Paul Wood, the BBC’s Washington correspondent, claimed CIA sources indicated there is more than one video of a “sexual nature” of Donald Trump in both Moscow and St Petersburg.
His source said the unverified allegations about Mr Trump being caught on film with prostitutes were “credible”, he said.
Mr Wood said: “I was able to send a message into the CIA at the beginning of November to ask them about these allegations.
“It was illegal for any official to talk to me about them but I got a message back through an intermediary which said the allegations were regarded as credible.
“And, more than that, there was more than a single source for them, not just this MI6 man but there was supposedly more than one tape, not just video but audio, more than one date and not just in Moscow but in St Petersburg as well.
“Now, obviously, if the Russians had blackmail material on Mr Trump, they’re hardly going to release it.
“These are necessarily allegations, but they are allegations that are regarded as credible. That’s not the same as saying accurate but they are regarded as credible by the US intelligence community.”
Mr Trump angrily denied the claims made in the dossier during his first press conference as president-elect yesterday.
The 35-page dossier compiled by a former MI6 agent contains unverified allegations that Russian security officials have compromising material on Mr Trump that could be used to blackmail him.
The billionaire businessman branded the dossier “fake news” and blamed the creation of the documents on his political opponents, who he said had “got together – sick people – and they put that crap together”.
He said some of the more lurid details of the allegations were highly improbable because he was a “germophobe” who hated uncleanliness.
Mr Trump told reporters: “A thing like that should never have been written, it should never have been had and it should certainly never have been released.”
The president-elect insisted Moscow had “no leverage” over him as he had “no deals, no loans, no nothing” with Russia.
Moscow has denied any links to the dossier.
CNN reported on Tuesday about the existence of the memo.
BuzzFeed published a fuller 35-page document produced by Christopher Steele, a former British foreign intelligence official, outlining the allegations of compromising behaviour by Mr Trump and alleged links between him and people in Russia.
The claims were included in opposition research reports that were made available to Democrats and US officials last year.