The unidentified staff member, a Democrat, was suspended this week by Chairman Peter Hoekstra, R-Mich., and is being denied access to classified information pending the outcome of a review, Hoekstra's spokesman, Jamal Ware, said Thursday.
The ranking Democrat on the committee said Hoekstra's action was "without basis."
The leak to The New York Times of a National Intelligence Estimate on global terror trends caused a political uproar last month. In the assessment, completed in April, analysts from the government's 16 spy agencies concluded that the Iraq war has become a "cause celebre" for Islamic extremists, breeding deep resentment of the U.S. that probably will get worse before it gets better.
President Bush, who suggested the document was leaked for "political purposes" weeks before the midterm elections, later made public four pages of the estimate's key findings.
In a letter to Hoekstra dated Sept. 29, Rep. Ray LaHood, R-Ill., a committee member, said the Democratic staffer requested the document from National Intelligence Director John Negroponte three days before a Sept. 23 story by the Times on its conclusions.
"I have no credible information to say any classified information was leaked from the committee's minority staff, but the implications of such would be dramatic," LaHood said in the letter, a copy of which was obtained by The Associated Press. "This may, in fact, be only coincidence, and simply 'look bad.' But coincidence, in this town, is rare."
The Intelligence Committee's top Democrat, Jane Harman of California, wrote to Hoekstra that she was "appalled" by his action, which was "without basis."
"I demand that you immediately reinstate the staffer's access to classified information," she said.
A conference call to the committee's nine Democrats on Wednesday to inform them of the aide's suspension prompted outrage, said two congressional officials, who spoke on condition of anonymity because they were not authorized to speak publicly about internal committee business.
The officials said that the National Intelligence Estimate was marked "secret," rather than "top secret" or another more restrictive classification. As a result, thousands of people would have had access to it, including the intelligence, armed services and international relations committees of the House.
The officials said the staff member acted appropriately in requesting the document on behalf of a committee member.