The Spice Girl, 43, said the photo and racy text message were meant for her long-term partner Jade Jones, 40, who she was missing while on tour with the band over the summer.
But luckily her mother just made fun of her as the pair are such firm friends.
The singer explained on the pilot for the new Paul O'Grady show, according to The Mirror: "I was away from my other half for a few days. But we are very much in love and I love sleeping next to him.
"We are together all the time. So I decided that I would send a mucky text. A cheeky text. A sext.
"I did a little selfie with the boobies. I did have a bra on. But I did a sleazy kind of little selfie and a 'Miss you' and 'Wish you...' and sent it to my mother."
She added: "Luckily I speak to my mum 10 times a day and we are the best of friends. She has got a great sense of humor but I was mortified."
Baby Spice started dating Jones — who was in 90s boy band Damage — 21 years ago.
She started dating him in 1998, but split several times before committing in 2004.
They announced their engagement in 2011 and have two sons together, Beau, 12, and Tate, 8.
The singer opened up about how working on a song together "renewed their romance."
Speaking on Lorraine, she said: "[Working with] my other half Jade, it was so romantic. Being in the studio and doing this video, we had a great time. We just spent the day kind of canoodling.
"It was a joy to work with him."
This article originally appeared in The Sun.