Sharon Osbourne says her stomach would be 'knotted with anxiety' at the prospect of sitting next to former panellist Dannii Minogue during her previous stint on The X Factor.
She said she found working with her to be 'unbearable' as Dannii became increasingly close to X Factor boss and head judge Simon Cowell and began calling the shots.
And in Sharon's new autobiography, being serialised by The Sun, she said the situation between her and the Australian singer - who it later transpired had been having an affair with Simon - became 'unbelievably bad'.
Sharon said of Dannii: "The antics behind the screen had gone up a gear with her sticking her tongue in Simon's ear and giggling like a b****y teenager as Louis Walsh and I stood there like a couple of gooseberries.
"For me it made her so unbearable to work with that I just couldn't take it. It was horrible. My stomach knotted with anxiety about it and as each show loomed I would wake up and think 'Oh God, I have to spend the day sitting alongside her again'.
"During filming it was obvious to me that there was some sort of relationship going on between them. And the more it progressed, the worse it became between her and me. It was unbelievably bad."
She said Dannii would walk past her without even making eye contact and, after three enjoyable series, Dannii's arrival meant it was 'rapidly turning into an odious chore - I found it hard dealing with a sulker'.
A bid to clear the air between them fell on deaf ears, Sharon said, so she eventually called a meeting with Simon, giving him an ultimatum that either Dannii was axed or she intended to quit.
X Factor creator Simon said he wanted both to stay, but during protracted negotiations about fees in 2008 Sharon felt she could no longer handle 'that toxic atmosphere of standing behind that screen inches away from someone exuding utter disdain'.
She admits in her book Unbreakable - to be published on October 10 by Little, Brown - that the main reason she left the series was because she didn't get the pay she was demanding, but added: "The Dannii business was in there too."
