Vice President Cheney instructed a former aide who now faces criminal charges, I. Lewis Libby, to leak information to the press about a classified intelligence estimate on Iraq, according to a report yesterday in a Washington magazine, National Journal.

In a letter filed in federal court last week, a special prosecutor, Patrick Fitzgerald, said Mr. Libby told a grand jury that in 2003 “his superiors” authorized him to give reporters details of an October 2002 National Intelligence Estimate on Iraq. The court filing did not identify the “superiors” by name, but the news account yesterday said the instruction came from Mr. Cheney.

Mr. Libby resigned last fall after being indicted on perjury and obstruction of justice charges in connection with an investigation into the leak of the identity of a CIA officer, Valerie Plame. There is no indication in the recent filings that Mr. Libby has claimed Mr. Cheney authorized the leak of Ms. Plame’s identity. However, prosecutors have alleged that Mr. Libby discussed Ms. Plame with a New York Times reporter at a July 8, 2003, meeting where he also relayed information about the intelligence estimate. Portions of that estimate were officially declassified 10 days later and discussed at a White House briefing.

An attorney for Mr. Libby, William Jeffress Jr., yesterday denied an assertion in the National Journal article that Mr. Libby plans to argue in court that his actions were authorized by Mr. Cheney. “There is no truth at all to the story that Mr. Libby’s lawyers have advised the Court or the Special Counsel that he will raise a defense based on authorization by superiors,” Mr. Jeffress said in a statement. He did not address whether Mr. Cheney told Mr. Libby to give classified information to journalists.

The White House press secretary, Scott McClellan, and a spokeswoman for Mr. Cheney, Lea Anne McBride, refused to address the matter, citing the ongoing probe.

In a statement, Senator Kennedy, a Democrat of Massachusetts, suggested Mr. Cheney should leave office if the account of his involvement is accurate. “These charges, if true, represent a new low in the already sordid case of partisan interests being placed above national security.” Mr. Kennedy also said President Bush should tell the public if he authorized the release of information classified in connection with the war effort.

An expert on the handling of classified information, Steven Aftergood, said the disclosure makes it more likely that Mr. Cheney will be forced to appear at Mr. Libby’s trial, which is set for January 2006. “What it may do is set the stage for Cheney to be called to testify. It links him in a direct way to the larger story,” Mr. Aftergood, an analyst at the Federation of American Scientists, said.

Mr. Aftergood said the intelligence estimate should not have been delivered to handpicked reporters, but there was no legal obstacle to the vice president releasing it. “The president and vice president have broad discretion to declassify information on their own judgment,” Mr. Aftergood said.