According to STV, Cornish has agreed to appear in W.E., the pop icon's second film as a director, which centres on the relationship between Britain's King Edward VIII and Wallis Simpson, the Duchess of Windsor.
Madonna, who was originally planning to play the part of Wallis, has reportedly reconsidered and is now said to be in talks with Up In The Air actress Vera Farmiga.
The 51-year-old, who shares writing credits on the film's screenplay with Alek Keshishian, is to also direct the movie. Madonna has previously directed Filth And Wisdom and served as a writer on the documentary I Am Because We Are.
W.E is currently in pre-production and is slated for release sometime in 2011.