Australia could have its first minority government in 70 years.
Around 14 million people will have voted in the country's general election when polls close this morning.
A hung parliament is a worst-case scenario for investors with one financial analyst tipping a 2-5 per cent fall in the Aussie dollar as a result.
Without a clear winner, the next government would have to rely on a handful of independent or Green MPs to form a government, leaving policies such as Labor's new mining tax in limbo and creating market uncertainty.
Two of the three key independents, who may decide who takes office in the event of a hung parliament, have said they cannot guarantee passage of a minority government budget, leaving the possibility of a fiscal crisis or a short-lived government.
Even a razor-thin win by Gillard would diminish her mandate to introduce the 30 percent resource tax, the cornerstone policy of her campaign, and leave her weakened as she seeks to have a hostile Senate pass the tax.
Labor has also pledged to take action on climate change with a possible carbon trading scheme and to construct a $38 billion fibre-optic national broadband network. The Liberal-National opposition opposes these plans.
The vote looks very tight, the result may be based more on which leader, Labor Prime Minister Julia Gillard or the opposition's Conservative Tony Abbott, is favoured most.