Sharon Osbourne has come clean about the intense rivalry between her and Danni Minogue during the period they spent as fellow judges on the X Factor.

"Dannii had taken to walking past me in the hallway without even making eye contact. I'd like to say it didn't bother me, but it did," Osbourne reveals in her new book Unbreakable, currently serialised in The Sun.

As Simon Cowell and Dannii grew closer, Osbourne said she felt her "stomach was constantly knotted with anxiety".

"The more it progressed, the worse it became between her and me," the 60-year old recalled. "It was unbelievably bad.

"The antics behind the screen had gone up a gear, with her sticking her tongue in Simon's ear and giggling like a bloody teenager as Louis Walsh and me stood there like a couple of gooseberries."

Simon, Sharon and Danni were fellow judges on the X Factor in 2007

Sharon, who has returned as a judge on this year’s X Factor, did her best to resolve the situation by arranging talks between her, Dannii and the show’s executive producer Richard Holloway. Unfortunately this did little to resolve the situation.

In her autobiography, Osbourne wrote that she was forced to give Simon Cowell an ultimatum between herself and Minogue, although the X Factor boss refused to choose.

"'Sharon, I'm not doing it.' His firm tone left me in no doubt this wasn't a matter for debate," she recalled. "'I don't want you to go and I don't want her to go either. So think about it.'"

Osbourne admitted that the money was the main issue for leaving the talent show, "but the Dannii business was mixed in there too".

Unbreakable by Sharon Osbourne is published on October 10.