Under fire from tribal leaders and others for the campaign war whoops and tomahawk chops, Brown said he "regrets" the "unacceptable" behavior by those who took part, including members of his staff.
"Senator Brown has spoken to his entire staff -- including the individuals involved in this unacceptable behavior -- and issued them their one and only warning that this type of conduct will not be tolerated," Brown spokeswoman Alleigh Marre said.
"As we enter the final stretch of this campaign, emotions are running high, and while Senator Brown can't control everyone, he is encouraging both sides to act with respect. He regrets that members of his staff did not live up to the high standards that the people of Massachusetts expect and deserve."
Cherokee Nation Principal Chief Bill John Baker says use of American Indian stereotypes by Brown's backers was "downright racist."
In a statement posted on the Cherokee Nation website, Baker called on Brown to apologize for "the offensive actions of his staff and their uneducated, unenlightened and racist portrayal of native peoples."
WCVB-TV, Boston, reported members of Brown's staff joined supporters in using war whoops and tomahawk chops to mock Democratic Senate nominee Elizabeth Warren at a campaign rally Saturday. WCVB said Brown's deputy chief of staff, Greg Casey, and another staffer, Jack Richard, along with Brad Garrett, identified as a Republican Party operative, are shown using the gestures in a video posted online by the liberal Blue Mass Group.
"The Cherokee Nation is disappointed in and denounces the disrespectful actions of staffers and supporters of Massachusetts Senator Scott Brown," Baker said Wednesday. "The conduct of these individuals goes far beyond what is appropriate and proper in political discourse. The use of stereotypical 'war whoop chants' and 'tomahawk chops' are offensive and downright racist. It is those types of actions that perpetuate negative stereotypes and continue to minimize and degrade all native peoples."
Baker said a campaign "that would allow and condone such offensive and racist behavior must be called to task for their actions."
Brown has raised the issue of Warren's ethnicity, suggesting she falsely claimed to be part American Indian to advance her career.
He told reporters Tuesday he was not aware of the video involving his staffers but "certainly that's not something I condone."
"It's certainly something that if I am aware of it, I'll tell that [staff] member to never do it again," Politico quoted Brown as saying in an audio clip provided by his campaign. "But the real issue here is, and the real offense is the fact that Professor Warren checked the box. She said that she was white, and then she checked the box saying she was Native American and then she changed her profile in the law directory once she attained her tenure. That's quite offensive to Native Americans."