The firm that created the now-infamous "Russian dossier" on President Trump published before his inauguration is stonewalling investigators who want to know more about its connections to the Democratic Party and the FBI is refusing to confirm if it has documents showing a relationship with the firm.

The New York Post reported Monday the firm that assembled the document, Fusion GPS, "is stonewalling congressional investigators trying to learn more about its connections to the Democratic Party."

On the same day, the watchdog group Cause of Action said the FBI would "neither confirm nor deny" the existence of any records the bureau might have which could establish the FBI's relationship to the dossier, in response to a Freedom of Information Act request.

The dossier was assembled in 2016 by former British intelligence officer Christopher Steele as part of opposition research from Trump's political opponents. After it was put into the public record in a controversial publishing by Buzzfeed, many of the claims within have been debunked or are no longer taken seriously.

Whether the document is legitimate at all is still a fiery debate among partisans.

An earlier media report claimed the FBI considered paying Steele to continue digging into Trump's background, but then abandoned the idea.

The dossier now has a long history in the Russia affair and has become a cudgel with which the Democrats have hammered the Trump administration.

In 2016, media reports said the dossier was used in part by the FBI to obtain a surveillance warrant against Carter Page, who briefly served as a foreign affairs advisor to the Trump campaign.

In the March open hearing into the Russia investigation held by the House Intelligence Committee, several committee members relied upon and referenced the dossier when questioning then-FBI Director Comey and NSA Director Admiral Mike Rogers.

For example, Rep. Andre Carson, D-Ind., said, "In fact, the dossier written by former MI6 agent, Christopher Steele alleges that Trump agreed to sideline Russian intervention in Ukraine as a campaign issue, which is effectively a priority for Vladimir Putin.

"There's a lot in the dossier that is yet to be proven, but increasingly as we'll hear throughout the day, allegations are checking out."

In the same hearing, Rep. Jackie Speier, D-Calif., relied on the dossier to question Comey and Rogers about an allegation that Page had been offered a commission on an upcoming sale of a percentage of Rosneft, a state-owned gas company in Russia.

Page, however, has denied that he was ever offered to participate in any part of the Rosneft sale at any level at all.

Earlier this month, Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, threatened to subpoena Fusion GPS if they refused to provide documentation that the committee was seeking.

Additionally, a Russian bank that was mentioned in the dossier is suing Buzzfeed, the outlet that originally published the document.