During a garden party last week, Yamamoto gave a letter to Emperor Akihito outlining what he believes were problems stemming from radioactive fallout from the Fukushima No. 1 nuclear power plant. Yamamoto was criticized for attempting to use the emperor for political purposes, an accusation the lawmaker denied.
Upper House President Masaaki Yamazaki proposed Friday that Yamamoto not be allowed to participate in any event hosted by the Imperial family for the remainder of his six-year year term unless the chamber decides to lift the ban, The Japan Times reported.
The Times said Yamamoto's name no longer would be on a list submitted to the Imperial Household Agency by the chamber's secretary of members who can participate in parties, ceremonies and other events hosted by the Imperial family.
The steering committee also said it would submit a resolution to the full chamber that would punish lawmaker Antonio Inoki for visiting North Korea without the upper house's permission, the Times said.
If members approve the resolution next week, the chamber's Political Ethics Committee will decide the specific punishment, one of four actions ranging from admonition to expulsion.
Inoki, a former pro wrestler elected in July on the opposition Japan Restoration Party ticket, returned to Tokyo Thursday after visiting North Korea and meeting with top officials. Inoki went to Pyongyang after the Upper House Steering Committee voted not to approve the visit.