Shadow attorney-general Mark Dreyfus in a letter on Wednesday told Prime Minister's Department secretary Martin Parkinson parts of the Australian Public Service were being politicised.

Responding to the leak of classified Home Affairs Department advice, Mr Dreyfus said bureaucrats had been used to serve the Coalition's partisan causes, referring also to Treasury modelling the government employed to attack Labor's negative gearing plans.

The Home Affairs Department had also failed to provide a number of answers to questions until after MPs had finalised a report into allegations regarding minister Peter Dutton's use of powers with respect to the visa status of au pairs, while the bureaucracy had disclosed the personal information of a Centrelink client who had criticised its welfare debt raising methods.

"We would be very concerned if this behaviour reflected a growing trend within the public service of departments bowing to undue and inappropriate partisan political pressure in the conduct of their duties," Mr Dreyfus said.

The episodes marked a break from the convention that the public service remained impartial, he said.

"It would be concerning if, following the recent ministry changes, this type of activity was now being adopted more broadly," Mr Dreyfus said.

He told Dr Parkinson the incidents should not become the new norm for the APS.

"Politicisation of departments is corrosive to public debate. It undermines the public's faith in the public service and the work it does.

"It also impairs morale, harms recruitment, and jeopardises the career prospects of individual public servants."

Dr Parkinson on Thursday relayed Mr Dreyfus' concerns to department leaders.

In reply to Mr Dreyfus he said he took seriously any suggestion the public service was being politicised.

"I regard acts that have the substance, or appearance, of politicising the APS as threats to the effectiveness of Australia's democracy," he said.

At a Senate estimates hearing on Monday, Labor senator Penny Wong referred to leaks including the disclosure of a classified Home Affairs briefing about Australia's asylum seeker offshore processing regime, and asked the Prime Minister's Department how the public service was responding.

Department deputy secretary Stephanie Foster said Dr Parkinson discussed leaks with other secretaries as they occurred, or at regular periods.

"Were the public service to be implicated in those leaks, then that would be a very grave concern," she said, referring to the recent disclosures.

Departmental heads had discussed the need to maintain the bureaucracy's apolitical status in the lead-up to a federal election, when perceptions of partisanship became more acute, she said.

Australian Federal Police told senators it was evaluating the apparent disclosure of classified briefings after Home Affairs Department secretary Mike Pezzullo referred the case to them.

Dr Parkinson and Mr Pezzullo both used speeches at the Institute of Public Administration Australia last year to promote the non-partisan role of the federal bureaucracy.

Speaking to public servants, Dr Parkinson in December said an apolitical public service was "one of the key institutions in our Westminster system" and "part of the bedrock of democratic governance."

"The APS also has to contribute to the health of our democracy by guarding our independence and providing advice without fear or favour," he said.

Mr Pezzullo in October said bureaucrats must absent themselves "from any partisan discussions and avoid exposure to raw politics, especially as it might relate to electoral considerations or criticisms of the opposition", and referred to a "boundary between the political and the administrative."