Billionaire activist investor Daniel Loeb sent a letter to Sotheby's shareholders on Friday calling for the ousting of the auction house's board members.

Loeb insists that a “dysfunctional corporate culture” at Sotheby's is resulting in lackluster results and poor management. He is pushing for 3 seats on Sotheby's board for his hedge fund, Third Point, and sued the company last week over a poison pill provision that prevents the board changes he wants.

Sotheby's shares fell 2.4 percent, to $42.78, after the letter's release.