Michael Flynn. Win McNamee/Getty Images The former top ethics lawyer for President George W. Bush said new revelations about axed national security adviser Michael Flynn demonstrate he should be stripped of his title as a three-star general.

Richard Painter, who served under Bush from 2005 to 2007 and is now a professor at the University of Minnesota, told Business Insider that stripping Flynn, a retired lieutenant general, of his military title is the next logical step forward in the saga.

"I think that's the next step is the president should take," Painter said. "The president is the commander in chief. We have a subordinate in the military who is in violation of the Emoluments Clause, taking payments from a foreign government and two, lied about it."

"So, it's good that he's out of the White House, but he should lose his status," Painter continued. "That's the next appropriate step. Someone does something that is unconstitutional, and they not only do it but they were told not to do it and they do it anyway, he's out. That's the only appropriate answer."

Democratic Rep. Elijah Cummings of Maryland, the ranking member of the House Oversight Committee, released documents Thursday that showed the Defense Intelligence Agency, the outlet that Flynn led as director from 2012 to 2014 before being forced out, told Flynn in a letter that he could not accept money from foreign governments after his retirement from the military. The DIA sent the letter to Flynn in response to a request he made "regarding the ethics restrictions" that applied to him in retirement.

But in 2015, Flynn was compensated for speaking at a Russia Today gala in Moscow, where he was seated next to Russian President Vladimir Putin. RT is Russia's state-owned news agency.

A subsequent DIA letter also made public by Cummings on Thursday said Flynn did not seek permission from the DIA before accepting the payments. The letter also said he did not disclose them afterward, appearing to contradict a statement from Flynn's lawyer. Cummings also released a letter from the Inspector General of the Army that said the office was looking into whether Flynn violated the Emoluments Clause of the Constitution. That clause prohibits retired military personnel from accepting a foreign-source payment without prior permission.

In a joint press conference Tuesday, Cummings and House Oversight Committee chair Jason Chaffetz, a Utah Republican, announced that Flynn did not appear to comply with the law.

Donald Trump and Flynn. George Frey/Getty Images

Painter said future criminal charges could stem from Flynn's apparent failure to disclose the payments, as he could be found in violation of US Code 1001. The Emoluments Clause has not led to a criminal prosecution in US history, and Painter said the appropriate punishment for a violation of it would be firing, something to which Flynn has already been subjected.

He firmly believes that Flynn violated the Emoluments Clause by accepting the payment in 2015.

"He was told not to do it, he did it anyway, and then he lied about it," Painter said. "So ... his lying about it is clearly a crime."

Painter, who supported Democratic presidential nominee Hillary Clinton in the general election campaign, said the White House should "immediately" turn over all relevant documents pertaining to Flynn over to Congress. Asked during Thursday's press briefing, White House press secretary Sean Spicer said there were not any documents pertaining to Flynn that needed be given to Congress that he was "aware of at this point."

"They ought to be subpoenaed and they ought to be turned over," Painter said. "That ought to be non-negotiable. Second, the White House ought to fire anybody who knew about the payments from Russia and didn't disclose it up the ladder to the president of the United States. Anybody who knew about the payments from Russia, and who concealed it rather than taking an appropriate action should be fired. And we need to find out who those people are in the White House."

Painter called the Emoluments Clause "a conflict of interest so serious that the founders addressed it in the Constitution."

"So the receipt of illegal payments from a foreign government, and lying about it, particularly when that foreign government has been one that for decades has been an adversary of the United States and sought to destabilize our government and conducted spying activities inside the United States, that's the absolute most serious," he said. "But I think the most important is finding out who else in the White House knew about this and covered it up. Whoever it is ought to be gone and the documents turned over to Congress."

During a Thursday press conference announcing the findings, Sen. Richard Blumenthal of Connecticut said the evidence released was "powerful, mounting, and incontrovertible ... that there has been a violation of criminal law."

"This evidence is powerful in showing that Gen. Flynn broke significant criminal laws," the Connecticut Democrat said. "The DIA letter, the DOD letter, the inspector general letter, all testify to a flagrant violation of federal criminal statutes that must be investigated and prosecuted." Michael Flynn. Mario Tama /Getty Images

During his Thursday briefing, Spicer pointed to the fact that Flynn had passed a security clearance in the final year of President Barack Obama's administration to argue that he did not need to be vetted again before being appointed as national security adviser. Spicer added that Trump made the "right call at the right time" in pushing out Flynn back in February. Spicer called the investigation launched by the Inspector General of the Army "appropriate."

"If they think that there's wrongdoing then the department's inspector general should look into that," he said.

Flynn was forced to step down as Trump's national security adviser after just 24 days on the job, after multiple outlets reported he misled Vice President Mike Pence about conversations he had with Russian ambassador Sergey Kislyak prior to Trump's inauguration.

Last month, Flynn offered to testify in front of the House and Senate intelligence committees in exchange for immunity from prosecution, a sign that legal experts believe indicated he thought he may have committed a crime. Neither committee, in addition to the FBI, which is investigation potential collusion between Trump associates and Russian government officials to influence last year's election, has taken him up on the offer.

Flynn told NBC in September "when you are given immunity, that means you have probably committed a crime," after being asked about the partial immunity given to a handful of Clinton aides in the FBI investigation into her use of a private email server while she served as secretary of state.

Pamela Engel and Natasha Bertrand contributed to this report.