Prosecutors in Shanghai have filed charges against a foreign couple for illegally obtaining private information on Chinese citizens, the Xinhua News Agency reported on Monday.

It is the first time foreigners have been arrested in China on the charge of conducting illegal investigations.

The couple, 58-year-old British national Peter William Humphrey, a former Reuters reporter, and his 61-year-old American wife, Yu Yingzeng, were detained last year for working as private eyes for GlaxoSmithKline (GSK) China's then general manager Mark Reilly.

Humphrey and Yu registered an investigation company in Hong Kong in 2003, according to CCTV news. The company is only a shell firm, with no office, no receptionist and only a telephone that transfers to a secretary, China Central Television (CCTV) quoted Ding Zhidong, an official at the Shanghai public security bureau, as saying.

In 2004, the couple registered another company in Shanghai. From 2009 to 2014, they received requests to investigate thousands of companies and individuals, CCTV reported.

The couple exchanged money for information, including information on individuals' family background, real estate holdings, vehicle and household registration details, as well as exit-entry records.

Besides illegally purchasing information, the couple also obtained information through photographic surveillance, infiltration and tailing the subjects of their investigations, Xinhua said. The couple compiled reports based on the information obtained and sold them at high prices to their clients, mostly multinational corporations, including GSK China.

Xinhua reported that Humphrey admitted he was contacted by Reilly and GSK's legal department director Zhao Hongyan in 2013. The couple was prepaid 100,000 yuan ($16,143) to find the informant who sent anonymous e-mails of intimate video of Reilly and his girlfriend, as well as e-mails that disclosed GSK China's bribery scandals to Chinese authorities and GSK's executives.

Humphrey told CCTV in a Shanghai police station that he "deeply regrets" breaking Chinese law. 

According to Chinese Criminal Law, people who sell or illegally provide Chinese citizens' private information to others will be sentenced to no more than three years in prison as well as charged a fine.