The FBI reportedly applied for a warrant to monitor Donald Trump’s presidential election campaign over links to Russian officials.
The request by US investigators, to track four members of his team, was allegedly rejected but then eventually granted in October last year.
The claims come amid potentially highly embarrassingly and damaging allegations that Russian intelligence has compromising material, some of a graphic sexual nature, on the President-elect just nine days before his inauguration.
The Guardian reports that the FBI applied for the warrant from the foreign intelligence surveillance (Fisa) court over the summer to keep an eye on Mr Trump team members suspected of irregular contacts with Russian officials.
Fisa reportedly turned it down in June 2016 and asked investigators to narrow their focus.
The warrant was reportedly granted in October, but it is not clear whether any full investigation took place.
The allegation comes amid the publication of an unverified 35-page report, compiled by a British intelligence agent for opponents of Mr Trump, alleging that the Kremlin has been “cultivating, supporting and assisting” Mr Trump for at least five years.
The two-page synopsis, which the Federal Security Service of the Russian Federation (FSB) says has compromised the 70-year-old enough to blackmail him, was presented to Mr Trump and President Barack Obama last week – according to CNN.
They include allegations that Mr Trump or his surrogates had direct contact with the Kremlin for at least five years before and during the 2016 election campaign.
The report also details "perverted sexual acts" involving prostitutes alleged to have taken place in a hotel room in Moscow. The suggestion is that the claims could have been used by Russia to compromise the incoming US President.
Mr Trump has strenuously denied the unverified allegations, which came in a two-page synopsis attached to a classified intelligence report into Russian interference in the US election. A declassified version was distributed publicly last week.
The documents have reportedly been circulated for months and acquired a legendary status among journalists, lawmakers and intelligence officials.
The document, dated 13 December, makes various errors which includes misspelling Alfa Group and an inaccurate description about Moscow suburb Barvikha.
Mr Trump dismissed the claims on Twitter as "fake news".
The President-elect’s attorney Michael Cohen told Mic: “It’s so ridiculous on so many levels.
“Clearly, the person who created this did so from their imagination or did so hoping that the liberal media would run with this fake story for whatever rationale they might have.”
Mr Trump’s senior advisor Kellyanne Conway, speaking on Late Night With Seth Meyers, stressed “nothing’s been confirmed” and “nobody has sourced it”.
The Independent has contacted the FBI for comment.
