'The board asked me to step down as chairman without apparently doing any investigation.
In the report last week, Forbes said Schnatter used the N-word during a media training session in May, and that the incident led the marketing agency to sever its ties with the company.
Recently, the board committee barred Schnatter from talking to the press and moved to remove his likeness from all marketing materials.
The letter was written in advance of a Sunday board meeting in which the directors took actions to further shun Schnatter, including canceling his contractual "founder" duties and evicting him from office space at the company's corporate headquarters in Jeffersontown.
Schnatter alleged in the WLKY interview that he was "kind of provoked" into using the slur in the call, and he thought that the content of the call would be confidential.
Papa John's is struggling to revive its business as Domino's Pizza Inc. and a resurgent Pizza Hut eat into its market share. The board is now trying to kick him off entirely and, in response, Schnatter has now said it was a mistake for him to step down as chairman.
He added: "I will not allow either my good name or the good name of the company I founded and love to be unfairly tainted".
John Schnatter says a media agency tried to extort after he used the n-word during a conference call with them in May.
Laundry Service representatives did not immediately respond to a request for comment.
The company has yet to comment to Schnatter's accusation, but continues to distance itself from its founder.
Schnatter said he is "absolutely not" a racist. He stepped down as CEO in December after criticizing National Football League players for kneeling during the national anthem, blaming the outcry surrounding their protests for slowing sales growth at Papa John's, at the time an NFL sponsor and advertiser.