NBC News pushed back against the investigative journalist Ronan Farrow on Monday, denying his allegations that the network tried to conceal complaints about the former “Today” host Matt Lauer and obstruct Mr. Farrow’s reporting into the film mogul Harvey Weinstein.

“We have no secrets and nothing to hide,” the NBC News president, Noah Oppenheim, wrote in an extensive memo, which was sent to employees of NBC News and MSNBC in response to reporting in Mr. Farrow’s new book, “Catch and Kill.”

Mr. Oppenheim, who is portrayed in the book as failing to understand the newsworthiness of Mr. Farrow’s investigation into sexual misconduct allegations involving Mr. Weinstein, described the reporting in it as a “smear” and a “conspiracy theory.”

Mr. Farrow has also blamed the NBC News chairman, Andrew Lack, for impeding his reporting on Mr. Weinstein. Mr. Farrow left the network in 2017 and later won a Pulitzer Prize for his work on the article, which was published in The New Yorker.