Former national security adviser Michael Flynn is either "one of the dumbest individuals who's ever lived or ... he really had some nefarious purposes" in failing to disclose payments he received from Russia on his 2016 security-clearance application, retired Army Col. Lawrence Wilkerson told MSNBC on Tuesday.

Wilkerson, who served as the chief of staff to Secretary of State Colin Powell, told MSNBC's Chris Hayes "there were certain things I didn't do" as a military professional in the "highest levels of government."

"Not necessarily because it was against the law," Wilkerson said, "but because of the impropriety and how it would look to the American people. So either Flynn is one of the dumbest individuals who ever lived, or, as some are insinuating, he really had some nefarious purposes."

Reps. Jason Chaffetz and Elijah Cummings, the top Republican and Democrat on the House oversight committee, said in a joint press conference on Tuesday that Flynn appeared to have broken the law by not disclosing the payment he received from Russia's state-owned news agency, Russia Today, in December 2015.

Chaffetz, the committee's chairman, and Cummings told reporters they had obtained the SF86 security-clearance application that Flynn filed in January 2016, one month after he traveled to Moscow to speak at a gala celebrating RT's 10th anniversary.

Wilkerson explained in an email on Wednesday that by "nefarious purposes" he meant activities ranging from "taking money for influencing your government on behalf of another government, to using your influence with the President and his cabinet on an issue for another government whom you are privately advising, even if pro bono."

"What I recall most vividly from [my] briefings is the admonition that, for high-level officials — particularly political appointees — even the possible perception of impropriety is to be avoided," said Wilkerson, who is now an adjunct professor of government and public policy at William and Mary.

"In other words, the action might not be strictly speaking illegal, but if it were perceived by the public as unethical, immoral, or even 'beneath a government official on the taxpayers dollar,' it should be avoided."

Documents the committee obtained later from Flynn's speaking bureau revealed that Flynn, a former military officer who headed the Defense Intelligence Agency from 2012 to 2014, was paid about $33,000 for the speaking engagement. But Chaffetz and Cummings said he appeared not to have disclosed those funds on his application.

"I see no evidence or no data to support the notion that Gen. Flynn complied with the law," Chaffetz said. "He was supposed to seek permission and receive permission from both the secretary of state and the secretary of the Army prior to traveling to Russia to not only accept that payment, but to engage in that activity."

Cummings said that while Flynn's negligence on his SF86 forms could be punished by up to five years in prison, that decision was not up to the oversight committee.

Flynn was forced to step down from his position in February after only 24 days amid revelations that he misled Vice President Mike Pence about his conversations with Russia's ambassador to the US, Sergey Kislyak. Flynn's contact with Kislyak and other foreign nationals is being investigated by the House Intelligence Committee, which Chaffetz said would take the lead on examining whether those contacts themselves were inappropriate.

Flynn last month offered to testify before the congressional intelligence committees in exchange for immunity from prosecution — a signal to some legal experts that he thought he may have committed a crime. Neither of the committees have taken him up on the offer.

The oversight committee's announcement that Flynn's SF86 ommissions were legally questionable has fueled calls from House Democrats for Trump's son-in-law, Jared Kushner, to have his security clearance suspended.

Kushner reportedly ommitted dozens of foreign contacts from his security-clearance form, including his meetings with Kislyak and Russian bank CEO Sergey Gorkov in December.

"Mr. Kushner's lack of candor about meetings with Russian officials appears to be part of a larger pattern of dissembling and deception on Russian contacts from the Trump team, and we believe the public deserves the truth about what connection, if any, exists between these incidents," five House Democrats said in a statement released earlier this month.

Democratic Rep. Ted Lieu tweeted a blunt assessment on Tuesday night: "Dear Jared Kushner: Lying on the SF-86 security clearance form is a crime. Michael Flynn hired a lawyer. You may also want to hire a lawyer."