As well as Canberra, Yang Hengjun has been detained for almost five years on espionage allegations.

Premier Anthony Albanese’s sons have written to him ahead of the leader’s historic visit to Beijing this weekend.

In 2021, Dr Yang was secretly tried, and his charges have not been made public.

According to the petition, Dr Yang’s health has “rapidly deteriorated” in recent weeks, and Mr Albanese should “do everything in your power to save his life”.

In 2016, a series of prickly disputes led to the suspension of high-level meetings between Australia and China. Mr Albanese will be the first Australian leader to visit China since then.

In Beijing, he will meet Chinese President Xi Jinping and Premier Li Qiang.

Formerly a scholar and novelist in Australia, Dr Yang blogged about Chinese affairs while working for China’s Ministry of State Security. The “democracy peddler” avoided direct criticism of the government in his writings.

In January 2019, the 57-year-old was arrested at Guangzhou airport and accused of spying. Since then, most of his case has been conducted behind closed doors.

China’s foreign ministry has warned Australian officials not to interfere in the case, and to respect the nation’s “judicial sovereignty.”

In detention, Dr Yang was subjected to “more than 300 interrogations” and “six months of intense torture,” according to his family.

He discovered that he had a large cyst on his kidney in August. In the letter, he writes that he hasn’t been able to walk for the past 3 weeks and remains mostly bedridden. He even has difficulty walking four metres from his bed to the toilet in his cell.