The 54-year-old singer says she had remained silent until now because she was afraid because people in the music industry would view her as "public enemy number one" for "snitching".
“I was afraid to speak out as I didn’t want to end up in somebody’s car boot. These men are all powerful people," she said.
But the #MeToo movement has finally given her the courage to speak out now.
“I’m talking now as I don’t want any more girls and women in the industry to have to go through what I did.”
In an interview with the Mirror newspaper, Sinitta told how she had to fight off one man at one of Simon Cowell's parties. She told the man to "keep his fucking hands off”.
In an extract from her forthcoming "video book" entitled 'Who Put The Sin In Sinitta' , she recalls how on another occasion an influential music figure tried to force her to perform oral sex on him.
"I remember being sat down and he was stood up. He started to unzip his trousers and exposed his manhood," she recalled.
“He grabbed the back of my head and tried to force me towards him.
"I pushed him away and told him my mother would be arriving soon, which was a lie. He eventually left. I felt traumatised.
“I initially thought he wanted to help with my career. But, as I found later on, people always wanted more.”
She recalled how Simon Cowell, who was her boyfriend for a period back in the 1980s, came to her rescue on another occasion when she was being sexually harassed
"An artist grabbed me up. He was a big star I had watched since I was tiny," she explained.
"I was coming out of the toilet and he was going in. He pushed me into a corner and touched me up. He tried to put his tongue down my throat. I froze.
“It was horrible. I stumbled down the stairs and told Simon. Simon went off at him. When he loses his temper it’s quite scary as you’re not used to it.”
She said the last horrific incident occurred two years ago when an influential figure grabbed her and attempted to stick his tongue down her throat.
Her new video book, which is a series of 60 videos, will be available from her website this Friday - www.Sinitta.com