"Sept. 11 was terrible, but if one goes back over the history of the IRA, what happened to the Americans wasn't that terrible," the Nobel Literature Prize winner told the leading Spanish daily El Pais.
"Some Americans will think I'm crazy. Many people died, two prominent buildings fell, but it was neither as terrible nor as extraordinary as they think. They're a very naive people, or they pretend to be," she said in an interview published Sunday.
"Do you know what people forget? That the IRA attacked with bombs against our government; it killed several people while a Conservative congress was being held and in which the prime minister, Margaret Thatcher, was (attending). People forget," she said.
Nearly 3,000 people were killed in the Sept. 11 attacks. About 3,700 died and tens of thousands of people were maimed in more than 30 years of violence in Northern Ireland. The Irish Republican Army guerrilla group, which caused most of the deaths, disarmed in 2005.
Attempts by The Associated Press to reach Lessing in London for comment Monday were unsuccessful. Her agent's office said the author was unavailable because she was not feeling well.
In the El Pais interview, Lessing had sharp words for both President Bush and his ally, former British premier Tony Blair.
"I always hated Tony Blair, from the beginning," El Pais quoted Lessing as saying. "Many of us hated Tony Blair, I think he has been a disaster for Britain and we have suffered him for many years. I said it when he was elected: This man is a little showman who is going to cause us problems and he did."
"As for Bush, he's a world calamity," added Lessing. "Everyone is tired of this man. Either he is stupid or he is very clever, although you have to remember he is a member of a social class which has profited from wars."
Iran also came in for a lashing from Lessing, who was born to British parents who were living in what is now Bakhtaran, Iran.
"I hate Iran, I hate the Iranian government. It's a cruel and evil government," she was quoted as saying.
"Look what happened to its president in New York. They called him evil and cruel in Columbia University. Marvelous! They should have said more to him! Nobody criticizes him, because of oil."
The author of dozens of works from short stories to science fiction, including the classic "The Golden Notebook," Lessing won the Nobel Prize for literature earlier this month. She was praised by the judges for her "skepticism, fire and visionary power."