The singer, aka Baby Spice, was onstage at the Staples Center as part of the girl group's Return of the Spice Girls tour, when milk leaked from her boobs onto the designer outfit.
Four months prior to the U.S. shows, the mother-of-two had given birth to son Beau, now 13, and she recalls her partner, Jade Jones, rushing to find her pads backstage to stop the breast milk ruining the outfit.
In an excerpt from her "Mama You Got This" book, published in The Sun newspaper, Emma writes, "Our costumes had been designed by Roberto Cavalli, who Victoria [Beckham] knew, and oh my goodness they were beautiful. But stage costumes are different to evening wear. These were heavy, highly structured pieces (they had to withstand quite a lot of activity!) and there were frequent changes."
"I remember it happened during 'Say You'll Be There' - I was wearing a rose-gold dress with an empire line and a high neck, with gold lame that was quite close-fitting over my boobs. I had to get through a whole other track, Headlines, just hoping nothing was showing."
"As it ended I came running off stage screaming at Jade, 'Babes, get the pads! Get the pads!' Luckily, as it turns out, gold lame isn't very porous and most of the milk had just drizzled down my stomach. But anyone looking close enough would definitely have been able to spot wet patches on my boobs during that number."
She adds, "I can look back and smile about it now, but when I look at the pictures I also see a woman who really wasn't ready to be throwing herself into that kind of physically demanding regime. I simply hadn't understood the huge processes that my body would be going through after birth and, in particular, how breastfeeding would require so much energy."