Fisher was due to return to The Sound of Music tour for its dates in Cardiff, Manchester, Newcastle and Wimbledon from 23 August to 22 October, having last appeared in the musical's Oxford dates, taking over from Emmerdale star Verity Rushworth.
In a statement released this morning, the show's producers have confirmed that despite "intensive therapy and coaching" Fisher's voice "has not recovered sufficiently for her to tackle the demands of the role of Maria."
Fisher said in the statement: "After many months of battling with a throat condition known as congenital sulcus vocalis, my vocal range has altered dramatically and it is with much regret that I have to withdraw from The Sound of Music as I no longer have the range to sing the part of Maria.
"My journey with this amazing show has been such a magical one and I am devastated that I am not able to close the tour."
The show's producers David Ian and Andrew Lloyd Webber's Really Useful Group have announced that Rushworth will continue in the role, playing Maria alongside Jason Donovan's Captain von Trapp for the remainder of the tour.
The Sound of Music has music by Richard Rodgers and lyrics by Oscar Hammerstein, with a book by Howard Lindsay and Russel Crouse. The touring production is directed by Jeremy Sams, with choreography by Arlene Phillips, design by Robert Jones, sound by Mick Potter and lighting by Mark Henderson.
The musical launched its first tour from Wales Millennium Centre in July 2009 following 954 performances at the London Palladium. This tour embarked from Hull's New Theatre on 29 January 2011 and has visited Mold, Stoke-on-Trent, Derry, Dublin, Glasgow, Leeds, Oldham and Nottingham. The show opens in Norwich this evening (9 August), running until 20 August 2011.
The Sound of Music first opened in London in 1961 and was revived in London in 1981. The 1965 Hollywood film, which starred Julie Andrews and Christopher Plummer, won five Oscars, including Best Picture.