"I'm not aware of any other instance in Australian history where a foreign power has stopped publication of a book that criticises it,"Dr Hamilton said.

"The reason they've decided not to publish this book is the very reason the book needs to be published."

He was concerned that a perceived and vexatious threat,rather than an actual or justified legal action,had prompted the decision to ditch the book.

Allen&Unwin said on Sunday:"Allen&Unwin has published a number of books with Clive Hamilton,and has enormous respect for him and his work. After extensive legal advice we decided to delay publication of Clive's bookSilent Invasion until certain matters currently before the courts have been decided. Clive was unwilling to delay publication and requested the return of his rights,as he is entitled to do. We continue to wish him the best of luck with the book."

China's Australian embassy did not respond to efforts to seek comment.

The book by Dr Hamilton,who has published eight previous books with Allen&Unwin and has received an Order of Australia for his contribution to public debate,examines evidence that suggests various Chinese Communist Party agencies are seeking to extend Beijing's influence in Australia for strategic and political gains.

While such activity is carried out by other states,elements of Beijing's influence campaign are clandestine or highly opaque. According tomedia investigations andwarnings from spy agency ASIO,these efforts are targeted at Australian politicians and academics.

In response,the Turnbull governmenthas plans to legislate to counter Beijing-linked influence operations by introducing new offences prohibiting foreign interference.

Mr Gorman said in his email to Dr Hamilton that the publisher's position"would be stronger once proposed legislation targeting foreign influence in Australia passes through Parliament".

However,"it sounds as though this is now unlikely to happen until next year",he wrote.

Mr Gorman also wrote that the publisher believed the Chinese government is co-ordinatingattacks on Australian media reports it believes critique or undermine its authoritarian regime.

"It seems that Beijing is currently focusing on larger targets. If pursued with malice,this kind of vexatious legal action from a'whale'or a small Beijing agent mentioned in the book could result in the book being withdrawn from sale,and both you and Allen&Unwin being tied up in expensive legal action for months on end or longer,"Mr Gorman warned Dr Hamilton.

A former senior national security official told Fairfax Media that the Chinese government sought to use Western legal systems to advance or protect its interests.

Australia's defamation laws arenotoriously weighted towards litigants,unlike the legal system in the US or Britain,which have greater free speech or public interest protections.

"The Chinese government seeks to use the West's legal systems against the West,"the former official said.

Dr Hamilton said he rewrote the book to minimise legal risks,"but I can't stop an authoritarian foreign power exploiting our defamation laws to suppress criticism of it".

Some China watchers,along with Chinese-born businessmen named in media reports and ASIO briefings,including millionaire Sydney property developer and political donor Huang Xiangmo,have dismissed allegations of undue influence as unfounded and unjust.

Chau Chak Wing,a big Chinese-Australian political donor,is suing Fairfax Media over two stories that included allegations that ASIO had warned political parties against dealing with him.

TheHerald Sun recently printed a correction in connection to a report suggesting Huang Xiangmo was an agent of influence. The correction was issued after Mr Huang launched defamation action. The newspaper report was based on a leaked federal parliamentary library paper that examines Mr Huang's political donations and describes how he heads a Sydney-based lobbying organisation aligned with the Chinese Communist Party's United Front Work Department.

President Xi Jinping has described the United Front Work Department as Beijing's"magic weapon"to entrench and extend the Chinese Communist Party's influence in China and abroad. Dr Hamilton's book details its activities in Australia.

Mr Huang,who has repeatedly dismissed claims of impropriety,has also helped set up and provide seed funding to a China research institute at the University of Technology Sydney,the Australian China Research Institute,which is directed by former foreign minister Bob Carr and economist James Laurenceson. The institute is also examined in Dr Hamilton's book.

Mr Carr and Mr Laurenceson have both critiqued reports of Beijing's influence as overblown,while Mr Laurenceson recently tweeted theHerald Sun correction,describing it as a court"ruling",and appearing to endorse its coverage in the Chinese government-controlled press. A report by the Communist Party-controlledGlobal Times described the correction as a victory for overseas Chinese and attacked the Western media for failing to report on it.

Mr Laurenceson and Mr Carr have also been dismissive of concerns around political donations linked to Chinese government-aligned businessmen such as Mr Huang. Concerns about donations have been raised repeatedly by ASIO,and acknowledged by senior Labor and Coalition figures and former chief diplomat Peter Varghese.

Dr Hamilton's book includes a detailed examination of Mr Carr's advocacy for Australia to increase efforts to build relations with Beijing. It also examines concerns that some Australian universities have failed to appreciate the risks ofco-operating with researchers from the Beijing-controlled military and industrial research complex.

In August,Cambridge University Press was subject to intense criticism after it decided to censor the website of itsChina Quarterly journal to comply with Chinese demands. The articles to be censored detailed the Tiananmen Square massacre as well as President Xi Jinping's leadership,but the British publisher backflipped after an international outcry.

"Cambridge University Press censored their publications for sale in China. It wouldn't dare censor criticism of the Chinese Communist Party in publications for sale in Britain. But that is precisely what has now happened in Australia,"Dr Hamilton said.