It costs taxpayers almost nothing extra when federal civil servants call in sick, according to a report, as a battle looms between the Treasury Board and public-sector unions over salaries and benefits.

The report from the Parliamentary Budget Office (PBO) released Wednesday shows wide variances in how much sick leave is taken from one department to another.

Jean-Denis Fréchette, Canada's parliamentary budget officer, says in a report published Wednesday that most federal departments don't backfill employees on paid sick leave. (HO, PBO/Canadian Press) But parliamentary budget officer Jean-Denis Fréchette​ says most departments don't have policies to backfill for sick leave. Fréchette​backfill

That means most sick employees are not replaced, resulting in no incremental cost to departments.

The governing Conservatives have been looking to cut the cost of public-service salaries, pensions and sick leave as part of efforts to balance the federal budget by next year.

President of the Treasury Board Tony Clement said in a statement Wednesday what the new report "does not address is the loss of productivity and employee morale" caused by the lack of backfill for sick leave.

"My managers have told me this leads to teammates picking up extra workloads, or work not being completed in a timely manner," he said.

Clement reiterated the government's commitment to replace the "current outdated system of sick leave."

But the Professional Institute of the Public Service of Canada said in a statement that the new report reveals that "the overwhelming majority of federal employees must often make up for work when they return — at no additional cost to the government and taxpayers."

PIPSC Vice President Shannon Bittman argued that the government's plan to replace the short term disability plan with a "for-profit system" will in the end "cost both employees and the public more than the existing one."

Cost of paid sick leave "not fiscally material"

The new report was requested by NDP MP Paul Dewar after the PBO estimated this February that the fiscal impact of paid sick leave in the federal public service was $871 million in 2011-12.

The report instead found there is "a notable variance among organizations in the use of sick leave," and that the cost of paid sick leave "was not fiscally material and did not represent material costs for departments in the CPA."

But the report also notes that data from some departments were incomplete, and sometimes unavailable.

The Canada Border Services Agency, for example — which was expected to have high sick leave costs because officers need to be backfilled for operational, health and safety reasons — said it does not track data on backfill costs due to sick leave.

The five federal departments that logged the most paid sick days in 2011-12 are:

Correctional Service of Canada: 14.6. Human Resources and Skills Development Canada: 13.8. Canada Border Services Agency: 13.5. Veterans Affairs Canada: 13.3. Public Works and Government Services Canada: 11.8.

The five federal departments that logged the least paid sick days in 2011-12 are: