Hillary Clinton on Monday accused WikiLeaks of working with Russia to deflect attention away from an infamous tape of Donald Trump bragging about groping women in the run-up to the US presidential election.
"Assange has become a kind of nihilistic opportunist who does the bidding of a dictator," she said in an interview with the Australian Broadcasting Corporation, referring to Russian president Vladimir Putin.
"WikiLeaks is unfortunately now practically a fully-owned subsidiary of Russian intelligence."
The US intelligence community concluded Putin ordered an influence campaign to discredit Clinton and had a "clear preference" for Trump in last year's poll.
Clinton used the bombshell Trump tape as an example of how WikiLeaks allegedly tried to deflect attention away from a bad news story, resurrecting the incident in the wake of Hollywood mogul Harvey Weinstein's fall from grace over his treatment of women.
In the 2005 videotape, which surfaced in October last year, Trump brags about being able to get away with groping women.
Trump said the comments were "locker-room banter". Several women subsequently accused him of sexual misconduct, which he denounced as lies.
Within hours of the tape emerging, WikiLeaks published more than 2,000 hacked emails from the personal account of Clinton's campaign chair John Podesta, which she said blunted its impact.
"WikiLeaks, which in the world in which we find ourselves promised hidden information, promised some kind of secret that might be of influence, was a very clever, diabolical response to the Hollywood Access tape," she said, referring to the Trump recording.
"And I've no doubt in my mind that there was some communication if not coordination to drop those the first time in response to the Hollywood Access tape."
Clinton claimed WikiLeaks' actions were motivated by Assange's personal dislike of her.
"I had a lot of history with him because I was secretary of state when WikiLeaks published a lot of very sensitive information from our State Department and our Defence Department," she said.
"If he's such a martyr of free speech, why doesn't WikiLeaks ever publish anything coming out of Russia? You don't see damaging, negative information coming out about the Kremlin on Wikileaks," Clinton added.
Australian Assange, who has spent five years inside the Ecuador embassy in London to avoid extradition to Sweden on sexual assault charges, has denied Russia was the source behind the leaked documents.