Obama administration reviewed Mike Flynn's security clearance, Trump WH says The ex-Trump adviser is under investigation by the Department of Defense.

 -- The White House today attempted to shift blame to the previous administration for the Trump transition team's approval of Mike Flynn's security clearance when he was brought on as national security adviser.

"His [security] clearance was last reissued by the Obama administration in 2016 with full knowledge of his activities that occurred in 2015," press secretary Sean Spicer told reporters this afternoon.

President Trump tapped Flynn to be his first national security adviser in November 2016, a position within the incoming administration that did not need Senate confirmation.

Documents released in March showed Flynn was paid a total of $56,200 in 2015 by three Russian firms owned by or closely tied to the Kremlin.

Flynn was the director of the Defense Intelligence Agency under President Obama but, after two years, he was forced out of that role and ultimately retired.

In February, Flynn was pushed out of his position as national security adviser by Trump after it was discovered that he misled Vice President Mike Pence about conversations he had with a Russian ambassador.

When asked today whether Flynn would still have his job if he hadn't been fired by the president, Spicer said, "I will just say they think the president made the right call at the right time and it's clearly paid off."

During the briefing, Spicer also went into the process of how to obtain a security clearance.

"There's an investigation done. You are re-investigated every five years if you are able to maintain that clearance,” he said. “And whoever owns that clearance, whether it's the FBI or the Department of Defense, goes out, does the investigation."

The press secretary added, "In between that period you're responsible for updating the information that you've provided in accordance with the agency that issued that."

Flynn had been warned in a letter from the Pentagon against receiving payments from foreign governments in 2014 after leaving the Defense Intelligence Agency, Rep. Elijah Cummings, D-Md., revealed today.

The letter, released today by Cummings, was a primer on ethics restrictions that apply to retired military officers and it warned that Flynn, a retired lieutenant general, was prohibited from receiving foreign payments without prior approval, under the emoluments clause of the U.S. Constitution.

The Defense Department's inspector general opened the probe today into whether Flynn received permission to accept foreign payments.

Spicer said today the Trump administration welcomes the Department of Defense investigation of Flynn.

Spicer also responded to Rep. Cummings's accusations that the White House is staging a "cover-up."

“I was frankly taken back by his comments today because they're frankly not true,” Spicer said.

ABC News' Benjamin Siegel contributed to this report.