The Shanghai court that will try two foreign investigators linked to the bribery case of drugmaker GlaxoSmithKline (GSK) in China said Thursday it will hold an open trial, following diplomatic and family protests.

British national Peter Humphrey and his wife Yu Yingzeng, a naturalised US citizen, were indicted for illegally obtaining private information on Chinese citizens, state media said earlier this week, citing prosecutors.

GSK had hired Humphrey, founder of a Shanghai-based risk advisory firm, to investigate the origin of a sex tape of the former boss of its China division, which emerged just before Beijing launched a bribery probe into the British company, the Sunday Times newspaper has reported.

Yu was general manager of the couple's firm, ChinaWhys.

Prosecutors told the Xinhua news agency that the two illegally sold personal information including details of household registrations, property and car ownership, call logs and immigration exit-entry records to multinational corporations, including GSK.

The Shanghai Number One Intermediate People's Court said it held a pre-trial meeting on Thursday and decided to make the trial a public hearing.

"After listening to the views of all parties, the court has decided to hear this case in an open trial after review according to the law," it said in a statement.

The court gave no trial date, but said the timing would be "adjusted accordingly", according to the statement. The court could not be reached for comment.

A family friend had previously told AFP the two will be tried on August 7 in a closed session shut to relatives as well as US and British diplomats.

The US Embassy in Beijing had expressed concern that US government representatives were barred from attending, despite an agreement allowing them to do so.

The couple's son, Harvey Humphrey, said Thursday that he had not been informed by the family's lawyers yet but hoped to attend the trial.

"I am very pleased and grateful. I certainly will attend and I can't wait to see my parents," he said through a representative.

The US Embassy in Beijing did not immediately respond to request for comment.

Police have accused the former boss of GSK's China division, Mark Reilly, of ordering employees to bribe hospitals, doctors and health institutions to gain billions of dollars in revenue, Chinese authorities said in May after a 10-month investigation.

China's healthcare sector is widely considered to be riddled with graft, partly the result of an opaque tendering system for drugs and doctors' low salaries.