The richest 1% of Australians now own the same wealth as the bottom 60%, according to a new report designed to bolster the case for global and domestic action to shrink the gap between rich and poor.

The Oxfam Australia report also indicated that the nation’s nine richest individuals had a net worth of US$54.8bn, which was more than the combined bottom 20% of the population, or 4.54m people.

The report, released on Monday, follows previous warnings by Oxfam International that the 85 richest people in the world now own the same as half of the world’s population, or 3.5bn people.

“Income inequality in Australia has been on the rise since the mid-1990s, despite all sections of Australian society experiencing some increase in income during the same period,” the report said.

“In 1995, Australia had an average level of inequality compared to other wealthy OECD member countries. Today, we are below average, having become less equal than our peers despite having a better-performing economy than most.”

The report said some economic growth was essential to drive growth and progress, but extreme wealth concentration threatened to exclude hundreds of millions of people around the globe from realising the benefits of their talents and hard work. It could also affect economic growth and poverty reduction.

The chief executive of Oxfam Australia, Helen Szoke, said Australia should use its role as the host of November’s G20 meeting in Brisbane to put inequality on the body’s agenda.

“It’s about what role can Australia play in ensuring that gap doesn’t grow so big that we have major problems globally in the future,” she said.

Szoke said an Oxfam-commissioned poll of 1,016 people across Australia found that 79% of people surveyed felt the gap between the rich and the poor had widened over the past decade “and the majority of those people said that’s made Australia a worse place to live”.

The poll, conducted by Research Now between 28 May and 2 June, showed there was an appetite for Australia to lead the way in global reforms to crack down on tax avoidance, she said.

Oxfam’s report argued tax avoidance by digital brands in developed countries had gained attention but the shifting of profits by multinational companies out of developing and least developed countries was “even more pernicious” and undermined strong global growth.

Transparency was vital in reducing tax avoidance and cracking down on tax havens, the report said.

The treasurer, Joe Hockey, addressed concerns about the issue of inequality when he gave a speech to the Sydney Institute last week denying the budget was unfair.

“The gap between rich and poor has often been used to attack governments when all other avenues have been exhausted,” Hockey said. “But I would argue the comments about inequality in Australia are largely misguided, both from an historical perspective and from the perspective of the budget.”

Hockey said uninterrupted economic growth over two decades had served Australia well, with official data showing average real household disposable income had increased from $540 per week in 1994 to over $820 per week now. He said the growth had been “broadly based across society”.

“And while much focus has been on the ‘rich getting richer’, the more accurate story is the fact that everyone is getting richer as a result of economic development,” Hockey said.

Szoke said: “What is happening globally and the same here is that the gap is widening between the richest and the poorest people. We’re not arguing for equality … our point is not to leave the poorest people behind, whether domestically or globally.”

Former Liberal leader John Hewson last week spoke out against the budget as he launched a separate report pointing to rising income inequality in Australia.

