The director of the U.S. Secret Service, Julia Pierson, has resigned.
Administration officials say Pierson offered her resignation to President Barack Obama, and that he accepted it.
Earlier Wednesday, key lawmakers voiced new criticism of her and the Secret Service, after recent lapses in White House security.
House of Representatives Speaker John Boehner said that as more details emerge about the security breaches, "the clearer it becomes that the Secret Service is beset by a culture of complacency and incompetence." He called for an independent investigation.
House Democratic leader Nancy Pelosi also urged a new investigation.
Their criticism of the Secret Service, the agency charged with protecting Obama and his family, came as accused White House fence-jumper Omar Gonzalez appeared in a Washington court. He pleaded not guilty to charges that he eluded security and ran into the presidential mansion September 19 with a serrated knife in his pants pocket before he was apprehended.
In a separate incident three days before in the southern city of Atlanta, Georgia, a security contractor armed with a gun who had previously been convicted of assault rode on an elevator with Obama and his security detail, even through the Secret Service did not know of his background or that he was armed.
The Atlanta incident was revealed hours after Pierson testified Tuesday before a congressional committee investigating shortcomings at the agency, but never mentioned the elevator security breach.
Pierson said the intrusion into the White House was unacceptable, took "full responsibility" for it and vowed that it would not happen again.
She said the 42-year-old Gonzalez barreled past one agent, and was only caught after running into the ceremonial rooms on the first floor of the presidential mansion, one of the most secure buildings in the United States.
The Secret Service at first said Gonzalez was arrested just inside an unlocked White House door, and that he was unarmed at the time. The president and his daughters had left the residence shortly before the incident, while first lady Michelle Obama had departed earlier.
In one 2011 incident, gunfire hit the White House, but damage from the bullets was only discovered four days later.
In other Secret Service wrongdoing, agents were involved in a prostitution scandal on a presidential trip to Colombia in 2012, and a night of drinking in March led to three agents being sent home from a presidential trip to Amsterdam.
Gonzalez served with the U.S. Army during the nine-year war in Iraq. If convicted, he faces up to 10 years in prison.