The White House on Thursday asserted President Bush's executive privilege in refusing to disclose documents subpoenaed by the Senate in the investigation of alleged political firings of eight federal prosecutors.

The announcement set off angry Democratic congressional leaders, who labeled the decision "stonewalling" and "obfuscation."

"Maybe everyone has acted honorably. But show me an administration that craves secrecy and I'll show you an administration that probably has something to hide," Sen. Chuck Schumer, D-N.Y., who has led the probe.

Democrats have charged that the firings of at least eight U.S. attorneys last year were politically motivated and used the dismissals as ammunition in their calls for Attorney General Alberto Gonzales to step down.

The House and Senate Judiciary committees issued subpoenas on June 11 for documents and testimony relating to the White House involvement in the Justice Department process.

The White House said Thursday that it would not turn over papers relating to the roles of former White House counsel Harriet Miers and former political director Sara Taylor.

The decision — which sets the stage for a possible firefigtht in court between Congress and the White House — came as the deadline to respond to the subpoenas expired and one day after the Senate Judiciary panel issued broad new subpoenas in a separate investigation involving the administrations warrantless wiretapping program begun in the weeks after the Sept. 11, 2001, terrorist attacks.

"With respect, it is with much regret that we are forced down this unfortunate path which we sought to avoid by finding grounds for mutual accommodation," White House counsel Fred Fielding said in a letter to Leahy and the chairman of the House Judiciary Committee. "We had hoped this matter could conclude with your committees receiving information in lieu of having to invoke executive privilege. Instead, we are at this conclusion."

Click here to read the full White House response to Congress

"The president's response to our subpoena shows an appalling disregard for the right of the people to know what is going on in their government," House Judiciary Committee Chairman John Conyers said Thursday in a prepared statement.

"This response indicates the reckless disrespect this administration has for the rule of law. ... At this point, I see only one choice in moving forward, and that is to enforce the rule of law set forth in these subpoenas," Conyers said.

Senate Judiciary Committee Chairman Patrick Leahy compared the Bush administration's response to the notoriously secretive administration of Richard M. Nixon.

"This is a further shift by the Bush administration into Nixonian stonewalling and more evidence of their disdain for our system of checks and balances. ... Increasingly, the president and vice president feel they are above the law. In America no one is above law," said Leahy, D-Vt.

Senior administration officials who asked to not be quoted by name said the executive privilege the administration is asserting, for now, only pertains to the documents demanded by Congress with respect to the Miers and Taylor subpoenas. They did not speculate on whether they would also assert executive privilege with respect to the subpoenas issued Wednesday regarding the warrantless wiretapping program.

The subpoenas issued so far also have demanded testimony from the witnesses and the officials did not rule out asserting executive privilege on that as well. The officials added that Miers and Taylor, while no longer employed by the administration, are covered by executive privilege.

The officials added that the president had no personal contact with Miers or Taylor or officials at the White House or Justice Department over the firings.

In his letter, Fielding said Bush had "attempted to chart a course of cooperation" by releasing more than 8,500 pages of documents and sending Gonzales and other senior officials to testify before Congress.

The White House also had offered a compromise in which Miers, Taylor, White House political strategist Karl Rove and their deputies would be interviewed by Judiciary Committee aides in closed-door sessions, without transcripts. Leahy and Conyers rejected that offer.

For his part, Conyers said that the White House now is reneging earlier offers to provide documents under a "take it or leave it" option.

But Sen. Orrin Hatch, R-Utah, a member of the Senate Judiciary Committee, said the Democrats should have accepted that offer.

"We would be much farther ahead in finding out whether there's any real impropriety here or not," said Hatch, a former chairman of the committee. He said presidents have legitimate reasons to protect the confidentiality of the advice they get.

Fielding said Bush "was not willing to provide your committees with documents revealing internal White House communications or to accede to your desire for senior advisers to testify at public hearings.

"The reason for these distinctions rests upon a bedrock presidential prerogative: for the president to perform his constitutional duties, it is imperative that he receive candid and unfettered advice and that free and open discussions and deliberations occur among his advisors and between those advisors and others within and outside the executive branch," Fielding said.

"The doctrine of executive privilege exists, at least in part, to protect such communications from compelled disclosure to Congress, especially where, as here, the president's interests in maintaining confidentiality far outweigh Congress's interests in obtaining deliberative White House communications," Fielding said.

"Further, it remains unclear precisely how and why your committees are unable to fulfill your legislative and oversight interests without the unfettered requests you have made in your subpoenas," Fielding said. "Put differently, there is no demonstration that the documents and information you seek by subpoena are critically important to any legislative initiatives that you may be pursuing or intending to pursue."

This is the second time the Bush administration has exercised its executive privilege, said White House deputy press secretary Tony Fratto. The first instance was in December, 2001, in response to demands for Clinton administration documents.

In the subpoenas issued this week, the Senate Judiciary Committee targeted the White House, the office of the vice president, the National Security Council and the Justice Department.

White House press secretary Tony Snow, aboard Air Force One, told reporters that the new subpoenas are "an outrageous request" designed by congressmen who are "engaged in an attempt to do what they can to make life difficult for the White House," adding it also explains why "this is the most unpopular Congress in decades."

In addition, the Senate Judiciary Committee is summoning Gonzales to discuss the so-called Terrorist Surveillance Program, the prosecutor firings, and other matters. Several Justice Department officials have resigned in the wake of the investigation.

And at least one presidential candidate wasted no time in using the flap over the subpoenas as a platform to launch criticism against the administration.

In a fundraising letter to supporters, Sen. Hillary Clinton, D-N.Y., wrote: "Dear Friend, — U.S. Attorneys fired for trying to uphold the law. Government scientists silenced for telling the truth. Secret White House e-mail accounts. Secret wiretaps. Secret military tribunals. And a war that George Bush catastrophically mismanaged, a war that has cost nearly $500 billion dollars and taken a human toll beyond measure.

"Ready for change? Me too. I'm ready to push the restart button on the 21st century. Ready to say goodbye to Dick Cheney, Alberto Gonzalez (sic), Karl Rove, and George Bush."

FOX News' Anne McGinn and Rich Johnson and The Associated Press contributed to this report.