The country’s top intelligence chief has warned that foreign interference against Australia is occurring on an unprecedented scale.

Duncan Lewis, director-general of the Australian Security Intelligence Organisation, says countries are trying to access classified information about the nation’s global alliances and military, economic and energy systems.

“Espionage, interference, sabotage and malicious insider activities can inflict catastrophic harm on our country’s interests,” Mr Lewis told a Senate estimates hearing on Thursday night.

“It undermines potentially our sovereignty, our security and our prosperity.”

Mr Lewis said foreign actors were attempting to covertly influence and shape the views of the Australian public, its media and officials in the Australian government, as well as members of diaspora communities.

Senators were told these efforts could have an immediate impact, but in some cases the harm may not materialise for decades.

“This is not a theoretical proposition,” Mr Lewis said.

“The reality is that acts of espionage and foreign interference are occurring against Australian interests, both in Australia and overseas.”

Mr Lewis urged senators to pass the Turnbull government’s proposed foreign interference laws, saying the “grim reality” was there were more foreign intelligence officers now than during the Cold War.

Asked about the potential fallout from a Liberal backbencher’s decision to accuse a political donor of involvement in a bribery scandal, Mr Lewis said it would not damage international intelligence partnerships.

-AAP