Carl Icahn speaking at the World Business Forum in New York in 2007 Mark Lennihan/Associated Press

Billionaire investor Carl Icahn stepped down Friday as a special regulatory adviser to President Donald Trump, citing “partisan bickering” over whether he was leveraging his White House role to advance his business interests.

Icahn’s resignation came with Trump’s blessing, the investor wrote, and capped a week marked by an exodus of top executives and business leaders from White House advisory panels in response to the president’s comments to the recent violence in Charlottesville.

The resignation letter, posted on Icahn’s personal website, makes no mention of Trump’s widely criticized reaction to the white supremacists who descended upon the Virginia city. Instead, Icahn said he did not want the conflict-of-interest concerns surrounding his role to “in any way cloud your administration or Ms. Rao’s important work”—a reference to Neomi Rao, administrator of the Office of Information and Regulatory Affairs.

Icahn denied profiting off of his role and downplayed his involvement with the Trump administration, writing Trump that “because of your extremely busy schedule, as well as my own, I have not had the opportunity to spend nearly as much time as I’d hoped on regulatory issues.”

“I never had a formal position with your administration nor a policymaking role. And contrary to the insinuations of a handful of your Democratic critics, I never had access to nonpublic information or profited from my position, nor do I believe that my role presented conflicts of interest,” he wrote. “Indeed, out of an abundance of caution, the only issues I ever discussed with you were broad matters of policy affecting the refining industry. I never sought any special benefit for any company with which I have been involved, and have only expressed views that I believed would benefit the refining industry as a whole.”

Icahn wrote that he had received numerous inquiries about whether his unofficial position overlapped with Rao’s U.S. Senate-confirmed role.

“As I know you are aware, the answer to that question is an unequivocal no, for the simple reason that I had no duties whatsoever,” he wrote.