She said she was disappointed panel members recently praised the surveillance program's safeguards that a federal judge initially ruled as illegal.
"It remains clear that this program was built outside of, and in direct contradiction to, the Foreign Intelligence Surveillance Act and Fourth Amendment guaranteed protections," she said.
"This panel's integrity and usefulness will be questioned if it dodges its duty to undertake a full review," Frederickson said.
Board members defended their role, saying that as an advisory panel to the president it was not their job to determine whether the eavesdropping program was illegal, but to find ways, in consultation with Congress and Bush -- to improve it.
"Congress put us in the office of the president," said former Clinton White House counsel Lanny Davis, the panel's lone Democrat, after several audience members unsuccessfully asked the panel to divulge what issues it has raised with the White House.
"Had Congress wanted us to be an independent body, they would have made us an independent body," he said, explaining that as a result, many of the board's deliberations will be kept secret. "Why Congress did what it did, that's an open question."
Privacy officers from the Office of Director of National Intelligence and the Departments of Justice and Homeland Security also attended in a hearing described by the board as a "listening session."
The panel was created as a compromise between Congress and the White House amid growing public concern about the government's tactics in the war on terror, including the eavesdropping program, a financial transactions tracking system and secret CIA prisons where terrorism suspects have been interrogated.
Bush appointed Carol Dinkins, a Houston Republican, to chair the board. The panel's other GOP members include vice chairman Alan Raul, a Washington lawyer, former US solicitor general Theodore B. Olson, and former ambassador Francis Taylor.
Raul and Davis have said that they were impressed by the protections and indicated that Americans might be "more reassured" if they knew all the details.
Yesterday, privacy advocates said they were worried the board might be partly missing the point.
"We continue to be troubled by the argument that a president has no obligation to follow the law or respect other constitutional guarantees whenever he invokes national security as a justification for his actions," David Keene, chairman of the American Conservative Union, told the panel.
