The Greens have launched a campaign to encourage first-time voters to enrol, as the Coalition vows to block legislation in the Senate to keep the electoral roll open for seven days after an election is called.

"It's disappointing to see the Coalition under Tony Abbott using this Howard-style tactic of trying to disenfranchise younger voters," said the Greens Spokesperson for Youth Senator Sarah Hanson-Young, who launched an online video today encouraging first-time voters to enrol.

According to the Auditor-General's report on the 2007 election, there are 1.4 million eligible voters currently not on the roll. The AEC also reports that 70 per cent of voters missing from the roll are aged 18-39.

"A million votes could dramatically change the election outcome - a million votes could determine who holds the balance of power in the Senate, or who wins the key to the Lodge,'' Senator Hanson-Young said. "In some seats there are significant under-enrolments, and in a tight election these missing voters could hold the key to the election.

"The Greens will be doing all we can to raise awareness of this issue. My message to those Australians who face their first election this year is clear - don't waste your first time, get on the roll and make your vote count.''

Senator Hanson-Young's video is available online: http://sarah-hanson-young.greensmps.org.au/content/dont-waste-your-first-time

The Greens have also prepared a kit to help first-time voters.