Rep. Devin Nunes said his team of investigators knows a memo from the British government disavowing British ex-spy Christopher Steele, the author of the anti-Trump dossier, is real.

A letter from the British Embassy to the incoming national security team after President Trump was elected to the White House is mentioned in a newly unsealed filing in federal court by former national security adviser Michael Flynn’s lawyers. The filing claims this letter was also sent to outgoing national security adviser Susan Rice and "apparently disavows former British Secret Service Agent Christopher Steele, calls his credibility into question and declares him untrustworthy."

Nunes, the top Republican on the House Intelligence Committee, said on Wednesday his team of investigators have been looking for that same document.

"We know that document exists," Nunes said on Fox News. "This document that came from the British government. But yet nobody can seem to find it."

Steele's dossier, which contained allegations about Trump's ties to Russia, was used by the FBI and Justice Department to obtain Foreign Intelligence Surveillance Act to surveil onetime Trump campaign adviser Carter Page. Republicans allege the FBI knew very well it was unverified and should not have used it before the Foreign Intelligence Surveillance Court.

Nunes said he hopes the Flynn case will shed a light on the elusive letter from the United Kingdom.

"I know there are witnesses out there that know this. And I hope that the judge in this case will actually get those witnesses that know this document exists and let them come in and talk to the court or at least give an affidavit to the court," he said.