Activist investor Ron Burkle sent a letter to Barnes & Noble Inc. seeking to acquire as much as 37 percent of the company, up from his current stake of 19 percent, and blasting the book retailer for having different sets of anti-takeover rules for big investors: one applying to insiders and one applying to outsiders.

In November Barnes & Noble disclosed that its board had adopted a shareholder-rights plan, also known as a “poison pill,” in response to the recent rapid accumulation of the bookstore chain’s stock by an unnamed investor, who turned out to be Burkle.

Now the billionaire and his investment firm, Yucaipa Cos., are seeking to raise their stake to 37 percent without triggering the shareholders-rights plan. In his letter to the Barnes & Noble board, Burkle said it was unfair for the Riggio family, which founded the company, to own 37 percent of the shares while no other shareholder can hold 20 percent without triggering the rights plan, designed to thwart any potential hostile-takeover effort.

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