Two former Treasury bosses say cuts and constant changes have left the abilities of the public service dangerously degraded.

In a damning assessment of the state of the bureaucracy, Ken Henry and Martin Parkinson say it can no longer provide proper or useful advice to politicians and the voting public.

“Many departments have lost the capacity to develop policy; but not just that, they have lost their memory,” Dr Henry has told Fairfax reporters.

“I seriously doubt there is any serious policy development going on in most government departments.”

Dr Parkinson - who succeeded Dr Henry as Treasury secretary – says the boundaries between public servants and political advisors have been blurred, and there is now a “relentless focus on message over substance” in government.

He said this “results in a diminution of the 'space' in which the independent advisor can operate.”

Dr Parkinson also lamented the lack of proper mentoring for young policy advisers.

“Becoming an effective policy advisor requires 'learning by doing' under the guidance of experienced hands - an apprenticeship if you will,” he said.

“Today, in some institutions, smart people look around at their colleagues and find there is no one to talk to, to learn from, who has experience in delivering real reform.

“The combination of these two things is a decline in the quality of advice and an erosion of capability, to the detriment of good government,” Dr Parkinson told reporters.

The comments come as part of an essay entitled Political amnesia: How We Forgot How to Govern – in which writer Laura Tingle questions the true cost and benefit outsourcing of political advice; the politicisation of departmental leadership; the habit of continuously moving top public servants between departments; and “periodic mass axing of public service heads upon the arrival of incoming conservative governments” as well.

In one of the essay’s key examples of the shift to a sluggish and stymied public service, Dr Parkinson recalls the Treasury’s role in beginning the tax reform debates of the 1980s and 1990s.

He said that Treasury's expertise was vital in the introduction of capital gains tax, fringe benefits tax, dividend imputation and the introduction of the GST some years later.

But thirty years on from these milestone, he says Treasury now struggles to get good people in its tax division.

On top of that, sacking of over 12,000 public servants in the Gillard and Abbott government's redundancy rounds have hit older staff in the tax and revenue areas, cutting long-standing sources of valuable advice to save money in the short term.

“Many of the older and more senior staff in this area were the last of those who had come through the ranks during the era of big change under Paul Keating and Peter Costello,” Ms Tingle writes.

“Even as Treasury was being asked to prepare for a new round of tax reform - in conjunction with a group in Treasurer Joe Hockey's office - its tax division had a third less staff than it had three years earlier.

“About half the public service doesn't remember the place working any differently to the way it has worked from the Howard era onwards – cannot recall a time when policy-makers in departments had a real role to play and there was a vital and active engagement with executive government.

“Ultimately, it is as though we as a community have ceased to recognise what a valuable repository of memory, and what a valuable institution, the public service is.”