Hillary ClintonHillary Diane Rodham ClintonGillibrand urges opposition to Kavanaugh: Fight for abortion rights 'is now or never' Bannon announces pro-Trump movie, operation team ahead of midterms: report Fox News host hits Giuliani: Dossier isn't why Mueller probe was started MORE's former campaign manager Robby Mook said on Friday evening that he did not know who funded the controversial, unverified dossier about President TrumpDonald John TrumpGillibrand urges opposition to Kavanaugh: Fight for abortion rights 'is now or never' Trump claims tariffs on foreign nations will rescue US steel industry: report Bannon announces pro-Trump movie, operation team ahead of midterms: report MORE, despite revelations that the law firm representing the campaign sponsored the document. 

"I didn't know that we were paying the contractor that created that document," Mook told CNN's Anderson Cooper. 

"When we started to look into Donald Trump's business dealings, it was this massive tree of LLCs and shell companies. We were overwhelmed, we were on it, frankly," he continued. 

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"I asked our lawyer and I gave him a budget allocation to investigate this, particularly the international aspect. My understanding is that dossier is the product of not just research that was funded by our campaign, but also by Republican donors," he said. 

Mook added that the campaign received briefings from the law firm during the campaign. 

The comments from Clinton's former campaign manager come after Reuters reported that opposition research firm Fusion GPS told Congress that it paid former MI6 officer Christopher Steele's company, Orbis Business Intelligence, $168,000 in 2016.

The money from Fusion GPS came from $1.02 million it had received from the Perkins Coie law firm, which represented the Democratic National Committee (DNC) and Clinton's campaign. 

No senior members of the Clinton campaign have denied that the campaign and DNC funded the dossier through payments to Perkins Coie. So far, however, everyone involved has said they did not know about the dossier in particular.