Spy chief says foreign espionage and interference an 'existential threat' to Australia

Asio boss Duncan Lewis says risk of of terrorism 'unacceptably high' but it is not the most serious issue for Australia

Australia's outgoing spy chief says malevolent state espionage and foreign interference poses an "existential threat" to Australia in a way that extremist terrorism does not.

Duncan Lewis, the director general of the Australian Security Intelligence Organisation, will retire this month after a five-year term, handing over to Signals Directorate boss Mike Burgess.