At a public meeting, Obasanjo rebuffed accusations he had done little to stop the fighting, and lashed out at the regional religious leaders.
Last week in the town of Yelwa in Plateau State, there was a massacre by Christian militants, while in the mainly Muslim city of Kano, Muslims youths attacked Christians and others from outside the state with knives and machetes.
Obasanjo was infuriated when Yakubu Pam, head of the Plateau State's Christian Association of Nigeria's branch known as CAN, asked why the president had not come to the area two months ago when dozens of Christians were killed in a Muslim raid.
"What role have you played to bring about peace as CAN chairman in Plateau State?" Obasanjo responded. "You are an idiot. A total idiot. And I have no apologies for that."
He also responded sharply when Abdulazeez Yusuf, secretary general of the Muslim association Jamu'atu Nasril Islami, asked whether Obasanjo was serious about bringing peace to Nigeria.
Some 10,000 people have been killed in ethnic and religious clashes in Nigeria since Obasanjo was elected in 1999.