With rare exception, special counsel Robert Mueller has emerged from the past two years unscathed — seemingly immune to cable news criticism. But on Monday, one man who previously ran a high-profile independent investigation of a president came after him with a blistering take.

Appearing on The Story, Ken Starr — the man who led the investigation into former President Bill Clinton in the late ’90s — shredded Mueller for his letter to Attorney General William Barr, which took the AG to task for his four-page Mueller Report summary.

“His letter, that was then leaked on the very eve of Bill Barr’s testimony, was essentially, I believe, an unfair, whiny complaint,” Starr told Fox’s Martha MacCallum.

“Whiny” was just the beginning of Starr’s blistering critique. The former independent counsel went on to refer to the leaked letter as an “unforgivable sin” against Barr.

“Here comes Bob Mueller with this letter which is then leaked. That is, to me, the unforgivable sin,” Starr said. “He, Bob Mueller, badly injured this attorney general and the attorney general didn’t deserve that but, of course, that created its own huge firestorm including suggestions that the attorney general was totally mischaracterizing the report and so forth.”

Watch above, via Fox News.

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