Canada's budget watchdog says the federal government lost at least $439 million so far this year in productivity through a policy that allows civil servants to stay home, with pay, during emergencies such as the COVID-19 pandemic.

The Parliamentary Budget Office says most of that total was a result of employees at the Canada Revenue Agency staying home, unable to work, between March 15 and May 31.

That one department accounted for just over $311 million in paid leave, far ahead of the second-costliest department, Correctional Services Canada, at more than $33.8 million.

The PBO report was compiled at the request of Edmonton Conservative MP Kelly McCauley, who wanted to know the financial impact of the policy, known as pay code 699.

The policy allows federal employees paid leave for emergencies such as being sick with COVID-19, having to quarantine, not being able to access the technology they need to complete their work and having to care for dependants.

It does not require employee to first use up other forms of paid leave, such as vacation, family emergencies or accumulated sick leave.

The PBO said 699 costs could be closer to $623 million, government wide, because the Treasury Board Secretariat, which is responsible for the civil service, only provided information from 62 of the 88 federal public service organizations, representing about 70 per cent of government departments.