US President Donald Trump has fired Michael Atkinson, a senior official who first alerted Congress to a whistleblower complaint that led to his impeachment trial.
Mr Trump said he no longer had confidence in Atkinson, the inspector general of the intelligence community.
Democrats said the president was settling scores during a national emergency caused by the coronavirus.
They also accused him of trying to undermine the intelligence community.
Last year, Mr Atkinson informed Congress of the complaint that President Trump had allegedly abused his office by pressuring Ukraine to open an investigation into Democratic presidential candidate Joe Biden and his son.
In letters to Congress, Mr Atkinson described the complaint as “urgent” and “credible”.
The Democratic-majority House of Representatives voted to impeach the president, but a trial in the Republican-led Senate later acquitted him of all charges.
On Friday, Mr Trump notified Congress that Mr Atkinson would be removed from his post within 30 days. Sources told the Associated Press the official had been placed on administrative leave and would not serve out his 30 days.
“It is vital that I have the fullest confidence in the appointees serving as inspectors general,” Mr Trump wrote. “This is no longer the case with regard to this inspector general.”
He said he would name a successor “at a later date”. Officials quoted by Reuters said Thomas Monheim, a career intelligence professional, would serve as acting inspector general in the meantime.
Democrats reacted angrily to the move.
“In the midst of a national emergency, it is unconscionable that the president is once again attempting to undermine the integrity of the intelligence community by firing yet another intelligence official simply for doing his job,” said Senator Mark Warner, the most senior Democrat on the Senate Intelligence Committee.
Congressman Adam Schiff, who chaired the House impeachment hearings, said “the president’s dead of night decision puts our country and national security at even greater risk.”
“President Trump’s decision to fire intelligence community inspector General Michael Atkinson is yet another blatant attempt by the president to gut the independence of the intelligence community and retaliate against those who dare to expose presidential wrongdoing,” he said.
Last month President Trump replaced his acting chief of staff, Mick Mulvaney, who was perceived to have implicated the president in the impeachment inquiry with an off-the-cuff remark at the White House podium.
Mr Trump has recently come under fire for his handling of the coronavirus outbreak in the US which has so far claimed more than 7,000 lives.
