Taylor Budowich filed a lawsuit in federal court in the District of Columbia on Friday in which he claimed to have produced more than 1,700 pages of documents and provided about four hours of sworn testimony to the House of Representatives select committee.
At a recent deposition, he answered questions about the financing and planning of a speech by the former president to his supporters that preceded the violence.
Mr Budowich is also fighting a subpoena sent by the congressional panel to JPMorgan Chase for his financial records.
He argued that he is being denied due process in the matter and is seeking a restraining order to prevent the bank from releasing his information.
“The subpoena seeks personal financial material that is irrelevant to any conceivable legislation and not pertinent to any purported purpose of the Select Committee,” Mr Budowich said in the lawsuit.
Reuters said a spokesperson for the panel did not respond to a request for comment.
Mr Budowich’s lawsuit is the latest in an array of litigation filed against the committee, seeking to prevent it from enforcing its subpoenas.
An appeals court rejected the argument on 9 December and ruled that the committee was valid and entitled to see White House records that Mr Trump has tried to shield from public view.
The former president on Thursday filed a petition with the Supreme Court for an injunction that would halt the committee’s requests for records.
Mr Trump’s lawyers argued that the committee’s request should be rejected because the panel “declined to either meaningfully limit the areas of inquiry, based upon a legitimate legislative purpose or seek the information elsewhere.”
The committee has issued more than 50 subpoenas and heard from more than 300 witnesses in its investigation of the attack.
At least five people died and 100 police officers sustained injuries when a mob, including the former president’s supporters, laid siege to the Capitol building.
Additional reporting by agencies
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