President Donald Trump’s personal attorney demanded NBC Universal and one of its MSNBC primetime hosts issue a retraction and apology for a report aired Tuesday night that bank records showed Russian oligarchs co-signed Trump Organization loans.

Lawrence O’Donnell dropped a would-be bombshell at the beginning of his show during a conversation with fellow MSNBC host Rachel Maddow. The story, if accurate, would support a theory floated by Democrats and liberal pundits that Trump’s Deutsche Bank records contain information about illicit business dealings between the bank and Trump’s real estate firm.

“These statements are false and defamatory, and extremely damaging,” Charles Harder, a lawyer for Trump, wrote in a letter to NBC Universal general counsel Susan E. Weiner, according to the Hollywood Reporter.

He then demanded that O’Donnell and NBCU “immediately and prominently retract, correct and apologize for the aforementioned false and defamatory statements.” (RELATED: Lawrence O’Donnell Floats Bombshell Claim About Trump Taxes, Later Admits Story ‘Will Need A Lot More Verification’)

“This single source close to Deutsche Bank has told me that Donald Trump’s loan documents there show that he has co-signers. That’s how he was able to obtain those loans, and that the co-signers are Russian oligarchs,” O’Donnell said on his show.

Maddow responded: “What? Really?”

O’Donnell acknowledged again at the end of his hour-long show that he hadn’t seen the Deutsche Bank records himself and that his report was based on a single source. NBC News had also not verified the report, he added.

“As I said at the beginning of this hour, and I want to say this carefully: A source close to Deutsche Bank revealed to me — a single source close to Deutsche Bank — that Donald Trump’s tax returns show that he pays very little income tax, and more importantly, that his loans with Deutsche Bank have Russian co-signers,” said O’Donnell.

He continued that the story has “not been confirmed by NBC News,” and that he hadn’t seen “any documentation from Deutsche Bank that supports this and verifies this. This is just a single source who has revealed that to me,” adding that, “it’s going to need a lot more verification before that can be a confirmable fact.”

WATCH:

Harder rebutted O’Donnell’s claims about co-signers to Trump loans, saying Trump entities were the “only borrowers” on the loans, and that “Mr. Trump is the only guarantor.”

“Numerous documents for each of these loans are also recorded, publicly available and searchable online,” said Harder. “Thus, actual malice can easily be proven based on your reckless disregard of the truth and unreasonable reliance on an alleged ‘source’ who you will not even identify in your story and likely is seeking to mislead you and the public for political reasons or other ulterior motives.”

Harder, who demanded that MSNBC retain all communications related to O’Donnell’s report, said if the company does not issue the retraction and apology, Trump and the Trump Organization will explore additional legal options “which could include immediate legal proceedings” against O’Donnell and NBC.

NBC Universal did not immediately respond to a request for comment on O’Donnell’s thinly sourced story, or Harder’s demands.

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