The top federal prosecutor in Manhattan has resigned after the Justice Department ordered her to drop corruption charges against the mayor of New York City.

A spokesperson for the U.S. attorney's office for the Southern District of New York (SDNY) confirmed Danielle Sassoon's resignation on Thursday.

It comes four days after acting deputy attorney general Emil Bove sent a memo to Sassoon ordering her to drop the case against New York Mayor Eric Adams. Prosecutors in Sassoon's office have not yet filed a formal motion seeking to have the case dismissed.

The Justice Department did not immediately respond to a request for comment.

Adams, a former police captain, is accused of taking illegal campaign contributions and bribes from foreign nationals, including lavish overseas trips. He faces conspiracy, wire fraud and bribery charges in a five-count indictment sworn last September.

Adams, a Democrat who has forged ties with U.S. President Donald Trump, has pleaded not guilty.

The Southern District, known for bringing high-profile cases on financial crimes, public corruption and national security, has long been known for its independence from the Justice Department in Washington.

It was not immediately clear who would take Sassoon's place.

WATCH | Breaking down Adams's indictment: 

New York City Mayor Eric Adams charged with bribery, fraud

New York City Mayor, and former NYPD officer, Eric Adams has been indicted on five federal charges related to allegations he took illegal campaign contributions and bribes from foreign nationals in exchange for favours.

A half-dozen former SDNY prosecutors told Reuters that the order from Bove, himself a former SDNY prosecutor who also served as Trump's personal criminal defence lawyer, raised questions about whether the office can remain independent of political pressure during Trump's second White House term.

In his memo, Bove said the decision to drop the case had nothing to do with its merits. Instead, he wrote that the case was distracting Adams from helping Trump crack down on illegal immigration, one of the Republican president's top priorities.

Trump has overhauled the Justice Department to end what he calls its weaponization against political opponents during former Democratic president Joe Biden's administration, but which critics say threatens to subject the department to political whims.