The director of the Office of Government Ethics, for months a vocal and active critic of the Trump administration’s various financial entanglements, announced his resignation Thursday, six months before the scheduled end of his term.

Walter Shaub Jr. announced his resignation in a short letter posted to his Twitter account:

In an interview with the Washington Post published at the same time, Shaub said he hadn’t been pressured out of the position, but that he felt he had done as much as he could within the limitations of the office.

“It’s clear that there isn’t more I could accomplish,” he said.

The Campaign Legal Center, an advocacy group that focuses primarily on government ethics, campaign finance and election law, announced that Shaub would join the group’s staff. CLC was founded by Trevor Potter, once a Republican appointee to the Federal Election Commission who became somewhat of a household name as legal counsel to Stephen Colbert’s conservative, Comedy Central-era persona.

CLC said Shaub would work with Larry Noble, its chief counsel and himself an outspoken critic of the Trump administration for its plethora of conflicts of interest and brushes with the law.

“In working with the current administration, it has become clear to me that we need improvements to the existing ethics program,” Shaub was quoted as saying in a statement on CLC’s website. “I look forward to working toward that aim at Campaign Legal Center, as well as working on ethics reforms at all levels of government.”

Beginning with Trump’s announcement in January that he would not divest from his massive web of businesses, nor would he even put them into a blind trust, Shaub positioned himself squarely against the new administration.

Shaub called the plan “wholly inadequate” and said it “doesn’t meet the standards that the best of his nominees are meeting and that every president in the last four decades have met.”

His prodding of the administration continued for months, including when White House aide Kellyanne Conway plugged Ivanka Trump’s clothing line in her official capacity, and in response to Trump’s after-the-fact waivers for many members of his administration who were in violation of the Presidential ethics pledge.

This post has been updated.