It also chastised him for announcing, again without Justice Department backing, that the investigation would be reopened because of newly discovered Clinton emails found on the laptop of Anthony Weiner, who was married to a Clinton aide.
Sessions spoke at Lackawanna College in Scranton, Pennsylvania.
Then he turned to other reporters and went over the same list for another 20 minutes.
A new report from the Department of Justice's Office of Inspector General states that former FBI Director James Comey "clearly and dramatically from FBI and department norms" in his treatment of the investigation into Hillary Clinton's emails.
In his Friday tweetstorm, Trump retweeted clip after clip from Fox News highlighting Comey's impropriety, and showing evidence of bias from others within the agency.
"I think Comey was the ringleader of this whole den of thieves". "Obstruction is dead. There was no obstruction", said one source close to Trump, adding that his team believes there is now no need to interview the President.
PAUL ADDS: John has identified what I consider the most important aspect of the IG's report - what it tells us about the motive behind the Russian Federation investigation in its early days.
Across the political spectrum, politicians - Donald Trump, Bernie Sanders, Paul Ryan - were excoriated by a pair of FBI agents whose texts were disclosed in a report on the FBI's handling of the Hillary Clinton email investigation.
NK leader arrives in Singapore for historic summit with Trump
Accompanying him was Kim Yong Chol, who earlier this month met with President Trump to hand deliver a letter from Kim. We are where we are because Mr Trump has taken a sword and sliced his way through conventional diplomatic behaviour.
Social Security trust fund reserves on track to be depleted by 2034
The trustees are the commissioner of Social Security and the secretaries of labor, health and human services, and the treasury. After that, the government predicts it will be able to pay 91 percent of promised benefits.
Kim, Trump and tourists - Singapore cashes in on historic summit
Donald Trump then guided Kim Jong-un to the library where the one-on-one meeting was to take place. The president also said the he trusts Kim will follow through, but won't admit if he got it wrong.
"The IG Report is a total disaster for Comey, his minions and sadly, the FBI", Trump tweeted earlier.
"The opinions I care the most about are the opinions of the people who actually really know us and know us through our work", he said.
Trump quickly retweeted at least a half dozen posts about the report from the "Fox & Friends" morning show on Fox News Channel.
Trump distanced himself from his former campaign manager Paul Manafort, whose bail was revoked by a federal judge on Friday.
"Among the text exchanges that have been made public is one from August 2016 in which Page said, "(Trump's) not ever going to become president, right?
It concluded there was no evidence of bias in the FBI investigation of Clinton's use of a private email server but was sharply critical of former FBI Director James Comey, saying he violated policy and practice in his handling of the email probe.
The report gave Mr Trump fresh ammunition for continued attacks on Mr Comey and for his defence that Mr Comey's firing in May 2017 - an act now central to special counsel Robert Mueller's investigation into whether the president sought to obstruct justice - was wholly justified.
"We are concerned that during this time, people may have changed the report in a way that obfuscates your findings", they wrote.
The report was also critical of the exchange of anti-Trump text messages between Federal Bureau of Investigation agent Peter Strzok and former Federal Bureau of Investigation lawyer Lisa Page.
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