Members of Libya’s mission to the United Nations renounced Col. Muammar el-Qaddafi on Monday, calling him a genocidal war criminal responsible for mass shootings of demonstrators protesting against his four decades in power. They called upon him to resign.

The repudiation, led by Libya’s deputy permanent representative at a news conference at the mission’s headquarters in New York, amounted to the most high-profile defection of Libyan diplomats in the anti-Qaddafi uprising that has convulsed Libya over the past week.

“We are sure that what is going on now in Libya is crimes against humanity and crimes of war,” the deputy permanent representative, Ibrahim O. Dabbashi, told reporters in the ground-floor lobby of the Libyan mission on Manhattan’s East Side, adorned by a large portrait of Colonel Qaddafi in tribal dress atop a white horse.