Nearly half of 18-year-olds and one-third of 19-year-olds are not enrolled to vote as the nation prepares for a federal election that could be called within weeks, the Australian newspaper wrote this week.

The Australian Electoral Commission will today launch a web-based campaign to sign up more than 1.4 million Australians who are eligible to vote but who are not on the rolls.

AEC spokesman Phil Diak said 18 to 39-year-olds made up about 70 per cent of the "missing" 1.4 million voters. Queensland has proportionally the highest number of voters who are not enrolled, at 390,000.

NSW had the highest estimated number of missing voters at 440,000, followed by Queensland, Victoria (390,000) and Western Australia (160,000).

Independent research found that many people were unaware there was an election due this year.

Many unenrolled voters were people who had moved address and not re-enrolled. But others were turned off by negative campaigning or the view that politicians were all the same.

The web-based campaign is part of a move to reach out to more young people. Mr Diak said a traditional mail-out campaign would also be used, with targeted letters to be sent to 3 million Australians by June 30.

But the response rate for mail-out campaigns could be as low as 20 per cent and the AEC was being forced to look to other means to drive up enrolments.

The AEC has sent out 70,000 SMS messages to voters it believed were not enrolled to encourage them to sign up.