Andrew McCabe, the FBI deputy director targeted by US President Donald Trump and congressional Republicans as the agency continues its Russia investigation, has resigned.
Press Secretary Sarah Huckabee Sanders said the White House played no role in his resignation.
"The President wasn't part of this decision-making process," she told reporters on Monday (local time).
The New York Times reported that McCabe told friends that he felt pressure from FBI director Christopher Wray to step down.
But Trump had publicly attacked him and wrote on Twitter in December, "How can FBI Deputy Director Andrew McCabe, the man in charge, along with leakin' James Comey, of the Phony Hillary Clinton investigation (including her 33,000 illegally deleted emails) be given $700,000 for wife's campaign by Clinton Puppets during investigation?"
There had been speculation that McCabe would step down in March, once he was eligible to receive full retirement benefits.
But he has been the target of right-wing media claiming that he is part of the so-called "deep state" undermining the Trump presidency.
McCabe served as interim FBI director, after Trump fired James Comey. McCabe returned to his post, after Wray was confirmed as the new director.
The Washington Post reported last week that shortly after McCabe was appointed deputy FBI director, Trump asked him who he voted for in the 2016 election.
McCabe's wife, Jill, was the recipient of $US500,000 from Virginia Governor Terry McAuliffe in her bid for a state senate seat. Trump was reportedly upset by Jill McCabe's political involvement.
McAuliffe is a long-time ally of Trump's 2016 foe, Hillary Clinton.
The network also said that Trump suggested that McCabe ask his wife how she felt being a loser. She failed to win her campaign for office.
McCabe replied: "OK, sir."
Democrat Seanator Richard Blumenthal called for a "full explanation" of the circumstances of McCabe's departure.
He said that McCabe "was subject to baseless political attacks, levelled by President Trump's sycophantic supporters in an effort to discredit the work of the FBI and the integrity of the Russia investigation".