"This sort of rigged process has never been attempted before," O'Malley said. He added, "We are the Democratic Party, not the undemocratic party."
Despite public objections from O'Malley and Sen. Bernie Sanders (I-Vt.), who have called for more debates, DNC Chairwoman Debbie Wasserman-Schultz has sanctioned six debates, only four before next February's Iowa caucuses.
O'Malley, speaking from the DNC dais with Wasserman-Schultz sitting a few feet to his left, slammed what he called a "cynical move to delay or limit our own party debates."
"Who’s decree is this exactly? Where did it come from? To what end or purpose?" O'Malley asked. He added, "We put our forward-thinking ideas on the back-burner as if we're trying to hide them from the airwaves."
O'Malley made no reference to the Democratic front-runner, former secretary of state Hillary Rodham Clinton, but it was clear in his remarks that he believes fewer debates make it more difficult for him and other challengers to defeat Clinton for the nomination.
O'Malley argued that with Donald Trump and other Republican candidates making headlines with inflammatory rhetoric, Democrats should hold more, not fewer, debates.
"Will we let the circus run unchallenged on every channel while we cower in shadows under a decree of silence in the ranks? Or will we demand equal time to showcase our ideas?" O'Malley asked. He added, "Silence and complacency in the face of hate is not an honorable option for the Democratic Party."
DNC spokeswoman Holly Shulman, responding to O'Malley's remarks, said in a statement: "We are thrilled the candidates are so eager to participate in our debates. We believe that six debates will give plenty of opportunity for the candidates to be seen side-by-side. I'm sure there will be lots of other forums for the candidates to make their case to voters, and that they will make the most out of every opportunity."