She was one fifth of the most successful British girl group of all time, but Victoria Beckham "always felt uncomfortable" in the Spice Girls, according to media mogul Simon Fuller.
The band's former manager said Beckham could sing and dance "pretty well" when she found fame as Posh Spice but only discovered her "true vocation" when she quit music and began working in the fashion industry.
Simon, who continues to manage Victoria and her husband David, was speaking on stage after he was named entrepreneur of the year at the Business Innovation Awards in Los Angeles.
He said: "Victoria, coming out of the Spice Girls, being married to David Beckham, launched a solo career. She never felt comfortable. Even in the Spice Girls - it was great fun, she was in the world's biggest group for two or three years - but she didn't feel comfortable.
"She could sing pretty well, she could dance pretty well, but she always felt uncomfortable.
"When the Spice Girls broke up, she had a few songs as a solo artist but she wasn't happy and she said to me 'Simon, I just don't want to do music any more. What do you think I should do?'
"It was one of those things that you get this kind of clarity of vision. I've known Victoria since she was 18 and her passion in life was always clothes. She was called Posh Spice because she always wore the best dresses and she knew everything about clothes.
"I said 'You should be in fashion. You should be a designer'."
Speaking to television producer Nigel Lythgoe, Simon said Victoria, 42, had since found her "passion in life" and true vocation.
"She's now a legitimate fashion designer," he added. "Her company is worth literally hundreds of millions of dollars and there's no stopping her. She will be - without any doubt - one of the world's greatest designers in the next few years."
Victoria has reportedly ruled out performing with the Spice Girls for a planned 20th anniversary tour, while a source told The Sun that Mel C had also dropped out of talks.
Simon, 55, built his multimillion-pound fortune creating television shows such as Pop Idol and American Idol and managing musicians including Annie Lennox, Amy Winehouse, Will Young and Kelly Clarkson. His management agency XIX Entertainment has looked after talent including David Beckham, Andy Murray, Sir Bradley Wiggins and Lewis Hamilton.
During the ceremony at the InterContinental Hotel, a message from Prime Minister David Cameron paying tribute to Simon was read by Chris O'Connor, British consul general in south-west US.
The Prime Minister said: "Simon Fuller represents an impressive example of British entrepreneurial talent.
"It's great we have successful business role models like Simon showing how British creativity and entrepreneurial spirit can flourish on the world stage. I congratulate him on this award."