Mel B feels Geri Horner is trying to "erase their history" by denying they got intimate once over 20 years ago.
The 'Wannabe' hitmaker is said to be angry at her Spice Girls bandmate for denying that they had a "one time" fling together.
A friend of Mel's told the Daily Mirror newspaper: "Mel is totally perplexed by Geri's denials. Mel feels Geri is making her out to be a liar. She said, 'It's almost as if she is trying to erase our history.' There is a lot of bad blood simmering away. It's going to be interesting."
In a statement, Geri denied the claims and said it was "very hurtful to her family" as she hit back at Mel's story.
A statement released through Geri's representative recently said: "It has been very disappointing to read about all these rumours again, especially on Mother's Day of all days. Geri is really grateful for your support and loyalty for so many years. She loves the Spice Girls: Emma, Melanie, Melanie and Victoria. She would like you to know that what has been reported recently is simply not true and has been very hurtful to her family. Moving forward, Geri can't wait to see the girls and all the fans on the tour, have an amazing time with everyone, and make some new memories. She wishes you a Happy Mother's Day."
Mel claimed she and Geri slept together when the band were in their infancy in the 1990s.
She said: "We were best friends. It just happened. It wasn't a thing. It just happened. We just giggled at it and that was it. It just happens one time and then you talk about it and it does not really happen again. It was just that one time ... Hopefully when Geri gets asked she wont deny it, because it was just a thing. It was not anything major. It was just a fun thing. You asked me a question and I answered it. She is going to hate me for this because she is all posh in her country house and her husband. But its' a fact. She is going to kill me and so is her husband."