Informal votes at last year's federal election reached their highest rate in three decades, the latest Australian Electoral Commission (AEC) data reveals.
Last September's total rate of informal votes - 5.91 per cent for the House of Representatives - was the largest in Australia since 1984.
That coincides with what the Museum of Australian Democracy, Old Parliament House (MOADOPH) said is growing opposition to compulsory voting among younger Australians, after a survey of Australian voters this year.
People from older generations had less negative views about compulsory voting, MOADOPH said.
The AEC data said Australia's informal votes grew 0.31 per cent between the last two elections.
The AEC's final report on informal voting in the September election has not been released.
Australia’s rate of informal voting is in deep contrast to New Zealand’s and Ireland’s, where voting is not compulsory.
Those countries had invalid voting rates of one per cent or less at their latest parliamentary elections.
Brazil and Argentina have compulsory voting and the latest data from their parliamentary elections returned informal voting rates of 8.64 and 4.45 per cent respectively.
The AEC's latest Analysis of Informal Voting, House of Representatives, 2010 Federal Election report says no one factor was the cause of informal voting at the 2010 election.
Language barriers, numbers of candidates on ballot papers and misunderstandings of differences between state and federal elections contributed to Australia's largest rate of informal voting in just shy of three decades.
"However, there are likely to be many other factors (such as public commentary in the lead up to an election) that might also influence levels or patterns of informality," the 2010 report said.
While knowing voters' intentions was impossible, the proportion of assumed intentional informal votes nearly passed the assumed unintentional informal votes in 2010, the AEC report said.
Blank ballots and those with scribbles, slogans or other protest vote marks were assumed to be intentionally informal.
The recent MOADOPH survey of 826 Australians, spanning four generations, found 30 per cent of survey participants had negative views of compulsory voting.
Daryl Karp, MOADOPH Director, said there had never been a more important time to have this discussion about democracy.
Bold lines are years when elections coincided. Dotted lines represent one country only. Data from various governments, aggregated by IDEA.