Nearly a third of government staff leave their jobs within a year - compared to an international average of just eight percent.
The figures - showing that 30 percent of staff don't last a year - have appear in the Treasury's latest report on public-sector jobs.
The Public Service Association said the high staff turnover reflected an increasingly poor workplace culture.
National secretary Erin Polaczuk said having so many leave early reduced morale and increased costs for the employer.
She said the report showed the Government needed to do more to create a good work environment for its employees.