"I am stepping down from your finance committee so I can speak for myself and you can continue to speak for yourself about what is at stake in this campaign," Ferraro, the first female vice presidential candidate, wrote in a letter to Clinton, D-N.Y. "The Obama campaign is attacking me to hurt you. I won't let that happen."
Ferraro told CNN she sent the letter to Clinton Wednesday.
Ferraro caused an uproar by suggesting the Illinois rookie senator achieved his place in the Democratic presidential race because he is black.
"If Obama were a white man he would not be in this position," Ferraro told a California newspaper.
Obama's campaign called the remarks outrageous and demanded that Clinton repudiate them.
Clinton has said she does not agree with Ferraro's remarks.
"Ms. Ferraro is speaking for herself. We have made clear that we do not agree with her remarks," campaign spokesman Mo Eleithee told CNN.