TOKYO, Oct 24 (Reuters) - Cosmo Energy Holdings said on Tuesday it would call another shareholder vote on a "poison pill" takeover defence against a group of activist investors, escalating the high-profile battle.

Cosmo, however, said it will not eliminate the group, led by prominent activist Yoshiaki Murakami, from voting this time, unlike the previous vote in June.

The tactics, a so-called majority-of-minority vote, has fuelled concerns among governance experts that it could be interpreted as authorising a board to refuse to count the votes of certain unwelcome shareholders in some circumstances. (Reporting by Makiko Yamazaki; Editing by Christian Schmollinger)