“That’s something that Nazi Germany would have done,” he said.
He was replying to unsubstantiated allegations that his election team colluded with Russia and there were salacious videos of his private life.
Head of US spy agencies James Clapper denied that intelligence had leaked the content from a classified briefing.
Intelligence agencies considered the claims relevant enough to brief both Mr Trump and President Obama last week.
Mr Trump also said for the first time that he accepted Russia was behind hacking attacks that took place during the presidential campaign.
In his first briefing as president-elect, Mr Trump also confirmed he was handing total control of his businesses to his two sons.
The press conference was scheduled in order for Mr Trump to give details about his business affairs but was dominated by the allegations of compromising material.
Mr Trump said the information “should have never been written and certainly should never have been released”.
“It’s all fake news, it’s phoney stuff, it didn’t happen,” he said, adding that “sick people” had “put that crap together… it’s an absolute disgrace”.
Mr Trump said he could not talk about what he had heard in last week’s intelligence agency briefing but said there had been “many witnesses” there and that it would be a “tremendous blot” on the reputation of intelligence agencies if they had been responsible for leaking the details.
He added later in the briefing: “I think it was disgraceful – disgraceful that the intelligence agencies allowed any information that turned out to be so false and fake out. I think it’s a disgrace… and that’s something that Nazi Germany would have done and did do.”
In response White House spokesman Josh Earnest said it was “deeply misguided for anybody, at any level, to question the integrity and motives of the patriots” in the nation’s intelligence agencies.