NEW YORK — The chief lobbyist for AT&T is leaving the company after overseeing a $50,000-per-month contract for President Donald Trump’s attorney Michael Cohen to serve as a political consultant.

In a memo to employees, AT&T CEO Randall Stephenson said the company made a “big mistake” in hiring Cohen as a political consultant. While everything the company did was legal, Stephenson said that the association with Cohen was “a serious misjudgment.”

Stephenson noted that the company’s reputation has been damaged and that the vetting process used by its team in Washington “clearly failed.” The Washington team had hired Cohen under a one-year contract that paid $50,000 a month.

Stephenson said Bob Quinn, senior executive VP of the external and legislative affairs group, “will be retiring.”

The Justice Department is seeking to block AT&T’s $85 billion purchase of Time Warner on the grounds that it would stifle competition. AT&T disagreed, sending the battle into a federal trial. U.S. District Judge Richard Leon is expected to rule next month.