The Director of the Office of U.S. Government Ethics announced his resignation on Thursday.

Walter Shaub Jr.’s resignation is effective as of July 19, he wrote in a letter he posted on Twitter. Shaub’s letter did not include a reason for his departure, but he had previously clashed with the White House.

Shaub is joining the Campaign Legal Center, a nonpartisan campaign finance reform group, as Senior Director of Ethics, that organization announced Thursday.

“In working with the current administration, it has become clear to me that we need improvements to the existing ethics program,” Shaub said in a release from the Campaign Legal Center. “I look forward to working toward that aim at Campaign Legal Center, as well as working on ethics reforms at all levels of government.”

In his resignation letter, Shaub praised the dedication of his office’s staff, calling it “the great privilege and honor of my career” to lead the agency.

Shaub first joined the Office of Government Ethics, or OGE, in 2006, during the George W. Bush administration. He worked his way up the ranks until he was appointed Director by President Barack Obama in 2013.

Shaub only worked with the Trump Administration for about five months. However, it was a period fraught with conflict. In March, he blasted the White House for failing to discipline Senior Adviser Kellyanne Conway after she promoted Ivanka Trump’s clothing line on Fox News, arguing that a lack of action “risks undermining the ethics program.” Even before Trump was inaugurated, Shaub lamented that the OGE was facing pressure to rush through ethics reviews before confirmation hearings for cabinet nominees, and that some nominees had their confirmation hearings scheduled before their ethics reviews were completed.

Shaub also criticized President Trump’s decision to turn the Trump Organization over to his sons, Eric and Donald Trump Jr, for the duration of his presidency and putting his assets in a trust. He argued that only full divestment would be sufficient.

“Stepping back from running his business is meaningless from a conflict of interest perspective,” Shaub said at the Brookings Institute the day Trump announced his plan, January 11, nine days before Trump’s inauguration. “The Presidency is a full-time job and he would have had to step back anyway. The idea of setting up a trust to hold his operating businesses adds nothing to the equation. This is not a blind trust—it’s not even close.”

The White House said Thursday it had accepted Shaub’s resignation and appreciated his service. Trump, who is currently abroad, will nominate a replacement.

-With reporting by Zeke J. Miller

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