TV personality Esther Rantzen, who founded children's helpline ChildLine, has said she was the victim of child abuse herself as a schoolgirl.
As the charity approaches its 25th anniversary, Ms Rantzen admitted she was molested by a "relative" in the 1950s.
The That's Life star, who campaigned to become an MP in Luton last year, made the disclosure when being interviewed about the creation of ChildLine in 1986.
Ms Rantzen founded the service after a one-off BBC TV programme Childwatch was inundated with calls by children desperate for help.
The charity now offers a 24/7 helpline for children in danger or distress.
Today Ms Rantzen said she decided to talk about what happened to her when she was asked by a journalist if any one moment in her own childhood had influenced her decision to want to set up ChildLine.
"I went to talk about the beginning of ChildLine and how it happened and then he said, 'have you ever experienced something like this in your own life?, and you've got the decision at that moment, you either refuse to answer or you tell the truth.
"I felt that it was really incumbent on me, since we encourage children to talk to us, and since the book I'm doing called Running out of Tears is based on adults' memories of their own childhood, I couldn't very well not go down that road myself."
She has described the incident, which happened when she was a schoolgirl, as a "grope" by the man, who was not a blood relative, but "somebody who was called an uncle".
Ms Rantzen said the man, now dead, did not repeat the abuse, but had told her not to tell anyone.
"What I would stress is that my experience was nothing compared with the children that ring ChildLine," she said.
"This was not a prolonged gruelling process. It was not something that happened over many years, which happens to many children who ring ChildLine.
"Although he tried to shut me up he didn't do it by saying I brought it on myself or it was all my fault. He just told me not to tell anyone."
Ms Rantzen tried to tell her mother, but admitted it "was not her finest hour".
"I told my mum, but it wasn't her finest hour bless her," she said. "She was a fantastic mother in every way, but in this case she couldn't accept it was a fact."
Ms Rantzen said what had happened to her did not spark her efforts to launch ChildLine but may have contributed to them.
"From my point of view I don't feel that it in any way prompted the creation of ChildLine although there may have been, at a level, a sensitivity in me, an understanding of how children feel when somebody within the family circle treats them badly.
"But in those early days, in our very earliest times, I thought children would be asking us to put them in touch with social services, I didn't realise that that's the last thing that most children want.
"What they want is to talk safely about their own feelings, often the feeling that they are to blame for what has happened, and our job is to raise their feeling of self-esteem and confidence so they recognise that abuse is never the child's fault, never.
"And then we explore options with them, like who they can talk to safely in their life.
"And if they want us to refer them to social services and the police, we do, but we work at the child's pace because what we don't want is for a child to be so frightened that they never call us back."