(CNN) -- In an extraordinary new letter, NBC News president Noah Oppenheim says former employee Ronan Farrow is engaged in an "effort to defame NBC News."

Oppenheim says Farrow "is clearly motivated not by a pursuit of truth, but an axe to grind." And he says Farrow's new book "Catch and Kill" is "built on a series of distortions, confused timelines, and outright inaccuracies."

Farrow, meanwhile, says NBC is putting out "lies."

The dispute centers on Farrow's account of a "corporate coverup" at NBC, where he was investigating Harvey Weinstein in 2017.

He reluctantly took his reporting to The New Yorker after being stymied by NBC News executives.

In "Catch and Kill," which comes out Tuesday, Farrow alleges that his Weinstein reporting effort was shut down for inappropriate reasons. He asserts that the network's own secrets weighed on the judgments of his reporting, noting that some high-ranking executives have skeletons in their own closets. And he says that Weinstein claimed to have a deal with those executives.

NBC says there was no such deal with Weinstein. Ever since Farrow's Weinstein investigation was published in 2017 by The New Yorker, NBC has said that he did not have a single on-camera on-the-record interview with a Weinstein accuser, and thus his reporting did not meet standards for broadcast.

In a memo to staffers on Monday, Oppenheim said that NBC "assigned Farrow the Weinstein story and actively supported it, editorially and financially, for seven months. We encouraged Farrow to go back to Rose McGowan and get her to name Harvey Weinstein on camera."

He also said NBC encouraged Farrow to get the full recording of actress Ambra Gutierrez catching Weinstein in the act of groping her in 2015, "and to arrange for his editor and an NBC lawyer to meet with her."

"And," Oppenheim said, "we repeatedly encouraged him to get a victim or witness on camera, on the record. He was unable to do so during his time at NBC."

But Farrow had more leads to pursue when, in August, he was told to stop reporting.

In "Catch and Kill," he methodically makes the case that something nefarious happened — perhaps a secret agreement between Weinstein and NBC.

And he portrays the news division as a boy's club where harassment was covered up and women were paid off — certainly not a newsroom hospitable to an investigation into a movie mogul's abuse of women.

Oppenheim challenges that premise by saying, in Monday's memo, that "over the last decade, NBC News has been on the front line of exposing sexual misconduct involving USA Gymnastics, Silicon Valley, Penn State and many other universities and prep schools, the Jehovah's Witnesses, the State Department, the Secret Service, Capitol Hill, Bill Cosby, professional athletes, Fox News, the Catholic Church, Jeffrey Epstein, Dominique Strauss-Kahn. Roman Polanski, the US Military, sex trafficking rings in the US and abroad, and hundreds more."

But did Farrow's reporting on Weinstein hit a nerve closer to home?

Farrow writes that former "Today" host Matt Lauer's alleged treatment of women, "and NBC's wider use of nondisclosure agreements with women who experienced harassment, were under threat of exposure during our reporting." And he says "that precarious culture of secrecy made NBC more vulnerable to Harvey Weinstein's intimidation and enticement, delivered through lawyers, and intermediaries, and calls to" multiple executives up and down the corporate chain of command.

But Oppenheim says that Weinstein's phone calls were par for the course — no different "from the calls we receive [about] other difficult stories our investigative unit regularly breaks. And none of it played any role in our decision-making."

His producer at NBC, Rich McHugh, shares Farrow's suspicions of a coverup. "One year ago, I resigned from NBC News because they ordered me to stop reporting on Harvey Weinstein, and I did not believe that they had been truthful with me or Ronan," he wrote in an essay for Vanity Fair last Friday.

McHugh recounted Weinstein's surveillance campaign against the pair of journalists and said "what I faced from my bosses at NBC, though, felt worse than being spied on by Weinstein's paid thugs. As a reporter, you expect the powerful people you're investigating to play rough. What's harder to experience is the stress and anxiety of being attacked from the inside, by the people who are supposed to have your back."

McHugh responded to Oppenheim's memo in a tweet that said it's "flatly untrue. I know because I have witnessed their coverup and lies firsthand."

Speaking on "The View" on Monday, Farrow said that the overarching theme of his book is about "systems designed to silence," and how those systems must be ended.

One such system, he asserts, are settlement deals with employees who allege wrongdoing.

And that, too, is a matter of dispute with NBC.

Oppenheim seemingly timed the release of his memo to Farrow's appearance on a rival network, "CBS This Morning," on Monday. In the appearance, Farrow defended his reporting about alleged settlements.

"They had a euphemism at this company called enhanced severance," he said, citing anonymous sources who said "these were explicitly arrangements to shut up women with allegations of misconduct within this company."

Oppenheim, however, says "enhanced severance" was "a standard option for departing employees prior to May 2014, and the severance amount paid was based on years of service. Enhanced severance was the norm; it was paid to hundreds if not thousands of employees regardless of whether the employee had any claim against the company."

NBC is adamant that news division management did not know about allegations against Lauer until he was fired for "inappropriate sexual behavior in the workplace" in November 2017. His termination came one day after an employee, publicly identified for the first time in Farrow's book, lodged a complaint with HR.

The employee, Brooke Nevils, told Farrow in an interview that Lauer raped her during a work trip in Sochi, Russia, in 2014. Nevils described the encounter in detail to NBC lawyers in November 2017, but did not use the word rape at that time.

Lauer categorically denies her allegation and says he has never assaulted anyone.

And his attorney Libby Locke said in a recent statement that, "in 25 years at NBC, Matt Lauer did not have a single complaint brought to his attention until November 28, 2017. NBC has already stated this for the record after an internal investigation."

So what about the "enhanced severance" paid to multiple women in the years before Lauer was fired?

"Farrow alleges there were employees who reported Lauer's behavior prior to November of 2017 and were paid settlements to silence them," Oppenheim wrote Monday. "Not only is this false, the so-called evidence Farrow uses in his book to support the charge collapses under the slightest scrutiny."

He said NBC lawyers "have reviewed both the book and the referenced agreements" and "the only three examples we can find that Farrow alleges are Lauer-related before 2017, with even minimal detail, involve employees who by their own admission made no complaint to management, and whose departure agreements were unrelated to Lauer and completely routine."

"There is no evidence of any reports of Lauer's misconduct before his firing, no settlements, no 'hush money' -- no way we have found that NBC's current leadership could have been aware of his misdeeds in the past," he wrote. "We can all agree those misdeeds should have come to light sooner, and that we should have had a culture in which anyone who knew about his abuse would have felt comfortable telling management. And if anyone on any past management team knew, they should have taken action. But we cannot undo mistakes that may have been made by people who have long since left the company."

Farrow, though, asserts that NBC continues to use settlements to protect corporate secrets, including in the Lauer case.

Nevils, he reports, signed away her right to speak critically about NBC News management when she left the company last year.

"It's telling that NBC News paid her a seven-figure settlement to ensure that she can't talk about what the network knew about this," Farrow said on CBS.

The fact-checker Farrow hired to work on the book, Sean Lavery, made a similar point on Twitter: "NBC News President says network has 'no secrets and nothing to hide' but the settlements with Lauer accusers are contingent on their total silence about NBC. Nevils and her fiancé are barred from speaking about Oppenheim and Lack."

On CBS, Farrow said he is hearing from some of his ex-colleagues at NBC: "There are fantastic journalists at that company," and "they are anguished over what's happening right now and some of the lies being put out by their own corporate leadership."

Other staffers, however, said they are glad Oppenheim has released detailed responses to Farrow.

The-CNN-Wire