Philip Zelikow, the commission's executive director, worked on the Bush-Cheney transition team as the new administration took power, advising his longtime associate and former boss, national security adviser Condoleezza Rice, on the incoming National Security Council.
"He came forward (to answer questions) in case he might have useful information," said Al Felzenberg, the commission spokesman.
The news was greeted with dismay by many of the relatives of the victims who campaigned for the commission to be set up.
"This is beginning to look like a whitewash," Kristen Breitweizer, who lost her husband Ron in tower two of the World Trade Center, told United Press International.
Jamie S. Gorelick, one of the 10 members of the commission itself, and the other official who has answered investigators' questions, was deputy attorney general in Janet Reno's Justice Department during the Clinton administration.
"She was a very senior person," said Felzenberg. "She had an interesting perspective."
The families have said for many months that they are not happy with Zelikow's role, which they argue creates at least an appearance of a conflict of interest. They were furious Thursday that they learned from the newspapers he had given evidence.
"Did he interview himself about his own role in the failures that left us defenseless?" asked Lori Van Auken, the widow of Kenneth. "This is bizarre."
Zelikow -- an historian based at the Miller Center for Public Affairs at the University of Virginia -- has also come under fire from some critics for his close ties to senior administration officials. He has had a longstanding relationship with Rice, who hired him to work for her when she was a White House official in the first Bush administration. The two have written a book together.
More recently, some relatives have accused him of being in touch with White House political supreme Karl Rove -- the man widely believed to be the most powerful figure in the administration.
Zelikow was not available to answer questions Thursday, but Felzenberg did not deny the allegation.
"He has not spoken with Karl Rove about commission business," he said. "Like many others on the commission, he has a job he hopes to go back to afterwards. The Miller Center is dedicated to the study of the presidency, and (Zelikow) has contacts with a wide range of people from all recent administrations."
Zelikow, who the commission says has withdrawn himself from those parts of its investigation directly connected with the transition -- a process known as recusal -- was also appointed to the President's Foreign Intelligence Advisory Board in October 2001.
The board provides the White House with advice about the quality, adequacy and legality of the whole spectrum of intelligence activities.
"Zelikow resigned (from the PFIAB) as soon as he signed the contract to be director of the commission," said Felzenberg. "He's recused himself from the relevant parts of the inquiry.
"Frankly, we don't see what the fuss is about."
"If (Zelikow and Gorelick) had not been commission officials, we would probably have interviewed them anyway. We've interviewed hundreds of people."
The question of the transition is a significant one, because critics of President Bush contend that the incoming administration "dropped the ball" on the fight against Osama bin Laden, which had been ramping up under President Clinton, especially after a suicide attack by his al-Qaida network nearly destroyed the USS Cole in Yemen in October 2000.
According to one former Bush White House official, the incoming administration downgraded the interagency committee that handles the nation's counter-terrorism policy and operations on a day-to-day basis.
The Counter-Terrorism Security Group had, under Clinton, reported directly to the so-called Principles' Committee, the meeting of Cabinet-level officials that sets policy for presidential consideration.
"They stopped it reporting directly," the former official told UPI on condition of anonymity. "It had to report to deputies. ... It slowed down consideration of policy initiatives quite a bit."
Under Clinton, the former official added, the chairman of the counter-terror group, Richard Clarke, had been a member of the Principles' Committee, sitting with the secretaries of Defense and State and the national security adviser.
"They eliminated that ... It meant that the CSG didn't have that spokesperson to represent them and put the issue in front of (the principles) over and over again," the former official said.
Moreover, the deputies' committee, to which Clarke was now reporting, didn't meet properly until April, and -- partly as a result of these changes -- there was no Principles' Committee meeting on how to deal with the al-Qaida threat until Sept. 4.
Bush's supporters, for their part, say Clinton's failure to capture or kill bin Laden after his network destroyed two U.S. embassies in east Africa emboldened the extremists to attack America on Sept. 11.
Relatives say the news about Gorelick and Zelikow is a particularly sharp blow to the commission's credibility because they are the two officials to whom the White House has granted the greatest access to the most secret and sensitive national security documents, the presidential daily briefings.
Last year, officials acknowledged that one such briefing in August 2001, more than a month prior to the attacks, warned that al-Qaida was determined to strike in the United States. Some reports suggested that hijacking -- and even the use of airplanes as missiles -- was mentioned as the mode of assault.
"We want the whole issue of who has access to the briefings revisited," said Breitweizer, "the entire commission has to have access to them."
A delegation of relatives traveled to Washington Thursday for an evening meeting with commission staff, which was expected to be stormy.