According to new unauthorised biography, `Sweet Revenge: The Intimate Life of SimonCowell`, the 59-year-old matriarch "exploded" with rage upon learning that Simon was sleeping with Dannii Minogue when they all worked on the UK `X Factor`.
Now the matriarch - who eventually quit the show in 2008 because she no longer wanted to work with Dannii - has taken aim at her old boss from involving her in his "world of debauchery".
She said: "I`m not Simon`s mother - I don`t give a toss who he f***s.
"That`s none of my business. I think Simon thought he`d have complete control over this book. "But how dare he bring me into it now? I don`t want to be dragged into his little world of debauchery, thank you very much.
"I get on absolutely fine withSimon - and he will be fine - but I am p***ed off to be brought into it all again."
Her rows with Dannii became notorious, although Sharon argues they had nothing to do with Dannii`s reported romance withSimon.
She told the Daily Mirror: "Dannii wanted to be the mistress of SimonCowell - and the mistress of `X Factor`.
"But I didn`t leave the show because Simon and Dannii were f***ing, I left because she became unbearable. She started bossing everyone around, even the producers.
"We all knew Simon and Dannii were seeing each other, it wasn`t a secret. I don`t know why he tried to hide it from everyone though."