Lawmakers and congressional insiders continue to raise questions about a senior Obama administration official and proponent of its Iran diplomacy following revelations he was denied interim security clearance before being given a senior role in the White House, according to conversations with multiple sources.

The Washington Free Beacon first disclosed last week that Ben Rhodes, a White House deputy national security adviser who handled the administration's efforts to mislead the public about the terms of the Iran nuclear agreement, is being probed by Congress following disclosures the FBI may have denied him top-level security clearances.

Lawmakers told the Free Beacon that the Obama administration has been obstructing formal efforts to obtain information about why Rhodes was initially denied FBI clearance and how he ultimately received top-secret clearances.

The latest disclosures have cast a cloud over the Obama administration's diplomacy with Iran just weeks before the president and his senior officials vacate their West Wing offices ahead of President-elect Donald Trump's inauguration.

"When the news broke that the FBI had denied Ben Rhodes an interim security clearance during the 2008 Obama transition, I, like many Americans, was deeply troubled that a man unworthy of a security clearance was nevertheless made a senior Obama adviser," Rep. Trent Franks (R., Ariz.), one of the leaders of the current inquiry, told the Free Beacon.

"Ben Rhodes used his position to create the Iran deal ‘echo chamber' by admittedly lying to the gullible media in order to willfully mislead the American people about the [Iran nuclear deal]—consequently, questions abound," Franks said, adding that multiple questions remain about the circumstances surrounding FBI investigations into Rhodes' past.

"What did the FBI find that led them to suggest Ben Rhodes be denied a security clearance? Why was Ben Rhodes the only applicant out of 187 to be rejected for an interim security clearance? Why did he go on to become the president's most trusted foreign policy advisor?" Franks asked. "We need to know this information in order to judge Mr. Rhodes' legacy as a senior foreign policy adviser, and protect the integrity of our security clearance processes."

Franks disclosed that the Obama administration has declined to answer congressional questions regarding the situation.

"So far the Obama administration has refused to answer," he said. "I sent the letter to [FBI Director James] Comey in order to get the answers to these important questions."

An Obama administration official who spoke to the Free Beacon about the congressional inquiry dismissed concerns about Rhodes, saying he has long had all necessary and relevant White House security clearances.

The official also said the administration has not heard from Franks' office about the matter.

One senior congressional adviser who has fought with the White House National Security Council about its diplomacy with Iran told the Free Beacon that answers about Rhodes' past issues with the FBI screening process could shed light on the administration's subsequent outreach to Iran.

"Ben Rhodes systematically misled the American people and Congress about the goal of the nuclear deal, which was to ally with Iran at the expense of our traditional allies," said the source, who was authorized only to speak on background. "His foreign policy unleashed Iran across the region. It's no wonder the White House doesn't want to talk about the details of Rhodes being denied security clearance."

The Free Beacon first disclosed last week that Franks and Rep. Jim Bridenstine (R., Okla.) sent an inquiry to Comey requesting information about disclosures that Rhodes was denied initial security clearance in 2008.

Individuals can be denied security clearance for a number of reasons, including a criminal record, history of drug use, or "questionable foreign ties or relationships."

"For the FBI to evidently find something in Mr. Rhodes' background that led it to potentially deny him a security clearance only to have Mr. Rhodes work at the highest levels of the Obama administration shakes the entire clearance process to the core," the lawmakers wrote. "Mr. Rhodes was working in the White House for the past seven years and is the architect of the Iran deal ‘echo chamber,' as he recently described himself."

White House officials declined to comment on the record about the matter.