Twelve of the public service's largest departments could be ripe for decentralisation if they can't justify their continued presence in Canberra, analysis by Fairfax shows.
New figures reveal the agencies have massed their workforces in the capital at levels above the APS average, which could leave them more potential to move staff to bush towns as the federal government begins forcing departments to relocate.
But the Nationals leading the decentralisation charge have said staff with policy roles won't be moved from Canberra, and that Sydney and Melbourne-based offices would be moved too.
While Deputy Prime Minister Barnaby Joyce has ruled out moving the Tax Office and the departments of Treasury and Finance from Canberra, other agencies including Environment and Energy, Infrastructure and Regional Development, and Communications have concentrated their staff in the capital.
Figures provided to Senate estimates hearings last month show Canberra is home to more than 85 per cent of staff at the department of Infrastructure, a portfolio overseen by National Party ministers Fiona Nash and Darren Chester.
Senator Nash, spearheading the decentralisation push, is also the junior minister in the Communications portfolio, with 84 per cent of departmental staff based in Canberra, ahead of the Environment Department at 69 per cent.
The National Party-led push to force relocations of departments and agencies will be considered by cabinet in August, and comes after Mr Joyce faced accusations of pork barrelling over the controversial pesticides authority move to his own electorate of New England.
Treasury is the department with the largest concentration of staff in Canberra at more than 94 per cent, ahead of Finance with 90 per cent. Foreign Affairs and Prime Minister and Cabinet, both unlikely to face forced moves, have about 70 per cent of their workforce in the capital.
More than 87 per cent of Education Department staff are currently in Canberra, compared with 83 per cent from Social Services and 79 per cent of Health.
Other agencies with above average Canberra concentration include Employment with 81 per cent, Attorney-General's with 71 per cent and Comcare with 68 per cent. An Industry spokesman said 66.1 per cent of departmental staff were in Canberra.
The government is yet to outline its criteria for moving departments and agencies, but a spokesman for Senator Nash said policy functions would not be moved in the decentralisation bid.
Decisions to move departments would be based on factors including whether they required close and frequent contact with ministers, relied on other agencies to function properly, and whether stakeholders would be impacted positively or negatively, he said.
Labor regional spokesman Joel Fitzgibbon said by exempting the Australian Taxation Office, Finance and Treasury from moving, Mr Joyce had in a "clumsy way" also ruled out relocating any department with a policy role.
"Those smaller agencies that don't have a policy development role should be very nervous," he said.
"I feel for APS staff. It must be a very stressful time for all of them except those that have been explicitly ruled out."
Community and Public Sector Union national secretary Nadine Flood said the percentage of workers in agencies who were based in Canberra should not be a basis for the government to make decisions on decentralisation.
"The reality is that the distribution of staff in departments overwhelmingly reflects what's needed for each agency to operate effectively, including in the many policy areas that require multi-agency interactions," she said.
Cabinet will decide who stays and who goes by the end of the year, with any new relocation costs incorporated into the 2018-19 federal budget.