Iranian President Mahmoud Ahmadinejad has accused the US and UK of using the UN Security Council for their own ends.
Mr Ahmadinejad again defended Iran's nuclear programme
In a speech to the UN General Assembly, he accused the two of being prosecutor, judge and jury whenever they have a difference with another country.
But they use their privileged position whenever the international body tries to hold them to account, he said.
The US and Britain are two of the five permanent members of the security council with the power of veto.
The others are France, China and Russia.
In his speech, Mr Ahmadinejad defended Iran's nuclear programme, which he again said was peaceful.
He contrasted this with the possession and past use of nuclear weapons by countries criticising Iran.
"Some of them 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," he said.
He described his own country's nuclear activities as "transparent, peaceful and under the watchful eyes" of the International Atomic Energy Agency (IAEA).
Turning to the US and Britain, he asked: "Which of the organs of the UN can hold them to account?
"Can a council in which they are privileged members address their violations? Has this ever happened?"
Mr Ahmadinejad has said Tehran will not yield to international pressure to suspend its uranium enrichment programme.
Earlier, the UN General Assembly gathering of world leaders heard forceful calls for action to end violence in Sudan's Darfur region.
US President George W Bush warned that the credibility of the UN was at stake and announced the appointment of a special American envoy to help in the efforts.
President Jacques Chirac of France warned that a crime against humanity was being prepared in Darfur.
The Sudanese government has so far refused to allow UN peacekeepers into the country.
In his address, Mr Bush defended his policies on the Middle East.
He said democracy was gaining ground in the region and terrorists were being marginalised.
The meeting was opened by the outgoing Secretary General, Kofi Annan.
He said he was proud of the role of the UN in ending wars, but there were still far too many people exposed to conflicts.