No public servant is safe from the Abbott government's privatisations agenda, one of the pioneers of federal government outsourcing has warned.

The scope of the "contestability agenda" already underway in some departments is "truly limitless" according Alan Hepner, a key figure in public service's 1990s-era outsourcing drive, and the potential loss of tens of thousands of APS jobs to the private sector might be just the "first wave".

But Mr Hepner says privatisations can end up doing more harm than good, costing taxpayers more money and providing substandard services, if handled by public servants who are not up to the job.

The Canberra Times revealed last week that that "portfolio stocktakes" are already under way assessing government departments to see if their work can be farmed out, either to the private sector or the Commonwealth's growing "shared services" operation.

Mr Hepner, who was recruited by the Keating government from the US early 1990s for a management reform taskforce, says the Abbott government's plans dwarf anything that has ever been tried before.

"The difference, this time around, is the scale of the endeavour, systematised stocktakes, efficiency reviews and a truly limitless scope envisaged for determining which, not necessarily whether, to privatise government services," he told The Canberra Times.

"Most importantly, the 30,000 potential public service job losses that professor [Janine]  O'Flynn mentions ... are merely the first wave of constituents affected by this ambitious exercise."

Mr Hepner, who was co-author of the 1994 report The APS Reformed, wrote one of the earliest pieces of work on contestability in the Commonwealth Government in 1995 and later led a multi-departmental taskforce on public service competitive tendering and contracting.

Two "pilot stocktakes" have begun at the Finance and Communication departments in an effort to fine-tune methodology before all Commonwealth operations, including big frontline Departments such as Human Services and the Australian Taxation Office, get the  contestability treatment in a process that could take three years.

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But Mr Hepner said that contestability agendas around the world had a patchy record for actually delivering the goals of the governments which launched them.

"The results from contestability exercises and large scale privatisations around the world are quite mixed," he said.

The former senior Finance Department bureaucrat is also worried that little attention has been paid to the question of existing public servants having the skills and abilities to manage dramatic increases in public-private contracts.

"Ensuring that public service staff have the proper skills and abilities to successfully manage large-scale contracts is no small matter," Mr Hepner said.

"The current public sector mandarins need to be very careful about what they wish for.

"Numerous studies…have shown that if not properly managed, privatisations can in fact cost the taxpayer more, while lessening the quality of the public service on offer.  "