "under siege".

Electoral Commissioner David Kerslake used the WAEC's annual report to argue the need for direct enrolment to bring WA into line with the federal system.

It would mean West Australians are automatically added to the state electoral roll when they turn 18, rather than having to submit a form.

Change of address details would also be updated based on information provided to other government agencies.

The report warned of a "widening divergence" between the state and federal systems, with figures showing the number of West Australians enrolled to vote at federal elections, but not state ones, grew from 25,7000 in June 2013 to 114,796 in March 2015.

There are fears the number could grow to more than 200,000 by the time of the next state election in March 2017.

The report also raised concerns that the proportion of people voting was declining across the country.

"In the lead-up to the 2013 elections, almost 1.5 million Australians were not enrolled despite being eligible, 170,000 in Western Australia alone," it said.

"These missing electors were not just 18-year-olds intending to enrol and yet to get around to it, or electors whose enrolment had lapsed through failure to keep their address details up to date.

"Of particular concern, a high proportion were citizens aged between 30 and 50 who had never been enrolled, indicative of a conscious decision to opt out of the electoral system altogether.

"This should sound alarm bells, the historical high level of participation in Australian democracy is under siege."

Electoral Affairs Minister Peter Collier has previously expressed support for direct enrolment, saying he hoped it would be introduced before the next election.

"There shouldn't be a disconnect between the federal and the state enrolment system, so I'm looking at the moment at rectifying that," he said in August.