"On behalf of Glenn Simpson, we are responding to the subpoena issued by the House Committee on the Judiciary for a confidential deposition," the letter said on Thursday. "Mr. Simpson, whose testimony is a matter of public record, will not be participating in a confidential deposition before this Committee."
Simpson’s firm Fusion GPS hired former UK spy Christopher Steele to compile a disparaging dossier about Trump in an effort partly funded by the Clinton campaign during 2016 that was based on largely unsubstantiated allegations.
In particular, the dossier contained unverified allegations that Trump participated in activities that could make him vulnerable to Russian blackmail attempts. The White House has firmly rejected the allegations and Trump has dismissed the dossier as "fake news."
READ MORE: US State Department Ex-Official Refuses to Testify in Congress on Trump Dossier
The United States has repeatedly accused Russia of interference in the 2016 presidential election and is investigating Trump's team members' alleged links to the Kremlin. Top Russian officials have refuted such allegations. Kremlin spokesman Dmitry Peskov has called all such claims groundless. Russian Foreign Minister Sergey Lavrov has stressed that the accusations of Russia meddling in the elections of foreign states were unsubstantiated.