China has reacted angrily to Australia's criticism of the corruption trial of businessman Stern Hu and his Rio Tinto colleagues.

Prime Minister Kevin Rudd and Foreign Minister Stephen Smith say there are "serious unanswered questions" about the evidence used to convict Hu, who is an Australian citizen, on a charge of stealing commercial secrets.

The charge was heard in secret and no official evidence has been made public.

When the ABC asked Chinese foreign ministry spokesman Qin Gang for his reaction to the comments, there was an angry reply.

"We express serious concern about the Australian statements on the Rio Tinto case," Mr Qin said.

"The Rio case is a criminal case and the Chinese side has already given its verdict.

"Australia should respect this outcome and stop making irresponsible comments."

Mr Qin also refused to timetable when China would ratify a prisoner exchange agreement it has made with Australia that would potentially allow Hu to serve part of his sentence in Australia.

Hu and three Chinese colleagues, who were tried last week in Shanghai, were convicted of accepting bribes totalling about $14 million and stealing trade secrets.

Hu, who headed Rio Tinto's Shanghai office, was sentenced to 10 years in prison, while Wang Yong, Ge Minqiang and Liu Caikui were given jail terms of 14, eight and seven years, respectively.

Rio Tinto has now sacked the men, saying their actions are totally at odds with the company's strong ethical culture.

'Harsh' sentence

Mr Smith described Hu's 10-year jail sentence as harsh by anyone's measure and said the Government was disappointed with several aspects of the trial.

"On the bribery charge, this to me seems to be a very harsh sentence," he said.

"And on the commercial secrets matter, because we've had no access to that part of the trial, there are serious unanswered questions which the international business community will want to continue to pursue with China."

Prime Minister Kevin Rudd also said there were serious doubts about the conviction on the charge of obtaining commercial secrets.

"When it comes to bribery, the Australian Government's position is consistent. We condemn bribery wherever it occurs," Mr Rudd said.

"The trial on the second charge was held in secret with no media and no Australian officials present for it.

"This has left, therefore, serious unanswered questions about this conviction. And holding this part of the trial in secret, China, I believe, has missed an opportunity to demonstrate to the world at large transparency that would be consistent with its emerging global role."