Sony, the Japanese electronics company, has made an important breakthrough in its efforts to combat large-scale piracy of its PlayStation games console in China after a long investigati on that uncovered parts being assembled in a prison.

The probe, conducted over five years, has unearthed a web of at least 10 sub- contractors with a production capacity of 50,000 units a day for PlayStation consoles and controllers, as well as "modifying" chips.