The finance minister, Mathias Cormann, has refused to be drawn on how many jobs would be lost by further cuts to the public service, expected to be announced in Tuesday’s federal budget.

News Ltd reports that slashing public sector departments and selling off of public assets will net the federal government more than $4bn.

Eight departments will join the departments of health and education in undertaking a so-called “functional review” to identify areas where jobs can be cut and savings can be found.

Cormann would not put a figure on how many jobs would go as a result of the reviews, saying only that their purpose was to make the public sector more efficient.

“This is part of our rolling smaller government reform agenda,” he told ABC Radio on Monday. “We’ve been focused ever since we came into government on making sure that the public service is as efficient, as effective and as well-targeted as possible.”

“We’ve been focused on getting rid of any waste and duplication and getting government out of those areas where government’s shouldn’t be involved.”

Around 16,500 full-time jobs have already been shed from the public service since the Coalition took office in 2013, with around 11,000 losses since last year’s federal budget.

“Demand for services continues to rise as the population continues to grow and more Australians turn to the government for first-class services. It just doesn’t add up,” head of the Community and Public Sector Union (CPSU), Nadine Flood, told a conference in Melbourne last week. “The sooner this government realises that the public service is running on empty the better. Cuts of this order are unsustainable.

“This government likes to pretend it can solve its budgetary woes by cutting the public service. The cost of the public service is just 6% of the commonwealth’s budget. If it wants to get back to surplus then it needs to look at the other 94% of government outlays and at ways to raise more revenue,” Flood said.

“You cut the public service and you end up cutting services for the public. It’s as simple as that.”

About 15 commonwealth agencies are engaging in industrial action, or about to embark on it, after the breakdown of wage negotiations with employment minister Eric Abetz.

Union members at the Bureau of Meteorology are the latest to vote for industrial action.

“I believe a majority of public servants would prefer a responsible wage rise with job security, rather than engage in the CPSU’s outlandish pay claims and industrial actions,” Abetz said earlier this month. “They appreciate that the government inherited an enormous debt and deficit burden from Labor and that wage growth must be responsible in this climate.”

The government is also expected to gain a windfall from merging some commonwealth entities and abolishing others.

Privatising the Australian Rail Track Corporation and the Intra Government Communications Network, and selling off assets near Parliament House in Canberra will also result in budget savings for the government.

Slated for sell-off are the east and west blocks near old Parliament House. The buildings were constructed in the 1920s as supplementary office space for ministers and officials working in the original Parliament House. The east block now houses the National Archives of Australia.

The government will conduct a scoping study to access the possibility of privatising the registration system of the Australian Securities and Investments Commission, but the sale of the Treasury building in Canberra has reportedly been shelved.