"They are plaintiff, judge and jury in a logic that belongs to the pharaohs. The UN Security Council lacks legitimacy and its decisions are illegitimate," he told a pro-Palestinian demonstration in Tehran.

He also reaffirmed Iran's refusal to back down over its nuclear programme despite the threat of sanctions, saying it would not "tolerate the slightest pressure".

"Iran is ready to negotiate but will not tolerate the slightest pressure," he told the demonstrators.

His comments came as France and Britain, both Security Council permanent members, and Germany work on a draft resolution to put to the Council that would impose sanctions on Iran for its failure to suspend uranium enrichment.

Ahmadinejad also recalled that on a recent visit to the United States he had dared Western powers in an address to a think-tank to shut their own nuclear fuel programmes and let Iran supply the material.

"I told them 'You shut down (your nuclear programmes) and we will produce fuel from the fuel cycle in five years time and sell it to you at a 50 percent discount!'"

The United States accuses Iran of seeking nuclear weapons, a charge vehemently denied by Tehran.

In a Friday prayer sermon after Ahmadinejad's speech, former president Akbar Hashemi Rafsanjani warned Security Council members would do themselves no favours by imposing sanctions but admitted they could harm Iran.

"I am sure if they move on with this new action that is taking place in the UN Security Council against us, in a close future, both themselves, the region and of course our country will be harmed.

"But we advise them not to welcome such a risk for our region and the world. You people should be sure that your rulers will not renounce your undeniable rights, especially to nuclear energy," he added.