The US Secret Service director has told lawmakers she takes full responsibility for the serious breach of White House security when an Army veteran with a knife climbed the fence and made his way into the executive mansion before he was tackled.
Julia Pierson also told committee there have been six fence-jumpers this year alone, including one just eight days before the latest intrusion.
Ms Pierson was testifying before the House Oversight and Government Reform Committee in her first public accounting of the episode.
The Army veteran, Omar J Gonzalez, made it much further into the White House on September 19 than previously disclosed by the embattled agency assigned to protect president Barack Obama.
The Washington Post and New York Times said Gonzalez ran past the guard at the front door and into the East Room, which is about halfway across the first floor of the building.
He was eventually tackled by a counter-assault agent, according to the Post.
In the hours after the incident, Secret Service spokesman Ed Donovan told reporters the suspect had been apprehended just inside the North Portico doors of the White House.
The Secret Service also said that night that the suspect had been unarmed - an assertion that was revealed to be false the next day when officials acknowledged Gonzalez had a knife.
Getting so far would have required Gonzalez to dash through the main entrance hall, turn a corner, then run through the centre hallway half-way across the first floor of the building, which spans 168ft, according to the White House Historical Association.
Ms Pierson told the committee that the latest security breach was unacceptable and added she would make sure it "never happens again".
Ms Pierson admitted the agency's security plan to protect the White House was not properly executed when Gonzalez made his way into the mansion.
She said all decisions and actions made on September 19 are being reviewed, including when it is appropriate for the Secret Service to use force. Critics have questioned why officers did not shoot the intruder.
Ms Pierson said the front door to the White House now locks automatically in the case of a security breach.
She told the committee that a Secret Service agent was attempting to lock one of the doors manually when the intruder knocked the agent down.
Ms Pierson said officers and agents are allowed to use "lethal force" to stop someone from getting into the White House.
She was not clear about whether the Secret Service is authorised to shoot people trying to jump over the White House fence, but she said they can shoot if there is an imminent threat to them or others.
Earlier committee chairman Darrell Issa told the panel: "The fact is the system broke down. An intruder walked in the front door of the White House, and that is unacceptable."
Not only that, he said, but the intruder penetrated at least five rings of security protecting what is supposed to be one of the world's most secure properties.
"How on earth did it happen?" he asked. "This failure ... has tested the trust of the American people in the Secret Service, a trust we clearly depend on to protect the president."
Jason Chaffetz, a Republican, said: "I'm worried that over the last several years, security has gotten worse - not better."
He said his committee's request for a briefing from the Secret Service on the incident was denied, a response he called "disappointing and frustrating".
Asked whether he would seek an apology from Ms Pierson, he said: "We're going to let things play out."
Ms Pierson's predecessor, Mark J Sullivan, apologised to lawmakers in 2012 after details emerged of a night of debauchery involving 13 Secret Service agents and officers in advance of the president's arrival at a summit in Colombia. Mr Sullivan retired about 10 months later.