(Reuters) - The California Public Employees' Retirement System said on Monday it will vote against all 12 director nominees at Exxon, citing the company's lawsuit against activist investors.

The system known as CalPERS said in a letter to its members posted online that if successful, Exxon's legal action "could diminish the role-and the rights-of every investor in improving a company's bottom line."

Exxon's shareholder meeting is set for May 29.