A series of data leaks from a $20bn internet company masterminded by SoftBank founder Masayoshi Son is straining relations between allies and showing how government concerns over digital security can curb tech groups’ international ambitions.

Japan and South Korea have been at loggerheads since Line Yahoo — originally a messaging app in Japan created by South Koreans — suffered network breaches that were blamed on insecure systems at Seoul-based Naver, its joint owner. 

Officials in Tokyo have used national and economic security grounds to argue that Naver should now cut its 50 per cent stake in A Holdings, the holding company for Line and Yahoo Japan, according to people familiar with the matter. But this would give the other joint owner, SoftBank Corp, the chance to seize control.