President’s pick, who served in role under George HW Bush, is already facing calls to recuse himself from Russia investigation

Donald Trump has named William Barr as his next attorney general, a move that raises fresh concerns about the future of special counsel Robert Mueller’s investigation into Russian election interference.

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If confirmed by the Senate, Barr – who held the same role under the late George HW Bush from 1991 to 1993 – will take over from Matthew Whitaker, who has served in an acting capacity since Jeff Sessions was forced out a month ago.

Democrats have threatened to examine whether Whitaker can legally serve as acting attorney general despite not being approved by senators, which put Trump under pressure to nominate a permanent successor.

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Barr was “my first choice from day one” and “a terrific man, a terrific person, a brilliant man”, the president told reporters outside the White House. He described the 68-year-old as “one of the most respected jurists in the country”, adding: “I think he will serve with great distinction.”

Barr would lead the justice department and be ultimately responsible for Mueller’s investigation into alleged collusion between the Trump election campaign and Moscow.

But he is already facing calls to recuse himself because of previous statements. He has defended Trump’s decision to fire the FBI director, James Comey, in May 2017 when he was leading the Russia investigation. “Comey’s removal simply has no relevance to the integrity of the Russian investigation as it moves ahead,” Barr wrote in the Washington Post.

Barr has also said there is more reason to scrutinise potential wrongdoing by Trump’s election opponent, Democrat Hillary Clinton, than look into any potential collusion with Republicans.

And he claimed that political donations to Democrats suggest Mueller’s team of prosecutors tilts to the left. “I would have liked to see him have more balance on this group,” Barr told the Washington Post in July last year.

The comments are likely to play well with Trump, who continues to rail against Mueller and his team. On Friday the president tweeted: “We will be doing a major Counter Report to the Mueller Report. This should never again be allowed to happen to a future President of the United States!”

Facebook Twitter Pinterest William Barr served as attorney general under President George HW Bush. Photograph: Scott Applewhite/AP

But Barr’s opinions could prompt opposition from Senate Democrats, though the nomination is unlikely to come up for a vote until next year. Republicans will control the upper chamber with a 53-47 majority in the new Congress convening in January.

Richard Blumenthal of Connecticut, a member of the Senate judiciary committee, said on Friday: “I will demand that Mr Barr make a firm and specific commitment to protect the Mueller investigation, operate independently of the White House and uphold the rule of law.

Richard Painter, former White House chief ethics lawyer, tweeted: “Barr is a good pick but he should recuse from the Russia investigation. The president who nominated him has been a subject of the investigation for over a year before this nomination and has sought an AG who will end it. Unacceptable.”

Matthew Miller, a former justice department spokesman, posted on Twitter: “Big burden on the Senate to extract commitments that Barr will either recuse or not interfere with investigations into Trump.”

Barr holds degrees in government and Chinese studies from Columbia University. He studied law at George Washington University and worked at the CIA from 1973 to 1977. He served in the justice department at the same time that Mueller oversaw its criminal division. Barr later worked as a corporate general counsel and is currently a counsel at the international law firm Kirkland & Ellis.