When the joint Congressional committee investigating the Sept. 11, 2001, terrorist attacks learned in August 2002 that a longtime, San Diego-based FBI informant had rented a room to two of the hijackers, lawmakers and panel investigators wanted to ask a few questions.

But those questions remain unanswered. The FBI refused to produce the informant for an interview. When the panel tried to issue a Congressional subpoena seeking the informant’s deposition, the FBI — supported by Attorney General John Ashcroft — refused to serve the papers on the informant.

And when the panel and the FBI finally settled on sending the informant a set of written questions that would be answered in writing, the informant, advised by legal counsel not to cooperate without a grant of immunity, refused to comply.

The vain effort to question a key source who had direct contact with two of the terrorists was just one of the many roadblocks encountered by lawmakers and Congressional investigators that are detailed in an appendix to the long-awaited report on the intelligence failures that preceded the Sept. 11, 2001, attacks.

Although granted access to some of the most sensitive, classified materials held by the intelligence community, the legislative panel tasked with overseeing intelligence activities often found itself blocked, stymied and thwarted by an administration that took unusual steps to control information and outright delay the pace of the probe.

“The administration’s various techniques of withholding and limiting access to vital evidence amounts to a de facto cover-up,” said Charles Tiefer, a former deputy general counsel for the House who gained extensive experience in fighting for access to intelligence information during the Congressional investigation of the Iran-Contra affair in the late 1980s.

While the Bush administration’s refusal to make copies of the daily briefs prepared by the CIA for the president has received a great deal of attention, the barriers to full access came in many forms, according to the report.

For example, the intelligence agencies refused to provide any information in an electronic format, insisting that everything was to be put on paper. “This not only slowed production of the material, but also hindered the efficient review and utilization of this information by the Inquiry,” the report said.

In other instances, the panel met with downright snubs.

One area that the panel wanted to examine was whether the super-secret National Security Agency, which monitors electronic signals around the world, is planning and dealing with changing technologies and priorities in countering terrorist threats.

But “despite numerous requests for specific planning and other documents and briefings, NSA provided very limited responsive information in this area,” the report said.

And despite the legislative branch’s power of the purse, the Congressional panel was not able to obtain a complete financial picture of the intelligence community. Although numerous intelligence officials complained about a lack of resources at various agencies, the panel was rebuffed by the White House Office of Management and Budget from obtaining the budgetary requests each agency made to OMB.

The report said that OMB and the White House “prevented the agencies from sharing information regarding budget requests that were submitted by the agencies to OMB and the actions OMB took to increase or decrease those requests before they were submitted to Congress. This limited the Inquiry’s ability to determine where in the budget process requests for additional counterterrorism resources were changed.”

Steven Aftergood, director of the Federation of American Scientist’s Project on Government Secrecy, found this particular rebuff by the administration to be “outrageous.” His group has conducted a long legal fight to make the overall budget number spent on intelligence public. He said he was stunned that Congress was denied access to basic information about the resource requests.

Tiefer, noting some reports that Ashcroft may have short-changed counter-terrorism funding during the first months of the Bush administration, also called the OMB refusal “outrageous.”

“The joint inquiry was not pursuing some routine pork-barrel effort to second guess regular budget decisions, but was studying how government processes of several kind, including budgets, failed to avert the greatest tragedy in recent American history,” Tiefer said.

Trent Duffy, an OMB spokesman, said, “It’s policy that every administration uses, which is that any deliberative material used to develop the budget or other administration policy is not released. In order to have deliberative discussions, it has to remain private.”

The administration also just made it difficult for Hill investigators to examine key documents.

The CIA and the administration took the position that classified documents known as “operational cables” from the field and certain other documents it deemed to be sensitive “could be subject to Joint Inquiry review at CIA Headquarters, but that no copies could be brought to the Joint Inquiry’s office.”

The National Security Agency adopted a similar position regarding its transcripts and intelligence reports “and, ultimately, almost all other materials. This prevented the incorporation of the original documents in the Inquiry’s central records where they could be drawn upon effectively for research and reference purposes,” the report noted.

Instead, both agencies allowed the panel’s staff to take verbatim notes of the material they read and to carry those notes back to the committee’s office.

Although the agencies later agreed on a procedure to allow some files to leave their offices and the committee signaled its willingness to accept the arrangement, the agencies “decided that such an agreement was no longer desirable and returned to their original positions.”

The report also noted that the Congressional panel was denied access to the staff of the president’s National Security Council, which Aftergood noted is the “nerve center of the entire intelligence community.”

The White House rejected a panel request to hear from National Security Adviser Condoleezza Rice and was slow to respond to written questions sent to her deputy.

The same issues may be confronted again very soon. As Congress struggles with its inquiry over pre-war intelligence on Iraq, senior lawmakers are trying to get the White House, especially the National Security Council, to voluntarily comply with their requests for information, something that up until now the Bush administration has refused to do.

Senate Intelligence Chairman Pat Roberts (R-Kan.) had a conversation with Rice about having NSC aides appear before the Intelligence Committee. Roberts and Sen. Jay Rockefeller (D-W.Va.) both are seeking such cooperation, and Rockefeller cited several examples when previous administrations allowed such testimony to occur, including the Iran-Contra scandal.

Roberts, however, cautioned that no agreement had been reached with the White House. By late in the week, it was not clear if any further progress had been made on the request.