Corporate donations are “state-sanctioned bribery”, Richard Di Natale has said in a speech calling for reforms to rid democracy of their “corrupting influence”.

Di Natale made the comments to the National Press Club on Wednesday as well as calling for a range of progressive, state-led initiatives including a “people’s bank”, a four-day working week and consideration of a universal basic income.

The Greens leader said the biggest problem in Australia was not the budget deficit but the “democratic deficit”.

Calling for an end to “big money politics”, Di Natale said corporations weren’t philanthropic entities but rather donated because they “expect a return on their investment”.

“Let’s just call them what they are: state-sanctioned bribery.”

Di Natale derided the Coalition and Labor as the “Coles and Woolworths of politics” and said that, regardless of who won the next election, “we are going to see the big donors knocking on their doors … wanting to collect the rent”.

Di Natale called for several measures including a federal anti-corruption watchdog, fixed parliamentary terms and trials of “deliberative democracy that puts everyday people at the heart of government decision-making”.

Asked if he was suggesting politicians were corrupt, Di Natale replied that, without an anti-corruption watchdog, “we don’t know the extent of corruption at a federal level”.

“I make no apologies for saying that big corporate political donations are a very corrosive influence on our democracy,” he said, citing lobbying by the hotels and gambling industry against poker machine reform after he entered parliament.

Asked if he would ban union donations, Di Natale said it had long been Greens policy to cap – but implicitly not to ban – donations from individuals and unions, a point that the leader stumbled on in September leading to a correction by the Greens’ democracy spokeswoman, Lee Rhiannon.

In an effort to underscore the need for broad political participation, Di Natale invited a young Islamic woman, Nada Kalam, to take the stage and she delivered a short presentation about her experience of racism and concerns about the future including global warming.

Di Natale called for a “people’s bank” to improve competition and provide “real help” for first home buyers and people in regional areas.

“Imagine a bank that pursues social objectives like housing affordability, not just profit-driven ones. Which bank? A people’s bank.”

Di Natale said there was a role for government intervention where market failure existed, including in banking and the energy sector.

He argued that the Western Australian state election, in which Labor, One Nation and the Greens campaigned against asset privatisation, showed people are “sick and tired off flogging off any public asset that isn’t nailed down”.

“Governments have been punished for [the privatisation] agenda ... So we don’t make any apologies for standing with the great majority of Australians who recognise that having a state-owned enterprise might actually deliver things for them, not just for shareholders.”

After Di Natale said the Greens would introduce a policy to phase out stamp duty, he was asked whether that would be paid for by broader land taxes or increased council rates.

Di Natale replied that phasing out land tax would need to be “revenue neutral and can’t disadvantage people who bought under the existing circumstances”. He said the suggested alternative taxes were “a pathway forward” but did not reveal whether they would be the Greens policy.

Di Natale defended his suggestion of a four-day working week and consideration of a universal basic income but refused to give further detail about whether employers or the government would pay for such new entitlements.

The Greens leader said that, given 16% of Australians are underemployed, but about one in four wanted to work less, there was a problem with the distribution of work hours.

“We have an issue when people can’t achieve work/life balance and we need legislation to force employers to offer it to them,” he said, before adding that some employers offered shorter work weeks already.

Asked how the Greens could achieve political outcomes, Di Natale said it didn’t oppose things in the national interest for partisan advantage and had passed legislation with the government including the backpacker tax, Senate voting reform and multinational tax avoidance.

Di Natale took aim at the media, describing it as part of the establishment that was mistrusted by the public and against which Donald Trump had rallied to win popularity.

After a sharp question from the Australian about why the Greens primary vote was behind One Nation and controversy around payment of his au pair, Di Natale joked that News Corp was “the love media”.

“When we have got the Australian telling our story for us, it is a challenge … particularly when it is inaccurate,” he said, labelling Fairfax’s story about his au pair as “rubbish”.

He cited a Press Council ruling that found there was “no reasonable basis” to imply his au pair may have worked up to 40 hours a week.

Di Natale said the Greens found that, when they had “unmediated conversations” with voters, they liked their policies, which made him “confident” the party could achieve his goal of a 20% primary vote within a decade.