(Reuters) - Blackwells Capital said on Monday Walt Disney failed to tell shareholders that ValueAct Capital Management had invested more than $350 million of the U.S. entertainment giant's pension fund assets, creating a conflict of interest.

"ValueAct's management of Disney's pension funds is not disclosed anywhere in any of the referenced communications," Blackwells Chief Investment Officer Jason Aintabi wrote in a public letter to Disney shareholders.

"Meanwhile, Disney's entire shareholder franchise population has been led to believe that ValueAct provided its independent and unqualified support of the Board independently."

Blackwells urged shareholders to disregard ValueAct's endorsement of Walt Disney's board in the upcoming elections of the board of directors.

Disney is relying on ValueAct's endorsement at a time when it is fighting to fend off two other activist-investors - Blackwells and Trian Fund Management - as each firm lobbies for seats on the Disney board.

Neither Disney nor ValueAct immediately responded to requests for comment.

ValueAct, which built a stake in Disney last year and reached an information sharing agreement in January to help advise Disney on strategic matters, last week publicly supported the Disney board at the Council of Institutional Investors conference.

Like many hedge funds, ValueAct and Trian also earn fees by investing capital on behalf of big corporations.

(Reporting by Chandni Shah in Bengaluru and Svea Herbst-Bayliss; Editing by Sherry Jacob-Phillips)