FBI Deputy Director Andrew McCabe has reportedly stepped down as the agency's second in command, a source familiar with the matter has said.

Mr McCabe was criticised by US President Donald Trump for alleged bias against him and in favour of his 2016 Democratic opponent Hillary Clinton.

Mr McCabe had been expected to leave the Federal Bureau of Investigation in March.

He will remain on leave until his retirement date, the source said, speaking on condition of anonymity because a public announcement has not yet been made.

When asked about Mr McCabe's departure, White House spokeswoman Sarah Sanders told reporters: "I can tell you the president wasn't part of this decision-making process."

She also said Mr Trump continues to have "full confidence" in the FBI director, Christopher Wray.

Mr McCabe has become a target of Republican politicians and the Republican president in connection with the FBI's investigation into Mrs Clinton's use of a private email server while she served as US secretary of state.

No charges were brought against Mrs Clinton.

A handful of Republican-led congressional committees have launched inquiries into whether the FBI botched the Clinton investigation and showed bias in her favour.

Democrats have said those inquires are intended to undermine and distract from Special Counsel Robert Mueller's investigation into whether Mr Trump's 2016 presidential campaign colluded with Russia.

Mr McCabe became a target of Republican ire in part because his wife previously ran for a seat in Virginia's state Senate and received donations from then-Virginia Governor Terry McAuliffe, a close ally of Hillary and Bill Clinton, the former president.

Mr Trump has taken to Twitter in recent months to blast Mr McCabe, asking how he could be in charge of the Clinton probe when his wife got donations from "Clinton Puppets."