The 43-year-old's interview with the British broadcaster, which is yet to air, has already hit headlines after Mel confessed to Piers that she had sex with Geri Halliwell during their Spice Girls heyday.
According to editors at The Sun, Mel also discussed the fashion designer in the candid chat and dubbed her a "bit of a b***h", and admitted she is "gutted" Victoria won't be joining her, Geri, Mel C (Melanie C) and Emma Bunton on the Spice Girls reunion tour later this year.
"I am sad she is not going to be there," Mel says. "But she is busy with what she is doing with her fashion line and her family."
"I am gutted that she is not going to be with us, but I am still going to hold that candle and hope that she will."
A source told the paper: "Victoria has made it very clear she doesn't want to be part of the tour, and she just wants Mel to respect her wishes and stop banging on about it."
In a chat with "Good Morning America" in January, Victoria spoke about her decision not to join her former bandmates.
"I'll always be a Spice Girl and I'm so proud of everything I achieved; I'm proud of them," she said. "It's gonna be the best show. I can't wait to take my kids and see it, but with my business now, I just wouldn't be able to do it... but I wish them so much luck and love and it's gonna be great."
Mel's comments come after her revelation that she and Geri "had a thing" back when the Spice Girls were touring in the '90s.
"She's going to hate me for this because she's all posh in her country house and her husband. But it's a fact," Mel claimed.
Later Mel shared that she had spoken to Geri about her admission, explaining to the mother of two, who is married to Red Bull Formula One boss Christian Horner, that she "didn't go into detail" in a chat with an Australian radio show.