"This White House promised or assured the American people that at some point when this was behind us they would talk publicly about it. And they have refused to," McClellan told the House Judiciary Committee. "And that's why I think more than any other reason we are here today and the suspicion still remains."
He suggested that Mr. Bush could do much to redeem his credibility on the Plame matter and his reasons for going to war in Iraq if he would embrace "openness and candor and then constantly strive to build trust across the aisle."
There was no indication that the Bush administration was going to take McClellan's advice. In fact, the White House was dismissive of the event and McClellan himself.
"I think Scott has probably told everyone everything he doesn't know, so I don't know if anyone should expect him to say anything new today," said White House spokesman Tony Fratto.
In his recently-released book, "What Happened: Inside the Bush White House and Washington's Culture of Deception," McClellan said he was instructed to lie about the role of senior White House officials in the leak of Plame's name.
Mr. Bush's spokesman from 2003-2006, McClellan said that former White House Chief of Staff Andy Card told him that the president and vice president wanted him to publicly say that I. Lewis "Scooter" Libby, Vice President Dick Cheney's chief of staff at the time, was not involved in the leak.
"I was reluctant to do it," McClellan said. "I got on the phone with Scooter Libby and asked him point-blank, 'Were you involved in this in any way?' And he assured me in unequivocal terms that he was not."
In fact, both Libby and former presidential adviser Karl Rove had discussed Plame's identity with reporters. Libby resigned from office the day he was indicted on charges of covering up the leak. Rove remained, eventually leaving office in August 2007. Rove has never been charged in the case.
Plame maintains the White House quietly outed her to reporters as retribution for criticism from her husband, former Ambassador Joseph Wilson, of Bush's reasons for going to war in Iraq.
Last July, Mr. Bush commuted Libby's 2½-year sentence, sparing him from serving any prison time. "It was special treatment," McClellan said of the commutation.
McClellan told the House Judiciary Committee that he doesn't know if a crime was committed and does not believe that Mr. Bush knew about or directed the leak. When asked about Cheney, he replied: "I do not know. There's a lot of suspicion there."
Lingering public mistrust of the administration in the sunset of the president's second term is a direct cause of Mr. Bush's justification for the war, later deemed in error and several broken presidential promises, McClellan told the panel.
First, he said, the White House "packaged" prewar intelligence to justify going to war.
"It's public record that they were ignoring caveats and ignoring contradictory intelligence," McClellan said.
Mr. Bush also backtracked or outright broke his promise of accountability in the Plame matter, McClellan said.
The White House had said in 2003 that anyone who leaked classified information in the case would be dismissed. Mr. Bush reiterated that promise in June 2004.
By July 2005, Mr. Bush qualified his position, saying he would fire anyone for leaking classified information if that person had "committed a crime." He then commuted Libby's sentence.
McClellan said the White House was helping the Justice Department investigate the leak, but he knew of no internal White House probe to ferret out and fire the leaker.
"I certainly think that the president should have stuck by his word on the matter, and I certainly view the commutation as it was special treatment," McClellan said. "It does undermine our system of justice."
Republicans cast his testimony as old news. Ranking Republican Lamar Smith questioned the impartiality of McClellan's publisher and said that whatever the witness was instructed to say about the Plame affair was typical work of the White House press office.
"It should be of no surprise that there was spin in the White House Press Office," said Smith. "What White House has not had a communications operation that advocates for its policies? Any recent administration that did not try to promote its priorities should be cited for dereliction of duty."
Rather than discuss the substance of the book, former and current Bush aides "sought to turn it into a game of 'gotcha,' misrepresenting what I wrote and seeking to discredit me though inaccurate personal attacks," McClellan said.
Stunned White House aides fired back at McClellan in May, and Bush press secretary Dana Perino issued a statement that was highly critical of their former colleague.
"Scott, we now know, is disgruntled about his experience at the White House," she said last month. "For those of us who fully supported him, before, during and after he was press secretary, we are puzzled. It is sad - this is not the Scott we knew."
"Scott himself repeatedly made the case for the war from the podium and even after he left the White House, I remember watching him on Bill Maher's show - about one year ago - making the case for the war," former White House Press Secretary Ari Fleischer wrote in a statement. "If Scott had such deep misgivings, he should not have accepted the press secretary position as a matter of principle."
Said former top aide Karl Rove, in an interview with Fox News Channel: "If he had these moral qualms, he should have spoken up about them. And frankly I don't remember him speaking up about these things. I don't remember a single word."
McClellan's book draws a portrait of his former boss as smart, charming and politically skilled, but unwilling to admit mistakes and susceptible to his own spin. Mr. Bush "convinces himself to believe what suits his needs at the moment," McClellan wrote.
He also faults Mr. Bush for a "lack of inquisitiveness."
"President Bush has always been an instinctive leader more than an intellectual leader," McClellan writes. "He is not one to delve deeply into all the possible policy options-including sitting around engaging in extended debate about them-before making a choice. Rather, he chooses based on his gut and his most deeply held convictions. Such was the case with Iraq."