A top White House lawyer wrote to Attorney General William Barr in April to express his displeasure with special counsel Robert Mueller's investigation and report, claiming Mueller made "political statements" and mishandled obstruction of justice allegations.

In the five-page April 19 letter obtained by CBS News, White House lawyer Emmet Flood suggested Mueller did a disservice to the president by failing to come to a conclusion on obstruction of justice. Mueller's report, which determined no Trump associates were guilty of conspiracy with Russia, listed 10 instances of potential obstruction, but made no determination on the matter. After receiving Mueller's report, Barr decided the evidence was insufficient to show the president obstructed justice.

"Because they do not belong to our criminal justice vocabulary, the [special counsel's office's] inverted-proof-standard and 'exoneration' statements can be understood only as political statements, issuing from persons (federal prosecutors) who in our system of government are rightly expected never to be political in the performance of their duties," Flood wrote to Barr. "The inverted burden of proof knowingly embedded in the SCO's conclusion shows that the special counsel and his staff failed in their duty to act as prosecutors and only as prosecutors."

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"Second, and equally importantly: In closing its investigation, the SCO had only one job — to 'provide the attorney general with a confidential report explaining the prosecution or declination decisions reached by the special counsel," Flood continued. "Yet the one thing the SCO was obligated to do is the very thing the SCO — intentionally and unapologetically — refused to do. The SCO made neither a prosecution decision nor a declination decision on the obstruction question."

The letter also says the Mueller report "suffers from an extraordinary legal defect: It quite deliberately fails to comply with the requirements of governing law."

Flood said Mueller's investigation and the allegations of Russian collusion "placed a cloud over the presidency that has only begun to lift in recent weeks."