Michael Atkinson said in a statement on Sunday that he was “disappointed and saddened” by the decision.
“It is hard not to think that the President’s loss of confidence in me derives from my having faithfully discharged my legal obligations as an independent and impartial Inspector General, and from my commitment to continue to do so,” said Mr Atkinson in a statement released on Sunday.
The intelligence community’s inspector general last year told Congress that he had received a complaint stating that president Trump had pressured Ukraine to open an investigation into Democratic presidential candidate Joe Biden and his son.
Mr Trump said on Friday that he “no longer” had confidence in the outgoing inspector general, who would be removed from office within 30 days.
On Saturday, Mr Trump defended his decision before describing Mr Atkinson as a “disgrace” who had done a “terrible job”.
Democrats described the dismissal as the latest retaliation against officials who were involved in the president’s impeachment trial, after Gordon Sondland was fired as US Ambassador to the EU following his witness testimony against Mr Trump.
In a memo to senior members of the House and Senate Intelligence committees, the president wrote: “it is vital that I have the fullest confidence in the appointees serving as Inspectors General. That is no longer the case with regard to this Inspector General.”
Mr Atkinson called on the intelligence community to continue protecting whistleblowers independently and effectively. He added: “Please do not allow recent events to silence your voices.”
Mr Atkinson had served in his position since May 2018, and is set to be replaced by Thomas Monheim as acting intelligence community inspector general.