Australia's leaders made last-gasp pitches Friday to woo voters on the eve of elections as polls pointed to a cliffhanger and the media swung behind "reformer" Prime Minister Malcolm Turnbull.

Liberal Turnbull and Labor opposition leader Bill Shorten both campaigned in Sydney on their final day on the hustings as a poll in The Sydney Morning Herald showed them locked in a dead heat on a two-party basis.

But the survey of 1,377 people also said that when all candidates were included, 27 percent planned to vote for the Greens or other minor parties and independents, raising the prospect of a hung parliament where no side commands a majority in the 150-seat lower house.

Turnbull, who has capitalised on the instability sparked by Britain's decision to exit the European Union, said the uncertainty of a hung parliament would be a disaster as he appealed for voters not to go down that road.

"We have seen that film before. It's not a pretty one," he said, referring to the 2010 elections where a similar scenario occurred after Julia Gillard failed to win majority rule.

"Right now, Australia needs strong majority government, a clear national economic plan. That's the economic leadership only the coalition can deliver."

He added that the alternative was "chaos, uncertainty, dysfunction, higher deficits, higher debt, higher taxes, less investment, less jobs".

"That's what Labor and the Greens and independents are offering," he said.

Economic management has been a key election battleground with last week's shock decision by Britain stoking anxiety about pressures facing Australia's economy.

Ex-union chief Shorten has campaigned on improving health and education while pledging more renewable energy and a fairer tax system, and remained upbeat that Labor could cause an upset.

"I am talking to millions of Australians who want to see Labor lunge with every inch of energy towards the finishing line," he said.

"I say to these people, we do not give up and we are confident and we believe there's a good chance we can win the election."

Another poll in Sydney's Daily Telegraph has Turnbull's conservatives 51-49 percent in front on a two-party basis, as the country's major newspapers also rallied behind the ruling party, with News Corp Australia and Fairfax Media mastheads citing the need for stability.

Rupert Murdoch's The Australian said Turnbull offered "a path to national economic success", a stance backed by its tabloid stablemate The Daily Telegraph.

"The prime minister has demonstrated he knows the importance of a firm rein on public spending and offering a leg up for private sector growth," The Australian said in an editorial about the former banker.

"Mr Turnbull may be just the leader to urge the nation back on the path of meaningful reform."

The Fairfax-owned Sydney Morning Herald also endorsed Turnbull on its front-page.

"Given the choice between a coalition led by the socially progressive economic reformer Mr Turnbull, and a Shorten-led Labor party backed by reform-resistant unions, we support the election of a Turnbull government," it said.

One punter is so confident Turnbull will get back in that they staked Aus$250,000 (US$186,000) on it Friday, according to Luxbet, which said it was its biggest ever political bet.

"The good news for this punter is that all the money is coming in for the (Liberal-National) coalition, so they aren't the only one who thinks Malcolm Turnbull is a safe bet," said Luxbet's Shaun Anderson.

Voting is mandatory in Australia and by mid-week some 2.2 million of the 15.6 million enrolled voters had already cast their ballots at pre-polling stations and via postal votes, the electoral commission said.