His name is Bruce Fein. He is a constitutional scholar who has served as a legal official in previous Republican administrations.

But now Bruce Fein is one of the leaders of a conservative alliance that believes President Bush has overstepped his power in the aftermath of the 2001 terrorist attacks on the United States.

"I voted for President Bush twice. I served in the administrations of President Ronald Reagan and Richard Nixon," he noted. "But on matters of this importance, we are all Americans, we are all devoted to the Constitution above any partisan advantage."

Fein and other prominent conservatives argue that the time has come to restore the balance of power among the president, the Congress and the courts. They are proposing what they call the American Freedom Agenda to ensure civil liberties protections by, among other things, reining in the government's power to monitor the phone calls and letters of American citizens in the course of terrorism investigations.

President Bush has often defended these law enforcement tactics as a critical part of his administration's domestic anti-terror efforts.

"I just want to assure the American people that one, I have got the authority to do this," said Mr. Bush. "Two, it is a necessary part of my job to protect you. Three, we are guarding your civil liberties."

The latest controversy to cause alarm among civil liberties advocates on both sides of the political spectrum is the FBI's abuse of what are known as national security letters.

These letters are used by law enforcement to gather private data, including telephone, e-mail and financial records, without prior approval from a judge.

The abuses of the national security letters were brought to light by the Justice Department's office of inspector general, which found numerous violations of law and government regulations.

That report has angered Republicans and Democrats alike in Congress, including the chairman of the House Judiciary Committee, Democrat John Conyers of Michigan.

"It appears to be a part of a pattern in which the Department of Justice violated not only our trust, but the very laws they are charged with enforcing," he said.

Civil liberties advocates have condemned the FBI violations and are demanding new safeguards. Mike German is a former FBI agent who now works for the American Civil Liberties Union.

"What the inspector general documented was a pattern of intentional misconduct and that this goes far beyond simple mismanagement," he noted.

Republicans acknowledge the FBI needs to be more mindful of protecting civil liberties in the course of its domestic terror investigations.

But Republican Congressman Lamar Smith of Texas says the use of the national security letters remains an important investigative tool for law enforcement.

"It has allowed the FBI and intelligence agencies to identify terrorists and spies, the sources of their financing and their plans to attack or harm our national security," he said.

FBI Director Robert Mueller also defends the use of the national security letters, even as he acknowledges the agency must move quickly to correct the abuses cited in the inspector general's report.

"But it is equally important that as we exercise these authorities, we do it consistent with the privacy protections and civil liberties that we in the FBI are sworn to uphold," said Mr. Mueller.

But civil liberties activists on both the right and left say what they want now from the administration is action, not promises.

David Keene is chairman of the American Conservative Union. Keene is also a member of the conservative alliance that is calling on President Bush to do a better job of protecting civil liberties as the U.S. wages the war on terror.

"In this international crisis, as in international crises throughout out history, there has been too great a willingness on the part of many to trade a little bit of freedom for what they see as a little more security," explained Mr. Keene.

The conservative activists say they will reach out to liberal groups to join them and are also appealing for support from the numerous candidates seeking the Democratic and Republican presidential nominations.