Several Australian politicians have accused China of meddling in its politics. Australia’s intelligence chief identified Dr. Chau, an Australian citizen, in June as a possible agent of the Chinese government.

Duncan Lewis, the director of the Australian Security Intelligence Organization, warned politicians against accepting contributions from Dr. Chau and another man of Chinese descent because of their ties to China’s government.

Dr. Chau, a billionaire property developer who immigrated to Australia decades ago, has said his campaign contributions are benign and unrelated to the Chinese government. He could not be reached for comment on Tuesday.

Dr. Chau is chairman of the Kingold Group, a business conglomerate based in Guangzhou, China, that has expanded to Australia. His name graces the modernist Dr. Chau Chak Wing Building at the University of Technology Sydney, to which he donated $15 million. The Chau family also owns New Express Daily, an Australian newspaper.

Dr. Chau filed a defamation suit last year aimed at two Australian news media companies: the Australian Broadcasting Corporation, the national broadcaster, and Fairfax Media, a newspaper publisher. He has sought damages from them for a news report that the suit says damaged his personal and professional reputation.

In his speech, Mr. Hastie argued that Dr. Chau was trying to silence the press.

“My concern is that defamation cases can have a chilling effect on our free press,” Mr. Hastie said. “Any attempt to silence our media from telling the truth — provided it is the truth — through a defamation claim cannot stand.”

In the speech, Mr. Hastie said Australians “deserve the truth.”

Since the accusations of political meddling, Australia has taken steps to curb foreign interference. A series of bills introduced in December would strengthen the country’s espionage laws, outlaw foreign political donations and criminalize efforts to interfere in Australian democracy.