Richard Di Natale has criticised the union movement for “robocalling constituents” and said unions were strongest when they were independent of “one side of politics or another”.

The comments were made at the end of a speech at the Australian Council of Social Services conference in Melbourne on Tuesday. Asked how he saw the union movement surviving in the future, the Greens leader said unions functioned best when they were “independent.”

“It’s not for me to outline a future for the union movement except to say I think the union movement is strongest when it’s independent, making decisions that are in the interests of people and not in the interests of one side of politics or the other,” Di Natale said.

“Some people will argue against that but I have always believed that the union movement is strongest when it is organising, collectively, to advance the interests of workers, and I don’t think that dedicating resources to robocalling constituents actually does much to advance that.”

The 2017 Acoss conference is themed around a vision of Australia in 2030, which Di Natale said would see a country that had begun to dismantle its current political system in order to better address the challenges posed by growing inequality and climate change.

“We’re not going to be able to tackle climate change, tackle inequality, unless we start to dismantle the model that we have right now, neoliberal capitalism, and to really confront the assumptions that are built into it,” he said.

Di Natale said the assumption that environmental concerns must always come at a personal cost to people should be debunked, particularly around renewable power generation.

“They’re heading in the same direction,” he said. “People are putting solar panels on their roofs, not because they want to help the environment – although that is often a fringe benefit – but ... because it brings the power prices down.”

He also addresed the need for greater diversity in parliament, saying he was proud disability advocate Jordon Steele-John was set to replace the WA senator Scott Ludlam in parliament, after Ludlam quit during the dual citizenship saga that also claimed Queensland senator Larissa Waters.

“We lost Scott and Larissa earlier this year but we’re going to see such an impressive young man, a young man living with cerebral palsy, who’s going to come into parliament to replace Scott soon,” he said. “And I tell you what, I can’t wait until I hear the sound of those saws and hammers in the Senate chamber because they have to install disability ramps.”

The Acoss conference will run for two days and issued speaking invitations to all three major political parties. The opposition leader, Bill Shorten, will address the conference on Wednesday.

Earlier on Tuesday, the economist Saul Eslake warned of a looming crisis in retiree incomes as a greater proportion of people enter retirement either with a mortgage or living in rented accommodation.

“It’s a longstanding assumption of Australia’s retirement income system that the vast majority of retirees will have close to zero housing costs, either because they own their own homes outright, as historically more than 80% of retirees have done, or if they don’t then they will be accommodated in social or community housing where rents are fixed as a proportion of their relatively low income,” Eslake said.

“That assumption has in turn allowed Australia to spend less on aged pensions than other countries with similar standards of living.”

Eslake said the next 15 years would see a continued decline in home ownership, combined with a projected increase in the number of people who still owe money on their mortgage.

“It will be rational for them to use what superannuation they have to pay off their mortgage, thus defeating the whole point of the tax-supported superannuation system.”

Eslake said tax reforms that make the property market less attractive to investors, such as removing negative gearing and winding back the capital gains discount, would allow more first home owners into the market and reduce pressure on rental accommodation.

He also advocated for removing the principal residence exemption from the pension assets test to encourage “more sensible use of land and discouraging overconsumption of owner-occupied housing by people in the final years of their life”.

Eslake said intergenerational inequality was one of the biggest issues facing Australia and was driven in large part by declining home ownership among people under the age of 55.

According to the 2016 census, rates of home ownership have declined to 65.5%, lower than any time since the census began in 1954. Since 1991, the rate of home ownership among households of people aged 25-34 has fallen 11 percentage points, while home ownership among households aged 35-44 has fallen 10 percentage points and home ownership among households of people aged 45-54 has fallen 9 percentage points.