The Texas congressman is the second GOP presidential aspirant to say he won't be part of the Dec. 27 debate. Former Utah Gov. Jon Huntsman also has declined, with his spokesman saying the Republican Party "deserves a serious discussion of the issues."
In a statement release on Paul's campaign Web site, Paul campaign Chairman Jesse Benton said the campaign committee "rejects" the selection of Trump as moderator.
"The selection of a reality television personality to host a presidential debate that voters nationwide will be watching is beneath the office of the presidency and flies in the face of that office's history and dignity," Benton's statement said. "Mr. Trump's participation as moderator will distract from questions and answers concerning important issues such as the national economy, crushing federal government debt, the role of the federal government, foreign policy, and the like.
"To be sure, Mr. Trump's participation will contribute to an unwanted circus-like atmosphere.
"Mr. Trump's selection is also wildly inappropriate because of his record of toying with the serious decision of whether to compete for our nation's highest office, a decision he appeared to make frivolously."
Benton also castigated Trump for leaving Iowa Republicans "holding the bag" by pulling out at the last minute as the keynote speaker for the state party's annual Reagan fundraising dinner.
"Our candidate will not even consider participating in the late-December debate until Mr. Trump publicly apologizes to Iowa party leaders and rectifies in full the situation," Benton said.
Christopher Ruddy, chief executive of the conservative news organization Newsmax Media that is sponsoring the Des Moines debate, told The New York Times Friday Trump was selected because people "really love" him and see him as not "owned by the Washington establishment [or] the media establishment."
Trump, a wealthy real estate developer, told MSNBC he decided to take on the role of debate moderator for "a little change of pace" and thinks he has "a lot of good questions to ask."
The debate will be broadcast on ION Television, a week before the Iowa caucuses Jan. 3.