In a disturbing assessment of the attitude of many ministers toward the public service, former Department of Human Services secretary Renee Leon said the importance of evidence and expertise had been downgraded and public servants were being pressured to change advice.

Ms Leon, who was among five department secretaries who were axed by the government as part of a shake-up to the structure of the Australian Public Service late last year, said increasingly anecdote was trumping evidence in shaping government decisions.

"We have seen an attack on expertise in the last decade where to be an expert was almost to be reviled for being part of an elite of people," the former department secretary said in an interview with The Conversation and contentgroup.

"Government was certainly sick of experts, with all their pesky evidence and so on that was not necessarily in alignment with their more favoured decision making input, which is anecdote."

The importance of expertise in informing government decision-making has been elevated during the COVID-19 pandemic.

The national cabinet has relied heavily on advice from top public health experts in shaping the nation's handling of the outbreak, and Chief Medical Officer Brendan Murphy has regularly briefed the nation alongside Prime Minister Scott Morrison.

Ben Morton, Assistant Minister to the Prime Minister and Cabinet, said the government had "enormous respect for the advice of the Australian Public Service".

"The government's response to COVID-19 is an excellent example of the executive government working closely with the APS to deliver real outcomes for Australians," Mr Morton said.

Ms Leon said this was a welcome development that ran counter to the trend of recent years where ministers have increasingly relied upon advice from outside the bureaucracy.

In the four years to 2017, government spending on consultants soared 40 per cent to reach $545 million.

Ms Leon said that although external views were important, successive governments had increasingly neglected public service expertise.

"None of us mind [ministers getting] views from outside, I just think most of us think that going to consultants and thinking you are going to get a magic answer is more a testament to the wonders of marketing of consultants than it is to the greatness of the product they produce," she said.

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The former top public servant said the role of public servants in giving frank and fearless advice was more challenging with some ministers than others.

"I think some ministers have not understood that it is perfectly all right for them to get advice from the public service and disagree with it, but they ought to get the advice," she said.

"There are [some] who see it as an affront to their ego if you don't agree with them all the time.

"And of course they are much more difficult to work with because of the fear that you will offend them and pay the price."

She described situations in which public service middle managers were pressured to "change their advice so the minister will agree with it".