The head of a minor opposition party critical of public broadcaster NHK was referred to prosecutors Wednesday on suspicion of threatening an assemblyman in Tokyo in a YouTube video, sources close to the matter said.

Takashi Tachibana of the NHK Kara Kokumin Wo Mamoru To (the party to protect the people from NHK) allegedly intimidated the assembly member of Tokyo's Chuo Ward in July by uploading the video in which he said, "I'll ruin this guy's life thoroughly," according to the sources.

The assemblyman, who was supported by Tachibana's party in April's local election, has left the party over a financial problem, the sources said. The police questioned Tachibana after the man filed a complaint with the police.

Tachibana has recently said his remarks should not be a problem but he would resign as a House of Councillors member if he is convicted.

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