A top State Department official, Richard Armitage, disclosed the identity of a CIA officer, Valerie Plame, to at least two prominent reporters and failed to tell prosecutors about one of those contacts for more than two years, according to an account in Newsweek magazine.

The confirmation of Mr. Armitage’s role, which had been widely assumed in Washington, undercut claims by liberal activists that Ms. Plame was deliberately exposed in retaliation for criticism her husband, Joseph Wilson IV, had leveled at President Bush.

An investigation of the leak led to the indictment of the former chief of staff to Vice President Cheney, I. Lewis Libby Jr., for perjury and obstruction of justice. Neither Mr. Armitage nor anyone else has been charged for disclosing Ms. Plame’s CIA ties.

Mr. Libby’s backers argued that Mr. Armitage’s alleged role and the lack of any charges against him indicated prosecutors had applied a double standard. “If you were against the war, it was okay to forget or to reveal details about Valerie Plame, but if you supported the war, you get indicted,” a Justice Department official in the Reagan administration, Victoria Toensing, said in an interview yesterday. “It’s a simple as that.”

The latest report, based on a forthcoming book co-written by an investigative reporter for Newsweek, Michael Isikoff, and the Washington bureau chief for the Nation, David Corn, identifies Mr. Armitage as the primary source for the first article to out Ms. Plame, a July 2003 column by Robert Novak.

“The initial leak, seized on by administration critics as evidence of how far the White House was willing to go to smear an opponent, came from a man who had no apparent intention of harming anyone,” Mr. Isikoff wrote in Newsweek.

He said Mr. Armitage realized he was Mr. Novak’s first source only after the syndicated columnist wrote a follow-up in October 2003, saying he learned of Ms. Plame’s affiliation with the CIA in “an offhand revelation” from an official “who is no partisan gunslinger.”

“I’m sure he’s talking about me,” Mr. Armitage told his boss, Secretary of State Powell, according to the new book, “Hubris.” The State Department is reported to have notified the Justice Department immediately but given the White House only sketchy hints about Mr. Armitage’s role.

Some details of the ex-diplomat’s involvement were attributed to anonymous sources, but a former head of intelligence for the State Department, Carl Ford Jr., quoted Mr. Armitage as saying, “I’m afraid I may be the guy that caused this whole thing.”

On NBC’s “Meet the Press” yesterday, Mr. Novak refused to confirm Mr. Armitage was his primary source, but expressed some exasperation. “I’m going to say one thing, though, I haven’t said before. And that is that I believe that the time has way passed for my source to identify himself,” the veteran columnist said.

Ms. Toensing said Mr. Armitage acted irresponsibly by saying nothing publicly as complaints about a White House smear campaign morphed into a full-scale criminal investigation. “He could have saved everybody some grief,” Ms. Toensing said. “There should be some kind of indictment for this behavior.”

Mr. Armitage, who resigned along with Mr. Powell at the end of Mr. Bush’s first term, could not be reached for comment yesterday.

One question underscored by recent reports is why Mr. Armitage seems to have waited until late 2005 to notify prosecutors that he also discussed Ms. Plame’s CIA status with another top journalist, Bob Woodward of the Washington Post.

The Associated Press disclosed last week that Mr. Armitage’s official calendar, obtained through the Freedom of Information Act, shows a scheduled meeting with the Post reporter on June 13, 2003. That is 10 days before Mr. Libby is alleged to have discussed the same subject with a reporter for the New York Times, Judith Miller.

Mr. Armitage’s prolonged failure to mention to investigators the contact with Mr. Woodward could be explained by a faulty memory, but for the fact that Mr. Woodward claims that on three occasions, one as early as 2004, he asked his source to set aside the agreed confidentiality and allow the journalist to write about the early disclosure.

The Watergate veteran said the source, now identified by Newsweek as Mr. Armitage, would not budge, though in late 2005 he gave permission for Mr. Woodward to discuss their conversation with the special prosecutor, Patrick Fitzgerald.

The Newsweek report said Mr. Armitage “was aggressively investigated” by Mr. Fitzgerald but never charged. However, on PBS’s “Charlie Rose Show” earlier this year, the former diplomat said the questions were of so little concern that he didn’t bother to seek legal counsel.

“I’m not worrying about my situation. I don’t even have an attorney and haven’t had an attorney,” Mr. Armitage said.

A spokesman for Mr. Fitzgerald declined to comment for this article, as did a spokeswoman for Mr. Libby’s defense team.

The new reports do not undermine evidence that Mr. Libby and Mr. Bush’s top political aide, Karl Rove, discussed Ms. Plame’s then-classified CIA connection with reporters. But, in a concession striking for a liberal journalist who helped launch the furor over Ms. Plame’s outing, Mr. Corn acknowledged that the story line touted by the left had flaws.

“The Armitage news does not fit neatly into that framework,” Mr. Corn wrote on his Web site yesterday.