The actress spoke out after a Sunday Mirror article said that she had signed up to play Elsie Tanner in Street of Dreams.
Street of Dreams is a live musical event which has its world premiere in Manchester next month, exploring the most memorable moments from Coronation Street's 51-year history.
Writing on Twitter last night (February 19), Marsh commented: "Just wanted to put the record straight regarding Corrie musical. I have been in talks but nothing is confirmed yet."
She added: "I feel the story is a little premature."
A number of Coronation Street stars past and present have already been confirmed for the production, including Bill Roache (Ken Barlow), Katy Cavanagh (Julie Carp), Kevin Kennedy (Curly Watts), Julie Goodyear (Bet Lynch) and Brian Capron (Richard Hillman).
Comedian Paul O'Grady will narrate the show and interact with the characters on stage.
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Watch a promo for Coronation Street's Street of Dreams musical below: