Security practices at the White House are dangerously inadequate say current and former employees of the security office there, according to a letter sent today from the House Oversight Committee to former White House Chief of Staff Andrew Card, asking that he cooperate with the committee's investigation into the alleged security lapses.

"These security officials described a systemic breakdown in security procedures at the White House," wrote the chairman of the committee, Rep. Henry Waxman, D-Calif.

Among the lapses cited by the security officers, who spoke to the committee anonymously, are multiple instances of breaches being reported to the security office that were ignored and never investigated. Several of those instances allegedly involved the mishandling of SCI (Sensitive Compartmentalized Information), which is the highest level of classified information.

In one instance, a White House official reportedly left SCI material behind in a hotel room during a foreign trip with the president. The CIA did recover the highly classified material, but the security office did not investigate the incident or discipline the individual, according a security officer's account in the letter.

The letter states that the security officers were also very critical of the senior management at the security office, including James Knodell, the director of the White House Security Office, and Ken Greeson, the deputy director.

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Officers reported that Knodell and Greeson "routinely violate basic security guidelines" themselves.  In one instance,  Greeson allegedly put classified material on an unsecured computer.

The letter also states that over half of the White House security officers have left the department in the past year due to frustration and poor management.

The letter states that many of the current and former officers came forward following Knodell's testimony last month on Capitol Hill during the Valerie Plame hearings. During his questioning, Knodell testified that the White House never conducted any internal investigation to identify the source of the leak.

Late today, White House Deputy Press Secretary Tony Fratto told ABCNews.com, "I have to give Representative Waxman credit for persistence, if not creativity," said Fratto. "We haven't arrived at any new policies to make senior White House officials available to testify to Congress since Representative Waxman's previous letter. I also don't expect a new policy when we receive tomorrow's letter."Card could not be reached for comment.

This post has been updated.