Graham stated in the letter that during the 2016 election, the U.S. law enforcement and intelligence communities used a “deeply flawed dossier filled with hearsay and written by a biased, former United Kingdom intelligence officer” — a reference to the so-called Steele dossier — as part of its investigation.

He also added that law enforcement had received “intelligence from an Italian ‘professor’” — referring to Joseph Mifsud, whose interactions with a former Trump campaign adviser, George Papadopoulos, prompted the FBI to open its counterintelligence investigation — and accepted information from an Australian diplomat. That was a reference to a reported tip from an Australian official, Alexander Downer, to the FBI about possible collusion between Russia and Trump’s 2016 campaign.

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Graham’s letter came after The New York Times reported last week that Trump had asked Prime Minister Scott Morrison of Australia to help Barr with his investigation. In the letter, Graham defended Barr’s work.

“That the Attorney General is holding meetings with your countries to aid in the Justice Department’s investigation of what happened is well within the bounds of his normal activities,” Graham wrote. “He is simply doing his job.”

Darren Samuelsohn contributed to this report.