WASHINGTON — In a newly revealed letter obtained by USA TODAY, dated April 19, White House counsel Emmet Flood accused special counsel Robert Mueller's office of making "political statements," and of issuing a report with "an extraordinary legal defect."

The letter, sent to Attorney General William Barr, is dated one day after the unredacted Mueller report was released, though it is unclear if it was delivered to the attorney general on that day.

According to Flood, Mueller's office "quite deliberately fails to comply with the requirements of governing law" as it produced a "prosecutorial curiosity — part 'truth commission' report and part law school exam paper."

Flood took issue with the way that the special counsel addressed the question of obstruction of justice. President Trump had claimed "complete and total exoneration" after Attorney General Barr released a four-page summary of the Mueller report on March 24, but the 448-page report did not actually entirely exonerate the president of the charge of obstruction of justice.

Mueller's report said that while the special counsel's office could not "conclude that the President committed a crime, it also does not exonerate him." The report went on to present evidence of the president's attempts to derail the investigation.

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Flood saw part of the special counsel's report instead as "political statements," in which the special counsel and his staff had "failed in their duty to act as prosecutors and only as prosecutors" because, rather than ask for an indictment or decline to pursue the case further, Mueller's team had instead declined to determine whether Trump's actions constituted obstruction of justice.

Anticipating the wave of subpoenas and hearings that would follow the release of the report, Flood also declared that "the President is determined to protect from congressional scrutiny not only the advice rendered by his own advisors, but also by advisors to future Presidents."

The fight between Congress and the White House has escalated as the White House has so far resisted attempts by congressional Democrats to obtain documents related to the special counsel's investigation or to call witnesses to testify before Congress. Attorney General Barr refused to appear before the House Judiciary Committee Thursday morning over disagreements about the format of the hearing and House Democrats' demands for the release of the unredacted Mueller report.

The House Judiciary Committee, under the control of Democrats, also subpoenaed former White House counsel Don McGahn to testify, something that the White House has suggested it will not allow him to do, citing executive privilege.

Also on Thursday morning, House Speaker Nancy Pelosi, D-Calif., said that Barr had "lied to Congress" and had committed a crime when he said he did not know about officials in Mueller's office that were "frustrated" with Barr's handling of the report's release.

Contributing: David Jackson