Mel, 44, and Peter, 46, dated secretly for nine months back in 1996 and she revealed that even her bandmates - Emma Bunton, Geri Horner, Mel C and Victoria Beckham - had no idea the pair were a couple during that time.
Metro.co.uk reports Mel spoke about the relationship during her 'A Brutally Honest Evening With Mel B' show in London and said: ''They didn't know until years later when he wrote it in his autobiography. They were like: 'Are you kidding me?! Peter Andre was on tour with us?!'
''Back in the day, it was a thing - boy bands and girl bands were never to be seen with boyfriends or girlfriends. Which I can understand because you want to be appealing to your audience. Now it's more acceptable, but back then it wasn't. He's a very lovely guy. We came up in the pop industry in the 90s at the same time.''
Mel previously called Peter her ''booty call'' and revealed she would fly him over to wherever she was touring with the Spice Girls so that they could have sex.
She said: ''The Spice Girls didn't know he was my booty call so I had to explain it to them that all this time in different hotels I would fly him in and fly him back out!''
She also said: ''He was my booty call - a fantastic lover. And he was so polite. He'd ask before he kissed me!''
Mel has accused her former husband Stephen Belafonte of being abusive and alleged her other ex-husband Jimmy Gulzar had anger issues but she insisted that Peter was among her best relationships.
She said: ''Max Beesley. Peter Andre. Eddie Murphy. They're all lovely guys. I've had some really kind, loving relationships.''
Meanwhile, Peter - who has children Junior, 14, and Princess, 12, with his ex-wife Katie Price, and Amelia, five, and Theo, two, with his spouse Emily MacDonagh - previously revealed that Mel broke his heart.
He said: ''I really liked Mel but she broke my heart. She treated me like I'd treated other women in the past and she made me grow up.''
Ahead of their upcoming tour, and prior to the release of their long awaited album, Smoke Fairies played a great warm-up gig at Elsewhere in Margate.