Michael Wolff, author of Fire and Fury: Inside the Trump White House, implied in an interview with Bill Maher on Friday that President Donald Trump is currently having an affair.
Wolff initially played coy when Maher asked him to tell him something that was in book that people had missed.
"There is something in the book that I was absolutely sure of but it was so incendiary, that I just didn't have the ultimate proof," Wolff said to Maher, reports the Daily Mail.
"Is it a woman thing?" Maher asked.
"I didn't have the blue dress," Wolff responded, referencing the dress that became the centerpiece of the Bill Clinton-Monica Lewinksy affair scandal.
That tipped off Maher to what Wolff might be referring to.
"Is it about a woman?" Maher asked.
"It is," Wolff said.
"Oh, it's somebody he's f***king now," Maher said, less like a question than a statement of fact.
"It is," Wolff confirmed. "You just have to read between the lines."
This seemed to irritate Maher, who appeared to grow tired of the cat and mouse game the author was playing.
"What lines?" Maher asked. "You say it's in the book."
"It's toward the end of the book," Wolff said. "Now that I've told ya, when you hit that paragraph, you're gonna say, 'Bingo.'"
This allegation from Wolff comes amidst reports earlier this week that Trump had an affair with adult actor Stormy Daniels, whose real name is Stephanie Clifford, in 2006, shortly after Melania Trump gave birth to his youngest son.
Both Trump and Daniels have denied the affair.
It was first reported by the Wall Street Journal on January 12 that Trump had his attorney, Michael Cohen, pay Daniels $130,000 (NZD $178,633), just before the 2016 presidential election, in exchange for her silence about her alleged physical relationship with Trump.
Earlier this month, Steve Bannon suggested that Donald Trump's lawyers paid off 100 women who had sexual encounters with the then-candidate during the 2016 presidential campaign.
Bannon, in an interview for Wolff's tell-all book, suggested that Clifford wasn't the only woman to receive a similar payout.
"Look, Kasowitz has known [Trump] for twenty-five years," Bannon allegedly said.
"Kasowitz has gotten him out of all kinds of jams. Kasowitz on the campaign - what did we have, a hundred women? Kasowitz took care of all of them."
The remark takes on new significance after the Wall Street Journal reported that another of the president's lawyers, Michael Cohen, sent hush money to Clifford just weeks before the 2016 election.
As part of the alleged deal, the 38-year-old agreed to not speak publicly about it.
The alleged incident occurred at a hotel in Lake Tahoe during the July 2006 American Century Celebrity Golf Championship at the Edgewood Tahoe in Stateline, Nevada.
It was described this week in a Wall Street journal report which disclosed the sum allegedly paid.
In response to that report, the president's lawyer vehemently denied that any such sexual encounter ever occurred.
A friend of Clifford's came forward to say she had been told about it by her in 2006.
Clifford's friend Alana Evans, who is also a porn star, told The Daily Beast that how Clifford confided in her about it at the time and that she was even invited into the hotel room - an invitation she declined.
"All I'm going to say is: I ended up with Donald in his hotel room. Picture him chasing me around his hotel room in his tighty-whities," she is alleged to have said.
In 2006, Trump had been married to the first lady for a year.
Evans and Clifford were close friends at that time, and were also neighbors.
• Fire and Fury is available for purchase now, online and in stores.