With wage talks in stalemate across the 160,000-strong Commonwealth bureaucracy, departmental bosses have been given a little more flexibility to try to break the impasse and can now put their workplaces' soaring sickie rates on the table.

With "unscheduled absence" in the Australian Public Service estimated to be costing more than half a billion dollars annually, sickies have been in the sights of the Coalition since before it won government in September 2013.

Strike action is now under way or planned at 15 departments and agencies after their bosses have failed to put together pay offers tough enough for public service minister Eric Abetz and acceptable to their workforces.

The Commonwealth's workplace authority, The Public Service Commission, insists the tough bargaining framework has not changed, but confirmed that departmental chiefs in Canberra have been granted some wriggle room in negotiations.

The commission says departments now have some extra flexibility around the bitterly resented demands for "productivity offsets", allowing greater scope to find savings to pay for wage rises.

These might include management and workers striking deals to tackle the public service's "unscheduled absence" problem; the high level of sick, personal and carers' leave taken by Commonwealth bureaucrats.

The rate of unscheduled absences, across all federal public service agencies, rose last financial year by 0.4 days to a median of 12 days a year per employee.

In some departments, the figure was higher, with staff in the giant Human Services Department, where ill-feeling over the wage dispute is running high, taking 16.3 days unscheduled leave in 2013-14, including 12 sick days.

Former public service commissioner Stephen Sedgwick described the problem as "seemingly intractable" in one of his last acts before retiring in late 2014, and one of Senator Abetz's first forays into APS workplace policy was to call for action on sickies.

A commission spokeswoman confirmed that the shackles had been loosened for senior mandarins looking for savings to fund wage increases and said that sickies could be on the table.

"Agencies are now able to take into account productivity improvements based on a wider range of measures," she said.

"These would include, for example, removing restrictive working arrangements from agreements which, once implemented, would lead to cost savings, or initiatives to reduce unscheduled absences."

But the commission spokeswoman insisted that the tough bargaining framework was here to stay.

"The bargaining policy parameters have not changed," she said.

"Agencies must be in a position to pay for wage increases provided under new enterprise agreements.

"They must also be able to demonstrate genuine productivity gains to offset any proposed wage increases."

The main public sector union, the CPSU, voted on Friday to step up its industrial action in Commonwealth workplaces, and promised the "fight of our lives" against the wage offers and cuts to conditions and entitlements made under the bargaining framework.

Senator Abetz was unmoved, saying the union was overestimating the level of support among public servants for strike action.