"Buzzfeed is a failing pile of garbage and they're going to pay the consequences," he said.
"I think it's a disgrace that information would be let out," he said.
"It's all fake news, its phony stuff, it doesn't happen ... It was a group of opponents who got together, sick people and they put that crap together."
The extraordinary press conference was the first the President-elect has held since July and covered a range of issues from his business interests to Obamacare.
On US intelligence reports of Russian hacking in the US election, Mr Trump said: "I think it was Russia but I think we also get hacked by other countries and by other people."
"If Putin likes Donald Trump I consider that an asset not a liability because we have a horrible relationship with Russia."
He also said reports of lewd sexual acts in a hotel room in Moscow were not true, not least because he was a "germophobe" who is constantly aware of being caught on camera.
"No matter where you go you're going to probably have cameras," he said. "You can't see them and you won't know. You better be careful or you're watching yourself on nightly television. I tell this to people all the time."
With nine days to go before the inauguration, Mr Trump outlined plans to separate himself from his business which he will turn over to his sons, Eric and Donald Jr.
His lawyer said Ivanka will also resign from her role at the company and Mr Trump bragged about he turned down an opportunity for a $2 billion series of deals with a "great guy" from Dubai. Mr Trump's lawyer Sheri Dillon said no new foreign deals would be undertaken while he is in office.
On the domestic front, the President-elect said Obamacare will be repealed and replaced "on the same day" and a Supreme Court justice will be chosen "within two weeks" of his inauguration.
He also reaffirmed commitments to build a wall on the border with Mexico and said he would bring in a border tax for companies that choose to move operations offshore.
Earlier, the President-elect took to Twitter to slam US intelligence agencies for "leaking" an unverified dossier into the public domain, claiming it was "one last shot" at him after winning the election.
In a string of tweets, Trump said Russia has "never tried to use leverage" over him and he has "no deals, no loans, no nothing" with the country.
He asked, "Are we living in Nazi Germany?" and slammed "crooked opponents" for trying to belittle him with "fake news".
Earlier, President Putin's spokesman Dmitry Peskov said the dossier, which claimed Trump had engaged in lewd sexual acts in Moscow, was "complete fabrication and utter nonsense".
"This is an evident attempt to harm our bilateral ties," he said, adding that it was "pulp fiction" and a "clear attempt to damage relations".
"The Kremlin does not engage in collecting compromising information," he said.
On Tuesday, Buzzfeed news published a dossier that been circulating in government and media circles for months that contained a number of unsubstantiated claims about Trump.
The document, purportedly from a British intelligence official, states Russia had been cultivating and supporting Trump for at least five years and that he had been "compromised" through his activities in Moscow "sufficiently to be able to blackmail him".
It said Russian Secret Service initiatives to exploit Trump's sexual desires had "borne fruit" and that compromising material had been found about him in the presidential suite of the Ritz Carlton Hotel where the Obamas had stayed including "defiling the bed" with prostitutes used to perform "lewd sex acts".
It also contains information about Russian cyberhacking and alleged meetings by Trump's adviser Carter Page in Moscow. Peskov was named as the owner of a similar dossier on Hillary Clinton that had been ordered directly by Putin.
Claims in the document were unable to be verified, but were presented by US intelligence to President Obama and the President-elect.
The President-elect denied the report as "FAKE NEWS - A TOTAL POLITICAL WITCH HUNT!"
