The special counsel Robert Mueller wrote a letter to the US attorney general, William Barr, expressing frustration with how the attorney general characterized the conclusions of Mueller’s investigation into potential ties between Donald Trump’s presidential campaign and Russia, according to multiple reports.

The Washington Post, the New York Times and NBC reported on Tuesday that Mueller penned the letter in late March, after Barr wrote a four-page summary of the special counsel’s work that largely cleared Trump on potential obstruction of justice.

Mueller wrote that Barr “did not fully capture the context, nature, and substance” of the special counsel’s findings, according to an excerpt of the letter published by the Post.

“There is now public confusion about critical aspects of the results of our investigation,” Mueller added. “This threatens to undermine a central purpose for which the Department appointed the Special Counsel: to assure full public confidence in the outcome of the investigations.”

A spokesman for Mueller declined to comment on the matter.

A justice department spokeswoman, Kerri Kupec, said Barr called Mueller upon receiving his letter and that the two had had a “cordial and professional conversation”.

“The Special Counsel emphasized that nothing in the Attorney General’s March 24 letter was inaccurate or misleading. But, he expressed frustration over the lack of context and the resulting media coverage regarding the Special Counsel’s obstruction analysis,” Kupec said in a statement.

Kupec said Mueller and Barr then discussed “whether additional context from the report would be helpful and could be quickly released”, but that the attorney general decided it would be counterproductive to release the report in “piecemeal fashion”.

It was after their conversation, she noted, that Barr released a second letter to Congress saying his first assessment was not intended to be a summary of Mueller’s report.

Barr, who is set to begin two days of testimony before Congress on Wednesday, has vigorously defended his framing of Mueller’s conclusions amid intense scrutiny over his conduct.

Earlier on Tuesday, Senate Democrats called on the justice department’s watchdog to independently investigate Barr’s handling of the Mueller report and “whether he has demonstrated sufficient impartiality” to continue overseeing 14 criminal matters related to the special counsel’s investigation.

Mueller concluded the two-year investigation into Russian interference in the 2016 presidential election last month and subsequently delivered a final report to Barr. It spanned more than 400 pages.

Barr initially released a letter on 24 March citing Mueller’s conclusion that there was no criminal conspiracy between the Trump campaign and Moscow. Barr declared in the same letter that he did not believe there was sufficient evidence to charge Trump with obstruction of justice.

But a redacted version of Mueller’s report, which was made public on 18 April, revealed nearly a dozen instances in which the actions of the president and his campaign may have amounted to obstruction. The report also stated that the Trump campaign was “receptive” to assistance from Moscow during the 2016 election and expected to benefit from Russian interference.

Barr nonetheless delivered a press conference, before his public release of the redacted report, that essentially sought to absolve the president of wrongdoing. In his statement, Barr repeatedly echoed Trump’s claims of “no collusion” with the Russians and downplayed the president’s attempts to impede the special counsel investigation.

House Democrats have issued a subpoena for the full Mueller report and underlying evidence, setting the stage for what is expected to be a protracted legal battle with the justice department and the White House.

Top Democrats in Congress said reports around Mueller’s letter reinforced the need for the special counsel to testify on Capitol Hill.

“No one can place any reliance on what Barr says. We need to hear from Mueller himself,” Adam Schiff, the House intelligence committee chairman, said.

Now it is confirmed Mueller objected to the “context, nature, and substance” of Barr’s misleading summary of the report.



And the false public narrative it allowed the White House to create.



No one can place any reliance on what Barr says. We need to hear from Mueller himself. https://t.co/ET7tQxnGQG — Adam Schiff (@RepAdamSchiff) May 1, 2019

The House judiciary committee chairman, Jerry Nadler, said he would press the justice department to schedule a hearing with Mueller “without delay”.

“The Special Counsel’s concerns reflect our own,” Nadler wrote in a statement. “The Attorney General should not have taken it upon himself to describe the Special Counsel’s findings in a light more favorable to the President.”

“It was only a matter of time before the facts caught up to him.”