Two lawmakers who fought to create the independent commission on the Sept. 11 attacks urged the panel Thursday to blow the whistle on bureaucratic barriers and government failures that left the nation vulnerable to terrorism.

"The American people deserve to know the full and objective truth, the best it can be determined. Today we have not yet received that, unfortunately," Sen. Joe Lieberman, D-Conn., told the National Commission on Terrorist Attacks Upon the United States (search).

Lieberman, who is seeking the Democratic nomination for president, accused the Bush administration of "stepping delicately around the bureaucratic failures that have long plagued our domestic defenses at the federal level." He said government officials and employees should be held personally accountable for such failures.

Sen. John McCain, R-Ariz., said the panel should look more broadly at U.S. policies and practices through the past four presidential administrations, especially responses to terror attacks against U.S. interests.

"The role of U.S. policy in responding to these attacks, and the ways in which American leaders failed to adequately counter the threat posed by international terrorism, should be central areas of inquiry for the commission," McCain said.

But he too criticized the Bush administration's response so far to questions about the Sept. 11, 2001, attacks.

"Excessive administration secrecy ... feeds conspiracy theories and reduces the public's confidence in government," said McCain, who worked with Lieberman last year to overcome White House opposition to an independent commission.

Opening a two-day public hearing, the bipartisan 10-member panel sought input from leading lawmakers, including two senators who hope to challenge President Bush next year -- Lieberman and fellow Democrat Bob Graham of Florida (search).

Graham said the commission should pursue links between foreign governments and the Sept. 11 hijackers. "I am troubled by the lack of attention that the current administration has given to this critical aspect," he said.

McCain and House Minority Leader Nancy Pelosi, D-Calif., said the panel should get access to National Security Council records not made available to last year's joint congressional inquiry into intelligence failures before Sept. 11.

Rep. Porter Goss, R-Fla., chairman of the House Intelligence Committee (search), urged the panel to study how domestic intelligence-gathering can be strengthened without violating civil liberties.

The lawmakers were selected because of their efforts to create the commission, or their work on committees that oversee U.S. intelligence gathering and government operations.

But the hearing had obvious political overtones. Graham and Lieberman, among other Democratic presidential contenders, have made homeland security a central theme in their fledgling campaigns.

Graham, who chaired a joint congressional inquiry last year on intelligence failures, says the Bush administration missed warning signs before Sept. 11.

Lieberman, an early proponent of creating a Department of Homeland Security, says the Bush administration is not spending enough on homeland defenses.

The commission's chairman, Thomas H. Kean, said in an interview that he hopes the panel can steer clear of partisan politics, especially since its report will come out during next year's presidential campaign.

"One of the few things that can destroy our work is to have partisanship get in the way," said Kean, a former Republican governor of New Jersey whom Bush appointed chairman.

The independent commission has until next May to report on the Sept. 11 airline hijackings that killed thousands at the World Trade Center, the Pentagon and in southwestern Pennsylvania.

Kean said he hopes this week's hearings will help the panel understand how well Congress is overseeing and funding homeland defense. Other witnesses Thursday and Friday were to address aviation security before and after Sept. 11.