LARRY BIRKHEAD has promised to take legal action against the author of a new book about the death of his ex-girlfriend Anna Nicole Smith - if the tome states he and Smith's attorney HOWARD K. STERN were gay lovers. Journalist Rita Cosby's Blonde Ambition: The Untold Story Behind Anna Nicole Smith's Death, which is released on Tuesday (04Sep07), also claims Birkhead and Stern struck a deal to share Smith's millions, according to the New York Daily News. A furious Birkhead insists he will sue Cosby if either accusation does prove to be in the book. He tells website TMZ.com, "If she printed that (Stern and I were lovers) then she is really getting sued. My attorneys are going after her and that is absolutely false. "And I am sure Howard and the estate and everyone else involved is going to sue her too. This is just nonsense." Birkhead won his paternity battle with Stern to be named the biological father of Smith's one-year-old daughter Dannielynn in April (07). Smith died in February (07).