Foreign Ministry spokesman Hassan Qashqavi accused Japan of monopolizing the Asian seat on the 15-seat Council, after Tokyo overwhelmingly defeated Tehran in a U.N. assembly vote on Friday for the right to sit on the council for two years.
Japan has held a council seat several times since Iran last served its turn in 1956, when the U.S.-backed Shah, later ousted in a 1979 Islamic revolution, ruled the Middle Eastern country.
"I think that this is blatant injustice ... We will continue to try to establish justice in this part of the United Nations organization," Qashqavi told reporters.
"We don't see any logical reason for monopolizing this seat in the Security Council."
Iran’s neighbor, Turkey, lobbied hard to receive 151 votes for a seat on the Security Council, the first time since 1961.
The Security Council has slapped three sets of sanctions on Iran over its refusal to halt sensitive nuclear work. The West believes Iran is seeking to build atomic bombs, a charge Tehran denies saying its plans are peaceful and aimed at generating electricity.
Turkey believes it is Iran's legitimate right to pursue nuclear works but is against any country in the region acquiring nuclear weapons and also taken on a kind of mediatory role in Iran's nuclear row with the West.
Turkish President Abdullah Gul had urged his Iranian counterpart during a working visit to Turkey in August to accept a new incentives package presented by Western countries and warned on a possible U.S. military operation.
The Security Council is the powerhouse of the United Nations with the ability to impose sanctions and dispatch peacekeepers. It has five permanent members, with veto power, and 10 non-permanent members.