CANBERRA - Australia's opposition leader Peter Dutton has been declared the winner of the third debate against incumbent Prime Minister Anthony Albanese ahead of the May 3 general elections.

Following a debate on Tuesday night that was dominated by cost-of-living and housing issues, the expert panel of host broadcaster the Nine Network deemed Dutton the winner 2-1, although all three hosts noted that it was a close contest.

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It marked Dutton's first debate victory over Albanese. The incumbent prime minister was declared the winner of the first contest and no victor was officially named in the second. Dutton's first debate victory provided a boost for the opposition leader, with opinion polls widely suggesting his Coalition is facing election defeat.

Albanese and Dutton will go head-to-head in a fourth and final leaders' debate on Sunday night.

The third debate coincided with the opening of early voting in the elections at over 500 centers across Australia at 8:30 am local time on Tuesday.

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Approximately half of Australia's 18 million registered voters are expected to cast their mandatory ballots before election day either in person at early voting centers or by post.

According to the Australian Electoral Commission, 230,000 people had voted as of midday on Tuesday, a figure it said was a "bit more than normal".

When voting in federal elections, Australians cast two ballots, one for the lower house of parliament and one for the upper house.

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The government is formed in the lower house. If neither Labor nor the Coalition win a clear majority of the 150 seats, they will enter negotiations with minor parties and independent elected members for their support to form a minority government.