Political donations made in the final days of last year's federal election campaign will stay secret for another 12 months, with donors able to exploit a loophole that could shield transactions worth millions of dollars from public scrutiny.
The Australian Electoral Commission will on Wednesday release its annual "financial disclosure returns" - data about all donations, loans and other financial assistance given to the political parties during the 2015-16 financial year.
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The documents are expected to reveal for the first time how much of his own fortune Prime Minister Malcolm Turnbull contributed to the Liberal Party's troubled campaign. Some estimates have put Mr Turnbull's donation at as high as $2 million.
The returns will capture most of the eight week election campaign but there's a loophole: donations given the day before the July 2 poll, on polling day itself or in its immediate aftermath, will not be released until this time next year - 20 months after the vote.
Publisher and donations expert Stephen Mayne said it would have been easy for donors who know their way around the system to exploit the loophole and suggested as many as a third of donations could fall into that category.
"We've never had an election on that cusp before," Mr Mayne said. "Donors really do not like scrutiny so it would have been very easy for them to say 'I will give you a pledge now but the money will come through on July 1'."
"So we'll get a picture tomorrow - but we won't get the full picture until this time next year."
The loophole is another example of the laxity of Australia's political financing system.
Under the latest AEC rules, parties and donors are only required to disclose donations over $13,000 - anything under that is considered "private".
Donors can also split their contributions to escape scrutiny - for example, by giving multiple payments of $12,999 to more than one branch of a party. That means donors can give six-figure donations without it being made public.
Labor and the Greens voluntarily declare any donations above $1000 - but the Liberal Party, Nationals and most of the smaller parties do not.
Donors also make use of so-called "associated entities" - party-aligned fundraising vehicles, think tanks or unions that channel donations to the parties but are not subjected to the same levels of scrutiny in terms of the source of their cash.
Last year almost 40 per cent of the $173 million that flowed to political parties was considered "dark money", meaning the source was not clear. And donors who make late disclosures, and therefore dodge a lot of scrutiny, face little penalty.
Political parties are not required to provide audited financial statements or balance sheets - even to their own members - meaning it's impossible to know how donations are actually spent, Mr Mayne said.
The chairman of Transparency International Australia, Anthony Whealy QC, said the system needed urgent reform.
"We're going through a stage now where democracy is under attack by populism and the only way we can counter that is for the community to have complete confidence in the democratic institutions. Unless we fix the political donations system the community will never have that confidence."
The AEC data will also reveal how much money flowed to the parties from foreign sources. The disclosure is the first since Labor's Sam Dastyari was forced to resign from the frontbench last year amid furore over the influence of Chinese donors on Australian politics.
Opposition Leader Bill Shorten on Tuesday repeated his pledge to clamp down on foreign donations and improve transparency. He also said it was about time Australians were told just how much Mr Turnbull donated.
"You've all asked him. He's always known this day would come. Why wait? Why hide behind a technicality? It's tricky, it's shifty – the Prime Minister owes Australians a lot better than the bare minimum," he told the National Press Club.
Mr Turnbull has previously declined to reveal how much he had donated and said the figure would be disclosed in accordance with the Electoral Act.