Foreign Minister Marise Payne has voiced serious concerns about the detention of Chinese-Australian writer Yang Hengjun in Beijing.
Senator Payne said Dr Yang was being kept in isolation from the outside world, with restrictions on his communications with family and friends, and being subjected to daily interrogation while wearing shackles.
"I am very concerned by reports from a recent consular visit to Australian citizen Dr Yang Hengjun, who remains in criminal detention in China," she said in a statement on Monday.
"This is unacceptable."
Australia has repeatedly asked Chinese authorities for an explanation of the charges against Dr Yang.
Australian writer Yang Hengjun. Source: ICHPL Imaginechina
It has also asked that he be given access to his lawyers and family.
"This has not led to any substantive changes in his treatment," Senator Payne said.
"We will continue to express our expectations in clear terms to the Chinese authorities - both in Beijing and in Canberra - including that Dr Yang be released and that, while his detention continues, he be treated fairly and humanely."
The 53-year-old Australian citizen has been accused by Chinese authorities of spying since being detained after landing at Guangzhou airport with his family in January.
Prime Minister Scott Morrison said he was "very concerned" by reports about the treatment Dr Yang has confronted.
"The most recent consular access was a matter of great concern to me and the Foreign Minister and we will continue to make those representations on behalf of an Australian citizen," he said.
"Australia always has to stand up for our citizens and we have to be true to who we are as a people."