About 110 Department of Education staff will be made redundant in the coming months.
Department staff were told the news on Monday and also were advised a job swap program would be offered.
Job cuts had been outlined in the May budget.
The voluntary redundancy program will gauge the number of job cuts that cannot be achieved through natural attrition.
A department spokesman said: "The Department of Education needs to reduce costs to meet reductions to the departmental budget for 2015-16 associated with programmes which are ending and other measures."
Community and Public Sector Union deputy secretary Beth Vincent-Pietsch said department staff were already facing significant increases in workloads.
"Like much of the public service, ever since the recruitment freeze was put in place a year ago Education has been under increasing workload pressures and a cut of this size is only going to make matters worse," she said.
"The CPSU has questioned how the department is going to manage workloads and the delivery of services.
"Unfortunately, this is what we have come to expect under the Abbott government – more cuts.
"We have already seen at least 8000 jobs go this year [across the public service], the deepest cuts to the public service in over a decade, and the government is forecasting thousands more are on the line.
"This is life for the public sector under [Prime Minister Tony] Abbott."
The department is responsible for national policies and programs that help Australians access quality and affordable child care, early childhood education, school education, higher education, international education and academic research.