Mr Somchai, 61, will not take office until he is endorsed by King Bhumibol Adulyadej, a process that could take several days. However, anti-government protesters who have occupied the grounds of the prime minister’s offices for three weeks have already vowed to continue their rally to force Mr Somchai from power.

It is the first ruling against the family of telecommunications tycoon Thaksin Shinawatra’s family since the 2006 military coup that toppled him from power. The military junta has long alleged that Mr Thaksin and his family engaged in corrupt practices during his time in office.