A group of CBS Corp. investors have joined the fray in the ongoing legal battle over control of the media giant, accusing Shari Redstone and her family’s National Amusements Inc. holding company of improperly trying to block a CBS stock dividend that would dilute Redstone’s voting rights.

The new lawsuit, filed Thursday by a Pennsylvania-based pension fund, asserted individual and class action claims against CBS’s controlling stockholder, adding yet another layer to the unfolding saga in Delaware Chancery Court.