LOS ANGELES—Howard K. Stern says claims in a new book that he and Anna Nicole Smith’s ex-boyfriend Larry Birkhead had a videotaped gay sexual encounter before her death are absurd and could psychologically damage Smith’s infant daughter.

“It’s ridiculous. I mean it’s absolutely absurd,” Stern told ETonline.com.

The website said it obtained the comments from Stern during a birthday party for Smith’s 1-year-old daughter, Dannielynn, in Louisville, Kentucky, Sept. 8. The party was held by Birkhead, who has custody of the girl after Stern, Smith’s lawyer and companion, initially claimed to be Dannielynn’s father.

Birkhead and an attorney for Stern previously indicated they would sue over claims made in Rita Cosby’s book “Blonde Ambition: The Untold Story Behind Anna Nicole Smith’s Death.” Birkhead, who is Dannielynn’s father, also has denied any encounter occurred.

Smith, a former Playboy Playmate, gave birth to Dannielynn a few days before the death of her son, Daniel, 20, last September in the Bahamas. Smith died of an accidental drug overdose in Florida in February at age 39.