Glyn Davis (Image: AAP/Alan Porritt)

One of Australia's foremost public policy experts has strongly criticised the dramatic expansion in outsourcing of policy advice by the federal government, warning that it risks corruption and has created a vicious circle of declining public sector expertise.

Glyn Davis, a former senior public servant at the state and federal levels, former University of Melbourne Vice-Chancellor and a prominent public policy academic, on Friday delivered the annual Jim Carlton Integrity Lecture at the University of Melbourne.

He used three major reviews of the public service -- by John Reid in 1983, Terry Moran's Ahead of the Game review in 2010 and David Thodey's review, commissioned by Malcolm Turnbull -- as a guide to reflect on the shifts in the conduct of public administration at the Commonwealth level, and in particular the increasing outsourcing of government functions.