Yang Hengjun: Spy claims against writer detained in China 'absolutely untrue'

Prime Minister Scott Morrison says allegations a Chinese-Australian writer detained in Beijing has spied on behalf of Australia are "absolutely untrue".

Dr Yang Hengjun is a former Chinese diplomat who went on to become a pro-democracy campaigner and was made an Australian citizen in 2002.

The 54-year-old was detained in Guangzhou in January after flying into the country from New York where he was living with his family and working as a visiting scholar at Columbia University.

China has warned Australia to respect its sovereignty and butt out of the case, but Mr Morrison says the government is concerned about Dr Yang.

"We will expect him to be treated appropriately and his human rights to be respected," Mr Morrison told Today.

"There is their own justice process they will follow in China and that is appropriate.

"But these suggestions he has acted as a spy for Australia are absolutely untrue and we will be protecting and seeking to support our citizen as we have been doing now for some period of time.

"We make no apologies for standing up for one of our citizens."

Mr Morrison said he respects China's sovereignty.

"But we do expect Australians, indeed all citizens, to have their human rights appropriately looked after," Mr Morrison said.

Foreign Minister Marise Payne has been focused on Dr Yang's welfare as she endeavours to seek his release, describing the conditions of his detention for the past seven months as harsh.

Australian officials visited Dr Yang in detention in Beijing on Tuesday.

He pleaded for Mr Morrison to help him go home as soon as possible, the Australian Financial Review reported.

Victorian barrister Julian McMahon - who helped try to save two Australian members of the Bali Nine from the death penalty - has recently joined the case alongside Melbourne lawyer Rob Stary.

Mr McMahon said it could be months before details of the broad spying allegations are known.

Unlike the Australian system, people in China are detained, arrested and charged in three separate steps.

"The problem we have at the moment is that although our client has been detained, we don't have material, we don't have the basis of the detention except a vague allegation," he said.

"And we don't have the timetable."

But Mr McMahon understands Dr Yang is in good spirits.

Senator Payne has reminded China it must comply with international laws banning torture, inhumane treatment and arbitrary detention.