Senator John McCain passed documents to the FBI director, James Comey, last month alleging secret contacts between the Trump campaign and Moscow and that Russian intelligence had personally compromising material on the president-elect himself.
The material, which has been seen by the Guardian, is a series of reports on Trump’s relationship with Moscow. They were drawn up by a former western counter-intelligence official, now working as a private consultant.
The Guardian has not been able to confirm the veracity of the documents’ contents, and the Trump team has consistently denied any hidden contacts with the Russian government.
Trump’s transition team did not immediately respond to a request for comment, but late on Tuesday, Trump tweeted: “FAKE NEWS - A TOTAL POLITICAL WITCH HUNT!” He made no direct reference to the allegations.
An official in the US administration who spoke to the Guardian described the source who wrote the intelligence report as consistently reliable, meticulous and well-informed, with a reputation for having extensive Russian contacts.
Some of the reports – which are dated from 20 June to 20 October last year – also proved to be prescient, predicting events that happened after they were sent.
One report, dated June 2016, claims that the Kremlin has been cultivating, supporting and assisting Trump for at least five years, with the aim of encouraging “splits and divisions in western alliance”.
It claims that Trump had declined “various sweetener real estate deals offered him in Russia” especially in developments linked to the 2018 World Cup finals but that “he and his inner circle have accepted a regular flow of intelligence from the Kremlin, including on his Democratic and other political rivals.”
Most explosively, the report alleges: “FSB has compromised Trump through his activities in Moscow sufficiently to be able to blackmail him.” The president-elect has not responded to the allegations.