Moses Farrow, the adopted son of Woody Allen and Mia Farrow, posted a 4,600-word essay on Wednesday defending his father against sexual molestation allegations and claiming his mother was abusive.

In the blog post, titled “A Son Speaks Out,” Mr. Farrow, 40, described repeated spankings by his mother and other abuse, and what he called “a deep and persistent darkness within the Farrow family.”

He recalled, too, his version of the events on Aug. 4, 1992, when his sister, Dylan Farrow, then 7, claimed Mr. Allen, one of the most prolific directors in modern cinema, sexually molested her at their home in Bridgewater, Conn. Moses was 14.

On Thursday night, Mia Farrow said that her estranged son’s claims were “completely made up.”

And Dylan Farrow, now 32, responded to the essay in a tweet, writing that her brother sought to “impugn my mother who has only ever been supportive of me and my siblings.”