The Community and Public Sector Union on Wednesday said government departments have been told to cut 10 per cent of staff, the equivalent of up to 6000 jobs.
CPSU federal secretary Karen Batt said the proposed cuts were the biggest hit to the public service since former premier Ted Baillieu slashed 3600 jobs in 2012.
"We've highlighted the wasteful spend on consultants but we want a Labor government to commit to protecting jobs," Ms Batt told AAP.
"We're happy to talk about where other waste or duplication is that should be eliminated. Maybe a marquee or two less at the Formula One Grand Prix this weekend."
Assistant Treasurer Danny Pearson denied the government had decided to cut jobs.
"We've not made any decision in terms of those issues," he said on Wednesday.
"But we've given the commitment that we're going to honour each of our election commitments and we've given a commitment that we will have a operating surplus at the end of forward estimates."
Shadow Treasurer Brad Rowswell said he didn't believe Mr Pearson, adding Victorians would suffer if the jobs were cut.
"Mass job losses mean only one thing - it means cuts to education, it means cuts to essential services," Mr Rowswell told reporters on Wednesday.
"Five thousand people who are currently employed, who because of the government's financial mismanagement will now be unemployed, is a bad thing."
Victorian budget papers show public sector wages will reach $37 billion over this financial year before rising to more than $40 billion in another three years.
The state's net debt is forecast to hit $165.9 billion by mid-2026.
Treasurer Tim Pallas will hand down the state budget in May.
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