Singapore-based Effissimo Capital Management, which owns around 10% of Toshiba, on Thursday said it wants to determine whether the July 31 AGM "was conducted in a fair and impartial manner".
The Japanese firm has said over 1,000 postal voting forms went uncounted due to inappropriate vote-counting practices by its shareholder registry administrator Sumitomo Mitsui Trust Bank.
Reuters reported that representatives of Japan's government contacted several foreign shareholders ahead of the AGM in what at least one described as an attempt to influence voting.
Effissimo in a statement on Thursday said Toshiba did not respond to a request to establish a committee made up exclusively of independent members to investigate whether the meeting was conducted fairly.
The activist hedge fund said it interviewed "several dozen" major shareholders and "confirmed that there were in fact shareholders that have given up exercising their voting rights due to such pressure."
It also said there are "a number of abnormal facts" related to the tallying of votes which cannot be explained by Sumitomo Mitsui Trust Bank's inappropriate vote counting.
Toshiba said it a statement that it would carefully review the convocation request for the extraordinary shareholders meeting and consider how Toshiba deals with such request.
(Reporting by Makiko Yamazaki; Editing by Himani Sarkar, Christopher Cushing and David Evans)
By Makiko Yamazaki
