Kerry Katona, who was performing alongside Atomic Kitten bandmates Liz McClarnon and Natasha Hamilton for the first time in 13 years, suffered a nip-slip as she belted out one of their hit tracks.
The 32-year-old singer wore a tight bright lime green top under a black boiler suit, for the concert at the Hammersmith Apollo, the Sun reported.
As the re-united band performed a string of their hits, including The Tide Is High, Whole Again and Right Now, the mum-of-four's outfit could no longer contain her breasts, and one spilled out.
Meanwhile, McClarnon, 31, showed off her legs in a green mini-skirt and black strappy heels, which she teamed with a lacy black top.
While Natasha, 30, performed in a see-through orange skirt, with what looked to be a black leotard underneath and bright turquoise heels.