Judy Lewis, who learned as an adult that she was the illegitimate daughter of classic Hollywood stars Clark Gable and Loretta Young, has died aged 76.

Ms Young became pregnant with Ms Lewis during the filming of The Call of the Wild (1935). She concealed the pregnancy to avoid scandal and then raised the child as her adopted daughter.

Clark Gable, the dashing star of Gone with the Wind, never acknowledged his daughter but visited her once when she was 15.

Ms Lewis recounted her story in a 1994 memoir entitled Uncommon Knowledge.

Ms Young was single and 22 when she became pregnant and Clark Gable was married. To avoid scandal the devoutly Catholic actress went abroad during the later stage of her pregnancy and returned to Los Angeles to give birth in secret.

When Ms Lewis was eight months old, her mother placed her in a Catholic orphanage but went back a month later to adopt her.

Ms Lewis’s origins were an open secret in Hollywood, but her friends were instructed never to tell her. However, her ears stuck out from the sides of her head the same way Clark Gable’s did, to the extent that she first concealed them under bonnets and then underwent surgery when she was seven to pin them back.

One day in 1950 Ms Lewis came home from school to find the screen legend Gable standing in her front hallway. “I couldn’t believe my eyes,” she wrote in her memoir. “He was right in front of me, and he was smiling at me. His eyes were crinkled into smile lines at the corners and he was so tall that I had to look up.

“He was much more handsome than I remembered him from the movies... I was speechless.”

He spoke to her for the next hour, asking her about herself, then kissed her on the forehead and left. She never saw him again, and was not told he was her father until her fiance broke the news several years later. Ms Lewis initially followed in her parents’ footsteps as an actress, starring in soap operas and Broadway shows, but later became a marriage and family therapist, working with pregnant teens and foster children.

When Ms Lewis’s memoir came out, Ms Young publicly denied that Gable was the father of her child, and only ever admitted to the affair from the grave, in an authorised biography published after her death in 2000.

In 2002 Lewis told the London Telegraph how she would cry when she watched the tender scenes of Gable and his on-screen daughter in “Gone with the Wind.”

“It’s very sad to me... because he’s so dear with her. I pretend it’s me.”

Ms Lewis died of cancer in Gladwyne, Pennsylvania yesterday, according to her daughter, Maria Tinney Dagit. She is also survived by two grandsons and three half-brothers.