Sharon: "We all knew about Simon & Dannii"

Sharon Osbourne has insisted "everyone knew" about the affair between fellow X Factor judges Dannii Minogue and Simon Cowell.

She told The Mirror: "Dannii wanted to be the mistress of Simon - and the mistress of X Factor," the Daily Mail reports.

Sharon insisted the affair "wasn't a secret", as Simon had already publicly split from Terri Seymour.

RELATED: Simon & Dannii's secret fling

News of Simon and Dannii's 2008 fling broke with the release of former BBC journalist Tom Bower's new book Sweet Revenge: The Intimate Life of Simon Cowell, which claims that the music mogul had a 'genuine love' for Minogue during their time as X Factor judges.

Ozzy Osbourne, Richard Desmond, Sharon Osbourne and Simon Cowell at the Elton John AIDS Foundation Oscar Party in 2007. Source: Getty

Sharon has had an ongoing feud with Dannii since appearing with her on X Factor and leaving abruptly in 2008.

But the reality TV star insists she didn't leave show because of Simon and Dannii: "I left because she became unbearable. She started bossing everyone around, even the producers."