Investor Carl Icahn announced Friday that he is stepping down from his role as special adviser to President Trump on issues relating to regulatory reform.

Icahn, who owns a substantial stake in the oil and refining company CVR Energy, said in a letter to Trump on Friday that he is choosing to “end this arrangement (with your blessing) because I did not want partisan bickering about my role to in any way cloud your administration or Ms. Rao’s important work,” referring to newly minted Office of Information and Regulatory Affairs Administrator Neomi Rao.

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“While I do not know Ms. Rao and played no part in her appointment, I am confident based on what I’ve read of her accomplishments that she is the right person for this important job.” he said.

Earlier this year six Senate Democrats, including Sens. Al Franken Alan (Al) Stuart FrankenGOP Senate candidate says Trump, Republicans will surprise in Minnesota Peterson faces fight of his career in deep-red Minnesota district Getting tight — the psychology of cancel culture MORE (D-Minn.) and Elizabeth Warren Elizabeth WarrenGOP set to release controversial Biden report Biden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt MORE (D-Mass.), reportedly called on the White House Counsel to investigate Icahn’s refusal to divest his private sector interests, citing conflicts of interest, after reports Icahn had worked closely on a planned executive order to overhaul the Environmental Protection Agency’s Renewable Fuel Standard.

The senators claimed Icahn significantly benefited from a policy proposal to shift the burden of complying with biofuel quotas from refiners to fuel blenders. They cited the Wall Street Journal, which reported CVR stocks increasing by 3.5 percent the day the proposal was sent to the White House.

In his letter to Trump Friday, Icahn denied claims that he benefited from his advisory 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 said. “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 was appointed by Trump in December to serve the president in an "individual capacity" not as a federal employee.

The billionaire investor was a strong supporter of the president from the beginning of his presidential campaign.