Carl Icahn, the billionaire activist investor, said Friday that he had agreed with President Trump to stop acting as an outside adviser on regulatory matters.

Icahn posted a letter to Trump on his website, dated Friday, in which he stated that he was ending the relationship in order to prevent "partisan bickering" from harming the administration's work and out of deference to Neomi Rao, the administrator of the Office of Information and Regulatory Affairs.

Democrats had long criticized the unusual arrangement in which Icahn was supposed to advise Trump on regulatory affairs without joining the administration and submitting to any of the related ethics rules or divesting any of his assets.

Earlier this year, some Senate Democrats called for an investigation into the possibility that Icahn used the unique position to profit off of insider information, particularly related to renewable fuel credits.

In Friday's letter, Icahn pushed back against those accusations. "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. He claimed that the only topics he discussed in his conversations with Trump were related to the refining industry and that he had no formal duties.

Icahn gave up his adviser status the same week that Trump disbanded two councils of CEOs meant to discuss manufacturing and the economy. Business leaders began to defect from those bodies in reaction to Trump's comments on the racist violence in Charlottesville, prompting him to dissolve them.