Australian writer Yang Hengjun could spend the rest of his life in a Chinese prison after he was handed a suspended death sentence on national security charges.
Foreign Affairs Minister Penny Wong said the federal government was appalled.
"This is harrowing news for Dr Yang, his family and all who have supported him," she told reporters in Canberra.
"Our thoughts are with them. I acknowledge the acute distress they will all be feeling, after many years of uncertainty."
The sentence could be commuted to a life sentence after two years if he does not commit any serious crimes.
A spokesman for Dr Yang's family said they were shocked and devastated.
"We know our father has done nothing wrong," they said in a statement on Monday.
"He is in jail because he represents truth, democracy, respectful exchange of rational ideas."
The writer still has avenues for appeal and the government will continue to advocate for him.
Human rights organisation Amnesty International said it was horrified by the sentence.
"To this day, the Chinese authorities have failed to substantiate their allegations that Hengjun is a spy," Amnesty said in a statement.
"Rather, this sentence and his prosecution appear to be purely motivated by Hengjun's advocacy for democracy and because of his writings critical of the Chinese government."
The Australian government hauled in Chinese ambassador Xiao Qian for a dressing down, with foreign affairs secretary Jan Adams voicing objections to the ruling.
Mr Xiao remained silent as he left the department's offices after less than half an hour.
Australia's ambassador in Beijing would not be recalled, Senator Wong said.
"Australia will not relent in our advocacy for justice for Dr Yang's interests and well-being, including appropriate medical treatment," she said.
Opposition foreign affairs spokesman Simon Birmingham said all legal avenues needed to be explored.
"I'm sure Australians will be aghast and appalled at the decision of Chinese authorities to level a sentence of this nature against an Australian citizen," he said.
"It must be the top priority for the Albanese government in their engagement with Chinese officials to continue to advocate on Hengjun's behalf."
Dr Yang was detained in 2019 and has consistently denied working as a spy.
The case against him has never been publicly disclosed and his trial was held in secret in May 2021.
His verdict was plagued by continuous delays, having been postponed more than eight times since the conclusion of his trial.
In August, Dr Yang expressed concerns he could die in a Chinese prison without proper medical attention after developing a 10-centimetre cyst on his kidney.
He was subject to more than 300 interrogations over 18 months, the family spokesman said, including six months of intense torture.
During his detention, he was deprived of sleep and had his wrists and ankles strapped and pinned to a chair for days at a time.
The Australian government recently welcomed the release of journalist Cheng Lei, who was freed from China in 2023 after three years behind bars.
The Chinese ambassador previously said Dr Yang's case could not be resolved in the same way.
