"I think the White House has to understand that some of this is coming from their ranks," Sen. Dianne Feinstein told a World Affairs Council forum.
The California lawmaker said she was certain that President Barack Obama, who receives a daily intelligence briefing, isn't disclosing secret information, but she was uncertain about others at the White House. "I don't believe for a moment that he goes out and talks about it," she said.
Republicans have criticized the disclosures, arguing that members of the Obama administration were intentionally leaking classified material to enhance the president's reputation in an election year.Attorney General Eric Holder has appointed two attorneys to lead the investigation into who leaked information about U.S. involvement in cyberattacks on Iran and about an al-Qaida plot to place an explosive device aboard a U.S.-bound airliner.
That hasn't satisfied some Republicans who have pressed for a special prosecutor.
Last Thursday, Defense Secretary Leon Panetta and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, testified in closed session before the House Armed Services Committee on the leaks. The committee's chairman, Rep. Howard "Buck" McKeon, R-Calif., told reporters afterward that he did not believe the Pentagon was responsible for recent national security leaks.
"I feel pretty secure they were not" from the Pentagon, McKeon said after the three-hour hearing.
Separately, the Pentagon announced that it was taking new steps to try to clamp down on leaks of classified information, saying unauthorized disclosures undermine national security and in some cases rise to the level of criminal acts.
Pentagon press secretary George Little said Panetta has ordered him to join the Pentagon's top intelligence official in monitoring all "major, national level" news media reports for unauthorized disclosures of secrets.
Panetta also reiterated guidance issued by his predecessor, Robert Gates, that the Pentagon's public affairs office should be the only source of defense information provided to the news media in Washington.
Feinstein said her committee would meet Tuesday to craft legislation that would address the leaks of classified information, including additional authorities and rules to stop the leaks.
Her comments came as U.S. officials said the number of people with access to some of the nation's most carefully guarded secrets topped 4.86 million in 2011.
That's up from 4.7 million people granted security clearances the year before, likely reflecting new hires approved by Congress as part of expanded clandestine operations in the Obama administration.
The latest intelligence report to Congress also corrects previous figures, to reflect new guidance that everyone with access to such information be counted — even if they never used the data or no longer hold a job that requires the clearance.
Clearance levels range from confidential to secret to top secret. Top secret clearances in 2011 numbered 1.4 million, down slightly from 1.43 million the year before.