Mel C snubbed the Spice Girls' manager Simon Fuller by not thanking him in the cover notes for the band's new album.
The singer - who had to be persuaded by Fuller to reunite with Victoria Beckham, Emma Bunton, Geri Halliwell and Mel B - is reportedly the only one of the five girls who didn't thank the music mogul in the album sleeve of their greatest hits LP.
Her relationship with Fuller has always been tempestuous, but allegedly worsened recently after he ordered her to have singing lessons before the band's world tour begins.
A source close to the group said: "The girls have been told by Simon Fuller that they need to get their voices back in training and should start having singing lessons as soon as possible.
"But Mel C is furious as she thinks her voice is already in shape."
The Spice Girls tour begins in Vancouver, Canada, on December 2, and the band will be performing together for the first time in seven years tonight (15.11.07) as part of the Victoria's Secret fashion show.
They will also be performing live from Los Angeles on the BBC's 'Children In Need' charity telethon tomorrow night.