Key public service chiefs to retire

The head of the prime minister's department, Michael Thawley, will retire in January to return to the private sector.

His departure will be followed six months later by Peter Varghese, who will leave his role as secretary of the Department of Foreign Affairs and Trade to become chancellor of the University of Queensland.

Prime Minister Malcolm Turnbull also confirmed on Tuesday his acting chief of staff Drew Clarke - the former secretary of the communications department - would permanently take on the key role in his office.