National Security Agency leaker Edward Snowden is not a whistleblower and most of the documents he stole were defence secrets that had nothing to do with privacy, an official US report has said.
The House of Representatives intelligence committee released a three-page unclassified summary of its two-year examination of the case.
It looked at how Mr Snowden was able to remove more than 1.5 million classified documents from secure NSA networks, what the documents contained and the damage their removal caused to US national security.
Mr Snowden was an NSA contract employee when he took the documents and leaked them to journalists who revealed massive domestic surveillance programmes begun in the aftermath of the 9/11 attacks.
The programmes collected the telephone metadata records of millions of Americans and examined emails from overseas.
Mr Snowden fled to Hong Kong, then Russia, to avoid prosecution and now wants a presidential pardon as a whistleblower.
Republican Devin Nunes, chairman of the committee, said Mr Snowden betrayed his colleagues and his country.
"He put our service members and the American people at risk after perceived slights by his superiors," he said.
"In light of his long list of exaggerations and outright fabrications detailed in this report, no one should take him at his word. I look forward to his eventual return to the United States, where he will face justice for his damaging crimes."
Mr Snowden insists he has not shared the full cache of 1.5 million classified documents with anyone.
However, the report notes that in June, the deputy chairman of the Russian parliament's defence and security committee publicly conceded that "Snowden did share intelligence" with his government.
Ben Wizner, Mr Snowden's lawyer at the American Civil Liberties Union, blasted the report, saying it was an attempt to discredit a "genuine American hero".
He said: "After years of investigation, the committee still can't point to any remotely credible evidence that Snowden's disclosures caused harm."
Mr Snowden is seeking a presidential pardon because he says he helped his country by revealing secret domestic surveillance programmes.
All the members of the committee sent a bipartisan letter to President Barack Obama urging him not to pardon Mr Snowden.
"The vast majority of what he took has nothing to do with American privacy," said Adam Schiff of California, the leading Democrat on the committee.
The report says that Mr Snowden was a "disgruntled employee who had frequent conflicts with his managers".
According to the committee, he began mass downloads of classified material two weeks after he was reprimanded for engaging in a row with NSA managers.
The committee also described Mr Snowden as a "serial exaggerator and fabricator".
Speaking by video link from Moscow, Mr Snowden said on Wednesday that whistleblowing "is democracy's safeguard of last resort, the one on which we rely when all other checks and balances have failed and the public has no idea what's going on behind closed doors".
The report was released a day before Friday's opening of director Oliver Stone's film Snowden.