Kaiser Aluminum criticized an investor’s bid.

The Oakland-based company said the investment group, led by J. A. Frates of Tulsa, Okla., doesn’t have “anything at all to offer Kaiser Aluminum shareholders.” The group, which controls about 5.65% of Kaiser’s shares, said it was dissatisfied with the slowness of Kaiser’s restructuring. Kaiser’s response reaffirmed its plan and called the proposals completely unsolicited, unwelcome and without substance. The company also said that the group lacks the financial resources to execute its plans.