Scott Morrison has appointed his one-time chief of staff Phil Gaetjens to head the prime minister’s department. He replaces Martin Parkinson, who finds himself out of a top public service job for the second time under the Coalition government.

Gaetjens has most recently been secretary of the Treasury, a position to which he was appointed when Morrison was treasurer.

Morrison told a news conference: “Following the election, the secretary of Prime Minister and Cabinet and I have agreed that it is an opportune time for new leadership of the Department of Prime Minister and Cabinet”.

Parkinson, a highly respected career public servant, was sacked as Treasury secretary by the Abbott government, and brought back to the public service as head of the prime minister’s department by Malcolm Turnbull. His current contract ran until early 2021.

He said in a statement to departmental staff on Thursday: “This timing works for me personally and allows the PM to make a transition to a secretary who will be able to support him through the full parliamentary term”.

He was quoted in Thursday’s The Australian as saying, “Absolutely I would not want anyone to think there was anything about my relationship with the Prime Minister that was leading me to leave”.

Although prime ministerial sources dispute that Parkinson was pushed, it had been rumoured since the election that Morrison wanted a change at the top of his department.

Gaetjens’ public service career appeared doomed only months ago when a Labor government seemed likely. Then-shadow treasurer Chris Bowen had criticised his appointment as political and made it clear he would be removed under a Shorten government.

The new head of Treasury will be Steven Kennedy, who is now secretary of the infrastructure department.

Earlier Kennedy was a deputy secretary in the prime minister’s department. In that position, he was in charge of innovation and transformation, as well as leading work on cities, regulatory reform, public data and digital innovation. He also served in the office of Julia Gillard when she was prime minister, seconded as the director of cabinet and government business and senior economic adviser.

Morrison pointed out both Gaetjens - who was also Peter Costello’s chief of staff - and Kennedy had had experience in the political realm, noting that while Gaetjens had worked on the Coalition side Kennedy had worked on the Labor side.

The PM was ready for a question suggesting the choice of Gaetjens would be seen as politicisation of the public service, reeling off appointments Labor had made of people who had worked in the political arena.

Morrison left the way open for further shake ups at the top of the service. “I will always reserve that right to make further changes where I believe they are necessary. I think these are the ones that are necessary right now”. There will be an acting secretary in the Infrastructure department for the time being.

Morrison is Minister for the Public Service and has strong ideas on how it should operate. At his news conference he once again stressed the emphasis he is placing on its responsibility for efficient implementation.

He summed up his attitude: “When it comes to the public service, my view is to respect and expect”.

Asked about the service’s role in giving advice, he said, “It is the job of the public service to advise you of the challenges that may present to a government in implementing its agenda. That is the advisory role of the public service. […] But the government sets policy. The government is the one that goes to the people and sets out an agenda, as we have”.

Parkinson in his statement to his departmental staff told them: “I want to continue to encourage you to have a view, be curious, understand what is happening at the forefront of policy and policy-related research, engage widely with stakeholders from all parts of the community, and be resolutely committed to advocating for truly evidence-based policy”.

Michelle Grattan does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.