The federal public service has been paying rent for almost 18,000 empty desks in Canberra alone and a total of 34,000 vacant workspaces in offices  across Australia.

The federal government's large-scale problem of paying for phantom office space is revealed in a Finance Department list that has been given to Parliament's public works committee this week.

The list shows Canberra has a 22 per cent vacancy rate in its Commonwealth-leased buildings which means 17,536 desks are sitting empty in the nation's capital.

The public service has been renting office space for 4948 empty desks in NSW, 3552 in Victoria, 3157 in Queensland, 1970 in West Australia, 1431 in South Australia, 599 in Tasmania and 448 unmanned work stations in the Northern Territory.

The cost to rent enough space for one desk has been conservatively estimated at $5000 a year by Fairfax Media, but it could well be more meaning the cost to taxpayers was at least $170 million a year.

The most vacant work points in Canberra were 745 at ABS House in Belconnen, another 703 at 50 Marcus Clarke Street, a building leased by the Department of Education and Training, followed by 641 at 21 Genge Street in Civic, leased by the Australian Taxation Office.

There were 606 at Campbell Park in space leased by the Defence Department and another 521 empty desks at the Sirius Building leased by the Health Department in Woden.

All of these leases had a higher vacancy rate than the national average.

Numerous leases held by the Department of Immigration and Border Protection, which was in the process of consolidating its 5500 ACT staff into one place, had a total of about 1200 empty desks in Canberra.

The list detailing vacancy rates for 195 leases held by the federal government in the ACT handed to the committee this week was dated September last year.

Some inroads may have been made to change the empty space held in some of the buildings since the list was compiled.

Austender records show the Department of Education and Training has just spent $40,000 to relocate staff to 50 Marcus Clarke Street.

A spokesperson for Finance Minister Mathias Cormann said the list would help the committee scrutinise proposals from government departments and agencies wanting to sign new leases.

"This is inherited inefficiency," the spokesperson said.

"The former government signed up to many of these leases, while the vacant desks are mainly the result of job reductions which the former government set in train.

"Under Labor individual agencies were responsible for managing their own vacant leases."

Senator Cormann has launched Operation Tetris to move agencies into vacant leases instead of signing up to any new leases.

Leases will now be considered at a whole-of-government level.

Tetris will start in the ACT by reducing about 30,000 square metres of office space by moving agencies between premises and saving an estimated $200 million in a decade.

"This will be on top of $84 million of savings already achieved over 17 years from co-locating the Department of Veterans Affairs with the ATO," the spokesperson said.