Legal & General Investment Management (LGIM) will also vote against all Topix 100 <.TOPX100> companies in Japan that do not have at least one woman on their board, it said in a statement.
The separation of CEO and board chair roles provides a better balance of authority and responsibility, Sacha Sadan, director of investment stewardship at LGIM said, adding there was "a worrying trend of companies splitting the roles after a scandal, then recombining over time".
"We are sending a very clear message that we will not support a combined role going forward,” Sadan said.
LGIM said the issue was particularly acute in the United States, France and Spain. Forty-seven percent of S&P 500 boards have combined CEO and board chair roles and 20% of IBEX 35 companies in Spain do, along with 53% of France's CAC 40 companies, it said.
The percentage of women board members at Japan's TOPIX 100 companies rose above 10% for the first time last year, but this compares with 30% of Britain's FTSE 350 and 27% of the S&P 500, LGIM said.
It said it would also vote against the largest 100 companies in the S&P 500 and Canada's S&P/TSX where there are currently fewer than 25% of women on boards, as it extends voting on board diversity first introduced in 2015.
(Reporting by Carolyn Cohn; Editing by Rachel Armstrong and Mark Potter)
