The Turnbull government’s budget forecasts will blow out by $9.6bn over the next four years, or $44.7bn within a decade, if it fails to clinch parliamentary approval for stalled savings measures, new figures show.

A report by the independent parliamentary budget office (PBO) reveals the cumulative impact of measures that are yet to pass parliament but are already factored into the budget bottom line.

The shortfall is much smaller than a previous estimate in September last year but remains substantial.

Wednesday’s report emboldened the government’s political opponents, who argued it showed the flimsy state of the deficit forecasts and also proved many Tony Abbott-era cuts remained on the agenda.

The figures also illustrate the Coalition’s continuing difficulties in the Senate, as the government considers changes to electoral laws to counter the impact of micro-parties before the next election. The prime minister, Malcolm Turnbull, said last week the government was trying to make “prudent” savings but “one of our challenges is that so many of them are being blocked in the Senate”.

Scott Morrison’s budget update in December predicted an underlying cash deficit of $37.4bn this financial year, adding up to deficits of $108.3bn over the four-year cycle. But the PBO report indicates the deficit figures would be $9.6bn worse over four years if the treasurer’s mid-year economic and fiscal outlook had not assumed the passage of a raft of contentious savings measures.

The PBO’s list of outstanding measures included the Coalition’s higher education overhaul, its family payment cuts, its proposed increase in copayments for the pharmaceutical benefits scheme and the abolition of the Australian Renewable Energy Agency. It also included one Julia Gillard-era measure: the university efficiency dividend that Labor now opposes.

The Greens MP Adam Bandt said the government should devise “a plan B that had a chance of passing the Senate, instead of sticking with unfair measures that will grow the gap between rich and poor”.



“The PBO report released today shows that the treasurer’s pigheadedness will blow out the deficit by almost $45bn,” he said.

“Instead of continuing Tony Abbott’s attacks on the young, the old, the sick and the poor that will increase inequality in this country, Scott Morrison should end the billions of dollars a year spent on unfair tax breaks that benefit the very wealthy.”

Labor issued a series of media releases accusing the government of maintaining “its attacks on renewable energy”, pushing ahead with the “Americanisation of Australian universities” and clinging to “billions of dollars in further health cuts”.

The opposition’s families spokeswoman, Jenny Macklin, said the report also showed the government’s policy to stop so-called “double dipping” in paid parental leave would shave $3.7bn from the system over a decade.

The finance minister, Mathias Cormann, in turn accused Labor of “standing in our way at every turn stopping the necessary fixing of many of the budget problems they left behind” and compounding the problem with new “multibillion-dollar spending promises”



“As a country we are still working to digest Labor’s last spending binge during their last period in office,” Cormann said.

The PBO routinely updates its estimates of unlegislated budget items but this time it included the underlying cash balance – the measure generally cited in public debates about deficit and surplus.

When considered on the same basis as previous PBO reports – fiscal balance – the unlegislated measures now amount to $9.2bn over four years or $36.5bn over the decade to 2025-26.

This reflects a turnaround from the previous such report, published in September 2015, when the fiscal balance shortfall was assessed to be about $18bn over four years or $74bn over a decade.