The Labor and Liberal leaders engaged in a media blitz, hoping to sway undecided voters in an election that's likely to be a photo finish.
Polls indicated the results could come down to the wire, with some analysts warning we might have a hung parliament for the first time in decades.
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The Prime Minister was criticised for negative messages in the last 24 hours of campaigning, by warning against an Abbott-run government, and raising the spectre of Work Choices.
"There is a real risk that Mr Abbott will be the prime minister of Australia on Sunday," she told reporters on Friday morning.
"And that's a real risk for the future of Australian families. It certainly means that there is a real risk that Work Choices will be back."
Mr Abbott ended a marathon 36 straight hours of campaigning by reiterating that a vote for Labor would be a vote for a bigger national deficit.
The issue of asylum seekers dogged the Opposition Leader, as Mr Abbott backtracked on a promise to stop the boats coming to Australia within three months of winning office.
"If we can get the number of boats down from three a week to three a year ... I will regard myself as having very substantially succeeded," he told reporters in Sydney.
Speculation is mounting that the Greens will win their first ever House of Representatives seat, in Melbourne.
"Everywhere people, are saying `go Greens, good on you Bob, I'm going to vote Green,'" Greens leader Bob Brown says.
"I have never had a feedback like that for the Greens in all my years in politics."
Mr Brown says the party is well-equipped to negotiate in a hung parliament.
"If there were to be a balance of power in the lower house, then we would use all our experience - and it's greater than the other parties - to ensure that Australians get the best possible outcome," Senator Brown told reporters in Hobart on Friday.
Also responding to questions on a hung parliament, former Nationals MP turned Independent, Bob Katter, says the Coalition should not automatically count on his backing.
He says, if he holds sway in a hung parliament, he would support which ever party offers the best deal for rural communities.
