Two weeks after he exonerated US President Donald Trump in the Russia meddling investigation, Attorney General Bill Barr faces mounting pressure to show the full evidence behind his decision.

Allegations last week that the US Justice chief downplayed serious evidence of illegal obstruction by Trump in Special Counsel Robert Mueller’s final report are fueling demands that he release the entire, unexpurgated document to Congress.

News reports, citing unnamed members of Mueller’s staff, said Barr ignored the summaries Mueller’s team prepared for public release, and instead issued his own on March 24, in which he peremptorily cleared the president of any wrongdoing.

And Barr now says he will not release key evidence given to Mueller’s grand jury, a special panel used by prosecutors in politically-sensitive cases. Democrats suspect the evidence could be damning to the president – setting up a legal and political showdown.

The Democrat-led House Judiciary Committee last week prepared to subpoena the full report, a move Barr and the White House will almost certainly contest.

And on Thursday Jerry Nadler, the committee chairman, demanded Barr turn over all communications between his office and Mueller’s, following the reports Mueller’s staff were unhappy with the way Barr presented their conclusions.

Barr’s distillation “appears to minimise the implications of the report as to the president,” said Nadler.

“Releasing the summaries – without delay – would begin to allow the American people to judge the facts for themselves,” Nadler wrote.

‘Witch Hunt’

At stake is the president’s ability to put the Russia probe behind him and look to 2020 for reelection.

Trump, who declared a “complete and total exoneration” when Barr announced Mueller’s conclusions, said this week that Democrats “are fighting hard to keep the Witch Hunt alive”.

“This is the highest level of Presidential Harassment in the history of our Country!” he tweeted.

On Tuesday, members of Congress might get their first chance to press Barr in public about the Mueller report, when he appears before the House Appropriations Committee in a hearing nominally focused on the Justice Department Budget.

In his four-page summation of the 22-month investigation on March 24, Barr said that Mueller found no evidence of collusion between Trump’s campaign and Russia in the 2016 election, and that there was insufficient evidence to charge Trump with obstruction.

Yet Barr also conceded that Mueller did compile evidence of obstruction, and quoted the special counsel as saying that: “While this report does not conclude that the president committed a crime, it also does not exonerate him.”

Suspicions are deep among Democrats that Barr took advantage of his position to clear Trump and now wants to keep the most damaging parts of the report secret to protect the White House.

Trump chose the veteran Republican lawyer to lead the Justice Department after firing his predecessor Jeff Sessions, whom the president resented for recusing himself from oversight of the Russia probe.

Is Barr protecting Trump?

In June last year, with Sessions’s job already known to be imperiled, Barr sent an unsolicited legal memo to the Justice Department and White House strongly criticising the Mueller investigation and its impingement on the president’s prerogatives.

Then a Washington corporate attorney – but without knowledge of the internal work of the Russia probe – Barr declared that “Mueller’s obstruction theory is fatally misconceived” and based on “a novel and legally unsupportable reading of the law”.

The memo only came to light in December after Trump had sacked Sessions and chosen Barr to replace him.

So far, Barr has held firm to his stance that he will release this month more of the Mueller report, but stripped of evidence and testimony given to Mueller’s grand jury.

The grand jury material is essential. As is done frequently in such high-profile cases, Mueller used the panel of citizens to develop and hear the evidence and depose key witnesses behind closed doors.

But that evidence is usually kept secret by law unless a prosecutor ultimately decides to level charges in the case.

Democrats argue that Congress, in its constitutional responsibility to enforce the law against the president, has the right to review any evidence against him of wrongdoing, even that of a grand jury.

On Friday, the Justice Department, commenting on a fresh ruling in a case on grand jury secrecy, signaled its stance against that.

“The Department of Justice will continue to defend the long established tradition of protecting grand jury information,” said spokeswoman Kelly Laco.