An Australian academic has told a US congressional committee China is waging a “campaign of psychological warfare” against Australia.

Clive Hamilton, vice-chancellor’s chair in public ethics at Charles Sturt University, said the campaign is undermining democracy and cowing free speech.

He is the author of Silent Invasion: China’s Influence in Australia, a book which Allen & Unwin dumped over concerns of legal action by Beijing.

However it was published by Hardie Grant.

Appearing before the Congressional-Executive Commission on China in Washington DC he said Australia is being subjected to a Chinese Communist party-sponsored campaign of “subversion, cyber intrusions, and harassment on the high seas”.

“Beijing knows that it cannot bully the United States – in the current environment the consequences would be unpredictable and probably counterproductive – so it is instead pressuring its allies,” Hamilton said according to The Guardian.

Hamilton cited an incident which saw the PLA Navy challenge three Australian warships sailing through the contentious South China Sea last week.

“It has scaled up its threats of economic harm unless Australia changes its ‘anti-China’ path. This psychological warfare is only stage one, with real punishment to follow if needed,” he said.

He claimed since his book was published in February he has had to go to “extensive measures” to secure his personal safety.

Hamilton said Allen & Unwin’s decision to dump his book had an impact on free discussion of China and its geopolitical influence.