The head of a major US evangelical college has quit his job after being accused of hypocrisy.
Mr Falwell Jr came in for criticism after posting a photo of himself with his trousers unzipped on Instagram.
A business partner has also claimed to have been involved in a sexual relationship with Mr Falwell Jr, who heads Liberty University, and his wife.
The college has a strict honour code which bans sexual relations “outside of a biblically ordained marriage”.
A vocal supporter of US President Donald Trump, Mr Falwell Jr took over at the college in 2007 after the death of his father, Jerry Falwell.
Mr Falwell Sr founded the university in the 1970s as well as the conservative Moral Majority movement.
Back and forth
Jerry Falwell Jr first took an indefinite leave of absence from Liberty University earlier this month after posting a photo of himself with his trousers unzipped on Instagram.
On Monday, US media reported he had resigned, citing officials from the institution. Mr Falwell Jr denied the reports, telling Politico news site they were untrue.
The university issued a statement saying Mr Falwell Jr had changed his mind: “On the first day of classes of Liberty University’s fall term, Jerry Falwell Jr, agreed to resign as its President and from its Board of Directors, but following media reports about the resignation, withdrew it.”
In a further U-turn, Mr Falwell Jr eventually confirmed to ABC News and the Wall Street Journal that he had resigned.
The executive committee and board of the evangelical college said it would meet on Tuesday to discuss the matter.
What are the allegations?
Mr Falwell Jr was already under scrutiny for a photograph he posted online earlier this month. He appeared in the image with his trousers unzipped and his arm around a woman.
The image provoked outrage and charges of hypocrisy from the political right and left and Liberty University asked Mr Falwell to take an “indefinite leave of absence” soon after.
Further allegations emerged. Giancarlo Granda, a business partner of Falwell Jr’s, told Reuters news agency on Monday that he had a six-year sexual relationship with the evangelical leader and his wife, Becki Falwell.
“Becki and I developed an intimate relationship and Jerry enjoyed watching from the corner of the room,” Mr Granda reportedly said in an interview.
The college’s honour code states that “sexual relations outside of a biblically ordained marriage between a natural-born man and a natural-born woman are not permissible at Liberty University”.
A lawyer for Mr Falwell Jr told Reuters before their article came out that his client “categorically denies everything you indicated you intend to publish about him”.
On Sunday, Mr Falwell Jr released a statement to the Washington Examiner saying his wife had had an affair and that the man involved had threatened to “deliberately embarrass my wife, family, and Liberty University”.
He also spoke of the “emotional toll” the affair had had on him.