The girl group, which also included Natasha Hamilton, was plagued by in-fighting and one bust-up resulted in a physical fight between Katona and McClarnon.
Speaking about the drama on Thursday's episode of The Big Reunion, which documents the band, among other UK acts, forging a comeback, Katona reveals she fell out with her bandmate after bringing McFadden with her to an event.
She says: "I rang the tour manager up and said: 'Look, can Brian come with us in the car?'. We picked Tash up and then went to pick Liz up and Liz had come walking out with her younger brother Joe..."
McClarnon adds: "Because Brian was already in the car, the main thing was that Joe was just not going to be able to get in the car so that really, really, really annoyed me. I hit her..."
Katona recalls: "Well that was it, I undid my seat belt, I jumped over, I've gone for her. She's absolutely s***ing herself in the back of the car. I kicked her out the car, (we) drove off and left her in the street. I was screaming, I was so angry."
Katona quit the band just days before the release of breakthrough international hit Whole Again in 2001 and was replaced by singer Jenny Frost, but the original trio has reunited for the reality show and a one-off comeback show in London later this month.