The Spice Girl joined Gary Barlow, Louis Walsh and Tulisa for three days of try outs in Manchester earlier this year.
Speaking about her rather harsh and often brutal judging style, Mel admitted: "I’m a very honest person and say what I feel. I thoroughly enjoyed being a Judge.
"Before The Spice Girls, I used to attend up to six auditions a week. I know what it feels like to be rejected. You’re not doing anyone any favours by lying to them about being talented if they’re not. I don't sugar-coat stuff."
In an interview with the ITV1 official X Factor website, Mel named Lucy Spraggan as her favourite contestant from this year's auditions.
She raved: "I didn’t want her performance to end. I could have listened to her for hours. Nicola Marie was fun – those splits were incredible."
Meanwhile on her fellow judges Mel revealed that Louis is a bit of a prankster bheind the scenes while Gary reminds her of Victoria Beckham!
"Louis is lovely. He’s always pranking people backstage. We spent a lot of time teasing him about his hair. Gary’s brilliant; he was really serious at first but I livened him up. He’s got a very dry sense of humour, he reminds me of Victoria in that respect," Mel explained.
She added: "I got on like a house on fire with Tulisa. She’s really down to earth and you know where you stand with her. Tulisa also has a very sweet side to her."