* China case against GSK-linked investigator couple lodged with court
* Couple alleged to have illegally obtained private information
* Humphrey apologises for breaking any Chinese law - state TV
* Trial to begin behind closed doors on Aug. 7 - family friends (Adds comment from family member)
By Adam Jourdan
SHANGHAI, July 14 (Reuters) - Prosecutors in China have filed charges against British investigator Peter Humphrey and his American wife, the official Xinhua news agency said on Monday, after the couple were detained last year following work they did for British drugmaker GlaxoSmithKline Plc.
The case against Humphrey and his wife, Yu Yingzeng, has become a key piece in a long-running investigation into GSK, whose China executives have been charged with orchestrating a widespread network of bribery to promote sales.
The case against the couple, who have been accused of illegally obtaining private information, has been formally lodged with the Shanghai Number One Intermediate People's Court for trial, Xinhua said in a report.
Two family friends with knowledge of the matter told Reuters this month that the couple's trial was set for Aug. 7 and would be closed to the public. The secrecy surrounding the trial has raised concern among British and U.S. officials.
China's foreign ministry said last week the trial would be handled in accordance with the law.
ChinaWhys, the risk consultancy run by the couple, was employed by GSK in April 2013 to investigate an ex-employee suspected of sending anonymous emails, including the circulation of an intimate video of former GSK China head Mark Reilly with his girlfriend, as well as emails containing allegations of widespread bribery at the British drugmaker.
In an eight-minute news report aired on Monday by state run China Central Television (CCTV), Humphrey said he and his wife "deeply regret" breaking any Chinese law. He added ChinaWhys would not have worked with GSK if the drugmaker had informed him about the full details of the whistleblower emails.
"It was certainly not our intention to violate Chinese law," Humphrey, wearing an orange vest over his clothes, said in the interview, which the state broadcaster said was conducted a few days ago in a Shanghai police station.
Humphrey's apology reiterated a similar statement he made to CCTV in August last year after the couple were arrested.
In an emailed statement sent to Reuters, the couple's teenage son, Harvey Humphrey, said he welcomed the increased disclosure of information surrounding the case.
"If China is prepared to release so much detail about my parents, I hope I can be given access to the trial and be allowed to see them for the first time in over a year," he said.
Xinhua said Humphrey and Yu had paid people in Beijing and Shanghai to purchase personal information. Citing the prosecutor on the case, the news agency added that the couple had been fully aware of the illegality of their actions.
Between 2009 and 2013, the couple illegally obtained private information during investigations into close to a thousand firms and a large number of private individuals, including household registration data, real estate and vehicle documents, as well as phone records, it added.
GSK officials could not be immediately reached for comment.
Humphrey worked for Reuters as a journalist in the 1980s and 90s. (Additional reporting by Hui Li; Editing by Kazunori Takada, Edwina Gibbs and Robert Birsel)
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