Australian writer and democracy advocate Yang Hengjun has been charged with espionage by Chinese authorities, sparking deep concern and disappointment from the Morrison government.

Foreign Minister Marise Payne holds serious concerns for his welfare and the harsh conditions under which he has been held in Beijing 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,” Senator Payne said on Tuesday.

“It is important, and we expect, that basic standards of justice and procedural fairness are met.

“I respectfully reiterate my previous requests that if Dr Yang is being held for his political beliefs, he should be released.”

Dr Yang’s Melbourne lawyer Rob Stary said the basis for the espionage charges was unclear.

“We think it relates to espionage on behalf of Australia, but it’s not specified on the charge sheet,” Mr Stary told AAP.

“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 in January after flying in from New York.

Mr Stary suspects the espionage charge relates to Dr Yang’s 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.”

Labor has joined the government in demanding the Chinese government clarify the reasons for Dr Yang’s detention.

“If Dr Yang is being detained purely for his political views then he should be released,” Labor foreign affairs spokeswoman Penny Wong said.

Mr Stary said the matter needed to be resolved diplomatically.

“If there is no real or proper foundation for those charges, then he ought to be released and repatriated.”

Senator Payne has discussed his plight with China’s foreign minister twice, and has written to him three times.

Embassy officials have visited Dr Yang seven times since his detention, most recently on July 25.

They have another visit approved for Tuesday.

“I will continue to advocate strongly on behalf of Dr Yang to ensure a satisfactory explanation of the basis for his arrest, that he is treated humanely and that he is allowed to return home,” Senator Payne said.

Last month, China lashed out at the Australian minister’s public statements about Dr Yang’s case.

“China deplores the statement made by the Australian foreign minister and urges the Australian side to stop interfering in the handling of the case by the Chinese side and stop issuing irresponsible remarks,” a spokesperson said.

“The Chinese authority will handle the case in strict accordance with the law and fully protect his legal rights.”

The 53-year-old, who has held Australian citizenship since 2002 and has a doctorate from the University of Technology Sydney, was living in New York as a visiting scholar at Columbia University.

-AAP