The Greens leader has revealed that a ban on corporate donations and a federal anti-corruption body would be key demands in a hung parliament.

Richard Di Natale outlined the demands on Radio National on Thursday, ahead of his National Press Club address.

Di Natale said corporate donations had a “corrosive influence” on politics, helping lobbyists buy access and scuttle reforms.

He cited fossil-fuel industry contributions to Labor, Liberal and the Nationals as a reason for lack of action on climate change, and gambling and alcohol industry campaigns and donations for sinking gambling reform.

The Greens policy is to ban donations from for-profit corporations, which faces a constitutional hurdle after the high court struck down laws that did so in New South Wales in 2013.

The Greens want to cap donations from individuals and not-for-profit organisations, which means unions could continue to contribute to Labor and the Greens.

Their policy would also require “continuous, comprehensive public disclosure of political donations and funding on a public website”.

Di Natale said the system should be backed up by a federal anti-corruption watchdog, because cases such as Parakeelia giving $1m to the Liberal party showed there were “significant questions” around the claim the federal system is free of corruption.

“If we’re in a position, if it’s a close election, and we can bring some of these issues to the negotiating table, this will be front and centre: ending corporate donations, publicly funded elections, and establishment of a national anti-corruption watchdog,” he said.

However, both Labor and the Coalition have ruled out forming government with the Greens if there is a hung parliament.

Di Natale has said that despite the prime minister, Malcolm Turnbull, and the Labor leader, Bill Shorten, ruling it out, “wiser heads will prevail” in the event of a hung parliament, although it would be “inconceivable” the Greens would help the Coalition form government.

On Thursday he said “there is a prospect of a power-sharing government ... it’s a possibility”, although he rated the odds of a hung parliament at 50/50 or less.

Radio National host Fran Kelly challenged the Greens on why they accepted corporate and union donations.

Di Natale said they have an “ethical screen” over all corporate donations, with a standing committee scrutinising donations to ensure they are consistent with Greens values.

Although the Greens have received hundreds of thousands of dollars from the construction and electrical unions in the past, Di Natale said he suspected the party had received very little from unions in this campaign.

“We play by the rules,” he said. “In fact, we go over and above the rules.”

Di Natale said the Greens do not accept money from developers and the mining, gambling and alcohol industries.

He said if they didn’t accept any corporate donations it would “not be able to compete” and get elected to parliament.

“The fact we have one set of rules doesn’t mean we shouldn’t change them,” he said. “You play by the rules, but that doesn’t mean the rules don’t stink – they do.”