Theatre impresario Andrew Lloyd Webber has hit back at claims that How Do You Solve A Problem Like Maria? is a con.
Lord Lloyd Webber said Connie Fisher was his choice for the role
Connie Fisher, 23, won the BBC One talent show to find a newcomer to play the lead role in his forthcoming West End version of The Sound of Music.
But critics have raised questions over how many times Ms Fisher will perform.
Lord Lloyd-Webber said she would appear at the London Palladium six times a week, adding it was his "duty" to protect her voice from damage.
He said it was "absolutely normal" for a younger leading lady to sing fewer than eight performances a week.
"I am irritated by some of the nonsense that has been written about this," he said.
"We have a duty to consider what is best for Connie's career in the longer run.
"We certainly do not want her ending up like Julie Andrews who strained her voice when young and who can no longer sing."
Emma Williams, who has previously starred in Chitty Chitty Bang Bang, will play Maria on the nights Fisher does not perform.
"It is absolutely normal for a younger leading lady to sing only six out of eight possible performances a week," explained Lord Lloyd-Webber.
"This was the case when Sarah Brightman starred in The Phantom of the Opera at the age of 22.
"It was the same for Elaine Paige in Evita and is true of Elena Roger who is starring in the new production of Evita."
The new production of The Sound of Music will open in November.
Ms Fisher, a call centre worker, beat fellow Maria contestants Helena Blackman and Siobhan Dillon in the grand final on Saturday night.
She said she hoped the opportunity would lead to a long career in musical theatre.
"I would love to do eight shows a week," she told BBC News 24. "But I have to test my stamina."