US President Donald Trump fired the State Department’s head of internal audits, inspector general Steve Linick, late on Friday, according to media reports.
Linick played a “small” role in the impeachment proceedings against Trump, according to broadcaster CNN.
After being informed of the dismissal, House Speaker Nancy Pelosi issued a statement on the “late-night firing,” accusing Trump of punishing Linick for protecting the Constitution and national security.
Eliot Engel, chairman of the House Foreign Affairs Committee, criticised Trump for dismissing Linick to protect “one of his most loyal supporters,” Secretary of State Mike Pompeo.
Engel said he had learned that Linick’s office had opened an investigation into Pompeo.
“Mr Linick’s dismissal in the midst of such an investigation strongly suggests that this is an unlawful act of retaliation,” Engel said, though he did not elaborate on the Pompeo investigation.
The Democrat-dominated House of Representatives impeached Trump last year, after he was accused of pressuring the Ukrainian government to investigate his Democratic rival, Joe Biden.
In February, Trump was acquitted in the impeachment trial by the Senate, which is controlled by Trump’s party, the centre-right Republicans.
Last month, Trump dismissed Michael Atkinson, the inspector general for the US intelligence community who dealt with the whistleblower complaint that ultimately led to his impeachment.
Following Trump’s acquittal, a Ukrainian expert from the National Security Council at the White House, and the US ambassador to the European Union were also relieved of their duties.
Both had testified in Congress against the president after they had been summoned under threat of punishment.