The growing number of middle managers in the federal bureaucracy has created a career "bottleneck" that drives some staff out of the public service, a research paper says.
The report on workforce trends, written by Public Service Commission staff, draws attention to the burgeoning ranks of executive level 1 officers, which have grown faster than any other level.
The Australian Public Service's workforce expanded by 41 per cent in the 10 years to June 2011, though the number of EL1s grew 112 per cent – almost three times as quickly.
In contrast, the senior executive service's ranks – whose growth regularly attracts the public's ire – increased by just 74 per cent.
EL1 officers, who are nominally employed as supervisors or subject-area specialists, now comprise the largest cohort of Canberra-based staff. Their median base salary is about $102,100.
The paper said the growth in EL1 ranks "has not been matched by the APS6 or EL2 cohorts".
"As demand to replenish the EL1 workforce increases, the demand for talented APS6s may begin to exceed the supply, and dependence on the external labour market may increase,'' it said.
"Furthermore, as the supply of experienced EL1s increases beyond the demand of the EL2 cohort, a bottleneck will be created that may lead to an increase in turnover of EL1s as they pursue career advancement outside the APS."
The research paper also warned that the bureaucracy had become less effective in recent years at retaining its graduates.
It suggested government agencies do more to promote the long-term returns of staying in the public service.
"This could also be done by: increasing the availability of graduate programs and ongoing work outside the ACT; tailoring aspects of the program to suit graduates' individual interests and experience, particularly in relation to assigning rotations; and providing challenging work to keep graduates engaged during and after the program."
Widespread concerns about so-called "classification creep" led to a review in 2010 by former senior mandarin Roger Beale, though his report was limited to senior executives' workloads.
Mr Beale said the SES's growth had been largely justified, though the government agreed to his recommendation to cap its numbers.
The commission said the report on workforce trends, which was the work of six of its staff, did not reflect its formal views.