Greens leader Richard Di Natale is taking a sensible, thoughtful approach to the huge problem of drugs. Credit:Andrew Meares The independent PBO research was commissioned by the Greens, which had opposed both measures, against the support of the government and the opposition. Greens leader Richard Di Natale, who is to address the Australian Council of Social Services annual conference this week, has used the data to launch a stinging attack on the major parties for adding to the problem of growing inequality. The PBO modelled the impact of the two tax changes against a typical household structure where two "owner-occupier" parents were working to support two children aged 10 and 14 but with one parent earning 65 per cent of the household income. The assessment found that where their combined income was $90,000 per year, the two tax measures together resulted in a cash penalty of $1683 over a year, and where that income was $110,000, the penalty was $1,393.

For those couples earning more, however – say $180,000 – the cost penalty disappeared, to be replaced by a small $315 annual benefit. That benefit doubled when the combined household income reached $350,000 a year. Dr Di Natale criticised the government for making inequality worse. "The Turnbull government says it's all about creating 'jobs and growth', but in reality it's determined to shrink the economy, to prevent the market's capacity to create jobs and growth," Dr Di Natale will tell the ACOSS conference. "The Abbott-Turnbull budgets have ripped billions out of the pockets of those who can least afford it, which restricts their ability to consume and to access services at a time when the economy is already flat." The government recently shifted the cut-in point for the penultimate tax bracket from 37¢ paid out of every dollar earned above $80,001, to 37¢ on income earned after $87,001.

A 45¢ rate applies to all income earned above $180,000 a year. Changes to Family Tax Benefit (Part A) were included in the recently agreed "omnibus" savings bill, which included extending a pause in indexation of Part A thresholds; closing off the clean energy supplement (carbon tax compensation) to new FTB recipients; and the introduction of an $80,000 income limit for the FTB (Part A) supplement. Dr Di Natale will argue the PBO result shows that the government "remains trapped in the logic of the 'old consensus', in which budget surpluses matter more than making sure everyone gets a fair go, and markets matter more than the people who sustain them". He will say it shows so-called "trickle down" economics is a fiction. "CEO remuneration, for instance, has grown 90 times faster than the income of average workers since 1978," his speech notes say.

"This inequality affects all of us, not just people on the lowest incomes. People's health, for example, is correlated more closely with the level of equality in a society than it is with total GDP. "This Parliament has passed two pieces of legislation which have had the effect of making the income gap even wider than it was already. They were Turnbull government bills, and the Abbott-Turnbull government has never once demonstrated any concern for the growing inequality in Australia." But the Greens leader said it wasn't just the Coalition that supported the tax changes, with the ALP and One Nation – two parties that claim to represent low-income Australians – also supporting the legislation.