A 33-page report on the House of Representatives intelligence committee questions whether Snowden, a former NSA contractor now in exile in Moscow, took his concerns about intelligence community activities to internal channels for complaints before he took them to journalists. It also attacks Snowden's presentation of himself as a whistleblower seeking only to reveal the overreach of the US and its allies in surveillance.
"Snowden was, and remains, a serial exaggerator and fabricator," the report says in its executive summary. The body of the report, which was declassified on Wednesday, says Snowden lied about his educational background, experience in the Army and the importance of his role in the CIA, among other things, leading the committee to its conclusion.
Snowden shot back immediately, saying on Twitter the committee provided no proof of its assessment.
"Bottom line: this report's core claims are made without evidence, and are often contrary to both common sense and the public record," Snowden wrote after several tweets aimed at debunking the report's claims.
"The House committee spent three years and millions of dollars in a failed attempt to discredit Edward Snowden, whose actions led to the most significant intelligence reforms in a generation," said Snowden's lawyer, Ben Wizner of the ACLU, in a statement.
The report contends the overwhelming majority of the documents Snowden leaked were about military programs rather than snooping on civilians. The 22-person committee includes Republican Devin Nunes and Democrat Adam Schiff, both of California.
"A review of the materials Snowden compromised makes clear that he handed over secrets that protect American troops overseas and secrets that provide vital defenses against terrorists and nation-states," the report reads. The list of documents that the committee reviewed is fully redacted.
In his tweetstorm, Snowden acknowledged some of the committee's comments about his work, including complaints that he harangued his superiors, were justified.
"Was I a pain in the ass to work with?" Snowden tweeted. "Perhaps; many technologists are. But this report establishes no worse."
Snowden also says the report's characterization of his disagreements with superiors as examples of his principles, not a tendency to fabricate.
The report also had choice words for the NSA.
"The Committee remains concerned that NSA, and the [intelligence community] as a whole, have not done enough to reduce the chances of future insider threats like Snowden," the report reads.
The NSA didn't respond to a request for comment on the report in general or the claim that it hasn't done enough to prevent future leaks.