The youngest female cast member of Australian television comedy Hey Dad! says she was sexually abused on the set of the top-rating program.

Sarah Monahan played schoolgirl Jenny Kelly. She was nine years old when she began work on the series, which aired on the Seven Network from 1987 to 1994.

Monahan has told Woman’s Day magazine that a male who worked on the show fondled her and exposed himself to her.

She did not name the man, nor did she say if he was a member of the cast or crew.

“This person used to sit me on his lap or tickle me, but then he started putting his arm around me and trying to do this reach-around and grabbing me, but at the same time trying to feel me up,” she was quoted as saying in the magazine.

“He was always there flashing me or trying to cop a feel.

“I quickly learned never to be alone in private with him, especially when he started flashing me.”

Monahan was her family’s breadwinner after her father died and she feared speaking up would mean she would lose her job.

Former co-star Julie McGregor, who played Betty Wilson, described Monahan as a “very popular little girl” and says she is shocked by the allegations.

“I had heard something but I had no idea the extent of the monstering … and I feel sorry for her that there was no-one that she could feel she could turn to,” she told the Nine Network.

“I think whoever this person was was very clever. They knew how to operate.”

Chris Truswell, who played family friend Gerald “Nudge” Noritis, fears people will think he is the alleged assailant.

Both Truswell and McGregor say they have no idea of the identity of Monahan’s alleged assailant and never saw any inappropriate behaviour.

Monahan now lives in the US making TV programs with her husband.

- AAP