THE state's most influential union boss wants radical reform that would bar unions and big business from bankrolling political campaigns, in a bid to stop political donations influencing election outcomes.

Shop Distributive and Allied Employees' Association secretary Peter Malinauskas told The Advertiser that donations to political parties should be "severely restricted" as part of dramatic electoral funding reforms. to avoid a "political arms race" before elections.

"Put bluntly, this means if Labor wants to restrict corporate and business donations, it must also accept the restriction on union donations, including union affiliation fees, and vice-versa with the Liberal Party," Mr Malinauskas writes in a column for The Advertiser.

"In my view, the best way to do this is to severely restrict private donations, or ban them altogether, and replace this with a model based around public funding."

The best way to do this is to severely restrict private donations, or ban them altogether.

The SDA is among the South Australian Labor Party's biggest financial backers and Mr Malinauskas' suggestion is bound to outrage some in a party that relies heavily on union funds to finance its campaigns.

The man who told Mike Rann he would be replaced as Premier by Jay Weatherill intends to take his reform agenda to Labor's state convention in October.

He says a discussion on electoral funding is needed and any reform should be bipartisan. He suggested a model that placed caps on both the size of donations and how much could be spent on campaigns in order to "address the supply and the demand", but did not specify the size of the caps.

"If we are to have electoral funding reform, it is important that whoever is the government of the day is doing it in a manner that will enjoy bipartisan support," Mr Malinauskas said.

"For that to occur, I think the Labor movement has to acknowledge that union donations have to be part of that discussion.

"As a union leader who does believe in electoral reform with bipartisan support, I am happy to start that discussion."

NSW, Victoria, Queensland, WA and the ACT all provide public funding for elections and have varying restrictions on donations.

In South Australia, the major parties rely heavily on donations. The SDA contributed more than $180,000 to the ALP during the 2010/11 financial year, while fellow union United Voice donated almost $190,000.

Undeclared donors contributed more than $205,000 via Labor's fundraising arm SA Progressive Business, run by former Senator Nick Bolkus. Benefactors to the Liberals during that period included Santos, which donated $150,000 and Beach Petroleum, which contributed $100,000.

Donations increase considerably before election campaigns.

The Labor and Liberal Parties do not have electoral funding policies.

The SA Greens believe elections should be publicly funded, with business and union donations banned and individual donations capped.

Mr Malinauskas says that any time a political party enters a campaign with a financial disadvantage, it left open the prospect of political debate being "skewed in favour of the party with the most cash rather than the party with the best policies".

"This in turn results in a political arms race for financial resources, which necessitates candidates spending considerable time fundraising rather than campaigning on the ground, talking to the people that matter most - everyday voters," he writes.

Mr Malinauskas said the state must avoid reforms that tipped the scale in favour of a particular party.

The Liberal NSW Government recently introduced rules allowing only individuals on the electoral roll to make donations, while Queensland is also introducing legislation to restrict union contributions.

Mr Malinauskas said his opinion was not based on saving the SDA money.