The Spice Girls singer is said to have impressed viewers and show bosses after she appeared in last weekend's first episode as a guest judge.
Producers have now agreed a last minute five-figure contract with Mel C to join Lord Andrew Lloyd Webber, Dawn French and Jason Donovan on a permanent basis.
"I am absolutely delighted," she is quoted as saying in The Sun.
"It's been an incredible experience so far and I just can't wait for the nation to decide who will be playing Jesus in the amazing arena tour of the production."
She will take on the role of Mary Magdalene in the new arena tour of Jesus Christ Superstar, alongside Chris Moyles and Tim Minchin and the show's chosen Jesus.