"All our nuclear activities are transparent, peaceful and under the watchful eyes of IAEA (International Atomic Energy Agency) inspectors," the Iranian leader said in a scathing attack delivered to almost 90 world leaders assembled in New York.
He charged that some of the governments objecting to the Iranian nuclear program "have abused nuclear technology for non-peaceful ends including the production of nuclear bombs" and "some even have a bleak record of using them against humanity."
"Some permanent members of the Security Council, even when they are themselves parties to international disputes, conveniently threaten others with the Security Council and declare, even before any decision by the council, the condemnation of their opponents by the council," he said.
Tehran has refused to comply with a Security Council demand that it suspend sensitive nuclear fuel work, arguing that it has the right to conduct uranium enrichment and that its nuclear program is peaceful.
Ahmadinejad also accused the United States and Britain of manipulating the Security Council to further their own agendas.
"The question needs to be asked: if the governments of the United States or the United Kingdom who are permanent members of the Security Council, commit aggression, occupation and violation of international law, which of the organs of the UN can take them to account?," he said.
"As long as the council is unable to act on behalf of the entire international community in a transparent, just and democratic manner, it will neither be legitimate nor effective," he added.