A growing number of Democrats are calling for an independent investigation into whether White House officials illegally leaked the name of a covert Central Intelligence Agency operative to the news media.

At issue is the public disclosure that the wife of former U.S. Ambassador Joseph Wilson was an undercover CIA operative specializing in weapons of mass destruction.

The Washington Post reports the name was disclosed to several reporters after Ambassador Wilson criticized Bush administration policy on Iraq. Presidential Spokesman Scott McClellan says he sees no evidence of White House involvement in the leaks.

Shortly after Ambassador Wilson challenged U.S. evidence about Iraq's weapons of mass destruction program in a New York Times commentary in July, journalist Robert Novak named the former diplomat's wife in a syndicated column.

Although the Justice Department has begun a preliminary inquiry into the controversy at the request of CIA Director George Tenet, Democrats say an outside probe is needed to avoid a conflict of interest.

"Leaking the name of a CIA agent is a horrible thing to do," said Senator Chuck Schumer, a New York Democrat and a member of the Senate Judiciary Committee. "Leaking the name of a CIA agent is tantamount to putting a gun to that agent's head. It compromises the agent's safety, the safety of that agent's loved ones, the safety of that agent's network of intelligence, and all other operatives that agent may have dealt with."

Some Democrats seeking their party's nomination for President next year are also calling for independent probes, including Congressman Dick Gephardt, former Governor Howard Dean and retired General Wesley Clark.

Republicans, including Senator John McCain of Arizona, are dismissing calls for an independent investigation, saying the Justice Department would act impartially. "I believe a thorough investigation will be conducted," he said.

Presidential spokesman McClellan said the White House said an independent inquiry is not necessary, but said the White House will cooperate with the Justice Department probe.