Hagan Scotten, the lead prosecutor on the federal corruption case against Mayor Eric Adams of New York City, resigned after Justice Department officials ordered the dismissal of charges he had helped bring, suggesting that only a “fool” or a “coward” would obey.

In an undated, scathing resignation letter, Mr. Scotten wrote that any federal prosecutor “would know that our laws and traditions do not allow using the prosecutorial power to influence other citizens, much less elected officials.”

He added: “If no lawyer within earshot of the President is willing to give him that advice, then I expect you will eventually find someone who is enough of a fool, or enough of a coward, to file your motion. But it was never going to be me.”

Mr. Scotten was responding to a Justice Department official’s directive this week to dismiss the bribery, fraud and other charges against Mr. Adams so the mayor could help with President Trump’s immigration crackdown.

The official, Emil Bove III, who is the acting deputy attorney general, gave the order to Danielle R. Sassoon, the acting U.S. attorney for the Southern District of New York. She resigned on Thursday rather than carry out the order to seek dismissal of the charges against Mr. Adams.