Today they are called duds, or the officially preferred term "lower-value employees", but in 1920, bosses in the fledgling public service were worrying about the "manifestly incompetent" bureaucrats who had been hanging around for years and were proving next to impossible to dislodge from their jobs.

In many cases, the 1920 royal commission into the public service found, incompetents were being protected by their superiors on the grounds that they were "decent duffers".

Royal commissioner Duncan Clark McLachlan found that then, as now, it was very difficult to sack an underperforming public servant and one of the toughest tasks was to persuade bureaucrats to dob on their colleagues.

Ninety-five years later, the public service is still fretting about what to do about underperformers with just 72 public servants, from a workforce of 160,000, shown the door in 2013-14 for failing to do their jobs.

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But the Australian Taxation Office is leading the charge against the bureaucracy's present-day decent duffers, pushing for changes to its "performance management" rules after taking action against just two alleged underperformers last year - from a workforce of 23,000.

The government's biggest department, Human Services, is also moving to strip away legal workplace protections for bureaucrats at Centrelink, Medicare and the Child Support Agency regarded as "lower-quality employees".

Back in 1920, Mr McLachlan, found the mechanism for firing a public servant, which involved hauling them before a board of senior bureaucrats, was a failure because "sentimental considerations" by the board members would often allow the underperformer to keep his job.

"I am convinced that the service will never be relieved of the incubus of inefficient and incompetent officers so long as the present provision on the statute book remains unaltered," the royal commissioner wrote.

Then there was the problem of gathering evidence against duffers, which may sound familiar to modern-day Commonwealth line managers.

"Generally such evidence can be tendered only by those connected with the officer in his work and who from long association with him and appreciation of his personal qualities, or other reasons of sentiment, feel a natural revulsion towards publicly testifying against a fellow officer whose position in the service is at stake," Mr McLachlan wrote.

The code of silence went all the way to the top of departments, the commissioner discovered.

"Even the heads of branches who are directly responsible for the output of work and the efficiency of services rendered by officers, will not hesitate to shield men who are 'decent duffers'," the commissioner wrote.

"The departments continue to retain the services of officers overpaid for the work performed by them, or so manifestly incompetent through lack of physical or mental capacity that their maintenance in the service is unjustified.

"Shielded and aided by their fellow officers, they continue ostensibly to fill the positions while the general efficiency of the service suffers."