The Immigration Department is under fire over plans to spend a quarter-of-a-billion dollars to move public servants to a new office nine kilometres away.
The fit-out and relocation is one of the most expensive in public service history.
The new four building precinct would have "a unified watch floor, situation rooms, briefing rooms, incident rooms, operations planning rooms and intelligence support rooms".
The $255 million move 10 minutes' drive across town to the Canberra Airport was approved by Finance Minister Mathias Cormann in May last year.
But the spend has drawn criticism from Labor Senator Kim Carr who is concerned the costs are an unnecessary burden on the taxpayer.
Senator Carr asked whether taxpayer money would have been saved by purchasing the buildings, rather than renting them.
Department officials said they had not assessed whether buying the building would have been cheaper.
"It strikes me as extraordinary that if you are spending that amount of money, [you don't know] how much savings there would be if you owned the building and didn't pay the rent," Senator Carr said.
"If you are going to be in the building for nearly 30 years and it's going to cost you nearly $3 billion, how much would it cost to build a building and not pay the rent?
"With this amount of money going to a private owner, surely you would have considered what it would cost the Commonwealth to purchase the building itself."
Move to save $324 million in leasing costs
When pressed about costs, department secretary Michael Pezzullo said he recalled bringing his own chair to the department from his former office to save money.
"In the bathroom that I have, I even take the towels home to wash them myself because I am trying to save as much as I can," he joked.
The Immigration Department employs about 14,300 people, with 6,000 public servants based in Canberra.
The relocation would reduce the number of Immigration Department buildings in Canberra from 12 to five
Department officials said the move would save close to $324 million in leasing costs over 30 years.
Immigration officials told senators the cost per square metre at the Canberra Airport precinct would be $2,053, averaged across four buildings.
Senator Carr said cost was "substantially above" the Government spend of between $1,200 and $1,800 per square metre.
The department's existing property leases are set to end progressively between 2017 and 2020.
The department merged with the former customs agency in 2015 to unlock millions of dollars in savings.
The new headquarters would also boast an "armoury" for Border Force and Immigration staff.
Border Force Commissioner Roman Quaedvlieg told the Senate estimates hearing 957 staff currently carried weapons.
Mr Quaedvlieg said some of these staff were based in Canberra and there were no plans to increase the number of staff with weapons.
