Brendan Smialowski for The New York Times

The White House on Wednesday invoked the separation of powers to keep Desiree Rogers, President Obama’s social secretary, from testifying on Capitol Hill about how a couple of aspiring reality television show celebrities crashed a state dinner for the prime minister of India last week.

And the couple will not testify, either, according to a statement released late Wednesday by a public relations firm.

The statement says that the Virginia couple, Michaele and Tareq Salahi, have provided to the Secret Service and to the ranking members of the House committee conducting the hearing “all relevant e-mails and cellphone records that detail communications with a White House official,” and can do nothing else to help in the inquiry.

That evidence, the statement says, shows that no laws were broken, that White House protocol “was either deficient or mismanaged” and that there were “honest misunderstandings and mistakes made by all parties involved.”

Earlier Wednesday at his regular briefing with reporters, Mr. Obama’s press secretary, Robert Gibbs, said Ms. Rogers would not testify. “I think you know that, based on separation of powers, staff here don’t go to testify in front of Congress,’’ he said. “She won’t — she will not be testifying in front of Congress.’’

Mr. Gibbs also said the flap over the unauthorized intruders has prompted the White House to change its procedures; from now on, a representative of the social secretary’s office will be stationed at Secret Service checkpoints for major social events in case questions arise. The White House deputy chief of staff, Jim Messina, conducted a review and issued a directive to the staff.

“After reviewing our actions, it is clear that the White House did not do everything we could have done to assist the United States Secret Service in ensuring that only invited guests enter the complex,’’ Mr. Messina wrote in the memo, posted on the White House web site late Wednesday afternoon. “White House staff were walking back and forth outside between the check points helping guests and were available to the Secret Service throughout the evening, but clearly we can do more, and we will do more.’’

The memo was the first admission by the White House of failures on the part of its own staff, and it came as scrutiny intensified on the social office and Ms. Rogers, its director. The House Homeland Security Committee is conducting a hearing on Thursday into the security lapse; Representative Peter T. King of New York, who is the senior Republican on the panel, had wanted Ms. Rogers to testify and criticized the administration for not allowing her to be a witness.

White Houses have often tried to prevent top advisers to the president from testifying on Capitol Hill; the Bush administration worked assiduously to prevent Karl Rove, the top political strategist to former President George W. Bush, from talking to lawmakers under oath about the firing of federal prosecutors. That sparked an intense fight between the Bush administration and Democrats on Capitol Hill.

Now, it is the Republicans’ turn to balk. Mr. King on Wednesday called Ms. Rogers’ decision not to testify “stonewalling” that would cause an “unnecessary confrontation with Congress.”

“I don’t want the Secret Service to be taking the hit here, what went wrong was the responsibility of the White House,” he said, adding, “for them not to be here just raises real questions.”

The director of the Secret Services, Mark Sullivan, is the only witness confirmed for tomorrow morning’s hearing. Even before the Salahis’ public relations firm released its statement, Mr. King said he thought it would be unlikely that the couple would appear at tomorrow’s hearing.

“They’d be crazy to testify,” he said, after meeting with the lawyers. “Their story, if they testify, would just not hold up.”

He said the couple has switched legal advisers from Paul Gardner, an entertainment lawyer, to a powerful Wall Street firm, Dewey & LeBoeuf.

The office of the committee’s chairman, Representative Bennie Thompson, would not comment on the couple’s apparent decision not to appear.

Already the glamorous and successful Ms. Rogers – she possesses a Harvard M.B.A. and was a powerful social player in Chicago before joining the Obama White House — is taking a hit in the press for being more interested in showcasing herself in fashion magazines than in the traditional, behind-the-scenes role of the White House social secretary.

During the White House briefing, Mr. Gibbs answered a series of questions about Ms. Rogers’ role as the social secretary:



Q. Has there been any concern about Desiree Rogers’ performance prior to this instance? Mr. Gibbs: No. Q. No one has questioned the president or told the president that she is a very last-minute person, poor planner? Mr. Gibbs: No, I think you — you all have been to and seen, either whether you’re part of a pool, whether some of you’ve been to receptions, the remarkable work that they have done in pulling off a lot of events here. The first family is quite pleased with her performance, and I’ve heard nothing uttered of what you talked about. Q. Well, what about the issues of her being in fashion spreads early on in the administration? Did you put the brakes on that? I mean, that is — it’s been raised. It’s now public. It’s — you know, you saw it in the magazines, her pictorials. You saw her on the cover of — Mr. Gibbs: There’s a — I get Sports Illustrated in my house.

The brouhaha over how the Salahis managed to talk their way into the dinner has been a major distraction for the White House at a time when Mr. Obama is trying to focus on the economy, health care and the war in Afghanistan. At his briefing on Wednesday, Mr. Gibbs finally cut off the questions, declaring, “I’m going to get back to weightier topics, like 98,000 men and women in Afghanistan.’’