The singer was invited by producers to audition for the show and come face to face with her former bandmate in Mel.
It turns out that she and Lianne had been a girl group before The Spice Girls, but Lianne was replaced by Emma Bunton just before the five piece hit the big time.
After singing for the judges in London however, Mel was unimpressed with Lianne and told her: “Were you in pain?
“You looked like you were in pain. It was painful to listen to.”
Speaking at the weekend, Lianne complained: “Mel was very cruel and it shocked me that she tore into me so easily.
"I know she’s got a reputation to maintain as a feisty, fiery character but she got really personal.
“I wouldn’t usually take it to heart but producers tracked me down and begged me to go on the show only to try to make me look stupid.”
Speaking to The Sun on Sunday newspaper, Lianne also complained that Mel claimed that to didn't remember who she was.
She told the tabloid: “Mel B was very different back then. She was young, ambitious and hungry. We all had a real laugh and she was very down to earth.
“Mel and I were at the same point of our lives, trying to get on as singers, so she would definitely have remembered me.”
Lianne added: "Mel spoke so coldly. I was in a band with her once but she just cut me down. I have never got personal with her.
A spokesperson for the show said: “Mel genuinely didn’t recognise Lianne as they were only together for a very short time 20 years ago.”