Hillary ClintonHillary Diane Rodham ClintonGrassley blasts Democrats over unwillingness to probe Clinton GOP lawmakers cite new allegations of political bias in FBI Top intel Dem: Trump Jr. refused to answer questions about Trump Tower discussions with father 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 TrumpHouse Democrat slams Donald Trump Jr. for ‘serious case of amnesia’ after testimony Skier Lindsey Vonn: I don’t want to represent Trump at Olympics Poll: 4 in 10 Republicans think senior Trump advisers had improper dealings with Russia 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.