She wrote on Twitter that she is actually a fan of Rihanna but feels, nonetheless, that the singer should feel more responsibility towards her younger fans.
Rihanna frequently takes to the stage in little more than knickers, bra tops and stockings to perform sexually provocative routines.
Mel C wrote: "For the record. I am a big fan of Rihanna, I am also a mother."
And it is being a mother to her two-year-old daughter, Scarlet Starr, that is making her think more deeply about the example being set to children by the global pop star.
"People have to take some responsibility because we've got to a point where over-sexualisation of young children has gone too far," she wrote, according to the Mirror.
"I think music is a big part of that. Women in music, very successful women, are extremely sexual and they have young fans. It is inappropriate."
"Rihanna has responsibility and although culture's always changing, it's changed too much.
"It needs to be dealt with. It's reached saturation point, we owe it to our kids to protect them.
"Rihanna's free to do as she pleases, of course, but I think her take on the criticism she's had is interesting."
Rihanna recently came under fire for her music video to 'Man Down', in which she shot dead a man who raped her.
She was defiant in the face of criticism, saying that the music industry "isn't exactly Parents R Us!" and that pop stars should be free to "make art".
The Spice Girls were one of the biggest girl groups of all time. The girls have all gone on to do their own thing and Mel C has recently been in the studio recording her new album, Sea.
She added: "It's a long time ago since the Spice Girls were first together and we were criticised for being sexual. Yes, we wore crop tops, I mean look how much has changed."