Mel B "doesn't believe" Geri Horner is 51 years old.
The 48-year-old singer urged people to "embrace" their ages as she claimed her Spice Girls bandmate was always protective of her passport when the group went on tour so no one would find out how old she actually is.
During an appearance on Olivia Attwood's 'So Wrong It's Right' podcast, Mel insisted it was "wrong" for a person to lie about their age.
The host replied: "My mum was here the other day and she said, Oh no, it's right, because I don't even know how old she is."
Mel said: "No, well no one knows how old Geri is. No one's seen her passport. I mean, I know we've travelled the world, but I still don't know how old she is.
"Well, she claims she just had her 50th birthday, but I don't believe her."
Elsewhere on the podcast, the 'Stop' singer promised there is "definitely" a Spice Girls reunion on the way, but she "doesn't think" they'll be playing at Glastonbury.
She said: "I don't think its going to be at Glastonbury but its definitely going to happen."
Mel – who has three children, Phoenix, 25, Angel, 16, and 12-year-old Madison, from previous relationships – recently declared being in her 40s had been "really freeing".
She told Britain's HELLO! magazine:
“Numbers aren’t relevant. You can have a bit of a panic when you come into your 40s, because you haven’t got things quite as you thought they were going to be.
“You have some of your hardest challenges. But there’s also something really freeing about it.
“I don’t know if it’s because you’re putting yourself out there or just ready for it in life. But there’s a lot to be said about women in their 40s because they’re more aware and self-assured. It’s an age not to mess with.”
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