Yang Hengjun's lawyer Rob Stary, who is based in Australia, said it was still unclear what the espionage his client is suspecting of engaging in.
"We think it relates to espionage on behalf of Australia, but it's not specified on the charge sheet," Mr Stary told AAP on Tuesday.
"We'd obviously be disturbed by that if it was the allegation because there is absolutely no foundation for it at all."
The Chinese-born writer was detained in Guangzhou earlier this year after flying in from New York. He has been held without charge in Beijing since January - without access to his family or a lawyer.
READ MORE
Mr Stary suspects the espionage charge relates to Mr Yang's democracy activism.
"He's a blogger and that's what he does, he's an academic, he's of a different ilk," he told AAP.
"He had been active and he's been politically active in promoting democratic values. That's the basis of it, as we understand."
Mr Stary wants the Australian government to get involved.
"We need intervention from the government," he said.
"It has to be resolved diplomatically and if there is no real or proper foundation for those charges, then he ought to be released and repatriated."
AAP
Alex Joske, researcher with the Australian Strategic Policy Institute (ASPI), told SBS News: "China has a history of detaining people for political reasons - to build leverage in broader strategic issues."
"China has done the same thing to Canada - arresting two of its citizens in response to the arrest of the Huawei CFO, and it has also done the same to the British government, arresting a staff member of the British consulate in Hong Kong," he said in Canberra.
"All countries that hold liberal values have an interest in protecting the rights of Dr Yang, and their own citizens in China, who might be used as pawns and prosecuted in a similar way."
Payne 'concerned and disappointed'
Foreign Minister Marise Payne said she was concerned and disappointed the writer and former diplomat had been formally arrested and will continue to be criminally detained.
"Our thoughts are with Dr Yang and his family at this very difficult time," Ms Payne said in a statement.
"Dr Yang has been held in Beijing in harsh conditions without charge for more than seven months.
"Since that time, China has not explained the reasons for Dr Yang’s detention, nor has it allowed him access to his lawyers or family visits."
AAP
Ms Payne said she had raised the matter twice with her Chinese counterpart State Councillor Wang Yi and written to him three times about Australia's "serious concerns for Dr Yang's welfare".
"I respectfully reiterate my previous requests that if Dr Yang is being held for his political beliefs, he should be released."
Australian embassy officials are expected to visit Dr Yang on Tuesday.
Shadow foreign affairs minister Penny Wong backed the government's efforts to advocate for Dr Yang.
"We continue to call on the Chinese Government to clarify the reasons for Dr Yang's detention and to ensure Dr Yang is treated in a fair, unbiased and transparent manner in accordance with international human rights law," Ms Wong said in a statement.
