Thousands of public servants are expected to walk off the job as part of a 24 hour strike on Friday, as tensions mount between the Turnbull government and the country's public sector.
The Department of Human Services — which covers Medicare, Centrelink and Child Support — has warned of "reduced numbers of staff in service centres and on the phone, and increased wait times".
There have been warnings of possible delays at airports. The all-day strike would involve staff across agencies including Human Services, Medicare, Centrelink, Child Support, the Tax Office, Defence, the Bureau of Meteorology, Agriculture and Water Resources and Prime Minister and Cabinet, the Community & Public Sector Union said.
The CPSU says it has negotiated with the government for more than three years but don't have new enterprise agreements.
"The buck absolutely stops with Prime Minister Malcolm Turnbull and the minister responsible Michaelia Cash, yet they still won't even talk let alone abandon their harsh and counter-productive attack on critical workplace rights and conditions," said CPSU National Secretary Nadine Flood in a statement.
Employment Minister Michaelia Cash has accused the CPSU of "playing games with public services," The Australian reports.
"In the 12 months from October 2015 to 30 September 2016, there are only 29 out of 366 days where the CPSU had not notified that its members would engage in some form of protected industrial action,'' Senator Cash is reported to have said.
"This includes weekends."