Republicans on Sunday renewed their attacks on the Obama administration over suspected leaks of classified security information, with one influential senator saying the Justice Department should appoint a special prosecutor to investigate.
Among the government secrets leaked to the media in recent months were reports on U.S. cyber warfare against Iran, procedures for targeting militants for drone attacks and the existence of a double agent who penetrated a militant group in Yemen.
Republicans have also criticized the administration for disclosing details of the Navy SEAL team that killed al Qaeda leader Osama bin Laden in a raid on his Pakistan hideout last year.
"Our intelligence people say this is the worst breach they've ever seen," Senator John McCain, senior Republican on the Senate Armed Services Committee, said in an interview on CNN's "State of the Union" program.
"It's very clear that this information had to come from this administration. It couldn't have come from anywhere else," McCain said. "This needs a special counsel - someone who is highly independent of the Justice Department."
While government leaks are a staple of Washington political life, the issue has taken on a special significance ahead of the November 6 election, with some Republicans charging that the leaks appear calculated to boost the President Barack Obama's re-election prospects.
Obama has reacted with indignation. "The notion that my White House would purposely release classified national security information is offensive," he said on Friday."
Asked about Obama's remarks, Democratic Senator Diane Feinstein, chairwoman of the Senate Select Committee on Intelligence, said, "I take the president at face value" and that she did not believe information was leaked to help Obama.
"The investigation has to be non-partisan, it's got to be vigorous and it's got to move ahead rapidly," she told the CBS program "Face the Nation."
Attorney General Eric Holder announced late Friday that he had appointed two chief federal prosecutors to lead an investigation into the leaks.
The investigation would be headed by U.S. Attorneys Ronald Machen Jr. of Washington, D.C., and Rod Rosenstein of Maryland, who would be "fully authorized to prosecute criminal violations discovered as a result of their investigation," Holder said.
"Good start, maybe, but we need to find out if they'll have that independence," Mike Rogers, chairman of the House of Representatives Intelligence Committee, told "Face the Nation."
He said his panel conducted a preliminary review of the "parade of leaks" that raised serious questions.
"Many asked the question, me included: 'Can you have the U.S. attorney, assigned through the attorney general, investigate something that is clearly going to be at the most senior levels of all of the executive branch?" said Rogers.
"Some of the leaks and the public leaks are self-described aides or people who were in the situation room - that's a pretty small but pretty important group of people," he said.
McCain ratcheted up the pressure by calling for a probe by a prosecutor with special powers, independent of the Justice Department.
"I have great respect for the two individuals that were appointed. But this - if it is, and it certainly is, the most egregious breach of intelligence in anybody's memory - that certainly requires a special counsel who is completely independent, someone with credibility ...," he told CNN.
Some special counsels, such as Patrick Fitzgerald who conducted an investigation into the leak of the identity of a covert CIA operative that led to the conviction of a senior aide to former Vice President Dick Cheney on obstruction and perjury charges, have been accused of conducting witch-hunts.