US ATTORNEY GENERAL William Barr has said he will testify before Congress for the first time as it examines whether he has inappropriately politicised the Justice Department.

One of Barr’s federal prosecutors has told the House Judiciary Committee that Roger Stone, a close ally of Donald Trump, was given special treatment ahead of his sentencing because of his relationship with the president.

As the hearing began, Justice Department spokeswoman Kerri Kupec tweeted that Mr Barr would accept the panel’s invitation to give evidence on 18 July.

Aaron Zelinsky, a career Justice Department prosecutor who was part of special counsel Robert Mueller’s team and worked on the case against Stone, said he was told by supervisors that political considerations influenced the decision to overrule the recommendation of the trial team and propose a lighter prison sentence.

Zelinsky now works in the US attorney’s office in Maryland, and his evidence features the spectacle of a current prosecutor castigating decisions made by the leadership of the Justice Department where he still serves.

The hearing is likely to add to scrutiny of Barr, who has alarmed Democrats in recent months with his efforts to scrutinise, and even undo, some of the results of Mueller’s Russia’s investigation.

“What I heard – repeatedly – was that Roger Stone was being treated differently from any other defendant because of his relationship to the president,” Mr Zelinsky says in his evidence.

The panel subpoenaed Zelinksy and John Elias, a career official in the department’s antitrust division, as part of its probe into the politicisation of the department under Mr Barr.

The Democratic-led panel and Barr have been feuding since shortly after he took office in early 2019, when he declined to give evidence about Mueller’s report.

The Democrats launched the investigation earlier this year over Barr’s handling of the Stone case but have expanded their focus to several subsequent episodes in which they believe Barr is doing Trump’s bidding.

That includes the department’s efforts to dismiss the criminal case against General Michael Flynn and the firing last weekend of the the top prosecutor in New York’s Southern District. The prosecutor, Geoffrey Berman, has been investigating the president’s personal lawyer Rudy Giuliani.

House Judiciary Committee chairman Jerrold Nadler had threatened to subpoena Barr himself for the hearing next week if he did not agree to appear. The attorney general has never given evidence before the panel.

Zelinsky, one of four lawyers who quit the Stone case after the department overruled their sentencing recommendation, said the acting US attorney at the time, Timothy Shea, was “receiving heavy pressures from the highest levels of the Department of Justice to give Stone a break”.

He does not say who was doing the pressuring, but says there was “significant pressure” on line prosecutors to “obscure” the correct sentencing guidelines and “water down and in some cases outright distort” what happened at Stone’s trial and the events that resulted in his conviction.

Before Stone’s sentencing on 20 February, Justice Department leadership changed the sentencing recommendation just hours after Trump tweeted his displeasure at the recommendation of up to nine years in prison, saying it had been too harsh.

Stone was later sentenced to serve more than three years in prison plus two years’ probation and a $20,000 fine.

Barr said Trump’s tweet played no role in the change. He said he ordered the new filing hours before the president’s tweet because he was caught off guard by the initial sentencing recommendation and believed it was excessive based on the facts of the case.