The federal government’s top ethics watchdog is resigning after months of mounting tension with the Trump administration and White House allegations of a political witch-hunt by his agency. Walter Shaub, the director of the Office of Government Ethics, informed President Donald Trump of his resignation in a letter on Thursday. He will officially step down on July 19, and will join the Campaign Legal Center, a nonprofit ethics group. Shaub told The Washington Post that he “was not leaving under pressure, adding that no one in the White House or the administration pushed him to leave. But the ethics chief said he felt that he had reached the limit of what he could achieve in this administration, within the current ethics framework.” But he added: “In working with the current administration, it has become clear that we need to strengthen the ethics program.” His resignation comes in the wake of allegations by the White House that Shaub was “distorting facts and attempting to tarnish the White House for purposes of a partisan agenda” by pursuing ethics complaints against White House officials, including the West Wing lawyer in charge of ensuring ethics compliance. Shaub had also clashed with Office of Management and Budget director Mick Mulvaney, who questioned the scope of OGE’s authority over ethics rules implemented by Trump in January. OGE has been tasked with implementing ethics restrictions that the administration has circumvented at a far higher rate than that of Trump’s predecessor.