Mr Smith was appointed as special counsel in 2022 to oversee two Justice Department cases into Trump – one over the alleged improper hoarding of classified documents and the other over an alleged attempt to interfere in the 2020 election outcome.

Both cases resulted in criminal charges against Trump, who pleaded not guilty and and sought to cast the prosecutions as politically motivated.

Mr Smith’s cases against the president-elect were closed last year following Trump’s presidential election win. Prosecutors wrote that Justice Department regulations forbid the prosecution of a sitting president.

CBS reported in November that Mr Smith’s resignation was expected as it would allow him to leave his post without being fired by Trump or the incoming president’s attorney general.

His exit means he leaves without either of his criminal prosecutions of Trump seeing trial.

Earlier this week, US District Judge Aileen Cannon – who oversaw the classified documents case and controversially dismissed it last July – temporarily barred Mr Smith and Attorney General Merrick Garland from “releasing, sharing, or transmitting” the report about the case.

Trump’s legal team received a draft copy of the report last weekend and it was expected to be released as soon as Friday.

The move by Judge Cannon came after attorneys for Trump’s former co-defendants in the case – Walt Nauta and Carlos de Oliveir – called on her to intervene. Both men had pleaded not guilty.

Judge Cannon ordered the release be put on hold until a higher appeals court, the Eleventh Circuit in Atlanta, considered an emergency appeal from Mr Nauta and Mr De Oliveir.

By law, special counsels must present the findings of their investigations to the Justice Department, which is headed by the attorney general. Garland has promised to release all reports to the public and has so far done so.