WASHINGTON — The White House's current explanation for why allegations against top aide Rob Porter failed to have an impact for roughly a year pins the blame on an obscure internal office of personnel security — but more than a day after they first pointed to it, it remains far from clear that office serves the function that the Trump administrations said it does.

Former White House officials paint a different picture of the security office, saying the career professionals who staff it perform largely administrative functions, lacking the authority to keep information from senior administration officials or to make the final determination on whether or not personnel are granted permanent security clearance.

One former senior White House official told NBC News Tuesday night that the personnel security office does "not make decisions," nor do they "do vetting" of White House aides. While they might make recommendations based on background check investigations completed by the FBI, the ultimate decision would be left to senior White House staff, according to this official.

Bob Bauer, former White House counsel to President Barack Obama, described the personnel security office as playing "a logistical role" during an interview on MSNBC Wednesday.

Bauer said that the description Sanders offered of the role of the personnel security office — which she said Tuesday was responsible for making "a recommendation for adjudication" regarding Porter's permanent security clearance — "doesn't correspond" with his experience with the office "at all."

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Another former Obama senior White House official, speaking anonymously with NBC in order to talk freely about their past interactions with the office, said that the career staffers in the personnel office are primarily responsible for passing along information to top White House aides, including the White House counsel, in a timely fashion.

"That's their obligation," the official said. "If they get something, they gotta push it."

The final impact of the completed investigations is then up to the political staff, said the official. Those staffers who are approved for security clearances are contacted by the personnel security office — which may have been referred to by different names during past administrations — to go over how to handle that information, and details about their clearances.

Asked Wednesday on MSNBC if there was any way the White House counsel could have been unaware of the outstanding allegations uncovered over the course of Porter's security clearance investigation, former chief of staff to President Barack Obama Bill Daley said "absolutely not."

"The story just doesn't hold up," he said. "People didn't want to know why Mr. Porter couldn't get cleared...and they didn't ask or they kept hoping that the issue would go away," he said.

To date, White House counsel Don McGahn has been the target of less scrutiny with regard to his role in the Porter clearance scandal than has Chief of Staff John Kelly. Experts have told NBC News that McGahn deserves scrutiny over what he knew, and when, about Porter.

The White House first made mention of the "White House personnel security office" on Tuesday, hours after FBI Director Chris Wray upended their previous narrative, which blamed the administration's failure to act on the serious allegations against Porter on an ongoing FBI investigation into his background.

White House Press Secretary Sarah Huckabee Sanders said Tuesday that the office, which staffers later said was located next to the White House in the New Executive Office Building, may have received details unearthed in the FBI's background investigation into Porter that they did not fully pass along to top West Wing aides because they had not yet made a final recommendation on Porter's security clearance. She did not specify whether the details she referred to included all allegations of domestic abuse.

Several other questions remain unanswered about the role of the personnel security office in the Trump administration: The White House did not answer questions from NBC about how many employees staff the office, who runs it, and whether or not the Trump administration has fundamentally altered its role, asking it to serve a different function than it has under prior presidents.

The Porter story has dominated coverage of the White House for over a week, as the West Wing struggles to produce a consistent account of the timeline that led up to the former staffer's exit.

Messaging isn't the only Porter-linked problem plaguing the Trump administration. In the wake of the incident, and questions raised over the chief of staff's handling of the situation, the president has also been polling allies on possible replacements — though Sanders said Tuesday that John Kelly still has Trump's confidence.