Foreign Minister Marise Payne has raised serious concerns about the "unacceptable" detention of Chinese-Australian writer Yang Hengjun in Beijing.
Dr Yang is being held in solitary confinement and subjected to daily interrogation while shackled in chains.
His communication with family and friends has been heavily restricted.
"This is unacceptable," Sentor Payne said on Monday.
But China has disputed those claims, and says Dr Yang's rights and interests were fully guaranteed.
Foreign ministry spokeswoman Hua Chunying told a daily news briefing in Beijing Yang was "now in good health condition and there is no so-called torture at all", Reuters reported.
Australia has repeatedly asked Chinese authorities for an explanation of the charges against Dr Yang.
It has also asked that the former Chinese diplomat 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."
Prime Minister Scott Morrison said the unacceptable conditions came to light during a recent visit to Dr Yang by Australian consular staff.
"Australia always has to stand up for our citizens and we have to be true to who we are as a people," he told reporters in Canberra.
"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."
Dr Yang has been accused of espionage - charges denied by him and the Australian government.
Labor's foreign affairs spokeswoman Penny Wong has also raised concerns about his poor treatment and continued criminal detention.
"We join the government in calling for Dr Yang to be treated humanely and in accordance with international human rights law, and for him to have access to his lawyer," Senator Wong said.
"Labor fully supports the government's efforts to advocate for Dr Yang and we urge the Chinese government clarify the reasons for Dr Yang's detention."
Dr Yang is a former official in the Ministry of Foreign Affairs in Beijing who went on to become a pro-democracy campaigner. He became an Australian citizen in 2002.
He was detained earlier this year after flying into China from New York where he had been a visiting scholar at Columbia University for two years.
Australia has consistently lobbied Chinese authorities for his release.
But China has told Australia to respect the nation's "judicial sovereignty" and not interfere in the case.