A two-month Australian election campaign is expected to officially start on Sunday, with climate change, climbing house prices, company tax rates and union corruption in the national building industry shaping into the key issues.

Prime Minister Malcolm Turnbull, who heads the center-right Liberal Party, has said he will likely tell Governor-General Peter Cosgrove to lock down a July 2 election date this weekend and trigger the unusually long campaign.

He and Bill Shorten, leader of the center-left Labor Party, recently outlined their conflicting economic policies on how Australia should rein in mounting debt without slowing an already sluggish economy.

Neither Turnbull nor Shorten has ever led his party into an election campaign before.