FBI Director James Comey considered an anti-Trump dossier compiled by a former British intelligence officer so important that he insisted the document be included in January's final intelligence community report on Russian meddling in the U.S. election, Fox News was told.

Sources would not speak on the record, citing the sensitivity of the matter and its current relevance to upcoming testimony on the unmasking of American citizens as part of the FBI probe into alleged contacts between Trump campaign advisers and Moscow. 

Asked for a response to the claims, the FBI and Office of the Director of National Intelligence said they could not comment on a classified document. 

It was reported last month that the unverified dossier was part of the evidence the FBI used to obtain a FISA warrant for Carter Page, a peripheral figure in the Trump campaign. In an interview with Fox News, Page denied the dossier’s central allegations that he was the Trump campaign’s point person for Moscow.

The dossier also contained salacious allegations about then-candidate Donald Trump. The classified version of the intelligence report issued at the end of the Obama administration included a summary of the document, as an attachment. Both then-President Barack Obama and President-elect Trump were presented with the findings. 

In a remarkable exchange Wednesday between Sen. Lindsey Graham, R-S.C., and Comey during a Senate hearing, more questions were raised about the bureau’s relationship with the former British officer who wrote the dossier, Christopher Steele, and his British company Orbis -- and its relationship to Washington, D.C.-based Fusion GPS.