"Iran cannot take part in a political process," Ali Akbar Salehi told the official news agency IRNA in an interview after he walked out of Friday's International Atomic Energy Agency (IAEA) meeting in Vienna.
Salehi said the resolution was unacceptable. "Some of the articles are in breach of international regulations and oppose the spirit of the NPT agreement. Iran opposes the content of the resolution," he said.
He also accused some Western states of not wishing "to resolve the issue technically and legally".
"The Western group in the (IAEA) board of governors, in line with their political goals, have made illegitimate, illegal and impractical requests from Iran," he said, labelling the United States, Britain, Germany and France as "extremist countries".
"Even if all the claims on our programme's shortcomings are true, they cannot be resolved within the 45 days given to Iran," Salehi said.
"Even if all the claims on our programme's shortcomings are true, they cannot be resolved within the 45 days given to Iran"
Ali Akbar Salehi
Iran's ambassador to IAEA
The resolution passed by the IAEA on Friday - a compromise text submitted by Canada, Australia and Japan - said it was "essential and urgent" for Iran to "remedy all failures" in compliance reported by the IAEA since it began inspections in February, after Iran was revealed to have more nuclear facilities than previously thought.
It called for Iran to suspend its uranium enrichment programme and reveal whether it was enriching uranium to weapons-grade level.
But the language of the resolution had been toned down from the original version, "requesting" rather than "calling" for Iran to sign an additional protocol to the NPT to allow IAEA inspectors to make surprise visits to suspect sites.
France and Germany supported the US in setting the deadline on Iran, which Washington accuses of developing weapons of mass destruction.
This contrasted sharply to their opposition earlier this year to the US-led invasion of Iraq, which was also alleged to have had weapons of mass destruction, although none have beed discovered to date.
IAEA director Muhammad ElBaradei has warned Iran it could be declared to be in non-compliance with the Non-Proliferation Treaty (NPT) if it failed to answer all the agency's questions on its nuclear activities.