Donald Trump's senior adviser has denied allegations that the President-elect's campaign team communicated with Russian authorities throughout the election and that he was involved in sexual acts in Moscow that were arranged and monitored by Kremlin spies.

Kellyanne Conway was interviewed on the Late Night With Seth Meyers about the unverified claims, reportedly made by a former British spy and recently briefed to Mr Trump by the FBI.

The allegations were included in a series of memos compiled by the supposed ex-operative initially as opposition research on Mr Trump.

They allege secret contact between the Trump campaign and Moscow for at least five years and details of "perverted sexual acts" involving prostitutes alleged to have taken place in a hotel room in Moscow.

The potentially highly embarrassing and damaging claims have been made public just nine days before Mr Trump's inauguration.

They were made public hours after news reports circulated that Trump had been briefed by intelligence officials about the existence of the dossier on him by the US news outlet BuzzFeed News, which published the document in full. It published despite its editor noting that there is reason to doubt the truth of them.

She criticised news outlets for using "unnamed, unspoken sources" and US intelligence agencies for leaking the documents.

She said: "Nobody has sourced it. They're all unnamed, unspoken sources in the story, and it says it was based on a Russian investigator to begin with."

When Mr Meyers said that "it was based on an MI6 British investigator," Ms Conway replied, "It also may have—may have—originated with a Russian investigator."

She added: "It also says that Hillary Clinton and groups that wanted Hillary Clinton to win may have been behind the investigations themselves. And, most importantly, it says that the FBI is trying to confirm it.

"So nothing's been confirmed and I have to say, as an American citizen, regardless of your party or if you don't like politics at all, which are many Americans, we should be concerned that intelligence officials leak to the press and won't go and tell the President-elect or the President of the United States himself now, Mr Obama, what the information is."

Mr Meyers said: "The press report was about them going to the President."

Ms Conway replied: "And it says they never briefed him on it, they appended two pages to the bottom of his intelligence report.

Mr Meyers said: "I believe it said they did brief him on it."

Ms Conway said: "He has said that he is not aware of that."

Mr Trump denied the claims in a tweet almost immediately, saying: "FAKE NEWS - A TOTAL POLITICAL WITCH HUNT!"

The New York Times reported that the operative had previously worked for British intelligence. It has not been possible to substantiate the information in the dossier, which contains numerous factual errors including the misspelling of the name of Russia's largest bank.

It is unclear why the intelligence officials decided to brief the president and Mr Trump on the uncorroborated information at this time, but politicians and others have repeatedly noted that Russia collects intelligence on both Democrats and Republicans.

"The Russians also hacked systems associated with the Republicans. They just chose not to release that material yet," Senator Mark Warner of Virginia, the most senior Democrat on the Senate intelligence committee, said.

"There's nothing that prevents them from doing so at a time of their choosing in the future."

The report has been circulating in Washington for months.

In October, former Senate minority leader Harry Reid wrote to the FBI asking the bureau to publicly disclose what it knew about the Trump campaign's ties to Russia.

Mr Reid was aware of the dossier before he wrote the letter, according to a person knowledgeable about the subject.

FBI director James Comey has refused to say whether the FBI was investigating any possible ties between Russia and Mr Trump's presidential campaign, citing policy not to comment on what the FBI might or might not be doing.

Mr Comey was pressed by Democrats on the committee about whether the FBI was conducting an investigation.

There was no mention during the hearing about the summary of the dossier, which was attached to the classified hacking assessment.

"I would never comment on investigations - whether we have one or not - in an open forum like this so I can't answer one way or another," Mr Comey told the panel during his first public appearance before Congress since the election.