The top writer for Tucker Carlson’s Fox News program has resigned after it was revealed he’d secretly posted racist and sexist messages for five years on an online forum, CNN Business reported Friday.

Blake Neff, who worked for the right-wing Daily Caller before moving over to Fox News four years ago, had been posting the messages under the pseudonym CharlesXII and sometimes referred to work he did for Carlson in his messages, according to CNN.

The message board was AutoAdmit — also known as XOXOhth — which often features racist, sexist and vulgar content, CNN reported. 

Neff’s messages included racist posts about Black men and a mocking, years-long detailed account of the love life of a woman, who was then harassed by his online followers.

Fox News issued a statement to employees Saturday noting that management first learned Friday that “now former employee Blake Neff” made “horrendous and deeply offensive racist, sexist and homophobic comments under a pseudonym” on AutoAdmit.

“We want to make abundantly clear that Fox News Media strongly condemns this horrific racist, misogynistic and homophobic behavior,” the statement added. “Neff’s abhorrent conduct on this forum was never divulged to the show or the network until Friday, at which point we swiftly accepted his resignation. Make no mistake, actions such as his cannot and will not be tolerated at any time in any part of our work force.” 

In a 2018 interview on Fox News, Carlson called Neff a “great writer.” He also acknowledged Neff in the credits for his book “Ship of Fools” for research and for “greatly” improving “our nightly show on Fox.”

There was no immediate comment from Carlson. But shortly after the CNN report, Carlson exploded in his program over “cancel culture.” He added: “We are in a situation where it’s… individuals against the mob — online, other news organisations, CNN particularly.”

The Fox News statement said he would address the issue on his program Monday.

Neff did not respond to repeated calls by CNN for comment and could not be reached for comment by HuffPost. His social media accounts have been deleted.

Carlson’s Twitter critics hailed Neff’s departure — and eagerly awaited any other comment from the Fox News host.  

This story has been updated to include comment from Fox News.